Preparation Of Co-MOF Based Materials And Their Application In Lithium Sulfur Batteries

Lithium sulfur(Li-S)battery has been considered as one of the promising next generation high energy storage systems due to the high theoretical specific capacity(1675m Ah/g)and high theoretical energy density(2600 Wh/kg)as well as the abundant natural reserves and low cost of the sulfur element.However,the practical applications of Li-S batteries are still hindered by obstacles,among which the shuttle effect caused by the solution of lithium polysulfide during the charging and discharging process.Therefore,solve the shuttle effect of polysulfide is the top priority in the research of Li-S battery.Herein,this paper demonstrate two aspects to inhibits the shuttle effect of polysulfide:size sieving and catalysis.The thickness of 1.6?m Co-MOF-71 membrane was prepared by vacuum filtration for Li-S battery.Physical and electrochemical studies show that Co-MOF-71 can suppress the shuttling effect of polysulfide through size sieving.On the other hand,MOFs membrane has good macroscopic flexibility,which can also avoid the collapse of MOF structure during the battery assembly process.The initial discharge capacity of 1272 m Ah g^-1 was achieved at the current density of 0.5 C.Co-MOF-PP based separator can maintain348 m Ah g^-1 discharge capacity after 200 cycles of initial discharge capacity of 516 m Ah g^-1 at current density of 2 C,and the average capacity decay of each cycle is only 0.16%.Compared with pure PP membrane,the electrochemical performance of the battery has been greatly improved.The CuCo alloy was prepared by high temperature pyrolysis.On the one hand,Cu metal doping will affect the electronic structure of Co metal atoms,will affect the activity of Co metal;On the other hand,due to the difference in electronegativity between bimetallic alloy and N-doped graphite carbon,charge transfer is induced from CCu-NC alloy to graphite carbon,which not only improves the chemical adsorption performance of CCu-NC to polysulfides,but also ensures the long-term conductivity of cathode materials and improves the electrochemical performance of the battery.At the current density of 2 C for 100 cycles,the average capacity decay rate of each cycle is only0.0007%.Even at a high sulfur load of 4.4 mg cm^-2,CCu-NC has an initial discharge capacity of 1225.2 m Ah g^-1,and can maintain a specific discharge capacity of 1000.4m Ah g^-1 after 50 cycles.