Positive Electrode PTFE Gradient for Uniform Electrolyte Diffusion
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Solution Overview
Problem
Conventional non-aqueous electrolyte secondary batteries face challenges in achieving improved output characteristics while maintaining good cycle characteristics, particularly due to the presence of a sulfonate compound on the surfaces of lithium-containing transition metal composite oxide particles, which reduces electrolyte diffusivity and reaction uniformity in the positive electrode mixture layer.
Innovation Solution
The positive electrode mixture layer is designed with a specific distribution of polytetrafluoroethylene (PTFE) content across three equal parts, combined with a sulfonate compound on the surfaces of lithium-containing transition metal composite oxide particles, ensuring uniform electrolyte distribution and reaction uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sulfonate compound is present on the surfaces of lithium-containing transition metal composite oxide particles, then reaction resistance is reduced, but electrolyte diffusivity and reaction uniformity in the positive electrode mixture layer deteriorate
Solution Approach 1:
The patent applies local quality by creating a specific spatial distribution of PTFE within the positive electrode mixture layer. The PTFE content is controlled to be 0.1-5 mass% in the region within 10 μm from the aluminum foil surface, and 0.1-2 mass% in other regions. This localized variation in PTFE concentration optimizes electrolyte distribution and reaction uniformity at the electrode-substrate interface while maintaining the beneficial low reaction resistance properties provided by the sulfonate compound on the active material surfaces.
2Stability of the object's composition
If PTFE is uniformly distributed in the positive electrode mixture layer, then electrolyte diffusivity is improved, but manufacturing precision deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the PTFE content as a critical parameter in different regions of the positive electrode mixture layer. By specifying quantitative ranges (0.1-5 mass% within 10 μm from aluminum foil, 0.1-2 mass% elsewhere), the invention transforms the qualitative goal of 'uniform distribution' into controllable quantitative parameters that balance electrolyte diffusivity improvement with manufacturing precision requirements.
Data Source
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AI summary
A positive electrode (11) for a nonaqueous electrolyte secondary battery according to the present disclosure is characterized by having a positive electrode mixture layer (31), and is characterized in that: the positive electrode mixture layer (31) includes a positive electrode active material and PTFE; the positive electrode active material includes a lithium-containing transition metal composite oxide having a layered structure; a sulfonic acid compound represented by formula (I) is present on the surfaces of secondary particles of the lithium-containing transition metal composite oxide; and, when the positive electrode mixture layer (31) is divided into three equal parts in the thickness direction, if said parts in order from a positive electrode core body (30) side are defined as a first region, a second region, and a third region, the content (s) of PTFE in the first region, the content (t) of PTFE in the second region, and the content (u) of PTFE in the third region satisfy (us)/(s+t+u)≤±10%. (In the formula, A represents a group 1 element or a group 2 element, R represents a hydrocarbon group, and n is 1 or 2.)