Solid-state battery
Encyclopedia
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 ion
s but are essentially insulating toward electron
s, properties that are prerequisites for any electrolyte
. 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 shelf life.
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. Glass
y and polymer
ic 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
it could make them ideal for use in electric vehicles as they are estimated to have twice to three times the energy density
of existing automotive batteries.
Solid-state ionics
Solid-state ionics is the study of solid electrolytes and their uses. Some materials that fall into this category include inorganic crystalline and polycrystalline solids, ceramics, glasses, polymers, and composites...
, a solid-state battery is a battery
Battery (electricity)
An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery in 1800 by Alessandro Volta and especially since the technically improved Daniell cell in 1836, batteries have become a common power...
that has both solid electrodes and solid electrolytes
Fast ion conductor
In solid-state ionics, fast ion conductors, also known as solid electrolytes and superionic conductors, are materials that act as solid state ion conductors and are used primarily in solid oxide fuel cells. As solid electrolytes they conduct due to the movement of ions through voids, or empty...
. As a group, these materials are very good conductors of ion
Ion
An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...
s but are essentially insulating toward electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
s, properties that are prerequisites for any electrolyte
Electrolyte
In chemistry, an electrolyte is any substance containing free ions that make the substance electrically conductive. The most typical electrolyte is an ionic solution, but molten electrolytes and solid electrolytes are also possible....
. The high ionic conductivity
Ionic conductivity
Ionic conduction is the movement of an ion from one site to another through defects in the crystal lattice of a solid. Ionic conduction is one aspect of current....
minimizes the internal resistance of the battery, thus permitting high power densities, while the high electronic resistance
Electrical resistance
The electrical resistance of an electrical element is the opposition to the passage of an electric current through that element; the inverse quantity is electrical conductance, the ease at which an electric current passes. Electrical resistance shares some conceptual parallels with the mechanical...
minimizes its self-discharge
Self-discharge
Self-discharge is a phenomenon in batteries in which internal chemical reactions reduce the stored charge of the battery without any connection between the electrodes...
rate, thus enhancing its shelf life.
Examples of such materials include Ag4RbI5 for Ag+
Silver
Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...
conduction, LiI
Lithium iodide
Lithium iodide, or LiI, is a compound of lithium and iodine. When exposed to air, it becomes yellow in color, due to the oxidation of iodide to iodine.-Applications:...
/Al2O3
Aluminium oxide
Aluminium oxide is an amphoteric oxide with the chemical formula 23. It is commonly referred to as alumina, or corundum in its crystalline form, as well as many other names, reflecting its widespread occurrence in nature and industry...
mixtures for Li+
Lithium
Lithium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly...
conduction, and the clay
Clay
Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...
and β-alumina group of compounds (NaAl11O17) for Na+
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
and other mono- and divalent
Divalent
In chemistry, a divalent ion or molecule has a valence of two and thus can form two bonds with other ions or molecules. An older term for divalent is bivalent....
ions. At room temperature the ionic conductivity of a single crystal
Crystal
A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is known as crystallography...
of sodium β-alumina is 0.035 S/cm, comparable to the conductivity of a 0.1 M HCl solution
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
. This conductivity, however, is reduced in a battery by a factor of 2–5, because of the use of powdered or ceramic
Ceramic
A ceramic is an inorganic, nonmetallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous...
material rather than single crystals. Glass
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
y and polymer
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...
ic materials that can be readily made in thin film
Thin film
A thin film is a layer of material ranging from fractions of a nanometer to several micrometers in thickness. Electronic semiconductor devices and optical coatings are the main applications benefiting from thin film construction....
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
Specific power
In physics and engineering, surface power density or sometimes simply specific power is power per unit area.-Applications:* The intensity of electromagnetic radiation can be expressed in W/m2...
and high-energy density
Energy density
Energy density is a term used for the amount of energy stored in a given system or region of space per unit volume. Often only the useful or extractable energy is quantified, which is to say that chemically inaccessible energy such as rest mass energy is ignored...
category. The former limitation arises because of the difficulty of getting high currents across solid–solid interfaces
Interface (chemistry)
An interface is a surface forming a common boundary among two different phases, such as an insoluble solid and a liquid, two immiscible liquids or a liquid and an insoluble gas. The importance of the interface depends on which type of system is being treated: the bigger the quotient area/volume,...
. 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
Power-to-weight ratio
Power-to-weight ratio is a calculation commonly applied to engines and mobile power sources to enable the comparison of one unit or design to another. Power-to-weight ratio is a measurement of actual performance of any engine or power sources...
it could make them ideal for use in electric vehicles as they are estimated to have twice to three times the energy density
Energy density
Energy density is a term used for the amount of energy stored in a given system or region of space per unit volume. Often only the useful or extractable energy is quantified, which is to say that chemically inaccessible energy such as rest mass energy is ignored...
of existing automotive batteries.