Capacity fade, a common phenomenon observed in lithium-ion batteries (LIBs), refers to the gradual loss of capacity with repeated charging and discharging cycles. This phenomenon is a significant bottleneck to the longevity and performance of Lithium-ion batteries, impacting everything from electric vehicles to portable electronic devices.
The Mechanism of Capacity Fade
It is a complex problem resulting from the physical and chemical changes that occur within the battery during its operation.
1. Solid-Electrolyte Interphase (SEI) Layer Formation: The SEI layer forms on the anode surface during the first few charging cycles, and it is crucial for the battery's operation by preventing direct contact between the electrode and the electrolyte. However, continuous SEI growth leads to a reduction in the amount of lithium ions available for charge transfer.
2. Lithium Plating: During rapid charging and/or low-temperature conditions, lithium ions may not have enough time to intercalate into the anode and instead deposit on the anode surface as metallic lithium. This lithium plating is irreversible and contributes to capacity loss.
3. Electrode Material Deterioration: Both cathode and anode materials undergo structural changes due to repeated intercalation and deintercalation of lithium ions. These changes can lead to active material loss, cracking, or particle isolation, all of which contribute to capacity fade.
4. Electrolyte Decomposition: High voltages or temperatures can cause the electrolyte to decompose, producing gas and other byproducts that consume active lithium ions and result in capacity fade.
The Consequences of Capacity Fade-
1. Reduced runtime for devices
2. Lower Efficiency
3. Increased Safety Risks due to plating/dendrites leading to thermal runaway
Mitigating Capacity Fade-
1. Material Innovation: Researchers are exploring novel electrode and electrolyte materials that can resist the structural changes associated with capacity fade.
2. Battery Management Systems (BMS): Advanced BMS can optimize charging and discharging conditions, minimizing conditions that promote capacity fade, such as high current densities or extreme states of charge.
3. Protective Coatings: Coating electrode materials with protective layers can help limit unwanted side reactions, reducing the formation of the SEI layer and suppressing lithium plating.
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