Lithium Nickel Composite Oxide Electrode Particle Structure
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Solution Overview
Problem
Lithium nickel-based composite oxides used in non-aqueous electrolyte secondary batteries experience significant capacity degradation due to crystal structure collapse and temperature-related expansion issues, particularly in high-cycle applications like electric vehicles, where long-term cycle characteristics and high volume energy density are required.
Innovation Solution
A positive electrode active substance with a composite oxide structure of lithium and nickel, featuring secondary particles formed by aggregation of primary particles with controlled average particle diameters and standard deviations, and a tap density of 2.3 g/cm³ or more, which suppresses particle displacement and cracking during charge and discharge cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium nickel-based composite oxide is used as positive electrode active substance, then high capacity and low cost are achieved, but crystal structure collapse occurs during charge-discharge cycles leading to significant capacity degradation
Solution Approach 1:
The positive electrode active substance is divided into secondary particles composed of multiple primary particles. Each primary particle has a controlled average particle diameter of 0.9 μm or less, and the secondary particles have a controlled average particle diameter of 3 μm to 15 μm. This segmentation prevents crystal structure collapse during charge-discharge cycles while maintaining high capacity, as the smaller primary particles experience less structural stress during lithium ion insertion/extraction.
Solution Approach 2:
The invention controls specific parameters including the average particle diameter of primary particles (0.9 μm or less), the average particle diameter of secondary particles (3 μm to 15 μm), and the ratio between them. By optimizing these parameters, the patent achieves both high capacity and excellent cycle characteristics, resolving the contradiction between quantity and reliability.
2Reliability
If particle size is reduced to prevent crystal structure collapse, then cycle characteristics improve, but volume energy density decreases
Solution Approach 1:
The invention employs a nested structure where multiple primary particles (each with diameter ≤0.9 μm) are aggregated to form secondary particles (with diameter 3-15 μm). This nested arrangement allows the benefits of small primary particle size (improved cycle characteristics) while achieving higher volume energy density through the compact aggregation of multiple particles into larger secondary particles that fill space more efficiently.
3Quantity of substance
If lithium cobalt composite oxide is used for high voltage and high energy density, then performance is improved, but raw material cost increases and supply stability decreases due to cobalt scarcity
Solution Approach 1:
The invention replaces expensive cobalt-based materials with lithium nickel-based composite oxide, which uses more abundant and cheaper nickel. Although nickel-based materials traditionally have poorer cycle characteristics, the patent overcomes this limitation through the controlled particle size structure (primary particles ≤0.9 μm aggregated into secondary particles of 3-15 μm), achieving both cost-effectiveness and durable performance.
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
This approach significantly improves the cycle characteristics and minimizes capacity loss in lithium nickel-based composite oxide batteries, ensuring stable performance over long periods and high volume energy density, even in extreme temperature conditions.
Implementation Method 1
since the composite oxide undergoes shrinkage and expansion in conjunction with the desorption and insertion of lithium ions
Data Source
Figure 1A~1B
Figure 2
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AI summary
[Object] Provided is a means which is capable, with respect to a non-aqueous electrolyte secondary battery, of suppressing a decrease in capacity when the battery is used for a long period of time, and improving cycle characteristics. [Solving Means] Disclosed is a positive electrode active substance for a non-aqueous electrolyte secondary battery comprising a composite oxide containing lithium and nickel, in which the positive electrode active substance has a structure of secondary particles formed by aggregation of primary particles, the average particle diameter of the primary particles (D1) is 0.9 µm or less, and the average particle diameter of the primary particles (D1) and the standard deviation (σ) of the average particle diameter of the primary particles (D1) meet the relationship of D1/σ2 ≥ 24.