Insulated Double-Layer Cathode for Nail-Piercing Battery Safety
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Solution Overview
Problem
Existing lithium ion batteries face safety concerns due to potential internal short circuits when pierced by external forces, which compromises their safety performance without reducing energy density.
Innovation Solution
The implementation of a cathode with a double-layer structure, featuring a first cathode active material layer with small particle size and high binder content, and a second cathode active material layer, combined with an insulating layer on the uncovered foil regions of the cathode current collector, enhances the safety performance by preventing short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-layer cathode structure is used, then the device complexity is low, but the safety performance deteriorates due to internal short circuit risks when pierced
Solution Approach 1:
The cathode is divided into two distinct layers: a first cathode active material layer and a second cathode active material layer. This segmentation allows each layer to serve different functions - the first layer provides electrochemical activity while the second layer acts as a protective barrier, particularly on uncovered foil regions, preventing direct contact between the piercing object and conductive materials, thus improving safety without excessive complexity
Solution Approach 2:
The cathode employs a composite structure combining different cathode active materials in two layers. The first layer contains cathode active material suitable for electrochemical reactions, while the second layer contains cathode active material with insulating properties or different electrochemical characteristics, creating a composite structure that simultaneously provides both safety protection and functional performance
2Reliability
If safety measures are added to prevent short circuits, then the safety performance improves, but the energy density deteriorates
Solution Approach 1:
The protective second cathode active material layer is applied specifically to uncovered foil regions of the cathode current collector where short circuit risks are highest, rather than uniformly across the entire cathode structure. This localized approach provides safety protection precisely where needed while minimizing the volume occupied by non-active materials, thereby preserving energy density
Solution Approach 2:
The invention applies safety protection through a partial layering approach where the second cathode active material layer covers only the uncovered foil regions rather than the entire cathode surface. This partial coverage is sufficient to prevent the critical short circuit failure mode while maintaining high active material content and energy density in the covered regions
Data Source
Figure 1A~2A
Figure 2B
Figure 3A
AI summary
The present application relates to an electrochemical device and an electronic device including the same. The electrochemical device includes a cathode, a separator and an anode, wherein the cathode includes a cathode current collector; a first cathode active material layer including a first cathode active material; a second cathode active material layer including a second cathode active material, wherein the first cathode active material layer is disposed between the cathode current collector and the second cathode active material layer, and the first cathode active material layer is disposed on a first surface, facing the anode, of the cathode current collector; and an insulating layer, wherein the insulating layer is disposed on a second surface, that is not facing the anode, of the cathode current collector. According to the present application, arranging the cathode by combining the double cathode active material layers with an insulating layer in the electrochemical device, the electrochemical device will not catch on fire or fail when being pierced, so that the mechanical safety performance of the electrochemical device is ensured.