阅读说明：本技术 一种碱性锌-铁镍混合型液流电池 (Alkaline zinc-iron-nickel mixed flow battery ) 是由 李先锋 袁治章 张华民 于 2019-10-11 设计创作，主要内容包括：本发明涉及一种碱性锌-铁镍混合型液流电池及包含其的电池系统,所述电池由单电池或二节以上的单电池串/并联组成的电池模块、正负极电解液、正负极电解液储罐、正负极循环管路、正负极循环泵组成；单电池按顺序依次包括正极端板、正极集流体、正极电极、离子传导膜、负极电极、负极集流体、负极端板。所述的电池及包含其的电池系统负极活性物质为溶于强碱的高浓度锌酸盐溶液,正极活性物质为溶于强碱溶液的亚铁氰化物和/或铁氰化物和固定在正极电极上的氢氧化镍和/或镍的氧化物固体活性物质。与传统的碱性锌铁液流电池和碱性锌镍单液流电池相比,该碱性锌-铁镍混合型液流电池具有电池效率高、能量密度高的特点,同时该体系具有系统成本低的特点,在分布式储能领域具有很好的应用前景。(The invention relates to an alkaline zinc-iron-nickel mixed flow battery and a battery system comprising the same, wherein the battery consists of a battery module formed by connecting single batteries or more than two single batteries in series/parallel, positive and negative electrolyte storage tanks, positive and negative circulation pipelines and positive and negative circulation pumps; the monocell sequentially comprises a positive electrode end plate, a positive electrode current collector, a positive electrode, an ion conduction membrane, a negative electrode current collector and a negative electrode end plate. The negative active substance of the battery and the battery system comprising the same is a high-concentration zincate solution dissolved in strong base, and the positive active substance is ferrocyanide and/or ferricyanide dissolved in the strong base solution and a nickel hydroxide and/or nickel oxide solid active substance fixed on a positive electrode. Compared with the traditional alkaline zinc-iron flow battery and alkaline zinc-nickel single flow battery, the alkaline zinc-iron-nickel mixed flow battery has the characteristics of high battery efficiency and high energy density, and meanwhile, the system has the characteristic of low system cost and has good application prospect in the field of distributed energy storage.)

1. An alkaline zinc-iron-nickel mixed flow battery comprises a negative electrode, a negative electrode electrolyte, a positive electrode electrolyte and a positive electrode;

the negative electrode electrolyte is a mixed aqueous solution formed by dissolving zinc salt or/and zinc oxide in strong alkali liquor, and the active substance in the negative electrode electrolyte is Zn (OH)₄ ^2-The concentration of the alkali is 0.1-2 mol/L, preferably 0.4-1.0 mol/L, and the concentration of the alkali in the aqueous solution is 1.2-10 mol/L, preferably 3-7 mol/L;

the positive electrode active material is composed of two parts: (1) the concentration of ferrocyanide and/or ferricyanide dissolved in the positive electrolyte is 0.01-1 mol/L, preferably 0.4-0.8 mol/L, and the concentration of strong base in the aqueous solution is 0.05-6 mol/L, preferably 1-4 mol/L, so as to form the positive electrolyte; (2) nickel hydroxide and/or nickel oxide fixed on the positive electrode in an amount of 0.05g/cm²～2g/cm²Preferably 0.1g/cm²～1.5g/cm²。

2. The battery of claim 1, wherein:

the positive electrode is one or more of the following,

A. a composite electrode obtained by laminating foamed nickel supporting nickel hydroxide and/or nickel oxide and a carbon felt, a carbon paper or a carbon cloth which is not coated with nickel hydroxide and/or nickel oxide,

B. a carbon felt, carbon paper or carbon cloth electrode coated with nickel hydroxide and/or nickel oxide,

C. a composite electrode which is formed by laminating a carbon felt, a carbon paper or a carbon cloth coated with nickel hydroxide and/or nickel oxide and a foam nickel layer,

D. and a composite electrode in which a carbon felt, a carbon paper or a carbon cloth coated with nickel hydroxide and/or an oxide of nickel and a carbon felt, a carbon paper or a carbon cloth not coated with nickel hydroxide and/or an oxide of nickel are laminated.

3. The battery of claim 1, wherein:

the electrochemical reaction equation of the deposition and dissolution on the cathode electrode is as follows:

the electrochemical reaction occurring at the positive electrode is the following equation:

4. the battery of claim 1, wherein: the zinc oxide is zinc oxide, and the zinc salt is one or two of zinc chloride and zinc sulfate;

the strong base is one or more of sodium hydroxide, potassium hydroxide or lithium hydroxide.

5. The alkaline zinc-iron-nickel hybrid flow battery of claim 1, wherein:

one or more of potassium chloride, sodium sulfate, sodium chloride and potassium sulfate can be added into the positive and/or negative electrolyte as auxiliary electrolyte to improve the conductivity of the supporting electrolyte; the concentration of the auxiliary electrolyte in the strong alkali liquor is 0-30 wt%, preferably 0-20 wt%.

6. The alkaline zinc-iron-nickel hybrid flow battery of claim 1, wherein: the battery is a single battery or comprises a battery module formed by connecting more than two single batteries in series and/or in parallel, a liquid storage tank filled with positive electrolyte, a liquid storage tank filled with negative electrolyte, a positive circulating pump, a negative circulating pump, a positive circulating pipeline and a negative circulating pipeline, wherein the single batteries comprise a positive end plate, a positive current collector, a positive electrode, an ion conduction membrane, a negative electrode, a negative current collector and a negative end plate which are sequentially stacked.

7. The alkaline zinc-iron-nickel hybrid flow battery as defined in claim 6, wherein: the ion conducting membrane is an ion exchange membrane or a porous ion conducting membrane or a composite ion conducting membrane, and the negative electrode is one or more than two of carbon felt, carbon paper, carbon cloth, graphite plate or zinc plate; the positive and/or negative current collecting plate is a graphite plate or a copper plate.

Technical Field

The invention relates to the field of flow batteries, in particular to the technical field of alkaline zinc-iron-nickel mixed flow batteries.

Background

The flow battery energy storage technology has the outstanding advantages of mutual independence of output power and energy storage capacity of an energy storage system, large energy storage scale, flexible design and arrangement, long service life, safety and reliability, recyclable materials and components, environmental friendliness and the like, and becomes a preferred technology for large-scale energy storage. The all-vanadium redox flow battery is one of the most developed and mature redox flow battery technologies at present, is also one of the energy storage technologies (100MW grade all-vanadium redox flow battery energy storage power stations) which are mainly supported by the country, and is in the industrial demonstration stage at present. However, the battery has the problems of low energy density and high cost, and the industrial application of the battery is limited.

Unlike all-vanadium flow batteries, alkaline zinc-iron flow batteries use a self-made non-fluorine ion conductive membrane as a diaphragm, use zinc with abundant resources as a negative active material of the battery, and use a salt additive, namely potassium (sodium) ferrocyanide, as an active material for a positive electrode (figure 1), so that the cost of the battery is low (about $120/kWh), and the open circuit voltage of the system is up to 1.74V in an alkaline environment. However, compared with the all-vanadium flow battery, the concentration of the active material of the positive electrode of the alkaline zinc-iron flow battery is lower, and the concentration of the active material of the all-vanadium flow battery is usually 1.5mol L^-1And the concentration of the positive active material of the alkaline zinc-iron flow battery is only 0.4mol L^-1. Too low a concentration of active substance results in a large system volume, high material consumption and high cost. Although patent CN108461784A discloses an alkaline zinc-iron flow battery and increases the concentration of positive active material to 1.0mol L^-1However, the energy density of this system was still low (30Wh/L to 40 Wh/L).

The zinc-nickel single flow battery has the advantages of simple structure and low material cost, but compared with the all-vanadium flow battery and the alkaline zinc-iron flow battery, the zinc-nickel single flow battery has lower power density, and the working current density of the all-vanadium flow battery and the alkaline zinc-iron flow battery is usually 80mA/cm²The current working current density of the zinc-nickel single flow battery is only 20mA/cm². The low operating current density causes the battery to have large volume, large consumption of battery materials and high cost, and becomes a key technical bottleneck of large-scale application.

Disclosure of Invention

In order to solve the technical problems, an alkaline zinc-iron-nickel mixed flow battery with low cost, high energy density and excellent electrochemical performance is developed, and in order to achieve the purpose, the invention develops an alkaline zinc-iron-nickel mixed flow battery, and the specific technical scheme is as follows:

the battery comprises a single cell or a battery module formed by connecting one single cell or more than two single cells in series/parallel, a liquid storage tank filled with positive and negative electrolyte, a positive and negative circulating pump and a positive and negative circulating pipeline. The single cell comprises a positive electrode end plate, a positive electrode current collector, a positive electrode, an ion conduction membrane, a negative electrode current collector and a negative electrode end plate.

The positive and negative current collecting plates are graphite plates or copper plates.

The ion conducting membrane is an ion exchange membrane or a porous ion conducting membrane or a composite ion conducting membrane, such as a sulfonated polyether ether ketone ion exchange membrane, a perfluorinated sulfonic acid ion exchange membrane, a polybenzimidazole ion exchange membrane, a polyolefin porous ion conducting membrane, a polysulfone (polyether sulfone) porous ion conducting membrane, a sulfonated polyether ether ketone composite porous ion conducting membrane and the like.

The cathode electrode is a porous electrode such as carbon felt, carbon paper, carbon cloth and the like or a flat electrode such as a graphite plate, a zinc plate and the like.

The negative electrode electrolyte is a mixed aqueous solution of zinc salt or/and zinc oxide and strong base, and the active substance in the negative electrode electrolyte is Zn (OH)₄ ^2-The concentration of the alkali is 0.1-2 mol/L, preferably 0.4-1.0 mol/L, and the concentration of the alkali in the aqueous solution is 1.2-10 mol/L, preferably 3-7 mol/L. Wherein, the zinc oxide is zinc oxide, the zinc salt is one or two of zinc chloride and zinc sulfate, and the strong base is one or more than two of sodium hydroxide, potassium hydroxide or lithium hydroxide.

The positive electrode active material is composed of the following two components:

(1) the concentration of ferrocyanide and/or ferricyanide dissolved in the electrolyte is 0.01-1 mol/L, preferably 0.4-0.8 mol/L, and the concentration of strong base in the aqueous solution is 0.05-6 mol/L, preferably 1-4 mol/L;

(2) nickel hydroxide and/or nickel oxide fixed on the electrode in an amount of 0.05g/cm²～2g/cm²Preferably 0.1g/cm²～1.5g/cm²。

The positive electrode is a composite electrode formed by laminating foamed nickel carrying nickel hydroxide and/or nickel oxide with a carbon felt, a carbon paper or a carbon cloth which are not coated with nickel hydroxide and/or nickel oxide, a carbon felt, a carbon paper or a carbon cloth electrode coated with nickel hydroxide and/or nickel oxide, a composite electrode formed by laminating a carbon felt, a carbon paper or a carbon cloth coated with nickel hydroxide and/or nickel oxide with a foamed nickel layer, and a composite electrode formed by laminating a carbon felt, a carbon paper or a carbon cloth coated with nickel hydroxide and/or nickel oxide with a carbon felt, a carbon paper or a carbon cloth which are not coated with nickel hydroxide and/or nickel oxide.

One or more than two of soluble salts of potassium chloride, sodium sulfate, sodium chloride and potassium sulfate can be added into the positive and negative electrolytes as auxiliary electrolytes to improve the conductivity of the supporting electrolyte; the concentration of the auxiliary electrolyte is 0-30 wt% of the concentration of the strong base, and preferably 0-20 wt%.

The positive and negative electrolyte tanks are connected with the positive and negative inlets and outlets of the single cell or the galvanic pile through the pipeline by the liquid delivery pump.

When the single cell or the pile is charged, the electrolyte is respectively conveyed to the anode and the cathode from the anode and cathode liquid storage tanks by a pump, and the active substance Zn (OH) in the cathode liquid storage tank₄ ^2-Ions are directly deposited on the cathode electrode in the form of a zinc simple substance; active material Fe (CN) in positive electrode reservoir₆ ^4-Electrochemical oxidation reaction takes place to produce Fe (CN)₆ ^3-Meanwhile, the nickel hydroxide on the electrode is converted into hydroxyl nickel oxide; when discharging, the zinc simple substance of the negative electrode is oxidized into Zn (OH) in the alkaline solution environment₄ ^2-The ions are pumped back to the negative electrode liquid storage tank, and the active material Fe (CN) in the positive electrode electrolyte corresponding to the ions₆ ^3-Electrochemical reduction takes place to form Fe (CN)₆ ^4-And the nickel hydroxide is pumped back to the anode liquid storage tank, and meanwhile, the nickel oxyhydroxide is converted into nickel hydroxide. The electrochemical reaction equation of the deposition and dissolution on the cathode electrode is as follows:

the electrochemical reaction occurring at the positive electrode is the following equation:

the working current density of the alkaline zinc-iron-nickel mixed flow battery is 1mA cm^-2～100mA cm^-2In the meantime.

Through structural design of electrodes and an ion conduction membrane, the composition of electrolyte is optimized, and the assembled alkaline zinc-iron-nickel mixed flow battery can be 1mA cm^-2～100mA cm^-2The working current density of the vanadium redox flow battery is continuously and stably operated, and the battery performance and the energy density are equivalent to or even better than those of the all-vanadium redox flow battery.

The invention has the following beneficial results:

1. the invention skillfully combines the advantages of an alkaline zinc-iron flow battery and an alkaline zinc-nickel single flow battery, and invents the alkaline zinc-iron-nickel mixed flow battery with low cost, high energy density and excellent electrochemical performance. The positive electrode of the alkaline zinc-iron-nickel mixed flow battery adopts liquid-liquid phase electrochemical reaction of ferrocyanide/ferricyanide and solid-solid phase electrochemical reaction of nickel hydroxide/nickel oxyhydroxide, the battery performance and energy density shown by the positive electrode are equivalent to or even better than those of the current mature all-vanadium flow battery, the reserves of active substances of zinc, iron and nickel of the battery are rich, the cost is far lower than that of the all-vanadium flow battery, the requirements of large-scale application are met, and the positive electrode of the alkaline zinc-iron-nickel mixed flow battery shows good application prospects.

2. The problems that the energy density of a traditional alkaline zinc-iron flow battery is low and the operating current density of a traditional alkaline zinc-nickel single flow battery is low are solved.

3. The alkaline zinc-iron-nickel mixed flow battery has the characteristics of high safety, good stability, low cost and simple structure and manufacturing process.

Drawings

Fig. 1 is a schematic structural diagram of an alkaline zinc-iron-nickel hybrid flow battery.

Figure 2 performance graph of alkaline zinc-iron flow cell in comparative example 1 (a) cycle efficiency graph; (b) capacity and energy maps.

FIG. 3 is a graph of performance of an alkaline zinc-nickel flow battery in comparative example 2 (a) cycle efficiency; (b) capacity map.

Figure 4 performance graph of alkaline zinc-iron-nickel hybrid flow battery in example 1 (a) cycle efficiency graph; (b) capacity and energy maps.

Fig. 5 shows the effect of different nickel loading on the performance of alkaline zinc-iron-nickel hybrid flow batteries.

Table 1 performance plots of the alkaline zinc-iron-nickel hybrid flow battery of example 2 at different discharge current densities.

Detailed Description

Assembling single cells: the cells were assembled in the following order: positive electrode end plate, graphite current collector, positive electrode (area 6x8 cm)²) Ion conductive membrane, negative electrode (area 6x8 cm)²) A current collector and a negative end plate. The cell structure is shown in fig. 1.

Comparative example 1

Alkaline zinc-iron flow battery: polybenzimidazole (PBI) is taken as an ion conduction membrane, carbon felts are taken as electrodes of a positive electrode and a negative electrode, and the electrolyte of the positive electrode is 0.8mol/L Fe (CN)₆ ^4-+3mol/L OH^-A solution; the negative electrode electrolyte is 0.8mol/L Zn (OH)₄ ^2-+5mol/L OH^-A solution; the volumes of the positive electrolyte and the negative electrolyte are respectively 60 mL; the battery adopts a constant current charge-discharge mode at 40mA cm^-2Under the condition of current density of (1), charging for 30min, and then cutting off the voltage to obtain a voltage of 40mA cm^-2Is discharged to 0.8V under the current density condition of (2). As can be seen from the battery cycle performance diagram (fig. 2a), the Coulombic Efficiency (CE) of the battery is kept at about 99%, and the Energy Efficiency (EE) is kept at about 95%; since the concentration of the positive electrode active material was as low as 0.8mol/L, the discharge capacity (0.95Ah) and the discharge energy (1.68Wh) of the battery were low (see the figure)2b)。

Comparative example 2

Alkaline zinc-nickel single flow battery: polybenzimidazole (PBI) is taken as an ion conduction membrane, a carbon felt is taken as an electrode as a negative electrode, a carbon felt coated with a nickel hydroxide active substance is taken as an electrode as a positive electrode, and the supporting amount of the nickel hydroxide active substance on the carbon felt electrode is 0.8g/cm²The electrolyte of the anode and the cathode is 0.4mol/L Zn (OH)₄ ^2-+3mol/L OH^-A solution; before the battery runs, the anode electrode is fully soaked in the electrolyte, and the volume of the cathode electrolyte is 60 mL; the battery adopts a constant current charge-discharge mode at 40mA cm^-2Under the condition of current density of (1), charging for 30min, and then cutting off the voltage to obtain a voltage of 40mA cm^-2Is discharged to 0.8V under the current density condition of (2). It can be seen from the battery cycle performance diagram (fig. 3a) that the CE and EE of the battery gradually increase with the progress of the cycle, then the CE is stabilized at about 99%, and the EE is stabilized at about 84%, mainly because the nickel hydroxide coated on the electrode needs to be activated earlier, which results in low efficiency in the early stage of the battery, and the discharge energy of the battery is only about 0.71Ah (fig. 3 b).

Example 1

Alkaline zinc-iron-nickel hybrid flow battery: polybenzimidazole (PBI) is taken as an ion conduction membrane, a carbon felt is taken as an electrode as a negative electrode, a carbon felt coated with a nickel hydroxide active substance is taken as an electrode as a positive electrode, and the supporting amount of the nickel hydroxide active substance on the carbon felt electrode is 0.8g/cm²The positive electrolyte is 0.8mol/L Fe (CN)₆ ^4-+3mol/L OH^-A solution; the negative electrode electrolyte is 0.8mol/L Zn (OH)₄ ^2-+5mol/L OH^-A solution; the volumes of the positive electrolyte and the negative electrolyte are respectively 60 mL; the battery adopts a constant current charge-discharge mode at 40mA cm^-2Under the condition of current density of (1), charging for 60min, and then cutting off the voltage to obtain the condition of 40mA cm^-2Is discharged to 0.8V under the current density condition of (2). As can be seen from the battery cycle performance diagram (fig. 4a), an activation process is also required at the early stage of the battery, the efficiency gradually increases along with the progress of the cycle, the Coulombic Efficiency (CE) of the battery is finally maintained at about 98%, the Energy Efficiency (EE) is maintained at about 88%, and the performance of the battery is basically maintained within 50 cyclesAnd keeping stable. As can be seen from fig. 4b, the discharge capacity of the battery reaches 1.89Ah, and the discharge energy is also as high as 3.18Wh, which is 2 times higher than that of the alkaline zinc-iron flow battery (1.68 Wh).

Example 2

Alkaline zinc-iron-nickel hybrid flow battery: polybenzimidazole (PBI) is taken as an ion conduction membrane, a carbon felt is taken as an electrode as a negative electrode, a carbon felt coated with a nickel hydroxide active substance is taken as an electrode as a positive electrode, and the supporting amount of the nickel hydroxide active substance on the carbon felt electrode is 0.8g/cm²The positive electrolyte is 0.8mol/L Fe (CN)₆ ^4-+3mol/L OH^-A solution; the negative electrode electrolyte is 0.8mol/L Zn (OH)₄ ^2-+5mol/L OH^-A solution; the volumes of the positive electrolyte and the negative electrolyte are respectively 60 mL; the battery adopts a constant current charge-discharge mode at 40mA cm^-2Charging for 60min under the condition of current density, and then cutting off the voltage under the condition of different working current densities (40-60-80-100mA cm)^-2) Discharge to 0.8V under the condition. The cell performance is shown in table 1.

TABLE 1

Example 3

Alkaline zinc-iron-nickel hybrid flow battery: polybenzimidazole (PBI) is taken as an ion conduction membrane, a carbon felt is taken as an electrode as a negative electrode, carbon felts coated with nickel hydroxide active substances with different supporting amounts are taken as electrodes as a positive electrode, and the supporting amounts of the nickel hydroxide active substances on the carbon felts are respectively 0.1g/cm²，0.5g/cm²，1.0g/cm²The positive electrolyte is 0.8mol/L Fe (CN)₆ ^4-+3mol/L OH^-A solution; the negative electrode electrolyte is 0.8mol/L Zn (OH)₄ ^2-+5mol/L OH^-A solution; is justThe volume of the cathode electrolyte is 60mL each; the battery adopts a constant current charge-discharge mode at 40mA cm^-2Under the condition of current density of (1), charging for 60min, and then cutting off the voltage to obtain the condition of 40mA cm^-2Is discharged to 0.8V under the current density condition of (2). As can be seen from fig. 5, as the loading of the nickel hydroxide active material on the carbon felt electrode increased, both the CE and EE of the battery exhibited a tendency to increase and then decrease, with 0.5g/cm of these three loadings²The supported nickel electrode exhibited the best cell performance in alkaline zinc-iron-nickel hybrid flow batteries.

Example 4

Alkaline zinc-iron-nickel hybrid flow battery: polybenzimidazole (PBI) is taken as an ion conduction membrane, a carbon felt is taken as an electrode as a negative electrode, carbon felts coated with nickel hydroxide active substances with different supporting amounts are taken as an electrode as a positive electrode, and the supporting amount of the nickel hydroxide active substances on the carbon felt electrode is 1.8g/cm²The positive electrolyte is 0.8mol/L Fe (CN)₆ ^4-+3mol/L OH^-A solution; the negative electrode electrolyte is 0.8mol/L Zn (OH)₄ ^2-+5mol/L OH^-A solution; the volumes of the positive electrolyte and the negative electrolyte are respectively 60 mL; the battery adopts a constant current charge-discharge mode at 40mA cm^-2Under the condition of current density of (1), charging for 60min, and then cutting off the voltage to obtain the condition of 40mA cm^-2Is discharged to 0.8V under the current density condition of (2). The nickel hydroxide active material on the electrode has high loading capacity and occupies most of the active sites of the electrode, so that the nickel hydroxide active material can be supplied to Fe (CN)₆ ^4-The active sites of the reaction are few, so that the Coulombic Efficiency (CE) of the battery is only about 88 percent, and the Energy Efficiency (EE) is kept about 75 percent.

Example 5

Alkaline zinc-iron-nickel hybrid flow battery: polybenzimidazole (PBI) is taken as an ion conduction membrane, a carbon felt is taken as an electrode as a negative electrode, carbon felts coated with nickel hydroxide active substances with different supporting amounts are taken as an electrode as a positive electrode, and the supporting amount of the nickel hydroxide active substances on the carbon felt electrode is 0.5g/cm²The positive electrolyte is 0.1mol/L Fe (CN)₆ ^4-+3mol/L OH^-A solution; the negative electrode electrolyte is 0.8mol/L Zn (OH)₄ ^2-+5mol/L OH^-A solution; the volumes of the positive electrolyte and the negative electrolyte are respectively 60 mL; the battery adopts a constant current charge-discharge mode at 40mA cm^-2Under the condition of current density of (1), charging for 60min, and then cutting off the voltage to obtain the condition of 40mA cm^-2Is discharged to 0.8V under the current density condition of (2). Because of Fe (CN) in the positive electrode electrolyte₆ ^4-The amount of the electrolyte is small, and the battery can not be at 40mA cm^-2The charging voltage sharply increases at the end of charging the battery, and the battery cannot obtain the preset charging capacity, so that the discharging energy of the battery is only 1.02Wh, and the energy efficiency of the battery is only 72%.

Example 6

Alkaline zinc-iron-nickel hybrid flow battery: sulfonated polyether ether ketone (SPEEK) is used as an ion conduction membrane, a carbon felt is used as an electrode as a negative electrode, a carbon felt coated with a nickel hydroxide active substance is used as an electrode as a positive electrode, and the supporting amount of the nickel hydroxide active substance on the carbon felt electrode is 0.8g/cm²The positive electrolyte is 0.8mol/L Fe (CN)₆ ^4-+3mol/L OH^-A solution; the negative electrode electrolyte is 0.8mol/L Zn (OH)₄ ^2-+5mol/L OH^-A solution; the volumes of the positive electrolyte and the negative electrolyte are respectively 60 mL; the battery adopts a constant current charge-discharge mode at 40mA cm^-2Under the condition of current density of (1), charging for 60min, and then cutting off the voltage to obtain the condition of 40mA cm^-2Is discharged to 0.8V under the current density condition of (2). The battery still needs an activation process in the early stage, the efficiency gradually rises along with the progress of the cycle, the Coulombic Efficiency (CE) of the battery is finally kept at about 99%, the Energy Efficiency (EE) is kept at about 89%, the performance of the battery is basically kept stable within 45 cycles, the discharge capacity reaches 1.90Ah, and the discharge energy also reaches 3.20 Wh.

Example 7

Alkaline zinc-iron-nickel hybrid flow battery: polyether sulfone (PES) -sulfonated polyether ether ketone (SPEEK) porous ion conduction membrane is used as a diaphragm, a carbon felt is used as an electrode as a negative electrode, a carbon felt coated with a nickel hydroxide active substance is used as an electrode as a positive electrode, and the supporting amount of the nickel hydroxide active substance on the carbon felt electrode is 0.8g/cm²The positive electrolyte is 0.8mol/L Fe (CN)₆ ^4-+3mol/L OH^-A solution; the negative electrode electrolyte is 0.8mol/L Zn (OH)₄ ^2-+5mol/L OH^-A solution; the volumes of the positive electrolyte and the negative electrolyte are respectively 60 mL; the battery adopts a constant current charge-discharge mode at 40mA cm^-2Under the condition of current density of (1), charging for 60min, and then cutting off the voltage to obtain the condition of 40mA cm^-2Is discharged to 0.8V under the current density condition of (2). The Coulombic Efficiency (CE) of the battery is finally stabilized to about 96%, the Energy Efficiency (EE) is kept to about 87%, the performance of the battery is basically kept stable within 34 cycles, the discharge capacity reaches 1.86Ah, and the discharge energy also reaches 3.15 Wh.

Example 8

Alkaline zinc-iron-nickel hybrid flow battery: polybenzimidazole (PBI) is taken as an ion conduction membrane, a carbon felt is taken as an electrode as a negative electrode, a carbon felt coated with a nickel hydroxide active substance and a carbon felt not coated with a nickel hydroxide active substance are taken as composite electrodes as a positive electrode, wherein the carbon felt not coated with the nickel hydroxide active substance is contacted with the ion conduction membrane, the carbon felt coated with the nickel hydroxide active substance is contacted with a current collecting plate, and the loading of the nickel hydroxide active substance on the carbon felt electrode is 0.8g/cm²The positive electrolyte is 0.8mol/L Fe (CN)₆ ^4-+3mol/L OH^-A solution; the negative electrode electrolyte is 0.8mol/L Zn (OH)₄ ^2-+5mol/L OH^-A solution; the volumes of the positive electrolyte and the negative electrolyte are respectively 60 mL; the battery adopts a constant current charge-discharge mode at 40mA cm^-2Under the condition of current density of (1), charging for 60min, and then cutting off the voltage to obtain the condition of 40mA cm^-2Is discharged to 0.8V under the current density condition of (2). As can be seen from the battery cycle performance diagram (fig. 4a), an activation process is also required at the early stage of the battery, the efficiency gradually increases along with the progress of the cycle, the Coulombic Efficiency (CE) of the battery is finally kept at about 99%, the Energy Efficiency (EE) is close to 90%, the performance of the battery is basically kept stable within 43 cycles, the discharge capacity of the battery reaches 1.90Ah, and the discharge energy is close to 3.21Wh, compared with the alkaline zinc-iron-nickel mixed flow battery in example 1, the battery has higher performance, mainly because the carbon felt which is not coated with the nickel hydroxide active material can be fe (cn)₆ ^4-/Fe(CN)₆ ^3-Electrochemical reaction of electricity pairMore reaction sites are provided, so that the alkaline zinc-iron-nickel mixed flow battery assembled by the composite electrode has higher battery performance.