Study On Solid State Lithium Ion Battery Materials For Multielement Nickel Manganese System Of Vehicle

In terms of the technical route used in various high-power lithium-ion batteries,the first problem to be solved is the high safety and high energy density of the batteries.The current commercial lithium cobalt acid battery and the high cycle performance lithium iron phosphate battery have energy density of 180 Wh/kg and160 Wh/kg,respectively,although the energy density of 5V nickel-manganese spinel and ternary has exceeded the level of 220Wh/Kg.But there is still a gap from the2020 standard value of 300 Wh/kg.In addition,due to the thermal stability of nickel-manganese base and the flammability and explosion of organic electrolyte,the development of solid-state electrolyte for solid-state battery is a practical solution to solve the above-mentioned safety problems,the solid-state battery without organic electrolyte,The safety problems such as micro-short circuit caused by lithium dendrite and breakdown leakage of electrolyte can be completely eliminated.The solid electrolyte with high electrochemical stability can match the electrode materials with high voltage and capacity to achieve the energy density and high safety index.In this paper,the modification of 5V Ni-mn spinel materials for solid-state batteries and the preparation and performance of solid-state electrolytes were studied based on the shortcomings of traditional lithium battery structure and technology.We found that Li_1.3Al_0.3Ti_1.7?PO₄?₃ can effectively avoid the negative effect of direct contact between cathode material and electrolyte on the surface of lithium nickel manganate coated with appropriate amount of solid electrolyte sodium ion fast conductor Li_1.3Al_0.3Ti_1.7?PO₄?₃.The results show that the direct contact between cathode material and electrolyte can avoid the negative effect caused by direct contact between cathode material and electrolyte.And Li_1.3Al_0.3Ti_1.7?PO₄?₃ can provide more lithium ion transport paths,increase the specific capacity(120mAh?g^-1)of lithium nickel manganate,and can still reach 60mAh/kg at high current rate of 1C,and the voltage platform is close to 4.6V.Li_1.3Al_0.3Ti_1.7?PO₄?₃ synthesized by solid phase method and PVDF as polymer material were prepared by solution casting method,which had good stability,and the best scheme was selected with different weight ratio.When the ratio of LATP to PVDF was 9:1,it was found that the solid electrolyte dispersed uniformly in the PVDF matrix,and the breaking of the polymer chain also decreased the crystallinity of PVDF and increased the ionic conductivity(6.26×10^-4S×cm^-1,30?).The addition of polymer matrix also avoids the direct contact between solid electrolyte and cathode material,and the electrochemical window reaches 5.25V,which can match all kinds of nickel-manganese-based cathode materials nowadays.All-solid-state batteries composed of nickel-manganese-based cathode materials and polymer solid-state electrolytes have considerable cyclic and multiple performance.The specific capacities of the solid-state batteries at 0.2C,0.5C,1C and 2C are119.9,113.8104.5,92.1mAh·g^-1,respectively.The specific capacity of the first 0.2C discharge is 117mAh·g^-1,and after 200 cycles,the specific capacity of 0.2C discharge is 119.9,113.8104.5 and 92.1 mAh·g^-1,respectively.The specific capacity retention rate was 97.7%,and the charge and discharge efficiency remained at 100%for 200cycles.