CN102867978B - Flow energy storage battery structure - Google Patents

Abstract

The invention relates to a flow energy storage battery structure, characterized in that an infill panel is arranged between a bipolar plate and a porous electrode in an electrode frame, the infill panel is made from carbon materials with good electrical conductivity and low porosity or metal materials which are stable in acidic mediums, reduces the body resistances of the electrodes and electrolyte and contact resistance between the electrode bipolar plates to finally reduce the ohmic resistance of the flow energy storage battery. According to the invention, the energy efficiency and voltage efficiency of the flow energy storage battery are raised, so that the working current density is raised, and the weight, volume and cost of the battery with same output power are greatly reduced.

Description

A liquid flow energy storage battery structure

technical field

The invention relates to the technical field of liquid flow energy storage batteries, in particular to a structure of an all-vanadium flow energy storage battery.

Background technique

All-vanadium redox flow energy storage battery has independent output power and capacity, flexible system design; high energy efficiency, long life, high operation stability and reliability, low self-discharge; large degree of freedom in site selection, no pollution, easy maintenance It has the advantages of simplicity, low operating cost, and high safety. It has broad development prospects in large-scale energy storage. It is considered to be an effective method to solve the random and intermittent unsteady characteristics of renewable energy generation systems such as solar energy and wind energy. There are significant demands in renewable energy power generation and smart grid construction.

However, the working current density of all vanadium redox flow energy storage battery is low (<100mA/cm ² ), which is only one-tenth of the working current density of proton exchange membrane fuel cell, resulting in large battery module volume and large demand for materials ,high cost. The increase in working current density can increase the power density of the battery, reduce the cost of the entire system, reduce the footprint and space of the energy storage system, improve its environmental adaptability and system mobility, and expand the application of flow energy storage batteries. field.

Since the current efficiency of the all-vanadium redox flow energy storage battery increases with the increase of the working current density, increasing the working current density of the battery requires keeping the voltage efficiency at a high value, that is, reducing the battery polarization as much as possible. , reduce voltage loss. Polarization that causes voltage efficiency mainly includes ohmic polarization, electrochemical polarization and concentration polarization.

The methods for reducing battery polarization in the published patent literature mainly include:

(1) Metallize or oxidize electrode materials such as graphite felt, carbon paper, etc., and modify the surface of carbon fibers with metal ions or oxygen-containing functional groups to improve the electrocatalytic activity of the electrode and reduce the electrochemical polarization of the battery. As disclosed in patents CN 101465417A and CN 101182678A, graphite felt is electrochemically oxidized. However, this method only reduces the electrochemical polarization of the battery, and does not help to reduce the ohmic polarization of the battery. The reduction of ohmic polarization is more important to improve the working current density of the battery, because the electrochemical polarization is proportional to the logarithm of the current, and the ohmic voltage drop is proportional to the magnitude of the current. Therefore, as the operating current density increases, the impact of the ohmic internal resistance of the battery will become greater and greater.

(2) Research and develop composite electrodes that integrate electrodes and bipolar plates, that is, integrated electrode bipolar plates to reduce the contact resistance between electrode bipolar plates. As disclosed in CN 101009376A, the bipolar plate and the porous electrode are bonded together by a conductive bonding material to form an integrated electrode bipolar plate. However, the ohmic internal resistance of the all-vanadium redox flow energy storage battery mainly includes the bulk resistance of the electrodes, bipolar plates, electrolyte and separator, and the contact resistance between the electrodes and the bipolar plates. This method only reduces the contact resistance between the electrode bipolar plates, and has no effect on the bulk resistance of the electrodes and the electrolyte, which account for a large proportion of the internal resistance of the battery, so the improvement of the voltage efficiency and energy efficiency is limited.

Contents of the invention

The purpose of the present invention is to provide a liquid flow energy storage battery structure.

To achieve the above object, the technical solution adopted in the present invention is:

A liquid flow energy storage battery structure, the battery includes a bipolar plate and an electrode, and a filling plate is arranged between the bipolar plate and the electrode.

The filling plate is a carbon material with good conductivity and low porosity and/or a metal material stable in acidic medium. The setting of the filling plate can make full use of the conductive points on the surface of the bipolar plate and the porous electrode to reduce the contact resistance; and correspondingly reduce the thickness of the porous electrode and reduce the bulk resistance of the electrode; at the same time, the low porosity of the filling material can reduce the contact resistance. The storage capacity of the electrolyte in the battery is to reduce the body resistance of the electrolyte, and finally achieve the purpose of reducing the ohmic internal resistance of the battery.

The carbon material is non-porous graphite plate, flexible graphite plate, graphite felt with high carbon fiber volume fraction or carbon felt with high carbon fiber volume fraction; the metal material is titanium plate or stainless steel plate.

The high carbon fiber volume fraction of the high carbon fiber volume fraction graphite felt or the high carbon fiber volume fraction carbon felt is 10-60%, preferably 30%-60%.

The battery also includes an electrode frame, the thickness of the filling plate is 5-80% of the thickness of the electrode frame, and its length and width are equivalent to the size of the electrode.

The filling board can be an integral board, or formed by direct stacking of two or more boards of the same size and specification, or formed by hot pressing of two or more boards of the same size and specification.

In order to reduce the flow resistance of the electrolyte, the surface of the filling plate can be processed into serpentine or parallel flow channels, which further reduces the flow resistance of the electrolyte and is more conducive to the circulation of the electrolyte.

When assembling the battery, the carbon material or metal material can be placed directly in the electrode frame, and then the porous electrode is placed on it; it is also possible to press the carbon material or metal material and the bipolar plate first After integration, place the electrode frame and assemble the electrodes.

The beneficial effects of the present invention are as follows:

(1) Adopt the battery structure of the present invention, owing to have used the filling plate of good conductivity, low porosity carbon material or metal material between bipolar plate and porous electrode, make bipolar plate and filling plate and porous electrode The contact points with the filling plate are all conductive points, so that the conductive points on the surface of the bipolar plate and the porous electrode can be utilized to the greatest extent to build a better conductive network and reduce the contact resistance between the electrode bipolar plates;

(2) Adopt the battery structure of the present invention, because the filling board of carbon material or metal material with low porosity is placed between the bipolar plate and the porous electrode, reduce the storage capacity of electrolyte in the battery to reduce electrolyte body resistance; and correspondingly reduce the thickness of the porous electrode, reduce the body resistance of the electrode, reduce the ohmic internal resistance of the battery from many aspects, thereby reducing the ohmic polarization and improving the energy efficiency of the flow energy storage battery And voltage efficiency, thereby improving its working current density, so that the weight, volume and cost of batteries with the same output power are greatly reduced.

(3) The flow energy storage battery adopting the battery structure of the present invention can increase the working current density to 120mA/cm ² under the premise that the energy efficiency is kept above 80%, so that the weight, volume and cost of the battery with the same output power are equal. Greatly reduced;

(4) The present invention has a simple structure, is easy to operate and assemble, and the filler used can be cheap and easy-to-obtain carbon materials, which has commercial promotion and application value.

Description of drawings

Fig. 1 is a schematic diagram of the single cell structure of the liquid flow energy storage battery of the present invention;

Among them: 1 battery end plate; 2 current collector plate (bipolar plate); 3 sealing gasket; 4 electrode frame; 5 filling plate; 6 electrode; 7 ion exchange membrane;

2 is a charge-discharge curve diagram of a single cell at different current densities in Example 1 of the present invention;

FIG. 3 is an AC impedance spectrum of the single cell in Example 1 and the single cell with the original structure in an open circuit state.

Detailed ways

The present invention is described in detail below by specific examples.

A liquid flow energy storage battery structure, the battery includes a bipolar plate, an electrode, and a membrane. A filling plate is arranged between the bipolar plate and the electrodes. As shown in FIG. 1 , a filling plate 5 is placed between the bipolar plate 2 and the electrode 6 in the electrode frame 4 .

Example 1

According to the structure shown in Figure 1, an all-vanadium liquid flow energy storage single cell is assembled, wherein the electrode frame 4 is 3 mm thick, the filler plate 5 is a non-porous graphite plate with a thickness of 2 mm, and the electrode 6 is a carbon felt with a thickness of 3 mm, and a non-porous graphite plate. The areas of carbon felt and carbon felt are both 12cm ² , the sealing gasket 3 is 0.5mm thick silicone rubber; the initial positive electrode electrolyte is 40ml of 1.5M VO ²⁺ 3M H ₂ SO ₄ solution, and the initial negative electrode electrolyte is 1.5M V ³⁺ 40ml of 3M H ₂ SO ₄ solution. The battery charge termination voltage is 1.55V, and the discharge termination voltage is 0.9V. The charge-discharge curves and battery efficiencies of the battery at different current densities are shown in Figure 2 and Table 1. For a single cell using the battery structure of the present invention, when the current density is 80mA/cm ² , the voltage efficiency and energy efficiency are 90% and 85.4% respectively; when the current density is increased to 120mA/cm ² , the voltage efficiency and energy efficiency remain at 85.3% % and 82%.

Fig. 2 is an AC impedance spectrogram of a single cell adopting the structure of the present invention and a single cell without a filler plate in an open circuit state. It can be seen that the ohmic internal resistance of the single cell using the original battery structure is 817m Ωcm ² , but with the battery structure of the present invention, the ohmic internal resistance of the single cell is significantly reduced to only 614m Ωcm ² , which is different from the original battery structure compared to a 25% reduction.

Example 2

According to the structure shown in Figure 1, an all-vanadium liquid flow energy storage single cell is assembled, wherein the electrode frame 4 is 3mm thick, the filling plate 5 is a 2mm thick flexible graphite plate, the density of the flexible graphite plate is 1.5g/cm ³ , and the porous electrode 6 3mm thick carbon felt, the area of the flexible graphite plate and the carbon felt is 12cm ² , the sealing gasket 3 is 0.5mm thick silicon rubber; the initial positive electrode electrolyte is 40ml of 3M H ₂ SO ₄ solution of 1.5M VO ²⁺ , the initial negative electrode electrolyte is 40ml of 1.5M V ³⁺ 3M H ₂ SO ₄ solution. The battery charge termination voltage is 1.55V, and the discharge termination voltage is 0.9V.

The cell efficiencies of the single cells of this embodiment at different current densities are shown in Table 1. When the current density increases to 120mA/cm ² , the voltage efficiency and energy efficiency remain at 84.3% and 81.4%.

Example 3

According to the structure shown in Figure 1, an all-vanadium liquid flow energy storage single cell is assembled, in which the electrode frame 4 is 3mm thick, the filling plate 5 is a 1mm thick flexible graphite plate, the density of the flexible graphite plate is 1.5g/cm ³ , and the porous electrode 6 4mm thick carbon felt, the area of the flexible graphite plate and carbon felt is 12cm ² , the sealing gasket 3 is 0.5mm thick silicon rubber; the initial positive electrode electrolyte is 1.5M VO ²⁺ 3M H ₂ SO ₄ solution 40ml , the initial negative electrode electrolyte is 40ml of 1.5M V ³⁺ 3M H ₂ SO ₄ solution. The battery charge termination voltage is 1.55V, and the discharge termination voltage is 0.9V.

The cell efficiencies of the single cells of this embodiment at different current densities are shown in Table 1. When the current density increases to 120mA/cm ² , the voltage efficiency and energy efficiency remain at 82.4% and 79.9%.

Example 4

According to the structure shown in Figure 1, an all-vanadium liquid flow energy storage single cell is assembled, wherein the electrode frame 4 is 3mm thick, the filler plate 5 uses 3mm thick graphite felt, the porous electrode 6 is 3mm thick carbon felt, graphite felt and carbon felt The area of each is 12cm ² , the sealing gasket 3 is 0.5mm thick silicone rubber; the initial positive electrode electrolyte is 40ml of 3M H ₂ SO ₄ solution of 1.5M VO ²⁺ , and the initial negative electrode electrolyte is 1.5M V ³⁺ of 3M H ₂ SO ₄ solution 40ml. The battery charge termination voltage is 1.55V, and the discharge termination voltage is 0.9V.

The cell efficiencies of the single cell in this embodiment at different current densities are shown in Table 1. When the current density increases to 120mA/cm ² , the voltage efficiency and energy efficiency remain at 80.9% and 83.6%. Table 1 is a comparison of the battery efficiencies of the all-vanadium flow energy storage cells in Examples 1-4 at different current densities.

In the present invention, a filling plate is placed between the bipolar plate and the porous electrode in the electrode frame. The filling plate is a carbon material with good conductivity and low porosity or a metal material stable in acidic medium, which reduces the bulk of the electrode and the electrolyte. The resistance and the contact resistance between the electrode bipolar plates finally reduce the ohmic internal resistance of the flow energy storage battery. The invention improves the energy efficiency and voltage efficiency of the liquid flow energy storage battery, thereby increasing its working current density, so that the weight, volume and cost of the battery with the same output power are greatly reduced.

Claims (6)

1. A liquid flow energy storage battery structure, the battery includes a bipolar plate, an electrode frame and an electrode, and is characterized in that: a filling plate is arranged between the bipolar plate and the porous electrode in the electrode frame, and the thickness of the filling plate is the electrode 5-80% of the thickness of the frame, its length and width are equivalent to the size of the electrode; the electrode is carbon felt, the thickness of the carbon felt is 3mm, the thickness of the filling plate is 2mm, and the thickness of the electrode frame is 3mm; the filling plate is good in conductivity, Carbonaceous materials with low porosity and/or metallic materials stable in acidic media. 2. The battery structure according to claim 1, characterized in that: the carbonaceous material is a non-porous graphite plate, a flexible graphite plate, a graphite felt with a high carbon fiber volume fraction or a carbon felt with a high carbon fiber volume fraction; acid-resistant The metal material is titanium plate or stainless steel plate. 3. The battery structure according to claim 2, wherein the high carbon fiber volume fraction of the high carbon fiber volume fraction graphite felt or the high carbon fiber volume fraction carbon felt is 10-60%. 4. The battery structure according to claim 1, characterized in that: the filler plate is an integral plate, or is formed by directly stacking two or more plates of the same size and specification, or is composed of two or more plates of the same size and specification Made by hot pressing. 5. The battery structure according to claim 1, characterized in that: serpentine or parallel flow channels are provided on the surface of the filling plate. 6. The battery structure according to claim 1, wherein the battery is an all-vanadium flow energy storage battery, a zinc-bromine flow battery, a sodium polysulfide-bromine flow battery or a tin-vanadium flow battery.