基于富锂锰基正极材料的全固态锂电池设计及晶格氧损失调控

High energy-density Li-rich Mn-based cathode materials have been regarded as appealing candidates for the next generation of Li-ion battery cathode. Different from the typical cation redox mechanism, some activated lattice oxygen ions of these series of materials can participate in redox process, resulting in extra capacity. Unfortunately, the anionic redox usually brings about the lattice oxygen loss, which causes irreversible structural transformation, capacity deterioration and voltage decay. In order to suppress the oxygen loss of Li1.2Mn0.54Ni0.13Co0.13O2 (LLMNCO) derived from the side reaction between the activated lattice oxygen and organic electrolyte, the employment of solid electrolyte has been proposed to substitute the traditional organic electrolyte. A new all-solid-state Li battery has been designed through elaborate electrode/electrolyte interface construction. Additionally, the mechanism for controllable lattice oxygen loss of LLMNCO will be demonstrated at the presence of solid electrolyte coating layer, establishing the connection between the anionic redox reversibility with the electrochemical stability. Therefore, the implementation of this project provides a new method to solve the problems of capacity loss and voltage decay for high-energy Li-rich Mn-based cathode, and also exhibits great significance on research and application for the next generation of solid-state Li battery.

高能量密度的富锂锰基正极材料是新一代锂离子电池用正极材料的研究热点。与传统阳离子氧化/还原反应机理不同，该材料中部分活化的氧阴离子参与可逆氧化/还原反应以提供更多的容量，但循环过程中晶格氧的损失将引发不可逆的结构转化，导致容量衰减与电压下降等问题。为了抑制富锂锰基正极材料Li1.2Mn0.54Ni0.13Co0.13O2（LLMNCO）中活化的晶格氧与有机电解液发生副反应而造成的氧损失，本研究拟采用固体电解质替代有机液体电解质，通过界面调控设计基于富锂锰基正极材料的高性能全固态锂电池，并阐明固体电解质薄层对抑制LLMNCO电化学循环过程中晶格氧损失的作用机制，揭示晶格氧阴离子氧化/还原可逆性与电化学稳定性的内在联系。本研究的实施将为解决高能富锂锰基正极材料电压降及容量衰减等问题提供新的思路，同时也对开发新型全固态锂电池具有十分重要的理论意义和应用价值。

为了解决富锂锰基正极材料晶格氧损失所引发的不可逆结构转化问题，克服及由此导致的容量衰减与电压下降等缺陷，本项目通过界面调控设计了固态电解质表面修饰的复合富锂锰基正极Li7La3Zr2O12@Li1.2Mn0.54Ni0.13Co0.13O2和LiNbO3@Li1.2Mn0.54Ni0.13Co0.13O2，改善了循环过程中的结构稳定性和动力学特性，并研究了固体电解质薄层对晶格氧行为的影响机制。为了探索富锂锰基正极在全固态锂电池的应用，分别对氧化物电解质Li6.75La3Zr1.75Ta0.25O12和硫化物电解质Li7P3S11进行组分优化，设计制备出宽电化学窗口、高离子电导率、高稳定性的复合型固态电解质。为改善与固态电解质之间的界面接触，设计制备了析氧较少、相变不明显的O2型富锂锰基正极，有效缓解了电极在循环过程中的电压下降和电压滞后现象。本项目的研究成果为理解晶格氧阴离子行为与电化性能性之间的联系提供了实验支持和理论依据，也为开发新型全固态电池提供了新的设计思路。