Preparation And Properties Of Llto Solid Electrolyte Thin Films

In recent years,lithium-ion batteries have played an important role in people’s production and life,and its high energy density,high portability and long working-life bring us a better life.With the rapid development of electronic products towards portable miniaturization,all-solid-state thin-film lithium-ion batteries have emerged.All-solid-state thin-film lithium-ion batteries have the advantages of small size,high energy density,long cycle life and good safety.The performance is largely determined by the solid electrolyte membrane.The perovskite lithium titanate(Li_0.33La_0.56TiO₃)solid electrolyte block has an ionic conductivity of 10^-3 S·cm^-1 at normal temperature,comparable to liquid electrolyte,and has low activation.Energy（0.3eV to 0.4eV）is a popular material for lithium-ion battery solid electrolyte research and an ideal material for solid-state thin film electrolytes.Based on this,we studied the preparation and properties of lithium niobate(Li_0.33La_0.56TiO₃)solid electrolyte membrane.In this paper,the lithium titanate(Li_0.33La_0.56TiO₃)target was prepared by solid phase reaction.The sintering process was optimized,and the standard Li_0.33La_0.56TiO₃target with high purity and good crystallinity was obtained.The LLTO solid electrolyte membrane and the Al/LLTO/Al sandwich structure were prepared on different substrates by RF magnetron sputtering.The oxygen partial pressure,substrate temperature and the temperature of the heat treating were studied by a series of observations and electrochemical tests on the LLTO film.The results show that the LLTO solid electrolyte membranes prepared under different oxygen-argon ratio conditions are dense amorphous films.The surface root mean square roughness of the films is ideal.The film preparation speed is fast between1.76nm and 2.84nm.The sputtering rate is about 1nm/min.When the ratio of oxygen to argon is 3:7,the optimal ionic conductivity is 4.93×10^-5 S·cm^-1 in normal temperature.With the increase of substrate temperature,the surface roughness of the film has become big.When the substrate temperature is 300°C,the LLTO film can get the optimum ionic conductivity of 4.98×10^-5 S·cm^-1 in normal temperature;when the annealing temperature is higher than 600°C,the LLTO electrolyte film starts to crystallize,but for the ionic conductivity in normal temperature did not play a positive role,and the optimal ionic conductivity was obtained at an annealing temperature of 300°C,which was 6.35×10^-5S·cm^-1 in normal temperature;We also explored the effect of LLTO film coating on the electrode material LiCoO₂on the performance of the LCO electrode.Compared with the original LiCoO₂ electrode material,when it is coated with LLTO electrolyte film,its initial discharge specific capacity increases.At 0.2C discharge rate,the battery charge and discharge cycle is less than 50 cycles.The specific discharge capacity is reduced.The LLTO-LCO film can slightly reduce the electrochemical impedance of LiCoO₂ material and improve the high rate performance of the battery.