Redox Shuttle Additives for Sodium-Ion Batteries

Abstract

Redox shuttle additives are already known in the battery field to provide overcharge protection, mainly at high-voltage cathode electrodes. The electroactive species can get either oxidized at the cathode side or reduced at the anode side, preferentially during the battery cycling. The mechanism involves the generation of positively charged radicals during oxidation and the subsequent diffusion and reduction at the anode surface. This shuttling process continues between the electrodes through baseline electrolytes. Redox shuttle additives are extensively studied in Li-ion batteries (LIBs).1–3 Benzophenone (BP) is one of the redox shuttle additives used successfully in lithium-ion batteries.4 No report exists in the literature for BP additives in sodium-ion batteries (SIBs).This work investigates BP (an already known overcharge protecting additive) and substituted 4-methyl BP (4-methyl benzophenone) as an electrolyte additive in baseline electrolyte containing NaClO4 in EC/PC solvent on both electrodes. The aim is to investigate BP's SEI-forming properties in sodium-ion batteries. The initial half-cell test with a Hard Carbon anode without and with 0.5 wt% 4-methyl BP as the additive is shown in Fig.1. 4-Methyl BP additive shows a large increase in specific capacity from 337 mAh gm-1 to 438 mAh gm-1 at 0.1C rate in a 5 mV - 1.5 V voltage range. The oral presentation will focus on the effect of additive concentration on the battery performance of HC and polyanionic cathode NVP in half-cell and full-cell configurations in Na-ion batteries.