High-Nickel Cathode Material Structure for Crack-Resistant Output
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Solution Overview
Problem
Positive electrode active materials for non-aqueous electrolyte secondary batteries with high nickel content face challenges in achieving desired output characteristics due to cracking during pressure application and expansion/contraction cycles, and existing methods do not adequately address the need for improved initial efficiency and durability.
Innovation Solution
A lithium-transition metal composite oxide with a layered structure containing lithium, nickel, cobalt, and manganese, having specific mole ratios and a D50/DSEM ratio of 1 to 4, is produced through a method involving heat treatment and dry-dispersion treatment, which enhances the material's stability and resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If aggregated particles are used to improve output characteristics, then power density is improved, but cracks occur during pressure application and expansion/contraction cycles
Solution Approach 1:
The positive electrode active material is divided into multiple primary particles (each with D50 of 0.5-2.0 μm) that aggregate to form secondary particles. This segmentation allows the material to achieve high power density through aggregation while maintaining crack resistance at the primary particle level, as the smaller primary particles can better withstand expansion and contraction stresses.
Solution Approach 2:
The patent applies different structural characteristics to different levels: primary particles are designed with specific size and composition properties for crack resistance, while secondary particles are formed by aggregation for high power density. The local composition is also optimized with Ni3+ sites at specific ratios to enhance structural stability at critical locations.
2Quantity of substance
If high nickel content is used to improve charge and discharge capacities, then capacity is improved, but structural stability deteriorates during cycling
Solution Approach 1:
The patent changes the oxidation state parameter of nickel from the conventional Ni2+ to Ni3+, creating a high-nickel layered oxide with Ni3+ sites occupying 96.0% or more of the 3a lithium sites. This parameter change enables achieving high charge and discharge capacities while maintaining structural stability through the unique electronic configuration and bonding characteristics of Ni3+.
Solution Approach 2:
The patent creates a composite structure by combining high-nickel layered oxide (providing high capacity) with small amounts of cobalt and manganese (providing structural stability). The multi-element composite approach allows the material to achieve both high capacity and stability during charge-discharge cycling.
3Reliability
If single particle-type structure is used to avoid cracks, then durability is improved, but output characteristics are insufficient
Solution Approach 1:
The patent segments the particle structure into primary particles (for durability) and secondary particles (for output characteristics). The primary particles maintain single-particle integrity for crack resistance, while their aggregation into secondary particles provides the necessary power density and output characteristics.
4Stability of the object's composition
If manganese content is increased to improve structural stability, then stability is improved, but manganese resistance increases reducing efficiency
Solution Approach 1:
The patent changes the primary stabilizing element from manganese to nickel in the Ni3+ oxidation state. By using high-nickel content (greater than 0.8 ratio of nickel to total metals other than lithium) with Ni3+ sites, the material achieves structural stability through nickel's inherent stability at this oxidation state, thereby reducing manganese content and minimizing manganese-related resistance losses.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The resulting positive electrode active material achieves superior initial efficiency and durability, with improved discharge capacity and capacity maintenance rate, while minimizing the impact of manganese resistance.
Implementation Method 1
heat treating the lithium mixture at a temperature of from 650° C. to 800° C. to obtain a heat-treated product
Implementation Method 2
dry-dispersion treating the heat-treated product to obtain a first dispersed product
Data Source
AI summary
Provided is a positive electrode active material for a non-aqueous electrolyte secondary battery, the active material including a lithium-transition metal composite oxide containing lithium, nickel, cobalt, and manganese, having a layered structure, having a ratio D50/DSEM of from 1 to 4, and having a ratio of a number of moles of nickel to a total number of moles of metals other than lithium of greater than 0.8 and less than 1, a ratio of a number of moles of cobalt to the total number of moles of metals other than lithium of less than 0.2, a ratio of a number of moles of manganese to the total number of moles of metals other than lithium of less than 0.2, and a ratio of the number of moles of manganese to a sum of the number of moles of cobalt and the number of moles of manganese of less than 0.58.