Battery Cell Electroactive Material Volume Compensation

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Solution Overview

Problem

Lithium-ion and lithium-metal battery cells experience volume and shape changes during charging and discharging, leading to local spatial displacements and non-uniform performance due to the expansion and contraction of electrodes, which complicates battery design and can result in mechanical stresses.

Innovation Solution

Incorporating an electroactive material that can change volume and shape in response to voltage, either within the electrode active material composition or as a separate layer, to counteract these changes, ensuring minimal or no displacements occur within the battery cell.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If lithium ions are reversibly incorporated into or removed from the active material of the negative electrode during charging and discharging, then the battery cell can store and release electrical energy, but the volume and shape of the negative electrode change significantly (up to 15% volume increase when fully charged)

Engineering Contradiction:

Improveenergy storage capacityVSAvoidvolume of negative electrode

Core Design Contradiction:

Use of energy by moving objectVSVolume of moving object

Solution Approach 1:

The negative electrode is segmented into an active material layer and a separate compensating material layer. The compensating material layer is designed to independently respond to volume changes of the active material, allowing the electrode to maintain overall structural stability while accommodating local volume expansions and contractions during lithiation and delithiation processes.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The negative electrode is constructed as a composite material system combining the active material (such as silicon or lithium-containing materials) with a compensating material that has opposite or counteracting volume change characteristics. This composite structure enables the electrode to undergo minimal net volume change during charging and discharging cycles, preventing mechanical stress and structural degradation.

Inventive Principle:

Principle #40Composite materials

2Productivity

If the volume and shape of the negative electrode change during charging and discharging, then lithium ion insertion and extraction can occur, but local spatial displacements and mechanical stresses occur within the battery cell

Engineering Contradiction:

Improvecharging and discharging rateVSAvoidstructural stability of battery cell

Core Design Contradiction:

ProductivityVSStrength

Solution Approach 1:

The compensating material is pre-configured in the negative electrode structure to counteract the volume changes of the active material before they occur. During lithiation, when the active material expands, the compensating material contracts; during delithiation, when the active material contracts, the compensating material expands. This preliminary anti-action prevents mechanical stress accumulation and maintains structural stability throughout the battery cell.

Inventive Principle:

Principle #9Preliminary anti-action

3Stability of the object's composition

If foams or similar materials are used to compensate for volume changes, then spatial displacements can be reduced, but different pressures act on the electrodes and separator depending on charge state, resulting in non-uniform performance

Engineering Contradiction:

Improvevolume stabilityVSAvoidperformance uniformity

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The compensating material is designed with specific physical and chemical parameters that enable it to change volume in response to the charge state of the battery. By carefully selecting materials with appropriate thermal expansion coefficients, compressibility, and electrochemical properties, the compensating material can maintain uniform pressure distribution on the electrodes and separator across different charge states, ensuring consistent performance throughout the battery's service life.

Inventive Principle:

Principle #35Parameter changes

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 approach effectively stabilizes the battery cell by reducing mechanical stresses and maintaining uniform performance throughout the charging and discharging process, as the electroactive material compensates for volume and shape changes, ensuring consistent operation.

Implementation Method 1

at least one electroactive material which may be prompted to undergo a change in volume and/or shape by way of an application of a voltage

Methodology Applied

Scientific EffectElectroactive material response: Electroactive Polymer

Data Source

PatentUS10665853B2Battery cell and battery including electroactive material

Publication Date: 2020.05.26 ROBERT BOSCH GMBH

AI summary

A battery cell which includes at least one negative electrode, at least one positive electrode, and at least one electrolyte, the battery cell further including at least one electroactive material which may be prompted to undergo a change in volume and/or shape by way of an application of a voltage. A battery is also described which includes at least one battery cell, the battery further including at least one electroactive material which may be prompted to undergo a change in volume and/or shape by way of an application of a voltage. A method is also described for compensating for changes in volume and/or shape in a battery cell and in a battery.