A lithium cobalt oxide cathode material, its preparation method and application

Abstract

This disclosure provides a lithium cobalt oxide cathode material, its preparation method, and its application, belonging to the field of cathode material technology. The preparation method of the lithium cobalt oxide cathode material disclosed herein involves subjecting a mixture comprising lithium cobalt oxide, ammonium fluoride, and lithium fluoride to a first sintering treatment to obtain the lithium cobalt oxide cathode material; wherein the ammonium fluoride is at least two of (NH4)2ZrF6, (NH4)2TiF6, (NH4)3AlF6, and (NH4)2SnF6, and the temperature of the first sintering treatment is 600-800℃. The preparation method of the lithium cobalt oxide cathode material disclosed herein can improve the charge / discharge capacity, cycle performance, thermal stability, and storage performance of the battery, as well as reduce the gas generation performance of the battery.

Description

Technical Field

[0001] This disclosure relates to the field of cathode material technology, specifically to a lithium cobalt oxide cathode material, its preparation method, and its application. Background Technology

[0002] Lithium cobalt oxide cathode materials are widely used in 3C electronic products due to their high compaction density. However, the increasing multifunctionality, miniaturization, and intelligence of 3C electronic products have placed higher demands on the volumetric energy density of lithium-ion batteries. The theoretical capacity of lithium cobalt oxide cathode materials is 274 mAh / g, while the capacity of currently widely used lithium cobalt oxide cathode materials is only 140 mAh / g. This means that only half the capacity of Li... + While increasing the charging voltage can improve the battery's specific capacity, it also causes a sharp decline in capacity during cycling and high-temperature storage, resulting in extremely poor cycle stability. This is currently the main bottleneck restricting the application of high-voltage, high-energy-density lithium cobalt oxide cathode materials. Therefore, there is an urgent need to develop a lithium cobalt oxide cathode material with high charge-discharge capacity, cycle performance, and thermal stability. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a lithium cobalt oxide cathode material, its preparation method and application.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a method for preparing lithium cobalt oxide cathode material, comprising the following steps:

[0005] A mixture comprising lithium cobalt oxide, ammonium fluoride, and lithium fluoride is subjected to a first sintering treatment to obtain a lithium cobalt oxide cathode material; wherein the ammonium fluoride is at least two of (NH4)2ZrF6, (NH4)2TiF6, (NH4)3AlF6, and (NH4)2SnF6, and the temperature of the first sintering treatment is 600-800℃.

[0006] In some embodiments, the mass of the ammonium fluoride salt is 1-3% of the mass of the lithium cobalt oxide.

[0007] In some embodiments, the mass of the lithium fluoride is 0.5-1.5% of the mass of the lithium cobalt oxide.

[0008] In some embodiments, the lithium cobalt oxide is prepared by subjecting a mixture comprising a first lithium cobalt oxide, a second lithium cobalt oxide, and additives to a second sintering treatment to obtain the lithium cobalt oxide.

[0009] In some embodiments, the median particle size D of the first lithium cobalt oxide v 501 has a particle size of 18-21 μm, and the median particle size D of the second lithium cobalt oxide is... v 502 has a thickness of 4.5-6 μm.

[0010] In some embodiments, the first lithium cobalt oxide contains a first doped metal element; optionally, the first doped metal element includes at least one of Ca, Zn, Ti, Fe, Mg, Al, Y, La, and Zr.

[0011] In some embodiments, the second lithium cobalt oxide contains a second doped metal element; optionally, the second doped metal element includes at least one of Ca, Zn, Ti, Fe, Mg, Al, Y, La, and Zr.

[0012] In some embodiments, the mass ratio of the first lithium cobalt oxide to the second lithium cobalt oxide is 3-4:1.

[0013] In some embodiments, the mass of the additive is 2.8-4.2% of the total mass of the first lithium cobalt oxide and the second lithium cobalt oxide.

[0014] In some embodiments, the additive is a compound containing a third doped metal element.

[0015] In some embodiments, the compound containing a third doped metal element includes at least one of an oxide of a third doped metal element, a hydroxide of a third doped metal element, and an inorganic salt of a third doped metal element.

[0016] In some embodiments, the third doped metal element includes at least one selected from Co, Ni, V, Mn, Al, Ti, F, Y, La, Zr, Ge, Ba, W, Nb, Cu, B, Sr, Ga, Zn, Mo, Si, and Sb.

[0017] Secondly, a lithium cobalt oxide cathode material is provided, wherein the lithium cobalt oxide cathode material is prepared by the method for preparing the lithium cobalt oxide cathode material.

[0018] Thirdly, a positive electrode sheet is provided, comprising the aforementioned lithium cobalt oxide positive electrode material.

[0019] Fourthly, a lithium-ion battery is provided, including the aforementioned positive electrode.

[0020] Fifthly, an electronic device is provided, including the aforementioned lithium-ion battery.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] (1) A mixture of lithium cobalt oxide, ammonium fluoride, and lithium fluoride is subjected to a first sintering treatment at a temperature of 600-800℃. This process forms a uniform first coating layer on the surface of the lithium cobalt oxide, which improves the charge-discharge capacity, cycle performance, thermal stability, and storage performance of the lithium cobalt oxide cathode material. The NH4+ in the ammonium fluoride... + Heating decomposes the lithium cobalt oxide to produce NH3. NH3 reacts with lithium cobalt oxide to generate oxygen vacancies. These oxygen vacancies can reduce the O 2p orbitals, decreasing the overlap between O 2p and Co 3d orbitals and thus reducing the oxygen activity on the surface of the lithium cobalt oxide cathode material. Secondly, the F- ions in the ammonium fluoride metal salt can replace the O- ions on the surface of the lithium cobalt oxide. 2- The formation of Co-F bonds inhibits the dissolution of cobalt in the electrolyte, reducing cobalt loss and improving the stability, cycle performance, and storage performance of the lithium cobalt oxide cathode material. Furthermore, the metal ions in the ammonium fluoride salt can form a metal fluoride layer on the surface of lithium cobalt oxide, inhibiting direct contact between the lithium cobalt oxide and the electrolyte, thus improving the stability, cycle performance, and storage performance of the lithium cobalt oxide cathode material. Lithium fluoride can act as a lithium supplement, increasing the capacity of the lithium cobalt oxide cathode material; simultaneously, the synergistic effect of lithium fluoride and the ammonium fluoride salt improves the charge-discharge capacity, cycle performance, thermal stability, and storage performance of the lithium cobalt oxide cathode material.

[0023] (2) The method for preparing lithium cobalt oxide cathode material disclosed herein adopts solid-phase reaction, which is simple and easy to implement, has low manufacturing cost, good reproducibility, and is convenient for large-scale industrial production. Attached Figure Description

[0024] Figure 1 This is a scanning electron microscope image of the lithium cobalt oxide cathode material from Example 1;

[0025] Figure 2 This is a scanning electron microscope image of the lithium cobalt oxide cathode material in Comparative Example 1. Detailed Implementation

[0026] To facilitate understanding of this disclosure, a more complete description will be provided below. However, this disclosure may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure.

[0027] For simplicity, this disclosure only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly stated; and any lower limit can be combined with other lower limits to form a range not explicitly stated, just as any upper limit can be combined with any other upper limit to form a range not explicitly stated. Furthermore, although not explicitly stated, every point or individual value between the endpoints of a range is included within that range. Therefore, each point or individual value can be used as its own lower or upper limit and combined with any other point or individual value or with other lower or upper limits to form a range not explicitly stated.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terminology used herein in the specification of this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of this disclosure. It should be noted that, unless otherwise stated, the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items, "above," "below," includes the stated number, and "one or more" means two or more.

[0029] The foregoing description of this application is not intended to describe every disclosed implementation or method. Instead, the following description provides more specific examples of exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments that can be used in various combinations. The examples listed are representative only and should not be construed as exhaustive.

[0030] The first aspect of this disclosure provides a method for preparing a lithium cobalt oxide cathode material, comprising the following steps:

[0031] S1: A mixture comprising lithium cobalt oxide, ammonium fluoride metal salt and lithium fluoride is subjected to a first sintering treatment to obtain lithium cobalt oxide cathode material; wherein, the ammonium fluoride metal salt is at least two of (NH4)2ZrF6, (NH4)2TiF6, (NH4)3AlF6 and (NH4)2SnF6; the temperature of the first sintering treatment is 600-800℃, for example, but not limited to 600℃, 650℃, 700℃, 750℃ and 800℃.

[0032] In step S1, ammonium fluoride and lithium fluoride are added and sintered at a temperature of 600-800°C to form a uniform first coating layer on the surface of lithium cobalt oxide. The first coating layer can improve the charge-discharge capacity, cycle performance, thermal stability and storage performance of lithium cobalt oxide cathode material.

[0033] NH4 in ammonium fluoride metal salts +Heating decomposes the lithium cobalt oxide to produce NH3. NH3 reacts with lithium cobalt oxide to generate oxygen vacancies. These oxygen vacancies can reduce the O 2p orbitals, decreasing the overlap between O 2p and Co 3d orbitals and thus reducing the oxygen activity on the surface of the lithium cobalt oxide cathode material. Secondly, the F- ions in the ammonium fluoride metal salt can replace the O- ions on the surface of the lithium cobalt oxide. 2- The formation of Co-F bonds inhibits the dissolution of cobalt in the electrolyte, reduces cobalt loss, and improves the stability, cycle performance, and storage performance of the lithium cobalt oxide cathode material. Furthermore, the metal ions in the ammonium fluoride salt can form a metal fluoride layer on the surface of lithium cobalt oxide, inhibiting direct contact between lithium cobalt oxide and the electrolyte, and improving the stability, cycle performance, and storage performance of the lithium cobalt oxide cathode material.

[0034] Lithium fluoride can supplement lithium and improve the capacity of lithium cobalt oxide cathode materials. At the same time, lithium fluoride and ammonium fluoride metal salts work synergistically to improve the charge-discharge capacity, cycle performance, thermal stability and storage performance of lithium cobalt oxide cathode materials.

[0035] When the temperature of the first sintering treatment is within the above-mentioned range, the charge-discharge capacity, cycle performance, thermal stability, and storage performance of the lithium cobalt oxide cathode material can be improved. If the temperature of the first sintering treatment is <600℃, the decomposition of ammonium fluoride salts will be insufficient, resulting in a decrease in the charge-discharge capacity, cycle performance, thermal stability, and storage performance of the lithium cobalt oxide cathode material. If the temperature of the first sintering treatment is >800℃, an irreversible phase transformation will occur on the surface of the lithium cobalt oxide cathode material to form a rock salt phase, which will lead to a decrease in the charge-discharge capacity, cycle performance, thermal stability, and storage performance of the lithium cobalt oxide cathode material.

[0036] It should be noted that the "lithium cobalt oxide" and "lithium cobalt oxide" mentioned in this disclosure are not limited to LiCoO2. Any oxide containing lithium and cobalt, such as oxides containing lithium and cobalt doped with other metal elements (such as transition metal elements), are within the scope of protection of this disclosure.

[0037] In some embodiments, the first sintering treatment time is 5-8 hours, for example, but not limited to 5 hours, 6 hours, 7 hours, or 8 hours.

[0038] In some embodiments, the mass of the ammonium fluoride metal salt is 1-3% of the mass of the lithium cobalt oxide, for example, but not limited to 1%, 1.2%, 1.5%, 2%, 2.5%, 2.7%, and 3%.

[0039] In some embodiments, the mass of the lithium fluoride is 0.5-1.5% of the mass of the lithium cobalt oxide, for example, but not limited to 0.5%, 0.8%, 1%, 1.2%, and 1.5%.

[0040] Adding the above-mentioned amounts of ammonium fluoride and lithium fluoride in step S1 can achieve a suitable thickness for the first coating layer. Therefore, when this lithium cobalt oxide cathode material is used in a battery, it can effectively resist the corrosion of the lithium cobalt oxide cathode material by electrolyte byproducts, reduce the dissolution of transition metals, and at the same time avoid the first coating layer being too thick, which would affect ion transport and improve the capacity, cycle performance, storage performance and thermal stability of the lithium cobalt oxide cathode material.

[0041] If the amount of ammonium fluoride salt and lithium fluoride added is too high, the resulting first coating layer is relatively thick, which affects ion transport and leads to a decrease in the capacity of the lithium cobalt oxide cathode material. If the amount of ammonium fluoride salt and lithium fluoride added is too low, the resulting first coating layer is relatively thin, which is not conducive to resisting the corrosion of the lithium cobalt oxide cathode material by electrolyte byproducts, leading to a decrease in the cycle performance, thermal stability and storage performance of the lithium cobalt oxide cathode material.

[0042] In this disclosure, the median particle size D of the lithium cobalt oxide is... v 505 is 16-18μm, for example, it can be, but is not limited to, 16μm, 16.5μm, 17μm, 17.5μm, and 18μm.

[0043] In some embodiments, this disclosure also includes a method for preparing lithium cobalt oxide, comprising the following steps: S2: subjecting a mixture containing a first lithium cobalt oxide, a second lithium cobalt oxide and an additive to a second sintering treatment to obtain lithium cobalt oxide.

[0044] In some embodiments, the median particle size D of the first lithium cobalt oxide v 501 has a particle size of 18-21 μm, for example, but not limited to 18 μm, 18.5 μm, 19 μm, 19.5 μm, 20 μm, 20.5 μm, and 21 μm; the median particle size D of the second lithium cobalt oxide v 502 has a thickness of 4.5-6μm, for example, it can be, but is not limited to, 4.5μm, 4.8μm, 5.0μm, 5.2μm, 5.5μm, 5.7μm, and 6μm.

[0045] The median particle size D of the first lithium cobalt oxide v Median particle size D of 501 and the second lithium cobalt oxide v 502 falls within the aforementioned range, enabling the formation of a combination of large and small particles in lithium cobalt oxide cathode materials, thereby improving the compaction density of lithium cobalt oxide cathode materials.

[0046] In some embodiments, the first lithium cobalt oxide contains a first doped metal element; optionally, the first doped metal element includes at least one of Ca, Zn, Ti, Fe, Mg, Al, Y, La, and Zr.

[0047] In some embodiments, the second lithium cobalt oxide contains a second doped metal element; optionally, the second doped metal element includes at least one selected from Ca, Zn, Ti, Fe, Mg, Al, Y, La, and Zr.

[0048] In some embodiments, the mass ratio of the first lithium cobalt oxide to the second lithium cobalt oxide is 3-4:1, for example, but not limited to 3:1, 3.2:1, 3.4:1, 3.6:1, 3.8:1, or 4:1.

[0049] When the mass ratio of the first lithium cobalt oxide to the second lithium cobalt oxide is within the aforementioned range, it is beneficial to improve the compaction density of the lithium cobalt oxide cathode material and the volumetric energy density of the battery. If the mass ratio of the first lithium cobalt oxide to the second lithium cobalt oxide is greater than 4:1, it is likely to lead to a decrease in the charge and discharge capacity of the battery.

[0050] In some embodiments, the mass of the additive is 2.8-4.2% of the total mass of the first lithium cobalt oxide and the second lithium cobalt oxide, for example, but not limited to 2.8%, 3.0%, 3.2%, 3.4%, 3.5%, 3.8%, 4.0%, and 4.2%.

[0051] Adding additives in step S2 in accordance with the above-mentioned addition amount can form a thin and uniform second coating layer on a portion of the surface of the first lithium cobalt oxide and the second lithium cobalt oxide. The second coating layer can promote the increase of the thermal stability of the cathode material, thereby improving the high-temperature cycle stability of the lithium-ion battery.

[0052] In some embodiments, the additive is a compound containing a third doped metal element;

[0053] In some embodiments, the compound containing a third doped metal element includes at least one of an oxide of a third doped metal element, a hydroxide containing a third doped metal element, and an inorganic salt containing a third doped metal element.

[0054] In some embodiments, the third doped metal element includes at least one selected from Co, Ni, V, Mn, Al, Ti, F, Y, La, Zr, Ge, Ba, W, Nb, Cu, B, Sr, Ga, Zn, Mo, Si, and Sb.

[0055] The second coating layer contains a third doped metal element, which helps to further suppress the direct contact between lithium cobalt oxide and the electrolyte, further suppress the dissolution of cobalt in the electrolyte, reduce cobalt loss, improve the stability of the cathode material structure, and thus further improve the cycle performance of the battery.

[0056] In some embodiments, the temperature of the second sintering treatment is 900-950°C, for example, but not limited to 900°C, 910°C, 920°C, 930°C, 940°C, and 950°C.

[0057] In some embodiments, the second sintering treatment time is 6-10 hours, for example, but not limited to 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours.

[0058] In some embodiments, this disclosure also includes a method for preparing a first lithium cobalt oxide, comprising the following steps:

[0059] A mixture containing a first lithium source and a first cobalt source is subjected to a first calcination treatment to obtain a first lithium cobalt oxide.

[0060] In some embodiments, the temperature of the first calcination treatment is 1050-1100°C, for example, but not limited to 1050°C, 1060°C, 1070°C, 1080°C, 1090°C, and 1100°C.

[0061] In some embodiments, the first calcination treatment time is 8-12 hours, for example, but not limited to 8 hours, 9 hours, 10 hours, 11 hours, or 12 hours.

[0062] In some embodiments, the molar ratio of lithium in the first lithium source to cobalt in the first cobalt source is 1.07-1.09, for example, but not limited to 1.07, 1.075, 1.08, 1.085, 1.09.

[0063] When the molar ratio of lithium to cobalt is within the aforementioned range, the residual alkali, pH value, particle size, tap density, and compaction density in the first lithium cobalt oxide are all within a suitable and optimal range. If the molar ratio of lithium to cobalt exceeds the aforementioned range, parameters such as residual alkali and pH value are prone to being too high, which ultimately leads to a decrease in the cycle performance of the lithium cobalt oxide cathode material.

[0064] In some embodiments, the median particle size D of the first cobalt source v 503 has a thickness of 13.5-18.5μm, for example, it can be, but is not limited to, 13.5μm, 14μm, 15μm, 16μm, 17μm, and 18.5μm.

[0065] In some embodiments, the mixture comprising the first lithium source and the first cobalt source further includes a compound containing a first doped metal element.

[0066] In some embodiments, the mass of the compound containing the first doped metal element is 0.3-3.5% of the mass of the first cobalt source, for example, but not limited to 0.3%, 0.5%, 1%, 1.5%, 2%, 2.5%, 2.8%, and 3%.

[0067] In some embodiments, the first doped metal element includes at least one of Ca, Zn, Ti, Fe, Mg, Al, Y, La, and Zr.

[0068] In some embodiments, this disclosure also includes a method for preparing a second lithium cobalt oxide, comprising the following steps:

[0069] A mixture containing a second lithium source and a second cobalt source is subjected to a second calcination treatment to obtain a second lithium cobalt oxide.

[0070] In some embodiments, the temperature of the second calcination treatment is 1000-1050°C, for example, but not limited to 1000°C, 1010°C, 1020°C, 1030°C, 1040°C, and 1050°C.

[0071] In some embodiments, the second calcination treatment time is 8-12 hours, for example, but not limited to 8 hours, 9 hours, 10 hours, 11 hours, or 12 hours.

[0072] In some embodiments, the molar ratio of lithium in the second lithium source to cobalt in the second cobalt source is 1.07-1.09, for example, but not limited to 1.07, 1.075, 1.08, 1.085, 1.09.

[0073] When the molar ratio of lithium to cobalt is within the aforementioned range, the residual alkali, pH value, particle size, tap density, and compaction density in the second lithium cobalt oxide are all within a suitable and optimal range. If the molar ratio of lithium to cobalt exceeds the aforementioned range, parameters such as residual alkali and pH value are prone to being too high, which ultimately leads to a decrease in the cycle performance of the lithium cobalt oxide cathode material.

[0074] In some embodiments, the median particle size D of the second cobalt source v 504 has a thickness of 1.5-6.5μm, for example, it can be, but is not limited to, 1.5μm, 2μm, 3μm, 4μm, 5μm, 6μm, and 6.5μm.

[0075] In some embodiments, the mixture containing a second lithium source and a second cobalt source further includes a compound containing a second doped metal element.

[0076] In some embodiments, the mass of the compound containing the second doped metal element is 0.2-1.6% of the mass of the second cobalt source, for example, but not limited to 0.2%, 0.4%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, and 1.6%.

[0077] In some embodiments, the second doped metal element includes at least one of Ca, Zn, Ti, Fe, Mg, Al, Y, La, and Zr.

[0078] In some embodiments, the first lithium source and the second lithium source are each independently at least one of lithium carbonate, lithium nitrate, lithium acetate, lithium hydroxide, lithium oxide, lithium chloride, lithium bromide and lithium fluoride.

[0079] In some embodiments, the first cobalt source and the second cobalt source are each independently at least one of cobalt tetroxide, cobalt hydroxide, cobalt sulfide, cobalt nitrate, cobalt sulfate, and cobalt hydroxyoxide.

[0080] In this disclosure, the median particle size D v The value of 50 can be obtained using a laser particle size analyzer.

[0081] In a second aspect, a lithium cobalt oxide cathode material is provided, wherein the lithium cobalt oxide cathode material is prepared by the method for preparing the lithium cobalt oxide cathode material described in the first aspect.

[0082] Thirdly, a positive electrode sheet is provided, comprising the lithium cobalt oxide positive electrode material described in the second aspect.

[0083] Fourthly, a lithium-ion battery is provided, comprising the positive electrode sheet described in the third aspect.

[0084] In some embodiments, the lithium-ion battery further includes a negative electrode, an electrolyte, and a separator. During charging and discharging, lithium ions repeatedly insert and extract between the positive and negative electrodes. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0085] Fifthly, an electronic device is provided, comprising the lithium-ion battery described in the fourth aspect.

[0086] In some implementations, the type of electronic device is not particularly limited, and it can be any electronic device known in the prior art. For example, the electronic device may include, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, etc.

[0087] Example 1

[0088] A method for preparing a lithium cobalt oxide cathode material includes the following steps:

[0089] (1) D v 50% of cobalt tetroxide (15.5 μm), lithium carbonate, and a compound containing the first dopant element were mixed uniformly to obtain a first mixture; wherein the molar ratio of lithium to cobalt was 1.08, and the compound containing the first dopant element was obtained by mixing magnesium oxide, aluminum oxide, and titanium oxide in a mass ratio of 1:1:1, with the mass of the compound containing the first dopant element being 2.3% of the mass of cobalt tetroxide; the first mixture was sintered in a high-temperature box furnace at 1070℃ in an air atmosphere for 10 hours, cooled, and crushed to D... v 50 is 18.8 μm, and the first lithium cobalt oxide is obtained.

[0090] (2) D v 50% of cobalt tetroxide (3.2 μm), lithium carbonate, and a compound containing a second dopant element were mixed uniformly to obtain a second mixture; wherein the molar ratio of lithium to cobalt was 1.08, and the compound containing the second dopant element was obtained by mixing magnesium oxide, aluminum oxide, and titanium oxide in a mass ratio of 1:1:1, with the mass of the compound containing the second dopant element being 1.2% of the mass of cobalt tetroxide; the second mixture was sintered in a high-temperature box furnace at 1020℃ in an air atmosphere for 10 h, cooled, and crushed to D v 50 is 5.5 μm, and a second lithium cobalt oxide is obtained.

[0091] (3) The first lithium cobalt oxide, the second lithium cobalt oxide, and the additives are mixed evenly to obtain a third mixture; wherein the mass ratio of the first lithium cobalt oxide to the second lithium cobalt oxide is 4:1, and the additives are obtained by mixing aluminum oxide, lanthanum oxide, yttrium oxide, zinc oxide, and zirconium oxide in a mass ratio of 1:1:1:1:1, and the mass of the additives is 3.5% of the total mass of the first and second lithium cobalt oxides; the third mixture is sintered in a high-temperature box furnace at 920℃ in an air atmosphere for 8 hours, cooled, and crushed to D v 50 is 16.5 μm, and the third lithium cobalt oxide is obtained.

[0092] (4) The third lithium cobalt oxide, ammonium fluoride and lithium fluoride are mixed evenly to obtain the fourth mixture, wherein the ammonium fluoride is (NH4)2ZrF6 and (NH4)2TiF6 are mixed in a mass ratio of 1:1, the mass of the ammonium fluoride is 2% of the mass of the lithium cobalt oxide, and the mass of the lithium fluoride is 1% of the mass of the lithium cobalt oxide; the fourth mixture is sintered in a high temperature box furnace at 700℃ in an air atmosphere for 6 hours, and then cooled to obtain the lithium cobalt oxide cathode material.

[0093] Example 2

[0094] A method for preparing a lithium cobalt oxide cathode material includes the following steps:

[0095] (1) D v Cobalt tetroxide (13.5 μm), lithium carbonate, and a compound containing a first dopant element were mixed uniformly to obtain a first mixture; wherein the molar ratio of lithium to cobalt was 1.08, and the compound containing the first dopant element was obtained by mixing magnesium oxide, aluminum oxide, and titanium oxide in a mass ratio of 1:1:1, with the mass of the compound containing the first dopant element being 0.3% of the mass of cobalt tetroxide; the first mixture was sintered in a high-temperature box furnace at 1050℃ in an air atmosphere for 10 hours, cooled, and crushed to D v 50 is 18.1 μm, and the first lithium cobalt oxide is obtained.

[0096] (2) D v 50% of cobalt tetroxide (1.6 μm), lithium carbonate, and a compound containing a second dopant element were mixed uniformly to obtain a second mixture; wherein the molar ratio of lithium to cobalt was 1.08, and the compound containing the second dopant element was obtained by mixing magnesium oxide, aluminum oxide, and titanium oxide in a mass ratio of 1:1:1, with the mass of the compound containing the second dopant element being 0.2% of the mass of cobalt tetroxide; the second mixture was sintered in a high-temperature box furnace at 1020℃ in an air atmosphere for 10 h, cooled, and crushed to D v 50 is 4.5 μm, and a second lithium cobalt oxide is obtained.

[0097] (3) The first lithium cobalt oxide, the second lithium cobalt oxide, and the additives are mixed evenly to obtain a third mixture; wherein the mass ratio of the first lithium cobalt oxide to the second lithium cobalt oxide is 3:1, and the additives are obtained by mixing aluminum oxide, lanthanum oxide, yttrium oxide, zinc oxide, and zirconium oxide in a mass ratio of 1:1:1:1:1, and the mass of the additives is 2.8% of the total mass of the first and second lithium cobalt oxides; the third mixture is sintered in a high-temperature box furnace at 920℃ in an air atmosphere for 8 hours, cooled, and crushed to D v 50 is 16.5 μm, and the third lithium cobalt oxide is obtained.

[0098] (4) The third lithium cobalt oxide, ammonium fluoride and lithium fluoride are mixed evenly to obtain the fourth mixture, wherein the ammonium fluoride is (NH4)2ZrF6 and (NH4)2AlF6 are mixed in a mass ratio of 1:1, the mass of the ammonium fluoride is 1% of the mass of the lithium cobalt oxide, and the mass of lithium fluoride is 0.5% of the mass of the lithium cobalt oxide; the fourth mixture is sintered in a high temperature box furnace at 700℃ in an air atmosphere for 6 hours, and then cooled to obtain the lithium cobalt oxide cathode material.

[0099] Example 3

[0100] A method for preparing a lithium cobalt oxide cathode material includes the following steps:

[0101] (1) D v Cobalt tetroxide (18.4 μm), lithium carbonate, and a compound containing the first dopant element were mixed uniformly to obtain a first mixture; wherein the molar ratio of lithium to cobalt was 1.08, and the compound containing the first dopant element was obtained by mixing magnesium oxide, aluminum oxide, and titanium oxide in a mass ratio of 1:1:1, with the mass of the compound containing the first dopant element being 3.5% of the mass of cobalt tetroxide; the first mixture was sintered in a high-temperature box furnace at 1050℃ in an air atmosphere for 10 hours, cooled, and crushed to D v 50 is 20.9 μm, and the first lithium cobalt oxide is obtained.

[0102] (2) D v Cobalt tetroxide (6.3 μm), lithium carbonate, and a compound containing a second dopant element were mixed uniformly to obtain a second mixture. The molar ratio of lithium to cobalt was 1.08. The compound containing the second dopant element was obtained by mixing magnesium oxide, aluminum oxide, and titanium oxide in a mass ratio of 1:1:1, and the mass of the compound containing the second dopant element was 1.6% of the mass of cobalt tetroxide. The second mixture was sintered in a high-temperature box furnace at 1020℃ in an air atmosphere for 10 hours, cooled, and crushed to D... v 50 is 5.8 μm, and a second lithium cobalt oxide is obtained.

[0103] (3) The first lithium cobalt oxide, the second lithium cobalt oxide, and the additives are mixed evenly to obtain a third mixture; wherein the mass ratio of the first lithium cobalt oxide to the second lithium cobalt oxide is 3.5:1, and the additives are obtained by mixing aluminum oxide, lanthanum oxide, yttrium oxide, zinc oxide, and zirconium oxide in a mass ratio of 1:1:1:1:1, and the mass of the additives is 4.2% of the total mass of the first and second lithium cobalt oxides; the third mixture is sintered in a high-temperature box furnace at 920℃ in an air atmosphere for 8 hours, cooled, and crushed to D v 50 is 17.8 μm, and the third lithium cobalt oxide is obtained.

[0104] (4) The third lithium cobalt oxide, ammonium fluoride and lithium fluoride are mixed evenly to obtain the fourth mixture, wherein the ammonium fluoride is (NH4)2ZrF6 and (NH4)2SnF6 are mixed in a mass ratio of 1:1, the mass of the ammonium fluoride is 3% of the mass of the lithium cobalt oxide, and the mass of lithium fluoride is 1.5% of the mass of the lithium cobalt oxide; the fourth mixture is sintered in a high temperature box furnace at 700℃ in an air atmosphere for 6 hours, and then cooled to obtain the lithium cobalt oxide cathode material.

[0105] Example 4

[0106] The difference between the preparation method of lithium cobalt oxide cathode material in this embodiment and that in Example 1 is only that the ammonium fluoride salt in step (4) is different. The ammonium fluoride salt in this embodiment is obtained by mixing (NH4)2TiF6 and (NH4)2AlF6 in a mass ratio of 1:1. The remaining steps and parameters are the same as in Example 1.

[0107] Example 5

[0108] The difference between the preparation method of lithium cobalt oxide cathode material in this embodiment and that in Example 1 is only that the ammonium fluoride salt in step (4) is different. In this embodiment, the ammonium fluoride salt is obtained by mixing (NH4)2TiF6 and (NH4)2SnF6 in a mass ratio of 1:1. The remaining steps and parameters are the same as in Example 1.

[0109] Example 6

[0110] The difference between the preparation method of lithium cobalt oxide cathode material in this embodiment and that in Example 1 is only that the ammonium fluoride salt in step (4) is different. The ammonium fluoride salt in this embodiment is obtained by mixing (NH4)2ZrF6, (NH4)2TiF6 and (NH4)2AlF6 in a mass ratio of 1:1:1. The remaining steps and parameters are the same as in Example 1.

[0111] Example 7

[0112] The difference between the preparation method of lithium cobalt oxide cathode material in this embodiment and that in Example 1 is only that the ammonium fluoride salt in step (4) is different. The ammonium fluoride salt in this embodiment is obtained by mixing (NH4)2TiF6, (NH4)2AlF6 and (NH4)2SnF6 in a mass ratio of 1:1:1. The remaining steps and parameters are the same as in Example 1.

[0113] Example 8

[0114] The only difference between the preparation method of the lithium cobalt oxide cathode material in this embodiment and that in Example 1 is that the ammonium fluoride salt in step (4) is different. The ammonium fluoride salt in this embodiment is obtained by mixing (NH4)2ZrF6, (NH4)2TiF6, (NH4)2AlF6 and (NH4)2SnF6 in a mass ratio of 1:1:1:1. The remaining steps and parameters are the same as in Example 1.

[0115] Example 9

[0116] The only difference between the preparation method of the lithium cobalt oxide cathode material in this embodiment and that in Example 1 is that the sintering temperature in step (4) is 600°C, while the other steps and parameters are the same as in Example 1.

[0117] Example 10

[0118] The only difference between the preparation method of the lithium cobalt oxide cathode material in this embodiment and that in Example 1 is that the sintering temperature in step (4) is 800°C, while the other steps and parameters are the same as in Example 1.

[0119] Comparative Example 1

[0120] The difference between the preparation method of the lithium cobalt oxide cathode material in this comparative example and that in Example 1 is that step (4) is not performed, that is, the third lithium cobalt oxide is the lithium cobalt oxide cathode material in this comparative example, and the remaining steps and parameters are the same as in Example 1.

[0121] Comparative Example 2

[0122] The only difference between the preparation method of the lithium cobalt oxide cathode material in this comparative example and that in Example 1 is that the ammonium fluoride salt in step (4) is different. The ammonium fluoride salt in this comparative example is (NH4)2ZrF6. The other steps and parameters are the same as in Example 1.

[0123] Comparative Example 3

[0124] The only difference between the preparation method of the comparative lithium cobalt oxide cathode material and Example 1 is that lithium fluoride is not added in step (4), while the other steps and parameters are the same as in Example 1.

[0125] Comparative Example 4

[0126] The only difference between the preparation method of the comparative lithium cobalt oxide cathode material and Example 1 is that ammonium fluoride salt is not added in step (4), while the other steps and parameters are the same as in Example 1.

[0127] Comparative Example 5

[0128] The only difference between the preparation method of the comparative lithium cobalt oxide cathode material and Example 1 is that the sintering temperature in step (4) is 400℃, and the other steps and parameters are the same as in Example 1.

[0129] Comparative Example 6

[0130] The only difference between the preparation method of the comparative lithium cobalt oxide cathode material and Example 1 is that the sintering temperature in step (4) is 900℃, and the other steps and parameters are the same as in Example 1.

[0131] Performance testing

[0132] 1. The lithium cobalt oxide cathode materials prepared in the examples and comparative examples were used as cathode active materials. They were mixed with conductive carbon and vinylidene fluoride in deionized water at a mass ratio of 95:2:3, and then coated onto aluminum foil. After vacuum drying, the mixture was pressed into sheets and cut to the required size as cathode sheets for the battery. A lithium sheet was used as the cathode, and the sheets were assembled into coin cells. The assembly of the coin cells was carried out in a glove box with oxygen and water content both below 1 ppm. The assembled coin cells were used for charge-discharge capacity testing, with a test voltage of 2.3-4.55V and a current density of 1 / 3C.

[0133] 2. The lithium cobalt oxide cathode materials prepared in the examples and comparative examples were used as cathode active materials. They were mixed with conductive carbon and vinylidene fluoride in deionized water at a mass ratio of 95:2:3 and then coated onto aluminum foil. After vacuum drying, the foil was taken out, pressed into sheets, and cut into cathode sheets of the required size as the cathode of the battery.

[0134] A negative electrode slurry was prepared using artificial graphite as the negative electrode active material. It was then mixed evenly with conductive carbon and vinylidene fluoride in deionized water at a mass ratio of 95:2:3 and coated onto aluminum foil. After vacuum drying, the slurry was pressed into sheets and cut into negative electrode sheets of the required size to serve as the negative electrode of the battery.

[0135] 1 mol / L LiPF6 was dissolved in a mixed solvent of ethylene carbonate / diethyl carbonate (volume ratio 1:1), and 3 wt% fluoroethylene carbonate was added and mixed evenly to obtain the electrolyte.

[0136] The pouch cell is assembled from the aforementioned positive electrode, negative electrode, PP / PE / PP composite film between the positive and negative electrodes, and electrolyte. The assembled pouch cell is used to test its cycle performance, thermal stability, storage performance, and gas generation performance.

[0137] The cycle performance test procedure is as follows: At 25℃, the soft pack battery is subjected to 100 cycles at a charge-discharge current of 1C within a voltage range of 2.3-4.5V to test the battery's capacity retention rate.

[0138] The thermal stability test procedure is as follows: The soft-pack battery is cycled 100 times at 45℃ with a 1C charge / discharge current and a voltage range of 2.3-4.5V to test the battery's capacity retention rate.

[0139] The storage performance test procedure is as follows: Store the fully charged battery in a 45°C constant temperature chamber, and test the recovery capacity every 15 days and then recharge it before storing it again.

[0140] The gas production performance test procedure is as follows: Store the fully charged battery in a 70℃ constant temperature chamber, test the cell volume every day, and fully charge it once every 7 days.

[0141] Table 1

[0142]

[0143] As can be seen from the experimental data in Table 1, the lithium cobalt oxide cathode material disclosed herein can improve the charge and discharge capacity, cycle performance, thermal stability and storage performance of the battery, as well as reduce the gas generation performance of the battery.

[0144] Comparing Example 1 and Comparative Examples 1-4, it can be seen that when at least one of ammonium fluoride and lithium fluoride is missing, the charge / discharge capacity, cycle performance, thermal stability, and storage performance of the battery decrease significantly, while the gas generation performance increases significantly. When only one type of ammonium fluoride is added, the charge / discharge capacity of the battery decreases, while the gas generation performance of the battery increases. This indicates that the ammonium fluoride and lithium fluoride disclosed in this invention have a synergistic effect.

[0145] Comparing Examples 1, 9-10 and 5-6, it can be seen that sintering temperatures below 600°C or above 800°C will lead to a decrease in charge / discharge capacity, cycle performance, thermal stability and storage performance, and will increase the gas generation performance of the battery.

[0146] Figure 1 This is a scanning electron microscope image of the lithium cobalt oxide cathode material from Example 1; Figure 2 This is a scanning electron microscope (SEM) image of the lithium cobalt oxide cathode material in Comparative Example 1. From... Figure 1 and Figure 2 As can be seen from the data, the material surface of Example 1 has obvious small particles attached, while the material surface of Comparative Example 1 is smoother.

[0147] Finally, it should be noted that the above embodiments are used to illustrate the technical solutions of the present invention and not to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a lithium cobalt oxide cathode material, characterized in that, Includes the following steps: A mixture comprising lithium cobalt oxide, ammonium fluoride, and lithium fluoride is subjected to a first sintering treatment to obtain a lithium cobalt oxide cathode material; wherein the ammonium fluoride is at least two of (NH4)2ZrF6, (NH4)2TiF6, (NH4)3AlF6, and (NH4)2SnF6, and the temperature of the first sintering treatment is 600-800℃.

2. The method for preparing the lithium cobalt oxide cathode material as described in claim 1, characterized in that, The mass of the ammonium fluoride salt is 1-3% of the mass of the lithium cobalt oxide; and / or, the mass of the lithium fluoride is 0.5-1.5% of the mass of the lithium cobalt oxide.

3. The method for preparing the lithium cobalt oxide cathode material as described in claim 1, characterized in that, The method for preparing the lithium cobalt oxide is as follows: a mixture containing a first lithium cobalt oxide, a second lithium cobalt oxide, and additives is subjected to a second sintering treatment to obtain the lithium cobalt oxide.

4. The method for preparing the lithium cobalt oxide cathode material as described in claim 3, characterized in that, The median particle size D of the first lithium cobalt oxide v 501 has a particle size of 18-21 μm, and the median particle size D of the second lithium cobalt oxide is... v 502 has a thickness of 4.5-6 μm.

5. The method for preparing the lithium cobalt oxide cathode material as described in claim 3, characterized in that, At least one of the following conditions must be met: (1) The first lithium cobalt oxide contains a first doped metal element; the first doped metal element includes at least one of Ca, Zn, Ti, Fe, Mg, Al, Y, La, and Zr; (2) The second lithium cobalt oxide contains a second doped metal element; the second doped metal element includes at least one of Ca, Zn, Ti, Fe, Mg, Al, Y, La, and Zr; (3) The mass ratio of the first lithium cobalt oxide to the second lithium cobalt oxide is 3-4:1; (4) The mass of the additive is 2.8-4.2% of the total mass of the first lithium cobalt oxide and the second lithium cobalt oxide.

6. The method for preparing the lithium cobalt oxide cathode material as described in claim 3, characterized in that, The additive is a compound containing a third doped metal element; The compound containing a third doped metal element includes at least one of the following: an oxide of a third doped metal element, a hydroxide containing a third doped metal element, and an inorganic salt containing a third doped metal element. The third doped metal element includes at least one of Co, Ni, V, Mn, Al, Ti, F, Y, La, Zr, Ge, Ba, W, Nb, Cu, B, Sr, Ga, Zn, Mo, Si, and Sb.

7. A lithium cobalt oxide cathode material, characterized in that, The lithium cobalt oxide cathode material is prepared by the method for preparing lithium cobalt oxide cathode material according to any one of claims 1-6.

8. A positive electrode sheet, characterized in that, Including the lithium cobalt oxide cathode material as described in claim 7.

9. A lithium-ion battery, characterized in that, Including the positive electrode sheet as described in claim 8.

10. An electronic device, characterized in that, Including the lithium-ion battery as described in claim 9.

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