A high-voltage lithium cobalt oxide positive electrode material and preparation method thereof

Abstract

The present invention proposes a high-voltage lithium cobalt oxide cathode material and a preparation method thereof, belonging to the field of lithium-ion battery electrode materials. The high-voltage lithium cobalt oxide cathode material comprises a core and a near-surface layer. The core is doped with NiAl, and the near-surface layer is a continuous hexagonal layered structure doped with nano-cations layer by layer. The near-surface layer is doped layer by layer to ensure uniform distribution of dopant atoms in each layer, avoid localized enrichment of dopant atoms in micro-regions, and achieve continuity and structural stability. The present invention solves the thermal instability caused by Ni redox, achieving excellent structural stability from the core to the near-surface in a highly delithiated state, resulting in high specific energy and long cycle life.

Description

Technical Field

[0001] The invention relates to lithium cobalt oxide with high specific capacity and high voltage and a preparation method thereof, and belongs to the field of lithium ion battery electrode materials. Background Art

[0002] High capacity, long life, and high safety have always been the pursuit of lithium-ion batteries. Lithium cobalt oxide (LCO), a cathode material, is primarily used in portable devices such as 3C devices, laptops, and tablets. To maximize capacity, increasing the operating voltage is the most direct solution. The operating voltage of commercial lithium-ion batteries has gradually increased from 4.35V to 4.45V, making the application of LCO at higher operating voltages (≥4.45V) a research hotspot. While operating voltages ≥4.45V further improve specific capacity, LCO with high levels of delithiation undergoes a structural transformation from the layered O3 phase to the H1-3 phase. This structural change significantly reduces cycling performance. Numerous studies and patents have been published in this area, primarily focusing on doping and surface coating. Doping can inhibit phase transformation, but doping with inactive materials inevitably reduces specific capacity. Coating primarily protects the near-surface layer, but the coating typically has a different lattice structure from the LCO. During long cycles at high voltages and high temperatures, the unit cell undergoes multiple contractions and expansions, which can cause the coating to detach, reducing cycling performance. Therefore, in order to obtain lithium-ion batteries with high energy density and long life, improving the structural stability of lithium cobalt oxide at higher operating voltages is a technical difficulty.

[0003] From the perspective of crystal field, Ni and Co have energy level splitting in d orbitals in octahedron, forming t2g and eg orbitals. 3+ (t2g6eg0) and Ni 3+ (t2g6e1) are all in a low spin state. During the charge and discharge process, Co 3+ / Co 4+ Corresponding to t2g6eg0 / t2g5eg0, Ni 3+ / Ni 4+ Corresponding to t2g6eg1 / t2g6eg0. Ni 3+ / Ni 4+ The corresponding redox active eg band has very little overlap with the top of the O2-2p band, while Co 3+ / Co 4+ The corresponding redox reaction active t2g band has a large overlap with the top of the O2-2p band. 3+ / Ni 4+ Has lower band overlap. 3+ / Co 4+The t2g energy band and the O2-2p energy band have a large overlap. LiCoO2 is very unstable when more than 50% of lithium is removed. In particular, when the operating voltage is ≥4.50V, the highly delithiated lithium cobalt oxide transforms from the layered O3 phase to the H1-3 phase, and Ni4+ can exist in the layered structure of the material in the state of removing more Li, and exert a specific capacity of up to 220mAh / g. On the other hand, during the charge and discharge process, Co 3+ / Co 4+ The energy change is small, so the radius change is small (RCo 3+ =0.0545nm, RCo 4+ =0.053nm). And Ni 3+ / Ni 4+ Because the electron changes between the t2g and eg orbits, the energy change is relatively large, so the radius changes greatly before and after the reaction (RNi 3+ =0.056nm,RNi 4+ =0.048nm), this phenomenon will have a great negative impact on nickel-based materials, causing intense heat release in the deep de-Li state, deteriorating thermal stability, and causing surface side reactions.

[0004] The Ni doping amount in CN104466113B is 0.45-0.55. Due to the high Ni doping amount, although the specific capacity can be improved, the disadvantages of Ni are not fully considered, especially the cycle attenuation problem at higher voltages cannot be solved.

[0005] Because of Ni 3+ Very unstable, storing Ni 3+ It will react with carbon dioxide and water molecules in the air to generate Ni 2+ Therefore, LiNiO2, LiNi 1-x-y Co x M n yO2 material, there will be Ni on the surface of the particles during storage 2+ Precipitation reduces specific capacity and cycle performance.

[0006] Under high voltage and high temperature working conditions, after multiple charge and discharge cycles, various defects such as vacancies, lattice mismatches, and even holes and cracks will appear in the near-surface layered structure of the particles, reducing the cycle performance. In order to solve the problem of surface structure stability, the usual method is to perform surface coating, but because the structure of the generated coating material is different from the structure of lithium cobalt oxide, there is a lattice interface, and the coating layer falls off due to lattice expansion and contraction during the cycle. On the other hand, the structure and thickness of the coating material will directly affect the transfer of lithium ions and electrons. Therefore, it is particularly important that the near-surface particles have a stable layered structure that is the same as the bulk structure and has good lithium ion and electron conductivity.

[0007] The existing high-voltage lithium cobaltate has a working voltage of 4.40 - 4.50V with a carbon negative electrode as the counter electrode. Currently, there are no related applications with higher voltages.

[0008] Therefore, in the present invention, by doping NiAl in the core body of lithium cobaltate, the instability of the layered LiCoO2 structure in the high lithium-depleted state is solved, and the high specific capacity of Ni is utilized. At the same time, by doping Al in the core, the excellent heat transfer property of Al is utilized to solve the thermal instability caused by the redox of Ni. On the other hand, non-Ni element doping is designed on the near surface of the particles, and elements with invariant valence are doped to change the electronic structure and improve the stability of the near surface structure. To achieve excellent structural stability from the core to the near surface in the high lithium-depleted state, it is applied to a higher working voltage of ≥4.50V, obtaining a high specific capacity while still having excellent high cycle life. Summary of the Invention

[0009] The object of the present invention is to provide a high-voltage lithium cobaltate cathode material and its preparation method, which solve the thermal instability caused by the redox of Ni, improve the stability of the near surface structure, and achieve excellent structural stability from the core to the near surface in the high lithium-depleted state, and are applied to lithium-ion batteries with a higher working voltage of ≥4.50V to obtain high specific energy and long cycle life.

[0010] To achieve the above object, the present invention adopts the following technical solutions:

[0011] A high-voltage lithium cobaltate cathode material includes a core and a near surface layer; the core is doped with NiAl, and its chemical general formula is LiCo1- x-y Ni x Al y O2, where 0 < x ≤ 0.20, 0 < y ≤ 0.20; the near surface layer is a continuous hexagonal layered structure with nano-layered doped cations, and its chemical general formula is LiCo 1-a-b Al a M b O 2-c N c , where M is at least one combination of Mg, Ti, Zr, Y, La, Nb, W, N is F, PO4, a = 0.01 - 0.10, b = 0.005 - 0.04, 0 < c ≤ 0.05.

[0012] Preferably, the radius of the lithium cobaltate cathode material is not greater than 36μm, and the thickness of the near surface layer is not greater than 400nm.

[0013] A preparation method of a high-voltage lithium cobaltate cathode material includes the following steps:

[0014] 1) Prepare a mixed salt solution from cobalt salt, nickel salt, and aluminum salt,

[0015] 2) Add the carbonate solution and the mixed salt solution from step 1) into the nucleation reactor together for granulation reaction, control the pH to form the inner core;

[0016] 3) Add the slurry in the nucleation reactor from step 2) into the particle growth reactor containing the carbonate solution for stirring; at the same time, add the carbonate solution and the mixed salt solution from step 1) into this particle growth reactor together, control the pH, and continuously centrifuge until the inner core grows to a certain particle size;

[0017] 4) Add the slurry in the particle growth reactor from step 3) into the optimization reactor containing the carbonate solution for stirring; then conduct element doping from the first layer to the Nth layer in sequence. The process of element doping for each layer is as follows: configure a mixed solution of cobalt salt, aluminum salt and the doping element M of the current layer, continuously add this mixed solution and the carbonate solution into the optimization reactor together, control the pH value, and grow the particle size on the surface of the inner core; stop feeding when the target particle size of the current layer is reached, and then conduct aging;

[0018] 5) After completing the Nth layer of element doping, take out the slurry in the optimization reactor, and successively pass through filtration, washing, drying, sintering under an oxidizing atmosphere, and pulverization to obtain the oxide;

[0019] 6) Mix the lithium source with the oxide obtained in step 5) and sinter under an oxidizing atmosphere or in air to finally obtain the high-voltage lithium cobalt oxide cathode material with near-surface layer-by-layer doping.

[0020] Preferably, in step 1), the molar ratio of Co:Ni:Al in the mixed salt solution is (1 - x - y):x:y, where 0 < x ≤ 0.20 and 0 < y ≤ 0.20, and the concentration is 100 g / L.

[0021] Preferably, in step 2), the flow rate of the mixed salt solution added to the nucleation reactor is 260 L / h, the flow rate of the carbonate solution added to the nucleation reactor is 600 L / h, pH = 6.8 - 8.5, and the granulation reaction time is 3 - 10 h.

[0022] Preferably, in step 3), the flow rate of the mixed salt solution added to the particle growth reactor is 600 - 700 L / h, the flow rate of the carbonate solution added to the particle growth reactor is 300 - 1800 L / h, pH = 6.8 - 8.0, and the growth rate of the inner core D50 is 0.1 - 0.3 μm / h.

[0023] Preferably, in step 4), N = 4 - 7; for each layer, the doping element M selects one of Mg, Ti, Zr, Y, La, Nb, W as the basic doping element, and at least one of the additional doping elements F, PO4 is added or not added in the outermost layer and / or the second outermost layer, and the basic doping elements of each layer without additional doping elements are different.

[0024] Preferably, in each layer in step 4), the molar ratio of the cobalt salt, the aluminum salt and the doping element M is the following: Co:Al:M=(1-ab):a:b, a=0.01-0.1, b=0.005-0.04.

[0025] Preferably, in step 4), the additional doping elements F and PO4 are added in the form of acid radical solution.

[0026] Preferably, the carbonate solution in steps 2) to 4) is an ammonium bicarbonate solution with a concentration of 300 g / L; when the acid radical solution of the additional doping element is added, the total concentration of the carbonate solution and the acid radical solution is 300 g / L, and the molar ratio of the acid radical to the carbonate radical is 1:1.

[0027] Preferably, when each layer of element doping is performed in step 4), the flow rate of the mixed solution added to the optimized reactor is 175 L / h, and the flow rate of the carbonate solution added to the optimized reactor is 75-500 L / h; pH = 6.8-8.0; D50 particle size growth rate is 0.05-0.15 μm / h; and aging time is 40-200 min.

[0028] Preferably, the temperature of the materials in each reactor in steps 2) to 4) is maintained at 40-60° C.; and the stirring speed is 300-1800 r / min.

[0029] Preferably, in step 5), centrifugal filtration is used, hot pure water is used for washing, and the mixture is dried at 100° C.; the sintering conditions in an oxidizing atmosphere are: oxygen to nitrogen volume ratio = m:(100-m), m = 25-45, sintering temperature 700-850° C., and sintering time 4-6 h.

[0030] Preferably, in step 6), the molar ratio of lithium source to oxide Li:(Co+Ni)=1.005-1.065; the sintering conditions under an oxidizing atmosphere are: the volume ratio of oxygen to nitrogen = n:(100-n), n=25-45; the sintering conditions are: from room temperature to 850-1060°C over 90-180 minutes, and keep warm for 400-900 minutes; then cool to 800-850°C, keep warm for 120-360 minutes; and finally cool to room temperature; and control the gas flow rate to 60-200 ml / min.

[0031] The advantages of the present invention are as follows:

[0032] 1. From the core 0% to the first target radius, trivalent Ni is uniformly doped to obtain a single crystal particle with a well-crystalline layered structure. In the highly delithiated state, Ni 4+While maintaining a layered structure, high capacity is achieved. Therefore, doping trivalent Ni from 0% of the core to the first target radius not only increases specific capacity but also prevents the transition from the O3 phase to the H1-3 phase under high delithiation conditions, stabilizing the cobalt-oxygen octahedron structure and preventing Co dissolution, thereby improving high-voltage and high-temperature cycling performance.

[0033] 2. On the one hand, the amount of Ni doping is regulated, and on the other hand, during the sintering process, oxidation conditions (such as increasing the oxygen partial pressure) are used to fully oxidize and avoid Ni 3+ Easy to undergo reduction reaction to generate Ni 2+ The problem is that Ni exists completely in trivalent form and Ni 2+ The Li / Ni mixed arrangement problem of occupying the Li site realizes the full utilization of specific capacity and ensures that the lithium ion transfer channel is not blocked by Ni. 2+ It occupies a certain area and improves the cycle performance of the battery under high temperature and high voltage.

[0034] 3. In the radius range from the first target to 100% of the precursor, elements are uniformly doped, and then reacted with the Li source to obtain a continuous layered structure in which NiAl is uniformly doped from 0% to the first target radius of the core, there is no Ni from the first target to 100% radius, and other elements are uniformly doped layer by layer. On the one hand, under high lithium removal, during long cycles, due to different crystal phases and different lattice orientations, when the lattice expands and contracts multiple times, cracking occurs at the boundaries of different crystal phase orientations and grain boundaries of different crystal phases. As the number of cycles increases, macroscopic cracks may even occur, and even the shedding of coatings of different crystal phases may occur. The uniform doping of NiAl in the core and the uniform doping of the near-surface layer by layer eliminates the problem of lattice interface mismatch and ensures a continuous layered structure from the inside out. On the other hand, the near-surface layer is not doped with Ni, which avoids the occurrence of Ni on the surface of the particles during storage. 2+ That is, to give full play to Ni's advantages and avoid Ni's disadvantages.

[0035] 4. In the process of preparing the precursor, doping elements are introduced, Ni and Al are uniformly doped from the core to the first target radius, and different doping elements Mg, Ti, Zr, Y, Nb, La, W, F, PO4 are doped at different depths (different target radius values) from the first target radius to 100% radius. 3- , among which anions F, PO4 3- The cations occupy the oxygen sites, while other cations occupy the Co sites. The resulting cathode material has an O3 layered structure, a stable near-surface layer with good ionic and electronic conductivity. The continuous cation doping of each nanolayer suppresses phase transitions and avoids various defects such as vacancies, lattice mismatches, and even holes and cracks, thereby improving cycling performance.

[0036] 5. The doped cations occupy the cobalt site in the cobalt-oxygen octahedron. By regulating the atomic ratio of the doped atoms at the nanoscale depth near the surface of the particles, the electronic conductivity is improved without affecting the lithium ion migration channel.

[0037] 6. In the near-surface layer, layer-by-layer doping is employed to ensure uniform distribution of dopant atoms in each layer, avoiding localized enrichment of dopant atoms in micro-regions, resulting in a continuous, stable near-surface layer. Furthermore, the thickness of each layer is controlled to a nanometer size of ≤50nm, which maximizes the role of each dopant element while ensuring electronic conductivity and avoiding loss of specific energy and specific capacity due to inactive dopant elements. This fully utilizes the specific capacity while achieving excellent cycling performance.

[0038] 7. Doping Al near the surface, on the one hand, inhibits the transformation of O3 to H1-3, and on the other hand, since Al occupies the Co site, it reduces the proportion of active material Co, thereby reducing the specific capacity. Therefore, doping Mg changes the micro-area electronic structure and improves the electronic conductivity; doping Ti increases the Co valence state, which is beneficial to charge transfer, reduces the charge transfer resistance, and is beneficial to circulation; doping La, due to the large radius of La ions, occupies the Co site, increases the interlayer spacing of the Li-O octahedron, which is beneficial to lithium ion transmission; doping W is beneficial to improve electronic conductivity; doping Zr and Y, since Zr-O and YO have lone pairs of electrons and are Lewis alkaline, they capture HF in the electrolyte, improve the surface resistance to hydrofluoric acid in the electrolyte, and thus improve the surface structure stability.

[0039] 8. Anions are doped near the surface to occupy the oxygen sites in the cobalt-oxygen octahedron. In the highly delithiated state, PO steric hindrance inhibits the O 2- Charge transfer of ions stabilizes the near-surface structure.

[0040] 9. By doping anions near the surface, they occupy the oxygen sites in the cobalt-oxygen octahedron. F ions have a flame retardant effect, thus improving the battery safety under high delithiation state.

[0041] 10. The process of the present invention has low cost and is easy to produce on a large scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a schematic structural diagram of lithium cobalt oxide prepared by the present invention.

[0043] Figure 2 This is a flow chart of the present invention for preparing high-voltage lithium cobalt oxide positive electrode materials.

[0044] Figure 3 This is a performance test chart of the product prepared in Example 1.

[0045] Figure 4 This is a performance test diagram of the coated lithium cobalt oxide of comparative example 1.

[0046] Figures 5A-5B This is the XPS graph of the lithium cobalt oxide prepared in Example 1.

[0047] Figure 6 This is a TEM image of the lithium cobalt oxide prepared in Example 1.

[0048] Figure 7 This is a graph showing the capacity retention rate and cycle number at 45°C for soft-pack batteries made of lithium cobalt oxide in Examples 1, 2, and Comparative Example 2. DETAILED DESCRIPTION

[0049] In order to make the above features and advantages of the present invention more clearly understood, embodiments are given below and described in detail with reference to the accompanying drawings.

[0050] Comparative Example 1: Common coated lithium cobalt oxide.

[0051] Example 1: Preparation of 150nm near-surface layer doped lithium cobalt oxide layer by layer, the structure of which is shown in Table 1:

[0052] Table 1

[0053] Main core <![CDATA[Li 1.0013 Co 0.960 Ni 0.020 Al 0.020 O2]]> Tier 1 <![CDATA[Li 1.0013 What 0.975 Al 0.020 Mg 0.005 O2]]> Layer 2 <![CDATA[Li 1.0013 What 0.975 Al 0.020 Those 0.005 O2]]> Layer 3 <h2 style=";text-align:left;direction:ltr"><![CDATA[Li <h2 style=";text-align:left;direction:ltr"> 1.0013 <h2 style=";text-align:left;direction:ltr"> Co<h2 style=";text-align:left;direction:ltr"> 0.975 <h2 style=";text-align:left;direction:ltr"> Al<h2 style=";text-align:left;direction:ltr"> 0.020 <h2 style=";text-align:left;direction:ltr"> Zr<h2 style=";text-align:left;direction:ltr"> 0.005 <h2 style=";text-align:left;direction:ltr"> O2]]><h2 style=";text-align:left;direction:ltr"> Layer 4 <![CDATA[Li 1.0013 Yes 0.975 Al 0.020 Y 0.005 O2]]> Layer 5 <![CDATA[Li 1.0013 Co 0.975 Al 0.020 Day 0.005 O2]]> Layer 6 <![CDATA[Li 1.0013 What 0.975 Al 0.020 Y 0.005 ABOUT 1.95 F 0.05 ]]> Layer 7 <![CDATA[Li 1.0013 What 0.975 Al 0.020 Y 0.005 ABOUT 1.95 (PO4) 0.05 ]]>

[0054] This embodiment uses the following steps to prepare a high-voltage lithium cobalt oxide positive electrode material:

[0055] 1. Preparation of oxides

[0056] 1) Core NiAl doping nucleation step: A 300 g / L ammonium bicarbonate base solution and a 100 g / L cobalt-nickel-aluminum nitrate mixed solution were added to the nucleation reactor at a molar ratio of Co:Ni:Al = 0.96:0.02:0.02. The mixture was added at a flow rate of 260 L / h and a 300 g / L ammonium bicarbonate solution was added at a flow rate of 600 L / h to the nucleation reactor for granulation reaction. The pH value was controlled at 6.8, the reaction time was 10 h, and the nuclei grew to a median diameter of 10.0 μm.

[0057] 2) Core NiAl doped particle growth step: a 300 g / L ammonium bicarbonate bottom solution was added to the particle growth reactor, the slurry in the crystal nucleation reactor was added to the particle growth reactor, and the stirring device was turned on. At the same time, a 100 g / L cobalt nickel aluminum nitrate mixed solution with a molar ratio of Co:Ni:Al=0.96:0.02:0.02 was added to the particle growth reactor at a flow rate of 600 L / h and a 300 g / L ammonium bicarbonate solution was added to the particle growth reactor at a flow rate of 1500 L / h. The pH value was controlled at 6.8. When the volume of the material in the particle growth reactor reached 80% of the reactor volume, the solid content of the reaction system in the particle growth reactor was increased by continuous centrifugation until the particle median diameter reached 19.0 μm; the particle D50 growth rate was 0.1 μm / h.

[0058] 3) Near-surface layer doping steps:

[0059] Add 300 g / L ammonium bicarbonate bottom solution into the optimized reactor, add the slurry from the particle growth reactor into the optimized reactor, start the stirring device, and simultaneously perform the following multi-layer element doping:

[0060] The first doping layer, Mg, consisted of a 100g / L cobalt-aluminum-magnesium nitrate solution with a molar ratio of Co:Al:Mg = 0.975:0.020:0.005. This solution was fed into the optimized reactor at a flow rate of 175L / h, along with a 300g / L ammonium bicarbonate solution at a flow rate of 75L / h. The pH of each solution was controlled within the range of 6.8. The particle D50 growth rate was 0.05μm / h. When the particle size reached 19.15μm, the feed was stopped and the particles were placed in an aging tank for 80 minutes.

[0061] The second doping layer, Ti, consisted of a 100g / L cobalt-aluminum-titanium nitrate solution with a molar ratio of Co:Al:Ti = 0.975:0.020:0.005. This solution was fed into the optimized reactor at a flow rate of 175L / h, along with a 300g / L ammonium bicarbonate solution at a flow rate of 75L / h. The pH of each solution was controlled within the range of 6.8. The particle D50 growth rate was 0.05μm / h. When the particle size reached 19.30μm, the feed was stopped and the particles were placed in an aging tank for 80 minutes.

[0062] The third doping layer, Zr, consisted of a 100g / L cobalt-aluminum-zirconium nitrate solution with a molar ratio of Co:Al:Zr = 0.975:0.020:0.005. This solution was fed into the optimized reactor at a flow rate of 175L / h, along with a 300g / L ammonium bicarbonate solution at a flow rate of 75L / h. The pH of each solution was controlled within the range of 6.8. The particle D50 growth rate was 0.05μm / h. When the particle size reached 19.45μm, the feed was stopped and the particles were placed in an aging tank for 80 minutes.

[0063] The fourth doping element, Y, was added to the optimized reactor at a flow rate of 175 L / h. A 100 g / L cobalt-aluminum-yttrium nitrate solution with a molar ratio of Co:Al:Y = 0.975:0.020:0.005 was added concurrently with a 300 g / L ammonium bicarbonate solution at a flow rate of 75 L / h. The pH of each solution was controlled within the range of 6.8. The particle D50 growth rate was 0.05 μm / h. When the particle size reached 19.60 μm, the feed was stopped and the particles were placed in an aging tank for 80 minutes.

[0064] The fifth doping element, La, consisted of a 100g / L cobalt-aluminum-lanthanum nitrate solution with a molar ratio of Co:Al:La = 0.975:0.020:0.005. This solution was fed into the optimized reactor at a flow rate of 175L / h, along with a 300g / L ammonium bicarbonate solution at a flow rate of 75L / h. The pH of each solution was controlled within the range of 6.8. The particle D50 growth rate was 0.05μm / h. When the particle size reached 19.75μm, the feed was stopped and the particles were placed in an aging tank for 80 minutes.

[0065] The sixth doping layer, Y+F, consisted of a 100g / L cobalt-aluminum-yttrium nitrate solution with a molar ratio of Co:Al:Y = 0.975:0.020:0.005. This solution was added to the optimized reactor at a flow rate of 175L / h, along with a 300g / L ammonium bicarbonate and ammonium fluoride solution with a 1:1 molar ratio of carbonate to fluoride ions. The pH was controlled within the range of 6.8. The particle D50 growth rate was 0.05μm / h. When the particle size reached 19.90μm, the feed was stopped and the particles were placed in an aging tank for 80min.

[0066] The seventh doping element, Y+PO4, consisted of a 100g / L cobalt-aluminum-yttrium nitrate solution with a molar ratio of Co:Al:Y = 0.975:0.020:0.005. This solution was fed into the optimized reactor at a flow rate of 175L / h, along with a 300g / L ammonium bicarbonate and ammonium hydrogen phosphate solution with a 1:1 carbonate to phosphate molar ratio. The pH was controlled within the range of 6.8. The particle size growth rate (D50) was 0.05μm / h. When the particle size reached 20.30μm, the feed was stopped and the particles were placed in an aging tank for 80 minutes.

[0067] Among them, in the core growth step, particle growth step, inner layer doping step, and aging step, the temperature of the materials in each reactor is maintained at 40°C; the stirring speed is 300r / min; and the temperature of each solution is maintained within 25°C.

[0068] 4) After the aging reaction, the slurry was filtered through a centrifuge and washed six times with hot pure water. The filter cake was dried at 100°C and then sintered in an oxidizing atmosphere (oxygen to nitrogen ratio = 25:75 by volume) at 700°C in a muffle furnace for 6 hours. The calcined slurry was crushed and passed through a 300-mesh sieve to obtain the oxide.

[0069] 2. Preparation of lithium cobalt oxide

[0070] The oxide and lithium source in step 1 were weighed according to a Li / (Co+Ni) molar ratio of 1.065 and sintered in air. The sintering conditions were as follows: from room temperature to 1030°C over 150 minutes, kept warm for 600 minutes, then cooled to 800°C, kept warm for 240 minutes, and finally cooled to room temperature. The gas flow rate was controlled at 60 ml / min and ventilation was continued until it cooled to room temperature to obtain high-voltage lithium cobalt oxide with 150 nm near-surface layer-by-layer doping.

[0071] Comparative Example 2: According to Co 0.960 Ni 0.020 Al 0.020 Nickel-aluminum doped oxides and lithium carbonate are weighed according to a Li / (Co+Ni) molar ratio of 1.065, mixed in the solid phase, and sintered at high temperature once to obtain single crystal particles. The single crystal particles are then solid-phase mixed with Mg, Ti, La, Y, and Zr nano-oxides used as surface modification elements, and sintered twice to obtain surface-doped lithium cobalt oxide.

[0072] Example 2: Preparation of 50nm near-surface layer doped lithium cobalt oxide layer by layer, the structure of which is shown in Table 2:

[0073] Table 2

[0074] Main core <![CDATA[Li 1.0013 Co 0.980 Ni 0.010 Al 0.010 O2]]> Tier 1 <![CDATA[Li 1.0013 What 0.98 Al 0.01 Mg 0.01 O2]]> Layer 2 <![CDATA[Li 1.0013 What 0.98 Al 0.01 Those 0.01 O2]]> Layer 3 <![CDATA[Li 1.0013 Yes 0.98 Al 0.01 Y 0.01 O2]]> Layer 4 <![CDATA[Li 1.0013 What 0.98 Al 0.01 Y 0.01 ABOUT 1.95 (PO4) 0.05 ]]>

[0075] This embodiment uses the following steps to prepare a high-voltage lithium cobalt oxide positive electrode material:

[0076] 1. Preparation of oxides

[0077] 1) Core NiAl doping nucleation step: A 300 g / L ammonium bicarbonate base solution and a 100 g / L cobalt-nickel-aluminum nitrate mixed solution were added to the nucleation reactor at a molar ratio of Co:Ni:Al = 0.98:0.01:0.01. The mixture was added at a flow rate of 260 L / h and a 300 g / L ammonium bicarbonate solution was added at a flow rate of 600 L / h to the nucleation reactor for granulation reaction. The pH value was controlled at 7.5, the reaction time was 8 h, and the nuclei grew to a median diameter of 10.0 μm.

[0078] 2) Core NiAl doped particle growth step: a 300 g / L ammonium bicarbonate bottom solution was added to the particle growth reactor, the slurry in the crystal nucleation reactor was added to the particle growth reactor, and the stirring device was turned on. At the same time, a 100 g / L cobalt nickel aluminum nitrate mixed solution with a molar ratio of Co:Ni:Al=0.98:0.01:0.01 was added to the particle growth reactor at a flow rate of 700 L / h and a 300 g / L ammonium bicarbonate solution was added to the particle growth reactor at a flow rate of 300 L / h. The pH value was controlled at 7.5. When the volume of the material in the particle growth reactor reached 80% of the reactor volume, the solid content of the reaction system in the particle growth reactor was increased by continuous centrifugation until the particle median diameter reached 19.87 μm; the growth rate was 0.2 μm / h.

[0079] 3) Near-surface layer doping steps:

[0080] Add 300 g / L ammonium bicarbonate bottom solution into the optimized reactor, add the slurry from the particle growth reactor into the optimized reactor, start the stirring device, and simultaneously perform the following multi-layer element doping:

[0081] The first doping layer, Mg, consisted of a 100g / L cobalt-aluminum-magnesium nitrate solution at a molar ratio of 0.98:0.01:0.01. This solution was fed into the optimized reactor at a flow rate of 175L / h, along with a 300g / L ammonium bicarbonate solution at a flow rate of 200L / h. The pH of each solution was controlled within the range of 7.5. The particle D50 growth rate was 0.10μm / h. When the particle size reached 19.98μm, the feed was stopped and the particles were placed in an aging tank for 40 minutes.

[0082] The second doping layer, Ti, consisted of a 100g / L cobalt-aluminum-titanium nitrate solution at a molar ratio of 0.98:0.01:0.01, fed into the optimized reactor at a flow rate of 175L / h and a 300g / L ammonium bicarbonate solution at a flow rate of 200L / h. The pH of each solution was controlled within the range of 7.5. The particle D50 growth rate was 0.10μm / h. When the particle size reached 20.09μm, the feed was stopped and the particles were placed in an aging tank for 40 minutes.

[0083] The third doping element, Y, was added to the optimized reactor at a flow rate of 175 L / h. A 100 g / L cobalt, aluminum, and yttrium nitrate solution, with a molar ratio of 0.98:0.01:0.01, was co-flowed with a 300 g / L ammonium bicarbonate solution at a flow rate of 200 L / h. The pH of each solution was controlled within a range of 7.5. The particle D50 growth rate was 0.10 μm / h. When the particle size reached 20.2 μm, the feed was stopped and the particles were placed in an aging tank for 40 minutes.

[0084] The fourth doping layer, Y+PO4, consisted of a 100g / L cobalt-aluminum-yttrium nitrate solution with a molar ratio of Co:Al:Y = 0.98:0.01:0.01. This solution was fed into the optimized reactor at a flow rate of 175L / h, along with a 300g / L ammonium bicarbonate and ammonium hydrogen phosphate solution with a carbonate-to-phosphate molar ratio of 1:1. The pH was controlled within the range of 7.5. The particle size growth rate (D50) was 0.10μm / h. When the particle size reached 20.30μm, the feed was stopped and the particles were placed in an aging tank for 40min.

[0085] Among them, in the core growth step, particle growth step, inner layer doping step, and aging step, the temperature of the materials in each reactor is maintained at 45°C; the stirring speed is 400r / min; and the temperature of each solution is maintained within 30°C.

[0086] 4) After the aging reaction, the slurry was filtered through a centrifuge and washed six times with hot pure water. The filter cake was dried at 100°C and then sintered in an oxidizing atmosphere (oxygen to nitrogen ratio = 30:70 by volume) at 800°C in a muffle furnace for 4 hours. The calcined slurry was crushed and passed through a 300-mesh sieve to obtain the oxide.

[0087] 2. Preparation of lithium cobalt oxide

[0088] The oxide and lithium source in step 1 were weighed according to a Li / (Co+Ni) molar ratio of 1.065 and sintered in air. The sintering conditions were as follows: from room temperature to 1060°C over 180 minutes, kept warm for 540 minutes, then cooled to 800°C, kept warm for 120 minutes, and finally cooled to room temperature. The gas flow rate was controlled at 80 ml / min and ventilation was continued until it cooled to room temperature to obtain high-voltage lithium cobalt oxide with 50 nm near-surface layer-by-layer doping.

[0089] Example 3: Preparation of 100nm near-surface layer doped lithium cobalt oxide layer by layer, the structure of which is shown in Table 3:

[0090] Table 3

[0091] Main core <![CDATA[Li 1.0013 Co 0.920 Ni 0.040 Al 0.040 O2]]> Tier 1 <![CDATA[Li 1.0013 What 0.92 Al 0.04 Mg 0.04 O2]]> Layer 2 <![CDATA[Li 1.0013 What 0.92 Al 0.04 Those 0.04 O2]]> Layer 3 <h2 style=";text-align:left;direction:ltr"><![CDATA[Li <h2 style=";text-align:left;direction:ltr"> 1.0013 <h2 style=";text-align:left;direction:ltr"> Co<h2 style=";text-align:left;direction:ltr"> 0.92 <h2 style=";text-align:left;direction:ltr"> Al<h2 style=";text-align:left;direction:ltr"> 0.04 <h2 style=";text-align:left;direction:ltr"> Zr<h2 style=";text-align:left;direction:ltr"> 0.04 <h2 style=";text-align:left;direction:ltr"> O2]]><h2 style=";text-align:left;direction:ltr"> Layer 4 <![CDATA[Li 1.0013 Co 0.92 Al 0.04 Nb 0.04 O2]]> Layer 5 <![CDATA[Li 1.0013 Co 0.92 Al 0.04 Day 0.04 O2]]> Layer 6 <![CDATA[Li 1.0013 What 0.92 Al 0.04 Y 0.04 ABOUT 1.95 (PO4) 0.05 ]]>

[0092] 1. Preparation of oxides

[0093] 1) Core NiAl doping nucleation step: A 300 g / L ammonium bicarbonate base solution and a 100 g / L cobalt-nickel-aluminum nitrate mixed solution were added to the nucleation reactor at a molar ratio of Co:Ni:Al = 0.92:0.04:0.04. The mixture was added at a flow rate of 260 L / h and a 300 g / L ammonium bicarbonate solution was added at a flow rate of 600 L / h to the nucleation reactor for granulation reaction. The pH value was controlled at 8.5, the reaction time was 6 h, and the nuclei grew to a median diameter of 10.0 μm.

[0094] 2) Core NiAl doped particle growth step: add a 300g / L ammonium bicarbonate bottom solution into the particle growth reactor, add the slurry in the crystal nucleation reactor into the particle growth reactor, and start the stirring device. At the same time, a 100g / L cobalt nickel aluminum nitrate mixed solution with a molar ratio of Co:Ni:Al=0.92:0.04:0.04 is added into the particle growth reactor at a flow rate of 700L / h and a 300g / L ammonium bicarbonate solution at a flow rate of 1000L / h. The pH value is controlled at 8.0. When the volume of the material in the particle growth reactor reaches 80% of the reactor volume, the solid content of the reaction system in the particle growth reactor is increased by continuous centrifugation until the median diameter of the particles reaches 19.43μm; the growth rate is 0.3μm / h.

[0095] 3) Near-surface layer doping steps:

[0096] Add 300 g / L ammonium bicarbonate bottom solution into the optimized reactor, add the slurry from the particle growth reactor into the optimized reactor, start the stirring device, and simultaneously perform the following multi-layer element doping:

[0097] The first doping layer, Mg, consisted of a 100g / L cobalt-aluminum-magnesium nitrate solution with a molar ratio of Co:Al:Mg = 0.92:0.04:0.04. This solution was fed into the optimized reactor at a flow rate of 175L / h, along with a 300g / L ammonium bicarbonate solution at a flow rate of 500L / h. The pH of each solution was controlled within the range of 8.0. The particle D50 growth rate was 0.15μm / h. When the particle size reached 19.58μm, the feed was stopped and the particles were placed in an aging tank for 60 minutes.

[0098] The second doping layer, Ti, consisted of a 100g / L cobalt-aluminum-titanium nitrate solution with a molar ratio of Co:Al:Ti = 0.92:0.04:0.04. This solution was fed into the optimized reactor at a flow rate of 175L / h, along with a 300g / L ammonium bicarbonate solution at a flow rate of 500L / h. The pH of each solution was controlled within the range of 8.0. The particle D50 growth rate was 0.15μm / h. When the particle size reached 19.72μm, the feed was stopped and the particles were placed in an aging tank for 60 minutes.

[0099] The third doping element, Zr, consisted of a 100g / L cobalt-aluminum-zirconium nitrate solution with a molar ratio of Co:Al:Zr = 0.92:0.04:0.04. This solution was fed into the optimized reactor at a flow rate of 175L / h, along with a 300g / L ammonium bicarbonate solution at a flow rate of 500L / h. The pH of each solution was controlled within the range of 8.0. The particle D50 growth rate was 0.15μm / h. When the particle size reached 19.86μm, the feed was stopped and the particles were placed in an aging tank for 60 minutes.

[0100] The fourth doping element, Nb, consisted of a 100 g / L cobalt-aluminum-niobium nitrate solution with a molar ratio of Co:Al:Nb = 0.92:0.04:0.04. This solution was fed into the optimized reactor at a flow rate of 175 L / h, along with a 300 g / L ammonium bicarbonate solution at a flow rate of 500 L / h. The pH of each solution was controlled within the range of 8.0. The particle D50 growth rate was 0.15 μm / h. When the particle size reached 20.01 μm, the feed was stopped and the particles were placed in an aging tank for 60 minutes.

[0101] The fifth doping element, La, consisted of a 100g / L cobalt-aluminum-lanthanum nitrate solution with a molar ratio of Co:Al:La = 0.92:0.04:0.04. This solution was fed into the optimized reactor at a flow rate of 175L / h, along with a 300g / L ammonium bicarbonate solution at a flow rate of 500L / h. The pH of each solution was controlled within the range of 8.0. The particle D50 growth rate was 0.15μm / h. When the particle size reached 20.15μm, the feed was stopped and the particles were placed in an aging tank for 60 minutes.

[0102] The sixth doping layer, Y+PO4, consisted of a 100g / L cobalt-aluminum-yttrium nitrate solution with a molar ratio of Co:Al:Y = 0.92:0.04:0.04. This solution was fed into the optimized reactor at a flow rate of 175L / h, along with a 300g / L ammonium bicarbonate and ammonium hydrogen phosphate solution with a 1:1 carbonate to phosphate molar ratio, at a flow rate of 500L / h. The pH was controlled within the range of 8.0. The particle size growth rate (D50) was 0.15μm / h. When the particle size reached 20.30μm, the feed was stopped and the particles were placed in an aging tank for 60min.

[0103] Among them, in the core growth step, particle growth step, inner layer doping step, and aging step, the temperature of the materials in each reactor is maintained at 50°C; the stirring speed is 500r / min; and the temperature of each solution is maintained within 35°C.

[0104] 4) After the aging reaction, the slurry was filtered through a centrifuge and washed six times with hot pure water. The filter cake was dried at 100°C and then sintered in an oxidizing atmosphere with an oxygen to nitrogen ratio of 35:65 by volume in a muffle furnace at 750°C for 5 hours. The calcined slurry was crushed and passed through a 300-mesh sieve to obtain the oxide.

[0105] 2. Preparation of lithium cobalt oxide

[0106] The oxide and lithium source in step 1 were weighed according to a Li / (Co+Ni) molar ratio of 1.065 and sintered in an oxidizing atmosphere with a volume ratio of oxygen to nitrogen of 35:65. The sintering conditions were as follows: rising from room temperature to 1030°C over 100 minutes, holding for 720 minutes, then cooling to 850°C, holding for 360 minutes, and finally cooling to room temperature. The gas flow rate was controlled at 90 ml / min and ventilation was continued until it dropped to room temperature to obtain high-voltage lithium cobalt oxide with 100 nm near-surface layer-by-layer doping.

[0107] Example 4: Preparation of 200nm near-surface layer doped lithium cobalt oxide layer by layer, the structure of which is shown in Table 4:

[0108] Table 4

[0109] Main core <![CDATA[Li 1.0013 Co 0.800 Ni 0.100 Al 0.100 O2]]> Tier 1 <![CDATA[Li 1.0013 What 0.895 Al 0.100 Mg 0.005 O2]]> Layer 2 <![CDATA[Li 1.0013 What 0.895 Al 0.100 Those 0.005 O2]]> Layer 3 <h2 style=";text-align:left;direction:ltr"><![CDATA[Li <h2 style=";text-align:left;direction:ltr"> 1.0013 <h2 style=";text-align:left;direction:ltr"> Co<h2 style=";text-align:left;direction:ltr"> 0.895 <h2 style=";text-align:left;direction:ltr"> Al<h2 style=";text-align:left;direction:ltr"> 0.100 <h2 style=";text-align:left;direction:ltr"> Zr<h2 style=";text-align:left;direction:ltr"> 0.005 <h2 style=";text-align:left;direction:ltr"> O2]]><h2 style=";text-align:left;direction:ltr"> Layer 4 <![CDATA[Li 1.0013 Co 0.895 Al 0.100 Nb 0.005 O2]]> Layer 5 <![CDATA[Li 1.0013 Co 0.895 Al 0.100 Day 0.005 O2]]> Layer 6 <![CDATA[Li 1.0013 What 0.895 Al 0.100 Y 0.005 ABOUT 1.95 F 0.05 ]]> Layer 7 <![CDATA[Li 1.0013 What 0.895 Al 0.100 Y 0.005 ABOUT 1.95 (PO4) 0.05 ]]>

[0110] This embodiment uses the following steps to prepare a high-voltage lithium cobalt oxide positive electrode material:

[0111] 1. Preparation of oxides

[0112] 1) Core NiAl doping nucleation step: A 300 g / L ammonium bicarbonate base solution and a 100 g / L cobalt-nickel-aluminum nitrate mixed solution were added to the nucleation reactor at a molar ratio of Co:Ni:Al = 0.80:0.10:0.10. The mixture was added at a flow rate of 260 L / h and a 300 g / L ammonium bicarbonate solution was added at a flow rate of 600 L / h to the nucleation reactor for granulation reaction. The pH value was controlled at 8.5, the reaction time was 4 h, and the nuclei grew to a median diameter of 10.0 μm.

[0113] 2) Core NiAl doped particle growth step: a 300 g / L ammonium bicarbonate bottom solution was added to the particle growth reactor, the slurry in the crystal nucleation reactor was added to the particle growth reactor, and the stirring device was turned on. At the same time, a 100 g / L cobalt nickel aluminum nitrate mixed solution with a molar ratio of Co:Ni:Al=0.80:0.10:0.10 was added to the particle growth reactor at a flow rate of 700 L / h and a 300 g / L ammonium bicarbonate solution was added to the particle growth reactor at a flow rate of 1800 L / h. The pH value was controlled at 8.0. When the volume of the material in the particle growth reactor reached 80% of the reactor volume, the solid content of the reaction system in the particle growth reactor was increased by continuous centrifugation until the particle median diameter reached 18.57 μm; the growth rate was 0.2 μm / h.

[0114] 3) Near-surface layer doping steps:

[0115] Add 300 g / L ammonium bicarbonate bottom solution into the optimized reactor, add the slurry from the particle growth reactor into the optimized reactor, start the stirring device, and simultaneously perform the following multi-layer element doping:

[0116] The first doping layer, Mg, consisted of a 100 g / L cobalt-aluminum-magnesium nitrate solution with a molar ratio of Co:Al:Mg of 0.895:0.10:0.005. This solution was fed into the optimized reactor at a flow rate of 175 L / h, along with a 300 g / L ammonium bicarbonate solution at a flow rate of 300 L / h. The pH of each solution was controlled within the range of 8.0. The particle D50 growth rate was 0.05 μm / h. When the particle size reached 18.81 μm, the feed was stopped and the particles were placed in an aging tank for 100 minutes.

[0117] The second doping layer, Ti, consisted of a 100 g / L cobalt-aluminum-titanium nitrate solution with a molar ratio of Co:Al:Ti = 0.895:0.10:0.005. This solution was fed into the optimized reactor at a flow rate of 175 L / h, along with a 300 g / L ammonium bicarbonate solution at a flow rate of 300 L / h. The pH of each solution was controlled within the range of 8.0. The particle D50 growth rate was 0.05 μm / h. When the particle size reached 19.06 μm, the feed was stopped and the particles were placed in an aging tank for 100 minutes.

[0118] The third doping layer, Zr, consisted of a 100 g / L cobalt-aluminum-zirconium nitrate solution with a molar ratio of Co:Al:Zr = 0.895:0.10:0.005. This solution was fed into the optimized reactor at a flow rate of 175 L / h, along with a 300 g / L ammonium bicarbonate solution at a flow rate of 300 L / h. The pH of each solution was controlled within the range of 8.0. The particle D50 growth rate was 0.05 μm / h. When the particle size reached 19.31 μm, the feed was stopped and the particles were placed in an aging tank for 100 minutes.

[0119] The fourth doping element, Nb, consisted of a 100 g / L cobalt-aluminum-niobium nitrate solution with a molar ratio of Co:Al:Nb = 0.895:0.10:0.005. This solution was fed into the optimized reactor at a flow rate of 175 L / h, along with a 300 g / L ammonium bicarbonate solution at a flow rate of 300 L / h. The pH of each solution was controlled within the range of 8.0. The particle D50 growth rate was 0.05 μm / h. When the particle size reached 19.56 μm, the feed was stopped and the particles were placed in an aging tank for 100 minutes.

[0120] The fifth doping element, La, consisted of a 100 g / L cobalt-aluminum-lanthanum nitrate solution with a molar ratio of Co:Al:La = 0.895:0.10:0.005. This solution was fed into the optimized reactor at a flow rate of 175 L / h, along with a 300 g / L ammonium bicarbonate solution at a flow rate of 300 L / h. The pH of each solution was controlled within the range of 8.0. The particle D50 growth rate was 0.05 μm / h. When the particle size reached 19.80 μm, the feed was stopped and the particles were placed in an aging tank for 100 minutes.

[0121] The sixth doping element, Y+F, consisted of a 100g / L cobalt-aluminum-yttrium nitrate solution with a molar ratio of Co:Al:Y = 0.895:0.10:0.005. This solution was added to the optimized reactor at a flow rate of 175L / h, along with a 300g / L ammonium bicarbonate and ammonium fluoride solution with a carbonate to fluoride molar ratio of 1:1. The pH was controlled within the range of 8.0. The particle D50 growth rate was 0.05μm / h. When the particle size reached 20.05μm, the feed was stopped and the particles were placed in an aging tank for 100min.

[0122] The seventh doping element, Y+PO4, consisted of a 100g / L cobalt-aluminum-yttrium nitrate solution with a molar ratio of Co:Al:Y = 0.895:0.10:0.005. This solution was fed into the optimized reactor at a flow rate of 175L / h, along with a 300g / L ammonium bicarbonate and ammonium hydrogen phosphate solution with a carbonate-to-phosphate molar ratio of 1:1. The pH was controlled within the range of 8.0. The particle size growth rate (D50) was 0.05μm / h. When the particle size reached 20.30μm, the feed was stopped and the particles were placed in an aging tank for 100min.

[0123] Among them, in the core growth step, particle growth step, inner layer doping step, and aging step, the temperature of the materials in each reactor is maintained at 55°C; the stirring speed is 700r / min; and the temperature of each solution is maintained within 35°C.

[0124] 4) After the aging reaction, the slurry was filtered through a centrifuge and washed six times with hot pure water. The filter cake was dried at 100°C and then sintered in an oxidizing atmosphere with an oxygen to nitrogen ratio of 40:60 by volume in a muffle furnace at 800°C for 6 hours. The calcined slurry was crushed and passed through a 300-mesh sieve to obtain the oxide.

[0125] 2. Preparation of lithium cobalt oxide

[0126] The oxide and lithium source in step 1 were weighed according to a Li / (Co+Ni) molar ratio of 1.065 and sintered in an oxidizing atmosphere with a volume ratio of oxygen to nitrogen of 40:60. The sintering conditions were as follows: the temperature was raised from room temperature to 1000°C over 100 minutes, kept warm for 900 minutes, then cooled to 850°C, kept warm for 300 minutes, and finally cooled to room temperature. The gas flow rate was controlled at 150 ml / min and ventilation was continued until it dropped to room temperature to obtain high-voltage lithium cobalt oxide with 200 nm near-surface layer-by-layer doping.

[0127] Example 5: Preparation of 400nm near-surface layer doped lithium cobalt oxide layer by layer, the structure of which is shown in Table 5:

[0128] Table 5

[0129] Main core <![CDATA[Li 1.0013 Co 0.600 Ni 0.200 Al 0.200 O2]]> Tier 1 <![CDATA[Li 1.0013 What 0.97 Al 0.025 Mg 0.005 O2]]> Layer 2 <![CDATA[Li 1.0013 What 0.97 Al 0.025 Those 0.005 O2]]> Layer 3 <h2 style=";text-align:left;direction:ltr"><![CDATA[Li <h2 style=";text-align:left;direction:ltr"> 1.0013 <h2 style=";text-align:left;direction:ltr"> Co<h2 style=";text-align:left;direction:ltr"> 0.97 <h2 style=";text-align:left;direction:ltr"> Al<h2 style=";text-align:left;direction:ltr"> 0.025 <h2 style=";text-align:left;direction:ltr"> Zr<h2 style=";text-align:left;direction:ltr"> 0.005 <h2 style=";text-align:left;direction:ltr"> O2]]><h2 style=";text-align:left;direction:ltr"> Layer 4 <![CDATA[Li 1.0013 Co 0.97 Al 0.025 Nb 0.005 O2]]> Layer 5 <![CDATA[Li 1.0013 Co 0.97 Al 0.025 Day 0.005 O2]]> Layer 6 <![CDATA[Li 1.0013 What 0.97 Al 0.025 IN 0.005 O2]]> Layer 7 <![CDATA[Li 1.0013 Co 0.97 Al 0.025 Y 0.005 O 1.90 F 0.05 (PO4) 0.05 ]]>

[0130] This embodiment uses the following steps to prepare a high-voltage lithium cobalt oxide positive electrode material:

[0131] 1. Preparation of oxides

[0132] 1) Core NiAl doping nucleation step: A 300 g / L ammonium bicarbonate base solution and a 100 g / L cobalt-nickel-aluminum nitrate mixed solution were added to the nucleation reactor at a molar ratio of Co:Ni:Al = 0.60:0.20:0.20. The mixture was added at a flow rate of 260 L / h and a 300 g / L ammonium bicarbonate solution was added at a flow rate of 600 L / h to the nucleation reactor for granulation reaction. The pH value was controlled at 8.5, the reaction time was 3 h, and the nuclei grew to a median diameter of 10.0 μm.

[0133] 2) Core NiAl doped particle growth step: a 300 g / L ammonium bicarbonate bottom solution was added to the particle growth reactor, the slurry in the crystal nucleation reactor was added to the particle growth reactor, and the stirring device was turned on. At the same time, a 100 g / L cobalt nickel aluminum nitrate mixed solution with a molar ratio of Co:Ni:Al=0.60:0.20:0.20 was added to the particle growth reactor at a flow rate of 700 L / h and a 300 g / L ammonium bicarbonate solution was added to the particle growth reactor at a flow rate of 300 L / h. The pH value was controlled at 8.0. When the volume of the material in the particle growth reactor reached 80% of the reactor volume, the solid content of the reaction system in the particle growth reactor was increased by continuous centrifugation until the median diameter of the particles reached 16.83 μm; the growth rate was 0.3 μm / h.

[0134] 3) Near-surface layer doping steps:

[0135] Add 300 g / L ammonium bicarbonate bottom solution into the optimized reactor, add the slurry from the particle growth reactor into the optimized reactor, start the stirring device, and simultaneously perform the following multi-layer element doping:

[0136] The first doping layer, Mg, consisted of a 100g / L cobalt-aluminum-magnesium nitrate solution with a molar ratio of Co:Al:Mg = 0.97:0.025:0.005. This solution was fed into the optimized reactor at a flow rate of 175L / h, along with a 300g / L ammonium bicarbonate solution at a flow rate of 300L / h. The pH of each solution was controlled within the range of 8.0. The particle D50 growth rate was 0.15μm / h. When the particle size reached 17.27μm, the feed was stopped and the particles were placed in an aging tank for 200min.

[0137] The second doping layer, Ti, consisted of a 100g / L cobalt-aluminum-titanium nitrate solution with a molar ratio of Co:Al:Ti = 0.97:0.025:0.005. This solution was fed into the optimized reactor at a flow rate of 175L / h, along with a 300g / L ammonium bicarbonate solution at a flow rate of 300L / h. The pH of each solution was controlled within the range of 8.0. The particle D50 growth rate was 0.15μm / h. When the particle size reached 17.70μm, the feed was stopped and the particles were placed in an aging tank for 200min.

[0138] The third doping layer, Zr, consisted of a 100 g / L cobalt-aluminum-zirconium nitrate solution with a molar ratio of Co:Al:Zr = 0.97:0.025:0.005. This solution was fed into the optimized reactor at a flow rate of 175 L / h, along with a 300 g / L ammonium bicarbonate solution at a flow rate of 300 L / h. The pH of each solution was controlled within the range of 8.0. The particle D50 growth rate was 0.15 μm / h. When the particle size reached 18.13 μm, the feed was stopped and the particles were placed in an aging tank for 200 minutes.

[0139] The fourth doping element, Nb, consisted of a 100 g / L cobalt-aluminum-niobium nitrate solution with a molar ratio of Co:Al:Nb = 0.97:0.025:0.005. This solution was fed into the optimized reactor at a flow rate of 175 L / h, along with a 300 g / L ammonium bicarbonate solution at a flow rate of 300 L / h. The pH of each solution was controlled within the range of 8.0. The particle D50 growth rate was 0.15 μm / h. When the particle size reached 18.57 μm, the feed was stopped and the particles were placed in an aging tank for 200 minutes.

[0140] The fifth doping element, La, consisted of a 100 g / L cobalt-aluminum-lanthanum nitrate solution with a molar ratio of Co:Al:La = 0.97:0.025:0.005. This solution was fed into the optimized reactor at a flow rate of 175 L / h, along with a 300 g / L ammonium bicarbonate solution at a flow rate of 300 L / h. The pH of each solution was controlled within the range of 8.0. The particle D50 growth rate was 0.15 μm / h. When the particle size reached 19.00 μm, the feed was stopped and the particles were placed in an aging tank for 200 minutes.

[0141] The sixth doping element, W, consisted of a 100g / L cobalt-aluminum-tungsten nitrate solution with a molar ratio of Co:Al:W = 0.97:0.025:0.005. This solution was fed into the optimized reactor at a flow rate of 175L / h, along with a 300g / L ammonium bicarbonate solution at a flow rate of 300L / h. The pH of each solution was controlled within the range of 8.0. The particle D50 growth rate was 0.15μm / h. When the particle size reached 19.43μm, the feed was stopped and the particles were placed in an aging tank for 60 minutes.

[0142] The seventh doping layer, Y+F+PO4, consisted of a 100g / L cobalt-aluminum-yttrium nitrate solution with a molar ratio of Co:Al:Y = 0.97:0.025:0.005. This solution was fed concurrently into the optimized reactor at a flow rate of 175L / h along with 300g / L ammonium bicarbonate, ammonium hydrogen phosphate, and ammonium fluoride solutions with a molar ratio of carbonate, phosphate, and fluoride of 1:1:1. The pH was controlled within the range of 8.0. The particle D50 growth rate was 0.15μm / h. When the particle size reached 20.30μm, the feed was stopped and the particles were placed in an aging tank for 200min.

[0143] Among them, in the core growth step, particle growth step, inner layer doping step, and aging step, the temperature of the materials in each reactor is maintained at 60°C; the stirring speed is 1200r / min; and the temperature of each solution is maintained within 25°C.

[0144] 4) After the aging reaction, the slurry was filtered through a centrifuge and washed six times with hot pure water. The filter cake was dried at 100°C and then sintered in an oxidizing atmosphere with an oxygen to nitrogen ratio of 45:55 by volume in a muffle furnace at 850°C for 4 hours. The calcined slurry was crushed and passed through a 300-mesh sieve to obtain the oxide.

[0145] 2. Preparation of lithium cobalt oxide

[0146] The oxide and lithium source in step 1 were weighed according to a Li / (Co+Ni) molar ratio of 1.035 and sintered in an oxidizing atmosphere with a volume ratio of oxygen to nitrogen of 45:55. The sintering conditions were as follows: the temperature was raised from room temperature to 960°C over 90 minutes, kept warm for 400 minutes, then cooled to 800°C, kept warm for 300 minutes, and finally cooled to room temperature. The gas flow rate was controlled at 200 ml / min and ventilation was continued until it dropped to room temperature to obtain high-voltage lithium cobalt oxide with 400 nm near-surface layer-by-layer doping.

[0147] Example 6: Preparation of 150nm near-surface layer doped lithium cobalt oxide layer by layer, the structure of which is shown in Table 6:

[0148] Table 6

[0149] Main core <![CDATA[Li 1.0013 Co 0.960 Ni 0.020 Al 0.020 O2]]> Tier 1 <![CDATA[Li 1.0013 What 0.975 Al 0.020 Mg 0.005 O2]]> Layer 2 <![CDATA[Li 1.0013 What 0.975 Al 0.020 Those 0.005 O2]]> Layer 3 <h2 style=";text-align:left;direction:ltr"><![CDATA[Li <h2 style=";text-align:left;direction:ltr"> 1.0013 <h2 style=";text-align:left;direction:ltr"> Co<h2 style=";text-align:left;direction:ltr"> 0.975 <h2 style=";text-align:left;direction:ltr"> Al<h2 style=";text-align:left;direction:ltr"> 0.020 <h2 style=";text-align:left;direction:ltr"> Zr<h2 style=";text-align:left;direction:ltr"> 0.005 <h2 style=";text-align:left;direction:ltr"> O2<h2 style=";text-align:left;direction:ltr"><!-- 12 --> ]]><h2 style=";text-align:left;direction:ltr"> Layer 4 <![CDATA[Li 1.0013 Yes 0.975 Al 0.020 Y 0.005 O2]]> Layer 5 <![CDATA[Li 1.0013 Co 0.975 Al 0.020 Day 0.005 O2]]> Layer 6 <![CDATA[Li 1.0013 What 0.975 Al 0.020 Y 0.005 ABOUT 1.95 F 0.05 ]]> Layer 7 <![CDATA[Li 1.0013 What 0.975 Al 0.020 Y 0.005 ABOUT 1.95 (PO4) 0.05 ]]>

[0150] This embodiment uses the following steps to prepare a high-voltage lithium cobalt oxide positive electrode material:

[0151] 1. Preparation of oxides

[0152] 1) Core NiAl doping nucleation step: A 300 g / L ammonium bicarbonate base solution and a 100 g / L cobalt-nickel-aluminum nitrate mixed solution were added to the nucleation reactor at a molar ratio of Co:Ni:Al = 0.96:0.02:0.02. The mixture was added at a flow rate of 260 L / h and a 300 g / L ammonium bicarbonate solution was added at a flow rate of 600 L / h to the nucleation reactor for granulation reaction. The pH value was controlled at 6.8, the reaction time was 5 h, and the nuclei grew to a median diameter of 5.0 μm.

[0153] 2) Core NiAl doped particle growth step: a 300 g / L ammonium bicarbonate bottom solution was added to the particle growth reactor, the slurry in the crystal nucleation reactor was added to the particle growth reactor, and the stirring device was turned on. At the same time, a 100 g / L cobalt nickel aluminum nitrate mixed solution with a molar ratio of Co:Ni:Al=0.96:0.02:0.02 was added to the particle growth reactor at a flow rate of 700 L / h and a 300 g / L ammonium bicarbonate solution was added to the particle growth reactor at a flow rate of 1000 L / h. The pH value was controlled at 6.8. When the volume of the material in the particle growth reactor reached 80% of the reactor volume, the solid content of the reaction system in the particle growth reactor was increased by continuous centrifugation until the median diameter of the particles reached 5.17 μm; the growth rate was 0.1 μm / h.

[0154] 3) Near-surface layer doping steps:

[0155] Add 300 g / L ammonium bicarbonate bottom solution into the optimized reactor, add the slurry from the particle growth reactor into the optimized reactor, start the stirring device, and simultaneously perform the following multi-layer element doping:

[0156] The first doping layer, Mg, consisted of a 100g / L cobalt-aluminum-magnesium nitrate solution with a molar ratio of Co:Al:Mg of 0.975:0.020:0.005. This solution was fed into the optimized reactor at a flow rate of 175L / h, along with a 300g / L ammonium bicarbonate solution at a flow rate of 300L / h. The pH of each solution was controlled within the range of 6.8. The particle D50 growth rate was 0.10μm / h. When the particle size reached 5.23μm, the feed was stopped and the particles were placed in an aging tank for 80 minutes.

[0157] The second doping layer, Ti, consisted of a 100g / L cobalt-aluminum-titanium nitrate solution with a molar ratio of Co:Al:Ti = 0.975:0.020:0.005. This solution was fed into the optimized reactor at a flow rate of 175L / h, along with a 300g / L ammonium bicarbonate solution at a flow rate of 300L / h. The pH of each solution was controlled within the range of 6.8. The particle D50 growth rate was 0.10μm / h. When the particle size reached 5.46μm, the feed was stopped and the particles were placed in an aging tank for 80 minutes.

[0158] The third doping layer, Zr, consisted of a 100 g / L cobalt-aluminum-zirconium nitrate solution with a molar ratio of Co:Al:Zr = 0.975:0.020:0.005. This solution was fed into the optimized reactor at a flow rate of 175 L / h, along with a 300 g / L ammonium bicarbonate solution at a flow rate of 300 L / h. The pH of each solution was controlled within the range of 6.8. The particle D50 growth rate was 0.10 μm / h. When the particle size reached 5.70 μm, the feed was stopped and the particles were placed in an aging tank for 80 minutes.

[0159] The fourth doping element, Y, consisted of a 100g / L cobalt-aluminum-yttrium nitrate solution with a molar ratio of Co:Al:Y = 0.975:0.020:0.005. This solution was fed into the optimized reactor at a flow rate of 175L / h, along with a 300g / L ammonium bicarbonate solution at a flow rate of 300L / h. The pH of each solution was controlled within the range of 6.8. The particle D50 growth rate was 0.10μm / h. When the particle size reached 5.93μm, the feed was stopped and the particles were placed in an aging tank for 80 minutes.

[0160] The fifth doping element, La, consisted of a 100g / L cobalt-aluminum-lanthanum nitrate solution with a molar ratio of Co:Al:La = 0.975:0.020:0.005. This solution was fed into the optimized reactor at a flow rate of 175L / h, along with a 300g / L ammonium bicarbonate solution at a flow rate of 300L / h. The pH of each solution was controlled within the range of 6.8. The particle D50 growth rate was 0.10μm / h. When the particle size reached 6.16μm, the feed was stopped and the particles were placed in an aging tank for 80 minutes.

[0161] The sixth doping layer, Y+F, consisted of a 100g / L cobalt-aluminum-yttrium nitrate solution with a molar ratio of Co:Al:Y = 0.975:0.020:0.005. This solution was fed into the optimized reactor at a flow rate of 175L / h, along with a 300g / L ammonium bicarbonate and ammonium fluoride solution with a carbonate to fluoride molar ratio of 1:1. The pH was controlled within the range of 6.8. The particle D50 growth rate was 0.10μm / h. When the particle size reached 6.39μm, the feed was stopped and the particles were placed in an aging tank for 80min.

[0162] The seventh doping element, Y+PO4, consisted of a 100g / L cobalt-aluminum-yttrium nitrate solution with a molar ratio of Co:Al:Y = 0.975:0.020:0.005. This solution was fed into the optimized reactor at a flow rate of 175L / h, along with a 300g / L ammonium bicarbonate and ammonium hydrogen phosphate solution with a carbonate-to-phosphate molar ratio of 1:1. The pH was controlled within the range of 6.8. The particle size growth rate (D50) was 0.10μm / h. When the particle size reached 6.63μm, the feed was stopped and the particles were placed in an aging tank for 80min.

[0163] Among them, in the core growth step, particle growth step, inner layer doping step, and aging step, the temperature of the materials in each reactor is maintained at 40°C; the stirring speed is 1800r / min; and the temperature of each solution is maintained within 30°C.

[0164] 4) After the aging reaction, the slurry was filtered through a centrifuge and washed six times with hot pure water. The filter cake was dried at 100°C and then sintered in an oxidizing atmosphere (oxygen to nitrogen ratio = 25:75 by volume) at 700°C in a muffle furnace for 6 hours. The calcined slurry was crushed and passed through a 300-mesh sieve to obtain the oxide.

[0165] 2. Preparation of lithium cobalt oxide

[0166] The oxide and lithium source in step 1 are weighed according to a Li / (Co+Ni) molar ratio of 1.005 and sintered in an oxidizing atmosphere, wherein the volume ratio of oxygen to nitrogen is 25:75, wherein the volume ratio of oxygen to nitrogen is 25:75, and the sintering conditions are: from room temperature to 850°C for 90 minutes, kept warm for 600 minutes, then cooled to 820°C, kept warm for 240 minutes, and finally cooled to room temperature, wherein the gas flow rate is controlled at 80 ml / min, and ventilation is continued until it drops to room temperature, to obtain high-voltage lithium cobalt oxide with 150nm near-surface layer-by-layer doping.

[0167] Example 7: Preparation of 150nm near-surface layer doped lithium cobalt oxide layer by layer, the structure of which is shown in Table 7:

[0168] Table 7

[0169] Main core <![CDATA[Li 1.0013 Co 0.960 Ni 0.020 Al 0.020 O2]]> Tier 1 <![CDATA[Li 1.0013 What 0.975 Al 0.020 Mg 0.005 O2]]> Layer 2 <![CDATA[Li 1.0013 What 0.975 Al 0.020 Those 0.005 O2]]> Layer 3 <h2 style=";text-align:left;direction:ltr"><![CDATA[Li <h2 style=";text-align:left;direction:ltr"> 1.0013 <h2 style=";text-align:left;direction:ltr"> Co<h2 style=";text-align:left;direction:ltr"> 0.975 <h2 style=";text-align:left;direction:ltr"> Al<h2 style=";text-align:left;direction:ltr"> 0.020 <h2 style=";text-align:left;direction:ltr"> Zr<h2 style=";text-align:left;direction:ltr"> 0.005 <h2 style=";text-align:left;direction:ltr"> O2]]><h2 style=";text-align:left;direction:ltr"> Layer 4 <![CDATA[Li 1.0013 Yes 0.975 Al 0.020 Y 0.005 O2]]> Layer 5 <![CDATA[Li 1.0013 Co 0.975 Al 0.020 Day 0.005 O2]]> Layer 6 <![CDATA[Li 1.0013 What 0.975 Al 0.020 Y 0.005 ABOUT 1.95 F 0.05 ]]> Layer 7 <![CDATA[Li 1.0013 What 0.975 Al 0.020 Y 0.005 ABOUT 1.95 (PO4) 0.05 ]]>

[0170] This embodiment uses the following steps to prepare a high-voltage lithium cobalt oxide positive electrode material:

[0171] 1. Preparation of oxides

[0172] 1) Core NiAl doping nucleation step: A 300 g / L ammonium bicarbonate base solution and a 100 g / L cobalt-nickel-aluminum nitrate mixed solution were added to the nucleation reactor at a molar ratio of Co:Ni:Al = 0.96:0.02:0.02. The mixture was added at a flow rate of 260 L / h and a 300 g / L ammonium bicarbonate solution was added at a flow rate of 600 L / h to the nucleation reactor for granulation reaction. The pH value was controlled at 6.8, the reaction time was 10 h, and the nuclei grew to a median diameter of 10.0 μm.

[0173] 2) Core NiAl doped particle growth step: a 300 g / L ammonium bicarbonate bottom solution was added to the particle growth reactor, the slurry in the crystal nucleation reactor was added to the particle growth reactor, and the stirring device was turned on. At the same time, a 100 g / L cobalt nickel aluminum nitrate mixed solution with a molar ratio of Co:Ni:Al=0.96:0.02:0.02 was added to the particle growth reactor at a flow rate of 700 L / h and a 300 g / L ammonium bicarbonate solution was added to the particle growth reactor at a flow rate of 1200 L / h. The pH value was controlled at 6.8. When the volume of the material in the particle growth reactor reached 80% of the reactor volume, the solid content of the reaction system in the particle growth reactor was increased by continuous centrifugation until the median diameter of the particles reached 10.10 μm; the growth rate was 0.2 μm / h.

[0174] 3) Near-surface layer doping steps:

[0175] Add 300 g / L ammonium bicarbonate bottom solution into the optimized reactor, add the slurry from the particle growth reactor into the optimized reactor, start the stirring device, and simultaneously perform the following multi-layer element doping:

[0176] The first doping layer, Mg, consisted of a 100g / L cobalt-aluminum-magnesium nitrate solution with a molar ratio of Co:Al:Mg = 0.975:0.020:0.005. This solution was fed into the optimized reactor at a flow rate of 175L / h, along with a 300g / L ammonium bicarbonate solution at a flow rate of 300L / h. The pH of each solution was controlled within the range of 6.8. The particle D50 growth rate was 0.10μm / h. When the particle size reached 10.19μm, the feed was stopped and the particles were placed in an aging tank for 80 minutes.

[0177] The second doping layer, Ti, consisted of a 100g / L cobalt-aluminum-titanium nitrate solution with a molar ratio of Co:Al:Ti = 0.975:0.020:0.005. This solution was fed into the optimized reactor at a flow rate of 175L / h, along with a 300g / L ammonium bicarbonate solution at a flow rate of 300L / h. The pH of each solution was controlled within the range of 6.8. The particle D50 growth rate was 0.10μm / h. When the particle size reached 10.37μm, the feed was stopped and the particles were placed in an aging tank for 80 minutes.

[0178] The third doping layer, Zr, consisted of a 100g / L cobalt-aluminum-zirconium nitrate solution with a molar ratio of Co:Al:Zr = 0.975:0.020:0.005. This solution was fed into the optimized reactor at a flow rate of 175L / h, along with a 300g / L ammonium bicarbonate solution at a flow rate of 300L / h. The pH of each solution was controlled within the range of 6.8. The particle D50 growth rate was 0.10μm / h. When the particle size reached 10.56μm, the feed was stopped and the particles were placed in an aging tank for 80 minutes.

[0179] The fourth doping element, Y, consisted of a 100g / L cobalt-aluminum-yttrium nitrate solution with a molar ratio of Co:Al:Y = 0.975:0.020:0.005. This solution was fed into the optimized reactor at a flow rate of 175L / h, along with a 300g / L ammonium bicarbonate solution at a flow rate of 300L / h. The pH of each solution was controlled within the range of 6.8. The particle D50 growth rate was 0.10μm / h. When the particle size reached 10.74μm, the feed was stopped and the particles were placed in an aging tank for 80 minutes.

[0180] The fifth doping element, La, consisted of a 100g / L cobalt-aluminum-lanthanum nitrate solution with a molar ratio of Co:Al:La = 0.975:0.020:0.005. This solution was fed into the optimized reactor at a flow rate of 175L / h, along with a 300g / L ammonium bicarbonate solution at a flow rate of 300L / h. The pH of each solution was controlled within the range of 6.8. The particle D50 growth rate was 0.10μm / h. When the particle size reached 10.93μm, the feed was stopped and the particles were placed in an aging tank for 80 minutes.

[0181] The sixth doping element, Y+F, consisted of a 100g / L cobalt-aluminum-yttrium nitrate solution with a molar ratio of Co:Al:Y = 0.975:0.020:0.005. This solution was fed into the optimized reactor at a flow rate of 175L / h, along with a 300g / L ammonium bicarbonate and ammonium fluoride solution with a carbonate-to-fluoride molar ratio of 1:1. The pH was controlled within the range of 6.8. The particle D50 growth rate was 0.10μm / h. When the particle size reached 10.11μm, the feed was stopped and the particles were placed in an aging tank for 80min.

[0182] The seventh doping element, Y+PO4, consisted of a 100g / L cobalt-aluminum-yttrium nitrate solution with a molar ratio of Co:Al:Y = 0.975:0.020:0.005. This solution was fed into the optimized reactor at a flow rate of 175L / h, along with a 300g / L ammonium bicarbonate and ammonium hydrogen phosphate solution with a 1:1 carbonate to phosphate molar ratio. The pH was controlled within the range of 6.8. The particle size growth rate (D50) was 0.10μm / h. When the particles reached a size of 10.30μm, the feed was stopped and the particles were placed in an aging tank for 80min.

[0183] Among them, in the core growth step, particle growth step, inner layer doping step, and aging step, the temperature of the materials in each reactor is maintained at 40°C; the stirring speed is 1800r / min; and the temperature of each solution is maintained within 25°C.

[0184] 4) After the aging reaction, the slurry was filtered through a centrifuge and washed six times with hot pure water. The filter cake was dried at 100°C and then sintered in an oxidizing atmosphere (oxygen to nitrogen ratio = 25:75 by volume) at 700°C in a muffle furnace for 6 hours. The calcined slurry was crushed and passed through a 300-mesh sieve to obtain the oxide.

[0185] 2. Preparation of lithium cobalt oxide

[0186] The oxide and lithium source in step 1 are weighed according to a Li / (Co+Ni) molar ratio of 1.005 and sintered in an oxidizing atmosphere, wherein the volume ratio of oxygen to nitrogen is 25:75, wherein the volume ratio of oxygen to nitrogen is 25:75, and the sintering conditions are: from room temperature to 900°C for 140 minutes, kept warm for 600 minutes, then cooled to 800°C, kept warm for 240 minutes, and finally cooled to room temperature, wherein the gas flow rate is controlled at 80 ml / min, and ventilation is continued until it drops to room temperature, to obtain high-voltage lithium cobalt oxide with 150nm near-surface layer-by-layer doping.

[0187] The relevant performance tests of the above embodiments and comparative examples are as follows:

[0188] Figure 3 The figure shows the performance test results of the 150nm near-surface layer of lithium cobalt oxide doped layer by layer prepared in Example 1. It can be seen that for the 3.0-4.83v Li negative electrode, the (003) crystal plane only undergoes angular displacement during charge and discharge, but does not split to form a second peak, indicating that under high voltage and high delithiation state, the complete layered structure is still maintained and no phase transition from O3 to H1-3 occurs.

[0189] Figure 4 The following are the performance test results of the common coated lithium cobalt oxide used in Comparative Example 1. It can be seen that for the 3.0-4.83vLi negative electrode, the (003) crystal plane gradually splits during charge and discharge to form a second peak, indicating that a transition from the O3 phase to the H1-3 phase occurs, and the layered structure is unstable under high delithiation state.

[0190] Figures 5A-5B This is the XPS graph of the lithium cobalt oxide prepared in Example 1. It can be seen that no Ni is found in the graphs with etching depths of 15 nm and 100 nm, indicating that there is no Ni near the surface. At the same time, other doping elements are seen, indicating that other elements are distributed in the near-surface layer.

[0191] Figure 6 This is a TEM image of the lithium cobalt oxide prepared in Example 1, which shows that the near-surface layer is a layer-by-layer structure.

[0192] Figure 7 Figure 2 shows the capacity retention versus cycle number at 45°C for the lithium cobalt oxide soft-pack batteries made from Examples 1, 2, and Comparative Example 2. After every 20 cycles, the nominal capacity was re-determined and the subsequent rate current was calculated. This demonstrates that uniform doping within the same crystalline phase layer by layer near the surface improves cycling performance.

[0193] Table 8 is the test result of the selected area of ​​the lens energy spectrum in Example 1, which further illustrates that Ni is distributed in the inner core layer.

[0194] Table 8 Lens energy spectrum selection test results of Example 1

[0195]

[0196] Table 9 shows the specific energy, specific capacity, and cycle results of the 4.53V full battery, indicating that Ni doping improves the specific capacity and specific energy.

[0197] Table 9 3.0~4.53V full battery specific energy, specific capacity, and cycle results

[0198]

[0199] Table 10 shows the charge transfer impedance and metal dissolution amount before and after cycling, indicating that the NiAl doping of the core and the layer-by-layer doping near the surface significantly reduced the Co dissolution amount, and the charge transfer impedance was also significantly reduced after cycling, indicating that the NiAl doping of the core and the layer-by-layer doping near the surface significantly improved the structural stability of the core and the near surface, which is beneficial to improving the cycle capacity retention rate.

[0200] Table 10 Charge transfer impedance and metal dissolution before and after cycling

[0201]

[0202]

[0203] Although the present invention has been disclosed as above by way of embodiments, they are not intended to limit the present invention. Any appropriate modification or equivalent substitution of the technical solution of the present invention by a person skilled in the art should be included in the protection scope of the present invention. The protection scope of the present invention shall be based on that defined in the claims.

Claims

1. A high voltage lithium cobalt oxide positive electrode material, characterized in that: It includes the core and the near surface layer; the core is doped with NiAl, and its chemical formula is LiCo 1-x-y Ni x Al y O2, where 0 < x ≤ 0.20, 0 < y ≤ 0.20; the near-surface layer is a continuous hexagonal layered structure doped with cations layer by layer, and its general chemical formula is LiCo 1-a-b Al a M b O 2-c N c , wherein M is a combination of at least one of Mg, Ti, Zr, Y, La, Nb, and W, N is F or PO4, a=0.01-0.10, b=0.005-0.04, and 0 ≤ c ≤ 0.05; the doping element M of each layer is selected from one of Mg, Ti, Zr, Y, La, Nb, and W as a basic doping element, and at least one of additional doping elements F and PO4 may or may not be added to the outermost layer and / or the second outermost layer, wherein the basic doping elements of each layer not containing additional doping elements are different.

2. The high-voltage lithium cobalt oxide positive electrode material according to claim 1, characterized in that The radius of the lithium cobalt oxide positive electrode material is no greater than 36 μm, and the thickness of the near-surface layer is no greater than 400 nm.

3. A method for preparing the high-voltage lithium cobalt oxide positive electrode material according to claim 1, characterized in that: The following steps are involved: 1) Prepare a mixed salt solution of cobalt salt, nickel salt and aluminum salt. 2) adding the carbonate solution and the mixed salt solution from step 1) into a crystal nucleation reactor to perform a granulation reaction, controlling the pH, and generating a core; 3) adding the slurry in the crystal nucleation reactor from step 2) into a particle growth reactor containing a carbonate solution and stirring; simultaneously adding the carbonate solution and the mixed salt solution from step 1) into the particle growth reactor, controlling the pH, and continuously centrifuging until the cores grow to a certain particle size; 4) The slurry in the particle growth reactor from step 3) is added to an optimized reactor containing a carbonate solution and stirred. Then, element doping is performed sequentially from the first layer to the Nth layer. The element doping process for each layer is as follows: a cobalt salt, an aluminum salt, and the doping element M of the current layer are prepared into a mixed solution, and the mixed solution and the carbonate solution are continuously added to the optimized reactor. The pH value is controlled, and the particle size is grown on the surface of the core. When the target particle size of the current layer is reached, the feed is stopped, and then aging is performed. 5) After the Nth layer of element doping is completed, the slurry in the optimized reactor is taken out and filtered, washed, dried, sintered in an oxidizing atmosphere, and crushed to obtain an oxide; 6) Mixing the lithium source with the oxide obtained in step 5) and sintering them in an oxidizing atmosphere or in air to finally obtain a high-voltage lithium cobalt oxide positive electrode material with layer-by-layer doping near the surface.

4. The method according to claim 3, wherein The molar ratio of the mixed salt solution in step 1) is Co:Ni:Al=(1-xy):x:y, 0 < x ≤ 0.20, 0 < y ≤ 0.

20.

5. The method according to claim 3, wherein In step 2), the pH value is 6.8-8.5, and the granulation reaction time is 3-10 hours. In step 3), the pH value is 6.8-8.0, and the inner core D50 growth rate is 0.1-0.3 μm / h.

6. The method according to claim 3, wherein In step 4), N=4~7; the doping element M of each layer is selected from one of Mg, Ti, Zr, Y, La, Nb, and W as the basic doping element, and at least one of the additional doping elements F and PO4 is added or not added to the outermost layer and / or the second outermost layer, wherein the basic doping elements of each layer not containing additional doping elements are different; in each layer, the element molar ratio of cobalt salt, aluminum salt and doping element M is the following molar ratio Co:Al:M=(1-ab):a:b, a=0.01~0.1, b=0.005~0.04; the additional doping elements F and PO4 are added in the form of acid radical solutions.

7. The method according to claim 3, wherein The carbonate solution in steps 2) to 4) is an ammonium bicarbonate solution. When the acid radical solution of the additional doping element is added, the molar ratio of the acid radical to the carbonate radical is 1:

1. The temperature of the materials in each reactor is maintained at 40-60° C. The stirring speed is 300-1800 r / min.

8. The method according to claim 3 or 7, wherein: In step 4), the pH value is 6.8-8.0; the D50 particle size growth rate is 0.05-0.15 μm / h; and the aging time is 40-200 min.

9. The method according to claim 3, wherein In step 5), centrifugal filtration is performed, hot pure water is used for washing, and drying is performed at 100° C. The sintering conditions in an oxidizing atmosphere are: oxygen to nitrogen volume ratio = m:(100-m), m = 25-45, sintering temperature 700-850° C., and sintering time 4-6 hours.

10. The method according to claim 3, wherein In step 6), the molar ratio of lithium source to oxide is Li:(Co+Ni)=1.005-1.

065. The sintering conditions in an oxidizing atmosphere are: oxygen to nitrogen volume ratio = n:(100-n), n=25-45. The sintering conditions are: heating from room temperature to 850-1060°C over 90-180 minutes, holding for 400-900 minutes, then cooling to 800-850°C, holding for 120-360 minutes, and finally cooling to room temperature. The gas flow rate is controlled at 60-200 ml / min.

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