Foamed Graphene Oxide Separator Layer for Li-Ion Battery Electrodes
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Solution Overview
Problem
Current lithium-ion battery separators are thin, non-electrically and non-thermally conductive, prone to cracking and powdering, and have high thermal shrinkage rates, leading to safety risks and reduced energy density.
Innovation Solution
A chemical foaming method is used to coat the negative electrode with a foaming material containing porous graphene oxide, which decomposes to form a separator-like layer during baking, enhancing thermal conductivity, mechanical strength, and ductility without the need for a physical separator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a polyolefin separator is used, then the battery can be assembled with standard components, but the separator is thin, non-thermally conductive, and prone to cracking and powder dropping at the corner of the negative electrode sheet
Solution Approach 1:
The separator material parameters are fundamentally changed from polyolefin to aluminum foil with specific thickness range (5-20 μm). This parameter change provides thermal conductivity, mechanical strength, and dimensional stability, eliminating cracking and powder dropping issues while maintaining manufacturability through standard battery assembly processes
Solution Approach 2:
The separator is constructed as a composite structure combining aluminum foil base material with functional coatings (heat-resistant coating and/or conductive coating). This composite approach integrates thermal conductivity, electrical conductivity, and heat resistance properties that single-material separators cannot achieve, while maintaining structural integrity at electrode corners
2Reliability
If a heat-resistant coating is applied on the separator surface, then the high-temperature stability is improved, but the energy density of the battery is reduced
Solution Approach 1:
The separator thickness is optimized within 5-20 μm range, achieving a balance between heat resistance and energy density. This parameter optimization ensures sufficient thermal stability while minimizing the volume occupied by the separator, thereby maximizing the active material content and energy density of the battery
3Quantity of substance
If the base film or coating of the isolation film is thinned, then the electrolyte permeability is improved, but the puncture ability and thermal shrinkage resistance are decreased
Solution Approach 1:
The separator uses aluminum foil as the base material, which inherently provides high puncture resistance and thermal stability. Functional coatings are applied on this robust base to enhance electrolyte permeability without compromising the underlying mechanical strength and thermal shrinkage resistance, achieving a synergistic effect that single-thin-film structures cannot provide
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 approach improves energy density, thermal conductivity, and mechanical strength while maintaining safety by controlling pore size and preventing cracking, thus addressing the limitations of traditional separators.
Implementation Method 1
the foaming agent is decomposed, causing the active material to foam
Implementation Method 2
when baked, the foaming agent is decomposed, causing the active material to foam
Implementation Method 3
since graphene oxide is thermally conductive but not electrically conductive, graphene oxide may conduct the heat generated during acupuncture
Implementation Method 4
adopts porous graphene oxide as the active material. First, this avoids excessive cell growth of the foaming material, thereby limiting the foaming pore size of the material
Data Source
AI summary
The invention provides a secondary battery and a preparation method thereof. The secondary battery includes a separator disposed at a side of a positive electrode and/or a negative electrode; the separator includes an active material, an initiator, and a foaming agent. The active material includes a porous graphene oxide; a mass ratio of the initiator, the foaming agent, and the porous graphene oxide is (1-5):(1-10):(1-5). In the invention, a foaming material is coated at a surface of a side of the positive electrode and/or the negative electrode, so that the foaming material may foam during baking to form a separator-like layer having good ductility.