Cathode Active Material Layer Particle Distribution

Solution Overview

Problem

The configuration of the cathode active material layer in secondary batteries often results in a trade-off between suppressing exfoliation and improving battery characteristics, as smaller particle diameters enhance diffusion but lead to inadequate adhesive properties, while larger diameters improve binding but reduce energy density.

Innovation Solution

The cathode active material layer is structured with spherical active materials of larger primary particle diameter closer to the current collector and planular active materials of smaller primary particle diameter farther from it, optimizing both adhesive characteristics and battery performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If smaller particle diameter active materials are used, then diffusion characteristics are improved, but adhesive characteristics deteriorate

Engineering Contradiction:

Improvediffusion characteristicsVSAvoidadhesive characteristics

Core Design Contradiction:

SpeedVSStrength

Solution Approach 1:

The patent applies local quality by creating a cathode active material layer with non-uniform particle size distribution. Specifically, smaller particle diameter active materials (first particles) are concentrated in a first region of the layer, while larger particle diameter active materials (second particles) are concentrated in a second region. This spatial differentiation allows the first region to provide superior diffusion characteristics while the second region provides superior adhesive characteristics, thereby resolving the contradiction between diffusion and adhesion.

Inventive Principle:

Principle #3Local quality

2Strength

If larger particle diameter active materials are used, then adhesive characteristics are improved, but energy density decreases

Engineering Contradiction:

Improveadhesive characteristicsVSAvoidenergy density

Core Design Contradiction:

StrengthVSQuantity of substance

Solution Approach 1:

The patent applies local quality by creating a cathode active material layer with non-uniform particle size distribution. Specifically, smaller particle diameter active materials (first particles) are concentrated in a first region of the layer, while larger particle diameter active materials (second particles) are concentrated in a second region. This spatial differentiation allows the first region to provide superior diffusion characteristics while the second region provides superior adhesive characteristics, thereby resolving the contradiction between diffusion and adhesion.

Inventive Principle:

Principle #3Local quality

3Speed

If smaller particle diameter active materials are used, then diffusion characteristics are improved, but load characteristics deteriorate

Engineering Contradiction:

Improvediffusion characteristicsVSAvoidload characteristics

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent applies local quality by creating a cathode active material layer with non-uniform particle size distribution. Specifically, smaller particle diameter active materials (first particles) are concentrated in a first region of the layer, while larger particle diameter active materials (second particles) are concentrated in a second region. This spatial differentiation allows the first region to provide superior diffusion characteristics while the second region provides superior adhesive characteristics, thereby resolving the contradiction between diffusion and adhesion.

Inventive Principle:

Principle #3Local quality

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

This configuration effectively suppresses exfoliation while enhancing battery characteristics, such as load characteristics and energy density, by leveraging the strengths of both particle sizes in the cathode active material layer.

Implementation Method 1

secondary batteries that utilize insertion and extraction of electrode reactants such as lithium ions

Methodology Applied

Scientific EffectDiffusion: Diffusion

Data Source

PatentUS9287567B2Electrode, secondary battery, battery pack, electric vehicle, electric power storage system, electric power tool, and electronic apparatus

Publication Date: 2016.03.15 MURATA MFG CO LTD

AI summary

A secondary battery includes: a cathode including a cathode active material layer on a cathode current collector; an anode; and an electrolytic solution. The cathode active material layer includes spherical active materials each being a secondary particle and planular active materials each being a secondary particle. The spherical active materials are each included in a region closer to the cathode current collector, and the planular active materials are each included in a region farther from the cathode current collector. Primary particles of the spherical active materials have an average particle diameter that is larger than an average particle diameter of primary particles of the planular active materials.