Local Concentration Effect-Derived Heterogeneous Li<sub>2</sub>S<sub>2</sub>/Li<sub>2</sub>S Deposition on Dual-Phase MWCNT/Cellulose Nanofiber/NiCo<sub>2</sub>S<sub>4</sub> Self-Standing Paper for High Performance of Lithium Polysulfide Batteries
Haiwei Wu, Li Wang, Jingxuan Bi, Yiyi Li, Xiaofei Pang, Zhijian Li, Qingjun Meng, Hanbin Liu, Lei Wang
Abstract
Lithium–sulfur (Li–S) batteries are highly attractive for their theoretical energy density and natural abundance, but the drawbacks of low sulfur utilization and rapid capacity fade in high-sulfur-loading cathodes still retard their practical use. To enhance kinetics in high-sulfur-loading Li–S cells, it is important to first understand and control the deposition of Li2S/Li2S from highly soluble lithium polysulfide (LiPS) during discharge processes. Here, we presented a series of multiphase-derived self-standing papers with diverse electronic conductivity and LiPS affinity for highly concentrated LiPS discharge processes and explained the Li2S/Li2S deposition behavior in detail. We demonstrated that high rate capacity and long cycle life of as-assembled paper–LiPS cathodes can be greatly depended on their phase material with high conductivity and LiPS affinity. A high-performance self-standing LiPS host–multiwalled carbon nanotube (MWCNT)/cellulose nanofiber (CNF)/NiCo2S4 (3.5 mg cm–2) can catalyze 2.85 mg cm–2 (based on sulfur) loaded LiPS to deliver a high specific capacity of 1154 mAh g–1 at 0.1C and a high rate performance of 963 mAh g–1 at 1C. We suggest that the insulating phase defect of nano-CNF and both highly electronic conductive (above 50 S cm–1) and LiPS adsorptive NiCo2S4 can promote the local concentration effect of LiPS, thus contributing to fast and stable heterogeneous particle-shaped deposition of Li2S2/Li2S and leading to high kinetics of the LiPS cathode.