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Polysulfide–bromide battery
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Polysulfide–bromide 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, 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. A similar demonstration plant located at the Tennessee Valley Authority (TVA) facility in Columbus, Mississippi, United States, was never completed.
Two different salt solution electrolytes are contained in two separate tanks. When energy is required, a solution of Na2S2 (sodium disulfide) is pumped to the anode, and NaBr3 (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:
At the positive electrode, the cathodic reaction is:
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.
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. They secured a DOE grant for detailed studies that revealed MoS2 as a preferred (yet less than ideal) electrocatalyst for the negative electrode reaction.
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 K2S and K2S4 solutions—and later demonstrated this with a sulfur/polysulfide–aluminum battery. 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).
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Polysulfide–bromide 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, 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. A similar demonstration plant located at the Tennessee Valley Authority (TVA) facility in Columbus, Mississippi, United States, was never completed.
Two different salt solution electrolytes are contained in two separate tanks. When energy is required, a solution of Na2S2 (sodium disulfide) is pumped to the anode, and NaBr3 (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:
At the positive electrode, the cathodic reaction is:
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.
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. They secured a DOE grant for detailed studies that revealed MoS2 as a preferred (yet less than ideal) electrocatalyst for the negative electrode reaction.
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 K2S and K2S4 solutions—and later demonstrated this with a sulfur/polysulfide–aluminum battery. 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).