Positive Electrode Safety Layer for Battery Heat and Ignition Suppression
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Solution Overview
Problem
Rechargeable lithium batteries are prone to internal heat generation and ignition due to short circuits or exposure to high temperatures, which can be triggered by penetration from sharp objects or high-temperature environments, posing safety risks.
Innovation Solution
Incorporating a safety functional layer on the positive electrode current collector, comprising a lithium iron phosphate-based compound and an endothermic material, which includes a composite of metal hydroxide and phosphorus-based flame retardant, to reduce current and absorb heat, thereby preventing ignition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rechargeable lithium battery is exposed to high temperature or sharp object penetration, then internal heat generation and ignition occur, but safety is compromised
Solution Approach 1:
The patent applies preliminary action by forming a safety functional layer on the positive electrode current collector before battery operation. This layer contains lithium iron phosphate-based compound and endothermic material that are pre-positioned to activate when thermal runaway occurs, absorbing heat and generating protective gas to prevent ignition before it can propagate
Solution Approach 2:
The safety functional layer acts as an intermediary between the positive electrode current collector and the external environment. It mediates the thermal runaway process by absorbing heat through endothermic reactions and generating protective gas, thereby preventing direct heat transfer and ignition to surrounding components
2Temperature
If the positive electrode structure is exposed to high temperature, then oxygen radicals are generated causing oxidative decomposition, but this leads to internal heat generation and ignition
Solution Approach 1:
The patent converts the harmful high-temperature oxidative decomposition into a beneficial process by incorporating endothermic materials that undergo endothermic reactions at elevated temperatures. These reactions absorb the heat that would otherwise cause oxidative decomposition, transforming the thermal runaway hazard into a heat-absorbing protective mechanism
Solution Approach 2:
The endothermic materials in the safety functional layer undergo phase transitions or chemical reactions at specific temperatures, absorbing heat in the process. This phase change mechanism provides passive thermal management during thermal runaway, preventing the temperature from reaching levels that would cause oxidative decomposition of the electrolyte
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 safety functional layer effectively reduces or suppresses heat generation and ignition in lithium batteries, enhancing safety under conditions of short circuits or high temperatures.
Implementation Method 1
the safety functional layer includes a lithium iron phosphate-based compound and an endothermic material
Implementation Method 2
the safety functional layer includes a lithium iron phosphate-based compound and an endothermic material
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 includes 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 lithium iron phosphate-based compound and an endothermic material.