Positive Electrode Buffer Layer for Battery Cycle Stability

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Solution Overview

Problem

Existing secondary batteries, such as lithium ion batteries, face challenges in maintaining cycle characteristics due to volume changes of positive electrode active materials leading to particle cracking, which reduces battery capacity over charge-and-discharge cycles.

Innovation Solution

Incorporating a particulate aggregate composed of inorganic particles that do not intercalate or deintercalate Li, a conductive agent, and a binder in the positive electrode mixture layer to act as a buffer and alleviate volume changes, thereby reducing particle cracking and improving cycle characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a water-soluble polymer binder is used to bind primary particles and a fluororesin binder is used to bind aggregates to the current collector, then the binding force of the positive electrode mixture layer increases, but the cycle characteristics still have room for improvement due to volume changes causing particle cracking

Engineering Contradiction:

Improvebinding force of positive electrode mixture layerVSAvoidcycle characteristics

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent introduces a buffer layer containing inorganic particles (such as alumina, silica, or titania) that do not intercalate or deintercalate Li, along with a conductive agent and binder. This buffer layer is positioned between the positive electrode active material particles and the current collector to beforehand cushion and absorb the volume changes that occur during charge and discharge cycles, preventing particle cracking and improving cycle characteristics while maintaining binding force.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Use of energy by moving object

If positive electrode active material particles undergo volume changes during charge and discharge, then Li intercalation and deintercalation occurs, but particle cracking is caused reducing battery capacity

Engineering Contradiction:

ImproveLi intercalation and deintercalationVSAvoidparticle integrity

Core Design Contradiction:

Use of energy by moving objectVSStrength

Solution Approach 1:

The patent introduces an intermediary buffer layer composed of inorganic particles that do not intercalate or deintercalate Li, combined with conductive agent and binder. This intermediary layer is positioned between the positive electrode active material particles and the current collector to mediate the volume changes during Li intercalation and deintercalation, allowing the energy storage function to proceed while preventing particle cracking through mechanical buffering.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS12199267B2Secondary battery positive electrode and secondary battery

Publication Date: 2025.01.14 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

In the present invention, this positive electrode is provided with: a collector; and a composite material layer that is formed on at least one surface of the collector. The composite material layer includes a particulate aggregate formed from inorganic substance particles which do not occlude or emit Li, a conductive material, and a binding material for binding the inorganic particles and the conductive material. According to an exemplary embodiment, the aggregate is present closer to the collector side at least with respect to the thickness-direction center of the composite material layer, and accounts for at least 1.3 vol % with respect to the volume of the composite material layer.