Silicon (Si) attracts attention for its ultra-high theoretical specific capacity (3579 mAh g −1 ) as anodes for lithium-ion batteries (LIB). However, adjusting the contradiction between long life and volume expansion has always been a great challenge for Si-based anodes. In this work, we designed a mulberry-like Si-based anode material (p-SiO x /SiC@C) by an in situ self-assembly and magnesium reduction approach. The most outstanding advantage of this strategy is the formation of silicon carbide (SiC) interlayer between SiO x and carbon coating, which hinders the further reduction of SiO x and realizes controllable specific capacity. The SiC interlayer on the SiO x surface can effectively prevent the electrolyte from penetrating and stabilize the solid electrolyte interphase (SEI) well. As a result, p-SiO x /SiC@C shows stable Li + storage performance and ultra-long cycle stability. Even after 2000 cycles under 2.0 A g −1 , p-SiO x /SiC@C still maintains a complete morphology; the capacity retention rate is about 79%; the capacity loss rate is only 0.01% per cycle on average; and it is even more gratifying that the average coulombic efficiency reaches 99.7%. This work opens up a new direction for the practical application of Si-based anode materials.
Yolk-shell silicon/carbon composite encapsulated by uniform carbon shell (Si@C) are becoming an effective method to mitigate volume-related issues of Si-based anodes and maintain an excellent performance for lithium-ion batteries (LIBs). However, a uniform carbon shell in Si@C is difficult to guarantee. Herein, a facile surface-engineering-assisted strategy is described to prepare Si@C composite with low-cost modified recycled waste silicon powders (RWSi) as core coated by a uniform carbon shell-protective layer derived from the pyrolysis of poly (methyl methacrylate) (PMMA) as carbon source (m-RWSi@PMMA-C). In this process, surface-engineering is performed with silane coupling agent kh550 to functionalize the RWSi particles via a silanization reaction, guaranteeing a uniform PMMA coating which will be transformed into carbon shell-protective layer after carbonization. The m-RWSi@PMMA-C electrode delivers an optimal discharge capacity of 1083 mAhg −1 at 200 mAg −1 after 200 cycles with an initial capacity of 3176.2 mAhg −1 and a high initial Coulombic efficiency (ICE) of 75.6%. Based on these results, the recycled silicon-based anode with a uniform carbon shell-protective layer displays great application potential and it also brings a new perspective on silicon-based anodes via surface-engineering method for LIBs.
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 MoO 3 /Si@CFNT, in which MoO 3 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 MoO 3 /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 MoO 3 buffering layers. Furthermore, we revealed the ion/electron transport kinetics of MoO 3 /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.
Yang Jiyuan,Shi Minghui,Wu Wei,Zhang Qunchao,You Jun,Shi Dean,Jiang Tao
Silicon has become one of the most emerging anode materials in Li-ion batteries due to its excellent specific capacity. The incorporation of binders can significantly reduce the volume expansion of silicon during the cycling process. In this work, a novel type of cross-linked siloxane-based copolymer, poly (tert-butyl acrylate-co-vinyl tri-lactate ethyl silane) (TBA-VTLES) was designed and utilized as the binder for the silicon anode in Li-ion batteries to alleviate the inner stress of adverse volume changes and improve the electrochemical performance. The hard TBA and soft VTLES were interwoven into a 3D network to achieve the adhesive action via free radical polymerization. The soft chains in TBA-VTLES can enhance the cohesion of the copolymer to disperse residual stress, and thus avoid structural damage during lithiation. Meanwhile, the rigid chains can provide sufficient mechanical strength to maintain the integrity of silicon anode during de-lithiation. Moreover, the presence of TBA-VTLES can improve the adhesive strength between the copper collector and the binder. This novel type of siloxane-based copolymer binder with hardness and softness provides a feasible way to improve the silicon anode performance of Li-ion batteries. Graphical abstract
The synthesized cross-linked copolymer binder can improve the interfacial interaction and electrochemical performance of Si anode-- present in Graphical abstract figure-- need or not.
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