Zn / Li / Zr co-doped high-voltage P2 layered positive electrode material and application thereof

Abstract

The invention belongs to the field of sodium ion batteries, and discloses a Zn / Li / Zr co-doped high-voltage P2 layered positive electrode material and application thereof. The chemical general formula of the Zn / Li / Zr co-doped high-voltage P2 layered positive electrode material is Na < 0.67 + y > Zn < x > Li < y > Ni < 0.33-x-y > Mn < 0.67-z > Zr < z > O2, wherein x is greater than or equal to 0.01 and less than or equal to 0.1, y is greater than or equal to 0.01 and less than or equal to 0.1, and Z is greater than or equal to 0.01 and less than or equal to 0.05. Zn / Li / Zr co-doping is adopted, a solid solution reaction is formed through the synergistic effect of Zn, Li and Zr, P2-O2 phase change is perfectly inhibited, and the layered positive electrode material of the sodium-ion battery has excellent cycle stability. The ultrahigh capacity at 10C is 99.04 mAh g <-1 >, the capacity retention ratio after 500 cycles within 2-4.3 V is 87.2%, and the capacity retention ratio after 200 cycles at 2-4.5 V is still 87%.

Description

Technical Field

[0001] The present invention belongs to the field of sodium-ion batteries, and particularly relates to a high-voltage P2 layered cathode material co-doped with Zn / Li / Zr and its application. Background Art

[0002] In today's society, energy storage devices are crucial for meeting the growing energy demands. Among them, lithium-ion batteries are widely used in fields such as electronic devices and electric vehicles due to their high energy density and long cycle life. However, due to the limited lithium resources, their sustainability has attracted wide attention. Therefore, sodium-ion batteries (SIBs) have emerged as a highly potential alternative. Among various sodium-ion battery cathode materials, layered oxide cathode materials NaxTMO 2 have attracted much attention due to their high tap density, high conductivity, and easy synthesis.

[0003] However, there is still a significant energy density gap between sodium-ion batteries and commercial lithium-ion batteries (LIBs), which poses a challenge to meeting the actual application requirements. To improve the energy density of sodium-ion batteries, it is usually necessary to operate the cathode in the high-voltage region. However, P2-type layered oxides have serious problems at high voltages. When the charging voltage exceeds 4.2 V, a phase change occurs, resulting in lattice distortion and intragranular cracking. At the same time, side reactions on the electrode surface consume the electrolyte, causing the dissolution of transition metal ions and the formation of a high-resistance CEI film, ultimately leading to a rapid shortening of the battery life. Summary of the Invention

[0004] To overcome the above-mentioned disadvantages and deficiencies of the prior art, the primary object of the present invention is to provide a preparation method of a high-stability Zn / Li / Zr co-doped high-voltage P2 layered cathode material.

[0005] Another object of the present invention is to provide the high-stability Zn / Li / Zr co-doped high-voltage P2 layered cathode material prepared by the above method. The present invention adopts multi-element (Zn / Li / Zr) co-doping, and the synergistic effect of the three forms a solid solution reaction, perfectly suppressing the P2-O2 phase change and endowing the sodium-ion battery layered cathode material with excellent cycle stability.

[0006] Another object of the present invention is to provide the application of the above high-stability Zn / Li / Zr co-doped high-voltage P2 layered cathode material in sodium-ion batteries.

[0007] The objects of the present invention are achieved by the following solutions:

[0008] A high-voltage P2 layered cathode material co-doped with Zn / Li / Zr, whose chemical general formula is: Na 0.67+y Zn x Liy Ni 0.33-x-y Mn 0.67-z Zr z O 2 , where 0.01≤x≤0.1, 0.01≤y≤0.1, 0.01≤Z≤0.05.

[0009] Furthermore, x=0.05, y=0.06, and Z=0.01.

[0010] A method for preparing the above-mentioned Zn / Li / Zr co-doped high voltage P2 layered positive electrode material comprises the following steps:

[0011] (1) weighing a sodium source, a manganese source, a nickel source, a lithium source, a zinc source and a zirconium source according to a stoichiometric ratio and mixing them, adding a dispersant, ball milling, and then drying to obtain a precursor;

[0012] (2) The precursor powder obtained in step (1) is tableted and then calcined at high temperature in a muffle furnace to obtain a layered oxide material.

[0013] The sodium source in step (1) is one or more of sodium carbonate, sodium acetate, sodium nitrate and sodium hydroxide;

[0014] The nickel source described in step (1) is one or more of nickel oxide, nickel sulfate, nickel carbonate, nickel acetate and nickel nitrate;

[0015] The manganese source in step (1) is selected from one or more of manganese dioxide, manganese trioxide, manganese nitrate, manganese oxalate and manganese sulfate;

[0016] The lithium source in step (1) is selected from one or more of lithium carbonate, lithium hydroxide, lithium acetate, and lithium nitrate;

[0017] The zinc source in step (1) is selected from one or more of zinc oxide, zinc acetate, zinc carbonate and zinc nitrate;

[0018] The zirconium source described in step (1) is selected from one or more of zirconium oxide and zirconium sulfate.

[0019] In step (1), before adding the dispersant, in order to fully mix, it is preferred to grind manually first and then add the dispersant for ball milling.

[0020] The dispersant described in step (1) is an alcohol solvent, preferably anhydrous ethanol.

[0021] The ball-milling mixed material mass ratio in step (1) is (5-25), the rotation speed is 300-600 rpm, specifically 300 rpm; the ball-milling time is 4h-12h, specifically 10h.

[0022] The drying in step (1) is preferably carried out at 40 °C to 80 °C for 6 h to 12 h, more preferably at 60 °C for 12 h.

[0023] The pressure used for pressing the mixed powder into flakes in step (2) is preferably 10 - 20 MPa, and specifically can be 15 MPa.

[0024] Preferably, in step (2), the calcination temperature is 850 - 1200 °C, the heating rate is 1 - 5 °C / min, the calcination time is 10 - 16 h, the calcination atmosphere includes but is not limited to air atmosphere, argon atmosphere, oxygen atmosphere, helium atmosphere, nitrogen atmosphere, and the sampling temperature for furnace cooling is 100 - 500 °C.

[0025] Application of the above-mentioned Zn / Li / Zr co-doped high-voltage P2-type layered cathode material in sodium-ion batteries.

[0026] A positive electrode plate of a sodium-ion battery, which is prepared by the following steps:

[0027] (1) Mixing a cathode active material, a conductive agent and a binder in a solvent to prepare a cathode slurry;

[0028] (2) Coating on an aluminum foil current collector using a coating die with a thickness of 100 - 500 μm;

[0029] (3) Drying in a vacuum oven at 80 °C - 120 °C for 5 - 12 hours.

[0030] The cathode active material, conductive agent and binder described in step (1) are mixed in a solvent according to a mass ratio of (8 - 7):(1 - 2):1; the conductive agent is preferably one or more of Super-P, carbon black and Ketjenblack; the binder is selected from one or more of polyvinylidene fluoride, polyacrylic acid, sodium carboxymethyl cellulose and sodium alginate; the solvent is selected from one of N-methylpyrrolidone or deionized water.

[0031] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0032] (1) Using Li ions to activate the ARR reaction to improve the discharge capacity of the material, Zn ions can effectively prevent the collapse of the high-voltage structure and Zr can stabilize the surface oxygen stability during high-voltage charge and discharge, further inhibiting irreversible phase transformation and forming a protective layer on the outside of the material, fully improving the electrochemical performance of the material.

[0033] (2) The cathode material has good cycle stability, good rate performance and low cost at high voltage, and is an ideal cathode material for sodium-ion batteries.

[0034] (3) NZNLMZO has 99.04 mAh g at 10C -1With ultra-high capacity and a capacity retention rate of 87.2% after 500 cycles within 2 - 4.3V, and a capacity retention rate of 87% after 200 cycles at 2 - 4.5V. Description of the Drawings

[0035] Figure 1 XRD patterns of the cathode materials for sodium-ion batteries in Examples 1 - 5;

[0036] Figure 2 XRD refinement pattern of the cathode material for the sodium-ion battery obtained in Example 1 of the present invention;

[0037] Figure 3 Scanning electron microscope (SEM) morphology and EDS energy spectrum diagrams of the cathode material for the sodium-ion battery obtained in Example 1 of the present invention;

[0038] Figure 4 Charge-discharge curves of the sodium-ion cathode material obtained in Example 1 at a rate of 0.2C.

[0039] Figure 5 Charge-discharge curves of the sodium-ion cathode material obtained in Example 2 at a rate of 0.2C.

[0040] Figure 6 Charge-discharge curves of the sodium-ion cathode material obtained in Example 3 at a rate of 0.2C.

[0041] Figure 7 Charge-discharge curves of the sodium-ion cathode material obtained in Example 4 at a rate of 0.2C.

[0042] Figure 8 Charge-discharge curves of the sodium-ion cathode material obtained in Example 5 at a rate of 0.2C.

[0043] Figure 9 Comparison chart of the rate performance of the sodium-ion cathode materials obtained in Examples 1 - 5 within the range of 0.2C - 20C;

[0044] Figure 10 Comparison chart of the 1C rate cycling performance of the cathode materials for sodium-ion batteries obtained in Examples 1 - 5 within the voltage range of 2 - 4.3V;

[0045] Figure 11 Comparison chart of the 10C rate cycling performance of the cathode materials for sodium-ion batteries obtained in Examples 1 - 5 within the voltage range of 2 - 4.3V;

[0046] Figure 12 Comparison chart of the 10C rate cycling performance of the cathode material for the sodium-ion battery obtained in Example 1 within the voltage range of 2 - 4.5V;

[0047] Figure 13Cycling performance of the full cell composed of Example 1 and commercial hard carbon at a rate of 1C. Detailed implementation manners

[0048] The present invention will be further described in detail below in conjunction with examples and drawings, but the implementation manners of the present invention are not limited thereto. For those conditions not specified in the examples, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For those reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0049] Unless otherwise specified, the reagents used in the examples can be conventionally purchased from the market.

[0050] Example 1

[0051] This example provides a method for preparing a cathode material for a sodium-ion battery and its electrode sheet, with the chemical formula Na 0.73 Zn 0.05 Ni 0.22 Li 0.06 Mn 0.66 Zr 0.01 O 2 (NZNLMZO)

[0052] Step 1: Prepare the cathode material for the sodium-ion battery

[0053] Mix Na 2 CO 3 , ZnO, NiO, Li 2 CO 3 , MnO 2 , ZrO 2 in a stoichiometric ratio of 0.73:0.05:0.22:0.06:0.66:0.01 (sodium carbonate is in excess by 3% to make up for the high-temperature loss) in an agate jar, with absolute ethanol as the dispersant. Use a planetary ball mill to ball mill at 300 r / min for 10 h, dry at 60 °C for 12 h, then press the powder into a mold with a tablet press under a pressure of 15 MPa, and then calcine in air at 950 °C for 15 h, with the heating and cooling rates of 2 °C / min -1 . After cooling to 150 °C, transfer it to a glove box filled with Ar and finely grind the material into powder for storage.

[0054] Step 2: Prepare the cathode sheet for the sodium-ion battery

[0055] Mix the cathode active material (80 wt%), super-p Li (10 wt%), and polyvinylidene fluoride (10 wt%) in N-methyl-2-pyrrolidone to prepare the cathode slurry. After grinding for 1 hour, the resulting slurry is then coated on an aluminum foil current collector. Then it is dried in a vacuum oven at 80 °C for 12 hours. In the half-cell assembly, the synthesized layered oxide material is used as the cathode, with a loading of 2 mg cm -2 。

[0056] Step 3: Assemble a sodium-ion half-cell with 0.73 Zn 0.05 (Ni 0.22 Li 0.06 Mn 0.66 Zr 0.01 )O 2 as the cathode.

[0057] Using sodium metal as the counter electrode, a Whatman glass fiber filter as the separator, and the electrolyte being a 1M NaClO 4 PC (propylene carbonate) solution with 5 vol% of FEC (fluoroethylene carbonate) additive, and test it in a CR2032 battery.

[0058] Step 4: Assemble a sodium-ion full cell with 0.73 Zn 0.05 Ni 0.22 Li 0.06 Mn 0.66 Zr 0.01 O 2 as the cathode and commercial hard carbon as the anode.

[0059] The electrolyte and separator are the same as those in the half-cell. Due to the irreversible capacity problem of hard carbon in the first cycle, assemble the hard carbon electrode with sodium metal into a half-cell for pre-sodiation treatment, that is, cycle the half-cell 8 times and finally discharge it to 0.01 V. Disassemble the battery in the glove box, take out the hard carbon electrode sheet, and assemble it with the layered oxide in a 2032-type button cell to evaluate its electrochemical performance.

[0060] Figure 1 The XRD picture of the cathode material obtained in Example 1 is shown. As can be seen from the figure, the synthesized layered oxide cathode material has good crystallinity, is a standard P2-phase structure, and belongs to the hexagonal crystal system P63 / mmc space group.

[0061] Figure 2 This is the Rietveld refinement processing (using GSAS-II) of the XRD pattern of Example 1. It can be seen from the figure that all the reflection peaks in the XRD pattern are Figure 1 consistent with the standard spectrum, there are no impurity peaks and the intensity of the diffraction peaks is relatively high, indicating that the material has excellent crystallinity.

[0062] Figure 3 The SEM image of Example 1 shows the typical and uniform layered shape of the obtained crystals, and the interplanar spacing of its crystal plane is 0.554 nm, corresponding to the (002) crystal plane of the typical p2-type structure. The energy-dispersive spectroscopy (EDS) mapping shows the uniform distribution of Na, Zn, Ni, Mn, Zr, and O elements in the particles.

[0063] Figure 4 For Example 1, the charge-discharge curve at 0.2C (1C = 100 mA g -1 ) has a relatively high discharge specific capacity of 131.4 mAh g -1 in the sodium-ion half-cell.

[0064] Figure 9 For the rate performance of the sodium-ion half-cell of Example 1 in the voltage range of 2 - 4.3 V, it shows 135.94, 132.24, 126.99, 120.83, 110.70, 99.04, 82.03 mAh g -1 respectively at 0.2, 0.5, 1, 2, 5, 10, 20C.

[0065] Figure 10 For the cycling performance of the sodium-ion half-cell of Example 1 at 1C in the voltage range of 2 - 4.3 V, the capacity retention rate of NZNLMZO is 98.1% after 100 cycles.

[0066] Figure 11 For the cycling performance of the sodium-ion half-cell of Example 1 at 10C in the voltage range of 2 - 4.3 V, the capacity retention rate of NZNLMZO is 87.2% after 500 cycles.

[0067] Figure 12 For the cycling performance of the sodium-ion half-cell of Example 1 at 10C in the voltage range of 2 - 4.5 V, the capacity retention rate of NZNLMZO is 87% after 500 cycles.

[0068] Figure 13 For the cycling performance of the full cell assembled with Example 1 and hard carbon at 1C, the capacity retention rate reaches 87.4% after 100 cycles.

[0069] Example 2

[0070] The difference between Example 2 and Example 1 is that Li is not doped during the solid-phase method process, and other conditions are the same as those in Example 1. Na 0.67 Zn 0.05 Ni 0.28 Mn 0.66 Zr 0.01 O 2 (NZNMZO) cathode material is obtained.

[0071] Figure 1 The XRD pattern of the cathode material obtained in Example 2 is shown. It can be seen from the figure that the synthesized layered oxide cathode material has good crystallinity, is a standard P2-phase structure, and belongs to the hexagonal crystal system P63 / mmc space group.

[0072] Figure 5 The charge-discharge curve of Example 2 at 0.2C (1C = 100 mA g -1 ) shows a relatively high discharge specific capacity of 121.9 mAh g -1 in the sodium-ion half-cell.

[0073] Figure 9 The rate performance of the sodium-ion half-cell of Example 2 in the voltage range of 2 - 4.3 V is shown. At 0.2, 0.5, 1, 2, 5, 10, and 20C, it shows 121.8, 112.88, 103.19, 91.09, 72.62, 60.50, and 48.88 mAh g -1 , respectively.

[0074] Figure 10 The cycling performance of the sodium-ion half-cell of Example 2 at 1C in the voltage range of 2 - 4.3 V is shown. After 100 cycles, the capacity retention rate of NZNMZO is 93.4%.

[0075] Figure 11 The cycling performance of the sodium-ion half-cell of Example 2 at 10C in the voltage range of 2 - 4.3 V is shown. After 500 cycles, the capacity retention rate of NZNMZO is 87.7%.

[0076] Example 3

[0077] The difference between Example 3 and Example 1 is that Zn is not doped during the solid-phase method process, and other conditions are the same as those in Example 1. Na 0.73 Ni 0.27 Li 0.06 Mn 0.66 Zr 0.01 O 2 (NNLMZO) cathode material is obtained.

[0078] Figure 1 The XRD pattern of the cathode material obtained in Example 3 is shown. It can be seen from the figure that the synthesized layered oxide cathode material has good crystallinity, is a standard P2-phase structure, and belongs to the hexagonal crystal system P63 / mmc space group.

[0079] Figure 6 The charge-discharge curve of Example 3 at 0.2C (1C = 100 mA g -1 ) shows a discharge specific capacity of 124.7 mAh g in the sodium-ion half-cell.-1 Higher discharge specific capacity.

[0080] Figure 9 The rate performance of the sodium-ion half-cell of Example 3 in the voltage range of 2 - 4.3 V showed 121.13, 114.15, 107.99, 100.68, 90.43, 75.94, 56.65 mAh g at 0.2, 0.5, 1, 2, 5, 10, 20 C respectively. -1 .

[0081] Figure 10 The cycle performance of the sodium-ion half-cell of Example 3 at 1 C in the voltage range of 2 - 4.3 V. After 100 cycles, the capacity retention rate of NNLMZO was 81.4%.

[0082] Figure 11 The cycle performance of the sodium-ion half-cell of Example 3 at 10 C in the voltage range of 2 - 4.3 V. After 500 cycles, the capacity retention rate of NNLMZO was 87%.

[0083] Example 4

[0084] The difference between Example 4 and Example 1 is that Zr is not doped during the solid-phase method process, and other conditions are the same as those in Example 1. Na 0.73 Zn 0.05 Ni 0.22 Li 0.06 Mn 0.67 O 2 (NZNLMO) cathode material was obtained.

[0085] Figure 1 The XRD pattern of the cathode material obtained in Example 4 is shown. It can be seen from the figure that the synthesized layered oxide cathode material has good crystallinity, is a standard P2-phase structure, and belongs to the hexagonal crystal system P63 / mmc space group.

[0086] Figure 7 The charge-discharge curve of Example 4 at 0.2 C (1 C = 100 mAg -1 ). It has a discharge specific capacity of 120.8 mAh g in the sodium-ion half-cell. -1

[0087] Figure 9 The rate performance of the sodium-ion half-cell of Example 4 in the voltage range of 2 - 4.3 V showed 125.13, 113.08, 105.33, 95.49, 81.70, 69.94, 56.73 Ah g-1 at 0.2, 0.5, 1, 2, 5, 10, 20 C respectively.

[0088] Figure 10For the cycling performance of the sodium-ion half-cell of Example 4 at a voltage range of 2 - 4.3V at 1C, the capacity retention rate of NZNLMO was 90.8% after 100 cycles.

[0089] Figure 11 For the cycling performance of the sodium-ion half-cell of Example 4 at a voltage range of 2 - 4.3V at 10C, the capacity retention rate of NZNLMO was 80.7% after 500 cycles.

[0090] Example 5

[0091] The difference between Example 5 and Example 1 is that there is no doping element in the solid-phase method process, and other conditions are the same as those in Example 1, obtaining the cathode material Na 0.67 Ni 0.33 Mn 0.67 O 2 (NNMO).

[0092] Figure 1 The XRD pattern of the cathode material obtained in Example 5 is shown. It can be seen from the figure that the synthesized layered oxide cathode material has good crystallinity, is a standard P2-phase structure, and belongs to the hexagonal crystal system P63 / mmc space group.

[0093] Figure 8 The charge-discharge curve of Example 5 at 0.2C (1C = 100 mAg -1 ) shows a relatively high discharge specific capacity of 142.6 mAh g -1 in the sodium-ion half-cell.

[0094] Figure 9 For the rate performance of the sodium-ion half-cell of Example 5 at a voltage range of 2 - 4.3V, it shows 127.61, 97.09, 80.47, 63.46, 44.62, 35.26, 22.61 mAh g-1 at 0.2, 0.5, 1, 2, 5, 10, 20C respectively.

[0095] Figure 10 For the cycling performance of the sodium-ion half-cell of Example 5 at a voltage range of 2 - 4.3V at 1C, the capacity retention rate of NNMO was 55.3% after 100 cycles.

[0096] Figure 11 For the cycling performance of the sodium-ion half-cell of Example 5 at a voltage range of 2 - 4.3V at 10C, the capacity retention rate of NNMO was 55.88% after 500 cycles.

[0097] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A Zn / Li / Zr co-doped high voltage P2 layered cathode material, characterized in that Its chemical formula is: Na 0.67+ y Zn x Li y Ni 0.33-x-y Mn 0.67-z Zr z O2, where 0.01≤x≤0.1, 0.01≤y≤0.1, 0.01≤Z≤0.

05.

2. The Zn / Li / Zr co-doped high voltage P2 layered positive electrode material according to claim 1, characterized in that: x=0.05, y=0.06, Z=0.

01.

3. A method for preparing a Zn / Li / Zr co-doped high voltage P2 layered positive electrode material according to claim 1 or 2, characterized in that The following steps are involved: (1) weighing a sodium source, a manganese source, a nickel source, a lithium source, a zinc source and a zirconium source according to a stoichiometric ratio and mixing them, adding a dispersant, ball milling, and then drying to obtain a precursor; (2) The precursor powder obtained in step (1) is tableted and then calcined at high temperature in a muffle furnace to obtain a layered oxide material.

4. The method for preparing the Zn / Li / Zr co-doped high voltage P2 layered positive electrode material according to claim 3, characterized in that: The sodium source in step (1) is one or more of sodium carbonate, sodium acetate, sodium nitrate and sodium hydroxide; The nickel source described in step (1) is one or more of nickel oxide, nickel sulfate, nickel carbonate, nickel acetate and nickel nitrate; The manganese source in step (1) is selected from one or more of manganese dioxide, manganese trioxide, manganese nitrate, manganese oxalate and manganese sulfate; The lithium source in step (1) is selected from one or more of lithium carbonate, lithium hydroxide, lithium acetate, and lithium nitrate; The zinc source in step (1) is selected from one or more of zinc oxide, zinc acetate, zinc carbonate and zinc nitrate; The zirconium source described in step (1) is selected from one or more of zirconium oxide and zirconium sulfate.

5. The method for preparing the Zn / Li / Zr co-doped high voltage P2 layered positive electrode material according to claim 3, characterized in that: The dispersant described in step (1) is an alcohol solvent; The ball-milling mixture described in step (1) has a mass ratio of (5-25), a rotation speed of 300-600 rpm, and a ball-milling time of 4h-12h; The drying in step (1) is performed at 40° C. to 80° C. for 6 h to 12 h.

6. The method for preparing the Zn / Li / Zr co-doped high voltage P2 layered positive electrode material according to claim 3, characterized in that: The pressure used for pressing the mixed powder into a sheet in step (2) is 10 to 20 MPa; In step (2), the calcination temperature is 850-1200° C., the heating rate is 1-5° C. / min, the calcination time is 10-16 hours, and the calcination atmosphere includes at least one of air atmosphere, argon atmosphere, oxygen atmosphere, helium atmosphere, and nitrogen atmosphere.

7. Use of the Zn / Li / Zr co-doped high voltage P2 layered positive electrode material according to claim 1 or 2 in sodium ion batteries.

8. A positive electrode plate for a sodium ion battery, characterized in that Prepared by the following steps: (1) Mixing the positive electrode active material according to claim 1 or 2, a conductive agent and a binder in a solvent to prepare a positive electrode slurry; (2) Apply the coating on the aluminum foil current collector using a coating die with a thickness of 100 to 500 μm; (3) Dry in a vacuum oven at 80°C to 120°C for 5 to 12 hours.

9. The positive electrode sheet of a sodium ion battery according to claim 8, characterized in that: The positive electrode active material, conductive agent and binder described in step (1) are mixed in a solvent according to a mass ratio of (8-7):(1-2):1; the conductive agent is one or more of Super-P, carbon black and Ketjen black; the binder is one or more of polyvinylidene fluoride, polyacrylic acid, sodium carboxymethyl cellulose and sodium alginate; the solvent is one of N-methylpyrrolidone and deionized water.

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