Lithium-Doped Carbon Negative Electrode for Low-Resistance Output

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Solution Overview

Problem

Existing electrochemical devices combining lithium ion secondary battery and electric double layer capacitor principles face limitations in achieving high output and stability, particularly in maintaining low internal resistance and float characteristics.

Innovation Solution

The electrochemical device incorporates a negative electrode with a mixture layer containing non-graphitizable carbon and a binding agent with an average particle size of 140 nm or larger, pre-doped with lithium ions, and uses an acrylic resin and ammonium salt of carboxymethylcellulose to reduce internal resistance and enhance float characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If conventional binding agents with smaller particle sizes are used in the negative electrode mixture layer, then the electrode structure may be more densely packed, but the internal resistance increases and output characteristics deteriorate

Engineering Contradiction:

Improveoutput characteristicVSAvoidinternal resistance

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent changes the particle size parameter of the binding agent to 140 nm or more, which is a specific quantitative parameter change. This parameter modification optimizes the balance between electrode structure density and electrical conductivity, reducing internal resistance while maintaining structural integrity, thereby improving power output characteristics

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses a composite binding agent system comprising acrylic resin and ammonium salt of carboxymethylcellulose. This composite material approach combines the adhesive properties of acrylic resin with the film-forming and conductive benefits of ammonium salt of carboxymethylcellulose, creating a synergistic effect that reduces internal resistance and enhances output characteristics

Inventive Principle:

Principle #40Composite materials

2Productivity

If the negative electrode is pre-doped with lithium ions to achieve low potential, then rapid charge and discharge capabilities are enhanced, but the stability and float characteristics may be compromised

Engineering Contradiction:

Improvecharge and discharge capabilityVSAvoidfloat characteristic

Core Design Contradiction:

ProductivityVSStability of the object's composition

Solution Approach 1:

The patent applies preliminary doping of the negative electrode with lithium ions before the electrochemical device is put into service. This preliminary action ensures that the negative electrode maintains a low potential state during operation, enabling rapid charge and discharge capabilities while the specific binding agent composition stabilizes the electrode structure during floating conditions

Inventive Principle:

Principle #10Preliminary action

3Quantity of substance

If non-graphitizable carbon is used as the negative electrode active material, then high energy density is achieved, but the internal resistance increases at low temperatures

Engineering Contradiction:

Improveenergy densityVSAvoidinternal resistance at low temperature

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The ammonium salt of carboxymethylcellulose acts as an intermediary substance between the non-graphitizable carbon particles and the electrolyte. It forms a conductive network that facilitates ion transport at low temperatures, mediating the interaction between the carbon material and electrolyte to reduce internal resistance while preserving the high energy density benefits of non-graphitizable carbon

Inventive Principle:

Principle #24Intermediary (Mediator)

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 enables high-output performance with reduced internal resistance and improved float characteristics, allowing for rapid charge and discharge capabilities and maintaining low internal resistance even at low temperatures.

Implementation Method 1

a negative electrode active material reversibly doped with a lithium ion

Methodology Applied

Scientific EffectDoping: Dopants

Implementation Method 2

The negative electrode active material contains non-graphitizable carbon... a negative electrode active material reversibly doped with a lithium ion

Methodology Applied

Scientific EffectIntercalation: Absorption (physical)

Implementation Method 3

An average particle size of the binding agent is more than or equal to 140 nm

Methodology Applied

Scientific EffectParticle size effect:

Implementation Method 4

electrochemical device including a positive electrode, a negative electrode, and a separator... The negative electrode includes a negative electrode mixture layer

Methodology Applied

Scientific EffectElectrochemical reaction:

Data Source

PatentUS20240170670A1Electrochemical device

Publication Date: 2024.05.23 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

The electrochemical device includes a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode. The negative electrode includes a negative electrode mixture layer, the negative electrode mixture layer contains a binding agent and a negative electrode active material reversibly doped with a lithium ion. The negative electrode active material contains non-graphitizable carbon. An average particle size of the binding agent is more than or equal to 140 nm. In a discharged state, a potential of the negative electrode is less than or equal to +0.2 V with respect to a potential of a Li counter electrode.