Suppressing the dissolution of organic components to construct a low-solubility SEI in sodium-ion batteries: the critical role of electrolyte additive TMSPi

Abstract

The solid electrolyte interphase (SEI) formed during repeated cycling plays crucial roles in determining the cycling stability of sodium-ion batteries (SIBs). However, SEI dissolution in SIBs is more severe than in the case of lithium-ion batteries and leads to continuous SEI fracture and recombination, as well as irreversible capacity loss, which in turn severely restricts the achievement of long-term cycling stability of SIBs. Here, tris(trimethylsilyl)phosphite (TMSPi) is proposed as an additive to promote the formation of an SEI with low solubility. TMSPi with lone-pair electrons on the phosphorus atom regulates the Na⁺ solvation structure and induces anion aggregation through interactions between TMSPi and solvents, reducing the formation of easily soluble organic components. TMSPi constructs a low solubility, dense and stable SEI by introducing Si-/P-containing organic and inorganic components through its decomposition. The HC‖NFPP pouch cell with this electrolyte demonstrates 88.53% capacity retention after 1200 cycles. In addition, TMSPi reduces the change in self-discharge voltage at 65 °C after 50 hours, 72 hours and 100 hours from 53.30 mV, 54.05 mV and 56.25 mV to 39.50 mV, 41.50 mV and 43.50 mV, respectively. The proposed strategy for SEI modulation provides a new path for the suppression of SEI dissolution, thus enhancing the cycling stability of SIBs.