Cycle-stable Si-based composite anode for lithium-ion batteries enabled by the synergetic combination of mixed lithium phosphates and void-preserving F-doped carbon

Silicon-based materials have been considered as the promising anode candidates for next-generation high-energy-density lithium-ion batteries (LIBs). However, their widespread application is unfortu-nately restricted by severe volume variations during cycling and poor electronic conductivity. To over-come these challenges, we showcase an innovative design of dual core-shell structured Si-based nanocomposites working as anode for LIBs with boosted performance, where the Si nanoparticle core is tightly wrapped by a mixed lithium phosphate (Li3PO4/Li4P2O7) shell and void-preserving F-doped car-bon shell (denoted as Si@LPO@void@FC). For such novel structured composite, the inner L3PO4/Li4P2O7 layer acting as artificial solid-electrolyte interphase (SEI) and the outer void-preserving F-doped C can effectively tolerate the volume changes while ensuring the stability of SEI layer, facilitate the Li+ migration and electron transfer, and reinforce the structural stability during cycling. Consequently, the as-fabricated Si@LPO@void@FC anode exhibits a reversible capacity of 569 mAh/g after 500 cycles at 1 A/ g, and an exceptional long-term cycling stability with 76% capacity retention over 1000 cycles at 4.0 A/g can be achieved. Additionally, the full cell assembled with Si@LPO@void@FC anode and LiFePO4 cathode also demonstrates a good cycling performance with 117 mAh/g at 1 C for over 150 cycles with 92% ca-pacity retention, suggesting the potentiality for practical application. Furthermore, the mechanisms of the enhanced structural stability of Si@LPO@void@FC anode are carefully elaborated by substantial in situ/ex situ microscopic techniques and electrochemical tests. It is expected that our findings in this work can provide guiding significance for improving the cycling performance of Si-based composite anodes toward high-performance LIBs.(c) 2023 Elsevier Ltd. All rights reserved.