Development and improvement of the MoS6 cathode material for rechargeable all-solid-state lithium batteries

Abstract

All-solid-state lithium batteries without any liquid organic electrolytes can realize high energy density while eliminating flammability issues. The sulfide solid electrolytes with high ionic conductivity and attractive mechanical feature of plastic deformation, become the most promising solid electrolyte. Moreover, active materials such as transition metal sulfides with high specific capacity are essential to the realization of good electrochemical performance. However, the limited reversible specific capacity and large volume change of the sulfide cathodes upon cycling still hinder their application in the all-solid-state lithium batteries using sulfide electrolytes. Constructing electronic/ionic conductive networks in the cathode and realizing intimate interfacial contact at the electrolyte/cathode interface are prominent strategies to address the above issues.
Herein, MoS6 is employed as the active material of the sulfide cathode, owing to its high specific capacity enabled by the multi electron reactions of S2 2− + 2e − → 2S 2− proceeding during the charge-discharge process. Consequently, MoS6 with high S2 2− content possesses an ultra-high theoretical specific capacity of 1117 mAh g−1 , showing potential applications in constructing high energy all-solid-state battery. Furthermore, two modified composites are designed, with aims of achieving high and stable reversible specific capacity for long-term cycling. By coating a thin layer of Li7P3S11 solid sulfide electrolyte on the MoS6 particles, the Li/Li6PS5Cl/MoS6@15%Li7P3S11 all-solid-state lithium batteries show a high initial discharge capacity of 1083.8 mAh g−1 at 0.1 A g−1 and long cycle life of 1000 cycles under 1A g−1 at 25 oC. Furthermore, through ball milling of MoS6 and LiI, the as-obtained 95MoS65LiI cathode exhibit a high initial capacity of 1016.3 mAh g−1 at 0.1 A g−1 within 1.0–3.0 V and capacity retention of 301.1 mAh g−1 at 1 A g−1 after 500 cycles.
This thesis provides a material preparation guidance of alternative cathodes of MoS6 and its derivates such as MoS6@15%Li7P3S11 and 95MoS65LiI, with noticeable electrochemical performances, including high reversible capacity, long-term cycling stability, and good compatibility for all-solid-state lithium rechargeable batteries.

Date of Award	Nov 2024
Original language	English
Awarding Institution	University of Nottingham
Supervisor	Tao Wu (Supervisor), Ping Cui (Supervisor) & Xiayin Yao (Supervisor)