Modification Of The Anode/electrolyte Interface Of High Voltage Lithium Ion Battery By Polyethyl Cyanoacrylate

The commercial lithium-ion batteries have been applied for close to 30 years.With the lithium ion batteries widespread utilization in consumer electronics,electric vehicles and energy storage equipment,humans urgently need the lithium ion batteries with higher energy density to meet the requirements of market.Choosing high-voltage cathode materials was an effective solution to improve the energy density of lithium ion batteries.However,high-voltage cathode materials existed a series of challenges for commercial carbonate electrolyte,because of easy electrolyte decomposition,electrode and electrolyte interface reaction,transition metal ion dissolution and other interface problems,so that reduced the high-voltage lithium-ion batteries cycle performance.Therefore,this paper with LiCoO2 and LiNi0.5Mn1.5O4 used as the research objects,studied the effect of poly(ethyl α-cyanoacrylate)(PECA)on the interface of high-voltage cathode materials/electrolyte and preliminarily discussed the mechanism of modification.Firstly,the interfacial modification of PECA coating on high-voltage LiCoO2/PEO/Li solid lithium ion batteries was studied.The results of XRD,SEM and TEM showed that the crystal structure of LiCoO2 remained constant after LiCoO2 particles coated with a layer of about 50 nm thick PECA film by in situ polymerization.FTIR,XPS and electrochemical measurements further showed that the PECA suppressed the decomposition of LiDFOB and maintained the interaction between PEO and LiDFOB during high-voltage cycles.Therefore,compared to LiCoO2/PEO/Li batteries,PECA-LiCoO2/PEO/Li batteries showed stable interfacial resistance and excellent cycling stability during high-voltage cycles.This indicated that the PECA coating layer could effectively improve the interfacial stability between high-voltage LiCoO2 cathode and all solid PEO electrolyte.Secondly,the interfacial modification of conformal PECA nano-coating on high-voltage Li Ni0.5Mn1.5O4 was studied.Meanwhile,the modification mechanism was preliminarily discussed.The results showed that the PECA polymer could form a continuous about 10 nm thick surface coating layer and provide a fast transfer channel for lithium ions.This avoided interfacial reactions due to direct contact of LiNi0.5Mn1.5O4 with the electrolyte and ensured that lithium ions effectively transferred between the electrode and the electrolyte.Therefore,PECA conformal nano-coating layer could improve the interface stability between LiNi0.5Mn1.5O4 and electrolyte,reduce the interface impedance,and remarkably improve the cycle stability of the batteries.In addition,the strong interaction of the polyvalent metal ions with the PECA inhibited the dissolution of the transition metal ions and prevented from depositing on the anode,thereby which eliminated the resulting loss of active lithium and increased the capacity retention of the cells.