Aqueous electrolyte energy storage device

#The present invention is directed to aqueous batteries and hybrid energy storage devices, and in particular to electrochemical storage devices without metal parts in contact with the aqueous electrolyte.

#Small renewable energy harvesting and power generation technologies (such as solar arrays, wind turbines, micro sterling engines, and solid oxide fuel cells) are proliferating, and there is a commensurate strong need for intermediate size secondary (rechargeable) energy storage capability. Batteries for these stationary applications typically store between 1 and 50 kWh of energy (depending on the application) and have historically been based on the lead-acid (Pb acid) chemistry. Banks of deep-cycle lead-acid cells are assembled at points of distributed power generation and are known to last 1 to 10 years depending on the typical duty cycle. While these cells function well enough to support this application, there are a number of problems associated with their use, including: heavy use of environmentally unclean lead and acids (it is estimated that the Pb-acid technology is responsible for the release of over 100,000 tons of Pb into the environment each year in the US alone), significant degradation of performance if held at intermediate state of charge or routinely cycled to deep levels of discharge, a need for routine servicing to maintain performance, and the implementation of a requisite recycling program. There is a strong desire to replace the Pb-acid chemistry as used by the automotive industry. Unfortunately the economics of alternative battery chemistries has made this a very unappealing option to date.

#Despite all of the recent advances in battery technologies, there are still no low-cost, clean alternates to the Pb-acid chemistry. This is due in large part to the fact that Pb-acid batteries are remarkably inexpensive compared to other chemistries ($200/kWh), and there is currently a focus on developing higher-energy systems for transportation applications (which are inherently significantly more expensive than Pb-acid batteries).

#FIG. 1 is a schematic illustration of a prismatic stack of electrochemical cells according to an embodiment.

#FIG. 2 is a schematic illustration of a detail of a sandwiched current collector according to an embodiment.

#FIG. 3 is a perspective view of an electrochemical device having a plurality of prismatic stacks of electrochemical cells according to an embodiment.

#Embodiments of the invention are drawn to electrochemical energy storage systems, such as primary and secondary batteries and hybrid energy storage systems described below. While secondary hybrid aqueous energy storage systems described below are preferred embodiments of the invention, the invention is also applicable to any suitable electrochemical energy storage systems, such as aqueous and non-aqueous electrolyte containing batteries (e.g., having anodes and cathodes which intercalate ions from the electrolyte, including Li-ion batteries, etc.) or electrolytic capacitors (also known as supercapacitors and ultracapacitors, e.g., having capacitor or pseudocapacitor anode and cathode electrodes that store charge through a reversible nonfaradiac reaction of cations on the surface of the electrode (double-layer) and/or pseudocapacitance rather than by intercalating alkali ions).

#Hybrid electrochemical energy storage systems of embodiments of the present invention include a double-layer capacitor or pseudocapacitor electrode (e.g., anode) coupled with an active electrode (e.g., cathode). In these systems, the capacitor or pseudocapacitor electrode stores charge through a reversible nonfaradiac reaction of alkali cations on the surface of the electrode (double-layer) and/or pseudocapacitance, while the active electrode undergoes a reversible faradic reaction in a transition metal oxide that intercalates and deintercalates alkali cations similar to that of a battery.

#An example of a Na-based system has been described in U.S. patent application Ser. No. 12/385,277, filed on Apr. 3, 2009 and incorporated herein by reference in its entirety, which utilizes a spinel structure LiMn2O4 battery electrode, an activated carbon capacitor electrode, and an aqueous Na2SO4 electrolyte. In this system, the negative anode electrode stores charge through a reversible nonfaradiac reaction of Na-ion on the surface of an activated carbon electrode. The positive cathode electrode utilizes a reversible faradiac reaction of Na-ion intercalation/deintercalation in spinel lambda-MnO2.