Lithium-ion batteries experience two primary aging mechanisms: cyclic aging (from charge-discharge cycles) and calendar aging (time-dependent degradation, even without use). Here’s how aging impacts degradation susceptibility:
1. Calendar Aging Dominates Over Time
- Without usage, batteries degrade due to parasitic side reactions at electrode-electrolyte interfaces.
- Key drivers:
- Temperature: Higher temperatures accelerate chemical reactions, thickening the SEI layer (Surface Electrolyte Interphase) on the anode.
- State of Charge (SOC): Storing batteries at high SOC increases electrolyte oxidation/reduction rates.
- Time: Degradation compounds annually, even in storage.
2. Cycling Accelerates Mechanical Stress
During use, aging susceptibility increases due to:
- Lithium plating: High charging rates or low temperatures trap lithium metal on the anode surface, permanently reducing capacity.
- Electrode cracking: Repeated expansion/contraction of materials (e.g., graphite anode or NMC cathode) fragments active particles.
- SEI growth: Each cycle slightly thickens the SEI layer, increasing internal resistance and reducing power output.
3. Synergistic Effects of Combined Aging
- Calendar aging often dominates in applications with long idle periods (e.g., EVs parked 90% of the time).
- Cycling-Induced Vulnerability: Aged batteries (with high internal resistance from SEI growth) suffer worse degradation under load, as voltage drops more rapidly during high-current discharges.
Degradation Outcomes
- Capacity Fade: Loss of active lithium ions and electrode material reduces energy storage.
- Power Loss: Increased internal resistance limits peak current output, critical for acceleration in EVs or grid response times.
- Nonlinear Progression: Degradation often follows three-phase patterns: rapid initial loss, linear mid-life decline, and accelerated end-of-life failure.
Battery management systems (BMS) mitigate these effects by optimizing charge protocols and thermal conditions.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/how-does-the-age-of-a-battery-impact-its-susceptibility-to-degradation/
