Battery Resistive Layer to Limit Thermal Runaway Current
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Solution Overview
Problem
Lithium-ion batteries face safety hazards due to thermal runaway caused by internal short circuits and overcharging, leading to potential fires or explosions, as they lack effective protection mechanisms against excessive internal current and heat generation.
Innovation Solution
Incorporating a non-sacrificial resistive layer with fixed resistance between the separator and current collectors in lithium-ion batteries to limit internal discharge and joule heat generation during separator failures, maintaining stability even at elevated temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a lithium-ion battery uses high energy density materials to store large amounts of electrical energy, then the energy storage capacity is improved, but the risk of thermal runaway and fire hazard increases
Solution Approach 1:
A resistive layer is introduced as an intermediary component between the separator and current collectors. This layer acts as a mediator that limits internal discharge current through its resistance properties, preventing excessive current from causing thermal runaway while allowing normal battery operation. The resistive layer specifically activates during abnormal conditions to protect the high energy density battery system.
2Device complexity
If the battery operates at high energy density without additional protective layers, then the device complexity is reduced, but the safety protection against internal short circuits is insufficient
Solution Approach 1:
The protective function is merged with existing battery components by placing the resistive layer on the current collectors, which are already present in the battery structure. This integration approach adds safety functionality without requiring completely separate protective systems, thereby limiting the increase in device complexity while significantly improving reliability against internal short circuits.
3Reliability
If a resistive layer is added to limit internal discharge current, then the safety protection is improved, but the device complexity increases
Solution Approach 1:
The resistive layer is implemented as a thin film coating on the current collectors rather than a bulky separate component. This thin film approach provides the necessary resistive protection while minimizing the added structural complexity and volume. The flexible thin film can be applied during manufacturing processes without requiring complex assembly steps.
4Ease of manufacture
If the battery uses conventional separator alone to prevent internal discharge, then the manufacturing process is simple, but the separator may fail under thermal stress and cause thermal runaway
Solution Approach 1:
The resistive layer is positioned between the separator and current collectors to provide beforehand cushioning protection. When the separator fails under thermal stress, the resistive layer acts as a secondary barrier that limits the internal discharge current, cushioning against the catastrophic failure that would otherwise occur. This pre-positioned protective layer ensures thermal stability without complicating the manufacturing process.
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 resistive layer effectively prevents temperatures from exceeding the safety limit, reducing the risk of thermal runaway and preventing fires by controlling internal discharge rates, thus enhancing the safety and reliability of high energy density rechargeable batteries.
Implementation Method 1
limiting the rate of internal discharge through the failed separator and the generation of joule heat resulting therefrom
Implementation Method 2
The fixed resistivity of the resistive layer remains stable when the battery is overheated and the fixed resistivity of the resistive layer is greater than the internal resistivity of either energy layer
Data Source
AI summary
An improved high energy density rechargeable (HEDR) battery with an anode energy layer, a cathode energy layer, a separator between the anode and cathode energy layers for preventing internal discharge thereof, and at least one current collector for transferring electrons to and from either the anode or cathode energy layer, includes a resistive layer interposed between the separator and one of the current collectors for limiting the rate of internal discharge through the failed separator in the event of separator failure. The resistive layer has a fixed resistivity at temperatures between a preferred temperature range and an upper temperature safety limit for operating the battery. The resistive layer serves to avoid temperatures in excess of the upper temperature safety limit in the event of separator failure in the battery, and a fixed resistivity of the resistive layer is greater than the internal resistivity of either energy layer.