Lithium-Rich Cathode Composition for Stable Lattice Oxygen
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Solution Overview
Problem
Lithium-rich manganese-based cathode materials face issues with lattice oxygen evolution and large voltage drop, leading to poor cycling performance, especially at high temperatures, which conventional doping methods fail to address effectively.
Innovation Solution
A hyper-lithiation manganese-based cathode material is developed with a chemical formula of xLi2MnO3·(1-x-y)LiNiaTM(1-a)O2·yLiMnbA(1-b)PO4, incorporating a third lithiation compound LiMnbA(1-b)PO4 to form a super-crystalline domain structure, stabilizing lattice oxygen and enabling continuous phase transition, thereby reducing voltage drop and improving cycling stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium-rich manganese-based cathode materials are used to achieve high capacity, then the voltage must be 4.4 V or higher, but lattice oxygen evolution and large voltage drop occur leading to poor cycling performance
Solution Approach 1:
The patent applies composite materials by combining Li2MnO3 phase with LiNiaTM(1-a)O2 phase in a controlled ratio to form a lithium-rich manganese-based cathode material with chemical formula xLi2MnO3·(1-x)LiNiaTM(1-a)O2. This composite structure leverages the high capacity of Li2MnO3 while the LiNiaTM(1-a)O2 phase provides structural stability, thereby achieving high capacity (4.4V or higher) while improving cycling performance through synergistic effects between the two phases
Solution Approach 2:
The patent applies local quality by creating a multi-phase composite where different regions have different functions: Li2MnO3 domains provide high capacity through lithium extraction/insertion reactions, while LiNiaTM(1-a)O2 domains provide structural stability and electron conduction. The local composition is optimized with specific ratios (0.1≤x≤0.9) to ensure that high-capacity regions are surrounded by stabilizing phases, thus achieving high capacity without sacrificing cycling performance
2Stability of the object's composition
If conventional element doping schemes are applied to lithium-rich manganese-based materials, then the structure is modified, but the voltage drop cannot be reduced or lattice oxygen stabilized
Solution Approach 1:
The patent applies parameter changes by precisely controlling the composition parameters of the composite material, specifically the ratio parameter x in xLi2MnO3·(1-x)LiNiaTM(1-a)O2 where 0.1≤x≤0.9, and the doping parameters a and b where 0<a≤1 and 0<b≤1. By optimizing these parameters, the material achieves optimal balance between capacity and stability, stabilizing lattice oxygen while minimizing voltage drop through controlled phase composition rather than random doping
Solution Approach 2:
The patent uses composite materials to simultaneously address lattice oxygen stability and voltage drop issues. The Li2MnO3 phase stabilizes lattice oxygen through its stable layered structure, while the LiNiaTM(1-a)O2 phase reduces voltage drop by providing efficient electron conduction pathways and buffering volume changes during cycling. This composite approach overcomes the limitations of conventional single-phase doping strategies
Data Source
AI summary
Provided in the present application are a positive electrode material, and a preparation method therefor and the use thereof. The chemical formula of the positive electrode material is xLi2MnO3:(1-x-y)LiNiaTM(1-a)O2·yLiMnbA(1-b)PO4, wherein O<x<1, 0<y<1, 0≤a≤1, 0.5≤b≤1, and TM and A respectively and independently comprise a metal element. The positive electrode material can form continuous phase transformation, has a super-domain structure and a stable layered structure, and can stabilize lattice oxygen and reduce voltage drop, such that the cycling performance of a battery under a high voltage can be significantly improved.