Battery Negative Electrode Composition for High-Rate Output Stability
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Solution Overview
Problem
Lithium secondary batteries with small particle size negative electrode active materials face challenges in achieving high-output characteristics while minimizing capacity loss and cycle degradation due to increased side reactions during high-rate charge/discharge processes.
Innovation Solution
A negative electrode composition with a first active material of large particle size and a second active material of small particle size, where the second material is limited to 10% by weight, and optimized particle size ratios and tortuosity, along with an amorphous carbon coating, to enhance lithium ion diffusion and reduce side reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a negative electrode active material having a small particle size is used to increase specific surface area, then output characteristics are improved, but capacity loss increases due to increased side reactions
Solution Approach 1:
The patent applies parameter changes by precisely controlling the particle size of the negative electrode active material within the range of 3 μm to 7 μm and limiting its content to 5 wt% or less based on the total weight of negative electrode active materials. This optimization of particle size parameter balances the specific surface area for output characteristics while minimizing side reactions that cause capacity loss
Solution Approach 2:
The patent uses composite materials by combining small particle size negative electrode active materials (3-7 μm) with large particle size negative electrode active materials in a specific ratio. The small particle size material (5 wt% or less) provides high output characteristics, while the majority large particle size material (95 wt% or more) maintains stability and reduces side reactions, creating a synergistic composite structure
2Power
If a negative electrode active material having a small particle size is used to increase specific surface area, then output characteristics are improved, but cycle characteristics are significantly reduced during repeated high-rate charge/discharge processes
Solution Approach 1:
The patent optimizes the particle size parameter to 3-7 μm and limits the content to 5 wt% or less, which provides sufficient specific surface area for good output characteristics while maintaining structural stability during repeated charge/discharge cycles, thus preserving cycle characteristics
Solution Approach 2:
The composite structure combines small particle size materials (providing output characteristics) with large particle size materials (providing structural stability), where the small particle content is limited to 5 wt% or less. This composite approach allows the electrode to maintain both high output performance and good cycle characteristics during repeated high-rate charge/discharge processes
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 solution effectively improves output characteristics while reducing irreversible capacity loss and long-term performance deterioration, maintaining high capacity density and lifespan.
Implementation Method 1
The second negative electrode active material may include an amorphous carbon coating layer formed on the secondary particle.
Data Source
AI summary
Provided is a negative electrode for a secondary battery including: a current collector, and a negative electrode active material layer formed on the current collector and containing a first negative electrode active material having a large particle size and a second negative electrode active material having a small particle size, wherein the second negative electrode active material is contained in an amount of 10% by weight or less based on the total weight of the negative electrode active material, and the following Relational Equation 1 is satisfied: [Relational Equation 1] 0.4<D2/D1<0.7; wherein D1 and D2 are the particle sizes (D50, μm) of the first and second negative electrode active materials, respectively.