Alkaline secondary battery positive electrode cobaltate-doped additive and preparation method and application thereof

Abstract

The invention discloses an alkaline secondary battery positive electrode cobaltate-doped additive and a preparation method and application thereof, the cobaltate-doped additive is composed of metal ion-doped cobaltate represented by a general formula MxN1-xCoO2, and the cobaltate-doped additive is prepared from a recycled waste lithium cobaltate positive electrode material as a raw material, the preparation method comprises the following steps: mixing a cobalt-containing intermediate with an M-containing metal compound and an N-containing metal compound according to a stoichiometric ratio, calcining, and adding the prepared additive into an alkaline secondary battery positive electrode as a performance enhancing component. According to the invention, high-valued recycling of the waste lithium battery material is realized, the process is green and environment-friendly, and the obtained additive can significantly improve the cycle life, rate capability and structural stability of alkaline secondary batteries such as nickel-hydrogen, zinc-nickel and the like, and has significant economic benefits and environmental benefits.

Description

Technical Field

[0001] This invention belongs to the technical field of positive electrode additives for alkaline secondary batteries, specifically relating to a cobaltate doped positive electrode additive for alkaline secondary batteries, its preparation method, and its application. Background Technology

[0002] Alkaline secondary batteries (such as nickel-metal hydride, nickel-zinc, and nickel-cadmium batteries) are an important class of chemical power sources. Due to their mature technology, high safety, good power characteristics, and excellent low-temperature performance, they continue to play an irreplaceable role in hybrid electric vehicles, rail transportation, backup power supplies, and special equipment. Their positive electrode typically uses nickel hydroxide (Ni(OH)₂) as the active material. However, Ni(OH)₂ itself is a p-type semiconductor with poor conductivity, resulting in high internal resistance of the electrode. During charging and discharging, especially under high current conditions, charge transfer is difficult, leading to severe electrode polarization. This not only limits the deep utilization of the active material and the battery's rate performance but also accelerates the accumulation and damage of mechanical stress in the electrode structure, ultimately manifesting as core problems such as a decrease in the battery's discharge voltage plateau, rapid reversible capacity decay, and insufficient cycle life.

[0003] To overcome the aforementioned bottlenecks, a long-standing and effective strategy in the industry has been to introduce cobalt-based additives into the cathode. These additives (such as metallic Co, CoO, and Co(OH)₂) can be oxidized in situ on the surface of Ni(OH)₂ particles and reconstructed into a highly conductive cobalt hydroxyl oxide (CoOOH) network during alkaline electrolyte and initial charging. This conductive network can improve the electrode's electronic conductivity, reduce polarization, and increase the oxygen evolution overpotential, thereby significantly improving the battery's capacity, rate performance, and cycle stability. However, this performance improvement scheme is highly dependent on metallic cobalt. As a strategic rare metal, cobalt is expensive and its price fluctuates wildly, directly leading to high battery production costs and severely restricting the further promotion and application of alkaline rechargeable batteries in cost-sensitive markets. Therefore, developing low-cost, high-performance alternatives or improved cobalt-based additives is one of the key requirements for the continued development of this technology.

[0004] For example, patent document CN200810135390.8 discloses an alkaline secondary battery positive electrode material, a positive electrode, and an alkaline secondary battery. The alkaline secondary battery positive electrode material contains a positive electrode active material, a binder, and a cobalt additive, which is one or more of Co, Co(OH)2, Co2O3, Co3O4, and CoO. Patent document CN200510126001.1 discloses an alkaline secondary battery positive electrode material and an alkaline secondary battery. The alkaline secondary battery positive electrode material contains nickel hydroxide powder, a cobalt additive, and a binder. This positive electrode material also contains metal powder, with the metal selected from one or more of vanadium, titanium, molybdenum, manganese, niobium, hafnium, zirconium, yttrium, and tantalum. The cobalt additive is one or more of Co, Co(OH)2, Co2O3, Co3O4, and CoO. The performance improvement of alkaline secondary batteries in the above patented technologies is highly dependent on metallic cobalt, which severely restricts the further promotion and application of alkaline secondary batteries in cost-sensitive markets.

[0005] On the other hand, with the rapid iteration of consumer electronics products, a large number of lithium-ion batteries are reaching the end of their service life. Their cathode material, lithium cobalt oxide (LiCoO2), contains valuable cobalt and lithium elements. Traditional lithium-ion battery cathode recycling often employs hydrometallurgical processes such as strong acid leaching and chemical precipitation, which are complex, costly, and may generate secondary pollution. Therefore, developing a green, low-cost pathway for the high-value reuse of waste lithium cobalt oxide and transforming it into high-performance materials for other energy storage systems has significant environmental and economic value. In particular, how to convert the massive amounts of waste lithium battery materials from the consumer end into low-cost, high-performance raw materials required for other industrial energy storage systems has become a topic of great economic and environmental significance.

[0006] For example, patent document CN201410366935.1 discloses a method for recovering cobalt, lithium, and aluminum from the positive electrode sheets of discarded lithium-ion batteries. The method involves discharging and disassembling the discarded lithium-ion batteries, calcining the discarded positive electrode sheets, dissolving them in water, and filtering to obtain discarded lithium cobalt oxide powder and aluminum foil. The discarded lithium cobalt oxide powder is then mixed with sodium bisulfate or sodium pyrosulfate in a certain proportion, ball-milled, and calcined at a low temperature. The calcined product is leached with water, and the leachate is subjected to cobalt precipitation and lithium precipitation to obtain cobalt oxalate and lithium carbonate. Patent document CN201611114126.7 discloses a method for recovering and preparing new electrodes from discarded ion batteries. Waste lithium-ion batteries are discharged and manually disassembled to obtain positive electrode material. This material is calcined, added to water and stirred, then sieved and dried to obtain lithium cobalt oxide powder. After ball milling, a mixed solution of natural organic acid and hydrogen peroxide is added. After the reaction is complete, ammonium oxalate solution is added to precipitate cobalt oxalate. Lithium salt powder is then added, ground evenly, and calcined to obtain lithium cobalt oxide powder that can be directly used as an electrode material. Waste lithium-ion batteries are recycled, and new lithium cobalt oxide electrodes are synthesized from the recycled lithium cobalt oxide material. Natural organic acid raw materials are used in the preparation process to avoid secondary pollution caused by waste liquid treatment. None of the above patented technologies mention the recovery of cobalt using a mixture of ethylene glycol and oxalic acid, nor do they mention using cobalt from recycled waste lithium cobalt oxide positive electrode material as an additive for alkaline secondary battery positive electrodes.

[0007] In summary, performance improvements in alkaline rechargeable batteries are limited by the high cost of cobalt-based additives, while the vast amounts of cobalt resources in spent lithium-ion batteries urgently require an innovative, green, and high-value recycling pathway. Currently, there are no reports on the targeted conversion of lithium cobalt oxide materials from spent lithium-ion batteries into cathode additives suitable for alkaline rechargeable battery systems using green processes. Existing technologies lack a synergistic solution that can simultaneously address the dual goals of reducing alkaline battery costs and achieving high-value recycling of spent lithium batteries. This invention is proposed based on this profound technological contradiction and industry demand. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a low-cost, high-performance cobaltate-doped positive electrode additive for alkaline secondary batteries. Another purpose of this invention is to provide a green preparation method for this cobaltate-doped additive, enabling the high-value recycling of waste lithium cobalt oxide. A third purpose of this invention is to provide a positive electrode plate and an alkaline secondary battery containing this cobaltate-doped additive.

[0009] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a cobaltate doped additive for the positive electrode of an alkaline secondary battery, wherein the cobaltate doped additive is formulated with general formula M x N 1-xCoO2 is a metal ion-doped cobaltate, wherein M is selected from one or more of Zn, Ca, Y, Ni and Er, N is selected from one or more of Na, K and Li, and 0.05≤x≤0.5. This cobaltate additive is made from recycled waste lithium cobalt oxide cathode material.

[0010] A method for preparing a cobaltate-doped additive for the positive electrode of an alkaline secondary battery, the specific preparation steps of which are as follows:

[0011] Step S1, raw material pretreatment: crush, grind and sieve the waste lithium cobalt oxide cathode material to obtain lithium cobalt oxide raw material powder;

[0012] Step S2, wet processing and intermediate preparation: Ethylene glycol and oxalic acid are mixed evenly to form a mixed solution, and then lithium cobalt oxide raw material powder is added to the mixed solution. The mixture is stirred at 50-100°C for 2-16 hours. After the reaction is completed, solid-liquid separation is performed, and the obtained solid is dried to obtain a cobalt-containing intermediate.

[0013] Step S3, Batching and Calcination: The cobalt-containing intermediate, the M-containing metal compound, and the N-containing metal compound are prepared according to the general formula M x N 1-x The stoichiometric ratio of CoO2 is mixed and then calcined at 700–850°C for 2–24 hours in air. After calcination, the mixture is cooled and pulverized to obtain a cobaltate additive for the positive electrode of an alkaline secondary battery.

[0014] Furthermore, in step S2, the solid-liquid ratio of the lithium cobalt oxide raw material powder in the mixed solution is 5-40 g / L; the molar ratio of ethylene glycol to oxalic acid in the mixed solution is 2:1-10:1; and the ethylene glycol recovered from the filtrate after solid-liquid separation by distillation is recycled.

[0015] Furthermore, the M-containing metal compound in step S3 is selected from one or more of zinc oxide, zinc carbonate, zinc acetate, calcium hydroxide, calcium carbonate, calcium acetate, calcium oxide, yttrium oxide, erbium oxide, nickel hydroxide, nickel oxide, and nickel acetate; the N-containing metal compound is selected from one or more of sodium carbonate, sodium hydroxide, sodium chloride, potassium carbonate, potassium hydroxide, potassium chloride, lithium carbonate, and lithium hydroxide.

[0016] The cobaltate additive described in this invention is applied to the field of alkaline secondary batteries, including nickel-hydrogen batteries, nickel-zinc batteries, nickel-iron batteries, nickel-cadmium batteries, nickel-bismuth batteries, alkaline zinc-manganese batteries, or alkaline silver-zinc batteries.

[0017] An alkaline secondary battery positive electrode plate includes a positive electrode current collector and a positive electrode material coated on the positive electrode current collector. The positive electrode material includes a positive electrode active material, a conductive agent, and a binder. The positive electrode material also includes the aforementioned cobaltate dopant additive, the amount of which is 1 wt% to 15 wt% of the positive electrode active material.

[0018] An alkaline secondary battery includes a battery casing, an electrode assembly sealed within the battery casing, and an electrolyte, wherein the electrode assembly includes a positive electrode plate, a negative electrode plate, and a separator, and the positive electrode plate is the alkaline secondary battery positive electrode plate described above.

[0019] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0020] 1. The M provided by this invention x N 1-x During the first charge of the battery, the CoO2 additive can generate a uniform, highly conductive, and highly stable conductive network in situ on the surface of nickel hydroxide particles. By flexibly selecting the types of elements M and N and adjusting the doping amount x, the structure and electrochemical properties of the additive can be specifically optimized to meet the performance requirements of different alkaline battery systems (such as zinc-nickel batteries, nickel-hydrogen batteries, etc.), effectively reducing electrode internal resistance and polarization, and improving oxygen evolution overpotential, thereby significantly improving the battery's discharge capacity, rate performance, and cycle stability.

[0021] 2. This invention uses waste lithium cobalt oxide as the core raw material, and recovers valuable metals such as cobalt through a green wet process, directly converting them into high-value-added products. This approach not only significantly reduces the raw material cost of high-performance additives, but also provides a new, efficient, and high-value recycling method for waste lithium-ion batteries, combining economic and environmental benefits.

[0022] 3. The ethylene glycol-oxalic acid mixed solution system used in the preparation process of this invention is relatively mild, and the ethylene glycol recovered by distillation after use can be recycled and reused, which reflects the concept of green chemistry. The whole process is simple and easy to scale up. Attached Figure Description

[0023] Figure 1 The images show the XRD patterns of the alkaline secondary battery additive materials prepared in the examples and comparative examples.

[0024] Figure 2 Ca prepared for the example 0.3 Na 0.7 SEM image of CoO2 additive material.

[0025] Figure 3 Ca prepared for the example 0.3 Na 0.7 EDX elemental distribution diagram of CoO2 additive materials. Detailed Implementation

[0026] The following examples further illustrate the above-described content of the present invention, but it should not be construed as limiting the scope of the subject matter of the present invention to the following examples. All technologies implemented based on the above-described content of the present invention fall within the scope of the present invention.

[0027] Example 1

[0028] Ca 0.3 Na 0.7 Preparation of CoO2 additive materials:

[0029] Obtaining waste lithium cobalt oxide: After discharging the waste lithium cobalt oxide battery, mechanically disassemble it to obtain the positive electrode sheet. Calcinate the positive electrode sheet at 450℃ for 1 hour. Crush, grind and sieve the black material that falls off to obtain the pretreated waste lithium cobalt oxide material.

[0030] Material preparation: Ethylene glycol and oxalic acid (molar ratio 5:1) were stirred and mixed evenly at 50℃. After the solution became clear, pretreated waste lithium cobalt oxide material was added to the mixed solution, controlling the solid-liquid ratio at 16 g / L. The mixture was stirred and reacted at 90℃ for 12 hours, then filtered and dried to obtain a cobalt-containing intermediate product. The cobalt-containing intermediate product was ball-milled with sodium carbonate and calcium acetate at a stoichiometric ratio of Ca / Na / Co = 0.3:0.7:1, and then calcined at 850℃ for 12 hours to obtain Ca 0.3 Na 0.7 CoO2 material.

[0031] Example 2

[0032] Zn 0.4 Na 0.6 Preparation of CoO2 additive materials:

[0033] The acquisition of waste lithium cobalt oxide material is the same as in Example 1.

[0034] Material preparation: Ethylene glycol and oxalic acid (molar ratio 6:1) were stirred and mixed evenly at 50℃. After the solution became clear, pretreated waste lithium cobalt oxide material was added to the mixed solution, controlling the solid-liquid ratio at 16 g / L. The mixture was stirred and reacted at 85℃ for 7 hours, then filtered and dried to obtain a cobalt-containing intermediate product. The cobalt-containing intermediate product was ball-milled with sodium hydroxide and zinc acetate at a stoichiometric ratio of Zn / Na / Co = 0.3:0.7:1, and then calcined at 830℃ for 20 hours to obtain Zn. 0.4 Na 0.6 CoO2 cathode additive material.

[0035] Example 3

[0036] Zn 0.1 Ca 0.2Na 0.7 Preparation of CoO2 additive materials:

[0037] The acquisition of waste lithium cobalt oxide material is the same as in Example 1.

[0038] Material preparation: Ethylene glycol and oxalic acid (molar ratio 7:1) were stirred and mixed evenly at 60℃. After the solution became clear, pretreated waste lithium cobalt oxide material was added to the mixed solution, controlling the solid-liquid ratio at 30 g / L. The mixture was stirred and reacted at 80℃ for 8 hours, then filtered and dried to obtain a cobalt-containing intermediate product. The cobalt-containing intermediate product was ball-milled with sodium chloride, zinc oxide, and calcium oxide at a stoichiometric ratio of Zn / Ca / Na / Co = 0.1:0.2:0.7:1, and then calcined at 800℃ for 10 hours to obtain Zn. 0.1 Ca 0.2 Na 0.7 CoO2 material.

[0039] Example 4

[0040] Ca 0.3 Li 0.2 Na 0.5 Preparation of CoO2 additive materials:

[0041] The waste lithium cobalt oxide material was obtained in the same way as in Example 1.

[0042] Material preparation: Ethylene glycol and oxalic acid (molar ratio 5:1) were stirred and mixed evenly at 40℃. After the solution became clear, pretreated waste lithium cobalt oxide material was added to the mixed solution, controlling the solid-liquid ratio at 16 g / L. The mixture was stirred and reacted at 90℃ for 12 hours, then filtered and dried to obtain a cobalt-containing intermediate product. The cobalt-containing intermediate product was ball-milled with sodium hydroxide, lithium carbonate, and calcium hydroxide at a stoichiometric ratio of Ca / Li / Na / Co = 0.3:0.2:0.5:1, and then calcined at 780℃ for 24 hours to obtain Ca 0.3 Li 0.2 Na 0.5 CoO2 additive material.

[0043] Example 5

[0044] Ni 0.3 Li 0.3 Na 0.4 Preparation of CoO2 additive materials:

[0045] The acquisition of waste lithium cobalt oxide material is the same as in Example 1.

[0046] Material preparation: Ethylene glycol and oxalic acid (molar ratio 8:1) were stirred and mixed evenly at 50℃. After the solution became clear, pretreated waste lithium cobalt oxide material was added to the mixed solution, controlling the solid-liquid ratio at 30 g / L. The mixture was stirred and reacted at 90℃ for 12 hours, then filtered and dried to obtain a cobalt-containing intermediate product. The cobalt-containing intermediate product was ball-milled with sodium carbonate, nickel acetate, and lithium hydroxide at a stoichiometric ratio of Ni / Li / Na / Co = 0.3:0.3:0.4:1, and then calcined at 800℃ for 24 hours to obtain Ca. 0.3 Li 0.2 Na 0.5 CoO2 additive material.

[0047] Example 6

[0048] Y 0.05 Na 0.95 Preparation of CoO2 additive materials:

[0049] The acquisition of waste lithium cobalt oxide material is the same as in Example 1.

[0050] Material preparation: Ethylene glycol and oxalic acid (molar ratio 4:1) were stirred and mixed evenly at 50℃. After the solution became clear, pretreated waste lithium cobalt oxide material was added to the mixed solution, and the solid-liquid ratio was controlled at 32 g / L. The mixture was stirred and reacted at 90℃ for 12 hours. After filtration and drying, a cobalt-containing intermediate product was obtained. The cobalt-containing intermediate product was ball-milled with sodium carbonate and yttrium oxide at a stoichiometric ratio of Y / Na / Co = 0.05:0.95:1, and then calcined at 830℃ for 16 hours to obtain Y. 0.05 Na 0.95 CoO2 additive material.

[0051] Example 7

[0052] Y 0.05 K 0.2 Na 0.75 Preparation of CoO2 additive materials:

[0053] The acquisition of waste lithium cobalt oxide material is the same as in Example 1.

[0054] Material preparation: Ethylene glycol and oxalic acid (molar ratio 6:1) were stirred and mixed evenly at 50℃. After the solution became clear, pretreated waste lithium cobalt oxide material was added to the mixed solution, controlling the solid-liquid ratio at 18 g / L. The mixture was stirred and reacted at 90℃ for 12 hours, then filtered and dried to obtain a cobalt-containing intermediate product. The cobalt-containing intermediate product was ball-milled with sodium carbonate, potassium hydroxide, and yttrium oxide at a stoichiometric ratio of Y / K / Na / Co = 0.05:0.2:0.75:1, and then calcined at 850℃ for 20 hours to obtain Y. 0.05 K 0.2 Na 0.75 CoO2 additive material.

[0055] Application of the additive materials prepared in Examples 1-7 in zinc-nickel alkaline secondary batteries:

[0056] Positive electrode plate preparation: Commercial nickel hydroxide, the additive materials synthesized in Examples 1-7 above, polytetrafluoroethylene (PTFE) suspension, and polyhydroxymethyl cellulose (HPMC) solution were mixed in a mass ratio of 80:10:5:5 and stirred evenly. Then, a certain amount of deionized water was added to make a paste. The paste was then coated onto 2cm×2cm nickel foam using a scraper, and after drying, rolling, and cutting, the positive electrode plate was formed.

[0057] Assembly of zinc-nickel alkaline secondary batteries: The prepared positive electrode plate, commercial negative electrode plate and alkaline battery separator are put into a special simulated battery case, and a saturated ZnO solution of 6M KOH is injected as the electrolyte to assemble a semi-sealed alkaline secondary battery.

[0058] Example 8

[0059] Ca 0.2 Zn 0.1 Na 0.7 Preparation of CoO2 additive materials:

[0060] The acquisition of waste lithium cobalt oxide material is the same as in Example 1.

[0061] Material preparation: Ethylene glycol and oxalic acid (molar ratio 4.5:1) were stirred and mixed evenly at 60℃. After the solution became clear, pretreated waste lithium cobalt oxide material was added to the mixed solution, controlling the solid-liquid ratio at 25 g / L. The mixture was stirred and reacted at 90℃ for 12 hours, then filtered and dried to obtain a cobalt-containing intermediate product. The cobalt-containing intermediate product was ball-milled with sodium hydroxide, zinc carbonate, and calcium oxide at a stoichiometric ratio of Ca / Zn / Na / Co = 0.2:0.1:0.7:1, and then calcined at 850℃ for 24 hours to obtain Ca 0.2 Zn 0.1 Na 0.7 CoO2 additive material.

[0062] Example 9

[0063] Ca 0.5 Na 0.5 Preparation of CoO2 additive materials:

[0064] The lithium cobalt oxide material dismantled from waste lithium cobalt oxide batteries was crushed, ground, and sieved to obtain pretreated waste lithium cobalt oxide material. Ethylene glycol and oxalic acid (molar ratio 5:1) were stirred and mixed evenly at 50°C. After the solution became clear, the pretreated waste lithium cobalt oxide material was added to the mixed solution, controlling the solid-liquid ratio at 16 g / L. The mixture was stirred and reacted at 90°C for 12 hours, then filtered and dried to obtain a cobalt-containing intermediate product. The cobalt-containing intermediate product was ball-milled with sodium carbonate and calcium hydroxide at a stoichiometric ratio of Ca / Na / Co = 0.5:0.5:1, and then calcined at 850°C for 24 hours to obtain Ca... 0.5 Na 0.5 CoO2 additive material.

[0065] Application of the additive materials prepared in Examples 8-9 in iron-nickel alkaline secondary batteries:

[0066] Positive electrode plate preparation: The positive electrode plate preparation method is the same as that in Examples 1 to 7 above. The additive materials prepared in Examples 8 to 9 are used to prepare positive electrode plates.

[0067] Assembly of nickel-iron alkaline secondary batteries: The prepared positive electrode plate, commercial negative electrode plate and alkaline battery separator are put into a special simulated battery case, and KOH solution with a mass concentration of 30% and LiOH solution with a mass concentration of 2% are injected as electrolytes to assemble a semi-sealed alkaline secondary battery.

[0068] Example 10

[0069] Ca 0.2 Li 0.1 Na 0.7 Preparation of CoO2 additive materials:

[0070] The lithium cobalt oxide material dismantled from waste lithium cobalt oxide batteries was crushed, ground, and sieved to obtain pretreated waste lithium cobalt oxide material. Ethylene glycol and oxalic acid (molar ratio 5:1) were stirred and mixed evenly at 50°C. After the solution became clear, the pretreated waste lithium cobalt oxide material was added to the mixed solution, controlling the solid-liquid ratio at 16 g / L. The mixture was stirred and reacted at 90°C for 12 hours, then filtered and dried to obtain a cobalt-containing intermediate product. The cobalt-containing intermediate product was ball-milled with sodium carbonate, lithium carbonate, and calcium carbonate at a stoichiometric ratio of Ca / Li / Na / Co = 0.2:0.1:0.7:1, and then calcined at 850°C for 24 hours to obtain Ca... 0.2 Li 0.1 Na 0.7 CoO2 additive material.

[0071] Example 11

[0072] Ca 0.2 K 0.2 Na 0.6Preparation of CoO2 additive materials:

[0073] The lithium cobalt oxide material dismantled from waste lithium cobalt oxide batteries was crushed, ground, and sieved to obtain pretreated waste lithium cobalt oxide material. Ethylene glycol and oxalic acid (molar ratio 5:1) were stirred and mixed evenly at 50°C. After the solution became clear, the pretreated waste lithium cobalt oxide material was added to the mixed solution, controlling the solid-liquid ratio at 16 g / L. The mixture was stirred and reacted at 90°C for 12 hours, then filtered and dried to obtain a cobalt-containing intermediate product. The cobalt-containing intermediate product was ball-milled with sodium carbonate, lithium carbonate, and calcium carbonate at a stoichiometric ratio of Ca / K / Na / Co = 0.2:0.2:0.6:1, and then calcined at 850°C for 24 hours to obtain Ca... 0.2 K 0.2 Na 0.6 CoO2 additive material.

[0074] Application of the additive materials prepared in Examples 10-11 in nickel-hydrogen alkaline secondary batteries:

[0075] Positive electrode plate preparation: The positive electrode plate preparation method is the same as that in Examples 1 to 7 above. The additive materials prepared in Examples 10 to 11 are used to prepare the positive electrode plate.

[0076] Assembly of nickel-hydrogen alkaline secondary battery: The prepared positive electrode plate, commercial hydrogen storage alloy negative electrode plate and alkaline battery separator are put into a special simulated battery case, and KOH solution with a mass concentration of 30% and LiOH solution with a mass concentration of 2% are injected as electrolytes to assemble a semi-sealed alkaline secondary battery.

[0077] Comparative Example 1

[0078] Preparation of NaCoO2 additive materials:

[0079] The lithium cobalt oxide material dismantled from waste lithium cobalt oxide batteries was crushed, ground, and sieved to obtain pretreated waste lithium cobalt oxide material. Ethylene glycol and oxalic acid (molar ratio 5:1) were stirred and mixed evenly in a solvent at 50°C. After the solution became clear, the pretreated waste lithium cobalt oxide material was added to the mixed solution, and the solid-liquid ratio was controlled at 20 g / L. The mixture was stirred and reacted at 80°C for 12 hours. After filtration and drying, a cobalt-containing intermediate product was obtained. The cobalt-containing intermediate product was ball-milled and mixed with sodium carbonate at a stoichiometric ratio of Na / Co = 0.7:1. Then, it was calcined at 850°C for 16 hours to obtain NaCoO2 additive material.

[0080] Comparative Example 2

[0081] Commercial nickel hydroxide with added CoO additives was used as the cathode material.

[0082] Comparative Example 3

[0083] Commercially available nickel hydroxide without any additives was used as the cathode material.

[0084] The comparative examples are all applied in zinc-nickel alkaline secondary batteries. The preparation method of the positive electrode plate and the battery assembly steps are the same as those in the examples above, and the above steps can be referred to.

[0085] Characterization of some samples:

[0086] The X-ray diffraction (XRD) results of some products in the above embodiments and comparative examples are as follows: Figure 1 As shown, the XRD patterns indicate that all samples can be classified as representative P2 layered structures with the P63 / mmc space group. No impurity phases were found, the (002) diffraction peaks shifted to lower positions, and the c-axis length increased.

[0087] Ca 0.3 Na 0.7 SEM results of CoO2 additive materials are as follows: Figure 2 As shown in the figure. Scanning electron microscopy (SEM) observations revealed that the obtained product exhibited a regular micro-flaky morphology with a smooth surface. The lateral size distribution of these micro-flasks ranged from 2 to 8 μm, and their thickness was approximately 800 nm.

[0088] Ca 0.3 Na 0.7 The DEX results of the CoO2 additive material are as follows: Figure 3 As shown. EDX results indicate that Ca 0.3 Na 0.7 CoO2 is composed of Ca, Na, Co and O elements, which are evenly distributed in the micro-flakes.

[0089] Table 1 Battery charge / discharge performance test

[0090]

[0091]

[0092] The test results above show that batteries assembled with positive electrode plates made using the positive electrode additive prepared in this invention exhibit high specific capacity, excellent rate performance, and cycle stability, meeting the requirements of commercial batteries, especially zinc-nickel secondary batteries. These performance improvements are mainly attributed to the fact that the metal ion-doped cobaltate material, as an additive, can form a structurally stable conductive network on the surface of the positive electrode active material during the first charge, reducing resistance, enhancing conductivity, increasing oxygen evolution overpotential, and effectively improving battery capacity and positive electrode stability. Furthermore, this invention enables the resource recycling of waste lithium cobalt oxide, possessing significant economic and social benefits, and providing more methods and ideas for the recycling of waste lithium cobalt oxide.

[0093] The above embodiments describe the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are only illustrative of the principles of the present invention. Various changes and modifications can be made to the present invention without departing from the scope of the principles of the present invention, and all such changes and modifications fall within the protection scope of the present invention.

Claims

1. A positive electrode doped-cobaltate additive for alkaline secondary batteries, characterized by: The cobalt-doped additive is composed of a metal ion-doped cobaltate represented by a general formula M x N 1-x CoO2, wherein M is selected from one or more of Zn, Ca, Y, Ni and Er, N is selected from one or more of Na, K and Li, and 0.05≤x≤0.5, and the cobalt-doped additive is prepared from a recovered waste lithium cobalt oxide cathode material.

2. A method for producing the positive electrode doped-cobaltate additive for alkaline secondary batteries according to claim 1, characterized by The specific preparation steps are as follows: Step S1, raw material pretreatment: the waste lithium cobalt oxide positive electrode material is crushed, ground and sieved to obtain lithium cobalt oxide raw powder; Step S2, wet treatment and intermediate preparation: ethylene glycol and oxalic acid are mixed uniformly to form a mixed solution, and then the lithium cobalt oxide raw powder is added into the mixed solution, and stirred and reacted at 50-100℃ for 2-16 hours. After the reaction is completed, solid-liquid separation is carried out, and the obtained solid is dried to obtain a cobalt-containing intermediate; Step S3, mixing and calcination: the cobalt-containing intermediate, the M-containing metal compound and the N-containing metal compound are mixed in a stoichiometric ratio of CoO2 x N 1- x M and N, and then calcined at 700-850°C for 2-24 hours in an air atmosphere, and after calcination, the mixture is cooled and crushed to obtain the positive electrode doped cobaltate additive for alkaline secondary batteries.

3. The method of producing a positive electrode doped-cobaltate additive for alkaline secondary batteries according to claim 2, characterized by: The solid-liquid ratio of the lithium cobalt oxide raw powder in the mixed solution in step S2 is 5-40 g / L; the molar ratio of ethylene glycol to oxalic acid in the mixed solution is 2:1-10:1; the ethylene glycol recovered by distillation of the filtrate after solid-liquid separation is recycled and used repeatedly.

4. The method of producing a positive electrode doped-cobaltate additive for alkaline secondary batteries according to claim 2, characterized by: The M-containing metal compound in step S3 is selected from one or more of zinc oxide, zinc carbonate, zinc acetate, calcium hydroxide, calcium carbonate, calcium acetate, calcium oxide, yttrium oxide, erbium oxide, nickel hydroxide, nickel oxide and nickel acetate; the N-containing metal compound is selected from one or more of sodium carbonate, sodium hydroxide, sodium chloride, potassium carbonate, potassium hydroxide, potassium chloride, lithium carbonate and lithium hydroxide.

5. The cobalt-doped acid salt additive of claim 1 is applied to the field of alkaline secondary batteries, including hydrogen-nickel batteries, zinc-nickel batteries, iron-nickel batteries, cadmium-nickel batteries, nickel-bismuth batteries, alkaline zinc-manganese batteries or alkaline silver-zinc batteries.

6. A positive electrode plate for an alkaline secondary battery, comprising a positive electrode current collector and a positive electrode material coated on the positive electrode current collector, characterized by: The positive electrode material comprises a positive electrode active material, a conductive agent and a binder, and further comprises the cobalt-doped acid salt additive of claim 1, and the addition amount of the cobalt-doped acid salt additive is 1wt%-15wt% of the positive electrode active material.

7. An alkaline secondary battery comprising a battery case, and a group of electrode plates and an electrolyte solution sealed in the battery case, wherein the group of electrode plates comprises a positive electrode plate, a negative electrode plate, and a separator, characterized by: The positive plate adopts the alkaline secondary battery positive plate of claim 6.

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