Lithium cobalt oxide positive electrode material, preparation method therefor and use thereof

Abstract

A lithium cobalt oxide positive electrode material, a preparation method therefor and the use thereof. The positive electrode material comprises large particles and small particles. The large particles have a lower content of nickel and manganese; a small amount of the nickel element increases the capacity and a small amount of manganese stabilizes the structure; the presence of nickel and manganese inhibits cobalt dissolution to a certain degree, thus improving battery storage; additionally, the slight doping of nickel and manganese enhances intrinsic properties and allows the large particles to normally grow, thus improving the compaction density of an electrode sheet and ensuring the compression resistance. The small particles have a higher content of nickel and manganese; since the small particles have a small size and a larger BET, small particles are likely to grow into quasi-single crystals, so that compared with the slight doping of nickel and manganese, the presence of higher amounts of nickel and manganese is more beneficial for improving the storage and gas generation properties while improving the battery capacity.

Description

Lithium cobalt oxide positive electrode material and preparation method and application thereof Technical Field

[0001] The present disclosure relates to the technical field of lithium-ion batteries, and in particular to a lithium cobalt oxide positive electrode material and a preparation method and application thereof. Background Art

[0002] Rechargeable lithium-ion batteries are a new generation of green energy storage batteries, mainly composed of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium nickel oxide, ternary lithium nickel cobalt manganese oxide, and lithium cobalt oxide / ternary lithium nickel cobalt manganese oxide composites. Currently, ternary lithium nickel cobalt manganese oxide has excellent storage performance and high rate performance and is widely used in the field of power batteries with high endurance requirements. Lithium iron phosphate has excellent safety performance and is widely used in the fields of energy storage and electric vehicles.

[0003] The volume energy density of lithium-ion batteries = discharge capacity × discharge voltage platform × compaction density. Currently, lithium iron phosphate is a single-channel lithium deintercalation battery, and its energy density is lower than that of ternary nickel cobalt manganese oxide. Ternary nickel cobalt manganese oxide batteries have been upgraded from 5 series to 9 series, and their volume energy density has made great progress. However, the lower discharge platform and relatively low compaction density of the ternary 9 series have limited further improvement in the energy density of the ternary 9 series. High-voltage lithium cobalt oxide above 4.5V has a high discharge platform, exceeding 4.2g / cm 3 The electrode is compacted and has a volume energy density greater than that of the ternary 9 series, and has broad application potential in the field of high-endurance power batteries.

[0004] The charging voltage of lithium cobalt oxide has been increased to 4.50V and even higher, and the specific capacity has increased to 187mAh / g and even higher. With the development of technology, lithium cobalt oxide has become a new development trend in the power battery field, placing higher demands on its storage performance, cycle performance, and gas production performance. Compared with the 3C industry, the power battery industry has higher requirements for battery storage, gas production, and stability.

[0005] As the voltage increases, more lithium ions are released from the lithium cobalt oxide lattice, causing structural instability; the degree of delithiation on the material surface becomes higher, and the structural phase change extends from the material surface to the interior of the particles; due to the obvious overlap of the energy band structures of cobalt and oxygen, the dissolution and precipitation of cobalt will be accelerated under high delithiation, resulting in intensified interfacial side reactions, worsening storage and gas production, and affecting the practical application of lithium cobalt oxide in the field of power batteries.

[0006] Currently, the common optimization methods are doping, coating and process optimization. Coating and sintering under high temperature conditions can absorb excess lithium and reduce residual lithium, which helps to improve the high-temperature safety performance of the material and reduce gas production. However, under high voltage conditions, as the number of lithium ions released increases, the valence of trivalent cobalt tends to increase to tetravalent cobalt, which is prone to side reactions with the electrolyte, causing capacity attenuation and deterioration of storage performance.

[0007] Therefore, it is necessary to provide a new doping, coating and optimization process to reduce cobalt dissolution, reduce interface side reactions, reduce gas production, and improve storage performance, which is suitable for lithium cobalt oxide at 4.50V or even higher voltage.

[0008] In view of this, the present disclosure is proposed.

[0009] Summary of the Invention

[0010] The purpose of the present disclosure is to provide a lithium cobalt oxide positive electrode material and its preparation method and application, which can improve the storage and gas production performance of lithium-ion batteries at voltages above 4.50V.

[0011] The present disclosure is achieved as follows:

[0012] In a first aspect, the present disclosure provides a lithium cobalt oxide positive electrode material, including large particles and small particles,

[0013] The large particles include the general formula Li a Co1-b1-b2-b3-cNi b1 Mn b2 Al b3 Q c The large particle core of O2 is coated with a general formula T g E h O k The cladding layer;

[0014] The small particles include the general formula Li d Co1-e1-e2-e3-fNi e1 Mn e2 Al e3 Q′ f The surface of the small particle core of O2 is coated with a general formula T g E h O k The cladding layer;

[0015] The median particle size of the large particle core is 18 μm to 21.5 μm, the median particle size of the small particle core is 3.5 μm to 6.5 μm, the molar ratio of the small particles to the large particles is 0.135 to 0.43, the large particle core is a layered single crystal structure, and the small particle core is a layered single crystal or layered single crystal-like structure;

[0016] Among them, 0.98≤a≤1.02, 0.0015≤b1≤0.01 ，0.002≤b2≤0.02, 0.02≤b3≤0.03, 0.01≤c≤0.05, b2>b1, 0.98≤d≤1.01, 0.45≤e1≤0.95 ， 0.01≤e2≤0.45, 0.02≤e3≤0.04, 0.01≤f≤0.055, e2>e1, 0.8≤g≤3, 0≤h≤3, 1.5≤k≤5;

[0017] Q and Q' are each independently selected from at least one of Mg, La, Zr, Cu, Na, W, Sr and Y;

[0018] T and E are each independently selected from at least one of Li, Mg, B, La, Sn, W, Y, Zr, Ni, Al, F, P, and C.

[0019] In some embodiments, the general formula is: (1-x)·[Li a Co1-b1-b2-b3-cNi b1 Mn b2 Al b3 Q c O2·n Li d Co1-e1-e2-e3-fNi e 1Mn e2 Al e3 Q′ f O2]·xT g E h O k , where 0.001≤x≤0.05, and 0.12≤n / (1+n)≤0.30.

[0020] In some embodiments, 0.18≤n / (1+n)≤0.24.

[0021] In some embodiments, both Q and Q' include at least one of Mg, La, and Zr.

[0022] In some embodiments, the T is at least one of Mg, Al, Ti, and Zr.

[0023] In some embodiments, the E is at least one of F, P and C.

[0024] In a second aspect, the present disclosure provides a method for preparing the lithium cobalt oxide positive electrode material as described in any one of the aforementioned items, comprising a coating step: mixing the large particle core, the small particle core and the coating layer raw materials and sintering them to obtain the lithium cobalt oxide positive electrode material.

[0025] In some embodiments, in the coating step, the coating layer raw material includes an auxiliary agent for reducing the sintering temperature, and the auxiliary agent is at least one of boric acid, magnesium fluoride, lithium hydroxide and lithium carbonate.

[0026] In some embodiments, the total molar ratio of the auxiliary agent to the coating layer raw material is (0.03-0.4):1.

[0027] In some embodiments, the particle size of the auxiliary agent is 0.01 μm to 20 μm.

[0028] In some embodiments, the preparation of large-particle cores is also included: a precursor mixture containing lithium, nickel, cobalt, manganese, aluminum, and Q is sintered to obtain a large-particle core, wherein the ratio of the total molar amount of lithium to nickel, cobalt, manganese, aluminum, and Q in the precursor mixture is m1+m2, wherein m1 is 1.04 to 1.12, and m2=(N1*n1) / 3, wherein N1 is the molar amount of the Q element replacing the Co position, and n1 is the valence state of the Q element replacing the Co position.

[0029] In some embodiments, in the large particle core preparation step, the sintering temperature is 950° C. to 1100° C., the sintering time is 8 h to 12 h, and the sintering is performed in an oxygen-containing atmosphere.

[0030] In some embodiments, the Q-containing compound used in the large particle core preparation step is at least one of a Q-containing oxide, hydroxide, and carbonate.

[0031] In some embodiments, the preparation of small particle cores is also included: a precursor mixture containing lithium, nickel, cobalt, manganese, aluminum, and Q' is sintered to obtain large particle cores, wherein the ratio of the total molar amount of lithium to nickel, cobalt, manganese, aluminum and Q' in the precursor mixture is m3+m4, wherein m3 is 1.02~1.09, m4=(N2*n2) / 3, wherein N2 is the molar amount of the Q' element replacing the Co position, and n2 is the valence state of the Q' element replacing the Co position.

[0032] In some embodiments, in the small particle core preparation step, the sintering temperature is 550° C. to 850° C., the time is 8 h to 12 h, and the sintering is performed in an oxygen-containing atmosphere.

[0033] In some embodiments, the particle size of the Q-containing compound and the Q′-containing compound used in the steps of preparing the large particle core and the small particle core is 1 to 200 nm.

[0034] In some embodiments, the Q′-containing compound used in the small particle core preparation step is at least one of a Q′-containing oxide, a hydroxide, and a carbonate.

[0035] In some embodiments, the coating layer raw material includes at least two of oxides, hydroxides, fluorides, and phosphides.

[0036] In some embodiments, in the coating step, the sintering temperature is 700° C. to 920° C., the sintering time is 7 h to 13 h, and the sintering is performed in an oxygen-containing atmosphere.

[0037] In a third aspect, the present disclosure provides a lithium-ion battery positive electrode, comprising the lithium cobalt oxide positive electrode material described in any one of the aforementioned embodiments or the lithium cobalt oxide positive electrode material obtained by the method described in any one of the aforementioned embodiments.

[0038] In a fourth aspect, the present disclosure provides a lithium-ion battery comprising the lithium-ion battery positive electrode described in the aforementioned embodiment.

[0039] In a fifth aspect, the present disclosure provides an electrical device comprising the lithium-ion battery described in the aforementioned embodiment.

[0040] The present disclosure has the following beneficial effects:

[0041] The lithium cobalt oxide positive electrode material disclosed herein includes large particles and small particles, and the large and small particles have similarities and differences:

[0042] The similarities are that both large and small particles use nickel to replace cobalt to increase the volume, and manganese to replace cobalt to stabilize the structure. g 0 The corresponding coefficient is 0, so the cobalt redox reaction involves 3d t 2g Orbital cobalt (3+ / 4+) changes, where 3d t 2g There is a large overlap between orbital cobalt (3+ / 4+) and 2p orbital oxygen (2-), so the pure cobalt system is prone to cobalt dissolution and oxygen precipitation in a highly delithiated state, resulting in deterioration of circulation and storage; due to the trivalent nickel and trivalent manganese e g 1 The corresponding coefficient is 1, so the redox reaction of nickel and manganese involves 3d e g Track nickel (3+ / 4+) and manganese (3+ / 4+) changes, where trivalent nickel 3d e g The orbital energy level is higher than that of trivalent cobalt 3d t 2g energy level, nickel can achieve deeper delithiation before lattice oxygen precipitation, that is, higher capacity, and at the same time 3d e g The nickel orbital (3+ / 4+) has less overlap with the 2p orbital oxygen (2-), and has good stability under high delithiation; trivalent manganese 3d e g The orbital energy level is much higher than that of trivalent cobalt 3d t 2g energy level, and has no overlap with the 2p orbital oxygen (2-), and has better stability under high delithiation.

[0043] The difference is that the large particles contain less nickel and manganese, among which a small amount of nickel increases the capacity and a small amount of manganese stabilizes the structure. The presence of nickel and manganese inhibits the dissolution of cobalt to a certain extent and improves battery storage. At the same time, a small amount of nickel and manganese doping improves its own performance while the large particles can grow normally, increase the compaction density of the electrode, and ensure the compressive resistance. Nickel and manganese account for a larger proportion in small particles. Due to the small particle size and large BET of small particles, they are easy to grow into single crystals. Compared with a small amount of nickel and manganese doping, the large amount of nickel and manganese is more conducive to improving storage and gas production performance on the basis of increasing battery capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present disclosure and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0045] FIG1 is a flow chart of Example 1;

[0046] Figure 2 is the XRD image of the large particles of S1 obtained in Example 3

[0047] Figure 3 is an SEM image of large particles of S1 obtained in Example 3

[0048] FIG4 is a SEM image of the sample obtained in Example 3;

[0049] FIG5 is a SEM image of the sample obtained in Comparative Example 5. DETAILED DESCRIPTION

[0050] To make the purpose, technical solutions, and advantages of the embodiments of the present disclosure more clear, the technical solutions in the embodiments of the present disclosure are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer were followed. Reagents or instruments used where the manufacturer is not specified are conventional products that can be purchased commercially.

[0051] One embodiment of the present disclosure provides a lithium cobalt oxide positive electrode material, including large particles and small particles.

[0052] The large particles include the general formula Li a Co1-b1-b2-b3-cNi b1 Mn b2 Al b3 Q c The large particle core of O2 is coated with a general formula T g E h O k The cladding layer;

[0053] The small particles include the general formula Li d Co1-e1-e2-e3-fNi e1 Mn e2 Al e3 Q′ f The surface of the small particle core of O2 is coated with a general formula T g E h O k The cladding layer;

[0054] The median particle size of the large particle core is 18 μm to 21.5 μm, the median particle size of the small particle core is 3.5 μm to 6.5 μm, the molar ratio of the small particles to the large particles is 0.135 to 0.43, the large particle core is a layered single crystal structure, and the small particle core is a layered single crystal or layered single crystal-like structure;

[0055] Among them, 0.98≤a≤1.02, 0.0015≤b1≤0.01 ， 0.002≤b2≤0.02, 0.02≤b3≤0.03, 0.01≤c≤0.05, b2>b1, 0.98≤d≤1.01, 0.45≤e1≤0.95 ， 0.01≤e2≤0.45, 0.02≤e3≤0.04, 0.01≤f≤0.055, e2>e1, 0.8≤g≤3, 0≤h≤3, 1.5≤k≤5;

[0056] Q and Q' are each independently selected from at least one of Mg, La, Zr, Cu, Na, W, Sr and Y;

[0057] T and E are each independently selected from at least one of Li, Mg, B, La, Sn, W, Y, Zr, Ni, Al, F, P, and C.

[0058] In the lithium cobalt oxide positive electrode material of this embodiment, Li a Co1-b1-b2-b3-bNi b3 Mn b2 Al b1 Q b O2 is the general formula of large particle primary product, Li c Co1-d1-d2-d3-dNi d3 Mn d2 Al d1 Q′ d O2 is the general formula of small particle primary product, T e E f O gIn large particles, Co, Ni, Mn, and Al are skeleton elements, and Q is a doping element; in small particles, Co, Ni, Mn, and Al are skeleton elements, and Q' is a doping element.

[0059] The present disclosure introduces Q, Q', T, and E elements, among which Co, Ni, Mn, and Al elements occupy the Co position in the positive electrode material. When Q and Q' occupy the Co position, they inhibit the change in the Co valence state and inhibit the release of O; when they occupy the Li position, they improve the channel and enhance the ability to deintercalate and deintercalate lithium ions; the doping of Q and Q' elements is beneficial to stabilizing the structure, improving the channel and enhancing the ability to deintercalate and deintercalate lithium ions, while also improving electronic conductivity. E and T elements greatly improve interface stability. In addition, the introduction of Q, Q', T, and E elements can also inhibit the generation of microcracks on the surface of the positive electrode material, thereby improving the electrical performance of the positive electrode material under high voltage.

[0060] The nickel element in the skeleton of large particles and small particles can increase the capacity without destroying the structure, and manganese can stabilize the structure. The simultaneous presence of nickel and manganese changes the cobalt band structure, inhibits cobalt dissolution to a certain extent, improves storage, and the manganese doping amount is greater than the nickel doping amount, and the structural stability is better. When large particles adopt a single crystal structure and small particles adopt a single crystal or quasi-single crystal structure, the compaction density of the graded sample can be increased and the cycle performance can be improved. However, if there are too many nickel and manganese, the particles are easily crushed during sintering and polycrystalline is likely to appear. In particular, it is more difficult for large particles to grow, resulting in a decrease in compaction density, deterioration of circulation, and affecting overall performance. However, for small particles, it is relatively easy to form a single crystal structure or a quasi-single crystal structure. Therefore, in this disclosure, on the premise of ensuring that the small particles can be single crystals or quasi-single crystal structures, the doping amounts of nickel and manganese are increased, which is more conducive to improving storage and gas production on the basis of increasing capacity. It should be noted that the single crystal in this application refers to a structure formed by the aggregation of one particle rather than multiple particles.

[0061] In this embodiment, the median particle size of the large particle core is 18μm to 21.5μm, specifically 18μm, 19μm, 20μm, 21μm, 21.5μm or any value between 18μm and 21.5μm; the median particle size of the small particle core is 3.5μm to 6.5μm, specifically 3.5μm, 4.5μm, 5.5μm, 6.5μm or any value between 3.5μm and 6.5μm; the molar ratio of the small particles to the large particles is 2.0 to 7.5, specifically 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 7.5 or any value between 2.0 and 7.5. In this embodiment, the reasonable selection of the particle size and ratio of large particles and small particles is beneficial to improving the compaction density of the electrode. In addition, the types and doping amounts of the doping elements in the large particle core and the small particle core can be the same or different. When the types and doping amounts of the doping elements are different, or the element concentrations of the core and the coating are different, a concentration gradient will be formed in the positive electrode material, which is beneficial to improving the battery capacity and cycle performance.

[0062] In some embodiments, the general formula is: (1-x)[Li a Co1-b1-b2-b3-cNi b1 Mn b2 Al b3 Q c O2·nLi d Co1-e1-e2-e3-fNi e1 Mn e2 Al e3 Q′ f O2]·xT g E h O k , where 0.001≤x≤0.05, and 0.12≤n / (1+n)≤0.30.

[0063] When n / (1+n)>0.30, the cycle performance, gas production performance and compaction density of lithium cobalt composite oxide at high voltage cannot be guaranteed; when n / (1+n)<0.15, the capacity and storage performance of lithium cobalt composite oxide at high voltage cannot be guaranteed; preferably, 0.15≤n / (1+n)≤0.28; more preferably, 0.18≤n / (1+n)≤0.24; in this case, the compaction density of the battery plate is>4.2g / cm 3 , storage performance is better, and other performance is balanced.

[0064] In some embodiments, both Q and Q' include at least one of Mg, La, and Zr.

[0065] In some embodiments, the T is at least one of Mg, Al, Ti, and Zr.

[0066] In some embodiments, the E is at least one of F, P and C.

[0067] It is particularly noted that when the E element in the lithium cobalt oxide disclosed herein is F, the doping occupies the O position, lowering the overall Fermi level to match the reduction in the driving force for carbonate dehydrogenation; in the process of F replacing the O position, the Co element is reduced, which increases the energy barrier for electron conduction from the electrolyte, reduces interfacial side reactions, improves gas production, reduces Co dissolution, and improves storage.

[0068] In a second aspect, the present disclosure provides a method for preparing the lithium cobalt oxide positive electrode material as described in any one of the aforementioned items, comprising a coating step: mixing the large particle core, the small particle core and the coating layer raw materials and sintering them to obtain the lithium cobalt oxide positive electrode material.

[0069] When large and small cores are separately mixed with the coating material and sintered to produce large and small particles, respectively, the compatibility between the large and small particles is insufficient, reducing capacity and cycling performance. In the present disclosure, a large and small core is first prepared, and then both are coated simultaneously. This allows for element exchange between the large and small particles, improving compatibility and enhancing capacity and cycling performance. Furthermore, under high voltage conditions, the material maintains high-voltage density and excellent gas production performance.

[0070] In some embodiments, the coating layer raw material includes an auxiliary agent for reducing the sintering temperature, and the auxiliary agent is at least one of boric acid, magnesium fluoride, lithium hydroxide and lithium carbonate.

[0071] Small particles have better comprehensive performance when the sintering temperature is ≤850℃ during the coating process; when the sintering temperature is ≥870℃, small particles will produce large defects at high temperatures, causing their own performance to decline significantly; the large particle coating process requires a sintering temperature of usually ≥880℃ for better performance; the sintering temperature is ≤850℃, and the comprehensive performance declines significantly; large particles need to be coated at a higher temperature to achieve a better coating effect; the low-temperature coating effect is poor. Therefore, by directly mixing and sintering the large particle core, small particle core, and coating layer raw materials, the optimal sintering temperature between large and small particles does not match, and the performance of the graded sintered samples is poor. Therefore, in this embodiment, an additive is added to the coating step to ensure the coating effect while reducing the sintering temperature of the coating step, improving the comprehensive performance, and enabling large and small particles to obtain better comprehensive performance at the same sintering temperature.

[0072] In some embodiments, the total molar ratio of the additive to the coating layer raw material is (0.03-0.4):1, specifically 0.03:1, 0.05:1, 0.1:1, 0.2:1, 0.3:1, 0.4:1, or any value between (0.03-0.4):1. Adding too little additive has little effect on reducing the sintering temperature of the coating step, while adding too much additive may affect the material structure. Therefore, the amount of additive added needs to be reasonably set.

[0073] In some embodiments, the particle size of the auxiliary agent is 0.01 μm to 20 μm, specifically 10 nm, 100 nm, 1 μm, 10 μm, 20 μm or any value between 0.01 μm and 20 μm. Preferably, the particle size of the auxiliary agent is 0.1 to 15 μm. Small particles are conducive to uniform dispersion of elements.

[0074] In some embodiments, the preparation of large-particle cores is also included: a precursor mixture containing lithium, nickel, cobalt, manganese, aluminum, and Q is sintered to obtain a large-particle core, wherein the ratio of the total molar amount of lithium to nickel, cobalt, manganese, aluminum and Q in the precursor mixture is m1+m2, wherein m1 is 1.04~1.12, m2=(N1*n1) / 3, wherein N1 is the molar amount of the Q element replacing the Co position, and n1 is the valence state of the Q element replacing the Co position, specifically m1 can be at least one of 1.04, 1.06, 1.08, 1.10, 1.12 or 1.04~1.12. During the first sintering, excessive addition of lithium will, on the one hand, result in a small amount of lithium loss during the sintering process, and on the other hand, it will be beneficial to the growth of particles, promote fuller particles, eliminate secondary grain boundaries between particles, make up for the loss of sintering lithium, improve material processing performance, compaction density, reduce defects, and lower the sintering temperature. Excessive addition of lithium is especially necessary for the preparation of large-grained single crystals and small-grained single crystals or single-crystal-like materials.

[0075] In some embodiments, in the large particle core preparation step, the sintering temperature is 950°C to 1100°C, the time is 8h to 12h, and the sintering is carried out in an oxygen-containing atmosphere, specifically 950°C, 1000°C, 1050°C, 1100°C or at least one of 950°C to 1100°C, and the time is 8h to 12h, specifically 8h, 9h, 10h, 11h, 12h or at least one of 8h to 12h, and the sintering is carried out in an oxygen-containing atmosphere, such as a mixture of oxygen and nitrogen.

[0076] In some embodiments, the Q-containing compound used in the large particle core preparation step is at least one of a Q-containing oxide, hydroxide, and carbonate.

[0077] In some embodiments, the preparation of small particle cores is also included: a precursor mixture containing lithium, nickel, cobalt, manganese, aluminum, and Q' is sintered to obtain large particle cores, wherein the ratio of the total molar amount of lithium to nickel, cobalt, manganese, aluminum and Q' in the precursor mixture is m3+m4, wherein m3 is 1.02~1.09, m4=(N2*n2) / 3, wherein N2 is the molar amount of the Q' element replacing the Co position, and n2 is the valence state of the Q' element replacing the Co position, specifically m3 can be at least one of 1.02, 1.04, 1.06, 1.08, 1.09 or 1.02~1.09.

[0078] In some embodiments, in the small particle core preparation step, the sintering temperature is 550°C to 850°C, specifically 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C or any value between 550°C and 850°C, and the time is 8h to 12h, specifically 8h, 9h, 10h, 11h, 12h or at least one of 8h to 12h, and the sintering is carried out in an oxygen-containing atmosphere.

[0079] In some embodiments, the particle size of the Q-containing compound and the Q′-containing compound used in the steps of preparing the large particle core and the small particle core is 1 to 200 nm.

[0080] In some embodiments, the Q′-containing compound used in the small particle core preparation step is at least one of a Q′-containing oxide, a hydroxide, and a carbonate.

[0081] In some embodiments, the coating layer raw material includes at least two of oxides, hydroxides, fluorides, and phosphides.

[0082] In some embodiments, in the coating step, the sintering temperature is 700°C to 920°C, specifically 700°C, 750°C, 800°C, 850°C, 900°C, 920°C or any value between 700°C and 920°C, and the sintering time is 7h to 13h, specifically 7h, 8h, 9h, 10h, 11h, 12h, 13h or any value between 7h and 13h, and the sintering is carried out in an oxygen-containing atmosphere.

[0083] In a third aspect, the present disclosure provides a lithium-ion battery positive electrode, comprising the lithium cobalt oxide positive electrode material described in any one of the aforementioned embodiments or the lithium cobalt oxide positive electrode material obtained by the method described in any one of the aforementioned embodiments.

[0084] In a fourth aspect, the present disclosure provides a lithium-ion battery comprising the lithium-ion battery positive electrode described in the aforementioned embodiment.

[0085] In a fifth aspect, the present disclosure provides an electrical device comprising the lithium-ion battery described in the aforementioned embodiment.

[0086] The features and performance of the present disclosure are further described in detail below with reference to the embodiments.

[0087] Example 1

[0088] This embodiment provides a method for preparing a lithium cobalt oxide positive electrode material, as shown in FIG1 , comprising the following steps:

[0089] S1. According to the chemical formula Li 1.006 Co 0.9367 Ni 0.01 Mn 0.0218 Al 0.027 Mg 0.0045 The molar ratio of O2 is weighed, and lithium carbonate is added to make the ratio of the molar amount of lithium to the total molar amount of the five elements of cobalt, nickel, manganese, aluminum and magnesium to be 1.076. The mixture is evenly mixed and then calcined at a calcination temperature of 1070°C and a holding time of 12 hours. After natural cooling and crushing, the powder is pulverized and sieved to obtain large-particle lithium cobalt oxide primary powder.

[0090] S2. According to the chemical formula Li 1.001 Co 0.1845 Ni 0.49 Mn 0.29 Al 0.03 Mg 0.0055 The molar ratio of O2 is called 532 (NMC=532 means that the molar ratio of Ni:Mn:Co in the precursor is 5:3:2, abbreviated as 532, and the same applies to other series). Al precursor and magnesium oxide are doped, and lithium carbonate is added so that the ratio of the molar amount of lithium to the total molar amount of the five elements of cobalt, nickel, manganese, aluminum and magnesium is 1.060. The mixture is evenly mixed and then calcined at a calcination temperature of 800°C and a calcination time of 10 hours. After natural cooling and sieving, a ternary small particle primary powder is obtained.

[0091] S3. Place the large-particle primary powder and the small-particle primary powder in a molar ratio of 1:n=4:1, and the additives aluminum fluoride, titanium oxide and the auxiliary agent boric acid (molar ratio, aluminum fluoride: titanium oxide: boric acid = 1:1:1, corresponding to x = 0.004) in a three-dimensional mixing device, place it in a ball mill, rotate at 250r / min, and the mass ratio of the ball to the material is 1.2:1. Mix for 2 hours to obtain a mixed powder, calcine the mixed powder at a calcination temperature of 720℃, keep warm for 8 hours, and naturally cool and crush it to obtain 0.996 (Li 1.006 Co 0.9367 Ni 0.01 Mn 0.0218 Al 0.027 Mg0.0045 O2·0.25Li 1.001 Co 0.1845 Ni 0.49 Mn 0.29 Al 0.03 Mg 0.0055 O2)0.004BAlTiF3O 3.5 .

[0092] Example 2

[0093] This embodiment provides a method for preparing a lithium cobalt oxide positive electrode material, comprising the following steps:

[0094] S1. According to the chemical formula Li 1.006 Co 0.9632 Ni 0.0017 Mn 0.0036 Al 0.027 Mg 0.0045 Zr 0.001 The molar ratio of O2 is weighed. Ni-Mn-Al doped cobalt trioxide and magnesium oxide are weighed, and lithium carbonate is added so that the ratio of the molar amount of lithium to the total molar amount of the five elements of cobalt, nickel, manganese, aluminum and magnesium is 1.076. The mixture is evenly mixed and then calcined. The mixed powder is calcined at a temperature of 1070°C and the insulation time is 12 hours. After natural cooling and crushing, it is crushed and sieved to obtain large-particle primary powder of lithium cobalt oxide.

[0095] S2. According to the chemical formula Li 1.001 Co 0.1835 Ni 0.49 Mn 0.29 Al 0.03 Mg 0.0055 Zr 0.001 Weigh 532 doped Al precursor and magnesium oxide at a molar ratio of O2, and add lithium carbonate so that the ratio of the molar amount of lithium to the total molar amount of the five elements of cobalt, nickel, manganese, aluminum and magnesium is 1.060. Mix them evenly and then calcine. The mixed powder is calcined at a temperature of 800°C and a calcination time of 10 hours. After natural cooling and sieving, a ternary small particle primary powder is obtained.

[0096] S3. The large-particle primary powder and the small-particle primary powder were uniformly mixed in a molar ratio of 1:n=4:1, and the additives aluminum fluoride, titanium oxide and the auxiliary agent boric acid (molar ratio, aluminum fluoride: titanium oxide: boric acid = 1:1:1, corresponding to x = 0.004) and then calcined at a temperature of 780 ° C. for 8 hours. After natural cooling and crushing, 0.996 (Li 1.006 Co 0.9632 Ni 0.0017 Mn 0.0036 Al 0.027 Mg 0.0045 Zr0.001 O2·0.25Li 1.001 Co 0.1835 Ni 0.49 Mn 0.29 Al 0.03 Mg 0.0055 Zr 0.001 O2)·0.004BAlTiF3O 3.5 .

[0097] Example 3

[0098] This embodiment provides a method for preparing a lithium cobalt oxide positive electrode material, comprising the following steps:

[0099] S1. According to the chemical formula Li 1.006 Co 0.9632 Ni 0.0017 Mn 0.0036 Al 0.027 Mg 0.0045 The molar ratio of O2 is weighed. Ni-Mn-Al doped cobalt trioxide and magnesium oxide are weighed, and lithium carbonate is added so that the ratio of the molar amount of lithium to the total molar amount of the five elements of cobalt, nickel, manganese, aluminum and magnesium is 1.076. The mixture is evenly mixed and then calcined. The mixed powder is calcined at a temperature of 1070°C and the insulation time is 12 hours. After natural cooling and crushing, it is crushed and sieved to obtain large-particle primary powder of lithium cobalt oxide.

[0100] S2. According to the chemical formula Li 1.001 Co 0.1845 Ni 0.49 Mn 0.29 Al 0.03 Mg 0.0055 Weigh 532 doped Al precursor and magnesium oxide at a molar ratio of O2, and add lithium carbonate so that the ratio of the molar amount of lithium to the total molar amount of the five elements of cobalt, nickel, manganese, aluminum and magnesium is 1.060. Mix them evenly and then calcine. The mixed powder is calcined at a temperature of 800°C and a calcination time of 10 hours. After natural cooling and sieving, a ternary small particle primary powder is obtained.

[0101] S3. The large-particle primary powder and the small-particle primary powder were mixed uniformly in a molar ratio of 1:n=4:1, and the additives aluminum fluoride, titanium oxide and lithium hydroxide (molar ratio, aluminum fluoride: titanium oxide: lithium hydroxide = 1:1:1, corresponding to x = 0.004) and then calcined at a temperature of 830 ° C for 8 hours. After natural cooling and crushing, 0.996 (Li 1.00 6Co 0.9367 Ni 0.01 Mn 0.0218 Al 0.027 Mg 0.0045 O2·0.25Li1.001 Co 0.1845 Ni 0.49 Mn 0.29 Al 0.03 Mg 0.0055 O2)·0.004LiAlTiF3O 2.5 , the SEM image is shown in Figure 2.

[0102] Example 4

[0103] This embodiment provides a method for preparing a lithium cobalt oxide positive electrode material. The difference from Example 3 is that the molar ratio of small NiMnCo particles in step S2 is 6:2:2, and the sintering temperature is 760°C.

[0104] Example 5

[0105] This embodiment provides a method for preparing a lithium cobalt oxide positive electrode material. The difference from Example 3 is that the molar ratio of small particles NiMnCo in step S2 is 7:1.5:1.5, and the sintering temperature is 750°C.

[0106] Example 6

[0107] This embodiment provides a method for preparing a lithium cobalt oxide positive electrode material. The difference from Example 3 is that in step S2, the molar ratio of small NiMnCo particles is 8:1:1, and the sintering temperature is 700°C.

[0108] Example 7

[0109] This embodiment provides a method for preparing a lithium cobalt oxide positive electrode material. The difference from Example 3 is that in step S2, the molar ratio of small particles NiMnCo is 9:0.5:0.5, and the sintering temperature is 700°C.

[0110] Example 8

[0111] This embodiment provides a method for preparing a lithium cobalt oxide positive electrode material. The difference from embodiment 3 is that La and Y are added as doping elements in steps S1 and S2 to obtain a positive electrode material with a general formula of 0.996 (Li 1.006 Co 0.9349 Ni 0.01 Mn 0.0218 Al 0.027 Mg 0.0045 La 0.0007 Y 0.0011 O2·0.25Li 1.001 Co 0.1827 Ni 0.49 Mn 0.29 Al 0.03 Mg 0.0055 La 0.0007 Y 0.0011O2)·0.004LiAlTiF3O 2.5 .

[0112] Example 9

[0113] This embodiment provides a method for preparing a lithium cobalt oxide positive electrode material. The difference from embodiment 3 is that the coating elements in step S3 are Zr, Al, Mg, and F, and the positive electrode material obtained has a general formula of 0.996 (Li 1.006 Co 0.9367 Ni 0.01 Mn 0.0218 Al 0. 027 Mg 0.0045 O2·0.25Li 1.001 Co 0.1845 Ni 0.49 Mn 0.29 Al 0.03 Mg 0.0055 O2)·0.004ZrAlMgF2O 2.5 .

[0114] Example 10

[0115] This embodiment provides a method for preparing a lithium cobalt oxide positive electrode material. The difference from embodiment 3 is that in step S3, the coating element is increased by adding P element, and the positive electrode material obtained has the general formula of 0.996 (Li 1.006 Co 0.9367 Ni 0.01 Mn 0.0218 Al 0.027 Mg 0.0045 O2·0.25Li 1.001 Co 0.1845 Ni 0.49 Mn 0.29 Al 0.03 Mg 0.0055 O2)·0.004LiAlTiF3PO 2.5 .

[0116] Example 11

[0117] This embodiment provides a method for preparing a lithium cobalt oxide positive electrode material. The difference from Example 3 is that the auxiliary agent in step S3 is lithium carbonate, and the molar amount of the auxiliary agent lithium in Example 3 is consistent with that in Example 11.

[0118] Example 12

[0119] This embodiment provides a method for preparing a lithium cobalt oxide positive electrode material. The difference from Example 3 is that the auxiliary agent in step S3 is magnesium fluoride, and the molar amounts of lithium and magnesium in Example 3 and Example 12 are the same.

[0120] Example 13

[0121] This embodiment provides a method for preparing a lithium cobalt oxide positive electrode material. The difference from Embodiment 3 is that in step S3, the molar ratio of the large-particle primary powder to the small-particle primary powder is 1:n=4.3:0.7.

[0122] Example 14

[0123] This embodiment provides a method for preparing a lithium cobalt oxide positive electrode material. The difference from Embodiment 3 is that in step S3, the molar ratio of the large-particle primary powder to the small-particle primary powder is 1:n=3.5:1.5.

[0124] Example 15

[0125] This embodiment provides a method for preparing a lithium cobalt oxide positive electrode material. The difference from embodiment 3 is that in the coating step, the molar ratio of the primary powder to the large and small particles is x=0.01.

[0126] Example 16

[0127] This embodiment provides a method for preparing a lithium cobalt oxide positive electrode material. The difference from embodiment 3 is that in the coating step, the molar ratio of the primary powder to the large and small particles is x=0.001.

[0128] Example 17

[0129] This embodiment provides a method for preparing a lithium cobalt oxide positive electrode material, which differs from Example 3 in that the molar ratio of aluminum fluoride:titanium oxide:lithium hydroxide is 3:4:3.

[0130] Example 18

[0131] This embodiment provides a method for preparing a lithium cobalt oxide positive electrode material, which differs from Example 3 in that the molar ratio of aluminum fluoride:titanium oxide:lithium hydroxide is 3:3:4.

[0132] Example 19

[0133] This embodiment provides a lithium cobalt oxide. The preparation method differs from that of Example 2 only in that, in step S1, the calcination temperature is 950°C and the holding time is 12 hours; in step S2, the calcination temperature is 800°C and the holding time is 12 hours; and in step S3, the calcination temperature is 860°C and the holding time is 12 hours.

[0134] Example 20

[0135] This embodiment provides a lithium cobalt oxide. The preparation method differs from that of Example 2 only in that, in step S1, the calcination temperature is 1100° C. and the holding time is 8 hours; in step S2, the calcination temperature is 550° C. and the holding time is 12 hours; and in step S3, the calcination temperature is 860° C. and the holding time is 12 hours.

[0136] Comparative Example 1

[0137] This comparative example provides a method for preparing a lithium cobalt oxide positive electrode material, and the specific steps are as follows:

[0138] S1. According to the chemical formula Li 1.006 Co 0.9685 Al 0.027 Mg 0.0045 The molar ratio of O2 is 1.070, and the molar ratio of lithium to the total molar ratio of cobalt, nickel, manganese, aluminum and magnesium is weighed, and lithium carbonate is added so that the ratio of the molar amount of lithium to the total molar amount of the four elements of cobalt, nickel, manganese, aluminum and magnesium is 1.070. The mixture is evenly mixed and then calcined at a calcination temperature of 1070°C and a holding time of 12 hours. After natural cooling and crushing, the powder is pulverized and sieved to obtain large-particle lithium cobalt oxide primary powder.

[0139] S2. According to the chemical formula Li 1.001 Co 0.1845 Ni 0.49 Mn 0.29 Al 0.03 Mg 0.0055 Weigh 532 doped Al precursor and magnesium oxide at a molar ratio of O2, and add lithium carbonate so that the ratio of the molar amount of lithium to the total molar amount of the five elements of cobalt, nickel, manganese, aluminum and magnesium is 1.060. Mix them evenly and then calcine. The mixed powder is calcined at a temperature of 800°C and a calcination time of 10 hours. After natural cooling and sieving, a ternary small particle primary powder is obtained.

[0140] S3. The large-particle primary powder and the small-particle primary powder were uniformly mixed in a molar ratio of 1:n=4:1, and the additives aluminum fluoride, titanium oxide and the auxiliary agent boric acid (molar ratio, aluminum fluoride: titanium oxide: boric acid = 1:1:1, corresponding to x = 0.004) and then calcined at a temperature of 720 ° C. for 8 hours. After natural cooling and crushing, 0.996 (Li 1.006 Co 0.9685 Al 0.027 Mg 0.0045 O2·0.25Li 1.001 Co 0.1845 Ni 0.49 Mn 0.29 Al 0.03 Mg 0.0055 O2)·0.004BAlTiF3O 3.5 .

[0141] Comparative Example 2

[0142] This comparative example provides a method for preparing a lithium cobalt oxide positive electrode material, and the specific steps are as follows:

[0143] S1. According to the chemical formula Li 1.006 Co 0.9632 Ni 0.0017 Mn 0.0036 Al 0.027 Mg 0.0045 Zr 0.001 The molar ratio of O2 is weighed, and lithium carbonate is added to make the ratio of the molar amount of lithium to the total molar amount of the five elements of cobalt, nickel, manganese, aluminum and magnesium to be 1.076. The mixture is evenly mixed and then calcined at a calcination temperature of 1070°C and a holding time of 12 hours. After natural cooling and crushing, the powder is pulverized and sieved to obtain large-particle lithium cobalt oxide primary powder.

[0144] S2. According to the chemical formula Li 1.001 Co 0.9635 Al 0.03 Mg 0.0055 Zr 0.001 The doped Al precursor and magnesium oxide are weighed, and lithium carbonate is added so that the ratio of the molar amount of lithium to the total molar amount of the four elements of cobalt, nickel, manganese, aluminum and magnesium is 1.040. The mixture is evenly mixed and then calcined. The mixed powder is calcined at a temperature of 800°C and a calcination time of 10 hours. After natural cooling and sieving, a ternary small particle primary powder is obtained.

[0145] S3. The large-particle primary powder and the small-particle primary powder were uniformly mixed in a molar ratio of 1:n=4:1, and the additives aluminum fluoride, titanium oxide and the auxiliary agent boric acid (molar ratio, aluminum fluoride: titanium oxide: boric acid = 1:1:1, corresponding to x = 0.004) and then calcined at a temperature of 780 ° C. for 8 hours. After natural cooling and crushing, 0.996 (Li 1.006 Co 0.9632 Ni 0.0017 Mn 0.0036 Al 0.027 Mg 0.0045 Zr 0.001 O2·0.25Li 1.001 Co 0.9635 Al 0.03 Mg 0.0055 Zr 0.001 O2)·0.004BAlTiF3O 3. 5.

[0146] Comparative Example 3

[0147] This comparative example provides a method for preparing a lithium cobalt oxide positive electrode material, and the specific steps are as follows:

[0148] S1. According to the chemical formula Li 1.006 Co 0.9632 Ni 0.0017 Mn 0.0036 Al 0.027 Mg 0.0045 The molar ratio of O2 is weighed, and lithium carbonate is added to make the ratio of the molar amount of lithium to the total molar amount of the five elements of cobalt, nickel, manganese, aluminum and magnesium to be 1.076. The mixture is evenly mixed and then calcined at a calcination temperature of 1070°C and a holding time of 12 hours. After natural cooling and crushing, the powder is pulverized and sieved to obtain large-particle lithium cobalt oxide primary powder.

[0149] S2. According to the chemical formula Li 1.001 Co 0.1845 Ni 0.49 Mn 0.29 Al 0.03 Mg 0.0055 Weigh 532 doped Al precursor and magnesium oxide at a molar ratio of O2, and add lithium carbonate so that the ratio of the molar amount of lithium to the total molar amount of the five elements of cobalt, nickel, manganese, aluminum and magnesium is 1.050. Mix them evenly and then calcine. The mixed powder is calcined at a temperature of 800°C and a calcination time of 10 hours. After natural cooling and sieving, a ternary small particle primary powder is obtained.

[0150] S3. The large-particle primary powder and the small-particle primary powder were mixed uniformly in a molar ratio of 1:n=4:1, and the additives aluminum fluoride and titanium oxide (molar ratio, aluminum fluoride: titanium oxide = 1:1, corresponding to x = 0.004) were mixed and then calcined at a temperature of 830 ° C for 8 hours. After natural cooling and crushing, 0.996 (Li 1.006 Co 0.9367 Ni 0.01 Mn 0.0218 Al 0.027 Mg 0.0045 O2·0.25Li 1.001 Co 0.1845 Ni 0.49 Mn 0.29 Al 0.03 Mg 0.0055 O2)·0.004AlTiF3O2.

[0151] Comparative Example 4

[0152] This comparative example provides a method for preparing a lithium cobalt oxide positive electrode material, and the specific steps are as follows:

[0153] S1. According to the chemical formula Li1.006 Co 0.9632 Ni 0.0017 Mn 0.0036 Al 0.027 Mg 0.0045 The molar ratio of O2 is weighed, and lithium carbonate is added to make the ratio of the molar amount of lithium to the total molar amount of the five elements of cobalt, nickel, manganese, aluminum and magnesium to be 1.076. The mixture is evenly mixed and then calcined at a calcination temperature of 1070°C and a holding time of 12 hours. After natural cooling and crushing, the powder is pulverized and sieved to obtain large-particle lithium cobalt oxide primary powder.

[0154] S2. According to the chemical formula Li 1.006 Co 0.9495 Ni 0.005 Mn 0.01 Al 0.03 Mg 0.0055 Weigh 532 doped Al precursor and magnesium oxide at a molar ratio of O2, and add lithium carbonate so that the ratio of the molar amount of lithium to the total molar amount of the five elements of cobalt, nickel, manganese, aluminum and magnesium is 1.050. Mix them evenly and then calcine. The mixed powder is calcined at a temperature of 800°C and a calcination time of 10 hours. After natural cooling and sieving, a ternary small particle primary powder is obtained.

[0155] S3. The large-particle primary powder and the small-particle primary powder were mixed uniformly in a molar ratio of 1:n=4:1, and the additives aluminum fluoride, titanium oxide and lithium hydroxide (molar ratio, aluminum fluoride: titanium oxide: lithium hydroxide = 1:1:1, corresponding to x = 0.004) and then calcined at a temperature of 830 ° C for 8 hours. After natural cooling and crushing, 0.996 (Li 1.00 6Co 0.9367 Ni 0.01 Mn 0.0218 Al 0.027 Mg 0.0045 O2·0.25Li 1.006 Co 0.9495 Ni 0.005 Mn 0.01 Al 0.03 Mg 0.0055 O2)·0.004LiAlTiF3O 2.5 .

[0156] Comparative Example 5

[0157] This comparative example provides a method for preparing a lithium cobalt oxide positive electrode material, which adopts a method substantially the same as that of Example 3, except that the large and small particles are calcined respectively.

[0158] S1 according to the chemical formula Li 1.006 Co0.9632 Ni 0.0017 Mn 0.0036 Al 0.027 Mg 0.0045 The molar ratio of O2 is weighed. Ni-Mn-Al doped cobalt trioxide and magnesium oxide are weighed, and lithium carbonate is added so that the ratio of the molar amount of lithium to the total molar amount of the five elements of cobalt, nickel, manganese, aluminum and magnesium is 1.076. The mixture is evenly mixed and then calcined. The mixed powder is calcined at a temperature of 1070°C and the insulation time is 12 hours. After natural cooling and crushing, it is crushed and sieved to obtain large-particle primary powder of lithium cobalt oxide.

[0159] S2. The large-particle primary powder, additives aluminum fluoride, titanium oxide and auxiliary agent lithium hydroxide (molar ratio, aluminum fluoride: titanium oxide: lithium hydroxide = 1:1:1, corresponding to x = 0.004) were uniformly mixed and then calcined at a temperature of 830°C for 8 hours. After natural cooling and crushing, the large-particle secondary calcined sample was pulverized.

[0160] S3. According to the chemical formula Li 1.001 Co 0.1845 Ni 0.49 Mn 0.29 Al 0.03 Mg 0.0055 Weigh 532 doped Al precursor and magnesium oxide at a molar ratio of O2, and add lithium carbonate so that the ratio of the molar amount of lithium to the total molar amount of the five elements of cobalt, nickel, manganese, aluminum and magnesium is 1.060. Mix them evenly and then calcine. The mixed powder is calcined at a temperature of 800°C and a calcination time of 10 hours. After natural cooling and sieving, a ternary small particle primary powder is obtained.

[0161] S4. The small-particle primary powder, additives aluminum fluoride, titanium oxide and auxiliary agent lithium hydroxide (molar ratio, aluminum fluoride: titanium oxide: lithium hydroxide = 1:1:1, corresponding to x = 0.004) were uniformly mixed and then calcined at a temperature of 830°C for 8 hours. After natural cooling and crushing, the small-particle secondary calcined sample was obtained by pulverizing.

[0162] S5. The large particle secondary product and the small particle secondary product are synthesized in a molar ratio of 1:n=4:1 to 0.996 (Li 1.006 Co 0.9367 Ni 0.01 Mn 0.0218 Al 0.027 Mg 0.0045 O2·0.25Li 1.001 Co 0.1845 Ni 0.49 Mn 0.29 Al 0.03 Mg 0.0055 O2)·0.004LiAlTiF3O2.5 , the SEM image is shown in Figure 3.

[0163] Comparative Example 6

[0164] This comparative example provides a method for preparing a lithium cobalt oxide positive electrode material. All raw materials are directly mixed and sintered at 1070°C for 12 hours to obtain 0.996 (Li 1.006 Co 0.9367 Ni 0.01 Mn 0.0218 Al 0.027 Mg 0.0045 O2·0.25Li 1.001 Co 0.1845 Ni 0.49 Mn 0.29 Al 0.03 Mg 0.0055 O2)·0.004LiAlTiF3O 2.5 .

[0165] Comparative Example 7

[0166] This comparative example provides a method for preparing a lithium cobalt oxide positive electrode material, which differs from Example 3 in that the molar ratio of aluminum fluoride:titanium oxide:lithium hydroxide is 3:4:0.5.

[0167] Comparative Example 8

[0168] This comparative example provides a method for preparing a lithium cobalt oxide positive electrode material, which differs from Example 3 in that the molar ratio of aluminum fluoride:titanium oxide:lithium hydroxide is 3:2:6.

[0169] Comparative Example 9

[0170] This comparative example provides a method for preparing a lithium cobalt oxide positive electrode material, which differs from Example 3 in that, in step S1, lithium carbonate is added so that the ratio of the molar amount of lithium to the total molar amount of the five elements of cobalt, nickel, manganese, aluminum and magnesium is 1.060.

[0171] Comparative Example 10

[0172] This comparative example provides a method for preparing a lithium cobalt oxide positive electrode material, which differs from Example 3 in that, in step S1, lithium carbonate is added so that the ratio of the molar amount of lithium to the total molar amount of the five elements of cobalt, nickel, manganese, aluminum and magnesium is 1.120.

[0173] Comparative Example 11

[0174] This comparative example provides a method for preparing a lithium cobalt oxide positive electrode material, which differs from Example 3 in that, in step S1, the calcination temperature is 850° C. and the holding time is 12 hours.

[0175] Comparative Example 12

[0176] This comparative example provides a method for preparing a lithium cobalt oxide positive electrode material, which differs from Example 3 in that, in step S1, the calcination temperature is 1200° C. and the holding time is 12 hours.

[0177] Comparative Example 13

[0178] This comparative example provides a method for preparing a lithium cobalt oxide positive electrode material, which differs from Example 3 in that, in step S3, the calcination temperature is 600° C. and the holding time is 12 hours.

[0179] Comparative Example 14

[0180] This comparative example provides a method for preparing a lithium cobalt oxide positive electrode material, which differs from Example 3 in that, in step S3, the calcination temperature is 950° C. and the holding time is 12 hours.

[0181] Performance Testing

[0182] The lithium cobalt oxides obtained in the above examples and comparative examples are as follows:

[0183] The lithium cobalt oxide positive electrode material prepared in the embodiment or comparative example was used as the positive electrode material to prepare a lithium ion battery: the lithium cobalt oxide positive electrode material, SP (conductive agent), and PVDF (binder) were mixed in a mass ratio of 92:4:4, NMP (N-methylpyrrolidone) was added, and the mixture was stirred to form a slurry, which was coated on an aluminum foil and dried at 80°C to prepare a positive electrode sheet;

[0184] Graphite, SP (conductive agent), binder, and dispersant were mixed in a mass ratio of 96.5:1.5:1.5:1.5, and a solvent (H2O) was added. The mixture was stirred to form a slurry, which was then coated on aluminum foil and dried at 80°C to form a negative electrode sheet.

[0185] The above-mentioned positive electrode sheet, negative electrode, electrolyte and separator are used as raw materials to assemble into a soft-pack battery.

[0186] Capacity test: Four of the soft-pack batteries prepared above were taken as parallel samples, formed, and divided into different capacities. At room temperature (25°C), they were charged at a constant current rate of 0.2C to a voltage of V1. Further, they were charged at a constant voltage of V1 until the current was less than 0.05C, bringing them to a fully charged state of V1. The discharge capacity was then obtained by constant current discharge at a rate of 0.2C to V2. The discharge capacity in grams at a rate of 0.2C was calculated using the following formula: discharge capacity in grams = discharge capacity / mass of the positive electrode material. (V1 is 4.50V, and V2 refers to 3.0V)

[0187] The test results of each embodiment and comparative example are shown in Table 1.

[0188] Table 1

[0189] From the comparison of Examples 1 to 3 and Comparative Examples 1 to 3 in Table 1, it can be seen that nickel-manganese doping improves capacity, storage, and gas production performance, and has little effect on cycle performance. Comparative Example 3 adopts a one-sintering + one-sintering process without additives, and the overall performance is significantly reduced; high temperature destroys the structure of small particles. The capacity of the nickel-manganese doped sample is significantly higher than that of the undoped sample, indicating that nickel-manganese doping has a capacity-enhancing effect. The reason is that the nickel element has an additional capacity-enhancing effect. At the same time, nickel-manganese doping has the effect of improving storage and gas production performance, and the large and small particles are designed differently. Figure 2 is Example 3, the S1 large particle is pure corresponding to PDF#50-0653, and Figure 3 is the SEM of the S1 large particle, and the morphology is a single crystal morphology.

[0190] The resulting soft-pack batteries were tested at 45°C, 3.0-4.50V / 1.0C for 45°C cycling, 45°C storage performance, and 70°C storage gas generation. Examples 3-16 and Comparative Examples 3, 4, 5, and 6 were tested for 60-day storage gas generation at 70°C, 120-day storage capacity recovery at 45°C, and 450-cycle retention. The results are shown in Table 2.

[0191] Table 2

[0192] Comparing Example 3 with Comparative Example 3 in Table 2 shows that adding additives during the second sintering process lowers the sintering temperature and maintains structural stability. Example 3 and Comparative Example 4 show that the small particles doped with low nickel and manganese significantly improve circulation, but capacity, storage, and gas production deteriorate, indicating that high nickel and manganese content improves capacity and storage and gas production. Comparing Example 3 with Example 5 shows that the second sintering + second sintering process does not achieve optimal matching, with significant decreases in capacity and circulation, while storage and gas production are comparable. Comparing Example 3 with Example 6 shows that mixed doping with all elements improves capacity but sharply deteriorates overall performance, indicating that different element doping has different effects and that different element doping and coating locations vary. Comparing Examples 3-7 shows that as the nickel content of the small particles increases, capacity gradually improves, gas production gradually increases, and storage and circulation gradually deteriorate. As the nickel content increases, the stability of the small particles weakens, leading to a weakening of the stability of the large and small particle gradation system. Examples 3 and Examples 8-10 show that small changes in a single doping and coating element have relatively little impact on overall performance. In Example 3 and Examples 11-12, different additives have an impact on storage and gas production, mainly affecting the sintering activity of the second sintering and affecting the structural stability of the small-particle structure. Comparison between Example 3 and Examples 13-14 shows that increasing the amount of large particles significantly reduces the capacity, increasing the amount of large particles reduces the BET, and lengthens the lithium ion channel, resulting in reduced capacity. Increasing the amount of large particles worsens storage, while gas production and circulation improve. Large particles have a small BET, a small interface contact area, and smaller side reactions. Increasing the amount of small particles improves capacity, while other properties deteriorate. Comparison between Example 3 and Examples 15-16 shows that increasing the coating amount hinders lithium ion deintercalation and deteriorates capacity, while circulation and gas production improve, and storage deteriorates. Reducing the coating amount intensifies surface and interface side reactions, and significantly deteriorates performance.

[0193] In Examples 17-18, appropriate adjustment of the additives has little effect on the overall performance; in Examples 19-20, it can be seen that the sintering temperature of large particles S1 is too low, the crystallization is poor, and the circulation is poor; the sintering temperature of large particles S1 is too high, and the capacity decreases significantly. When the sintering temperature of S3 is 920°C, the capacity and storage decrease significantly.

[0194] The large particle cores obtained in each embodiment of the present application are all single crystal structures, with a median particle size between 18μm and 21.5μm. The median particle size of the small particle cores is about 3.5μm to 6.5μm, and the small particles are all single crystal or quasi-single crystal structures. In Comparative Example 9, due to insufficient lithium, the large particles are a polycrystalline structure formed by the agglomeration of small particles.

[0195] The doping of large particles with low nickel manganese and small particles with high nickel manganese can significantly improve the cycle and 45℃ storage, and the gas production is improved. The presence of nickel manganese improves the band structure of cobalt and inhibits the dissolution of cobalt, inhibits the valence change of cobalt to a certain extent, and indirectly inhibits oxygen precipitation, thereby reducing interface side reactions, improving interface stability, and improving storage and gas production. Nickel manganese doping generates a stable nickel-cobalt-manganese structure, inhibits phase change, and improves the cycle. Industrial Applicability

[0196] The present invention discloses a method for preparing lithium cobalt oxide positive electrode materials with good storage, circulation and gas production performance at a voltage of 4.50V or even higher, which has good industrial application prospects.

Claims

1. A lithium cobalt oxide cathode material, characterized in that, It includes large particles and small particles. The large particles include a general formula of Li a Co1-b1-b2-b3-cNi b1 Mn b2 Al b3 Q c O2 large particle core, the surface of the large particle core is coated with a general formula T g E h O k The coating layer; The small particles include small particle cores with a general formula of Li d Co1-e1-e2-e3-fNi e1 Mn e2 Al e3 Q′ f O2, and the surfaces of the small particle cores are coated with a coating layer with a general formula of T g E h O k ; The median particle size of the large particle core is 18 μm to 21.5 μm, the median particle size of the small particle core is 3.5 μm to 6.5 μm, the molar ratio of the small particles to the large particles is 0.135 to 0.43, the large particle core is a layered single crystal structure, and the small particle core is a layered single crystal or layered single crystal-like structure. Among them, 0.98 ≤ a ≤ 1.02, 0.0015 ≤ b1 ≤ 0.01, 0.002 ≤ b2 ≤ 0.02, 0.02 ≤ b3 ≤ 0.03, 0.01 ≤ c ≤ 0.05, b2 > b1, 0.98 ≤ d ≤ 1.01, 0.45 ≤ e1 ≤ 0.95, 0.01 ≤ e2 ≤ 0.45, 0.02 ≤ e3 ≤ 0.04, 0.01 ≤ f ≤ 0.055, e2 > e1, 0.8 ≤ g ≤ 3, 0 ≤ h ≤ 3, 1.5 ≤ k ≤ 5. Q and Q' are each independently selected from at least one of Mg, La, Zr, Cu, Na, W, Sr, and Y. T and E are each independently selected from at least one of Li, Mg, B, La, Sn, W, Y, Zr, Ni, Al, F, P, and C.

2. The lithium cobalt oxide cathode material according to claim 1, characterized in that, General formula: (1 - x)·[Li a Co 1- b1 - b2 - b3 - cNi b1 Mn b2 Al b3 Q c O2·nLi d Co1 - e1 - e2 - e3 - fNi e1 Mn e2 Al e3 Q′ f O2]·xT g E h O k , where 0.001 ≤ x ≤ 0.05 and 0.12 ≤ n / (1 + n) ≤ 0.

30.

3. The lithium cobalt oxide cathode material according to claim 2, wherein 0.18 ≤ n / (1 + n) ≤ 0.

24.

4. The lithium cobalt oxide cathode material according to any one of claims 1-3, characterized in that Both the Q and Q' include at least one of Mg, La, and Zr.

5. The lithium cobalt oxide cathode material according to any one of claims 1-4, characterized in that, The T is at least one of Mg, Al, Ti, and Zr.

6. The lithium cobalt oxide cathode material according to any one of claims 1-5, characterized in that, The E is at least one of F, P, and C.

7. A method for preparing the lithium cobalt oxide cathode material according to any one of claims 1-6, characterized in that, It includes a coating step: mixing the large particle core, small particle core, and coating layer raw materials and then sintering to obtain a lithium cobalt oxide cathode material.

8. The preparation method of the lithium cobalt oxide cathode material according to claim 7, wherein The coating layer raw materials include an auxiliary agent for reducing the sintering temperature, and the auxiliary agent is at least one of boric acid, magnesium fluoride, lithium hydroxide, and lithium carbonate.

9. The preparation method of the lithium cobalt oxide cathode material according to claim 8, wherein The total molar ratio of the auxiliary agent to the coating layer raw materials is (0.03 - 0.4):

1.

10. The preparation method of the lithium cobalt oxide cathode material according to claim 8 or 9, characterized in that, The particle size of the auxiliary agent is 0.01 μm to 20 μm.

11. The preparation method of the lithium cobalt oxide cathode material according to any one of claims 7-10, characterized in that, It also includes the preparation of the large particle core: sintering a precursor mixture containing lithium, nickel, cobalt, manganese, aluminum, and Q to obtain a large particle core, where the total molar ratio of lithium to nickel, cobalt, manganese, aluminum, and Q in the precursor mixture is m1 + m2, where m1 is 1.04 to 1.12, and m2 = (N1 * n1) / 3, where N1 is the molar amount of the Q element substituting for the Co site and n1 is the valence state of the Q element substituting for the Co site.

12. The preparation method of the lithium cobalt oxide cathode material according to claim 11, wherein In the step of preparing the large particle core, the sintering temperature is 950°C to 1100°C, the time is 8 h to 12 h, and the sintering is carried out in an oxygen-containing atmosphere.

13. The preparation method of the lithium cobalt oxide cathode material according to claim 11 or 12, characterized in that, The Q compound used in the step of preparing the large particle core is at least one of an oxide, hydroxide, and carbonate containing Q.

14. The preparation method of the lithium cobalt oxide cathode material according to any one of claims 7-13, characterized in that, It also includes the preparation of the small particle core: sintering a precursor mixture containing lithium, nickel, cobalt, manganese, aluminum, and Q' to obtain a large particle core, where the total molar ratio of lithium to nickel, cobalt, manganese, aluminum, and Q' in the precursor mixture is m3 + m4, where m3 is 1.02 to 1.09, and m4 = (N2 * n2) / 3, where N2 is the molar amount of the Q' element substituting for the Co site and n2 is the valence state of the Q' element substituting for the Co site.

15. The preparation method of the lithium cobalt oxide cathode material according to any one of claims 14, characterized in that, In the step of preparing the small particle core, the sintering temperature is 550°C to 850°C, the time is 8 h to 12 h, and the sintering is carried out in an oxygen-containing atmosphere.

16. The preparation method of the lithium cobalt oxide cathode material according to claim 14 or 15, characterized in that, In the steps of preparing the large particle core and the small particle core, the particle sizes of the Q-containing compound and the Q'-containing compound used are 1 to 200 nm.

17. The preparation method of the lithium cobalt oxide cathode material according to any one of claims 14-16, characterized in that, In the step of preparing the small particle core, the Q'-containing compound used is at least one of an oxide, a hydroxide, and a carbonate containing Q'.

18. The preparation method of the lithium cobalt oxide cathode material according to any one of claims 7-17, characterized in that, The coating layer raw material includes at least two of an oxide, a hydroxide, a fluoride, and a phosphide.

19. The preparation method of the lithium cobalt oxide cathode material according to any one of claims 7-18, characterized in that, In the coating step, the sintering temperature is 700°C to 920°C, the time is 7 h to 13 h, and the sintering is carried out in an oxygen-containing atmosphere.

20. A positive electrode of a lithium-ion battery, characterized in that, It includes the lithium cobalt oxide cathode material according to any one of claims 1-6 or the lithium cobalt oxide cathode material obtained by the method according to any one of claims 7-19.

21. A lithium-ion battery, characterized in that, It includes the lithium ion battery cathode according to claim 20.

22. An electrical device, characterized in that, It includes the lithium ion battery according to claim 21.

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