Li-Ion Battery Insulating Layer Prevents Short Circuits
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Solution Overview
Problem
Lithium ion secondary batteries face issues with internal short circuits and abnormal overheating due to the shrinkage of microporous films at high temperatures, which can lead to contact between electrode current collecting portions, causing significant heat generation and potential battery damage.
Innovation Solution
A lithium ion secondary battery design that includes a porous electron-insulating layer made of an inorganic oxide filler and a binder, interposed between the positive and negative electrodes, covering the current collecting portions and material mixture layers to prevent contact and heat generation, even when the separator shrinks or is exposed to high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a microporous film separator is used to insulate between electrodes, then electronic insulation is achieved, but the separator shrinks at high temperatures causing short circuits
Solution Approach 1:
The separator is constructed as a composite material combining a microporous film base layer with a heat-resistant coating layer containing inorganic particles (such as alumina, silica, or titania) dispersed in a binder resin. This composite structure provides both the electronic insulation function of the microporous film and the high-temperature dimensional stability of the heat-resistant coating, preventing shrinkage-induced short circuits while maintaining operational reliability.
2Temperature
If the separator shrinks due to high temperature, then the structure deforms, but this causes expansion of short circuit portions and accelerates abnormal overheat
Solution Approach 1:
The heat-resistant coating layer is applied in advance to the microporous film separator to prevent the harmful effects of high-temperature shrinkage before they occur. The coating layer restrains the separator from shrinking when exposed to high temperatures (150°C or more), thereby preventing the expansion of short circuit portions and the generation of reaction heat that would lead to abnormal overheat and battery damage.
3Reliability
If a porous protection film is formed on the electrode surface, then some short circuit prevention is achieved, but contact between current collecting portions cannot be avoided
Solution Approach 1:
The heat-resistant coating layer serves multiple functions simultaneously: it provides high-temperature dimensional stability to the separator, acts as an additional insulating barrier, and extends protection to the current collecting portions of the electrodes. By making the coating layer universal in its protective function across different battery components (separator and electrode surfaces), it comprehensively prevents both separator shrinkage and current collector contact, achieving complete short circuit prevention.
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 effectively suppresses internal short circuits and abnormal overheating by preventing contact between electrode current collecting portions, maintaining the integrity of the porous electron-insulating layer and ensuring battery safety, while maintaining manufacturing cost-effectiveness.
Implementation Method 1
a porous electron-insulating layer interposed between the positive electrode and the negative electrode and including an inorganic oxide filler and a binder; the porous electron-insulating layer being carried on a region including surfaces of the positive electrode current collecting portion and the positive electrode material mixture layer
Implementation Method 2
a separator interposed between the positive electrode and the negative electrode
Implementation Method 3
the porous electron-insulating layer interposed between the positive electrode and the negative electrode and including an inorganic oxide filler and a binder
Data Source
AI summary
A lithium ion secondary battery in which an abnormal overheat due to a short circuit of a current collecting portion of one electrode and an electrode material mixture of the other is prevented. The lithium ion secondary battery has: a positive electrode including a core material having a current collecting portion and a material mixture carrying portion and a material mixture layer carried thereon; a negative electrode including a core material having a current collecting portion and a material mixture carrying portion and a material mixture layer carried thereon; a separator and a porous electron-insulating layer including an inorganic oxide filler and a binder both interposed between the positive and negative electrodes; and a non-aqueous electrolyte. The insulating layer is carried on a region including surfaces of the positive electrode current collecting portion and material mixture layer, and/or a region including surfaces of the negative electrode current collecting portion and material mixture layer. The positive and negative electrodes are wound with the separator and the insulating layer interposed therebetween.