硫掺杂 Cu₃Mo₂O₉ 负极材料结构设计及其电化学储锂特性分析

Lithium-ion batteries (LIBs) are widely used in renewable energy storage because of their high energy density, long-term rechargeability, good cycling stability, non-pollution and high output voltage. However, with the increasing requirements for energy and power density, the conventional graphite anode materials with low theoretical capacity (only 372 mA·h/g) cannot meet these higher requirements. Therefore, there is an urgent need to develop new anode materials with long cycle life and high capacity. Copper-molybdenum-based oxides are considered as one of the most ideal anode materials for lithium-ion batteries due to their low cost and high theoretical capacity, but they still suffer from the problems of large volume change and low intrinsic conductivity, which can lead to rapid capacity decay and poor rate performance. In this regard, a novel hollow-structured Cu₃Mo₂O₉ microsphere was synthesized through a solvothermal method, and a sulfur-doped Cu₃Mo₂O₉ single-crystalline material was designed by using a simple in-situ pyrolysis process. By adjusting the annealing temperature, the synergistic modulation of phase structure and morphology is realized, which improves the electrochemical lithium storage performance. The S-CMO-450 electrode exhibits high lithium storage capacity, excellent cycling stability, and superior rate performance, with a high reversible capacity of up to 894.5 mA·h/g at 0.2 A/g, and a capacity of 733.1 mA·h/g after 250 cycles even at a high current density of 0.5 A/g. The excellent electrochemical performance is attributed to the multiple synergistic effect of the S-doping modification strategy and the heterostructure of CuMoO₄, CuO, and Cu₃Mo₂O₉. The introduction of sulfur atoms can not only change the electronic structure of the electrode material to improve its electrical conductivity; it can also form active sites on the surface or inside the electrode material to increase the storage capacity of lithium ions in the electrode material and improve the specific capacity of the battery. In addition, sulfur doping can expand the layer spacing of the electrode material, provide a more spacious channel for the embedding and detachment of lithium ions, shorten the diffusion path of lithium ions, accelerate the diffusion speed of lithium ions in the electrode material, and thus improve the rate performance of the battery, so that the battery can be charged and discharged quickly at high current density, to meet the application scenarios of some of the requirements for fast charging and high power output. Multivariate heterostructure anode materials can provide more lithium ion storage sites, which can form a variety of compounds with lithium ions, thus significantly increasing the lithium storage capacity of the battery; the different phases in the multivariate heterostructure can form a stable interface between different phases, so that when some of the materials undergo a volume change, the other materials can maintain the overall structural integrity of the electrode to a certain extent, reducing the shedding of the active substance and the side reaction between the electrolyte and the electrode, thus improving the cycle life of the battery. In addition, the multivariate heterostructure makes the battery capable of rapid ion and electron transfer during high-rate charging and discharging, reduces the polarization phenomenon, and improves the rate performance of the battery.