Composite Separator Coating for Electrode Expansion Buffering
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Solution Overview
Problem
Conventional ceramic and aramid-coated separators in lithium-ion batteries face challenges in controlling electrode sheet expansion during charging and discharging, leading to wrinkling and increased thickness, while aqueous spray-coated adhesive separators have lower production capacity and higher costs.
Innovation Solution
A composite separator with a porous substrate and a porous active layer containing a base coating and non-binder polymer C, where the non-binder polymer C has a specific particle size and coverage rate, forming protrusions that enhance bonding and gap regulation between the separator and electrode sheets, ensuring structural stability and electrolyte immersion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ceramic-coated separators or aramid-coated separators are used, then chemical stability and mechanical strength are improved, but adhesive property deteriorates causing electrode sheet expansion control failure
Solution Approach 1:
The patent uses a composite coating structure combining inorganic particles (ceramic coating) with a specific polymer material that has both adhesive and buffering functions. This composite approach allows the separator to simultaneously achieve chemical stability from the ceramic coating and adhesive property from the polymer matrix, resolving the contradiction between reliability and ease of manufacture.
2Ease of manufacture
If aqueous spray-coated adhesive separators are used, then adhesive property is improved, but production capacity deteriorates and cost increases
Solution Approach 1:
The patent modifies the coating material parameters by using a polymer with specific glass transition temperature range (0°C to 100°C) and controlled compression ratio (20%-50%). This parameter optimization allows the coating to be applied more efficiently while maintaining adhesive properties, thereby improving production capacity without sacrificing ease of manufacture.
3Stability of the object's composition
If electrode sheets are tightly bonded to separator, then structural stability is improved, but gap regulation deteriorates reducing electrolyte immersion
Solution Approach 1:
The patent employs a polymer material with specific glass transition temperature that allows the coating to dynamically adjust its properties. At operating temperatures, the polymer maintains sufficient adhesion for structural stability while its compressibility (20%-50% compression ratio) allows it to dynamically create gaps for electrolyte immersion, resolving the contradiction between structural stability and volume regulation.
4Volume of moving object
If non-binder polymer C with large particle size is used, then gap formation and electrolyte immersion are improved, but bonding strength deteriorates
Solution Approach 1:
The patent uses a porous coating structure with non-binder polymer particles creating voids and gaps for electrolyte immersion. The porous structure maintains bonding strength through the binder polymer matrix while the non-binder particles create the necessary volume for electrolyte contact, resolving the contradiction between gap formation and bonding strength.
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 composite separator effectively buffers electrode expansion, maintains structural integrity, and improves cycling performance by regulating gaps and ensuring adequate electrolyte immersion, thus enhancing the stability and efficiency of the lithium-ion battery.
Implementation Method 1
The composite separator is compressed for 1 min under a pressure of 5 kgf at 60°C, d1 and d2 of the non-binder polymer C protruding from the base coating are measured after the compression
Implementation Method 2
The protruding non-binder polymer C can not only achieve good bonding with the electrode sheets but also regulate the gaps between the composite separator and the electrode sheets. Consequently, the gaps can buffer the expansion generated during the charging and discharging process
Implementation Method 3
the base coating includes inorganic particles A and a binder polymer B
Data Source
AI summary
The present disclosure provides a composite separator, a wound core, and a lithiumion battery. The composite separator includes a porous substrate and a porous active layer; the porous active layer is arranged on at least one face of the porous substrate and includes a base coating and a non-binder polymer C embedded in the base coating, and the base coating includes inorganic particles A and a binder polymer B; the non-binder polymer C has a particle size D50 greater than a thickness of the base coating; a coverage rate of the non-binder polymer C is in a range of 2%-50%; and an average compression ratio P of the non-binder polymer C protruding from the base coating is in a range of 20%-50%.