Composite Battery Diaphragm With Porous Coating for Low Resistance
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Solution Overview
Problem
The transmission efficiency of lithium ions through the diaphragm in lithium-ion batteries is hindered by defects, leading to increased internal resistance and reduced cycle performance.
Innovation Solution
A composite diaphragm with a porous substrate and a porous active layer containing inorganic particles and a non-binder polymer, where the tortuosity is optimized to 1.1 to 1.7, enhancing lithium-ion transport and adhesion with electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the diaphragm uses a conventional structure, then it maintains basic isolation and ion transmission, but the transmission efficiency of lithium ions is hindered by defects, leading to increased internal resistance and reduced cycle performance
Solution Approach 1:
The patent employs a porous coating layer formed by phase separation technology on the diaphragm surface. This porous structure provides optimized pathways for lithium ion transmission, reducing resistance while maintaining effective isolation between electrodes. The porous morphology allows ions to pass through more efficiently, directly addressing the cycle performance and internal resistance issues.
Solution Approach 2:
The patent creates a composite diaphragm structure combining a base diaphragm layer with a porous coating layer containing polymer particles. This composite architecture integrates the isolation function of the base layer with the enhanced ion transmission properties of the porous coating, resolving the contradiction between reliability and harmful factors by synergizing multiple material functions.
2Productivity
If the diaphragm increases ion permeability to improve transmission efficiency, then cycle performance improves, but the mechanical strength and chemical stability may be compromised
Solution Approach 1:
The patent divides the diaphragm into two functional segments: a base diaphragm layer providing mechanical strength and chemical stability, and a porous coating layer optimized for ion transmission. This segmentation allows each layer to specialize in its primary function without compromising the other, enabling high transmission efficiency while maintaining structural integrity.
Solution Approach 2:
The porous coating layer is applied locally on the surface of the base diaphragm, creating a region with optimized pore structure for ion transmission. The bulk of the diaphragm retains its original dense structure for strength, while the local porous region enhances transmission efficiency. This local quality modification resolves the contradiction between productivity and strength.
3Reliability
If the diaphragm structure is optimized for ion transmission, then cycle performance improves, but the complexity of manufacturing and controlling tortuosity increases
Solution Approach 1:
The phase separation technology enables the coating layer to self-organize into a porous structure during the coating process. The polymer particles naturally phase-separate and form the desired porous morphology without requiring complex post-processing or precise control of tortuosity parameters. This self-service mechanism simplifies manufacturing while achieving the tortuosity optimization needed for improved cycle performance.
Solution Approach 2:
The patent controls the porous structure formation through parameter changes during the coating and drying process, such as solvent evaporation rate and polymer concentration. By adjusting these parameters, the desired tortuosity range is achieved naturally during manufacturing, avoiding the need for complex post-processing steps and reducing overall manufacturing complexity while maintaining improved reliability.
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 diaphragm improves lithium-ion transport kinetics and storage performance, resulting in lithium-ion batteries with better cycle performance and lower internal resistance.
Implementation Method 1
the non-binder polymer C forms an obvious raised structure on the surface of the porous active layer
Implementation Method 2
the tortuosity T of the composite diaphragm T=√{square root over (σ1/σ2×P)}, where σ1 is an ionic conductivity of an electrolyte, σ2 is an ionic conductivity of the composite diaphragm
Data Source
AI summary
A composite diaphragm and a lithium-ion battery. The composite diaphragm includes a porous substrate and a porous active layer. The porous active layer is arranged on at least one surface of the porous substrate; the porous active layer includes a base coating and a non-binder polymer C embedded in the base coating; the base coating includes inorganic particles A and a binder polymer B; D50 of the non-binder polymer C is greater than a thickness of the base coating; a tortuosity of the composite diaphragm T=√{square root over (σ1/σ2×P)}, where σ1 is an ionic conductivity of an electrolyte, σ2 is an ionic conductivity of the composite diaphragm, and P is a porosity of the composite diaphragm; the tortuosity T of the composite diaphragm is in a range of 1.1 to 1.7.