Core-Shell LiMnFePO4 Cathode for Energy Density and Conductivity
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Solution Overview
Problem
Lithium manganese phosphate (LiMnPO4) has a higher theoretical energy density but lower electronic conductivity and lithium ion diffusion rate compared to lithium iron phosphate, limiting its electrochemical performance as a positive electrode material in batteries due to longer ion and electron transmission distances.
Innovation Solution
A battery positive electrode material is developed with a core of LiMnxFe1-xPO4 (0<x≤0.4) and a shell layer of LiMnyFe1-yPO4 (0.6≤y≤0.9), where the core has high iron content for improved conductivity and the shell has high manganese content for energy density, effectively shortening the transmission distance of ions and electrons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium manganese phosphate (LiMnPO4) is used as positive electrode material to achieve higher theoretical energy density, then energy density is improved, but electronic conductivity and lithium ion diffusion rate deteriorate
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the core region (LiMnxFe1-xPO4 with x≤0.4) has high manganese content for energy density, while the shell layer (LiMnyFe1-yPO4 with y≥0.6) has high iron content for conductivity. This spatial differentiation of composition allows each region to optimize its local function: the core maximizes energy density while the shell ensures efficient electron and ion transport.
Solution Approach 2:
The patent employs composite materials by combining two different lithium manganese iron phosphate compositions with distinct properties. The core uses LiMnxFe1-xPO4 (x≤0.4) for high energy density, while the shell uses LiMnyFe1-yPO4 (y≥0.6) for high conductivity. This composite structure integrates the advantages of both compositions, achieving both high energy density and excellent electrochemical performance.
2Use of energy by moving object
If high manganese content is used to increase energy density, then energy density is improved, but transmission distance of ions and electrons increases
Solution Approach 1:
The patent addresses this contradiction by concentrating high manganese content (x≤0.4) in the core region where energy storage occurs, while placing high iron content (y≥0.6) in the shell layer where ion and electron transport occurs. This local quality differentiation ensures that the transmission path for ions and electrons passes through the conductive iron-rich shell, minimizing transmission distance resistance while maintaining high energy density in the manganese-rich core.
Solution Approach 2:
The patent introduces a dimensional solution by adding the shell layer dimension around the core. Instead of uniformly distributing manganese throughout the material, the invention creates a layered structure where the shell dimension provides a conductive pathway for ion and electron transport, effectively separating the energy storage function (core) from the transport function (shell).
Data Source
AI summary
A battery positive electrode material includes a core and a first shell layer arranged on a surface of the core. The core includes LiMnxFe1-xPO4. The first shell layer includes LiMnyFe1-yPO4, where 0<x≤0.4, and 0.6≤y≤0.9. The battery positive electrode material has a multi-layer distribution structure. A preparation method and use of the battery positive electrode material are further provided.