KR20180036389A - Preparation method of bipolar plate for vanadium redox flow battery - Google Patents

Abstract

The present invention relates to a method for manufacturing a bipolar plate for a vanadium redox flow battery, comprising: a step for forming a sheet-like first molded article comprising a step of heating and pressing a first compounding material containing 30 wt% or less of a polyolefin resin and 70 wt% or more of a carbon compound; a step for forming a frame-like second molded article having an opening which can be installed on the first molded article by heating and pressing a second compounding material containing at least 50 wt% of a polyolefin resin and at most 50 wt% of a carbon compound in a mold frame; and a step for heating and pressing in a state in which a rim of the first molded article is in contact with a rim of the opening of the second molded article.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a bipolar plate for a vanadium redox flow battery,

The present invention relates to a method of manufacturing a bipolar plate for a vanadium redox flow cell and a method of manufacturing a bipolar plate and a flow frame composite using the bipolar plate.

Existing power generation systems, such as thermal power generation using nuclear fossil fuels and large-scale greenhouse gas and environmental pollution problems, and nuclear power generation, which have the problems of stability of the facility itself or waste disposal problems, have various limitations and are more environmentally friendly and highly efficient Research on the development of energy and the development of power supply system using it has been greatly increased.

Particularly, the power storage technology makes it possible to utilize renewable energy which is greatly influenced by external conditions in a wider and wider range, and the efficiency of power utilization can be further increased. And research and development have been increasing.

The redox flow cell is an oxidation / reduction cell that can convert the chemical energy of the active material directly into electrical energy. It stores renewable energy with high output fluctuation depending on the external environment such as sunlight and wind power and converts it into high quality power Energy storage system. Specifically, in the redox flow cell, the electrolyte containing the active material causing the oxidation / reduction reaction circulates between the opposite electrode and the storage tank, and charging / discharging proceeds.

In the redox flow cell, the vanadium redox flow cell is composed of an ion exchange membrane in which ions can move during charging and discharging and a carbon felt electrode in which an active material acts as an oxidizing source, while preventing mixing of the cathode active material and the anode active material. A bipolar plate that allows different poles to be formed on the surface, a flow frame that forms a space through which the electrolyte can flow, and a gasket that prevents electrolyte leakage in the material and the flow frame.

The vanadium redox flow cell is mainly made of a low resistance material. Typically, a Nafion type separator is used for the ion exchange membrane and a graphite plate in which the resin is impregnated to about 5% is used as the bipolar plate. A conventional bipolar plate for a vanadium redox flow battery uses a method of inserting a gasket to prevent leakage of electrolyte when applying to a stack of a flow cell, and then tightening the stack using a bolt and a nut.

In this type of fastening using gaskets, bolts and nuts, the life of the gasket and the restoring force of the gasket are not semi-permanent. Therefore, the restoring force of the gasket is shortened in a short period of time and the electrolyte is leaked to the outside of the stack. Causing problems. In addition, when such a fastening method is used, there is a limit in that manual operation is mobilized in the production process of a vanadium redox flow cell or introduction of an automated production process is difficult.

In addition, a method of manufacturing a bipolar plate for a vanadium redox flow cell by impregnating a graphite plate with a polymer resin is also known. However, a bipolar plate for a vanadium redox flow battery known in the prior art is not easy to melt press in a plastic flow frame, It is not easy to solve the electrolyte leakage problem.

The present invention provides a bipolar plate for a vanadium redox flow battery which can be easily and strongly coupled to a flow frame and has a lower contact resistance or an internal resistance, thereby improving the performance, durability and efficiency of the redox flow battery And a method for producing the same.

The present invention also provides a method of manufacturing a bipolar plate and a flow frame composite using the bipolar plate.

The present invention relates to a sheet-shaped first molded article forming step comprising heating and pressing a first compounded material containing 30 wt% or less of a polyolefin resin and 70 wt% or more of a carbon compound; A second compounded material containing at least 50% by weight of a polyolefin resin and at most 50% by weight of a carbon compound is heated and pressed in a mold having a predetermined shape to form a frame-shaped A second shaped article forming step; And heating and pressing the rim of the first molded article in a state in which the rim of the first molded article is in contact with the rim of the opening of the second molded article.

Hereinafter, a method for manufacturing a bipolar plate for a vanadium redox flow battery according to a specific embodiment of the present invention will be described in detail.

As described above, according to one embodiment of the present invention, there is provided a method of manufacturing a sheet-shaped first molded article comprising a step of thermally pressing a first compounded material containing 30 wt% or less of a polyolefin resin and 70 wt% ; A second compounded material containing at least 50% by weight of a polyolefin resin and at most 50% by weight of a carbon compound is heated and pressed in a mold having a predetermined shape to form a frame-shaped A second shaped article forming step; And heating and pressing the rim of the first molded article in a state where the rim of the first molded article is in contact with the rim of the opening of the second molded article.

The present inventors have conducted studies on a vanadium redox flow cell and a bipolar plate applicable to the same, and have found that by using each of the first compounding material and the second compounding material of the above-mentioned specific composition, 1, a bipolar plate for a vanadium redox flow battery was prepared by forming a frame-shaped second molded article having openings in which a molded article could be installed, and heating and pressing them.

The bipolar plate for the vanadium redox flow battery can be more easily and strongly bonded to the flow frame and has a lower contact resistance or an internal resistance, thereby improving the performance, durability and efficiency of the redox flow battery.

The second compounding material forming the second molded product may be at least 50% by weight of the polyolefin-based resin, and at least 50% by weight of the carbon compound 50 By including less than or equal to% by weight, the bipolar plate produced can be more easily and strongly bonded to the flow frame.

The bipolar plate is manufactured in such a manner that a rim of the first molded article is in contact with a rim of the opening of the second molded article. The first compounded material forming the sheet- Or less and a carbon compound of 70 wt% or more, and has a lower contact resistance or an internal resistance, thereby improving the performance, durability and efficiency of the redox flow cell.

More specifically, the first compounding comprises 10 to 30% by weight of a polyolefin-based resin; And 70% to 90% by weight of carbon compounds.

Also, the second compounding may include 70 to 90 wt% of a polyolefin resin; And 10 to 30% by weight of a carbon compound.

Meanwhile, the polyolefin resin contained in each of the first compounding and the second compounding may include a polypropylene resin or an ethylene-propylene copolymer. More specifically, the polyolefin-based resin contained in each of the first compounding and the second compounding may include a polypropylene resin or an ethylene-propylene copolymer, preferably a polypropylene homopolymer, and the polypropylene The homopolymer has a melt flow index (MI) of 4 to 80, a density of 0.850 to 0.950 g / cc and a weight average molecular weight of 200,000 to 400,000 (measured by the GPC method) under the load conditions of 190 and 2.16 kg according to ASTM 1238 Weight-average molecular weight in terms of polystyrene).

The carbon compound contained in each of the first compounding and the second compounding may be at least one selected from the group consisting of carbon felt, natural graphite, graphite, expanded graphite, carbon fiber, hard graphitizable carbon, Carbon nanotube, fullerene, activated carbon, and ordered mesoporous carbon having an average diameter of 3 nm to 4 nm in average diameter of the pores.

The carbon compound may be a powder of a carbon compound having a maximum diameter of 5 mu m to 100 mu m so as to be more uniformly dispersed in the bipolar plate and to realize improved physical properties and electrical conductivity.

The carbon compound included in each of the first compounding and the second compounding may include ordered mesoporous carbon having an average pore diameter of 3 nm to 4 nm.

The term 'ordered mesoporous carbon' refers to carbon having three-dimensionally regular and interconnected pores (about 2 nm to 50 nm in diameter), and also known as 'OMC' . The ordered mesoporous carbon is generally prepared by charging a carbon precursor to pores of a mesoporous material (e.g., a silica material such as SBA-15, MCM-41 and MCM-48) and carbonizing the mesoporous material And then removing it.

Regular mesoporous carbon having an average diameter of the pores of 3 nm to 4 nm can provide a uniform pore distribution structure so that the bipolar plate can be more easily and strongly bonded to the flow frame, Contact resistance, or internal resistance, thereby improving the performance, durability and efficiency of the redox flow cell.

Meanwhile, the step of heat-pressing each of the first compounding material and the second compounding may be performed at a temperature of 200 to 300 and a pressure of 10 kg / cm2 to 20 kg / cm2.

The sheet-shaped first molded article may have a thickness of 0.5 mm to 1.5 mm, or 0.6 mm to 1.2 mm.

The frame-shaped second molded article may have a thickness of 0.5 mm to 1.5 mm, or 0.6 mm to 1.2 mm. The frame shape refers to a shape in which an opening having a polygonal, spherical or circular cross section is present therein, and a rim surrounding the opening exists.

Wherein the step of heating and pressing the rim of the first molded article in a state in which the rim of the first molded article is in contact with the rim of the opening of the second molded article is carried out under a temperature of 200 to 300 and a pressure of 10 to 20 kg / And heating and pressing the edge portion so that the edge portion is in contact with the rim portion of the opening portion of the second molded article.

Meanwhile, the bipolar plate and the polyolefin resin for the vanadium redox flow battery manufactured above may be insert-injected to produce an integrated bipolar plate and a flow frame composite.

According to the present invention, there is provided a bipolar plate for a vanadium redox flow battery capable of easily and strongly bonding with a flow frame and having a lower contact resistance or an internal resistance to improve the performance, durability and efficiency of the redox flow battery And a bipolar plate and a flow frame composite using the bipolar plate manufactured as described above can also be provided.

The invention will be described in more detail in the following examples. However, the following examples are illustrative of the present invention, and the present invention is not limited by the following examples.

[ Example : Vanadium Redox  For flow cell Bipolar  Preparation of plate]

(1) Production of sheet-shaped first molded article

A first compounding composition having the composition shown in Table 1 below was prepared. The first compounded material was subjected to a temperature of 220 ° C. and a pressure of 15 kg / cm 2 using a device using a hot press and a molding to prepare a 1.0 mm thick sheet (size: 65 mm width × 45 mm length).

(2) Production of a frame-shaped second molded product having an opening

A first compounding composition having the composition shown in Table 2 below was prepared.

The second compounding was applied to a frame sheet (size: 75 mm width * 55 mm length / 70 mm width in the center) of 1.0 mm thickness by applying a temperature of 220 and a pressure of 15 kg / * Forming a 50 mm long opening).

(3) Insert injection between the first molded article and the second molded article

The bipolar plate having a size of 75 mm width * 55 mm can be manufactured by hot-press molding at a temperature of 220 and a pressure of 15 kg / cm 2 by overlapping the molded article 1 and the molded article 2. The average temperature in the injector is 270, Was set to 100, and the mold was closed at a pressure of 500 mT. The bipolar plate and the polyolefin resin thus prepared were injection-injected to prepare a monolithic bipolar plate flow frame having a size of 105 mm width and 105 mm length.

Carbon compound (wt%) Polypropylene resin (wt%) Additive (wt%) CNT Carbon Black Graphite Carbon Fiber Molded article 1 10 20 12 8 40 10 Molded product 2 5 15 6 4 60 10

Polypropylene resin: A melt flow index (MI) of 20, 0.900 g / cc and a weight average molecular weight of 250,000 measured under 190, 2.16 kg load conditions according to ASTM 1238

CNT: Carbon nanotubes (Nanocyl, PP2001)

Carbon Black: Carbon black (Mitsubishi 300J)

Graphite: Graphite (SGL, GHG5)

Carbon Fiber: Carbon fiber (Toho, Panex80-0150)

[ Comparative Example : Electrode and Bipolar  Preparation of plate combination]

As the bipolar plate of the comparative example, a graphite plate impregnated with 9% of polypropylene resin was used. Since the graphite plate had a very high carbon content, it was not easy to bond with the polyolefin resin.

[ Experimental Example : Redox  Manufacturing and performance measurement of flow cell]

The bipolar plates for the vanadium redox flow battery obtained in each of the Examples and Comparative Examples were subjected to the conditions shown in Table 2 below to prepare redox flow cells.

Contents Specification / Product name Electrode Material SGL GFD 5 Area (cm ² ) 35 (7 cm x 5 cm) Thickness (mm) 5 Membrane Material GEFC 104 Area (cm ² ) 35 (7 cm x 5 cm) Thickness (mm) 100 The flow material (frame material) PVC (thickness 3 mm) Electrolyte (ml) GEFC V (III) / V (IV), each 100 ml Gasket PVC Operating temperature Room temp. Charge / discharge Current density (mA / cm ² ) 50 Limit voltage range (V) 1.0 to 1.6 Flow Rate (ml / min) 40

(1) Measurement of internal resistance

As shown in FIG. 3, the redox flow cell to which the composite obtained in the above example and the comparative example were respectively applied was driven 30 times by applying the charging / discharging conditions and the flow rate shown in Table 1, The resistance was measured.

It was confirmed that the redox flow cell to which the composite obtained in the above example was applied had an internal resistance of 40 mΩ and had a lower internal resistance than the redox flow battery to which the composite of the comparative example was applied.

(2) Confirmation of leakage of electrolyte

When the electrolyte was circulated to the inside of the cell for the first time in the test of the single cell, it could be visually confirmed by coming out of the cell of the electrolyte. In order to measure the final internal resistance, electrolyte circulation was performed for 1 hour.

(3) Measurement of charging / discharging performance

The redox flow cell to which the composite obtained in the above example and the comparative example were respectively applied was driven 30 times by applying the charging / discharging conditions and the flow rate shown in Table 1, and the battery was charged from 1.75 A to 1.6 V The current efficiency (CE) and discharge capacity (Ah) / charge capacity (Ah) were measured by dividing the discharge time from 1.75 A to 1 V by the time.

At this time, the voltage efficiency [VE, calculation method is discharge average voltage (V) / charge average voltage (V)] is measured by dividing charge average voltage and discharge average voltage, (Energy Efficiency, EE, Calculation Method: Charge Output (Wh) / Discharge Output (Wh)).

Characteristics of charging / discharging operation CE
(%) AND
(%) EE
(%) Example 94.8 84.9 80.5 Comparative Example 94.2 85.4 80.4

As shown in Table 3, it was confirmed that the redox-blurred cell using the composite obtained in the examples can realize current efficiency, voltage efficiency and energy efficiency equal to or more than that of the comparative example at a thinner thickness.

In addition, the composite of the embodiment exhibits a high bonding strength while lowering the bonding pressure between the electrode and the bipolar plate, and can have a lower contact resistance or an internal resistance, so that the performance, durability and efficiency of the redox flow cell can be improved.

Claims (8)

Molding a first compounded product comprising a polyolefin resin in an amount of 30% by weight or less and a carbon compound in an amount of 70% by weight or more;
A second compounded material containing at least 50% by weight of a polyolefin resin and at most 50% by weight of a carbon compound is heated and pressed in a mold having a predetermined shape to form a frame-shaped A second shaped article forming step; And
And heating and pressing the rim of the first molded article in a state in which the rim of the first molded article is in contact with the rim of the opening of the second molded article.
A method for manufacturing a bipolar plate for a vanadium redox flow cell.
The method according to claim 1,
Wherein the first compounding comprises 10 to 30% by weight of a polyolefin-based resin; And 70 to 90% by weight of a carbon compound.
The method according to claim 1,
Wherein the second compounding comprises from 70% to 90% by weight of a polyolefin-based resin; And 10 to 30% by weight of a carbon compound, based on the total weight of the bipolar plate.
The method according to claim 1,
The polyolefin-based resin contained in each of the first compounding and the second compounding has a melt flow index (MI) of 4 to 80, a melt flow index (Melt) of 0.850 to 0.950 g / cc And a polypropylene resin or an ethylene-propylene copolymer having a weight average molecular weight of 200,000 to 400,000,
A method for manufacturing a bipolar plate for a vanadium redox flow cell.
The method according to claim 1,
The carbon compound contained in each of the first compounding and the second compounding may be at least one selected from the group consisting of carbon felt, natural graphite, graphite, expanded graphite, carbon fiber, hard graphitizable carbon, carbon black And ordered mesoporous carbon having an average diameter of 3 nm to 4 nm in average diameter of carbon nanotubes, fullerene, activated carbon, and pores.
A method for manufacturing a bipolar plate for a vanadium redox flow cell.
The method according to claim 1,
The step of heat-pressing each of the first compounding and the second compounding may be performed by applying a pressure of 10 kg / cm 2 to 20 kg /
A method for manufacturing a bipolar plate for a vanadium redox flow cell.
The method according to claim 1,
If the sheet-shaped first molded product has a thickness of 0.5 mm to 1.5 mm,
Wherein the frame-shaped second molded product has a thickness of 0.5 mm to 1.5 mm.
The method according to claim 1,
And heating and pressing the rim of the first molded article in a state in which the rim of the first molded article is in contact with the rim of the opening of the second molded article
Pressing the first molded product so that the rim of the first molded product comes into contact with the rim of the opening of the second molded article under a temperature of 200 to 300 and a pressure of 10 kg / cm 2 to 20 kg / cm 2
A method for manufacturing a bipolar plate for a vanadium redox flow cell.