Positive Electrode Safety Layer for Lithium Battery Heat Suppression
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Solution Overview
Problem
Rechargeable lithium batteries are prone to internal heat generation and ignition due to short circuits caused by penetration of sharp objects or exposure to high temperatures, which can lead to safety hazards.
Innovation Solution
A positive electrode design incorporating a safety functional layer with a lithium iron phosphate-based compound and an endothermic material, which includes a composite particle of metal hydroxide and phosphorus-based flame retardant, to reduce or suppress heat generation and ignition by reducing current and absorbing heat.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sharp object penetrates the rechargeable lithium battery, then a short circuit occurs causing internal heat generation, but the battery structure lacks sufficient safety protection against penetration
Solution Approach 1:
The patent introduces a safety functional layer as an intermediary component between the positive electrode active material layer and the current collector. This layer includes a lithium iron phosphate-based compound that acts as a mediator to reduce current during short circuit events, thereby reducing heat generation from penetration-induced short circuits without compromising the battery's operational reliability.
Solution Approach 2:
The patent applies beforehand cushioning by incorporating an endothermic material layer in advance within the safety functional layer. This layer is positioned to absorb heat before it can propagate through the battery structure during penetration events, providing preemptive thermal protection that reduces the severity of heat generation from short circuits.
2Reliability
If the rechargeable lithium battery is exposed to high temperature environment, then the positive electrode active material structure collapses generating oxygen radicals, but the battery lacks sufficient thermal stability
Solution Approach 1:
The safety functional layer serves as a protective intermediary between the positive electrode active material and the external environment. The lithium iron phosphate-based compound in this layer stabilizes the electrode structure during thermal exposure, preventing direct thermal degradation and oxygen radical generation from the active material while maintaining thermal stability.
Solution Approach 2:
The endothermic material layer provides beforehand cushioning by absorbing excess heat before it can cause the positive electrode active material structure to collapse. This preemptive heat absorption prevents thermal runaway and oxygen radical generation, thereby protecting the electrolyte from oxidative decomposition and ensuring thermal stability.
3Reliability
If the positive electrode uses conventional structure without safety functional layer, then manufacturing is simpler, but safety against heat generation and ignition is compromised
Solution Approach 1:
The patent segments the positive electrode structure into distinct functional layers: a positive electrode active material layer, a safety functional layer with specific safety components, and a current collector. This segmentation allows the safety functional layer to independently provide heat generation suppression and ignition prevention functions without complicating the overall manufacturing process, as each layer can be applied through standard coating techniques.
Solution Approach 2:
The safety functional layer utilizes composite materials comprising a lithium iron phosphate-based compound and an endothermic material. This composite structure provides enhanced safety functionality against heat generation and ignition while maintaining compatibility with conventional battery manufacturing processes, avoiding significant increases in device complexity.
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 electrode design effectively reduces or suppresses heat generation and ignition in lithium batteries, ensuring safety in various situations, including penetration by sharp objects or exposure to high temperatures.
Implementation Method 1
the safety functional layer includes a lithium iron phosphate-based compound... to reduce or suppress heat generation and ignition by reducing current
Implementation Method 2
a second safety functional layer including an endothermic material... to reduce or suppress heat generation and ignition by reducing current and absorbing heat
Data Source
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AI summary
Disclosed are a positive electrode for a rechargeable lithium battery, and a rechargeable lithium battery including the positive electrode, the positive electrode including a positive electrode current collector; a safety functional layer on the positive electrode current collector, and a positive electrode active material layer on the safety functional layer, wherein the safety functional layer includes a first safety functional layer including a lithium iron phosphate-based compound and a second safety functional layer including an endothermic material.