Composite Battery Diaphragm With Low Tortuosity Ion Pathways
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Solution Overview
Problem
The transmission efficiency of lithium ions through the diaphragm in lithium-ion batteries affects the cycle performance, leading to increased internal resistance and attenuation, as defects in the diaphragm hinder ion transmission.
Innovation Solution
A composite diaphragm with a porous substrate and a porous active layer, comprising a base coating with inorganic particles and a non-binder polymer, has a tortuosity of 1.1 to 1.7, ensuring efficient lithium-ion transport and adhesion with the electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the diaphragm has defects that hinder the transmission of lithium ions, then the isolation property is improved, but the transmission efficiency of lithium ions deteriorates
Solution Approach 1:
The patent employs a porous substrate as the base structure of the diaphragm, which provides inherent ion transmission channels. The porous structure allows lithium ions to pass through efficiently while maintaining the diaphragm's isolation function, resolving the contradiction between blocking electrons and transmitting ions.
Solution Approach 2:
The patent uses a composite structure consisting of a porous substrate combined with a porous active layer containing inorganic particles and binder polymers. This composite material design enables the diaphragm to simultaneously achieve good isolation properties and high lithium ion transmission efficiency by combining the advantages of different materials.
2Productivity
If the tortuosity of the composite diaphragm is reduced to improve lithium-ion transport, then the transmission efficiency is improved, but the mechanical strength and isolation property may deteriorate
Solution Approach 1:
The patent applies local quality by creating a porous active layer with specific local structural characteristics on the porous substrate. The tortuosity is controlled within an optimal range (1.05-1.30) in the active layer while maintaining the overall structural integrity, allowing improved ion transport without compromising mechanical strength.
Solution Approach 2:
The patent optimizes the tortuosity parameter of the composite diaphragm to a specific range (1.05-1.30) to achieve the best balance between lithium-ion transport efficiency and mechanical properties. By controlling this parameter, the patent improves ion transport while maintaining adequate mechanical strength and isolation properties.
3Strength
If the base coating thickness is increased to improve adhesion with the electrode, then the adhesion property is improved, but the lithium-ion transmission efficiency deteriorates
Solution Approach 1:
The base coating is designed with a porous structure that allows lithium ions to pass through efficiently even when the coating has adequate thickness for adhesion. The porous architecture provides transmission channels that reduce the effective path length for ions while maintaining the coating's adhesive function.
Solution Approach 2:
The base coating is formulated as a composite material containing inorganic particles and binder polymers in specific proportions. This composite structure provides both adequate adhesion strength and sufficient ion transmission capability, resolving the contradiction between these two requirements.
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 enhances lithium-ion transport kinetics and storage performance, resulting in lithium-ion batteries with improved cycle performance and lower internal resistance.
Implementation Method 1
a tortuosity T of the composite diaphragm is 1.1 to 1.7, where T＝(σ 1 /σ 2 )×P 1/2，σ 1 is an ionic conductivity of an electrolyte, σ 2 is an ionic conductivity of the composite diaphragm, and P is a porosity of the composite diaphragm
Implementation Method 2
the transmission efficiency of lithium ions on the diaphragm directly affects the cycle performance of the lithium-ion battery
Implementation Method 3
the non-binder polymer C forms an obvious raised structure on the surface of the porous active layer, whereby a gap can be defined between the composite diaphragm and the electrode by means of the raised structure, which not only forms a good adhesion with the electrode
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=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.