| As an efficient energy storage device,Li-ion battery has been widely used.The electrochemical performance of cathode materials plays an important role in the energy density,power density,cycle life and safety of the lithium-ion battery.The surface coating materials can effectively reduce the direct contact between the electrolyte and the cathode material and improve the electrochemical performance of the cathode material,but the properties and thickness of the coating are often the main factors restricting the performance of the material.In addition,in the process of calcining the precursor at high temperature,the coating will react with the matrix material and transform into a new coating material.Firstly,the oxide coating layers such as TiO2,Al2O3,CuO and Mg O were designed on the surface of LCO.The structure and composition of the coating layer at different calcination temperature were analyzed by XRD characterization.It was found that the specific coating material and LCO could react at a certain calcination temperature to form a new multiphase coating layer.In order to further explore the effect of coating on the electrochemical performance of LCO,a liquid button semi-cell was assembled and tested.The results show that the multiphase coating plays a positive role in improving the performance of LCO.However,the performance of the LCO coated with different coating materials is not as good as that of the unmodified LCO after matching the sulfide solid electrolyte and assembling the solid-state battery,which may be related to the low ionic conductivity of the coating layer.Based on the above results,Li2TiO3 and Li4Ti5O12 coating layers with higher ionic conductivity are designed in this paper.It is found that these two kinds of cladding layers and LCO are relatively stable and will not form multiphase cladding layer due to the control of coating sintering temperature.Compared with electronic conductors such as metal oxides,the coating of fast ionic conductors can better match sulphide solid electrolytes.Li Co O2|Li Si PSCl|Li-In all-solid-state batteries were assembled to evaluate their electrochemical performance and the effects of different coatings on the cathode/sulfide interface.The results show that the surface Li2TiO3 and Li4Ti5O12coating can effectively improve the electrochemical performance of LCO in the solid system and greatly reduce the interfacial impedance.The Raman spectrum test results also show that there is no side reaction product at the cathode/sulfide electrolyte interface after cycles.At the same time,it is found that the coating of TiO2and Al2O3has a negative effect on the electrochemical performance of LCO,indicating that the effective transport of Li+is one of the key factors affecting the performance of solid-state battery,and the ionic conductivity of the coating is very important.The above results provide a new strategy for the design of cathode material coating for all-solid-state sulphide batteries. |
