Exfoliated Graphite Worms for Lithium Battery Cathodes

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Solution Overview

Problem

Current lithium-ion batteries face limitations due to low energy and power density, slow lithium intercalation rates, and safety concerns related to thermal runaway, primarily attributed to the poor electrical and thermal conductivity of cathode active materials, which restrict their widespread adoption in high-capacity applications such as electric vehicles.

Innovation Solution

A cathode layer comprising exfoliated graphite worms with metal fluoride or metal chloride particles lodged in their pores, providing a robust 3-D network for electron conduction and accommodating volume expansion during charge-discharge cycles, enhancing both electrical and thermal conductivity while maintaining mechanical strength.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If metal fluoride or metal chloride is used as cathode active material to achieve high theoretical energy density, then energy density is improved, but electrical conductivity deteriorates due to highly ionic character and large band gap

Engineering Contradiction:

Improveenergy densityVSAvoidelectrical conductivity

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent creates a composite structure where metal fluoride or metal chloride particles are embedded within a conductive graphite matrix. The graphite component provides the necessary electrical conductivity while the metal fluoride/chloride particles provide the high theoretical energy density through conversion reactions, resolving the contradiction between energy density and electrical conductivity.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The conductive graphite acts as an intermediary material that facilitates electron transport between the highly ionic metal fluoride/chloride particles and the current collector. This mediator overcomes the poor electrical conductivity of the metal fluoride/chloride while maintaining their high energy density characteristics.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Stability of the object's composition

If high-temperature sintering is used to produce cathode active materials to achieve desired crystalline structure, then material structure is improved, but manufacturing complexity and energy consumption increase

Engineering Contradiction:

Improvecrystalline structureVSAvoidmanufacturing complexity

Core Design Contradiction:

Stability of the object's compositionVSEase of manufacture

Solution Approach 1:

The patent changes the processing parameters from high-temperature sintering to low-temperature synthesis methods. By using alternative synthesis approaches such as hydrothermal treatment, solvothermal processing, or chemical vapor deposition, the desired crystalline structure is achieved at lower temperatures, reducing manufacturing complexity and energy consumption while maintaining material stability.

Inventive Principle:

Principle #35Parameter changes

3Duration of action of stationary object

If solid-state diffusion is used for lithium insertion and extraction in cathode materials to achieve stable operation, then operational stability is improved, but power density deteriorates due to slow diffusion coefficients

Engineering Contradiction:

Improveoperational stabilityVSAvoidpower density

Core Design Contradiction:

Duration of action of stationary objectVSPower

Solution Approach 1:

The patent replaces the solid-state diffusion mechanism with a conversion reaction mechanism. Instead of relying on slow solid-state diffusion of lithium through the cathode material lattice, the conversion reaction allows for faster lithium insertion and extraction at the particle surface, significantly improving power density while maintaining operational stability through the reversible nature of the conversion reaction.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 achieves high energy and power density, improved cycle stability, and reduced risk of thermal runaway, enabling lithium-ion batteries to operate effectively at high charge-discharge rates with increased safety and efficiency.

Implementation Method 1

providing a robust 3-D network for electron conduction

Methodology Applied

Scientific EffectElectron conduction: Conduction (electrical)

Implementation Method 2

enhancing both electrical and thermal conductivity

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS10777808B2Exfoliated graphite worm-protected metal fluoride and metal chloride cathode active materials for lithium batteries

Publication Date: 2020.09.15 HONEYCOMB BATTERY CO

AI summary

A lithium battery cathode layer containing multiple particles or coating of a cathode active material (metal fluoride or metal chloride) and a layer of exfoliated graphite worms composed of interconnected graphite flakes and inter-flake pores, wherein (a) the graphite worms are selected from exfoliated natural graphite, exfoliated artificial graphite, exfoliated meso carbon micro-beads, exfoliated coke, exfoliated meso-phase pitch, exfoliated carbon or graphite fiber, or a combination thereof; (b) the cathode active material particles or coating has a size from 0.4 nm to 10 μm, and is in an amount from 1% to 99% by weight based on the total weight of graphite worms and the cathode active material combined; and (c) some of the pores are lodged with particles or coating of the cathode active material.