Lithium Manganese Cathode Morphology for Higher Volumetric Energy Density
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Solution Overview
Problem
Conventional lithium manganese-based oxides exhibit low energy density per unit volume and poor electrochemical characteristics, limiting their effectiveness as positive electrode active materials in lithium secondary batteries, especially when compared to commercialized ternary lithium composite oxides.
Innovation Solution
A lithium manganese-based oxide with a controlled primary particle shape, forming a solid solution of phases belonging to the C2/m and R-3m space groups, is synthesized to improve the capacity and rate characteristics. The primary particles on the surface of secondary particles are oriented, having thin plate-like, thin rod-like, or fine needle-like forms, and a bimodal or trimodal particle size distribution is employed to enhance performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If overlithiated lithium manganese-based oxide (OLO) is used as positive electrode active material, then high capacity under high voltage operating environment can be achieved, but electrical conductivity is low and rate characteristic is poor
Solution Approach 1:
The patent changes the particle shape parameter from conventional spherical or irregular shapes to plate-like, rod-like, or needle-like shapes with specific aspect ratios. This parameter change increases the surface area to volume ratio, improving electrical conductivity and lithium ion diffusion pathways, thereby enhancing rate characteristics while maintaining high capacity
Solution Approach 2:
The patent creates a composite structure where primary particles with controlled shapes aggregate to form secondary particles. This composite approach combines the high capacity benefit of OLO with improved conductivity through the optimized morphology and aggregation structure, resolving the contradiction between capacity and rate performance
2Quantity of substance
If OLO is used as positive electrode active material, then high capacity can be achieved, but energy density per unit volume is lower compared to high-Ni-type positive electrode active materials
Solution Approach 1:
The patent optimizes the size parameter of primary particles (0.1-10 μm) and their aggregation structure to increase volumetric energy density. By controlling particle dimensions and density of aggregation, the material achieves both high capacity and high energy density per unit volume
Solution Approach 2:
The patent transitions from considering only particle size to considering particle shape dimensions (plate-like, rod-like, needle-like). This dimensional approach allows optimization of packing efficiency and volumetric energy density while maintaining the high capacity characteristics of OLO
3Ease of manufacture
If lithium manganese-based oxide is used as positive electrode active material, then thermal safety and low cost advantages are achieved, but capacity and high-temperature characteristics are poor
Solution Approach 1:
The patent changes the morphological parameters of lithium manganese-based oxide to plate-like, rod-like, or needle-like shapes. This parameter change increases surface area and improves lithium ion diffusion, thereby enhancing capacity and high-temperature characteristics while maintaining the inherent cost and thermal safety advantages of lithium manganese-based materials
Data Source
AI summary
The present invention relates to a positive electrode active material and a lithium secondary battery comprising the same. More specifically, the present invention relates to a positive electrode active material comprising a lithium manganese oxide in which lithium and manganese are present in excess, having an improved energy density per unit volume, and a lithium secondary battery comprising the same, thereby exhibiting enhanced electrochemical characteristics.