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.

The huge volume change of silicon anode during cycling results in unstable solid electrolyte interface (SEI), causing rapid performance degradation. Natural SEI layer has a heterogeneous structure, results in the inhomogeneous Li+ diffusion. The repeated destruction and regeneration of SEI aggravate the inhomogeneity of Li+ diffusion at the interface, leading to non-uniform alloy reaction in the Si bulk. In this work, the silicon surface is passivated by an ultrathin uniform chitosan layer with abundant lithiophilic groups. The capacity of chitosan-coated Si (Si@CS) could reach 1500 mAh g(-1) at a current density of 1 A g(-1), and the capacity retention remains 91% after 400 cycles. It is demonstrated that the oxygen and nitrogen atoms in chitosan are coordinated with Li+, providing uniformly distributed Li+ transfer sites, results in a homogeneous Li+ flux in the surface layer. Interestingly, a nano-scale ordered atomic arrangement is observed in the delithiated Si@CS, which contributes to more stable and reversible lithiation/delithiation reaction of the Si@CS electrode. It is proposed that optimizing the reaction interface on the Si surface is able to alter the Li-ion diffusion kinetics and structure transition behavior of silicon, which can improve the structure reversibility and stability during cycling.

Herein, the coordination-induced increase in the electron density of fused C6 rings in MOFs as high performance anode materials for Li+ ion batteries is described. Zn-PTCA is able to deliver a high specific capacity of 700 mA h g-1 at 50 mA g-1 and exhibits excellent cycle performance over 1100 cycles and good rate capability.