Reinforcement of Positive Electrode‐Electrolyte Interface without Using Electrolyte Additives Through Thermoelectrochemical Oxidation of LiPF₆ for Lithium Secondary Batteries

Abstract

Owing to the limited electrochemical stability window of carbonate electrolytes, the initial formation of a solid electrolyte interphase and surface film on the negative and positive electrode surfaces by the decomposition of the electrolyte component is inevitable for the operation of lithium secondary batteries. The deposited film on the surface of the active material is vital for reducing further electrochemical side reactions at the surface; hence, the manipulation of this formation process is necessary for the appropriate operation of the assembled battery system. In this study, the thermal decomposition of LiPF6 salt is used as a surface passivation agent, which is autocatalytically formed during high‐temperature storage. The thermally formed difluorophosphoric acid is subsequently oxidized on the partially charged high‐Ni positive electrode surface, which improves the cycleability of lithium metal cells via phosphorus‐ and fluorine‐based surface film formation. Moreover, the improvement in the high‐temperature cycleability is demonstrated by controlling the formation process in the lithium‐ion pouch cell with a short period of high‐temperature storage before battery usage.

Modulation of lithium iron phosphate electrode architecture by magnetic ordering for lithium-ion batteries

“…5c). 27–29 The pristine LFP electrode exhibited significant deposition of C–O–, O–CO–, and CO-based components on its surface. By contrast, the magnetically aligned LFP electrodes exhibited reduced surface film formation after a cycle, owing to reduced polarization.…”

Vulnerable Solid Electrolyte Interphase Deposition in Sodium-Ion Batteries from Insufficient Overpotential Development during Formation

“…Notably, the SEI is typically considered less suitable for ensuring long-term stability in SIBs, compared with LIBs. − One of the least understood characteristics of the SEI in SIB systems is its thermal stability, , which is a significant attribute for electric vehicle applications. In particular, electric vehicle operation corresponds to a high current application charge and discharge, in which the cell is exposed to elevated temperatures, such as during quick charging and discharging of batteries. , Thus, the thermal stability and passivation ability of SEI film significantly influences the aging of the batteries. ,,,− The imperfections in the SEI on the hard carbon electrode in the presence of Na-ion electrolytes lead to the consumption of Na ions in the confined cell volume through the cathodic decomposition of the electrolyte coupled to the self-discharging of the negative electrode during operation. These phenomena may result in inferior cycle performance of SIBs compared with LIBs.…”