Stable Silicon Anode for Lithium Ion Battery through Covalent Bond

Research Article Cite This: ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX

www.acsami.org

Stable Silicon Anode for Lithium-Ion Batteries through Covalent Bond Formation with a Binder via Esterification Chul-Ho Jung, Kyeong-Ho Kim, and Seong-Hyeon Hong* Department of Materials Science and Engineering and Research Institute of Advanced Materials, Seoul National University, Seoul 151-744, Republic of Korea

Downloaded via UNIV OF SOUTHERN INDIANA on July 18, 2019 at 13:47:15 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

S Supporting Information *

ABSTRACT: Silicon (Si) is considered to be one of the most promising anode candidates for next-generation lithium-ion batteries because of its high theoretical specific capacity and low discharge potential. However, its poor cyclability, caused by tremendous volume change during cycling, prevents commercial use of the Si anode. Herein, we demonstrate a high-performance Si anode produced via covalent bond formation between a commercially available Si nanopowder and a linear polymeric binder through an esterification reaction. For efficient ester bonding, polyacrylic acid, composed of −COOH groups, is selected as the binder, Si is treated with piranha solution to produce abundant −OH groups on its surface, and sodium hypophosphite is employed as a catalyst. The as-fabricated electrode exhibits excellent high rate capability and long cycle stability, delivering a high capacity of 1500 mA h g−1 after 500 cycles at a high current density of 1000 mA g−1 by effectively restraining the susceptible sliding of the binder, stabilizing the solid electrolyte interface layer, preventing the electrode delamination, and suppressing the Si aggregation. Furthermore, a full cell is fabricated with as-fabricated Si as an anode and commercially available LiNi0.6Mn0.2Co0.2O2 as a cathode, and its electrochemical properties are investigated for the possibility of practical use. KEYWORDS: silicon, binder, esterification reaction, covalent bond, lithium-ion battery

1. INTRODUCTION Lithium-ion batteries (LIBs) have served as the main energy storage device for portable electronics.1 However, nextgeneration LIBs for electric vehicles, hybrid electric vehicles, and large-scale energy storage systems require high energy density, high power density, lower cost, and improved safety.2 Graphite is a commercialized anode material in LIBs, but its relatively low specific capacity (372 mA h g−1) and poor capacity retention at high current density cannot meet the high demand for large-scale energy storage devices.3 Silicon (Si) is recognized as a promising anode candidate for high power density LIBs because of its abundance, high theoretical specific capacity (3579 mA h g−1 for Li15Si4), and relatively low discharge potential (∼0.4 V vs Li+/Li).4 However, the massive volume change, low electrical conductivity, and unstable solid electrolyte interface (SEI) layer of Si-based anodes lead to the drastic capacity fading, which severely hinders the commercialization.5,6 Various strategies have been proposed to overcome these challenges, including size control, surface coating, active/ inactive alloy, void space engineering, and composites.7 In addition, polymeric binders have received much attention because they act a crucial role in maintaining the structural integrity of the electrode and stabilizing the electrode− electrolyte interface.8,9 A variety of polymeric binders have © XXXX American Chemical Society

been suggested to replace the conventionally used polyvinylidene fluoride (PVDF), which does not work properly in Si-based electrodes.10,11, The reported polymeric binders for Si anodes have been examined in-depth in terms of polymer interactions, polymer architectures, conductive polymeric binders, and topological cross-linking.9,12−15 Among them, polymeric networks produced from the cross-linking reaction between two polymers, such as polyacrylic acid (PAA)/ polyvinyl alcohol, PAA/carboxymethyl cellulose (CMC), chitosan/glutaraldehyde, and chitosan/PAA, are cost-effective and eco-friendly, accommodating the large volume change upon lithiation/delithiation while preserving the physical integrity of the Si electrode.16−19 The strong interactions between remaining free functional groups (−OH, −COOH, and −NH2) of the polymer networks and the Si surface have been suggested to additionally contribute to the high mechanical strength of adhesion between the active material and the binder, which further restrains the sliding of the binder. Much emphasis has been placed on the binders that can cross-link and covalently attach to Si. However, little attention has been paid to develop the fully covalent-bonded Si Received: March 3, 2019 Accepted: July 5, 2019 Published: July 5, 2019 A

DOI: 10.1021/acsami.9b03866 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX

Research Article

ACS Applied Materials & Interfaces

Scheme 1. Graphical Representation of the Preparation of Three Types of Si Anodes (HB, PE, and FE Electrodes) and Chemical Interactions between Si Nanoparticles and PAA bindera

a

HB: hydrogen bonded, PE: partially esterificated, FE: fully esterificated, and PAA: polyacrylic acid. (98%), hydrogen peroxide (30%), and acetic acid were purchased from DaeJung Chemicals & Metals Co. Ltd. 2.2. Experimental Procedure. In a typical procedure, 0.2 g of Si was pretreated in 60 mL of piranha solution (sulfuric acid/hydrogen peroxide = 3:1) at 85 °C for 1 h.27 The solution was centrifuged, washed with deionized water, and dried in an oven at 65 °C. The electrode was prepared by mixing pretreated Si (65 wt %), PAA binder (20 wt %, Sigma-Aldrich), and Super-P (15 wt %) in Nmethylpyrrolidone and casting onto a copper (Cu) foil with a Si mass loading of 0.7−1.2 mg cm−2. After drying overnight, the electrode was punched into a 1 cm × 1 cm coin-type cell and a calendaring process was conducted. Afterward, the punched electrode was dipped into a sodium hypophosphite solution (0.05 g of sodium hypophosphite in 20 mL of deionized water) for 30 s and annealed at 180 °C for 1 h under N2 flow. After annealing, sodium hypophosphite was removed by washing the electrode in deionized water and drying in vacuum overnight. 2.3. Materials Characterization. The phase of Si was examined by X-ray diffraction (XRD, D-MAX 2500-PC, Rigaku). The morphology was observed by field emission scanning electron microscopy (SEM, Hitachi SU-70). Fourier transformation infrared (FT-IR) spectroscopy was employed to characterize the chemical bonds and the spectra were recorded in ATR mode between 600 and 3600 cm−1 (Nicolet 6700, Thermo Scientific). The chemical status was determined by X-ray photoelectron spectroscopy (XPS, AXIS SUPRA, Kratos). For the investigation of the SEI layer by XPS, the cycled electrodes were dipped in dimethyl carbonate to wash out the residual electrolyte salts. 29Si nuclear magnetic resonance (NMR) spectra were conducted using a 500 MHz solid NMR system (ADVANCE 2, Bruker). The O/Si atomic ratio of the bulk powder was determined by a wavelength-dispersive X-ray fluorescence (XRF) spectrometer II (Bruker). The mechanical strength was measured by nano-indentation (TriboLab nanoindentation system, Hysitron), which was carried out under a force of 1000 μN. 15 individual indents were adopted for accuracy. A nanoscratch test was conducted with a constant load of 2000 μN, a scratch length of 100 μm, and a speed of 50 μm min−1. For the cross-sectional images, Pt was predeposited to protect the cross-sectional spots and the electrodes were dissected in focused-ion beam (FIB, AURIGA) using gallium (Ga)-ion beam. 2.4. Electrochemical Measurements. The electrochemical properties were investigated using a 2032 coin-type cell (Welcos, Korea).28 The half-cells were assembled in an argon-filled glovebox with a Si-based working electrode, Li metal as a counter electrode, and Celgard as a separator. The electrolyte was 1 M LiPF6 in ethylene carbonate/diethyl carbonate/dimethyl carbonate (1:1:1 volume ratio) with 10% fluoroethylene carbonate. The galvanostatic cycling test was

with a linear polymeric binder via an esterification reaction with a low-cost and eco-friendly process. In this work, we propose a facile method to fabricate a stable Si anode by introducing mechanically robust covalent bonding between a commercially available Si nanopowder and a linear polymeric binder through an esterification reaction and examined its electrochemical properties as an anode for LIBs. The esterification reaction can be expressed as RCOOH + R′OH → RCOOR′ + H 2O

For an efficient esterification reaction, PAA, which is composed of the carboxylic acid group (−COOH), was selected as a binder in this study because the hydroxyl group (−OH) on the surface of Si hardly reacts with the carboxylate group (−COO−)-terminated binders, such as sodium CMC (Na-CMC).20−22 Si nanopowder commonly has an −OH functional group on the surface because of a partially hydrolyzed SiO2 layer.10 However, the density of the surface hydroxyl group is not sufficient to react with the carboxylic acid group of the binder via the esterification reaction. Piranha solution was used to produce abundant −OH groups on the surface of Si nanopowder.23 In addition, the treatment in piranha solution improves the dispersion property of Si to prepare the uniform slurry of Si and PAA, which can aid the effective esterification reaction between the two materials.24 Finally, the esterification reaction is known to be a kinetically sluggish reaction,25 and thus, sodium hypophosphite, which has been used as an esterification catalyst in the cotton textile industry, was employed as a reaction catalyst. 26 In consequence, the as-fabricated Si electrode exhibited excellent high rate capability and long cycle stability, delivering a high capacity of 1500 mA h g−1 after 500 cycles at a high current density of 1000 mA g−1 by effectively restraining the susceptible sliding of the binder and maintaining the structural integrity. The proposed concept is expected to be applied to other anode materials for LIBs that undergo a massive volume change during charging/discharging.

2. EXPERIMENTAL SECTION 2.1. Material Preparation. Sodium hypophosphite was purchased from Sigma-Aldrich. Si nanopowder (APS 50 nm) was purchased from Alfa Aesar. Acetonitrile, methanol, sulfuric acid B


Research Article


Figure 1. FT-IR spectra of (a) PAA binder, (b) as-received and piranha solution-treated Si nanopowder, and (c) HB-1, PE-1, and FE-1 electrodes, which were fabricated using −OH-terminated Si nanopowder and PAA binder (mass ratio of 65:20) without a Super P conductive material.

terminated Si and −COOH-terminated PAA. Additionally, a PE electrode (PE electrode) was fabricated by annealing at 180 °C without a sodium hypophosphite catalyst, which resulted in the partial ester bonding between Si nanoparticles and PAA binder. The surface morphologies of the three electrodes observed by SEM were similar (Figure S2), indicating that the morphology and size of the Si nanopowder were not affected by annealing and/or catalyst treatment. Afterward, the cointype half cells were assembled using HB, PE, and FE electrodes as the working electrode and lithium foil as the counter electrode. FT-IR analysis was conducted to confirm the esterification reaction between −OH-terminated Si nanopowder and −COOH-terminated PAA binder (Figure 1). The PAA film exhibited a strong absorption peak at 1701.1 cm−1, which corresponds to the CO stretching band of −COOH in PAA (Figure 1a).18 Si nanoparticles commonly have an amorphous SiO2 layer on the surface, which tends to form the surface hydroxyl (Si−OH) group in aqueous solutions.29 However, the as-received Si nanopowder showed no distinct absorption peak in the range of 2400−3600 cm−1 (Figure 1b), indicating a little or no hydroxyl group on the surface. After treating in the piranha solution, a broad absorption band, centered at 3340 cm−1, appeared, which corresponds to the −OH stretching vibration of Si−OH on the Si surface (Figure 1b).23 29Si NMR spectra showed that the peak intensity around 100−120 ppm increased significantly after the piranha solution treatment, further confirming the termination of abundant −OH functional group on Si (Figure S3).30 The O/Si atomic ratio of the bulk and surface of the piranha solution-treated Si nanopowder was analyzed by XRF (Figure S4) and XPS (Figure S5), respectively. The O/Si ratio of the bulk increased slightly from 0.0277 (as-received Si) to 0.0288 (piranha

performed at room temperature using a battery testing system (WonATech, Korea) in a voltage range of 0.01−1.0 V (vs Li/Li+). The cyclic voltammetry (CV) measurement was conducted at a scan rate of 0.05 mV s−1. The galvanostatic intermittent titration technique (GITT) test was performed by applying a 200 mA g−1 current for 1 h and subsequently resting for 1 h. The electrochemical impedance spectroscopy (EIS) measurement was carried out in a frequency range of 100 kHz to 10 mHz with a 10 mV ac amplitude (ZIVE SP1, WonA Tech). The full-cell was assembled with the Si-based electrode as an anode and LiNi0.6Mn0.2Co0.2O2 (LNCM, E&D Co., Ltd.) as a cathode. The cathode was prepared by mixing LNCM (80 wt %), PVDF binder (10 wt %), and Super-P (10 wt %). Before the full-cell assembly, the anode was prelithiated for a stable SEI layer formation. The areal capacity of anode and cathode was 1.5−1.6 and ∼1.4 mA h cm−2, respectively, giving a capacity ratio of ∼1.1. The full cell was electrochemically tested in the potential range of 2.5−4.1 V at the current density of 50 mA g−1.

3. RESULTS AND DISCUSSION Scheme 1 illustrates the preparation process of three types of Si electrodes [HB (hydrogen-bonded), PE (partially esterificated), and FE (fully esterificated)] and chemical interactions between Si nanoparticles and PAA binder in these electrodes. As-received Si nanopowder, ∼50 nm in size, as confirmed by SEM and XRD (Figure S1), was pretreated in piranha solution to produce hydroxyl (−OH) groups on the surface. The electrode was prepared by compressing a mixture of −OHterminated Si nanopowder, Super P conductive material, and PAA binder onto a Cu foil. The as-prepared electrode contained the hydrogen-bonding interaction between Si nanoparticles and PAA binder (referred to as the HB electrode). The FE electrode (FE electrode) was prepared by dipping the as-prepared electrode into a sodium hypophosphite solution and annealing at 180 °C under N2 flow, which induced the covalent ester bonding between −OHC


Research Article


Figure 2. (a) Nano-indentation profiles for HB-1, PE-1, and FE-1 electrodes, (b) friction coefficient obtained by the nanoscratch test, and SEM images after the scratch test for (c,d) HB-1, (e) PE-1, and (f) FE-1 electrodes.

functional groups cannot be quantified by FT-IR, the absence of −COOH and −OH groups in the spectrum of the FE-1 electrode was assumed to be close to the full esterification reaction (Figure S7). In addition, when the piranha solutiontreated Si was replaced with hydrofluoric acid (HF)-treated Si (terminated with a proton rather than −OH),36 the CO stretching band of −COOH in PAA remained, and the −COO− peak was not observed even under 180 °C annealing with a sodium hypophosphite catalyst (Figure S8). This is due to the absence of −OH functional group on the surface of Si to react with the −COOH group of the PAA binder. Thus, the robust covalent bonding was successfully achieved between Si nanopowder and PAA binder through piranha solution treatment and the esterification reaction with a sodium hypophosphite catalyst (FE electrode). As the ester bond hardly hydrolyzes under the LIB electrolyte system,37,38 it is expected that the PAA−Si covalent bond is preserved and the electrode integrity is maintained during cycling, improving the electrochemical performance. To investigate the effects of esterification on the mechanical stability of the bulk electrode films, nano-indentation and nanoscratch tests were performed on the HB-1, PE-1, and FE-1 electrodes with a film thickness of 25 μm. Figure 2a shows the load versus indenter displacement data for the three electrodes under a force of 1000 μN. The nano-indentation force at a given indentation depth increased in the order of HB-1, PE-1, and FE-1. The higher indentation force (mechanical strength) of the FE-1 electrode indicates a stronger binding force between the binder and Si.39 In addition, the FE-1 electrode exhibited a smaller residual impression depth after the final unloading (hf), implying a smaller extent of irreversible deformation after the loading and unloading process. Thus,

solution-treated Si), whereas the surface O/Si ratio increased sharply from 0.58 (as-received Si) to 1.75 (piranha solutiontreated Si). Thus, we confirmed that a significant amount of Si−OH group was introduced to the Si nanopowder surface through the piranha solution treatment. For FT-IR measurement, three new electrodes (HB-1, PE-1, and FE-1) were prepared by mixing −OH-terminated Si nanopowder and PAA binder (mass ratio of 65:20) without a conductive agent (Figure 1c). The spectrum of HB-1 electrode showed that the CO stretching band of −COOH was slightly shifted from 1701.1 to 1699.2 cm−1, indicating the hydrogen bonding formation between Si nanopowder and PAA binder.18 In the PE-1 electrode, the intensity of the peak at 1699.2 cm−1 decreased considerably, and a new peak appeared at a higher wavenumber (1750.23 cm−1). This vibration peak is related to the CO stretching band of −COO−, indicating a new covalent bond between Si−OH of Si nanopowder and −COOH of PAA through an esterification reaction.31,32 The peak appearing at 1018.35 cm−1 can be assigned to Si−O−C and/or C−O−C vibration.33,34 However, the peak at 1750.23 cm−1 was relatively weak, and a partial cross-linking occurred between PAA and Si resulting from annealing without an esterification catalyst.25,26 On the contrary, the FE-1 electrode exhibited a sharp peak at 1750.23 cm−1 with a shoulder at 1699.2 cm−1, demonstrating the abundant covalent bond formation between Si nanopowder and PAA binder and proving that the sodium hypophosphite is an effective esterification catalyst in this system. The absence of characteristic peaks for sodium hypophosphite, such as the PH2 vibration at 806 and 2320 cm−1 (Figure S6),35 indicates that the catalyst was removed completely from the FE-1 electrode after the esterification reaction. As the concentration of D


Research Article


Figure 3. (a) CV curves of FE and HB electrodes at a scan rate of 0.05 mV s−1, (b) initial charge/discharge voltage profiles for HB, PE, and FE electrodes between 0.01 and 1 V (vs Li+/Li) at a current density of 500 mA g−1, (c) long term cycle stability of HB, PE, and FE electrodes at the current density of 500 (1 cycle)-1000 mA g−1 (subsequent cycles), (d) rate capability of FE electrode from 500 to 6000 mA g−1, (e) cycle performance of the fabricated electrode without Super-P (FE-1 electrode, mass ratio of Si/PAA binder = 65:20) at a current density of 1000 mA g−1.

five cycles, implying the presence of electrochemical activation processes in the Si anode.43 No specific peak was found in the CV curves of the FE electrode compared to those of the HB electrode (inset of Figure 3a), which indicates that the esterification reaction had a negligible effect on the electrochemical reaction of the Si anode. The first discharge/charge voltage profiles of HB, PE, and FE electrodes are shown in Figure 3b. No significant difference was found in the shape of the voltage profiles, and all the observed plateaus in the voltage profiles well corresponded to the reduction/oxidation peaks in the CV curves. The first discharge and charge capacity of the FE electrode was 3503 and 2876 mA h g−1, respectively, corresponding to a Coulombic efficiency of 82.1%. The Coulombic efficiency of HB and PE electrodes was 78.1 and 82.9%, respectively. The high initial Coulombic efficiency of the FE and PE electrodes is related to the stable SEI layer formed on the covalent ester-bonded electrodes.17,18 While the chemical bonding between Si and PAA binder did not greatly affect the voltage profile and Coulombic efficiency of the first cycle, the cycle performance of the three electrodes differed considerably as shown in Figure 3c, which was measured at a current density of 1000 mA g−1 after one cycle at 500 mA g−1 for activation (Si mass loading of 0.75 mg cm−2). In the HB electrode, a rapid capacity fading was observed, and the reversible capacity was reduced to 335 mA h g−1 after 50 cycles with an unstable Coulombic efficiency (Figure S10), indicating that the hydrogen bonding between Si and PAA binder cannot withstand the large volume change that occurs during

the FE-1 electrode is expected to maintain better structural integrity against volume changes during cycling. For adhesion properties, a nanoscratch test was performed under a constant load of 2000 μN and a scratch length of 100 μm, and the friction coefficient versus lateral displacement data for the three electrodes are shown in Figure 2b. The average friction coefficient of the FE-1 electrode was higher than that of HB-1 and PE-1 electrodes and remained constant throughout the entire scratch process, demonstrating the higher and more stable adhesion force between Si and PAA binder.40,41 Furthermore, the SEM images of the electrodes after the nanoscratch test revealed that the HB-1 electrode had numerous cracks on its scratch track, whereas PE-1 and FE-1 electrodes displayed a smooth track with limited cracks. In high-magnification images (Figure S9), the PE-1 electrode had more small cracks on its scratch track, exhibiting lower mechanical stability than the FE-1 electrode. As the scratch test simulates the stress induced by volume change,41 the obtained results imply that the FE-1 electrode with robust covalent ester bonding has higher mechanical stability to restrain the sliding of the binder during cycling, which is consistent with the nanoindentation results. The electrochemical properties of the FE electrode was determined by CV over the voltage of 0.01−1.0 V (vs Li/Li+) at 0.05 mV s−1 (Figure 3a). The specific capacity values were estimated based on the mass of Si. The first five CV curves of the FE electrode showed the typical cathodic and anodic peaks of the Si anode.42 The peak intensity increased over the first E


Research Article


Figure 4. Cycle performance of (a) electrodes fabricated using piranha solution-treated, as-received, and HF-treated Si with PAA binder. All three electrodes were treated with heat and catalyst and (b) electrodes fabricated using piranha solution-treated Si with Na-CMC binder tested at the current density of 1000 mA g−1.

cycling.17,44 Compared to the HB electrode, both PE and FE electrodes with covalent ester bonding exhibited much improved cycle performance. The PE electrode initially had a cycle stability comparable to that of the FE electrode; however, the capacity decreased rapidly after 350 cycles and only 448 mA h g−1 was retained after 500 cycles. The FE electrode exhibited a stable cycle performance up to 500 cycles, and thus, the discharge capacity of 1560 mA h g−1 with a Coulombic efficiency of 99.9% was maintained. Thus, the full esterification reaction using a sodium hypophosphite catalyst was very effective for improving the cycle stability of the Si anode. The cycle performance of the FE electrode was comparable to that of previously reported best binders for the Si anode.45 The reproducible cycle performance of the FE electrode was confirmed by fabricating seven additional cells and testing them under the same cycling conditions, which exhibited an identical cycling behavior (Figure S11). Some of the electrodes were fabricated without washing the sodium hypophosphite after the esterification reaction, which resulted in no different cycle performance. This indicates that sodium hypophosphite acts as an esterification catalyst, but not as a special electrolyte additive. In addition, a high areal capacity is a crucial requirement for high-performance practical batteries, but the increase in mass loading for high areal capacity commonly induces a significant capacity decay because of the electrodelevel disintegration and increased series resistance of the particle−electrolyte interface.46 For high areal capacity, the Si mass loading in the FE electrode increased from 0.75 to 1.12 mg cm−2, and the cyclability was evaluated at the current density of 500 mA g−1 (0.535 mA cm−2). The FE electrode exhibited a stable areal capacity of 2 mA h cm−2 after 150 cycles at a relatively high Si mass loading of 1.12 mg cm−2 (Figure S12), which was comparable to the best reported values for Si-based anodes.47 The rate capability of the FE electrode was evaluated by varying the current density from 500 to 6000 mA g−1 (Figure 3d). The reversible capacity in the 10th cycle of each current density was 2,750, 2,333, 2,046, 1,845, 1,574, and 1550 mA h g−1, respectively. Thus, the FE electrode delivered a high capacity of 1550 mA h g−1 at a high current density of 6000 mA g−1. Note that the high value obtained in this work was achieved even without a conducting phase coating on Si, while most of the previous studies had required it.48−50 When the current density returned to 1000 mA g−1, the reversible capacity fully recovered to its original capacity, demonstrating an excellent high rate capability. Furthermore, the shape of the voltage profiles did not change when the current density increased from 1000 to 6000 mA g−1, indicating the good electrode kinetics of the FE electrode (Figure S13). To demonstrate the high electrode kinetics of

the FE electrode, the electrochemical properties of the FE-1 electrode without any conductive agent were further examined (Figure 3e). Surprisingly, the FE-1 electrode showed excellent cycle performance, delivering a high capacity of 2000 mA h g−1 after 200 cycles at a high current density of 1000 mA g−1 with a Si mass loading of 0.69 mg cm−2. On the contrary, the HB-1 electrode did not operate at a high current density of 500 or 1000 mA g−1, but only operated at a low current density of 200 mA g−1 (Figure S14). This observation implies that the covalent bond between Si and PAA contributes to the improved electrode kinetics. The enhanced kinetics in covalent-bonded Si−PAA appears to be associated with the intramolecular charge transfer between Si and PAA, but further studies are required.27,51−54 The superior electrochemical performance of the FE electrode has been attributed to the formation of covalent bond by inducing an esterification reaction between −OHterminated Si nanopowder and −COOH-terminated PAA binder. Two other control electrodes were designed to confirm this fact (Figure 4). The first type had a different amount of −OH functional groups, achieved using HF-treated, asreceived, and piranha solution-treated Si with PAA binder. The electrodes with HF-treated and as-received Si nanopowder displayed the rapid capacity fading, and the cycle stability increased with increasing the amount of −OH groups available to react with the −COOH group of PAA binder (Figure 4a). The second type corresponded to the electrodes using piranha solution-treated Si with a Na-CMC binder, which has a carboxylate (−COO−) functional group rather than −COOH. The FT-IR spectrum of the Na-CMC binder showed a characteristic peak at 1589 cm−1 for the CO stretching band of −COO− with no peak at 1701.1 cm−1, which corresponds to the CO stretching band of −COOH (Figure S15a).55 The punched electrode annealed at 180 °C with the addition of the sodium hypophosphite catalyst still showed the CO stretching band of the −COO− peak, while only a small peak arose at 1750.23 cm−1 from the CO stretching band of −COO− (Figure S15b), indicating that only part of −COO− had undergone the esterification reaction with the −OH of Si. The cycle performance of the second electrode type was not comparable to that of FE electrode (Figure 4b), and only 51% of the capacity was retained after 50 cycles, which indicates that the −COO−-terminated binders such as Na-CMC, sodium alginate (Na-Alg), and sodium acrylic acid (NaPAA) cannot be properly covalently bonded to −OH of Si via an esterification reaction. Thus, the formation of covalent bond between −OH-terminated Si nanopowder and −COOHterminated PAA binder by inducing an esterification reaction F


Research Article


Figure 5. Internal resistance calculated from GITT measurements during (a) lithiation and (b) delithiation. EIS data (c) before cycle and (d) after 20 cycles in HB and FE electrodes, and (e) calculated resistances for after-cycled electrodes.

slightly smaller resistance than the HB electrode (Figure 5c). After 20 cycles at the current density of 1000 mA g−1, the HB electrode showed a larger semicircle at high frequency, a larger semicircle at middle frequency, and a gentle slope line at low frequency compared to the FE electrode, which are related to unstable SEI formation, high charge transfer resistance resulting from Si delamination from the current collector, and lower lithium diffusion rate induced by Si aggregation, respectively (Figure 5d). Compared to the HB electrode, the FE electrode showed excellent cyclability and high rate performance, because of stable SEI layer formation and its ability to maintain structural integrity during repeated cycling. This was further confirmed by observing the morphology of the electrodes after cycles. The optical micrographs showed that most of the electrode had disintegrated from the current collector in the HB electrode after 20 cycles at a current density of 1000 mA g−1, which indicates the loss of electrical contact between Si and current collector (Figure S18a). Furthermore, the crosssectional SEM images showed that in the pristine state, the electrode had a thickness of 12.9 μm (Figure S18b), whereas the thickness of HB and FE electrodes were 24.2 and 18.8 μm, respectively (Figure 6a,b). The large thickness variation of the HB electrode compared to the FE electrode is due to continuous SEI formation and Si aggregation.44 The surface morphology of the cycled HB electrode revealed the multiple cracks with a non-uniform SEI layer on the surface (Figure 6c). In contrast, the smooth surface without severe crack or fracture was found on the FE electrode, indicating stable SEI formation (Figure 6d). Energy-dispersive X-ray spectroscopy (EDS) element mapping showed that the content of O and F on the surface of the HB electrode was higher than that of the FE electrode (Figure S19) revealing the thicker SEI layer formation in the HB electrode, resulting from the severe cracks and continuous exposure of the fresh surface to the electrolyte.60 The XPS analysis was further conducted to

was a crucial factor for obtaining a high-performance Si anode for LIBs. To ascertain the reasons for the superior cycle stability of the FE electrode, the internal resistance was measured by a GITT measurement and compared with that of the HB electrode. In GITT measurements, the current pulse of 200 mA g−1 was applied for 1 h and subsequently rested for 1 h to obtain the closed-circuit voltage (CCV) and quasi-open-circuit voltage (QOCV), respectively (Figure S16). The internal resistance was determined by dividing the voltage difference between CCV and QOCV by the pulse current (Figure 5a,b).56 During lithiation, the internal resistance of the HB and FE electrodes was nearly the same and gradually decreased because of the enhancement of Si electronic conductivity by Li−Si alloying and/or increased contact area between Si and Super-P by volume expansion (Figure 5a).56,57 However, the internal resistances of the two electrodes were significantly different during the delithiation process, and the HB electrode showed more than 2-fold higher internal resistance than the FE electrode at 0.7 V (Figure 5b). The noticeable increase in the internal resistance of the HB electrode is attributable to the sliding of PAA binder from Si powder, which would eventually lead to severe issues such as SEI breakdown or Si aggregation. In the FE electrode, the internal resistances of first and second cycles were similar and lower than that of the HB electrode, which indicates that the covalent bonding between Si and PAA effectively restrains binder sliding and is maintained during cycles. The presence of ester bonding in the cycled FE electrode was checked by FT-IR, but −COO− peak could not be identified due to the SEI layer (Figure S17).58 The GITT results were further supported by EIS. The impedance spectra (Nyquist plots) consisted of the semicircles at high and middle frequencies relating to the SEI and charge transfer resistances, respectively, and the straight sloping line at low frequency corresponding to lithium diffusion in electrode bulk.59 In the pristine state (before cycling), the FE electrode showed a G


Research Article


pulverization was very limited in the FE electrode.64 The morphology observation demonstrates that the covalent bond between Si and PAA through an esterification reaction can provide a strong tolerance to restrain the sliding of a linear binder, which can in turn aid in forming the stable SEI layer, reducing the agglomeration of Si, and suppressing the electrode delamination from the current collector, resulting in superior cycle performance and high rate capability as an anode for LIBs. We have demonstrated the superior effects of an intramolecular covalent bond between the binder and the active material on the electrochemical performance as an anode for LIBs, and the proposed mechanism is schematically illustrated in Scheme 2. As the PAA linear binder slides upon the volume change of Si during the delithiation process (Scheme 2a), the contact loss between binder, conductive agent, and Si increases the internal resistance of the electrode.65 At the same time, Si aggregates with the adjacent Si. Because the aggregated Si experiences more stress during cycling, the accumulated stress results in breakdown of the SEI layer and electrode delamination.66 However, by inducing the mechanically robust covalent bond between binder and Si via an esterification reaction, the sliding of the binder can be effectively restrained during cycling. The electrical contact could be preserved while the binder between the adjacent Si can inhibit the aggregation of Si, which eventually results in superior cycle performance by stabilizing the SEI layer and preventing the electrode delamination (Scheme 2b). To evaluate the feasibility for practical use, a full-cell was assembled with the FE electrode as a negative (N) and commercially available LNCM electrode as a positive (P). To compensate the lithium loss during the first cycle, the FE electrode was precycled using Li metal as a counter electrode before the full-cell assembly. Figure 7a shows the charge/ discharge voltage profiles of FE/LNCM between 2.5 and 4.1 V. The first charge and discharge capacities are 207 and 170 mA h g−1, respectively, with a Coulmbic efficiency of 82.1% (specific capacity values were estimated based on the LNCM cathode weight). However, the Coulmbic efficiency steadily increased to 99.5%, delivering more than 106 mA h g−1 after 50 cycles (Figure 7b). Thus, stable cycling was achieved with the FE electrode in the full-cell configuration; however, further improvements are expected by optimizing the FE/LNCM full-cell with a proper separator, electrolyte, and N/P ratio.

Figure 6. (a,b) FIB cross-sectional SEM images of HB and FE electrodes after 20 cycles. SEM images of the SEI layers for (c) HB and (d) FE electrodes after 20 cycles, and SEM images of SEI rinsed (e) HB and (f) FE electrodes after 20 cycles.

confirm the thick and unstable SEI layer formation in the HB electrode (Figure S20). In the XPS spectra, the C 1s peak at 290 eV corresponding to lithium carbonates and diverse semiorganic lithium carbonates (Li2CO3 or ROCO2Li)61 and the F 1s peak at 687 eV corresponding to LixPOyFz62,63 were relatively strong in the cycled HB electrode, implying unstable SEI formation.44 To observe the structural stability in the cycled electrodes, the dissembled electrodes were rinsed with acetonitrile to remove the SEI layer and observed by SEM. In the HB electrode, a massive agglomeration occurred and micrometer-sized aggregated particles were found (Figure 6e). On the other hand, in the FE electrode, the spherical nanopowder morphology was well maintained and no severe agglomeration was observed (Figure 6f). The size of the Si nanopowder used in this study was ∼50 nm, and thus, the

Scheme 2. Schematic Illustration for (a) HB and (b) FE Electrodes during Lithiation and Delithiation with a red dot Representing the Covalent bond

H


Research Article


Figure 7. (a) Voltage profile and (b) cycle performance of FE/LNCM full-cell between 2.5 and 4.1 V at a current density of 50 mA g−1.

■

4. CONCLUSIONS In this work, we have successfully introduced the mechanically robust covalent bond between Si nanopowder and PAA binder through piranha solution treatment and the esterification reaction with the sodium hypophosphite catalyst. Nanoindentation and nanoscratch tests indicated that the Si electrode with a covalent ester bond had a sufficiently high mechanical stability to endure the massive volume change by restraining the binder from sliding during cycling. The asfabricated Si electrode exhibited long cycle stability and excellent high rate capability, delivering a capacity of 1500 mA h g−1 after 500 cycles at a current density of 1000 mA g−1. The Si electrode showed reproducible cycle performance and delivered a high capacity under high mass loading or without a conductive agent. Consequently, robust ester bonding effectively restrained the susceptible sliding of the binder, stabilized the SEI layer, prevented electrode delamination, and suppressed Si aggregation. The methodology developed in this work is expected to be utilized in other anode materials for LIBs and SIBs that undergo a massive volume change during charging/discharging.

■

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsami.9b03866. SEM images of the as-received Si, HB, PE, and FE electrodes; NMR, XRF, and XPS analyses of as-received Si and piranha solution-treated Si; FT-IR of sodium hypophosphite and electrodes; areal capacity, galvanostatic voltage graph, and reproducibility test of FE electrode; galvanostatic voltage graph of HB-1 electrode; optical micrograph and cross-section image of electrode; EDS and XPS analyses of SEI layer; and cycle data of LNCM cathode (PDF)

■

REFERENCES

(1) Li, J.-Y.; Xu, Q.; Li, G.; Yin, Y.-X.; Wan, L.-J.; Guo, Y.-G. Research Progress Regarding Si-Based Anode Materials Towards Practical Application in High Energy Density Li-Ion Batteries. Mater. Chem. Front. 2017, 1, 1691−1708. (2) Feng, K.; Li, M.; Liu, W.; Kashkooli, A. G.; Xiao, X.; Cai, M.; Chen, Z. Silicon-Based Anodes for Lithium-Ion Batteries: From Fundamentals to Practical Applications. Small 2018, 14, 1702737. (3) Rahman, M. A.; Song, G.; Bhatt, A. I.; Wong, Y. C.; Wen, C. Nanostructured Silicon Anodes for High-Performance Lithium-Ion Batteries. Adv. Funct. Mater. 2016, 26, 647−678. (4) Ji, J.; Ji, H.; Zhang, L. L.; Zhao, X.; Bai, X.; Fan, X.; Zhang, F.; Ruoff, R. S. Graphene-Encapsulated Si on Ultrathin-Graphite Foam as Anode for High Capacity Lithium-Ion Batteries. Adv. Mater. 2013, 25, 4673−4677. (5) Wu, H.; Cui, Y. Designing Nanostructured Si Anodes for High Energy Lithium Ion Batteries. Nano Today 2012, 7, 414−429. (6) Zuo, X.; Zhu, J.; Müller-Buschbaum, P.; Cheng, Y.-J. Silicon Based Lithium-Ion Battery Anodes: A Chronicle Perspective Review. Nano Energy 2017, 31, 113−143. (7) Chae, S.; Ko, M.; Kim, K.; Ahn, K.; Cho, J. Confronting Issues of the Practical Implementation of Si Anode in High-Energy LithiumIon Batteries. Joule 2018, 1, 47−60. (8) Choi, N.-S.; Ha, S.-Y.; Lee, Y.; Jang, J. Y.; Jeong, M.-H.; Shin, W. C.; Ue, M. Recent Progress on Polymeric Binders for Silicon Anodes in Lithium-Ion Batteries. J. Electrochem. Sci. Technol. 2015, 6, 35−49. (9) Kwon, T.-W.; Choi, J. W.; Coskun, A. The Emerging Era of Supramolecular Polymeric Binders in Silicon Anodes. Chem. Soc. Rev. 2018, 47, 2145−2164. (10) Kwon, T.-W.; Jeong, Y. K.; Lee, I.; Kim, T.-S.; Choi, J. W.; Coskun, A. Systematic Molecular-Level Design of Binders Incorporating Meldrum’s Acid for Silicon Anodes in Lithium Rechargeable Batteries. Adv. Mater. 2014, 26, 7979−7985. (11) Lim, S.; Chu, H.; Lee, K.; Yim, T.; Kim, Y.-J.; Mun, J.; Kim, T.H. Physically Cross-linked Polymer Binder Induced by Reversible Acid−Base Interaction for High-Performance Silicon Composite Anodes. ACS Appl. Mater. Interfaces 2015, 7, 23545−23553. (12) Kang, S.; Yang, K.; White, S. R.; Sottos, N. R. Silicon Composite Electrodes with Dynamic Ionic Bonding. Adv. Energy Mater. 2017, 7, 1700045. (13) Guo, S.; Li, H.; Li, Y.; Han, Y.; Chen, K.; Xu, G.; Zhu, Y.; Hu, X. SiO2-Enhanced Structural Stability and Strong Adhesion with a New Binder of Konjac Glucomannan Enables Stable Cycling of Silicon Anodes for Lithium-Ion Batteries. Adv. Energy Mater. 2018, 8, 1800434. (14) Jeong, Y. K.; Kwon, T.-W.; Lee, I.; Kim, T.-S.; Coskun, A.; Choi, J. W. Millipede-Inspired Structural Design Principle for High Performance Polysaccharide Binders in Silicon Anodes. Energy Environ. Sci. 2015, 8, 1224−1230. (15) Higgins, T. M.; Park, S.-H.; King, P. J.; Zhang, C.; McEvoy, N.; Berner, N. C.; Daly, D.; Shmeliov, A.; Khan, U.; Duesberg, G.; Nicolosi, V.; Coleman, J. N. A Commercial Conducting Polymer as both Binder and Conductive Additive for Silicon Nanoparticle-Based Lithium-Ion Battery Negative Electrodes. ACS Nano 2016, 10, 3702− 3713. (16) Song, J.; Zhou, M.; Yi, R.; Xu, T.; Gordin, M. L.; Tang, D.; Yu, Z.; Regula, M.; Wang, D. Interpenetrated Gel Polymer Binder for

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Seong-Hyeon Hong: 0000-0001-8350-2724 Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (no. 2017R1A2B4009757). I


Research Article

ACS Applied Materials & Interfaces High-Performance Silicon Anodes in Lithium-Ion Batteries. Adv. Funct. Mater. 2014, 24, 5904−5910. (17) Koo, B.; Kim, H.; Cho, Y.; Lee, K. T.; Choi, N.-S.; Cho, J. A Highly Cross-Linked Polymeric Binder for High-Performance Silicon Negative Electrodes in Lithium Ion Batteries. Angew. Chem. 2012, 51, 8762−8767. (18) Chen, C.; Lee, S. H.; Cho, M.; Kim, J.; Lee, Y. Cross-Linked Chitosan as an Efficient Binder for Si Anode of Li-Ion Batteries. ACS Appl. Mater. Interfaces 2016, 8, 2658−2665. (19) Zhao, X.; Yim, C.-H.; Du, N.; Abu-Lebdeh, Y. Crosslinked Chitosan Networks as Binders for Silicon/Graphite Composite Electrodes in Li-Ion Batteries. J. Electrochem. Soc. 2018, 165, A1110−A1121. (20) Profatilova, I. A.; Langer, T.; Badillo, J. P.; Schmitz, A.; Orthner, H.; Wiggers, H.; Passerini, S.; Winter, M. Thermally Induced Reactions between Lithiated Nano-Silicon Electrode and Electrolyte for Lithium-Ion Batteries. J. Electrochem. Soc. 2012, 159, A657−A663. (21) Mazouzi, D.; Lestriez, B.; Roué, L.; Guyomard, D. Silicon Composite Electrode with High Capacity and Long Cycle Life. Electrochem. Solid-State Lett. 2009, 12, A215−A218. (22) Hebeish, A.; Higazy, A.; El-Shafei, A.; Sharaf, S. Synthesis of Carboxymethyl Cellulose (CMC) and Starch-Based Hybrids and their Applications in Flocculation and Sizing. Carbohydr. Polym. 2010, 79, 60−69. (23) Li, C.; Shi, T.; Li, D.; Yoshitake, H.; Wang, H. Effect of Surface Modification on Electrochemical Performance of Nano-Sized Si as an Anode Material for Li-Ion Batteries. RSC Adv. 2016, 6, 34715−34723. (24) Yoo, S.; Lee, J.-I.; Ko, S.; Park, S. Highly Dispersive and Electrically Conductive Silver-Coated Si Anodes Synthesized via a Simple Chemical Reduction Process. Nano Energy 2013, 2, 1271− 1278. (25) Yang, C. Q. FTIR Spectroscopy Study of Ester Crosslinking of Cotton Cellulose Catalyzed by Sodium Hypophosphite. Text. Res. J. 2001, 71, 201−206. (26) Yang, C. Q.; Chen, D.; Guan, J.; He, Q. Cross-linking Cotton Cellulose by the Combination of Maleic Acid and Sodium Hypophosphite. 1. Fabric Wrinkle Resistance. Ind. Eng. Chem. Res. 2010, 49, 8325−8332. (27) Jung, C.-H.; Kim, K.-H.; Hong, S.-H. An in situ Formed Graphene Oxide−Polyacrylic Acid Composite Cage on Silicon Microparticles for Lithium Ion Batteries via an Esterification Reaction. J. Mater. Chem. A 2019, 7, 12763−12772. (28) Jung, C.-H.; Choi, J.; Kim, W.-S.; Hong, S.-H. A NanoporeEmbedded Graphitic Carbon Shell on Silicon Anode for High Performance Lithium Ion Batteries. J. Mater. Chem. A 2018, 6, 8013− 8020. (29) Bie, Y.; Yang, J.; Liu, X.; Wang, J.; Nuli, Y.; Lu, W. Polydopamine Wrapping Silicon Cross-Linked with Polyacrylic Acid as High-Performance Anode for Lithium-Ion Batteries. ACS Appl. Mater. Interfaces 2016, 8, 2899−2904. (30) Chuang, I. S.; Chuang, G. E. Probing Hydrogen Bonding and the Local Environment of Silanols on Silica Surfaces Via Nuclear Spin Cross Polarization Dynamics. J. Am. Chem. Soc. 1996, 118, 401−406. (31) Biesta, W.; van Lagen, B.; Gevaert, V. S.; Marcelis, A. T. M.; Paulusse, J. M. J.; Nielen, M. W. F.; Zuilhof, H. Preparation, Characterization, and Surface Modification of Trifluoroethyl EsterTerminated Silicon Nanoparticles. Chem. Mater. 2012, 24, 4311− 4318. (32) Moini, N.; Kabiri, K.; Zohuriaan-Mehr, M. J.; Omidian, H.; Esmaeili, N. Fine Tuning of SAP Properties Via Epoxy-Silane Surface Modification. Polym. Adv. Technol. 2017, 28, 1132−1147. (33) Kaspar, J.; Terzioglu, C.; Ionescu, E.; Graczyk-Zajac, M.; Hapis, S.; Kleebe, H.-J.; Riedel, R. Stable SiOC/Sn Nanocomposite Anodes for Lithium-Ion Batteries with Outstanding Cycling Stability. Adv. Funct. Mater. 2014, 24, 4097−4104. (34) Cheng, Q.; Wu, M.; Li, M.; Jiang, L.; Tang, Z. Ultratough Artificial Nacre Based on Conjugated Cross-linked Graphene Oxide. Angew. Chem. 2013, 125, 3838−3843.

(35) Wu, W.; Lv, S.; Liu, X.; Qu, H.; Zhang, H.; Xu, J. Using TGFTIR and TG-MS to Study Thermal Degradation of Metal Hypophosphites. J. Therm. Anal. Calorim. 2014, 118, 1569−1575. (36) Li, X.; He, Y.; Swihart, M. T. Surface Functionalization of Silicon Nanoparticles Produced by Laser-Driven Pyrolysis of Silane followed by HF−HNO3 Etching. Langmuir 2004, 20, 4720−4727. (37) Lee, J. S.; Quan, N. D.; Hwang, J. M.; Bae, J. Y.; Kim, H.; Cho, B. W.; Kim, H. S.; Lee, H. Ionic Liquids Containing an Ester Group as Potential Electrolytes. Electrochem. Commun. 2006, 8, 460−464. (38) Takeuchi, E. S.; Gan, H.; Palazzo, M.; Leising, R. A.; Davis, S. M. Anode Passivation and Electrolyte Solvent Disproportionation: Mechanism of Ester Exchange Reaction in Lithium-Ion Batteries. J. Electrochem. Soc. 1997, 144, 1944−1948. (39) Bie, Y.; Yang, J.; Nuli, Y.; Wang, J. Natural Karaya Gum as an Excellent Binder for Silicon-Based Anodes in High-Performance Lithium-Ion Batteries. J. Mater. Chem. A 2017, 5, 1919−1924. (40) Li, G.; Ling, M.; Ye, Y.; Li, Z.; Guo, J.; Yao, Y.; Zhu, J.; Lin, Z.; Zhang, S. Acacia Senegal-Inspired Bifunctional Binder for Longevity of Lithium-Sulfur Batteries. Adv. Energy Mater. 2015, 5, 1500878. (41) Ling, M.; Xu, Y.; Zhao, H.; Gu, X.; Qiu, J.; Li, S.; Wu, M.; Song, X.; Yan, C.; Liu, G.; Zhang, S. Dual-Functional Gum Arabic Binder for Silicon Anodes in Lithium Ion Batteries. Nano Energy 2015, 12, 176−185. (42) Kim, J. M.; Guccini, V.; Kim, D.; Oh, J.; Park, S.; Jeon, Y.; Hwang, T.; Salazar-Alvarez, G.; Piao, Y. A Novel Textile-like Carbon Wrapping for High-performance Silicon Anodes in Lithium-Ion Batteries. J. Mater. Chem. A 2018, 6, 12475−12483. (43) Shin, H.-C.; Corno, J. A.; Gole, J. L.; Liu, M. Porous Silicon Negative Electrodes for Rechargeable Lithium Batteries. J. Power Sources 2005, 139, 314−320. (44) Choi, S.; Kwon, T.-W.; Coskun, A.; Choi, J. W. Highly Elastic Binders Integrating Polyrotaxanes for Silicon Microparticle Anodes in Lithium Ion Batteries. Science 2017, 357, 279−283. (45) Huang, S.; Ren, J.; Liu, R.; Yue, M.; Huang, Y.; Yuan, G. The Progress of Novel Binder as a Non-ignorable Part to Improve the Performance of Si-based Anodes for Li-Ion Batteries. Int. J. Energy Res. 2018, 42, 919−935. (46) Chen, Z.; Wang, C.; Lopez, J.; Lu, Z.; Cui, Y.; Bao, Z. HighAreal-Capacity Silicon Electrodes with Low-Cost Silicon Particles Based on Spatial Control of Self-Healing Binder. Adv. Energy Mater. 2015, 5, 1401826. (47) Jin, Y.; Zhu, B.; Lu, Z.; Liu, N.; Zhu, J. Challenges and Recent Progress in the Development of Si Anodes for Lithium-Ion Battery. Adv. Energy Mater. 2017, 7, 1700715. (48) Wang, X.; Li, G.; Seo, M. H.; Lui, G.; Hassan, F. M.; Feng, K.; Xiao, X.; Chen, Z. Carbon-Coated Silicon Nanowires on Carbon Fabric as Self-Supported Electrodes for Flexible Lithium-Ion Batteries. ACS Appl. Mater. Interfaces 2017, 9, 9551−9558. (49) Luo, W.; Wang, Y.; Wang, L.; Jiang, W.; Chou, S.-L.; Dou, S. X.; Liu, H. K.; Yang, J. Silicon/Mesoporous Carbon/Crystalline TiO2 Nanoparticles for Highly Stable Lithium Storage. ACS Nano 2016, 10, 10524−10532. (50) Yang, J.; Wang, Y.-X.; Chou, S.-L.; Zhang, R.; Xu, Y.; Fan, J.; Zhang, W.-X.; Kun Liu, H.; Zhao, D.; Xue Dou, S. Yolk-Shell SiliconMesoporous Carbon Anode with Compact Solid Electrolyte Interphase Film for Superior Lithium-Ion Batteries. Nano Energy 2015, 18, 133−142. (51) Zhuang, X.-D.; Chen, Y.; Liu, G.; Li, P.-P.; Zhu, C.-X.; Kang, E.-T.; Noeh, K.-G.; Zhang, B.; Zhu, J.-H.; Li, Y.-X. ConjugatedPolymer-Functionalized Graphene Oxide: Synthesis and Nonvolatile Rewritable Memory Effect. Adv. Mater. 2010, 22, 1731−1735. (52) Ling, Q.-D.; Liaw, D.-J.; Zhu, C.; Chan, D. S.-H.; Kang, E.-T.; Neoh, K.-G. Polymer Electronic Memories: Materials, Devices and Mechanisms. Prog. Polym. Sci. 2008, 33, 917−978. (53) Xu, Y.; Liu, Z.; Zhang, X.; Wang, Y.; Tian, J.; Huang, Y.; Ma, Y.; Zhang, X.; Chen, Y. A Graphene Hybrid Material Covalently Functionalized with Porphyrin: Synthesis and Optical Limiting Property. Adv. Mater. 2009, 21, 1275−1279. J


Research Article

ACS Applied Materials & Interfaces (54) Liu, J.; Xue, Y.; Zhang, M.; Dai, L. Graphene-based Materials for Energy Applications. MRS Bull. 2012, 37, 1265−1272. (55) Jeschull, F.; Scott, F.; Trabesinger, S. Interactions of Silicon Nanoparticles with Carboxymethyl Cellulose and Carboxylic Acids in Negative Electrodes of Lithium-Ion Batteries. J. Power Sources 2019, 431, 63−74. (56) Lee, J.-I.; Ko, Y.; Shin, M.; Song, H.-K.; Choi, N.-S.; Kim, M. G.; Park, S. High-Performance Silicon-Based Multicomponent Battery Anodes Produced Via Synergistic Coupling of Multifunctional Coating Layers. Energy Environ. Sci. 2015, 8, 2075−2084. (57) Ryu, J. H.; Kim, J. W.; Sung, Y.-E.; Oh, S. M. Failure Modes of Silicon Powder Negative Electrode in Lithium Secondary Batteries. Electrochem. Solid-State Lett. 2004, 7, A306−A309. (58) Nguyen, C. C.; Lucht, B. L. Comparative Study of Fluoroethylene Carbonate and Vinylene Carbonate for Silicon Anodes in Lithium Ion Batteries. J. Electrochem. Soc. 2014, 161, A1933−A1938. (59) Chen, Y.; Hu, Y.; Shen, Z.; Chen, R.; He, X.; Zhang, X.; Li, Y.; Wu, K. Hollow Core−Shell Structured Silicon@Carbon Nanoparticles Embed in Carbon Nanofibers as Binder-Free Anodes for Lithium-Ion Batteries. J. Power Sources 2017, 342, 467−475. (60) Luo, F.; Chu, G.; Xia, X.; Liu, B.; Zheng, J.; Li, J.; Li, H.; Gu, C.; Chen, L. Thick Solid Electrolyte Interphases Grown on Silicon Nanocone Anodes During Slow Cycling and their Negative Effects on the Performance of Li-Ion Batteries. Nanoscale 2015, 7, 7651−7658. (61) Jaumann, T.; Balach, J.; Klose, M.; Oswald, S.; Langklotz, U.; Michaelis, A.; Eckert, J.; Giebeler, L. SEI-Component Formation on Sub 5 nm Sized Silicon Nanoparticles in Li-Ion Batteries: the Role of Electrode Preparation, FEC Addition and Binders. Phys. Chem. Chem. Phys. 2015, 17, 24956−24967. (62) Etacheri, V.; Haik, O.; Goffer, Y.; Roberts, G. A.; Stefan, I. C.; Fasching, R.; Aurbach, D. Effect of Fluoroethylene Carbonate (FEC) on the Performance and Surface Chemistry of Si-Nanowire Li-Ion Battery Anodes. Langmuir 2012, 28, 965−976. (63) Schroder, K.; Alvarado, J.; Yersak, T. A.; Li, J.; Dudney, N.; Webb, L. J.; Meng, Y. S.; Stevenson, K. J. The effect of Fluoroethylene carbonate as an Additive on the Solid Electrolyte Interphase on Silicon Lithium-Ion Electrodes. Chem. Mater. 2015, 27, 5531−5542. (64) Liu, X. H.; Zhong, L.; Huang, S.; Mao, S. X.; Zhu, T.; Huang, J. Y. Size-dependent Fracture of Silicon Nanoparticles during Lithiation. ACS Nano 2012, 6, 1522−1531. (65) Müller, S.; Pietsch, P.; Brandt, B.-E.; Baade, P.; Andrade, V. D.; Carlo, F. D.; Wood, V. Quantification and Modeling of Mechanical Degradation in Lithium-Ion Batteries Based on Nanoscale Imaging. Nat. Commun. 2018, 9, 2340. (66) Zhao, C.; Wada, T.; De Andrade, V.; Gürsoy, D.; Kato, H.; Chen-Wiegart, Y.-C. K. Imaging of 3D Morphological Evolution of Nanoporous Silicon Anode in Lithium Ion Battery by X-ray NanoTomography. Nano Energy 2018, 52, 381−390.

K


Stable Silicon Anode for Lithium Ion Battery through Covalent Bond

Recommend Documents