Positive Electrode Layer Composition for Low-Impedance Fast Cycling
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries face challenges in heat resistance and rapid charge/discharge cycling performance, and existing methods do not adequately address the need for improved peel strength and reduced impedance.
Innovation Solution
A positive electrode for non-aqueous electrolyte secondary batteries is designed with a current collector and a positive electrode active material layer that includes specific distribution profiles of spreading resistance, optimized amounts of conducting agents, and surface coatings with conductive materials to enhance performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional positive electrode structures are used, then manufacturing is simple, but heat resistance is insufficient
Solution Approach 1:
The positive electrode active material layer is segmented into multiple layers with different functions: a first layer containing conducting agent particles for basic conductivity, and a second layer containing low-resistance conductive carbon material for enhanced heat resistance. This segmentation allows each layer to optimize its specific function while collectively improving overall heat resistance without excessive complexity.
Solution Approach 2:
Different regions of the positive electrode are given different properties: the first layer uses conventional conducting agents (acetylene black, graphite) for general conductivity, while the second layer uses low-resistance conductive carbon material specifically for improving heat resistance. This local differentiation of material properties addresses the heat resistance issue without requiring complete restructuring of the entire electrode.
2Productivity
If conventional conducting agent amounts are used, then manufacturing is simple, but rapid charge/discharge cycling performance is insufficient
Solution Approach 1:
The conducting agent is segmented into two distinct components: conventional conducting agent particles in the first layer and low-resistance conductive carbon material in the second layer. This segmentation enables the electrode to achieve rapid charge/discharge performance through the low-resistance material while maintaining manufacturing feasibility through standardized layering processes.
Solution Approach 2:
The positive electrode uses a composite structure combining conventional conducting agents (acetylene black, graphite) with low-resistance conductive carbon material. This composite approach leverages the proven manufacturing processes for conventional materials while introducing a new material component that specifically enhances rapid charge/discharge cycling performance.
3Reliability
If surface coating with carbon is applied, then cycling performance is improved, but impedance is not sufficiently reduced
Solution Approach 1:
The conductive carbon material is segmented into two functional zones: a first layer with conventional conducting agents that maintains cycling performance through proven interfaces, and a second layer with low-resistance conductive carbon material that specifically targets impedance reduction. This segmentation allows simultaneous optimization of both cycling performance and impedance without compromising either aspect.
Solution Approach 2:
The electrical resistance parameter of the conductive carbon material is changed by using low-resistance material in the second layer. This parameter change directly addresses the impedance issue while the layered structure preserves the cycling performance benefits of carbon coating through the first layer.
Data Source
AI summary
A positive electrode (1) for non-aqueous electrolyte secondary batteries, including a collector (11) and an active material layer (12), wherein a spreading resistance distribution of the layer (12) shows a profile with a sum of frequencies of resistance values 4.0 to 6.0 (log Ω) accounting for 0.0 to 5.0% relative to a total, 100%, of frequencies of resistance values 4.0 to 12.5 (log Ω). A positive electrode (1) for non-aqueous electrolyte secondary batteries, including a collector (11) and an active material layer (12), wherein the layer (12) includes an active material and a conductive carbon material, and an amount of a low-resistance conductive carbon material having a resistivity of 0.10 Ω·cm or less is 0.5% by mass or less, based on a total mass of the layer (12). A positive electrode (1) for non-aqueous electrolyte secondary batteries, including a collector (11) and an active material layer (12), wherein the active material has a coated section including a conductive material, and the layer (12) has a powder resistivity of 10 to 1,000 Ω·cm.