Single-crystal cathode material and method for manufacturing the same, lithium-ion battery

Abstract

A single-crystal cathode material and a method for manufacturing the same, and a lithium-ion battery, wherein the single-crystal cathode material is a particulate material, the particulate material includes an inner layer material and a coating layer covering the surface of the inner layer material, the particulate material includes first particles with an average particle size F1 of 1.0 to 2.0 μm and second particles with an average particle size F2 of 2.5 to 6.0 μm, the average thickness T1 of the coating layer of the first particles is smaller than the average thickness T2 of the coating layer of the second particles, the coating layer contains a high-speed ion conductor, and the molecular formula of the inner layer material is Li 1+a [Ni x Co y M z Q b ]O 2±c A d Therefore, 0≦a<0.20, 0.60≦x<1.0, 0

Description

[Technical Field]

[0001] This application relates to the field of secondary battery cathode material technology, and more particularly to single-crystal cathode materials, methods for manufacturing the same, and lithium-ion batteries. [Background technology]

[0002] With the development of the new energy industry, lithium-ion batteries have also developed significantly, and their industrial applications are becoming increasingly widespread. A lithium-ion battery is a type of battery consisting of a positive electrode, a negative electrode, and a non-aqueous electrolyte. The performance of the positive electrode material, which is placed on the positive electrode side, has an extremely important impact on the performance of lithium-ion batteries, such as their rate of operation, energy density, and service life.

[0003] The cathode materials for lithium-ion batteries include single-crystal cathode materials and polycrystalline cathode materials. Because polycrystalline cathode materials have a large number of brittle grain boundaries, the anisotropic expansion and contraction of the material during the charging and discharging of lithium-ion batteries easily causes phenomena such as cracking and differentiation in the polycrystalline cathode material, further leading to capacity degradation and safety risks.

[0004] For this reason, the use of single-crystal cathode materials is gradually increasing. Compared to polycrystalline cathode materials, single-crystal cathode materials have the characteristic of being relatively small in size, but smaller cathode materials do not have the same compaction performance as larger cathode materials. If the size of a single-crystal cathode material is increased to improve its compaction performance, electrochemical performance such as capacitance decreases. Therefore, current single-crystal cathode materials have the problem of not being able to achieve both compaction performance and capacitance performance. [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] This application provides a single-crystal cathode material, a method for manufacturing the same, and a lithium-ion battery, in order to provide a single-crystal cathode material that is excellent in both compaction performance and capacity density. [Means for solving the problem]

[0006] In the first aspect, an embodiment of the present application provides a single crystal cathode material. The single crystal cathode material is a particulate material. The particulate material includes an inner layer material and a coating layer of the inner layer material. The coating layer includes a high-speed ion conductor. The particulate material includes a first particle with an average particle size F1 of 1.0 to 2.0 μm and a second particle with an average particle size F2 of 2.5 to 6.0 μm. The average thickness T1 of the coating layer of the first particle is smaller than the average thickness T2 of the coating layer of the second particle. The coating layer includes a high-speed ion conductor. The molecular formula of the inner layer material is Li 1+a [Ni x Co y M z Q b O 2±c A d where 0 ≤ a < 0.20, 0.60 ≤ x < 1.0, 0 < y < 0.30, 0 < z < 0.30, 0 ≤ b < 0.20, c ≤ 0.02, 0 ≤ d ≤ 0.05, and x + y + z + b = 1. M is Mn and / or Al. Q is selected from at least one of Zr, Mg, Ti, Te, Ca, Sr, Sb, Nb, Pb, V, Ge, Se, W, Mo, Zn, Ce, and Y. A is selected from at least one of F, Cl, and S.

[0007] In one possible embodiment, the high-speed ion conductor includes a metal lithium compound and / or a non-metal lithium compound.

[0008] In one possible embodiment, the single crystal cathode material is obtained by co-sintering a mixture including a first inner layer material and a second inner layer material. The residual alkali content on the particle surface of the first inner layer material is lower than the residual alkali content on the particle surface of the second inner layer material.

[0009] In one possible embodiment, F2 - F1 ≥ 0.6 μm.

[0010] In one possible embodiment, the metallic lithium oxide comprises at least one of lithium iron phosphate, lithium cobaltate, lithium nickel cobalt manganeseate, lithium manganeseate, lithium nickelate, lithium titanate, lithium titanium aluminum phosphate, lithium lanthanum titanate, lithium lanthanum tantalate, lithium germanium aluminum phosphate, lithium lanthanum zirconium oxide, lithium lanthanum zirconium aluminum oxide, niobium-doped lithium lanthanum zirconium oxide, and tantalum-doped lithium lanthanum zirconium oxide, and the nonmetallic lithium oxide comprises at least one of lithium boro compounds, lithium sulfur compounds, and lithium phosphate compounds.

[0011] In one possible embodiment, the thickness of the coating layer is 5 to 100 nm.

[0012] In one possible embodiment, T1 ≥ 5 nm and T2-T1 ≥ 10 nm.

[0013] In one possible embodiment, T1 < 20 nm and 10 nm ≤ T2 < 100 nm.

[0014] In one possible embodiment, 8nm ≤ T1 < 15nm.

[0015] In one possible embodiment, 20nm ≤ T2 < 50nm.

[0016] In one possible embodiment,

number

[0017] In a second aspect, the embodiments of the present application provide a method for manufacturing the single-crystal cathode material described in the first aspect and any possible embodiment. A step of coating and sintering a mixture containing a first cathode material and a second cathode material to obtain the single crystal cathode material is included, The mass ratio between the first cathode material and the second cathode material is 2:3 to 3:2, the average particle size of the first cathode material is 1.0 to 2.0 μm, the average particle size of the second cathode material is 2.5 to 6.0 μm, and the difference between the residual alkali content on the surface of the second cathode material and the residual alkali content on the surface of the first cathode material is greater than 500 ppm. The molecular formulas of the first cathode material and the second cathode material are Li 1+a [Ni x Co y M z Q b O 2±c A d where 0 ≤ a < 0.20, 0.60 ≤ x < 1.0, 0 < y < 0.30, 0 < z < 0.30, 0 ≤ b < 0.20, c ≤ 0.02, 0 ≤ d ≤ 0.05, and x + y + z + b = 1. M is Mn and / or Al, Q is selected from at least one of Zr, Mg, Ti, Te, Ca, Sr, Sb, Nb, Pb, V, Ge, Se, W, Mo, Zn, Ce, and Y, and A is selected from at least one of F, Cl, and S.

[0018] In one possible embodiment, the first cathode material and the second cathode material are obtained by a method of sintering a first mixture containing a first precursor and a first lithium source under first conditions to obtain the first cathode material, and sintering a second mixture containing a second precursor and a second lithium source under second conditions to obtain the second cathode material. The molecular formulas of the first precursor and the second precursor are [Ni r Co s M t Q u TM, where 0.60 ≤ r < 1.0, 0 < s < 0.30, 0 < t < 0.30, 0 ≤ u < 0.20. M is Mn and / or Al, Q is selected from at least one of Zr, Mg, Ti, Te, Al, Ca, Sr, Sb, Nb, Pb, V, Ge, Se, W, Mo, Zn, Ce, and Y, and TM is CO3 2- and / or OH- selected from The first sintering temperature in the first condition and the second sintering temperature in the second condition are both selected from 750 to 980 °C, and the difference between the second lithium content per mole of the second precursor in the second mixture and the first lithium content per mole of the first precursor in the first mixture is 0.005 to 0.1.

[0019] In one possible embodiment, the molecular formula of the first precursor is [Ni r1 Co s1 M t1 Q’ u1 TM1, and the molecular formula of the second precursor is [Ni r2 Co s2 M t2 Q” u2 TM2, where 0.60 ≦ r1 < 10, 0 < s1 < 0.30, 0 < t1 < 0.30, 0 ≦ u1 < 0.20, 0.60 ≦ r2 < 10, 0 < s2 < 0.30, 0 < t2 < 0.30, 0 ≦ u2 < 0.20, and Q’ and Q” are each independently selected from at least one of Zr, Mg, Ti, Te, Al, Ca, Sr, Sb, Nb, Pb, V, Ge, Se, W, Mo, Zn, Ce, and Y, and TM1 and TM2 are each independently CO3 2- and / or OH - selected from.

[0020] In one possible embodiment, Q’ and Q” are the same and u1 = u2.

[0021] In one possible embodiment, the step of obtaining the single crystal cathode material by coating and sintering a mixture containing the first cathode material and the second cathode material is sintering the mixture at a temperature of 480 to 520 °C for 2 to 3 h to obtain an intermediate mixture, and coating and sintering the mixture of the intermediate mixture and the coating agent to obtain the single crystal cathode material.

[0022] In the third aspect, the embodiments of the present application provide a lithium ion battery, and the lithium ion battery includes The material includes the single-crystal cathode material described in the first embodiment and any possible embodiment.

[0023] One or more embodiments according to the examples of the present application have at least the following technical effects: First, the embodiment of the present application provides a single-crystal cathode material in which the particle size is matched to the thickness of the coating layer, by comprising a first particle with an average particle size of 1.0 to 2.0 μm and a second particle with an average particle size of 2.5 to 6.0 μm, and the average thickness of the coating layer also differs accordingly. This provides a single-crystal cathode material that is high-pressure, dense, and high-capacity.

[0024] Next, in the method for manufacturing a single-crystal cathode material provided by the embodiment of the present application, a single-crystal cathode material with a coating layer thickness matched to the particle size can be manufactured in one step using a first cathode material and a second cathode material with different residual alkali contents, making it possible to efficiently manufacture a high-pressure, dense, and high-capacity single-crystal cathode material. [Effects of the Invention]

[0025] Other features and advantages of the Application are described in the following specification, partially revealed, or understood by practicing the Application. The purposes and other advantages of the Application can be achieved and obtained by the configurations specifically shown in the description, claims and drawings. It should be understood that the above general description and the following detailed description are illustrative and explanatory and do not limit the Disclosure. [Brief explanation of the drawing]

[0026] To more clearly explain the embodiments of this application or the technical solutions in the prior art, the drawings necessary for describing the embodiments or the prior art will be briefly described below. However, the drawings in the following description are only a few of the embodiments described in this application, and it is clear that a person skilled in the art can obtain other drawings based on these drawings without expending any creative effort. [Figure 1]This is a schematic SEM (scanning electron microscope) diagram of the single-crystal cathode material in Example 1 according to the embodiments of the present invention. [Modes for carrying out the invention]

[0027] The technical solutions of this application will be clearly and completely described below with reference to the attached drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are only a part of the embodiments of this application, not all of them, and are for illustrative purposes only and should not be considered to limit the scope of this application. All other embodiments obtained by those skilled in the art without creative work based on the embodiments of this application shall be within the scope of this application. Embodiments for which specific conditions are not described shall be carried out under ordinary conditions or conditions suggested by the manufacturer. For reagents and equipment for which the manufacturer is not specified, common commercially available products shall be used.

[0028] In response to the conventional problem of a lack of single-crystal cathode materials that excel in both compaction and capacitance performance, the embodiment of the present invention provides a single-crystal cathode material that contains first particles with an average particle size of 1.0 to 2.0 μm and second particles with an average particle size of 2.5 to 6.0 μm, thereby providing excellent compaction performance. Furthermore, the single-crystal cathode material has a coating layer with a thickness approximately matched to the particle size, and the average thickness of the coating layer for larger particles is greater than the average thickness of the coating layer for smaller particles. Such differentiated coating significantly improves the capacitance of the single-crystal cathode material while avoiding a significant decrease in cycle performance due to the larger thickness of the coating layer for smaller particles.

[0029] The single-crystal cathode material, its manufacturing method, and lithium-ion battery provided by the embodiments of this application will be described in detail below. Note that the embodiments described below are only a portion of the embodiments of this application, and not all of them. All other embodiments that a person skilled in the art could obtain without creative work based on the embodiments of this application shall be within the scope of protection of this application.

[0030] This application first provides a single-crystal cathode material, which has excellent compaction performance and capacity. Referring to FIG. 1, the single-crystal cathode material is a particulate substance.

[0031] The particulate substance includes an inner layer material and a coating layer coated on the surface of the inner layer material.

[0032] The coating layer includes a fast ion conductor. The coating layer may further include an oxide of a metal element other than lithium in the fast ion conductor. For example, when the fast ion conductor is lithium cobalt oxide, cobalt hydroxide is also included in the coating layer. The fast ion conductor may include a metal lithium compound and / or a non-metal lithium compound.

[0033] The molecular formula of the inner layer material is Li 1+a [Ni x Co y M z Q b O 2±c A d where 0 ≦ a < 0.20, 0.60 ≦ x < 1.0, 0 < y < 0.30, 0 < z < 0.30, 0 ≦ b < 0.20, c ≦ 0.02, 0 ≦ d ≦ 0.05, and x + y + z + b = 1, M is Mn and / or Al, Q is selected from at least one of Zr, Mg, Ti, Te, Ca, Sr, Sb, Nb, Pb, V, Ge, Se, W, Mo, Zn, Ce, and Y, and A is selected from at least one of F, Cl, and S.

[0034] The particulate substance includes a first particle with an average particle size of 1.0 to 2.0 μm and a second particle with an average particle size of 2.5 to 6.0 μm. Thereby, the compaction density of the single-crystal cathode provided by the examples of this application material is ensured (the compaction density is 3.24 g / cm 3 or more).

[0035] Furthermore, the particulate substance is obtained by co-sintering a mixture including a first inner layer material and a second inner layer material. The mixture further includes a coating agent. The molecular formulas of the first inner layer material and the second inner layer material are Li 1+a[Ni x Co y M z Q b O 2±c A d where 0 ≦ a < 0.20, 0.60 ≦ x < 1.0, 0 < y < 0.30, 0 < z < 0.30, 0 ≦ b < 0.20, c ≦ 0.02, 0 ≦ d ≦ 0.05, and x + y + z + b = 1; M is Mn and / or Al; Q is selected from at least one of Zr, Mg, Ti, Te, Ca, Sr, Sb, Nb, Pb, V, Ge, Se, W, Mo, Zn, Ce, and Y; and A is selected from at least one of F, Cl, and S.

[0036] The purpose of co-sintering the mixture of the first inner layer material and the second inner layer material is actually to achieve the coating of the first inner layer material and the second inner layer material. Since the thickness of the coating layer is at the nanolevel and has little effect on the particle size of the particulate matter, the particulate matter of the first inner layer material has the same average particle size as the first particles, both being 1.0 - 2.0 μm, and the particulate matter of the second inner layer material has the same average particle size as the second particles, both being 2.5 - 6.0 μm.

[0037] The residual alkali content on the surface of the first inner layer material is lower than that on the surface of the second inner layer material, thereby forming coating layers with different thicknesses during the sintering of the mixture.

[0038] Furthermore, the specific surface area and average particle size of each of the first particles and the second particles satisfy the following relational expression.

Equation

[0039] In the above relational expression, the preset coefficient is consistent with the mass ratio of the mixing of the inner layer materials (i.e., the first inner layer material and the second inner layer material) in the manufacturing process, for example, the mixing of two cathode materials Mass ratioIf the ratio is 1:1, then m is 0.5. For example, a mixture of two types of positive electrode materials. Mass ratio If the ratio is 2:3, then m = 0.4.

[0040] Furthermore, the single-crystal cathode material provided by the embodiment of this application has the characteristic that the thickness of the coating layer is approximately matched to the particle size. The average thickness T1 of the coating layer of the first particles is smaller than the average thickness T2 of the coating layer of the second particles. In this way, the problem of a significant decrease in cycle performance due to the high thickness of the coating layer of particulate matter with small particle size can be avoided.

[0041] In the embodiments of this application, the first particles and the second particles are particles obtained by sieving. The sieving of the first and second particles will be described in detail below.

[0042] First, the target particle size of the particulate matter of the first and second particles is determined, and the target particle size values ​​of the first and second particles in the single-crystal cathode material are obtained by analyzing the particulate matter of the single-crystal cathode material with a particle size analyzer.

[0043] The target particle size is the median particle size D of the particulate matter in the first inner layer material. 50 , the median particle size D of the particulate matter of the second inner layer material 50 , and the target particle size in the single-crystal cathode material obtained after co-sintering of the two sizes of inner layer particles is determined by the mixing mass ratio of the first inner layer material and the second inner layer material (i.e., the predetermined coefficient mentioned above). That is, the target particle size in the single-crystal cathode material obtained after co-sintering of the two sizes of inner layer particles is determined according to the mixing ratio of the two sizes of inner layer particles. For example, if the mass ratio of the first inner layer material and the second inner layer material is 1:1, i.e., m=0.5, the target particle size of the first particle is D 25 Therefore, the target particle size for the second particle is D 75 For example, if the mass ratio of the first inner layer material to the second inner layer material is 2:3, i.e., m=0.4, then the target particle size of the first particle is D 20 Therefore, the target particle size for the second particle is D 80 Therefore, if the mass ratio of the first inner layer material to the second inner layer material is 3:2, i.e., m=0.6, then the target particle size of the first particle is D30 Therefore, the target particle size for the second particle is D 70 That is the case.

[0044] After determining the target particle size of the first particle and the target particle size of the second particle using the method described above, the target particle size of the single-crystal cathode material can be measured using a particle size analyzer. The measured target particle size values ​​are the target particle size of the first particle and the target particle size of the second particle, respectively.

[0045] A sieve can be selected based on the target particle size, and a single-crystal cathode material with a mass of 10 g can be sieved to obtain first and second particles. Next, we will explain using the example where the mass ratio of the first inner layer material to the second inner layer material is 1:1.

[0046] Based on the target particle size, select at least two sieves with different mesh counts. First, use the sieve with the smaller mesh count to sieve the single-crystal cathode material and obtain the unsieved material. Next, use the other sieve to sift through the unsieved material and take the sieved material to obtain particulate matter containing particles of the target particle size. For example, first, sieve the particulate matter of the single-crystal cathode material using a 4500-mesh sieve (particle size approximately 2.8 ± 0.5 μm) and take the unsieved material. Then, sieve through a 5500-mesh sieve (particle size approximately 2.3 ± 0.5 μm), and the sieved material obtained at this stage becomes the first particle.

[0047] Similarly, first, the particulate matter of the single-crystal cathode material is sieved using an 1800-mesh sieve (with a particle size of approximately 7.2 ± 0.5 μm), and the material that does not pass through the sieve is removed. Then, the material that does not pass through the sieve is sieved again using a 2200-mesh sieve (with a particle size of approximately 5.9 ± 0.5 μm), and the material obtained at this stage becomes the second set of particles.

[0048] The sieving and selection methods for the first and second particles corresponding to the mixing ratio of the first and second inner layer materials are consistent with the previously mentioned example and will not be explained again here.

[0049] After sieving to obtain the first and second particles, sampling can be performed and measured using SEM imaging. At least three samples were taken for each of the first and second particles. When imaging each sample, the electron microscope lens was moved at a scanning rate of 2000x to capture at least three observation areas. The particle sizes of 100 particulate matter particles were randomly measured in the captured SEM images, and the average value was calculated.

[0050] The particle size of each particle was calculated by measuring the length of the straight line between the two furthest points on the particulate matter in the captured image, and the length of a perpendicular line that is perpendicular to that line and passes through its midpoint. The average of the perpendicular line length and the aforementioned straight line length was then used as the particle size of the particulate matter. Here, the endpoints of the perpendicular line are the edges of the particulate matter.

[0051] Furthermore, the measurement of the coating layer thickness will be explained below.

[0052] Samples for TEM imaging were prepared by sampling from the previously sieved first and second particles, respectively. Next, the thickness of the coating layer of at least 50 particles was randomly photographed and measured at a scanning rate of 20,000x by moving the lens. This yielded the coating layer thickness of at least 30 particulate matter particles, and their average value was determined as the average coating layer thickness of the aforementioned first or second particles. The coating layer thickness of each particulate matter particle was determined by measuring at least three different locations on the same particulate matter and calculating the average value. A Nano Measurer, for example, can be used as a measuring tool.

[0053] Furthermore, because single-crystal cathode materials have a very high tendency to aggregate, the average particle size measured after sieving the first and second particles in the embodiment of this application can more accurately reflect the size distribution of the particulate matter of the single-crystal cathode material compared to the particle size value measured directly with a particle size analyzer.

[0054] Furthermore, since the particle size distribution of particulate matter exhibits characteristics of a normal distribution or a similar normal distribution, the first particles obtained by sieving the first and second particles according to their respective target particle sizes contain a small amount of sintered product corresponding to the second inner layer material, and the second particles also contain a small amount of sintered product corresponding to the first inner layer material.

[0055] Nevertheless, the majority of the particulate matter in the first particles (at least 85% or more) is still single-crystal cathode material with a thin coating layer obtained from the first inner layer material with a low residual alkali content on the surface. Similarly, the majority of the second particles (at least 85% or more) is still single-crystal cathode material with a thick coating layer obtained from the second inner layer material with a high residual alkali content on the surface. Therefore, even if the average thickness of the coating layers of the first and second particles is determined after this sieving, it is still possible to relatively accurately reflect the characteristic that the thickness of the coating layers of the cathode material corresponding to the first inner layer material and the cathode material corresponding to the second inner layer material in the single-crystal cathode material differ, and to relatively accurately reflect the specific circumstances of this difference.

[0056] In some embodiments, a>0, b>0, and c>0.

[0057] In some examples, F2-F1 ≥ 0.6 μm.

[0058] In some examples, 1.0 μm <F2-F1<2.5μmである。

[0059] The above-mentioned metallic lithium oxides include at least one of lithium iron phosphate, lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium nickel oxide, lithium titanate, lithium titanium aluminum phosphate, lithium lanthanum titanate, lithium lanthanum tantalate, lithium germanium aluminum phosphate, lithium lanthanum zirconium oxide, lithium lanthanum zirconium aluminum oxide, niobium-doped lithium lanthanum zirconium oxide, and tantalum-doped lithium lanthanum zirconium oxide. The non-metallic lithium oxides include at least one of lithium boro compounds, lithium sulfur compounds, and lithium phosphate compounds.

[0060] Materials doped with a certain element in the above-mentioned metallic lithium and / or nonmetallic lithium indicate that the content of that element relative to other major elements in the material is trace. For example, niobium-doped lithium lanthanum zirconium oxide indicates that the content of lithium, lanthanum, and zirconium in the oxide is relatively high, while the relative content of niobium is low.

[0061] In some examples, the metallic lithium oxide consists of at least one of lithium iron phosphate, lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium nickel oxide, lithium titanate, lithium titanium aluminum phosphate, lithium lanthanum titanate, lithium lanthanum tantalate, lithium germanium aluminum phosphate, lithium lanthanum zirconium oxide, lithium lanthanum zirconium aluminum oxide, niobium-doped lithium lanthanum zirconium oxide, and tantalum-doped lithium lanthanum zirconium oxide. The nonmetallic lithium oxide consists of at least one of lithium boro compounds, lithium sulfur compounds, and lithium phosphate compounds.

[0062] Furthermore, in this single-crystal cathode material, the thickness of the particulate matter coating layer is 5 to 100 nm.

[0063] In some examples, the average thickness T1 of the coating layer of the first particles is ≥ 5 nm, and the difference between the average thickness T2 of the coating layer of the second particles and T1 is T2-T1 ≥ 10 nm.

[0064] In some examples, T1 < 20 nm and 10 nm ≤ T2 < 100 nm.

[0065] In some examples, 8nm ≤ T1 < 15nm.

[0066] In some examples, 20nm ≤ T2 < 50nm.

[0067] Furthermore, the method for manufacturing the single-crystal cathode material described above will be explained below. The method includes at least the following steps.

[0068] A mixture containing the first cathode material and the second cathode material is coated and sintered to obtain the aforementioned single-crystal cathode material.

[0069] The mass ratio between the first positive electrode material and the second positive electrode material in the aforementioned mixture is 2:3 to 3:2. The average particle size of the first positive electrode material is 1.0 to 2.0 μm, and the average particle size of the second positive electrode material is 2.5 to 6.0 μm.

[0070] The above mixture may further contain a coating agent such that the coating layer on the surface of the particulate matter of the single-crystal cathode material contains a high-speed ion conductor.

[0071] The average particle sizes of the first and second positive electrode materials are obtained by the following two embodiments. (1) Obtained by directly measuring each particle size using a particle size analyzer. (ii) It can be obtained by the aforementioned method of sampling, taking SEM images, and measuring.

[0072] Similarly, since the single crystal cathode material is prone to aggregation, in order to avoid the inaccuracy of the average particle size obtained by the particle size analyzer, in the embodiments of the present application, the measurement method of the average particle size of the first cathode material and the second cathode material is preferably (ii).

[0073] The difference between the residual alkali content on the surface of the second cathode material and the residual alkali content on the surface of the first cathode material is greater than 500 ppm.

[0074] The molecular formulas of the first cathode material and the second cathode material are Li 1+a [Ni x Co y M z Q b O 2±c A d where 0 ≤ a < 0.20, 0.60 ≤ x < 1.0, 0 < y < 0.30, 0 < z < 0.30, 0 ≤ b < 0.20, c ≤ 0.02, 0 ≤ d ≤ 0.05, and x + y + z + b = 1, M is Mn and / or Al, Q is selected from at least one of Zr, Mg, Ti, Te, Ca, Sr, Sb, Nb, Pb, V, Ge, Se, W, Mo, Zn, Ce and Y, and A is selected from at least one of F, Cl and S.

[0075] Specifically, the sintering temperature of the above coating sintering is selected from 750 to 980 °C.

[0076] In the embodiments of the present application, by adjusting the residual alkali content on the surface of the first cathode material (i.e., the aforementioned first inner layer material) and the residual alkali content on the surface of the second cathode material (i.e., the aforementioned second inner layer material) to be different, the adjustment of the thickness of the coating layer on the surface of the two sizes of cathode materials is realized. The residual alkali on the surface of the first cathode material and the residual alkali on the surface of the second cathode material mainly consist of Li2CO3 and LiOH.

[0077] The above residual alkali content is obtained by converting the measured Li2CO3 content h1 and LiOH content h2 to obtain the free lithium content. The conversion formula is (h1 * 2 / 73.88 + h2 / 23.94) * 6.941.

[0078] On the surface of the first positive electrode material, the Li₂CO₃ content is 500 - 3000 ppm, and the LiOH content is 5000 - 10000 ppm. On the surface of the second positive electrode material, the Li₂CO₃ content is 800 - 3500 ppm, and the LiOH content is 8000 - 18000 ppm.

[0079] Furthermore, the following provides embodiments for manufacturing the first positive electrode material and the second positive electrode material. Sinter a first mixture containing a first precursor and a first lithium source under first conditions to obtain a first positive electrode material. Sinter a second mixture containing a second precursor and a second lithium source under second conditions to obtain a second positive electrode material.

[0080] The molecular formulas of the first precursor and the second precursor are [Ni r Co s M t Q u TM, where 0.60 ≤ r < 1 . 0, 0 < s < 0.30, 0 < t < 0.30, 0 ≤ u < 0.20, and Q is selected from at least one of Zr, Mg, Ti, Te, Al, Ca, Sr, Sb, Nb, Pb, V, Ge, Se, W, Mo, Zn, Ce, and Y, and TM is selected from CO₃ 2- and / or OH - selected from.

[0081] The above first mixture may contain a first dopant. Similarly, the second mixture may contain a second dopant. The amounts of the first dopant and the second dopant may be the same or different.

[0082] The doping elements corresponding to the first dopant and the second dopant may be the same or different. The specific addition amounts and types (i.e., doping elements) are respectively set corresponding to the doping elements in the first precursor and the first positive electrode material, and the doping elements in the second precursor and the second positive electrode material.

[0083] In order to make the difference between the residual alkali content on the surface of the second cathode material and the residual alkali content on the surface of the first cathode material 500 ppm, the first sintering temperature in the first condition and the second sintering temperature in the second condition are both selected from 750 to 980°C, and the first sintering temperature is less than or equal to the second sintering temperature. The difference between the second sintering temperature and the first sintering temperature is set to be 20°C or more. On the other hand, the amount of lithium in the first mixture is set to be lower than the amount of lithium in the second mixture, and since the residual alkali content decreases as the sintering temperature increases, in the example where the first sintering temperature is lower than the second sintering temperature, the amount of lithium used when manufacturing the second cathode material should be increased so that the difference between the residual alkali content on the surface of the second cathode material and the residual alkali content on the surface of the first cathode material is 500 ppm or more. Furthermore, the difference between the amount of second lithium per mole of second precursor in the second mixture and the amount of first lithium per mole of first precursor in the first mixture is set to 0.005 to 0.1.

[0084] The molecular formulas of the first and second precursors described above may be the same or different. To achieve an average particle size of 1.0 to 2.0 μm for the first cathode material and an average particle size of 2.5 to 6.0 μm for the second cathode material, the corresponding adjustment methods include, but are not limited to, several embodiments described below.

[0085] (1) Use the same precursor and adjust the sintering temperature of each. The larger the temperature difference between the first sintering temperature and the second sintering temperature, the greater the difference between the average particle size of the first cathode material and the average particle size of the second cathode material.

[0086] In some examples, a first precursor and a second precursor having the same average particle size and less than or equal to 1.0 μm are sintered, respectively. The nickel content in the first precursor and the second precursor is the same, i.e., r1 = r2, and in this case, the sintering temperature of the first precursor is lower than that of the second precursor.

[0087] For example, to make the difference between the average particle size of the first cathode material and the average particle size of the second cathode material 0.5 to 4.5 μm, the difference is adjusted so that for every 4°C increase in the temperature difference, the difference between the average particle size of the second cathode material and the average particle size of the first cathode material increases by 0.1 μm, or If the difference between the average particle size of the first cathode material and the average particle size of the second cathode material is greater than 4.5 μm, the difference is adjusted so that for every 4°C increase in temperature, the difference between the average particle size of the second cathode material and the average particle size of the first cathode material increases by 0.1 μm. It should be understood that when calculating the temperature difference and the first and second sintering temperatures based on this, the calculated first and second sintering temperatures must be adaptively adjusted based on parameters such as lithium content.

[0088] As a result, the difference between the second sintering temperature and the first sintering temperature becomes 20°C or more. For example, if the average particle size of the first and second precursors is the same, and both are 3.5 μm, then to make the average particle size of the first cathode material 1.5 μm lower than that of the second cathode material, and to make the second sintering temperature 50°C higher than that of the first sintering temperature, in this case, the first sintering temperature can be set to 870°C and the second sintering temperature to 920°C. In this case, the molecular formulas of the first and second precursors are the same.

[0089] (ii) Prepare the precursor by bringing it to a similar sintering temperature. In this embodiment, the average particle size of the first cathode material is set to 1.0 to 2.0 μm and the average particle size of the second cathode material is set to 2.5 to 6.0 μm by adjusting the types of elements and / or atomic exponents in the precursors, which have similar average particle sizes. In this case, the molecular formula of the first precursor is [Ni r1 Co s1 M t1 Q' u1 The second precursor is TM1, and its molecular formula is [Ni r2 Co s2 M t2 Q" u2 It is TM2. Here, 0.60 ≤ r1 < 10, 0 <s1<0.30、0<t1<0.30、0≦u1<0.20である。 0.60 ≤ r² < 10, 0 <s2<0.30、0<t2<0.30、0≦u2<0.20である。 Q' and Q'' are each independently selected from at least one of the following: Zr, Mg, Ti, Te, Al, Ca, Sr, Sb, Nb, Pb, V, Ge, Se, W, Mo, Zn, Ce, and Y.

[0090] TM1 and TM2 each independently emit CO3 2- and / or OH - They are selected from among them.

[0091] For example, under conditions where the second sintering temperature and the first sintering temperature are the same, or the temperature difference is 30°C or less, by adjusting the nickel content in the first and second precursors to be different, and / or the doping element content and / or type to be different, the average particle size of the first cathode material can be made 1.0 to 2.0 μm and the average particle size of the second cathode material 2.5 to 6.0 μm. Specifically, the Ni content r1 in the first precursor may be smaller than the Ni content r2 in the second precursor, and for every approximately 0.1 increase in the difference between r2 and r1 (e.g., 0.05 to 0.12), the difference between the first and second sintering temperatures may decrease by 50°C (at which point the first sintering temperature is greater than the second sintering temperature). By making such adjustments, first and second cathode materials with different nickel content can be obtained at similar sintering temperatures. Alternatively, The doping elements in the first precursor include at least one of W, Mo, and Mg, but not at least one of Ce, Zr, Sr, and Nb, so as to increase the first sintering temperature. Simultaneously, the doping elements in the second precursor include at least one of Ce, Zr, Sr, and Nb, but not at least one of W, Mo, and Mg, so as to decrease the second sintering temperature. Furthermore, the relative molar content of the doping elements in each precursor can be adjusted accordingly. By making these adjustments, first and second cathode materials can be obtained at similar sintering temperatures from first and second precursors with different nickel content.

[0092] To further improve the uniformity of the coating layer and to make the thickness of the coating layer approximately the same at each location on the particulate matter of the single-crystal cathode material, in some examples, the mixture can be sintered for a short time at a low temperature to redistribute the residual alkali on the surface of the particulate matter of the first cathode material and the second cathode material in a molten state. In this way, the residual alkali in the molten state will exhibit a state in which it more uniformly coats the surface of the particulate matter. That is, the mixture is sintered for 2 to 3 hours under temperature conditions of 480 to 520°C to obtain an intermediate mixture. Next, the mixture of the intermediate mixture and the coating agent is coated and sintered to obtain the aforementioned single-crystal cathode material.

[0093] In the embodiments of this application, the subscripts in the molecular formulas are atomic indices and are used to indicate the relative molar content between corresponding atoms in the molecule. For example, the precursor [Ni r Co s M t Q u In TM, r, s, t, and u are all atomic exponents, meaning that r, s, t, and u represent the relative molar content of Ni, Co, M, and doped element Q in the molecule, respectively. For example, r represents the molar ratio of Ni in the precursor.

[0094] The present invention further provides another method for manufacturing the above single-crystal cathode material. The method includes the step of coating and sintering the first cathode material and the second cathode material respectively, mixing the obtained coated and sintered products to obtain a single-crystal cathode material. The mass ratio between the first cathode material and the second cathode material is 2:3 to 3:2. The average particle size of the first cathode material is 1.0 to 2.0 μm, and the average particle size of the second cathode material is 2.5 to 6.0 μm. The difference between the residual alkali content on the surface of the second cathode material and the residual alkali content on the surface of the first cathode material is greater than 500 ppm. The molecular formulas of the first cathode material and the second cathode material are Li 1+a [Ni x Co y M z Q b O 2±c A d where 0 ≦ a < 0.20, 0.60 ≦ x < 1.0, 0 < y < 0.30, 0 < z < 0.30, 0 ≦ b < 0.20, c ≦ 0.02, 0 ≦ d ≦ 0.05, and x + y + z + b = 1. M is Mn and / or Al. Q is selected from at least one of Zr, Mg, Ti, Te, Ca, Sr, Sb, Nb, Pb, V, Ge, Se, W, Mo, Zn, Ce, and Y. A is selected from at least one of F, Cl, and S.

[0095] This method is substantially the same as the first method for manufacturing the single-crystal cathode material provided by the present invention. The difference is that the first method for manufacturing the single-crystal cathode material provided by the present invention is to coat and sinter a mixture containing the first cathode material and the second cathode material, while this method is to coat and sinter the first cathode material and the second cathode material respectively, and then mix the obtained coated and sintered products. This method can also obtain the single-crystal cathode material provided by the present invention.

[0096] Furthermore, the first cathode material and the second cathode material are obtained by a method of sintering a first mixture containing a first precursor and a first lithium source under first conditions to obtain the first cathode material, and sintering a second mixture containing a second precursor and a second lithium source under second conditions to obtain the second cathode material. The molecular formulas of the first precursor and the second precursor are [Ni r Cos M t Q u is a TM, where 0.60 ≦ r < 1.0, 0 < s < 0.30, 0 < t < 0.30, 0 ≦ u < 0.20, M is Mn and / or Al, Q is selected from at least one of Zr, Mg, Ti, Te, Al, Ca, Sr, Sb, Nb, Pb, V, Ge, Se, W, Mo, Zn, Ce, and Y, and TM is CO3 2- and / or OH - selected from, the first sintering temperature under the first condition and the second sintering temperature under the second condition are both selected from 750 to 980 °C, and the difference between the amount of the second lithium compounded per mole of the second precursor in the second mixture and the amount of the first lithium compounded per mole of the first precursor in the first mixture is 0.005 to 0.1.

[0097] Hereinafter, it will be described in detail by examples and comparative examples. (1) Production Example 1 In S1, the first precursors Ni 0.82 Co 0.1 Mn 0.08 , the first lithium source lithium hydroxide, and the first dopant SrO were sintered at a first sintering temperature of 875 °C for 15 hours at an element molar ratio of Sr: M M = 0.02:1 to obtain a first cathode material LiNi 0.8 Co 0.1 Mn 0.08 Sr 0.02 O2 with an average particle size of 1.51 μm. Here, M M refers to Ni, Co, and Mn. In S2, the second precursors Ni 0.82 Co 0.1 Mn 0.08 , the second lithium source lithium hydroxide, and the second dopant SrO were sintered at a second sintering temperature of 925 °C for 14 hours at a molar ratio of Sr: M M = 0.02:1 to obtain a second cathode material LiNi 0.8 Co 0.1 Mn 0.08 Sr 0.02 O2 with an average particle size of 3.12 μm. In step S3, a first cathode material and a second cathode material, having a mass ratio of 1:1, were mixed with 10,000 ppm of a coating agent Co(OH)2 to obtain a first mixture. In S4, the first mixture was coated and sintered at 670°C for 10 hours to obtain a single-crystal cathode material. The form of this single-crystal cathode material is particulate matter. The coating layer of the particulate matter is LiCoO2, and the inner layer material is LiNi 0.8 Co 0.1 Mn 0.08 Sr 0.02 It is O2.

[0098] Examples 2 to 5

[0099] Compared to Example 1, the main differences between Examples 2 to 5 are the different sintering temperatures and the differences in the residual alkali content on the surfaces of the first and second cathode materials. See Table 1 for details.

[0100] Examples 6 to 10 Compared to Example 1, the main differences between Examples 6 to 10 are the sintering temperature and the coating agent and residual alkali content. See Table 1 for details.

[0101] Examples 11-12 Compared to Example 1, the differences between Examples 11 and 12 are mainly the different sintering temperatures and the change in the first positive electrode material, which in turn results in correspondingly different residual alkali content on the surface.

[0102] Example 13 Compared to Example 1, the mass ratio between the first positive electrode material and the second positive electrode material in Example 13 is 2:3; see Table 1 for details.

[0103] Example 14 Compared to Example 1, in Example 14, after step S3, step S4 before Next, the first mixture was sintered for 2 hours under conditions of 500°C. See Table 1 for details.

[0104] Examples 15-16 Compared to Example 1, Example 15~ 16 The main differences between them are their respective sintering temperatures and the residual alkali content on the surfaces of the first and second cathode materials. See Table 1 for details.

[0105] Examples 17-19 Compared to Example 1, Examples 17 to 19 differ in their sintering temperatures, use different coating agents and coating amounts, and have different residual alkali content on the surfaces of the first and second cathode materials. See Table 1 for details.

[0106] Comparative Example 1 Comparative Example 1 differs from Example 1 in that the first positive electrode material and the second positive electrode material are coated before mixing. That is, steps S1 to S2 are the same as in Example 1. In step S3, the first cathode material and coating agent were mixed at 10,000 ppm, and the coating sintered at 670°C for 10 hours to obtain the first single-crystal cathode material. In step S4, the second cathode material and coating agent were mixed at 10,000 ppm, and the coating sintering was performed at 670°C for 10 hours to obtain the second single-crystal cathode material. Both the first and second single-crystal cathode materials have a coating layer containing LiCoO2 and an inner layer material containing LiNi 0.8 Co 0.1 Mn 0.08 Sr 0.02 It is particulate matter of O2. In step S5, the first single-crystal cathode material and the second single-crystal cathode material were mixed to obtain a single-crystal cathode material.

[0107] Comparative Example 2 Comparative Example 2 differs from Example 1 in that it does not include steps S3 to S4.

[0108] The relevant parameters for the first sintering temperature T1 and first sintering time t1 of the first cathode material, the second sintering temperature T2 and second sintering time t2 of the second cathode material, and the coating sintering temperature T3 and coating time t3 are summarized below; please refer to Tables 1 and 2. The coating sintering temperature is mainly determined by the coating agent. High-precision EDS (Energy-dispersive spectroscopy, energy-dispersive X-ray spectrometer) The molecular formulas of the inner layer materials are detected and summarized, and refer to Table 3.

[0109] [Table 1]

[0110] [Table 2]

[0111] [Table 3]

[0112] (2) Measurement The residual alkali content of the first and second cathode materials obtained in steps S1 and S2 in the examples and comparative examples was measured, and the D of the single-crystal cathode material obtained in step S4 was determined. 25 and D 75 The compaction density was also measured. Details are described below.

[0113] 1. For the measurement of residual alkalinity, 30 g (accuracy 0.0001 g) of the sample was weighed, placed in a 100 mL beaker, 50 mL of deionized water was added, magnetic beads were placed in the beaker, and it was sealed with plastic wrap. The beaker was placed in a magnetic stirrer and stirred for approximately 25 minutes, then removed, allowed to stand for 5 minutes, filtered using a glass funnel, and the filtered clarified liquid was used as the measurement solution. Refer to Table 3 for the corresponding measurement data.

[0114] Specifically, 0.1 M HCl was added to the sample solution at a rate of 0.5 ml / min, and a suitable mixture of LiOH and Li2CO3 dissolved at low concentrations in deionized water was titrated to obtain a reference voltage curve. In most cases, two different platforms were identified. The upper platform, with an endpoint V1 (in ml) between pH 8 and 9, was the equilibrium OH - It is H2O, and then equilibrium CO3 2- / HCO 3- The lower platform, which has an endpoint V2 (in ml units) between pH 4 and 6, is HCO3 3- / H2CO 3 The inflection points V1 between the first and second platforms and V2 after the second platform can be determined from the corresponding minimum values ​​of the derivative dpH / dVol of the pH curve. The second inflection point is generally obtained at a position close to pH 4.7. Next, the results are shown in the weight percentages of LiOH and Li2CO3 as shown in equations (a) and (b) below. Li2CO3wt%=73.89 / 1000*(V2-V1) Formula (a) LiOHwt%=23.95 / 1000*(2V1-V2) Formula (b)

[0115] 2. For particle size analysis, the single-crystal cathode material is analyzed using a particle size analyzer, D 25 and D 75 The first and second particles were separated accordingly. The corresponding analytical data is shown in the table. 4 See below.

[0116] 3. For the consolidation density, the pressure was maintained at 3T for 30s, thereby obtaining the corresponding consolidation density. See Table 4 for the corresponding analytical data.

[0117] [Table 4]

[0118] Furthermore, based on the target particle size values ​​for the first and second particles in Table 4, a sieve was determined to separate the first and second particles. The particles were then sieved according to the following embodiments to obtain the first and second particles for each example and comparative example.

[0119] In Example 1, the single-crystal cathode particles were first sieved using a 4500-mesh sieve (with a particle size of approximately 2.8 ± 0.5 μm), and the material below the sieve was collected. The material below the sieve was then sieved through a 5500-mesh sieve (with a particle size of approximately 2.3 ± 0.5 μm), and the resulting material above the sieve was designated as the first particle. Next, the single-crystal cathode particles were sieved using an 1800-mesh sieve (with a particle size of approximately 7.2 ± 0.5 μm), and the material below the sieve was collected. Furthermore, the material was sieved again using a 2200-mesh sieve (with a particle size of approximately 5.9 ± 0.5 μm), and the resulting material above the sieve was designated as the second set of particles.

[0120] In Example 2, single-crystal cathode particles were sieved using a 4500-mesh sieve (particle size approximately 2.8 ± 0.5 μm), and the material below the sieve was collected. The material below the sieve was then sieved through a 5500-mesh sieve (particle size approximately 2.3 ± 0.5 μm), and the resulting material above the sieve was designated as the first particle. Next, the single-crystal cathode particles were sieved using a 1500-mesh sieve (with a particle size of approximately 8.7 ± 0.5 μm), and the sieved material was collected. The sieved material was then passed through an 1800-mesh sieve (with a particle size of approximately 7.2 ± 0.5 μm), and the resulting sieved material was designated as the second set of particles.

[0121] In Example 3, the single-crystal cathode particles were first sieved using a 3400-mesh sieve (with a particle size of approximately 3.8 ± 0.5 μm), and the material below the sieve was collected. The material below the sieve was then sieved through a 3900-mesh sieve (with a particle size of approximately 3.3 ± 0.5 μm), and the resulting material above the sieve was designated as the first particle. Next, the single-crystal cathode particles were sieved using an 1100-mesh sieve (with a particle size of approximately 11.8 ± 0.5 μm), and the material below the sieve was collected. The material below the sieve was then sieved through a 1400-mesh sieve (with a particle size of approximately 9.3 ± 0.5 μm), and the resulting material above the sieve was designated as the second set of particles.

[0122] In Example 4, the same sieve selected in Example 1 was used.

[0123] In Example 5, the single-crystal cathode particles were first sieved using a 3400-mesh sieve (with a particle size of approximately 3.8 ± 0.5 μm), and the material below the sieve was collected. The material below the sieve was then sieved through a 3900-mesh sieve (with a particle size of approximately 3.3 ± 0.5 μm), and the resulting material above the sieve was designated as the first particle. Next, the single-crystal cathode particles were sieved using an 1800-mesh sieve (with a particle size of approximately 7.2 ± 0.5 μm), and the material below the sieve was collected. Furthermore, the material was sieved using a 2200-mesh sieve (with a particle size of approximately 5.9 ± 0.5 μm), and the resulting material above the sieve was designated as the second set of particles.

[0124] In Example 6, the single-crystal cathode particles were first sieved using a 3400-mesh sieve (with a particle size of approximately 3.8 ± 0.5 μm), and the material below the sieve was collected. The material below the sieve was then sieved through a 3900-mesh sieve (with a particle size of approximately 3.3 ± 0.5 μm), and the resulting material above the sieve was designated as the first particle. Next, the single-crystal cathode particles were sieved using a 1500-mesh sieve (with a particle size of approximately 8.7 ± 0.5 μm), and the material below the sieve was collected. The material below the sieve was then sieved through an 1800-mesh sieve (with a particle size of approximately 7.2 ± 0.5 μm), and the resulting material above the sieve was designated as the second set of particles.

[0125] In Example 7, the same sieve selected in Example 1 was used.

[0126] In Example 8, the single-crystal cathode particles were first sieved using a 4500-mesh sieve (with a particle size of approximately 2.8 ± 0.5 μm), and the material below the sieve was collected. The material below the sieve was then sieved through a 5500-mesh sieve (with a particle size of approximately 2.3 ± 0.5 μm), and the resulting material above the sieve was designated as the first particle. Next, the single-crystal cathode particles were sieved using a 1500-mesh sieve (with a particle size of approximately 8.7 ± 0.5 μm), and the sieved material was collected. The sieved material was then passed through an 1800-mesh sieve (with a particle size of approximately 7.2 ± 0.5 μm), and the resulting sieved material was designated as the second set of particles.

[0127] In Example 9, the same sieve selected in Example 1 was used.

[0128] In Example 10, the single-crystal cathode particles were first sieved using a 3400-mesh sieve (with a particle size of approximately 3.8 ± 0.5 μm), and the material below the sieve was collected. The material below the sieve was then sieved through a 3900-mesh sieve (with a particle size of approximately 3.3 ± 0.5 μm), and the resulting material above the sieve was designated as the first particle. Next, the single-crystal cathode particles were sieved using an 1800-mesh sieve (with a particle size of approximately 7.2 ± 0.5 μm), and the material below the sieve was collected. Furthermore, the material was sieved using a 2200-mesh sieve (with a particle size of approximately 5.9 ± 0.5 μm), and the resulting material above the sieve was designated as the second set of particles.

[0129] Examples 11 to 13 were carried out using the same sieve selected in Example 1 described above.

[0130] In Example 14, the single-crystal cathode particles were first sieved using a 3400-mesh sieve (with a particle size of approximately 3.8 ± 0.5 μm), and the material below the sieve was collected. The material below the sieve was then sieved through a 3900-mesh sieve (with a particle size of approximately 3.3 ± 0.5 μm), and the resulting material above the sieve was designated as the first particle. Next, the single-crystal cathode particles were sieved using an 1800-mesh sieve (with a particle size of approximately 7.2 ± 0.5 μm), and the material below the sieve was collected. Furthermore, the material was sieved through a 2200-mesh sieve (with a particle size of approximately 5.9 ± 0.5 μm), and the resulting material above the sieve was designated as the second particle.

[0131] Examples 15-16 and Comparative Example 1 were performed using the same sieve selected in Example 1 described above.

[0132] Furthermore, the average particle size, average thickness of the coating layer, and specific surface area were measured for the first and second sieved particles, respectively. The measured data can be found in Table 5.

[0133] 1) For specific surface area BET, approximately 5g of the sample was taken and placed in a long tube with a bubble. First, it was vacuum-treated at 200°C for 2 hours, and then N2 was passed through to adsorb gas. The amount of adsorbed material (N2) of the sample to be measured was determined according to the change in pressure or weight before and after adsorption, and the specific surface area B1 of the first particle and the specific surface area B2 of the second particle were obtained. 2) For the average particle size, the number of samples for both the first and second particles was set to three. The following analysis was performed on each sample. An SEM was taken at a rate of 2000, and three imaging areas were selected and photographed so that each sample corresponded to three SEM images. Then, 100 particulate matter particles were randomly selected from each SEM image, and the particle size of each particulate matter particle was measured. The average particle size of the particulate matter in each sample was calculated, and then the average particle size of the particulate matter in the three samples was calculated to determine the average particle size of the first particle and the average particle size of the second particle. 3) To determine the average thickness of the coating layer, the samples were weighed, dispersed, and then TEM imaging was performed. After randomly imaging and measuring the thickness of the coating layer of 50 particulate matter particles, the average value was calculated to determine the average thickness T1 of the first particle's coating layer and the average thickness T2 of the second particle's coating layer.

[0134] Based on the measurement data of the first and second particles, the relational equation

number

[0135] [Table 5]

[0136] By adjusting the lithium content so that the thickness of the coating layer on the surfaces of the first and second cathode materials differs, the difference in residual alkali content on the surfaces of the first and second cathode materials can be made to correspond to the difference in the average thickness of the coating layer. Combining Tables 1-2 and 4-5, it can be seen that different adjustments to residual alkali content were achieved by using different lithium content at the same cathode material and sintering temperature, and correspondingly, the average thickness of the coating layer on the first and second particles was adjusted to be different.

[0137] (iii) Manufacturing and testing of lithium-ion batteries To test the electrochemical performance of the cathode materials in the examples and comparative examples, the cathode materials were mounted in lithium-ion button batteries and their capacity was tested. Furthermore, the cathode materials were mounted in all batteries and their cycle performance was tested.

[0138] Specifically, at 25°C and under normal pressure (0.1 MPa), the positive electrode plate, lithium foil, separator, and electrolyte are assembled as a button cell in a glove box. On the positive electrode plate, the surface on the side where the positive electrode material is placed has an area of ​​1.54 cm². 2 The surface load is 15 mg / cm². 2 That is the case.

[0139] The test parameters were as follows: the button cell was charged at a constant current rate of 0.2C until the voltage reached the cutoff voltage (4.25V for nickel ratio 8 or higher, and 4.3V for nickel ratio 7). Next, under cutoff voltage conditions, it was charged at a constant voltage until the current fell below 0.05C. The charge capacity at this point was defined as the initial charge capacity. After that, it was left to stand for 5 minutes, and then discharged at a constant current rate of 0.2C until the voltage reached 2.5V. The discharge capacity at this point was defined as the initial discharge ratio capacity of the battery, i.e., the initial capacity.

[0140] Furthermore, a positive electrode material was coated onto the electrode plate, and graphite was used for the negative electrode. These positive and negative electrodes, along with a polyethylene separator and an electrolyte (the electrolyte is LiPF6, and the solvent is EC / DMC), constituted the entire battery. On the positive electrode plate, the surface on the side where the positive electrode material is placed has an area of 1.54cm 2 and The surface load is 15 mg / cm². 2 That is the case.

[0141] As test parameters, all batteries under a 1C rate charge / discharge condition under which charge / discharge cycles were performed. The ratio of the capacity in each cycle to the capacity in the first cycle was confirmed as the capacity retention rate, and this capacity retention rate was calculated after 300 cycles under 45°C conditions.

[0142] Refer to Table 6 of the test data above.

[0143] [Table 6]

[0144] As can be seen from Table 6, the cycle performance of the single-crystal cathode material in the examples is significantly improved. Referring to Table 1, the difference in residual alkali content on the surface of the first cathode material and the second cathode material in Example 3 is similar to the difference in residual alkali content on the surface of the first cathode material and the second cathode material in Example 5 and Comparative Example 1, respectively. Referring to Table 5, Examples 3 and 5 have higher capacity retention rates than Comparative Example 1. As can be seen from this, compared to the method in Comparative Example 1 in which single-crystal cathode material is obtained by mixing after coating each material, the method according to the examples of the present application can avoid the problem of uneven coating caused by the coating of single-crystal particles of similar size in an aggregated state, and especially in a state in which single-crystal particles are extremely prone to aggregation. For this reason, the capacity retention rates of Examples 3 and 5 are higher than that of Comparative Example 1.

[0145] It will be apparent to those skilled in the art that various modifications and alterations can be made to the present application without departing from its spirit and scope. Thus, if such modifications and alterations fall within the scope of the claims of the present application and the equivalent art, the present application is intended to include such modifications and alterations.

[0146] <Cross-reference of related applications> This application claims priority to the Chinese patent application filed with the China National Patent Office on October 26, 2023, with application number 202311408941.4 and title "Single Crystal Cathode Material and Method for Manufacturing the Same, Lithium-ion Battery," all of which are incorporated herein by reference.

Claims

1. A single-crystal cathode material, wherein the single-crystal cathode material is a particulate material, and the particulate material includes an inner layer material and a coating layer of the inner layer material. The particulate matter has an average particle size F. １ The first particles are 1.0 to 2.0 μm in size and the average particle size F ２ The first particle contains second particles measuring 2.5 to 6.0 μm, and the average thickness T of the coating layer of the first particle is... １ The average thickness T of the coating layer of the second particles is ２ Smaller, The coating layer contains a fast ion conductor, and the molecular formula of the inner layer material is Li １＋ａ [Ni ｘ Co ｙ M ｚ Q ｂ O ２±ｃ A ｄ where 0 ≦ a < 0.20, 0.60 ≦ x < 1.0, 0 < y < 0.30, 0 < z < 0.30, 0 ≦ b < 0.20, c ≦ 0.02, 0 ≦ d ≦ 0.05, and x + y + z + b = 1, M is Mn and / or Al, Q is selected from at least one of Zr, Mg, Ti, Te, Ca, Sr, Sb, Nb, Pb, V, Ge, Se, W, Mo, Zn, Ce, and Y, and A is a single crystal cathode material selected from at least one of F, Cl, and S.

2. The single-crystal cathode material according to claim 1, wherein the single-crystal cathode material is obtained by co-sintering a mixture containing a first inner layer material and a second inner layer material, and the residual alkali content on the particle surface of the first inner layer material is lower than the residual alkali content on the particle surface of the second inner layer material.

3. F ２ -F １ The single-crystal cathode material according to claim 1, wherein the thickness is ≥ 0.6 μm.

4. The single-crystal cathode material according to claim 1, wherein the thickness of the coating layer is 5 to 100 nm.

5. T1 ≥ 5 nm, and T ２ -T １ A single-crystal cathode material according to any one of claims 1 to 4, wherein the nm is ≥ 10 nm.

6. T １ <20 nm, 10 nm ≤ T ２ The single-crystal cathode material according to claim 5, wherein the wavelength is 100 nm.

7. 8 nm ≤ T １ <15 nm, 20 nm ≤ T ２ The single-crystal cathode material according to claim 5, wherein the nm is 50 nm. [Request Item 8] [Number 1] Let m be a predetermined coefficient, where 0.4 ≤ m ≤ 0.6, and B １ and B ２ The single-crystal cathode material according to claim 1, wherein is the specific surface area of ​​the first particle and the second particle, respectively.

9. A method for producing a single-crystal cathode material according to any one of claims 1 to 8, The process includes the step of coating and sintering a mixture containing a first positive electrode material and a second positive electrode material to obtain the single-crystal positive electrode material, The mass ratio between the first positive electrode material and the second positive electrode material is 2:3 to 3:2, the average particle size of the first positive electrode material is 1.0 to 2.0 μm, the average particle size of the second positive electrode material is 2.5 to 6.0 μm, and the difference between the residual alkali content on the surface of the second positive electrode material and the residual alkali content on the surface of the first positive electrode material is greater than 500 ppm. The molecular formulas of the first and second cathode materials are Li １＋ａ [Ni ｘ Co ｙ M ｚ Q ｂ ]O ２±ｃ A ｄ A method for producing a single-crystal cathode material wherein 0 ≤ a < 0.20, 0.60 ≤ x < 1.0, 0 < y < 0.30, 0 < z < 0.30, 0 ≤ b < 0.20, c ≤ 0.02, 0 ≤ d ≤ 0.05, and x + y + z + b = 1, M is Mn and / or Al, Q is selected from at least one of Zr, Mg, Ti, Te, Ca, Sr, Sb, Nb, Pb, V, Ge, Se, W, Mo, Zn, Ce and Y, and A is selected from at least one of F, Cl and S.

10. The first positive electrode material and the second positive electrode material are, The first positive electrode material is obtained by sintering a first mixture containing a first precursor and a first lithium source under first conditions, and then sintering a second mixture containing a second precursor and a second lithium source under second conditions. The molecular formulas of the first and second precursors are [Ni ｒ Co ｓ M ｔ Q ｕ ]TM is such that 0.60 ≤ r < 1.0, 0 < s < 0.30, 0 < t < 0.30, 0 ≤ u < 0.20, M is Mn and / or Al, Q is selected from at least one of Zr, Mg, Ti, Te, Al, Ca, Sr, Sb, Nb, Pb, V, Ge, Se, W, Mo, Zn, Ce and Y, and TM is CO ３ ２－ and / or OH － The first sintering temperature in the first condition and the second sintering temperature in the second condition are both selected from 750 to 980°C. The method according to claim 9, wherein the difference between the amount of second lithium per mole of the second precursor in the second mixture and the amount of first lithium per mole of the first precursor in the first mixture is 0.005 to 0.

1.

11. The step of obtaining the single-crystal cathode material is to coat and sinter a mixture containing a first cathode material and a second cathode material, The step of sintering the mixture under a temperature of 480 to 520°C for 2 to 3 hours to obtain an intermediate mixture, The method according to claim 9 or 10, comprising the step of coating and sintering the mixture of the intermediate mixture and the coating agent to obtain the single-crystal cathode material.

12. A method for producing a single-crystal cathode material according to any one of claims 1 to 8, The process includes the steps of coating and sintering a first positive electrode material and a second positive electrode material, mixing the resulting coated sintered products, and obtaining the single-crystal positive electrode material. The mass ratio between the first positive electrode material and the second positive electrode material is 2:3 to 3:2, the average particle size of the first positive electrode material is 1.0 to 2.0 μm, the average particle size of the second positive electrode material is 2.5 to 6.0 μm, and the difference between the residual alkali content on the surface of the second positive electrode material and the residual alkali content on the surface of the first positive electrode material is greater than 500 ppm. The molecular formulas of the first cathode material and the second cathode material are Li １＋ａ [Ni ｘ Co ｙ M ｚ Q ｂ ]O ２±ｃ A ｄ A method for producing a single-crystal cathode material wherein 0 ≤ a < 0.20, 0.60 ≤ x < 1.0, 0 < y < 0.30, 0 < z < 0.30, 0 ≤ b < 0.20, c ≤ 0.02, 0 ≤ d ≤ 0.05, and x + y + z + b = 1, M is Mn and / or Al, Q is selected from at least one of Zr, Mg, Ti, Te, Ca, Sr, Sb, Nb, Pb, V, Ge, Se, W, Mo, Zn, Ce and Y, and A is selected from at least one of F, Cl and S.

13. A lithium-ion battery comprising the single-crystal cathode material according to any one of claims 1 to 8.

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