Solid-state battery

In solid state ionics, a solid-state battery is a battery that has both solid electrodes and solid electrolytes. As a group, these materials are very good conductors of ions, which is necessary for good electrolyte and electrode performance, and are essentially insulating toward electrons, which is desirable in electrolytes but undesirable in electrodes. The high ionic conductivity minimizes the internal resistance of the battery, thus permitting high power densities, while the high electronic resistance minimizes its self-discharge rate, thus enhancing its charge retention.

Examples of such materials include Ag₄RbI₅ for Ag⁺ conduction, LiI/Al₂O₃ mixtures for Li⁺ conduction, and the clay and β-alumina group of compounds (NaAl₁₁O₁₇) for Na⁺ and other mono- and divalent ions. At room temperature the ionic conductivity of a single crystal of sodium β-alumina is 0.035 S/cm, comparable to the conductivity of a 0.1 M HCl solution. This conductivity, however, is reduced in a battery by a factor of 2–5, because of the use of powdered or ceramic material rather than single crystals. Glassy and polymeric materials that can be readily made in thin film form, thus enhancing the rate capability of the overall system, are of increasing interest in the industry.

Solid-state batteries generally fall into the low-power density and high-energy density category. The former limitation arises because of the difficulty of getting high currents across solid–solid interfaces. However, these batteries do have certain advantages that outweigh this disadvantage: They are easy to miniaturize (for example, they can be constructed in thin film form), and there is no problem with electrolyte leakage. They tend to have very long shelf lives, and usually do not have any abrupt changes in performance with temperature, such as might be associated with electrolyte freezing or boiling.

As the batteries can exhibit a high power-to-weight ratio, they may be ideal for use in electric vehicles. Such batteries are estimated to have two-to-three times the energy density of existing automotive batteries.

See also

• Solid-state lithium-ion battery
• Ionic crystal
• Fast ion conductor
• Divalent
• Ionic conductivity
• Lithium-air battery
• Smartphone and tablet computer

Further reading

• Dudney, Nancy J.; Wes, William C,; Nanda, Jagjit (2015). Handbook of Solid State Batteries and Capacitors (2nd ed.). World Scientific Publishing. ISBN 978-981-4651-89-9.{{cite book}}: CS1 maint: extra punctuation (link) CS1 maint: multiple names: authors list (link)