SCPS developed a low-cost technology for the industrial production of copper foam. The copper foam collector forms a dense and very conductive network within the anodic active material.
Société de Conseil et de Prospective Scientifique (SCPS), located in Rosny-sous-Bois, France, developed a technology that allows the nickel-zinc battery system to work as close as possible to its theoretical performance, with a long cycle life.
Nickel-zinc battery systems have been known for over 100 years, but only recently has the technology been made viable and competitive with other commercially available rechargeable battery systems. The main battery systems on the market can be grouped into three families:
Systems with acid electrolyte:
Lead acid batteries (PbPbO2)
Systems with alkaline electrolyte:
Nickel-cadmium batteries (NiCd)
Nickel-metal hydrid batteries (NiMH)
Nickel-zinc batteries (NiZn)
Systems with organic electrolyte:
Lithium batteries: lithium-ion (Li-ion) and Li-metal-polymer (LiMP)
PbPbO2 and NiCd present deficiencies in terms of technical performances and environmental-friendliness, due to the presence of heavy metals. LiMP batteries have a relatively short cycle life and weak level of power. Li-ion contains volatile organic compounds that are difficult to recycle; NiMH uses rare earths able to store hydrogen, which are very difficult to recycle; and LiMP contains vanadium oxide, a toxic compound. Lithium systems also have an issue with safety, as there is a risk of explosion or fire during manufacture, use, and recycling at the end of life.
NiZn is plentiful, non-toxic, and has completely recyclable components. Until recently, NiZn had never been able to correctly cycle its negative zinc electrode, driving it to strong capacity losses and to short circuit.
The need to store energy in batteries for stationary or mobile uses increases continuously, as well as the demand for safe, low cost, environmental friendly and easy to recycle battery systems.
The NiZn battery known since the end of the nineteenth century meets these requirements … but could not be used so far like commercial batteries of today : the rapid formation of zinc anarchic growths, and the massive zinc redistribution on cycling reduced cycle life to only some tens of charge-discharge cycles.
The battery developed by SCPS totally solves this issue by combining two main components in the zinc electrode :
a copper foam used as a mechanical support and a current collector,
a mix of conductive ceramic and co-additives added to the active mass.
By completely suppressing the formation of zinc growths, and by reducing drastically the shape changes during cycling, the battery can be cycled more than 1000 times with full discharges, and a capacity loss of 20% of the initial capacity.
This cycling is obtained without addition of water, thanks to a gas recombination process.
Nickel and zinc electrodes are plastic-bonded type, produced by filling their foam collector (nickel for the positive, copper for the negative).
Electrodes thickness can vary in a wide range, from 0.3 to 1.2mm, according to the application.
Based on the flexible design of electrodes, to a low internal impedance resulting from the high conductivity of the electrolyte and from the nature of the separator, the NiZn battery can be designed for applications requesting energy or power.
Official expertises of the NiZn technology made by industrial groups (EDF, AREVA), R&D centres and Universities (CEA, Bar-Ilan University of Tel-Aviv) have confirmed the main features of the technology:
capability to meet a wide range of specifications.
SCPS analyzed the causes of the problems, relative to progressive and fast shape modifications of the negative zinc electrode:
the spreading in all the cell of the zinc anode active material, dissolved during discharges into soluble zincates, the loss of the electrical characteristics of the anode when discharged, and the rapid loss of the necessary porosity of the zinc anode, after recharges.
The most critical issue to solve in the battery was the behavior of the zinc anode. The zinc anode developed by SCPS is a plasticized electrode, characterized essentially by the combination of two key elements:
a copper foam collector, forming a dense and very conductive network within the anodic active material, and
a powder of associated additives, distributed through the zinc anode, having a combined action that eliminates any undesired shape evolution of the electrode.
These anodic components, and the association with a specially system-adapted positive nickel electrode, allow for the resolution of previous NiZn problems, and enable NiZn to be suited for energy and power applications (with its concentrated electrolyte, and its monolayer microporous separator). SCPS' NiZn battery works as a maintenance-free system and is safe in all conditions of use.
For more information, visit SCPS (http://scps.fr/en)
External link: http://scps.fr/en