Improving the electrochemical performance of Si-based anode via gradient Si concentration

Silicon (Si) has long been regarded as one of the most promising anode materials for the next-generation lithium-ion batteries (LIBs) due to its exceptional specific capacity and apt working voltage. However, the drastic volume change of Si during lithiation/delithiation processes tends to cause various mechanical failure problems including the delamination between current collector and electrode materials, resulting in poor stability and degradation of LIBs. Inspired by the functional graded design in natural biomaterials, we propose to solve the interfacial delamination problem by reallocating the Si in the electrode in a graded manner. The prepared graded electrodes especially those after gradient optimization are found quite successful in alleviating the interfacial delamination, resulting in higher capacity and capacity retention, higher coulombic efficiency, higher effective mass loading in comparison to the traditional ones. Specifically, the optimal graded electrode shows a charge capacity of 1299 mAh g⁻¹ after 50 cycles, which is much higher than that of the homogeneous electrode (66 mAh g⁻¹). Such a graded electrode can be easily implemented by existing manufacturing techniques and synergize with other strategies for solving the large-volume-change problem of Si. Our work provides a guideline for the design and manufacture of the graded Si-based electrodes for LIBs.