Fabrication and Lithium Storage Performance of Trigonal W2N Thin-Film Anode

Abstract The preparation, characterization of materials, and electrochemical performance of trigonal W2N thin film as the anode material for lithium-ion batteries have been reported. The trigonal W2N thin film with the space group of P3̅ was synthesized by the sputtering deposition followed by a nitridation treatment. The first-principles calculations reveal that the adsorption energy of Li+ on the (001) crystal plane of trigonal W2N is −1.55 eV and the Li+ diffusion energy barrier is only 0.23 eV, indicating a significant kinetic superiority for rapid Li+ transport. The results of electrochemical tests demonstrate that the trigonal W2N thin-film electrode maintains a stable specific capacity of 700 mA h g–1 at the current density of 0.1 A g–1 after 100 cycles. Even at the current density of 1 A g–1, the specific capacity is initially decreased but subsequently rebounded, finally retaining that at 680 mA h g–1 after 300 cycles. The results of cyclic voltammetry and ex situ XPS analyses confirm that the lithium storage mechanism involves Li+ intercalation/deintercalation and a reversible conversion reaction. Owing to its high specific capacity, good cycling stability, and superior rate performance, the trigonal W2N thin-film electrode offers a promising research direction for high-performance anode materials of thin-film lithium-ion batteries in the future.