Local Concentration Effect-Derived Heterogeneous Li2S2/Li2S Deposition on Dual-Phase MWCNT/Cellulose Nanofiber/NiCo2S4 Self-Standing Paper for High Performance of Lithium Polysulfide Batteries.
2020
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.
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