Magnesium phosphate cement based bipolar plate composite material

Patent metadata

Field	Value
Publication number	US-2017062845-A1
Application number	US-201514841692-A
Country	US
Kind code	A1
Filing date	Aug 31, 2015
Priority date	Aug 31, 2015
Publication date	Mar 2, 2017
Grant date	—

Abstract

This invention provides a composite material for bipolar plates for fuel cells including cemented by a MPC binder and electrically conductive fillers, and a method of manufacturing the same. The resulting bipolar plate achieves low gas permeability, high electrical conductivity, high flexural strength and good corrosion resistance. The flexural strength and corrosion resistance can further be enhanced by the incorporation of macro-reinforcement and a polymer based surface treatment, respectively.

First claim

What is claimed is:

1 . A bipolar plates composite material comprises
a. an inorganic low-pH cement based binder with grains, wherein said binder can achieve fast setting and high strength; and b. electrically conductive filler selected from a group consisting of graphite powder, carbon black, carbon nanotubes, carbon fibers, and any combination thereof; wherein particle size of said filler is at least one order of magnitude smaller than the particle size of said gains in said binder such that the distribution of said filler particles are restricted in a narrow space by said binder particles to form a percolated conductive pathway with improved conductivity.

2 . The composite material of claim 1 , wherein said acidic cement based binder is magnesium phosphate cement based binder comprising magnesia, potassium di-hydrogen phosphate, borax and water; the magnesia-to-potassium di-hydrogen phosphate molar ratio of said binder is 6-12:1.

3 . The composite material of claim 2 , wherein said magnesia is dead burnt magnesia.

4 . The composite material of claim 2 , wherein in said binder, said borax is 5% of the weight of said magnesia; and water-to-cement ratio is 0.2-0.3 by weight.

5 . The composite material of claim 1 , wherein said binder further comprises fly ash replacing 20-40% of the mass of said magnesia in said binder.

6 . The composite material of claim 1 , wherein said fillers are loaded at 40-56% of the total volume of said binder; said fillers are selected from a group consisting of graphite powder of 35-50% by weight, carbon black of 2-10% by weight, carbon nanotubes of 5-4% by weight, carbon fibers of 0.5-3% by weight, and any combination thereof.

7 . The composite material of claim 2 further comprising a composition of 52% by volume of said binder and 48% by volume of said filler;
wherein said filler comprises 45% by volume of said graphite powder; 1% by volume of said carbon fibers; and 2% by volume of said carbon nanotubes,
wherein said binder comprises a composition of 38.05% by weight of said magnesia; 22.93% by weight of said potassium di-hydrogen phosphate; 2.72% by weight of said borax; 16.3% by weight of said fly ash; and 20% by weight of said water.

8 . A bipolar plates composite material comprises
a. a magnesium phosphate cement based binder; and b. electrically conductive fillers; wherein said binder is a multi-component inorganic binder comprising magnesia, potassium di-hydrogen phosphate, borax and water; the magnesia-to-potassium di- hydrogen phosphate molar ratio of said binder is 6-12:1; wherein said fillers are selected from a group consisting of graphite powder, carbon black, carbon nanotubes, carbon fibers, and any combination thereof.

9 . The composite material of claim 8 , wherein said binder further comprises fly ash replacing 20-40% of the weight of said magnesia in said binder.

10 . The composite material of claim 9 further comprising a composition of 52% by volume of said binder and 48% by volume of said filler;
wherein said filler comprises 45% by volume of said graphite powder; 1% by volume of said carbon fibers; and 2% by volume of said carbon nanotubes,
wherein said binder comprises a composition of 38.05% by weight of said magnesia; 22.93% by weight of said potassium di-hydrogen phosphate; 2.72% by weight of said borax; 16.3% by weight of said fly ash; and 20% by weight of said water.

11 . A method for preparing a bipolar plates composite material, comprising steps of:
a. mixing magnesium phosphate cement raw materials and said fillers; b. mixing said mixed product from step (a) with water to form a wet powder; c. transferring said wet powder from step (b) into a mold; d. using hot-press to convert said wet powder in said mold into a plate; and e. curing said plate to achieve properties of interest.

12 . The method of claim 11 , wherein said mixing in step (a) and step (b) are conducted in an automatic mechanical grinding setup to achieve a homogeneous distribution of said fillers in said binder.

13 . The method of claim 11 , wherein said step (d) is processed under a compressive pressure of 70 MPa and a temperature of up to 140° C., with a loading duration up to 60 min.

14 . The method of claim 11 , wherein in said step (e), said plate of said step (d) is sandwiched between two steel plates for air curing for one day.

15 . The method of claim 11 further comprising step (f) of incorporating a macro-reinforcement to further enhance the flexural strength of said composite material, wherein said macro-reinforcement is placed in said steel mold in said step (c).

16 . The method of claim 15 , wherein said macro-reinforcement is a thin acrylonitrile butadiene styrene co-polymer net produced by 3D printing.

17 . The method of claim 11 further comprising step (g) of polymer based surface treatment of said composite material after step (d) to further enhance the corrosion resistance of said composite material.

18 . The method of claim 17 , wherein said polymer is ultra-high molecular weight polyethylene powder, with a molecular weight of 3,500,000 and a melting point of 142° C.

19 . The method of claim 17 , wherein said polymer replaces 30% of said binder in the said surface layer of said composite material.

20 . The method of claim 17 , wherein after said step (g) comprises increasing the mold temperature 160° C. to allow melting of said polymer and the formation of an organic-inorganic interpenetrated structure, and cooling said heated product to allow formation of a polymer enhanced surface layer for said composite material.

Assignees

• Nano & Advanced Materials Inst Ltd

Inventors

• Li Zongjin
• Ma Hongyan
• Hao Wenbin

Classifications

• H01M8/0236

  Glass; Ceramics; Cermets · CPC title

• H01M8/0243 Primary

  in the form of mixtures · CPC title

• H01M8/0213 Primary

  Gas-impermeable carbon-containing materials · CPC title

• H01M8/0234

  Carbonaceous material · CPC title

• H01M8/0226

  in the form of mixtures · CPC title