A kind of acicular spherical nickel powder and its preparation method and use

Abstract

The present application relates to a kind of thorn ball nickel powder and its preparation method and use, the oxygen content in the thorn ball nickel powder is less than 0.45%, carbon content is less than 0.1%, the balance is nickel;The tap density of the thorn ball nickel powder is 1.5~2.8g / cm 3 , Particle size≤10.5 μm;The outer surface of the thorn ball nickel powder is uniformly and completely coated with the oxidation layer with thickness of 2~5nm, the oxidation layer of the thorn ball nickel powder is amorphous coating layer, and the nickel core is in the oxidation layer, and the crystallinity of the nickel core is >99%.The thorn ball nickel powder of the present application can be used in the slurry part of photovoltaic cell instead of silver, and the thorn ball nickel powder has high oxidation resistance, high lap conductive property and good sintering stability.

Description

Technical Field

[0001] This invention relates to the field of metal nanomaterials technology, specifically to a spiky nickel powder, its preparation method, and its uses. Background Technology

[0002] Crystalline silicon solar cells are photovoltaic devices based on semiconductor materials. They utilize the built-in electric field of a PN junction to achieve the photovoltaic effect, converting solar radiation into electrical energy. Their main types include monocrystalline silicon, polycrystalline silicon, and amorphous silicon thin-film cells. Currently, crystalline silicon solar cells primarily use silver paste for screen printing, drying, and high-temperature sintering. Research institutions and companies mainly focus on cost reduction in two aspects: firstly, optimizing the cell structure design to improve the conversion efficiency of photovoltaic cells; and secondly, reducing the manufacturing cost of existing processes. The latter mainly involves replacing or reducing silver, such as using electroplated Cu or Ag-coated Cu powder instead of silver powder. However, electroplated Cu has a higher overall process cost and is more difficult to control environmentally. Ag-coated Cu powder is only suitable for low-temperature sintered HJT cells. Copper diffuses rapidly in silicon, easily causing low cell efficiency and abnormalities, thus it is not suitable for high-temperature sintering. Furthermore, Cu has insufficient weather resistance and stability.

[0003] Nickel has good weather resistance and a high melting point, making it an ideal alternative to partially replace silver. However, on the one hand, the sintering atmosphere for crystalline silicon is air, and the sintering speed is fast. During this sintering process, Ni powder is easily oxidized and loses its conductivity. Furthermore, mainstream gas-atomized Ni powder, water-atomized Ni powder, and evaporation-condensation Ni powder all suffer from low yields (below 10%) in this particle size range (3-5 micrometers). On the other hand, the spherical powder structure also leads to low conductive overlap, which further results in severe conductivity degradation after replacing silver with nickel powder, making it difficult to meet the high conversion efficiency requirements of photovoltaic cells. Summary of the Invention

[0004] The purpose of this invention is to provide a spiky nickel powder that can partially replace silver and has high oxidation resistance, high lap conductivity and good sintering stability, as well as its preparation method and uses.

[0005] A spiky nickel powder, wherein the oxygen content is less than 0.45%, the carbon content is less than 0.1%, and the balance is nickel; the tap density of the spiky nickel powder is 1.5~2.8 g / cm³. 3 Particle size ≤10.5μm; The outer surface of the spiky nickel powder is uniformly and completely covered with an oxide layer with a thickness of 2-5 nm.

[0006] Spiky spherical nickel powder specifically refers to a spherical matrix with numerous protruding spiky structures growing on its surface. Specifically, the spherical matrix has a relatively clear outline, while the spiky structures extend outwards from the spherical surface, giving the particles a "spiky spherical" shape. The spherical surface is not smooth but covered with tiny protrusions resembling "spiky points"; these spiky structures increase the surface roughness and specific surface area of ​​the particles, and the spiky structures are relatively evenly distributed on the spherical matrix.

[0007] Furthermore, the oxide layer of the spiky nickel powder of the present invention is an amorphous coating layer, and the oxide layer contains nickel nuclei with a crystallinity >99%. The crystallinity of the nickel nuclei in the spiky nickel powder significantly affects its conductivity, and its conductivity increases with increasing crystallinity.

[0008] Furthermore, the D50 of the spiky nickel powder of the present invention satisfies 1.2μm≤D50≤6.5μm.

[0009] A method for preparing spiky nickel powder based on any of the above-described methods includes the following steps: 1) Add an appropriate amount of sodium hydroxide to the nickel salt aqueous solution until the pH is 10-12, filter, wash and disperse to obtain a nickel hydroxide suspension; 2) Add an appropriate amount of hydrazine hydrate to the nickel hydroxide suspension, and react at a temperature of 80℃~120℃ and a stirring speed of 300r / min~500r / min for 30min~150min to obtain a mixed solution. The reaction pressure is 0.3~0.5MPa. 3) The mixture is filtered, washed, and then vacuum dried to obtain primary nickel powder; 4) The raw nickel powder is placed in a deionized water saturated solution of water-soluble salt to perform salt coating treatment to obtain coated powder; 5) After filtering and drying the coated powder, heat it to 700~850℃ in a hydrogen atmosphere and hold it at that temperature for 0.5~2h to obtain crystallized powder. 6) The crystallized powder is ultrasonically cleaned, filtered, and dried in deionized water to obtain crude nickel powder; 7) The crude nickel powder is pre-oxidized by a treatment agent and then coated with a coupling agent to obtain any of the above-mentioned spiky nickel powders.

[0010] Furthermore, in the preparation method described in this invention, the mass ratio of nickel hydroxide to water in the nickel hydroxide suspension in step 1) is 1:(2.5~4.7); the mass ratio of hydrazine hydrate to nickel hydroxide added in step 2) is (2.5~3.5):1. The amount of sodium hydroxide added in step 1) must be appropriate. If too much sodium hydroxide is added, the reducing agent's reducing power will be enhanced, and the powder particle size will decrease; if too little is added, the reduction will be insufficient. Too much nickel hydroxide in the nickel hydroxide suspension will cause a relative decrease in the concentration of the reducing agent in the system, resulting in incomplete reduction; too little will cause an increase in the reduction rate, and a decrease in the powder particle size.

[0011] In step 2), excessive hydrazine hydrate enhances the reducing power, resulting in rapid powder reduction and smaller particle size; insufficient hydrazine hydrate prolongs the reaction time, leading to incomplete reduction. Furthermore, the reaction temperature in step 2) should not be too high or too low. Excessive temperature results in high energy consumption, fine powder particle size, and agglomeration; excessively low temperature leads to excessively long reaction times, causing slow growth of primary powder particles. Excessively long reaction time in step 2) increases energy consumption; too short a time results in incomplete reaction; each has its negative impact. Excessively high reaction pressure in step 2) increases production control difficulty and increases powder nucleation rate, resulting in finer particle size; too low a pressure leads to rapid deterioration of powder particle size uniformity. Excessively fast stirring speed in step 2) increases energy consumption and hinders powder particle growth; too slow a speed results in uneven mass transfer, uneven powder particle size, and agglomeration.

[0012] If the heating temperature in the hydrogen atmosphere in step 5) is too high, the powder will form a sintering neck and agglomerate, resulting in particle size growth; if it is too low, the reaction will be incomplete and the degree of powder crystallization will decrease. If the holding time in the hydrogen atmosphere in step 5) is too long, the powder will form a sintering neck and agglomerate, resulting in particle size growth; if it is too low, the reaction will be incomplete and the degree of powder crystallization will decrease.

[0013] Furthermore, in the preparation method of the present invention, the pH value of the mixture in step 2) is >11.

[0014] Furthermore, in the preparation method of the present invention, the nickel salt aqueous solution in step 1) includes any one or a combination of NiCl2, NiNO3, NiSO4 or NiC2O4 solution.

[0015] Furthermore, in the preparation method of the present invention, the water-soluble salt in step 4) includes any one or a combination of NaCl, K2SO4, KCl, Na2SO4, and Na2C2O4.

[0016] Furthermore, in the preparation method of the present invention, the treatment agent in step 7) is any one or a combination of potassium dichromate, phosphite, polyvinylpyrrolidone, dodecyl mercaptan, and citric acid; the coupling agent is at least one of silane coupling agent, titanate coupling agent, aluminate coupling agent, zirconate coupling agent, or zirconium aluminate coupling agent.

[0017] Furthermore, in the preparation method of the present invention, the pre-oxidation treatment process in step 7) includes preparing a deionized aqueous solution with a treatment agent concentration of 0.1~0.2 mol, immersing the crude nickel powder in the above-mentioned treatment agent-deionized aqueous solution at room temperature for 0.5~1 h, and then washing it multiple times.

[0018] Furthermore, in the preparation method of the present invention, the coupling agent coating in step 7) includes: preparing a solution of coupling agent with a mass of 0.5~1.0%, and hydrolyzing the coupling agent in the solution for 1~2 hours. The solvent is 95% water and 5% ethanol. Then, crude nickel powder that has undergone oxidation treatment is added, and the mixture is stirred and reacted for 0.5~1.0 hours. Finally, the mixture is washed multiple times at room temperature and dried at 60~80°C to obtain any of the above-described spiky nickel powders.

[0019] Furthermore, in the preparation method described in this invention, the ultrasonic cleaning temperature in deionized water in step 6) is 50~80℃. Excessively high ultrasonic cleaning temperatures increase process difficulty and energy consumption, while excessively low temperatures reduce washing efficiency, increasing the number of washing cycles and waste liquid volume.

[0020] An application of a spiky nickel powder, wherein the spiky nickel powder is any of the spiky nickel powders described above, and the spiky nickel powder prepared by any of the spiky nickel powder preparation methods described above, wherein the spiky nickel powder is used in the slurry of photovoltaic cells to replace silver.

[0021] Due to the requirements of screen printing, if the particle size of the spiky nickel powder is greater than 10.5μm, it will cause screen clogging and fail to meet the usage requirements. Conversely, if the particle size of the spiky nickel powder is too small, it is easy to oxidize during high-temperature sintering, causing the wire resistance to rise rapidly and significantly deteriorating the conversion efficiency Eff of the photovoltaic panel. Therefore, the spiky nickel powder described in this invention must meet the following requirements: particle size ≤ 10.5μm, and 1.2μm ≤ D50 ≤ 6.5μm.

[0022] The sintering atmosphere for photovoltaic silver paste is air, which has strong oxidizing properties. Therefore, incompletely coated spiky nickel powder is prone to uncontrollable rapid oxidation during sintering, resulting in excessively high sintering resistance. Moreover, because the nickel powder is spiky with a sharp surface morphology covered with tiny protrusions resembling "spiky points," an excessively thin coating makes it difficult to ensure coating integrity, while an excessively thick coating significantly deteriorates the lap conductivity of the nickel powder, increasing the sintering resistance.

[0023] Compared with the prior art, the present invention has the following beneficial technical effects: This invention fundamentally solves the industry challenge of simultaneously achieving conductivity, oxidation resistance, and stability of nickel powder in photovoltaic pastes through the synergistic design of a unique "spiky spherical" morphology and a "homogeneous oxide layer." On one hand, the sharp, protruding spherical structure significantly increases the specific surface area and surface roughness of the particles, enabling them to form more and more effective physical contact points in the paste, thereby constructing a highly conductive three-dimensional conductive network and significantly improving "overlap conductivity." On the other hand, the uniform, complete, and precisely controlled-thickness amorphous oxide layer (2-5 nm) acts like a dense "armor" for the highly reactive nickel core. Under air sintering conditions, this oxide layer effectively blocks oxygen diffusion into the core, preventing further deep oxidation of nickel and loss of conductivity, thus endowing the material with high oxidation resistance and good sintering stability.

[0024] Secondly, the preparation method of this invention establishes physical isolation between primary powder particles through "salt coating" treatment, followed by a "hydrogen reduction crystallization" step. This significantly increases the crystallinity of the nickel core to over 99% while avoiding sintering and agglomeration, laying the foundation for high conductivity. Subsequently, a nanoscale oxide layer of controllable thickness is generated in situ on the surface of the spiked balls through pre-oxidation with a treatment agent. Finally, a coupling agent is used to further improve the dispersion and compatibility of the powder in the organic slurry system. The entire process chain is interconnected, especially the precise control of key parameters (such as the ratio of reducing agent, crystallization temperature, and oxidant concentration), which ensures the stability and reproducibility of the final product's morphology, purity, crystallinity, and coating quality, solving the problems of low yield and uneven performance of traditional methods.

[0025] The spiky spherical nickel powder (Ni A) prepared using the method of this invention, after replacing 20% ​​of the silver powder, shows only a very slight decrease in the battery's conversion efficiency (Eff%) (-0.012%), and the increase in series resistance (Rs) is negligible. Its overall electrical performance is far superior to untreated raw powder (Ni C, performance substandard NG) and commercially available near-spherical nickel powder (Ni D, with significant efficiency degradation). The spiky spherical nickel powder of this invention has excellent compatibility with existing photovoltaic silver paste processes and sintering conditions. It can meet the fineness requirements of screen printing (D50≤6.5μm, particle size≤10.5μm) and maintain stable performance under harsh air sintering conditions, providing a practical and feasible high-performance material solution for cost reduction in the photovoltaic industry. Attached Figure Description

[0026] Figure 1 This is a microscopic morphology diagram of the spiky nickel powder described in this invention; Figure 2 This is a transmission electron microscope image of the spiky nickel powder described in this invention. Figure 3 This is an HRTEM morphology image of the spiky nickel powder described in this invention. Detailed Implementation

[0027] To provide a clearer understanding of the technical features, objectives, and effects of this invention, specific embodiments are now described in detail with reference to the accompanying drawings. The described embodiments are merely some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. Where specific conditions are not specified in the detailed embodiments, conventional conditions or conditions recommended by the manufacturer shall apply.

[0028] In the following description, when referring to the accompanying drawings, the same numbers in different drawings denote the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of this disclosure.

[0029] The present invention will be further described in detail below with reference to specific embodiments. Specific Implementation Method 1

[0030] A spiky nickel powder, wherein the oxygen content is less than 0.45%, the carbon content is less than 0.1%, and the balance is nickel; the tap density of the spiky nickel powder is 1.5~2.8 g / cm³. 3 Particle size ≤10.5μm; The outer surface of the spiky nickel powder is uniformly and completely covered with an oxide layer with a thickness of 2-5 nm.

[0031] In other embodiments, the oxide layer is an amorphous coating layer, and the oxide layer contains a nickel core with a crystallinity > 99%.

[0032] In other embodiments, the D50 of the spiked nickel powder satisfies 1.2μm≤D50≤6.5μm. Specific Implementation Method Two

[0033] A method for preparing the spiky nickel powder according to any of the above embodiments includes the following steps: 1) Add an appropriate amount of sodium hydroxide to the nickel salt aqueous solution until the pH is 10-12, filter, wash and disperse to obtain a nickel hydroxide suspension; 2) Add an appropriate amount of hydrazine hydrate to the nickel hydroxide suspension, and react at a temperature of 80℃~120℃ and a stirring speed of 300r / min~500r / min for 30min~150min to obtain a mixed solution. The reaction pressure is 0.3~0.5MPa. 3) The mixture is filtered, washed, and then vacuum dried to obtain primary nickel powder; 4) The raw nickel powder is placed in a deionized water saturated solution of water-soluble salt to perform salt coating treatment to obtain coated powder; 5) After filtering and drying the coated powder, heat it to 700~850℃ in a hydrogen atmosphere and hold it at that temperature for 0.5~2h to obtain crystallized powder. 6) The crystallized powder is ultrasonically cleaned, filtered, and dried in deionized water to obtain crude nickel powder; 7) The crude nickel powder is pre-oxidized by a treatment agent and then coated with a coupling agent to obtain any of the above-mentioned spiky nickel powders.

[0034] In other embodiments, the mass ratio of nickel hydroxide to water in the nickel hydroxide suspension in step 1) is 1:(2.5~4.7); the mass ratio of hydrazine hydrate to nickel hydroxide added in step 2) is (2.5~3.5):1.

[0035] In other embodiments, the pH value of the mixture described in step 2) is >11.

[0036] In other embodiments, the nickel salt aqueous solution in step 1) includes any one or a combination of NiCl2, NiNO3, NiSO4, or NiC2O4 solutions.

[0037] In other embodiments, the water-soluble salt in step 4) includes any one or a combination of NaCl, K2SO4, KCl, Na2SO4, and Na2C2O4.

[0038] In other embodiments, the treatment agent in step 7) is any one or a combination of potassium dichromate, phosphite, polyvinylpyrrolidone, dodecyl mercaptan, and citric acid; the coupling agent is at least one of silane coupling agent, titanate coupling agent, aluminate coupling agent, zirconate coupling agent, or zirconium aluminate coupling agent.

[0039] In other embodiments, the temperature for ultrasonic cleaning in deionized water in step 6) is 50~80°C. Specific Implementation Method 3

[0040] An application of a spiky nickel powder, wherein the spiky nickel powder is the spiky nickel powder described in any of the above embodiments, or the spiky nickel powder prepared by the preparation method of the spiky nickel powder described in any of the above embodiments, and the spiky nickel powder is used to replace silver in the slurry of photovoltaic cells. Example 1

[0041] A method for preparing spiky nickel powder includes the following steps: 1) Add an appropriate amount of sodium hydroxide to the nickel salt aqueous solution until the pH is 10-12, filter, wash and disperse to obtain a nickel hydroxide suspension; 2) Add an appropriate amount of hydrazine hydrate to the nickel hydroxide suspension, and react at a temperature of 80℃~90℃ and a stirring speed of 400r / min~500r / min for 60min~150min to obtain a mixed solution. The reaction pressure is 0.3~0.5MPa. 3) The mixture is filtered, washed, and then vacuum dried to obtain primary nickel powder; 4) The raw nickel powder is placed in a deionized water saturated solution of water-soluble salt to perform salt coating treatment to obtain coated powder; 5) After filtering and drying the coated powder, heat it to 800~850℃ in a hydrogen atmosphere and keep it at that temperature for 1~2 hours to obtain crystallized powder. 6) The crystallized powder is ultrasonically cleaned, filtered, and dried in deionized water to obtain crude nickel powder; 7) The crude nickel powder is pre-oxidized by a treatment agent and then coated with a coupling agent to obtain #1 spiky nickel powder.

[0042] In this Example 1, the mass ratio of nickel hydroxide to water in the nickel hydroxide suspension in step 1) is 1:4; the mass ratio of hydrazine hydrate to nickel hydroxide added in step 2) is 3:1. The nickel salt aqueous solution in step 1) is NiSO4. The water-soluble salt in step 4) is K2SO4. The treatment agent in step 7) is potassium dichromate; the coupling agent is a titanate coupling agent. The ultrasonic cleaning temperature in deionized water in step 6) is 70°C.

[0043] The oxygen content of the No. 1 spiky nickel powder is 0.35%, and the tap density is 2.3~2.4 g / cm³. 3 The particle size is <10.2μm, the D50 is 4.2μm, the crystallinity of the nickel core is 99.2%, and the oxide layer thickness is 3~4nm. Example 2

[0044] The only difference between this embodiment 2 and embodiment 1 is that: In step 1), the mass ratio of nickel hydroxide to water in the nickel hydroxide suspension is 1:3; the nickel salt aqueous solution in step 1) is NiCl2. In step 4), the water-soluble salt is NaCl. In step 7), the coupling agent is a silane coupling agent.

[0045] The obtained No. 2 spiky nickel powder has an oxygen content of 0.40% and a tap density of 2.2~2.3 g / cm³. 3 The particle size is <9.6μm, the D50 is 3.8μm, the crystallinity of the nickel core is 99.1%, and the oxide layer thickness is 3~5nm. Example 3

[0046] The only difference between Example 3 and Example 1 is that: In this Example 3, the nickel salt aqueous solution in step 1) is NiNO3. The water-soluble salt in step 4) is KCl. The treatment agent in step 7) is polyvinylpyrrolidone; the coupling agent is a silane coupling agent.

[0047] The obtained No. 3 spiky nickel powder has an oxygen content of 0.40% and a tap density of 2.1~2.3 g / cm³. 3 The particle size is <10.5μm, the D50 is 4.5μm, the crystallinity of the nickel core is 99.0%, and the oxide layer thickness is 3~5nm. Example 4

[0048] The only difference between Example 4 and Example 1 is that: In step 2), the mass ratio of hydrazine hydrate to nickel hydroxide added is 2.5:1. In step 1), the nickel salt aqueous solution is NiC2O4. In step 4), the water-soluble salt is Na2SO4. In step 7), the treatment agent is citric acid; the coupling agent is an aluminate coupling agent. In step 6), the ultrasonic cleaning temperature in deionized water is 70℃.

[0049] The obtained No. 4 spiky nickel powder has an oxygen content of 0.38% and a tap density of 2.5~2.7 g / cm³. 3 The particle size is <10.2μm, the D50 is 3.9μm, the crystallinity of the nickel core is 99.0%, and the oxide layer thickness is 2~3nm. Example 5

[0050] The only difference between Example 5 and Example 1 is that: In step 1), the mass ratio of nickel hydroxide to water in the nickel hydroxide suspension is 1:2.5; in step 2), the mass ratio of hydrazine hydrate to nickel hydroxide is 3.5:1. The nickel salt aqueous solution in step 1) is NiC2O4. The water-soluble salt in step 4) is Na2SO4. The treatment agent in step 7) is citric acid; the coupling agent is an aluminate coupling agent.

[0051] The obtained No. 4 spiky nickel powder has an oxygen content of 0.37% and a tap density of 2.1~2.2 g / cm³. 3 The particle size is <8.9μm, the D50 is 3.5μm, the crystallinity of the nickel core is 99.1%, and the oxide layer thickness is 2~3nm.

[0052] Comparative Example 1: The only difference between Comparative Example 1 and Example 1 is that: In this Example 1, the mass ratio of nickel hydroxide to water in the nickel hydroxide suspension in step 1) is 1:2; the mass ratio of hydrazine hydrate to nickel hydroxide added in step 2) is 4:1. The nickel salt aqueous solution in step 1) is NiC2O4. The water-soluble salt in step 4) is Na2SO4. The treatment agent in step 7) is citric acid; the coupling agent is an aluminate coupling agent.

[0053] The obtained nickel powder has an oxygen content of 0.45%, a tap density of 2.0~2.1 g / cm3, a particle size of <7.0 μm, a D50 of 0.8 μm, a crystallinity of 98.7% for the nickel core, and an oxide layer thickness of 4~5 nm.

[0054] Comparative Example 2: The only difference between Comparative Example 2 and Example 1 is that: In this Example 1, the mass ratio of nickel hydroxide to water in the nickel hydroxide suspension in step 1) is 1:1; the mass ratio of hydrazine hydrate to nickel hydroxide added in step 2) is 4:1. The nickel salt aqueous solution in step 1) is NiNO3. The water-soluble salt in step 4) is NaCl. The treatment agent in step 7) is citric acid; the coupling agent is a zirconate ester coupling agent.

[0055] The obtained nickel powder has an oxygen content of 0.57% and a tap density of 1.8~2.0 g / cm³. 3 The particle size is <5.1μm, the D50 is 0.4μm, the crystallinity of the nickel core is 96.1%, and the oxide layer thickness is 3~4nm. Example 6

[0056] The #1 spiky spherical nickel powder obtained in Example 1 was named Ni A. Ni B, which underwent only antioxidant treatment without organic coating, was prepared according to the process in Example 1. Ni C, which underwent neither antioxidant treatment nor organic coating, was prepared using the same process. Commercially available spherical nickel powder, Ni D, was selected as a control sample. The commercially available powder was spherical nickel powder with a particle size of D50 of 2.0 μm produced by Boqian New Materials.

[0057] The four powders mentioned above were respectively mixed with glass powder, resin and silver powder of a fixed formula to form a slurry, wherein the amount of powder added accounted for 20% of the silver powder. After squeegee printing, the slurry was sintered and cured at 750°C in air atmosphere.

[0058] Test IV characteristics by simulating the measurement of current-voltage curves under sunlight.

[0059] Standard Test Conditions (STC): Irradiance: AM 1.5G spectrum, irradiance 1000 W / m²; Temperature: 25±2℃; Environment: Nitrogen or air atmosphere to prevent sample oxidation. Eff / Eta: Photoelectric conversion efficiency = maximum output power / incident light power (1000 W / m²).

[0060] Uoc: Open-circuit voltage, the voltage value when I=0.

[0061] Isc: Short-circuit current, the current value when V=0.

[0062] Rs: Series resistance, calculated from the slope of the IV curve near Voc.

[0063] Rsh: Parallel resistance, calculated from the slope of the IV curve near Isc.

[0064] FF / %: Fill factor, a measure of the "rectangularity" of the battery IV curve, representing the ratio of maximum output power to Isc×Uoc, in percentage (%).

[0065] Table 1. Electrical performance data after use as solar energy paste and sintering: Eff% Uoc / mV Isc / A Rs / mΩ Rsh / Ω Ni A (antioxidant + organic coating) -0.012 -0.1 0.014 0.0001 120 Ni B (antioxidant) -0.004 0.2 0.007 0.00001 160 Ni C (untreated raw powder) NG NG NG NG NG Ni D (spherical nickel powder) -0.463 0.9 0.0002 0.015 780 In Table 1, NG represents the baseline comparison value for other values. As shown in Table 1, the nickel powder treated with anti-oxidation and organic coating exhibits excellent dispersion uniformity in silver paste, and does not significantly reduce the conversion efficiency Eff of the system after high-temperature sintering. The series resistance and parallel resistance data also show only a small increase, indicating that the spiky nickel powder described in this invention has excellent sintering compatibility and anti-oxidation ability after treatment, and has great application potential.

[0066] Table 2. Performance test results of solar slurry Isc / A Uoc / V Eta / % FF / % Rs / Ω Wet weight / mg Baseline 16.230 0.7422 26.96 85.41 -0.00089 54.3 Experimental Example 16.232 0.7423 26.73 84.69 -0.00059 56.0 In Table 2, the baseline is the control sample without added nickel powder; the experimental example is the replacement of 10% of the silver powder with spiky nickel powder.

[0067] This invention has been described through the specific embodiments described above. Those skilled in the art should understand that various modifications and equivalent substitutions can be made to this invention without departing from its scope. Parts not described in detail in this specification are well-known to those skilled in the art. Furthermore, various modifications can be made to this invention for specific situations or circumstances without departing from the scope of this application. Therefore, this invention is not limited to the specific embodiments disclosed, but should include all embodiments falling within the scope of the claims of this invention.

Claims

1. A spiky nickel powder, characterized in that, The spiky nickel powder has an oxygen content of less than 0.45%, a carbon content of less than 0.1%, and the balance is nickel; the tap density of the spiky nickel powder is 1.5~2.8 g / cm³. 3 Particle size ≤10.5μm; The outer surface of the spiky nickel powder is uniformly and completely covered with an oxide layer with a thickness of 2-5 nm.

2. The spiky nickel powder according to claim 1, characterized in that, The oxide layer is an amorphous coating layer, and the oxide layer contains nickel cores with a crystallinity greater than 99%.

3. The spiky nickel powder according to claim 2, characterized in that, The D50 of the spiky nickel powder satisfies 1.2μm≤D50≤6.5μm.

4. A method for preparing spiky nickel powder according to any one of claims 1 to 3, characterized in that, Includes the following steps: 1) Add an appropriate amount of sodium hydroxide to the nickel salt aqueous solution until the pH is 10-12, filter, wash and disperse to obtain a nickel hydroxide suspension; 2) Add an appropriate amount of hydrazine hydrate to the nickel hydroxide suspension, and react at a temperature of 80℃~120℃ and a stirring speed of 300r / min~500r / min for 30min~150min to obtain a mixed solution. The reaction pressure is 0.3~0.5MPa. 3) The mixture is filtered, washed, and then vacuum dried to obtain primary nickel powder; 4) The raw nickel powder is placed in a deionized water saturated solution of water-soluble salt to perform salt coating treatment to obtain coated powder; 5) After filtering and drying the coated powder, heat it to 700~850℃ in a hydrogen atmosphere and hold it at that temperature for 0.5~2h to obtain crystallized powder. 6) The crystallized powder is ultrasonically cleaned, filtered, and dried in deionized water to obtain crude nickel powder; 7) The crude nickel powder is pre-oxidized by a treatment agent and then coated with a coupling agent to obtain the spiky nickel powder as described in any one of claims 1 to 3.

5. The preparation method according to claim 4, characterized in that, In step 1), the mass ratio of nickel hydroxide to water in the nickel hydroxide suspension is 1:(2.5~4.7); in step 2), the mass ratio of hydrazine hydrate to nickel hydroxide is (2.5~3.5):

1. The pH value of the mixture described in step 2) is >11.

6. The preparation method according to claim 4, characterized in that, The nickel salt aqueous solution in step 1) includes any one or a combination of NiCl2, NiNO3, NiSO4 or NiC2O4 solutions.

7. The preparation method according to claim 4, characterized in that, In step 4), the water-soluble salt includes any one or a combination of NaCl, K2SO4, KCl, Na2SO4, and Na2C2O4.

8. The preparation method according to claim 4, characterized in that, The treatment agent in step 7) is any one or a combination of potassium dichromate, phosphite, polyvinylpyrrolidone, dodecyl mercaptan, and citric acid; the coupling agent is at least one of silane coupling agent, titanate coupling agent, aluminate coupling agent, zirconate coupling agent, or zirconium aluminate coupling agent.

9. The preparation method according to claim 4, characterized in that, In step 6), the ultrasonic cleaning temperature in deionized water is 50~80℃.

10. The use of a spiky nickel powder, characterized in that, The spiky nickel powder is the spiky nickel powder according to any one of claims 1 to 3, and the spiky nickel powder prepared by the preparation method of the spiky nickel powder according to any one of claims 4 to 9. The spiky nickel powder is used in the slurry of photovoltaic cells to replace silver.

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