- device storing chemical energy and converting it to electrical energy on demand
- electrochemical cell: anode, cathode, electrolyte, separator
- types: lithium-ion, lead-acid, nickel-metal hydride, solid-state, sodium-ion, flow
- lithium-ion dominates portable electronics, EVs, and grid storage
- solid-state batteries promise higher energy density and safety
- charge/discharge cycles degrade capacity over time (calendar and cycle aging)
- energy density measured in Wh/kg (gravimetric) and Wh/L (volumetric)
- enables mobile engine electrification and renewable energy time-shifting
- recycling recovers lithium, cobalt, nickel, reducing mining pressure
- semiconductor battery management systems control charge, temperature, and cell balancing