Preparation And Properties Of Soluble Poly(Arylene Ether) Single-ion Gel Polymer Electrolyte

The electrolyte is an important part to pursue safe lithium batteries with highenergy densityrequired for next generation of electric vehicles and other advanced applications.The conventional Li-ion batteries(LIBs)electrolyte is composed of lithium salt and liquid organic solvent,which has been the key factor in the wide application of LIBs and a major challenge for its further improvements.In addition,high-energy lithum metal anodes are not stable enough in binary electrolytes.The competitive transport of Li⁺and counteranions promotes the growth of lithium dendrite,which eventually leads to the short circuit and safety hazard of battery.It is well known that the different mobility of cations and anions causes concentration polarization,which affects the power and energy density of LIBs.All-solid-state lithium batteries have obvious advantages in terms of safety,wide temperature stability and energy density,and have attracted wide attention in the field of new energy.Solid polymer electrolyte(SPE)is a key part of solid lithium batteries.People are exploring SPE with high lithium-ion transferance number,high Li⁺conductivity,high dimensional thermal stability and high mechanical properties.Among them,single ion polymer electrolyte(SIPE)is an attractive option.SIPE was prepeared by fixing anions on the polymer backbone through a covalent bond,which can limit the migration of anions,and can significantly increase the lithium-ion transferrance number to close to 1.Adding plasticizers to SIPE can significantly increase the ionic conductivity,thereby forming a single-ion gel polymer electrolyte.In this study,two soluble poly(arylene ether)single-ion gel polymer electrolytes were prepared and their application performance in solid-state lithium batteries was studied.In order to inhance the mechanical properties and dimensional thermal stability of polymer electrolytes,First,poly(ether sulfone)s containing hydroxyl groups(PES-OH)and lithium 3-chloropropanesulfonyl(trifluoromethanesulfonyl)imide(Li CPSI)were prepared.Then,the poly(ether sulfone)single-ion polymer(PES-LICPSI)was prepared by Williamson synthesis method,and its structure was characterized by FT-IR and NMR.The PES-LICPSI and PVDF-HFP were compouned to obtain the casting liquid,and the poly(ether sulfone)single-ion polymer electrolyte(PES-SIPE)was prepared by the solution casting method,and thereafter,PES-SIPE was soaked in plasticizer(EC/PC)to improve the dissociation and migration of Li⁺.Finally,the poly(ether sulfone)single-ion gel polymer electrolyte(PES-GPE)was obtained.The thermodynamic properties,micromorphology,electrochemical and battery performance of the obtained PES-SIGPE were discussed.The tensile strength of PES-SIPE was 50.5 MPa;and there was no obvious thermal shrinkage when kept at 200?for 30 min,which indicated that the prepared electrolyte possessed excellent thermal demensional properties,and could effectively avoid the dangers caused by thermal shrinkage.The ionic conductivity reached 7.1×10^-5 S cm^-1 at 20?,and the electrochemical window was 4.2 V.The lithium-ion transference number was as high as 0.92 which can effectively inhibit the growth of lithium dendrites.The assembled Li Fe O₄/PES-GPE/Li battery exhibited a discharge capacity of 128 m Ah/g at 0.2 C and a capacity retention rate of 97%after 370 cycles.Li/PES-GPE/Li cells were assembled to test the stability of lithium metals.The overpotential of lithium stripping/deposition was stabilized at 56 m V,and remained unchanged for 1200 h without short circuit,which proved that the prepared PES-GPE successfully inhibited the growth of lithium dendrites.To further improve the lithium-ion dissociation capacity of the electrolyte and the discharge capacity of the LIBs on the premise of maintaining the mechanical properties,in this work,polyaryletherketone with allyl double bond(PAEK₅₀)were first synthesized.To immobilize the anions,an organic lithium salt,lithium(4-styrenesulfonyl)(trifluoromethansulfonyl)imide(Li STFSI),was synthesized,and used as the lithium source,and then grafted with PAEK₅₀ to obtain the polyaryletherketone single-ion polymer(PAEK-Li STFSI).The introduction of PAEK₅₀ was expected to enhance the thermal and mechanical stability of the polymer electrolyte.The corresponding polyaryletherketone single-ion gel polymer electrolyte(PAEK-GPE)was obtained through the solution casting of PAEK-Li STFSI and PEO composite solution.The obtained polyaryletherketone single-ion polymer electrolyt did not shrink after being kept at 200?for 30 min.And the ion conductivity of PAEK-GPE was 7.8×10^-5 S cm^-1,the lithium-ion migration number was as high as 0.95,and the electrochemical window reached 4.2 V.The discharge capacity of the Li Fe O₄/PAEK-GPE/Li half-cell was reduced from 140 m Ah/g to 134 m Ah/g after 400 cycles at 0.2 C,and the capacity retention rate was as high as 95%,suggesting that PAEK-GPE had good electrochemical stability and long cycle life.Moreover,The Li/PAEK-GPE/Li battery was assembled for constant current cycling.The battery had a constant polarization voltage of 45m V,and exhibited a very stable constant current cycle performance during cycling of up to1200 h.Then,the Li/PAEK-GPE/Li battery was disassembled,and the surface of the lithium foil was smooth by SEM analysis,indicating that the growth of lithium dendrites was effectively inhibited.In conclusion,the soluble poly(arylene ether)single-ion gel polymer electrolyte obtained through molecular structure design possesses excellent comprehensive performance,and has good practical application value for solid-state LIBs.