A solid-state battery is a battery technology that uses solid electrodes and a solid electrolyte, instead of the liquid or polymer gel electrolytes found in lithium-ion or lithium polymer batteries. Materials proposed for use as solid electrolytes in solid-state batteries include ceramics (e.g. oxides, sulphides, phosphates), and solid polymers. Solid-state batteries have found use in pacemakers, RFID and wearable devices. They are potentially safer, with higher energy densities, but at a much higher cost.

Materials proposed for use as solid electrolytes in solid-state batteries include ceramics, glass and sulphides .Solid-state batteries have found use in pacemakers, RFID and wearable devices & Electric vehicles.

Hybrid and plug-in electric cars use a variety of battery technologies, including Li-ion, Nickel–metal hydride (NiMH), Lead–acid, and Electric double-layer capacitor (or ultra capacitor), led by Li-ion

Between 1831 and 1834, Michael Faraday discovered the solid electrolytes silver sulphide and lead (II) fluoride, which laid the foundation for solid-state ionics. High performance batteries are considered to be solid-state ionic devices.

In the late 1950s, efforts were made to develop a solid-state battery. The first solid-state batteries utilized a silver ion conducting electrolyte, had low energy density and cell voltages, and high internal resistance. A new class of solid-state electrolyte, developed by the Oak Ridge National Laboratory in the 1990s, was later incorporated into certain thin film lithium-ion batteries.

In 2011, Bolloré launched BlueCar with 30kWh lithium metal polymer (LMP) battery, which used solid polymeric electrolyte created by dissolving a lithium salt in a solvating co-polymer (polyoxyethylene).

In 2013, researchers at University of Colorado Boulder announced the development of a solid-state lithium battery, with a solid composite cathode based upon an iron-sulphur chemistry,  that promised higher energy capacity.

In 2014, researchers at Sakti3 announced a solid-state electrolyte lithium-ion battery, and claimed higher energy density for lower cost. Toyota announced its solid-state battery development efforts and holds the most patents. In 2015, Sakti3 was acquired by Dyson.

In 2017, John Goodenough, the co-inventor of Li-ion batteries, unveiled a solid-state battery, using a glass electrolyte and an alkali-metal anode consisting of lithium, sodium or potassium. In 2017 Toyota announced the deepening of a decades-long partnership with Panasonic, including collaboration on solid-state batteries. Other car makers developing solid-state battery technologies include BMW, Honda, Hyundai Motor Company and Nissan. Dyson, a company known for manufacturing household appliances, announced plans to launch an electric car by 2020. 

Two years prior to the announcement, Dyson bought Sakti3, a company researching solid-state batteries. Dyson abandoned the electric car project in 2019, but stated that the battery technology would be developed further. Fisker Automotive claims its solid-state battery technology will be ready for "automotive-grade production" in 2023. NGK, a company known for spark plugs, is developing ceramic-based solid state batteries, utilizing its expertise in the area of ceramics.

In 2018, Solid Power announced it had received $20 million in funding for a small manufacturing line to produce all-solid-state, rechargeable lithium-metal batteries. The line will be able to produce batteries with about 10 megawatt hours of capacity per year. Volkswagen announced a $100 million investment in QuantumScape, a solid-state battery start up that spun out of Stanford. Chinese company Qing Tao started a production line of solid-state batteries.
Solid-state battery technology is believed to be capable of higher energy density (2.5x), because of the use of lithium metal anode.

They may avoid the use of dangerous or toxic materials found in commercial batteries, such as organic electrolytes.

Because most liquid electrolytes are flammable and solid electrolytes are non-flammable, solid-state batteries are believed to be safer. Fewer safety systems are needed further increasing energy density. Recent studies show that the heat generation inside are only ~20-30% of conventional batteries with liquid electrolyte under thermal runaway.

Solid-state battery technology is believed to allow for faster recharge. Higher voltage and longer cycle life is possible.