LMFP Cathode Core-Shell Structure for Energy Density
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Solution Overview
Problem
Olivine lithium manganese iron phosphate (LMFP) cathode materials suffer from low energy and power densities, poor cycling performance, and reduced specific capacity due to structural instability and charge transport issues when manganese replaces iron, limiting their effectiveness in lithium batteries.
Innovation Solution
A cathode material with the empirical formula Li a Mn b Fe c D d PO 4, where a is 1.04 to 1.08, b is 0.70 to 0.85, c is 0.15 to 0.25, and d is 0.02 to 0.10, with a dopant metal ion selected from magnesium or cobalt, is synthesized using a method involving precursor mixing, milling, and calcination to enhance cycle life, specific capacity, and high-rate performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If manganese substitutes iron in LiFePO4 to produce LMFP cathode material, then working voltage and energy density are improved, but structural stability and charge transport deteriorate
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the core region contains high manganese content (0.7-0.85) for high energy density, while the shell region contains lower manganese content (0.1-0.3) for structural stability. This spatial differentiation of composition allows each region to optimize its local properties, resolving the contradiction between energy density and structural stability.
Solution Approach 2:
The patent creates a composite cathode material consisting of multiple phases with different compositions (high-Mn core and low-Mn shell) within a single olivine structure. This composite approach combines the high energy density benefits of high-Mn regions with the structural stability of low-Mn regions, simultaneously achieving both improving and worsening feature targets.
2Use of energy by moving object
If manganese substitutes iron in LiFePO4 to produce LMFP cathode material, then working voltage and energy density are improved, but charge transport deteriorates
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the core region contains high manganese content (0.7-0.85) for high energy density, while the shell region contains lower manganese content (0.1-0.3) for structural stability. This spatial differentiation of composition allows each region to optimize its local properties, resolving the contradiction between energy density and structural stability.
Solution Approach 2:
The patent creates a composite cathode material consisting of multiple phases with different compositions (high-Mn core and low-Mn shell) within a single olivine structure. This composite approach combines the high energy density benefits of high-Mn regions with the structural stability of low-Mn regions, simultaneously achieving both improving and worsening feature targets.
3Use of energy by moving object
If high manganese content is used in LMFP cathode material, then energy density is improved, but cycling performance deteriorates
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the core region contains high manganese content (0.7-0.85) for high energy density, while the shell region contains lower manganese content (0.1-0.3) for structural stability. This spatial differentiation of composition allows each region to optimize its local properties, resolving the contradiction between energy density and structural stability.
Solution Approach 2:
The patent creates a composite cathode material consisting of multiple phases with different compositions (high-Mn core and low-Mn shell) within a single olivine structure. This composite approach combines the high energy density benefits of high-Mn regions with the structural stability of low-Mn regions, simultaneously achieving both improving and worsening feature targets.
4Use of energy by moving object
If iron is replaced by manganese in LiFePO4, then working voltage increases, but specific capacity falls short of theoretical levels
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the core region contains high manganese content (0.7-0.85) for high energy density, while the shell region contains lower manganese content (0.1-0.3) for structural stability. This spatial differentiation of composition allows each region to optimize its local properties, resolving the contradiction between energy density and structural stability.
Solution Approach 2:
The patent creates a composite cathode material consisting of multiple phases with different compositions (high-Mn core and low-Mn shell) within a single olivine structure. This composite approach combines the high energy density benefits of high-Mn regions with the structural stability of low-Mn regions, simultaneously achieving both improving and worsening feature targets.
Data Source
AI summary
Particulate LMFP cathode materials having high manganese contents and small amounts of dopant metals are disclosed. These cathode materials are made by milling a mixture of precursor materials in a wet or dry milling process. Preferably, off- stoichiometric amounts of starting materials are used to make the cathode materials. Unlike other high manganese LMFP materials, these cathode materials provide high specific capacities, very good cycle life and high energies even at high discharge rates.