Polymer-Aluminum Current Collector for Short-Circuit Limiting
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Solution Overview
Problem
Lithium metal secondary batteries face issues with lithium dendrite formation leading to volume expansion, capacity deterioration, short circuits, and reduced cycle lifespan, necessitating a solution to prevent overheating and improve safety while reducing thickness and weight.
Innovation Solution
A current collector for a positive electrode using a polymer film coated with a thin layer of aluminum conductive material, functioning as an electrochemical fuse to block or reduce short-circuit current paths during internal or external short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal foil current collector is used, then electrical conductivity is ensured, but thickness and weight increase
Solution Approach 1:
The patent employs a composite structure consisting of a polymer film substrate combined with a thin aluminum conductive layer. This composite material approach allows the current collector to achieve both lightweight properties from the polymer and sufficient electrical conductivity from the aluminum coating, resolving the contradiction between weight reduction and conductivity maintenance.
Solution Approach 2:
The patent replaces traditional thick metal foil with a thin-film composite structure where a polymer film serves as the base and a thin aluminum layer (0.25-0.6 μm) provides conductivity. This thin-film approach significantly reduces weight while maintaining the necessary electrical properties through the aluminum conductive material.
2Weight of moving object
If a thin current collector is used, then weight and thickness are reduced, but safety during short circuit deteriorates
Solution Approach 1:
The patent converts the potential harm of a thin current collector (insufficient safety during short circuit) into a benefit by designing the thin aluminum layer to function as an electrochemical fuse. During short circuit conditions, the aluminum layer reacts with the electrolyte to generate gas that blocks the short circuit current path, transforming the thin structure's vulnerability into an active safety mechanism.
Solution Approach 2:
The current collector structure is designed to automatically activate its safety function during short circuit without external intervention. The thin aluminum conductive layer self-reacts with the electrolyte under short circuit conditions, generating protective gas bubbles that block the current path, thereby providing self-protection functionality.
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 polymer-based current collector reduces thickness and weight, enhances safety by limiting short-circuit current and preventing temperature increase, thereby improving the stability and energy density of lithium secondary batteries.
Implementation Method 1
the conductive material reacts with an electrolyte and is corroded or broken in a thickness direction over an entire thickness of the conductive material so as to block a short-circuit current path
Data Source
AI summary
Proposed is a current collector for a positive electrode that substitutes for metal foil and includes a polymer film made of a nonmetal, nonconductor material, and an aluminum conductive material configured to define an outermost surface of the current collector for a positive electrode by being formed or applied, with a thickness of 0.25 to 0.6 μm, onto at least one of upper and lower surfaces of the polymer film, in which the conductive material serves as an electrochemical fuse or performs a function of blocking or reducing short-circuit current in the event of an internal short circuit or an external short circuit.