Dielectric polarization of a high-energy density graphite anode and its

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Dielectric polarization of a high-energy density graphite anode and its physicochemical effect on Li-ion batteries Hyunjung Park, Donghyeok Shin, Ungyu Paik, and Taeseup Song Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.7b03797 • Publication Date (Web): 02 Nov 2017 Downloaded from http://pubs.acs.org on November 6, 2017

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Industrial & Engineering Chemistry Research

Dielectric polarization of a high-energy density graphite anode and its physicochemical effect on Li-ion batteries

Hyunjung Park1,2, Donghyeok Shin2, Ungyu Paik2, and Taeseup Song2*

1

School of Chemical and Biomedical Engineering, Nanyang Technological University, 62

Nanyang Drive, Singapore 637459, Singapore. 2

Department of Energy Engineering, Hanyang University, Seoul 133-791, Korea

ACS Paragon Plus Environment

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ABSTRACT The high energy density graphite anode for the commercial LIBs has critical problems on Li+ ion kinetics due to decreases both in electrode porosity and electrolyte permeability. To overcome issues, interfaces of graphite particles in the anode are polarized using poly(vinylidene fluoride)hexafluoropropylene (PVDF-HFP) with the high dielectric constant (ɛ = 8.4), high solubility with lithium salt, and ability to trap a large amount of liquid electrolyte. The PVDF-HFP treatment promoted electrolyte permeability into the graphite electrode with a high mass loading of 13.8 mg cm-2 and a density of 1.7 g cc-1 (a current density over 5 mA cm-2) which particularly leads to an improvement of capacity retention from 77% of a bare electrode to 95% over 40 cycles. These achievements were attributed not only to the enhancement of the lithium ion kinetics, but also to the stable formation of a solid electrolyte interface (SEI) layer on the graphite surface.


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Introduction The increasing demand for consumer electronics such as mobile phones, tablets, music players, and laptops has accelerated the development of a wide variety of functionalities and user interfaces to attract the attention of smart consumers. This trend requires more power for the stable long-term operation of devices. Among the various types of rechargeable battery, lithium ion batteries (LIBs) are considered the most promising energy storage system due to their high energy and power densities1-3. Despite the breakthroughs in LIB technology over the decades, the energy density of LIBs has remained at ~200 Wh kg-1, obtained by combining state of the art cathode, anode, and cell technologies4-6. For the development of the LIBs with the high energy density, industrial and lab-scale studies have been conducted on high-capacity cathode and anode materials7-10, for example, Nirich LiNixCoyMnzO2 (NCM, x ≥ 0.5) or Li-rich Li1.2Mn0.55Ni0.15Co0.1O2 for cathodes

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and Si

or Sn for anodes10, 17-19. However, those materials have never been successfully commercialized due to structural instability and pulverization upon cycling20. On the other hand, great advances in energy density have been achieved by using a compact cell configuration, especially in industry21. The LIBs used in portable devices have recently achieved cell capacities over ~3000 mAh and generally consist of LCO (cathode) and graphite (anode) with thicknesses of 40–50 and 50–60 µm and densities of 4.0 and 1.5 g cc-1, respectively22. To increase the cell capacity, more active materials should be loaded in the anode and cathode that accompanies an increase in a thickness of an electrode. To pack the electrode in a confined space of the cell, however, high pressure must be applied on the electrode by a roll press for the higher electrode density. This causes longer pathways for Li+ ions from top to bottom of the electrode and lower electrode porosity as well as electrolyte permeability, resulting in a decrease in Li+ ion diffusivity and a


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degradation of the overall electrochemical performance21, 23. To solve these problems, control of the electrode microstructure has become a major issue for advanced high-capacity LIBs with stable electrochemical performances24. As one of the main components of LIBs, the binder strongly affects the physicochemical properties and integrity of the electrode. Among conventional binder systems, sodium carboxymethyl cellulose (CMC) and emulsified styrene-butadiene rubber (SBR) have been widely used as promising materials due to their aqueous processing, environmental friendliness, and low cost. When CMC binder dissolves in water, it swells due to the repulsion force between carboxylate (COO-) and dispersed graphite particles in the slurry. SBR, as a synthetic rubber, provides good flexibility and adhesion force between particles in the electrode. The SBR binder is highly stable with electrolytes, but it has a low dielectric constant (ɛ ≤ 3.0) and poor affinity with other organic species. In this regard, the CMC/SBR binder system has limitations in thick and dense electrodes due to decreases in electrolyte permeability and Li+ ion diffusivity. Moreover, this could cause an unstable formation of solid electrolyte interface (SEI) layers on the graphite particles, and the edges of graphene layers are exposed to the electrolyte and disordered during cycling, which results in a loss of active sites and poor cycle performance25. In this work, we report a thick and dense graphite anode polarized with poly(vinylidene fluoride)-hexafluoropropylene (PVDF-HFP) as an interface modification for high-energy density LIBs. PVDF-HFP is often used as a polymer electrolyte and was chosen in this experiment due to its high dielectric constant (ɛ = 8.4) and ability to dissolve lithium salts and trap the liquid electrolyte, which can lead to enhanced ionic conductivity26. Our approach provides the following key features, which are intimately related to improvement in electrochemical properties. Firstly, an optimized amount of PVDF-HFP coated on the interfaces between graphite


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particles provides an efficient pathway for electrolyte permeation and Li+ ion migration. Secondly, enhanced electrolyte permeation through the electrode leads to a more stable formation of solid electrolyte interface layer on the graphite surfaces in the electrode, which is known to be critical for stable cycle performance of the graphite. Thirdly, the PVDF-HFP-coated graphite anode shows improved electrochemical performance, including charge/discharge capacity and cycle life. From a viewpoint of industrial aspects, binders take a lowest portion of 2 % in the cost of Li-ion batteries. A development of a new binder and/or a binder composition can be a more efficient way for a cost-down rather than a development of positive and negative active materials that account higher cost of 18 % and 13 %, respectively.

Experimental section Preparation of a thick and dense graphite electrode A graphite electrode with high energy density was prepared in an aqueous system for low cost and environmental friendliness. Graphite (SAMSUNG SDI) was used as the active material with sodium carboxymethyl cellulose (CMC)/emulsified styrene-butadiene rubber (SBR, 40 wt % in D/I water) as binders. In detail, as one batch of slurry, 19.5 g of graphite particles, 0.2 g of CMC powder, 0,75 g of SBR solution (a weight ratio of 97.5:1:1.5) were put into a 50 ml vial with 20 ml deionized water, and the mixture is thoroughly mixed using a Thicky mixer at 2000 rpm for 5 minutes. The as-prepared slurry was cast onto a Cu current collector (7 µm thickness) using a surgical blade and then dried at 110 oC for 10 min in an oven. After drying, the mass loading level (L/L) and the electrode thickness (not including the Cu foil) were 13.8 mg cm-2 and ~120 µm, respectively. To increase the packing density, the dried electrode was thoroughly


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pressed using a rolling press machine. The final density and thickness of the graphite electrode were 1.7 g cc-1 and ~70 µm, respectively. PVDF-HFP coating The PVDF-HFP binder was dissolved in acetone at a concentration of 0.1–5.0 wt %. After stirring for 12 hours, the mixed solutions were dropped onto a thick graphite electrode before pressing. The coating was conducted in an argon-filled glove box to prevent the electrode from contacting humidity in air. During the permeation of the solution from top to bottom, the electrode was kept in a small glass Petri dish to prevent fast volatilization of the solution. After coating for 30 min, the PVDF-HFP-coated electrode was pressed under the same conditions as the electrode without PVDF-HFP. Measurement of electrode porosity Electrode porosity was determined by mercury intrusion porosimetry. To investigate an effect of a density increase on the porosity, electrodes with the same mass loading level of 13.8 mg cm-2 and different densities from 1.6 to 1.9 g cc-1 were used. 0.32 wt % of PVDF-HFP, optimal condition in this experiment, is a small amount less than 2.5 wt % of CMC/BSR which is not likely to affect electrode porosity. To check a difference in porosity, electrodes with/without 0.32 wt% PVDF-HFP were used. Material characterization As-prepared samples were characterized using various tools as follows. Electrical microscope images were observed using a field emission scanning electron microscope (FESEM, JEOL JSM07600F). Electrolyte permeability was measured by making a pellet and treating it with an electrolyte. Firstly, 1.0 g powder was obtained by drying a slurry with graphite, CMC, and SBR in a respective weight ratio of 97.5:1.0:1.5. Solutions of PVDF-HFP and acetone


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with different concentrations (see Table 2) were added to the powder and thoroughly mixed. The powders were dried in an oven at ~110 oC. Then 1,800–2,500 kPa of pressure was loaded on the powders by pelletizer to achieve a target density of ~1.8 g cc-1. After that, a certain mass of electrolyte (50 µl, 1.3 M LiPF6 in EC/DEC 3:7 (V/V)) was dropped onto the pellet. Finally, the permeation time was measured until the droplet totally penetrated the pellet. X-ray photoelectron spectrometry (XPS, VG Microtech ESCA2000) was used for the analysis of the solid electrolyte interface (SEI) layer. Electrochemical impedance spectra were produced using an impedance analyzer (PARSTAT 2273, Princeton Applied Research). Evaluation of electrochemical performances Before the evaluation, the electrode was dried at 145 oC for 4 hours in a vacuum oven to eliminate the moisture in the electrode. Then, coin-type cells (2032 R type) were fabricated using the graphite electrode as a working electrode, lithium foil with a thickness of 1.0 µm as a counter electrode, 1.3 M LiPF6 in ethylene carbonate/diethyl ethylene carbonate (EC/DEC, 3/7 vol %, PANAX StarLyte) with 5 wt % fluoroethylene carbonate (FEC) as an electrolyte, and a polypropylene (PP) film as a separator. All coin cells were tested using a battery cycle tester (TOSCAT 3000, Toyo System, Tokyo, Japan).

Results and discussion Characterization of graphite particles Characterizations of synthetic graphite particles used in this experiment were performed. A Granule size is in the range of 10 – 20 µm as shown in Figure 1a and b. Figure 1c shows XRD patterns of the sample which confirms the graphite has 3.3572 Å of d (002) value and high crystallinity.


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Figure 1. (a), (b) SEM images, and (c) corresponding XRD patterns of the synthetic graphite particles used. Studies on physicochemical properties of graphite electrodes Figure 2 shows top- and cross-section view SEM images of graphite electrodes with a high mass loading level (L/L) of 13.8 mg cm-2 and different densities (D) from 1.6 to 1.9 g cc-1 after roll pressing. It clearly visualizes the decreases in porosity and volume of electrodes with the increase in the density which can have a negative effect on Li ion kinetics.

Figure 2. Scanning electron microscope (SEM) observations of the graphite electrodes with high mass loading of 13.8 g cm-1 and densities of 1.6, 1.7, 18, and 1.9 g cc-1. (a–d) Top-view images and (d–g) cross-sectional images.


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In this respect, changes in physicochemical properties of the electrodes in terms of the density were investigated. Mercury intrusion porosimetry was used to quantitatively measure the porosity of the graphite electrodes. Figure 3a exhibits a downward shift in the overall pore distribution curves with an increase in the electrode density. As a result, the porosity decreased from 46 % for 1.6 g cc-1 to 38% for 1.9 g cc-1. It is worth noting that the pores within a range of 1–2 µm almost disappeared and were replaced by smaller pores of ~800 nm. To investigate an effect of the porosity change on the graphite electrode, the electrolyte permeation was studied by counting time for electrolyte absorption by electrode pellets with densities in the range of 1.5–1.8 g cc-1. Figure 3c reveals that there is a linear relationship between the time and the pellet density which indicates the decrease in the pore size and volume of the electrode can eventually deteriorate Li ion diffusivity and electrochemical performances. In contrast, electrical conductivity was enhanced as shown in Figure 3c. This might be due to more close packing and better contact between graphite particles which is also supported by a peeling test of the graphite electrodes in Figure 3d. An adhesion strength enlarged with the increase of the electrode density. Even though the electrical conductivity and the adhesion strength were improved, electrochemical impedance spectroscopy (EIS) spectra in Figure 3e demonstrates that the density increases cause larger charge transfer resistance which can have a negative effect on electrochemical properties. In this respect, cycle performance of three different electrodes were evaluated to give an insight on how much the high energy density graphite electrode is degraded compared to low and middle energy density electrodes. As shown in Figure 3f, the graphite electrodes with low one (L/L 6.5 and D 1.6) and middle one (L/L 9.5 and D 1.6; currently used level in electronics) shows stable performances of 100 % and 97 % capacity retentions,


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respectively. However, the high energy density sample (L/L 13.8 and D 1.7) exhibits the 77 % retention over 40 cycles.

Figure 3. Study on the physical properties of the graphite electrodes in terms of density. (a) Pore size distribution measured by mercury intrusion porosimetry, (b) electrolyte permeability, and (c) electrical conductivity measured by two probe station. (e) EIS spectra of graphite electrode with the mass loading level of 13.8 mg cm-2 and densities from 1.6 to 1.9 g cc-1. (f) Cycle performances of three different graphite electrodes at a current density of 0.5 C in a potential window of 0.01–1.5 V vs. Li/Li+. This continuous capacity decay can be attributed to the graphite disordering. According to the previous reports, the Li+ surface-bulk concentration gradient on graphite particles induce local stresses within the lattice which can cause structural damages such as a deformation of the graphene layers, breaking of C–C bonds, and carbon disordering. In this respect, those negative effects can more severely be developed in the high energy density graphite anode27. From the preliminary tests, we reached the conclusion that to use the high energy density graphite


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electrode over L/L 9.5 and D 1.6 is challenging for the degradation of the electrochemical performances due to poor electrolyte permeation and Li ion kinetics. Interface polarization of graphite electrode using PVDF-HFP To overcome this problem, PVDF-HFP binder was introduced to take advantage of its high dielectric constant and good affinity with the liquid electrolyte. For interface modification with an optimized condition, PVDF-HFP/acetone solutions were prepared with various concentrations. Compositions of anodes after PVDF-HFP treatment are summarized in Table 1. Figure 4 shows SEM cross-view images of the electrodes coated with PVDF-HFP of different concentrations of 0.00–1.70 wt %. The PVDF-HFP/acetone solution was dropped onto the thick graphite electrode before pressing so that the mixture solution could easily penetrate through the open pores between graphite particles, which can provide better permeation pathways for the carbonate electrolyte into the thick and dense electrode. In comparison of the bare electrode (Figure 4a), the electrodes with 0.08 and 0.32 wt % of PVDF-HFP show no significant difference, but binders, presumably PVDF-HFP, were observed between graphite particles (Figure 4 b and c). In contrast, for a much higher concentration of 1.70 wt %, the electrode clearly exhibits PVDF-HFP binder as agglomerates as well as layers on the top of the electrode. Mercury intrusion porosimetry was used to investigate electrode porosity before/after PVDF-HFP coating. The porosities of the bare electrode and the electrode with 0.32 wt % were determined to be 45.61 % and 45.58 % that indicates there is a no significant change within the range of 0.32 wt % because of a small amount of PVDF-HFP used.


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Table 1. Electrode compositions used in this experiment. The weight percent of PVDF-HFP in the electrode was determined assuming that 10 µl of each PVDF-HFP/acetone solution was used as a coating.

Figure 4. Cross-sectional scanning electron microscope images of the bare graphite electrode and the electrodes after PVDF-HFP treatment at concentrations of (a) 0.00, (b) 0.08, (c) 0.32, and (d) 1.70 wt %. (e) Low-magnification and (f) high-magnification Top-view image of the electrode with 0.32 wt % PVDF-HFP.


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SEM and energy dispersive X-ray spectroscopy (EDX) analyses were carried out to confirm the distribution of PVDF-HFP in the graphite anode. Figure 5a and b show the SEM cross-view images of the bare electrode and the electrode with 0.32 wt % PVDF-HFP after pressing. Figure 5 c and d show EDX mapping images of the carbon element, which was observed over the entire electrode which is originated from graphite particles as well as binders. Figure 5e and f exhibit maps of fluorine as one of the main elements of the PVDF-HFP binder. No sign of fluorine was detected in the bare electrode. In contrast, clear evidence of fluorine was observed in the 0.32 wt % PVDF-HFP electrode. It clearly demonstrated that the PVDF-HFP existed over the entire area of the electrode. Moreover, the EDX quantitative elemental analysis is summarized in Table 2. The 0.32 wt % PVDF-HFP electrode has 1.9 wt % of fluorine much higher than 0.5 wt % in the bare electrode.


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Figure 5. Scanning electron microscopy (SEM)/energy dispersive X-ray spectroscopy (EDX) analysis of the bare electrode without PVDF-HFP and the electrodes with 0.32 wt % PVDF-HFP before pressing. (a-b) Cross-sectional image, (c-d) carbon mapping, and (e-f) fluorine mapping.

Table 2. EDX quantitative elemental analysis of the corresponding SEM images. To demonstrate the direct effect of PVDF-HFP coating, electrolyte permeability of graphite/CMC/SBR pellets was studied by measuring absorption time in terms of the amount of the PVDF-HFP. As shown in Figure 6a, the electrode without PVDF-HFP took ~158 s to absorb the electrolyte. The permeation time linearly decreased to 99 s as the amount of PVDF-HFP coating increased from 0 to 0.3 wt %. In contrast, the time began to increase as the amount approached 1.7 wt %. Given that the improvement in the electrolyte permeation, lithium ion diffusivity can be enhanced either, if the electrolyte penetrated well into the thick and dense graphite electrode. To support this assumption, EIS spectra were measured in Figure 6b. The electrodes with PVDF-HFP binders in the range of 0.08–0.32 wt % showed reduced semi-circles, corresponding to decreased charge transfer resistance compared to that of references. Of these, the electrode with 0.32 wt % coating exhibited the smallest charge transfer resistance. However, the resistance increased when the coating amount reached 1.70 wt % in good agreement with the result of the electrolyte permeability. The reason for this might be that such large amount of PVDF-HFP binder forms a thick layer between graphite particles as shown in the SEM (Figure 4)


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which can act as a polymer electrolyte and/or a separator with lower ionic conductivity (~10-4 S/cm, LiPF6 in EC/DEC/ PVDF-HFP) than that of a bare liquid electrolyte (~10-2 S/cm, LiPF6 in EC/DEC)

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. Therefore, the 0.32 wt % of PVDF-HFP was considered as the optimal amount

for the high-energy density graphite anode.

Figure 6. (a) Permeation test on pellets as a function of absorption time of the electrolyte. Asprepared pellets have ~1.3 cm2 area, 2 mm thickness, and 0.5 g weight. (b) Electrochemical


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impedance spectra of the graphite/CMC/SBR electrodes with 0.00–1.70 wt % PVDF-HFP. The electrodes had the same mass loading level of 13.8 mg cm-2 and density of 1.8 g cc-1. Electrochemical properties of PVDF-HFP treated graphite electrodes


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Figure 7. Electrochemical performance of the graphite/CMC/SBR electrodes with PVDF-HFP of 0.00–0.32 wt% tested in a potential window of 0.01–1.5 V vs. Li/Li+. The electrodes had the same mass loading level of 13.8 mg cm-2 and density of 1.7 g/cc. (a) Voltage profiles at 0.05 C, (b) cyclability at 0.5 C over 45 cycles, and (c) rate capability with varying current density of 0.1– 1 C. Based on the systematic study and characterization of the PVDF-HFP coatings, the electrodes with 0.08 and 0.32 wt % PVDF-HFP were chosen for the evaluation of electrochemical performance. Figure 7a shows the first cycle voltage profiles of three electrodes with a high loading level of 13.8 mg cm-2 and a high density of 1.7 g cc-1, evaluated in a voltage window of 0.01–1.5 V vs. Li/Li+ at 0.05 C. The three electrodes, one without PVDF-HFP and two with 0.08 and 0.32 wt % PVDF-HFP, displayed first cycle Coulombic efficiencies of 90.7, 91.1, and 91.7 % and charge/discharge capacities of ~331/365, ~336/369, and 343/374 mAh g-1, respectively. A remarkable improvement was achieved in the cycle performance as shown in Figure 7b. The capacity retention of each electrode was ~77, 87, and 95 % over 40 cycles at 0.5 C, respectively. In addition, the Coulombic efficiencies of the three electrodes after the step formation at 0.05, 0.1, and 0.2 C were 96, 100, and 100 %, respectively, demonstrating the poor reversibility of the bare electrode due to slow Li+ ion kinetics. Moreover, rate capability of the electrodes with 0.08 and 0.32 wt % PVDF-HFP was improved. Specifically, they showed retentions of ~259 (74 %) and 264 mAh g-1 (77 %) at 1.0 C, respectively, which were slightly higher than ~248 mAh g-1 (71 %) achieved by the bare electrode. To corroborate this improvement in electrochemical performance, X-ray photoelectron spectrometry (XPS) was conducted to investigate the formation of a solid electrolyte interface (SEI) layer on the graphite surface. The SEI layer is an irreversible decomposition of the


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electrolyte and is formed on the negative electrode when the cell is tested below a potential of 1.0 V vs. Li/Li+, leading to capacity loss in the first cycle. However, it is well known that the stable formation of an SEI layer enables the sustained cycle performance of Li-ion batteries by preventing the continuous consumption of the electrolyte and side effects between active materials and the electrolyte. According to the previous studies, the SEI is mainly composed of lithium fluoride (LiF), lithium carbonate (Li2CO3), lithium alkyl carbonates (R-OCO2Li), and RCH2-OCO2Li)

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. Figure 8 shows the XPS spectra of the samples after a full charge. In

particular, F 1s, C 1s, and P 2p orbitals were examined to provide an insight into the components of the SEI layer. In the F 1s orbital (Figure 8a), two peaks were observed at ~687 and 685 eV, which represent LiPF6 and LiF, respectively. The bare electrode had only one peak of LiF and no sign of LiPF6. The PVDF-HFP-coated electrodes had two distinctive peaks, attributed to LiF and LiPF6, and the peak intensities became stronger with an increase in the amount of PVDF-HFP. For C 1s, the overlapped peaks of Li2CO3 and R-OCO2Li were detected at ~290 eV, and the RCH2-OCO2Li peak was observed at ~286.5 eV, as shown in Figure 8b. The latter is considered to be the main component of the SEI layer formed on the surface of graphite electrodes. The electrodes with 0.32 wt % PVDF-HFP showed the obvious peak of lithium alkyl carbonate (RCH2-OCO2Li), indicating the stable formation of the SEI layer. With respect to the P 2p orbital, the pristine electrode without PVDF-HFP showed no obvious peaks. As the amount of PVDF-HFP increased, two peaks at ~137 eV and ~133.2 eV, assigned to LiPF6 and PO43/PO(OR)3, respectively, became gradually stronger, as shown in Figure 8c. It is worth noting that the coexistence of LiPF6 and PO43-/PO(OR)3 is direct evidence of the strong affinity of PVDFHFP with the electrolyte because it stems from the liquid electrolyte used in this experiment. All


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of these results demonstrate that the stable formation of the SEI layer, which directly impacts the electrochemical performance, was achieved by adding PVDF-HFP.

Figure 8. X-ray photoelectron spectroscopy (XPS) spectra after full charge to 0.01 V vs. Li/Li+ at a current density of 0.05C. (a) F 1s, (b) C 1s, and (c) P sp spectra of the graphite/CMC/SBR electrodes with PVDF-HFP of 0.00–0.32 wt %. Conclusions


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In summary, a PVDF-HFP binder with a high affinity to the electrolyte was coated onto thick and dense graphite anodes to overcome the difficulty in electrolyte penetration presented by the decrease in both pore size and pore volume. PVDF-HFP/acetone solutions with various concentrations were prepared and dropped onto the electrodes to optimize the electrode composition. The PVDF-HFP coatings below 0.32 wt % improved the electrolyte permeation and reduced the charge transfer resistance compared to those of the electrode without PVDFHFP. The electrodes with PVDF-HFP concentrations of 0.08 and 0.32 wt % also showed the significant improvement in the cycle performance; as the amount of PVDF-HFP coating increased, the capacity retention improved. The 0.32 wt % PVDF-HFP-coated electrode had ~95 % retention, which was much higher than the 77 % shown by the electrode without PVDF-HFP. Moreover, XPS analysis revealed that the PVDF-HFP coating led to the uniform formation of an SEI layer on the surface of the graphite electrode, which enabled the stable electrochemical reaction. All of these achievements were enabled by the improvement in electrolyte permeability, demonstrating that a thick and dense graphite anode with a proper amount of PVDF-HFP is suitable for use in high-energy density lithium ion batteries. Our finding is meaningful to provide a cost-effective approach using a very small amount of PVDF-HFP below 1 wt % that, we believe, can be helpful in industrial aspects

AUTHOR INFORMATION Corresponding Author *Corresponding authors (T Song) E-mail: [email protected] ACKNOWLEDGMENT


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This work was supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) through the Energy Efficiency & Resources Core Technology Program (No. 20142020104190) and the Ministry of Trade, Industry, & Energy (MOTIE) of the Republic of Korea through the international reseach on Li-ion batteries (No. 20168510050080). REFERENCES (1)

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Table of Contents


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Dielectric polarization of a high-energy density graphite anode and its

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