Silicon oxide is one of the most representative anode materials for lithium-ion storage. However, the poor conductivity of silicon oxide and the large volume expansion during the repeated lithium alloying/dealloying reaction have a huge impact on the cycle stability of the electrode. Here, we propose a design strategy for constructing a yolk−shell structure to enhance the electrochemical performance of the silicon oxidebased anode. Using a silane coupling agent as the raw material, organosilicon nanoparticles are prepared by hydrolysis and a selfcondensation reaction. Combining with polydiallyldimethylammonium chloride modification and polymethyl methacrylate coating, the SiO x /C@C composite with a yolk−shell structure (YS-SiO x /C@C) was obtained by one-step carbonization. The modification of polydiallyldimethylammonium chloride ensures the formation of a stable cavity during the pyrolysis process, which can effectively relieve the volume variation of the silicon oxide electrode, and the carbon shell can enhance the overall conductivity. As the anode of lithium-ion batteries, the YS-SiO x /C@C electrode showed outstanding electrochemical stability with a high specific capacity of 770 mAh g −1 and a Coulombic efficiency of 99% after 500 cycles (0.5 A g −1 ). This research provides a direction for the preparation of yolk−shell electrode materials and promotes further development of high-performance silicon oxide-based anodes.
As one of the promising anode materials, silicon has
attracted
much attention due to its high theoretical specific capacity (∼3579
mAh g–1) and suitable lithium alloying voltage (0.1–0.4
V). Nevertheless, the enormous volume expansion (∼300%) in
the process of lithium alloying has a great negative effect on its
cyclic stability, which seriously restricts the large-scale industrial
preparation of silicon anodes. Herein, we design a facile synthesis
strategy combining vanadium doping and carbon coating to prepare a
silicon-based composite (V-Si@C). The prepared V-Si@C composite does
not merely show improved conductivity but also improved electrochemical
kinetics, attributed to the enlarged lattice spacing by V doping.
Additionally, the superiority of this doping strategy accompanied
by microstructure change is embodied in the relieved volume changes
during the repeated charging/discharging process. Notably, the initial
capacity of the advanced V-Si@C electrode is 904 mAh g–1 (1 A g–1) and still holds at 1216 mAh g–1 even after 600 cycles, showing superior electrochemical performance.
This study offers an alternative direction for the large-scale preparation
of high-performance silicon-based anodes.
The poor compatibility with Li metal and electrolyte oxidation stability preclude the utilization of commercial ester‐based electrolytes for high‐voltage lithium metal batteries. This work proposes a quasi‐localized high‐concentration electrolyte (q‐LHCE) by partially replacing solvents in conventional LiPF6 based carbonated electrolyte with fluorinated analogs (fluoroethylene carbonate (FEC), 2,2,2‐trifluoroethyl methyl carbonate (FEMC)) with weakly‐solvating ability. The q‐LHCE enables the formation of an anion‐rich solvation sheath, which functions like LHCE but differs in the partial participation of weakly‐solvating cosolvent in the solvation structure. With this optimized electrolyte, inorganic‐dominated solid electrolyte interphases are achieved on both the cathode and anode, leading to uniform Li deposition, suppressed electrolyte decomposition and cathode deterioration. Consequently, q‐LHCE supports stable cycling of Li | LiCoO2 (≈3.5 mAh cm−2) cells at 4.5 V under the whole climate range (from −20 to 45 °C) with limited Li consumption. A practical ampere‐hour level graphite | LiCoO2 pouch cell at 4.5 V and aggressive Li | LiNi0.5Mn1.5O4 cell at 5.0 V with excellent capacity retention further reveals the effectiveness of q‐LHCE. The refinement of old‐fashioned carbonate electrolytes provides new perspectives toward practical high‐voltage battery systems.
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