CN109755604B

CN109755604B - Neutral zinc-iodine flow battery

Info

Publication number: CN109755604B
Application number: CN201711091359.4A
Authority: CN
Inventors: 李先锋; 谢聪鑫; 张华民
Original assignee: Dalian Institute of Chemical Physics of CAS
Current assignee: Dalian Institute of Chemical Physics of CAS
Priority date: 2017-11-08
Filing date: 2017-11-08
Publication date: 2021-09-17
Anticipated expiration: 2037-11-08
Also published as: CN109755604A

Abstract

The invention relates to a zinc-iodine single flow battery, which comprises a galvanic pile formed by connecting one or more than two single cells in series, wherein each single cell comprises a positive electrode end plate, a current collector, a positive electrode with a flow frame, a membrane, a negative electrode with the flow frame and a negative electrode end plate which are sequentially stacked, electrolyte in a negative electrode electrolyte storage tank realizes the circulation of electrolyte between a negative electrode cavity and the storage tank through a pump, and meanwhile, a branch pipeline for the circulation of the positive electrode electrolyte is arranged on a negative electrode pipeline. The porous membrane between the positive and negative electrodes of the battery realizes the conduction of the supporting electrolyte and prevents I₃ ^‑Diffusion to the negative electrode. The electrolyte active material has high solubility and high energy density, and is particularly suitable for constructing a single flow battery; meanwhile, the electrolyte solution of the positive electrode and the electrolyte solution of the negative electrode are neutral, the problem of corrosivity of strong acid and strong alkali electrolyte of the traditional flow battery is solved, and meanwhile, the current density of the battery is high, the cycle life is long, and the cost is low.

Description

Neutral zinc-iodine flow battery

Technical Field

The invention relates to the field of flow batteries, in particular to the field of zinc-iodine flow batteries.

Background

The large use of fossil energy raises energy crisis and environmental issues. The development and utilization of non-renewable energy sources become the focus of attention of all countries in the world. However, the discontinuity and instability of renewable energy sources such as wind energy and solar energy make their direct utilization difficult, so that the continuous supply of renewable energy sources by using energy storage technology becomes the key to solve the above problems. The redox flow battery has become one of the technologies with the best prospect in the large-scale energy storage market due to the flexible design (energy and power separated design), good safety and long design life, wherein the all-vanadium redox flow battery enters the commercial demonstration stage by virtue of the unique technical advantages.

The current developed and mature liquid flow systems comprise all-vanadium liquid flow batteries, zinc-bromine liquid flow batteries, sodium polysulfide bromine and other systems. However, the all-vanadium redox flow battery has the problems of high cost and strong acidity and corrosivity of electrolyte; in addition, zinc bromine flow battery systems and sodium polysulfide bromine systems face the problems of volatility and corrosiveness of bromine, and the environmental pollution is serious.

The zinc-iodine flow battery uses neutral zinc salt and iodine salt as electrolytes, and has high solubility and high energy density; specific to Cl₂And Br₂Iodine is very corrosive; with iodine in solution as I₃ ^-The zinc-iodine flow battery has the characteristics of low steam pressure, difficult volatilization and the like, so that the zinc-iodine flow battery becomes a flow battery with a very prospect. The zinc-iodine flow battery adopts a double-pump double-pipeline design, and electrolyte circularly flows in the battery and a storage tank in the charging and discharging processes. However, the battery needs an electrolyte circulation system such as a pump and a storage tank, so that the energy efficiency of the system is greatly reduced due to the loss of the system, and on the other hand, the battery auxiliary equipment such as the pump and the storage tank makes the structure of the battery system complex, so that the energy density of the system is reduced, so that the research on the single flow battery is carried out on the basis of double flows, and the reduction of the energy loss of the system is an important method for improving the energy utilization efficiency and the energy density of the system. In addition, most of the zinc-iodine flow batteries reported at present use expensive perfluorosulfonic acid ion exchange membranes, but the ion exchange membranes are easily contaminated in a zinc-iodine system, which leads to an increase in the internal resistance of the battery and a deterioration in the cycle stability of the battery. In addition, the zinc-iodine flow battery mostly uses ZnI₂As electrolyte, but ZnI₂Is easy to be oxidized by air to generate ZnO precipitation, and I generated by the anode is generated in the process of high current density and long circulation₂Easy precipitation, poor electrolyte stability, poor battery cycle stability, and a working current density of only 10mA/cm²The power density of the battery is low.

Disclosure of Invention

In order to solve the above problems, the present invention comprises the following:

a zinc-iodine flow battery comprises a single cell and a pile formed by multiple single cells, wherein a porous electrode and a cavity on one side of a positive electrode are filled with electrolyte; the negative electrode utilizes a pump to realize the circulation of electrolyte in the battery and a negative storage tank, and a branch pipeline for anode circulation and a control valve are arranged on the negative electrode pipeline.

During charging I^-Oxidation reaction occurs and is oxidized to I on the positive electrode₃ ^-Zn on the negative electrode²⁺Is reduced to Zn; during discharge, the positive electrode undergoes a reduction reaction, I₃ ^-Reduction reaction is carried out to be reduced into I^-Zn is oxidized at the negative electrode to generate Zn²⁺。

The structure of the single cell comprises a positive/negative electrode end plate, a membrane, a positive/negative electrode, a current collector, a liquid flow frame, a pump and a pipeline.

The electrolyte of the positive electrode comprises an iodide salt, a zinc salt and a supporting electrolyte, wherein the iodide salt is CaI₂、MgI₂One or more of KI and NaI with the concentration of 2-8 mol/L, and the active material of the negative electrode is ZnNO₃，ZnBr₂、ZnSO₄、ZnCl₂The concentration of the one or more of (A) is 1-4 mol/L, the supporting electrolyte is one or more of KCl, KBr and NaCl, and the concentration of the supporting electrolyte is 1-2 mol/L. Wherein the iodine salt is preferably KI, and the zinc salt is preferably ZnBr₂The supporting electrolyte is preferably KCl.

The electrode material is one of carbon felt, graphite plate, metal plate or carbon cloth.

The diaphragm used by the zinc-iodine flow battery is a porous membrane, and the material comprises one or more than two of Polyethersulfone (PES), Polyethylene (PE), polypropylene (PP), Polysulfone (PS), Polyetherimide (PEI) and polyvinylidene fluoride (PVDF), the thickness of the membrane is 100-1000 μm, preferably 500-1000 μm, the pore diameter is 10-100 nm, and the porosity is 30-70%. The porous membrane material is preferably Polyethylene (PE) or polypropylene (PP).

The invention has the beneficial effects that:

1. compared with double liquid flows, the structure of the zinc-iodine single liquid flow battery is greatly simplified, the energy density of the battery is improved, meanwhile, the loss of the system is reduced, and the energy efficiency of the system is improved. In addition, the concentration of the zinc-iodine electrolyte is high, so that the zinc-iodine electrolyte is suitable for being used in a single flow battery; the zinc-iodine single flow battery solves the problems of strong acid and strong alkali of electrolyte, and has lower cost; meanwhile, the current density of the battery operation is very high, and the power density of the battery is high.

2. The positive electrolyte and the negative electrolyte are the same, so that the problems of migration of the electrolyte from one pole to the other pole and efficiency attenuation of the battery caused by inconsistent osmotic pressures of the positive electrolyte and the negative electrolyte in the operation process of the traditional zinc-iodine flow battery are effectively solved, mutual series of positive and negative active substances in the operation process of the battery is greatly reduced, the coulomb efficiency is improved, the system maintenance cost caused by migration of the electrolyte is effectively reduced, the electrolytes can be recovered on line due to the fact that the positive electrolyte and the negative electrolyte are the same, the replacement cost of the electrolytes is greatly saved, and the zinc-iodine flow battery has a good application prospect.

3. The cheap porous membrane replaces the traditional Nafion 115 membrane, so that the cost of the galvanic pile is greatly reduced; in addition, the porous structure is favorable for conducting neutral ions, and the current density of the battery can reach 140mA/cm²And the voltage efficiency of the battery is greatly improved; most importantly, the porous structure of the porous membrane is filled with I in an oxidation state₃ ^-The electrolyte has a dissolving effect on the zinc dendrite which is short-circuited after the battery is overcharged, so that the battery can be automatically recovered after short-circuiting, and the stability and the service life of the battery are greatly improved.

4. ZnI used in traditional zinc-iodine flow battery₂As active material, ZnO and I are easily oxidized at room temperature₂The cycle performance of the battery is poor; KI is used for replacing ZnI₂Greatly improves the stability of the positive electrolyte, and the price of KI is greatly lower than that of ZnI₂The cost of the electrolyte is greatly reduced.

5. Using ZnBr₂Introduce Br^-I formed when charging with positive electrode electrolyte₂Generation of I₂Br^-Inhibition of I₂The electrolyte can be kept stable when the battery runs at high SOC and high current density, and the cycle performance of the battery is greatly improved.

Drawings

FIG. 1 is a schematic structural view of a zinc-iodine single flow battery of the present invention

Wherein 1 is a positive electrode end plate and a negative electrode end plate; 2 are positive and negative current collectors; 3 liquid flow frames of positive and negative electrodes; 4 is a membrane of the battery; 5 is a positive electrolyte inlet and outlet valve; 6 is an electrolyte storage tank; 7 electrolyte circulation pump.

FIG. 2 is a graph of the cycling performance of the assembled zinc-iodine single flow battery cell of example 1; the positive and negative electrolytes are ZnBr₂: 4M, KI: 8M, KCl:1M, porous film thickness: 900 μm

FIG. 3 is a graph of energy density of a zinc-iodine single flow battery of example 1; the positive and negative electrolytes are ZnBr₂: 4M, KI: 8M, KCl:1M, porous film thickness: 900 μm

FIG. 4 is a graph of the cycling performance of the assembled zinc-iodine single flow battery of example 3; the positive and negative electrolytes are ZnBr₂: 4M, KI: 8M, KCl:1M, porous film thickness: 500 μm

FIG. 5 is a graph of the cycling performance of the assembled zinc-iodine single flow battery of example 5; the positive and negative electrolytes are ZnCl₂: 4M, KI: 8M, KCl:1M, porous film thickness: 900 μm

FIG. 6 is a graph of the cycling performance of the assembled zinc-iodine single flow battery of example 7; the positive and negative electrolytes are ZnBr₂: 4M, NaI: 8M, KCl:1M, porous film thickness: 900 μm

FIG. 7 is an energy density plot for the assembled zinc-iodine single flow battery of example 7; the positive and negative electrolytes are ZnBr₂: 4M, NaI: 8M, KCl:1M, porous film thickness: 900 μm

FIG. 8 is a graph of the cycling performance of the assembled zinc-iodine single flow battery of comparative example 2; the positive and negative electrolytes are ZnI₂: 4M, porous film thickness: 900 μm

Fig. 9 is a graph of the cycle performance of the assembled zinc-iodine single flow battery of comparative example 3; the positive and negative electrolytes are ZnBr₂: 4M, KI: 8M, KCl:1M, Nafion 115 film thickness: 125 μm

Fig. 10 is a graph of the cycle performance of the assembled zinc-iodine single flow battery of comparative example 5; the positive and negative electrolytes are ZnBr₂: 4M, KI: 8M, KCl:1M, porous film thickness: 65 μm

Detailed Description

Testing of battery performance: the assembly of the monocells sequentially comprises the following steps: the device comprises a positive electrode end plate, a current collector, a carbon felt positive electrode with a liquid flow frame, a diaphragm, a carbon felt negative electrode with a liquid flow frame and a negative electrode end plate. The flow rate of the electrolyte in the cell was 10mL/min, charging current of 80mA/cm²And controlling time, and doubly stopping voltage: the charge cut-off time was 45mins, the charge cut-off voltage was 1.5V, and the discharge cut-off voltage was 0.1V.

Fig. 2-3 are graphs of the cycling performance and energy density of the cell under the most preferred conditions. With KI-ZnBr₂The battery assembled by the porous membrane has good cycle stability as an electrolyte; meanwhile, the application of the porous membrane greatly improves the ion conductivity. The working current density of the battery can reach 80mA/cm²The power density is high; meanwhile, the concentration of KI in the electrolyte is as high as 8M, and the energy density of the battery is more than 90 Wh/L.

The cell of fig. 4 uses a much thinner porous membrane (500 μm) than the most preferred embodiment, and the coulombic efficiency of the cell decreases due to the increased electrolyte cross-talk; the electrolyte in FIG. 5 is ZnCl₂Substitute ZnBr₂The performance of the battery is greatly reduced, and the stability is poor, because the electrolyte is unstable, the iodine formed by charging the positive electrode precipitates, and in addition, the zinc chloride on the negative electrode hydrolyzes and precipitates; replacing KI with NaI in fig. 6, the overall efficiency of the cell, especially the voltage efficiency, is reduced, mainly due to the reduced conductivity of the electrolyte, which results in a reduced energy density of the cell in fig. 7.

FIGS. 8 to 10 are comparative experiments, and FIG. 8 uses ZnI₂As the electrolyte of the battery, the efficiency of the battery is reduced and the stability is deteriorated, mainly due to ZnI₂The conductivity of the solution is low, and meanwhile, the electrolyte of the battery is unstable and precipitates during the charging and discharging processes.In fig. 9, a Nafion 115 membrane is used as a membrane material of a battery, and serious membrane pollution occurs on the surface of the membrane in the charge and discharge processes, so that the polarization of the battery is increased, and the performance of the battery is reduced. Fig. 10 uses a very thin porous membrane, cross-contamination of the electrolyte is greatly exacerbated, and the efficiency of the cell, especially the coulombic efficiency, is severely degraded.

Claims

1. A zinc-iodine single flow battery comprises a negative electrolyte storage tank and is characterized in that: the zinc-iodine single flow battery comprises a pile formed by connecting one or more than two single batteries in series, the single batteries comprise a positive electrode end plate, a positive electrode current collector, a positive electrode with a liquid flow frame, a membrane, a negative electrode with a liquid flow frame, a negative electrode current collector and a negative electrode end plate which are sequentially stacked, the circulation of electrolyte between a negative electrode cavity and a storage tank is realized by electrolyte in a negative electrode electrolyte storage tank through a pump, a negative electrode liquid inlet and a negative electrode liquid outlet are arranged on the negative electrode cavity, the negative electrode electrolyte storage tank is respectively connected with the negative electrode liquid inlet and the negative electrode liquid outlet through a negative electrode liquid inlet pipeline and a negative electrode liquid outlet pipeline, meanwhile, branch pipelines for anode electrolyte circulation are respectively arranged on the anode liquid inlet pipeline and the anode liquid outlet pipeline, the branch pipelines on the anode liquid inlet pipeline are connected with the anode liquid inlet on the anode cavity, the anode cavity is provided with the anode liquid inlet and the anode liquid outlet, and the branch pipelines on the anode liquid outlet pipeline are connected with the anode liquid outlet on the anode cavity; the positive electrolyte and the negative electrolyte are the same, and the positive electrolyte and the negative electrolyte are made of zinc salt ZnBr₂Iodine salt KI and supporting electrolyte KCl; the membrane material is a porous membrane without ion exchange groups, and comprises one or two of Polyethylene (PE) and polypropylene (PP).

2. The zinc-iodine single flow battery of claim 1, wherein: the mol ratio of iodine to zinc in the electrolyte is 2: 1.

3. The zinc-iodine single flow battery of claim 1, wherein: the concentration of the supporting electrolyte in the electrolyte is 1-2 mol/L.

4. The zinc-iodine single flow battery of claim 1, wherein: the thickness of the porous membrane is 100-1000 mu m, the pore diameter of the porous membrane material is 1-10 nm, and the porosity: 20% -70%.

5. The zinc-iodine single flow battery of claim 4, wherein: the thickness of the porous membrane is 500-1000 mu m.

6. The zinc-iodine single flow battery of claim 1, wherein: positive electrode active material I during charging^-Oxidation reaction to form I₃ ^-Negative electrode active material Zn²⁺Carrying out reduction reaction to generate Zn; positive electrode during discharge I₃ ^-Reduction reaction to form I^-The cathode simple substance zinc is oxidized to generate Zn²⁺。