Lithium-Ion Cathode Additive for HF Scavenging and Overheat Cutoff
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Solution Overview
Problem
Lithium-ion rechargeable batteries face performance degradation due to hydrogen fluoride generation in the electrolytic solution, which attacks the positive electrode active material, and safety concerns arise from overheating due to lack of effective current interruption mechanisms.
Innovation Solution
Incorporating a lithium salt with a weak acidic dissociation constant of 3.15 or higher, such as lithium acetate, into the positive electrode mixture to react with hydrogen fluoride and produce an organic acid that consumes hydrogen fluoride, thereby preventing material denaturation and interrupting current flow by vaporizing and enveloping the active material when overheated.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fluorine-containing non-aqueous electrolytic solution is used to improve battery performance, then battery performance is enhanced, but hydrogen fluoride is generated which attacks and denatures the positive electrode active material
Solution Approach 1:
Lithium acetate is introduced as an intermediary substance that mediates between the hydrogen fluoride in the electrolytic solution and the positive electrode active material. The lithium acetate reacts with hydrogen fluoride to form acetic acid and lithium fluoride, preventing the hydrogen fluoride from directly attacking and denaturing the active material, thus protecting the battery performance while maintaining the benefits of the fluorine-containing electrolyte
2Device complexity
If no current interruption mechanism is provided to simplify the battery structure, then device complexity is reduced, but safety concerns arise from overheating due to inability to interrupt current flow
Solution Approach 1:
The lithium acetate in the positive electrode mixture serves a dual function: it reacts with hydrogen fluoride during normal operation to protect the active material, and acts as a self-activating current interruption mechanism when overheating occurs. Upon overheating, the lithium acetate decomposes to release acetic acid vapor that forms bubbles, automatically interrupting current flow without requiring external control systems, thus achieving safety through self-service
Solution Approach 2:
The safety mechanism utilizes phase transition of acetic acid from liquid to vapor form. When the battery overheats, the lithium acetate decomposes and the generated acetic acid undergoes phase transition to vapor, forming bubbles that physically block and interrupt the current flow between electrodes, providing automatic thermal protection
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
This configuration enhances battery performance by preventing material degradation and ensuring safety through effective hydrogen fluoride consumption and current interruption, maintaining high performance and safety even during overheating conditions.
Implementation Method 1
the hydrogen fluoride generated in the electrolytic solution is consumed by a weak acidic dissociation reaction of the lithium salt contained in the positive electrode mixture
Implementation Method 2
the organic acid, which is a product of the weak acidic dissociation reaction, is vaporized to form bubbles, and the bubbles envelop the positive electrode active material
Data Source
AI summary
A lithium-ion rechargeable battery includes a positive electrode mixture that includes a positive electrode active material and a lithium salt. The lithium salt reacts with hydrogen fluoride generated in an electrolytic solution to produce an organic acid that is a weak acid relative to the hydrogen fluoride, an acid dissociation constant of the organic acid being 3.15 or higher.