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What is the safety impact of electrolytes and diaphragms on lithium-ion batteries
2023-05-22
The electrolyte and separator play crucial roles in the safety of lithium-ion batteries. Here are the key impacts of these components on battery safety:
Electrolyte:
Flammability: The solvents used in electrolytes, typically organic carbonates, are highly reactive and easily combustible. This poses a significant safety risk.
Thermal Stability: The thermal stability of the interaction between the electrode and the electrolyte is a major factor affecting battery safety. Specifically, the reaction between the positive electrode and the electrolyte can have a significant impact on battery safety. Under certain abusive conditions, enough heat is generated inside the battery to cause the positive electrode to release oxygen, which provides oxygen to support the combustion of the electrolyte. However, the amount of oxygen generated is limited, often resulting in incomplete combustion of the electrolyte. Nevertheless, such combustion can still generate significant heat and gases, leading to damage to the battery system and potentially triggering violent combustion or explosions.
State of Matter: The liquid state of traditional electrolytes is not ideal for safety. Solid-state electrolytes with high lithium-ion conductivity (σLi+ > 10−4 S cm−1) can improve safety by preventing lithium dendrites from piercing the separator and reaching the positive electrode. Additionally, modifying liquid electrolytes by adding flame retardants can also enhance safety.
Separator:
Isolation Function: The separator's primary role is to isolate the positive and negative electrodes, preventing internal short circuits. It also provides structural support for the electrolyte, stabilizing the overall battery structure.
Mechanical Strength: The separator's mechanical strength, including tensile and puncture resistance, is crucial for battery safety. A thicker separator can better protect against internal short circuits caused by external impacts, thus enhancing safety.
Shutdown Function: The separator typically has a thermal shutdown feature that activates when the battery's internal resistance increases by three orders of magnitude. This helps mitigate potential safety hazards by reducing or stopping current flow within the battery.
In summary, the electrolyte and separator significantly impact the safety of lithium-ion batteries. Strict control over the quality and manufacturing processes of these components is essential to ensure the overall safety and performance stability of lithium-ion batteries.
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