Dependence of the lithiation/delithiation potentials of silicon microwire anodes on their state of charge and sizes

摘要

Cycle life and cycle stability are the crucial parameters when talking about batteries. The cycle life is affected when the operational voltage range is not correctly selected. In Si anodes, their intrinsic voltage limits are given by the phase transformation potentials. The voltage limits depend not only on external parameters like the voltage sweep rate, but mostly on internal parameters like the dimensions of the Si anode, and parameters of state like the state of charge. This is investigated in the present study, using Si microwires with different thicknesses and lengths. Additionally, the wires have been pre-lithiated to specific capacity limits. The analysis has been performed through cyclic voltammetry. It has been found that while short wires exhibit a lithiation limit at 50 % state of charge (SOC), the diffusion limitations are larger in long wires, which can be easily lithiated to a higher state of charge. The study showed that the optimal wire dimension has to be found to achieve better and stable cycling performance.