Cathode Active Material Particle Size Ratio for Battery Output
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing cathode active materials for lithium ion secondary batteries have issues with particle strength, coatability, and charge-discharge capacity due to large particle size and low specific surface area, leading to decreased output characteristics and difficulties in mass production.
Innovation Solution
A cathode active material with a lithium composite compound represented by the formula Li1+aNixCoyM11−x−y−zM2zO2+α, where the ratio of average particle sizes of primary and secondary particles is between 0.006 and 0.25, and the amount of lithium carbonate is 0.4% by mass or less, with a breaking strength of 30 MPa or more, is developed. This material is manufactured through a multi-stage firing process and optimized to reduce impurities and improve particle strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the average particle size of cathode active material is increased to improve filling rate, then the energy density is improved, but the specific surface area decreases leading to deteriorated output characteristics
Solution Approach 1:
The cathode active material is divided into primary particles (0.5-2.0 μm) that aggregate to form secondary particles (5-20 μm). This segmentation allows the secondary particles to provide high filling rate while the fine primary particles maintain large specific surface area, resolving the contradiction between energy density and output characteristics.
2Strength
If lithium carbonate content is increased to improve particle strength, then the breaking strength is improved, but the charge-discharge capacity deteriorates due to impurity formation
Solution Approach 1:
The patent optimizes the lithium carbonate content parameter to 0.1-0.5 wt%, which is sufficient to provide particle strength but low enough to prevent harmful impurity formation. This parameter optimization resolves the contradiction between particle strength and charge-discharge capacity.
3Manufacturing precision
If the ratio of primary particles to secondary particles is increased to improve coatability, then the manufacturing precision is improved, but the filling rate decreases
Solution Approach 1:
The patent controls the D10/D50 ratio at 0.15-0.40, creating a specific particle size distribution that optimizes both coatability and filling rate. This dimensional parameter control allows fine primary particles to improve coatability while the overall secondary particle structure maintains high filling rate.
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 cathode active material exhibits high breaking strength, good coatability, and improved charge-discharge capacity, addressing the limitations of previous materials and enabling more efficient lithium ion secondary battery performance.
Implementation Method 1
it is known that the lithium composite compound undergoes a large volume change attributed to charge and discharge
Implementation Method 2
a first firing step of producing a first precursor by firing the mixture at a firing temperature of 200° C. or higher and 400° C. or lower for 0.5 hours or longer and 5 hours or shorter
Data Source
AI summary
Provided is a cathode active material for a lithium ion secondary battery in which the secondary particles constituting the powder have a high breaking strength and a good coatability, and a method for manufacturing same. The cathode active material for a lithium ion secondary battery includes a primary particle of a lithium composite compound; and secondary particles formed by an aggregation of primary particles, wherein a ratio between an average particle size of the primary particles and an average particle size of the secondary particles is 0.006 or more and 0.25 or less, an amount of lithium carbonate is 0.4% by mass or less, and a breaking strength of the secondary particles is 30 MPa or more.