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Nanostructured silicon-based materials are the promising anodes for next-generation lithium-ion batteries. However, as the result of the weak adhesion of solid-electrolyte interphase (SEI) to Si, the fracture, exfoliation and subsequent regrowth of SEI layer on the expanded Si remains unsolved, leading to low initial Coulombic efficiency (ICE) (50–80%). Herein, the Ti‒Si covalent bond between nano-Si and MXene-derived artificial SEI layer is elaborately introduced, to effectively strengthen the interfacial stability and suppress the excessive interfacial side reaction. Upon the three-times expansion during first cycling, the as-obtained anodes with the ultrathin SEI still deliver a high ICE of 91.4%. Due to the stable interfacial ionic conduction, remarkable capacity retention of 90.7% after 1000 cycles at 5 A g−1 with an average Coulombic efficiency of 99.8% could be maintained. This strategy provides new insight into designing durable alloy anodes from the point of the interfacial adhesion strength. The low initial Coulombic efficiency (ICE) of nanostructured Si-based anodes remains unsolved. In this work, a covalently bonded SEI layer design is proposed for the first time to achieve high ICE. The high interfacial adhesion induced by the strong Ti‒Si covalent bond avoids the fracture and exfoliation of SEI layer, leading to the ultrathin SEI layer of 10 nm and high ICE of 91.4%. Our work provides a new insight into designing high ICE alloy anodes from the point of the interfacial adhesion strength. [Display omitted] • A robust artificial SEI layer with abundant covalent bonds on Si anode is rationally designed. • An ultrathin SEI layer of 10 nm is obtained owing to the tremendously decreased interfacial side reaction upon cycling. • High initial Coulombic efficiency of 91.4% and robust cycling stability over 1000 cycles are achieved. [ABSTRACT FROM AUTHOR]

• A 3D in situ crosslinked network is prepared as eco-friendly and low-cost binder. • Fluorinated carbon atoms and space linker groups of binder influence the capacity. • Cell performances are improved for Si and Si/SiO–graphite composite anodes. In this work, an in situ crosslinked network is prepared as the binder of silicon (Si), Si-graphite and silicon oxide (SiO)-graphite anodes. Fluorinated hydrolyzed corn starch synthesized by emulsifier-free polymerization is mixed with equal corn starch and 0.1 mg mL−1 dopamine, consequently form reversible interactions with electrode particles and copper foil, which plays a vital role in maintaining electrode structural integrity. It is found that the electrochemical performances of Si electrodes are heavily influenced by fluorinated carbon atoms and space linker groups of perfluoroalkyl side chains in polymeric binder. Binder with poly(N-methylperfluorobutane-1-sulfonamide ethyl acrylate) side chains (SSC4SA) exhibits the best performance, which realizes an initial discharge capacity of 3801 mAh g−1 and 88.0% capacity retention at 1 A g−1 after 100 cycles. Si-graphite and SiO–graphite composite electrodes with the mass ratio of 15:73 are prepared applying SSC4SA binder. The capacity retention of composite electrodes are 58.7% and 95.6% after 200 and 500 cycles respectively, which are far superior to commercial carboxyl methyl cellulose-styrene butadiene rubber (CMC-SBR) binder based electrodes. Such simply preparation method and the understanding of design principles for silicon anode binders in molecular-level are useful for further fundamental researches and practical applications. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Silicon is known for high-capacity yet large-volume-change properties when used as lithium storage material. Polymeric binders substantially contribute to improving the cycling life and increasing areal capacity of silicon anode. Herein, a robust network binder (PG-c-ECH) via localized linking by small molecules is proposed to achieve stable cycling performance of silicon anode with high areal capacity. Peach gum (PG) is rich in abundant hydroxyl and carboxyl groups that conventionally ensure a strong binding affinity between the PG and Si. The epichlorohydrin (ECH) introduced as the short-chain chemical crosslinker further enhances the localized linking for the polymer chains. The resultant PG-c-ECH owns durable interfacial adhesion and outstanding mechanical properties to stabilize the structural integrity of Si anode. Herein, a robust network binder (PG-c-ECH) via localized linking by small molecules is proposed for high-areal-capacity Si anode. Because of its strong interfacial adhesion and excellent mechanical properties, the PG-c-ECH binder could tolerate the huge volume changes of Si active materials during repeated cycling. The Si electrodes using PG-c-ECH as the binder exhibit stable cycling performances at practical-level areal capacities. ga1 • A robust network binder (PG-c-ECH) via localized linking by small molecules is proposed. • The Si@PG-c-ECH electrode can be cycled over 10 mAh cm−2 for 35 cycles. • The Si@PG-c-ECH electrode achieves an ultrahigh discharge areal capacity of 60.00 mAh cm−2. • The full-cell using the Si@PG-c-ECH anode shows a relatively stable cycling performance. [ABSTRACT FROM AUTHOR]

Silicon (Si) anodes are advantageous for application in lithium-ion batteries in terms of their high theoretical capacity (4200 mAh g -1 ), appropriate operating voltage (<0.4 V vs Li/Li + ), and earth-abundancy. Nevertheless, a large volume change of Si particles emerges with cycling, triggering unceasing breakage/re-formation of the solid-electrolyte interphase (SEI) and thereby the fast capacity degradation in traditional carbonate-based electrolytes. Herein, it is demonstrated that superior cyclability of Si anode is achievable using a nonflammable ether-based electrolyte with fluoroethylene carbonate and lithium oxalyldifluoroborate dual additives. By forming a high-modulus SEI rich in fluoride (F) and boron (B) species, a high initial Coulombic efficiency of 90.2% is attained in Si/Li cells, accompanied with a low capacity-fading rate of only 0.0615% per cycle (discharge capacity of 2041.9 mAh g -1 after 200 cycles). Full cells pairing the unmodified Si anode with commercial LiFePO 4 (≈13.92 mg cm -2 ) and LiNi 0.5 Mn 0.3 Co 0.2 O 2 (≈17.9 mg cm -2 ) cathodes further show extended service life to 150 and 60 cycles, respectively, demonstrating the superior cathode-compatibility realized with a thin and F, B-rich cathode electrolyte interface. This work offers an easily scalable approach in developing high-performance Si-based batteries through Si/electrolyte interphase regulation., (© 2021 Wiley-VCH GmbH.)

The huge volume change of silicon anode during cycling results in unstable solid electrolyte interface (SEI), causing rapid performance degradation. Natural SEI layer has a heterogeneous structure, results in the inhomogeneous Li+ diffusion. The repeated destruction and regeneration of SEI aggravate the inhomogeneity of Li+ diffusion at the interface, leading to non-uniform alloy reaction in the Si bulk. In this work, the silicon surface is passivated by an ultrathin uniform chitosan layer with abundant lithiophilic groups. The capacity of chitosan-coated Si (Si@CS) could reach 1500 mAh g−1 at a current density of 1 A g−1, and the capacity retention remains 91% after 400 cycles. It is demonstrated that the oxygen and nitrogen atoms in chitosan are coordinated with Li+, providing uniformly distributed Li+ transfer sites, results in a homogeneous Li+ flux in the surface layer. Interestingly, a nano-scale ordered atomic arrangement is observed in the delithiated Si@CS, which contributes to more stable and reversible lithiation/delithiation reaction of the Si@CS electrode. It is proposed that optimizing the reaction interface on the Si surface is able to alter the Li-ion diffusion kinetics and structure transition behavior of silicon, which can improve the structure reversibility and stability during cycling. An ultrathin chitosan layer is applied to improve the lithiation homogeneity of Si particles, which acts as a one-phase SEI layer. By providing homogeneous Li+ flux and constraining the stress, the chitosan layer adjusts the atomic arrangement of the delithiated Si to ordered nanostructure, and hence improves the Li+ diffusion property and reversibility in the Si bulk. Image 1 • The lithiophilic interface provides uniform Li+ flux enabling homogeneous lithiation. • Nano-ordered Si atomic arrangement is formed by homogeneous lithiation. • DRT function is applied to distinguish the different electrochemical processes. [ABSTRACT FROM AUTHOR]

Keywords: Core-shell nanostructures; heteroatom-doping; interfacial property; lithium-ion batteries; silicon anodes EN Core-shell nanostructures heteroatom-doping interfacial property lithium-ion batteries silicon anodes 1393 1393 1 05/06/20 20200504 NES 200504 B Silicon-based composites b have been recognized as a promising anode material for high-energy lithium-ion batteries (LIBs). In this Minireview, the effects of heteroatom doping on the interfacial properties of Si-based anodes and some typical strategies for interface doping are highlighted. Core-shell nanostructures, heteroatom-doping, interfacial property, lithium-ion batteries, silicon anodes. [Extracted from the article]

• Van der Waals interaction provides frameworks to Si for structural integrity. • Organic coating materials work as balloon on Si to ensure electrical contact. • Strong chemical interaction is a key to Si anode. • Various kinds of interaction are reviewed and some suggestions are discussed. Silicon (Si) is the most promising active anode material in lithium-ion batteries due to its high lithiation/delithiation capacity, abundant availability and low discharge potential as compared to graphite and other types of alloys. However, Si as an anode material faces volume change problem during electrochemical process as well as low electric and ionic conductivity which leads to formation of unstable solid electrolyte interphase (SEI) film and electrical contact loss. To overcome these challenges, many attempts have been made to modify Si-based anode materials. Coupling of Si with matrices (binders, amorphous carbon, polymers, graphene, carbon nanofibers and carbon nanotubes) has been considered the promising strategy for stable lithium storage due to high mechanical and electrical properties. The interaction between Si and matrices, however, has been rarely explored. In this review, we focused on exploring the physical and chemical interactions between Si and matrices (as an anode materials) as well as pros and cons associated with these variety of interactions. Our aim is to compile a comprehensive explanation on composites made up of Si/matrices and the nature of interactions exist within Si based anode materials. Moreover, keeping the future prospective in mind, some far-reaching suggestions have been proposed regarding stable Si anodes for next generation LIBs. [ABSTRACT FROM AUTHOR]

Silicon has been considered as a potential alternative of anodes for advanced lithium ion battery as it possesses high capacity and abundance. However, it encounters excessive volume expansion and inferior electoral conductivity, which imposes restrictions on its further development. In order to address these two problems, yolk-shell structure is employed, in which there is a suitable void for the expansion with a shell to protect the core and promote the conductivity. Here, by the inspiration from the egg holders and inverse-opal structure, an egg-stacking-like Si/C composite (ES) anode with spherical air holes was fabricated to gather the yolk-shell particles in a 3D carbon network with abundant channels allowing electrolyte to enter the material, which can facilitate the cycling performance. The half-cell battery assembled with these anodes presents high capacity and good rate performance, with a capacity reduction of only 2–7% per current density. And the cycling performance of ES anode is also praiseworthy that it delivers a high reversible discharge capacity of 2175 mAh g−1 after 300 cycles at 0.5 A g−1. This kind of structure design is expected to be applicative for most of large-volume-change anodes. • A novel structure is designed by the inspiration of egg-holders. • Such secondary particles can significantly limit the polarization and facilitate the cycling performance. • The anode delivers a high reversible discharge capacity of 2175 mAh g−1 after 300 cycles at 0.5 A g−1. [ABSTRACT FROM AUTHOR]

Si has attracted considerable interest as a promising anode material for next-generation Li-ion batteries owing to its outstanding specific capacity. However, the commercialization of Si anodes has been consistently limited by severe instabilities originating from their significant volume change (approximately 300%) during the charge-discharge process. Herein, we introduce an ultrafast processing strategy of controlled multi-pulse flash irradiation for stabilizing the Si anode by modifying its physical properties in a spatially stratified manner. We first provide a comprehensive characterization of the interactions between the anode materials and the flash irradiation, such as the condensation and carbonization of binders, sintering, and surface oxidation of the Si particles under various irradiation conditions (e.g., flash intensity and irradiation period). Then, we suggest an effective route for achieving superior physical properties for Si anodes, such as robust mechanical stability, high electrical conductivity, and fast electrolyte absorption, via precise adjustment of the flash irradiation. Finally, we demonstrate flash-irradiated Si anodes that exhibit improved cycling stability and rate capability without requiring costly synthetic functional binders or delicately designed nanomaterials. This work proposes a cost-effective technique for enhancing the performance of battery electrodes by substituting conventional long-term thermal treatment with ultrafast flash irradiation.

Establishing a stable, stress-relieving configuration is imperative to achieve a reversible silicon anode for high energy density lithium-ion batteries. Herein, we propose a silicon composite anode (denoted as T-Si@C), which integrates free space and mixed carbon shells doped with rigid TiO 2 /Ti 5 Si 3 nanoparticles. In this configuration, the free space accommodates the silicon volume fluctuation during battery operation. The carbon shells with embedded TiO 2 /Ti 5 Si 3 nanoparticles maintain the structural stability of the anode while accelerating the lithium-ion diffusion kinetics and mitigating interfacial side reactions. Based on these advantages, T-Si@C anodes demonstrate an outstanding lithium storage performance with impressive long-term cycling reversibility and good rate capability. Additionally, T-Si@C//LiFePO 4 full cells show superior electrochemical reversibility. This work highlights the importance of rational structural manipulation of silicon anodes and affords fresh insights into achieving advanced silicon anodes with long life.

Neutralization of poly(acrylic acid) (PAA)-based binders using lithium hydroxide is a common strategy for fabricating silicon anode laminates, which improves rheological properties of slurries toward high-quality electrode laminates. However, the significantly increased basicity causes degradation of Si particles while the irreversible conversion of carboxylic acid groups to lithium carboxylates undermines the binding strength, collectively leading to adverse cycling performance of the fabricated Si anodes. Herein, a novel neutralization process for PAA binders is developed. A weak base, ammonia (NH 3 ), was discovered as a neutralizing agent that still promotes rheological response of binder solutions but results in a reduced pH increase. Interestingly, the resulting ammonium carboxylate groups may cleave during the drying process to restore the neutralized PAA (PAA-NH 3 ) binders to their pristine states. The best-performing composition of 50% neutralization (PAA-50%NH 3 ) provides comparable rheological response as a PAA-Li binder as well as much improved cycling performance. The half-cells using the PAA-50%NH 3 binder can deliver 60% capacity retention over 100 cycles at C/3 rate, affording a 23.8% increase compared to PAA-Li half-cells. This restorable neutralization process of PAA binders represents an innovative strategy of mitigating issues from slurry processing of Si particles to achieve concurrent improvements in high-quality lamination and cycling performance.

Silicon anode with extremely high theoretical specific capacity (≈4200 mAh g -1 ), experiences huge volume changes during Li-ion insertion and extraction, causing mechanical fracture of Si particles and the growth of a solid-electrolyte interface (SEI), which results in a rapid capacity fading of Si electrodes. Herein, a mechanically reinforced localized structure is designed for carbon-coated Si nanoparticles (C@Si) via elongated TiO 2 nanotubes networks toward stabilizing Si electrode via alleviating mechanical strain and stabilizing the SEI layer. Benefited from the rational localized structure design, the carbon-coated Si nanoparticles/TiO 2 nanotubes composited electrode (C@Si/TiNT) exhibits an ideal electrode thickness swelling, which is lower than 1% after the first cycle and increases to about 6.6% even after 1600 cycles. While for traditional C@Si/carbon nanotube composited electrode, the initial swelling ratio is about 16.7% and reaches ≈190% after 1600 cycles. As a result, the C@Si/TiNT electrode exhibits an outstanding capacity of 1510 mAh g -1 at 0.1 A g -1 with high rate capability and long-time cycling performance with 95% capacity retention after 1600 cycles. The rational design on mechanically reinforced localized structure for silicon electrode will provide a versatile platform to solve the current bottlenecks for other alloyed-type electrode materials with large volume expansion toward practical applications., (© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The fabrication of silicon (Si) anode materials derived from high silica-containing plants enables effective utilization of subsidiary agricultural products. However, the electrochemical performances of synthesized Si materials still require improvement and thus need further structural design and morphology modifications, which inevitably increase preparation time and economic cost. Here, the conversion of corn leaves into Si anode materials is reported via a simple aluminothermic reduction reaction without other modifications. The obtained Si material inherits the structural characteristics of the natural corn leaf template and has many inherent advantages, such as high porosity, amorphous/crystalline mixture structure, and high-valence SiO x residuals, which significantly enhance the material's structural stability and electrode adhesive strength, resulting in superior electrochemical performances. Rate capability tests show that the material delivers a high capacity of 1200 mA h g -1 at 8 A g -1 current density. After 300 cycles at 0.5 A g -1 , the material maintains a high specific capacity of 2100 mA h g -1 , with nearly 100% capacity retention during long-term cycling. This study provides an economical route for the industrial production of Si anode materials for Lithium-Ion batteries., (© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Silicon-based materials are the desirable anodes for next-generation lithium-ion batteries; however, the large volume change of Si during the charging/discharging process causes electrode fracture and an unstable solid-electrolyte interphase (SEI) layer, which severely impair their stability and Coulombic efficiency. Herein, a bundle of silicon nanoparticles is encapsulated in robust micrometer-sized MXene frameworks, in which the MXene nanosheets are precrumpled by capillary compression force to effectively buffer the stress induced by the volume change, and the abundant covalent bonds (Ti-O-Ti) between adjacent nanosheets formed through a facile thermal self-cross-linking reaction further guarantee the robustness of the MXene architecture. Both factors stabilize the electrode structure. Moreover, the abundant fluorine terminations on MXene nanosheets contribute to an in situ formation of a highly compact, durable, and mechanically robust LiF-rich SEI layer outside the frameworks upon cycling, which not only shuts down the parasitic reaction between Si and an organic electrolyte but also enhances the structural stability of MXene frameworks. Benefiting from these merits, the as-prepared anodes deliver a high specific capacity of 1797 mA h g -1 at 0.2 A g -1 and a high capacity retention of 86.7% after 500 cycles at 2 A g -1 with an average Coulombic efficiency of 99.6%. Significantly, this work paves the way for other high-capacity electrode materials with a strong volume effect.

The investigation indicates that lithium trapping in Si anode of lithium‐ion battery is one of the key factors to affect the coulombic efficiency and capacity decay during high rate cycling. Here, it is demonstrated that LiAlO2 as an artificial solid electrolyte interphase (SEI) on commercial Si nanoparticles can effectively address the lithium trapping issues of Si anode to improve its electrochemical performance. By investigating the structure evolution of Si with in situ Raman and ex situ X‐ray diffraction measurements, it is demonstrated that artificial solid electrolyte interphase layer significantly improves the kinetics of lithium alloying/dealloying process due to its better electrochemical performance comparing to the natural SEI. Owing to the artificial SEI coating, the Si anode demonstrates a superior electrochemical performance, which offers a specific capacity of 1106 mAh g−1 at a current density of 4000 mA g−1 with capacity retention of 90.9% after 500 cycles. [ABSTRACT FROM AUTHOR]

Developing high‐performance batteries through applying renewable resources is of great significance for meeting ever‐growing energy demands and sustainability requirements. Biomaterials have overwhelming advantages in material abundance, environmental benignity, low cost, and more importantly, multifunctionalities from structural and compositional diversity. Therefore, significant and fruitful research on exploiting various natural biomaterials (e.g., soy protein, chitosan, cellulose, fungus, etc.) for boosting high‐energy lithium‐based batteries by means of making or modifying critical battery components (e.g., electrode, electrolyte, and separator) are reported. In this review, the recent advances and main strategies for adopting biomaterials in electrode, electrolyte, and separator engineering for high‐energy lithium‐based batteries are comprehensively summarized. The contributions of biomaterials to stabilizing electrodes, capturing electrochemical intermediates, and protecting lithium metal anodes/enhancing battery safety are specifically emphasized. Furthermore, advantages and challenges of various strategies for fabricating battery materials via biomaterials are described. Finally, future perspectives and possible solutions for further development of biomaterials for high‐energy lithium‐based batteries are proposed. [ABSTRACT FROM AUTHOR]

Although silicon is considered as one of the most promising anode materials in next‐generation lithium‐ion batteries, large volumetric expansion during cycling hampers its practical application. The fabrication of silicon/carbon composites is an effective way to improve electrical conductivity and inhibit electroactive material delaminating from the current collector. Herein, a graphitic carbon‐coated porous silicon nanospheres (p‐SiNSs@C) composite is prepared through a chemical vapor deposition (CVD) technique by using the magnesiothermic reduction by‐product MgO as a template and catalyst. With the template of in situ generation of MgO, the p‐SiNSs@C material is obtained in a very short time. Due to the graphitic carbon shell and porous structure inside the silicon nanospheres, the obtained p‐SiNSs@C, with 8 min carbon growing time (p‐SiNSs@C‐2), deliver a high initial reversible capacity of 2220 mAh g−1 at 0.1 A g−1 and respectable rate capability. Furthermore, the p‐SiNSs@C‐2//LiCoO2 Li‐ion full cell displays a high energy density of ≈409 Wh kg−1 and good cycling performance. The high performance of the p‐SiNSs@C‐2 composite can be attributed to the synergistic effect of nanoscale‐sized Si, porous structure, and stable carbon shell. [ABSTRACT FROM AUTHOR]

Silicon anodes are regarded as one of the most promising alternatives to graphite for high energy‐density lithium‐ion batteries (LIBs), but their practical applications have been hindered by high volume change, limited cycle life, and safety concerns. In this work, nonflammable localized high‐concentration electrolytes (LHCEs) are developed for Si‐based anodes. The LHCEs enable the Si anodes with significantly enhanced electrochemical performances comparing to conventional carbonate electrolytes with a high content of fluoroethylene carbonate (FEC). The LHCE with only 1.2 wt% FEC can further improve the long‐term cycling stability of Si‐based anodes. When coupled with a LiNi0.3Mn0.3Co0.3O2 cathode, the full cells using this nonflammable LHCE can maintain >90% capacity after 600 cycles at C/2 rate, demonstrating excellent rate capability and cycling stability at elevated temperatures and high loadings. This work casts new insights in electrolyte development from the perspective of in situ Si/electrolyte interphase protection for high energy‐density LIBs with Si anodes. [ABSTRACT FROM AUTHOR]

Silicon (Si) has been extensively studied as an anode material for lithium‐ion batteries due to its high specific capacity. However, the low conductivity and huge volume expansion of Si during cycles usually result in poor cyclic life span and poor rate performance. Herein, based on coordination engineering, a novel composite, i.e., Si@ZnS@ N,S‐doped reduced graphene oxide (rGO) is fabricated by the one‐step vulcanization of Si@ZIF‐8@rGO. In the composite material, N,S‐doped rGO can significantly improve the electronic conductivity, ZnS leads to the improvement in the ionic conductivity of the material, and the high capacity of ZnS improves the capacity of the composite material. As a result, the material exhibits good electrochemical performance with a high specific capacity of 1218 mAh g−1 even after 500 cycles at 0.5 A g−1. [ABSTRACT FROM AUTHOR]

The alloying reaction of silicon with lithium in negative electrodes for lithium‐ion batteries causes brutal morphological changes that severely degrade their cyclability. In this study, the dynamics of their expansion and contraction, of their cracking in the bulk and of their debonding at the interface with the current collector are visualized by in situ synchrotron X‐ray computed tomography and quantified from appropriate 3D imaging analyses. Two electrodes made with same silicon material having reasonable particle size distribution from an applied point of view are compared: one fabricated according to a standard process and the other one prepared with a maturation step, which consists in storing the electrode in a humid atmosphere for a few days before drying and cell assembly. All morphological degradations are significantly restrained for the matured electrode, confirming the great efficiency of this maturation step to produce a more ductile and resilient electrode architecture, which is at the origin of the major improvement in their cyclability. [ABSTRACT FROM AUTHOR]

Silicon (Si) has been well recognized as a promising candidate to replace graphite because of its earth abundance and high‐capacity storage, but its large volume changes upon lithiation/delithiation and the consequential material fracturing, loss of electrical contact, and over‐consumption of the electrolyte prevent its full application. As a countermeasure for rapid capacity decay, a composite electrode of graphite and Si has been adopted by accommodating Si nanoparticles in a graphite matrix. Such an approach, which involves two materials that interact electrochemically with lithium in the electrode, necessitates an analytical methodology to determine the individual electrochemical behavior of each active material. In this work, a methodology comprising differential plots and integral calculus is established to analyze the complicated interplay among the two active batteries and investigate the failure mechanism underlying capacity fade in the blend electrode. To address performance deficiencies identified by this methodology, an aluminum alkoxide (alucone) surface‐modification strategy is demonstrated to stabilize the structure and electrochemical performance of the graphite‐Si composite electrode. The integrated approach established in this work is of great importance to the design and diagnostics of a multi‐component composite electrode, which is expected to be high interest to other next‐generation battery system. In this study, a methodology comprising differential plots and integral calculus is established to analyze the failure mechanism underlying capacity fade of composite graphite–Si electrode. To address performance deficiencies identified by this methodology, an aluminum alkoxide surface‐modification strategy to stabilize the structure and electrochemical performance of the graphite–Si composite electrode is demonstrated. [ABSTRACT FROM AUTHOR]

Metallic matrix materials have emerged as an ideal platform to hybridize with next-generation electrode materials such as silicon for practical applications in Li-ion batteries. However, these metallic species commonly exist in the form of isolated particles, failing to provide enough free space for silicon volume changes as well as continuous charge transport pathways. Herein, three-dimensional (3D) metallic frameworks with interconnected pore channels and conductive skeletons, have been synthesized from inorganic gel precursors as buffering/conducting matrices to boost lithium storage performance of silicon anodes. As a proof-of-concept demonstration, commercial Si particles are in situ immobilized within the Sn-Ni alloy framework via a facile gel-reduction route, and the rearrangement of Si particles during cycling increases the dispersity of Si in the Sn-Ni framework as well as their synergic effects toward lithium storage. The Si@Sn-Ni all-metallic framework manifests high structural integrity, 3D Li + /e - mixed conduction pathway, and synergic effects of interfacial bonding and concurrent reaction dynamics between active Si and Sn, enabling long-term cycle life (1205 mA h g -1 after 100 cycles at 0.5 A g -1 ) and superior rate capability (653 mA h g -1 at 10 A g -1 ).

Despite its very high capacity (4200 mAh g -1 ), the widespread application of the silicon anode is still hampered by severe volume changes (up to 300%) during cycling, which results in electrical contact loss and thus dramatic capacity fading with poor cycle life. To address this challenge, 3D advanced Mxene/Si-based superstructures including MXene matrix, silicon, SiO x layer, and nitrogen-doped carbon (MXene/Si@SiO x @C) in a layer-by-layer manner were rationally designed and fabricated for boosting lithium-ion batteries (LIBs). The MXene/Si@SiO x @C anode takes the advantages of high Li + ion capacity offered by Si, mechanical stability by the synergistic effect of SiO x , MXene, and N-doped carbon coating, and excellent structural stability by forming a strong Ti-N bond among the layers. Such an interesting superstructure boosts the lithium storage performance (390 mAh g -1 with 99.9% Coulombic efficiency and 76.4% capacity retention after 1000 cycles at 10 C) and effectively suppresses electrode swelling only to 12% with no noticeable fracture or pulverization after long-term cycling. Furthermore, a soft package full LIB with MXene/Si@SiO x @C anode and Li[Ni 0.6 Co 0.2 Mn 0.2 ]O 2 (NCM622) cathode was demonstrated, which delivers a stable capacity of 171 mAh g -1 at 0.2 C, a promising energy density of 485 Wh kg -1 based on positive active material, as well as good cycling stability for 200 cycles even after bending. The present MXene/Si@SiO x @C becomes among the best Si-based anode materials for LIBs.

A modified natural polysaccharide (carboxymethylated gellan gum) is investigated as a water-soluble high-performance binder for silicon anodes in lithium-ion batteries to improve poor cycle life and fast capacity fade of silicon anodes due to dramatic volume expansion during lithiation/delithiation process. The numberof carboxyl and acetyl groups distributed homogeneously in the modified polysaccharide polymer chain can form strong hydrogen bonds with the surface of Si particle and copper current collector, thus effectively restricting the volume change of silicon and maintaining electronic integrity of Si electrodes during repeated charge/discharge cycles. As a result, Si anodes with carboxymethylated natural polysaccharide polymer present high capacity performance, excellent rate capability, and stable cycling.

Silicon (Si) has been well recognized as a promising candidate to replace graphite because of its earth abundance and high-capacity storage, but its large volume changes upon lithiation/delithiation and the consequential material fracturing, loss of electrical contact, and over-consumption of the electrolyte prevent its full application. As a countermeasure for rapid capacity decay, a composite electrode of graphite and Si has been adopted by accommodating Si nanoparticles in a graphite matrix. Such an approach, which involves two materials that interact electrochemically with lithium in the electrode, necessitates an analytical methodology to determine the individual electrochemical behavior of each active material. In this work, a methodology comprising differential plots and integral calculus is established to analyze the complicated interplay among the two active batteries and investigate the failure mechanism underlying capacity fade in the blend electrode. To address performance deficiencies identified by this methodology, an aluminum alkoxide (alucone) surface-modification strategy is demonstrated to stabilize the structure and electrochemical performance of the graphite-Si composite electrode. The integrated approach established in this work is of great importance to the design and diagnostics of a multi-component composite electrode, which is expected to be high interest to other next-generation battery system.

In situ weaving an all-carbon graphdiyne coat on a silicon anode is scalably realized under ultralow temperature (25 °C). This economical strategy not only constructs 3D all-carbon mechanical and conductive networks with reasonable voids for the silicon anode at one time but also simultaneously forms a robust interfacial contact among the electrode components. The intractable problems of the disintegrations in the mechanical and conductive networks and the interfacial contact caused by repeated volume variations during cycling are effectively restrained. The as-prepared electrode demostrates the advantages of silicon regarding capacity (4122 mA h g -1 at 0.2 A g -1 ) with robust capacity retention (1503 mA h g -1 ) after 1450 cycles at 2 A g -1 , and a commercial-level areal capacity up to 4.72 mA h cm -2 can be readily approached. Furthermore, this method shows great promises in solving the key problems in other high-energy-density anodes., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

With extremely high specific capacity, silicon has attracted enormous interest as a promising anode material for next-generation lithium-ion batteries. However, silicon suffers from a large volume variation during charge/discharge cycles, which leads to the pulverization of the silicon and subsequent separation from the conductive additives, eventually resulting in rapid capacity fading and poor cycle life. Here, it is shown that the utilization of a self-healable supramolecular polymer, which is facilely synthesized by copolymerization of tert-butyl acrylate and an ureido-pyrimidinone monomer followed by hydrolysis, can greatly reduce the side effects caused by the volume variation of silicon particles. The obtained polymer is demonstrated to have an excellent self-healing ability due to its quadruple-hydrogen-bonding dynamic interaction. An electrode using this self-healing supramolecular polymer as binder exhibits an initial discharge capacity as high as 4194 mAh g -1 and a Coulombic efficiency of 86.4%, and maintains a high capacity of 2638 mAh g -1 after 110 cycles, revealing significant improvement of the electrochemical performance in comparison with that of Si anodes using conventional binders. The supramolecular binder can be further applicable for silicon/carbon anodes and therefore this supramolecular strategy may increase the choice of amendable binders to improve the cycle life and energy density of high-capacity Li-ion batteries., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

New binder concepts have lately demonstrated improvements in the cycle life of high-capacity silicon anodes. Those binder designs adopt adhesive functional groups to enhance affinity with silicon particles and 3D network conformation to secure electrode integrity. However, homogeneous distribution of silicon particles in the presence of a substantial volumetric content of carbonaceous components (i.e., conductive agent, graphite, etc.) is still difficult to achieve while the binder maintains its desired 3D network. Inspired by mucin, the amphiphilic macromolecular lubricant, secreted on the hydrophobic surface of gastrointestine to interface aqueous serous fluid, here, a renatured DNA-alginate amphiphilic binder for silicon and silicon-graphite blended electrodes is reported. Mimicking mucin's structure comprised of a hydrophobic protein backbone and hydrophilic oligosaccharide branches, the renatured DNA-alginate binder offers amphiphilicity from both components, along with a 3D fractal network structure. The DNA-alginate binder facilitates homogeneous distribution of electrode components in the electrode as well as its enhanced adhesion onto a current collector, leading to improved cyclability in both silicon and silicon-graphite blended electrodes., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Silicon has been intensively studied as an anode material for lithium-ion batteries (LIB) because of its exceptionally high specific capacity. However, silicon-based anode materials usually suffer from large volume change during the charge and discharge process, leading to subsequent pulverization of silicon, loss of electric contact, and continuous side reactions. These transformations cause poor cycle life and hinder the wide commercialization of silicon for LIBs. The lithiation and delithiation behaviors, and the interphase reaction mechanisms, are progressively studied and understood. Various nanostructured silicon anodes are reported to exhibit both superior specific capacity and cycle life compared to commercial carbon-based anodes. However, some practical issues with nanostructured silicon cannot be ignored, and must be addressed if it is to be widely used in commercial LIBs. This Review outlines major impactful work on silicon-based anodes, and the most recent research directions in this field, specifically, the engineering of silicon architectures, the construction of silicon-based composites, and other performance-enhancement studies including electrolytes and binders. The burgeoning research efforts in the development of practical silicon electrodes, and full-cell silicon-based LIBs are specially stressed, which are key to the successful commercialization of silicon anodes, and large-scale deployment of next-generation high energy density LIBs., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Metal-assisted chemical etching (MACE) provides a versatile way to synthesize silicon nanowires (SiNW) of different morphologies. MACE was used to synthesize oxide-free porous and nonporous SiNW for use as anodes for lithium-ion batteries. To improve their processing behavior, the SiNW were functionalized using acrylic acid. Differential capacity plots were used as a way to identify the degradation processes during cycling through tracking the formation of Li 15 Si 4 and changes in polarization. The cycling performance between porous and nonporous SiNW differed regarding Coulombic efficiency and cycling stability. The differences were attributed to the porous hull and its ability to reduce the volume expansion, although not through its porous nature but the reduced uptake of Li ions., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Despite its highest theoretical capacity, the practical applications of the silicon anode are still limited by severe capacity fading, which is due to pulverization of the Si particles through volume change during charge and discharge. In this study, silicon nanoparticles are embedded in micron-sized porous carbon spheres (Si-MCS) via a facile hydrothermal process in order to provide a stiff carbon framework that functions as a cage to hold the pulverized silicon pieces. The carbon framework subsequently allows these silicon pieces to rearrange themselves in restricted domains within the sphere. Unlike current carbon coating methods, the Si-MCS electrode is immune to delamination. Hence, it demonstrates unprecedented excellent cyclability (capacity retention: 93.5% after 500 cycles at 0.8 A g -1 ), high rate capability (with a specific capacity of 880 mAh g -1 at the high discharge current density of 40 A g -1 ), and high volumetric capacity (814.8 mAh cm -3 ) on account of increased tap density. The lithium-ion battery using the new Si-MCS anode and commercial LiNi 0.6 Co 0.2 Mn 0.2 O 2 cathode shows a high specific energy density above 300 Wh kg -1 , which is considerably higher than that of commercial graphite anodes.

The electrochemical behavior of binder-free, germanium and silicon nanowires as high-capacity anode materials for lithium-ion battery systems is investigated in an ionic liquid electrolyte. Cyclic voltammetry, cycling tests, and impedance spectroscopy reveal a highly reversible lithium alloying/dealloying process, as well as promising compatibility between the Ge and Si materials and the electrolyte components. Reversible capacities of 1400 and 2200 mA h g -1 are delivered by the Ge and Si anodes, respectively, matching the values exhibited in conventional organic solutions. Furthermore, impressive extended cycling performance is obtained in comparison to previous research on Li alloying anodes in ionic liquids, with capacity retention overcoming 50% for Si after 500 cycles and 67% for Ge after 1000 cycles, at a current rate of 0.5C. This stable long-term cycling arises due to the ability of the electrolyte formulation to promote the transformation of the nanowires into durable porous network structures of Ge or Si nanoligaments, which can withstand the extreme volume changes associated with lithiation/delithiation. Remarkable capacity is exhibited also by composite Ge and Si nanowire electrodes. Preliminary tests with lithium cobalt oxide cathodes clearly demonstrate the feasibility of Ge and Si nanowires in full batteries.

To address the challenge of huge volume change and unstable solid electrolyte interface (SEI) of silicon in cycles, causing severe pulverization, this paper proposes a "double-shell" concept. This concept is designed to perform dual functions on encapsulating volume change of silicon and stabilizing SEI layer in cycles using double carbon shells. Double carbon shells coated Si nanoparticles (DCS-Si) are prepared. Inner carbon shell provides finite inner voids to allow large volume changes of Si nanoparticles inside of inner carbon shell, while static outer shell facilitates the formation of stable SEI. Most importantly, intershell spaces are preserved to buffer volume changes and alleviate mechanical stress from inner carbon shell. DCS-Si electrodes display a high rechargeable specific capacity of 1802 mAh g -1 at a current rate of 0.2 C, superior rate capability and good cycling performance up to 1000 cycles. A full cell of DCS-Si//LiNi 0.45 Co 0.1 Mn 1.45 O 4 exhibits an average discharge voltage of 4.2 V, a high energy density of 473.6 Wh kg -1 , and good cycling performance. Such double-shell concept can be applied to synthesize other electrode materials with large volume changes in cycles by simultaneously enhancing electronic conductivity and controlling SEI growth., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Si anodes generally suffer a tremendous volume variation during lithium alloying/dealloying reactions, resulting in severe mechanical fractures and side reactions. Therefore, managing the volume change remains a critical challenge for practical application of Si anodes in LIBs. Diverse strategies for accommodating the volume change of Si anodes are reviewed and perspectives and challenges for future research are presented. More details can be found in the Minireview by J. Cho et al. on page 1645 in Issue 11, 2015 (DOI: 10.1002/celc.201500254). [ABSTRACT FROM AUTHOR]

Si/C yolk-shell structures have been developed to deal with the major issues associated with Si anodes: the huge volume changes and the low electrical conductivity. However, the fabrication process often involves expensive starting materials and/or simultaneously generates insulated SiC, which is harmful for Si anodes. Here, silica wastes from the optical fibers industry are used as starting materials to prepare high performance Si/C materials with Si@void@C yolk-shell structure via a rational designed Al 2 O 3 coating assisted magnesiothermic process. The obtained yolk-shell Si@void@C materials have a capacity of more than 1450 mA h g -1 after 100 cycles at 0.4 A g -1 . Thanks to the easily coated and removed Al 2 O 3 layer, the general formation of SiC can be avoided which is beneficial for improving the rate performances, and a capacity of ≈800 mA h g -1 is still kept after 200 cycles at a high rate of 10 A g -1 with a low capacity loss of 0.08% per cycle., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We report novel salami-like core-sheath composites consisting of Si nanoparticle assemblies coated with indium tin oxide (ITO) sheath layers that are synthesized via coelectrospinning. Core-sheath structured Si nanoparticles (NPs) in static ITO allow robust microstructures to accommodate for mechanical stress induced by the repeated cyclical volume changes of Si NPs. Conductive ITO sheaths can provide bulk conduction paths for electrons. Distinct Si NP-based core structures, in which the ITO phase coexists uniformly with electrochemically active Si NPs, are capable of facilitating rapid charge transfer as well. These engineered composites enabled the production of high-performance anodes with an excellent capacity retention of 95.5% (677 and 1523 mAh g(-1,) which are based on the total weight of Si-ITO fibers and Si NPs only, respectively), and an outstanding rate capability with a retention of 75.3% from 1 to 12 C. The cycling performance and rate capability of core-sheath-structured Si NP-ITO are characterized in terms of charge-transfer kinetics.

We report supramolecular cross-linking of polymer binders via dynamic host-guest interactions between hyperbranched β-cyclodextrin polymer and a dendritic gallic acid cross-linker incorporating six adamantane units for high-capacity silicon anodes. Calorimetric analysis in the solution phase indicates that the given host-guest complexation is a highly spontaneous and enthalpically driven process. These findings are further verified by carrying out gelation experiments in both aqueous and organic media. The dynamic cross-linking process enables intimate silicon-binder interaction, structural stability of electrode film, and controlled electrode-electrolyte interface, yielding enhanced cycling performance. Control experiments using both α, γ-CDp with different cavity sizes and a guest molecule incorporating a single adamantane unit verified that the enhanced cycle life originates from the host-guest interaction between β-cyclodextrin and adamantane. The impact of the dynamic cross-linking is maximized at an optimal stoichiometry between the two components. Importantly, the present investigation proves that the molecular-level tuning of the host-guest interactions can be translated directly to the cycling performance of silicon anodes.

We investigate the structural, mechanical, and electronic properties of graphite-like amorphous carbon coating on bulky silicon to examine whether it can improve the durability of the silicon anodes of lithium-ion batteries using molecular dynamics simulations and ab-initio electronic structure calculations. Structural models of carbon coating are constructed using molecular dynamics simulations of atomic carbon deposition with low incident energies (1-16 eV). As the incident energy decreases, the ratio of sp ² carbons increases, that of sp ³ decreases, and the carbon films become more porous. The films prepared with very low incident energy contain lithium-ion conducting channels. Also, those films are electrically conductive to supplement the poor conductivity of silicon and can restore their structure after large deformation to accommodate the volume change during the operations. As a result of this study, we suggest that graphite-like porous carbon coating on silicon will extend the lifetime of the silicon anodes of lithium-ion batteries.

In order to keep pace with increasing energy demands for advanced electronic devices and to achieve commercialization of electric vehicles and energy-storage systems, improvements in high-energy battery technologies are required. Among the various types of batteries, lithium ion batteries (LIBs) are among the most well-developed and commercialized of energy-storage systems. LIBs with Si anodes and Li-rich cathodes are one of the most promising alternative electrode materials for next-generation, high-energy batteries. Si and Li-rich materials exhibit high reversible capacities of <2000 mAh g(-1) and >240 mAh g(-1) , respectively. However, both materials have intrinsic drawbacks and practical limitations that prevent them from being utilized directly as active materials in high-energy LIBs. Examples for Li-rich materials include phase distortion during cycling and side reactions caused by the electrolyte at the surface, and for Si, large volume changes during cycling and low conductivity are observed. Recent progress and important approaches adopted for overcoming and alleviating these drawbacks are described in this article. A perspective on these matters is suggested and the requirements for each material are delineated, in addition to introducing a full-cell prototype utilizing a Li-rich cathode and Si anode., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Coating silicon particles with a suitable thin film has appeared as a possible solution to accommodate the swelling of silicon upon lithiation and its posterior cracking and pulverization during cycling of Li-ion batteries. In particular, aluminum alkoxide (alucone) films have been recently deposited over Si anodes, and the lithiation and electrochemical behavior of the system have been characterized. However, some questions remain regarding the lithium molecular migration mechanisms through the film and the electronic properties of the alucone film. Here we use density functional theory, ab initio molecular dynamics simulations, and Green's function theory to examine the film formation, lithiation, and reactivity in contact with an electrolyte solution. It is found that the film is composed of Al-O complexes with 3-O or 4-O coordination. During lithiation, Li atoms bind very strongly to the O atoms in the most energetically favorable sites. After the film is irreversibly saturated with Li atoms, it becomes electronically conductive. The ethylene carbonate molecules in liquid phase are found to be reduced at the surface of the Li-saturated alucone film following similar electron transfer mechanisms as found previously for lithiated silicon anodes. The theoretical results are in agreement with those from morphology and electrochemical analyses.

Uniform porous silicon hollow nano-spheres are prepared without any sacrificial templates through a magnesio-thermic reduction of mesoporous silica hollow nanospheres and surface modified by the following in situ chemical polymerization of polypyrrole. The porous hollow structure and polypyrrole coating contribute significantly to the excellent structure stability and high electrochemical performance of the nanocomposite., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)