Composition-gradient Design of Silicon Electrodes to Mitigate Mechanochemical Coupling Degradation

As an anode for lithium-ion batteries, silicon material has the advantage of high energy density.However, the volume effect during charge-discharge cycles causes instability in the active coating's surfaces and diffusion stress induced by internal polarization, leading to inevitable structural degradation and capacity fading.Inspired by functionally gradient materials, this study proposed a five-layer composite gradient silicon electrode.Experiments and multi-scale electro-chemo-mechanical coupled model demonstrate that the designed symmetric and linear gradient silicon electrodes effectively mitigate mechanochemical coupled degradation, showing superior cycling and rate performance compared to traditional uniform electrode.Specifically, the symmetric gradient electrode retains a specific capacity of 2065 mAhg -1 after 100 cycles at 0.2C (1C=2.65 mAcm -2 ) rate, with a capacity retention rate of 81%, while that of uniform electrode is 51%.The linear gradient electrode exhibits an average discharge capacity 1.5 times that of the uniform electrode at 1C rate.Moreover, both types of gradient electrodes demonstrate smaller impedance variations before and after cycling compared to the uniform electrode.These composite gradient electrodes 7 , : - 773 are implemented through an innovative multi-layer coating process, and improved structural stability and electrochemical performance without material modifications, providing a reference for designing and fabricating high-performance silicon electrodes.