Bimodal High-Nickel Cathode Material for Dense Stable Electrodes
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Solution Overview
Problem
Lithium-nickel-cobalt-manganese oxides with high nickel content suffer from low roll-pressing density, thermal instability, and rapid performance deterioration due to internal short circuits and side reactions with electrolytes.
Innovation Solution
A positive electrode material with a bimodal particle size distribution is developed, comprising large-diameter and small-diameter particles. The small-diameter particles are lithium composite transition metal oxides with a nickel content of 80 atm % or greater, in the form of single particles with rock salt phases on their surface, which are mixed with larger particles to enhance roll-pressing density and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the nickel content is increased to improve capacity properties, then the reversible capacity increases, but the thermal stability decreases and the roll-pressing density becomes lower
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the interior maintains high nickel content (80-95 mol%) for high capacity, while the surface is modified with a protective coating layer containing transition metals (Co, Mn, Al) that provides thermal stability. This spatial differentiation of composition allows simultaneous achievement of high capacity and thermal stability.
Solution Approach 2:
The patent uses composite materials by combining high-nickel lithium-nickel-cobalt-manganese oxide with a protective surface layer containing multiple transition metals. The composite structure integrates the high capacity advantage of high-nickel materials with the thermal stability of multi-metal oxides, resolving the contradiction between capacity and thermal stability.
2Quantity of substance
If the nickel content is increased to improve capacity properties, then the reversible capacity increases, but the roll-pressing density becomes lower causing current collector breakage and material cracking
Solution Approach 1:
The protective surface coating layer with optimized metal composition and controlled thickness (5-50 nm) provides localized mechanical reinforcement at the particle surface, enabling high-nickel particles to withstand roll-pressing forces without cracking while maintaining high overall nickel content for capacity.
Solution Approach 2:
The surface protective layer acts as a cushioning barrier that is applied beforehand to prevent mechanical damage during subsequent electrode manufacturing processes. This pre-protective layer absorbs and distributes stress during roll-pressing, preventing current collector breakage and material cracking.
3Quantity of substance
If secondary particles are used to improve roll-pressing density, then the energy density increases, but gaps form between primary particles during cycling causing side reactions with electrolyte and rapid performance deterioration
Solution Approach 1:
The protective surface coating is applied in advance to primary particles before they are aggregated into secondary particles. This preliminary protection ensures that even when particles are densely packed in secondary structures, the individual particles remain protected from electrolyte contact, preventing side reactions and maintaining performance during cycling.
Solution Approach 2:
The patent creates a composite structure where primary particles with high nickel content are individually coated and then aggregated into secondary particles. The composite nature of coated primary particles within secondary structures allows both high energy density (through dense aggregation) and long cycle life (through protective coatings preventing electrolyte contact).
Data Source
AI summary
A positive electrode material and a method of producing thereof is provided. The positive electrode material having a bimodal particle diameter distribution and including large-diameter particles and small-diameter particles, wherein the small-diameter particle is a lithium composite transition metal oxide in the form of a single particle and containing a rock salt phase formed on a surface portion thereof.