Power Storage Device Load Applying Mechanism

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Solution Overview

Problem

Existing electricity storage devices, such as those in electric vehicles, face challenges in limiting the expansion of active material layers in electrodes due to lithium insertion and desorption, leading to delamination and performance degradation.

Innovation Solution

An electricity storage device with a load applying mechanism that aligns the expansion direction of carbon-based negative electrodes with the stacking direction of electrodes, using a carbon-based material with a density of 1.2 g/cm3 or higher and a low degree of orientation, and applying a load of 0.2 MPa or greater to limit delamination and expansion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If a load is applied to the electrode assembly in the stacking direction, then expansion of the active material layer is limited, but the device complexity increases due to the additional load applying mechanism

Engineering Contradiction:

Improveexpansion limitation of active material layerVSAvoidstructure complexity

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The patent applies a mechanical load (0.2 MPa or greater) to the electrode assembly in the stacking direction, changing the physical state and density of the carbon-based material. This parameter change limits the expansion of the active material layer during lithium insertion and desorption cycles, resolving the contradiction between maintaining compositional stability and avoiding excessive device complexity.

Inventive Principle:

Principle #35Parameter changes

2Stability of the object's composition

If the density of carbon-based material is increased to 1.2 g/cm3 or higher, then expansion of the active material layer is limited, but the manufacturing precision requirements increase

Engineering Contradiction:

Improveexpansion limitation of active material layerVSAvoiddensity control precision

Core Design Contradiction:

Stability of the object's compositionVSManufacturing precision

Solution Approach 1:

The patent specifies a minimum density threshold (1.2 g/cm3) for the carbon-based material in the active material layer. By controlling this physical parameter during manufacturing, the expansion of the active material layer is limited without requiring excessively complex manufacturing processes. The combination of density control and applied load achieves the desired stability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses carbon-based materials with specific crystal structures (graphite-like) that have inherent expansion characteristics. By selecting and processing these materials to achieve the specified density and orientation, the active material layer's expansion is controlled while maintaining manufacturability.

Inventive Principle:

Principle #40Composite materials

3Stability of the object's composition

If the degree of orientation is reduced to 0.3 or lower, then the expansion direction aligns with stacking direction, but the manufacturing control difficulty increases

Engineering Contradiction:

Improvealignment of expansion directionVSAvoidorientation control precision

Core Design Contradiction:

Stability of the object's compositionVSManufacturing precision

Solution Approach 1:

The patent controls the degree of orientation (I(100)/I(002) ratio) of the carbon-based material crystals as a key parameter. By maintaining this ratio at 0.3 or lower, the expansion direction of the active material layer is aligned with the stacking direction of the electrode assembly. This parameter control, combined with applied load, achieves proper alignment without excessive manufacturing complexity.

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 configuration effectively limits the expansion of active material layers, maintaining battery performance and capacity over cycles by aligning the expansion direction with the load application, thereby preventing misalignment and performance degradation.

Implementation Method 1

a load applying mechanism that applies, to the electrode assembly, a load in a direction in which the positive electrode and the negative electrode are stacked

Methodology Applied

Scientific EffectMechanical load: Mechanical Force

Implementation Method 2

delamination occurs due to insertion and desorption of lithium into and from between layers

Methodology Applied

Scientific EffectLithium insertion and desorption: Absorption (physical)

Implementation Method 3

expansion of active material layers can also be limited by applying load to electrode assemblies

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS10249853B2Power storage device

Publication Date: 2019.04.02 TOYOTA INDUSTRIES CORP

AI summary

An electricity storage device includes an electrode assembly and a load applying mechanism. The load applying mechanism applies, to the electrode assembly, a load in a direction in which the positive electrode and the negative electrode are stacked in the electrode assembly. The negative electrode includes a metal foil and an active material layer that covers at least part of the metal foil and contains a carbon-based material as an active material. The density of the carbon-based material in the active material layer is 1.2 g/cm3 or higher. The degree of orientation that is defined as a ratio (I(100)/I(002)) of an X-ray diffraction intensity I(100) of a (100) plane to a diffraction intensity I(002) of a (002) plane in the active material layer is lower than or equal to 0.3. The load applied by the load applying mechanism is greater than or equal to 0.22 MPa.