Method for preparing super capacitor electrode material Ni doped CoP.SUB.3./foam nickel

Abstract

A method for preparing a supercapacitor electrode material Ni doped CoP.sub.3/Ni foam is provided, and the CoP.sub.3 is applied to the supercapacitor for the first time. The method belongs to a technical field of synthesis and preparation of supercapacitor materials. The present invention adopts a low-temperature phosphating process to prepare the Ni-doped CoP.sub.3/foamed nickel as the electrode material of the supercapacitor, so as to provide advantages such as simple synthesis process, easy control, low cost and high specific capacity. The supercapacitor electrode material Ni doped CoP.sub.3/Ni foam prepared by the present invention has a hierarchical structure and a large specific surface area, which is beneficial to shorten an ion transmission path, reduce an interface resistance between the electrode material and electrolyte, provide more active sites, and provide a higher specific capacity in alkaline electrolyte. The electrode material shows great potential in electrochemical energy storage.

Claims

1. A method for preparing a supercapacitor electrode material Ni doped CoP.sub.3/Ni foam, comprising steps of: step 1: dissolving a raw material cobalt chloride CoCl.sub.2⋅6H.sub.2O in deionized water to form a solution A with a molar concentration of 0.04-0.06M and dissolving a raw material 2-methylimidazole C.sub.4H.sub.6N.sub.2 in deionized water to form a solution B with a molar concentration of 0.3-0.5M; then pouring the solution B into the solution A, and ultrasonicating for 5-10 minutes; adding processed sponge-like Ni foam, wherein the Ni foam is ultrasonicated with ethanol and 6M hydrochloric acid for 20 minutes, washed with deionized water to be neutral and then dried at 50 degrees Celsius; the Ni foam has an area density of 280-420 g/m.sup.2 and a pore diameter of 0.2-0.6 mm; after reacting at 20-30 degrees Celsius for 6-12 hours, washing the Ni foam with ionized water and absolute ethanol, and drying under vacuum at 60 degrees Celsius for 12 hours to obtain Co-precursor/Ni foam; step 2: placing the Co-precursor/Ni foam obtained in the step 1 in absolute ethanol solution containing 0.005-0.02M nickel acetate (C.sub.4H.sub.6O.sub.4Ni⋅4H.sub.2O) for 10-30 minutes, and washing with deionized water and absolute ethanol; then drying under vacuum at 60 degrees Celsius for 12 hours to obtain Ni-doped Co(OH).sub.2/Ni foam precursor; and step 3: placing the Ni-doped Co(OH).sub.2/Ni foam precursor obtained in the step 2 in a quartz boat, and placing the quartz boat at a downstream of a tube furnace; placing 0.5-1.5 g sodium hypophosphite NaH.sub.2PO.sub.2 on another quartz boat at an upstream; under nitrogen protection, setting a furnace temperature at 500-600 degrees Celsius and keeping for 1-2 hours; after the furnace temperature is naturally cooled to a room temperature, washing with deionized water and absolute ethanol; then drying under vacuum at 60 degrees Celsius for 12 hours to obtain the Ni-doped CoP.sub.3/Ni foam electrode material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is an X-ray diffraction pattern of a supercapacitor electrode material Ni-doped CoP.sub.3/Ni foam obtained in embodiment 2; wherein X-ray diffraction characteristic peaks are well matched with standard cards CoP.sub.3 JCPDS (24-0496) and Ni JCPDS (70-0989); because an amount of incorporated Ni is low, only characteristics diffraction peaks of the Ni foam and the CoP.sub.3 appear on spectrum, which proves that samples prepared in the embodiment 2 are indeed Ni-doped CoP.sub.3/Ni foam supercapacitor electrode materials;

(2) FIG. 2 is cyclic voltammetry curves of the supercapacitor electrode material Ni-doped CoP.sub.3/Ni foam obtained in the embodiment 2 at different scanning speed rates;

(3) FIG. 3 is constant current charging and discharging curves of the supercapacitor electrode material Ni-doped CoP.sub.3/Ni foam obtained in the embodiment 2 at different current densities:

(4) FIG. 4 illustrates a specific capacitance retention rate of the supercapacitor electrode material Ni-doped CoP.sub.3/Ni foam obtained in the embodiment 2 after 10,000 cycles of charging and discharging at a current density of 10 mA cm.sup.−2:

(5) FIG. 5 illustrates specific capacities of supercapacitor electrode materials Ni-doped CoP.sub.3/Ni foam obtained in embodiments 1-4 at different current densities.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(6) Referring to the drawings, embodiments of the present invention will be further illustrated.

Embodiment 1

(7) A method for preparing a supercapacitor electrode material Ni doped CoP.sub.3/Ni foam comprises steps of:

(8) step 1: respectively dissolving 0.476 g cobalt chloride CoCl.sub.2.6H.sub.2O and 1.312 g 2-methylimidazole C.sub.4H.sub.6N.sub.2 in 40 ml deionized water, and dispersing the solutions by ultrasonic to form uniform solutions; then pouring the solution of 2-methylimidazole into the solution of cobalt chloride, and ultrasonicating for 5-10 minutes; adding processed sponge-like Ni foam, wherein the Ni foam is ultrasonicated with ethanol and 6 M hydrochloric acid for 20 minutes, washed with deionized water to be neutral and then dried at 50 degrees Celsius; selecting Ni foam with an area density of 280, 400 and 420 g/m.sup.2 and a pore diameter of 0.2, 0.4 and 0.6 mm for studying impacts thereof on the supercapacitor; after reacting at 25 degrees Celsius for 12 hours, washing the Ni foam with ionized water and absolute ethanol, and drying under vacuum at 60 degrees Celsius for 12 hours to obtain Co-precursor/Ni foam:

(9) step 2: placing the Co-precursor/Ni foam obtained in the step 1 in 40 ml absolute ethanol solution containing 48 mg nickel acetate (C.sub.4H.sub.6O.sub.4Ni.4H.sub.2O) for 20 minutes, and washing with deionized water and absolute ethanol; then drying under vacuum at 60 degrees Celsius for 12 hours to obtain Ni-doped Co(OH).sub.2/Ni foam precursor; and

(10) step 3: placing the Ni-doped Co(OH).sub.2/Ni foam precursor obtained in the step 2 in a quartz boat, and placing the quartz boat at a downstream of a tube furnace; placing 0.5-1.5 g sodium hypophosphite NaH.sub.2PO.sub.2 on another quartz boat at an upstream; under nitrogen protection, setting a furnace temperature at 500 degrees Celsius and keeping for 2 hours; after the furnace temperature is naturally cooled to a room temperature, washing with deionized water and absolute ethanol; then drying under vacuum at 60 degrees Celsius for 12 hours to obtain the Ni-doped CoP.sub.3/Ni foam electrode material.

Embodiment 2

(11) step 1: respectively dissolving 0.476 g cobalt chloride CoCl.sub.2.6H.sub.2O and 1.312 g 2-methylimidazole C.sub.4H.sub.6N.sub.2 in 40 ml deionized water, and dispersing the solutions by ultrasonic to form uniform solutions: then pouring the solution of 2-methylimidazole into the solution of cobalt chloride, and ultrasonicating for 5-10 minutes: adding processed sponge-like Ni foam, wherein the Ni foam is ultrasonicated with ethanol and 6 M hydrochloric acid for 20 minutes, washed with deionized water to be neutral and then dried at 50 degrees Celsius: selecting Ni foam with an area density of 280, 400 and 420 g/m.sup.2 and a pore diameter of 0.2, 0.4 and 0.6 mm for studying impacts thereof on the supercapacitor; after reacting at 25 degrees Celsius for 12 hours, washing the Ni foam with ionized water and absolute ethanol, and drying under vacuum at 60 degrees Celsius for 12 hours to obtain Co-precursor/Ni foam;

(12) step 2: placing the Co-precursor/Ni foam obtained in the step 1 in 40 ml absolute ethanol solution containing 96 mg nickel acetate (C.sub.4H.sub.6O.sub.4Ni.4H.sub.2O) for 20 minutes, and washing with deionized water and absolute ethanol; then drying under vacuum at 60 degrees Celsius for 12 hours to obtain Ni-doped Co(OH).sub.2/Ni foam precursor: and

(13) step 3: placing the Ni-doped Co(OH).sub.2/Ni foam precursor obtained in the step 2 in a quartz boat, and placing the quartz boat at a downstream of a tube furnace, placing 0.5-1.5 g sodium hypophosphite NaH.sub.2PO.sub.2 on another quartz boat at an upstream; under nitrogen protection, setting a furnace temperature at 500 degrees Celsius and keeping for 2 hours; after the furnace temperature is naturally cooled to a room temperature, washing with deionized water and absolute ethanol; then drying under vacuum at 60 degrees Celsius for 12 hours to obtain the Ni-doped CoP.sub.3/Ni foam electrode material.

(14) The Ni-doped CoP.sub.3/Ni foam electrode material prepared in the embodiment 2 is used as a working electrode, a platinum sheet is used as an auxiliary electrode, and a HgO/Hg electrode is used as a reference electrode, which are all immersed in 6 M KOH electrolyte to form a three-electrode system. A supercapacitor performance test is performed at a potential window of 0-0.6V. FIG. 2 is cyclic voltammetry curves of the Ni-doped CoP.sub.3/Ni foam electrode material at different scanning speed rates. All curves have obvious redox peaks, indicating pseudocapacitance characteristics of such material. The curves maintain relatively consistent shapes from 2 mV s.sup.−1 to 15 mV s.sup.−1, showing rapid redox reaction. FIG. 3 is test curves of charge and discharge properties at different current densities, wherein all the test curves have discharge platforms, indicating redox capacitance characteristics. When the current density is 2.5 mA cm.sup.−2, an area specific capacitance is 5.1 F cm.sup.−2 (a corresponding mass specific capacitance is 2780 F g.sup.−1). At this time, the area density of the Ni foam used is 400 g/m.sup.2, and the pore diameter is 0.6 mm. When the current density is increased to 40 mA cm.sup.−2, the area specific capacitance is still 3.4 F cm.sup.−2, showing sufficient rate performance. FIG. 4 shows that the specific capacitance retention rate of the electrode material remains above 90% after 10,000 cycles of continuous charging and discharging at a scanning speed rate of 10 mA cm.sup.−2, indicating great advantage as the supercapacitor electrode material.

Embodiment 3

(15) step 1: respectively dissolving 0.476 g cobalt chloride CoCl.sub.2.6H.sub.2O and 1.312 g 2-methylimidazole C.sub.4H.sub.6N.sub.2 in 40 ml deionized water, and dispersing the solutions by ultrasonic to form uniform solutions; then pouring the solution of 2-methylimidazole into the solution of cobalt chloride, and ultrasonicating for 5-10 minutes; adding processed sponge-like Ni foam, wherein the Ni foam is ultrasonicated with ethanol and 6 M hydrochloric acid for 20 minutes, washed with deionized water to be neutral and then dried at 50 degrees Celsius; selecting Ni foam with an area density of 280, 400 and 420 g/m.sup.2 and a pore diameter of 0.2, 0.4 and 0.6 mm for studying impacts thereof on the supercapacitor; after reacting at 25 degrees Celsius for 12 hours, washing the Ni foam with ionized water and absolute ethanol, and drying under vacuum at 60 degrees Celsius for 12 hours to obtain Co-precursor/Ni foam;

(16) step 2: placing the Co-precursor/Ni foam obtained in the step 1 in 40 ml absolute ethanol solution containing 144 mg nickel acetate (C.sub.4H.sub.6O.sub.4Ni.4H.sub.2O) for 20 minutes, and washing with deionized water and absolute ethanol; then drying under vacuum at 60 degrees Celsius for 12 hours to obtain Ni-doped Co(OH).sub.2/Ni foam precursor; and

(17) step 3: placing the Ni-doped Co(OH).sub.2/Ni foam precursor obtained in the step 2 in a quartz boat, and placing the quartz boat at a downstream of a tube furnace, placing 0.5-1.5 g sodium hypophosphite NaH.sub.2PO.sub.2 on another quartz boat at an upstream: under nitrogen protection, setting a furnace temperature at 500 degrees Celsius and keeping for 2 hours; after the furnace temperature is naturally cooled to a room temperature, washing with deionized water and absolute ethanol; then drying under vacuum at 60 degrees Celsius for 12 hours to obtain the Ni-doped CoP.sub.3/Ni foam electrode material.

Embodiment 4

(18) step 1: respectively dissolving 0.476 g cobalt chloride CoCl.sub.2.6H.sub.2O and 1.312 g 2-methylimidazole C.sub.4H.sub.6N.sub.2 in 40 ml deionized water, and dispersing the solutions by ultrasonic to form uniform solutions; then pouring the solution of 2-methylimidazole into the solution of cobalt chloride, and ultrasonicating for 5-10 minutes; adding processed sponge-like Ni foam, wherein the Ni foam is ultrasonicated with ethanol and 6 M hydrochloric acid for 20 minutes, washed with deionized water to be neutral and then dried at 50 degrees Celsius; selecting Ni foam with an area density of 280, 400 and 420 g/m.sup.2 and a pore diameter of 0.2, 0.4 and 0.6 mm for studying impacts thereof on the supercapacitor: after reacting at 25 degrees Celsius for 12 hours, washing the Ni foam with ionized water and absolute ethanol, and drying under vacuum at 60 degrees Celsius for 12 hours to obtain Co-precursor/Ni foam:

(19) step 2: placing the Co-precursor/Ni foam obtained in the step 1 in 40 ml absolute ethanol solution containing 192 mg nickel acetate (C.sub.4H.sub.6O.sub.4Ni.4H.sub.2O) for 20 minutes, and washing with deionized water and absolute ethanol; then drying under vacuum at 60 degrees Celsius for 12 hours to obtain Ni-doped Co(OH)/Ni foam precursor: and

(20) step 3: placing the Ni-doped Co(OH).sub.2/Ni foam precursor obtained in the step 2 in a quartz boat, and placing the quartz boat at a downstream of a tube furnace; placing 0.5-1.5 g sodium hypophosphite NaH.sub.2PO.sub.2 on another quartz boat at an upstream; under nitrogen protection, setting a furnace temperature at 500 degrees Celsius and keeping for 2 hours: after the furnace temperature is naturally cooled to a room temperature, washing with deionized water and absolute ethanol; then drying under vacuum at 60 degrees Celsius for 12 hours to obtain the Ni-doped CoP.sub.3/Ni foam electrode material.

(21) XRD and supercapacitor performance tests are performed on the Ni-doped CoP.sub.3/Ni foam material prepared in the embodiments 1-4. Results are shown in FIGS. 1-5.

(22) FIG. 1 is an X-ray diffraction pattern of a supercapacitor electrode material Ni-doped CoP.sub.3/Ni foam obtained in embodiment 2; wherein X-ray diffraction characteristic peaks are well matched with standard cards CoP.sub.3 JCPDS (24-0496) and Ni JCPDS (70-0989); because an amount of incorporated Ni is low, only characteristics diffraction peaks of the Ni foam and the CoP.sub.3 appear on spectrum, which proves that samples prepared in the embodiment 2 are indeed Ni-doped CoP.sub.3/Ni foam supercapacitor electrode materials.

(23) FIG. 2 is cyclic voltammetry curves of the Ni-doped CoP.sub.3/Ni foam electrode material prepared in the embodiment 2 at different scanning speed rates. All curves have obvious redox peaks, indicating pseudocapacitance characteristics of such material. The curves maintain relatively consistent shapes from 2 mV s.sup.−1 to 15 mV s.sup.−1, showing rapid redox reaction. FIG. 3 is test curves of charge and discharge properties of the Ni-doped CoP.sub.3/Ni foam electrode material prepared in the embodiment 2 at different current densities (2.5 mA cm.sup.−2, 5 mA cm.sup.−2, 10 mA cm.sup.−2, 20 mA cm.sup.−2 and 40 mA cm.sup.−2), wherein all the test curves have discharge platforms, further indicating redox capacitance characteristics. When the current density is 2.5 mA cm.sup.−2, an area specific capacitance is 5.1 F cm.sup.−2 (a corresponding mass specific capacitance is 2780 F g.sup.−1). At this time, the area density of the Ni foam used is 400 g/m.sup.2, and the pore diameter is 0.6 mm. When the current density is increased to 40 mA cm.sup.−2, the area specific capacitance is still 3.4 F cm.sup.−2, showing sufficient rate performance. FIG. 4 shows that the specific capacitance retention rate of the electrode material remains above 90% after 10.000 cycles of continuous charging and discharging when a current density of the Ni-doped CoP.sub.3/Ni foam electrode material prepared in the embodiment 2 is 10 mA cm.sup.−2, indicating great advantage as the supercapacitor electrode material. FIG. 5 illustrates specific capacities of the Ni-doped CoP.sub.3/Ni foam electrode materials obtained in embodiments 1-4 at current densities of 2.5 mA cm.sup.−2. 5 mA cm.sup.−2, 10 mA cm.sup.−2, 20 mA cm.sup.−2 and 40 mA cm.sup.−2. Referring to the drawings, the Ni-doped CoP.sub.3/Ni foam electrode material obtained in the embodiment 2 has the largest specific capacity at each current density. The Ni-doped CoP.sub.3/Ni foam electrode materials prepared by the present invention have excellent supercapacitor performance, and the sample prepared in the embodiment 2 has the best performance.