Graphene Foam-Protected Anode for Lithium Battery Volume Expansion
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Solution Overview
Problem
Lithium-ion batteries face challenges with anode materials that experience mechanical degradation due to lithium ion insertion and extraction, leading to shortened cycle life, low reversible capacity, and high irreversible capacity, with existing protective materials being brittle, non-conductive, and unable to accommodate volume expansion effectively.
Innovation Solution
A graphene foam-protected anode active material is developed, where anode active materials are embedded in a solid graphene foam with elastic properties, allowing for volume expansion accommodation and maintaining contact with the anode layer, enhancing thermal and electrical conductivity, and mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional protective materials are used for anode active materials, then mechanical protection is provided, but the materials are brittle, non-conductive, and unable to accommodate volume expansion
Solution Approach 1:
The patent uses graphene foam as a flexible protective shell that can accommodate volume expansion of anode active materials. The foam structure provides mechanical protection while its inherent flexibility allows it to expand and contract with the active material during lithium insertion and extraction cycles, solving the contradiction between mechanical strength and adaptability.
Solution Approach 2:
The patent creates a composite structure where anode active materials are embedded within graphene foam. This composite combines the mechanical strength and electrical conductivity of graphene with the high capacity of active materials like silicon or tin, achieving both protection and volume expansion accommodation simultaneously.
2Quantity of substance
If high-capacity anode materials are used, then reversible capacity is improved, but mechanical degradation occurs due to expansion and contraction
Solution Approach 1:
The graphene foam acts as a flexible container that accommodates the expansion and contraction of high-capacity anode materials during cycling. This prevents mechanical degradation and maintains structural integrity over many cycles, enabling high reversible capacity to be achieved with long cycle life.
Solution Approach 2:
The graphene foam serves as an intermediary between the high-capacity anode active material and the electrolyte/external environment. It protects the active material from direct mechanical stress and chemical degradation while allowing lithium ion transport, thus improving both reliability and reversible capacity.
3Ease of manufacture
If conventional anode materials are used, then manufacturing is simple, but thermal and electrical conductivity are insufficient
Solution Approach 1:
The patent employs graphene foam as a conductive matrix in which anode active materials are embedded. This composite structure inherently provides excellent electrical and thermal conductivity through the graphene network, while the manufacturing process remains relatively simple involving dispersion, coating, and drying steps.
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 graphene foam-protected anode layer achieves improved reversible capacity, long-term cycling stability, and high-capacity lithium-ion batteries with enhanced thermal and electrical conductivity, addressing the limitations of previous anode materials.
Implementation Method 1
the graphene foam is sufficiently elastic to accommodate volume expansion and shrinkage of the particles of the anode active material during a battery charge-discharge cycle
Implementation Method 2
enhancing thermal and electrical conductivity
Implementation Method 3
enhancing thermal and electrical conductivity
Data Source
AI summary
A lithium-ion battery anode layer, comprising an anode active material embedded in pores of a solid graphene foam composed of multiple pores and pore walls, wherein (a) the pore walls contain a pristine graphene material having essentially no (less than 0.01%) non-carbon elements or a non-pristine graphene material having 0.01% to 5% by weight of non-carbon elements; (b) the anode active material is in an amount from 0.5% to 95% by weight based on the total weight of the graphene foam and the anode active material combined, and (c) some of the multiple pores are lodged with particles of the anode active material and other pores are particle-free, and the graphene foam is sufficiently elastic to accommodate volume expansion and shrinkage of the particles of the anode active material during a battery charge-discharge cycle to avoid expansion of the anode layer. Preferably, the solid graphene foam has a density from 0.01 to 1.7 g/cm3, a specific surface area from 50 to 2,000 m2/g, a thermal conductivity of at least 100 W/mK per unit of specific gravity, and/or an electrical conductivity no less than 1,000 S/cm per unit of specific gravity.