Annealing method of thin film magnesium battery magnesium cobaltate positive electrode target material, positive electrode target material and battery

Abstract

The application relates to an annealing method of a thin-film magnesium battery magnesium cobaltate positive electrode target material, a positive electrode target material and a battery, and belongs to the technical field of magnesium batteries. After three-stage heat preservation, the annealing method is adopted to cool the furnace to 175-185 DEG C for continuous heat preservation, then the furnace is naturally cooled to room temperature, and the annealed thin-film magnesium battery magnesium cobaltate positive electrode target material is obtained; the first-stage heat preservation temperature is less than the second-stage heat preservation temperature, the second-stage heat preservation temperature is less than the third-stage heat preservation temperature, and the third-stage heat preservation temperature is 445-455 DEG C. The thin-film magnesium battery magnesium cobaltate positive electrode target material treated by the annealing method is uniform in composition, free from segregation, good in grain size consistency, free from cracks, free from stratification, free from bulges, convenient to machine in subsequent machining, and convenient to thin-film deposition in preparation of a full-solid-state thin-film magnesium battery.

Description

Technical Field

[0001] This invention relates to the field of magnesium battery technology, and in particular to an annealing method for a magnesium cobalt oxide cathode target for a thin-film magnesium battery, the cathode target, and the battery. Background Technology

[0002] Currently, theoretical research on all-solid-state thin-film magnesium batteries has begun. All-solid-state thin-film magnesium batteries utilize solid-state materials for all cells, including the positive and negative electrodes and the electrolyte. Their structure is simpler than traditional magnesium-ion batteries. The solid electrolyte not only conducts magnesium ions but also acts as a separator, possessing advantages such as high mechanical strength, absence of liquid components, lack of flammable and volatile components, and good temperature resistance. However, research on all-solid-state thin-film magnesium batteries remains theoretical; no technology has yet been developed to provide the actual fabrication techniques and finished products that demonstrate the composition and functional structure of all-solid-state thin-film magnesium batteries. Summary of the Invention

[0003] In view of the above, the present invention aims to provide an annealing method for a magnesium cobalt oxide cathode target for a thin-film magnesium battery, a cathode target, and a battery. The present invention can provide a magnesium cobalt oxide cathode target for all-solid-state thin-film magnesium batteries.

[0004] The objective of this invention is mainly achieved through the following technical solutions:

[0005] On one hand, the present invention provides an annealing method for magnesium cobalt oxide cathode target material for thin-film magnesium batteries. The annealing method adopts a three-stage heat preservation, followed by furnace cooling to 175-185°C and continued heat preservation, and then natural cooling to room temperature in the furnace to obtain the annealed magnesium cobalt oxide cathode target material for thin-film magnesium batteries. The first stage heat preservation temperature is less than the second stage heat preservation temperature and less than the third stage heat preservation temperature, with the third stage heat preservation temperature being 445-455°C.

[0006] Furthermore, annealing methods include:

[0007] S1. Place the magnesium cobalt oxide cathode target for the thin-film magnesium battery into a vacuum annealing furnace and evacuate it to a vacuum level of 1-2 × 10⁻⁶. -4 Maintain this vacuum level for 3-4 hours.

[0008] S2. Introduce high-purity nitrogen gas to make the pressure inside the furnace greater than the atmospheric pressure outside the furnace, maintain this pressure for 30-40 minutes, then evacuate to a vacuum of 1-2 × 10⁻⁶. -4 Maintain this vacuum level for 3-4 hours.

[0009] S3. H2+Ar mixed gas is continuously introduced, and the temperature is raised from room temperature to 145-155℃ and held for 4-5 hours.

[0010] S4. H2+Ar mixed gas is continuously introduced, the furnace temperature is raised to 255-265℃, and held for 3-4 hours;

[0011] S5. Continuously introduce a mixture of H2 and Ar gas, raise the furnace temperature to 445–455℃, and hold for 6.5–7.5 hours;

[0012] S6. H2+Ar mixed gas is continuously introduced, and the furnace is slowly cooled to 175-185℃ and held for 4-5 hours.

[0013] S7, then evacuate to 1-2 × 10⁻⁶ -4 Maintain this vacuum level for 2.5–3.5 hours.

[0014] S8. High-purity nitrogen gas is introduced to make the pressure inside the furnace greater than the atmospheric pressure outside the furnace, and then the furnace is naturally cooled to room temperature to obtain the annealed thin-film magnesium battery magnesium cobalt oxide cathode target.

[0015] Furthermore, in S3 to S6, the volume ratio of H2 to Ar is 5–15:85–95.

[0016] Furthermore, from S3 to S6, the pressure inside the vacuum annealing furnace is always maintained to be greater than the atmospheric pressure outside the furnace.

[0017] Furthermore, the thin-film magnesium battery magnesium cobalt oxide cathode target in S1 is prepared using the following method, including:

[0018] Step 1: Mix magnesium salt powder with cobalt tetroxide powder to obtain a mixed powder;

[0019] Step 2: Place the above mixed powder into a ball mill jar and mix it with zirconia balls, then add a dispersant and continue mixing and ball milling;

[0020] Step 3: Then add binder into the ball mill jar and continue ball milling;

[0021] Step 4: After ball milling, the synthetic powder is passed through a 500-mesh sieve. The sieved synthetic powder is weighed and then poured into a vibrating mold. Pressure is applied to form a molded blank.

[0022] Step 5: Place the billet into a cold isostatic press, apply pressure and hold pressure to obtain the cold isostatically pressed magnesium cobalt oxide cathode target billet.

[0023] Step 6: Place the magnesium cobalt oxide cathode target blank into an atmosphere sintering furnace or a vacuum sintering furnace, and after multi-stage heat preservation and multi-stage cooling, allow it to cool naturally to room temperature with the furnace to obtain the magnesium cobalt oxide cathode target for thin-film magnesium batteries.

[0024] Furthermore, in step 1, the magnesium salt includes one or more of magnesium oxide, magnesium carbonate, magnesium nitrate, and magnesium hydroxide.

[0025] Furthermore, in step 1, the mass ratio of magnesium salt to cobalt tetroxide is controlled to be 1.1 to 1.3:1.

[0026] Furthermore, in step 2, the particle size of the zirconia spheres is controlled to be 0.5 mm to 1.6 mm.

[0027] On the one hand, the present invention also provides a magnesium cobalt oxide cathode target for thin-film magnesium batteries, which is prepared by any of the methods described above.

[0028] On the one hand, the present invention also provides an all-solid-state thin-film magnesium battery, wherein the positive electrode of the all-solid-state thin-film magnesium battery is prepared using the above-mentioned magnesium cobalt oxide positive electrode target for thin-film magnesium batteries.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] 1) The annealing method of the magnesium cobalt oxide cathode target for thin-film magnesium batteries of the present invention involves three stages of heat preservation, followed by furnace cooling to 175-185°C and continued heat preservation, and then natural cooling to room temperature to obtain the annealed magnesium cobalt oxide cathode target for thin-film magnesium batteries. It is necessary to precisely control the first stage heat preservation temperature < the second stage heat preservation temperature < the third stage heat preservation temperature, with the third stage heat preservation temperature being 445-455°C. The magnesium cobalt oxide cathode target for thin-film magnesium batteries obtained by the above annealing method has a uniform composition, no segregation, good grain size consistency, controllable grain deviation, no single phase or defect components, and no cracks, delamination, bulges, or fissures within the target. This facilitates subsequent machining, reduces internal stress, increases yield, and also facilitates thin-film deposition during the preparation of all-solid-state thin-film magnesium batteries.

[0031] 2) In the preparation of the thin-film magnesium cobalt oxide cathode target for magnesium batteries of the present invention, magnesium salt powder and cobalt tetroxide powder are first mixed to obtain a mixed powder. This mixed powder is then mixed with zirconium oxide balls, followed by the addition of a dispersant and further mixing and ball milling. A binder is then added, and ball milling continues. The ball-milled composite powder is sieved (e.g., 500 mesh), poured into a vibrating mold, and pressurized to form a molded blank. The blank is then placed in a cold isostatic press and pressurized and held to obtain a cold isostatically pressed magnesium cobalt oxide cathode target blank. Finally, the magnesium cobalt oxide cathode target blank is placed in an atmosphere sintering furnace or a vacuum sintering furnace for multi-stage heat preservation and cooling, followed by natural cooling to room temperature to obtain the thin-film magnesium cobalt oxide cathode target. The preparation method of the present invention ensures the successful preparation of the thin-film magnesium cobalt oxide cathode target by precisely controlling the proportion of raw materials, the order of addition of each raw material, the ball milling process parameters, the sintering steps, and the process parameters of each step.

[0032] 3) The positive electrode layer of the all-solid-state thin-film magnesium battery of the present invention is prepared using the magnesium cobalt oxide positive electrode target of the thin-film magnesium battery of the present invention. The all-solid-state thin-film magnesium battery of the present invention has high safety and extremely high capacity and capacity retention. In addition, the all-solid-state thin-film magnesium battery of the present invention also has excellent interfacial bonding and coordination, with very low interfacial internal resistance. It can easily realize the direct series connection of multiple single cells, the direct parallel connection of multiple single cells, and the series and parallel combination of multiple single cells, which conveniently achieves the goal of increasing the output voltage of the battery, increasing the single cell capacity of the battery pack, or achieving a perfect combination of voltage boosting and capacity expansion.

[0033] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objectives and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description. Attached Figure Description

[0034] The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of the invention.

[0035] Figure 1 This is a schematic diagram of the magnesium cobalt oxide cathode target for a thin-film magnesium battery according to Embodiment 1 of the present invention;

[0036] Figure 2 This is a schematic diagram of the magnesium cobalt oxide cathode target for a thin-film magnesium battery according to Embodiment 2 of the present invention;

[0037] Figure 3 This is a schematic diagram of the magnesium cobalt oxide cathode target for a thin-film magnesium battery according to Comparative Example 1 of the present invention.

[0038] Figure 4 This is a schematic diagram of the magnesium cobalt oxide cathode target for a thin-film magnesium battery according to Comparative Example 2 of the present invention.

[0039] Figure 5 This is a schematic diagram of the magnesium cobalt oxide cathode target for a thin-film magnesium battery according to Comparative Example 3 of the present invention.

[0040] Figure 6 This is a schematic diagram of the magnesium cobalt oxide cathode target for a thin-film magnesium battery according to Comparative Example 4 of the present invention. Detailed Implementation

[0041] The preferred embodiments of the present invention are described in detail below, which are mainly used to explain the principles of the present invention and are not intended to limit the scope of the present invention.

[0042] This invention provides an annealing method for magnesium cobalt oxide cathode targets for thin-film magnesium batteries. The annealing method involves three stages of heat preservation, followed by furnace cooling to 175-185°C and continued heat preservation, and then natural cooling to room temperature in the furnace to obtain the annealed magnesium cobalt oxide cathode target for thin-film magnesium batteries. The first stage heat preservation temperature is less than the second stage heat preservation temperature, which is less than the third stage heat preservation temperature. The third stage heat preservation temperature is 445-455°C.

[0043] Specifically, the above annealing methods include:

[0044] S1. Place the magnesium cobalt oxide cathode target for the thin-film magnesium battery into a vacuum annealing furnace and evacuate it to a vacuum level of 1-2 × 10⁻⁶. -4 Maintain this vacuum level for 3-4 hours.

[0045] S2. Introduce high-purity nitrogen gas to make the pressure inside the furnace greater than the atmospheric pressure outside the furnace, maintain this pressure for 30-40 minutes, then evacuate to a vacuum of 1-2 × 10⁻⁶. -4 Maintain this vacuum level for 3-4 hours.

[0046] S3. H2+Ar mixed gas is continuously introduced and heated from room temperature to 145-155℃, and held at this temperature for 4-5 hours; wherein the volume ratio of H2 to Ar is 5-15:85-95.

[0047] S4. H2+Ar mixed gas is continuously introduced, and the furnace temperature is raised to 255-265℃ and held for 3-4 hours; wherein the volume ratio of H2 to Ar is 5-15:85-95.

[0048] S5. H2+Ar mixed gas is continuously introduced, the furnace temperature is raised to 445~455℃, and held for 6.5~7.5h; wherein, the volume ratio of H2 to Ar is 5~15:85~95.

[0049] S6. H2+Ar mixed gas is continuously introduced and slowly cooled to 175-185℃ in the furnace, and held for 4-5 hours; wherein the volume ratio of H2 to Ar is 5-15:85-95.

[0050] S7, then evacuate to 1-2 × 10⁻⁶ -4 Maintain this vacuum level for 2.5–3.5 hours.

[0051] S8. High-purity nitrogen gas is introduced to make the pressure inside the furnace greater than the atmospheric pressure outside the furnace, and then the furnace is naturally cooled to room temperature to obtain the annealed thin-film magnesium battery magnesium cobalt oxide cathode target.

[0052] Specifically, in steps S3-S6 above, the pressure inside the vacuum annealing furnace is always kept greater than the atmospheric pressure outside the furnace.

[0053] Specifically, considering that too low a holding temperature for the magnesium cobalt oxide cathode target of the aforementioned thin-film magnesium battery will result in delamination defects, while too high a holding temperature will cause bulging or cracking, the above annealing method, after in-depth research, is precisely controlled to involve three stages of holding, followed by furnace cooling to 175–185°C for further holding, and then natural cooling to room temperature to obtain the annealed magnesium cobalt oxide cathode target for the thin-film magnesium battery. Furthermore, it is necessary to precisely control the first stage holding temperature to be less than the second stage holding temperature, which is less than the third stage holding temperature, with the third stage holding temperature being 445–455°C.

[0054] Specifically, the magnesium cobalt oxide cathode target for thin-film magnesium batteries after the above annealing treatment exhibits uniform composition, no segregation, good grain size consistency, controllable grain deviation, and no single-phase or defect components. The target material is free of cracks, delamination, bulges, and fissures, facilitating subsequent machining, reducing internal stress, increasing yield, and also aiding in subsequent thin-film deposition. Without treatment within these parameter ranges, the material is prone to cracking during machining, contains numerous micro-cracks, and produces large powder particles during sputtering deposition.

[0055] Specifically, the thin-film magnesium battery magnesium cobalt oxide cathode target in S1 above is prepared using the following method, including:

[0056] Step 1: Mix magnesium salt powder with cobalt tetroxide powder to obtain a mixed powder;

[0057] Step 2: Place the above mixed powder into a ball mill jar and mix it with zirconia balls, then add a dispersant and continue mixing and ball milling;

[0058] Step 3: Then add binder into the ball mill jar and continue ball milling;

[0059] Step 4: After ball milling, the synthetic powder is passed through a 500-mesh sieve. The sieved synthetic powder is weighed and then poured into a vibrating mold. Pressure is applied to form a molded blank.

[0060] Step 5: Place the billet into a cold isostatic press, apply pressure and hold pressure to obtain the cold isostatically pressed magnesium cobalt oxide cathode target billet.

[0061] Step 6: Place the magnesium cobalt oxide cathode target blank into an atmosphere sintering furnace or a vacuum sintering furnace, and after multi-stage heat preservation and multi-stage cooling, allow it to cool naturally to room temperature with the furnace to obtain the magnesium cobalt oxide cathode target for thin-film magnesium batteries.

[0062] Specifically, in step 1 above, the magnesium salt may include one or more of magnesium oxide, magnesium carbonate, magnesium nitrate, and magnesium hydroxide.

[0063] Specifically, in step 1 above, the mass ratio of magnesium salt to cobalt tetroxide is controlled to be 1.1 to 1.3:1.

[0064] Specifically, in step 2 above, to ensure uniform mixing of the powders and to control the particle size of the powders by adjusting the size of the zirconia balls, thus ensuring uniformity in grain size and crystal structure of the sintered magnesium cobaltate product, and guaranteeing sufficient and close contact of the powders to reduce the chemical kinetic barrier during synthesis, the particle size of the zirconia balls is controlled to be 0.5 mm to 1.6 mm. When the zirconia ball particle size is outside this range, the mixed powder has a large particle size deviation, resulting in uneven mixing, the presence of many elemental substances, and the inability to sputter the sintered target material.

[0065] Specifically, in step 2 above, the grinding jar is a hard ceramic jar or a stainless steel jar lined with hard ceramic.

[0066] Specifically, in step 2 above, the total volume of the zirconia balls is controlled to be no more than 2 / 5 of the volume of the ball mill jar, and the total volume of the mixed powder is 1 / 5 to 2 / 5 of the volume of the ball mill jar. Preferably, the total volume of the mixed powder is 1 / 3 of the volume of the ball mill jar.

[0067] Specifically, in step 2 above, considering that too much dispersant would be wasteful, while too little dispersant would cause the powder to agglomerate and fail to mix and contact sufficiently, which would be detrimental to synthesis and sintering, the mass ratio of dispersant to mixed powder is controlled to be 1–1.5:100.

[0068] Specifically, in step 2 above, the dispersant may include isopropanol and isotetracycline. Preferably, the mass ratio of isopropanol to isotetracycline is 1-3:4-6.

[0069] Specifically, in step 2 above, the ball milling process includes:

[0070] S201. Ball milling in the mill jar at an initial speed of 130-160 rpm for 2-4 hours;

[0071] S202. Grind the balls in a milling jar at a speed of 300-350 rpm for more than 12 hours.

[0072] Specifically, in step 2 above, the ball milling process first uses a lower rotation speed and then a higher rotation speed. This ensures that the powder is mixed evenly, facilitating subsequent synthesis reactions. Without using the appropriate ball milling parameters, the mixture will be uneven, containing many elemental substances, and the sintered target material will not be able to be sputtered.

[0073] Specifically, in step 3 above, polyvinyl butyral can be used as the binder. Too much binder will be wasteful, while too little binder will prevent the uniformly mixed raw material powder from fully contacting and rapidly participating in the chemical reaction during sintering. Therefore, the mass ratio of binder to mixed powder should be controlled at (0.4–1.0):100.

[0074] Specifically, in step 3 above, in order to ensure that the powder is mixed evenly, the ball mill speed is controlled at 140-160 rpm and the ball milling time is 4-6 hours.

[0075] Specifically, in step 4 above, to ensure the uniformity of grain size and crystal phase structure of the sintered magnesium cobalt oxide product, the synthetic powder is controlled to pass through a 500-mesh sieve. If this parameter is not within the specified range, the powder particle size will be dispersed, resulting in large voids in the target compact, preventing complete ceramization after sintering and hindering sputtering deposition.

[0076] Specifically, in step 4 above, considering that excessive pressure would place high demands on the equipment, while insufficient pressure would be ineffective, the pressure is controlled at 1150–1300 tons to form the molded blank.

[0077] Specifically, in step 5 above, considering that excessive pressure during the cold isostatic pressing process places high demands on the equipment, while insufficient pressure renders it ineffective, the pressure is controlled to be increased to 300–350 MPa and held for 30–50 minutes.

[0078] Specifically, step 6 above, which involves using an atmosphere sintering furnace, includes:

[0079] S601. Place the magnesium cobalt oxide cathode target blank into an atmosphere sintering furnace, continuously introduce N2+Ar mixed gas, raise the temperature from room temperature to 170-190℃, and hold for 3-4 hours; wherein, the volume ratio of N2 to Ar is 5-6:4.

[0080] S602, heat up again to 640-660℃, and continuously purge the N2+Ar mixed gas, and keep at this temperature for 11-13 hours; wherein the volume ratio of N2 to Ar is 6-7:3.

[0081] S603, heat again to 840-860℃, and continuously purge N2+Ar mixed gas, and keep at this temperature for 9-11 hours; wherein the volume ratio of N2 to Ar is 6-7:3.

[0082] S604, heat again to 1040~1060℃, and continuously pass through N2+Ar mixed gas, and keep at this temperature for 12~14h; wherein, the volume ratio of N2 to Ar is 6~7:3;

[0083] S605, heat again to 1240~1260℃, and continuously purge N2+Ar mixed gas for 7~9h; wherein, the volume ratio of N2 to Ar is 6~7:3;

[0084] S606, slowly cool to 490-520℃ in the furnace, and hold for 3-5 hours;

[0085] S607, and then naturally cooled to room temperature in the furnace to obtain the magnesium cobalt oxide cathode target for thin-film magnesium batteries.

[0086] Specifically, in S606 and S607 above, in order to ensure the uniformity of the microstructure of the obtained magnesium cobalt oxide cathode target, it is necessary to first slowly cool it to 490-520℃ in the furnace and hold it for 3-5 hours; then cool it naturally to room temperature in the furnace.

[0087] Specifically, step 6 above, which involves using a vacuum sintering furnace, includes:

[0088] S601. Place the magnesium cobalt oxide cathode target blank into a vacuum sintering furnace, maintaining a vacuum level of 10. -3 Below Pa, the temperature is raised from room temperature to 170–190℃ and held for 3–4 hours;

[0089] S602, heat again to 640-660℃, and keep warm for 11-13 hours;

[0090] S603, heat again to 840-860℃, and hold for 9-11 hours;

[0091] S604, heat again to 1040~1060℃, and keep warm for 12~14h;

[0092] S605, heat again to 1240~1260℃, and keep warm for 7~9 hours;

[0093] S606, slowly cool to 490-520℃ in the furnace, and hold for 3-5 hours;

[0094] S607, and then naturally cooled to room temperature in the furnace to obtain the magnesium cobalt oxide cathode target for thin-film magnesium batteries.

[0095] Specifically, in S602-S605 above, the vacuum level is always maintained at 10. -3 Below pa.

[0096] Specifically, in S606 and S607 above, in order to ensure the uniformity of the microstructure of the obtained magnesium cobalt oxide cathode target, it is necessary to first slowly cool it to 490-520℃ in the furnace and hold it for 3-5 hours; then cool it naturally to room temperature in the furnace.

[0097] Specifically, in step 6 above, the parameters such as temperature, atmosphere, and holding time for each of the multiple heating stages are all taken into account the chemical reaction kinetics requirements of sintering. These parameters are controlled to ensure the uniformity of composition and the required grain structure of the synthesized magnesium cobaltate during the sintering process. Sintering outside this temperature range will result in incomplete ceramization of the target material, leading to over-sintering, under-sintering, porosity, and deformation, rendering the target material unusable.

[0098] Specifically, in step 6 above, the magnesium cobalt oxide cathode target material for thin-film magnesium batteries has a uniform composition, no segregation, good grain size consistency, controllable grain deviation, no single phase or defect components, and no cracks in the target material.

[0099] Specifically, the annealed magnesium cobalt oxide cathode target for thin-film magnesium batteries exhibits uniform composition, no segregation, good grain size consistency, controllable grain deviation, no single-phase or defective components, and no cracks within the target, facilitating thin-film deposition. During machining, the target remains crack-free. The grain size of the annealed magnesium cobalt oxide cathode target for thin-film magnesium batteries is between 380nm and 460nm, the flatness is approximately 0.16–0.18mm, and the relative density is approximately 97.0%–97.5%.

[0100] The present invention also provides a magnesium cobalt oxide cathode target for thin-film magnesium batteries, which is prepared by the above-described annealing method.

[0101] The present invention also provides an all-solid-state thin-film magnesium battery, wherein the positive electrode of the all-solid-state thin-film magnesium battery is prepared using the above-mentioned magnesium cobalt oxide positive electrode target for thin-film magnesium batteries.

[0102] Specifically, the aforementioned all-solid-state thin-film magnesium battery includes a positive electrode layer, an electrolyte layer, and a negative electrode layer, with the positive electrode layer prepared using the aforementioned magnesium cobalt oxide positive electrode target for thin-film magnesium batteries.

[0103] Specifically, the preparation method of the above-mentioned all-solid-state thin-film magnesium battery includes:

[0104] Step 1: Deposit a thin film of magnesium anode on the surface of copper foil;

[0105] Step 2: Next, a solid electrolyte film is deposited on the negative electrode magnesium film;

[0106] Step 3: Deposit a positive electrode film on the solid electrolyte film using the magnesium cobalt oxide positive electrode target of the thin-film magnesium battery described above;

[0107] Step 4: After formation, an all-solid-state thin-film magnesium battery is obtained.

[0108] Specifically, the all-solid-state thin-film magnesium battery of the present invention, in addition to high safety, also has high capacity and capacity retention. For example, with a capacity of 15840 mAh or higher (e.g., 15840–46464 mAh), the capacity remains essentially unchanged after more than 10,000 cycles. Furthermore, the all-solid-state thin-film magnesium battery of the present invention also has excellent interfacial bonding and compatibility, with very low interfacial resistance, for example, less than 0.01 ohms / cm. 2 It can very easily realize the direct series connection of multiple single cells, the direct parallel connection of multiple single cells, and the series and parallel combination of multiple single cells, which can conveniently increase the output voltage of the battery, increase the single cell capacity of the battery pack, or achieve a perfect combination of voltage boosting and capacity expansion.

[0109] The preparation method and application of the magnesium cobalt oxide cathode target for thin-film magnesium batteries of the present invention will be further described below with reference to specific embodiments. Unless otherwise specified, all raw materials used are commercially available.

[0110] Example 1

[0111] This embodiment provides an annealing method for a magnesium cobalt oxide cathode target for a thin-film magnesium battery, including:

[0112] S1. Place the magnesium cobalt oxide cathode target for the thin-film magnesium battery into a vacuum annealing furnace and evacuate it to a vacuum level of 1.5 × 10⁻⁶. -4 Maintain this vacuum level for 3.5 hours.

[0113] S2. Introduce high-purity nitrogen gas to make the pressure inside the furnace greater than the atmospheric pressure outside the furnace, maintain this pressure for 35 minutes, and then evacuate to a vacuum of 1.5 × 10⁻⁶. -4 Maintain this vacuum level for 3.5 hours.

[0114] S3. A mixture of H2 and Ar gas is continuously introduced, and the temperature is raised from room temperature to 150℃ and held for 4.5 hours; wherein the volume ratio of H2 to Ar is 7:93.

[0115] S4. H2+Ar mixed gas is continuously introduced, the furnace temperature is raised to 260℃, and held for 3.5h; wherein the volume ratio of H2 to Ar is 7:93.

[0116] S5. H2+Ar mixed gas is continuously introduced, the furnace temperature is raised to 450℃ and held for 7 hours; wherein the volume ratio of H2 to Ar is 7:93.

[0117] S6. H2+Ar mixed gas is continuously introduced and slowly cooled to 180℃ in the furnace, and held at that temperature for 4.5h; wherein the volume ratio of H2 to Ar is 7:93.

[0118] S7, then evacuate to 1.5×10 -4 Maintain this vacuum level for 3 hours.

[0119] S8. High-purity nitrogen gas is introduced to make the pressure inside the furnace greater than the atmospheric pressure outside the furnace, and then the furnace is naturally cooled to room temperature to obtain the annealed thin-film magnesium battery magnesium cobalt oxide cathode target.

[0120] Specifically, the thin-film magnesium battery magnesium cobalt oxide cathode target in S1 above is prepared using the following method, including:

[0121] Step 1: Mix magnesium salt powder and cobalt tetroxide powder to obtain a mixed powder; the magnesium salt is magnesium oxide, and the mass ratio of magnesium oxide to cobalt tetroxide is 1.2:1;

[0122] Step 2: Place the above mixed powder into a ball mill jar and mix it with zirconia balls with a particle size of 0.5 mm to 1.6 mm. Then add a dispersant and continue mixing and ball milling. The ball mill jar is a hard ceramic jar. The total volume of the zirconia balls occupies 2 / 5 of the volume of the ball mill jar, and the total volume of the mixed powder occupies 1 / 3 of the volume of the ball mill jar. The mass ratio of dispersant to mixed powder is 1.3:100.

[0123] Specifically, in step 2, the ball milling process includes:

[0124] S201. The ball mill jar is used to ball mill at an initial speed of 150 rpm for 3 hours.

[0125] S202, ball milling in a milling jar at a speed of 340 rpm for 13 hours;

[0126] Step 3: Then add binder into the ball mill jar and ball mill at 145 rpm for 5 hours; the mass ratio of binder to mixed powder is 0.5:100.

[0127] Step 4: After ball milling, the synthetic powder is passed through a 500-mesh sieve. The sieved synthetic powder is weighed and then poured into a vibrating mold. It is then pressed with 1200 tons to form a molded blank.

[0128] Step 5: Place the billet into a cold isostatic press, pressurize it to 320 MPa, hold the pressure for 40 minutes, and obtain the cold isostatically pressed magnesium cobalt oxide cathode target billet.

[0129] Step 6: Place the magnesium cobalt oxide cathode target blank into an atmosphere sintering furnace for multi-stage heat preservation and multi-stage cooling, and then allow it to cool naturally to room temperature in the furnace to obtain the magnesium cobalt oxide cathode target for thin-film magnesium batteries.

[0130] Step 6 includes:

[0131] S601. Place the magnesium cobalt oxide cathode target blank into an atmosphere sintering furnace and continuously introduce a N2+Ar (ratio 6:4) mixed gas. Raise the temperature from room temperature to 180℃ and hold for 3.5 hours.

[0132] S602, raise the temperature to 650℃ again, and keep it at that temperature for 12 hours while continuously purging with a mixture of N2 and Ar (7:3 ratio);

[0133] S603, raise the temperature again to 850℃, and continuously introduce a N2+Ar (ratio 7:3) mixed gas, and keep it at this temperature for 10 hours;

[0134] S604, raise the temperature again to 1050℃, and continuously introduce a N2+Ar (ratio 7:3) mixed gas, and keep it at this temperature for 13 hours;

[0135] S605, raise the temperature again to 1250℃, and continuously introduce a N2+Ar (ratio 7:3) mixed gas, and keep it at this temperature for 8 hours;

[0136] S606, slowly cool to 500℃ in the furnace and hold for 4 hours;

[0137] S607, and then naturally cooled to room temperature in the furnace to obtain the magnesium cobalt oxide cathode target for thin-film magnesium batteries.

[0138] The magnesium cobalt oxide cathode target for thin-film magnesium batteries after annealing in this embodiment has a uniform composition, no segregation, good grain size consistency, controllable grain deviation, no single phase or defect components, no cracks in the target, which facilitates thin film deposition, and no cracking of the target during machining.

[0139] Specifically, the annealed thin-film magnesium battery magnesium cobalt oxide cathode target of this embodiment is as follows: Figure 1 As shown, the grain size of the magnesium cobalt oxide cathode target for thin-film magnesium batteries is between 390 nm and 410 nm, the flatness is about 0.17 mm, and the relative density is 97.1%.

[0140] Example 2

[0141] This embodiment provides an annealing method for a magnesium cobalt oxide cathode target for a thin-film magnesium battery, including:

[0142] S1. Place the magnesium cobalt oxide cathode target for the thin-film magnesium battery into a vacuum annealing furnace and evacuate it to a vacuum level of 1×10⁻⁶. -4 Maintain this vacuum level for 3 hours.

[0143] S2. Introduce high-purity nitrogen gas to make the pressure inside the furnace greater than the atmospheric pressure outside the furnace, maintain this pressure for 40 minutes, and then evacuate to a vacuum of 1.5 × 10⁻⁶. -4 Maintain this vacuum level for 3.5 hours.

[0144] S3. H2+Ar mixed gas is continuously introduced and heated from room temperature to 155℃ and held at that temperature for 4 hours; wherein the volume ratio of H2 to Ar is 10:90.

[0145] S4. H2+Ar mixed gas is continuously introduced, the furnace temperature is raised to 265℃ and held for 3.5h; wherein the volume ratio of H2 to Ar is 10:90.

[0146] S5. H2+Ar mixed gas is continuously introduced, the furnace temperature is raised to 455℃ and held for 6.5h; wherein the volume ratio of H2 to Ar is 8:92.

[0147] S6. H2+Ar mixed gas is continuously introduced and slowly cooled to 180℃ in the furnace, and held at that temperature for 4.5h; wherein the volume ratio of H2 to Ar is 7:93.

[0148] S7, then evacuate to 1.5×10 -4 Maintain this vacuum level for 3 hours.

[0149] S8. High-purity nitrogen gas is introduced to make the pressure inside the furnace greater than the atmospheric pressure outside the furnace, and then the furnace is naturally cooled to room temperature to obtain the annealed thin-film magnesium battery magnesium cobalt oxide cathode target.

[0150] Specifically, the thin-film magnesium battery magnesium cobalt oxide cathode target in S1 above is prepared using the following method, including:

[0151] Step 1: Mix magnesium salt powder and cobalt tetroxide powder to obtain a mixed powder; the magnesium salt is magnesium oxide, and the mass ratio of magnesium oxide to cobalt tetroxide is 1.3:1;

[0152] Step 2: Place the above mixed powder into a ball mill jar and mix it with zirconia balls with a particle size of 0.8 mm to 1.5 mm. Then add a dispersant and continue mixing and ball milling. The ball mill jar is a hard ceramic jar. The total volume of the zirconia balls occupies 2 / 5 of the volume of the ball mill jar, and the total volume of the mixed powder occupies 1 / 3 of the volume of the ball mill jar. The mass ratio of dispersant to mixed powder is 1.4:100.

[0153] Specifically, in step 2, the ball milling process includes:

[0154] S201, the ball mill jar is used to ball mill at an initial speed of 140 rpm for 3.5 hours;

[0155] S202, ball milling in a milling jar at a speed of 330 rpm for 13.5 hours;

[0156] Step 3: Then add binder into the ball mill jar and ball mill at 145 rpm for 5 hours; the mass ratio of binder to mixed powder is 0.6:100.

[0157] Step 4: After ball milling, the synthetic powder is passed through a 500-mesh sieve. The sieved synthetic powder is weighed and then poured into a vibrating mold. It is then pressed with 1250 tons to form a molded blank.

[0158] Step 5: Place the billet into a cold isostatic press, pressurize it to 330 MPa, hold the pressure for 35 minutes, and obtain the cold isostatically pressed magnesium cobalt oxide cathode target billet.

[0159] Step 6: Place the magnesium cobalt oxide cathode target blank into an atmosphere sintering furnace for multi-stage heat preservation and multi-stage cooling, and then allow it to cool naturally to room temperature in the furnace to obtain the magnesium cobalt oxide cathode target for thin-film magnesium batteries.

[0160] Step 6 includes:

[0161] S601. Place the magnesium cobalt oxide cathode target blank into an atmosphere sintering furnace and continuously introduce a N2+Ar (ratio 6:4) mixed gas. Raise the temperature from room temperature to 170℃ and hold for 3.5 hours.

[0162] S602, raise the temperature again to 660℃, and keep it at that temperature for 11 hours while continuously purging with a N2+Ar (ratio 6.5:3) mixed gas;

[0163] S603, heat up to 850℃ again, and continuously purify with a N2+Ar (ratio 6.5:3) mixed gas for 10 hours;

[0164] S604, raise the temperature again to 1050℃, and continuously introduce a N2+Ar (ratio 6.5:3) mixed gas, and keep it at this temperature for 13 hours;

[0165] S605, raise the temperature again to 1245℃, and continuously introduce a N2+Ar (ratio 6.5:3) mixed gas, and keep it at this temperature for 8 hours;

[0166] S606, slowly cooled to 495℃ in the furnace, and held for 4 hours;

[0167] S607, and then naturally cooled to room temperature in the furnace to obtain the magnesium cobalt oxide cathode target for thin-film magnesium batteries.

[0168] The magnesium cobalt oxide cathode target for thin-film magnesium batteries after annealing in this embodiment has a uniform composition, no segregation, good grain size consistency, controllable grain deviation, no single phase or defect components, no cracks in the target, which facilitates thin film deposition, and no cracking of the target during machining.

[0169] Specifically, the annealed thin-film magnesium battery magnesium cobalt oxide cathode target of this embodiment is as follows: Figure 2 As shown, the grain size of the magnesium cobalt oxide cathode target for thin-film magnesium batteries is between 400 nm and 420 nm, the flatness is about 0.16 mm, and the relative density is 97.3%.

[0170] Example 3

[0171] This embodiment provides an all-solid-state thin-film magnesium battery. The fabrication method of this embodiment for depositing a single-cell all-solid-state thin-film magnesium battery includes:

[0172] Step 1: Deposit a negative electrode magnesium film on a 1 square meter copper foil surface. The thickness of the negative electrode magnesium film is 4.5 μm.

[0173] Step 2: Next, a solid electrolyte film is deposited on the negative electrode magnesium film, with a thickness of 1.5 μm;

[0174] Step 3: Deposit a positive electrode film on the solid electrolyte film using the magnesium cobalt oxide positive electrode target of the thin-film magnesium battery described in Example 1; the thickness of the positive electrode film is 15 μm;

[0175] Step 4: After formation, an all-solid-state thin-film magnesium battery is obtained.

[0176] The interfacial resistance of the all-solid-state thin-film magnesium battery in this embodiment is less than 0.01 ohms / cm.2 With a capacity of 15840 mAh, the capacity remains essentially unchanged after more than 10,000 cycles.

[0177] Example 4

[0178] This embodiment provides an all-solid-state thin-film magnesium battery. The fabrication method for this embodiment involves depositing two series-connected all-solid-state thin-film magnesium batteries.

[0179] The magnesium anode film thickness of each thin-film magnesium battery was 5.5 μm, deposited on a 1 square meter copper foil surface. The solid electrolyte film thickness of each subsequent battery was 2.0 μm. Using the magnesium cobalt oxide cathode target from Example 1, the cathode film thickness of the resulting thin-film magnesium battery was 18.5 μm. After formation, the battery achieved a capacity of 19536 mAh; the capacity remained essentially unchanged after more than 10,000 cycles; and the interfacial resistance was less than 0.01 ohms / cm. 2 .

[0180] Example 5

[0181] This embodiment provides an all-solid-state thin-film magnesium battery. The method for depositing two parallel all-solid-state thin-film magnesium batteries includes:

[0182] The thickness of the negative electrode magnesium film deposited on the surface of a 1 square meter copper foil for each battery is 6.5 μm. The thickness of the solid electrolyte film deposited on each battery is then 2.5 μm. Finally, using the magnesium cobalt oxide positive electrode target from Example 2, the thickness of the positive electrode film deposited is 22 μm. The resulting battery, after formation, has a capacity of 46464 mA h; the capacity remains essentially unchanged after more than 10,000 cycles; and the interfacial resistance is less than 0.01 ohms / cm. 2 .

[0183] Comparative Example 1

[0184] This comparative example provides an annealing method for a magnesium cobalt oxide cathode target for thin-film magnesium batteries, as detailed below:

[0185] S1. Place the magnesium cobalt oxide cathode target for the thin-film magnesium battery into a vacuum annealing furnace and evacuate it to a vacuum level of 3×10⁻⁶. -4 Maintain this vacuum level for 3.5 hours.

[0186] S2. Introduce high-purity nitrogen gas to make the pressure inside the furnace greater than the atmospheric pressure outside the furnace, maintain this pressure for 35 minutes, and then evacuate to a vacuum of 1.5 × 10⁻⁶. -4 Maintain this vacuum level for 3.5 hours.

[0187] S3. H2+Ar mixed gas is continuously introduced and heated from room temperature to 130℃ and held for 5 hours; wherein the volume ratio of H2 to Ar is 7:93.

[0188] S4. H2+Ar mixed gas is continuously introduced, the furnace temperature is raised to 200℃ and held for 4 hours; wherein, the volume ratio of H2 to Ar is 7:93.

[0189] S5. H2+Ar mixed gas is continuously introduced, the furnace temperature is raised to 420℃ and held for 7 hours; wherein the volume ratio of H2 to Ar is 7:93.

[0190] S6. H2+Ar mixed gas is continuously introduced and slowly cooled to 180℃ in the furnace, and held at that temperature for 4.5h; wherein the volume ratio of H2 to Ar is 7:93.

[0191] S7, then evacuate to 1.5×10 -4 Maintain this vacuum level for 3 hours.

[0192] S8. High-purity nitrogen gas is introduced to make the pressure inside the furnace greater than the atmospheric pressure outside the furnace, and then the furnace is naturally cooled to room temperature to obtain the annealed thin-film magnesium battery magnesium cobalt oxide cathode target.

[0193] Specifically, the preparation method of the magnesium cobalt oxide cathode target for thin-film magnesium batteries in S1 is the same as that in Example 1, and will not be repeated here.

[0194] The annealed magnesium cobalt oxide cathode target for thin-film magnesium batteries in this comparative example is as follows: Figure 3 As shown, the magnesium cobalt oxide cathode target for thin-film magnesium batteries has delamination, and the target is prone to cracking during machining.

[0195] Comparative Example 2

[0196] This comparative example provides an annealing method for a magnesium cobalt oxide cathode target for thin-film magnesium batteries, as detailed below:

[0197] S1. Place the magnesium cobalt oxide cathode target for the thin-film magnesium battery into a vacuum annealing furnace and evacuate it to a vacuum level of 3×10⁻⁶. -4 Maintain this vacuum level for 3.5 hours.

[0198] S2. Introduce high-purity nitrogen gas to make the pressure inside the furnace greater than the atmospheric pressure outside the furnace, maintain this pressure for 35 minutes, and then evacuate to a vacuum of 1.5 × 10⁻⁶. -4 Maintain this vacuum level for 3.5 hours.

[0199] S3. H2+Ar mixed gas is continuously introduced and heated from room temperature to 190℃, and held at that temperature for 5 hours; wherein the volume ratio of H2 to Ar is 7:93.

[0200] S4. H2+Ar mixed gas is continuously introduced, the furnace temperature is raised to 270℃ and held for 4 hours; wherein the volume ratio of H2 to Ar is 7:93.

[0201] S5. H2+Ar mixed gas is continuously introduced, the furnace temperature is raised to 490℃ and held for 7 hours; wherein the volume ratio of H2 to Ar is 7:93.

[0202] S6. H2+Ar mixed gas is continuously introduced and slowly cooled to 180℃ in the furnace, and held at that temperature for 4.5h; wherein the volume ratio of H2 to Ar is 7:93.

[0203] S7, then evacuate to 1.5×10 -4 Maintain this vacuum level for 3 hours.

[0204] S8. High-purity nitrogen gas is introduced to make the pressure inside the furnace greater than the atmospheric pressure outside the furnace, and then the furnace is naturally cooled to room temperature to obtain the annealed thin-film magnesium battery magnesium cobalt oxide cathode target.

[0205] Specifically, the preparation method of the magnesium cobalt oxide cathode target for thin-film magnesium batteries in S1 is the same as that in Example 1, and will not be repeated here.

[0206] The annealed magnesium cobalt oxide cathode target for thin-film magnesium batteries in this comparative example is as follows: Figure 4 As shown, the magnesium cobalt oxide cathode target for thin-film magnesium batteries has bulges and cracks, and the target is prone to cracking during machining.

[0207] Comparative Example 3

[0208] This comparative example provides a method for preparing the magnesium cobalt oxide cathode target for thin-film magnesium batteries in S1, as detailed below:

[0209] In step 2 of this comparative example, the particle size of the zirconia spheres is 1.8–2.5 mm; the remaining steps are the same as those in Example 1.

[0210] The magnesium cobalt oxide cathode target for this comparative example of a thin-film magnesium battery is as follows: Figure 5 As shown, the target material has large grain deviations, uneven mixing, and contains many elemental substances, making it impossible to sputter the sintered target material.

[0211] Comparative Example 4

[0212] This comparative example provides a method for preparing the magnesium cobalt oxide cathode target for thin-film magnesium batteries in S1, as detailed below:

[0213] In step 4 of this comparative example, the synthetic powder is controlled to pass through a 300-mesh sieve; the remaining steps are the same as those in Example 1.

[0214] The magnesium cobalt oxide cathode target for this comparative example of a thin-film magnesium battery is as follows: Figure 6 As shown, the target compact in this comparative example has large voids, and cannot be fully ceramicized after sintering, thus preventing sputtering deposition.

[0215] Comparative Example 5

[0216] This comparative example provides a method for preparing the magnesium cobalt oxide cathode target for thin-film magnesium batteries in S1, as detailed below:

[0217] In step 6 of this comparative example, steps S602-S607 are performed directly; the remaining steps are the same as those in Example 1.

[0218] The target material in this comparative example cannot be fully ceramicized and is therefore unusable.

[0219] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. An annealing method for a magnesium cobalt oxide cathode target for thin-film magnesium batteries, characterized in that, The annealing method involves three stages of heat preservation, followed by furnace cooling to 175~185℃ and continued heat preservation, and then natural cooling to room temperature to obtain the annealed thin-film magnesium battery magnesium cobalt oxide cathode target; the first stage heat preservation temperature < the second stage heat preservation temperature < the third stage heat preservation temperature, and the third stage heat preservation temperature is 445~455℃. The annealing method includes: S1. Place the magnesium cobalt oxide cathode target for the thin-film magnesium battery into a vacuum annealing furnace and evacuate it to a vacuum level of 1-2 × 10⁻⁶. -4 Pa, maintain this vacuum level for 3~4 hours; S2. Introduce high-purity nitrogen gas to make the pressure inside the furnace greater than the atmospheric pressure outside the furnace, maintain this pressure for 30-40 minutes, then evacuate to a vacuum of 1-2 × 10⁻⁶. -4 Pa, maintain this vacuum level for 3~4 h; S3. H2+Ar mixed gas is continuously introduced, and the temperature is raised from room temperature to 145~155℃ and held for 4~5 hours. S4. H2+Ar mixed gas is continuously introduced, the furnace temperature is raised to 255~265℃, and held for 3~4 hours; S5. Continuously introduce a mixture of H2 and Ar gas, raise the furnace temperature to 445~455℃, and hold for 6.5~7.5 hours; S6. H2+Ar mixed gas is continuously introduced, and the furnace is slowly cooled to 175~185℃ and held for 4~5 hours. S7, then evacuate to 1-2 × 10⁻⁶ -4 Pa, maintain this vacuum level for 2.5~3.5h; S8. High-purity nitrogen gas is introduced to make the pressure inside the furnace greater than the atmospheric pressure outside the furnace, and then the furnace is naturally cooled to room temperature to obtain the annealed thin-film magnesium battery magnesium cobalt oxide cathode target. The magnesium cobalt oxide cathode target for thin-film magnesium batteries obtained by the annealing method has a uniform composition.

2. The annealing method according to claim 1, characterized in that, In the annealing method, S1, the magnesium cobalt oxide cathode target for the thin-film magnesium battery is placed in a vacuum annealing furnace and evacuated to a vacuum level of 1–1.5 × 10⁻⁶. -4 Pa, maintain this vacuum level for 3~4 hours.

3. The annealing method according to claim 2, characterized in that, In S3 to S6, the volume ratio of H2 to Ar is 5~15:85~95.

4. The annealing method according to claim 2, characterized in that, From S3 to S6, the pressure inside the vacuum annealing furnace is always kept greater than the atmospheric pressure outside the furnace.

5. The annealing method according to claim 2, characterized in that, The thin-film magnesium battery magnesium cobalt oxide cathode target in S1 is prepared using the following method, including: Step 1: Mix magnesium salt powder with cobalt tetroxide powder to obtain a mixed powder; Step 2: Place the above mixed powder into a ball mill jar and mix it with zirconia balls, then add a dispersant and continue mixing and ball milling; Step 3: Then add binder into the ball mill jar and continue ball milling; Step 4: After ball milling, the synthetic powder is passed through a 500-mesh sieve. The sieved synthetic powder is weighed and then poured into a vibrating mold. Pressure is applied to form a molded blank. Step 5: Place the billet into a cold isostatic press, apply pressure and hold pressure to obtain the cold isostatically pressed magnesium cobalt oxide cathode target billet. Step 6: Place the magnesium cobalt oxide cathode target blank into an atmosphere sintering furnace or a vacuum sintering furnace, and after multi-stage heat preservation and multi-stage cooling, allow it to cool naturally to room temperature with the furnace to obtain the magnesium cobalt oxide cathode target for thin-film magnesium batteries.

6. The annealing method according to claim 5, characterized in that, In step 1, the magnesium salt includes one or more of magnesium oxide, magnesium carbonate, magnesium nitrate, and magnesium hydroxide.

7. The annealing method according to claim 5, characterized in that, In step 1, the mass ratio of magnesium salt to cobalt tetroxide is controlled to be 1.1~1.3:

1.

8. The annealing method according to claim 5, characterized in that, In step 2, the particle size of the zirconia spheres is controlled to be 0.5 mm to 1.6 mm.

9. A magnesium cobalt oxide cathode target for thin-film magnesium batteries, characterized in that, The magnesium cobalt oxide cathode target for the thin-film magnesium battery is prepared by the method described in any one of claims 1-8.

10. A fully solid-state thin-film magnesium battery, characterized in that, The positive electrode of the all-solid-state thin-film magnesium battery is prepared using the magnesium cobalt oxide positive electrode target of the thin-film magnesium battery as described in claim 9.

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