Effective transport network driven by tortuosity gradient enables high-electrochem-active solid-state batteries
Qingsong Liu, Han-Wen An, Xufeng Wang, Fanpeng Kong, Ye-Cai Sun, Yuxin Gong, Shuaifeng Lou, Yifan Shi, Nan Sun, Biao Deng, Jian Wang, Jiajun Wang, Jia-Jun Wang, Jia-Jun Wang
Abstract
Simultaneously achieving high electrochemical activity and high loading for solid-state batteries has been hindered by slow ion transport within solid electrodes, in particular with an increase in electrode thickness. Ion transport governed by 'point-to-point' diffusion inside a solid-state electrode is challenging, but still remains elusive. Herein, synchronized electrochemical analysis using X-ray tomography and ptychography reveals new insights into the nature of slow ion transport in solid-state electrodes. Thickness-dependent delithiation kinetics are spatially probed to identify that low-delithiation kinetics originate from the high tortuous and slow longitudinal transport pathways. By fabricating a tortuosity-gradient electrode to create an effective ion-percolation network, the tortuosity-gradient electrode architecture promotes fast charge transport, migrates the heterogeneous solid-state reaction, enhances electrochemical activity and extends cycle life in thick solid-state electrodes. These findings establish effective transport pathways as key design principles for realizing the promise of solid-state high-loading cathodes.