Research On Polyvinyl Methyl Ether-maleic Anhydride As Polymer Electrolyte And Binder Material For High-voltage Lithium Batteries

At present,lithium battery has become a standard power source for mobile electronic devices such as mobile phones and laptops,and has begun to be applied in light and hybrid electric vehicles.In order to meet the growing demands for energy,it is imminent to develop high voltage and high energy lithium batteries.However,liquid electrolyte possesses narrow electrochemical window,which wo uld result in severe electrolyte decomposition under high voltage state.Additionaly,using liquid electrolyte still bring the potential safety hazards due to leakage.The polymer electrolyte not only has a wide electrochemical window,but also avoids the occurrence of leakage.Therefore,developing polymer electrolyte system to meet the requirements of high voltage lithium batteries is urgent.In this paper,we will adopt the design concept of ?rigid and soft? and use bacterial cellulose supported poly(methyl vinyl ether-alt-maleic anhydride)(hereafter abbreviated as ?P(MVE-MA)?)as a multifunctional polymer electrolyte for high voltage Li Co O 2 lithium metal battery.The assembled Li Co O2 lithium metal battery presented excellent performance.In addition,we adhere to the concept of "one kind of material,multiple uses" and successfully apply this polymer as a binder for Li Ni 0.5Mn1.5O4(hereafter abbreviated as ?LNMO?)electrode.The specific contents are as follows:(1)A multifunctional polymer electrolyte using bacterial cellulose as supporting material and poly(methyl vinyl ether-alt-maleic anhydride)coating on it was prepared by adopting the design concept of ?rigid and soft?.The polymer electrolyte(PMM-CPE)demonstrated high mechanical strength,wide electrochemical window,large lithium ion transference number and high ionic conductivity(25 oC,1.34×10-3 S cm-1;60 oC,2.83×10-3 S cm-1).The symmetric Li/Li cells presented steady lithium plating/striping even at a current density of 9.5 m A cm-2.More intriguingly,4.45 V-class Li Co O2 lithium metal batteries employing this polymer electrolyte delivered ultra-long cycle-life and superior rate capability.The capacity retention of Li Co O 2/Li cell using PMM-CPE was 73 % after 650 cycles at 25 oC and 85 % after 700 cycles at 60 oC.In addition,the rate capability was superior than that of liquid electrolyte.These exceptional battery performances were attributed to PMM-CPE which could promote favorable CEI film in Li Co O 2 cathode to avoid crystal structure failure and a stable SEI film in Li anode to suppress lithium dendrite growth,as evidenced by combined techniques such as scanning electron microscope(SEM),X-ray photoelectron spectroscopy(XPS),transmission electron microscope(TEM),inductively coupled plasma optical emission spectrometer(ICP-OES),X-ray diffraction(XRD)and theoretical calculations.(2)Poly(methyl vinyl ether-alt-maleic anhydride)was used as a binder for high voltage LNMO and the prepared LNMO electrode possesses high peel strength.The assembled 5.0 V LNMO/Li half battery with P(MVE-MA)binder presented excellent rate capability and long cycle performance: 5.0 V LNMO/Li cell with P(MVE-MA)binder had larger discharge capacities and smaller polarization voltage than those of LNMO/Li cells with PVDF binder when the current rate increases from 1 C to 15 C.The capacity retention of P(MVE-MA)-LNMO/Li cell was 86 % after 500 cycles at 1 C and 78 % after 1000 cycles at 10 C.