Dual-Coated Battery Separator for Cycle Stability and Electrolyte Flow
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Solution Overview
Problem
Conventional lithium-ion battery separators face deteriorating cycle performance due to increased positive electrode dissolution products, which affect the stability and efficiency of the battery, especially at high temperatures and low temperatures.
Innovation Solution
A separator design with a dense first coating layer and a high-porosity second coating layer on opposite sides, controlling porosity and pore diameters within specific ranges to block positive electrode dissolution products and enhance electrolyte transport, thereby improving cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional single-layer separator is used, then the structure is simple and manufacturing is easy, but the cycle performance deteriorates due to positive electrode dissolution products
Solution Approach 1:
The separator is divided into multiple functional layers: a base separator layer and a coating layer with specific pore structure. This segmentation allows each layer to perform its specialized function - the base layer provides mechanical support while the coating layer filters dissolution products, thereby improving cycle performance without excessive complexity
Solution Approach 2:
The coating layer is applied locally on one side of the separator facing the positive electrode, with specific porosity (30-70%) and pore diameter (0.01-1 μm) controlled to optimize filtration of dissolution products. This localized functional enhancement improves reliability without requiring the entire separator structure to be complex
2Productivity
If the porosity of the coating layer is increased to improve electrolyte transport, then the kinetic performance improves, but the blocking capability against dissolution products decreases
Solution Approach 1:
The porosity of the coating layer is precisely controlled within the range of 30-70%, and the pore diameter is controlled within 0.01-1 μm. These parameter optimizations create a balance where the pores are large enough to allow efficient electrolyte transport and lithium ion diffusion, yet small enough to effectively block larger dissolution products from the positive electrode
Solution Approach 2:
The separator combines a porous polymer base material with a ceramic or polymer coating layer having controlled porosity. This composite structure integrates the mechanical strength and chemical stability of the base separator with the selective filtration and electrolyte wettability of the coating layer, achieving both blocking capability and transport efficiency
3Reliability
If the thickness of the coating layer is increased to enhance blocking capability, then the dissolution product filtration improves, but the lithium ion transport resistance increases
Solution Approach 1:
The coating layer thickness is optimized within a specific range (typically 1-10 μm) to achieve the right balance. This controlled thickness provides sufficient path length for filtering dissolution products while maintaining low resistance to lithium ion transport, preventing both filtration failure and transport bottleneck
4Reliability
If a dense coating layer is used to block dissolution products, then the cycle performance improves, but the electrolyte infiltration into the negative electrode is hindered
Solution Approach 1:
The coating layer is applied selectively on the positive electrode side of the separator with controlled porosity (30-70%), creating a filtration barrier where it is needed most. The coating parameters are optimized to maintain sufficient permeability for electrolyte to reach the negative electrode while still effectively blocking dissolution products, thus improving cycle performance without sacrificing electrolyte infiltration speed
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 separator design significantly enhances battery cycle performance, particularly at high temperatures, while maintaining efficient electrolyte transport and reducing lithium-ion resistance, thus improving overall battery efficiency.
Implementation Method 1
The first coating layer is a solid filler coating with porosity D1 satisfying: 10% ≤ D1 < 30%, and average volume pore diameter D50 of 1 nm to 90 nm, constructing a pore channel capable of sifting
Implementation Method 2
the pore diameter D'50 of the second coating layer is 100 nm to 500 nm, constructing a electrolyte-philic channel on the negative electrode side of the separator, thereby improving the transport channel of the electrolyte solution
Data Source
Figure 1
AI summary
This application discloses a separator, an electrochemical device, and an electronic device. The separator includes a separator substrate, a first coating layer, and a second coating layer. The separator substrate includes a first surface and a second surface disposed opposite to each other. The first surface faces a positive electrode, and the second surface faces a negative electrode. The first coating layer is disposed on the first surface, and the second coating layer is disposed on the second surface. The first coating layer is a dense solid filler coating. A porosity of the first coating layer is denoted as D1, satisfying: 10% ≤ D1 < 30%. The second coating layer is a high-porosity solid filler coating. A porosity of the second coating layer is denoted as D2, satisfying: 30% ≤ D2 ≤ 60%. By disposing two coating layers of different performance parameters on two sides of the separator, this application improves the cycle performance, low-temperature discharge performance, and heat resistance of the battery.