Positive Electrode Surface Layer for High-Density Battery Compression

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Solution Overview

Problem

Existing secondary batteries face challenges in achieving high packing density of positive electrode active materials without compromising electron conductivity, as strong compression can lead to particle breakage and reduced capacity.

Innovation Solution

A secondary battery design with a positive electrode having a packing density of 3.2 g/cm3 or higher and a crushing rate of 30 particles of the positive electrode active material on its surface of 75% or lower, achieved by forming a surface layer with an inorganic compound to act as a cushioning layer during compression.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If the mixture layer is strongly compressed to increase the packing density of the positive electrode active material, then the packing density increases, but the positive electrode active material on the surface is likely to break

Engineering Contradiction:

Improvepacking density of positive electrode active materialVSAvoidparticle integrity of positive electrode active material

Core Design Contradiction:

Quantity of substanceVSStrength

Solution Approach 1:

A surface layer is formed on the positive electrode mixture layer before compression. This surface layer acts as a cushioning layer that absorbs compression stress, preventing direct transmission of force to the positive electrode active material particles. As a result, the particles are protected from breaking while still allowing the mixture layer to achieve high packing density through compression.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Quantity of substance

If the positive electrode active material is crushed, then the packing density increases, but the electron conductivity of the mixture layer decreases

Engineering Contradiction:

Improvepacking density of positive electrode active materialVSAvoidelectron conductivity of mixture layer

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The surface layer is formed beforehand to cushion the positive electrode active material during compression. This prevents particle breakage that would otherwise occur at high packing densities, thereby maintaining the structural integrity needed for electron conductivity while achieving the desired high packing density for increased capacity.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Reliability

If the crushing rate of positive electrode active material is reduced, then the electron conductivity is maintained, but the battery capacity is limited

Engineering Contradiction:

Improveelectron conductivity of mixture layerVSAvoidbattery capacity

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The surface layer is formed beforehand to protect the positive electrode active material particles from breaking during compression. This cushioning effect allows the mixture layer to be compressed to high packing densities without excessive particle breakage, thereby simultaneously achieving high battery capacity through increased active material density and maintaining electron conductivity through preserved particle integrity.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS12266785B2Secondary battery

Publication Date: 2025.04.01 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

This secondary battery comprises an electrode body that includes a positive electrode, a negative electrode, and a separator. The positive electrode has a positive electrode core, and a positive electrode mixture layer provided on the surface of the positive electrode core. The positive electrode mixture layer includes a positive electrode active material configured by secondary particles in which primary particles are aggregated. The packing density of the positive electrode active material in the positive electrode mixture layer is 3.2 g/cm3 or greater, and the crush rate of 30 pieces of the positive electrode active material existing on the surface of the positive electrode is 75% or less.