Study On The Preparation And Performance Of Solid Polymer Electrolytes For Lithium Ion Batteries

Because of the utilizing of carbonate-based liquid electrolytes with low flash and boiling point,traditional lithium ion batteries are prone to burn or even explode,which undoubtedly limits the development and application of it in the field of high energy density energy storage.The electrolyte solidification is expected to fundamentally eliminate a series of safety hazards caused by traditional carbonate-based electrolytes,while further improving the energy density of lithium-ion batteries.So far,solid-state electrolytes(SSE)mainly include organic(polymer)and inorganic(oxide or sulfide)electrolytes.Combining the advantages of the above two electrolytes,the organic/inorganic composite solid-state electrolyte(CSSE)has a broad application prospects in the field of all solid-state lithium-ion batteries(ASSLB).Herein,the electrochemical performance of the composite electrolyte and the influence of the addition of inorganic fillers on the electrode/electrolyte interface are studied.In addition,in view of the characteristics of solid polymer electrolytes that require high-temperature operation,a solid plasticizer is added to the composite electrolyte system to improve the room temperature operating capability.Firstly,Li₇La₃Zr₂O₁₂(LLZO),which has high mechanical strength and high ionic conductivity,is added into polyethylene oxide(PEO)matrix and shows excellent lithium-ion transport ability.The purpose of widening the electrochemical stability window,inhibiting the growth of lithium dendrites and building a stable electrolyte/anode interface is achieved.Given the feasibility of our strategy,the designed PEO-LLZO-Li TFSI(PLL)composite solid-state electrolyte exhibits an outstanding cycling property.The capacity retention is higher than 88%after 500 cycles and the Coulombic efficiency of 99.1%is obtained after 1000 cycles at 1 C in Li Fe PO₄-Li cell.More importantly,Raman and FT-IR spectra suggests that there exist a hydrogen bond-like interaction between the organic phase and the inorganic phase,therefore the inorganic filler can be uniformly dispersed in the polymer matrix,the uniform deposition of lithium ions will be regulated and the growth of lithium dendrites will be inhibited.Secondly,in order to improve the temperature adaptability of polymer electrolytes,a solid plasticizer succinonitrile(SN)is added to realize the operation at room temperature.Moreover,amorphous polymer matrix polypropylene carbonate(PPC)is mixture with SN to construct a dual-layer composite electrolyte based on PLL composite electrolyte.The PLL/SN-PPC-Li DFOB(PLL/SPL)dual-layer electrolyte shows the suppression of lithium dendrite growth and the operation capability at room temperature.The voltage of Li/(PLL/SPL)/Li symmetric cell is stabilized under the current density of 0.05 m A cm^-2,indicating a steady lithium plating/stripping behavior for more than 1000 h.The as-prepared PLL/SPL dual-layer electrolyte exhibits an outstanding cycling property.The capacity retention is 96%after 200 cycles at 25?and 0.2 C in Li Fe PO₄-Li cell.The composite electrolyte with a dual-layer design can realize room temperature operation,exhibits high cycling stability,and provides a new idea for the development of solid electrolytes.