Foamed Separator Layer for Lithium-Ion Battery Electrodes
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium-ion battery separators made of polyolefin are thin, non-conductive, and prone to cracking and powder shedding due to high tension during winding, leading to safety risks and reduced energy density, with existing heat-resistant coatings compromising thermal stability and 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 and mechanical strength without a physical separator, thus improving energy density and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a polyolefin separator is used, then the battery structure is simple and easy to manufacture, but the separator is thin, non-conductive, and prone to cracking and powder shedding due to high tension during winding, leading to safety risks
Solution Approach 1:
The patent uses a composite material consisting of polyolefin base film combined with heat-resistant coating layers containing inorganic particles (such as alumina, silica, or boehmite). This composite structure maintains the ease of manufacture of polyolefin while significantly improving the separator's mechanical strength, thermal stability, and resistance to cracking and powder shedding.
Solution Approach 2:
The patent employs porous heat-resistant coating layers with controlled porosity (30-70%) that allow electrolyte penetration while providing mechanical reinforcement. The porous structure of the inorganic coating layer maintains ion transport capability while preventing the separator from cracking under tension during winding.
2Temperature
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 patent applies heat-resistant coating only on the surface of the separator rather than using a thick uniform layer throughout. The coating thickness is controlled at 1-10 micrometers, providing localized heat resistance where needed (at the separator surface facing electrodes) while minimizing the overall volume occupied by non-active materials, thus preserving energy density.
Solution Approach 2:
The patent optimizes the parameters of the heat-resistant coating, including thickness (1-10 μm), porosity (30-70%), and inorganic particle size (0.1-10 μm), to achieve the minimum necessary protection against thermal shrinkage while minimizing space occupation. This parameter optimization ensures high-temperature stability without significantly reducing the active material volume and energy density.
3Quantity of substance
If the base film or coating is thinned, then the electrolyte permeability is improved, but the puncture ability and thermal shrinkage resistance are decreased
Solution Approach 1:
The patent uses a porous heat-resistant coating layer with controlled porosity (30-70%) that provides both mechanical strength and electrolyte permeability. The porous structure allows efficient ion transport while the inorganic framework (alumina, silica, or boehmite particles) provides puncture resistance and thermal shrinkage resistance, eliminating the need to thicken the base film.
Solution Approach 2:
The patent creates a composite structure where a thin polyolefin base film (providing electrolyte permeability) is reinforced with a porous inorganic coating layer (providing mechanical strength and thermal stability). This composite design allows the base film to remain thin for good ion transport while the coating layer compensates for the reduced mechanical properties.
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 method creates a separator-like layer with controlled pore size, improving thermal conductivity, mechanical strength, and elongation at break, while avoiding excessive cell growth and ensuring good compatibility with the negative electrode material, thereby enhancing the battery's energy density and safety.
Implementation Method 1
the foaming agent is decomposed, causing the active material to foam
Implementation Method 2
the foaming material foams during baking to form a separator-like layer
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
Micropores need to be created on the surface of the polyolefin-based film, so that the electrolyte solution may pass through
Data Source
Figure 1
AI summary
The invention provides a secondary battery and a preparation method thereof. The secondary battery includes a separator (1) disposed at a side of a positive electrode and/or a negative electrode; the separator (1) 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.