Bimodal Cathode Material for Dense and Stable Lithium Batteries
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Solution Overview
Problem
Overlithiated lithium manganese-based oxides used in lithium secondary batteries suffer from low energy density per unit volume and poor electrochemical properties and stability, limiting their replacement of commercially available ternary lithium composite oxides.
Innovation Solution
A bimodal-type positive electrode active material is developed by combining small and large particles of lithium manganese-based oxides with different average particle diameters, and incorporating a barrier layer on the surface of the small particles to reduce side reactions and elution of transition metals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If overlithiated lithium manganese-based oxide is used as positive electrode active material, then high capacity under high voltage operating environment is achieved, but energy density per unit volume is low and electrochemical stability is poor
Solution Approach 1:
The patent applies parameter changes by controlling the lithium content to satisfy 1 < x ≤ 1.5 in Li_xMnO_4, optimizing the transition metal composition ratios (Ni: 0.3-0.7, Mn: 0.1-0.5, Co: 0.05-0.3, Al: 0.05-0.3), and adjusting sintering temperature (900-1100°C) and time (5-20 hours) to achieve the desired capacity while improving electrochemical stability
Solution Approach 2:
The patent uses composite materials by combining multiple transition metals (Ni, Mn, Co, Al) in specific ratios within the lithium manganese-based oxide structure, creating a composite material that leverages the advantageous properties of each metal to achieve both high capacity and improved stability
2Power
If overlithiated lithium manganese-based oxide is used, then high voltage operating environment performance is improved, but rate performance is low due to low electrical conductivity
Solution Approach 1:
The patent improves electrical conductivity through parameter changes by optimizing the transition metal composition ratios and sintering conditions, which enhances the material's electrical conductivity and thereby improves rate performance while maintaining high voltage capability
3Quantity of substance
If lithium manganese-based oxide with excess Mn is used, then high capacity is achieved, but Li by-products are generated causing gelation and gas generation
Solution Approach 1:
The patent reduces Li by-product generation through parameter changes by optimizing the lithium content parameter (1 < x ≤ 1.5) and transition metal ratios, and by controlling sintering parameters (temperature and time) to minimize unwanted chemical reactions that produce LiOH and Li2CO3
Solution Approach 2:
The patent uses composite materials with multiple transition metals in optimized ratios to reduce the excessive reactivity of pure lithium manganese oxide, thereby minimizing by-product formation while maintaining high capacity
Data Source
AI summary
The present invention relates to a positive electrode active material and a lithium secondary battery including the same, and more particularly, to a bimodal-type positive electrode active material, in which low energy density per unit volume and low stability of an overlithiated lithium manganese-based oxide are improved, and a lithium secondary battery including the same.