Lithium-ion battery

A lithium-ion cell contains a negative electrode (the anode during discharge), a positive electrode (the cathode), an electrolyte and a porous separator that keeps the electrodes apart while allowing ions to pass. When the cell supplies power, lithium ions move through the electrolyte from the anode toward the cathode; electrons travel through the external circuit and provide electric current. Charging reverses the process, moving lithium ions back toward the anode. A battery pack combines cells, and often modules and control systems, to meet the voltage, capacity and safety needs of a device or vehicle.

Lithium-ion batteries are a family rather than a single design. Their names commonly reflect the cathode material: examples include lithium cobalt oxide, lithium iron phosphate and nickel-containing chemistries. Graphite is widely used for the anode, though designs vary. The choice of materials affects energy storage, power delivery, cost, service life and safety, so a chemistry suited to a phone may differ from one selected for an electric vehicle or a large storage installation. Their relatively high energy density and ability to recharge have supported use in portable electronics and transport; battery systems also store electricity for later use, including electricity generated from renewable sources.

Research that led to modern lithium-ion cells advanced through work by several scientists. In the early 1970s, M. Stanley Whittingham developed a functional rechargeable lithium battery. John B. Goodenough's 1980 work on a higher-potential cathode made more powerful designs possible. In 1985, Akira Yoshino developed a practical cell based on lithium ions rather than metallic lithium. Commercial lithium-ion cells reached the market in 1991. The 2019 Nobel Prize in Chemistry recognized Whittingham, Goodenough and Yoshino for their contributions to the battery's development.

No single performance profile applies to every lithium-ion battery: materials and cell design affect capacity, charging speed, durability and operating limits. Repeated charging and discharging can gradually change battery materials and reduce performance. Lithium-ion cells are generally safe when properly manufactured and used, but damaged, poorly stored or mishandled cells can catch fire or explode. Recycling can recover valuable materials and keep discarded batteries out of waste streams where fires may endanger workers and communities. Some used packs may also be repaired or repurposed for less demanding storage before recycling.