Expert-level battery technology covering electrochemistry, lithium-ion battery physics, battery management systems, degradation mechanisms, and next-generation battery chemistries.
Intercalation: lithium ions insert into and extract from electrode lattice. Cathode: LCO, NMC, NCA, LFP — determines energy density and safety. Anode: graphite standard, silicon adds capacity but causes volume expansion. Electrolyte: lithium salt in organic solvent, ionic conductivity, voltage window. SEI layer: solid electrolyte interphase on anode, protects but consumes lithium.
Energy density: Wh/kg or Wh/L, determines range and weight in applications. Power density: W/kg, determines acceleration and fast charging capability. C-rate: charge or discharge rate relative to capacity, 1C fills in one hour. Round-trip efficiency: energy out over energy in, typically 92-97% for Li-ion. Cycle life: number of cycles to 80% capacity retention at given conditions.
Cell balancing: passive wastes energy, active transfers energy between cells. State of charge estimation: coulomb counting, OCV lookup, Kalman filter. State of health: capacity fade and resistance growth tracking over lifetime. Thermal management: cooling to keep cells in optimal temperature range. Protection: overvoltage, undervoltage, overcurrent, overtemperature cutoff.
Capacity fade: lithium loss from SEI growth, active material loss. Resistance growth: electrolyte decomposition, contact resistance increase. Lithium plating: fast charging at low temperature, risk of dendrite formation. Calendar aging: degradation even without cycling, temperature dependent.
Solid-state: solid electrolyte, higher energy density, safer, manufacturing challenges. Sodium-ion: earth abundant, lower energy density than Li-ion, grid storage application. Flow batteries: vanadium redox, decouple power and energy, long duration storage. Lithium-air: theoretical 10x energy density of Li-ion, cycle life challenge.
| Pitfall | Fix |
|---|---|
| Fast charging without thermal management | Lithium plating and thermal runaway risk |
| Ignoring calendar aging | Batteries degrade in storage, not just cycling |
| Using Ah capacity without SoC correction | Capacity depends on temperature and rate |
| Underestimating pack-level losses | Cell-to-cell variation reduces usable capacity |