Electrochemical Performance Of Hollow Spherical Structure Design And Fluoride Coating Modification On Lithium Rich Manganese Based Cathode

Since the third quarter of the 2020,new energy vehicles have become a beautiful landscape in the A-share market,and its main energy component,lithium-ion batteries,has also become a research direction under the leadership of Tesla.To achieve the higher energy density requirements of lithium-ion batteries,lithium-rich oxide cathode materials with high capacity and high energy density may become the most promising system.Among them,the Lithium-rich manganese-based cathode material has the advantages of remarkable specific capacity,wide operating voltage（2.0-4.8 V）,and stable cycle performance.However,it cannot be fully used due to its own defect limitations,such as low 1st reversible capacity and poor structure Poor stability,serious voltage decay,etc.Therefore,creating a feasible framework and superficial polish are a powerful action to enhance the energy of Lithium-rich manganese-based Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ material cathode,focusing on two parts:The hollow spherical oxide is synthesized by the composite molten salt method,and the subdivision areas in the synthesis are determined by the high-quality conditions in the following:Hollow MnO₂ microspheres were regarded as templates and Li OH·H₂O was used as the lithium source.The temperature was raised directly from room temperature to 800℃and calcined in a liquid environment provided by a composite molten salt system with the same mass ratio as the raw materials for 15 h.The lithium-rich material prepared under this condition has an amazing performance in both the first Coulomb efficiency and the rate performance.The 1st output ability at 0.1rate is 280.9 mAhg^-1,and the 1st CE is 84.3%,and persisted 84.3%back of 200 cycles,an excellent thermal stability was proved under high temperature.The hollow structure produced by the mixed molten salt system possesses an outstanding performance in providing more active sites and an exceptional structure.The facile and economical synthesis scheme can meet the requirements of the positive electrode for high specific energy and high power.Aiming at the cycle stability and voltage decay of the LMO,a simple co-precipitation method was designed to coat different ratios of AlF₃/LaF₃ on the surface,and the property changes after co-coating with AlF₃@LaF₃ was explored.The results show that the fluorides AlF₃@LaF₃ coating layer is proved to have a more significant effect than the single fluoride layer used as a control in inhibiting the elution of transition metal ions and the growth of the SEI film,and also improves the structural stability during the cycle and suppresses partial voltage decay.Specifically,after double coating of 1 wt.%,the capacity retention rate of 250 cycles at 1 C is increased by 46.6%compared with the bare substrate,and the capacity is only lost 12.1 mAhg^-1 after 200 cycles at a high temperature of 60℃.In general,the fluorides AlF₃@LaF₃ surface co-coating is an idea that helps to improve the structure,electrochemical and thermal stability of the material,and it is a great message to suppress the voltage decay phenomenon.