Synthesis Of LaMO₃ Bimetallic Oxides And Their Application In Lithium-suful Batteries

Lithium-sulfur（Li-S）batteries are regarded as one of the most promising energy storage devices in automobiles,artificial intelligence systems,and smart grids because of their large theoretical specific capacitance(1675 m Ah g^-1),high energy density(2600 Wh Kg^-1),lower cost,and environmental friendliness.However,Li-S batteries are faced with problems such as poor conductivity of active substances,shuttle of soluble lithium polysulfide（Li₂S_x,4≤x≤8）and slow conversion,which seriously limit their practical application.Therefore,promoting the rapid transformation of polysulfides and inhibiting the shuttle effect are the key to improve the electrochemical performance of Li-S batteries and promote their commercial applications.Commercial separator modification is a simple and effective method to improve the electrochemical performance of Li-S batteries and has become one of the main research directions at present.In this paper,a multifunctional separator was prepared by coating lanthanide bimetallic oxide modified materials on a commercial separator,which can not only effectively adsorb polysulfides but also accelerate the catalytic conversion of polysulfides.The lanthanide-based bimetal oxide is La MO₃,where M is a metal atom,selected from one of Ni and Co.The research contents are as follows.（1）A novel bimetallic oxide LaNiO₃ functional material with excellent catalytic performances and high electronic conductivity was prepared by a sol-gel method as an efficient polysulfide barrier layer.Through a series of physical/chemical properties of LaNiO₃synthesized at three calcination temperatures（600 ^oC,800 ^oC and 1000 ^oC）,it is determined that LaNiO₃at 800 ^oC has excellent conductivity,catalysis,and good adsorption performance,which can significantly improve the polysulfide transformation kinetics.At a high sulfur loading of 6.05 mg cm^-2,the Li-S battery with 800 ^oC LaNiO₃-separator still can provide an area-capacity of 2.81m Ah cm^-2after 150 cycles.Specifically,Li-S battery can provide a high area-specific capacity of 5.98 m Ah cm^-2after 40 cycles at sulfur loading of 12.45 mg cm^-2with 7μL mg^-1electrolyte.Thus,it is concluded that 800 ^oC LaNiO₃-separator can effectively block polysulfides,and enhance the redox kinetics of adsorbed polysulfides to achieve their quick conversion（2）Honeycomb LaCoO₃materials with excellent adsorption and catalytic properties were prepared by a sol-gel method and subsequent calcination.At a current density of 1 C,the Li-S battery using La Co O₃-separator still can provide a specific capacity of 549 m Ah g^-1after 1000 stable cycles and the capacity decay rate per cycle is only 0.05%.Simultaneously,at a high current density of 6 C,Li-S cell still has a discharge capacity of 723 m Ah g^-1.The above research results show that La Co O₃functional separators can effectively intercept polysulfides,thereby improving the cycle stability and rate performances of Li-S batteries.