Solid-state battery is a battery technology that uses both solid electrodes and solid electrolytes, instead of the liquid or polymer electrolytes found in lithium-ion or lithium polymer batteries.
The technology is a proposed alternative to conventional lithium-ion battery technology.
Michael Faraday discovered the solid electrolytes silver sulfide 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, which utilized silver ion conducting electrolytes, had low energy density and cell voltages, in addition to very 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, which are considered to be a form of solid state battery.
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-sulfur 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. The company was acquired by Dyson in the following year.
In 2017, John Goodenough, the co-inventor of Li-ion batteries, unveiled a new solid-state battery, using glass electrolytes and an alkali-metal anode consisting of lithium, sodium or potassium, which is not possible with conventional batteries.
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.
Potential use in electric vehicles
Currently, 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 ultracapacitor), with many car makers adopting Li-ion technology for their EV offerings. A number of car makers and other companies, however, are looking into developing or using solid-state batteries due to the advantages described below.
Toyota announced in 2014 its solid-state battery development efforts. In 2017, the company announced the deepening of a decades-long partnership with Panasonic, which will include a collaboration on solid-state batteries. Volkswagen announced a $100 million investment in QuantumScape, a solid-state battery startup that spun out of Stanford. Other car makers developing solid-state battery technologies include BMW, Honda, Hyundai Motor Company, and Nissan.
Other companies are also developing solid-state battery for automotive applications. Dyson, a company known for manufacturing household appliances, announced in 2017 that it plans to launch an electric car by 2020. Two years prior to the announcement, Dyson bought Sakti3, a company researching solid-state batteries. 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.
A Chinese company, Qing Tao, started a production line of solid-state batteries. 
Solid-state batteries are traditionally expensive to make and current manufacturing processes are noted to be immune to economies of scale. It was estimated in 2012 that, based on then-current technology, a 20Ah solid-state battery cell would cost US$100,000, and a high-range electric car would require 800 to 1,000 of such cells. Cost is noted to be a factor that has impeded the adoption of solid-state batteries in certain areas, such as smartphones.
Meanwhile, solid-state batteries with ceramic electrolytes require high pressure to maintain contact with the electrodes. Solid-state batteries with ceramic separators may break from mechanical stress due to their rigid nature.
Solid-state battery technology is believed to be capable of higher energy density, because of their tolerance to higher temperatures, avoiding the use of materials in current batteries that may be dangerous or toxic.
Because most liquid electrolytes are considered to be flammable, solid state batteries are believed to be safer. As fewer safety systems are needed, a more compact battery is possible, improving energy and power densities.
Solid-state battery technology is also believed to allow for faster recharging for electric cars. In addition, higher voltage and longer cycle life is possible with solid-state batteries.
There have been efforts in researching hybrid battery technologies that utilize solid and liquid electrolytes together. One such battery was unveiled in 2015. Samsung SDI and LG Chem are also reportedly developing hybrid batteries.
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Solid state ionic devices such as high performance batteries...
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Researchers have tried to get around these problems by using an electrolyte made out of solid materials, such as some ceramics.
- See glass battery for further details on a battery design that utilizes glass electrolytes
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Researchers investigate mechanics of lithium sulfides, which show promise as solid electrolytes.
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Many automakers have adopted lithium-ion (Li-ion) batteries as the preferred EDV energy storage option, capable of delivering the required energy and power density in a relatively small, lightweight package.
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Samsung SDI and LG Chem are likely to unveil “solid-like” batteries for electric cars, instead of directly mass producing solid-state batteries. Solid-like batteries, which have some liquid electrolytes, are safer than lithium-ion batteries and easier to produce than solid-state batteries, experts said.
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