新型高性能、低成本Ti基固溶体氧化物电极材料开发与反应机制研究

Sodium has similar chemical properties with lithium, and is abundant in the earth crust. Therefore, room temperature sodium-ion batteries (NIBs) have attracted great attention in the large-scale energy-storage field. Currently, one of the hot research topics of NIBs is developing electrodes with high performance. Ti-based solid solution oxides (Ti-SSOs) are novel electrodes for NIBs, presenting excellent electrochemical performance with smooth charge/discharge curves when these Ti-SSOs are used as cathode or anode in NIBs. We have previously developed Ti/Ni, Ti/Co and Ti/Mn binary Ti-SSOs with different crystalline structures, and established the Ti-SSOs electrode research system. Based on our previous research results, this study will research the element substitution of Ni and Co in O3-type Ti/Ni cathode and P2-type Ti/Co anode materials by Fe, Mn and so on, establish the ternary or quaternary Ti-SSOs with decreased materials cost, improve their electrochemical performance through surface modification, research the electrochemical reaction mechanism of Ti-SSOs deeply, and investigate the reasons for Ti-SSOs with smooth curves during charging and discharging processes. The implementation of this project will develop the novel ternary or quaternary Ti-SSOs with good electrochemical performance and low cost, consummate Ti-SSOs research system, and has important significance on understanding Ti-SSOs deeply and promoting the utilization of Ti-SSOs in NIBs.

钠元素与锂元素化学性质相似，且储量丰富，因此室温钠离子电池（NIBs）在大规模储能领域很有吸引力。目前NIBs的研究重点是开发高性能电极材料。Ti基固溶体氧化物（Ti-SSOs）是一种新型电极材料，电化学性能优异且充放电曲线光滑。我们的前期研究已开发了不同结构的Ti/Ni、Ti/Co及Ti/Mn等二元Ti-SSOs，建立了Ti-SSOs材料研究体系。本研究拟在前期基础上，采用Fe、Mn等元素取代O3-型Ti/Ni正极与P2-型Ti/Co负极材料中的Ni与Co元素，实现Ti-SSOs材料的三元或四元固溶化并降低材料成本，结合表面改性进一步提高Ti-SSOs的电化学性能，深入研究Ti-SSOs的电化学反应机制，并探讨其充放电曲线光滑的原因。本项目的实施将开发新型高性能、低成本三元或四元Ti-SSOs，完善Ti-SSOs研究体系，对深入了解Ti-SSOs材料并推动其在NIBs上应用具有重要意义。

开发钠离子电池(NIBs)高性能电极材料对于大规模、低成本储能应用具有重要价值。Ti基固溶体过渡金属氧化物材料(Ti-SSOs)具有优异的倍率和循环性能，是室温NIBs电极材料的重要研究体系之一。但Ti-SSOs还需进一步拓展完善，其电化学性能还需提高，成本还需显著降低。同时，Ti-SSOs的电化学反应机制需要深入探究，尤其是充放电过程中多平台现象消失的原因需要阐明。本项目为解决上述科学问题和技术挑战，开展了成体系的研究工作。(1)利用Fe元素取代Co, Ni，制备出低成本P2(Na0.67Ni0.33Ti0.67O2), T1(Na2.65Ti3.35Fe0.65O9)和T2(NaTiFeO4)三相复合晶畴材料，通过改变Fe元素比例调控晶畴比例并优化电化学性能，阐明了电化学演化及Na+脱/嵌机理；(2)制备了P2-型Na2/3Ni1/3Ti2/3O2(NNT)和P2-型Na2/3Co1/3Ti2/3O2(NCT)材料，结合结构解析与理论计算揭示了反应机制和Na+的脱/嵌方式，证实材料充放电多平台消失现象是由于Ti元素得失电子不断地进行可逆偏移，从而降低Na+脱嵌迁移能垒并缓解材料内部应力所致；(3)制备了P2-tunnel型Na0.67Fe0.4Mn0.6O2及多金属P2-tunnel型Na0.67Fe0.25Mn0.65Mg0.05Ti0.05O2复合晶畴材料，通过调控元素比例以调节晶畴结构，并实现材料性能提高。(4)优化球磨法制备了SiP2/C复合材料并显著提升了SiP2的倍率及循环性能，综合原位及离线技术揭示了SiP2的放电产物、结构演化及无定形化规律。(5)利用球磨法调控了Sn4P3的结构转化，制备了系列二元Sn4P3/C、四元Sn4P3/Sn/P/C及三元Sn/P/C复合负极材料，通过优化复合材料的组成与结构提升了循环性能。(6)针对高性能NIBs关键材料，包括过渡金属氧化物材料、复合结构材料及固态电解质与界面进行了综述评论，对锂离子电池等体系开展了原创研究和综述评论工作。基于上述研究，撰写论文19篇(已发表17篇)，申请专利7项，培养博士后及研究生多人，其中硕士研究生马昊获“北京市优秀毕业生”称号。这系列工作开发了一系列高性能NIBs电极材料，揭示了材料电化学转化规律与机理，为进一步构筑高性能电极材料、提升NIBs综合性能提供了科学依据。