Views:17 Author:Site Editor Publish Time: 2018-04-14 Origin:Site
The lithium-air battery (Li-air) is a metal–air electrochemical cell or battery chemistry that uses oxidation of lithium at the anode and reduction of oxygen at the cathode to induce a current flow.
Pairing lithium and ambient oxygen can theoretically lead to electrochemical cells with the highest possible specific energy. Indeed, the theoretical specific energy of a non-aqueous Li-air battery, in the charged state with Li2O2 product and excluding the oxygen mass, is ~40.1 MJ/kg. This is comparable to the theoretical specific energy of gasoline, ~46.8 MJ/kg. In practice, Li-air batteries with a specific energy of ~6.12 MJ/kg at the cell level have been demonstrated. This is about 5 times greater than that of a commercial lithium-ion battery, and is sufficient to run a 2,000 kg EV for ~500 km (310 miles) on one charge using 60 kg of batteries. (A 2.52 MJ/kg battery with an e-motor would be comparable to an internal combusion engine in driving range per kg. Li-ion batteries have only 0.378 MJ/kg at the pack level, i.e., they are limited to <150 kilometres (93 mi) driving range). However, the practical power and life-cycle of Li-air batteries need significant improvements before they can find a market niche.
Significant electrolyte advances are needed to develop a commercial implementation. Four approaches are active: aprotic, aqueous, solid state and mixed aqueous–aprotic.
Metal-air batteries, specifically zinc-air, have received attention due to potentially high energy densities. The theoretical specific energy densities for metal-air batteries are higher than for ion-based methods. Lithium-air batteries can theoretically achieve 3840 mA·h/g.
A major market driver for batteries is the automotive sector. The energy density of gasoline is approximately 13 kW·h/kg, which corresponds to 1.7 kW·h/kg of energy provided to the wheels after losses. Theoretically, lithium-air can achieve 12 kW·h/kg (43.2 MJ/kg) excluding the oxygen mass. Accounting for the weight of the full battery pack (casing, air channels, lithium substrate), while lithium alone is very light, the energy density is considerably lower.
A Li-air battery potentially had 5–15 times the specific energy of a Li-ion battery as of 2016.