Negative electrode material for zinc secondary battery, negative electrode plate and battery

Abstract

In order to solve the problems that an existing nickel-zinc battery is poor in cycle performance and short in service life, the invention provides a negative electrode material for a zinc secondary battery, a negative electrode plate and a battery, the negative electrode material for the zinc secondary battery comprises the following components in percentage by mass: 70-91% of an active substance, 3-10% of an additive and 3-6% of a binder, the additive comprises a first additive, a second additive and a third additive, the first additive contains soluble calcium ions and borate ions.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and particularly relates to a negative electrode material for a zinc secondary battery, a preparation method thereof, a negative electrode sheet, and a battery. Background Art

[0002] Zinc-nickel batteries are green and environmentally friendly batteries that can replace nickel-metal hydride and lead-acid batteries. Compared with nickel-metal hydride and nickel-cadmium batteries, they have the characteristics of high voltage and strong discharge current, and have unparalleled advantages in digital cameras, flashlights, and electric toys. Compared with lead-acid batteries, they have the characteristics of being green and environmentally friendly, high specific power, high specific energy, and good low-temperature performance.

[0003] However, due to the inherent dissolution characteristics of the zinc negative electrode in aqueous nickel-zinc batteries, active material deposition is likely to occur during charge and discharge cycles, manifested as the phenomenon that the upper part of the electrode sheet is thin and the lower part is thick in the later stage of the cycle life, which affects the cycle charge and discharge performance of the battery and restricts the service life of nickel-zinc batteries. In the prior art, Ca(OH)2 is added to the zinc negative electrode slurry, and reacts with the negative electrode active material ZnO in an alkaline environment to form calcium zincate, which has low solubility in the alkaline solution and can effectively alleviate the deposition phenomenon of the negative electrode sheet during the cycle. However, calcium hydroxide is slightly soluble in water. During the preparation of the negative electrode slurry, the slurry becomes alkaline, causing the thickening agent CMC to fail, reducing the fluidity of the slurry during the preparation process, resulting in uneven stirring of the negative electrode slurry, affecting the consistency of the electrode sheet, and further affecting the cycle performance of the battery. Summary of the Invention

[0004] Aiming at the problems of poor cycle performance and short service life of existing nickel-zinc batteries, the present invention provides a negative electrode material, a negative electrode sheet, and a battery for a zinc secondary battery.

[0005] The technical solutions adopted by the present invention to solve the above technical problems are as follows: In the first aspect, the present invention provides a negative electrode material for a zinc secondary battery, including the following mass components: 70% - 91% of active material, 3% - 10% of additive, and 3% - 6% of binder. The additive includes a first additive, and the first additive contains soluble calcium ions and borate ions.

[0006] Optionally, the first additive includes one or more of calcium borate, calcium phosphate, and zinc borate.

[0007] Optionally, in the negative electrode material, the mass content of the first additive is 1% - 3.5%.

[0008] Optionally, the average particle size of the first additive is 100nm - 1μm.

[0009] Optionally, the average particle size of the first additive is 400nm - 800nm.

[0010] Optionally, the additive further includes a second additive, and the second additive includes one or more of Bi2O3, In2O3, KF, Al2O3 fiber cotton, and PP fiber.

[0011] Optionally, the active material includes one or more of ZnO, Zn alloy, and Zn.

[0012] Optionally, the binder includes one or more of carboxymethyl cellulose, polytetrafluoroethylene, styrene-butadiene rubber, and sodium polyacrylate.

[0013] In a second aspect, the present invention further provides a negative electrode sheet, including a current collector and an active material layer disposed on at least one side of the current collector, and the active material layer includes the negative electrode material for a zinc secondary battery described in any one of the above.

[0014] In a third aspect, the present invention provides a battery, including a positive electrode sheet, a separator, an electrolyte, and the negative electrode sheet described above.

[0015] In the present invention, calcium ions and borate ions are introduced simultaneously. The calcium ions can react with ZnO to form calcium zincate, reducing the dissolution of the active material during charge and discharge and improving the deposition phenomenon of the negative electrode sheet. The borate ions can reduce the solubility of Zn in the alkaline solution, improving the cycle performance and storage performance of the battery and increasing the service life of the battery. Specific Embodiments In order to make the technical problems, technical solutions, and beneficial effects solved by the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0016] An embodiment of the present invention provides a negative electrode material for a zinc secondary battery, including the following mass components: 70% - 91% of an active material, 3% - 10% of an additive, and 3% - 6% of a binder. The additive includes a first additive, and the first additive contains soluble calcium ions and borate ions.

[0017] In this embodiment, calcium ions and borate ions are introduced simultaneously. The calcium ions can react with ZnO to form calcium zincate, reducing the dissolution of the active material during charge and discharge and improving the deposition phenomenon of the negative electrode sheet. The borate ions can reduce the solubility of Zn in the alkaline solution, improving the cycle performance and storage performance of the battery and increasing the service life of the battery. In some embodiments, the first additive includes one or more of calcium borate, calcium phosphate, and zinc borate. By using the above first additive to replace calcium hydroxide, the influence of calcium hydroxide addition on the fluidity of the slurry is solved, the consistency of the slurry during the preparation of the negative electrode slurry is improved, and further the performance consistency of the finished battery is improved.

[0018] By selecting the above-mentioned first additive, the deposition phenomenon of the negative electrode sheet is effectively alleviated, and the solubility of Zn in the alkaline solution is reduced.

[0019] In one embodiment, in the negative electrode material, the mass content of the first additive is 1% - 3.5%. The first additive within the above range can further alleviate the deposition phenomenon of the negative electrode sheet, reduce the solubility of Zn in the alkaline solution, and ensure the fluidity of the slurry during the preparation of the negative electrode slurry, thereby improving the consistency of battery performance. In a specific embodiment, the mass content of the first additive includes but is not limited to 1%, 1.3%, 1.6%, 1.9%, 2.2%, 2.5%, 2.8%, 3.1% or 3.5%.

[0020] In some embodiments, the average particle size of the first additive is 100 nm - 1 μm. By selecting the first additive within the above particle size range, the negative electrode material is more easily dispersed uniformly during the preparation of the slurry, ensuring the consistency of the negative electrode sheet.

[0021] In a specific embodiment, the average particle size of the first additive includes but is not limited to 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm or 1 μm.

[0022] In a preferred embodiment, the average particle size of the first additive is 400 nm - 800 nm. The first additive within the above particle size range can further improve the consistency of the negative electrode sheet.

[0023] In some embodiments, the additive further includes a second additive, and the second additive includes one or more of Bi2O3, In2O3, KF, Al2O3 fiber cotton, and PP fiber. By adding indium oxide and bismuth oxide, the hydrogen evolution overpotential of the negative electrode is increased, and at the same time, the growth of zinc dendrites is inhibited. By adding Al2O3 fiber cotton and PP fiber, the toughness of the electrode sheet is enhanced, and the powder shedding condition of the electrode sheet is improved. By adding KF, it helps to disperse ZnO and optimize the dispersibility of the negative electrode slurry.

[0024] In one embodiment, in the negative electrode material, the mass content of the second additive is 2% - 6.5%.

[0025] In some embodiments, the active material includes one or more of ZnO, Zn alloy, and Zn. By adding zinc powder to the active material, the electrochemical capacity of the negative electrode is increased.

[0026] In some embodiments, the binder includes one or more of carboxymethyl cellulose (CMC), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), and sodium polyacrylate. Specifically, the sodium polyacrylate is selected from 5040. By selecting the above binder, the viscosity of the negative electrode paste is regulated to ensure the fluidity of the negative electrode paste formed by the negative electrode material.

[0027] An embodiment of the present invention further provides a negative electrode sheet, which includes a current collector and an active material layer disposed on at least one side of the current collector, and the active material layer includes the negative electrode material for a zinc secondary battery described in any one of the above embodiments.

[0028] Furthermore, the current collector is one of a punched copper strip, a punched tin-plated copper strip, a slant-drawn copper mesh, and a slant-drawn tin-plated copper mesh.

[0029] Specifically, the preparation of the negative electrode sheet includes the following steps: Preparation of the negative electrode paste: (1) According to the content of each mass component in the negative electrode material, 5040 and 3% - 6% of CMC are added to a stirring barrel for mixing, the stirring speed is 150 - 250 rpm, and stirring is carried out for 5 - 10 minutes; (2) Weigh the required Al2O3 fiber or PP fiber and add it to the stirring barrel, adjust the rotation speed to 450 - 550 rpm, and stir for 50 - 70 min; (3) Weigh the required Zn alloy powder, divide it into 3 equal parts, add one part every 5 minutes, adjust the rotation speed to 150 - 250 rpm, and reduce the heat generated by the friction of zinc metal to obtain a glue solution; (4) Weigh the required Bi2O3, In2O3, KF, and calcium borate respectively, add them to the well-stirred glue solution, then adjust the stirring speed to 350 - 450 rpm, and stir for 20 - 40 minutes. During the stirring process, the temperature of the paste is controlled below 25 degrees.

[0030] (5) Adjust the speed of the mixer to 250 - 350 rpm, and while stirring, add the weighed zinc oxide to the batching barrel, and control the powder adding time within 20 - 40 minutes.

[0031] (6) After all the above materials are added, adjust the speed of the mixer to 450 - 550 rpm, and carry out vacuum stirring at below 30 °C for 50 - 70 minutes to obtain the negative electrode paste.

[0032] Coat the negative electrode paste on the negative electrode current collector, and through rolling, softening, cutting, etc., obtain the negative electrode sheet of the nickel-zinc battery.

[0033] An embodiment of the present invention further provides a battery, which includes a positive electrode sheet, a separator, an electrolyte, and the negative electrode sheet described in the above embodiments.

[0034] The present invention will be further described by way of examples below.

[0035] Example 1 This example is used to illustrate the negative electrode material, negative electrode sheet, and battery for the zinc secondary battery disclosed by the present invention.

[0036] Negative electrode sheet The negative electrode material includes 82% zinc oxide, 7% zinc powder, 3% calcium borate (the first additive), 1% bismuth oxide, 0.5% indium oxide, 1.5% PA66 short-cut fibers, and 5% binder (composed of 2% CMC aqueous solution, 60% PTFE aqueous solution, and 38% 5040). The average particle size of calcium borate is 600 nm.

[0037] The negative electrode material is mixed and stirred with pure water to obtain a negative electrode slurry. After the negative electrode slurry is made uniform, it is coated on a copper-plated tin diagonal wire current collector, and then dried, rolled, and cut to obtain a negative electrode sheet.

[0038] Positive electrode sheet 73% spherical β-Ni(OH)2 (nickel hydroxide) with a surface layer coated with trivalent cobalt, 0.03% Ca(OH)2 (calcium hydroxide), 3.5% Ni powder, 0.7% Y2O3 (yttrium trioxide), 2.5% CMC, 1.5% xanthan gum, and the remaining amount being pure water are uniformly mixed to obtain a positive electrode slurry. The slurry is filled and pressed into nickel foam, dried, and then rolled and cut to obtain a positive electrode sheet.

[0039] Electrolyte NaOH and KOH are dissolved in water, ZnO and sodium phytate are added, and after mixing, sodium dihydrogen phosphate is added to adjust the pH of the electrolyte to 12. The concentration of ZnO in the electrolyte is 0.5 M, and the concentration of sodium phytate is 0.1 M.

[0040] Fabrication of the battery: The above positive electrode sheet, separator, and negative electrode sheet are wound / stacked to obtain a bare battery cell. The bare battery cell is placed in an aluminum-plastic film that has been shelled, and top-side sealing is completed. Through processes such as liquid injection, standing, formation, grading, and detection, the battery fabrication is completed.

[0041] Examples 2 to 12 The examples are used to illustrate the negative electrode material for the zinc secondary battery disclosed by the present invention, its preparation method, negative electrode sheet, and battery. It includes most of the operation steps in Example 1, and the difference is that: the formulations in Table 1 are adopted.

[0042] Comparative Examples 1 to 4 The comparative examples are used to comparatively illustrate the negative electrode material for the zinc secondary battery disclosed by the present invention, its preparation method, negative electrode sheet, and battery. It includes most of the operation steps in Example 1, and the difference is that: the formulations in Table 1 are adopted.

[0043] Table 1 Performance Test I. Perform the following performance tests on the batteries obtained from the above-mentioned examples and comparative examples: Battery activation method: 1. 0.05C * 10h, rest for 10 min, 0.05C - 1.3V; 2. 0.1C * 10h, rest for 10 min, 0.1C - 1.3V; 3. Charge at 0.2C to 1.9V, switch to constant voltage charging until the current ≤ 0.01C, 0.2C - 1.3V; (Taking the 2A1400 model battery as an example, the theoretical capacity is 1400 mAh, and 0.2C is 280 mAh).

[0044] Cycle performance test: 1. Charging: Constant current charging at 1C, 1.9V, rest for 10 min; Constant voltage charging at 1.9V, I < 0.01C, rest for 10 min; 2. Discharging: Constant voltage discharging at 1C, 1.2V, the battery is cycled 300 times.

[0045] Pole piece consistency test: Use the three-point method to measure the thickness of the pole piece, and then calculate the standard deviation STDEVA of the three thickness measurement values. A standard deviation < 0.01 is considered qualified.

[0046] The test results are shown in Table 2.

[0047] Table 2 From the test results of Examples 1 - 5, 12 and Comparative Examples 1 - 4 in Table 2, it can be seen that when the additive contains both soluble calcium ions and borate ions, the influence of calcium hydroxide addition on the slurry fluidity can be avoided, and the consistency of the negative electrode sheet can be improved. When the content of the first additive is less than 1% or higher than 3.5%, both the capacity retention rate of the battery and the consistency of the negative electrode sheet deteriorate. From the test results of Examples 1 and 6 - 11, it can be seen that when the average particle size of the first additive is less than 100 nm or higher than 1 μm, the consistency of the negative electrode sheet is significantly poor.

[0048] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A negative electrode material for a zinc secondary battery, characterized in that The invention comprises the following components by mass: 70% to 91% of active substances, 3% to 10% of additives and 3% to 6% of binders, wherein the additives include a first additive containing soluble calcium ions and borate ions.

2. The negative electrode material for zinc secondary battery according to claim 1, characterized in that: The first additive includes one or more of calcium borate, calcium phosphate, and zinc borate.

3. The negative electrode material for zinc secondary battery according to claim 2, characterized in that: In the negative electrode material, the mass content of the first additive is 1% to 3.5%.

4. The negative electrode material for zinc secondary battery according to claim 2, characterized in that: The average particle size of the first additive is 100 nm to 1 μm.

5. The negative electrode material for zinc secondary battery according to claim 4, characterized in that: The average particle size of the first additive is 400nm~800nm.

6. The negative electrode material for zinc secondary battery according to claim 1, characterized in that: The additives also include a second additive, which includes one or more of Bi2O3, In2O3, KF, Al2O3 fiber cotton, and PP fiber.

7. The negative electrode material for zinc secondary battery according to claim 1, characterized in that: The active material includes one or more of ZnO, Zn alloy and Zn.

8. The negative electrode material for zinc secondary battery according to claim 1, characterized in that: The binder includes one or more of carboxymethyl cellulose, polytetrafluoroethylene, styrene-butadiene rubber, and sodium polyacrylate.

9. A negative electrode sheet, characterized in that: It comprises a current collector and an active material layer arranged on at least one side of the current collector, wherein the active material layer comprises the negative electrode material for a zinc secondary battery according to any one of claims 1 to 8.

10. A battery, characterized in that: The invention comprises a positive electrode sheet, a separator, an electrolyte and the negative electrode sheet as claimed in claim 9.

Images