Nonaqueous Electrolyte Battery Protective Layer Particle Size Control
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries face issues with internal short circuits and inhibited lithium ion diffusion, which affect their output characteristics.
Innovation Solution
A nonaqueous electrolyte secondary battery configuration and production method that includes a protective layer with ceramic particles and a binder on the positive or negative electrode active material layers, where the ceramic particles have specific diameter ranges and the negative electrode active material layer contains carbon particles, styrene-butadiene rubber, and carboxymethyl cellulose, to prevent locally thick portions and enhance lithium ion diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective layer containing ceramic particles and a binder is provided on the surface of the positive electrode active material layer or the surface of the negative electrode active material layer, then internal short circuits are prevented, but lithium ion diffusion is inhibited and output characteristics deteriorate
Solution Approach 1:
The patent applies parameter changes by carefully controlling the particle size distribution of ceramic particles (D50: 1.0-1.8 μm, D90: 3.0-5.0 μm) and the composition ratio of binder components (carboxymethyl cellulose and styrene-butadiene rubber). This optimization allows the protective layer to prevent internal short circuits while minimizing lithium ion diffusion inhibition, thus resolving the contradiction between reliability and output characteristics.
Solution Approach 2:
The protective layer uses a composite material system combining ceramic particles (alumina, silica, or titania) with a binder composed of carboxymethyl cellulose and styrene-butadiene rubber. This composite structure provides both the protective function against internal short circuits and the controlled porosity needed for lithium ion diffusion, thereby maintaining output characteristics while ensuring safety.
2Reliability
If the protective layer is made thicker to better prevent internal short circuits, then reliability improves, but the formation of locally thick portions increases and lithium ion diffusion is further inhibited
Solution Approach 1:
The patent applies local quality by using a specific particle size distribution where smaller particles (D50: 1.0-1.8 μm) fill in local gaps and larger particles (D90: 3.0-5.0 μm) provide structural support. This distribution ensures uniform coverage without locally thick portions, maintaining both reliability and manufacturing precision simultaneously.
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 configuration effectively suppresses internal short circuits and improves output characteristics by preventing the formation of locally thick portions and inhibiting lithium ion diffusion, resulting in a battery with enhanced performance.
Implementation Method 1
A protective layer is formed on the positive electrode active material layer or the negative electrode active material layer, and the protective layer contains ceramic particles and a binder
Implementation Method 2
it is possible to effectively suppress the inhibition of lithium ion diffusion by a protective layer, and thus the nonaqueous electrolyte secondary battery has excellent output characteristics
Data Source
AI summary
A nonaqueous electrolyte secondary battery includes a positive electrode plate having a positive electrode active material layer formed on a positive electrode core, a negative electrode plate having a negative electrode active material layer formed on a negative electrode core, and a flat-shape wound electrode body in which the positive electrode plate and the negative electrode plate are wound through a separator. Further, a protective layer is formed on the positive electrode active material layer or the negative electrode active material layer. The protective layer contains ceramic particles and a binder, and the average particle diameter (D50) and the average particle diameter (D90) of the ceramic particles are 1.0 μm to 1.8 μm and 3.0 μm to 5.0 μm, respectively.