Thickness gradient promotes the performance of Si-based anode material for lithium-ion battery

The large volume change of the silicon (Si) during the lithiation and delithiation process has long been a problem impeding its application as one of the most promising anode materials for lithium-ion batteries (LIBs). In this paper, we proposed a conceptually new idea to address this problem simply by tapering the thickness of the electrode material film. The resulting thickness-gradient electrode exhibits considerable enhancement in the electrochemical performances including capacity, capacity retention, energy density, Coulombic efficiency, and rate capability in comparison to the traditional counterparts with uniform thickness. Such enhancement in the electrochemical performance can be attributed to the lessening of the stress concentration on the interface between the electrode film and the current collector upon the volume change of Si taking place in the lithiation and delithiation process. To make the best use of this strategy, the optimal design of the gradient thickness is proposed based on the theory of stress homogenization, followed by the experimental verification. The results of this paper provide a facile, cost-effective, and scalable way for enhancing the performance of Si-based anodes for LIBs. This strategy can be further extended to the other anode materials suffering the similar lithiation-induced volume change problem.