阅读说明：本技术 氧化还原流电池 (Redox flow battery ) 是由 J·弗里德尔 T·休斯 U·斯蒂明 H·沃尔夫施密特 于 2018-05-08 设计创作，主要内容包括：一种氧化还原流电池,其中阴极电解质和/或阳极电解质选自多种多金属氧酸盐化合物的一个限定组之中。(A redox flow battery, wherein the catholyte and/or anolyte is selected from a defined group of polyoxometallate compounds.)

1. A redox flow battery (1) comprising a first electrolyte storage tank (24) and a second electrolyte storage tank (30), said first electrolyte storage tank (24) storing an anolyte (18), said second electrolyte storage tank (30) storing a catholyte (22),

characterized in that one identical Polyoxometalate (POM) redox active material is used for both the anolyte and the catholyte, the identical Polyoxometalate (POM) redox active material comprising at least one of the following plurality of substances:

XMo_iT_jO_kor XW_iT_jO_kWherein:

x ═ Si, P, Ge, or Al; and is

T ═ Mn, Fe, V, Ti, Cr, Co, or Cu;

i. j, k are indices, where:

i ranges from 9 to 14;

j is in the range of 1 to 3; and is

k is in the range of 34 to 42.

2. A redox flow battery as claimed in claim 1 wherein i-9.

3. The redox flow battery of claim 1, wherein j-3.

4. A redox flow battery as claimed in claim 1 wherein k-34.

5. The redox flow battery of any preceding claim, wherein the anolyte and the catholyte are each provided in an aqueous solution having a supporting electrolyte that is one or a mixture of:

Na₂SO₄；

Li₂SO₄；

LiCH₃COO；

NaCH₃COO；

H₃PO₄。

Technical Field

The present invention relates to redox flow batteries. More particularly, the present invention relates to the selection of electrolytes for efficient energy storage and transfer.

Background

The following documents describe various flow batteries:

H.D.Pratt, N.S.Hudak, X.Fang and T.M.Anderson, J.Power Sources,2013,236, 259-264;

the Electrochemical Society "Interface" face 2010, pp.54-56, of T.Nguyen and R.F.Savinell; and

"Fundamental models for Flow batteries", Progress in Energy and Combustion Science 4992015) 40-58 of Q.xu and T.S.ZHao, and "APOLYOXOMETATE Flow batteries" of Pratt et al.

The following U.S. patents and patent applications also describe various examples of flow batteries:

US 2016/0043425 A1

US 2009/0317668 A1

US 2014/0004391 A1

US 2015/0349342 A1

US 4,786,567。

co-pending british patent application GB1606953.6 (publication No. GB 2549708 a) also relates to a number of polyoxometallate flow batteries.

Fig. 1, which is an article from Nguyen and Savinell, schematically illustrates a flow battery 1. A porous anode 10 and a porous cathode 12 are separated by an ion selective membrane 14. A first electrolyte reservoir 16 provides a first electrolyte solution 18 to the porous anode 10 on a surface remote from the ion selective membrane 14. A second electrolyte reservoir 20 provides a second electrolyte solution 22 to the porous cathode 12 on a surface remote from the ion-selective membrane 14. A first electrolyte storage tank 24 is linked to the first electrolyte container 16 by a plurality of pipes 26 and a pump 28. A second electrolyte storage tank 30 is linked to the second electrolyte reservoir 20 by a plurality of pipes 32 and a pump 34.

The first electrolyte storage tank 24 stores "negative electrolyte" or "anolyte" 18. The anolyte participates in electron uptake and release at redox equilibrium, which can be expressed as:

M^x-←→M^(x-n)-+ne^-。

the second electrolyte storage tank 30 stores either "positive electrolyte" or "cathode electrolyte" 22. The catholyte participates in electron release and uptake at redox equilibrium, which can be expressed as:

N^y-+ne^-←→N^(y+n)-。

due to the presence of these redox reactions, the anolyte and catholyte may be considered and referred to as "redox species".

Flow battery 1 may be charged and discharged through anode connector 36 and cathode connector 38.

In a typical application, a renewable energy source 50, such as a wind, solar or tidal generator, provides renewable power to a plurality of customers 52 at an AC voltage. However, when the demands of the plurality of customers 52 do not require the full amount of electricity generated by the generator 50, it is desirable to be able to store some of the power generated by the generator 50, and when the demands of the plurality of customers 52 exceed the amount of electricity generated by the generator 50, it is desirable to be able to release the stored power. A flow battery may be used to store and release such power. The power must first be converted from AC to DC by the converter 40. When the generator 50 generates excess power, positive and negative voltages from the generator are applied to the porous anode 10 and the porous cathode 12, respectively. A plurality of electrons are extracted from anolyte 18 and stored in catholyte 22. The plurality of electrolyte molecules in the anolyte becomes more positively charged and the plurality of electrolyte molecules on the catholyte becomes more negatively charged. Pumps 28, 34 circulate electrolyte from the electrolyte containers 16, 20 to the electrolyte storage tanks 24, 30. Power storage within the flow battery may continue until all of the redox species of at least one of the anolyte and catholyte are fully charged.

On the other hand, drawing power from the flow battery to provide to the plurality of clients 52 involves a process of back-discharging. In that case, a plurality of electrons are transferred from the catholyte to the anolyte. This DC current is converted to AC current by the converter 40 for supply to a plurality of customers 52.

Various combinations of electrolytes (anolyte/catholyte) are known, and each combination has its own characteristics. Some examples are provided in the above-mentioned papers by Nguyen and Savinell.

In one example of a vanadium-based electrolyte, the anodic redox equilibrium reaction may be:

V²⁺←→V³⁺+e^-，

and the cathodic equilibrium redox reaction may be:

VO₂ ⁺+2H⁺+e^-←→VO²⁺+H₂O。

in each case, it can be seen that each redox of the anolyte and catholyte ionic species stores and releases a single electron.

Co-pending british patent application GB1606953.6 (publication No. GB 2549708 a) provides various combinations of electrolytes in which each redox ionic species of the anolyte and catholyte can store and release several electrons.

Typically, the anolyte and catholyte will be in an aqueous solution with additional supporting electrolyte. In the exemplary vanadium-based system outlined above, the supporting electrolyte may be sulfuric acid H₂SO₄Which dissociate in aqueous solution into H⁺Ions and SO₄ ^2-Ions.

According to one aspect of the teachings of co-pending british patent application GB1606953.6, the catholyte and anolyte are selected from among the following respective groups of a plurality of polyoxometalate compounds:

cathode electrolyte:

(i)C₆V₁₀O₂₈having a cation C which is H⁺、Li⁺、Na⁺Or H⁺、Li⁺、Na⁺A mixture of (A) or (B)

(ii)C₉PV₁₄O₄₂Having a cation C which is H⁺、Li⁺、Na⁺Or H⁺、Li⁺、Na⁺The mixture of (a) and (b),

the catholyte has a supporting electrolyte that is one or a mixture of:

(i)Na₂SO₄

(ii)Li₂SO₄

(iii)LiCH₃COO, or

(iv)NaCH₃COO

(v)HCl

(vi)H₃PO₄

(vii)H₂SO₄

The supporting electrolyte increases the solubility of the redox species, increases the conductivity of the catholyte, and provides a balanced flow of ions across the membrane.

Anode electrolyte:

(i)C₄SiW₁₂O₄₀having a cation C which is: h⁺、Li⁺、Na⁺Or H⁺、Li⁺、Na⁺A mixture of (a).

(ii)C₄SiMo₁₂O₄₀Having a cation C which is: h⁺、Li⁺、Na⁺Or H⁺、Li⁺、Na⁺A mixture of (a).

(iii)C₃PW₁₂O₄₀Having a cation C which is: h⁺、Li⁺、Na⁺Or H⁺、Li⁺、Na⁺A mixture of (a).

(iv)C₅AlW₁₂O₄₀Having a cation C which is: h⁺、Li⁺、Na⁺Or H⁺、Li⁺、Na⁺A mixture of (a).

The anolyte has a supporting electrolyte which is one of the following or a mixture of the following:

(i)Na₂SO₄，

(ii)Li₂SO₄，

(iii)LiCH₃COO, or

(iv)NaCH₃COO，

(v)HCl，

(vi)H₃PO₄，

(vii)H₂SO₄。

The supporting electrolyte increases the solubility of the redox species, increases the conductivity of the anolyte, and provides a balanced flow of ions across the membrane.

During charging, tungsten or molybdenum redox centres are reduced from w (vi) to w (v), or from mo (vi) to mo (v), each releasing one electron.

The membrane 14 needs to be permeable to at least one ion of the cations that support the electrolyte, i.e., H⁺、Na⁺Or Li⁺But is impermeable to the redox species contained in the anolyte or catholyte. Suitable materials would be a variety of perfluorosulfonic acid membranes, such as nafion (rtm) N117 from DuPont (DuPont).

The combination of the porous anode 10, ion-selective membrane 14 and porous cathode 12 may be referred to as a "stack" or "flow plate".

The use of an electrolyte in accordance with the teachings of co-pending uk patent application GB1606953.6 (published as GB 2549708 a) provides at least some of the following several advantages.

Because each redox species ion of the electrolyte of the present invention is capable of transferring multiple electrons, it can be charged and discharged more efficiently and with greater stored charge density than with conventional vanadium ion-based flow batteries.

The lower charge transfer resistance of Polyoxometalate (POM) electrolytes compared to vanadium electrolytes improves voltage efficiency and increases power density.

The lower charge transfer resistance of POM electrolytes compared to vanadium electrolytes reduces capital costs because a smaller power converter is sufficient. Smaller power converters reduce the cost of multiple membranes and multiple battery components and reduce the geometric footprint of the battery.

Polyoxometallate (POM) electrolytes include large redox species ions that exhibit slower transmembrane permeation than vanadium ions, which reduces the self-discharge of the flow battery.

For a given volume of electrolyte, Polyoxometalate (POM) electrolytes can achieve higher energy densities than vanadium ions, which can reduce the geometric occupancy and thus the capital cost of the flow battery.

The described Polyoxometalate (POM) electrolyte for the catholyte is easy to prepare, which minimizes capital costs.

The described Polyoxometallate (POM) electrolytes for anolyte and catholyte are stable at pH 2-3 and are less corrosive than the commonly employed acidic solvents. This may also reduce capital costs because the requirements for the associated storage vessels are less stringent.

The Polyoxometalate (POM) electrolyte of co-pending british patent application GB1606953.6 (publication No. GB 2549708 a) allows more than one electron to be transferred using each redox species ion. The lower charge transfer resistance of the POM redox species ions compared to vanadium ions enables faster charging and discharging, increased current output, and higher current output per unit surface area of the membrane. Thus, a smaller membrane surface area may be used, and/or a smaller volume of electrolyte may be achieved, system cost and system size may be reduced, and/or improvements in charge/discharge rates and capacity may be achieved.

Since Polyoxometalate (POM) electrolytes include relatively large redox species, they can be confined by relatively thin films. Such a film may be relatively inexpensive. However, it is important that the anolyte and catholyte materials be kept separate without any degree of mixing.

Examples of suitable membrane materials include cation exchange membranes based on perfluorosulfonic acid polymer membranes such as nafion (rtm) N117 from dupont.

It has been found that Polyoxometallate (POM) electrolytes are more soluble in aqueous solvents than some vanadium ion electrolytes, to enable the production and use of higher concentrations of electrolytes.

With the Polyoxometalate (POM) electrolyte of co-pending british patent application GB1606953.6, a smaller membrane active area can be utilised to achieve a given power output.

Disclosure of Invention

The present invention does not suggest any modification to the device shown in fig. 1, but rather suggests a particularly advantageous combination of electrolyte species.

Drawings

The above and further objects, features and advantages of the present invention will become more apparent from the following description of certain exemplary embodiments thereof, given by way of example only, with reference to the accompanying drawings, in which:

fig. 1 illustrates one example structure of a conventional flow battery.

Detailed Description

According to the invention, the anolyte and catholyte are Polyoxometallate (POM) electrolytes. The present invention provides an all-Polyoxometallate (POM) electrolyte-to-symmetric flow battery cell in which one and the same Polyoxometallate (POM) redox active material is used for both the anolyte and catholyte.

The redox active material in the anolyte and catholyte M is a POM having the following chemical formula:

XMo_iT_jO_kor XW_iT_jO_kWherein:

x ═ Si, P, Ge, or Al;

t ═ Mn, Fe, V, Ti, Cr, Co, or Cu;

i. j, k are indices.

i ranges from 9 to 14, but is preferably 9;

j is in the range of 1 to 3, but is preferably 3;

k is in the range of 34 to 42, but is preferably 34.

The concentration of the redox active substance in the electrolyte is preferably greater than 20mM/L, more preferably greater than 500 mM/L.

The supporting electrolyte comprises one or a mixture of the following:

Na₂SO₄；

Li₂SO₄；

LiCH₃COO；

NaCH₃COO；

H₃PO₄。

the supporting electrolyte increases the solubility of the Polyoxometalate (POM) electrolyte redox species, improves the conductivity of the anolyte, and provides a balanced ion flow across the membrane.