三维Li通道的阳离子无序材料纳米结构调控及储Li特性

The research on Li-ion battery with high performance is not only very important to electric vehicles, but also very vital to using wind energy and solar energy effectively. Recently，a new series of the cation disordered rock salt Li2MTiO4 (M=Mn, Fe, Co, Ni) could be of interest in development of next-generation cathodes materials for lithium-ion batteries due to their high theoretical capacity (above 300 mAh g-1), and their 3D ion channels for the lithium ion diffusion. However, the other cations (M2+, Ti4+) distributed in the crystal lattice could also act as a barrier to the lithium ion diffusion, and therefore limit to the lithium ion transfer. How to reduce adverse effect of the cation disorder structure has become the critical research of these kind cathode materials. In this project, we mentioned that the limitation of lithium ion diffusion can be solved by nonstoichiometric cation disordered nano-materials. The cation disordered titanate with a controllable nano structure was synthesized by a sol-gel process. The Li-ion exchange mechanism during charging and discharging will be clarified by investigating the electrochemical performance of the titante electrode and characterization of the structure of the electrode materials.Then the cathode materials with high capactity of 200mAh/g, high rate capacity and good retention of 90% under 500 times of reversible cycling can be acquired.

高性能锂离子电池的开发不仅对电动汽车领域的发展非常重要，而且对风电、太阳能等清洁能源的有效储存利用也意义重大。近来，具有岩石结构的阳离子无序钛酸盐正极材料Li2MTiO4（M = Mn，Fe，Co，Ni）由于其极高的理论容量（约为300 mAh/g），三维Li离子扩散通道等优点而有望成为下一代高性能锂离子电池正极材料。然而，分布于晶格中的其它阳离子（M2+, Ti4+）成为Li离子迁移的屏障，限制Li离子的扩散。如何减小这一不利影响是此类材料研究的关键。本研究提出非化学计量的纳米可控材料是解决这一问题的有效方法。采用溶胶凝胶法制备具有可控纳米结构的阳离子无序钛酸盐材料，通过电化学性能测试和结构表征，阐明充放电过程中Li+脱出/嵌入反应的微观机制。并开发出最大放电容量在200 mAh/g以上，500次循环后容量保持率在90 %以上的Li离子电池正极材料。

高性能锂离子电池的开发不仅对电动汽车领域的发展非常重要，而且对风电、太阳能等清洁能源的有效储存利用也意义重大。近来，具有岩石结构的阳离子无序钛酸盐正极材料Li2MTiO4（M = Mn，Fe，Co，Ni）由于其极高的理论容量（约为300 mAh/g），三维Li离子扩散通道等优点而有望成为下一代高性能锂离子电池正极材料。然而，分布于晶格中的其它阳离子（M2+, Ti4+）成为Li离子迁移的屏障，限制Li离子的扩散。如何减小这一不利影响是此类材料研究的关键。本研究提出非化学计量的纳米可控材料是解决这一问题的有效方法。采用溶胶凝胶法制备具有可控纳米结构的阳离子无序Li2FeTiO4材料，通过电化学性能测试和结构表征，阐明充放电过程中Li+脱出/嵌入反应的微观机制。结果显示Li2FeTiO4材料在1.5-5.0 V的电压范围内能够实现Fe2+/Fe3+ 和 Fe3+/Fe4+之间的转变，且Li离子在体相中的交换属于固溶交换机制不存在相转变。经过石墨烯包覆之后，Li2FeTiO4材料具有较高的放电容量218.6 mAh/g (相当于每分子1.4 个Li)和循环稳定性。Li过量的材料，例如Li2.4FeTi0.9O4 和 Li2.4Fe0.8TiO4同样也能够呈现好的电化性能，最大放电容量分别可达224.1 mAh/g 和 242.1 mAh/g。