Binder-Free, Flexible, and Self-Standing Non-Woven Fabric Anodes Based on Graphene/Si Hybrid Fibers for High-Performance Li-Ion Batteries

Suppression Strategies for Si Anode Volume Expansion in Li-Ion Batteries Based on Structure Design and Modification: A Review

Silicon anodes have received increasing attention due to their exceptionally high theoretical capacity in lithium-ion batteries (LIBs). However, the defect of anode volume expansion caused by solid-electrolyte interphase (SEI) crushing limits the cycle life seriously. To overcome the obstacle, one must understand the mechanism behind anode volume expansion prior to exploring the suppression strategies. In this review, the recent advances in Si-based anode modification and structural design are categorized comprehensively, the scaled-up framework structures are deeply discussed, and the impacts of various composite structures on cycling performance and Coulombic efficiency are emphasized, particularly the synergistic effects of carbon/MXene assembled with silicon. Some reliable strategies for anode volume expansion restriction have been proposed. The porous structure of monocrystalline silicon spheres reconstructed by alloy sintering can restrain volume expansion effectively due to the reshaped uniform internal stress field. The inner-stress offset induced by Si anode expansion and two-dimensional material layer collapse can provide a perfect inhibition effect on SEI fragmentation when monocrystalline silicon spheres are assembled with graphene or MXene. Moreover, how special nanoshape structures provide anode stability after long cycles are summarized. This current review will be beneficial to facilitate the exploration of strategies for suppression of Si-based anode volume expansion and to pave an avenue for extensive application of Si-based LIBs in the future.

High-Strength Silicon Anodes with High Tap Density via Compression Carbonization for Liquid and All-Solid-State Lithium-Ion Batteries

Despite the advantages of nanostructure design with a balance of capacity and cycle life, the low tap density (<1 g cm-3) and high swelling properties make nanostructured silicon far from practical in applications. Here, we design a free-standing silicon graphite composite integrated anode through facile one-pot sintering with pitch under pressure. The thermomechanical effect during compression carbonization enables the integrated electrode to achieve a high tap density of 1.51 g cm-3, >2 times that of typical free-standing electrodes. In situ expansion measurements demonstrate that the longitudinal expansion of integrated electrodes is <20% of that of conventional electrodes. A rational conductive framework enables integrated electrodes to exhibit remarkable cycling stability in both liquid lithium-ion batteries (77.6% capacity retention after 500 cycles) and all-solid-state lithium-ion batteries (98.5% capacity retention after 1000 cycles). In particular, integrated electrodes remain stable even with a high areal capacity of 12.6 mAh cm-2.

Constructing three-dimensional N-doped carbon coating silicon/iron silicide nanoparticles cross-linked by carbon nanotubes as advanced anode materials for lithium-ion batteries

Silicon (Si), have been considered as promising anode material for lithium-ion batteries (LIBs), due to its high theoretical specific capacity of 4200 mAh g-1. However, the poor electrical conductivity and large volume change during lithiation/delithiation process, resulting in poor cycling stability, and seriously hindered the practical application in LIBs. Herein, a multiple Si/FexSiy@NC/CNTs composite is synthesized and investigated as advanced anode materials for LIBs via a simple one-step method. Such multiple Si/FexSiy@NC/CNTs composite has several merits including the FexSiy can not only accommodate the huge volume change of Si nanoparticles, but also enhance the conductivity upon discharge/charge process. Furthermore, the in-situ growth CNTs may help establish a long-range conductivity, and the Nitrogen-doped carbon (NC) layer can further improve the conductivity of Si, as well as inhibit the direct contract between electrolyte and Si during cycling process. Accordingly, the Si/FexSiy@NC/CNTs-1 exhibits excellent cycling stability (a high capacity of 994.4 mAh g-1 is maintained at 1.0 A g-1 after 600cycles) and outstanding rate capability (a suitable capacity of 441.7 mAh g-1 was obtained even at 5.0 A g-1). Moreover, the assembled full cell can achieve a capacity of 141.4 mAh g-1 after 65 cycles at 1.0C, exhibiting outstanding cycling stability. This work provides a prospective way for the commercial production of high-performance Si-based anode materials for LIBs.

Flexible Porous Silicon/Carbon Fiber Anode for High-Performance Lithium-Ion Batteries

We demonstrate a cross−linked, 3D conductive network structure, porous silicon@carbon nanofiber (P−Si@CNF) anode by magnesium thermal reduction (MR) and the electrospinning methods. The P−Si thermally reduced from silica (SiO₂) preserved the monodisperse spheric morphology which can effectively achieve good dispersion in the carbon matrix. The mesoporous structure of P–Si and internal nanopores can effectively relieve the volume expansion to ensure the structure integrity, and its high specific surface area enhances the multi−position electrical contact with the carbon material to improve the conductivity. Additionally, the electrospun CNFs exhibited 3D conductive frameworks that provide pathways for rapid electron/ion diffusion. Through the structural design, key basic scientific problems such as electron/ion transport and the process of lithiation/delithiation can be solved to enhance the cyclic stability. As expected, the P−Si@CNFs showed a high capacity of 907.3 mAh g⁻¹ after 100 cycles at a current density of 100 mA g⁻¹ and excellent cycling performance, with 625.6 mAh g⁻¹ maintained even after 300 cycles. This work develops an alternative approach to solve the key problem of Si nanoparticles’ uneven dispersion in a carbon matrix.

Enhanced Rate Performance of Lithium-Ion Battery Anodes Using Cobalt Incorporated Carbon Conductive Agent

Lithium-ion battery with enhanced rate performance is of crucial importance for practical applications. Extensive studies on structural design and surface modification of electrode materials to improve the rate performance have...

A Novel Tin-Bonded Silicon Anode for Lithium-Ion Batteries

Poor cyclic stability and low rate performance due to dramatic volume change and low intrinsic electronic conductivity are the two key issues needing to be urgently solved in silicon (Si)-based anodes for lithium-ion batteries. Herein, a novel tin (Sn)-bonded Si anode is proposed for the first time. Sn, which has a high electronic conductivity, is used to bond the Si-anode material and copper (Cu) current collector together using a hot-pressed method with a temperature slightly above the melting point of Sn. The cycling performance of the electrode is studied using a galvanostatic method. Nanoindentation and peeling tests are conducted to measure the mechanical strength of the electrodes. Direct current polarization and galvanostatic intermittent titration techniques are applied to assess the conductivity of the composites. Electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy are conducted to evaluate the effect of the coating layer on the cycling ability of the composites. The Sn-bonded Si anodes show superior cycling stability and high rate performance with an improved initial Coulombic efficiency. Analyses reveal that the low-melting-point Sn helps to markedly improve the electronic conductivity of the electrodes and serves as a metallic binder as well to enhance the adhesive strength of the electrode. It is hopeful that this novel Sn-bonded Si anode provides a new insight for the development of advanced Si-based anodes for LIBs.