Secondary Battery Separator Layer Design for High Conductivity

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Solution Overview

Problem

Conventional lithium ion secondary batteries face challenges in achieving high capacity and high output due to insufficient mechanical strength of solid electrolytes and difficulties in homogeneous application of thin film electrolytes, leading to internal short circuits and reduced practicality.

Innovation Solution

A secondary battery design featuring a stack structure with a positive electrode layer, a separator layer having a higher conductivity than the positive electrode layer, and a negative electrode layer, where the separator layer is integrated with a polymer electrolyte to enhance electrolyte transportability and prevent internal short circuits, while using a liquid electrolyte with high reactivity in the negative electrode layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of moving object

If a solid electrolyte is used to thin the battery, then the battery thickness is reduced, but the mechanical strength becomes insufficient

Engineering Contradiction:

Improvebattery thicknessVSAvoidmechanical strength

Core Design Contradiction:

Length of moving objectVSStrength

Solution Approach 1:

The patent employs a composite structure combining a solid electrolyte layer with a porous separator layer. The solid electrolyte provides high ion conductivity and thin film characteristics, while the porous separator provides mechanical strength and structural support. This composite approach allows the battery to achieve reduced thickness while maintaining sufficient mechanical integrity.

Inventive Principle:

Principle #40Composite materials

2Length of moving object

If a thin film electrolyte is applied, then the battery is thinned, but homogeneous application becomes difficult

Engineering Contradiction:

Improvebattery thicknessVSAvoidhomogeneous application

Core Design Contradiction:

Length of moving objectVSManufacturing precision

Solution Approach 1:

The patent utilizes a porous separator layer as the foundation for electrolyte application. The porous structure provides a three-dimensional network that facilitates uniform electrolyte distribution throughout the separator matrix. This porous architecture enables homogeneous electrolyte impregnation while maintaining thin film dimensions, solving the manufacturing challenge of uniform thin film application.

Inventive Principle:

Principle #31Porous materials

3Device complexity

If a solid electrolyte is used, then the battery structure is simplified, but internal short circuits occur due to insufficient mechanical strength

Engineering Contradiction:

Improvebattery structureVSAvoidinternal short circuit prevention

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent implements a composite structure where a solid electrolyte layer is combined with a porous separator layer. The porous separator provides mechanical strength and physical separation between electrodes, preventing internal short circuits. The solid electrolyte layer provides high ion conductivity. Together, they maintain structural integrity and prevent short circuits while preserving the simplified battery structure.

Inventive Principle:

Principle #40Composite materials

4Quantity of substance

If the separator layer is thinned to increase capacity, then the energy density improves, but the mechanical strength decreases

Engineering Contradiction:

Improveenergy densityVSAvoidmechanical strength

Core Design Contradiction:

Quantity of substanceVSStrength

Solution Approach 1:

The patent employs a porous separator layer that achieves thin film dimensions while maintaining mechanical strength through its three-dimensional porous network structure. The porosity provides structural integrity and surface area for electrolyte interaction, allowing the separator to be thin enough to increase energy density while remaining mechanically robust enough to prevent electrode contact and short circuits.

Inventive Principle:

Principle #31Porous materials

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

The design achieves high capacity and high output by thinning the separator layer, improving electrolyte transportability, and reducing interfacial resistance, thereby preventing lithium deposition and internal short circuits, and maintaining high reactivity and ion conductivity.

Implementation Method 1

a separator layer having a higher conductivity than the positive electrode layer

Methodology Applied

Scientific EffectIon conduction: Conduction (electrical)

Implementation Method 2

using a liquid electrolyte with high reactivity in the negative electrode layer

Methodology Applied

Scientific EffectElectrochemical reaction: Redox Reactions

Implementation Method 3

adhering the separator layer to each of the positive electrode layer and the negative electrode layer

Methodology Applied

Scientific EffectAdhesion: Adhesive

Data Source

PatentUS8852295B2Secondary battery and method of producing the secondary battery

Publication Date: 2014.10.07 ENVISION AESC JAPAN LTD

AI summary

A secondary battery includes: an electric cell layer including a stack structure sequentially including: a positive electrode layer, a separator layer, and a negative electrode layer having an electrolyte higher in conductivity than an electrolyte of at least one of the separator layer and the positive electrode layer.