Unveiling reaction mechanisms of non-aqueous aprotic Zn-ion batteries – Zn/LiFePO4 system

Abstract

Zinc-ion batteries (ZIBs) have recently gained significant attention as a supplementary option to lithium-ion batteries with the frequent use of MnO₂ as the positive active material and aqueous solution as the electrolyte. Exploration of a non-aqueous electrolyte of Zn(OTf)₂ – LiCl in tetraethylene glycol dimethyl ether (TEGDME) and a positive active material of lithium iron phosphate (LiFePO₄ or LFP) to be into ZIBs is proposed alternatively. TEGDME, also known as tetraglyme, is better than water because it has a high boiling point (> 250 °C at the ambient condition). This implies that ZIBs can be used in high-temperature applications, especially for large-scale energy storage with solar panels. The experimental findings indicate that the electrolyte exhibited enhanced the cycleability, demonstrating a capacity of LFP about 118.8 mAh g^-1 when subjected to a current density of 10 mA g^-1. Furthermore, we measured the specific capacity of the LFP to be 108.15 mAh g^-1 after undergoing 100 cycles. We examined the working mechanism of a LFP/Zn battery in details using XANES and XRD and found that Li⁺ is only extracted from/inserted into the cathode during cycling. The findings indicate that the utilization of this non-aqueous high-boiling-point electrolyte has the potential to enhance electrochemical properties, simultaneously prolonging capacity retention.