Flow Battery And Regeneration System With Improved Safety

Abstract

A method for producing electric power and regenerating an aqueous multi-electron oxidant (AMO) and a reducer in an energy storage cycle is provided. A discharge system includes a discharge unit, an acidification reactor, and a neutralization reactor. The acidification reactor converts an oxidant fluid including the AMO into an acidic oxidant fluid. The discharge unit generates electric power and a discharge fluid by transferring electrons from a positive electrode of an electrolyte-electrode assembly (EEA) to the AMO and from a reducer to a negative electrode of the EEA. The neutralization reactor neutralizes the discharge fluid to produce a neutral discharge fluid. The regeneration system splits an alkaline discharge fluid into a reducer and an intermediate oxidant in a splitting-disproportionation reactor and releases the reducer and a base, while producing the AMO by disproportionating the intermediate oxidant. The regenerated AMO and reducer are supplied to the discharge unit for power generation.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation-in-part application of non-provisional patent application Ser. No. 13 / 969,597 titled “Flow Battery And Regeneration System”, filed in the United States Patent and Trademark Office on Aug. 18, 2013, which claims priority to and the benefit of provisional patent application No. 61 / 684,805 titled “Fluid Battery With Water-compatible Oxidants”, filed in the United States Patent and Trademark Office on Aug. 19, 2012. The specifications of the above referenced patent applications are incorporated herein by reference in their entirety.BACKGROUND[0002]The first widely commercialized automobiles at the dawn of the last century were electric and powered by lead acid batteries. Lead acid batteries are currently used in cars for starting, lighting, and ignition purposes. Lead acid batteries cost, for example, about 170 dollars / kilowatt hour (kWh) and are cheaper than many other rechargeable batteries known. However,...

AI Technical Summary

Benefits of technology

The patent describes a new method and system for creating a mechanically refillable, electrochemical flow battery that provides high energy density, efficiency, and power at a low cost. The battery uses a reducer fluid and an oxidant fluid to create electric power. The major difference is that the oxidant is an aqueous multi-electron oxidant (AMO) which has a high solubility in water and can transfer more than one electron per molecule in a redox reaction. The reducer is an element or compound that donates electrons to another species or electroode. The method and system produce electric power from two fluids, with the system using AMO in a salt, acid, or other form. The concentration of lithium bromate in the oxidant fluid is between 1M and 10M. The method and system also allow for a short refill time, reduced usage of precious materials, and a reduction or elimination of humidification. The discharge system generates an acidic discharge fluid and a neutral discharge fluid. Overall, this patent provides a new way to create a cost-effective, efficient, and refillable battery.

Problems solved by technology

However, the energy content of lead acid batteries is rather low.

A long recharge time, for example, of about 2 hours required for lead acid batteries necessitates in many applications, a cumbersome mechanical swap of a discharged battery by a charged battery.

Although nickel-metal hydride batteries provided better performance than the lead acid batteries, for example, a driving range of about 60 km, a specific energy of about 60 Wh / Kg to about 90 Wh / Kg, an energy density of about 200 Wh / L-300 Wh / L, a specific power of about 200 W / kg, and an electric recharge of about 3 hours, albeit at a higher cost of about $1,000 / kWh, the nickel-metal hydride batteries were not an acceptable replacement for gasoline from the customer's perspective.

Despite the dedicated work of many scientists and engineers worldwide, the hydrogen fuelled polymer electrolyte membrane fuel cell (PEMFC) technology did not result in a market success of electric vehicles.

The reasons are as follows: to achieve practically useful power density on the positive electrode, high platinum (Pt) loading is required which increases the cost of the PEMFCs; the dissolution of a Pt catalyst at positive potentials makes the positive electrode less durable; the lack of an inexpensive, sustainable, and a clean hydrogen source; and the lack of a hydrogen manufacturing and distribution infrastructure.

However, the first lithium batteries had a poor cycle life since the electronically insulating surface film formed on metallic lithium leads to dendritic Li plating during recharge.

However, fully electric vehicles, unlike plug-in hybrids, based on lithium ion batteries (LIBs) did not achieve a widespread commercial success, primarily due to a low energy content, that is, a low driving range, and a high total cost of ownership of the batteries.

The often quoted statistics that 60% of daily car trips in the United States are less than 60 Km is apparently not helping the sales of lithium-ion battery powered cars as most drivers need the capability to make longer trips.

Apart from the low driving range, the LIBs also have a low electric recharge rate, for example, the Nissan Leaf® takes about 30 minutes for a charge of about 80% of full capacity, and the construction of a large scale battery swapping infrastructure is not justified due to the lack of a sizable LIB electric vehicle market, as illustrated by a recent bankruptcy of Better Place.

The scientists at General Motors (GM) arrived at the same conclusion, that is, the battery electric vehicles based on current and targeted Li ion battery technology will be limited to small vehicle, low mileage-per-day applications due to relatively low specific energy and long recharge time constraints, and it is possible that fundamental physical limitations may prevent pure Li ion based battery electric vehicles (BEVs) from delivering the freedom of providing long trips, with intermittent quick refills, that consumers currently receive from their cars.

We're going to have a more significant breakthrough and probably go into some other area of battery chemistry.” MIT's Yet-Ming Chiang concurs: “It is clear that long-term vehicle electrification—especially affordable 200 mile all-electric range—will require batteries with approximately three times greater energy densities at about one third the cost per kWh than that of LIBs.” Kevin See, analyst for Boston-based Lux Research, said “It is not realistic or feasible for automakers to significantly cut the price of lithium-ion batteries.

There is going to be incremental improvement, but we don't believe it will be enough to spur the huge adjustment everyone was hoping for.” Tesla Motors has conceded that new technologies will eventually be required.

It is just too expensive and they're too heavy.”

According to Takeshi Uchiyamada, Toyota's Vice Chairman, “the current capabilities of electric vehicles”, based on fuel cells or lithium ion batteries, “do not meet society's needs, whether it may be the distance the cars can run, or the costs, or the long time to charge.

Because of its shortcomings, that is, driving range, cost, and recharging time, the battery or fuel cell electric vehicle is not a viable replacement for most conventional cars.

Conventional redox flow batteries such as vanadium redox flow batteries have a low energy density that translates into a short driving range, because the components have low solubilities and a large amount of an otherwise useless solvent which has to be carried on-board to keep the components in the fluid state.

Improvements in packing factor, that is the ratio of practical to theoretical energy density, by using, for example, binder free SEAM batteries with a soluble mediator or a soluble redox couple or metal containing ionic liquid flow batteries or protected Li metal anode, run into the fundamental limitation that the intrinsic energy densities of known battery chemistries are not sufficiently high for fully electric vehicle applications.

Also, the cost of such batteries is likely to stay above the mid-term target of about $100 / kWh and about $30 / kW, or about $2,250 / car with about 100 horsepower.

However, the fundamental problems related to the slow kinetics of the oxygen electrode result in high cost and poor durability of PEM fuel cells due to the necessity of high Pt loading in the case of near ambient temperature fuel cells.

Another problem with fuel cells, in general, is the source of the fuel, for example, hydrogen.

Paul Zigouras, Director of New Business Development at EPC Corporation, eloquently summarizes the status quo as: “Flow batteries are a great idea, but unfortunately, no fluid currently exists that will hold a decent amount of energy.

I am hopeful, but also doubtful that a fluid will ever be developed that can effectively do this”.

As a result, F2 has poor cycle efficiency, in addition to material compatibility issues, whereas I2 has a low energy density in addition to solubility problems.

However, the chorine cells use an expensive ruthenium (Ru)-containing catalyst and provide poor energy efficiency.

Although hydrogen-oxoacid flow batteries such as H2—HNO3 have been considered in the past, these flow batteries have poor discharge efficiency and lack the ability of electrical recharge or regeneration of the reagents.

However, such reactions did not find applications in energy storage and conversion, mostly due to their poor reversibility.

Although the use of a mediator leads in theory to reduced energy efficiency compared to a direct electrode reaction, this thermodynamic loss of energy efficiency is often smaller than the kinetic loss associated with electrode over-voltage at the same power using oxidants such as oxygen or using direct electroreduction of the oxoanions.

However, this process irreversibly consumes Ba(OH)2, H2SO4 and generates BaSO4 waste.

Also, this process does not co-produce a stoichiometric amount of hydrogen, which is required for the complete energy cycle of discharge and regeneration.

Thus, this precipitation route does not meet the application requirements.

Although this method is chemical and waste free, this method has poor energy efficiency and a low throughput.

For example, semiconductor based photovoltaic solar panels, for example, polycrystalline silicon photovoltaic solar panels, multilayer photovoltaic solar panels, InxGa (1−x) Se2, etc., are either inefficient or too expensive.

Photoelectrochemical water splitting into hydrogen (H2) and oxygen (O2) using anatase TiO2 nanoparticles also suffers from a low efficiency due to the high over voltage of the oxygen production centers.

Hence, there is a long felt but unresolved need for an electrochemical flow battery that provides for a high energy density, that is, a long driving range, a high energy efficiency and power at a low operational and manufacturing cost, and requires a short refill time.

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