The Effect of Insertion Species on Nanostructured Open Framework Hexacyanoferrate Battery Electrodes

Abstract

Recent battery research has focused on the high power and energy density needed for portable electronics and vehicles, but the requirements for grid-scale energy storage are different, with emphasis on low cost, long cycle life, and safety. 1, 2 Open framework materials with the Prussian Blue crystal structure offer the high power capability, ultra-long cycle life, and scalable, low cost synthesis and operation that are necessary for storage systems to integrate transient energy sources, such as wind and solar, with the electrical grid. We have demonstrated that two open framework materials, copper hexacyanoferrate and nickel hexacyanoferrate, can reversibly intercalate lithium, sodium, potassium, and ammonium ions at high rates. These materials can achieve capacities of up to 60 mAh/g. The porous, nanoparticulate morphology of these materials, synthesized by the use of simple and inexpensive methods, results in remarkable rate capabilities: e.g. copper hexacyanoferrate retains 84% of its maximum capacity during potassium cycling at a very high (41.7C) rate, while nickel hexacyanoferrate retains 66% of its maximum capacity while cycling either sodium or potassium at this same rate. These materials show excellent stability during the cycling of sodium and potassium, with minimal capacity loss after 500 cycles.

An electrochemical system for efficiently harvesting low-grade heat energy

“…Considering these requirements, we have selected solid CuHCF as the positive electrode for the TREC because of its negative temperature coefficient ( À 0.36 mV K À 1 ), high specific charge capacity (60 mAh g À 1 ) compared with redox couples in solution, relatively low specific heat (1.07 JK À 1 g À 1 ), and ultra-low voltage hysteresis [19][20][21] to 70°C. Figure 2a shows the OCV change of the CuHCF electrode (50% state of charge), the Cu/Cu 2 þ (3 M) electrode and the full cell for each 10-°C increment when the voltage is set at 0 V at 10°C.…”

Electrochemical Systems for Renewable Energy Conversion from Salinity and Proton Gradients

“…50 Based on the charge/discharge curves, overpotentials are low at 0.83C rate, which demonstrates low irreversibility. 58 Added to these properties is the fact that the potential of modified PBA electrodes generally varies 59 mV per logarithm unit of the alkaline ion concentration. 59,60 NiHCF and CuHCF display properties that are worth exploring in MEB.…”

Full open-framework batteries for stationary energy storage

“…We recently demonstrated promising results with a new family of battery electrode materials based on the common, inexpensive Prussian Blue pigment [8][9][10][11] . Electrodeposited thin films of these materials have received substantial study in the past for their electrochromic properties, beginning with the pioneering work of Neff 12,13 .…”

“…The result is an extremely stable electrode: over 40,000 deep discharge cycles were demonstrated in the case of the Cu II -N C-Fe III/II cathode 10 . We later showed that related cathode materials including nickel hexacyanoferrate (Ni II -N C-Fe III/II ) 11 also have a very long cycle life when operated in a wide variety of aqueous alkali-ion electrolytes 8 , and that their reaction potentials can be controlled by altering their composition 9 .…”