Correlating electrochemical performance and heat generation of Li plating for lithium-ion battery with fluoroethylene carbonate additive

1.Introduction With the superior performance of high energy density,lightweight and long life span,lithium-ion battery(LIB)are perceived as an attractive and reliable power source for modern-used portable electronics,ecofriendly electric vehicles and power distribution,and thereby a remarkable solution to assuage energy dependence on fossil fuel and environmental concern.Nevertheless,the unexpected Li plating together with the Li dendrites growth on graphite anode surface has been a profound hindrance to the practical application of LIB,of which induces inferior Coulombic efficiency,poor lifespan and safety concern[1].

Additives to propylene carbonate-based electrolytes for lithium-ion capacitors

Nowadays,lithium-ion capacitors(LICs) have become a type of important electrochemical energy storage devices due to their high power and long cycle life characteristics with fast response time.As one of the essential components of LICs,the electrolytes not only provide the anions and cations required during charge and discharge processes,but also supply the liquid environment for ions to migrate between anodes and cathodes in LIC cells.It is well accepted that propylene carbonate(PC) cannot be used as a single solvent for Li-ion electrolyte due to the failure to form stable SEI film on graphite surface.In this work,the compatibility of PC-based electrolyte with commercial soft carbon anode and activated carbon cathode has been validated by using the laminated pouch LIC cells.The effects of additives on the electrochemical properties of PC-based LICs have been systematically investigated.Ethylene sulfite(ES) was proved to be an effective additive to promote capacity retention at high C-rate,which is superior to vinylene carbonate and fluoroethylene carbonate.The addition of 5 wt% ES plays an important role in reducing internal resistance,as well as improving electrochemical stability and low-temperature performances.This study is expected to be beneficial to explore robust electrolyte/additive combinations for LICs to reduce the internal resistance and to improve the lowtemperature performances.

The effect of electrolyte additives on the rate performance of hard carbon anode at low temperature for lithium-ion capacitor

Lithium-ion capacitor(LIC),which combines the advantages of lithium-ion battery(LIB)and electrical double layer capacitor(EDLC),has a rapid development during last decade,however,the poor low temperature performance still limits its application.In this paper,three electrolyte additives including vinylene carbonate(VC),fluoroethylene carbonate(FEC)and 1,3,2-dioxathiolane 2,2-dioxide(DTD)have been utilized and their effects on the rate performance of hard carbon(HC)anode of LIC at various temperatures ranging from 25℃ to-40℃ have been well evaluated.The cell containing FEC shows the best rate performance at various temperatures and has the charge and discharge capability even at-40℃.For HC anode,the charge transfer impedance(R_(CT))increases exponentially at low temperature,while the equivalent series resistance(Rs)and the impedance of solid electrolyte interface(SEI)increase relatively few.At low temperatures,the effect of FEC may be mainly reflected in its effect on the charge transfer process.