Research On Of Li_6.4La₃Zr_1.4Ta_0.6O₁₂ Composite Solid Electrolyte And Its Solid State Battery

Compared with traditional nickel-cadmium,nickel-metal hydride and lead-acid batteries,lithium-ion batteries have higher energy density and are more environmentally friendly.In addition,high coulomb efficiency,energy conversion rate and long cycle life are the characteristics of lithium-ion batteries.Therefore,lithium-ion batteries are considered one of the most promising energy storage devices.Although the traditional liquid electrolyte containing carbonate has high wetting ability and high ionic conductivity,due to its use of highly volatile,flammable and explosive organic solvents,it may appear parasitic interface reaction,leakage,thermal runaway reaction and other safety problems,which limit its further development.The use of solid electrolytes can overcome the above safety problems,but single ceramic structure electrolytes or polymer electrolytes have their own shortcomings,difficult to meet the application requirements.Therefore,people try to solve this problem by combining organic and inorganic methods.This paper is mainly divided into two parts to introduce the organic-inorganic composite electrolyte,the specific content is as follows:（1）The surface modification of Li_6.4La₃Zr_1.4Ta_0.6O₁₂（LLZTO）particles by PEG brush improves the dispersion of LLZTO in PEO,and a composite polymer electrolyte（PEG-g-LLZTO@PDA/PEO）with high ionic conductivity at room temperature has been obtained.The results show that the PEG brush coating on LLZTO@PDA significantly enhanced the interfacial compatibility between LLZTO and PEO,so made LLZTO nanoparticles more uniformly dispersed in PEG-g-LLZTO@PDA/PEO composite polymer electrolyte.The ionic conductivity of PEG-g-LLZTO@PDA/PEO composite polymer electrolyte is as high as 1.1×10^-4 S cm^-1 at room temperature.The tensile strength of PEG-g-LLZTO@PDA/PEO composite polymer electrolyte is 7times higher than that of PEO polymer electrolyte.In addition,PEG-g-LLZTO@PDA/PEO composite polymer electrolyte also shows excellent stability and inhibition of lithium dendrite.Li|PEG-g-LLZTO@PDA/PEO|Li Fe PO₄ solid-state lithium iron phosphate lithium battery at 60 ^oC and 0.5 C exhibits excellent cyclic stability.At the first cycle,the discharge capacity of Li|PEG-g-LLZTO@PDA/PEO|Li Fe PO₄ is 152.3 m Ah g^-1 with capacity retention of 90.35%at0.5 C after 500 cycles under 60 ^oC.（2）Ultrathin inorganic composite solid electrolyte is prepared by solvent-free curing.Will PEGDE,polyethylene glycol dimethyl ether（NHD）,ethylenediamine（DETA）,Bis（trifluoromethane）sulfonimide lithium salt（Li TFSI）and LLZTO according to certain proportion mixing,will get roll forming 60 ^oC after curing of uniform size 1.5 h,again carries on the cold isostatic pressing,pressure of 200 MPa and the holding 10 min,finally cured at 60 ^oC to continue its 4 h can be ultra-thin composite inorganic solid electrolyte.The electrolyte not only has an ultrahigh content of LLZTO（90%）and ultrathin thickness（～20μm）,and also has a high room temperatur conductivity of 1.04×10^-4 S cm^-1.Finally,the work of this paper is summarized,and the future development of organic-inorganic composite solid electrolyte is prospected.