Core-Shell Separator Binder for Heat-Resistant Electrode Adhesion
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Solution Overview
Problem
Conventional separators for rechargeable lithium batteries face challenges in maintaining stability and adhesion at high temperatures, leading to potential battery explosions due to mechanical shrinkage and contact between positive and negative electrodes.
Innovation Solution
A separator with a porous substrate and an adhesive layer featuring a particle-type binder with a core-shell structure, where the core has a glass transition temperature of ≤30°C and the shell ≥40°C, ensuring strong adhesion and air permeability while preventing clumping and maintaining ion paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a separator is coated with a mixture of inorganic particles and organic binder to increase thermal resistance, then heat resistance is improved, but adhesion is insufficient and uniform application to variously-sized separators is difficult
Solution Approach 1:
The patent uses a composite binder system comprising both organic binder and inorganic binder in the adhesive layer. The organic binder provides flexibility and initial adhesion, while the inorganic binder (such as colloidal silica or aluminum oxide) provides thermal stability and strengthens the bonding. This composite approach allows the separator to maintain both good adhesion to electrodes and high heat resistance, resolving the contradiction between these two properties.
Solution Approach 2:
The patent optimizes the weight ratio of organic binder to inorganic binder within specific ranges (organic binder: 1-10 parts by weight, inorganic binder: 90-90 parts by weight). By adjusting these parameter ratios, the adhesive layer achieves optimal balance between adhesion strength and thermal resistance. The inorganic particles are also controlled within specific size ranges (0.1-10 μm) to ensure both uniform application and effective thermal stability.
2Ease of manufacture
If the separator structure is simplified to improve manufacturing ease, then manufacturing precision and uniformity across variously-sized separators deteriorate
Solution Approach 1:
The patent employs a porous substrate (such as polyolefin nonwoven fabric or porous polymer film) as the base separator structure. This porous structure naturally provides uniform porosity and surface characteristics that facilitate consistent adhesive layer formation across different separator sizes. The porous structure also allows the adhesive to penetrate and bond effectively, ensuring uniform adhesion without requiring complex coating processes.
Solution Approach 2:
The adhesive layer is designed with specific local properties: it is applied only on the surfaces of the porous substrate that contact the electrodes, with controlled thickness (1-10 μm) and specific composition. This localized optimization ensures uniform application and performance across variously-sized separators while keeping the overall structure simple and manufacturable.
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 solution provides excellent electrode adhesion, air permeability, and stability, enhancing the battery's initial efficiency, charge-discharge characteristics, and cycle-life performance while preventing thermal expansion and side reactions.
Implementation Method 1
the core includes a first polymer having a glass transition temperature of less than or equal to 30° C.
Implementation Method 2
the shell includes a second polymer having a glass transition temperature of greater than or equal to 40° C.
Implementation Method 3
maintains ion conductivity continuously to enable charge and discharge of a battery
Data Source
AI summary
The present disclosure provides a separator for a rechargeable lithium battery and a rechargeable lithium battery including same, the separator includes a porous substrate; and an adhesive layer formed on the porous substrate. The adhesive layer includes a particle-type binder having a core-shell structure including a core and a shell surrounding the core, the core includes a first polymer having a glass transition temperature of less than or equal to 30° C., the shell includes a second polymer having a glass transition temperature of greater than or equal to 40° C., and the particle-type binder has a diameter of 50 nm to 500 nm.