Positive Electrode Coating with SWCNT Mesh for Low-Resistance Cells

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Solution Overview

Problem

Existing nonaqueous alkali metal power storage elements face challenges in reducing ion diffusion resistance and suppressing electron transfer resistance at high temperatures, particularly when carbon nanotubes are used in the active material layer, and there is a lack of a positive electrode coating liquid that effectively enhances both energy density and output characteristics.

Innovation Solution

A nonaqueous alkali metal power storage element comprising a positive electrode with activated carbon and single-wall carbon nanotubes, where the carbon nanotubes are uniformly distributed in a mesh-like pattern and crosslinked, and a positive electrode coating liquid with a specific composition that includes activated carbon and single-wall carbon nanotubes, ensuring reduced ion diffusion resistance and improved electron transfer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If carbon nanotubes are added to the active material layer to improve electron transfer and output characteristics, then output characteristics are improved, but ion diffusion resistance increases

Engineering Contradiction:

Improveoutput characteristicsVSAvoidion diffusion resistance

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent utilizes the porous structure of activated carbon as the main component of the positive electrode active material. The porous structure provides channels for ion diffusion while the carbon nanotubes are integrated within this porous matrix, allowing ions to diffuse through the pores while electrons are conducted through the nanotube network, thus resolving the contradiction between improving output and maintaining ion diffusion.

Inventive Principle:

Principle #31Porous materials

Solution Approach 2:

The patent creates a composite material system combining activated carbon (providing porous structure for ion diffusion) with carbon nanotubes (providing conductive network for electron transfer). This composite structure allows simultaneous optimization of both ion transport pathways and electron conduction pathways, resolving the technical contradiction between output characteristics and ion diffusion resistance.

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If the positive electrode coating liquid contains high concentration of solid components to increase energy density, then energy density is improved, but viscosity increases making coating difficult

Engineering Contradiction:

Improveenergy densityVSAvoidcoating processability

Core Design Contradiction:

Quantity of substanceVSEase of manufacture

Solution Approach 1:

The patent introduces a specific solvent system as an intermediary between the solid components (activated carbon and carbon nanotubes) and the coating process. The solvent acts as a medium that allows high concentration solid components to be uniformly dispersed and applied as a coating, then evaporates to leave the desired high-density electrode structure, thus enabling high energy density while maintaining coating processability.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent optimizes the viscosity parameters of the coating liquid by controlling the solvent composition and solid component concentration within specific ranges. By adjusting these parameters, the coating liquid achieves an optimal balance between containing sufficient solid components for high energy density and maintaining low enough viscosity for easy coating application.

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

The solution results in a power storage element with reduced ion diffusion resistance, increased energy density, and high output characteristics, while maintaining stability at elevated temperatures and voltages, thereby enhancing the overall performance of the nonaqueous alkali metal power storage system.

Implementation Method 1

the carbon nanotubes are uniformly distributed in a mesh-like pattern and crosslinked... improved electron transfer

Methodology Applied

Scientific EffectElectron conduction: Conduction (electrical)

Implementation Method 2

in the positive electrode, a non-Faraday reaction due to adsorption and desorption of anions at 3 V or more

Methodology Applied

Scientific EffectAdsorption: Adsorption

Data Source

PatentUS20230327112A1Nonaqueous Alkali Metal Power Storage Element and Positive Electrode Coating Liquid

Publication Date: 2023.10.12 ASAHI KASEI KOGYO KABUSHIKI KAISHA

AI summary

The purpose of one aspect of the present disclosure is to provide a nonaqueous alkali metal power storage element with which diffusion resistance of ions is reduced, while increase of electron transfer resistance at high temperature is suppressed. This nonaqueous alkali metal power storage element contains, in a positive electrode active material layer and a negative electrode active material layer, single-walled carbon nanotubes having a bundle structure that has an average fiber diameter of 5-20 nm. Another aspect of the present disclosure provides a positive electrode coating liquid that leads to provision of a nonaqueous alkali metal power storage element having high energy density and high output performance. The positive electrode coating liquid contains single-walled carbon nanotubes and has a specific viscosity.