Asymmetric Separator Coating for Li-Ion Cycle Stability
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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 with a dense first coating layer and a high-porosity second coating layer on opposite sides, with controlled porosities and pore diameters, to block positive electrode dissolution products and enhance electrolyte transport, thereby improving cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dense coating layer is applied on the positive electrode side to block dissolution products, then cycle performance is improved, but lithium-ion transport resistance increases
Solution Approach 1:
The separator employs asymmetric coating design where the positive electrode side features a dense coating layer with specific porosity (10-30%) to block dissolution products, while the negative electrode side has a highly porous coating layer (40-60%) to facilitate lithium-ion transport. This local differentiation resolves the contradiction by optimizing each side's coating density for its specific functional requirement.
Solution Approach 2:
The separator uses a composite structure combining a base separator substrate with two different coating layers having distinct porosity characteristics. The composite design integrates the blocking function of dense coatings with the transport function of porous coatings, simultaneously achieving both cycle performance improvement and low lithium-ion resistance.
2Reliability
If the porosity of the first coating layer is increased to facilitate dissolution product shuttling, then electrochemical reaction restriction is improved, but blocking capability of dissolution products decreases
Solution Approach 1:
The invention optimizes the porosity parameter of the first coating layer within a specific range (10-30%), which is dense enough to block dissolution products yet porous enough to allow their shuttling. This precise parameter control enables the coating to simultaneously achieve blocking capability and facilitate the migration of dissolution products away from the negative electrode.
3Productivity
If a high-porosity second coating layer is applied on the negative electrode side to enhance electrolyte infiltration, then kinetic performance is improved, but manufacturing complexity increases
Solution Approach 1:
The second coating layer on the negative electrode side utilizes highly porous material structure with porosity of 40-60%, which dramatically enhances electrolyte infiltration and kinetic performance. The porous material design allows efficient ion transport while the coating process remains compatible with existing separator manufacturing techniques.
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 low-temperature discharge efficiency and reducing lithium-ion resistance.
Implementation Method 1
The dense first coating layer helps to block a positive electrode dissolution product from entering internal pores of the separator substrate or even entering the negative electrode
Implementation Method 2
By controlling the porosities of the two coating layers to fall within an appropriate range, this application achieves a synergistic effect to improve the cycle performance of the battery
Data Source
AI summary
A 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%.