Stabilization of battery electrodes using polymer coatings

#The present invention relates generally to rechargeable energy accumulators, and more specifically, but not exclusively, to stabilization of electrodes used with aqueous electrolytes.

#The subject matter discussed in the background section should not be assumed to be prior art merely as a result of its mention in the background section. Similarly, a problem mentioned in the background section or associated with the subject matter of the background section should not be assumed to have been previously recognized in the prior art. The subject matter in the background section merely represents different approaches, which in and of themselves may also be inventions.

#In recent years, a variety of battery technologies have been developed for portable and stationary applications. These include lead acid, lithium ion, nickel/metal hydride, sodium sulfur, and flow batteries, among others. Unfortunately, not one of these technologies provides a sufficiently low cost, long enough cycle life, high enough rate capability, or high enough energy efficiency to provide useful energy storage and power for short-term, transient stationary storage applications. This includes the mitigation of costly transients on the electric grid, short term back up power and load management, regulatory services, and the deferral of investments in other power grid infrastructure components. Batteries may also support off-grid stationary electronic systems, whether by providing short-term backup power, or for facilities not connected to larger grids. Another large, unfulfilled market for batteries is the microhybrid, or stop-start automotive battery. The lead acid batteries currently used for this application must be oversized by an order of magnitude to avoid destruction due to repeated deep discharge cycling, resulting in heavy, expensive systems.

#The accompanying figures, in which like reference numerals refer to identical or functionally-similar elements throughout the separate views and which are incorporated in and form a part of the specification, further illustrate the present invention and, together with the detailed description of the invention, serve to explain the principles of the present invention.

#FIG. 1 illustrates a unit cell of the Prussian Blue crystal structure;

#FIG. 2 illustrates an X-ray diffraction spectrum of CuHCF;

#Embodiments of the present invention provide a system and method for slowing and/or preventing dissolution of electrodes into an operating electrolyte to extend a calendar life of the electrodes. The following description is presented to enable one of ordinary skill in the art to make and use the invention and is provided in the context of a patent application and its requirements.

#Various modifications to the preferred embodiment and the generic principles and features described herein will be readily apparent to those skilled in the art. Thus, the present invention is not intended to be limited to the embodiment shown but is to be accorded the widest scope consistent with the principles and features described herein.

#FIG. 1 illustrates a unit cell of the Prussian Blue crystal structure. The unit cell of copper hexacyanoferrate, a Prussian Blue analogue. In this material and all other Prussian Blue analogues, transition metal cations are linked in a face centered cubic framework by cyanide bridging ligands. In this case, iron is six-fold carbon coordinated, while copper is six-fold nitrogen coordinated. Each unit cell contains eight smaller cubic subcells, at the center of which is a large interstitice designated as the “A Site”. The A Sites contain zeolitic water and mobile alkali cations such as Na+ or K+. During the electrochemical cycling of a Prussian Blue analogue, alkali cations are inserted or removed from the A Sites.