A method for preparing zirconium-doped cobalt oxide and zirconium-doped lithium cobalt oxide

Abstract

A method for preparing zirconium-doped cobalt oxide and zirconium-doped lithium cobalt oxide, wherein the method for preparing zirconium-doped cobalt oxide is as follows: (1) adding an inorganic cobalt salt solution and a zirconium source solution to a closed reaction kettle containing a precipitant / complexing agent bottom solution, heating and stirring the reaction under an inert atmosphere, and performing solid-liquid separation, washing, and drying on the obtained zirconium-doped cobalt hydroxide slurry; (2) performing full oxidation under an oxidizing atmosphere. The method for preparing zirconium-doped lithium cobalt oxide is as follows: uniformly mixing the zirconium-doped cobalt oxide obtained by the preparation method with a lithium source, sintering under an oxidizing atmosphere, and cooling. The zirconium-doped cobalt oxide obtained by the method of the present invention has a regular and controllable morphology, good uniformity, easy-to-control reaction conditions, simple process, low cost, and is suitable for industrial production. The zirconium-doped lithium cobalt oxide obtained by the method of the present invention has a stable structure, can adapt to a high working voltage of 4.5 V, and has excellent electrochemical properties.

Description

Technical Field

[0001] The invention relates to a method for preparing cobalt trioxide and lithium cobaltate, and in particular to a method for preparing zirconium-doped cobalt trioxide and zirconium-doped lithium cobaltate. Background Art

[0002] In the application of lithium cobalt oxide positive electrode materials, it is found that the working voltage of lithium cobalt oxide is limited to 4.25V, otherwise the performance of lithium-ion batteries will drop sharply. At this time, lithium cobalt oxide will undergo an irreversible phase change process from hexagonal phase to monoclinic phase. This irreversible change reduces the material capacity and service life. In order to further increase the working voltage of lithium cobalt oxide, the material performance attenuation during high voltage charging and discharging can be suppressed by bulk element doping. Bulk element doping can effectively stabilize the material structure and slow down the stability of the material structure during the charge and discharge cycle.

[0003] The doping methods in the prior art are usually to mix the doping element with cobalt tetroxide and calcine, to add the solid phase doping element when preparing cobalt tetroxide by precipitation method, or to directly calcine the doping element with lithium cobaltate for doping.

[0004] CN110061196A discloses a method for surface doping and modifying lithium cobalt oxide positive electrode materials, which is to prepare a surface sulfur-doped lithium cobalt oxide positive electrode by a hydrothermal method, wherein the sulfur source used is a metal sulfide, and the sulfur source is doped into the surface of the lithium cobalt oxide under hydrothermal conditions. However, the lithium cobalt oxide obtained by this method has poor doping uniformity, and the hydrothermal method has certain safety hazards, which is not conducive to industrial application.

[0005] CN112010355A discloses a zirconium-doped cobalt oxide and its preparation method and application, which comprises mixing a suspension of zirconium oxide with a cobalt salt solution and adopting a coprecipitation reaction to prepare zirconium-doped cobalt oxide. However, there are no free zirconium ions in the suspension, and the zirconium source exists in the form of solid oxide, so that the mixing of zirconium ions and cobalt ions at the ion level cannot be achieved.

[0006] CN108011103A discloses a method for preparing a gradient-doped lithium cobalt oxide positive electrode, which is to perform gradient doping of elements such as magnesium and aluminum during the preparation of cobalt oxide, and dope cobalt oxide with elements such as manganese, titanium, zirconium and cerium by solid phase mixing, and finally mix and calcine with a lithium source to obtain a gradient-doped lithium cobalt oxide positive electrode. However, in this method, elements such as magnesium and aluminum are added when preparing cobalt oxide by precipitation, and elements such as manganese, titanium, zirconium and cerium are still doped by solid phase mixing, so the obtained lithium cobalt oxide positive electrode still has the problem of uneven doping, and the high-voltage electrochemical performance is not significantly improved.

[0007] CN116375102A discloses an aluminum-magnesium-zirconium co-doped cobalt oxide and its preparation method and application, wherein aluminum, magnesium and zirconium ions are added into an inorganic cobalt salt solution to prepare aluminum-magnesium-zirconium co-doped cobalt oxide by coprecipitation reaction. However, since the pH range of aluminum ion precipitation is significantly lower than that of magnesium ions, zirconium ions and cobalt ions, the uniformity of the coprecipitation doping process has not been demonstrated in this method.

[0008] Therefore, it is urgent to find a method for preparing zirconium-doped cobalt tetroxide with regular and controllable morphology, good uniformity, simple process, easy-to-control reaction conditions, low cost, and suitable for industrial production, as well as a method for preparing zirconium-doped lithium cobalt oxide with stable structure, adaptability to a high operating voltage of 4.5 V, and excellent electrochemical properties. Summary of the invention

[0009] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a method for preparing zirconium-doped cobalt tetroxide, which has regular and controllable morphology, good uniformity, simple process, easy-to-control reaction conditions, low cost and is suitable for industrial production.

[0010] The technical problem further to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a method for preparing zirconium-doped lithium cobalt oxide, which has a stable structure, can adapt to a high operating voltage of 4.5 V, and has excellent electrochemical properties.

[0011] The technical solution adopted by the present invention to solve the technical problem is as follows: a method for preparing zirconium-doped cobalt tetroxide, comprising the following steps:

[0012] (1) adding an inorganic cobalt salt solution and a zirconium source solution to a closed reaction kettle containing a precipitant / complexing agent bottom solution, respectively, heating and stirring the reaction under an inert atmosphere, and subjecting the obtained zirconium-doped cobalt hydroxide slurry to solid-liquid separation, washing, and drying to obtain a zirconium-doped cobalt hydroxide solid;

[0013] (2) The zirconium-doped cobalt hydroxide solid obtained in step (1) is fully oxidized in an oxidizing atmosphere to obtain zirconium-doped cobalt tetroxide.

[0014] Preferably, in step (1), the molar concentration of the inorganic cobalt salt solution is 1.2 to 2.8 mol / L. If the concentration of the inorganic cobalt salt solution is too high, the precipitant will be consumed too quickly during the reaction, causing the pH value of the reaction system to decrease, and a good coprecipitation effect cannot be achieved. If the concentration of the inorganic cobalt salt solution is too low, the reaction time required for the precursor to grow to the target particle size will be too long.

[0015] Preferably, in step (1), the molar concentration of the zirconium source solution is 0.01 to 0.03 mol / L. If the concentration of the zirconium source solution is too low, more zirconium source solution needs to be added during the reaction process to make the ratio of zirconium element to cobalt element reach the target ratio. However, adding too much zirconium source solution will over-dilute the precipitant and complexing agent in the reactor, causing drastic changes in the pH value and the concentration of the complexing agent. If the concentration of the zirconium source solution is too high, the precipitation rate of zirconium ions will be accelerated, causing zirconium ions to precipitate before cobalt ions, making it difficult to ensure the generation of uniform precursor materials.

[0016] Preferably, in step (1), the molar ratio of the zirconium element in the zirconium source solution to the cobalt element in the inorganic cobalt salt solution is 0.005 to 0.010: 1. By limiting the molar ratio of the zirconium source and the cobalt ions, the amount of doped zirconium element can be controlled. If the doping amount of zirconium is too small, it is difficult to effectively improve the cycle stability of lithium cobalt oxide under high voltage and it is difficult to exert the positive effect of the doping element. If the doping amount is too large, the high-valent zirconium ions will cause changes in the structure of the product lithium cobalt oxide.

[0017] Preferably, in step (1), the volume ratio of the feed amount of the inorganic cobalt salt solution and the zirconium source solution added to the precipitant / complexing agent base solution per hour to the precipitant / complexing agent base solution is 0.016-0.024:0.008-0.012:1. If the feed amount of the inorganic cobalt salt solution or the zirconium source solution is too large, too many cobalt ions or zirconium ions will enter the reactor in a short period of time, accelerating the consumption of the alkali in the reactor and causing a drastic change in the pH value of the reaction system. If the feed amount of the inorganic cobalt salt solution or the zirconium source solution is too small, the time required for coprecipitation will be too long.

[0018] Preferably, in step (1), the volume ratio of the inorganic cobalt salt solution, the zirconium source solution and the precipitant / complexing agent base solution is 0.2-0.6:0.1-0.3:1. By limiting the amount of the inorganic cobalt salt solution and the zirconium source solution at a certain concentration, it is ensured that the ratio of zirconium element to cobalt element in the product is close to 0.005-0.010:1, and the material in the reactor can reach the target particle size.

[0019] Preferably, in step (1), the inorganic cobalt salt includes one or more of cobalt sulfate, cobalt chloride or cobalt nitrate, and hydrates thereof.

[0020] Preferably, in step (1), the zirconium source includes one or more of zirconium oxychloride or zirconium tetrachloride, and hydrates thereof, etc. The zirconium source can be hydrolyzed in an alkaline environment to form zirconium hydroxide.

[0021] Preferably, in step (1), the preparation method of the precipitant / complexing agent base solution is: dropwise adding the precipitant solution into the complexing agent aqueous solution, and adjusting the pH value to 10.90-11.50 to obtain the precipitant / complexing agent base solution.

[0022] Preferably, the complexing agent aqueous solution includes an ammonia solution and / or an EDTA solution.

[0023] Preferably, the aqueous ammonia solution is prepared by diluting concentrated ammonia water with water to a free ammonia concentration of 4.0 to 8.0 g / L. The mass fraction of the concentrated ammonia water is 25 to 28%.

[0024] Preferably, the molar concentration of the EDTA solution is 0.3-0.5 mol / L.

[0025] Preferably, in step (1), the molar concentration of the precipitant solution is 2.5 to 4.0 mol / L.

[0026] Preferably, in step (1), the precipitant includes one or more of sodium hydroxide, sodium carbonate or sodium oxalate.

[0027] Preferably, in step (1), during the heating and stirring reaction, the pH value of the reaction system is controlled to be 10.90-11.50 by supplementing the precipitant solution, and the concentration of the chelating agent in the reaction system is maintained by supplementing the chelating agent or the chelating agent aqueous solution. If the pH value of the reaction system is too low, too few crystal nuclei are formed at the initial stage of the reaction, and hydroxides with too large particle sizes will be formed later. If the pH value of the reaction system is too high, the reaction equilibrium will move toward the precipitation direction, and the redissolution process of the chelating agent will not play a good role in regulating the particle morphology. If the concentration of free ammonia or EDTA in the reaction system is too high, the reaction equilibrium will move toward the complexation direction, affecting the formation of hydroxide crystal nuclei. If the concentration of free ammonia or EDTA is too low, it is difficult to effectively adjust the particle morphology.

[0028] Preferably, when the aqueous solution of the complexing agent is an ammonia solution, the free ammonia concentration in the reaction system is maintained at 4.0 to 8.0 g / L by supplementing concentrated ammonia solution, and when the aqueous solution of the complexing agent is an EDTA solution, the molar concentration of EDTA in the reaction system is maintained at 0.3 to 0.5 mol / L by supplementing EDTA solution with a concentration of 0.6 to 1.0 mol / L.

[0029] Preferably, in step (1), the inert atmosphere includes one or more of nitrogen, argon or helium. The inert atmosphere used in the method of the present invention is a high-purity atmosphere with a purity of ≥99.999%.

[0030] Preferably, in step (1), the temperature of the heating and stirring reaction is 45-65°C, the pressure is 0.3-0.5MPa, the stirring speed is 1000-1400rpm, and the time is 20-28h, until the D50 of the precipitated particle size reaches 3-8μm. The reactor is kept closed during the reaction. In the early stage of the reaction, cobalt ions and zirconium ions react with hydroxide ions to generate corresponding hydroxide nuclei. After the formation of the nuclei, part of the hydroxide will re-combine with the complexing agent and dissolve. New cobalt ions and zirconium ions also generate new hydroxides on the nuclei at the same time, so that the hydroxide solid grows, and at the same time, a dense particle morphology is formed through the redissolution process of the complex.

[0031] Preferably, in step (1), the solid-liquid separation is vacuum filtration.

[0032] The inventive concept of step (1) of the present invention is to control the reaction conditions on the basis of co-precipitation, and to control the particle size and morphology of the product by adjusting the pH value, free ammonia concentration and feed rate of the reaction system.

[0033] Preferably, in step (2), the oxidizing atmosphere includes air and / or oxygen, etc.

[0034] Preferably, in step (2), the temperature of the sufficient oxidation is 100-180°C and the time is 24-36 hours. Although cobalt hydroxide can be slowly oxidized to cobalt tetroxide at room temperature, if the oxidation temperature is too low, the cobalt hydroxide will not be completely oxidized. If the oxidation temperature is too high, the precursor particles will be sintered and the size of the primary particles will increase. In the subsequent sintering process of lithium cobalt oxide, the larger primary particles will affect the solid phase diffusion of lithium ions in the precursor.

[0035] The technical solution adopted by the present invention to further solve its technical problem is as follows: a method for preparing zirconium-doped lithium cobalt oxide, after uniformly mixing the zirconium-doped cobalt tetroxide obtained by the preparation method with a lithium source, sintering them in an oxidizing atmosphere, and cooling them to room temperature to obtain a zirconium-doped lithium cobalt oxide positive electrode material.

[0036] Preferably, the molar ratio of the sum of the moles of cobalt and zirconium in the zirconium-doped cobalt tetroxide to the lithium in the lithium source is 1:1.02-1.08.

[0037] Preferably, the lithium source includes one or more of lithium carbonate, lithium hydroxide or lithium nitrate, and hydrates thereof.

[0038] Preferably, the oxidizing atmosphere includes air and / or oxygen, etc. The oxygen atmosphere used in the present invention is a high-purity atmosphere with a purity of ≥99.999%.

[0039] Preferably, the sintering is a two-stage temperature-raising sintering, specifically: first, the temperature is raised to 500-700°C (more preferably 600-650°C) at a rate of 1-10°C / min (more preferably 4-6°C / min), sintered for 5-10h (more preferably 6-8h), and then the temperature is raised to 700-950°C (more preferably 850-900°C) at a rate of 1-10°C / min (more preferably 4-6°C / min), and sintered for 8-15h (more preferably 10-12h). During the two-stage temperature-raising sintering process, the temperature of the second sintering stage is higher than the temperature of the first sintering stage. During the first stage sintering process, the decomposition reaction of the lithium source mainly occurs, and during the second stage sintering process, the chemical reaction of cobalt tetroxide and the oxide decomposed from the lithium source in an oxidizing atmosphere mainly occurs. If the sintering temperature is too high or the time is too long, the material is prone to cracks and the crystal particles are broken, making it difficult to perform the electrochemical performance normally. If the sintering temperature is too low or the time is too short, it is difficult to form the desired morphology, and lithium cobalt oxide is difficult to form a crystal structure with electrochemical activity, which leads to the attenuation of electrochemical performance. If the heating rate is too fast, it is difficult to ensure that the material reacts fully, and the lithium ions are not fully diffused into the material, resulting in a decrease in the active lithium of the material and a decrease in capacity. If the heating rate is too slow, it affects the material production efficiency.

[0040] The method of the present invention adopts a coprecipitation method to achieve uniform and stable doping of zirconium in cobalt oxide, and further prepares zirconium-doped lithium cobalt oxide. The method of the present invention regulates the bulk structure of lithium cobalt oxide through the process of uniform coprecipitation doping and the various modification effects of zirconium elements on lithium cobalt oxide crystals, thereby improving the electrochemical performance of lithium cobalt oxide, which is specifically manifested in: 1) Zirconium ion doping usually replaces cobalt ions in lithium cobalt oxide crystals, and zirconium ions with large radius can effectively expand the layered structure spacing in lithium cobalt oxide. At the same time, when +4-valent zirconium ions replace +3-valent cobalt ions, lithium vacancies will appear in the crystal to maintain the electrical neutrality of the crystal, thereby reducing Li + The diffusion energy barrier of lithium cobalt oxide is improved comprehensively. + Transmission capacity; 2) In the process of reaction between the precursor and the lithium source, the zirconium ion can reduce the surface energy of some crystal faces, play a role in regulating the formation of crystal faces and optimizing the morphology of the product, so that the morphology of the product lithium cobalt oxide single crystal particles tends to be slender and flat, shortening the path of lithium ion migration to the crystal surface, which is beneficial to the improvement of electrochemical performance; 3) Zirconium ions do not participate in the electrochemical reaction process within the working voltage range of lithium cobalt oxide. Zirconium ions occupy the cobalt position in lithium cobalt oxide. During the charge and discharge process, the +4 valence zirconium ions can adjust the valence of cobalt in lithium cobalt oxide, preventing the cobalt ions from being over-oxidized at high voltage and causing irreversible structural changes, thereby improving the stability of lithium cobalt oxide working at high cut-off voltage.

[0041] The beneficial effects of the present invention are as follows:

[0042] (1) The zirconium-doped cobalt tetroxide obtained by the method of the present invention has a regular and controllable morphology, is in the form of spherical particles, has good doping uniformity, and has uniform element distribution. The method of the present invention has a simple process, is easy to control reaction conditions, has low raw material costs, and is suitable for industrial production;

[0043] (2) The zirconium-doped lithium cobalt oxide obtained by the method of the present invention has a stable structure, can adapt to a high operating voltage of 4.5 V, and has excellent electrochemical properties. At an operating voltage of 3.0 to 4.5 V and a current density of 1C (1C=200 mA / g), the discharge specific capacity can be as high as 193.8 mAh / g. After 100 cycles, the discharge specific capacity can still be as high as 175.5 mAh / g, and the capacity retention rate is 92.27%. After 200 cycles, the discharge specific capacity can still be as high as 160.9 mAh / g, and the capacity retention rate is as high as 84.60%. Before and after 10C high-rate charge and discharge, the battery assembled with the zirconium-doped lithium cobalt oxide obtained by the present invention has basically the same discharge specific capacity under the corresponding high and low rate conditions, without obvious decrease, indicating that its electrochemical performance is stable and the capacity does not decay significantly. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is a SEM image of zirconium-doped cobalt tetroxide obtained in Example 1 of the present invention;

[0045] Figure 2 is the XRD pattern of zirconium-doped cobalt tetroxide obtained in Example 1 of the present invention;

[0046] Figure 3 This is the full XPS spectrum of zirconium-doped cobalt tetroxide obtained in Example 1 of the present invention;

[0047] Figure 4 This is the Zr 3d fine spectrum of the zirconium-doped cobalt tetroxide XPS obtained in Example 1 of the present invention;

[0048] Figure 5 This is an EDS graph of O, Co, and Zr in zirconium-doped cobalt tetroxide obtained in Example 1 of the present invention;

[0049] Figure 6 is a SEM image of zirconium-doped lithium cobalt oxide obtained in Example 1-1 of the present invention;

[0050] Figure 7 is the XRD pattern of zirconium-doped lithium cobalt oxide obtained in Example 1-1 of the present invention;

[0051] Figure 8 The charge-discharge cycle curve and charge-discharge Coulomb curve of the battery assembled with zirconium-doped lithium cobalt oxide obtained in Example 1-1 of the present invention;

[0052] Fig. 9This is a rate performance test diagram of a battery assembled with zirconium-doped lithium cobalt oxide obtained in Example 1-1 of the present invention;

[0053] Fig.10 The charge-discharge cycle curve and charge-discharge Coulomb curve of the battery assembled with zirconium-doped lithium cobalt oxide obtained in Example 2 of the present invention;

[0054] Fig.11 The charge-discharge cycle curve and charge-discharge Coulomb curve of the battery assembled with zirconium-doped lithium cobalt oxide obtained in Example 3 of the present invention;

[0055] Fig.12 This is a SEM image of the lithium cobalt oxide obtained in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0056] The present invention will be further described below in conjunction with the embodiments and drawings.

[0057] The mass fraction of concentrated ammonia water used in the examples of the present invention and the comparative examples is 25%; the purity of the inert atmosphere and the oxygen atmosphere in the examples of the present invention and the comparative examples is ≥99.999%; the raw materials or chemical reagents used in the examples of the present invention and the comparative examples, unless otherwise specified, are obtained through conventional commercial channels.

[0058] A method for preparing zirconium-doped cobalt tetroxide Example 1

[0059] (1) 2L, 2mol / L cobalt sulfate heptahydrate solution at a feed rate of 100 mL / h and 1L, 0.02mol / L zirconium oxychloride octahydrate solution at a feed rate of 50 mL / h were added simultaneously to a closed reactor containing 5L of precipitant / complexing agent bottom solution, and heated and stirred for reaction at 55°C, 0.4MPa, and 1200 rpm for 24 hours under a high-purity argon atmosphere until the D50 of the precipitated particles reached 6 μm. The obtained zirconium-doped cobalt hydroxide slurry was vacuum filtered, washed, and dried to obtain zirconium-doped cobalt hydroxide solid; during the heating and stirring reaction, the pH value of the reaction system was controlled to be 11.20 by adding 3mol / L sodium hydroxide solution, and the free ammonia concentration in the reaction system was maintained at 6.0g / L by adding concentrated ammonia solution;

[0060] The preparation method of the precipitant / complexing agent base liquid is as follows: concentrated ammonia water is diluted with water to a free ammonia concentration of 6.0 g / L, 3 mol / L sodium hydroxide solution is added dropwise to the ammonia solution, and the pH value is adjusted to 11.20 to obtain the precipitant / complexing agent base liquid;

[0061] (2) The zirconium-doped cobalt hydroxide solid obtained in step (1) is placed in a forced air oven and fully oxidized at 120° C. for 24 hours in an air atmosphere to obtain zirconium-doped cobalt tetroxide.

[0062] like Figure 1 As shown, the zirconium-doped cobalt oxide obtained in the embodiment of the present invention has a spherical shape and an average particle size of 6 μm.

[0063] like Figure 2 As shown, the zirconium-doped cobalt tetroxide obtained in the embodiment of the present invention and the PDF card Co 3 O 4 The characteristic peaks of the product are consistent with those of the product, and no impurities are generated.

[0064] like Figure 3 , 4 As shown, the characteristic peaks of Co and Zr in the zirconium-doped cobalt tetroxide obtained in the embodiment of the present invention were detected by XPS, indicating that zirconium has been successfully doped into the structure of the precursor.

[0065] like Figure 5 As shown, it is detected by EDS that oxygen, cobalt and zirconium elements are uniformly distributed in the zirconium-doped cobalt tetroxide obtained in the embodiment of the present invention.

[0066] A preparation method of zirconium-doped lithium cobalt oxide Example 1-1

[0067] 1 g (Co: 12.36158 mmol, Zr: 0.06212 mmol) of zirconium-doped cobalt tetroxide obtained in Example 1 of the present invention was evenly mixed with 0.4820 g (6.52312 mmol) of lithium carbonate, and then subjected to two-stage temperature rising sintering in a high-purity oxygen atmosphere: first, the temperature was raised to 650°C at a rate of 5°C / min, sintered for 6 hours, and then the temperature was raised to 900°C at a rate of 5°C / min, sintered for 12 hours, and cooled to room temperature to obtain a zirconium-doped lithium cobalt oxide positive electrode material.

[0068] like Figure 6 As shown, the zirconium-doped lithium cobalt oxide particles obtained in the embodiment of the present invention are mainly composed of agglomerated single crystal particles, and most of the long flat particles are generated, indicating that the effect of zirconium doping on crystal plane regulation is obvious.

[0069] like Figure 7 As shown, the zirconium-doped lithium cobalt oxide obtained in the embodiment of the present invention and the PDF card LiCoO 2 The characteristic peaks of the samples are consistent with those of the samples without any impurities generated.

[0070] Battery assembly: Weigh 0.08g of the zirconium-doped lithium cobalt oxide obtained in the embodiment of the present invention, add 0.01g of acetylene black as a conductive agent and 0.01g of PVDF polyvinylidene fluoride as a binder, and use N-methylpyrrolidone as a solvent, mix and grind to form a positive electrode material; apply the obtained positive electrode material on the surface of aluminum foil to form a pole piece; in a closed glove box filled with argon, use the pole piece as the positive electrode, the metal lithium sheet as the negative electrode, the microporous polypropylene film as the diaphragm, and 1mol / L LiPF 6 / EC:DMC:DEC (volume ratio 1:1:1) was used as the electrolyte, assembled into CR2025 button cells, and the charge and discharge performance was tested.

[0071] like Figure 8 As shown, the battery assembled with the zirconium-doped lithium cobalt oxide obtained in the embodiment of the present invention has a charge and discharge voltage of 3.0-4.5V and a current density of 0.1C (1C=200mA / g) (the first 3 cycles), and the first discharge specific capacity is 201.7mAh / g, the charge specific capacity is 214.9mAh / g, and the first charge and discharge coulomb efficiency is 93.86%; at a current density of 1C (starting from the 4th cycle), the first discharge specific capacity is 190.2mAh / g, the charge specific capacity is 197.5mAh / g, and the first charge and discharge coulomb efficiency is 96.30 %, after 100 cycles, the discharge specific capacity can still be as high as 175.5mAh / g, and the capacity retention rate is 92.27%; after 200 cycles, the discharge specific capacity can still be as high as 160.9mAh / g, and the capacity retention rate is 84.60%; it shows that the method for preparing zirconium-doped lithium cobalt oxide in the embodiment of the present invention can improve the transmission efficiency of lithium ions in the positive electrode material, so that the material can exert a higher charge and discharge capacity; by zirconium doping, the discharge specific capacity, charge and discharge performance and coulomb efficiency of lithium cobalt oxide are stable during the cycle process, the cycle life is long, and the cycle performance is good.

[0072] like Fig. 9 As shown, the battery assembled with the zirconium-doped lithium cobalt oxide obtained in the embodiment of the present invention has a discharge specific capacity of 189.4 mAh / g at a charge and discharge voltage of 3.0-4.5V and a current density of 1C (starting from the 11th cycle), and the discharge specific capacity can reach 183.4 mAh / g at a current density of 2C (starting from the 16th cycle), and the discharge specific capacity can reach 175.9 mAh / g at a current density of 5C (starting from the 21st cycle), and the discharge specific capacity can reach 166.8 mAh / g at a current density of 10C (starting from the 26th cycle); and then the current density is gradually reduced, and the discharge specific capacity can still be as high as 174.7 mAh / g at a current density of 5C (starting from the 31st cycle), and the discharge specific capacity can still be as high as 181.5 mAh / g at a current density of 2C (starting from the 36th cycle), and the discharge specific capacity can still be as high as 185.3 at a current density of 1C (starting from the 41st cycle). mAh / g; that is, before and after 10C high-rate charge and discharge, the battery assembled with zirconium-doped lithium cobalt oxide obtained in the embodiment of the present invention has basically the same discharge specific capacity under the corresponding high and low rate conditions, without obvious decrease, indicating that the method of the present invention is helpful to improve the cycle stability of the material under high-rate current, and can maintain stable electrochemical performance under high-rate current charge and discharge, and the capacity does not decay significantly.

[0073] A preparation method of zirconium-doped lithium cobalt oxide Example 1-2

[0074] After 1 g (Co: 12.36158 mmol, Zr: 0.06212 mmol) of zirconium-doped cobalt tetroxide obtained in Example 1 of the present invention and 0.4820 g (6.52312 mmol) of lithium carbonate were evenly mixed, two-stage temperature rising sintering was carried out in a high-purity oxygen atmosphere: first, the temperature was raised to 700°C at a rate of 6°C / min, sintered for 10 hours, and then the temperature was raised to 950°C at a rate of 6°C / min, sintered for 15 hours, and cooled to room temperature to obtain a zirconium-doped lithium cobalt oxide positive electrode material.

[0075] After testing, it was found that the zirconium-doped lithium cobalt oxide particles obtained in the embodiment of the present invention were mainly composed of agglomerated single crystal particles, and most of the long flat particles were generated, indicating that the effect of zirconium doping on crystal plane regulation is obvious.

[0076] After testing, the zirconium-doped lithium cobalt oxide obtained in the embodiment of the present invention and the PDF card LiCoO 2 The characteristic peaks of the product are consistent with those of the product, and no impurities are generated.

[0077] Battery assembly: Same as Example 1-1.

[0078] After testing, the battery assembled with zirconium-doped lithium cobalt oxide obtained in the embodiment of the present invention has a charge and discharge voltage of 3.0-4.5V, a current density of 0.1C (1C=200mA / g) (the first 3 cycles), the first discharge specific capacity is 200.2mAh / g, the charge specific capacity is 216.5mAh / g, and the first charge and discharge coulomb efficiency is 92.47%; at a current density of 1C (starting from the 4th cycle), the first discharge specific capacity is 196.2mAh / g, the charge specific capacity is 209.5mAh / g, and the first charge and discharge coulomb efficiency is 93.65%. After 100 cycles, the discharge specific capacity can still be as high as 169.8mAh / g, and the capacity retention rate is 86.54%. After 200 cycles, the discharge specific capacity can still be as high as 155.3mAh / g, and the capacity retention rate is 79.15%. In the embodiment of the present invention, by appropriately increasing the sintering temperature of zirconium-doped lithium cobalt oxide and extending the sintering time, the obtained zirconium-doped lithium cobalt oxide still has a high discharge specific capacity.

[0079] A preparation method of zirconium-doped lithium cobalt oxide Example 1-3

[0080] 1 g (Co: 12.36158 mmol, Zr: 0.06212 mmol) of zirconium-doped cobalt tetroxide obtained in Example 1 of the present invention was evenly mixed with 0.4820 g (6.52312 mmol) of lithium carbonate, and then subjected to two-stage temperature rising sintering in a high-purity oxidizing atmosphere: first, the temperature was raised to 550°C at a rate of 4°C / min, and sintered for 5 hours, then the temperature was raised to 830°C at a rate of 4°C / min, sintered for 8 hours, and cooled to room temperature to obtain a zirconium-doped lithium cobalt oxide positive electrode material.

[0081] After testing, it was found that the zirconium-doped lithium cobalt oxide particles obtained in the embodiment of the present invention were mainly composed of agglomerated single crystal particles, and most of the long flat particles were generated, indicating that the effect of zirconium doping on crystal plane regulation is obvious.

[0082] After testing, the zirconium-doped lithium cobalt oxide obtained in the embodiment of the present invention and the PDF card LiCoO 2 The characteristic peaks of the samples are consistent with those of the samples without any impurities generated.

[0083] Battery assembly: Same as Example 1-1.

[0084] After testing, the battery assembled with the zirconium-doped lithium cobalt oxide obtained in the embodiment of the present invention has a charge and discharge voltage of 3.0-4.5V and a current density of 0.1C (1C=200mA / g) (the first 3 cycles). The first discharge specific capacity is 194.6mAh / g, the charge specific capacity is 208.4mAh / g, and the first charge and discharge coulomb efficiency is 93.38%; at a current density of 1C (starting from the 4th cycle), the first discharge specific capacity is 182.6mAh / g, the charge specific capacity is 193.3mAh / g, and the first charge and discharge coulomb efficiency is 94.46%. After 100 cycles, the discharge specific capacity can still be as high as 163.2mAh / g, and the capacity retention rate is 89.38%. After 200 cycles, the discharge specific capacity can still be as high as 146.3mAh / g, and the capacity retention rate is 80.12%. In the embodiment of the present invention, at a relatively low sintering temperature of zirconium-doped lithium cobalt oxide, the obtained zirconium-doped lithium cobalt oxide still maintains a relatively high capacity retention rate after a long cycle, and has good long cycle performance.

[0085] A preparation method of zirconium-doped cobalt tetroxide Example 2

[0086] The difference between the embodiment of the present invention and embodiment 1 is that: in step (1), the concentration of the zirconium oxychloride octahydrate solution is 0.03 mol / L; the heating and stirring reaction time is 28 hours, until the D50 of the precipitated particle size reaches 7 μm; the pH value of the precipitant / complexing agent base solution is adjusted to 10.90; during the heating and stirring reaction process, the pH value of the reaction system is controlled to be 10.90. The rest is the same as embodiment 1.

[0087] After testing, the zirconium-doped cobalt tetroxide obtained in the embodiment of the present invention has a spherical morphology and an average particle size of 7 μm.

[0088] After testing, the zirconium-doped cobalt tetroxide obtained in the embodiment of the present invention and the PDF card Co 3 O 4 The characteristic peaks of the product are consistent with those of the product, and no impurities are generated.

[0089] A preparation method of zirconium-doped lithium cobalt oxide Example 2

[0090] The difference between the present embodiment and the embodiment 1-1 is that 1 g (Co: 12.31440 mmol, Zr: 0.09305 mmol) of zirconium-doped cobalt tetraoxide obtained in the embodiment 2 of the present invention is uniformly mixed with 0.4813 g (6.51364 mmol) of lithium carbonate. The rest is the same as the embodiment 1-1.

[0091] After testing, it was found that the zirconium-doped lithium cobalt oxide particles obtained in the embodiment of the present invention were mainly composed of agglomerated single crystal particles, and most of the long flat particles were generated, indicating that the effect of zirconium doping on crystal plane regulation is obvious.

[0092] After testing, the zirconium-doped lithium cobalt oxide obtained in the embodiment of the present invention and the PDF card LiCoO 2 The characteristic peaks of the product are consistent with those of the product, and no impurities are generated.

[0093] Battery assembly: Same as Example 1-1.

[0094] like Fig.10 As shown, the battery assembled with the zirconium-doped lithium cobalt oxide obtained in the embodiment of the present invention has a charge and discharge voltage of 3.0-4.5V and a current density of 0.1C (1C=200mA / g) (the first 3 cycles), and the first discharge specific capacity is 195.8mAh / g, the charge specific capacity is 211.9mAh / g, and the first charge and discharge coulomb efficiency is 92.40%; at a current density of 1C (starting from the 4th cycle), the first discharge specific capacity is 183.6mAh / g, the charge specific capacity is 190.7mAh / g, and the first charge and discharge coulomb efficiency is 9 6.28%, after 100 cycles, the discharge specific capacity can still be as high as 160.5mAh / g, and the capacity retention rate is 87.42%. After 200 cycles, the discharge specific capacity can still be as high as 145.8mAh / g, and the capacity retention rate is 79.41%. This shows that the embodiment of the present invention can prepare a zirconium-doped cobalt tetroxide precursor with a larger particle size by adjusting the reaction time and the pH value of the reaction system, and prolonging the reaction time and appropriately lowering the pH value increase the particle size of the precursor, thereby achieving the regulation of the particle size without significantly affecting the electrochemical performance.

[0095] Example 3 of a method for preparing zirconium-doped cobalt tetroxide

[0096] The difference between the embodiment of the present invention and embodiment 1 is that: in step (1), the heating and stirring reaction time is 20 h, until the D50 of the precipitated particle size reaches 4 μm; the pH value of the precipitant / complexing agent base solution is adjusted to 11.50; during the heating and stirring reaction process, the pH value of the reaction system is controlled to be 11.50. The rest is the same as embodiment 1.

[0097] After testing, the zirconium-doped cobalt tetroxide obtained in the embodiment of the present invention has a spherical morphology and an average particle size of 4 μm.

[0098] After testing, the zirconium-doped cobalt tetroxide obtained in the embodiment of the present invention and the PDF card Co 3 O 4 The characteristic peaks of the samples are consistent with those of the samples without any impurities generated.

[0099] A preparation method of zirconium-doped lithium cobalt oxide Example 3

[0100] The difference between the present embodiment and the embodiment 1-1 is that 1 g (Co: 12.36158 mmol, Zr: 0.06212 mmol) of zirconium-doped cobalt tetraoxide obtained in the embodiment 3 of the present invention is evenly mixed with 0.4911 g (6.64628 mmol) of lithium carbonate. The rest is the same as the embodiment 1-1.

[0101] After testing, it was found that the zirconium-doped lithium cobalt oxide particles obtained in the embodiment of the present invention were mainly composed of agglomerated single crystal particles, and most of the long flat particles were generated, indicating that the effect of zirconium doping on crystal plane regulation is obvious.

[0102] After testing, the zirconium-doped lithium cobalt oxide obtained in the embodiment of the present invention and the PDF card LiCoO 2 The characteristic peaks of the samples are consistent with those of the samples without any impurities generated.

[0103] Battery assembly: Same as Example 1-1.

[0104] like Fig.11 As shown, the battery assembled with the zirconium-doped lithium cobalt oxide obtained in the embodiment of the present invention has a charge and discharge voltage of 3.0-4.5V and a current density of 0.1C (1C=200mA / g) (the first 3 cycles), and the first discharge specific capacity is 189.8mAh / g, the charge specific capacity is 207.7mAh / g, and the first charge and discharge coulomb efficiency is 91.38%; at a current density of 1C (starting from the 4th cycle), the first discharge specific capacity is 180.6mAh / g, the charge specific capacity is 190.6mAh / g, and the first charge and discharge coulomb efficiency is 91.38%. The coulombic efficiency is 94.75%. After 100 cycles, the discharge specific capacity can still be as high as 155.4 mAh / g, and the capacity retention rate is 86.05%. After 200 cycles, the discharge specific capacity can still be as high as 134.6 mAh / g, and the capacity retention rate is 74.53%. This shows that the embodiment of the present invention can reduce the particle size of the precursor by shortening the reaction time and increasing the pH value, and increasing the pH value can generate more precursor particles with smaller sizes in the initial stage of the reaction, thereby realizing the preparation of small-sized and high electrochemical performance materials.

[0105] A method for preparing zirconium-doped cobalt tetroxide Example 4

[0106] The difference between the embodiment of the present invention and embodiment 1 is that: in step (1), 1.6L and 2.5mol / L cobalt sulfate heptahydrate solution at a feed rate of 80mL / h and 0.8L and 0.025mol / L zirconium oxychloride octahydrate solution at a feed rate of 40mL / h are added simultaneously to a closed reactor containing 5L of precipitant / complexing agent bottom liquid; the temperature of the heating and stirring reaction is 65°C, the pressure is 0.5MPa, and the time is 28h, until the D50 of the precipitated particles reaches 5μm. The rest is the same as embodiment 1.

[0107] After testing, the zirconium-doped cobalt tetroxide obtained in the embodiment of the present invention has a spherical morphology and an average particle size of 5 μm.

[0108] After testing, the zirconium-doped cobalt tetroxide obtained in the embodiment of the present invention and the PDF card Co 3 O 4 The characteristic peaks of the product are consistent with those of the product, and no impurities are generated.

[0109] Example 4 of a method for preparing zirconium-doped lithium cobalt oxide

[0110] The difference between the present embodiment and the embodiment 1-1 is that 1 g (Co: 12.36158 mmol, Zr: 0.06212 mmol) of zirconium-doped cobalt tetraoxide obtained in the embodiment 4 of the present invention is evenly mixed with 0.4820 g (6.52312 mmol) of lithium carbonate. The rest is the same as the embodiment 1-1.

[0111] After testing, it was found that the zirconium-doped lithium cobalt oxide particles obtained in the embodiment of the present invention were mainly composed of agglomerated single crystal particles, and most of the long flat particles were generated, indicating that the effect of zirconium doping on crystal plane regulation is obvious.

[0112] After testing, the zirconium-doped lithium cobalt oxide obtained in the embodiment of the present invention and the PDF card LiCoO 2 The characteristic peaks of the product are consistent with those of the product, and no impurities are generated.

[0113] Battery assembly: Same as Example 1-1.

[0114] After testing, the battery assembled with the zirconium-doped lithium cobalt oxide obtained in the embodiment of the present invention has a first discharge specific capacity of 198.2 mAh / g, a charge specific capacity of 211.4 mAh / g, and a first charge and discharge coulomb efficiency of 93.76% at a charge and discharge voltage of 3.0 to 4.5 V and a current density of 0.1 C (1C = 200 mA / g) (the first 3 cycles); at a current density of 1 C (starting from the 4th cycle), the first discharge specific capacity is 189.1 mAh / g, the charge specific capacity is 203.5 mAh / g, and the first charge and discharge coulomb efficiency is 92.92%. After 100 cycles, the discharge specific capacity can still be as high as 171.4 mAh / g, and the capacity retention rate is 90.64%. After 200 cycles, the discharge specific capacity can still be as high as 154.3 mAh / g, and the capacity retention rate is 81.60%. The embodiment of the present invention can reduce the particle size of the precursor by reducing the feed amount of the cobalt salt solution and the zirconium salt solution and appropriately adjusting the temperature and the reaction time, while still maintaining a relatively high discharge specific capacity, and the discharge specific capacity does not show a significant attenuation after 200 cycles.

[0115] A method for preparing zirconium-doped cobalt tetroxide Example 5

[0116] (1) 2.5 L, 1.6 mol / L cobalt sulfate heptahydrate solution at a feed rate of 120 mL / h and 1.25 L, 0.016 mol / L zirconium oxychloride octahydrate solution at a feed rate of 60 mL / h were added simultaneously to a closed reaction kettle containing 5 L of precipitant / complexing agent bottom liquid, and heated and stirred for reaction at 45° C., 0.3 MPa, and 1200 rpm under a high-purity argon atmosphere for 24 h until the D50 of the precipitated particles reached 8 μm, and the obtained zirconium-doped cobalt hydroxide slurry was vacuum filtered, washed, and dried to obtain zirconium-doped cobalt hydroxide solid; during the heating and stirring reaction, the pH value of the reaction system was controlled to be 11.20 by adding 3 mol / L sodium hydroxide solution, and the free ammonia concentration in the reaction system was maintained at 6.0 g / L by adding concentrated ammonia solution;

[0117] The preparation method of the precipitant / complexing agent base liquid is as follows: concentrated ammonia water is diluted with water to a free ammonia concentration of 6.0 g / L, 3 mol / L sodium hydroxide solution is added dropwise to the ammonia solution, and the pH value is adjusted to 11.20 to obtain the precipitant / complexing agent base liquid;

[0118] (2) The zirconium-doped cobalt hydroxide solid obtained in step (1) is placed in a forced air oven and fully oxidized at 140° C. for 30 hours in an air atmosphere to obtain zirconium-doped cobalt tetroxide.

[0119] After testing, the zirconium-doped cobalt tetroxide obtained in the embodiment of the present invention has a spherical morphology and an average particle size of 8 μm.

[0120] After testing, the zirconium-doped cobalt tetroxide obtained in the embodiment of the present invention and the PDF card Co 3 O 4 The characteristic peaks of the product are consistent with those of the product, and no impurities are generated.

[0121] A preparation method of zirconium-doped lithium cobalt oxide Example 5

[0122] The difference between the present embodiment and the embodiment 1-1 is that 1 g (Co: 12.36158 mmol, Zr: 0.06212 mmol) of zirconium-doped cobalt tetraoxide obtained in the embodiment 5 of the present invention is evenly mixed with 0.4820 g (6.52312 mmol) of lithium carbonate. The rest is the same as the embodiment 1-1.

[0123] After testing, it was found that the zirconium-doped lithium cobalt oxide particles obtained in the embodiment of the present invention were mainly composed of agglomerated single crystal particles, and most of the long flat particles were generated, indicating that the effect of zirconium doping on crystal plane regulation is obvious.

[0124] After testing, the zirconium-doped lithium cobalt oxide obtained in the embodiment of the present invention and the PDF card LiCoO 2 The characteristic peaks of the product are consistent with those of the product, and no impurities are generated.

[0125] Battery assembly: Same as Example 1-1.

[0126] After testing, the battery assembled with the zirconium-doped lithium cobalt oxide obtained in the embodiment of the present invention has a charge and discharge voltage of 3.0-4.5V and a current density of 0.1C (1C=200mA / g) (the first 3 cycles). The first discharge specific capacity is 200.9mAh / g, the charge specific capacity is 215.3mAh / g, and the first charge and discharge coulomb efficiency is 93.31%; at a current density of 1C (starting from the 4th cycle), the first discharge specific capacity is 193.8mAh / g, the charge specific capacity is 209.4mAh / g, and the first charge and discharge coulomb efficiency is 92.55%. After 100 cycles, the discharge specific capacity can still be as high as 172.9mAh / g, and the capacity retention rate is 89.22%. After 200 cycles, the discharge specific capacity can still be as high as 156.9mAh / g, and the capacity retention rate is 80.96%. It is explained that the embodiment of the present invention can prepare a larger-sized zirconium-doped cobalt tetroxide material by appropriately increasing the feed amount of cobalt salt solution and zirconium salt solution and controlling the reaction time. The material also has the characteristics of high specific capacity, high capacity retention rate after long cycles, and excellent electrochemical performance.

[0127] Example 6 of a method for preparing zirconium-doped cobalt tetroxide

[0128] The difference between the embodiment of the present invention and embodiment 1 is that: in step (1), the heating and stirring reaction time is 20 h, until the D50 of the precipitated particle size reaches 6 μm; the preparation method of the precipitant / complexing agent base solution is: in a 0.4 mol / L EDTA solution, 3 mol / L sodium hydroxide solution is added dropwise, and the pH value is adjusted to 11.20 to obtain the precipitant / complexing agent base solution; during the heating and stirring reaction, 0.8 mol / L EDTA solution is added to maintain the EDTA concentration in the reaction system at 0.4 mol / L. The rest is the same as embodiment 1.

[0129] After testing, the zirconium-doped cobalt tetroxide obtained in the embodiment of the present invention has a spherical morphology and an average particle size of 6 μm.

[0130] After testing, the zirconium-doped cobalt tetroxide obtained in the embodiment of the present invention and the PDF card Co 3 O 4 The characteristic peaks of the samples are consistent with those of the samples without any impurities generated.

[0131] A preparation method of zirconium-doped lithium cobalt oxide Example 6

[0132] The difference between the present embodiment and the embodiment 1-1 is that 1 g (Co: 12.36158 mmol, Zr: 0.06212 mmol) of zirconium-doped cobalt tetraoxide obtained in the embodiment 6 of the present invention is evenly mixed with 0.4820 g (6.52312 mmol) of lithium carbonate. The rest is the same as the embodiment 1-1.

[0133] After testing, it was found that the zirconium-doped lithium cobalt oxide particles obtained in the embodiment of the present invention were mainly composed of agglomerated single crystal particles, and most of the long flat particles were generated, indicating that the effect of zirconium doping on crystal plane regulation is obvious.

[0134] After testing, the zirconium-doped lithium cobalt oxide obtained in the embodiment of the present invention and the PDF card LiCoO 2 The characteristic peaks of the samples are consistent with those of the samples without any impurities generated.

[0135] Battery assembly: Same as Example 1-1.

[0136] After testing, the battery assembled with the zirconium-doped lithium cobalt oxide obtained in the embodiment of the present invention has a charge and discharge voltage of 3.0-4.5V and a current density of 0.1C (1C=200mA / g) (the first 3 cycles), and the first discharge specific capacity is 197.7mAh / g, the charge specific capacity is 213.4mAh / g, and the first charge and discharge coulomb efficiency is 92.64%; at a current density of 1C (starting from the 4th cycle), the first discharge specific capacity is 190.5mAh / g, the charge specific capacity is 201.4mAh / g, and the first charge and discharge coulomb efficiency is 94.59%. After 100 cycles, the discharge specific capacity can still be as high as 174.1mAh / g, and the capacity retention rate is 91.39%. After 200 cycles, the discharge specific capacity can still be as high as 159.2mAh / g, and the capacity retention rate is 83.57%. The embodiment of the present invention uses EDTA as a complexing agent in the preparation process of zirconium-doped cobalt oxide. The obtained zirconium-doped lithium cobalt oxide has high discharge specific capacity and good long cycle performance. The electrochemical performance is similar to that of the highly doped lithium cobalt oxide in Example 1-1.

[0137] A method for preparing cobalt tetraoxide Comparative Example 1

[0138] (1) adding 2 L, 2 mol / L cobalt sulfate heptahydrate solution at a feed rate of 100 mL / h into a closed reactor containing 5 L of precipitant / complexing agent base liquid, and heating and stirring the reaction at 55° C., 0.4 MPa, and 1200 rpm for 24 h under a high-purity argon atmosphere until the D50 of the precipitated particles reaches 6 μm, and vacuum filtering the obtained cobalt hydroxide slurry, washing, and drying to obtain cobalt hydroxide solid; during the heating and stirring reaction, the pH value of the reaction system is controlled to be 11.20 by adding 3 mol / L sodium hydroxide solution, and the free ammonia concentration in the reaction system is maintained at 6.0 g / L by adding concentrated ammonia solution;

[0139] The preparation method of the precipitant / complexing agent base liquid is as follows: concentrated ammonia water is diluted with water to a free ammonia concentration of 6.0 g / L, 3 mol / L sodium hydroxide solution is added dropwise to the ammonia solution, and the pH value is adjusted to 11.20 to obtain the precipitant / complexing agent base liquid;

[0140] (2) The cobalt hydroxide solid obtained in step (1) is placed in a forced air oven and fully oxidized at 120° C. for 24 hours under an air atmosphere to obtain cobalt tetroxide.

[0141] After testing, the cobalt tetraoxide obtained in the comparative example of the present invention has a spherical morphology and an average particle size of 6 μm.

[0142] A preparation method of lithium cobalt oxide Comparative Example 1

[0143] After 1 g (4.15282 mmol) of cobalt tetroxide obtained in Comparative Example 1 of the present invention and 0.4833 g (6.54071 mmol) of lithium carbonate were uniformly mixed, two-stage temperature rising sintering was carried out in a high-purity oxygen atmosphere: first, the temperature was raised to 650°C at a rate of 5°C / min, sintered for 6 hours, then the temperature was raised to 900°C at a rate of 5°C / min, sintered for 12 hours, and cooled to room temperature to obtain a lithium cobalt oxide positive electrode material.

[0144] like Fig.12 As shown, the lithium cobalt oxide particles obtained in the comparative example of the present invention are mainly composed of agglomerated single crystal particles, with more spherical or quasi-spherical particles, which are significantly different from the morphology of the zirconium-doped lithium cobalt oxide particles obtained in Example 1-1 of the present invention, indicating that zirconium doping has a significant regulatory effect on the morphology of lithium cobalt oxide.

[0145] Battery assembly: Same as Example 1-1.

[0146] After testing, the battery assembled with the lithium cobalt oxide obtained in the comparative example of the present invention has a charge and discharge voltage of 3.0 to 4.5V and a current density of 0.1C (1C=200mA / g) (the first 3 cycles), and the first discharge specific capacity is only 186.08mAh / g, the charge specific capacity is only 194.54mAh / g, and the first charge and discharge coulomb efficiency is 95.65%; at a current density of 1C (starting from the 4th cycle), the first discharge specific capacity is only 176.06mAh / g, the charge specific capacity is only 181.81mAh / g, and the first charge and discharge coulomb efficiency is 96.84%. After 100 cycles, the discharge specific capacity is only 98.96mAh / g, and the capacity retention rate is only 56.21%. It is explained that compared with Example 1-1 of the present invention, since the comparative example of the present invention is not doped with zirconium element, the discharge specific capacity of lithium cobalt oxide cannot be effectively improved, especially at an operating voltage of 3.0 to 4.5 V. After 200 cycles, the discharge specific capacity and capacity retention rate in the long cycle state are greatly reduced.

[0147] A preparation method of zirconium-doped cobalt tetroxide Comparative Example 2

[0148] 0.0201 g (0.0623 mmol) of zirconium oxychloride and 1.0 g (4.1529 mmol) of cobalt tetroxide were mixed and ground evenly to obtain zirconium-doped cobalt tetroxide.

[0149] After testing, the morphology of the zirconium-doped cobalt oxide obtained in the comparative example of the present invention is spherical particles with uneven particle sizes.

[0150] A preparation method of zirconium-doped lithium cobalt oxide Comparative Example 2

[0151] After uniformly mixing 1 g (Co: 12.36158 mmol, Zr: 0.06212 mmol) of zirconium-doped cobalt tetroxide obtained in Comparative Example 2 of the present invention and 0.4820 g (6.52312 mmol) of lithium carbonate, two-stage temperature rising sintering was carried out in a high-purity oxygen atmosphere: first, the temperature was raised to 650°C at a rate of 5°C / min, sintered for 6 h, then the temperature was raised to 900°C at a rate of 5°C / min, sintered for 12 h, and cooled to room temperature to obtain a zirconium-doped lithium cobalt oxide positive electrode material.

[0152] Upon testing, it was found that the zirconium-doped lithium cobalt oxide particles obtained in the comparative example of the present invention were mainly spherical or quasi-spherical crystal particles, with a small amount of elongated single crystal particles, which was quite different from the morphology of the zirconium-doped lithium cobalt oxide particles obtained in Example 1-1 of the present invention.

[0153] Battery assembly: Same as Example 1-1.

[0154] After testing, the battery assembled with zirconium-doped lithium cobalt oxide obtained in the comparative example of the present invention has a charge and discharge voltage of 3.0-4.5V and a current density of 0.1C (1C=200mA / g) (the first 3 cycles), and the first discharge specific capacity is only 180.78mAh / g, the charge specific capacity is only 197.80mAh / g, and the first charge and discharge coulomb efficiency is 91.40%; at a current density of 1C (starting from the 4th cycle), the first discharge specific capacity is only 172.01mAh / g, the charge specific capacity is only 181.56mAh / g, and the first charge and discharge coulomb efficiency is 94.74%. After 100 cycles, the discharge specific capacity is only 127.77mAh / g, and the capacity retention rate is only 74.28%. Although the long cycle performance of the discharge specific capacity of the zirconium-doped lithium cobalt oxide prepared by solid-phase mixing in the comparative example of the present invention is improved, the performance of the comparative example of the present invention is still far inferior to that of Example 1-1 of the present invention, indicating that it is difficult to achieve uniform distribution of elements through solid-solid mixing. Example 1-1 of the present invention achieves uniform mixing of zirconium and cobalt elements at the ionic level through co-precipitation, so that the zirconium doping plays a more significant role.

Claims

1. A method for preparing zirconium-doped cobalt oxide, characterized in that: The following steps are involved: (1) adding an inorganic cobalt salt solution and a zirconium source solution to a closed reaction kettle containing a bottom solution of a precipitant and a complexing agent, respectively, heating and stirring the reaction under an inert atmosphere, and performing solid-liquid separation on the obtained zirconium-doped cobalt hydroxide slurry, washing, and drying to obtain a zirconium-doped cobalt hydroxide solid; the molar concentration of the zirconium source solution is 0.01-0.03 mol / L; the molar ratio of the zirconium element in the zirconium source solution to the cobalt element in the inorganic cobalt salt solution is 0.005-0.010:1; the volume ratio of the feed amount of the precipitant and the complexing agent bottom solution added to the inorganic cobalt salt solution and the zirconium source solution per hour to the precipitant and the complexing agent bottom solution is 0.016-0.024:0.008-0.012:1; the complexing agent includes an ammonia solution and / or an EDTA solution; during the heating and stirring reaction, the reaction is controlled by supplementing the precipitant solution. The pH value of the system is 10.90-11.50, and the concentration of the complexing agent in the reaction system is maintained by supplementing the complexing agent; when the complexing agent is an ammonia solution, the concentration of free ammonia in the reaction system is maintained at 4.0-8.0 g / L by supplementing concentrated ammonia water; the temperature of the heating and stirring reaction is 45-65° C., the pressure is 0.3-0.5 MPa, the stirring speed is 1000-1400 rpm, and the time is 20-28 hours, until the D50 of the precipitated particle size reaches 3-8 μm; (2) The zirconium-doped cobalt hydroxide solid obtained in step (1) is fully oxidized in an oxidizing atmosphere to obtain zirconium-doped cobalt tetroxide; the temperature of the full oxidation is 100 to 140° C. and the time is 24 to 36 hours.

2. The method for preparing zirconium-doped cobalt tetroxide according to claim 1, characterized in that: In step (1), the molar concentration of the inorganic cobalt salt solution is 1.2-2.8 mol / L; the volume ratio of the inorganic cobalt salt solution, the zirconium source solution and the base solution of the precipitant and the complexing agent is 0.2-0.6:0.1-0.3:1; the inorganic cobalt salt includes one or more of cobalt sulfate, cobalt chloride and cobalt nitrate; and the zirconium source includes zirconium oxychloride and / or zirconium tetrachloride.

3. The method for preparing zirconium-doped cobalt oxide according to claim 1 or 2, characterized in that: In step (1), the preparation method of the base solution of the precipitant and the complexing agent is as follows: in the complexing agent, a precipitant solution is added dropwise, and the pH value is adjusted to 10.90-11.50 to obtain the base solution of the precipitant and the complexing agent; the ammonia solution is diluted by adding water to concentrated ammonia water to a free ammonia concentration of 4.0-8.0 g / L; the molar concentration of the EDTA solution is 0.3-0.5 mol / L; the molar concentration of the precipitant solution is 2.5-4.0 mol / L; the precipitant includes one or more of sodium hydroxide, sodium carbonate, and sodium oxalate; when the complexing agent is an EDTA solution, the molar concentration of EDTA in the reaction system is maintained at 0.3-0.5 mol / L by supplementing an EDTA solution with a concentration of 0.6-1.0 mol / L.

4. The method for preparing zirconium-doped cobalt tetroxide according to claim 1 or 2, characterized in that: In step (1), the inert atmosphere includes one or more of nitrogen, argon, and helium; in step (2), the oxidizing atmosphere includes air and / or oxygen.

5. The method for preparing zirconium-doped cobalt tetroxide according to claim 3, characterized in that: In step (1), the inert atmosphere includes one or more of nitrogen, argon, and helium; in step (2), the oxidizing atmosphere includes air and / or oxygen.

6. A method for preparing zirconium-doped lithium cobalt oxide, characterized in that: The zirconium-doped cobalt oxide obtained by the preparation method according to any one of claims 1 to 5 is uniformly mixed with a lithium source, sintered in an oxidizing atmosphere, and cooled to room temperature to obtain a zirconium-doped lithium cobalt oxide positive electrode material.

7. The method for preparing zirconium-doped lithium cobalt oxide according to claim 6, characterized in that: The molar ratio of the sum of the moles of cobalt and zirconium in the zirconium-doped cobalt tetroxide to the lithium in the lithium source is 1:1.02-1.08; the lithium source includes one or more of lithium carbonate, lithium hydroxide and lithium nitrate.

8. The method for preparing zirconium-doped lithium cobalt oxide according to claim 6 or 7, characterized in that: The oxidizing atmosphere includes air and / or oxygen; the sintering is a two-stage temperature-raising sintering, specifically: firstly heating to 500-700°C at a rate of 1-10°C / min, sintering for 5-10h, then heating to 700-950°C at a rate of 1-10°C / min, sintering for 8-15h.

Images