1 MW 4 MWh Turner Energy Storage Project in Pullman, WA

The vanadium redox battery (VRB), also known as the vanadium flow battery (VFB) or vanadium redox flow battery (VRFB), is a type of rechargeable

flow battery A flow battery, or redox flow battery (after reduction–oxidation), is a type of electrochemical cell where chemical energy is provided by two chemical components dissolved in liquids that are pumped through the system on separate sides of a ...

. It employs

vanadium Vanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery-grey, malleable transition metal. The elemental metal is rarely found in nature, but once isolated artificially, the formation of an oxide layer ( pas ...

ions as

charge carrier In physics, a charge carrier is a particle or quasiparticle that is free to move, carrying an electric charge, especially the particles that carry electric charges in electrical conductors. Examples are electrons, ions and holes. The term is used ...

s. The battery uses vanadium's ability to exist in a solution in four different

oxidation state In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. C ...

s to make a battery with a single electroactive element instead of two. For several reasons, including their relative bulkiness, vanadium batteries are typically used for

grid energy storage Grid energy storage (also called large-scale energy storage) is a collection of methods used for energy storage on a large scale within an electrical power grid. Electrical energy is stored during times when electricity is plentiful and inexp ...

, i.e., attached to power plants/electrical grids. Pissoort explored the possibility of VRFB's in the 1930s.P. A. Pissoort, in FR Patent 754065 (1933) NASA researchers and Pellegri and Spaziante followed suit in the 1970s,A. Pelligri and P. M. Spaziante, in GB Patent 2030349 (1978), to Oronzio de Nori Impianti Elettrochimici S.p.A. but neither was successful. Maria Skyllas-Kazacos presented the first successful demonstration of dissolved vanadium in a solution of

sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular formu ...

in the 1980s.M. Rychcik and M. Skyllas-Kazacos, J. Power Sources, 22 (1988) 59–67 Her design used sulfuric acid electrolytes, and was patented by the

University of New South Wales The University of New South Wales (UNSW), also known as UNSW Sydney, is a public research university based in Sydney, New South Wales, Australia. It is one of the founding members of Group of Eight, a coalition of Australian research-intensive ...

in Australia in 1986. Numerous companies and organizations are involved in funding and developing vanadium redox batteries.

Advantages and disadvantages

Advantages

VRFB's main advantages over other types of battery: * no limit on energy capacity * can remain discharged indefinitely without damage * mixing electrolytes causes no permanent damage * single charge state across the electrolytes avoids capacity degradation * safe, non-flammable aqueous electrolyte;UniEnergy Technologies Products
Accessed 21 Jan 2016. * wide operating temperature range including passive coolingMiller, Kelsey

, Clean Tech Alliance, 7 July 2014. Accessed 21 Jan 2016. * long charge/discharge cycle lives: 15,000-20,000 cycles. * low levelized cost: (a few tens of cents), approaching the 2016 $0.05 target stated by the

US Department of Energy The United States Department of Energy (DOE) is an executive department of the U.S. federal government that oversees U.S. national energy policy and manages the research and development of nuclear power and nuclear weapons in the United State ...

and the

European Commission The European Commission (EC) is the executive of the European Union (EU). It operates as a cabinet government, with 27 members of the Commission (informally known as "Commissioners") headed by a President. It includes an administrative body o ...

Strategic Energy Technology Plan €0.05 target.

Disadvantages

VRFB's main disadvantages compared to other types of battery: * relatively poor energy-to-volume ratio compared to standard

storage batteries A rechargeable battery, storage battery, or secondary cell (formally a type of energy accumulator), is a type of electrical battery which can be charged, discharged into a load, and recharged many times, as opposed to a disposable or prima ...

* relatively poor round trip efficiency * high weight of aqueous electrolyte * relatively high toxicity of oxides of vanadium

Materials

A vanadium redox battery consists of an assembly of power

cells Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Locations * Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery w ...

in which two electrolytes are separated by a

proton exchange membrane A proton-exchange membrane, or polymer-electrolyte membrane (PEM), is a semipermeable membrane generally made from ionomers and designed to conduct protons while acting as an electronic insulator and reactant barrier, e.g. to oxygen and hydrogen g ...

. The electrodes in a VRB cell are carbon based. The most common types are carbon felt, carbon paper, carbon cloth, and graphite felt. Recently,

carbon nanotube A scanning tunneling microscopy image of a single-walled carbon nanotube Rotating single-walled zigzag carbon nanotube A carbon nanotube (CNT) is a tube made of carbon with diameters typically measured in nanometers. ''Single-wall carbon na ...

-based electrodes have attracted interest from the scientific community. Both electrolytes are

-based. The electrolyte in the positive half-cells contains VO₂⁺ and VO²⁺ ions, while the electrolyte in the negative half-cells consists of V³⁺ and V²⁺ ions. The electrolytes can be prepared by several processes, including electrolytically dissolving

vanadium pentoxide Vanadium(V) oxide (''vanadia'') is the inorganic compound with the formula V2 O5. Commonly known as vanadium pentoxide, it is a brown/yellow solid, although when freshly precipitated from aqueous solution, its colour is deep orange. Because o ...

(V₂O₅) in

(H₂SO₄). The solution remains strongly acidic in use. The membrane is another critical component. The most common membrane material is perfluorinated

sulfonic acid In organic chemistry, sulfonic acid (or sulphonic acid) refers to a member of the class of organosulfur compounds with the general formula , where R is an organic alkyl or aryl group and the group a sulfonyl hydroxide. As a substituent, it is kn ...

(PFSA) (Nafion). However, vanadium ions tend to penetrate the membrane and destabilize the cell. A 2021 Chinese study found that this penetration is reduced with hybrid sheets made by growing

tungsten trioxide Tungsten(VI) oxide, also known as tungsten trioxide is a chemical compound of oxygen and the transition metal tungsten, with formula WO3. The compound is also called tungstic anhydride, reflecting its relation to tungstic acid . It is a light ...

nanoparticles on the surface of single-layered graphene oxide sheets. These hybrid sheets are then embedded into a sandwich structured PFSA membrane reinforced with

polytetrafluoroethylene Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene that has numerous applications. It is one of the best-known and widely applied PFAS. The commonly known brand name of PTFE-based composition is Teflon by Chemour ...

(Teflon). The tungsten trioxide nanoparticles also promote proton transport, offering high

Coulombic efficiency Faraday efficiency (also called ''faradaic efficiency'', ''faradaic yield'', ''coulombic efficiency'' or ''current efficiency'') describes the efficiency with which charge (electrons) is transferred in a system facilitating an electrochemical reacti ...

and energy efficiency of more than 98.1 percent and 88.9 percent, respectively.

Operation

The reaction uses the

half-reaction A half reaction (or half-cell reaction) is either the oxidation or reduction reaction component of a redox reaction. A half reaction is obtained by considering the change in oxidation states of individual substances involved in the redox reaction. ...

s: : () : () Other useful properties of vanadium flow batteries are their very fast response to changing loads and their extremely large overload capacities. Studies by the University of New South Wales have shown that they can achieve a response time of under half a millisecond for a 100% load change, and allowed overloads of as much as 400% for 10 seconds. The response time is mostly limited by the electrical equipment. Unless specifically designed for colder or warmer climates, most sulfuric acid-based vanadium batteries work only between about 10 and 40 °C. Below that temperature range, the ion-infused sulfuric acid crystallizes. Round trip efficiency in practical applications is around 65–75 %.VRB Power Systems FAQ

Proposed improvements

Second generation vanadium redox batteries (

bromine Bromine is a chemical element with the symbol Br and atomic number 35. It is the third-lightest element in group 17 of the periodic table (halogens) and is a volatile red-brown liquid at room temperature that evaporates readily to form a simila ...

) may approximately double the energy density and increase the temperature range in which the battery can operate. The

and other vanadium based systems also reduce the cost of vanadium redox batteries by replacing the vanadium at the positive or negative electrolyte by cheaper alternatives such as cerium. Typically, perfluorinated sulfonic acid (PFSA) is used as the separator membrane. However, vanadium ions can cross the membrane and destabilize the battery. Researchers grew

nanoparticles on the surface of

graphene oxide An oxide () is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– (molecular) ion. with oxygen in the oxidation state of −2. Most of the ...

sheets and embedded them in a

-reinforced, sandwich-structured PFSA system. This reduced penetration and promoted proton transport, yielding Coulumbic efficiency and energy efficiency of greater than 98.1% and 88.9%, respectively.

Specific energy and energy density

Current production vanadium redox batteries achieve a specific energy of about 20 Wh/kg (72 kJ/kg) of electrolyte. More recent research at UNSW indicates that the use of precipitation inhibitors can increase the density to about 35 Wh/kg (126 kJ/kg), with even higher densities made possible by controlling the electrolyte temperature. The current

specific energy Specific energy or massic energy is energy per unit mass. It is also sometimes called gravimetric energy density, which is not to be confused with energy density, which is defined as energy per unit volume. It is used to quantify, for example, sto ...

is quite low compared to other

rechargeable battery A rechargeable battery, storage battery, or secondary cell (formally a type of Accumulator (energy), energy accumulator), is a type of electrical battery which can be charged, discharged into a load, and recharged many times, as opposed to ...

types (e.g., lead–acid, 30–40 Wh/kg (108–144 kJ/kg); and lithium ion, 80–200 Wh/kg (288–720 kJ/kg)). However, using precipitation inhibitors would place vanadium redox batteries on par with lead-acid batteries.

Applications

VRFB's large potential capacity may be best-suited to buffer the irregular output of utility-scale wind and solar systems. Their reduced self-discharge makes them potentially appropriate in applications that require long-term battery storage with little maintenance as in military equipment, such as the sensor components of the

GATOR mine system The GATOR mine system is a United States military system of air-dropped anti-tank and anti-personnel mines developed in the 1980s to be compatible with existing cluster dispensers. It is used with two dispenser systems—the Navy CBU-78/B and th ...

.Allbright, Greg, et al
A Comparison of Lead Acid to Lithium-ion in Stationary Storage Applications
All Cell, March 2012 They feature rapid response times well suited to

uninterruptible power supply An uninterruptible power supply or uninterruptible power source (UPS) is an electrical apparatus that provides emergency power to a load when the input power source or mains power fails. A UPS differs from an auxiliary or emergency power system ...

(UPS) applications, where they can replace lead–acid batteries or

diesel generators A diesel generator (DG) (also known as a diesel Genset) is the combination of a diesel engine with an electric generator (often an alternator) to generate electrical energy. This is a specific case of engine generator. A diesel compression-ig ...

. Fast response time is also appropriate for

frequency regulation Ancillary services are the services necessary to support the transmission of electric power from generators to consumers given the obligations of control areas and transmission utilities within those control areas to maintain reliable operations of ...

. These capabilities make VRBF's an effective "all-in-one" solution for

microgrids Distributed generation, also distributed energy, on-site generation (OSG), or district/decentralized energy, is electrical generation and storage performed by a variety of small, grid-connected or distribution system-connected devices referred to ...

, frequency regulation and load shifting.

Largest vanadium grid batteries

A 200 MW, 800 MWh (4 hours) vanadium redox battery is under construction in China; it was expected to be completed by 2018 and its 250 kW/ 1 MWh first stage was in operation in late 2018

Companies funding or developing vanadium redox batteries

Companies include CellCube (Enerox), UniEnergy Technologies, StorEn Technologies, Largo Energy and Ashlawn Energy in the United States; H2 in South Korea; Renewable Energy Dynamics Technology, Invinity Energy and VoltStorage in Europe; Prudent Energy in China; Australian Vanadium in Australia; EverFlow Energy JV SABIC SCHMID Group in Saudi Arabia and Bushveld Minerals in South Africa.

References

Additional references

Presentation paper from the IEEE summer 2001 conference

UNSW Site on Vanadium batteries

Report by World Energy

World Map Of Global Vanadium Deposits
Vanadium geology is fairly unusual compared to a base metals ore body. *

External links

The U.S. made a breakthrough battery discovery — then gave the technology to China
''The U.S. made a breakthrough battery discovery — then gave the technology to China''
VRFB developments at UNSW

VRB at everything2

The Need for Vanadium Redox Energy Storage in Wind Turbine Generators
''Net electricity generation from all forms of renewable energies in America increased by over 15% between 2005 and 2009.''
redT and Avalon have merged as Invinity Energy Systems, a global leader in Vanadium Flow Batteries
{{Galvanic cells Flow batteries Vanadium Grid energy storage