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The contributions of a number of scientists and innovators created our understanding of the forces of electricity, but Alessandro Volta is credited with the invention of the first battery in 1800. On its most basic level, a battery is a device consisting of one or more electrochemical cells that convert stored chemical energy into electrical energy. Each cell contains a positive terminal, or cathode, and a negative terminal, or anode. Electrolytes allow ions to move between the electrodes and terminals, which allows current to flow out of the battery to perform work.

Advances in technology and materials have greatly increased the reliability, output, and density of modern battery systems, and economies of scale have dramatically reduced the associated cost. Continued innovation has created new technologies like electrochemical capacitors that can be charged and discharged simultaneously and instantly and provide an almost unlimited operational lifespan. The following pages offer greater insight into these technologies and the many applications that they are utilized for in creating a more robust and adaptable energy grid.

Lithium Ion (Li-Ion) Batteries

After Exxon chemist Stanley Whittingham developed the concept of lithium-ion batteries in the 1970s, Sony and Asahi Kasei created the first commercial product in 1991. The first batteries were used for consumer electronics and now, building on the success of these Li-ion batteries, many companies are developing larger-format cells for use in energy-storage applications. Many also expect there to be significant synergies with the emergence of electric vehicles (EVs) powered by Li-ion batteries. The flexibility of Li-ion technology in EV applications, from small high-power batteries for power buffering in hybrids, to medium-power batteries providing both electric-only range and power buffering in plug-in hybrids, to high-energy batteries in electric-only vehicles, has similar value in stationary energy storage.

Lead Batteries

Lead batteries are the most extensively used rechargeable battery technology in the world. They have an unrivalled track record for reliability and safety, which together with a well-established worldwide supplier base, make them the dominant battery in terms of MWh of production. Lead batteries are widely used in cars and trucks, being used in virtually all vehicles, supporting increased vehicle hybridization and electrification, all the way from start-stop technology to full electric vehicles. In addition, lead batteries are widely used in industrial applications, where they provide energy for telecommunications, uninterrupted power supply, secure power, electric traction and for energy storage for utilities as well as domestic and commercial applications.

Redox Flow Batteries

Redox flow batteries (RFB) represent one class of electrochemical energy storage devices. The name “redox” refers to chemical reduction and oxidation reactions employed in the RFB to store energy in liquid electrolyte solutions which flow through a battery of electrochemical cells during charge and discharge.

Vanadium Redox (VRB) Flow Batteries

The Vanadium Redox Battery (VRB®)¹ is a true redox flow battery (RFB), which stores energy by employing vanadium redox couples (V2+/V3+ in the negative and V4+/V5+ in the positive half-cells). These active chemical species are fully dissolved at all times in sulfuric acid electrolyte solutions. Like other true RFBs, the power and energy ratings of Vanadium Redox Batteries are independent of each other and each may be optimized separately for a specific application. All the other benefits and distinctions of true RFBs compared to other energy storage systems are realized by VRBs. The first operational vanadium redox battery was successfully demonstrated at the University of New South Wales in the late 1980s and commercial versions have been operating on scale for over 8 years.

Nickel-Cadmium (NI-CD) Batteries

In commercial production since the 1910s, nickel-cadmium (Ni-Cd) is a traditional battery type that has seen periodic advances in electrode technology and packaging in order to remain viable. While not exceling in typical measures such as energy density or first cost, Ni-Cd batteries remain relevant by providing simple implementation without complex management systems, while providing long life and reliable service.

Sodium Sulfur (NaS) Batteries

Sodium Sulfur (NaS) Batteries were originally developed by Ford Motor Company in the 1960s and subsequently the technology was sold to the Japanese company NGK. NGK now manufactures the battery systems for stationary applications. The systems operate at a high temperature, 300 to 350 °C, which can be an operational issue for intermittent operation. Significant installations for energy storage have been used to facilitate distribution line construction deferral. The round trip efficiency is in the 90% range so provides an efficient use of energy.

Electrochemical Capacitors

Electrochemical capacitors (ECs) – sometimes referred to as “electric double-layer” capacitors – also appear under trade names like “Supercapacitor” or “Ultracapacitor.” The phrase “double-layer” refers to their physically storing electrical charge at a surface-electrolyte interface of high-surface-area carbon electrodes. There are two types of ECs, symmetric and asymmetric, with different properties suitable for different applications. Markets and applications for electrochemical capacitors are growing rapidly and applications related to electricity grid will be part of that growth.

Iron-Chromium (ICB) Flow Batteries

Iron-chromium flow batteries were pioneered and studied extensively by NASA in the 1970s – 1980s and by Mitsui in Japan. The iron-chromium flow battery is a redox flow battery (RFB). Energy is stored by employing the Fe2+ – Fe3+ and Cr2+ – Cr3+ redox couples. The active chemical species are fully dissolved in the aqueous electrolyte at all times. Like other true RFBs, the power and energy ratings of the iron-chromium system are independent of each other, and each may be optimized separately for each application. All the other benefits and distinctions of true RFBs compared to other energy storage systems are realized by iron-chromium RFBs.

Zinc-Bromine (ZNBR) Flow Batteries

The zinc-bromine battery is a hybrid redox flow battery, because much of the energy is stored by plating zinc metal as a solid onto the anode plates in the electrochemical stack during charge. Thus, the total energy storage capacity of the system is dependent on both the stack size (electrode area) and the size of the electrolyte storage reservoirs. As such, the power and energy ratings of the zinc-bromine flow battery are not fully decoupled. The zinc-bromine flow battery was developed by Exxon as a hybrid flow battery system in the early 1970s.

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