Li-Mn-Ni Cathode Composition Balancing Capacity and Material Density
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Solution Overview
Problem
Conventional positive electrode active materials for secondary batteries face challenges in enhancing energy density while maintaining capacity and active material density, leading to a trade-off relationship.
Innovation Solution
A lithium-transition metal composite oxide with a specific composition and structure, represented by the formula Li x Mn y Ni z Me 2-x-y-z O a F b, is used, featuring a BET specific surface area of 1-4 m^2/g and average pore size of 100 nm or less, which enhances energy density by optimizing the proportion of Li, Mn, Ni, and other elements like Co, Al, Ti, Ge, Nb, Sr, Mg, Si, P, and Sb, and incorporating fluorine to stabilize the crystal structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Li-excess positive electrode active material is used to increase capacity, then battery capacity increases, but active material density decreases leading to reduced energy density
Solution Approach 1:
The patent optimizes the chemical composition parameters of the lithium-transition metal composite oxide by precisely controlling the ratios of Li, Mn, Ni, and other elements according to specific formulas, and adjusts processing parameters such as sintering temperature and atmosphere to achieve both high capacity and high density simultaneously
Solution Approach 2:
The patent uses composite lithium-transition metal composite oxide materials combining multiple transition metals (Mn, Ni, Co, Al, Ti, Ge, Nb, Sr, Mg, Si, P, Sb) with lithium to create a material that achieves both high capacity and high density through synergistic effects of different elements
2Power
If particle aggregation is controlled to improve low-temperature output, then output at low temperature improves, but energy density enhancement is limited
Solution Approach 1:
The patent creates local quality variations by forming core-shell structures or surface-modified regions with different compositions and properties from the bulk material, allowing the surface to provide good low-temperature performance while the bulk maintains high density and capacity
Solution Approach 2:
The patent divides the positive electrode active material into particles with controlled size distributions and aggregation states, creating a hierarchical structure that improves both low-temperature output characteristics and overall energy density
Data Source
Figure 1
AI summary
This positive electrode active material for nonaqueous electrolyte secondary batteries contains a lithium transition metal composite oxide. This lithium transition metal composite oxide is represented by general formula LixMnyNizMe2-x-y-zOaFb (wherein 1 ≤ x ≤ 1.2; 0.4 ≤ y ≤ 0.7; 0.1 ≤ z ≤ 0.4; 0 < b ≤ 0.2; 1.9 ≤ a + b ≤ 2.1; and Me represents at least one element selected from among Co, Al, Ti, Ge, Nb, Sr, Mg, Si, P and Sb), while having a BET specific surface area of from 1 m2/g to 4 m2/g and an average pore diameter of 100 nm or less.