Phase-doped lithium cobalt oxide positive electrode material, preparation method thereof and lithium ion battery

Abstract

The invention provides a phase-doped lithium cobalt oxide positive electrode material, a preparation method thereof and a lithium ion battery, the lithium cobalt oxide positive electrode material comprises lithium cobalt oxide and a doping phase in a crystal structure of the lithium cobalt oxide, and the doping phase comprises any one or a combination of at least two of Li2Co [M2] 3O8, Li4 [M2] 5O12 or [M1] 4 [Li [M2]] O8. The lithium cobalt oxide positive electrode material provided by the invention has a doping phase, and the lithium cobalt oxide positive electrode material is strengthened by adopting a phase strengthening method, so that the conductivity of the lithium cobalt oxide positive electrode material under high voltage (gt; 4.55 V), and the charge-discharge cycle stability is improved; the doping phase is uniformly distributed in the crystal structure of the lithium cobalt oxide, and the size of the doping phase belongs to nanoscale, so that the stress concentration in the charge-discharge cycle process caused by the size effect is avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and relates to a phase-doped lithium cobaltate cathode material, in particular to a phase-doped lithium cobaltate cathode material, a preparation method thereof, and a lithium ion battery. Background Art

[0002] In recent years, with the diversification of the forms and the popularization of the distribution of mobile digital products, they have become essential consumer goods in people's daily lives, and thus have put forward higher and higher requirements for the performance of consumer batteries. Lithium ion batteries have always occupied the dominant position in consumer batteries due to their high energy density, long cycle life, and high safety. The cathode material is a key component determining the performance of lithium ion batteries and is also one of the current research hotspots. Developing cathode materials with more excellent performance is an effective means to improve the comprehensive performance of lithium ion batteries at present.

[0003] Lithium cobaltate is one of the most commercially successful cathode materials at present. It has the advantages of simple synthesis process, relatively high energy density, and excellent safety performance, and is also the best choice for the cathode material of consumer digital batteries. Raising the charge and discharge cut-off voltage to enable more lithium ions to escape from the layered structure of lithium cobaltate is a direct method to further improve the capacity and energy density of lithium cobaltate. However, excessive lithium ion extraction will cause severe lattice strain in lithium cobaltate, even structural collapse and particle pulverization, resulting in capacity decline and deterioration of cycle performance.

[0004] Research shows that heteroatom doping can effectively improve the lattice stability of lithium cobaltate, inhibit harmful phase transitions, and enhance its cycle stability. At present, most commercial lithium cobaltates use the means of co-doping with multiple elements to optimize their performance. However, the means of heteroatom doping still cannot meet the requirements of stabilizing the crystal structure of lithium cobaltate and alleviating the accumulation of stress and strain under the condition of a higher charge and discharge cut-off voltage (>4.55V).

[0005] CN115939329A discloses a lithium cathode hybrid material and a preparation method thereof, belonging to the field of positive active materials for lithium ion batteries. The lithium cathode hybrid material is composed of large lithium cobaltate particles doped with micron-sized spinel phases and coated with submicron-sized spinel phases, and small three-element particles coated with submicron-sized spinel phases. It is prepared by two methods, one is prepared by precursor doping and secondary coating, and the other is prepared by primary doping and secondary coating. The lithium cathode hybrid material has a high energy density and can be used in power lithium batteries, has a higher energy density than lithium iron phosphate, and at the same time has a long cycle life and good safety performance. However, for the technical method of strengthening the lattice structure of lithium cobaltate with micron-sized spinel phases, the doped phase has a relatively large microscopic size, and there is a risk of strain incoordination and becoming a stress concentration and breakage point during the charge and discharge cycle.

[0006] The lithium cobalt oxide cathode materials disclosed in the prior art all have certain defects. There are problems that the means of heteroatom doping cannot meet the requirements of stabilizing the crystal structure of lithium cobalt oxide and alleviating the accumulation of stress and strain under the conditions of higher charge-discharge cut-off voltages, and the microscale of the doped phase is relatively large, and there is a risk of strain incoordination and becoming stress concentration breakage points during the charge-discharge cycle. Therefore, it is crucial to develop and design a new type of phase-doped lithium cobalt oxide cathode material, its preparation method and lithium-ion battery. Summary of the Invention

[0007] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a phase-doped lithium cobalt oxide cathode material, its preparation method and lithium-ion battery. The lithium cobalt oxide cathode material provided by the present invention has a doped phase, and the lithium cobalt oxide cathode material is strengthened by a phase strengthening method, improving the charge-discharge cycle stability of the lithium cobalt oxide cathode material at high voltages (>4.55 V); the doped phase is uniformly distributed in the crystal structure of lithium cobalt oxide, and its size belongs to the nanoscale, avoiding stress concentration during the charge-discharge cycle caused by the size effect.

[0008] To achieve this purpose, the present invention adopts the following technical solutions:

[0009] In the first aspect, the present invention provides a phase-doped lithium cobalt oxide cathode material, the lithium cobalt oxide cathode material includes lithium cobalt oxide and a doped phase inside the crystal structure of the lithium cobalt oxide, and the doped phase includes Li 2 Co[M2] 3 O 8 , Li 4 [M2] 5 O 12 or [M1] 4 [Li[M2]]O 8 or a combination of any one or at least two of them.

[0010] Preferably, the doped phase includes Li 2 Co[M2] 3 O 8 , Li 4 [M2] 5 O 12 or [M1] 4 [Li[M2]]O 8 or a combination of any one or at least two of them. A typical but non-limiting combination includes Li 2 Co[M2] 3 O 8 and Li 4 [M2] 5 O 12 Li 4 [M2] 5O 12 in combination with [M1] 4 [Li[M2]]O 8 or Li 2 Co[M2] 3 O 8 、Li 4 [M2] 5 O 12 in combination with [M1] 4 [Li[M2]]O 8 .

[0011] The lithium cobalt oxide cathode material provided by the present invention has a doped phase. The lithium cobalt oxide cathode material is strengthened by a phase strengthening method, and the charge-discharge cycle stability of the lithium cobalt oxide cathode material at high voltages (>4.55 V) is improved; the doped phase is uniformly distributed in the crystal structure of lithium cobalt oxide, and its size belongs to the nanoscale, avoiding stress concentration during the charge-discharge cycle caused by the size effect.

[0012] Preferably, the size of the doped phase is 0.8 - 40.2 nm, for example, it can be 0.8 nm, 1 nm, 3 nm, 5 nm, 7 nm, 9 nm, 10 nm, 12 nm, 14 nm, 16 nm, 18 nm, 20 nm, 22 nm, 24 nm, 26 nm, 28 nm, 30 nm, 32 nm, 34 nm, 36 nm, 38 nm, 40 nm or 40.2 nm, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0013] In the lithium cobalt oxide cathode material provided by the present invention, the stacking structure of the O element of the doped phase grows coherently with the crystal structure of lithium cobalt oxide. At the same time, the doped phase also has stable electrochemical performance and stable mechanical performance, and can prevent excessive lattice stress and strain of the lithium cobalt oxide matrix during the high-voltage charge-discharge cycle, playing the role of stabilizing the lattice during the charge-discharge cycle.

[0014] Preferably, the mass fraction of the doping phase is 0.19 to 0.49 wt%, for example, it can be 0.19 wt%, 0.20 wt%, 0.21 wt%, 0.22 wt%, 0.23 wt%, 0.24 wt%, 0.25 wt%, 0.26 wt%, 0.27 wt%, 0.28 wt%, 0.29 wt%, 0.30 wt%, 0.31 wt%, 0.32 wt%, 0.33 wt%, 0.34 wt%, 0.35 wt%, 0.36 wt%, 0.37 wt%, 0.38 wt%, 0.39 wt%, 0.40 wt%, 0.41 wt%, 0.42 wt%, 0.43 wt%, 0.44 wt%, 0.45 wt%, 0.46 wt%, 0.47 wt%, 0.48 wt% or 0.49 wt%, but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0015] In the present invention, the mass fraction of the lithium cobaltate cathode material falls within the defined range, which can not only enhance the performance of the lithium cobaltate cathode material but also prevent excessive negative impacts on the capacity performance.

[0016] Preferably, M1 and M2 in the doping phase each independently include any one of Mg, Al, Mn, Ni, Ca, Zr, Cr, Ti, Cu, Zn, Y, Ce, Sm, Pr, La, Mo, Nb, Sn, Ga or V.

[0017] Preferably, the molar ratio of lithium to cobalt in the lithium cobaltate cathode material is (1 to 1.1):1, for example, it can be 1.05:1, 1.06:1, 1.07:1, 1.08:1, 1.09:1 or 1.1:1, but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0018] In a second aspect, the present invention provides a method for preparing the lithium cobaltate cathode material described in the first aspect, and the preparation method includes:

[0019] Mixing cobalt tetroxide doped with M1 and M2 elements with a lithium source, and then sintering in an air atmosphere to obtain a phase-doped lithium cobaltate cathode material.

[0020] Preferably, the method for preparing cobalt tetroxide doped with M1 and M2 elements includes coprecipitation and annealing sintering carried out in sequence.

[0021] Preferably, the mass fraction of M1 in the cobalt tetroxide doped with M1 and M2 elements is 1000 - 3000 ppm. For example, it can be 1000 ppm, 1200 ppm, 1400 ppm, 1600 ppm, 1800 ppm, 2000 ppm, 2200 ppm, 2400 ppm, 2600 ppm, 2800 ppm or 3000 ppm. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0022] Preferably, the mass fraction of M2 in the cobalt tetroxide doped with M1 and M2 elements is 200 - 500 ppm. For example, it can be 250 ppm, 300 ppm, 350 ppm, 400 ppm, 450 ppm or 500 ppm. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0023] Preferably, the lithium source includes any one or a combination of at least two of lithium oxalate, lithium carbonate, lithium hydroxide, lithium nitrate or lithium acetate. Typical but non - restrictive combinations include the combination of lithium oxalate and lithium carbonate, the combination of lithium carbonate and lithium hydroxide, the combination of lithium hydroxide and lithium nitrate, the combination of lithium nitrate and lithium acetate, or the combination of lithium oxalate, lithium carbonate and lithium hydroxide.

[0024] Preferably, the gas flow rate of the air introduced during sintering is 10 - 30 L / min. For example, it can be 10 L / min, 12 L / min, 14 L / min, 16 L / min, 18 L / min, 20 L / min, 22 L / min, 24 L / min, 26 L / min, 28 L / min or 30 L / min. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0025] Preferably, the sintering includes a first heating, a first heat preservation, a second heating and a second heat preservation carried out in sequence.

[0026] Preferably, the rate of the first heating is 1 - 5 °C / min, and the end temperature is 600 - 800 °C.

[0027] In the present invention, the rate of the first heating is 1 - 5 °C / min. For example, it can be 1 °C / min, 1 °C / min, 2 °C / min, 3 °C / min, 4 °C / min or 5 °C / min. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0028] In the present invention, the end temperature of the first temperature rise is 600 - 800 °C. For example, it can be 600 °C, 620 °C, 640 °C, 660 °C, 680 °C, 700 °C, 720 °C, 740 °C, 760 °C, 780 °C or 800 °C. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0029] Preferably, the time for the first heat preservation is 2 - 5 h. For example, it can be 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h or 5 h. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0030] Preferably, the rate of the second temperature rise is 1 - 5 °C / min, and the end temperature is 900 - 1080 °C.

[0031] In the present invention, the rate of the second temperature rise is 1 - 5 °C / min. For example, it can be 1 °C / min, 1 °C / min, 2 °C / min, 3 °C / min, 4 °C / min or 5 °C / min. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0032] In the present invention, the end temperature of the second temperature rise is 900 - 1080 °C. For example, it can be 900 °C, 920 °C, 940 °C, 960 °C, 980 °C, 1000 °C, 1020 °C, 1040 °C, 1060 °C or 1080 °C. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0033] Preferably, the time for the second heat preservation is 12 - 18 h. For example, it can be 12 h, 13 h, 14 h, 15 h, 16 h, 17 h or 18 h. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0034] Preferably, after sintering, it further includes crushing.

[0035] As a preferred technical solution of the preparation method of the present invention, the preparation method includes:

[0036] Carrying out coprecipitation and annealing sintering in sequence to prepare cobalt tetroxide doped with M1 and M2 elements; in the cobalt tetroxide doped with M1 and M2 elements, the mass fraction of M1 is 1000 - 3000 ppm, and the mass fraction of M2 is 200 - 500 ppm;

[0037] The obtained cobalt tetroxide doped with M1 and M2 elements is mixed with a lithium source, and then in an air atmosphere with air flowing at a gas flow rate of 10-30 L / min, it is heated to 600-800 °C at a rate of 1-5 °C / min and held for 2-5 h, and then heated to 900-1080 °C at a rate of 1-5 °C / min and held for 12-18 h. After pulverization, a phase-doped lithium cobaltate cathode material is obtained.

[0038] In a third aspect, the present invention provides a lithium-ion battery, and the lithium-ion battery includes the lithium cobaltate cathode material described in the first aspect.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] The lithium cobaltate cathode material provided by the present invention has a doped phase, and the lithium cobaltate cathode material is strengthened by a phase strengthening method, improving the charge-discharge cycle stability of the lithium cobaltate cathode material at high voltages (>4.55 V); the doped phase is uniformly distributed in the crystal structure of lithium cobaltate, and its size is in the nanoscale, avoiding stress concentration during the charge-discharge cycle caused by the size effect. Description of the Drawings

[0041] Figure 1 SEM diagram of the lithium cobaltate cathode material prepared in Example 1.

[0042] Figure 2 SEM diagram of the lithium cobaltate cathode material prepared in Comparative Example 1.

[0043] Figure 3 XRD diagram of the lithium cobaltate cathode material prepared in Example 1.

[0044] Figure 4 XRD diagram of the lithium cobaltate cathode material prepared in Comparative Example 1. Detailed Embodiments

[0045] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations of the present invention.

[0046] Example 1

[0047] This example provides a phase-doped lithium cobaltate cathode material. The molar ratio of lithium to cobalt in the lithium cobaltate cathode material is 1.05:1. The lithium cobaltate cathode material includes lithium cobaltate and a doped phase inside the crystal structure of the lithium cobaltate. The doped phase is 4 [La] 8 [Li[Mn]]O, with a mass fraction of 0.32 wt% and a size of 20 ± 0.2 nm;

[0048] The preparation method of the lithium cobalt oxide cathode material includes:

[0049] Carry out coprecipitation and annealing sintering in sequence to prepare cobalt tetroxide doped with La and Mn elements; the mass fraction of La in the cobalt tetroxide doped with La and Mn elements is 2000 ppm, and the mass fraction of Mn is 500 ppm;

[0050] Mix the obtained cobalt tetroxide doped with La and Mn elements with a lithium source, and then in an air atmosphere with an air flow rate of 20 L / min, heat it to 700 °C at a rate of 3 °C / min and hold for 3.5 h, and then heat it to 1000 °C at a rate of 3 °C / min and hold for 15 h, and obtain a phase-doped lithium cobalt oxide cathode material after pulverization.

[0051] Example 2

[0052] This example provides a phase-doped lithium cobalt oxide cathode material. The molar ratio of lithium to cobalt in the lithium cobalt oxide cathode material is 1:1. The lithium cobalt oxide cathode material includes lithium cobalt oxide and a doping phase inside the crystal structure of the lithium cobalt oxide. The doping phase is [La] 4 [Li[Mn]]O 8 , with a mass fraction of 0.19 wt%, and a size of 1 ± 0.2 nm;

[0053] The preparation method of the lithium cobalt oxide cathode material includes:

[0054] Carry out coprecipitation and annealing sintering in sequence to prepare cobalt tetroxide doped with La and Mn elements; the mass fraction of La in the cobalt tetroxide doped with La and Mn elements is 1000 ppm, and the mass fraction of Mn is 500 ppm;

[0055] Mix the obtained cobalt tetroxide doped with La and Mn elements with a lithium source, and then in an air atmosphere with an air flow rate of 10 L / min, heat it to 600 °C at a rate of 1 °C / min and hold for 5 h, and then heat it to 900 °C at a rate of 1 °C / min and hold for 18 h, and obtain a phase-doped lithium cobalt oxide cathode material after pulverization.

[0056] Example 3

[0057] This example provides a phase-doped lithium cobalt oxide cathode material. The molar ratio of lithium to cobalt in the lithium cobalt oxide cathode material is 1.1:1. The lithium cobalt oxide cathode material includes lithium cobalt oxide and a doping phase inside the crystal structure of the lithium cobalt oxide. The doping phase is [La] 4 [Li[Mn]]O 8 , with a mass fraction of 0.49 wt%, and a size of 40 ± 0.2 nm,;

[0058] The preparation method of the lithium cobaltate cathode material includes:

[0059] Carrying out coprecipitation and annealing sintering in sequence to prepare cobalt tetroxide doped with La and Mn elements; the mass fraction of La in the cobalt tetroxide doped with La and Mn elements is 3000 ppm, and the mass fraction of Mn is 200 ppm;

[0060] Mixing the obtained cobalt tetroxide doped with La and Mn elements with a lithium source, and then in an air atmosphere with an air flow rate of 30 L / min, heating to 800 °C at a rate of 5 °C / min and holding for 2 h, then heating to 1080 °C at a rate of 5 °C / min and holding for 12 h, and pulverizing to obtain a phase-doped lithium cobaltate cathode material.

[0061] Example 4

[0062] This example provides a phase-doped lithium cobaltate cathode material. Except that in the preparation method of the lithium cobaltate cathode material, heating to 700 °C at a rate of 3 °C / min and holding for 3.5 h is replaced by heating to 500 °C at a rate of 3 °C / min and holding for 3.5 h, the rest are the same as in Example 1.

[0063] Example 5

[0064] This example provides a phase-doped lithium cobaltate cathode material. Except that in the preparation method of the lithium cobaltate cathode material, heating to 700 °C at a rate of 3 °C / min and holding for 3.5 h is replaced by heating to 900 °C at a rate of 3 °C / min and holding for 3.5 h, the rest are the same as in Example 1.

[0065] Example 6

[0066] This example provides a phase-doped lithium cobaltate cathode material. Except that in the preparation method of the lithium cobaltate cathode material, heating to 700 °C at a rate of 3 °C / min and holding for 3.5 h is replaced by heating to 700 °C at a rate of 3 °C / min and holding for 1 h, the rest are the same as in Example 1.

[0067] Example 7

[0068] This example provides a phase-doped lithium cobaltate cathode material. Except that in the preparation method of the lithium cobaltate cathode material, heating to 700 °C at a rate of 3 °C / min and holding for 3.5 h is replaced by heating to 700 °C at a rate of 3 °C / min and holding for 6 h, the rest are the same as in Example 1.

[0069] Example 8

[0070] This embodiment provides a phase-doped lithium cobalt oxide cathode material. Except that in the preparation method of the lithium cobalt oxide cathode material, the heating rate to 1000 °C at 3 °C / min and then holding for 15 h is replaced by heating to 800 °C at 3 °C / min and then holding for 15 h, the rest is the same as in Example 1.

[0071] Example 9

[0072] This embodiment provides a phase-doped lithium cobalt oxide cathode material. Except that in the preparation method of the lithium cobalt oxide cathode material, the heating rate to 1000 °C at 3 °C / min and then holding for 15 h is replaced by heating to 1200 °C at 3 °C / min and then holding for 15 h, the rest is the same as in Example 1.

[0073] Example 10

[0074] This embodiment provides a phase-doped lithium cobalt oxide cathode material. Except that in the preparation method of the lithium cobalt oxide cathode material, the heating rate to 1000 °C at 3 °C / min and then holding for 15 h is replaced by heating to 1000 °C at 3 °C / min and then holding for 10 h, the rest is the same as in Example 1.

[0075] Example 11

[0076] This embodiment provides a phase-doped lithium cobalt oxide cathode material. Except that in the preparation method of the lithium cobalt oxide cathode material, the heating rate to 1000 °C at 3 °C / min and then holding for 15 h is replaced by heating to 1000 °C at 3 °C / min and then holding for 20 h, the rest is the same as in Example 1.

[0077] Comparative Example 1

[0078] This comparative example provides a lithium cobalt oxide cathode material, which is prepared by solid-phase sintering. The process of solid-phase sintering is as follows: Mix cobalt source particles with a lithium source in a molar ratio of Li / Co = 1.01 - 1.10 evenly, place the obtained mixture in a muffle furnace for high-temperature sintering reaction, pre-burn at a low temperature for 2 - 5 h first, and then sinter at a high temperature for 8 - 12 h. After cooling with the furnace, crush the material to obtain the lithium cobalt oxide cathode material.

[0079] The morphology of the lithium cobalt oxide cathode material obtained in Example 1 was tested by scanning electron microscopy, and the SEM image of the lithium cobalt oxide cathode material is as Figure 1 shown; The morphology of the lithium cobalt oxide cathode material obtained in Comparative Example 1 was tested by scanning electron microscopy, and the SEM image of the lithium cobalt oxide cathode material is as Figure 2As shown; the XRD pattern of the lithium cobaltate cathode material obtained in Example 1 was tested using an X-ray diffractometer, and the XRD pattern of the lithium cobaltate cathode material is as Figure 3 shown; the XRD pattern of the lithium cobaltate cathode material obtained in Comparative Example 1 was tested using an X-ray diffractometer, and the XRD pattern of the lithium cobaltate cathode material is as Figure 4 shown; by Figure 3 and Figure 4 comparison, it can be seen that the prepared lithium cobaltate cathode material in this application has peaks of the doped phase, proving that the doped phase has been successfully incorporated into the lithium cobaltate cathode material.

[0080] The lithium cobaltate cathode materials in Examples 1 to 11 and Comparative Example 1 were used to prepare lithium-ion batteries. The method for preparing lithium-ion batteries was as follows: the prepared lithium cobaltate was made into a positive electrode sheet (the mass ratio of the active material, conductive agent, and binder was 8:1:1, and aluminum foil was used as the current collector), a lithium metal was used as the negative electrode sheet, and a CR2032 type button battery was assembled; the prepared lithium-ion battery was subjected to a first charge capacity test and a cycle performance test at a high voltage of 4.6V; the method for the first charge capacity test was to perform constant current charge and discharge at 0.1C (1C = 220 mAg -1 ) in the voltage range of 3.0 to 4.6V, and the first capacity of the lithium-ion battery was tested as shown in Table 1; the method for the cycle performance test was to activate for 3 cycles at a current of 0.1C (1C = 220 mAg -1 ) in the voltage range of 3.0 to 4.6V, and then the capacity retention rate of the lithium-ion battery after 300 cycles of constant current charge and discharge at 1C current was tested as shown in Table 1.

[0081] Table 1

[0082] Initial Capacity (mAh) Capacity Retention Rate (%) Example 1 214.7 86.1％ Example 2 215.6 79.6％ Example 3 212.1 81.2％ Example 4 212.7 75.3％ Example 5 211.0 73.4％ Example 6 210.5 70.3％ Example 7 208.1 71.2％ Example 8 207.5 70.9％ Example 9 205.3 64.5％ Example 10 211.2 71.2％ Example 11 202.4 60.9％ Comparative Example 1 217.1 7.7％

[0083] It can be obtained from Table 1 that:

[0084] (1) Using the lithium cobaltate cathode materials prepared in Examples 1 to 3 to prepare lithium-ion batteries, the obtained lithium-ion batteries showed relatively high first capacity and high cycle stability;

[0085] (2) By comparing Example 1 with Examples 4 and 5, it can be seen that in the preparation method of the lithium cobaltate cathode material in the present invention, the end temperature of the first temperature rise during the sintering process affects the performance of the lithium cobaltate cathode material, thereby affecting the performance of the lithium-ion battery; when the end temperature of the first temperature rise is too low, it will lead to a decrease in the first capacity and a decrease in the capacity retention rate, which is because the first-stage reaction is incomplete and affects the crystallinity of the latter stage; when the end temperature of the first temperature rise is too high, it will lead to a decrease in the first capacity and a decrease in the capacity retention rate, which is because partial crystallization in the first stage affects the single crystal degree of the lithium cobaltate particles;

[0086] (3) It can be seen from the comparison between Example 1 and Examples 6 and 7 that in the preparation method of the lithium cobaltate cathode material of the present invention, the time of the first heat preservation during the sintering process will affect the performance of the lithium cobaltate cathode material, thereby affecting the performance of the lithium-ion battery; when the time of the first heat preservation is too short, it will cause a slight decrease in the initial capacity and a decrease in the capacity retention rate, which is because the insufficient first-stage reaction affects the subsequent crystallization process; when the time of the first heat preservation is too long, it will cause a slight decrease in the initial capacity and a decrease in the capacity retention rate, which is because the too long first-stage reaction time results in the compositional uniformity of the subsequent crystallization process.

[0087] (4) It can be seen from the comparison between Example 1 and Examples 8 and 9 that in the preparation method of the lithium cobaltate cathode material of the present invention, the end temperature of the second heating during the sintering process will affect the performance of the lithium cobaltate cathode material, thereby affecting the performance of the lithium-ion battery; when the end temperature of the second heating is too low, it will cause a decrease in the initial capacity and a decrease in the capacity retention rate, which is because the too low sintering temperature affects the formation of the overall crystal grains and the formation of the doped phase; when the end temperature of the second heating is too high, it will cause a decrease in the initial capacity and a decrease in the capacity retention rate, which is caused by overfiring;

[0088] (5) It can be seen from the comparison between Example 1 and Examples 10 and 11 that in the preparation method of the lithium cobaltate cathode material of the present invention, the time of the second heat preservation during the sintering process will affect the performance of the lithium cobaltate cathode material, thereby affecting the performance of the lithium-ion battery; when the time of the second heat preservation is too short, it will cause a decrease in the initial capacity and a decrease in the capacity retention rate, which is because the insufficient reaction time affects the crystallization process and the formation of the doped phase; when the time of the second heat preservation is too long, it will cause a decrease in the initial capacity and a decrease in the capacity retention rate, which is caused by overfiring resulting in the dispersed distribution of the doped elements and the failure to form the doped phase;

[0089] (6) It can be seen from the comparison between Example 1 and Comparative Example 1 that the lithium cobaltate cathode material provided by the present invention has a doped phase, and the lithium cobaltate cathode material is strengthened by the phase strengthening method, improving the charge-discharge cycle stability of the lithium cobaltate cathode material at high voltages; the doped phase is evenly distributed in the crystal structure of lithium cobaltate, and its size belongs to the nanoscale, avoiding stress concentration during the charge-discharge cycle caused by the size effect.

[0090] The above are only the specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A phase-doped lithium cobaltate cathode material, characterized in that, The lithium cobalt oxide cathode material includes lithium cobalt oxide and a doping phase inside the crystal structure of the lithium cobalt oxide, and the doping phase includes Li 2 Co[M2] 3 O 8 , Li 4 [M2] 5 O 12 or [M1] 4 [Li[M2]]O 8 or a combination of any one or at least two of them.

2. The lithium cobaltate cathode material according to claim 1, characterized in that, the size of the doped phase is 0.8 - 40.2 nm; preferably, the mass fraction of the doped phase is 0.19 - 0.49 wt%.

3. The lithium cobaltate cathode material according to claim 2, characterized in that, M1 and M2 in the doped phase each independently include any one of Mg, Al, Mn, Ni, Ca, Zr, Cr, Ti, Cu, Zn, Y, Ce, Sm, Pr, La, Mo, Nb, Sn, Ga or V.

4. The lithium cobaltate cathode material according to any one of claims 1 - 3, characterized in that, the molar ratio of lithium to cobalt in the lithium cobaltate cathode material is (1 - 1.1):

1.

5. A preparation method of the lithium cobaltate cathode material according to any one of claims 1 - 4, characterized in that, the preparation method includes: mixing cobalt tetroxide doped with M1 and M2 elements with a lithium source, and then sintering in an air atmosphere to obtain a phase-doped lithium cobaltate cathode material.

6. The preparation method according to claim 5, characterized in that, the method for preparing cobalt tetroxide doped with M1 and M2 elements includes coprecipitation and annealing sintering carried out in sequence; preferably, the mass fraction of M1 in the cobalt tetroxide doped with M1 and M2 elements is 1000 - 3000 ppm; preferably, the mass fraction of M2 in the cobalt tetroxide doped with M1 and M2 elements is 200 - 500 ppm; preferably, the lithium source includes any one or a combination of at least two of lithium oxalate, lithium carbonate, lithium hydroxide, lithium nitrate or lithium acetate.

7. The preparation method according to claim 5 or 6, characterized in that, the gas flow rate of the air introduced during sintering is 10 - 30 L / min; preferably, the sintering includes first heating, first heat preservation, second heating and second heat preservation carried out in sequence; preferably, the rate of the first heating is 1 - 5 °C / min, and the end temperature is 600 - 800 °C; preferably, the time of the first heat preservation is 2 - 5 h; preferably, the rate of the second heating is 1 - 5 °C / min, and the end temperature is 900 - 1080 °C; preferably, the time of the second heat preservation is 12 - 18 h.

8. The preparation method according to any one of claims 5 - 7, characterized in that, pulverization is further included after sintering.

9. The preparation method according to any one of claims 5 - 8, characterized in that, the preparation method includes: carrying out coprecipitation and annealing sintering in sequence to prepare cobalt tetroxide doped with M1 and M2 elements; the mass fraction of M1 in the cobalt tetroxide doped with M1 and M2 elements is 1000 - 3000 ppm, and the mass fraction of M2 is 200 - 500 ppm; Mix the obtained cobalt tetroxide doped with M1 and M2 elements with a lithium source, and then in an air atmosphere with air flowing at a gas flow rate of 10-30 L / min, heat it to 600-800 °C at a rate of 1-5 °C / min and hold for 2-5 h, then heat it to 900-1080 °C at a rate of 1-5 °C / min and hold for 12-18 h. After pulverization, a phase-doped lithium cobalt oxide cathode material is obtained.

10. A lithium-ion battery, characterized in that the lithium-ion battery comprises the lithium cobalt oxide cathode material according to any one of claims 1 to 3.

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