球形核壳P2层状-隧道复合钠锰氧正极材料制备及协同效应的原位研究

P2-type manganese (Mn)-based layered oxides with low-cost, environmental benign are regarded as one of the promising cathode candidates of room temperature sodium ion batteries, which could effectively support the large-scale energy storage system. Nevertheless, the practical application of P2-type Mn-based cathodes are heavily limited by poor air stability, deteriorative cycling and rate performance, which are the intrinsic drawbacks of layered cathode and could not be tackled with traditional P-/O- layered composite. Aiming to promote the performance of NaxMnO2, sphere-like core-shell structured P2-type layer-tunnel composite cathode is proposed to combine the high energy density of P2 layered cathode and the superior structural stability, rate capability of tunnel cathode. Focusing on the structure controlled synthesis and synergetic effect of composite cathode, we tried to track the preparation process and sodium storage behaviors with some operando tools, including on-line crystal workstation, in-situ XRD and so on. Basing on the respective theory of industrial crystallization, powder calcination, electrochemistry, we attempt to explore the crystallization mechanism and morphology tuning discipline of the sphere core-shell structured precursor during the precipitation reaction, interpret the formation procedure of layer-tunnel composite structure during the sintering treatment, and illuminate the synergy pattern of composite structure during sodiation/desodiation process. The fulfilment of this project would provide theoretical guidance for the design and optimization of layer-tunnel composite cathode, obtain Mn-based oxides with high energy density, long lifespan and excellent storage stability. In summary, the research would pave the development of sodium ion batteries with Mn-based oxides cathode.

室温钠离子电池是规模储能的理想配套技术之一，P2相层状锰基正极材料成本低廉、环境友好，应用前景明朗。本项目针对P2相材料空气稳定性差，循环和倍率性能受限的问题，突破现有层状-层状复合材料(P-/O-)的在结构稳定性上的限制，提出制备球形核壳结构P2相层状@隧道复合材料，结合P2相结构能量密度高，隧道结构稳定性及倍率性能优异的协同优势，改善锰基材料性能。项目拟围绕复合材料的可控制备及协同效应，利用在线结晶工作站、原位XRD等技术手段，对材料合成过程及储钠机制进行在线追踪，结合工业结晶、粉末烧制、电化学的相关理论，获得共沉淀反应过程中球形核壳结构前驱体的结晶机理与颗粒形貌、尺寸的调控规律，解译高温煅烧阶段P2相层状-隧道结构的形成过程，阐明充放电过程中两种结构的协同机制。本项目的实施将为复合材料的设计、制备及优化提供理论指导，制备得到循环寿命长、能量密度高的锰基材料，推动其实际应用。

本项目提出P2相层状@隧道复合材料，以及结合P2相结构能量密度高，隧道结构稳定性及倍率性能优异的协同优势。项目研究了层状-隧道复合结构的制备方法、形成机理、协同机制以及结构调控，并进一步拓展了新型复合结构。重点研究了草酸盐共沉淀法制备复合结构以及Na/Mn比例、煅烧温度等工艺条件的影响规律，利用高温原位XRD阐明了复合结构形成过程中的动力学/热力学规律，通过EIS、PITT等技术分析了复合结构的电流再分配协同机制，获得了Cr、Ti、Fe、Mg等异质离子调控复合结构的作用规律，以及复合结构中的氧离子氧化还原反应，拓展研究了P2/隧道/O3’三相复合结构。项目研究结果为钠锰氧正极的设计、调控提供了实验和理论基础。以通讯作者发表相关论文10篇，包括Nano Energy, Angewandte Chemie International Edition, Energy & Environmental Science等。项目先后资助硕士研究生3名，博士研究生1名。