Silicon Anodes In Lithium-ion Batteries Research Articles

Acrylic random copolymer and network binders for silicon anodes in lithium-ion batteries

The choice of a binder can greatly influence the electrochemical performance of lithium-ion batteries (LIBs), especially for silicon (Si) anodes. To systematically modulate the mechanical properties of binders and to investigate their impact on the electrochemical properties, we synthesize a series of random copolymers consisting of acrylic acid (AA) and n-butyl acrylate (n-BA) via reversible addition-fragmentation chain-transfer (RAFT) polymerization. The electrochemical properties of Si nanoparticle (SiNP) anodes prepared using copolymer binders exhibit a strong dependence on the relative composition of AA and n-BA. The incorporation of a moderate amount of n-BA (10–30 mol%) in the copolymer binder provides better cycling stability compared to a SiNP anode prepared using poly(acrylic acid) (PAA) binder. The binder containing 30 mol% of n-BA is further crosslinked by in-situ crosslinking using a variable amount of polyethylene glycol diglycidyl ether (PEGDE). The electrochemical properties (3050 mAh g−1 in the 1st cycle and 40% capacity retention in the 100th cycle at 0.5 A g−1) of a SiNP anode prepared using the crosslinked binder with 14 wt% of PEGDE show further improvement compared to those of a SiNP anode prepared using PAA binder (2310 mAh g−1 and 32% capacity retention in the 100th cycle at 0.5 A g−1).

Highly stable multi-layered silicon-intercalated graphene anodes for lithium-ion batteries

Abstract

Microporous Binder for the Silicon-Based Lithium-Ion Battery Anode with Exceptional Rate Capability and Improved Cyclic Performance.

Silicon anodes have attracted much attention owing to their high theoretical capacity. Nonetheless, an inevitable and enormous volumetric expansion of silicon in the lithiated state restrained the development of the silicon anode for lithium-ion batteries. Fortunately, the utilization of the high-performance binder is a promising and effective way to overcome such obstacles. Herein, a polymer of intrinsic microporosity (PIM) is applied as the binder for the silicon anode, which is composed of a rigid polymer backbone, an intrinsic porous structure, and active carboxyl groups (PIM-COOH). Compared to the traditional binder, both the long-term stability and rate performance of the electrode using PIM-COOH as the binder are significantly improved. The mechanism responsible for the enhanced performance is investigated. The PIM-COOH binder provides stronger adhesion toward the current collector than the conventional binders. The unique rigid polymer backbone and porous structure of the PIM-COOH binder enable a good capability to withstand the volume change and external stress generated by the Si anode. The porous structure of the PIM-COOH binder enhances lithium-ion transportation compared to the SA binder, which improves rate performance of the silicon anode. This work provides a unique insight into design, synthesis, and utilization of the binders for lithium-ion batteries.

A conductive self-healing hydrogel binder for high-performance silicon anodes in lithium-ion batteries

Although silicon has been viewed as the ideal anode material due to its superior specific capacity, silicon materials easily break down because of its large volume changes during frequent charge-discharge cycles. Polymeric binders play key roles on maintaining the mechanical integrity of electrodes and contributing substantially to improving cycle lives. Here, we design and prepare that a novel conductive self-healing hydrogel (ESVCA) binder with 3D conductive network, excellent stretchablity and fast self-healing ability coating on the surface the Si particle by in-situ polymerization method. The stretchable 3D self-healable network structure could effectively restrain the huge volume change of Si particles during lithiation and delithiation cycles to maintain mechanical integrity of the Si electrodes while 3D continuous electron transport pathways insuring the high conductivities and better electric contacts among active Si particles. The Si-ESVCA electrode not only exhibits a reversible capacity of 1786 mA h g−1 at 500 mA g−1 with a capacity retention of 71.3% after 200 cycles at ambient temperature, but also maintains superior cycling stability with a capacity retention of 74.1% and remains a high reversible capacity of 1743 mA h g−1 after 200 cycles at current density of 2000 mA g−1 at elevated temperature.

Electrochemical Amorphization As a Method to Increase the Rate Capability of Crystalline Silicon Anodes for Lithium-Ion Batteries

Anodes manufactured from macroporous silicon have been studied. Galvanostatic cycling tests in half-cells with Li counterelectrode in a regime of charging capacity limited to Q1 = 1000 mAh/g showed that the inclusion of a modifying cycle with increased time of electrochemical lithiation into the testing schedule allowed the charge/discharge rate to be increased upon return to the initial regime. The results are interpreted in terms of a two-phase model with a sharp a-LixSi/c-Si interface. The insertion of a large amount of lithium during the modifying cycle leads to an increase in the thickness of an amorphous layer, within which the insertion and extraction of lithium in subsequent cycles proceed at a higher rate.

Preparation of an Amorphous Cross-Linked Binder for Silicon Anodes.

An amorphous cross-linked binder is prepared from abundant and low-cost sodium alginate and carboxymethyl cellulose by protonation and mixing and is used to improve the electrochemical performance of silicon anodes in lithium-ion batteries. The amorphous cross-linked structure, formed by intermolecular hydrogen bonding between the functional groups in the two polymers, effectively enhances the flexibility and strength of the binder, resulting in strong adhesion between the binder and other components in the silicon anodes. Furthermore, the binder tolerates large volume changes and reduces the pulverization of silicon during the charge-discharge process. The hydrogen bonding in the binder helps to maintain the anode integrity during the volume change, leading to an excellent cycling stability and superior rate capability with a capacity of 1863 mAh g-1 at 500 mA g-1 after 150 cycles.

Cross-linked hyperbranched polyethylenimine as an efficient multidimensional binder for silicon anodes in lithium-ion batteries

We report the use of cross-linked hyperbranched polyethylenimine (PEI) as a commercially available, eco-friendly, water-soluble, efficient polymer binder for silicon anode of lithium ion battery for the first time. Compared with traditional one-dimensional linear binders, the PEI with 3-dimensional topological hyperbranched structure and high density of amino groups can facilitate stronger multidimensional hydrogen-bonding interactions with silicon nanoparticles which may more effectively buffer large volume change of silicon particles during lithiation/delithiation process. In addition, the cross-linked 3-dimensional network of PEI limits movement of silicon nanoparticles and maintains integrity of the anode. Through optimizing the amount of cross-linking agent, 1,4-butanediol diglycidyl ether, to balance bonding reversibility and mechanical strength of PEI, the cross-linked Si/PEI anode shows significantly improved cycling performance with a specific capacity of 2180 mAh g−1 at a current density of 500 mA g−1 after 100 cycles.

Tuning PAA-Based Binders Towards Optimized Performance for Silicon Anode in Lithium-Ion Batteries

Poly(acrylic acid) (PAA) based binders have been widely used for silicon anodes in lithium-ion batteries to mitigate the issues caused by reversible volumetric expansion of silicon nanoparticles during lithiation/delithiation process. However, the performance of silicon anodes using PAA-based binders is still far from meeting the requirement of practical applications and the factors affecting the performance of these binders are not fully understood. Neutralization of PAA binders using LiOH is a common strategy for processing silicon anodes in lithium-ion batteries. In our previous studies, lithiated PAA solutions showed significant increased viscosity compared to straight PAA ones, which could benefit the large-scale lamination process and enable the fabrication of mechanically robust electrodes. However, lithiated PAA binders suffer more capacity loss in cycling tests due to the weakened adhesion and more severe side reaction of silicon particles that are mostly related to the increase of pH value of the binder solutions. In this work, non-lithium bases (e.g., NBu4OH, NH4OH, and Et3N) were used to neutralize and tune the viscosity of PAA solution. The resulting modified PAA binder solutions achieved desired viscosity with less increase of pH value. Notably, electrodes made with PAA-NH4 binder showed improved cell performance than electrodes made with PAA-Li binder. Despite the pH difference between PAA and PAA-Li binder solutions, the solvation behavior of the binders could also affect cycling performance. Therefore, a series of PAA solutions were prepared and investigated by small-angle X-ray scattering. The radius of gyration (Rg) of the binders were found to be significantly different depends on lithiation and the choice of solvent. Electrodes made with these binder solutions were evaluated in half cells to explore the relationship between solvation and performance of binders.

Chitosan-g-Poly(acrylic acid) Copolymer and Its Sodium Salt as Stabilized Aqueous Binders for Silicon Anodes in Lithium-Ion Batteries

Silicon (Si) anodes display high specific capacity but mostly suffer from poor cycling ability owing to their dramatic volume expansion during the discharge/charge process. An effort was devoted to...

Use of Electrochemical Impedance Spectroscopy to Reveal Ageing Mechanisms in Silicon Anodes for Lithium-Ion Batteries

The key for the exploitation of renewable energy and thus the replacement of fossil fuels and traditional energy sources is the achievement of effective energy storage strategies. In this regard, rechargeable Lithium-ion batteries (LIBs) play a significant role due to the high gravimetric and volumetric energy, high power density, long cycle life and low self-discharge property. However, the new applications of LIBs need higher energy densities than the present LIB technology can offer. Replacing the commercially used carbon anodes with Silicon anodes can increase the capacity more than ten times. Unfortunately, implementing Silicon anodes is still challenging due to the poor cycling stability caused by the severe volume changes of Silicon upon lithiation and delithiation during charge and discharge respectively. To improve the cycling stability a fundamental understanding of the complex processes and the degradation mechanisms is necessary. The processes in a Silicon anode during cycling have been studied by using electrochemical impedance spectroscopy (EIS) as it is a powerful, noninvasive technique to resolve the various processes in an electrode. For the investigation, a Silicon electrode using 1 M LiPF6 in EC/DEC electrolyte was cycled between the voltage potential limits of 50 mV and 1 V at a constant current. EIS measurements have been conducted at different state of charge during 200 discharge/charge cycles. The experimentally obtained impedance data were analyzed by a semi-mathematical model based on a porous electrode model. The model simulates the impedance response of a porous Silicon electrode, composed of spherical intercalation particles. The radii of the particles are dynamically changing because of expansion and contraction due to lithiation and delithiation, respectively. The impedance of a single particle is calculated considering diffusion of the Lithium cations (Li+ ions) in the particles, the solid electrolyte interphase (SEI) film and interfacial process. The particle size distribution of the Silicon powder and porous electrode theory is used to simulate the total impedance of the Silicon anode. All complex spectra obtained from experiments and simulation showed the same elements reported in literature for Silicon anodes before[1,2]. The mathematical model was used to identify important parameters to analyze the experimental data on a fundamental basis. Evaluating the experimental data revealed the large impact of the porosity reduction on the impedance during cycling. It was shown that after an expected increase in active surface area with lithiation due to the expansion of the Silicon particles, the active surface area suddenly drops. This drop in active surface area was found to correlate to a critical porosity of 0.1. It was concluded that the decrease in porosity leads to a diffusion limitation of the ions in the electrode bulk and therefore to a severe decrease in accessible surface area. Increased surface area and reduced porosity after the same lithiation time with progressive cycling indicates that the expansion of the Silicon particle is not fully reversed with delithiation. This indicates an ageing mechanism of trapped Lithium in the electrode[3]. Discontinuous diffusion behavior were correlated to cracking of the Si particle which leads to new ions diffusion pathways. Furthermore, the results indicate a formation of new SEI with lithiation and a partially redissolution with delithiation, which was also reported by Philippe et al.[4]. The attached figure shows the ratio of the experimentally obtained active surface area Aexp and the modelled active surface area Amod (based on expansion due to lithiation) and the diffusion coefficient of Li+ ions in the electrode. The results are shown for cycle 12 during the lithiation from 1 V to 50 mV (a) and for the cycle 1 to 200 after a lithiation to 50 mV (b).

Structure design and mechanism analysis of silicon anode for lithium-ion batteries

Silicon-based material is one of the most promising substitutes of widely used graphite anodes for the next generation Li-ion batteries due to its high theoretical capacity, low working potential, environmental friendliness, and abundant natural resource. However, the huge volume expansion and serious interfacial side reactions during lithiation and delithiation progresses of the silicon anode are the key issues which impede their further practical applications. Rational designs of silicon nanostructures are effective ways to address these problems. In this progress report, we firstly highlight the fundamental scientific problems, and then focus on recent progresses in design, preparation, in - situ characterization methods and failure mechanism of nanostructured silicon anode for high capacity lithium battery. We also summarize the key lessons from the successes so far and offer perspectives and future challenges to promote the applications of silicon anode in practical lithium batteries.

A novel high-performance 3D polymer binder for silicon anode in lithium-ion batteries

For high-capacity silicon (Si) anodes, the design of new binder is a feasible way to overcome the rapid capacity decay attributed to the large volume change of silicon (Si) anode in the repeated charging/discharging process. Here a newly designed binder with 3D structure was developed using CMC as the backbone, and acrylamide (AM), acrylic acid (AA) as the branch. The molecular structure was characterized by Fourier transform infrared (FTIR), and ethanol washing was applied for getting rid of unreacted monomers. The multifunctional binder with 3D structure and rich polar groups was prepared by cross-linking grafting. Polyacrylamide provides a strong adhesion and contributes to the formation of the solid electrolyte intermediate phase (SEI) layers on the surface of electrodes. The results show that CMC and polyacrylic acid with carboxyl groups not only strengthened the bonding force between the current collectors and the silicon nanoparticles (SiNPs), also improved the linkage among SiNPs. Therefore, the loading weight of commercial Si was about 0.75 mg cm−2, even after 150 deep cycles, and a high capacity of 1210.7 mAh g−1 was resulted in the Si anode. The prepared novel high-performance binder shows a potential application on the silicon anode in lithium-ion batteries.

Stable Silicon Anode for Lithium-Ion Batteries through Covalent Bond Formation with a Binder via Esterification.

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.

Porous Metal–Organic Frameworks for Enhanced Performance Silicon Anodes in Lithium-Ion Batteries

Maintaining the physical integrity of electrode microstructures in Li-ion batteries is critical to significantly extend their cycle life. This is especially important for high-capacity anode materials such as silicon, whose operational volume expansion exerts huge internal stress within the anode, resulting in electrode destruction and capacity fade. In this study, we demonstrate that by incorporating metal–organic frameworks (MOFs) with carboxylate organic linkers into Si-based anodes, a stable and flexible pore network is generated to maximize and maintain Li-ion flux throughout the electrode’s architecture. We show that the zirconium carboxylate MOF UiO-67 is a versatile comaterial to boost performance and mitigate the rate of anode degradation that presently limits the lifetime of Si anodes. The cage-like pores in UiO-67 and flexural properties of the 4,4′-biphenyldicarboxylate organic linker are proposed to create robust “ionophores” in the anode film to enhance longer term durability and performance.

(Invited) Microcalorimetry of Silicon Anodes for Lithium-Ion Batteries

Isothermal microcalorimetry is a promising characterization tool to both enhance understanding of degradation processes of silicon anodes in lithium-ion batteries, as well as to measure the impacts of efforts to improve the performance of these electrode materials. Isothermal microcalorimetry is a thermal characterization technique in which a sample is held in isothermal conditions while heat flow into / out of the sample to maintain a constant temperature is measured. This heat flow is determined by endothermic or exothermic reactions within the prepared sample. Isothermal titration calorimetry is a similar technique in which controlled amounts of a reactant are introduced to the sample during measurement, allowing capture of the reaction energies between materials. Both techniques are employed in our study of silicon anodes. Silicon has long been pursued as a next generation anode material for lithium-ion batteries due to its very high theoretical capacity relative to the currently employed graphite anode. So far, however, the practical realization of silicon anodes has been limited by both mechanical degradation caused by volume change during lithiation / delithiation as well as electrode surface instability that combine to shorten battery life and reduce capacity. Mitigation of these issues is being pursued through advanced binder materials, electrolyte additives, nano-scale architectures, and composite active materials.1 Previous microcalorimetry work on graphite anodes has demonstrated the ability of the technique to discern different lithiation reactions, measure the severity of parasitic losses, and identify the points of electrolyte degradation.2 Sandia National Laboratories is employing isothermal microcalorimetry to study new composite anodes of 15 wt.% silicon combined with standard graphite active material. Our microcalorimetry characterization approach uses a TA Instruments TAM IV with resolution to ± 200 nW to analyze samples of silicon-composite electrodes and compare their thermal signatures to baseline graphite samples to offer an understanding of the impact of silicon during electrode processing and fabrication, initial active material passivation upon electrolyte exposure, and electrochemical cycling of the battery. Our initial work focuses on the impacts of processing various silicon materials using a commonly employed LiPAA binder in an aqueous solvent. While silicon has a naturally passivating surface oxide layer, heat and gas generation can be observed during slurry mixing with the sub-micron sized silicon materials used in lithium-ion batteries. This reactivity can serve to rob capacity and increase material impedance before the electrode is even built into a battery. Later work will focus on characterizing the composite silicon electrodes during electrochemical cycling. When cycled in situ, the microcalorimeter can capture heat flow related to both surface electrolyte reactions and lithiation reactions of the silicon electrodes as well as the impacts of new binders, additives, or surface passivation approaches to mitigate these effects. References Yang J., Wang B. F., Wang K., Liu Y., Xie J. Y., Wen Z. S., Solid-State Lett., 6, A154 (2003).Krause L. J., Jensen L. D., Dahn J. R., Electrochem. Soc., 159, A937 (2012). Acknowledgment: Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.

Tannic Acid As a Binder in Silicon Anodes for Lithium-Ion Batteries

Increasing demand for portable electronic devices, electric vehicles, and grid scale energy storage has spurred interest in developing high capacity rechargeable lithium ion batteries (LIBs). Due to this interest, researchers have been extensively studying materials with high lithium ion storage capability, such as silicon, to replace the graphite anode in LIBs. Silicon is a non-toxic, abundantly available material and has a theoretical gravimetric capacity of 3500 mAh/g with a low operating potential of 0 to 1 V vs. Li/Li+. However, silicon has not yet been commercialized as an anode material due to large volume variation (>300 %) during lithiation and delithiation. This causes pulverization and loss of electrical contact between components, leading to capacity degradation and short battery cycle life. These problems can be overcome by using a binder that can hydrogen bond with the silicon particles. Here, we demonstrate utilization of tannic acid (TA), a natural polyphenol derived from wood, as a binder for silicon anode in lithium ion batteries. The resulting silicon electrodes demonstrate good cycling stability with a capacity of 1000 mAh/g for 200 cycles. This cycling stability can be attributed to the presence of the many hydroxyl (OH) groups (14.8 mM of -OH per g of TA) that hydrogen bond with the silicon particles’ OH groups. Additionally, water processability makes the electrode synthesis process environmentally friendly. This work demonstrates that a molecule with high hydrogen bonding capability can be used as a binder. Furthermore, future modifications of TA can further improve its performance as a binder for silicon anodes.

Temperature Influence on Silicon-Based Anodes for Li-Ion Batteries

Nowadays, with the aim of reducing the pollution derived from the utilization of fossil fuel powered cars, the environmentally friendly hybrid (HEVs) and electric vehicles (EVs) are gaining importance[1], [2]. Although EVs already circulate on the roads, the search for next-generation lithium-ion batteries (LIBs) with larger specific capacity and, therefore, higher energy density is necessary to achieve similar driving performance (e.g., range and power) to those provided by internal combustion engines. A strategy to upgrade the specific capacity of current LIBs consists of replacing graphite, the anode par excellence in this technology, with other materials that can supply much larger capacities[3], [4]. In this sense, silicon is postulated as one of the most promising anode materials, since it is capable of delivering a capacity (~3579 mAh/g) almost 10 times larger than that of graphite (~370 mAh/g)[5], [6]. Additionally, silicon is the second most abundant element in the earth’s crust, making it an affordable substitute of carbonaceous anode materials for LIBs[7]. However, although numerous scientific studies have been performed on silicon anodes for LIBs, a parameter that has not been evaluated and that would be of interest is the impact that temperature would have on its cycle-life. To fill in this gap, we have performed galvanostatic experiments at different temperatures with silicon-based anodes in half-cells with and without fluoroethylene carbonate (FEC) as electrolyte additive. The different capacity fading behavior observed and the possible kinetic mechanisms behind them will be discussed here. We gratefully acknowledge support from the U. S. Department of Energy (DOE), Vehicle Technologies Office. Argonne National Laboratory is operated for DOE Office of Science by UChicago Argonne, LLC, under contract number DE-AC02-06CH11357. The U.S. government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the government. [1] M. Armand and J-M. Tarascon. Nature 2008, 451, 652-657. Building better batteries. [2] C. C. Chan. EEE 1999 International Conference on Power Electronics and Drive Systems, PEDS’99, Hong Kong. The Past, Present and Future of Electric Vehicle Development. [3] W-J. Zhang, J. Power Sources 2011, 196 (1), 12-24. A review of the electrochemical performance of alloy anodes for lithium-ion batteries. [4] V. Etacheri, R. Marom, R. Elazari, G. Salitra and D. Aurbach. Energy Environm. Sci. 2011, 4, 3243-3262. Challenges in the development of advanced Li-ion batteries: a review. [5] X. Su, Q. Wu, J. Li, X. Xiao, A. Lott, W. Lu, B. W. Sheldon and J. Wu. Adv. Energy Mater. 2014, 4, 1300882. Silicon-Based Nanomaterials for Lithium-Ion Batteries: A Review. [6] H. Wu and Y. Cui. Nanotoday 2012, 7(5), 414-429. Designing nanostructured silicon anodes for high energy lithium ion batteries. [7] U. Kasavajjula, C. Wang and A. J. Appleby. Journal of Power Sources 2007, 163, 1003. Nano- and bulk-silicon-based insertion anodes for lithium-ion secondary cells.

Heterostructured Nanoporous Silicon Anode for High Energy Density Lithium Ion Battery

Silicon has been identified as the best candidate element for next generation lithium-ion batteries (LIB) anode material. It is widely available and capacity is more than ten times of conventional graphite. However, using silicon anode in LIB, still remains an unfinished agenda despite very sincere global research efforts1-3. The reasons for this are ~300% expansion in volume upon lithiation, causing fracture or pulverization of the anode structure and sluggish diffusion of lithium in bulk silicon. These challenges can be addressed by using porous silicon. The porosity in silicon can accommodate the majority of the volume expansion during repeated charge-discharge cycling of battery. Most of the under-development processes for porous silicon necessitate sourcing the material from electronic grade Si-wafers. Though this is overkill for many applications, the reason for using electronic grade silicon is due to lack of a cost effective processing route for porous silicon. Here we report a novel and industrially scalable route for production of heterostructured nanoporous silicon particles with a high specific area from low grade Si raw material. We demonstrate capacity retention of more than 1000mAh/gm and columbic efficiency in excess of 98% even after 300+ cycles of operation, using this porous silicon as anode material in a coin cell. This process can also be easily integrated with existing battery fabrication methods, without requiring major changes. Our proposed method is likely to ensure a promising, high throughput process for production porous silicon and its use in lithium ion batteries.

Versatile Utilizations of Cellulose Nanofibers for High-Performance Silicon Anode in Lithium-Ion Batteries

Silicon is the most anticipated anode material in lithium-ion batteries due to its natural abundancy, low insertion voltage (<0.4 V vs. Li/Li+) and high specific capacity (<3579 mAh g-1). However, huge volume change (~ 300 %) during cycling which causes poor cycling stability and its insulating nature prohibit the practical use. In this research, cellulose nanofibers were utilized in various ways to enhance the performance of silicon nanoparticle anodes. As carbon sources, the ultrathin (~ 1.55 nm) cellulose nanofibers can provide an extensive conductive network to improve both the cycling stability and rate performance by mitigating the volume expansion of silicon and providing the efficient electron path. Furthermore, by using thicker (~ 30 nm) cellulose nanofibers as carbon sources, a porous conductive network can be achieved, which can provide both the efficient electron path and ion diffusion path. In addition, the void space generated by cellulose nanofibers became a buffer space which enhanced the cycling stability. Finally, as a binder additive, cellulose nanofiber can enhance the performance of carboxymethyl cellulose binder. It can act as both a filler and a binder to be utilized in an electrode composite, unlike the traditional reinforcing fillers. Therefore, the versatile, cheap and abundant cellulose nanofibers show great potential in lithium-ion batteries.

Influence of molecular structure of Carboxymethyl Cellulose on High Performance Silicon Anode in Lithium-Ion Batteries

Influence of molecular structure of Carboxymethyl Cellulose on High Performance Silicon Anode in Lithium-Ion Batteries