Positive Electrode Resistive Layer for Internal Short-Circuit Safety
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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, and explosion, primarily due to changes in internal stress conditions such as lithium dendrite growth or compression between electrodes.
Innovation Solution
A positive electrode design incorporating 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, thereby enhancing battery safety. This design includes a composite layer with stabilized lithium metal particles for increased thermal stability and specific capacity retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional positive electrode structure is used, then the battery has simple structure and easy manufacture, but the internal short circuit causes rapid energy release leading to safety hazards
Solution Approach 1:
The positive electrode is segmented into multiple functional layers: a positive electrode active layer and a first layer disposed on it. The first layer contains a lithium-iron-phosphorus-containing oxide with high electric resistance (resistance ratio ≥100), which segments the electrode structure to control energy release pathways during internal short circuits, thereby improving safety without excessive complexity
Solution Approach 2:
The first layer uses composite material comprising a lithium-iron-phosphorus-containing oxide and a first binder. This composite material provides both the high electric resistance needed for safety and the structural integrity required for electrode function, resolving the contradiction between safety improvement and structural simplicity
2Reliability
If the electric resistance of the protective layer is increased to slow down energy release, then the safety is improved, but the energy transfer efficiency may be reduced
Solution Approach 1:
The electric resistance parameter of the first layer is specifically optimized to be at least 100 times greater than that of the positive electrode active layer. This parameter change creates a controlled energy release rate during internal short circuits - high enough to slow down hazardous energy release but managed within the overall battery system to maintain functional energy transfer during normal operation
3Duration of action of moving object
If a fail-safe layer with high electric resistance is added, then the duration of energy release is extended improving safety, but the device complexity increases
Solution Approach 1:
The electrode is divided into distinct functional segments: the positive electrode active layer for normal energy storage and the first layer (fail-safe layer) with high electric resistance for controlled energy release. This segmentation extends the duration of energy release during internal short circuits while maintaining a relatively simple two-layer structure that doesn't excessively increase device complexity
Solution Approach 2:
The first layer acts as an intermediary between the positive electrode active layer and the external environment during internal short circuits. It mediates the energy release process by providing high electric resistance that extends the duration of energy release from milliseconds to a longer period, allowing safer energy dissipation without requiring complex multi-layer structures
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 positive electrode structure effectively prolongs the period of internal short circuits and slows down energy release, enhancing the safety and specific capacity of lithium-ion batteries while maintaining capacity retention, preventing explosions and maintaining battery performance.
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
AI summary
A positive electrode and a battery employing the same encapsulant composition 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.