JP2002525258A - Method for preparing reticulated copper sulfide or nickel sulfide - Google Patents

Abstract

  (57) [Summary] A process for preparing a reticulated copper sulfide and / or nickel sulfide, comprising the steps of: i) mixing a mixture comprising copper sulfide and / or nickel sulfide powder and salt at a hot and high pressure of hot isostatic pressure. Sintering by compression molding, wherein the salt is physically and chemically stable under the conditions of the hot isostatic pressing; and ii) the sintered body is soluble in the salt. A step of eluting said salt from said sintered body by treating with said solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a method for preparing reticulated copper sulfide or nickel sulfide, and reticulated copper sulfide or nickel sulfide for use as an electrocatalytic material. In particular, the present invention
The present invention relates to a method for preparing reticulated copper sulfide or nickel sulfide, including a hot isostatic pressing step.

[0002]

[Prior art]

Electrodes for use in electrochemical systems are known which contain as active substance one or more transition metal, copper or lead sulfides, selenides or tellurides or mixtures thereof. An electrode of this type is described in GB-A-2042250. Preferred actives are CoS, Cu ₂ S, PbS ₂ , RuS ₂ , MoS ₂ , NiTe, and C
u ₂ Se, which are redox systems such as S / S ²⁻ , Se / Se ²⁻ , and Te / Te ²⁻
It is said that it is useful as an electrode for use.

However, the electrocatalyst material described in GB-A-2042250 is produced by an electroplating technique using various electrodes or by other surface coating techniques, so that the electrocatalyst is deposited in a thin layer, Therefore, it does not have a three-dimensional structure. Therefore, this electrocatalyst material has a small surface area and is not suitable for producing a flow-through electrode. Furthermore, plating a thicker layer on the electrode results in mechanical instability.

[0004] US-A-3847674 discloses the use of eluted cupric sulfide porous cathodes having a porosity of at least 40% and a resistance of less than 0.5 ohm.cm.
These electrodes compress a finely divided powder mixture of copper and sulfur to a close contact by applying mechanical pressure at a temperature below the melting point of sulfur, and then heat the close contact at approximately atmospheric pressure to produce a fine It is formed by causing a reaction to form a cupric sulfide cathode structure in which the split copper and sulfur have eluted.

[0005] However, the electrodes produced according to the teachings of US-A-3847674 have a number of disadvantages. First, the porosity of the material cannot be controlled by this method. The porosity of the pores varies from 40% to 80%, with 75% of the pores being larger than 4 microns. This leaves most of the pores macro-sized, whereas mesopores are desirable in the case of electrocatalysts because they have a larger surface area. Secondly, the method is exothermic, difficult to control, and is capable of producing non-stoichiometric and even unreacted materials. The potential for non-reactive copper or sulfur presents chemical, and consequently mechanical, stability problems. The presence of non-constant materials may reduce the overall electrocatalytic efficiency of the material.

[0006] Applicants have created an improved method for the preparation of copper sulfide and / or nickel sulfide based electrocatalytic materials that have a reticulated morphology and are mechanically stable.

Accordingly, the present invention provides a method for preparing reticulated copper sulfide and / or nickel sulfide, the method comprising the steps of: (i) hot isostatic pressure at elevated temperature and pressure Sintering a mixture comprising copper sulfide and / or nickel sulfide powder and a salt by compression forming, wherein the salt is physically and chemically stable under the conditions of hot isostatic pressing And (ii) treating the sintered body with a solvent in which the salt is soluble to elute the salt from the sintered body.

Preferably, in a method of practicing the present invention, the mixture treated in the step (i) contains 30 to 70 parts by weight, preferably 60 to 70 parts by weight of copper sulfide or nickel sulfide, And it contains 70 to 30 parts by weight, preferably 40 to 30 parts by weight of the salt. Mixtures containing 60 to 70 parts by weight of copper sulfide or nickel sulfide provide mechanically stable products.

Generally, the copper sulfide or nickel sulfide has an average particle size in the range of 40 to 200 micrometers, preferably 60 to 100 micrometers, and more preferably about 80 micrometers, and the salt It has an average particle size in the range of ~ 500 micrometers, preferably 38-420 micrometers. Below 38 micrometers, the product breaks down into a powder. Above 420 micrometers, the product is weak and brittle. Most preferably, the particle sizes of the copper sulfide and salt particles are comparable, since this gives the best mechanical properties in the final product.

[0010] A preferred form of copper sulfide used in the present invention is cupric sulfide. Preferred form of nickel sulfide is Ni ₃ S _2. The salt used in the method of the present invention is soluble in the solvent used in step (ii) of the method. Thus, if the salt is water-soluble, the solvent in step (ii) can be water or a dilute acid or dilute alkaline solution. It will be appreciated that a very wide range of water-soluble salts can be used in the method of the present invention. Examples of such water-soluble salts that can be used include sodium chloride, sodium bromide, potassium chloride, potassium bromide, barium chloride, and potassium carbonate.

In a preferred embodiment, the method of the present invention comprises a total of five steps.
The first three steps are pretreatment steps performed before the method of the present invention. The first step is a mixing step that guarantees the production of a dense mixture of metal sulfide and salt. The mixing step can be performed, for example, using one of two techniques. The material is co-ground for 1 hour using a mechanical agate mortar and pestle, or the material is
Simply they may be tumbled together in a screw-capped container placed on a stirrer. The second step is a compression step that produces a powder compact that is most suitable for subsequent operations and encapsulation. The compression step can be performed, for example, by vacuum die-compression using a die having a suitable diameter at a pressure of 14-21 Mpa for about 1 minute. The third step is to encapsulate the compressed pellets in individual mild steel cans. The top of each can is welded and the cans are evacuated and sealed to maintain a reduced pressure. The degassing method removes gases trapped between the powder particles that would otherwise prevent densification. Preferably, a boron nitride lubricant can be used between the compressed pellets and the steel can to limit the amount of reaction between the two materials. The fourth step is a hot isostatic pressing step. Hydrostatic compression is used in the art,
Particularly well-known in the ceramic art is the technique of applying a high pressure evenly by applying the water pressure from the compressed liquid to the mixture formed, using a flexible membrane. This is a technology that guarantees high density over a wide range. In general, maximum compression can be achieved using this technique.
By performing the isostatic pressing at elevated temperatures, the particles in the resulting mixture agglomerate into a bulky material. The conditions in the hot isostatic pressing process are such that the pressure and temperature are high enough to cause densification, while the decomposition of the metal sulfide and the excess reaction between the metal sulfide and the mild steel can are Selected to be avoided. In practicing the method of the present invention, hot isostatic pressing is preferably performed at a temperature in the range of 300 ° C to 600 ° C, more preferably 300 ° C to 350 ° C, 100 to 300 MPa, more preferably 100 ° C.
It is carried out at a pressure in the range of from to 200 MPa and for a period of from 60 to 300 minutes, more preferably from 100 to 240 minutes. The final step is to remove soluble salts from the densified,
This is a leaching step to leave a porous metal sulfide structure. This step involves placing the densified material in a beaker and immersing it in a solvent for a time sufficient for elution. The leaching step can be facilitated by heating the solvent and stirring the solvent. The leaching step takes several days, and the solvent can be periodically replaced with fresh solvent as needed.

The present invention also includes within its scope the meso / macroporosity (ie, porosity due to meso and / or macropores) produced by the method of the present invention is 35-55%, preferably 45-50%. Containing reticulated copper sulfide or nickel sulfide. Macropores have a diameter
The pores have a pore size exceeding 50 nm, and the mesopores have a pore size of 2 nm or less in diameter. A mercury porosity measurement method (porosimetr) used to measure the porosity of reticulated copper or nickel sulfide produced by the method of the present invention.
In y), only porosity due to meso and macropores is detected.

[0013] It is clear to a skilled person in the art that a significant contribution to the total porosity of the material produced according to the invention also results from micropores in the structure. Thus, the present invention also includes within its scope, produced by the method of the present invention, a total porosity (ie, porosity due to micro and meso and / or macro pores) of 35 to 35.
80%, preferably 45-50%, of reticulated copper or nickel sulfide.

The reticulated copper or nickel sulfide produced by the process of the invention is used for a number of reasons, in particular as an electrocatalytic material. First, the pore size can be tailored for use in aqueous systems by varying the size of the soluble salt particles. Such pore size optimization provides a material with good mass transport within the structure, and consequently improved electrocatalytic performance. Secondly, the mechanical stability of the material is very good, which is beneficial when used in flow-through batteries with high flow rates, since decomposition is not a problem.

Accordingly, the present invention includes within its scope an electrode having an electrode core and a structure in contact with the electrode core and comprising a reticulated copper sulfide or nickel sulfide electrocatalyst material produced by the method of the present invention. It is.

The electrode core may be a conductive carbon polymer composite, for example, high density polyethylene mixed with synthetic graphite powder and carbon black.

The electrocatalyst material preferably forms the surface of the electrode and can form a single sheet or a mosaic of sheets of electrocatalyst material attached directly to the electrode core. Preferably, the sheet has a thickness of 1 to 7 mm, more preferably 2 to 4 mm. If the thickness is less than 1 mm, the mechanical stability of the sheet will be too low. If the thickness is greater than 7 mm, the resulting battery will have a large potential drop across the width of the electrocatalytic material.

The present invention also includes within its scope an electrochemical device comprising a single battery, or an array of batteries, wherein each battery has a positive chamber containing a positive electrode and an electrolyte and a negative chamber containing a negative electrode and an electrolyte. Having a chamber, the positive and negative chambers are separated from each other by a cation exchange membrane, and the negative electrode is an electrode as defined above.

The electrochemical device is preferably a device for energy storage and / or power transmission. The electrolyte in the negative chamber of the electrochemical device preferably contains sulfide, while the electrolyte in the positive chamber of the electrochemical device preferably contains bromine, iron, air, or oxygen.

The chemical reactions involved in these three systems are as follows:

(1) Br ₂ + S ²⁻ = 2Br ⁻ + S Although the above reactions actually occur separately, they are dependent bromine reactions and sulfur reactions, and the bromine reaction is based on the positive side of the membrane. Partial and sulfur reactions occur on the negative side of the membrane.

(2) 2Fe ³⁺ + S ^2- = 2F ²⁺ + S Again, this reaction actually occurs separately, but is a dependent iron and sulfur reaction, and the iron reaction is positive for the membrane. The sulfur reaction occurs on the negative side of the membrane.

(3) 4H ₂ O + 4S ²⁻ + 2O ₂ = 8OH ⁻ + 4S This reaction, also actually occurring separately, is a dependent oxygen and sulfur reaction, and the oxygen reaction is And the sulfur reaction occurs on the negative side of the membrane.

The electrodes used in the above battery arrangement are preferably bipolar electrodes,
The cathode surface is the electrode described above.

The present invention also includes within its scope the use of an electrode as defined in a method involving the electrochemical reduction or oxidation of a sulfur-containing species. Specifically, when the method is a sulfide
Uses that are storage of electrochemical energy, including redox reactions of polysulfides.

The present invention will be described in further detail with reference to the following examples.

[0027]

【Example】

(Example 1) Reticulated CuS pellets were prepared by the following procedure. 20 g of copper (II) sulfide powder
(Aldrich Chemical Co., 99% +, 100 mesh) with 30 g of sodium chloride (Al
drich Chemical Co., 99% +, 500 μm). The mixing weight ratio was 40:60. The mixture was compressed from a 50 g batch at 3000 psi for 1 minute at room temperature into pellets 4 cm in diameter and 1.2 cm in thickness. The pellets were placed in a mild steel can lined with boron nitride (BN) to stop the iron from diffusing into the mixture. Degas and seal this can,
The mixture was then hot isostatically pressed and sintered under the following conditions: Temperature: 300 ° C. Pressure: 200 Mpa Time: 4 hours.

After hot isostatic pressing, the pellets were removed from the can and the sodium chloride salts were eluted from the structure by immersing the pellets in water at 50 ° C. with stirring for several days. The treated pellet was visible to the naked eye and had a reticulated structure further confirmed by electron microscopy. Only X-ray diffraction analysis before leach (FIG. 1, top) revealed peaks due to copper sulfide and sodium chloride. Only the X-ray diffraction analysis after leaching (bottom Figure 1) revealed a peak due to copper sulfide.

Example 2 The procedure of Example 1 was repeated using 25 g of cupric (II) sulfide and 25 g of sodium chloride, ie, with a 50:50 mixture weight ratio.

Example 3 The procedure of Example 1 was repeated using 30 g of cupric (II) sulfide and 20 g of sodium chloride, ie, with a mixing weight ratio of 60:40. X-ray diffraction analysis before leaching
Only 2) revealed the peak of copper sulfide sodium chloride. Only X-ray diffraction analysis after leaching (FIG. 2, bottom) revealed a peak for copper sulfide.

Examples 4 and 5 Example 1 using NaCl particles of defined size and using the following operating conditions:
Was repeated.

[0032]

[Table 1]

The reticulated copper sulfide structure produced in these examples was analyzed by mercury porosity measurement and the following results were obtained. In the mercury porosity measurement method, mesopores (that is, 2 to
Note that only pores with macropores (i.e., diameters greater than 50 nm) and non-micropores (i.e., diameters less than 2 nm) are detected. is there.

[0034]

[Table 2]

Examples 6, 7, and 8 The method of Example 1 was repeated using NaCl particles of various sizes and using the following operating conditions.

[0036]

[Table 3]

Examples 6 and 7 (Example 8 decomposed after leaching) were analyzed by the mercury porosity test method, and the following results were obtained.

[0038]

[Table 4]

Example 9 A 3 kg mixture containing 70% CuS and 30% NaCl was prepared by weighing 2.1 kg CuS and 0.9 kg NaCl and tumbling the mixture in a plastic container. The mixture was divided into three portions and each was compressed at 3000 psi at room temperature to 25x25x2
The rod was 30 mm in size. The rods were placed side by side, encapsulated in mild steel, and then subjected to hot isostatic pressing at 400 ° C., 140 MPa, 240 minutes in one ASEA unit. The steel can was removed from the hot isostatically pressed slab using a band saw. The slab was placed in a large, beaker of circulating hot water to leach the salt, and the water was replaced with fresh water as needed. Upon completion of the leaching, the slab was dried in an oven at 100 ° C.

Example 10 Divide the slab produced in Example 9 into a number of blocks such that each block is approximately 2-3 mm thick, approximately 25 mm wide, and approximately 30 mm long. did. The blocks were mosaic-attached to a brass-backed polyvinylidene: graphite (50:50) electrode using colloidal carbon conductive glue. This electrode was introduced as a negative electrode into a monopolar battery. The positive electrode is a polyvinylidene: graphite (50:50) electrode lined with brass and does not have a reticulated copper sulfide mosaic structure. The electrodes are separated by a cation exchange membrane. The electrolyte in the negative compartment of the battery is 1M Na ₂ S ₄ and the electrolyte in the positive compartment of the battery is 1M bromine (in 5M NaBar).
When operating at a current density of 40 mA / cm ^2, the overvoltage is 100mV during battery charging,
At the time of battery discharge, it was found that the voltage was 30 mV. Similar battery using a negative electrode having no mosaic structure of copper sulfide of net, using a current density of 40 mA / cm ^2, the overvoltage of sulfur reduction, during charging of the battery is 400-600MV, at the time of discharge of the battery 300
mV. The reduction in overpotential observed for cells containing reticulated copper sulfide coated electrodes was maintained for hundreds of cycles without any degradation of the electrodes.

Example 11 The procedure of Example 1 was repeated using nickel sulfide instead of copper sulfide (supplied primarily by INCO with Ni ₃ S ₂ ) and using the following conditions:

[0042]

[Table 5]

A mechanically stable reticulated nickel sulfide compact was obtained. Only X-ray diffraction analysis before leaching (FIG. 3, top) revealed peaks due to nickel sulfide and sodium chloride. Only X-ray diffraction analysis after leaching (FIG. 3, bottom) revealed a peak due to nickel sulfide.

[Procedural Amendment] Submission of translation of Article 34 Amendment of the Patent Cooperation Treaty

[Submission date] September 29, 2000 (2000.9.29)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

──────────────────────────────────────────────────続 き Continuation of front page (81) Designated country EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE ), OA (BF, BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, KE, LS, MW, SD, SL, SZ, UG, ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AE, AL, AM, AT, AU, AZ, BA, BB, BG, BR , BY, CA, CH, CN, CR, CU, CZ, DE, DK, DM, EE, ES, FI, GB, GD, GE, GH, GM, HR, HU, ID, IL , IN, IS, JP, KE, KG, KP, KR, KZ, LC, LK, LR, LS, LT, LU, LV, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, UA, UG, US, UZ, VN, YU, ZA, ZW (72) Inventor Graham Edward Cooley UK SN7 / 7PE Oxfordshire near Farringdon Farnham Chapel Lane (no address) Forge House (72) Inventor Stuart Ernest Mail UK RH19.3QG West Sa Sex East Grinstead Farm Close 68 (72) Inventor Jonathan David Cox UK OX14.3UW Oxfu Deutscher Abingdon Curtis Avenue 74 F-term (Reference) 4G030 AA55 AA67 BA03 BA34 CA09 GA11 GA29 GA32 4G048 AA07 AB01 AB05 AC08 AD04 AE05 5H029 AJ14 AK05 AM01 CJ02 CJ03 EJ03 HJ00 HJ01 HJ04 HJ05 HJ04 HJ15 H05 GA02 GA03 HA01 HA04 HA09 HA10 HA20

Claims (21)

[Claims] 1. A process for preparing reticulated copper sulfide and / or nickel sulfide, comprising the steps of: i) mixing a mixture comprising copper sulfide and / or nickel sulfide powder and a salt at elevated temperature and pressure. Subjecting to sintering by hot isostatic pressing, wherein the salt is physically and chemically stable under the conditions of hot isostatic pressing; and ii) And eluting the salt from the sintered body by treating with a solvent in which the salt is soluble. 2. The method according to claim 1, wherein the mixture comprises 30 to 70 parts by weight of the copper sulfide and / or nickel sulfide and 70 to 30 parts by weight of the salt. 3. The powder of copper sulfide and / or nickel sulfide is 40 to 200
3. A method according to claim 1 or claim 2 having an average particle size in the range of micrometers. 4. The method according to claim 1, wherein said salt has an average particle size in the range of 30 to 500 micrometers. 5. The method according to claim 1, wherein said copper sulfide is copper (II) sulfide. 6. The method according to claim 1, wherein the nickel sulfide is Ni ₃ S ₂ . 7. The method according to claim 1, wherein the salt is water-soluble. 8. The method of claim 7, wherein said water-soluble salt is selected from sodium chloride, sodium bromide, potassium chloride, potassium bromide, barium chloride, and potassium carbonate. 9. The method according to claim 1, wherein the hot isostatic pressing is performed at a temperature in the range of 300 ° C. to 600 ° C. and a pressure in the range of 100 to 300 MPa for 60 to 300 minutes.
The method according to any one of the preceding claims. 10. A reticulated copper sulfide and / or nickel sulfide produced by the method according to claim 1. Description: 11. Reticulated copper sulfide and / or nickel sulfide according to claim 10, having a total porosity in the range from 35 to 80%. 12. The composition of claim 1, having a meso / macro porosity in the range of 35 to 55%.
12. A reticulated copper sulfide and / or nickel sulfide according to 0 or 11. 13. An electrocatalyst material comprising the reticulated copper sulfide and / or nickel sulfide according to any one of claims 10 to 12. 14. An electrode comprising the electrode core and the electrocatalyst material of claim 13 in electrical contact therewith. 15. The electrode according to claim 14, wherein said electrocatalytic material forms a surface of said electrode. 16. The electrode according to claim 15, wherein said electrocatalytic material is in the form of one or more sheets directly attached to said electrode core. 17. The electrode according to claim 16, wherein said sheet has a thickness of 1 to 7 mm. 18. An electrochemical device comprising a single battery or a battery array, comprising:
Each battery has a positive chamber containing a positive electrode and an electrolyte, and a negative chamber containing a negative electrode and an electrolyte, wherein the positive and negative chambers are separated from each other by a cation exchange membrane, and the negative electrode comprises Item 18. The device according to any one of items 14 to 17, wherein the electrode is an electrode. 19. The device according to claim 1, which is a device for energy storage and / or power transmission.
9. The electrochemical device according to 8. 20. Use of an electrode according to any one of claims 14 to 17 in a method comprising the electrochemical oxidation or reduction of sulfur. 21. The use according to claim 20, wherein said method is an electrochemical energy storage method comprising a sulfide / polysulfide redox reaction.