Zinc–cerium batteries are a type of redox flow battery first developed by Plurion Inc. (UK) during the 2000s. In this rechargeable battery, both negative zinc and positive cerium electrolytes are circulated though an electrochemical flow reactor during the operation and stored in two separated reservoirs. Negative and positive electrolyte compartments in the electrochemical reactor are separated by a cation-exchange membrane, usually Nafion (DuPont). The Ce(III)/Ce(IV) and Zn(II)/Zn redox reactions take place at the positive and negative electrodes, respectively. Since zinc is electroplated during charge at the negative electrode this system is classified as a hybrid flow battery. Unlike in zinc–bromine and zinc–chlorine redox flow batteries, no condensation device is needed to dissolve halogen gases. The reagents used in the zinc-cerium system are considerably less expensive than those used in the vanadium flow battery.
Due to the high standard electrode potentials of both zinc and cerium redox reactions in aqueous media, the open-circuit cell voltage is as high as 2.43 V. Among the other proposed flow battery systems, this system has the largest cell voltage and power density per electrode area. Methanesulfonic acid is used as supporting electrolyte, as it allows high concentrations of both zinc and cerium; the solubility of the corresponding methanesulfonates is 2.1 M for Zn, 2.4 M for Ce(III) and up to 1.0 M for Ce(IV). Methanesulfonic acid is particularly well suited for industrial electrochemical applications and is considered to be a green alternative to other support electrolytes. The Zn-Ce system has introduced the use of this acid to other flow batteries as a better alternative to sulphuric acid.
At the negative electrode (anode), zinc is electroplated and stripped on the carbon polymer electrodes during charge and discharge, respectively.
Zn2+(aq) + 2e− ↔ Zn(s) (−0.76 V vs. SHE)
At the positive electrode (cathode) (titanium based materials or carbon felt electrode), Ce(III) oxidation and Ce(IV) reduction take place during charge and discharge, respectively.
Ce3+(aq) − e− ↔ Ce4+(aq) (ca. +1.44 V vs. SHE)
Because of the large cell voltage, hydrogen (0 V vs. SHE) and oxygen (+1.23 V vs. SHE) could evolve theoretically as side reactions during battery operation (especially on charging).
History and development
The zinc–cerium redox flow battery was first proposed by Clarke and co-workers in 2004, which has been the core technology of Plurion Inc. (UK). In 2008, Plurion Inc. suffered a liquidity crisis and was under liquidation in 2010. However, the information of the experimental conditions and charge-discharge performance described in the early patents of Plurion Inc. are limited. Since the 2010s, the electrochemical properties and the characterisation of a zinc–cerium redox flow battery have been identified by the researchers of Southampton and Strathclyde Universities. During charge/discharge cycles at 50 mA cm−2, the coulombic and voltage efficiencies of the zinc–cerium redox flow battery were reported to be 92 and 68%, respectively. In 2011, a membraneless (undivided) zinc–cerium system based on low acid concentration electrolyte using compressed pieces of carbon felt positive electrode was proposed. Discharge cell voltage and energy efficiency were reported to be approximately 2.1 V and 75%, respectively. With such undivided configuration (single electrolyte compartment), self-discharge was relatively slow at low concentrations of cerium and acid. Major installation of the zinc–cerium redox flow battery was the > 2 kW testing facility in Glenrothes, Scotland, installed by Plurion Inc. The use of mixed acid electrolytes for the positive half-cell has been investigated as a mean to increase the kinetics of the cerium redox reaction in State Key Laboratory of Rare Earth Resource Utilization and the Jiangxi University of Science and Technology, China.
- Energy storage
- Load balancing
- Flow battery
- Rechargeable battery
- Battery (electricity)
- Electrochemical cell
- R.L. Clarke, B.J. Dougherty, S. Harrison, P.J. Millington, S. Mohanta, US 2004/ 0202925 A1, Cerium Batteries, (2004).
- R.L. Clarke, B.J. Dougherty, S. Harrison, J.P. Millington, S. Mohanta, US 2006/0063065 A1, Battery with bifunctional electrolyte, (2005).
- Gernon, M. D.; Wu, M.; Buszta, T.; Janney, P. (1999). "Environmental benefits of methanesulfonic acid: comparative properties and advantages". Green Chemistry 1 (3): 127–140. doi:10.1039/a900157c.
- Kreh, R.P.; Spotnitz, R.M.; Lundquist, J.T. (1989). "Mediated electrochemical synthesis of aromatic aldehydes, ketones, and quinones using ceric methanesulfonate". The Journal of Organic Chemistry 54 (7): 1526–1531. doi:10.1021/jo00268a010.
- Nikiforidis, G.; Berlouis, L.; Hall, D.; Hodgson, D. (2012). "Evaluation of carbon composite materials for the negative electrode in the zinc–cerium redox flow cell". Journal of Power Sources 206: 497–503. doi:10.1016/j.jpowsour.2011.01.036.
- Leung, P.K.; Ponce de León, C.; Low, C.T.J.; Shah, A.A.; Walsh, F.C. (2011). "Characterization of a zinc-cerium flow battery". Journal of Power Sources 196 (11): 5174–5185. doi:10.1016/j.jpowsour.2011.01.095.
- Leung P.K.; Ponce-de-Leon C.; Walsh F.C. (2011). "An undivided zinc–cerium redox flow battery operating at room temperature (295 K)". Electrochemistry Communications 13 770–773. doi:10.1016/j.elecom.2011.04.011
- Xie, Z.; Liu, Q.; Chang, Z.; Zhang, X. (2013). "The developments and challenges of cerium half-cell in zinc–cerium redox flow battery for energy storage". Electrochimica Acta 90: 695–704. doi:10.1016/j.electacta.2012.12.066.
-  University of Southampton Research Project: Zinc-cerium redox flow cells batteries
-  U.S. Department of Energy's Flow Cells for Energy Storage Workshop