Preparation And Research Of Polyurethane-based Polymer Electrolyte With Highly Elastic

Solid state batteries have many advantages,such as high energy density and good safety.All-solid-state batteries have a huge interfacial impedance because of solid-solid contact at electrode/electrolyte interfaces.At the same time,since the lithium metal anode have a huge volume change during plating and striping,it is easy to cause some voids formed at interface of lithium anode and SPE.Some voids at the interface will directly increase electrode polarization and even promote lithium dendrite growth in all-solid-state batteries.Herein,we prepare a PU-LiTFSI-SN polymer electrolyte with high elasticity.When lithium is plating,PU-LiTFSI-SN electrolytes is forced to deform but stably adhered to the lithium metal anode,PU-LiTFSI-SN electrolytes immediately rebounded for a stable interface when the lithium is striping.The polymer electrolyte with high elasticity could maintain a stable interface between the solid electrolyte and the electrode,forming a stable lithium ion transport channel during the charging and discharging process.The stable interface can promote cycle performance of solid-state batteries.Firstly,the PU is synthesized by the polyaddition reaction between polyethylene glycol(PEG)and isocyanate,and lithium bistrifluoromethanesulfonimide(LiTFSI)is added to prepare PU-LiTFSI electrolytes.Comparing with PEO-based polymer electrolytes,PU-LiTFSI electrolytes have higher mechanical strength,good electrochemical stability and unique high elasticity.The Li|PU-LiTFSI|LFP batteries have a discharge specific capacity of 141 m Ah/g after 100 cycles at 0.5 C(25 ^oC).Due to the PU-LiTFSI polymer electrolytes having low ionic conductivity at room temperature,the Li|PU-LiTFSI|LFP batteries cycle can't be carried out at room temperature.In order to improve the ionic conductivity of PU-LiTFSI,the PU-LiTFSI-SN polymer electrolyte is prepared by adding SN to PU-LiTFSI.The PU-LiTFSI-SN polymer electrolytes have 2.865×10^-4 S/cm ionic conductivity at room temperature and unique high elasticity.The polymer electrolyte with high elasticity can keep a stable interface with the electrode during the charging and discharging process.The Li|PU-LiTFSI-SN|LFP batteries still have a specific charge-discharge capacity of 149 m Ah/g after 200 cycles with 0.5 C at room temperature,and the charge capacity retention of 70%after 800 cycles at 0.5 C(25 ^oC).Our investigations effectively improve the stability of the electrode/electrolyte interface of all-solid-state batteries.