Background
Compared to lithium ion batteries using flammable and toxic organic electrolytes, water-based Zinc Ion Batteries (ZIBs) based on water-based electrolytes are a novel energy storage system with low cost, environmental protection, and safety, and may be applied to power grid energy storage systems and wearable devices in the future. In recent years, research on positive electrodes, zinc negative electrodes and electrolyte solutions of water-based ZIBs has been advanced, but the water-based ZIBs still face great challenges in terms of positive electrodes and negative electrodes. Problems such as cathode dissolution, adverse effects from electrostatic interactions, zinc dendrites, corrosion, passivation and byproducts can lead to capacity degradation, low coulombic efficiency, short circuits and the like of the water system ZIBs, which severely limits the development and commercialization of the water system ZIBs.
Among the many causes of the reduction in battery life of aqueous zinc ion batteries using aqueous electrolytes, zinc dendrites are one of the problems that are very difficult to solve. The zinc dendrite is characterized in that in the process of repeatedly generating battery reaction by taking zinc as a battery active substance, when eutectic alloy is crystallized, a later precipitated phase is precipitated by attaching to the surface of a leading phase to form a dual-phase core with a two-phase common growth interface, then solute atoms are used for transversely diffusing between two phases at the front edge of the interface to mutually and continuously provide components required by growth for each other, so that the two phases grow together, and finally a binary interphase lamellar structure is formed. The zinc dendrite will be higher than the battery electrode plate to pierce the diaphragm between the substrates, which is easy to cause short circuit failure of the battery. In addition, pure zinc is corroded to form ZnO and Zn (OH) on the surface during the charge and discharge of the aqueous electrolyte2The by-products affect the electric field distribution on the surface of the negative electrode, and the uneven deposition behavior after multiple charge and discharge processes can accelerate the growth of zinc dendrites, so that the time for puncturing the diaphragm is advanced, and the service life of the battery is further prolonged.
In the prior art, a complex negative electrode body is prepared by a special electrodeposition mode, for example, CN110660970A discloses a flexible self-supporting three-dimensional layered MXene/zinc composite electrode and a preparation method and application thereof. The three-dimensional layered MXene film is composed of one or a mixture of more than two of Ti3C2, Nb4C3, Ti2C, Ta4C3, TiNbC, (V0.5Cr0.5)3C2, V2C, Nb2C, Ti3CN, Ti3C2, Ti2C, Ta4C3, TiNbC, (V0.5Cr0.5)3C2, V2C, Nb2C, Nb4C3 or Ti3CN, and is loaded with zinc. The zinc-doped lithium ion battery has larger specific surface area, can load more zinc, can be used as a zinc metal negative electrode or a current collector of a lithium metal electrode, and can well inhibit the growth of zinc dendrites. In addition, CN110492069A discloses a synthesis method of a Zn @ metal organic framework composite electrode material, wherein the method comprises the steps of placing an AA type zinc cylinder treated by hydrochloric acid, acetone and methanol in a 2-methylimidazole methanol solution with a certain concentration, carrying out hydrothermal reaction, cleaning and drying to obtain the Zn @ ZiF-8 composite electrode material; the preparation method has the advantages of low energy consumption, simple and easily obtained raw materials, cheap used materials, simple operation, easy realization and realization of industrial production; the Zn @ ZiF-8 prepared by the method can effectively inhibit the growth of zinc dendrites, so that the cycle life of the battery is prolonged. Furthermore, CN108767215A discloses a material for inhibiting zinc dendrite, and a preparation method and an application thereof, wherein the material is a composite material of a zinc-based material and a simple substance carbon material, the zinc-based material is in a powder form or a plate form or a sheet form, and the simple substance carbon material is coated on the surface of the zinc-based material powder particles or attached to the surface of a zinc-based material plate or sheet. According to the invention, the metal zinc simple substance material is modified, the carbon layer is coated on the surface of the zinc plate, or the carbon layer is coated around the zinc powder particles, so that the obtained composite material can effectively inhibit the growth of zinc dendrites, and particularly can be used as a negative electrode material to be applied to a water-based zinc-based battery to exert the performance of inhibiting the growth of the zinc dendrites.
However, the cost of the cathode for suppressing dendrite production prepared by the method is too high, and the methods such as electrodeposition, organic compound method, sputtering and the like which are applied to the cathode are obviously incapable of large-scale industrial production. There is still a great need in the industry for a more simple and feasible negative electrode material capable of inhibiting the growth of zinc dendrites.
Disclosure of Invention
In order to achieve the purpose of realizing a simple and feasible negative electrode material capable of inhibiting the growth of zinc dendrites, through intensive research and experiments, the inventor finds that the zinc-aluminum-magnesium alloy prepared according to the proportion can effectively inhibit the formation of the zinc dendrites through the control of a cooling process, and finally improves the service life and the performance of the water system zinc ion battery.
Specifically, the invention aims to provide a preparation method of a cathode of a water-based zinc ion battery, which is simple to operate and easy to realize industrial production, and the method takes the prepared zinc-aluminum-magnesium alloy with the nanometer grain size as a cathode material of the battery, can obviously inhibit the growth phenomenon of zinc dendrites, greatly improves the cycle reversibility of the cathode material of the water-based zinc ion battery, and greatly prolongs the service life of the battery.
The specific embodiment of the invention is a preparation method of a cathode of an aqueous zinc ion battery, which comprises the following steps:
a metal material preparation process, wherein the metal zinc material, the aluminum material and the magnesium material are weighed according to the weight ratio of 83-88% of the zinc material, 11-15% of the aluminum material and 1-2% of the magnesium material, and the oxide layer is removed;
a smelting preparation process, namely putting the zinc material, the aluminum material and the magnesium material prepared in the metal material preparation process into a container, wherein the arrangement mode of the metal is that the magnesium material and the aluminum material are uniformly put on the lower layer, and the zinc material is tiled on the aluminum material and the magnesium material;
a heating and smelting step, namely heating and smelting zinc materials, aluminum materials and magnesium materials in a heating furnace in a protective atmosphere or a vacuum environment, controlling the temperature of molten alloy at 520-570 ℃, and controlling the heat preservation time at 5-10 minutes;
a speed-controlled cooling procedure, namely pouring the smelted melt into a mould for cooling and forming to obtain the zinc-aluminum-magnesium alloy, wherein the cooling rate is controlled to be R in the processT~5RTSpeed of (d), in units of ℃/s, said RTSatisfies the following relation formula,
wherein alpha is1Is the weight percentage of aluminum in unit percent; alpha is alpha2Is the weight proportion of magnesium, unit percent,
and an alloy shaping step of shaping the zinc-aluminum-magnesium alloy obtained in the speed-controlled cooling step into a required shape.
In a preferred embodiment, in the metal material preparation step, the zinc material is one selected from the group consisting of a zn99.995 zinc material, a zn99.99 zinc material, a zn99.95 zinc material, and a zn99.5 zinc material.
In a preferred embodiment, in the metallic material preparation step, the aluminum material is one selected from the group consisting of 1a99 aluminum material, 1a97 aluminum material, 1a95 aluminum material, and 1a93 aluminum material.
In a preferred embodiment, in the metal material preparation step, the magnesium material is one selected from the group consisting of MA18 magnesium material, commercially pure magnesium material, and MA21 magnesium material.
In a preferred embodiment, in the metal material preparation step, the oxide layer removal treatment is a step of mechanically polishing the surface of a zinc metal material, an aluminum material, or a magnesium material, performing a surface treatment using 75% alcohol or industrial acetone, and drying the surface.
In a preferred embodiment, in the controlled cooling step, the cooling rate is controlled to be RT~2RTSpeed of (d), unit ℃/s.
In a preferred embodiment, the heating and melting step performs melting in a protective atmosphere of argon or nitrogen, and stirring is used to ensure uniformity of melting.
The invention also provides an aqueous zinc ion battery negative electrode, which is manufactured by the preparation method. The invention also provides a battery using the cathode.
The invention has the following advantages:
the preparation method of the cathode of the water system zinc ion battery has the advantages that the required equipment is very common, the technological process is not complicated, compared with the conventional methods for preparing the cathode of the zinc ion battery for inhibiting dendritic crystals, such as electrolysis, electrodeposition, sputtering and the like, the method greatly improves the process operability, and is very beneficial to industrialization. The cathode of the water-based zinc ion battery prepared by the invention has excellent effect of inhibiting zinc dendrite generation, and can greatly improve the service life and performance of the water-based zinc ion battery.
Detailed Description
The present invention will be described in more detail below.
The preparation method of the cathode of the water system zinc ion battery mainly comprises the following steps:
a metal material preparation process, wherein the metal zinc material, the aluminum material and the magnesium material are weighed according to the weight ratio of 83-88% of the zinc material, 11-15% of the aluminum material and 1-2% of the magnesium material, and the oxide layer is removed;
a smelting preparation process, namely putting the zinc material, the aluminum material and the magnesium material prepared in the metal material preparation process into a container, wherein the arrangement mode of the metal is that the magnesium material and the aluminum material are uniformly put on the lower layer, and the zinc material is tiled on the aluminum material and the magnesium material;
a heating and smelting step, namely heating and smelting zinc materials, aluminum materials and magnesium materials in a heating furnace in a protective atmosphere or a vacuum environment, controlling the temperature of molten alloy at 520-570 ℃, and controlling the heat preservation time at 5-10 minutes;
a speed-controlled cooling procedure, namely pouring the smelted melt into a mould for cooling and forming to obtain the zinc-aluminum-magnesium alloy, wherein the cooling rate is controlled to be R in the processT~5RTSpeed of (d) in units of ℃/s, RTSatisfies the following relation formula,
wherein alpha is1Is the weight percentage of aluminum in unit percent; alpha is alpha2Is the weight proportion of magnesium, unit percent,
and an alloy shaping step of shaping the zinc-aluminum-magnesium alloy obtained in the speed-controlled cooling step into a required shape.
In the metal material preparation step, the source of the zinc material, aluminum material, or magnesium material is not particularly limited, and any simple material may be used. From the viewpoints of easy availability of raw materials and convenient operation, the zinc material is one selected from Zn99.995 zinc materials, Zn99.99 zinc materials, Zn99.95 zinc materials and Zn99.5 zinc materials, the aluminum material is one selected from 1A99 aluminum materials, 1A97 aluminum materials, 1A95 aluminum materials and 1A93 aluminum materials, and the magnesium material is one selected from MA18 magnesium materials, industrial pure magnesium materials and MA21 magnesium materials.
The weight ratio of 83-88% of zinc material, 11-15% of aluminum material and 1-2% of magnesium material is very important, the ratio determines the microscopic grain structure in the zinc alloy plate, the inventor finds that the proper ratio of aluminum and magnesium elements is mixed, the metal surface ion stripping and deposition process has higher stability, so that the electrochemical reaction of the zinc alloy material produced in the ratio is more uniform on the surface of the zinc alloy, the dendritic crystal growth is particularly favorably inhibited when the zinc alloy material is used in a battery, and the activity of the zinc alloy material as an active material is basically unaffected compared with that of a pure zinc material.
The treatment for removing the oxide layer is not limited, and any common physical or chemical method capable of removing the surface oxidation of these metal materials may be used. Generally, a zinc material, an aluminum material, or a magnesium material is mechanically polished on the surface, and is subjected to surface treatment using 75% alcohol or industrial acetone, and then dried for use.
The melting preparation step includes placing a zinc material, an aluminum material, or a magnesium material in a container, and the container may be any container suitable for melting, and for example, a graphite crucible or a corundum crucible may be used as long as impurities are not introduced during melting. Preferably, a graphite crucible is used.
In the preparation process, the arrangement mode of the metal is that the magnesium material and the aluminum material are uniformly placed on the lower layer, and the zinc material is flatly laid on the aluminum material and the magnesium material, the main reason is that the arrangement mode can enable the smelting liquid to be rapidly and uniformly distributed, because the aluminum and the magnesium which are input in small quantities are all metals with light specific gravity, and if the aluminum and the magnesium are placed on the zinc, the metals are difficult to be rapidly and uniformly mixed.
The heating and melting step is an oxygen-free melting process, and may be performed in a heating apparatus in a closed oxygen-free environment, for example, a sealed electromagnetic induction furnace or the like, and it is preferable to perform melting in a protective atmosphere of argon or nitrogen. In addition, if the heating means can provide stirring, the uniformity of melting can be further ensured, and therefore, it is preferable.
The temperature of the alloy melt is controlled to 520-570 ℃, the heat preservation time is controlled to 5-10 minutes, and the condition relates to the microstructure of the product zinc alloy material.
The rate-controlled cooling process is an important step in the present invention, and the inventors have found that it is only guaranteed to satisfy the above RT~5RTThe zinc alloy material prepared at the speed of the method can play a corresponding role in inhibiting zinc dendrites. The reason why this step is important is deduced by the inventors as follows:
the speed-controlled cooling can refine the crystal grains of the zinc alloy, even the size of the crystal grains reaches the nanometer level, and the refined crystal grains can improve the intercrystalline corrosion resistance of the zinc cathode, so that the uniform deposition of zinc ions on the surface of the cathode can be realized, the formation of zinc dendrites is greatly reduced, and the service life and the performance of the water system zinc ion battery are finally improved.
The inventors have found that when R is higher than RTWhen the speed is controlled and cooled, the zinc alloy with good capability of inhibiting dendritic crystals can be obtained, if the speed is too high, the speed is difficult to control, and 5RTThe speed of the speed can meet the requirement.
In conclusion, compared with the existing pure zinc cathode material, the zinc-aluminum-magnesium alloy prepared according to the proportion realizes grain refinement through rapid cooling, so that the grain size reaches the nanometer level, on one hand, the aluminum and magnesium elements enable the metal surface ions to have higher stability in the stripping and deposition processes, the surface corrosion resistance of the zinc cathode is increased, on the other hand, the refined grains can increase the intercrystalline corrosion resistance of the zinc cathode, thereby realizing the uniform deposition of the zinc ions on the cathode surface, greatly reducing the formation of zinc dendrites, and finally improving the service life and the performance of the water system zinc ion battery. In a preferred embodiment, in the controlled cooling step, the cooling rate is controlled to be RT~2RTSpeed of (d), unit ℃/s.
The zinc alloy obtained by the above method can be directly used for the cathode of the water-based zinc ion battery by proper shaping, and is not only an active material but also a current collector. The charge and discharge capacity of the battery manufactured by the zinc oxide positive electrode material is not greatly different from that of a battery with a negative electrode made of pure zinc, but the performance of inhibiting dendrites is very obvious. FIG. 4 shows a 2mA cm symmetric cell assembled by small sheets of Zn-Al-Mg alloy cathode prepared in example 1 of the present invention-2The surface morphology of the zinc-aluminum-magnesium alloy negative electrode after cycling at current density is greatly inhibited from dendrites, compared to the morphology of the negative electrode in the battery prepared with the pure zinc negative electrode of fig. 5.
Hereinafter, a method for producing a negative electrode for an aqueous zinc ion battery according to the present invention will be further described with reference to examples, in which Sn represents the code of the process step.
Example 1
Preparing an electrode:
s1, preparing Zn99.995 zinc material, 1A99 aluminum material and industrial pure magnesium, and mechanically polishing to remove surface oxides;
s2, according to weight: zinc material: 86.7g, aluminum material: 12g, magnesium material: 1.3g, cutting the material for standby;
s3, wiping the surface with alcohol, removing oil stain on the surface with acetone, wiping the surface with alcohol to remove residual acetone, and drying with a blower for later use;
s4, putting the proportioned metal material into a graphite crucible, firstly putting an aluminum block at the bottom of the crucible, then uniformly putting a magnesium block on the aluminum block, and finally putting a zinc block;
s5, heating and smelting in an electromagnetic induction furnace in a protective atmosphere or vacuum environment, wherein the smelting temperature is 530 ℃, the heat preservation time is 6min, and the smelting uniformity is ensured by utilizing electromagnetic stirring;
s6, pouring the smelted melt into a mould for cooling and forming, wherein the cooling speed is 220 ℃/S (about R)T) Obtaining zinc-aluminum-magnesium alloy;
s7, preparing the zinc-aluminum-magnesium alloy into a small negative electrode sheet, wherein the small negative electrode sheet is in a disc shape with the size of 12mm in diameter and 2mm in thickness.
Battery preparation i.e. cycling test:
the prepared zinc-aluminum-magnesium alloy cathode small sheets are assembled into a CR2025 symmetrical button cell, and compared with a CR2025 symmetrical button cell assembled by pure zinc cathode small sheets, a Wuhan blue current CT 2001A system is used for assembling the CR2025 symmetrical button cell at 2mA cm-2And carrying out cycle performance test under current density. In addition, the prepared zinc-aluminum-magnesium alloy cathode flake and the pure zinc cathode flake are respectively connected with V6O13The positive electrode is assembled into a full cell, and the total cell is 0.2A g-1Performance testing was performed at current density with electrolyte 3MZn (CF)3SO3)2And the diaphragm is glass fiber filter paper.
As shown in FIG. 1, the microstructure of the zinc-aluminum-magnesium alloy obtained in this example is fine, and the average size of the crystal grains is about 600 nm.
As shown in fig. 2, when the zinc-aluminum-magnesium alloy negative electrode obtained in this embodiment is assembled into a symmetric battery, compared with a pure zinc symmetric battery, the zinc-aluminum-magnesium alloy negative electrode has a lower overpotential and a stable cycle performance, and the charge-discharge cycle life is significantly prolonged.
As shown in FIG. 3, the cathode and V of the Zn-Al-Mg alloy obtained in this example6O13The positive electrode material is assembled into a full cell, and the full cell, the pure zinc negative electrode and the V are assembled6O13Compared with a full battery assembled by the anode material, the specific capacity of the water system zinc ion battery is greatly improved, and the performance is obviously improved.
As shown in fig. 4, the cathode of the zinc-aluminum-magnesium alloy symmetric battery is taken out to observe the surface morphology, and the observation shows that a uniform zinc deposition layer is formed, so that the cycle number of zinc ion stripping/releasing is increased, and the service life of the battery is greatly prolonged.
As shown in fig. 5, the cathode of the symmetrical battery with pure zinc short-circuited is taken out to observe the surface morphology of the pure zinc sheet, and a large amount of longitudinally-grown dendrites are generated on the surface of the pure zinc sheet, and the longitudinally-grown dendrites can pierce through the diaphragm to cause short circuit, so that the service life of the battery is shortened.
Example 2
Preparing an electrode:
s1, preparing Zn99.995 zinc material, 1A99 aluminum material and industrial pure magnesium, and mechanically polishing to remove surface oxides;
s2, according to weight: zinc material: 258.3g, aluminum material: 36.6g, magnesium material: 5.1g, cutting the material for standby;
s3, wiping the surface with alcohol, removing oil stain on the surface with acetone, wiping the surface with alcohol to remove residual acetone, and drying with a blower for later use;
s4, putting the proportioned metal material into a graphite crucible, firstly putting an aluminum block at the bottom of the crucible, then uniformly putting a magnesium block on the aluminum block, and finally putting a zinc block;
s5, heating and smelting in an electromagnetic induction furnace in a protective atmosphere or vacuum environment, wherein the smelting temperature is 560 ℃, the heat preservation time is 10min, and the uniformity of smelting is ensured by utilizing electromagnetic stirring;
s6, pouring the smelted melt into a mould for cooling and forming, wherein the cooling speed is 150 ℃/S (about R)T) Obtaining zinc-aluminum-magnesium alloy;
s7, preparing the zinc-aluminum-magnesium alloy into a small negative electrode sheet, wherein the small negative electrode sheet is in a disc shape with the size of 12mm in diameter and 2mm in thickness.
Battery preparation i.e. cycling test:
the prepared zinc-aluminum-magnesium alloy cathode small sheets are assembled into a CR2025 symmetrical button cell, and compared with a CR2025 symmetrical button cell assembled by pure zinc cathode small sheets, a Wuhan blue current CT 2001A system is used for assembling the CR2025 symmetrical button cell at 2mA cm-2And carrying out cycle performance test under current density. In addition, the prepared zinc-aluminum-magnesium alloy cathode flake and pure zinc cathode flake are respectively connected with V6O13The positive electrode is assembled into a full cell, and the total cell is 0.2A g-1Performance testing was performed at current density with electrolyte 3MZn (CF)3SO3)2And the diaphragm is glass fiber filter paper.
The prepared zinc-aluminum-magnesium alloy cathode has higher capacity and stronger cycle performance, zinc dendrite is obviously inhibited, and the service life of the water system zinc ion battery is greatly prolonged.
Finally, it should be noted that: the above-mentioned embodiments are only used for illustrating the technical solution of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.