A negative electrode material for zinc batteries and a preparation method and application thereof

Abstract

The application discloses a negative electrode material for a zinc battery and a preparation method and application thereof. The negative electrode material comprises a cellulose / conductive agent composite framework and zinc oxide, the cellulose / conductive agent composite framework is composed of a 3D cellulose network uniformly loaded with a conductive agent, and the zinc oxide is uniformly grown on the cellulose / conductive agent composite framework. The negative electrode material has excellent conductive performance, can effectively inhibit dendrite growth and electrode deformation, and when the negative electrode material is applied to a zinc secondary battery, the cycle life and specific capacity of the zinc secondary battery are significantly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of negative materials, specifically relates to a kind of negative material for zinc battery, and also relates to its preparation method and application, belongs to secondary battery technical field. BACKGROUND

[0002] Alkaline zinc secondary battery uses alkaline aqueous solution as electrolyte, compared with lithium ion battery using organic electrolyte system has high safety, environmental protection and easy operation etc.Advantages.At the same time, with zinc or zinc oxide as negative active material, with high volume capacity density and low price etc.Features, therefore, receives extensive attention.However, zinc negative electrode in the process of charge and discharge exists dendrite growth, electrode deformation, hydrogen evolution corrosion etc.Problems, lead to battery capacity reduction, cycle stability and rate performance deterioration etc., seriously restricts the commercialization process of zinc secondary battery.

[0003] Therefore, the structure design of zinc negative electrode is proposed to improve the performance of zinc negative electrode.Especially, zinc negative electrode with high specific surface area and porosity of 3D porous structure or network structure, shows stronger effect of inhibiting dendrite growth and electrode deformation than traditional two-dimensional material.Yan Y.etc.in the document“A Lasagna-Inspired Nanoscale ZnO Anode Design for High-Energy Rechargeable Aqueous Batteries”proposed a kind of zinc oxide / graphene oxide composite material with “lasagna” network structure, improved the capacity and cycle life of zinc negative electrode.But, the uneven distribution of zinc oxide in graphene oxide framework, lead to its capacity retention rate is lower (only 150 cycles greater than 80%) during cycle process.Wang.S etc.in the document“Conversion of cotton cellulose to ZnO / C anodes for lithium-ion batteries via a sustainable self-assembly process in a green solvent”compared the surface characteristics of 3D porous structure precursor and the final product of carbon-coated structure, found that although the precursor has higher specific surface area and porosity, but its average pore size is larger, which means that compared with other structures, 3D porous structure or network structure usually cannot effectively block the dissolution of zincate, and increase the contact area of active material and electrolyte, aggravate hydrogen evolution corrosion, reduce the cycle performance of zinc negative electrode. SUMMARY

[0004] In view of the deficiencies existing in the prior art, the first object of the present application is to provide a kind of negative material for zinc battery.The material has excellent electrical conductivity, can effectively inhibit dendrite growth and electrode deformation.

[0005] A second object of the present application is to provide a preparation method of a negative electrode material for zinc batteries.

[0006] A third object of the present application is to provide an application of a negative electrode material for zinc batteries.

[0007] In order to achieve the above technical objects, the present application provides a negative electrode material for zinc batteries, which comprises a cellulose / conductive agent composite framework and zinc oxide, wherein the cellulose / conductive agent composite framework is composed of a 3D cellulose network uniformly loaded with a conductive agent, and the zinc oxide is uniformly grown on the cellulose / conductive agent composite framework.

[0008] The present application forms a continuous and uniform conductive network framework by the combination of cellulose and conductive agent, enhances the conductive performance of the material, relieves the deformation of the electrode, in addition, the hydroxyl groups in the cellulose are conducive to promoting the uniform dispersion of zinc oxide, and can anchor the zincate ion, an intermediate product in the charging and discharging process, to inhibit the deformation of the electrode and the loss of active material, at the same time, the negative charge on the surface of cellulose is easy to form a continuous conductive network with the conductive agent, which not only reduces the impedance of the material, but also inhibits the growth of dendrites. Compared with the currently applied carbon material framework, the 3D conductive network framework formed by cellulose and conductive agent not only has the effect of enhancing the conductivity of the electrode and relieving the deformation of the electrode in the charging and discharging process as the carbon framework, but also has the effect that the carbon framework does not have, such as the adsorption of zinc ions and the anchoring of zincate, among which, the adsorption of zinc ions can realize the uniform deposition of the in-situ generated active material (zinc oxide), the anchoring of zincate can effectively inhibit the growth of zinc dendrites and the loss of active material, and the electrochemical performance of the material is improved.

[0009] As a preferred scheme, the mass ratio of the zinc oxide to the cellulose and the conductive agent is 70-90:5-15:5-15. The content of zinc oxide as the active material determines the capacity of the material, too low content will reduce the energy density of the material, and too high content will lead to the agglomeration of zinc oxide and reduce the utilization rate of active material; the cellulose as the main material of the framework determines the stability of the material, too low content will reduce the structural strength and stability of the material, and too high content will reduce the conductivity of the material; the conductive agent mainly improves the conductivity of the material, too low content will lead to poor conductivity of the material, and too high content will affect the energy density of the material.

[0010] As a preferred scheme, in the negative electrode material, the content of zinc oxide is 70-90wt%, the content of cellulose is 5-15wt%, and the content of conductive agent is 5-15wt%.

[0011] As a preferred scheme, the particle size of the zinc oxide is 10-100nm.

[0012] As a preferred scheme, the cellulose comprises cellulose nanofibers and cellulose microfibers.

[0013] As a preferred scheme, the mass ratio of the cellulose nanofibers to the cellulose microfibers is 7-9.9:3-0.1.

[0014] The specific surface area of the cellulose microfibers is smaller than that of the cellulose nanofibers, and the cellulose microfibers have fewer action sites with zinc ions and zinc acid radicals. When the amount of the cellulose microfibers is too high, the uniformity of the zinc oxide distribution is reduced, the zinc dendrite inhibition effect is reduced, the capacity of the material is weakened, and the cycle stability and cycle life are reduced. When the amount of the cellulose nanofibers is too high, the structural stability of the material is relatively reduced.

[0015] As a preferred scheme, the cellulose nanofibers comprise cellulose nanofiber A, cellulose nanofiber B and cellulose nanofiber C, wherein the cellulose nanofiber A has a diameter of 20-30 nm and a length of 600-900 nm; the cellulose nanofiber B has a diameter of 30-50 nm and a length of 900-1200 nm; and the cellulose nanofiber C has a diameter of 50-70 nm and a length of 1200-1500 nm. The present application improves the performance of the material by using multiple cellulose nanofibers. The cellulose nanofiber B used in the present application can make the material have a higher specific surface area, a more complete conductive network, and more uniform zinc oxide deposition, which is conducive to inhibiting the growth of zinc negative electrode dendrites and improving the capacity of the negative electrode material. The cellulose nanofiber A and the cellulose nanofiber C can enhance the effect of the cellulose nanofiber B and improve the local mechanical strength of the material.

[0016] As a preferred scheme, the mass ratio of the cellulose nanofiber A, the cellulose nanofiber B and the cellulose nanofiber C is 1.5-1:8.5-8.25:0.5-0.25.

[0017] As a preferred scheme, the cellulose microfibers comprise cellulose microfiber X and cellulose microfiber Y, wherein the cellulose microfiber X has a diameter of 80-100 nm and a length of 10-15 μm, and the cellulose microfiber Y has a diameter of 90-120 nm and a length of 20-24 μm. The combination of the cellulose microfibers can enhance the overall mechanical strength of the negative electrode material.

[0018] As a preferred scheme, the mass ratio of the cellulose microfiber X to the cellulose microfiber Y is 1.5-4.5:0.5-1.5.

[0019] As a preferred scheme, the conductive agent comprises carbon black and carbon nanotubes. The conductive agent used in the application is an electrically neutral conductive carbon material, wherein the carbon black is a spherical carbon particle that can be uniformly adsorbed on the surface of the negatively charged cellulose long chain to form a continuous conductive network, which not only improves the conductivity of the material, but also uniformly distributes the current and inhibits dendrite growth; the carbon nanotube is a fibrous conductive carbon material that can be crosslinked with the cellulose chain to enhance the conductivity of the material and improve the mechanical strength of the material.

[0020] As a preferred scheme, the carbon black comprises at least one of Super P, acetylene black and ketjen black.

[0021] As a preferred scheme, the carbon nanotube comprises single-walled carbon nanotubes and / or multi-walled carbon nanotubes.

[0022] As a preferred scheme, the mass ratio of the carbon black to the carbon nanotube is 5-9.9:5-0.1. More preferably, the mass ratio of the carbon black to the carbon nanotube is 8.5-9.5:1.5-0.5. Controlling the ratio of the amount of carbon black to the amount of carbon nanotube in the conductive agent in a suitable range is beneficial to improve the performance of the material. When the amount of carbon black in the conductive agent is too low, the amount of carbon black attached to the surface of the cellulose per unit will decrease, the continuity of the conductive network will decrease, and the impedance of the material will increase. When the amount of carbon nanotube is too low, the conductivity and stability of the material will relatively decrease.

[0023] The application also provides a preparation method of a negative electrode material for a zinc battery. The method comprises dispersing a zinc source, cellulose and a conductive agent in a solvent, adding an alkali and stirring to react, and then performing solid-liquid separation on the obtained reaction product to obtain a precipitate, mixing the precipitate with water and performing freeze-drying, thereby obtaining the negative electrode material.

[0024] In the application, the zinc ions can be adsorbed due to the interaction between the hydroxyl groups in the cellulose and the zinc ions in the zinc source, and the generated zinc oxide particles are uniformly deposited in the network framework. Meanwhile, the interaction between the hydroxyl groups in the cellulose and the zincate ions can effectively anchor the intermediate product zincate ions in the charging and discharging process, and inhibit the deformation of the electrode and the loss of active substances.

[0025] As a preferred scheme, the mass ratio of the zinc source to the cellulose is 13-27:0.5-1.5. The content of the zinc source determines the content of the zinc oxide in the final product, so when the proportion of the zinc source is too high, the generated zinc oxide is prone to agglomeration, which reduces the utilization rate of active substances; when the proportion of the zinc source is too low, the surface capacity of the material will decrease.

[0026] As a preferred scheme, the mass ratio of the cellulose to the conductive agent is 1-2:1-2.

[0027] As a preferred scheme, the concentration of the zinc source in water is 0.32-0.58 mol / L. Controlling the concentration of the zinc source in a proper range is beneficial to obtaining a composite material with excellent performance, and a too high concentration will cause serious cellulose dissolution and affect the stability of the material, and a too low concentration will affect the uniformity of the active material distribution.

[0028] As a preferred scheme, the concentration of the cellulose in water is 2.24-7.91 mg / mL. Controlling the concentration of the cellulose in a proper range is beneficial to obtaining a composite material with excellent performance, and when the concentration of the cellulose is too high, the cellulose is easy to aggregate into a colloidal state in water, which will cause the material synthesis to be unable to continue; and when the concentration is too low, the mechanical strength of the final product will be reduced, affecting the stability of the material.

[0029] As a preferred scheme, the concentration of the conductive agent in water is 1.12-15.82 mg / mL.

[0030] As a preferred scheme, the zinc source comprises at least one of zinc chloride, zinc nitrate, zinc sulfate and zinc acetate.

[0031] As a preferred scheme, the cellulose comprises cellulose nanofibers and cellulose microfibers, and the mass ratio of the cellulose nanofibers to the cellulose microfibers is 6-9.8:4-0.2.

[0032] As a preferred scheme, the conductive agent comprises carbon black and carbon nanotubes, and the mass ratio of the carbon black to the carbon nanotubes is 8-9:2-1.

[0033] As a preferred scheme, the molar ratio of the alkali to the zinc source is 2-4:1.

[0034] As a preferred scheme, the alkali comprises sodium hydroxide and / or potassium hydroxide.

[0035] As a preferred scheme, the stirring reaction process is that the stirring reaction is carried out at 30-80℃ for 1-5 h.

[0036] As a preferred scheme, the freeze-drying process is that the freeze-drying is first carried out at-48℃ to-68℃ for 24-48 h, and then the freeze-drying is carried out at-8℃ to-18℃ for 12-36 h. In the present application, two-stage freeze-drying treatment is adopted, the first-stage quick freezing can make the final product have sufficient porosity and the pore size will not be too large, and the second-stage slow freezing can prevent the material structure from collapsing seriously and also accelerate the material drying process.

[0037] The present application also provides an application of a negative electrode material for a zinc battery, which is applied to a negative electrode of an alkaline zinc secondary battery.

[0038] Compared with the prior art, the present application has the following beneficial effects:

[0039] (1) The electrode material has a 3D open network structure, the framework is composed of self-crosslinked cellulose with conductive agent attached, forming a uniform electric field distribution, relieving dendrite growth, at the same time, the 3D network structure design increases the specific surface area of the material, accelerates the mass transfer rate, and also can well improve the capacity decay and low cycle life caused by electrode deformation and dendrite growth;

[0040] (2) Using cellulose as the framework material, zinc oxide particles are generated in situ in the conductive network framework formed by cellulose and conductive agent, so that the zinc oxide is more uniformly distributed, and the cellulose can anchor zincate ions, an intermediate product in the charging and discharging process, to inhibit electrode deformation and active material loss, in addition, the negative charge on the surface of cellulose is easy to complex with conductive agent to form a continuous conductive network, which not only reduces the impedance of the material but also inhibits dendrite growth;

[0041] (3) Using cellulose loaded with conductive agent as the framework material, it has good adhesion and conductivity in aqueous solution, changing the method of adding additional binder and conductive agent when preparing traditional electrode materials, and improving the active material loading content in the electrode;

[0042] (4) The preparation method is simple, the cost is low, and it is convenient for large-scale industrial production, and the material has excellent cycle performance and coulombic efficiency when used as the negative electrode material of zinc secondary battery. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 The structure schematic diagram of the negative electrode material for zinc battery prepared by the present application.

[0044] Figure 2 The low magnification transmission electron microscopy diagram of the composite material prepared in Example 1.

[0045] Figure 3 The high magnification transmission electron microscopy diagram of the composite material prepared in Example 1. DETAILED DESCRIPTION

[0046] The following detailed description is a further detailed description of the present application, the examples are carried out within the scope of the present application, and do not limit the protection scope of the present application.

[0047] The carbon nanotubes used in the present application are purchased from Shanghai Maikelin Biochemical Technology Co., Ltd., and the product models are C805971 and C805976 respectively.

[0048] The cellulose used in the present application is purchased from Beifang Century (Jiangsu) Cellulose Material Co., Ltd.

[0049] Example 1

[0050] The cellulose nanofibers used in the preparation process include cellulose nanofiber A, cellulose nanofiber B and cellulose nanofiber C, wherein the diameter of cellulose nanofiber A is 20-30 nm and the length is 600-900 nm; the diameter of cellulose nanofiber B is 30-50 nm and the length is 900-1200 nm; the diameter of cellulose nanofiber C is 50-70 nm and the length is 1200-1500 nm.

[0051] The cellulose micron fibers used in the preparation process include cellulose micron fibers X and cellulose micron fibers Y, wherein the cellulose micron fibers X have a diameter of 80 to 100 nm and a length of 10 to 15 μm, and the cellulose micron fibers Y have a diameter of 90 to 120 nm and a length of 20 to 24 μm.

[0052] The following is the specific preparation process of negative electrode materials for zinc batteries:

[0053] 3.602g of zinc acetate dihydrate, 0.167g of a conductive agent (Super P to single-walled carbon nanotubes, mass ratio: 9.5:0.5), and 0.167g of cellulose (cellulose nanofiber to cellulose microfiber, mass ratio: 9.8:0.2, with cellulose nanofibers A, B, and C in a 1:8:1 mass ratio, and cellulose microfibers X and Y in a 1:1 mass ratio) were added to 30mL of deionized water and stirred in a 55°C water bath for 1 hour to obtain Solution A. 1.313g of sodium hydroxide was slowly added to Solution A and stirred at 55°C for 3 hours to obtain Solution B. Solution B was washed by centrifugation three times, added with 20mL of deionized water, and frozen at -48°C. The material was then placed in a freeze dryer and dried for 24 hours. The material was then removed, frozen at -18°C, and dried again for 36 hours to obtain the zinc oxide@cellulose / conductive agent composite. Testing revealed that the composite had an impedance of approximately 10Ω.

[0054] The microstructure of the composite material was characterized, such as Figure 2 As shown, from Figure 2 It can be seen that the cellulose and conductive agent composite chains are cross-linked to form a network skeleton, and zinc oxide grows on the composite chains. Figure 2 Local magnification Figure 3 ,from Figure 3 It can be seen that the conductive carbon black is evenly distributed on the surface of the cellulose chain in a spherical shape, and the zinc oxide appears as regular rod-shaped particles with a particle size of 20-100nm and is relatively evenly distributed.

[0055] Take the above zinc oxide @ cellulose / conductive agent composite material, add appropriate amount of deionized water to prepare zinc paste material, apply it on the copper mesh current collector with an area of ​​1cm × 1cm and compact it to 0.3mm thickness to obtain zinc negative electrode. -1 KOH and 0.5 mol L -1 A zinc oxide composite solution was used as the electrolyte and sintered nickel was used as the positive electrode. A zinc-nickel secondary battery was assembled and subjected to charge and discharge cycle tests. The test results are shown in Table 1.

[0056] Example 2

[0057] 1.852g of zinc sulfate, 0.15g of a conductive agent (mass ratio of acetylene black to multi-walled carbon nanotubes = 8.5:1.5), and 0.2g of cellulose (mass ratio of cellulose nanofibers to cellulose microfibers = 9.5:0.5, mass ratio of cellulose nanofibers A:cellulose nanofibers B:cellulose nanofibers C = 1.5:7:1.5, mass ratio of cellulose microfibers X:cellulose microfibers Y = 2:1) were added to 20mL of deionized water and stirred in a 40°C water bath for 2 hours to obtain Solution A. 1.835g of sodium hydroxide was slowly added to Solution A and stirred at 40°C for 5 hours to obtain Solution B. Solution B was washed by centrifugation three times, added with 20mL of deionized water, and frozen at -58°C. The material was then placed in a freeze dryer and dried for 24 hours. The material was removed, frozen at -8°C, and dried again for 24 hours to obtain the zinc oxide@cellulose / conductive agent composite. Testing showed that the impedance of the composite was 10-30Ω.

[0058] A nickel-zinc secondary battery was assembled in the manner of Example 1 and subjected to charge and discharge cycle tests. The results are shown in Table 1.

[0059] Example 3

[0060] 1.888g of zinc sulfate, 0.2g of a conductive agent (mass ratio of SuperP to single-walled carbon nanotubes = 9:1), and 0.1g of cellulose (mass ratio of cellulose nanofibers to cellulose microfibers = 9:1, mass ratio of cellulose nanofibers A: cellulose nanofibers B: cellulose nanofibers C = 1:8:1, mass ratio of cellulose microfibers X: cellulose microfibers Y = 1:1) were added to 20mL of deionized water and stirred in an 80°C water bath for 3 hours to obtain solution A. 1.376g of sodium hydroxide was slowly added to solution A and stirred at 80°C for 5 hours to obtain solution B. Solution B was centrifuged and washed three times, then added with 20mL of deionized water and frozen at -68°C. The material was then placed in a freeze dryer and dried for 48 hours. The material was then removed, frozen at -18°C, and dried again for 12 hours to obtain the zinc oxide@cellulose / conductive agent composite. Testing showed that the composite had an impedance of 10-30Ω.

[0061] Zinc-nickel secondary batteries were assembled in the manner of Example 1 and subjected to charge-discharge cycle tests, and the results are shown in Table 1.

[0062] Example 4

[0063] Example 4

[0064] Zinc-nickel secondary batteries were assembled in the manner of Example 1 and subjected to charge-discharge cycle tests, and the results are shown in Table 1.

[0065] Example 5

[0066] Example 5

[0067] Zinc-nickel secondary batteries were assembled in the manner of Example 1 and subjected to charge-discharge cycle tests, and the results are shown in Table 1.

[0068] Comparative Example 1

[0069] The composite material was prepared in the manner of Example 1, except that the amount of cellulose added was 0.501 g.

[0070] Comparative Example 2

[0071] The composite material was prepared by the method of Example 1, except that the amount of cellulose added was 0.0167 g.

[0072] Comparative Example 3

[0073] The composite material was prepared by the method of Example 1, except that solution B was dried at 80°C after centrifugal washing.

[0074] Comparative Example 4

[0075] The composite material was prepared by the method of Example 1, except that solution B was dried at 80°C after washing by suction filtration.

[0076] Comparative Example 5

[0077] The composite material was prepared by the method of Example 1, except that no conductive agent was added.

[0078] Comparative Example 6

[0079] The composite material was prepared by the method of Example 1, except that the conductive agent was only single-walled carbon nanotubes.

[0080] Comparative Example 7

[0081] The composite material was prepared by the method of Example 1, except that the conductive agent was only Super P.

[0082] Comparative Example 8

[0083] The composite material was prepared by the method of Example 1, except that 10 ml of deionized water was added when preparing solution A.

[0084] Comparative Example 9

[0085] The composite material was prepared by the method of Example 1, except that it was frozen at -48°C and dried in a freeze dryer for 72 h.

[0086] The composite materials prepared in Comparative Examples 1-9 were assembled into zinc-nickel secondary batteries by the method of Example 1, and subjected to charge-discharge cycle tests, with the results shown in Table 1.

[0087] Table 1

[0088]

[0089] As can be seen from Table 1, the performance of the material is affected by multiple factors, for example, the amount of cellulose added directly affects the cycle life of the battery, especially when the amount of cellulose is small, the stability of the battery decreases significantly; when the conductive agent contains carbon black and carbon nanotubes, the cycle stability of the battery is higher than that of a single component, and when no conductive agent is added, the battery cannot work normally; the drying method also affects the performance of the material, and the performance of the material is severely attenuated by drying, while the performance of the battery is more ideal by freeze-drying; when the concentration of zinc source is too high, the stability and capacity of the material decrease significantly.

Claims

1. A negative electrode material for a zinc battery, characterized in that: It includes a cellulose / conductive agent composite skeleton and zinc oxide, wherein the cellulose / conductive agent composite skeleton is composed of a conductive agent uniformly loaded on a 3D cellulose network, and the zinc oxide is uniformly grown on the cellulose / conductive agent composite skeleton; The mass ratio of zinc oxide to cellulose and conductive agent is 70-90:5-15:5-15; The cellulose comprises cellulose nanofibers and cellulose microfibers; The mass ratio of the cellulose nanofibers to the cellulose microfibers is 7-9.9:3-0.

1.

2. A negative electrode material for zinc batteries according to claim 1, characterized in that: The conductive agent comprises carbon black and carbon nanotubes; The mass ratio of the carbon black to the carbon nanotubes is 5-9.9:5-0.

1.

3. The method for preparing a negative electrode material for a zinc battery according to claim 1 or 2, characterized in that: The zinc source, cellulose and conductive agent are dispersed in water, and then a base is added to carry out stirring reaction. The obtained reaction product is subjected to solid-liquid separation to obtain a precipitate, and the precipitate is mixed with water and freeze-dried to obtain the product.

4. The method for preparing a negative electrode material for a zinc battery according to claim 3, wherein: The mass ratio of the zinc source to the cellulose is 13-27:0.5-1.5; The mass ratio of the cellulose to the conductive agent is 1-2:1-2; The concentration of the zinc source in water is 0.32-0.58 mol / L; The concentration of the cellulose in water is 2.24-7.91 mg / mL; The concentration of the conductive agent in water is 1.12-15.82 mg / mL.

5. The method for preparing a negative electrode material for a zinc battery according to claim 3 or 4, wherein: The zinc source includes at least one of zinc chloride, zinc nitrate, zinc sulfate, and zinc acetate dihydrate; The cellulose comprises cellulose nanofibers and cellulose microfibers, and the mass ratio of the cellulose nanofibers to the cellulose microfibers is 6-9.8:4-0.2; The conductive agent includes carbon black and carbon nanotubes, and the mass ratio of the carbon black to the carbon nanotubes is 8-9:2-1.

6. The method for preparing a negative electrode material for a zinc battery according to claim 3, wherein: The molar ratio of the base to the zinc source is 2 to 4:1; The base includes sodium hydroxide and / or potassium hydroxide.

7. The method for preparing a negative electrode material for a zinc battery according to claim 3, wherein: The stirring reaction process is: stirring the reaction at 30-80° C. for 1-5 hours; The freeze-drying process is as follows: first, freeze-drying at -48°C to -68°C for 24 to 48 hours, and then freeze-drying at -8°C to -18°C for 12 to 36 hours.

8. The use of a negative electrode material for zinc batteries according to claim 1 or 2, characterized in that: Used in alkaline zinc secondary battery negative electrode.

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