Improvement the"electrode/electrolyte"interface of sodium ion batteries by sodium difluorophosphate
Rechargeable sodium ion batteries(SIBs)have attracted significant attention as a promising energy storage supplement technology due to their similar working principle to lithium-ion batteries(LIBs)and the abundance of sodium resources.Compared to LIBs,SIBs offer several advantages,including wide resource distribution,low cost,and excellent rate performance,which display potential application prospects in markets such as energy storage,automotive start-stop supply,and low-speed two wheeled vehicles.However,under extreme conditions such as high voltage and high temperature,the stability of the"electrode/electrolyte"interface becomes a key factor restricting the cycling performance of sodium ion batteries.Unstable interfaces may lead to side reactions inside the battery,such as electrolyte decomposition,electrode material corrosion,and gas generation,all of which can seriously degrade the performance and lifespan of the battery.In this paper,a new functional additive-sodium difluorophosphate(NaPO2F2,abbreviated as NaDFP)was prepared.This additive synergistically promotes the formation of stable anode solid electrolyte interface(SEI)and cathode electrolyte interface(CEI)with commonly used functional additives such as ethylene carbonate(VC)and fluorinated ethylene carbonate(FEC).Experimental results demonstrate that incorporating NaDFP into the electrolyte significantly enhances the performance of NaNi1/3Fe1/3Mn1/3O2|hard carbon pouch cells.The modified electrolyte formulation results in improved initial capacity and first-cycle coulombic efficiency.Notably,under high-voltage conditions(2.0-4.0 V)and a current density of 1.0 C at 45 ℃,the battery achieves an impressive capacity retention rate of 96％after 400 cycles.The SEI and CEI interface layers constructed by NaDFP in collaboration with VC and FEC significantly reduce the interface impedance between the"electrode/electrolyte",effectively alleviate the interface side reactions,and finally significantly improve the cycling performance of SIBs under high voltage and high temperature conditions.
sodium-ion batteriesfunctional additivesodium difluorophosphate"electrode/electrolyte"interfacehigh voltagehigh temperature
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