A cathode material and its preparation method, and a lithium-ion battery.

Abstract

This invention claims protection for a cathode material and its preparation method, as well as a lithium-ion battery, to improve the capacity and rate performance of high-nickel cathode materials. The cathode material is a lithium oxide (Li₂O₃) surface-coated with lithium cobalt oxide. x Ni y Co z A 1‑y‑z O2, wherein the content of lithium cobalt oxide in each mole of the cathode material is less than 0.02 mol; wherein 1.0≤x≤1.1, 0.6≤y≤1, 0≤z≤0.4, 1-x-y>0, and A is selected from at least one of Mn, Al, W, B, F, P, Ti, V, Al, Ce, Zr, Mg, Y, Sr, Nb, Mo, Sb, Ta, and Ge; the cathode material is composed of Li oxide with residual alkali on its surface. x Ni y Co z A 1‑y‑z The oxide is obtained by co-sintering O2 with cobalt compounds; the surface of the oxide containing residual alkali has a SPAN of 1.15-1.35 and a D(104) of 55-70 nm.

Description

Technical Field

[0001] This application relates to the field of secondary battery cathode materials technology, and in particular to a cathode material and its preparation method, and a lithium-ion battery. Background Technology

[0002] Compared to other rechargeable batteries, lithium-ion batteries are increasingly being used due to their high capacity, long cycle life, and lack of memory effect.

[0003] Currently, improvements to lithium-ion battery performance often involve enhancing or replacing the cathode material. High-nickel cathode materials, with specific capacities exceeding 200 mAh / g, enable lithium-ion batteries with high energy density, supporting the demands of new energy devices, such as the long-range requirements of new energy vehicles. However, due to their high nickel content and highly active surface properties, high-nickel cathode materials are prone to over-washing under high-intensity washing conditions. Therefore, high-nickel cathode materials currently suffer from low capacity and rate performance due to their high residual alkali content. Summary of the Invention

[0004] This invention provides a cathode material and its preparation method, as well as a lithium-ion battery, to improve the capacity and rate performance of high-nickel cathode materials.

[0005] In a first aspect, embodiments of this application provide a cathode material, wherein the cathode material is an oxide Li coated with lithium cobalt oxide. x Ni y Co z A 1-y-z O2, the content of lithium cobalt oxide in each mole of the cathode material is less than 0.02 mol;

[0006] Wherein, 1.0≤x≤1.1, 0.6≤y≤1, 0≤z≤0.4, 1-xy>0, and A is selected from at least one of Mn, Al, W, B, F, P, Ti, V, Al, Ce, Zr, Mg, Y, Sr, Nb, Mo, Sb, Ta, and Ge; the positive electrode material is composed of Li oxide with residual alkali on its surface. x Ni y Co z A 1-y-z The oxide is obtained by co-sintering O2 with cobalt compounds; the SPAN of the oxide containing residual alkali on the surface is 1.15-1.35, and the D(104) of the oxide containing residual alkali on the surface is 55-70 nm.

[0007] One possible implementation is that 0.05 ≤ z ≤ 0.3.

[0008] In one possible implementation, the D(104) of the cathode material is 55-70 nm; the lithium-nickel mixing ratio of the cathode material is less than 2%.

[0009] In one possible implementation, the lithium-nickel mixing ratio of the cathode material is 0.5%-1.8%.

[0010] In one possible implementation, the oxide containing residual alkali on the surface is composed of lithium hydroxide and precursor Ni in a molar ratio of (1.04-1.12):1. a Co b A 1-a-b The lithium hydroxide is obtained by co-sintering with TM; preferably, the molar ratio is (1.04-1.07):1, and the lithium hydroxide is dehydrated coarse powder lithium hydroxide; the D of the coarse powder lithium hydroxide is... 50 ≥50μm, and D max ≥300μm.

[0011] Secondly, embodiments of this application also provide a method for preparing the cathode material described in the first aspect and any possible implementation, comprising:

[0012] Li oxides with residual alkali on the surface x Ni y Co z A 1-y-z O2 and a cobalt compound are sintered at a temperature of 200-700℃ to obtain the cathode material; wherein...

[0013] The oxide has a D(104) of 55-70 nm and a residual alkali content of 7500-12000 ppm; the oxide has a SPAN of 1.15-1.35.

[0014] In the mixture of the oxide and the cobalt compound, the ratio of the molar amount of cobalt to the molar amount of elements other than C and O in the mixture is 0.1-2.

[0015] In one possible implementation, the residual alkali comprises lithium hydroxide and lithium carbonate; the lithium hydroxide content is 4000-6000 ppm, and the lithium carbonate content is 3500-6000 ppm.

[0016] In one possible implementation, the cobalt compound includes at least one of Co(OH)2, CoCO3, Co2O3, Co(NO3)2·6H2O, and CoOOH.

[0017] In one possible implementation, the temperature condition is greater than or equal to 450°C.

[0018] One possible implementation is that the oxide containing residual alkali on the surface is obtained by the following method:

[0019] Under oxygen atmosphere conditions at 700-850℃, the reaction of lithium hydroxide and precursor Ni... a Co b A 1-a-b The mixture of TM is sintered to obtain the oxide; wherein 0.6≤a≤1, 0≤b≤0.4, 1-ab>0, TM is the anion of the precursor, and the molar ratio of lithium hydroxide to the precursor is 1.04-1.12; the D of the lithium hydroxide is... 50 <450μm, the D of the lithium hydroxide max <1000μm; preferably, the lithium hydroxide is dehydrated crude lithium hydroxide powder; the D of the crude lithium hydroxide powder is... 50 ≥50μm, and D max ≥300μm.

[0020] In one possible implementation, the molar ratio of lithium hydroxide to the precursor is 1.04-1.07.

[0021] In one possible implementation, the lithium hydroxide and the precursor mixture are obtained by mixing with a mixing device at a rotation speed of less than 200 rpm.

[0022] Thirdly, embodiments of this application also provide a lithium-ion battery, comprising:

[0023] The cathode material described in the first aspect and any possible implementation.

[0024] The one or more technical solutions provided in the embodiments of this application have at least the following beneficial effects:

[0025] First, the cathode material provided in this application embodiment is achieved by co-sintering cobalt compounds with oxides containing residual alkali on the surface. While ensuring the crystallinity of the inner oxide layer, the residual alkali on the surface is converted into trace amounts of lithium cobalt oxide, which is then coated on the surface of the oxide with good crystallinity. This achieves the purpose of improving the capacity and rate performance of the high-nickel cathode material.

[0026] Secondly, because the cathode material is coated with lithium cobalt oxide, it effectively alleviates the problem of cracking of the surface of high-nickel cathode materials under stress due to the release of active material during cycling, thus improving its cycling performance.

[0027] Furthermore, this cathode material can actually achieve high capacity and high rate capability with a relatively low cobalt content in the bulk phase (e.g., 0.05-3).

[0028] Furthermore, one of the raw materials for this cathode material is an oxide with residual alkali on its surface, which is processed by lithium hydroxide in a molar ratio of (1.04-1.12):1 and the precursor Ni.a Co b A 1-a-b The TM co-sintering process, especially when the lithium hydroxide is coarse powder, effectively improves the cycle performance of the cathode material by pre-dehydrating the coarse powder lithium hydroxide.

[0029] Finally, in the method for preparing the cathode material provided in this application embodiment, not only is the residual alkali caused by high-temperature lithium volatilization removed, but the residual alkali is also used as a raw material for forming the coating layer of lithium cobalt oxide, thereby converting the residual alkali into lithium cobalt oxide, so as to improve the utilization rate of lithium source (lithium hydroxide) and the capacity of cathode material.

[0030] Furthermore, the above method of preparing cathode materials can avoid the method of reducing the content of other metal or non-metal elements to increase capacity by introducing a large amount of cobalt into the bulk phase of the cathode material. Therefore, the cost can also be reduced by avoiding the introduction of cobalt into the bulk phase. Attached Figure Description

[0031] Figure 1 SEM image of Embodiment 1 provided in this application;

[0032] Figure 2 SEM image of Embodiment 2 provided in this application;

[0033] Figure 3 SEM image of Embodiment 3 provided in this application;

[0034] Figure 4 SEM image of Embodiment 4 provided in this application;

[0035] Figure 5 SEM image of Embodiment 5 provided in this application;

[0036] Figure 6 SEM image of Embodiment 6 provided in this application;

[0037] Figure 7 The SEM image of Comparative Example 1 provided in the embodiments of this application;

[0038] Figure 8 The SEM image of Comparative Example 3 provided in the embodiments of this application;

[0039] Figure 9 SEM image of Comparative Example 4 provided in the embodiments of this application;

[0040] Figure 10 The SEM image of Comparative Example 5 provided in the embodiments of this application;

[0041] Figure 11The image shown is a SEM image of Comparative Example 6 provided in this application embodiment. Detailed Implementation

[0042] To address the issue of low capacity and rate performance of current high-nickel cathode materials, this application provides a cathode material that is an oxide coated with lithium cobalt oxide. Lithium cobalt oxide is generated by reacting cobalt compounds with residual alkali on the oxide surface, so that each mole of cathode material contains trace amounts of lithium cobalt oxide (less than 0.02 mol), thereby improving the capacity and rate performance of the cathode material.

[0043] The following provides a detailed description of a cathode material, its preparation method, and a lithium-ion battery based on embodiments of this application. It should be noted that the embodiments described below are merely some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0044] This invention provides a cathode material, which is an oxide Li coated with lithium cobalt oxide. x Ni y Co z A 1-y- z O2. The lithium cobalt oxide content per mole of cathode material is less than 0.02 mol. This cathode material is composed of Li oxide with residual alkali on its surface. x Ni y Co z A 1-y-z It is obtained by co-sintering O2 with cobalt compounds.

[0045] The oxide has a D(104) of 55-70 nm. The residual alkali on the oxide surface provides cobalt compounds that generate lithium cobalt oxide at high temperature and coat the oxide surface.

[0046] The oxide has a SPAN of 1.15-1.35 and also has the characteristic of uniform particle size distribution, which can avoid the problem of overburning of small particles or insufficient sintering of large particles, and ensure that the crystallinity of the oxide particles is not affected during the sintering process with cobalt compounds, so that the D(104) of the cathode material is also located at 55-70nm.

[0047] in,

[0048] The molecular formula for this oxide is Li x Ni y Co z A 1-y-zO2; 1.0≤x≤1.1, 0.6≤y≤1, 0≤z≤0.4, 1-xy>0, A is selected from at least one of Mn, Al, W, B, F, P, Ti, V, Al, Ce, Zr, Mg, Y, Sr, Nb, Mo, Sb, Ta and Ge.

[0049] The aforementioned oxides with residual alkali on their surface have the same molecular expression as the oxides in the cathode material. Compared to the oxides with residual alkali on their surface, the D(104) of the oxides in the aforementioned cathode material remains at 55-70 nm, thus maintaining good crystallinity.

[0050] Please refer to Figure 1 If the cathode material is a spherical particle, then the aforementioned lithium cobalt oxide is coated on the surface of the spherical particle.

[0051] Furthermore, to reduce the cost of cathode materials and achieve low cobalt content while maintaining capacity and rate performance comparable to current high-nickel cathode materials, in some embodiments, 0.05 ≤ z ≤ 0.3. For example, z = 0.06.

[0052] Furthermore, the cathode material exhibits good crystallinity, with a D(104) of 55-70 nm.

[0053] In the embodiments of this application, D(104) refers to the grain size in the direction perpendicular to the crystal plane of the (104) diffraction peak.

[0054] This cathode material features a low lithium-nickel mixing ratio, which is less than 2%. Preferably, the lithium-nickel mixing ratio of this cathode material is 0.5%-1.8%.

[0055] Furthermore, the oxide containing residual alkali on the surface is composed of lithium hydroxide in a molar ratio of (1.04-1.12):1 and the precursor Ni. a Co b A 1-a-b TM co-sintering is obtained.

[0056] The preferred molar ratio is 1.04-1.07; the preferred lithium hydroxide is pre-dehydrated coarse lithium hydroxide powder.

[0057] Based on the same inventive concept, this application also provides a method for preparing a cathode material to improve the rate performance and capacity of high-nickel cathode materials, specifically including the following implementation steps:

[0058] Li oxides with residual alkali on the surface x Ni y Co z A 1-y-z O2 and cobalt compounds are sintered at temperatures of 200-700℃ to obtain the aforementioned cathode material.

[0059] In this case, the cation in the cobalt compound is cobalt.

[0060] The oxide has good crystallinity, with a D(104) of 55-70 nm; and the oxide has a narrow particle size distribution, with a SPAN of 1.15-1.35. Therefore, the oxide and cobalt compound can maintain good crystallinity during co-sintering, resulting in a D(104) of 55-70 nm for both the oxide and the cathode material.

[0061] The residual alkali content is 7500-12000 ppm. This residual alkali content allows it to act as a reactant for lithium cobalt oxide, reacting with cobalt compounds to generate lithium cobalt oxide, which coats the oxide surface to obtain the cathode material. The amount of cobalt compound added is determined by the molar ratio of cobalt element to the elements other than C and O in the mixture of oxide and cobalt compound. It is calculated as 0.1-2.

[0062] The above residual alkali content is the sum of the lithium hydroxide content and the lithium carbonate content.

[0063] In some embodiments, the cobalt compound is selected from at least one of Co(OH)2, CoCO3, Co2O3, Co(NO3)2·6H2O and CoOOH.

[0064] Further, the residual alkali includes lithium hydroxide and lithium carbonate. In some embodiments, the lithium hydroxide content is 4000-6000 ppm and the lithium carbonate content is 3500-6000 ppm.

[0065] In some embodiments, to promote a full reaction, the cobalt compound is rapidly dehydrated and reacts with residual alkali to generate lithium cobalt oxide, thereby improving reaction efficiency and the utilization rate of the cobalt compound. The temperature conditions described above can be greater than or equal to 450°C, even if the coating sintering temperature of lithium cobalt oxide is between 450-700°C.

[0066] In some embodiments, the sintering time can be 6-12 hours.

[0067] Furthermore, the preparation of the aforementioned oxides containing residual alkali on the surface will be described in detail below:

[0068] Under oxygen atmosphere conditions at 700-850℃, the reaction of lithium hydroxide and precursor Ni... a Co b A 1-a-b The mixture of TM is sintered to obtain the oxide.

[0069] Wherein, 0.6≤a≤1, 0≤b≤0.4, 1-ab>0, and TM is the anion of the precursor.

[0070] The molar ratio of lithium hydroxide to the precursor is 1.04-1.12.

[0071] The oxygen content in the aforementioned oxygen atmosphere should be no less than 90% to ensure the full occurrence of the oxidation reaction. Furthermore, when the oxygen content in the oxygen atmosphere is less than 100%, the gases in the atmosphere other than oxygen should be inert gases that do not chemically react with the reactants and sintering products, such as N2 or Ar2.

[0072] The anion in the above precursor can be OH - and O 2- At least one of them. When the precursor is a salt with different anion or cation contents, the sum of the contents of Ni, Co, and A in the final precursor mixture shall be equal to the contents of Ni, Co, and A in the cathode material.

[0073] To further reduce the lithium-nickel mixing ratio in the cathode material and improve its rate performance, in some embodiments, the molar ratio of lithium hydroxide to the precursor is 1.04-1.07, so that the lithium-nickel mixing ratio of the cathode material is 0.5%-1.8%.

[0074] Furthermore, the aforementioned lithium hydroxide can be either fine powder or coarse powder. Since lithium hydroxide is harder than the precursor, when mixing lithium hydroxide, especially coarse powder, with the precursor, the mixing equipment should operate at a low to medium speed, i.e., less than 200 rpm. This is to avoid the precursor breaking apart under the impact of lithium hydroxide at high speeds, which could lead to cyclic degradation. This mixing equipment can be a high-speed mixer.

[0075] The lithium hydroxide mentioned above is preferably coarse lithium hydroxide powder, so as to improve the cycle performance of the target product—the cathode material by pre-dehydrating the coarse lithium hydroxide powder, or the mixture of coarse lithium hydroxide powder and the precursor, before sintering: that is, pre-dehydrating at high temperature (around 500°C).

[0076] In some embodiments, the D of the above-mentioned crude lithium hydroxide powder 50 ≥50μm, and D max ≥300μm.

[0077] Furthermore, the D of the aforementioned lithium hydroxide 50 <450μm, and D max<1000μm, effectively mitigating the phenomenon of precursor breakage caused by excessively large coarse lithium hydroxide powder during the mixing stage. This avoids over-burning of the precursor and oxide, as well as the problem of low compaction density caused by small particles resulting from precursor breakage. It ensures that the oxides generated by the mixed precursor and lithium hydroxide under high temperature can form a uniform phase, thus guaranteeing the uniformity of crystallinity of each oxide particle.

[0078] The above precursor D 50 It can be 8-14μm, and Dmax < 40μm.

[0079] Based on the same inventive concept, embodiments of this application also provide a lithium-ion battery, which includes the aforementioned positive electrode material.

[0080] Because the capacity and rate performance of the cathode material in this embodiment are fully released under the action of the coating layer, the capacity and rate performance of the secondary battery containing the cathode material in this embodiment are higher than those of lithium-ion batteries containing cathode materials with the same content of elements such as Ni and Co in the prior art.

[0081] The following detailed description is provided through examples and comparative examples.

[0082] (I) Preparation of cathode materials

[0083] Example 1

[0084] S1, 20 kg of precursor Ni 0.83 Co 0.12 Mn 0.05 (OH)2 and 9.54 kg of crude lithium hydroxide powder (D 50 Mix the particles (250 μm, Dmax 750 μm) at 150 rpm for 10 min in a 60 L high-speed mixer.

[0085] S2. The mixture is placed in a rotary kiln for pre-oxidation. The sintering temperature is 500℃ and the time is 6h. Pure oxygen is used in the atmosphere and the gas flow rate is 500L / min to obtain the pre-oxidized material.

[0086] S3. The pre-oxidized material is sintered once in a pot at a rate of 10.6 kg / pot, with a loading height of about 8 cm. The sintering temperature is 765℃ and the time is 12 h. The sintering atmosphere is pure oxygen atmosphere with an oxygen flow rate of 1000 L / min to obtain the first sintered material.

[0087] S4. Crush the primary sintering material, D 50The particle size was controlled at 10.0±1.0μm. Then, the material was washed with water at a mass ratio of 1:1 for 2 minutes, with the washing temperature controlled between 15-25℃, the stirring rod speed at 40 rpm, and the water temperature at 5℃. Next, the washed material was pressure filtered and dried to control the moisture content below 0.5%.

[0088] S5. The dried first-stage sinter and 186g Co(OH)3 were added to a 30L high-speed mixer and stirred at 600rpm for 15min. Then, the mixture was placed in a roller kiln for secondary sintering. The sagger weight was 5.5kg / sagger, the sintering temperature was 600℃, and the holding time was 8h. After sieving, iron removal, and packaging, high-nickel ternary material Li was obtained. 1.055 Ni 0.827 Co 0.123 Mn 0.05 O2. See the SEM image of this cathode material. Figure 1 .

[0089] Example 2

[0090] S1, 20 kg of precursor Ni 0.8 3Co 0.12 Mn 0.05 (OH)2 and 9.54 kg of crude lithium hydroxide powder (D 50 Mix the particles (250 μm, Dmax 750 μm) at 150 rpm for 10 min in a 60 L high-speed mixer.

[0091] S2. The mixture is placed in a rotary kiln for pre-oxidation. The sintering temperature is 500℃ and the time is 6h. Pure oxygen is used in the atmosphere and the gas flow rate is 500L / min to obtain the pre-oxidized material.

[0092] S3. The pre-oxidized material is loaded into a pot at a rate of 10.6 kg / pot and sintered once. The loading height is about 8 cm, the sintering temperature is 765℃, the time is 12 h, the sintering atmosphere is pure oxygen atmosphere, and the oxygen flow rate is 1000 L / min to obtain the first sintered material.

[0093] S4. Crush the primary sintering material, D 50 The particle size was controlled at 10.0±1.0μm. Then, the material was washed with water at a mass ratio of 1:1 for 2 minutes, with the washing temperature controlled between 15-25℃, the stirring rod speed at 40 rpm, and the water temperature at 5℃. Next, the washed material was pressure filtered and dried to control the moisture content below 0.5%.

[0094] S5. The dried first-stage sinter and 136g Co3O4 were added to a 30L high-speed mixer and stirred at 600rpm for 15min. Then, the mixture was placed in a roller kiln for secondary sintering. The sagger weight was 5.5kg / sagger, the sintering temperature was 600℃, and the holding time was 8h. After sieving, iron removal, and packaging, high-nickel ternary material Li was obtained. 1.055 Ni 0.827 Co 0.123 Mn 0.05 O2. See the SEM image of this cathode material. Figure 2 .

[0095] Example 3

[0096] S1, 20 kg of precursor Ni 0.83 Co 0.12 Mn 0. 0.5(OH)2 and 9.54 kg of crude lithium hydroxide powder (D 50 The sample was mixed in a 60L high-speed mixer at a medium-low speed of 150 rpm for 10 min (240 μm, Dmax 720 μm).

[0097] S2. The mixture is placed in a rotary kiln for pre-oxidation. The sintering temperature is 500℃ and the time is 6h. Pure oxygen is used in the atmosphere and the gas flow rate is 500L / min to obtain the pre-oxidized material.

[0098] S3. The pre-oxidized material is sintered once in a pot at a rate of 10.6 kg / pot, with a loading height of about 8 cm. The sintering temperature is 765℃ and the time is 12 h. The sintering atmosphere is pure oxygen atmosphere with an oxygen flow rate of 1000 L / min to obtain the first sintered material.

[0099] S4. Crush the primary sintering material, D 50 The particle size was controlled at 10.0±1.0μm. Then, the material was washed with water at a mass ratio of 1:1 for 2 minutes, with the washing temperature controlled between 15-25℃, the stirring rod speed at 40 rpm, and the water temperature at 5℃. Next, the washed material was pressure filtered and dried to control the moisture content below 0.5%.

[0100] S5. The dried material and 2470g Co(NO3)2·6H2O were added to a 30L high-speed mixer and stirred at 600rpm for 15min. Then, the mixture was placed in a roller kiln for secondary sintering. The sagger filling rate was 5.5kg / sagger, the sintering temperature was 600℃, and the holding time was 8h. After sieving, iron removal, and packaging, high-nickel ternary material Li was obtained. 1.055 Ni 0.815 Co 0.135 Mn 0.05 O2. See the SEM image of this cathode material. Figure 3 .

[0101] Example 4

[0102] S1, 20 kg of precursor Ni 0.83 Co 0.12 Mn 0.05 (OH)2 and 9.40 kg of crude lithium hydroxide powder (D 50 Mix the particles (250 μm, Dmax 750 μm) at 150 rpm for 10 min in a 60 L high-speed mixer.

[0103] S2. The material is placed in a rotary kiln for pre-oxidation. The sintering temperature is 500℃ and the time is 6 hours. Pure oxygen is used in the atmosphere and the gas flow rate is 500L / min to obtain the pre-oxidized material.

[0104] S3. The pre-oxidized material is sintered once in a pot at a rate of 10.6 kg / pot, with a loading height of about 8 cm. The sintering temperature is 765℃ and the time is 12 h. The sintering atmosphere is pure oxygen atmosphere with an oxygen flow rate of 1000 L / min to obtain the first sintered material.

[0105] S4. The primary sintered material is pulverized, with D50 controlled at 10.0±1.0μm. Then, it is washed with water at a mass ratio of 1:1 for 2 minutes, with the washing temperature controlled between 15-25℃, the stirring rod speed at 40 rpm, and the water temperature at 5℃. Next, the washed primary sintered material is pressure filtered and dried to control the moisture content below 0.5%.

[0106] S5. The dried material and 186g Co(OH)3 were added to a 30L high-speed mixer and stirred at 600rpm for 15min. Then, the mixture was placed in a roller kiln for secondary sintering. The sagger filling rate was 5.5kg / sagger, the sintering temperature was 600℃, and the holding time was 8h. After sieving, iron removal, and packaging, high-nickel ternary material Li was obtained. 1.04 Ni 0.827 Co 0.123 Mn 0.05 O2. See the SEM image of this cathode material. Figure 4 .

[0107] Example 5

[0108] S1, 20 kg of precursor Ni 0.83 Co 0.12 Mn 0.05 (OH)2 and 9.54 kg of finely powdered lithium hydroxide (D 50 Mix the particles (15 μm, Dmax 50 μm) in a 60L high-speed mixer at a medium-low speed of 350 rpm for 10 min.

[0109] S2. The mixed material is sintered once in a pot at a rate of 5 kg / pot, with a loading height of about 8 cm, a sintering temperature of 765℃, a sintering time of 12 h, and a sintering atmosphere of pure oxygen with an oxygen flow rate of 1000 L / min, to obtain the first sintered material.

[0110] S3. Crush the primary sintering material, D 50 The particle size was controlled at 10.0±1.0μm. Then, the material was washed with water at a mass ratio of 1:1 for 2 minutes, with the washing temperature controlled between 15-25℃, the stirring rod speed at 40 rpm, and the water temperature at 5℃. Next, the washed material was pressure filtered and dried to control the moisture content below 0.5%.

[0111] S4. The dried first-stage sinter and 186g Co(OH)3 were added to a 30L high-speed mixer and stirred at 600rpm for 15min. Then, the mixture was placed in a roller kiln for secondary sintering. The sagger weight was 5.5kg / sagger, the sintering temperature was 600℃, and the holding time was 8h. After sieving, iron removal, and packaging, high-nickel ternary material Li was obtained. 1.055 Ni 0.827 Co 0.123 Mn 0.05 O2. See the SEM image of this cathode material. Figure 5 .

[0112] Example 6

[0113] S1, 20 kg of precursor Ni 0.83 Co 0.12 Mn 0.05 (OH)2 and 9.54 kg of crude lithium hydroxide powder (D 50 Mix the particles (250 μm, Dmax 750 μm) at 150 rpm for 10 min in a 60 L high-speed mixer.

[0114] S2. The mixture is placed in a rotary kiln for pre-oxidation. The sintering temperature is 500℃ and the time is 6h. Pure oxygen is used in the atmosphere and the gas flow rate is 500L / min to obtain the pre-oxidized material.

[0115] S3. The pre-oxidized material is loaded into a pot at a rate of 10.6 kg / pot for the first sintering. The loading height is about 8 cm. The sintering temperature is 745℃ and the time is 12 h. The sintering atmosphere is pure oxygen atmosphere with an oxygen flow rate of 1000 L / min to obtain the first sintered material.

[0116] S4. The primary sintered material is pulverized, with D50 controlled at 10.0±1.0μm. Then, it is washed with water at a mass ratio of 1:1 for 2 minutes, with the washing temperature controlled between 15-25℃, the stirring rod speed at 40 rpm, and the water temperature at 5℃. Next, the washed primary sintered material is pressure filtered and dried to control the moisture content below 0.5%.

[0117] S5. The dried material and 186g Co(OH)3 were added to a 30L high-speed mixer and stirred at 600rpm for 15min. Then, the mixture was placed in a roller kiln for secondary sintering. The sagger filling rate was 5.5kg / sagger, the sintering temperature was 600℃, and the holding time was 8h. After sieving, iron removal, and packaging, high-nickel ternary material Li was obtained. 1.055 Ni 0.827 Co 0.123 Mn 0.05 O2. See the SEM image of this cathode material. Figure 6 .

[0118] Comparative Example 1

[0119] S1, 20 kg of precursor Ni 0.83 Co 0.16 Mn 0.01 (OH)2 and 9.54 kg of crude lithium hydroxide powder (D50 = 250 μm, Dmax = 750 μm) were mixed in a 60 L high-speed mixer at a medium-low speed of 150 rpm for 10 min.

[0120] S2. The mixture is placed in a rotary kiln for pre-oxidation. The sintering temperature is 500℃ and the time is 6h. Pure oxygen is used in the atmosphere and the gas flow rate is 500L / min to obtain the pre-oxidized material.

[0121] S3. The pre-oxidized material is sintered once in a pot at a rate of 10.6 kg / pot, with a loading height of about 8 cm. The sintering temperature is 765℃ and the time is 12 h. The sintering atmosphere is pure oxygen atmosphere with an oxygen flow rate of 1000 L / min to obtain the first sintered material.

[0122] S4. Crush the primary sintering material, D 50 The particle size was controlled at 10.0±1.0μm. Then, the material was washed with water at a mass ratio of 1:1 for 2 minutes, with the washing temperature controlled between 15-25℃, the stirring rod speed at 40 rpm, and the water temperature at 5℃. Next, the washed material was pressure filtered and dried to control the moisture content below 0.5%.

[0123] S5. The dried primary sintering material is directly placed in a roller kiln for secondary sintering. The sagger loading is 5.5 kg / sagger, the sintering temperature is 600℃, and the holding time is 8 hours. After screening, iron removal, and packaging, high-nickel ternary material Li is obtained. 1.055 Ni 0.83 Co 0.16 Mn 0.01 O2. See the SEM image of this cathode material. Figure 7 .

[0124] Comparative Example 2

[0125] 20 kg of precursor Ni 0.83 Co 0.12 Mn 0.05 (OH)2 and 9.31 kg of crude lithium hydroxide (D) 50 =250μm, D max =750μm) was mixed in a 60L high-speed mixer at a medium-low speed of 150rpm for 10min. After the material was uniformly mixed, it was placed in a rotary kiln for pre-oxidation. The sintering temperature was 500℃ for 6h, and the atmosphere was pure oxygen with a gas flow rate of 500L / min to obtain the pre-oxidized material. The pre-oxidized material was then packed into bowls at a rate of 10.6kg / bowl, with a packing height of about 8cm. The sintering temperature was 765℃ for 12h, and the sintering atmosphere was pure oxygen with an oxygen flow rate of 1000L / min to obtain the primary sintered material. The primary sintered material was then pulverized, with the D50 controlled at 10.0±1.0μm. It was then washed with water at a 1:1 ratio for 2min at a temperature controlled between 15-25℃, with the stirring rod speed at 40rpm and the water temperature at 5℃. After that, it was pressure filtered and dried to control the moisture content below 0.5%. The dried material and 186g Co(OH)3 were added to a 30L high-speed mixer and stirred at 600rpm for 15min. After the material was uniformly mixed, it was placed in a roller kiln for secondary sintering. The sagger weight was 5.5kg / sagger, the sintering temperature was 600℃, and the holding time was 8h. After screening, iron removal, and packaging, high-nickel ternary material Li was obtained. 1.03 Ni 0.827 Co 0.123 Mn 0.05 O2.

[0126] Comparative Example 3

[0127] S1, 20 kg of precursor Ni 0.83 Co 0.12 Mn 0.05 (OH)2 and 9.54 kg of crude lithium hydroxide powder (D 50 Mix the particles (250 μm, Dmax 750 μm) at 150 rpm for 10 min in a 60 L high-speed mixer.

[0128] S2. The mixture is placed in a rotary kiln for pre-oxidation. The sintering temperature is 500℃ and the time is 6h. Pure oxygen is used in the atmosphere and the gas flow rate is 500L / min to obtain the pre-oxidized material.

[0129] S3. The pre-oxidized material is sintered for the first time at a rate of 10.6 kg / pot, with a loading height of about 8 cm, a sintering temperature of 765℃, a sintering time of 12 h, a pure oxygen atmosphere, and an oxygen flow rate of 1000 L / min to obtain the first sintered material.

[0130] S4. Crush the primary sintering material, control the D50 to 10.0±1.0μm, and then wash it with water at a mass ratio of 1:1 between the primary sintering material and water for 2 minutes. The washing temperature is controlled between 15-25℃, the stirring rod speed is 40rpm, and the water temperature is 5℃. Then, filter and dry it to control the moisture content to below 0.5%.

[0131] S5. The dried material is placed in a roller kiln for secondary sintering. The sagger weight is 5.5 kg / sagger, the sintering temperature is 600℃, and the holding time is 8 hours. After sieving, iron removal, and packaging, high-nickel ternary material Li is obtained. 1.055 Ni 0.827 Co 0.123 Mn 0.05 O2. See the SEM image of this cathode material. Figure 8 .

[0132] Comparative Example 4

[0133] S1, 20 kg of precursor Ni 0.83 Co 0.12 Mn 0.05 (OH)2 and 9.54 kg of crude lithium hydroxide powder (D 50 Mix the sample (600 μm, Dmax < 1200 μm) at a medium-low speed of 150 rpm for 10 min in a 60 L high-speed mixer.

[0134] S2. The mixture is placed in a rotary kiln for pre-oxidation. The sintering temperature is 500℃ and the time is 6h. Pure oxygen is used in the atmosphere and the gas flow rate is 500L / min to obtain the pre-oxidized material.

[0135] S3. The pre-oxidized material is packed into bowls at a rate of 10.6 kg / bowl, with a packing height of about 8 cm. The sintering temperature is 765℃, the time is 12 h, the sintering atmosphere is pure oxygen atmosphere, and the oxygen flow rate is 1000 L / min, to obtain the primary sintered material.

[0136] S4. Crush the primary sintering material, D 50The particle size was controlled at 10.0±1.0μm, and then washed with water at a 1:1 ratio for 2 minutes. The water temperature was controlled between 15-25℃, the stirring rod speed was 40rpm, and the water temperature was 5℃. Then, the mixture was pressure filtered and dried to control the moisture content to below 0.5%.

[0137] S5. The dried material and 186g Co(OH)3 were added to a 30L high-speed mixer and stirred at 600rpm for 15min. After the material was evenly mixed, it was placed in a roller kiln for secondary sintering. The sagger filling rate was 5.5kg / sagger, the sintering temperature was 600℃, and the holding time was 8h. After screening, iron removal, and packaging, high-nickel ternary material Li was obtained. 1.055 Ni 0.827 Co 0.123 Mn 0.05 O2. See the SEM image of this cathode material. Figure 9 .

[0138] Comparative Example 5

[0139] S1, 20 kg of precursor Ni 0.83 Co 0.12 Mn 0.05 (OH)2 and 9.54 kg of crude lithium hydroxide powder (D 50 =250μm, Dmax=750μm) were mixed at 250rpm for 10min in a 60L high-speed mixer.

[0140] S2. The mixture is placed in a rotary kiln for pre-oxidation. The sintering temperature is 500℃ and the time is 6h. Pure oxygen is used in the atmosphere and the gas flow rate is 500L / min to obtain the pre-oxidized material.

[0141] S3. The pre-oxidized material is packed into bowls at a rate of 10.6 kg / bowl, with a packing height of about 8 cm. The sintering temperature is 765℃, the time is 12 h, the sintering atmosphere is pure oxygen atmosphere, and the oxygen flow rate is 1000 L / min, to obtain the primary sintered material.

[0142] S4. Crush the primary sintered material, control the D50 to 10.0±1.0μm, and then wash it with water at a 1:1 ratio for 2 minutes. The water washing temperature is controlled between 15-25℃, the stirring rod speed is 40rpm, and the water temperature is 5℃. Then, filter and dry it to control the moisture content to below 0.5%.

[0143] S5. The dried material and 186g Co(OH)3 were added to a 30L high-speed mixer and stirred at 600rpm for 15min. After the material was evenly mixed, it was placed in a roller kiln for secondary sintering. The sagger filling rate was 5.5kg / sagger, the sintering temperature was 600℃, and the holding time was 8h. After screening, iron removal, and packaging, high-nickel ternary material Li was obtained. 1.055 Ni 0.827 Co 0.123 Mn 0.05 O2. See the SEM image of this cathode material. Figure 10 .

[0144] Comparative Example 6

[0145] S1, 20 kg of precursor Ni 0.83 Co 0.12 Mn 0.05 (OH)2 and 9.54 kg of crude lithium hydroxide powder (D50 = 250 μm, Dmax = 750 μm) were mixed in a 60 L high-speed mixer at a medium-low speed of 150 rpm for 10 min.

[0146] S2. The mixture is placed in a rotary kiln for pre-oxidation. The sintering temperature is 500℃ and the time is 6h. Pure oxygen is used in the atmosphere and the gas flow rate is 500L / min to obtain the pre-oxidized material.

[0147] S3. The pre-oxidized material is sintered once in a pot at a rate of 10.6 kg / pot, with a loading height of about 8 cm. The sintering temperature is 765℃ and the time is 12 h. The sintering atmosphere is pure oxygen atmosphere with an oxygen flow rate of 1000 L / min to obtain the first sintered material.

[0148] S4. Crush the primary sintering material, D 50 The particle size was controlled at 10.0±1.0μm. Then, the material was washed with water at a mass ratio of 1:1 for 2 minutes, with the washing temperature controlled between 15-25℃, the stirring rod speed at 40 rpm, and the water temperature at 5℃. Next, the washed material was pressure filtered and dried to control the moisture content below 0.5%.

[0149] S5. The dried first-stage sinter and 1860g Co(OH)3 were added to a 30L high-speed mixer and stirred at 600rpm for 15min. Then, the mixture was placed in a roller kiln for secondary sintering. The sagger weight was 5.5kg / sagger, the sintering temperature was 600℃, and the holding time was 8h. After sieving, iron removal, and packaging, high-nickel ternary material Li was obtained. 1.055 Ni 0.80 Co 0.15 Mn 0.05 O2. See the SEM image of this cathode material. Figure 11.

[0150] (II) Testing of the cathode materials in the examples and comparative examples

[0151] Specifically, for the primary sintering material obtained in step S3 and the secondary sintering material obtained in step S5 in each embodiment and comparative example: the high-nickel ternary materials were tested for residual alkali content, D(104), and powder resistance at 120 MPa (unit: Ω·cm). -2 Tests were conducted on particle strength and Li / Ni mixing ratio.

[0152] The following describes the methods or equipment used for each test:

[0153] (1) The test method for residual alkali content (i.e., the content of lithium hydroxide and lithium carbonate) and free lithium ions is as follows: First, weigh 30g of high-nickel ternary material, add 100ml of pure water, and stir for 30min. Then, filter using double-layer medium-speed filter paper and transfer 10ml of the solution. Finally, titrate with 0.05mol / L HCl, determine the titration endpoint according to the acid-base titration method, determine the content of lithium hydroxide and lithium carbonate, and calculate the content of free lithium ions.

[0154] (2) The powder resistance was tested using a PD-51 test equipment and an MCP-T700 impedance meter. The four-probe method was used. 4g of material was weighed and placed in a graduated cylinder with a radius of 10mm. The powder resistance value was tested and recorded under a pressure of 12MPa.

[0155] (3) The D(104) and Li / Ni mixing ratio were tested using a Bruker D8A A25 X-ray diffractometer (target material is Cu, voltage is 40kV, current is 40mA, Soller is 2.5). The test results were processed using data processing software EVAr and TOPAS.

[0156] (4) The surface lithium cobalt oxide content was obtained by X-ray photoelectron spectroscopy (XPS) analysis using an X-ray photoelectron spectroscopy instrument (Shimadzu AXIS Supra, Japan).

[0157] The test results are shown in Table 1.

[0158] Table 1

[0159]

[0160]

[0161] Note: The two sintering materials in Table 1 are the high-nickel ternary materials used in the examples and comparative examples.

[0162] As shown in Table 1, Examples 1-6 exhibit high particle strength, similar D(104) of the calcined material and the cathode material, and good crystallinity. Furthermore, compared to the comparative example, the particle strength of Examples 1-6 is improved, and the residual alkali content is reduced.

[0163] Continue to refer to Figure 1-6 As can be seen, the cathode materials in Examples 1-6 only show some small, but still rounded, spherical secondary particles due to agglomeration. Figures 9-10 In the middle, irregularly shaped fine particles can be observed. These fine particles are obviously due to the large particle size of lithium hydroxide in Comparative Example 4 and the excessively high rotation speed during mixing in Comparative Example 5.

[0164] (III) Preparation and Testing of Button Cells

[0165] The positive electrode material, acetylene black, and polyvinylidene fluoride (PVDF) from the examples or comparative examples were weighed at a mass ratio of 94:3:3, mixed evenly, and NMP was added and stirred for 2 hours to form a viscous slurry. This slurry was then evenly coated onto aluminum foil, vacuum baked at 80°C, pressed into sheets, and cut into positive electrode sheets with a diameter of 14 mm. A 16 mm diameter pure lithium sheet was used as the negative electrode, a 1 mol / L LiPF6 + DEC / EC (volume ratio 1:1) mixed solution was used as the electrolyte, and a polyCelgard propylene microporous membrane was used as the separator. The cells were assembled into coin cells in an argon-filled glove box.

[0166] Specifically, for the primary sintering material obtained in step S3 and the secondary sintering material obtained in step S5 of each embodiment and comparative example, the high-nickel ternary material (i.e., cathode material) was subjected to the following tests: first coulombic efficiency, rate performance, first discharge capacity, initial DCR (DC internal resistance) (unit: mΩ), 7-day gas production test at 70°C, and 300 cycles at 45°C.

[0167] The following section first explains the methods and key parameters for each test data point:

[0168] (a) The 0.2C capacity testing method is as follows: The assembled button cell battery is tested in a Blue Electric device at a temperature of 25±1℃ and a voltage of 2.5~4.25V. It is charged and discharged at 0.2C / 0.2C, and the charging cut-off current is 0.05C (1C nominal capacity is 200mAh / g).

[0169] (II) In the rate performance test, the Landon CT2001A equipment was used, and the following tests were conducted with a constant voltage cutoff current of 0.05C:

[0170] ① Charge at 0.1C to the cutoff voltage, let stand for 2 minutes, discharge at 0.1C to the termination voltage, and let stand for 2 minutes;

[0171] ② Charge at 0.2C to the cutoff voltage, and discharge at 0.2C to the termination voltage;

[0172] ③ Charge at 0.5C to the cutoff voltage, and discharge at 1C to the termination voltage;

[0173] ④ Charge at 0.5C to the cutoff voltage, and discharge at 3C to the termination voltage.

[0174] The ratio of the 3C discharge capacity to the 0.2C discharge capacity obtained from the above tests is used as the rate performance data.

[0175] The test results are shown in Table 2.

[0176] Table 2

[0177]

[0178]

[0179] According to Table 2, the capacity, rate performance and cycle performance of Examples 1-6 are all better than those of Comparative Examples 1-5.

[0180] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A positive electrode material, characterized in that, The positive electrode material is an oxide Li₂ with a surface coating of lithium cobalt oxide. x Ni y Co z A 1-y-z O2, the content of lithium cobalt oxide in each mole of the cathode material is less than 0.02 mol; Wherein, 1.0≤x≤1.1, 0.6≤y≤1, 0≤z≤0.4, 1-yz>0, and A is selected from at least one of Mn, Al, W, B, F, P, Ti, V, Al, Ce, Zr, Mg, Y, Sr, Nb, Mo, Sb, Ta, and Ge; the positive electrode material is composed of Li oxide with residual alkali on its surface. x Ni y Co z A 1-y-z The oxide is obtained by co-sintering O2 with cobalt compounds; the SPAN of the oxide containing residual alkali on the surface is 1.15-1.35, and the D(104) of the oxide containing residual alkali on the surface is 55-70 nm; the oxide containing residual alkali on the surface... D90 is the particle size of the oxide containing residual alkali on the surface, D10 is the particle size of the oxide containing residual alkali on the surface, D50 is the particle size of the oxide containing residual alkali on the surface, and D(104) is the grain size in the direction perpendicular to the (104) diffraction peak of the oxide containing residual alkali on the surface. The oxide containing residual alkali on the surface is composed of lithium hydroxide in a molar ratio of (1.04-1.12):1 and the precursor Ni. a Co b A 1-a-b TM is obtained by co-sintering, with 0.6≤a≤1, 0≤b≤0.4, 1-ab>0, where TM is the anion of the precursor; the D of the lithium hydroxide 50 The D of the lithium hydroxide is ≥50μm and <450μm. max ≥300μm and <1000μm.

2. The cathode material as described in claim 1, characterized in that, 0.05≤z≤0.3。 3. The positive electrode material as described in claim 1, characterized in that, The cathode material has a D(104) of 55-70 nm; the lithium-nickel mixing ratio of the cathode material is less than 2%.

4. The cathode material according to any one of claims 1-3, characterized in that, The lithium-nickel mixing rate of the cathode material is 0.5%-1.8%.

5. A method for preparing the cathode material according to any one of claims 1-4, characterized in that, include: Under oxygen atmosphere conditions at 700-850℃, the reaction of lithium hydroxide and precursor Ni... a Co b A 1-a-b A mixture of TM is sintered to obtain an oxide with residual alkali on the surface; wherein 0.6≤a≤1, 0≤b≤0.4, 1-ab>0, TM is the anion of the precursor, and the molar ratio of lithium hydroxide to the precursor is 1.04-1.12; the D of the lithium hydroxide is... 50 <450μm, the D of the lithium hydroxide max <1000μm; The oxide Li containing residual alkali on the surface x Ni y Co z A 1-y-z O2 and a cobalt compound are sintered at a temperature of 200-700℃ to obtain the cathode material; wherein... The D(104) of the oxide containing residual alkali on the surface is 55-70 nm, the content of residual alkali in the oxide containing residual alkali on the surface is 7500-12000 ppm, and the SPAN of the oxide containing residual alkali on the surface is 1.15-1.

35. In the mixture of the oxide containing residual alkali on the surface and the cobalt compound, the ratio of the molar amount of cobalt to the molar amount of elements other than C and O in the mixture is 0.1-2.

6. The method as described in claim 5, characterized in that, The molar ratio of lithium hydroxide to the precursor is 1.04-1.

07.

7. The method as described in claim 5 or 6, characterized in that, The lithium hydroxide and the precursor mixture are obtained by mixing with a mixing device with a rotation speed of less than 200 rpm.

8. A lithium-ion battery, characterized in that, include: The cathode material according to any one of claims 1-4.

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