Article Cite This: ACS Appl. Energy Mater. 2019, 2, 5066−5073
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Nature Plant Polyphenol Coating Silicon Submicroparticle Conjugated with Polyacrylic Acid for Achieving a High-Performance Anode of Lithium-Ion Battery Meng Tian‡ and Peiyi Wu*,†,‡
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†
State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Chemistry, Chemical Engineering and Biotechnology, Center for Advanced Low-Dimension Materials, Donghua University, Shanghai 201620, China ‡ State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Laboratory for Advanced Materials, Fudan University, Shanghai 200433, China S Supporting Information *
ABSTRACT: Silicon as an anode material of a Li-ion battery has attracted many researchers widespread attention for proper lithium intercalation potential and superhigh theoretical capacity. However, a Si-based anode possesses so poor a cycle life that it cannot be commercialized on account of the drastic volume expansion of silicon particles in the process of charge/discharge. Herein, we present a simple, green, and inexpensive way to improve cycle life of silicon-based electrodes by modifying active materials (more cheap and fragile Si submicroparticles (SiSMPs) than silicon nanoparticles) using tannic acid (TA) (a biocompatible nature plant polyphenol) and then interacting it with poly(acrylic acid) (PAA) binder. The tannic acid conformal coating can protect SiSMPs from side reactions with the electrolyte and can conjugate with the PAA binder and conductive materials, which keeps the electrode structure integrity during cycling. Furthermore, the TA coating makes the PAA binder form a 3D cross-linked network, which can enhance the binding strength compared with linear PAA chains, and the wet adhesion of the TA mussel-inspired coating can ensure good adhesion between SiSMPs and other components in electrolytes. Therefore, the combination between moderate amounts of TA coating and PAA can improve cycle performance and rate performance of low-cost submicrosized Si particle-based Li-ion battery anodes. KEYWORDS: Nature plant polyphenol, Submicrosized silicon particle, Modification of silicon, High-performance Si-based anode, Li-ion batteries
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INTRODUCTION Li-ion batteries (LIBs), extensively used in consumer electronics, electric vehicles, and power storage systems, have been a hot research area around the world.1 And LIBs have been one of the most important approaches to deal with the mounting global energy crisis and environmental issue at present.2 For now, however, commercialized LIBs with the relatively low energy densities and cycle life can hardly meet the increasing demand of practice in the field of electric vehicle and advanced electric devices.3 In the aspect of anode materials of LIBs, compared with a commercial graphite anode, Si possesses the higher theory capacity (∼4000 mAh g−1) and more appropriate intercalation potential, which makes it the most promising anode material of LIBs.4,5 Nevertheless, Si undergoes a drastic volume change during the charging/ discharging process, further causing silicon particle pulverization, electrode structure destruction, and unstable solid electrolyte interphase (SEI), which can issue in a dramatic capacity attenuation and eventually limit further development and commercialization of the Si-based anode.6 In order to deal with the above-mentioned volume expansion issue of the Si-based anode, researchers put forward © 2019 American Chemical Society
a large number of tactics including preparing nanostructure silicon (nanowires, nanotubes, and nanospheres),7−10 constructing varieties of wrapping structures (core−shell, yolk− shell, etc.),11,12 and designing different functional binders.13−16 Among these aforementioned strategies, using polymer binders is regarded as the most low-cost, simple, and effective means in that binder can adhere active materials and conductive agents together onto copper foil (current collector) and maintain anode integrity and good electric connectivity.17 Moreover, polymer binders can also be appropriate for inexpensive Si microparticles with high tap density, which can give rise to high initial Coulombic efficiency (ICE) and energy density compared with silicon nanoparticles.14,16,18 Up to now, multifarious polymer binders with different functions have been reported including nature gums,13,19 linear or cross-linked polymers containing polar groups,20−22 adhesive polymers mimicking mussel adhesion,15,23 elastic polymers,24 self-healing polymers,14,25 and conductive polymers,26,27 which could Received: April 12, 2019 Accepted: June 7, 2019 Published: June 7, 2019 5066
DOI: 10.1021/acsaem.9b00734 ACS Appl. Energy Mater. 2019, 2, 5066−5073
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Figure 1. Schematic illustration of the SiSMPs@TA-PAA synthetic process and interaction between TA and PAA.
tannic acid (TA) on the SiSMP surface and subsequently combining it with PAA binder to form the cross-linked network, as displayed in Figure 1. TA, as a biocompatible nature plant polyphenol, has previously been used as a precursor to form multifunctional coatings such as antifouling coatings, adhesive coatings, conformal coatings, and so on.31−33 Analogous to dopamine, TA can be coated spontaneously on almost any surface by a similar method at room temperature but it is significantly more inexpensive than dopamine. TA includes five pyrogallol and catechol groups, which can form multiple interaction sites to interact with diverse functional groups by hydrogen bonds, coordinate bonds, and hydrophobic interactions. SiSMPs with TA coating can conjugate with PAA binder and conductive materials efficiently, which keeps the electrode structural integrity during cycling. In addition, the TA coating makes the PAA binder form a 3D cross-linked network, which can enhance the binding strength compared with linear PAA chains. The TA conformal coating also protects SiSMPs from side reactions with the electrolyte, which is able to help form the stable SEI. Moreover, wet adhesion of the TA mussel-inspired coating can ensure good adhesion between SiSMPs and other components in electrolytes and the better wettability of TA with electrolyte can promote Li-ion diffusion in a silicon-based anode. The aforementioned advantages of the SiSMPs@TA-PAA electrode can result in excellent cycle stability and rate performance.
alleviate the problem of volume variation to some extent. Among these reported binders, adhesive polymers mimicking mussel adhesion could improve the wet-adhesion force between the binder and Si particles, which is important for battery operations in liquid environments.28 Carboxylic-rich binders, forming the strong hydrogen bonds interactions with Si particles, have been reported to promote cycle life growth of silicon nanoparticle-based electrodes.13,20,29 The performance of carboxylic-rich binders is able to be enhanced by inducting adhesive groups into polymer chains. The Choi group reported the mussel-inspired binders for Si nanoparticle-based anodes via introducing catechol groups playing a crucial role in mussel-inspired adhesive materials to PAA and SA backbones.15 Taking advantage of the wetness-resistant adhesion of catechol functional groups and the rigidity of polymer backbone, the mussel-inspired binders display enhanced adhesive interaction and improved cycle stability. Liu et al. synthesized a conductive polymer with catecholic building blocks for the Si-alloy anode.23 The combination of electrical conductivity and wet adhesion in polymer binders give the electrode better cycle performance. Heretofore, the majority of research for polymer binders of Si nanoparticle-based anodes centered on the complicated synthesis and functionalization of polymers. However, the modification of active materials is also important for improving electrochemical performance and the studies based on that are less reported, especially for Si submicroparticles. Last year, Jiang et al. modified silicon nanoparticles using an epoxy group to improve the electrochemical property of a silicon-based anode, which confirmed the feasibility of silicon surface modification.30 Herein we develop a simple, green, and cheap method to fabricate Si submicroparticle (SiSMP)-based anodes by coating
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EXPERIMENTAL SECTION
Materials. Polyacrylic acid (450, 000 g/mol) was obtained by Sigma-Aldrich Co., Ltd. SiSMPs were obtained from Evonik. Tannic acid and tris(hydroxymethyl)aminomethane (Tris) were purchased from Aladdin Industrial Corporation. 5067
DOI: 10.1021/acsaem.9b00734 ACS Appl. Energy Mater. 2019, 2, 5066−5073
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Figure 2. (a) FTIR spectra, (b) TGA curves, and (c) high-resolution TEM images of SiSMPs@TA-1, SiSMPs@TA-2, SiSMPs@TA-3, and SiSMPs. (d) XRD profiles of SiSMPs@TA-1, SiSMPs@TA-2, and SiSMPs@TA-3. (e) FTIR spectra of PAA, TA, and the SiSMPs@TA-1-PAA electrode. Synthesis of SiSMPs@TA Composites. TA was dissolved in Tris buffer solution (0.1 M, pH = 7−8) at room temperature. Afterward, various amounts of SiSMPs were added to the aforementioned tannic acid solution (the mass fractions between SiSMPs and TA were set at 1.0, 2.0, and 3.0, respectively), and the obtained suspension was whisked for 2 h. Subsequently, the resultant suspension was centrifuged at 8000 rpm and the precipitate collected was dried at 80 °C in a vacuum oven overnight. In this experiment, SiSMPs@TA composites with different amounts of TA coating were prepared as SiSMPs@TA-1, SiSMPs@TA-2, and SiSMPs@TA-3. Preparation of Electrodes. SiSMPs@TA composites were mixed with PAA solution (2 wt %) and Super P with a mass ratio of 8:1:1, and the mixtures were stirred well for 12 h at room temperature. Subsequently, we coated uniform-mixing slurries on the Cu foil in doctor-blade method and then vacuum dried the obtained Cu foils at 120 °C overnight. For comparison, the SiSMPs-PAA electrode without TA coating was prepared using the aforementioned method. Characterization. The surface area of silicon particles was characterized by N2 adsorption−desorption isotherms using a TriStar II 3020 volumetric adsorption analyzer from Micromeritics Instruments Corporation. The field-emission scanning electron microscopy (FE SEM) was executed using an Ultra-55 microscope by Carl Zeiss. The powder X-ray diffraction (XRD) profiles were obtained on the D8 ADVANCE ECO X-ray diffractometer from Bruker with Cu Kα radiation. The high-resolution transmission electron microscopy (TEM) images were observed using the JEM2011 microscope from
JEOL. Fourier transform infrared spectra (FTIR) were tested with the Nicolet 6700 spectrometer. Thermalgravimetric analysis (TGA) curves were obtained using the Pyris 1 TGA analyzer of PerkinElmer by heating from 50 to 600 °C at air flow in a heating-up rate of 10 °C min−1. The contact angles measurements were carried out using a OCA15 (Datapysics CO., Germany). Peeling tests of different electrodes were performed on a MTS mechanical tester (E43.104) at a displacement rate of 2 mm s−1. Electrochemical Characterization. The electrochemical performance of every electrode was tested in a CR2016 button cell. Polypropylene film (Celgard 2300) was used as the separator, and Li foil was used as the counter electrode. The electrolyte comprises 1.0 M LiPF6 dissolved in DEC and EC (volume rate of 1:1) as a mixed solvent and 5 wt % FEC as additive. The charge/discharge behavior of all cells were tested on Neware Battery test instrument using GCD test method. Cyclic voltammetry (CV) curves and electrochemical impedance spectroscopy (EIS) were achieved by the CHI600E electrochemical workstation.
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RESULTS AND DISCUSSION
In this research, a novel and cheap way was designed to ameliorate the cycling performance of silicon-based anodes for LIB. The SiSMPs@TA-PAA electrodes were prepared by a simple process. Herein, we used inexpensive and commercially available Si submicroparticles (SiSMPs) as the active materials. 5068
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Figure 3. (a) CV curves of the SiSMPs@TA-2-PAA electrode at a scan rate of 0.0001 V/s. (b) The initial discharge/charge voltage profiles of SiSMPs@TA-PAA electrodes and the SiSMPs-PAA electrode at 0.1 A g−1 in the 0.01−1.5 V vs Li/Li+ voltage range. (c) Initial Coulombic efficiency of SiSMPs@TA-PAA electrodes and SiSMPs-PAA electrodes. (d) Cycling performance of SiSMPs@TA-PAA electrodes and SiSMPsPAA electrodes at 0.1 A g−1 for the first cycle and 0.6 A g−1 for subsequent cycles. All specific capacities of electrodes are based on the mass of SiSMPs. (e) Rate capability of SiSMPs@TA-PAA electrodes and the SiSMPs-PAA electrode at different current densities.
1447 and 1331 cm−1 related to the CO stretching vibration in the presence of acid functional groups, which are the characteristic peaks of TA. In the light of the result of thermogravimetric analysis (TGA) (Figure 2b and Figure S6), the covering amounts of SiSMPs@TA-1, SiSMPs@TA-2, and SiSMPs@TA-3 are ca. 6, 15, and 20 wt %, respectively. Additionally, it can be found obviously that the surface of Si particles are covered by amorphous TA layers and the thicknesses of amorphous TA layers increase with the increase of the covering amounts according to transmission electron microscopy (TEM) images (Figure 2c) of SiSMPs@TA-1, SiSMPs@TA-2, and SiSMPs@TA-3. According to XRD patterns of SiSMPs@TA (Figure 2d), there are no changes in the crystal morphology compared with SiSMPs. SiSMPs@ TA- PAA electrodes were produced through evenly mixing SiSMPs@TA, PAA aqueous solution and conductive agent (Super P) to obtain a slurry and then coating the slurry on copper foil. To investigate the existence of cross-linking reaction between the TA coating and PAA, FTIR measurements of the SiSMPs@TA-1-PAA electrode, PAA, and TA were performed. As shown in Figure 2e, after mixing SiSMPs@ TA with PAA and heating at 120 °C, the characteristic peak of the O−H bond around 3350 cm−1 in TA shifted to 3220 cm−1 and the characteristic peak of CO stretching vibration at 1708 cm−1 in PAA displaced to a lower wavenumber of 1691 cm−1. The above-mentioned peak shifts suggest the ester bond formation derived from the reaction between PAA and TA, leading to the formation of a cross-linking network.34 Electrochemical performance tests of SiSMPs@TA-PAA electrodes were implemented by button-type half-cell using
As shown in Figures S1 and S2, the particle sizes of SiSMPs range from 100 to 700 nm and average about 500 nm. Compared with Si nanoparticles, SiSMPs possess the comparatively lower BET surface area (6.4078 m2 g−1) by the nitrogen adsorption−desorption isotherms measurement (Figure S3), which is important for improving the initial Columbic efficiency of the electrode. The crystal morphology of SiSMPs was confirmed by XRD profiles (Figure S4), which shows a cubic Si phase (ICDD JCPDS no. 27-1402). The highresolution TEM image of SiSMPs shows that SiSMPs are wrapped with an 1−2 nm amorphous SiO2 layer (Figure S5). TA as a low-cost natural polyphenol has mussel-inspired adhesive structure. The TA coating was formed by mixing TA and SiSMPs in Tris buffer solution (pH = 8.0). The intermolecular interactions between TA and the ultrathin SiO2 layer of SiSMPs (Figure S5) give rise to deposition of TA onto the surface of SiSMPs. The thicknesses of the TA coating can be regulated by the weight ratio of TA and SiSMPs. To adjust the thickness of the TA coating, the mass ratios of TA and SiSMPs were fixed on 1.0, 2.0, and 3.0, respectively. The prepared SiSMPs from the above-mentioned three mass ratios are denoted by SiSMPs@TA-1, SiSMPs@TA-2, and SiSMPs@ TA-3. Fourier transform infrared (FTIR) spectra (Figure 2a) confirm successful wrapping of TA on the surface of SiSMPs. Compared with uncoated SiSMPs, the FTIR spectra of SiSMPs@TA-1, SiSMPs@TA-2, and SiSMPs@TA-3 all have some new peaks, including the peak at 1708 cm−1 assigned to the carbonyl group (CO) vibration, the peak at 1505 cm−1 related to the C−O−H in-plane bend band, and two peaks at 5069
DOI: 10.1021/acsaem.9b00734 ACS Appl. Energy Mater. 2019, 2, 5066−5073
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Figure 4. (a) Nyquist plots of SiSMPs@TA-PAA electrodes and SiSMPs-PAA electrodes after the formation cycles. (b) Contact angles of electrolyte solvent on PAA film and PAA-TA film (5 wt % TA). (c) Force−displacement curves of SiSMPs@TA-PAA electrodes and SiSMPs-PAA electrodes after peeling tests. (d) Digital photographs of SiSMPs@TA-PAA electrodes and SiSMPs-PAA electrodes after peeling tests.
SiSMPs-PAA electrode as close as possible. The silicon loadings of SiSMPs@TA-1-PAA, SiSMPs@TA-2-PAA, and SiSMPs@TA-3-PAA electrodes and the SiSMPs-PAA electrode are ca. 0.499, 0.478, 0.510, and 0.515 mg cm−2, respectively. The first discharge−charge voltage profiles of all Si-based anodes are exhibited in Figure 3b. All electrodes display similar lithiation/delithiation behaviors in the first cycles. Obviously, there are long voltage platforms at 0.15 and 0.4 V during discharging and charging processes for all electrodes which correspond to the lithiation process (Li alloying reaction with Si) and the delithiation process, respectively. Significantly, SiSMPs@TA-PAA electrodes exhibit higher reversible capacities (3031, 3012, and 2752 mAh g−1) than the SiSMPs-PAA electrode (2389 mAh g−1), which is probably ascribed to excellent adhesive abilities and improved mechanical properties of SiSMPs@TA-PAA electrodes. The initial Coulombic efficiencies (ICE) of all electrodes are displayed in Figure 3c. SiSMPs@TA-PAA electrodes exhibit higher ICE (90.7% for SiSMPs@TA-1-PAA, 90.0% for SiSMPs@TA-2-PAA, and 84.2% for SiSMPs@TA-3-PAA) than the SiSMPs-PAA electrode (81.1%). These results indicate the TA coating can help form a smaller amount of SEI layer during first discharging−charging process by preventing the collapse of electrode to reduce electrolyte decomposition. Figure 3d displays the long-term cycle performance of different cells at constant current density for the first cycle and subsequent
lithium foil as the reference electrode. In particular, the SiSMPs-PAA electrode was used as a contrast sample to evaluate the effect of TA coating and a low ratio of PAA binder (10 wt %) was adopted in every electrode. Cyclic voltammetry (CV) measurements of SiSMPs@TA-PAA electrodes were carried out at a scan rate 0.0001 V s−1 in the 0.01−1.2 V vs Li/ Li+ voltage range. As shown in Figure 3a, the SiSMPs@TA-2PAA electrode shows electrochemical profile similar to those of reported Si-based anodes. In the first cycle, a sharp peak appears around 0.01 V during the discharging process, which is related to lithiation of crystalline silicon forming LixSi, and a peak appears at 0.52 V during the charging process, which is ascribed to delithiation of LixSi forming amorphous silicon. In subsequent cycles, during the discharging process, the new peaks around 0.2 V are attributed to the reversible lithiation of amorphous silicon and two peaks appear at 0.38 and 0.52 V during the charging process, which stand for delithiation of LixSi. CV curves of the SiSMPs@TA-1-PAA electrode and the SiSMPs@TA-3-PAA electrode are showed in Figure S7 and Figure S8, which are similar to that of the SiSMPs@TA-2-PAA electrode. In cycle performance tests, all half-cells were charged and discharged at 0.1 A g−1 in the first cycle to stabilize SEI layers and at the constant current 0.6 A g−1 in subsequent cycles in the 0.01−1.5 V vs Li/Li+ voltage range. For comparison, we make the loading of SiSMPs@TA-PAA electrodes and the 5070
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Figure 5. SEM images of the SiSMPs@TA-1-PAA electrode ((a) and (b)), SiSMPs@TA-2-PAA electrode ((c) and (d)), SiSMPs@TA-1-PAA electrode ((e) and (f)), and SiSMPs-PAA electrode ((g) and (h)) after 100 cycles with different magnifications.
cycles. The first discharge specific capacities of the SiSMPs@ TA-1-PAA electrode, the SiSMPs@TA-2-PAA electrode, and the SiSMPs@TA-3-PAA electrode reach up to 3271, 3274, and 3269 mAh g−1, respectively, which are higher than that of the SiSMPs-PAA electrode (2944 mAh g−1) and far higher than that of the current graphite anode (around 370 mAh g−1). What’s more, after 100 cycles, SiSMPs@TA-1-PAA, SiSMPs@ TA-2-PAA, and SiSMPs@TA-3-PAA electrodes still retain far higher reversible capacities of 1811, 2002, and 1591 mAh g−1, respectively, and possess much higher capacity retention rates, in comparison with the SiSMPs-PAA electrode (1225 mAh g−1). The high reversible capacity and excellent cycle stability of SiSMPs@TA-PAA electrodes could be due to these advantages as follows. On the one hand, the TA coating with multiple interaction sites can form a strong adhesive interaction with SiSMPs and conjugate with the PAA chains to form an entanglement network so that the electrodes can resist the dramatic volume change and retain their structural integrity in the charge/discharge process. On the other hand, the wet adhesion of the TA mussel-inspired coating can maintain adhesive interaction with other components under an electrolyte environment. To further study the improved the electrochemical property of SiSMPs@TA-PAA electrodes, we carried out the test of the rate performance of different electrodes at different current densities from 0.2 to 2 A g−1, and the results are exhibited in Figure 3e. At a low current density 0.2 A g−1, SiSMPs@TAPAA electrodes all exhibit the relatively higher reversible capacities up to above 3000 mAh g−1 compared with the SiSMPs-PAA electrode (2346 mAh g−1). As the current density increases, the reversible capacities of SiSMPs@TAPAA electrodes begin a slow and steady decline and still remain above 2000 mAh g−1 until at a high current density 2 A g−1, which is in stark contrast to the SiSMPs-PAA electrode. Furthermore, the reversible specific capacities of SiSMPs@TAPAA electrodes can nearly restore to the initial values after experiencing charging−discharging cycles at high current density, which show the excellent reversibility of SiSMPs@ TA-PAA electrodes. The dramatical improvement of the rate capability of a silicon-based anode by using TA coating should be ascribed to strong adhesive property and high mechanical strength of SiSMPs@TA-PAA electrodes. The TA coating
combined with PAA binder is capable of maintaining electrical contact and structure integrity of electrode under charging− discharging cycles with a high current density. However, significantly, in these SiSMPs@TA-PAA electrodes, the SiSMPs@TA-2-PAA electrode presents the most outstanding cycle property and rate capability, which is possibly because the amount of TA coating in the SiSMPs@ TA-1-PAA electrode is not sufficient to form a strong adhesive interaction while the excessive TA coating in the SiSMPs@TA3-PAA electrode could hinder the electrical conduction. This hypothesis is further evidenced by EIS measurements of different electrodes after the formation cycles (Figure 4a). In EIS profile, the semicircle is relevant to the charge-transfer resistance (Rct) including electronic and ionic resistance in the high-middle frequency region. In Figure 4a, we can find obviously all of SiSMPs@TA-PAA electrodes have much smaller semicircles than the SiSMPs-PAA electrode, which indicates the SiSMPs@TA-PAA electrodes have much better charge-transfer abilities; that is, the TA coating can help decrease Rct. To figure out the reason for this phenomenon, we investigate the effect of TA on the wettability of the electrode to electrolyte solution, which can influence Li-ion transfer in the electrolyte.18 We executed the contact angle measurements of electrolyte solvent on the PAA film and PAATA film (5 wt % TA) (Figure 4b). A smaller contact angle (10.4°) between the electrolyte solvent and PAA-TA film indicates TA can improve the wettability to the electrolyte, which can promote Li-ion diffusion. Therefore, the TA coating can indeed help decrease ionic resistance and lead to a decrease of Rct. However, we also find the semicircle becomes larger with the increase of TA coating in SiSMPs@TA-PAA electrodes, which indicates the excessive TA coating can hinder the electrical conduction and cause the charge-transfer resistance increase. To quantitatively evaluate if the combination of TA coating and PAA can improve the adhesive ability of binder, we carried out peeling tests of different electrodes. Figure 4c shows the force−displacement curves of different electrodes and obviously SiSMPs@TA-PAA electrodes present the much higher peeling forces compared with the SiSMPs-PAA electrode, which could be due to the wet adhesion of TA with many mussel-inspired functional groups and the hydrogen 5071
DOI: 10.1021/acsaem.9b00734 ACS Appl. Energy Mater. 2019, 2, 5066−5073
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ACS Applied Energy Materials bonding interactions between TA and the SiO2 layer and the cross-linked interaction of TA and PAA. From the photographs of different electrodes after peeling tests (Figure 4d), we also find obviously some active materials peeled off from the SiSMPs-PAA electrode while there were hardly any active materials in the tapes of SiSMPs@TA-PAA electrodes. In particular, the SiSMPs@TA-2-PAA electrode, which has the most excellent cycle performance, exhibits the highest peeling force up to about 15 N in SiSMPs@TA-PAA electrodes, which is possibly because the excessive TA coating can reduce the mechanical property of PAA. These results suggest the high adhesive strength is efficient for the improvement of the electrochemical property of Si-based anode. To further confirm the effect of the TA coating, the surface morphologies of different electrodes after 100 cycles were also characterized. As shown in Figure 5, it can be found that three SiSMPs@TA-PAA electrodes exhibit relatively smooth surface morphology, whereas the SiSMPs-PAA electrode shows large numbers of serious cracks. The emergence of these large cracks indicates the collapse of electrode structure in that the weak adhesion is unable to bear the stress generated by severe volume expansion and further leads to the decay of capacity. In contrast, the combination of the TA coating and PAA can hinder cracks further expanding and maintain the electrode structure integrity.
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. ORCID
Peiyi Wu: 0000-0001-7235-210X Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS The authors acknowledge financial support from the National Science Foundation of China (NSFC) (No. 51733003).
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REFERENCES
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CONCLUSION In conclusion, we reported a novel, cheap, and biocompatible method toward the preparation of a Si-based anode via TA, a nature plant polyphenol, mussel-inspired coating on the surface of low-cost SiSMPs, and the subsequent conjugation of TA coating with PAA and conductive agent. SiSMPs@TAPAA electrodes prepared by the aforementioned method possess excellent electrochemical performance compared with that of the SiSMPs-PAA electrode including the cycle performance and rate performance. Among SiSMPs@TAPAA electrodes, the SiSMPs@TA-2-PAA electrode with moderate amounts of TA coating shows the most outstanding properties. And these properties behave concretely as follows. The SiSMPs@TA-2-PAA electrode exhibits a high specific capacity up to 3274 mAh g−1 and a high ICE of 90%, which is more superior than results for most reported Si-based anodes.19,25,29 The SiSMPs@TA-2-PAA electrode also displays the outstanding long-term cycle property, in particular the specific capacity is maintained at2002 mAh g−1 after 100 cycles. And more notably, the SiSMPs@TA-2-PAA electrode can fulfill a specific capacity up to 2303 mAh g−1 at a high current density of 2 A g−1, which displays a outstanding rate capability. The melioration of the electrochemical property can be ascribed to the wet adhesion and protective effect of the TA coating for SiSMPs, the enhanced binding strength of PAA binder by the cross-linked point effect of TA and the increased Li-ion transfer on account of the wettability of the TA coating on the electrolyte. This study not only gives a new approach for the modification of active materials to meliorate the electrochemical property of silicon-based anodes but also emphasizes that the modification of a silicon particle can also enhance the adhesive ability of the electrode.
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Additional data of SiSMPs (SEM, size distribution, N2 sorption isotherms, XRD, TEM), TGA curve of TA and CV curves of SiSMPs@TA-PAA electrodes (PDF)
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsaem.9b00734. 5072
DOI: 10.1021/acsaem.9b00734 ACS Appl. Energy Mater. 2019, 2, 5066−5073
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DOI: 10.1021/acsaem.9b00734 ACS Appl. Energy Mater. 2019, 2, 5066−5073
