Volume Change Of Si Research Articles

Fast-chargeable lithium-ion batteries by μ-Si anode-tailored full-cell design

Silicon (Si) anodes have long been recognized to significantly improve the energy density and fast-charging capability of lithium-ion batteries (LIBs). However, the implementation of these anodes in commercial LIB cells has progressed incrementally due to the immense volume change of Si across its full state-of-charge (SOC) range. Here, we report an anode-tailored full-cell design (ATFD), which incorporates micrometer-sized silicon (μ-Si) alone, for operation over a limited, prespecified SOC range identified as 30−70%. This range allows homogeneous (de)lithiation throughout the electrode, accompanied by an acceptable level of volume change. The ATFD-based cell exhibits 21.3% higher gravimetric energy density than that of its graphite-based counterpart in a commercial 18650 cylindrical cell and 84.6% capacity retention after 500 cycles even at a fast-charging rate of 3 C. This study indicates that the partial, intermediate SOC operation of the μ-Si anode can markedly increase the energy density and boost the fast-charging capability of a LIB cell, a challenging task in traditional cell engineering.

Resilient Binder Network with Enhanced Ionic Conductivity for High-Areal-Capacity Si-Based Anodes in Lithium-Ion Batteries

Silicon (Si) anodes have attracted considerable attention for high-energy-density lithium-ion batteries (LIBs), owing to their high theoretical capacity (>3500 mAh g−1 at room temperature), low reaction potential (<0.4 V vs. Li/Li+), and natural abundance. However, the repeated volume changes of Si during the lithiation/delithiation process induce critical complications, such as the pulverization of Si particles, formation of a thick solid-electrolyte-interphase (SEI) layer, and electrode delamination, resulting in poor cycle performance. To mitigate these complications, several strategies have been proposed, including the nano/microstructural design of Si, employing a Si/C composite, and using multifunctional binders. Regarding the choice of the binder, the conventional poly(vinylidene fluoride) (PVDF) is inadequate as it cannot accommodate a large hoop stress because of its weak van der Waals force. Compatible binders, such as carboxymethyl cellulose, poly(acrylic acid) (PAA), and poly(vinyl alcohol), have been generally employed to improve the electrochemical performance of Si anodes. Although binders with abundant functional groups (e.g., –OH, –COOH, –CN, and –NH2) prevent the delamination of Si anodes from the current collector, they suffer from brittleness due to their serious chain-entanglement network and strong interactions, leading to a high glass transition temperature (Tg ). Moreover, polymeric binders with poor stretchability and self-healing ability degrade the structural integrity of the Si anode during repeated volume changes. Further, low ionic conductivity deteriorates the transport of Li ions in the Si anode, thereby impeding the effectiveness of fast-charging systems.Therefore, various physicochemical properties of a polymeric binder are required to improve the electrochemical performance of Si anodes besides adhesion property. First, stretchability and a high elastic modulus are essential for a binder to endure the stress of large volume expansions and recover to the original state after the lithiation process. A Si anode incorporating a rigid and stiff polymeric binder could crack and become damaged, resulting in drastic capacity decay and safety issues. Second, the self-healing ability is required for a binder to spontaneously recover from the damage induced by the significant volume changes. The mechanical fracture of Si particles induces the loss of the active material and exposes a highly reactive surface to the electrolyte. Third, in the LIB system, the rate performance highly depends on the ionic conductivity as well as the electronic conductivity. Thus, a binder with high ionic conductivity is highly desired to enhance the Li-ion diffusion coefficients and achieve a high-rate-performance. A binder design that satisfies the three requirements above is desperately desired.a series of poly(Li[3-sulfopropylmethacrylate]-r-acrylic acid) (PLSA) polymers with different moiety ratios was synthesized from 3-sulfopropyl acrylate lithium salt (Li[SPMA]) and acrylic acid (AA) monomers. Subsequently, glycerol, as a thermally stable plasticizer (high boiling point: 290 °C), was added to the polymer matrix to lower the Tg and maintain the softness of the polymers after water evaporation. The hydroxyl groups in the glycerol interact with the oxygen in the polymers, enhancing ion solvation for rapid Li-ion conduction. The ionic side chain of the polymer, as a mechanical modulator, formed the crosslinking via the electrostatic interaction between the polymers, conferring the stretching and self-healing properties. Furthermore, the mobile Li ions in the side chain enhanced the ionic conductivity of the polymers. Meanwhile, the carboxylic acid group (–COOH) in AA interacted with the current collectors (i.e., copper (Cu) foil) and the silanol groups (–SiOH) from the Si particles via hydrogen bonding, enhancing the adhesion properties. The rationally designed polymers with excellent physicochemical properties (i.e., high stretchability, rapid self-healing ability, and high ionic conductivity) were introduced as polymeric binders in the Si anode in LIBs. The Si anode with the PLSA75 binder (Si–PLSA75) exhibited stable cycling performance, retaining 81.2% of its initial capacity after 300 cycles at 0.5 C (1.5 A g−1) and exhibiting outstanding rate performance (815 mAh g−1 at 5 C (15 A g−1)). Moreover, compared with the Si–PAA, the half-cell with Si–PLSA exhibited lower internal resistance and higher diffusion coefficients of the Li ion during the whole lithiation/delithiation process. Based on the outstanding electrochemical performance in Si anodes, Si/graphite (Si/Gr) blend anode was also tested with PLSA binder which could afford around 840 mAh g-1. The blended anode with PLSA75 also maintained 82.7% of its initial capacity after 200 cycles at 0.5 C. Furthermore, the blended anode was paired with a nickel (Ni)-rich cathode, LiNi0.8Co0.1Mn0.1O2, for the full-cell test, and the full cell still delivered a reversible capacity of 139.2 mAh g−1 after 200 cycles at 0.5 C. This work provides insights into the rational design of polymeric binders for achieving Si anodes with fast-charging and stable cycling performance.

Anode Properties of Si-Based Composite Electrodes Containing Two Silicides with Different Functions for Lithium-Ion Batteries

A LaSi2/Si composite electrode has longer charge-discharge cycle life than a pure Si electrode. However, the capacity of the composite electrode decreases gradually over repeated cycles. We identified the microstructure of the electrode to ascertain factor of capacity fading by transmission electron microscopy. Before cycling, the pure Si phase was highly dispersed in the LaSi2 matrix phase. In such microstructure, the elastic LaSi2 could alleviate the stress caused by Si volume change during lithiation and delithiation; and hence it suppressed electrode disintegration.1 On the other hand, prior to capacity decline, the positions of LaSi2 and pure Si were reversed. The LaSi2 phase was surrounded by the pure Si matrix phase and the LaSi2 could not relax the stress. Hence, we added stiff silicide which withstands the Si-generated stress into the LaSi2/Si. As a result, the LaSi2/NbSi2/Si exhibited superior cycle life. Herein, we investigated the effect of difference in elastic silicides on cycle life. The MSi2/CrSi2/Si (M = Ni, La, or Sm) powder was prepared by mechanical alloying method. The composite powder was deposited on the Cu substrate using a gas-deposition (GD) method. The fabricated GD electrode was mounted in a 2032-type coin-cell as the working electrode. Li metal foil and glass fiber filter were also used as the counter electrode and separator, respectively. In addition, we used 1 mol dm–3 lithium bis(fluorosulfonyl)amide dissolved in N-methyl-N-propylpyrrolidinium bis(fluorosulfonyl)amide as an ionic liquid electrolyte. We conducted galvanostatic charge-discharge tests in constant current mode with a charge capacity limitation of 1000 mA h g(Si)–1. In the present study, we did not consider the capacity of the silicides: the Si-alone and silicide-alone electrodes stored Li, while the silicide in the silicide/Si electrodes did not show the reversible capacity2. Figure 1 shows the cycle life of the MSi2/CrSi2/Si electrodes with the different indentation work rates of MSi2. The indentation work rate means an indicator of elasticity: it indicates that how much the MSi2 layer returns to its original shape after deformation. The cycle life was the shortest when NiSi2 with the lowest indentation work rate was used. In contrast, when SmSi2 was used, it achieved the longest cycle life with high reversible capacity of 1000 mA h g(Si)–1 over 1900 cycles. We predicted that the cycle life improved using a more elastic silicide. However, the cycle life adversely lowered when LaSi2 with the highest elasticity was used. Thus, the excellent performance should be achieved based on the synergistic effects of stiff and elastic silicides.1) Y. Domi, H. Usui, K. Nishikawa, and H. Sakaguchi, ACS Appl. Nano Mater., 4, 8473 (2021).2) Y. Domi, H. Usui, K. Nishikawa, H. Sakaguchi, et al., Electrochemistry, 88, 548 (2020). Figure 1

Si anodes via dual strategies of coating Si with a rigid polymer and employing a polymer binder with improved mechanical properties

Si undergoes significant volume change over cycles which degrades the structural integrity and stability of the electrode. This volume change is the primary barrier to the commercialization of Si anodes, and it is more pronounced for Si particle sizes over 150 nm. In this study, a crosslinked polymer binder is developed using poly(acrylic acid-co-acrylamide) (PAAM) with enhanced elasticity compared to the widely used poly(acrylic acid). PAAM is further grafted with boronic acid and dopamine, yielding PAAM-B-D, a binder with improved adhesion due to its 3D crosslinked network. Additionally, 350-nm Si is coated with cyclized polyacrylonitrile (cPAN) and heat-treated to form a conjugated structure. The cPAN-coated Si (cSi) exhibits enhanced conductivity and mechanical stiffness and is used as an active material. The developed Si anode effectively combines cPAN-coated Si with the crosslinked network formed in the PAAM-B-D polymer for enhanced adhesion. The cSi@PAAM-B-D electrode sufficiently maintains its structural integrity and mitigates the Si volume change even with the large-sized 350-nm Si. The cSi@PAAM-B-D exhibits a high initial Coulombic efficiency of 86.5 %, at a Si mass loading of 2 mg cm−2. It also shows a capacity retention of 83.6 % and a high areal capacity of 3 mAh cm−2 after 50 cycles.

Evaluating the efficacy of strategies for silicon/graphite anodes in Li-ion batteries

Recent research has been focused on the utilization of silicon (Si) based anode for high-energy–density lithium-ion batteries (LIBs) owing to the high theoretical capacity of Si (∼ 3578 mAh g−1). To mitigate the intrinsic volume change of Si (∼ 300 %) upon cycling, research focused on the co-utilization strategy of Si with graphite anode (SiG) in the form of the blending (physical mixture of Si and graphite) and composite (building up material containing Si and graphite). However, the underlying mechanisms of the two strategies that cause different electrochemical results have not been thoroughly explored. In this study, we aimed to investigate the composite anode (C-SiG-650) and blending anode (B-SiG-650) with a specific capacity of ∼ 650 mAh g−1 in terms of electrochemical performance. The composite anode exhibited a uniform distribution of SiG particles, which helps for faster Li+ ion transport into bulk, whereas the blending anode exhibited aggregation of SiG particles, which impedes the Li+ ion transport into the bulk. As a result, the composite anode exhibited superior capacity retention and rate performance compared to the blending electrode. Moreover, the composite anode containing full-cell delivered a higher specific capacity of 162 mAh g−1 and capacity retention of 73.58 % after 100 cycles. This implies that directly utilizing composite anode with a low-capacity SiG particle is a promising way to achieve high volumetric energy density for commercial device applications.

Deciphering the Impact of Current, Composition, and Potential on the Lithiation Behavior of Si-Rich Silicon-Graphite Anodes.

Adding silicon (Si) to graphite (Gr) anodes is an effective approach for boosting the energy density of lithium-ion batteries, but it also triggers mechanical instability due to Si volume changes upon (de)lithiation reactions. In this work, component-specific (de)lithiation dynamics on Si-rich (30 and 70wt.% Si) SiGr anodes at various charge/discharge C-rates are unveiled and compared to a graphite-only electrode (100Gr) via operando synchrotron X-ray diffraction coupled with differential capacity plots analysis. Results show preferential lithiation of amorphous Si above ≈200mV and competing lithiation of Gr, amorphous Si, and crystalline Si below ≈200mV. Discharge proceeds via sequential delithiation of Gr and amorphous lithium silicide. Si shifts the interconversion potentials of graphite intercalation compounds, lowering the Gr state of charge compared to 100Gr. In the 30%Si electrode, crystalline Si amorphization at potentials <110mV is found to be kinetically hindered at C-rates higher than C/5, which can be key for enhancing the cycling stability of SiGr anodes. The 70%Si electrode exhibits restricted lithium diffusion in Gr, full Si amorphization, and Li15Si4 formation. These findings related to the potential- and current-dependent dynamic changes on SiGr blends are crucial for designing stable high energy density SiGr anodes.

Selective Methylation of Cyclic Ether Towards Highly Elastic Solid Electrolyte Interphase for Silicon-based Anodes.

Silicon (Si)-based anodes offer high theoretical capacity for lithium-ion batteries but suffer from severe volume changes and continuous solid electrolyte interphase (SEI) degradation. Here, we address these challenges by selective methylation of 1,3-dioxolane (DOL), thus shifting the unstable bulk polymerization to controlled interfacial reactions and resulting in a highly elastic SEI. Comparative studies of 2-methyl-1,3-dioxolane (2MDOL) and 4-methyl-1,3-dioxolane (4MDOL) reveal that 4MDOL, with its larger ring strain and more stable radical intermediates due to hyperconjugation effect, promotes the formation of high-molecular-weight polymeric species at the electrode-electrolyte interface. This elastic, polymer-rich SEI effectively accommodates volume changes of Si and inhibits continuous side reactions. Our designed electrolyte enables Si-based anode to achieve 85.4 % capacity retention after 400 cycles at 0.5 C without additives, significantly outperforming conventional carbonate-based electrolytes. Full cells also demonstrate stable long-term cycling. This work provides new insights into molecular-level electrolyte design for high-performance Si anodes, offering a promising pathway toward next-generation lithium-ion batteries with enhanced energy density and longevity.

Selective Methylation of Cyclic Ether Towards Highly Elastic Solid Electrolyte Interphase for Silicon‐based Anodes

Silicon (Si)‐based anodes offer high theoretical capacity for lithium‐ion batteries but suffer from severe volume changes and continuous solid electrolyte interphase (SEI) degradation. Here, we address these challenges by selective methylation of 1,3‐dioxolane (DOL), thus shifting the unstable bulk polymerization to controlled interfacial reactions and resulting in a highly elastic SEI. Comparative studies of 2‐methyl‐1,3‐dioxolane (2MDOL) and 4‐methyl‐1,3‐dioxolane (4MDOL) reveal that 4MDOL, with its larger ring strain and more stable radical intermediates due to hyperconjugation effect, promotes the formation of high‐molecular‐weight polymeric species at the electrode‐electrolyte interface. This elastic, polymer‐rich SEI effectively accommodates volume changes of Si and inhibits continuous side reactions. Our designed electrolyte enables Si‐based anode to achieve 85.4% capacity retention after 400 cycles at 0.5 C without additives, significantly outperforming conventional carbonate‐based electrolytes. Full cells also demonstrate stable long‐term cycling. This work provides new insights into molecular‐level electrolyte design for high‐performance Si anodes, offering a promising pathway toward next‐generation lithium‐ion batteries with enhanced energy density and longevity.

Influence of mechanochemical reactions between Si and solid electrolytes in the negative electrode on the performance of all-solid-state lithium-ion batteries

All-solid-state lithium-ion batteries that employ Si negative electrodes are the most promising candidates for next-generation batteries because of their high safety performance and energy density. However, the contact between Si and the solid electrolyte becomes insufficient because of the volume changes of Si associated with charging and discharging, resulting in a significant drop in battery performance. Although mechanical milling forms good interparticle contacts, the reaction between Si and a sulfide solid electrolyte increases the resistance, thereby decreasing battery performance. Therefore, in this study, we investigated the effects of the mechanochemical reactions between several solid electrolytes and Si on battery performance. A decrease in electronic conductivity was observed from the reaction between Si and sulfide or oxide solid electrolytes, whereas no significant decrease was observed with halide solid electrolytes. Consequently, an Si composite electrode constructed with a halide solid electrolyte showed high reversibility, achieving a high area capacity of 4.6 mA h cm−2 and specific energy density of 470 Wh kg−1 (masses of positive and negative composite electrodes) in a full-battery cell with an Li2S positive composite electrode at 0.25 mA cm−2 and 25 °C. The study contributes to understanding the important factors in the advancement of all-solid-state lithium-ion batteries.

A like-bulletproof glass structure flexibility-rigidity coating layer strategy for high-performance Li ion batteries Si anodes

In order to overcome the problems about the volume expansion and poor electronic conductivity of Si, a flexibility and rigidity double coating layer CNTs-rGO- PAIN was constructed. The CNTs-rGO-PANI network with porous structure and high electronic conductivity provides sufficient space to accommodate the volume change of Si, and abundant transmission path for electron and Li ion. Moreover, the coating network with flexibility and rigidity characteristic could absorb the expansion stress of Si, maintain electrode structural integrity, promote the growth of stable SEI. The polymer-nanocarbon network dual coating layer effectively safeguards the electrochemical-mechanical interplay within the electrode. The 20Si-CNTs-rGO-PANI exhibits a reversible capacity as high as 1856 mAh g−1 after 400 cycles at 0.2 A g−1 and a remarkable rate capacity of 570 and 459 mAh g−1, at 5 and 10 A g−1, respectively. The outstanding Li ion storage performance of 20Si-CNTs-rGO-PANI anode, suggests the flexibility-rigidity dual coating layer strategy is a potential way to improve the performance of alloy type anode.

Layer effects on MXenes electrode and it applied to silicon composite structures

Despite the very high capacity of Si (4200mAh g−1), the widespread application of Si anodes has been hampered by drastic volume changes (up to 300 %) during cycling, leading to electrical contact losses and thus a sharp drop in capacity as the cycle life is shortened. Here we present a class of layered MXene/Si electrodes, which consist of nano-Si embedded in the interlayers of MXene to form a coupling effect, which can inhibit the huge volume change of Si during cycling. Therefore, layered MXene/Si has a highly reversible capacity, much improved cycling performance and excellent mechanical properties. First-principles calculations reveal the excellent electronic conductivity and good diffusion ability of layered MXene/Si, confirming the rapid storage of Li ions. This study provides useful information for the development and production of anode materials with high energy density and good mechanical properties.

In Situ Integration of a Flame Retardant Quasisolid Gel Polymer Electrolyte with a Si-Based Anode for High-Energy Li-Ion Batteries.

Silicon (Si) stands out as a promising high-capacity anode material for high-energy Li-ion batteries. However, a drastic volume change of Si during cycling leads to the electrode structure collapse and interfacial stability degradation. Herein, a multifunctional quasisolid gel polymer electrolyte (QSGPE) is designed, which is synthesized through the in situ polymerization of methylene bis(acrylamide) with silica-nanoresin composed of nanosilica and a trifunctional cross-linker in cells, leading to the creation of a "breathing" three-dimensional elastic Li-ion conducting framework that seamlessly integrates an electrode, a binder, and an electrolyte. The silicon particles within the anode are encapsulated by buffering the QSGPE after cross-linking polymerization, which synergistically interacts with the existing PAA binder to reinforce the electrode structure and stabilize the interface. In addition, the formation of the LiF- and Li3N-rich SEI layer further improves the interfacial property. The QSGPE demonstrates a wide electrochemical window until 5.5 V, good flame retardancy, high ionic conductivity (1.13 × 10-3 S cm-1), and a Li+ transference number of 0.649. The advanced QSGPE and cell design endow both nano- and submicrosized silicon (smSi) anodes with high initial Coulombic efficiencies over 88.0% and impressive cycling stability up to 600 cycles at 1 A g-1. Furthermore, the NCM811//Si cell achieves capacity retention of ca. 82% after 100 cycles at 0.5 A g-1. This work provides an effective strategy for extending the cycling life of the Si anode and constructing an integrated cell structure by in situ polymerization of the quasisolid gel polymer electrolyte.

Enhanced interface protection of freestanding Si anodes in carbon fiber nanotube by introducing MoO3 buffering layers

Developing Silicon (Si) based flexible and freestanding anodes is crucial for future wearable lithium ion batteries (LIBs) with satisfiable energy density. Improving the poor conductivity and unstable structure of Si in the lithiation/delithiation processes is a significantly important challenge. In this work, we synthesized flexible composites MoO3/Si@CFNT, in which MoO3 as a decorative layer and Si nanoparticles are well encapsulated into carbon fiber nanotube (CFNT). As freestanding lithium ion battery (LIB) anodes, the as-synthesized MoO3/Si@CFNT composites exhibit excellent Li+ storage performance for both half-cell and full-cell (610 mAh g−1 @200 cycles at 0.2 A g−1 for half-cell and 159 mAh g−1 @100 cycles at 0.5 A g−1, with a capacity retention rate of 85.9 % and almost 99 % coulombic efficiency for full-cell). We demonstrated that CFNT reserves sufficient space for the volume change of Si caused by lithiation, meanwhile, the enhanced interface protection of freestanding Si anodes in CFNT was achieved by introducing MoO3 buffering layers. Furthermore, we revealed the ion/electron transport kinetics of MoO3/Si@CFNT flexible electrode by GITT and ex-situ EIS measurements. This work offers a good example and inspiring insights into the design of many other Si based flexible anodes.

Simple and Safe Synthesis of Yolk-Shell-Structured Silicon/Carbon Composites with Enhanced Electrochemical Properties.

With its substantial theoretical capacity, silicon (Si) is a prospective anode material for high-energy-density lithium-ion batteries (LIBs). However, the challenges of a substantial volume expansion and inferior conductivity in Si-based anodes restrict the electrochemical stability. To address this, a yolk-shell-structured Si-carbon composite, featuring adjustable void sizes, was synthesized using tin (Sn) as a template. A uniform coating of tin oxide (SnO2) on the surface of nano-Si particles was achieved through a simple annealing process. This approach enables the removal of the template with concentrated hydrochloric acid (HCl) instead of hydrofluoric acid (HF), thereby reducing toxicity and corrosiveness. The conductivity of Si@void@Carbon (Si@void@C) was further enhanced by using a high-conductivity carbon layer derived from pitch. By incorporating an internal void, this yolk-shell structure effectively enhanced the low Li+/electron conductivity and accommodated the large volume change of Si. Si@void@C demonstrated an excellent electrochemical performance, retaining a discharge capacity of 735.3 mAh g-1 after 100 cycles at 1.0 A g-1. Even at a high current density of 2.0 A g-1, Si@void@C still maintained a discharge capacity of 1238.5 mAh g-1.

Correlation between surface/bulk properties and electrochemical cycling performance of pure silicon anode materials

State-of-the-art lithium-ion batteries (LIBs) employ silicon (Si)-graphite composite anode with just a few percentages of Si active material, whose cycle-life relies on a stable solid electrolyte interphase (SEI) layer. As a number of various types of industrial Si active materials are currently available, an informative guideline based on the material properties and resultant cycling performance of different pure Si (i.e., without graphite) anode materials is strongly needed for material selection. The present study provides for the first time the correlation among material's surface and bulk properties, the SEI formation behavior, and cycling behavior of highly loaded pure Si anodes (2.3 mAh cm−2) prepared from four different industrial active materials, which are SiOx, carbon-coated Si, and bare Si with submicron and micron sizes. Commercial electrolyte with 10 wt% fluoroethylene carbonate additive is used for electrochemical performance evaluation. Based on solid-state NMR, XPS, and electrochemical analysis results, SiOx is determined to be relatively beneficial for practical applications beyond Si materials, in the aspects of high structural and particle morphology stability, cycling stability and suppressed interfacial resistance. This is mainly because of more effective accommodation of volume change of Si and oxygen-enriched surface (SEI) stability. The data give insight into the rational design of well-working Si-dominant or pure Si anodes for high energy density LIBs.

The Effect of the Ratio of C45 Carbon to Graphene on the Si/C Composite Materials Used as Anode for Lithium-ion Batteries

&lt;p&gt;Due to its high theoretical capacity, Silicon (Si) has shown great potential as an anode material for lithium-ion batteries (LIBs). However, the large volume change of Si during cycling leads to poor cycling stability and low Coulombic efficiency. In this study, we synthesized Si/Carbon C45:Graphene composites using a ball-milling method with a fixed Si content (20%) and investigated the influence of the C45/Gr ratio on the electrochemical performance of the composites. The results showed that carbon C45 networks can provide good conductivity, but tend to break at Si locations, resulting in poor conductivity. However, the addition of graphene helps to reconnect the broken C45 networks, improving the conductivity of the composite. Moreover, the C45 can also act as a protective coating around Si particles, reducing the volume expansion of Si during charging/discharging cycles. The Si/C45:Gr (70:10 wt%) composite exhibits improved electrochemical performance with high capacity (~1660 mAh g&lt;sup&gt;−1&lt;/sup&gt; at 0.1 C) and cycling stability (~1370 mAh g&lt;sup&gt;−1&lt;/sup&gt; after 100 cycles). This work highlights the effective role of carbon C45 and graphene in Si/C composites for enhancing the performance of Si-based anode materials for LIBs.&lt;/p&gt;

Electrophoretic Deposition as a Versatile Low-Cost Tool to Construct a Synthetic Polymeric Solid-Electrolyte Interphase on Silicon Anodes: A Model System Investigation.

The cycling of next-generation, high-capacity silicon (Si) anodes capable of 3579 mAh·g-1 is greatly hindered by the instability of the solid-electrolyte interphase (SEI). The large volume changes of Si during (de)lithiation cause continuous cracking of the SEI and its reconstruction, leading to loss of lithium inventory and extensive consumption of electrolyte. The SEI formed in situ during cell cycling is mostly composed of molecular fragments and oligomers, the structure of which is difficult to tailor. In contrast, ex situ formation of a synthetic SEI provides greater flexibility to deposit long-chain, polymeric, and elastomeric components potentially capable of maintaining integrity against the large ∼350% volume expansion of Si while also enabling electronic passivation of the surface for longer cycling and calendar life. Furthermore, polymers are amenable to structural modifications, and the desired elasticity can be targeted by selection of the SEI polymer feedstock. Herein, electrophoretic deposition (EPD) is used to apply chitosan as a synthetic SEI on model Si thin film electrodes. Comparison of synthetic SEIs obtained without (Si/Chit) and with CH3COOLi (Si/Chit+CH3COOLi) added during EPD is performed to demonstrate a facile route to tuning of the polymer SEI chemistry. Atomic force and scanning electron microscopy reveal that addition of CH3COOLi at EPD assists in conformal deposition of the synthetic SEI. During electrochemical cycling, the Chit+CH3COOLi coating nearly doubles the capacity retention versus the reference bare Si thin film. X-ray photoelectron and Fourier transform infrared spectroscopy reveal that CH3COOLi caps the -NH2 groups of chitosan through amidation during EPD, which suppresses the catalytic reduction of the electrolyte. The presented approach demonstrates and validates EPD as a low-capital route to achieving and chemistry-tuning synthetic SEIs on Si electrodes. More broadly, the method is a promising avenue toward controlled and tailored polymeric SEIs on various conversion-type electrodes with high particle volumetric expansion.

Interface engineering of Si-based anodes with fluorinated binder enabling lean-additive lithium-ion batteries

Silicon (Si) is a promising alternative to graphite anode for increasing the energy density of litihum-ion batteries owing to its high theoretical capacity. However, the severe volume change of Si during cycling leads to unstable solid electrolyte interphase (SEI) growth, resulting in rapid capacity fading, particularly under lean-additive electrolyte conditions. In this study, we introduce an innovative approach to interface engineering of Si anodes using a fluorinated binder, a method that forms a stable and uniform lithium fluoride (LiF)-based SEI layer under lean-additive electrolyte conditions without the need for common additives. The LiF layer not only improves the structural stability of Si electrodes but also enhances the electrolyte stability, thereby preventing undesired SEI growth by electrolyte decomposition. Benefiting from this proposed binder, the Si-based anode retains a high reversible capacity (93.7 %) after 400 cycles at 0.9 A g−1 and the full cell, pairing with LiNi0.8Co0.1Mn0.1O2 cathode, delivers a high areal capacity of 4.23 mAh cm−2 (93.4 % retention) after 200 cycles under a lean-additive electrolyte (only 3 wt% additive). The interface stabilization by fluorinated binder provides insights into the rational design of a binder for the application of Si anodes in high-energy-density lithium-ion batteries.

Rational design of three-dimensional pomegranate-shaped double-layer carbon-shell-coated Si nanoparticles as an excellent anode material for lithium-ion batteries

Double-layer carbon-shell-coated Si nanoparticles (Si@DCSS) exhibit a morphology similar to pomegranate. This structure effectively suppresses the volume change of Si in the process of ion transport, endowing Si@DCSS with excellent cyclic stability.

Self-standing high-performance Si nanoparticle anchored porous carbon fiber composites for Li-ion batteries

Silicon (Si) is a highly promising anode candidate for lithium-ion batteries. However, the huge volume change of Si during the lithiation/delithiation process might cause serious structural damage, thereby restricting its potential application. Herein, a novel self-standing electrode consisting of porous carbon coated Si (Si@p-C) nanoparticles and carbon fibers (Si@p-C/p-CF) is prepared by a facile electrospinning technique. The three-dimensional carbon fiber framework derived from polyacrylonitrile serves as the support for self-standing electrode, which exhibits superior flexibility and satisfactory electrolyte penetration ability. The porous carbon matrix on the surface of Si nanoparticles can effectively buffer the volume expansion of Si during cycling and prevent direct contact between Si and the electrolyte. Attributed to these merits, the obtained (Si@p-C)0.5/p-CF electrode exhibits outstanding cycling stability with a specific capacity of 940 mAh g−1 at 0.2 A g−1 after 400 cycles, delivering great application potential.