A polymeric cathode-electrolyte interface enhances the performance of MoS2-graphite potassium dual-ion intercalation battery

Habtom Desta Asfaw,Antonia Kotronia

doi:10.1016/j.xcrp.2021.100693

Abstract

Anion intercalation in the graphite cathode of a dual-ion battery (DIB) occurs at unusually high voltage (>4.5 V K + /K). This exacerbates electrolyte degradation and corrosion of Al current collectors, leading to poor coulombic efficiency (CE), typically <90%, and short cell life as a result. These limitations can be mitigated if a stable cathode-electrolyte interface layer (CEI) can form on the graphite electrode. In this study, we demonstrate that the performance of a potassium-based DIB can be improved with a triallyl phosphate (TAP) monomer added in 6 m KN(SO 2 CF 3 ) 2 (KTFSI)-dimethyl carbonate (DMC) electrolyte. The TAP additive forms a stable polymeric CEI on the graphite particles and thus increases the CE of the cell to 97%–99%. Together with MoS 2 -negative electrodes with a pre-formed solid electrolyte interphase (SEI) layer, the DIB concept has been shown to offer specific capacities from ∼40 to 80 mAh g −1 with an average discharge voltage of 3.7 V. • Design principle for high-performance MoS 2 -graphite dual-ion battery is proposed • Impact of electrolyte additives on the negative and positive electrodes is investigated • Triallyl phosphate is used to generate a polymeric CEI on graphite cathode • MoS 2 with pre-formed SEI layer ensures stable cycling and high coulombic efficiency A dual-ion battery operates at unusually high voltage, which is needed to intercalate anions in a graphite cathode. Asfaw et al. explore strategies to create more stable electrode-electrolyte interfaces in an effort to design potassium-based MoS 2 -natural-graphite dual-ion battery with high coulombic efficiency and long cycle life.

Highlights

We demonstrate that the performance of a potassium-based dual-ion battery (DIB) can be improved with a triallyl phosphate (TAP) monomer added in 6 m KN(SO2CF3)[2] (KTFSI)-dimethyl carbonate (DMC) electrolyte
This paper reports the design of MoS2-natural-graphite KDIB enabled by a polymeric cathode-electrolyte interface layer (CEI) layer generated in situ on graphite particles
Concentrated electrolytes suppress Al dissolution in addition to provision of ions for energy storage Raman spectroscopy was used to track ion coordination in the electrolytes consisting of KTFSI salt in DMC solvent

Summary

Introduction

Emerging battery technologies, such as potassium dual-ion batteries (KDIBs), are considered cost effective and promising for use in stationary and large-scale energy storage applications.[1,2,3] This is partly due to the relative abundance of potassium-containing minerals and the redox potential of potassium (À2.93 V versus standard hydrogen electrode [SHE]), which is comparable to that of lithium (À3.04 versus SHE) and is suited for constructing high-energy batteries.[4,5] To date, KDIBs have been demonstrated to offer specific capacities reaching $50– 100 mAh gÀ1 and cell voltages averaging $4.5–4.7 V versus K+/K.1–3,6–8 Recently, Yang et al.[9] reported that KDIBs with up to 232 mAh gÀ1 capacity can be realized using locally ordered graphitic carbon for anion storage. A 1–5 wt % of TAP additive was included in the 6 m KTFSI-DMC electrolyte to generate a stable CEI on the graphite electrode.

Results

Conclusion