Separator Coating with Boehmite and Binder for Thermal Stability
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Solution Overview
Problem
Lithium ion polymer batteries exhibit low capacity and insufficient discharge at low temperatures, and conventional separators show severe heat shrinking behavior, leading to safety concerns such as thermal runaway and short-circuits due to their material properties.
Innovation Solution
A separator with porous coating layers containing boehmite particles and a binder mixture of fluorine-based and rubber-based binders, where the binder is used in a specific weight ratio to enhance adhesion with electrodes and improve heat absorption, reducing the risk of internal short-circuits and weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polyolefin-based porous substrate is used as a separator, then it provides basic separation function, but it shows severe heat shrinking behavior at high temperature causing short-circuit
Solution Approach 1:
The patent applies composite materials by forming a porous coating layer containing inorganic particles (alumina, silica, titania, zirconia, magnesia) dispersed in a binder polymer on the polyolefin substrate. This composite structure combines the mechanical properties of the polyolefin substrate with the thermal stability of inorganic particles, preventing heat shrinking at high temperatures while maintaining the separation function.
2Reliability
If inorganic particles and binder are applied onto porous substrate to prevent heat shrinking, then thermal stability is improved, but adhesion with electrode deteriorates
Solution Approach 1:
The patent optimizes the binder content to 5-40 wt% of the porous coating layer and controls the weight ratio of fluorine-based to rubber-based binder within 95:5 to 50:50. These parameter changes ensure sufficient adhesion to the electrode while maintaining the thermal stability provided by the inorganic particles. The specific composition ratios balance the competing requirements of adhesion and thermal resistance.
Solution Approach 2:
The patent uses a composite binder system combining fluorine-based binder (providing thermal stability and chemical resistance) with rubber-based binder (providing flexibility and adhesion). This composite binder approach resolves the contradiction between maintaining thermal stability and achieving sufficient adhesion to the electrode.
3Strength
If binder content is increased to improve adhesion, then adhesion strength is improved, but heat absorption capability deteriorates
Solution Approach 1:
The patent precisely controls the binder content within 5-40 wt% of the porous coating layer, preventing excessive binder that would reduce heat absorption capability. Within this range, sufficient adhesion is achieved while the inorganic particles maintain the heat absorption and thermal stability functions.
Solution Approach 2:
The composite structure with inorganic particles dispersed in the binder polymer creates a material that combines the adhesion properties of the binder with the heat absorption and thermal stability of the inorganic particles, resolving the contradiction between adhesion strength and heat absorption capability.
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 significantly improves the adhesion between the separator and electrodes, enhances heat absorption, and reduces the risk of thermal runaway, thereby increasing battery life and safety while maintaining porosity and mechanical properties.
Implementation Method 1
a binder disposed partially or totally on the surface of the inorganic particles to connect and fix the inorganic particles with each other
Implementation Method 2
enhances heat absorption, and reduces the risk of thermal runaway
Data Source
AI summary
Disclosed are a separator and an electrochemical device including the same. The separator includes: a porous substrate having a plurality of pores; and a pair of porous coating layers formed on at least one surface of the porous substrate, and including a plurality of inorganic particles and a binder disposed partially or totally on the surface of the inorganic particles to connect and fix the inorganic particles with each other, wherein the binder is used in an amount of 5-40 wt % based on the total weight of the porous coating layer, the inorganic particles include boehmite particles, the binder includes a fluorine-based binder and a rubber-based binder, and the fluorine-based binder and the rubber-based binder are used at a weight ratio of 80:20-99.9:0.1.