Enabling Long-Cycling Life of Si-on-Graphite Composite Anodes via Fabrication of a Multifunctional Polymeric Artificial Solid-Electrolyte Interphase Protective Layer

Stress Mitigation of Nanosilicon Anode to Achieve Energy-Dense and Highly-Stable Full Cell

Nanosilicon (nano-Si) anode is subjected to significant stress concentration, which is caused by extrusion deformation of expanded Si nanoparticles with uneven distribution. The low-strength binder and adhesive interface are unable to withstand the stress, resulting in exfoliation and impeding the use of nano-Si anodes. This work aims to mitigate stress in a Si anode with flexible copper (Cu) skeletons that are metallurgically bonded to uniformly distributed Si nanoparticles. It is worth noting that the proposed porous Si-Cu anode exhibits improved high-load cycling performance and promising potential in the full cell, with an energy density of 463 Wh kg-1 at 0.5 C and retention of 81% after 500 cycles at 2 C. Chemo-mechanical simulation and in (ex) situ observation demonstrate that expansion stress is reduced and more evenly distributed in the anode due to uniform distribution of Si nanoparticles, flexible Cu skeletons, and adequate pores. More importantly, the stress is primarily distributed in the flexible Cu skeletons and bonding interface, preventing anode exfoliation, and ensuring efficient lithium ion/electron transference. This work sheds light on the structure construction of an alloy-type anode.

Surface ChemistryControlled SEI Layer on Silicon Electrodes by Regulating Electrolyte Decomposition

Unstable solid electrolyte interface (SEI) layers induced by significant volume changes and subsequent side reactions at the interface have prevented Si anodes from practical application in lithium-ion batteries. The interface stability plays an important role in the electrochemical performance of Si electrodes. Here, we modify the interface of a Si electrode with ion-conductive poly(ethylene glycol) diglycidyl ether (PEGDE), which controls the electrolyte decomposition route and stabilizes the SEI layer. It enables the Si electrode to achieve a capacity of more than 1800 mAh g^-1 at a current density of 2 A g^-1, with a capacity retention of 77.25% after 300 cycles. The PEGDE-decorated Si electrode also shows greatly improved rate capability, with specific capacity up to 777 mAh g^-1 even at 20 A g^-1. We demonstrate that PEGDE decoration greatly increases the Li₂CO₃ ratio in the SEI layer, which improves the interface stability and Li⁺ conductivity and hence suppresses continuous electrolyte decomposition. As a result, the structural integrity of the Si particles is maintained and capacity fading is retarded. This work reveals that surface design can effectively regulate the SEI layer composition and improve interface stability, which is a promising strategy for Si-electrode manufacture.