LMFP Positive Electrode Composition for Capacity and Cycle Stability
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Solution Overview
Problem
Existing lithium manganese iron phosphate (LMFP) materials face issues with manganese dissolution, cycle stability, and rate performance due to varying particle sizes and manganese-to-iron (Mn/Fe) molar ratios, leading to degraded battery performance.
Innovation Solution
A positive electrode material comprising five lithium manganese iron phosphate materials with specific particle size relationships and sequential Mn/Fe molar ratios, including aggregates and single-crystal-like forms, optimized to enhance compaction density and electrochemical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If aggregate LMFP material with small primary particles is used to achieve high capacity, then capacity is improved, but manganese dissolution increases and cycle performance degrades
Solution Approach 1:
The invention segments the particle size distribution into five distinct ranges (D501-D505) with specific ratios, creating a multi-size particle system where smaller particles provide high capacity while larger particles reduce dissolution. The particle size segmentation allows optimization of both capacity and stability by distributing different particle sizes in specific proportions.
Solution Approach 2:
The invention applies local quality by assigning different Mn/Fe molar ratios to different particle size ranges. Smaller particles (higher capacity contribution) have lower Mn/Fe ratios to reduce dissolution, while larger particles have higher Mn/Fe ratios to enhance stability. This local optimization resolves the contradiction between capacity and dissolution resistance.
2Object-generated harmful factors
If single-crystal-like LMFP material with large primary particles is used to reduce manganese dissolution, then manganese dissolution is reduced, but capacity decreases
Solution Approach 1:
The invention segments the particle population into five size groups, using the smallest particles (D505, 0.8-1.5 μm) to provide high capacity while the larger particles (D501, 6-10 μm) provide stability. This segmentation allows the system to achieve both high capacity and low dissolution simultaneously by combining particle sizes rather than using a single size.
Solution Approach 2:
The invention creates a composite particle size distribution system combining five different particle size ranges with specific ratios. This composite approach integrates the advantages of both small particles (high capacity) and large particles (low dissolution) into a single electrode material system, achieving synergistic performance.
3Stability of the object's composition
If higher Mn/Fe molar ratio is used to improve structural stability, then structural stability is improved, but rate performance and cycle stability may be affected
Solution Approach 1:
The invention applies local quality by varying Mn/Fe molar ratios across different particle size ranges. Smaller particles have lower Mn/Fe ratios (0.8-1.5) to maintain good rate performance and lithium ion diffusion, while larger particles have higher Mn/Fe ratios (1.8-2.5) to provide structural stability. This local optimization resolves the contradiction between stability and rate performance.
Solution Approach 2:
The invention changes the Mn/Fe molar ratio parameter across different particle size groups, creating a gradient distribution. This parameter variation allows the material to exhibit different properties at different scales, with smaller particles optimized for kinetics and larger particles optimized for stability, achieving both high rate performance and good cycle stability.
4Volume of stationary object
If multi-size particle distribution is used to optimize compaction density, then compaction density is improved, but manufacturing complexity increases
Solution Approach 1:
The invention segments the particle size distribution into five specific ranges with defined D50 values and ratios. This segmentation provides a clear manufacturing guideline that balances compaction density optimization with manufacturing feasibility. The specific ratio ranges (a=0.35-0.5, b=0.20-0.27, c=0.17-0.18, d=0.15-0.16) offer practical control parameters for production.
Data Source
AI summary
A positive electrode material includes a first lithium manganese iron phosphate material in an aggregate form, a second and third lithium manganese iron phosphate materials in an aggregate and/or single-crystal-like form, and a fourth and fifth lithium manganese iron phosphate materials in a single-crystal-like form. D505<D504<D503<D502<D501, D502=aD501, D503=bD501, D504=cD501, D505=dD501, and 5 μm≤D501≤15 μm. 0.35≤a≤0.5, 0.2≤b≤0.27, 0.17≤c≤0.18, and 0.15≤d≤0.16. Molar ratios of manganese to iron in the first, the second, the third and the fourth lithium manganese iron phosphate materials increase sequentially, and a molar ratio of manganese to iron in the fifth lithium manganese iron phosphate material is greater than that in the third lithium manganese iron phosphate material.