Abstract
Calendering is a critical manufacturing step in lithium-ion battery production, as it governs the electrode microstructure and strongly influences the electrochemical performance. Gradient electrode architectures have emerged as a promising strategy to simultaneously enhance the fast-charging capability and mechanical stability of thick electrodes. Despite this progress, the calendering behavior of gradient electrodes remains largely unexplored. In this study, a coupled discrete element method–finite element method framework is established for the first time, in which 3D representative volume elements for two-layer gradient electrodes and the corresponding half-cells are developed to simulate calendering and discharge, respectively. This framework enables a systematic investigation of the relationship between calendering-induced microstructural evolution and the electrochemical performance of two-layer electrodes with particle-size and porosity gradients. Experimental validation confirms that the model accurately captures the structural evolution during calendering and electrochemical performance during discharge. The results demonstrate that, for a two-layer particle-size gradient electrode with small active material particles near the separator and large particles near the current collector (CC), calendering naturally forms a favorable gradient microstructure, leading to excellent high-rate capacity retention. Furthermore, a two-step calendering strategy is proposed to fabricate electrodes with controllable porosity gradients—featuring high porosity near the separator and low porosity near the CC—which significantly improves the rate capability. These findings provide mechanistic insights and practical design guidelines for high-performance gradient electrodes.
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