Modification Of Lithium Metal Anode Enabled By Carbon-nitrogen Composites

Our society is facing a serious energy crisis.Traditional fossil energy causes great pollution to the environment and faces the dilemma of limited resources due to its non-renewable characteristics.Therefore,the use of clean and renewable energy is the most feasible solution.However,many clean energies such as solar energy are fluctuant and intermittent,which require additional devices to store energy.Among numerous energy storage devices,lithium-ion batteries have been widely used due to their advantages such as safety,low weight,high specific energy density and poor memory effect.However,the capacity of the battery is limited by positive and negative electrode materials.It is necessary to find new electrode materials to acquire higher energy density.Lithium metal anode stands out among kinds of anode candidates because of their high theoretical specific capacity and low potential.In addition,lithium metal anode can be matched with a variety of nonlithium cathode materials such as sulfur to achieve high-energy-density full batteries.However,the growth of dendrites and the low coulombic efficiency limit the application of lithium metal anode.This paper mainly studies the ways to suppression dendrites during cycling by using oxygen-doped g-C3N4(A-G)as the interface layer and composite electrode composed of N,Co co-doped three-dimensional hollow carbon material and nickel foam(CNC@Ni)as host The main contents are as follow:(1)An artificial A-G interface layer is conveniently coated on the lithium foil by an ex-situ method.The N and O contained functional groups in A-G can promote fast lithium ion transfer and uniform lithium deposition.Therefore,the electrochemical performance of the A-G-Li electrode has been greatly improved.The symmetric cells can be cycled for 400 hours in the ester-based electrolyte and 2100 hours in the ether-based electrolyte.The full cells paired with lithium iron phosphate cathode display good electrochemical performance that the capacity retention can be kept for 80%after 400 cycles at 1C.(2)A three-dimensional hollow carbon material co-doped with nitrogen and cobalt was designed,and the material is then coated on nickel foam.The composite electrode takes advantage of the low nucleation barrier of Co/CoO and N-doped functional groups.Besides,the advantage of high specific surface area of composite electrode which can reduce the local current density is fully used.The synergistic effects induce uniform lithium nucleation and growth.This composite anode can be cycled stably with high current density and high areal specific capacity.The Li-CNC@Ni anode can be cycled for 4000 hours with the current density of 5 mA cm-2 and areal capacity of 3 mA h cm-2 in ether-based electrolyte,superior to Li-Ni.