A 405 W h kg−1 Ah-level lithium–sulfur pouch battery stabilized over 200 cycles by an electron-triode-like GeS2–NiS2 heterostructure

Abstract

Lithium–sulfur batteries (LSBs) form soluble polysulfides (LiPSs) during discharge, leading to decline in cycling performance, especially the failure of pouch batteries. The failure may be due to the fact that conventional sulfur hosts can only adsorb LiPSs and cannot rapidly inject and transfer electrons in electrochemical reactions. The sluggish electrochemical interconversion of LiPSs leads to continuous loss of active sulfur materials, which is a barrier to long-life commercial LSBs. Herein, an electron-triode-like GeS₂–NiS₂ heterostructure is successfully designed and synthesized to serve as a catalytic sulfur host. An Ohmic contact rather than a Schottky contact is formed between GeS₂ and NiS₂, which is proven using the ultraviolet photoelectron spectra and X-ray absorption fine structure spectra. Therefore, the LiPSs can be interconverted with an electron-triode-like model: NiS₂ acts as the emitter and injects a batch of electrons into the LiPSs (the collector) collectively through the GeS₂ base electrode, with a maximum reaction current amplification factor (β_R) of 105.87. In situ XRD and ex situ AFM indicate that the collective injection of electrons can achieve an earlier deposition of Li₂S as early as ∼80% of SOC. Ultimately, the S@GeS₂–NiS₂/rGO battery achieves a high specific capacity of 1007.8 mA h g⁻¹ at 0.5C. The 1.2 Ah pouch battery can achieve a high energy density of 405 W h kg⁻¹ and work stably for 200 cycles, highlighting its great potential for practical applications.