Positive Electrode Fail-Safe Layer for Internal Short-Circuit Delay
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Solution Overview
Problem
Lithium-ion batteries face safety issues due to internal short circuits, which can lead to rapid energy release, causing safety hazards like leakage, swelling, heating, fuming, burning, or explosion, primarily due to changes in internal stress conditions such as lithium dendrite growth or compression between electrodes.
Innovation Solution
A positive electrode design featuring a lithium-iron-phosphorus-containing oxide layer with a high electric resistance ratio, acting as a fail-safe layer to prolong the occurrence period of internal short circuits and slow down energy release when a short circuit occurs, thereby enhancing battery safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional positive electrode structure is used, then the battery has simple structure and low cost, but the internal short circuit occurs rapidly causing safety hazards
Solution Approach 1:
The positive electrode is segmented into multiple functional layers: the positive electrode active layer and the first layer (fail-safe layer) with lithium-iron-phosphorus-containing oxide. This segmentation allows each layer to perform its specific function - the active layer for normal operation and the fail-safe layer for short circuit mitigation - thereby improving battery safety without excessive complexity.
Solution Approach 2:
The first layer containing lithium-iron-phosphorus-containing oxide acts as an intermediary fail-safe layer between the positive electrode active layer and the external environment. This intermediary layer provides high electric resistance (≥100 times that of the active layer) to slow down energy release during internal short circuits, enhancing safety while maintaining relatively simple overall structure.
2Reliability
If the electric resistance of the fail-safe layer is increased to slow down energy release, then the safety is improved, but the energy loss increases
Solution Approach 1:
The electric resistance of the first layer is optimized to be at least 100 times greater than that of the positive electrode active layer. This parameter change is sufficient to slow down energy release during internal short circuits and improve safety, while avoiding excessive resistance that would cause significant energy loss during normal operation.
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 proposed design effectively prolongs the period of internal short circuit occurrence and slows down energy release, enhancing the safety of lithium-ion batteries while maintaining or improving their discharge specific capacity without reducing capacity retention.
Implementation Method 1
the electric resistance ratio of the first layer to the positive electrode active layer is greater than or equal to 100
Data Source
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AI summary
A positive electrode and a battery employing the same are provided. The positive electrode includes a positive electrode active layer and a first layer, wherein the first layer is disposed on the positive electrode active layer, and the first layer includes a lithium-iron-phosphorus-containing oxide and a first binder. The electric resistance ratio of the first layer to the positive electrode active layer is greater than or equal to 100.