Lithium-Cobalt Oxide Particles for Low-Temperature Fine-Grain Cathodes
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Solution Overview
Problem
The challenge is to produce lithium-cobalt-based composite oxide particles with a small particle diameter to reduce the weight and thickness of positive electrode materials used in non-aqueous lithium secondary batteries and all-solid-state batteries, as traditional solid-phase processes require high firing temperatures leading to grain growth and larger particle sizes.
Innovation Solution
The solution involves using nano-level fine particles as a cobalt source to facilitate a reaction with a lithium source at lower temperatures, resulting in lithium-cobalt-based composite oxide particles with an average primary particle diameter of 0.50 µm or less, and a BET specific surface area of 2.0 m²/g or more.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high firing temperature is used in the solid-phase process to sufficiently react the raw material powders, then the crystallization and reaction completeness is improved, but the grain growth occurs causing large particle diameter
Solution Approach 1:
The patent applies preliminary action by pre-mixing the raw material powders (lithium compound and cobalt compound) at the nanometer level before firing. This preliminary mixing ensures that the reactants are in close contact and properly distributed, enabling the reaction to proceed completely at lower temperatures without requiring high-temperature processing that would cause grain growth.
Solution Approach 2:
The patent changes the particle size parameter of the raw materials from conventional sizes to nanometer-level fine particles. This parameter change increases the specific surface area and reactivity of the raw materials, allowing the solid-phase reaction to proceed efficiently at lower firing temperatures (900-1100°C), thereby preventing grain growth while ensuring complete reaction.
2Weight of stationary object
If the particle diameter of positive electrode material is reduced to reduce battery weight and thickness, then the battery weight and thickness are reduced, but the manufacturing difficulty increases
Solution Approach 1:
The patent applies segmentation by dividing the positive electrode material into fine particles with controlled particle diameters (D10: 0.01-0.5 μm, D50: 0.01-1.0 μm, D90: 0.01-2.0 μm). This segmentation reduces the battery weight and thickness while the specific particle size distribution ensures manageable manufacturing characteristics and proper electrode formation.
Solution Approach 2:
The patent uses composite materials by combining lithium compound and cobalt compound in a specific molar ratio (0.95-1.05 Li/Co). This composite approach creates a material with optimized properties that balances small particle size with manufacturing ease, as the composite structure maintains stability and reactivity during the firing process.
3Volume of moving object
If nano-level fine particles are used as cobalt source to enable low-temperature firing, then the particle diameter is reduced, but the firing temperature must be precisely controlled
Solution Approach 1:
The patent changes the particle size parameter of the cobalt source to nanometer-level fine particles (D50: 0.01-0.5 μm). This parameter change increases the reactivity and reduces the required firing temperature to 900-1100°C, while the narrow particle size distribution ensures uniform heating and reduces the risk of overheating or underheating.
Solution Approach 2:
The patent creates a composite material system with lithium compound and cobalt compound in a controlled molar ratio (0.95-1.05 Li/Co). This composite structure ensures that the reaction proceeds uniformly at the specified temperature range, as the stoichiometric balance prevents localized overheating or incomplete reaction that would occur with improper mixing or ratios.
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 allows for the production of lithium-cobalt-based composite oxide particles that effectively reduce the weight and thickness of positive electrode materials, while maintaining high charge-discharge capacity and crystallinity, thus enhancing the performance and efficiency of lithium batteries.
Implementation Method 1
a raw material using nano-level fine particles as a cobalt source allows a reaction with a lithium source to readily proceed so that crystallization well proceeds even by low-temperature firing
Implementation Method 2
This finding has led to the completion of the present invention. Specifically, the present invention (1) provides lithium-cobalt-based composite oxide particles formed of a lithium-cobalt-based composite oxide having an average primary particle diameter of 0.50 μm or less, the lithium-cobalt-based composite oxide particles showing a weight loss on heating at 850°C of 1.5 mass% or less
Data Source
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AI summary
Disclosed herein are lithium-cobalt-based composite oxide particles obtained by a solid-phase process and capable of reducing the weight and thickness of a positive electrode material when used as a positive electrode active material for non-aqueous lithium secondary batteries or all-solid-state batteries and a method for producing the same. The lithium-cobalt-based composite oxide particles are formed of a lithium-cobalt-based composite oxide having an average primary particle diameter of 0.50 µm or less and show a weight loss on heating at 850°C of 1.5 mass% or less.