Positive electrode for secondary batteries, and secondary battery

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Solution Overview

Problem

The provision of an intermediate layer between the positive electrode current collector and the positive electrode mixture layer in secondary batteries increases resistance, leading to deterioration in battery characteristics, and the heat generated during internal short circuits is not adequately addressed.

Innovation Solution

A secondary battery positive electrode design featuring a positive electrode current collector with surface irregularities, an intermediate layer with conductive agent and inorganic material particles, and a positive electrode mixture layer, where the ratios and depths of these particles are optimized to suppress resistance and heat generation during internal short circuits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If an intermediate layer is provided between the positive electrode current collector and the positive electrode mixture layer, then the amount of heat generated during internal short circuit is suppressed, but the resistance of the positive electrode increases

Engineering Contradiction:

Improveheat generation during internal short circuitVSAvoidresistance of positive electrode

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The intermediate layer is designed with non-uniform thickness, being thinner at the bottom portion (near current collector) and thicker at the top portion (near mixture layer). This local variation allows the bottom to maintain good electrical contact with the current collector while the top provides sufficient heat resistance, thus resolving the contradiction between low resistance and heat suppression

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The thickness of the intermediate layer is controlled within a specific range (1-10 μm overall, with bottom portion being 0.1-5 μm and top portion being 0.5-10 μm). By optimizing these dimensional parameters, the layer achieves both low electrical resistance and adequate thermal protection

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the intermediate layer is made thinner to reduce resistance, then the resistance of the positive electrode decreases, but the heat suppression capability during internal short circuit is reduced

Engineering Contradiction:

Improveresistance of positive electrodeVSAvoidheat generation during internal short circuit

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The intermediate layer has different thicknesses at different locations: the bottom portion (thickness 0.1-5 μm) provides low resistance by being thin, while the top portion (thickness 0.5-10 μm) provides heat suppression by being thicker. This local quality differentiation resolves the contradiction

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

Instead of uniformly reducing thickness in one dimension, the solution varies thickness across the vertical dimension, creating a gradient structure that simultaneously achieves low resistance (at the bottom interface) and heat suppression (at the top interface)

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 design effectively suppresses resistance and heat generation during internal short circuits by enhancing contact area and forming a conduction path, thereby maintaining battery performance and safety.

Implementation Method 1

the ratio of the median particle diameter of the conductive agent particles to the average depth of the irregularities of the positive electrode current collector and the ratio of the median particle diameter of the inorganic material particles to the average depth of the irregularities of the positive electrode current collector are both 5:6 or less

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS12620598B2Positive electrode for secondary batteries, and secondary battery

Publication Date: 2026.05.05 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

This positive electrode for secondary batteries is provided with: a positive electrode collector which has a plurality of recesses and projections in the surface; an intermediate layer which is provided on the surface of the positive electrode collector having the recesses and projections; and a positive electrode mixture layer which is provided on the intermediate layer and contains a positive electrode active material. This positive electrode for secondary batteries is configured such that: the intermediate layer contains conductive material particles and inorganic material particles that have a higher resistance than the positive electrode active material; and both the ratio of the central particle diameter of the conductive material particles to the average depth of the recesses and projections of the positive electrode collector and the ratio of the central particle diameter of the inorganic material particles to the average depth of the recesses and projections of the positive electrode collector are 5:6 or less.