View source for Polysulfide–bromide battery

{{Short description|Flow battery}}

The '''polysulfide–bromine battery''' (PSB; sometimes ''polysulphide–polybromide'' or "bromine–sulfur") is a type of rechargeable [[electric battery]] that stores electrical energy in liquids, such as water-based solutions of two salts: [[sodium bromide]] and [[sodium polysulfide]]. It is a type of [[redox]] (reduction–oxidation) [[flow battery]].

In 2002, a 12 MWe prototype electrical storage facility was built at [[Little Barford Power Station]] in the UK,<ref name="Price1999">{{cite journal | doi = 10.1049/pe:19990304 | volume=13 | issue=3 | title=A novel approach to utility-scale energy storage | year=1999 | journal=Power Engineering Journal | pages=122–129 | last1 = Price | first1 = A. | last2 = Bartley | first2 = S. | last3 = Cooley | first3 = G. | last4 = Male | first4 = S.| doi-broken-date=7 December 2024 }}</ref> which used polysulfide–bromide flow batteries. Although the facility was completed, due to engineering issues in scaling up the technology, it was never fully commissioned.<ref name="ENSG">{{cite web|url=http://www.ensg.gov.uk/assets/dgdti00055.pdf|archive-url=http://webarchive.nationalarchives.gov.uk/20100919181607/http://www.ensg.gov.uk/assets/dgdti00055.pdf|url-status=dead|archive-date=19 September 2010|title=Review of Electrical Energy Storage Technologies and Systems and of their Potential for the UK|accessdate=24 November 2012|page=24}}</ref> A similar demonstration plant located at the [[Tennessee Valley Authority]] (TVA) facility in Columbus, Mississippi, United States, was never completed.

==Chemistry==
Two different salt solution [[electrolyte]]s are contained in two separate tanks. When energy is required, a solution of Na<sub>2</sub>S<sub>2</sub> (sodium [[disulfide]]) is pumped to the anode, and NaBr<sub>3</sub> ([[sodium tribromide]]) is pumped to the cathode. The anode and cathode, along with their corresponding salt solutions, are separated by an [[ion exchange]] [[membrane]].

At the negative electrode, the anodic reaction is:

:<math>2\ \mathrm{Na_2S_2} \rightarrow \mathrm{Na_2S_4} + 2\ \mathrm{Na^+} + 2\ \mathrm{e}^-</math>

At the positive electrode, the cathodic reaction is:

:<math>\mathrm{NaBr_3} + 2\ \mathrm{Na^+} + 2\ \mathrm{e}^- \rightarrow 3\ \mathrm{NaBr}</math>

As energy is drawn from the system, the sodium disulfide becomes sodium [[polysulfide]], and the sodium tribromide becomes sodium bromide. This reaction can be reversed when a current is supplied to the electrodes, and the system's chemical salts are ''recharged''. The system is sometimes defined as a fuel cell because the electrodes are not consumed by the reaction; they act only as a surface for the reaction. However, the liquid is not a fuel that is consumed—it is a salt solution electrolyte that is changed by the process.

==History==
Although the possibilities of using polysulfide and bromine redox couples in flow and static batteries had been mentioned before, it was Robert Remick and Peter Ang of the Institute of Gas Technology (Chicago) who were the first to demonstrate (and claim in a patent) a rechargeable polysulfide–polybromide battery (SBB) in 1981.<ref name="Remick1981">{{cite patent
| country = US
| number  = US4304799A
| inventor= Robert Remick; Peter G. Ang
| invent1 = Robert Remick
| invent2 = Peter G. Ang
| status  = patent
| title   = Electrically rechargeable anionically active reduction-oxidation electrical storage-supply system
| pubdate = 1981-12-08
| url     = https://patents.google.com/patent/US4304799A/en
}}</ref> They secured a DOE grant for detailed studies that revealed MoS<sub>2</sub> as a preferred (yet less than ideal) electrocatalyst for the negative electrode reaction.<ref name="Remick1983">{{cite report |last1=Remick |first1=Robert |last2=Camara |first2=Emilio |title=Electrochemistry of the sulfide/polysulfide couple |publisher=Institute of Gas Technology |date=1983-07-01}}</ref>

In 1987, Stuart Licht, while at the [[Weizmann Institute of Science]] (Rehovot, Israel) and [[MIT]] (Cambridge, Massachusetts), demonstrated extraordinary aqueous solubility of potassium sulfides—for example, a 3:1 water:salt molar ratio for K<sub>2</sub>S and K<sub>2</sub>S<sub>4</sub> solutions—and later demonstrated this with a sulfur/polysulfide–aluminum battery.<ref>{{Cite journal |last=Licht |first=Stuart |date=1987-09-01 |title=An Energetic Medium for Electrochemical Storage Utilizing the High Aqueous Solubility of Potassium Polysulfide |url=https://doi.org/10.1149/1.2100838 |journal=Journal of the Electrochemical Society |volume=134 |issue=9 |pages=2137–2141 |doi=10.1149/1.2100838}}</ref><ref>{{cite patent
| country = US
| number  = US5413881A
| inventor= Stuart Licht; Dharmasena Peramunage
| invent1 = Stuart Licht
| invent2 = Dharmasena Peramunage
| status  = patent
| title   = Aluminum and sulfur electrochemical batteries and cells
| pubdate = 1995-05-09
| url     = https://patents.google.com/patent/US5413881A/en
}}</ref><ref name="Peramunage1993">{{Cite journal |last1=Peramunage |first1=Dharmasena |last2=Licht |first2=Stuart |date=1993-08-20 |title=A Solid Sulfur Cathode for Aqueous Batteries |url=https://www.science.org/doi/10.1126/science.261.5124.1029 |journal=Science |volume=261 |issue=5124 |pages=1029–1032 |doi=10.1126/science.261.5124.1029 |pmid=17739624}}</ref> Nevertheless, sodium chemistry remained the mainstream among polysulfide–polybromide RFB developers, perhaps because of the higher solubility of NaBr (8.82 molal at 20 °C) compared to KBr (5.49 molal at 20 °C).

In 1992, National Power PLC (formed in 1990 as a result of the privatization of the UK's electricity market) acquired from the Institute of Gas Technology the original US patent by Remick and Ang,<ref name="Remick1981" /> and started a research and development program in the field of polysulfide–polybromide RFBs. Initial work at National Power was done by Ralph Zito,<ref name="Zito1993a">{{cite patent
| country = US
| number  = US5256606A
| inventor= Ralph Zito
| invent1 = Ralph Zito
| status  = patent
| title   = Electrochemical energy storage and/or power delivery cell with pH control
| pubdate = 1993-10-26
| url     = https://patents.google.com/patent/US5256606A/en
}}</ref> who was famously known for his prior work on Zn–Br<sub>2</sub> RFBs.<ref name="Zito1966">{{cite patent
| country = US
| number  = US3279998A
| inventor= Ralph Zito Jr.
| invent1 = Ralph Zito Jr.
| status  = patent
| title   = Storage battery having bromine positive active material
| pubdate = 1966-10-18
| url     = https://patents.google.com/patent/US3279998A/en
}}</ref><ref name="Zito1967">{{cite patent
| country = US
| number  = US3355340A
| inventor= Ralph Zito Jr.
| invent1 = Ralph Zito Jr.
| status  = patent
| title   = Zinc–bromine secondary cell
| pubdate = 1967-11-28
| url     = https://patents.google.com/patent/US3355340A/en
}}</ref><ref name="Zito1983">{{cite patent
| country = US
| number  = US4388331A
| inventor= Ralph Zito
| invent1 = Ralph Zito
| status  = patent
| title   = Zinc–bromine battery with long term stability
| pubdate = 1983-06-14
| url     = https://patents.google.com/patent/US4388331A/en
}}</ref> During the reorganization of the UK electricity market in the 1990s, the National Power patents were transferred to Innogy Technology Ventures Ltd, which became in 2002 a subsidiary of the German multi-utility [[RWE]] group of companies. Regenesys Technologies Limited was spun off from RWE-Innogy with the task of expedient demonstration and commercialization of polysulfide–polybromide RFBs, which were branded as Regenesys® batteries. By 2001, Regenesys employed over 70 people and demonstrated 5 kW and 10 kW stacks.

In 2001, the UK's [[Department of Trade and Industry (United Kingdom)|Department of Trade and Industry]] funded approximately 50% of the total £2 million cost (with an expected cost-share from RWE-Innogy) of building a 100 kW Regenesys® battery at [[Little Barford]] in central England next to an existing gas-peaker plant and a proposed windmill site.<ref name="Regenesys2004">{{cite report |title=Regenesys utility scale energy storage: Report |publisher=Energy Storage Association |date=2004}}</ref> A similar plant was considered in [[Columbus, Mississippi]], USA,<ref>{{cite web|title=Requesting proposals for completing TVA's Regenesys plant in Columbus, Mississippi |url=https://www.osti.gov/etdeweb/servlets/purl/20517742 |accessdate=24 October 2023}}</ref><ref>{{cite conference |last=Grant |first=I. |title=TVA's Regenesys energy storage project |book-title=IEEE Power Engineering Society Summer Meeting |year=2002 |volume=1 |pages=321–323 |doi=10.1109/PESS.2002.1043242}}</ref> as part of the [[Tennessee Valley Authority]]'s initiatives. However, scaling from 10 kW to 100 kW stacks proved more difficult than expected. After addressing several technical challenges, RWE decided to abandon the Regenesys® technology in 2003. The cost of developing the polysulfide–polybromide RFBs between 1990 and 2004 amounted to over £140 million.<ref>{{cite news|title=RWE abandons Regenesys project |work=The Guardian |date=22 January 2004 |url=https://www.theguardian.com/business/2004/jan/22/5}}</ref>

Others also explored the feasibility of polysulfide–polybromide batteries. Around 2002, the [[Dalian Institute of Chemical Physics]] (China) launched its own SBB program. In 2004–2006, they reported 1 kW systems operating at 40 mA/cm<sup>2</sup> with the cycle energy efficiency improving from 67% to 82% due mostly to the development of new electrode materials.<ref>{{cite journal |last1=Zhao |first1=Ping |last2=Zhou |first2=Huamin |last3=Yi |first3=Baolian |title=Nickel foam and carbon felt applications for sodium polysulfide/bromine redox flow battery electrodes |journal=Electrochimica Acta |year=2006 |volume=51 |issue=6 |pages=1091–1098 |doi=10.1016/j.electacta.2005.06.008}}</ref><ref>{{cite journal |last1=Zhou |first1=Huamin |last2=Zhao |first2=Ping |last3=Yi |first3=Baolian |title=Novel cobalt coated carbon felt as high performance negative electrode in sodium polysulfide/bromine redox flow battery |journal=Electrochemistry |year=2006 |volume=74 |issue=4 |pages=296–299 |doi=10.5796/electrochemistry.74.296}}</ref> Nevertheless, the commercialization of SBBs has been limited due to technical challenges such as sulfur deposition in the porous negative electrode during long-term cycling and the success of vanadium redox flow batteries.

In recent years, SBBs with Li<sup>+</sup>- and Na<sup>+</sup>-conducting ceramic separators have been demonstrated. Although these cells showed good cycle life over 100 cycles without noticeable degradation, they were operated at low current densities due to the high ohmic resistance of the separator.<ref>{{cite journal |last1=Wang |first1=L. N. |last2=Liu |first2=X. F. |last3=Liu |first3=J. Y. |last4=Yang |first4=H. |last5=Fu |first5=C. M. |last6=Xia |first6=Y. Y. |last7=Liu |first7=T. X. |title=A rechargeable metal-free full-liquid sulfur–bromine battery for sustainable energy storage |journal=Journal of Materials Chemistry A |year=2018 |volume=6 |issue=42 |pages=20737–20744 |doi=10.1039/C8TA07951J}}</ref><ref>{{cite journal |last1=Gross |first1=M. M. |last2=Manthiram |first2=A. |title=Long-life polysulfide–polyhalide batteries with a mediator-ion solid electrolyte |journal=ACS Applied Energy Materials |year=2019 |volume=2 |issue=5 |pages=3445–3451 |doi=10.1021/acsaem.9b00253}}</ref>

==See also==
* [[List of battery types]]
* [[Flow battery]]
* [[Battery (electricity)]]
* [[Lead–acid battery]]
* [[Electrochemical cell]]
* [[Electrochemical engineering]]
* [[Fuel cell]]
* [[Energy storage]]

==References==
{{reflist}}

==External links==
* [https://web.archive.org/web/20070608013614/http://www.electricitystorage.org/tech/technologies_technologies_psb.htm Electricity Storage Association section on PSBs]

[[Category:Electrochemical_cells]]
[[Category:Flow batteries]]
[[Category:Sodium]]

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