DOI:
Authors:
Yong Xie, Guoyu Pan, Qiang Jin, Xiaoqun Qi, Tan Wang, Wei Li, Hui Xu, Yuheng Zheng, Sa Li, Long Qie, Yunhui Huang, Ju Li
Abstract:
Lean electrolyte (small E/S ratio) is urgently needed to achieve high practical energy densities in Li-S batteries, but there is a distinction between the cathode’s absorbed electrolyte (AE) which is cathode-intrinsic and total added electrolyte (E) which depends on cell geometry. While total pore volume in sulfur cathodes affects AE/S and performance, it is shown here that pore morphology, size, connectivity, and fill factor all matter. Compared to conventional thermally dried sulfur cathodes that usually render « open lakes » and closed pores, a freeze-dried and compressed (FDS-C) sulfur cathode is developed with a canal-capillary pore structure, which exhibits high mean performance and greatly reduces cell-to-cell variation, even at high sulfur loading (14.2 mg cm-2) and ultralean electrolyte condition (AE/S = 1.2 µL mg-1). Interestingly, as AE/S is swept from 2 to 1.2 µL mg-1, the electrode pores go from fully flooded to semi-flooded, and the coin cell still maintains function until (AE/S)min ≈ 1.2 µL mg-1 is reached. When scaled up to Ah-level pouch cells, the full-cell energy density can reach 481 Wh kg-1 as its E/S ≈ AE/S ratio can be reduced to 1.2 µL mg-1, proving high-performance pouch cells can actually be working in the ultralean, semi-flooded regime.