A single-crystal positive electrode material, a preparation method and application thereof

Abstract

The application provides a single crystal positive electrode material and a preparation method and application thereof. The single crystal positive electrode material is a composite metal oxide containing at least lithium and nickel, and the molar ratio of nickel to lithium in the single crystal positive electrode material is 0.7-0.96; the single crystal size of the single crystal positive electrode material is a, 2 mu m <= a <= 8 mu m; in the X-ray diffraction pattern, the single crystal positive electrode material has a 104 peak, and the intensity of the 104 peak is b, 15 <= b / a <= 50. The single crystal positive electrode material has excellent specific capacity, compaction density and charge-discharge performance.

Description

Technical Field

[0001] This invention relates to a single-crystal cathode material, its preparation method, and its application, belonging to the field of secondary battery technology. Background Technology

[0002] In recent years, among various commercially available rechargeable chemical energy storage devices, lithium-ion batteries have attracted much attention since their introduction to the market due to their environmental friendliness and long service life, and have been widely used in mobile phones, laptops, electric vehicles, and other fields. Cathode materials are a crucial component of lithium-ion batteries, and their performance directly affects the overall performance of the battery. Among them, nickel-cobalt-manganese ternary cathode materials (NCM), especially high-nickel ternary materials, are considered the most promising candidates for next-generation lithium-ion battery cathode materials due to their high specific capacity.

[0003] However, in cathode materials, an increase in nickel content inevitably leads to a decrease in lithium content. A lower lithium content is detrimental to lithium-ion insertion / extraction in the cathode material, affecting the battery's charge / discharge performance. Therefore, to improve the lithium-ion insertion / extraction rate of high-nickel ternary materials and thus enhance the battery's charge / discharge performance, the single-crystal size of these materials is typically made smaller (less than 2 μm). However, a smaller size reduces the compaction density of the high-nickel ternary material.

[0004] Therefore, there is a need to provide a cathode material that combines excellent specific capacity, compaction density, and charge / discharge performance. Summary of the Invention

[0005] This invention provides a single-crystal cathode material that possesses excellent specific capacity, compaction density, and charge / discharge performance.

[0006] This invention provides a method for preparing a single-crystal cathode material. This method can prepare the above-mentioned single-crystal cathode material, and the preparation process is simple and suitable for widespread application.

[0007] The present invention provides a battery comprising the above-mentioned monocrystalline cathode material, thus exhibiting excellent cycle performance and energy density.

[0008] This invention provides a single-crystal cathode material, wherein the single-crystal cathode material is a composite metal oxide comprising at least lithium and nickel, and the molar ratio of nickel to lithium in the single-crystal cathode material is 0.7-0.96.

[0009] The single crystal size of the single-crystal cathode material is a, where 2μm≤a≤8μm;

[0010] In the X-ray diffraction pattern, the single-crystalline cathode material has a 104 peak, the intensity of the 104 peak is b, and 15 ≤ b / a ≤ 50.

[0011] The single-crystalline cathode material as described above, wherein 2.5 μm ≤ a ≤ 4 μm; and / or

[0012] 20 ≤ b / a ≤ 40.

[0013] The single-crystalline cathode material as described above, wherein 60 ≤ b ≤ 120.

[0014] The single-crystalline cathode material as described above, wherein the specific surface area of the single-crystalline cathode material < 0.7 m ,

[0023] / g.

[0015] The single-crystalline cathode material as described above, wherein the Dv50 of the single-crystalline cathode material is c, and 1.5 ≤ c / a ≤ 3.5.

[0016] The single-crystalline cathode material as described above, wherein the molecular formula of the single-crystalline cathode material is Li 1+a [Ni x Co y Mn z M1 b O2;

[0017] Wherein, 0.7 ≤ x < 1, 0 < y < 0.3, 0 < z < 0.3, -0.1 < a < 0.2, 0 < b < 0.2, and x + y + z + b = 1, and M1 is a doping element.

[0018] The present invention provides a preparation method of the single-crystalline cathode material as described above, which includes:

[0019] Successively performing a first calcination treatment and a second calcination treatment on a raw material system including a cathode material precursor source and a lithium source to obtain the single-crystalline cathode material;

[0020] Wherein, the cathode material precursor source at least includes a cathode material precursor;

[0021] Based on the total molar content of metal elements in the cathode material precursor source, the molar content of nickel element is 0.7 - 0.96;

[0022] In the first calcination treatment, the first calcination temperature T1 satisfies: T0 + 30°C ≤ T1 ≤ T0 +​​​​

[0024] T0 is the median temperature of the original calcination temperature of the cathode material precursor source.

[0025] The preparation method described above, wherein t1 is 10-18 h.

[0026] In the preparation method described above, T0+40℃≤T1≤T0+65℃, and t1 is 12-16h;

[0027] T0-85℃≤T2≤T0-60℃, t2=t1 / 2.

[0028] The present invention provides a battery comprising a single-crystal cathode material as described above.

[0029] The monocrystalline cathode material of the present invention, by specifically selecting the single crystal size of the high-nickel monocrystalline cathode material and the ratio of the single crystal size to the surface intensity of the 104 peak, can improve the compaction density and charge-discharge performance of the monocrystalline cathode material, thereby improving the energy density and cycle performance of the battery.

[0030] The method for preparing the single-crystal cathode material of the present invention can prepare the above-mentioned single-crystal cathode material, and the preparation method is simple to operate and suitable for widespread application.

[0031] The battery of the present invention, having included the above-mentioned monocrystalline cathode material, has excellent cycle performance and energy density. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the accompanying drawings used in the description of the embodiments of the present invention or related technologies are briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a SEM image of the single-crystal cathode material in Example 2 of the present invention;

[0034] Figure 2 This is a SEM image of the single-crystal cathode material in Example 3 of the present invention;

[0035] Figure 3 This is a SEM image of the single-crystal cathode material in Example 7 of the present invention;

[0036] Figure 4 The XRD pattern of the single-crystal cathode material in Example 2 of this invention;

[0037] Figure 5The XRD pattern of the single-crystal cathode material in Example 3 of this invention;

[0038] Figure 6 The image shows the XRD pattern of the single-crystal cathode material in Example 7 of this invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0040] The first aspect of the present invention provides a single-crystal cathode material, wherein the single-crystal cathode material is a composite metal oxide comprising at least lithium and nickel, and the molar ratio of nickel to lithium in the single-crystal cathode material is 0.7-0.96;

[0041] The single-crystal size of the single-crystal cathode material is a, where 2μm≤a≤8μm;

[0042] In the X-ray diffraction pattern, the single-crystal cathode material has a 104 peak with an intensity of b, and 15 ≤ b / a ≤ 50.

[0043] The single-crystal cathode material of the present invention is a composite metal oxide comprising at least lithium and nickel. Exemplarily, the single-crystal cathode material of the present invention can be a composite metal oxide comprising lithium and nickel, or a composite metal oxide comprising lithium, nickel, manganese, and cobalt.

[0044] The single-crystal size of a single-crystal cathode material refers to the average particle size of the primary particles within the material. In some embodiments, SEM testing can be performed on the single-crystal cathode material to obtain an SEM image. The average particle size of the primary particles in the single-crystal cathode material can then be determined from the SEM image, thus yielding the single-crystal size of the single-crystal cathode material. In a specific embodiment, the SEM image of the single-crystal cathode material is magnified to 2000x. 300 test points can be selected from the SEM image, and the average particle size of each of the 300 primary particles can be measured (the average particle size of each primary particle refers to the average size in two mutually perpendicular directions). The average value is then calculated to obtain the single-crystal size of the single-crystal cathode material.

[0045] The single crystal of the single-crystal cathode material of the present invention has a 104 peak with a 2θ of 44.3-44.5° in the XRD pattern.

[0046] While reducing the single-crystal size of monocrystalline cathode materials is beneficial for lithium-ion insertion / extraction, thus overcoming to some extent the cycle performance degradation caused by lithium-nickel mixing in high-nickel monocrystalline cathode materials, smaller single-crystal sizes also reduce the compaction density of the single-crystal cathode material, affecting the energy density of the battery. This application, however, further limits the matching of the 104 peak intensity and size of the single crystal under the premise of a large single-crystal size. This not only ensures the compaction density of the monocrystalline cathode material but also overcomes the problem of lithium-nickel mixing caused by increased nickel content. Therefore, the monocrystalline cathode material of this invention can possess excellent specific capacity, compaction density, and lithium-ion insertion / extraction rate, thereby improving the cycle performance and energy density of the battery.

[0047] In some embodiments of the present invention, when the single crystal size a of the single crystal cathode material satisfies: 2.5μm≤a≤4μm, the migration rate of lithium ions in the single crystal cathode material can be further improved while ensuring the compaction density of the single crystal cathode material, thereby improving the charge and discharge performance of the single crystal cathode material and thus improving the cycle performance of the battery.

[0048] In some embodiments of the present invention, when 20 ≤ b / a ≤ 40, the single crystal size of the single-crystal cathode material is more closely matched with the migration rate of lithium ions in the single-crystal cathode material, which can further improve the charge-discharge performance of the single-crystal cathode material, thereby improving the cycle performance of the battery. Furthermore, when 25 ≤ b / a ≤ 35, the battery exhibits even better cycle performance.

[0049] In some embodiments of the present invention, 60 ≤ b ≤ 120 can further improve the discharge performance of the single-crystal cathode material. Further, 75 ≤ b ≤ 100; even further, 80 ≤ b ≤ 95.

[0050] In some embodiments of the present invention, the specific surface area of ​​the single-crystal cathode material is <0.7m². 2 / g.

[0051] In this invention, the specific surface area of ​​a single-crystal cathode material refers to the total surface area per unit mass of single-crystal cathode material. This invention can use nitrogen adsorption to test the specific surface area of ​​single-crystal cathode materials. When single-crystal cathode materials with a specific surface area meeting the above range are used in batteries, they produce less gas, which helps improve battery safety performance.

[0052] In some implementations, the specific surface area of ​​the single-crystal cathode material is <0.55 m². 2 When the concentration of this single-crystal cathode material is / g, it can generate less gas when applied to batteries, thus further improving the safety performance of the batteries.

[0053] In some embodiments of the present invention, the Dv50 of the single-crystalline cathode material is c, and 1.5 ≤ c / a ≤ 3.5.

[0054] In the present invention, Dv50 refers to the size of 50% of the volume of the single-crystalline cathode material in the single-crystalline cathode material. When the Dv50 of the single-crystalline cathode material and the single-crystalline size of the single-crystalline cathode material satisfy the above relationship, it indicates that the dispersibility of the single-crystalline cathode material is relatively high (fewer agglomerated particles), which helps to improve the cycle performance of the battery. In some embodiments, when 1.8 ≤ c / a ≤ 2.5, the cycle performance of the battery can be further improved.

[0055] In the present invention, the types and contents of metal elements in the single-crystalline cathode material can be further limited in order to further improve the cycle performance and energy density of the battery. Exemplarily, in some embodiments of the present invention, the molecular formula of the single-crystalline cathode material is Li 1+a [Ni x Co y Mn z M1 b O2;

[0056] Wherein, 0.7 ≤ x < 1, 0 < y < 0.3, 0 < z < 0.3, -0.1 < a < 0.2, 0 < b < 0.2, and x + y + z + b = 1, and M1 is a doping element.

[0057] It can be understood that the single-crystalline cathode material of the present invention can be a composite metal oxide including lithium element, nickel element, cobalt element, manganese element and doping element.

[0058] The present invention does not make special limitations on the doping element. The doping element M1 can be 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. Further, when the doping element M1 is selected from at least one of Zr, Ti, Al, Sr, Sb, Nb, V, W, Mo, Ce and Y, the cycle performance and energy density of the battery can be further improved.

[0059] The second aspect of the present invention provides a preparation method of the above single-crystalline cathode material, including:

[0060] Performing a first calcination treatment and a second calcination treatment on a raw material system including a cathode material precursor and a lithium source in sequence to obtain a single-crystalline cathode material;

[0061] Wherein, based on the total molar content of metal elements in the cathode material precursor, the molar content of nickel element is 0.7 - 0.96;

[0062] In the first calcination process, the first calcination temperature T1 satisfies: T0+30℃≤T1≤T0+80℃, and the first calcination time is t1;

[0063] In the second calcination process, the second calcination temperature T2 satisfies: T0-100℃≤T2≤T0-50℃, and the second calcination time is t2, t1 / 2-1h≤t2≤t1 / 2+1h;

[0064] T0 is the median temperature of the initial calcination temperature of the cathode material precursor.

[0065] It is understood that the cathode material precursor source of the present invention includes at least a cathode material precursor, and may also include a compound containing a dopant element. When the raw material system also includes a compound containing a dopant element, a single-crystal cathode material containing a dopant element can be obtained. The present invention does not particularly limit the compound containing a dopant element; for example, it may be an oxide containing a dopant element and / or a hydroxide containing a dopant element.

[0066] In this invention, the initial calcination temperature of the cathode material precursor source refers to the calcination temperature typically used when calcining the cathode material precursor source and lithium source to prepare single-crystal cathode materials. The initial calcination temperature of the cathode material precursor source can be obtained by consulting existing literature. The median temperature of the initial calcination temperature of the cathode material precursor source refers to the temperature located in the middle among the initial calcination temperatures of the cathode material precursor source.

[0067] It is understandable that different cathode material precursor sources have different initial calcination temperatures. Typically, cathode material precursor sources can include 8-series, 9-series, 94-series, 96-series, and 7-series cathode material precursor sources.

[0068] In the 8-series cathode material precursor source, the molar percentage of nickel in the total metal elements is 0.8. This means that when the 8-series cathode material precursor source only includes the cathode material precursor, the molar content of nickel is 0.8 based on the total molar content of metal elements in the cathode material precursor; when the 8-series cathode material precursor source includes both the cathode material precursor and a compound containing doped elements, the molar content of nickel is 0.8 based on the total molar content of metal elements in the cathode material precursor source (the sum of the total molar content of metal elements in the cathode precursor and the molar content of doped elements).

[0069] In some embodiments, when the 8-series cathode material precursor source only includes a cathode material precursor, the cathode material precursor may include: a cathode material precursor with a molar percentage ratio of nickel, cobalt, and manganese of 80:10:10; a cathode material precursor with a molar percentage ratio of nickel, cobalt, and manganese of 80:5:15; a cathode material precursor with a molar percentage ratio of nickel, cobalt, and manganese of 80:15:5; or a cathode material precursor with a molar percentage ratio of nickel, cobalt, and aluminum of 80:18:2.

[0070] The definitions of 9-series cathode material precursor sources, 94-series cathode material precursor sources, 96-series cathode material precursor sources, and 7-series cathode material precursor sources can be referred to the definitions of 8-series cathode material precursor sources, respectively.

[0071] In some embodiments, when the 9-series cathode material precursor source only includes a cathode material precursor, the cathode material precursor may include: a cathode material precursor prepared with a molar percentage of nickel, cobalt, and manganese of 90:5:5; a cathode material precursor prepared with a molar percentage of nickel, cobalt, and manganese of 90:6:4; or a cathode material precursor prepared with a molar percentage of nickel, cobalt, and aluminum of 90:8:2.

[0072] When the 94 cathode material precursor source only includes cathode material precursors, the cathode material precursors may include: cathode material precursors prepared with a molar percentage of nickel, cobalt and manganese of 94:3:3; and cathode material precursors prepared with a molar percentage of nickel, cobalt and aluminum of 94:4:2.

[0073] When the 96 cathode material precursor source only includes cathode material precursors, the cathode material precursors may include: cathode material precursors prepared with a molar percentage of nickel, cobalt and manganese of 96:2:2; and cathode material precursors prepared with a molar percentage of nickel, cobalt and aluminum of 96:2:2.

[0074] When the 7-series cathode material precursor source only includes cathode material precursors, the cathode material precursors may include: cathode material precursors with a molar percentage ratio of nickel, cobalt, and manganese of 70:20:10; cathode material precursors with a molar percentage ratio of nickel, cobalt, and manganese of 70:15:15; and cathode material precursors with a molar percentage ratio of nickel, cobalt, and manganese of 70:10:20.

[0075] In this invention, the initial calcination temperature of the 8-series cathode material precursor source is 860±10℃, with a median temperature T0 of 860℃; the initial calcination temperature of the 9-series cathode material precursor source is 800±10℃, with a median temperature T0 of 800℃; the initial calcination temperature of the 94-series cathode material precursor source is 750±10℃, with a median temperature T0 of 750℃; the initial calcination temperature of the 96-series cathode material precursor is 710±10℃, with a median temperature T0 of 710℃; and the initial calcination temperature of the 7-series cathode material precursor is 900±10℃, with a median temperature T0 of 900℃.

[0076] In this invention, t1 / 2-1h≤t2≤t1 / 2+1h means that t1≥2h. t1 / 2+1h refers to half of the first calcination time plus one hour, and t1 / 2-1h refers to half of the first calcination time minus one hour. For example, if the first calcination time is 3h, then 0.5h≤t2≤2h; if the first calcination time is 240min, then 60min≤t2≤180min.

[0077] In this invention, during the first and second calcination processes, lithium elements in the lithium source combine with the cathode material precursor to obtain a single-crystal cathode material containing lithium. This invention first uses a higher temperature to perform a longer first calcination process on the raw material system including the cathode material precursor and the lithium source, which increases the single-crystal size of the single-crystal cathode material. Then, a lower temperature is used to perform a shorter second calcination process on the system after the first calcination, which controls the intensity of the 104 peak of the single-crystal cathode material and reduces lithium-nickel mixing, ensuring that the single-crystal size and the intensity of the 104 peak satisfy 15 ≤ b / a ≤ 50. The preparation method of this invention can produce the aforementioned single-crystal cathode material, and this method is simple to operate and suitable for widespread application.

[0078] In some embodiments of the present invention, the ratio of the total molar content of metal elements in the cathode material precursor source to the molar content of lithium elements in the lithium source can be 1:1.05.

[0079] This invention does not impose any particular limitation on the lithium source, as long as lithium can be provided. For example, the lithium source can be lithium hydroxide.

[0080] In some embodiments, the cathode material precursor and lithium hydroxide can be added to a high-speed mixer and mixed for 1 hour to obtain a raw material system; the raw material system is then placed in an atmosphere sintering furnace for a first calcination treatment and a second calcination treatment to obtain a single-crystal cathode material.

[0081] In some embodiments of the present invention, when t1 is 10-18h, it is easier to obtain single-crystal cathode materials with specific single-crystal sizes as described in the present invention.

[0082] Furthermore, when T0+40℃≤T1≤T0+65℃, t1 is 12-16h;

[0083] When T0-85℃≤T2≤T0-60℃ and t2=t1 / 2, a single-crystal cathode material with superior overall performance can be obtained.

[0084] A third aspect of the present invention provides a battery comprising the above-described monocrystalline cathode material.

[0085] In this invention, a cathode sheet can be prepared using the aforementioned monocrystalline cathode material, and then a battery can be prepared using the cathode sheet containing the aforementioned monocrystalline cathode material. The battery of this invention, because it includes the aforementioned monocrystalline cathode material, exhibits excellent cycle performance and energy density.

[0086] The technical solution of the present invention will be further explained and described below with reference to specific embodiments.

[0087] Example 1

[0088] The single-crystal cathode material of this embodiment is prepared by a method including the following steps:

[0089] The raw material system, including the cathode material precursor source and lithium hydroxide, was subjected to a first calcination treatment, a second calcination treatment, and an air jet milling treatment in sequence to obtain a single crystal cathode material. The molecular formula of the single crystal cathode material is shown in Table 1.

[0090] Among them, the cathode material precursor source includes the cathode material precursor diagram and the compound containing doped elements; the ratio of the total molar content of metal elements in the cathode material precursor source to the molar content of lithium elements in the lithium source is 1:1.05.

[0091] The molecular formula of the cathode material precursor is [Ni 0.82 Co 0.1 Mn 0.08 [(OH)2, the compound containing doped elements is SrO, and the ratio of the total molar percentage of metal elements in the positive electrode active material precursor to the molar percentage of Sr elements in SrO is 1:0.02.

[0092] In the first calcination treatment, the temperature was 900℃ and the time was 10h;

[0093] In the second calcination process, the temperature was 790℃ and the time was 5 hours.

[0094] In the airflow pulverization process, the grading frequency is 105 Hz, and the induced draft frequency is 50 Hz.

[0095] Example 2

[0096] The preparation method of the single-crystal cathode material in this embodiment is basically the same as that of the single-crystal cathode material in Example 1, except that:

[0097] In the first calcination treatment, the temperature was 915℃ and the time was 12 hours.

[0098] In the second calcination process, the temperature was 800℃ and the time was 7 hours.

[0099] Example 3

[0100] The preparation method of the single-crystal cathode material in this embodiment is basically the same as that of the single-crystal cathode material in Example 1, except that:

[0101] In the first calcination treatment, the temperature was 920℃ and the time was 14h.

[0102] In the second calcination process, the temperature was 805℃ and the time was 7 hours.

[0103] In the airflow pulverization process, the grading is performed at 30 Hz, and the induced draft is at 50 Hz.

[0104] Example 4

[0105] The preparation method of the single-crystal cathode material in this embodiment is basically the same as that of the single-crystal cathode material in Example 1, except that:

[0106] In the first calcination treatment, the temperature was 950℃ and the time was 18 hours.

[0107] In the second calcination process, the temperature was 760℃ and the time was 10h;

[0108] In the airflow pulverization process, the grading frequency is 27 Hz and the induced draft frequency is 50 Hz.

[0109] Example 5

[0110] The preparation method of the single-crystal cathode material in this embodiment is basically the same as that of the single-crystal cathode material in Example 1, except that:

[0111] In the first calcination treatment, the temperature was 935℃ and the time was 12h.

[0112] In the second calcination process, the temperature was 795℃ and the time was 7 hours.

[0113] In the air jet milling process, the grading is performed at 35 Hz, and the induced draft is at 50 Hz.

[0114] Example 6

[0115] The preparation method of the single-crystal cathode material in this embodiment is basically the same as that of the single-crystal cathode material in Example 1, except that:

[0116] The compound containing doped elements is MoO3, and the ratio of the total molar percentage of metal elements in the precursor source of the positive electrode active material to the molar percentage of Mo elements in MoO3 is 1:0.02.

[0117] In the first calcination treatment, the temperature was 925℃ and the time was 14 hours.

[0118] In the second calcination process, the temperature was 770℃ and the time was 6 hours.

[0119] In the air jet milling process, the grading is performed at 35 Hz, and the induced draft is at 50 Hz.

[0120] Example 7

[0121] The preparation method of the single-crystal cathode material in this embodiment is basically the same as that of the single-crystal cathode material in Example 6, except that:

[0122] In the first calcination treatment, the temperature was 920℃ and the time was 12h.

[0123] In the second calcination process, the temperature was 800℃ and the time was 6 hours.

[0124] In the air jet milling process, the grading is performed at 42 Hz, and the induced draft is at 50 Hz.

[0125] Example 8

[0126] The preparation method of the single-crystal cathode material in this embodiment is basically the same as that of the single-crystal cathode material in Example 6, except that:

[0127] In the first calcination treatment, the temperature was 920℃ and the time was 10h;

[0128] In the second calcination process, the temperature was 790℃ and the time was 6 hours.

[0129] In the air jet milling process, the grading is performed at 42 Hz, and the induced draft is at 50 Hz.

[0130] Example 9

[0131] The preparation method of the single-crystal cathode material in this embodiment is basically the same as that of the single-crystal cathode material in Example 6, except that:

[0132] In the first calcination treatment, the temperature was 940℃ and the time was 18h.

[0133] In the second calcination process, the temperature was 805℃ and the time was 10 hours.

[0134] In the airflow pulverization process, the grading is performed at 30 Hz, and the induced draft is at 50 Hz.

[0135] Example 10

[0136] The preparation method of the single-crystal cathode material in this embodiment is basically the same as that of the single-crystal cathode material in Example 6, except that:

[0137] In the first calcination treatment, the temperature was 925℃ and the time was 12h.

[0138] In the second calcination process, the temperature was 795℃ and the time was 5 hours.

[0139] In the air jet milling process, the grading is performed at 45 Hz, and the induced draft is at 50 Hz.

[0140] Example 11

[0141] The preparation method of the single-crystal cathode material in this embodiment is basically the same as that of the single-crystal cathode material in Example 1, except that:

[0142] The molecular formula of the cathode material precursor is [Ni 0.72 Co 0.2 Mn 0.08 [(OH)2, the compound containing doped elements is TiO2, and the ratio of the total molar percentage of metal elements in the positive electrode active material precursor to the molar percentage of Ti element in TiO2 is 1:0.02;

[0143] In the first calcination treatment, the temperature was 965℃ and the time was 16h.

[0144] In the second calcination process, the temperature was 840℃ and the time was 8 hours.

[0145] In the air jet milling process, the grading is performed at 38 Hz, and the induced draft is at 50 Hz.

[0146] Example 12

[0147] The preparation method of the single-crystal cathode material in this embodiment is basically the same as that of the single-crystal cathode material in Example 1, except that:

[0148] The molecular formula of the cathode material precursor is [Ni 0.97 Co 0.02 Mn 0.01 [(OH)2, the compound containing doped elements is Y2O3, and the ratio of the total molar percentage of metal elements in the positive electrode active material precursor to the molar percentage of Y element in Y2O3 is 1:0.01;

[0149] In the first calcination treatment, the temperature was 765℃ and the time was 16h.

[0150] In the second calcination process, the temperature was 640℃ and the time was 7 hours.

[0151] In the air jet milling process, the grading is performed at 35 Hz, and the induced draft is at 50 Hz.

[0152] Example 13

[0153] The preparation method of the single-crystal cathode material in this embodiment is basically the same as that of the single-crystal cathode material in Example 1, except that:

[0154] The molecular formula of the cathode material precursor is [Ni 0.82 Co 0.1 Mn 0.08 The compounds containing doped elements are WO3 and CeO2. The ratio of the total molar percentage of metal elements in the positive electrode active material precursor, the molar percentage of W in WO3, and the molar percentage of Ce in CeO2 is 1:0.01:0.01.

[0155] In the first calcination treatment, the temperature was 920℃ and the time was 11 hours;

[0156] In the second calcination process, the temperature was 795℃ and the time was 6.5h.

[0157] In the air jet milling process, the grading is performed at 42 Hz, and the induced draft is at 50 Hz.

[0158] Example 14

[0159] The preparation method of the single-crystal cathode material in this embodiment is basically the same as that of the single-crystal cathode material in Example 1, except that:

[0160] The molecular formula of the cathode material precursor is [Ni 0.82 Co 0.1 Mn 0.08 The compounds containing doped elements are MgO and ZrO2. The ratio of the total molar percentage of metal elements in the positive electrode active material precursor, the molar percentage of Mg in MgO, and the molar percentage of Zr in ZrO2 is 1:0.01:0.01.

[0161] In the first calcination treatment, the temperature was 930℃ and the time was 14h.

[0162] In the second calcination process, the temperature was 805℃ and the time was 8 hours.

[0163] In the air jet milling process, the grading is performed at 35 Hz, and the induced draft is at 50 Hz.

[0164] Example 15

[0165] The preparation method of the single-crystal cathode material in this embodiment is basically the same as that of the single-crystal cathode material in Example 2, except that:

[0166] In the airflow pulverization process, the grading is performed at 30 Hz, and the induced draft is at 50 Hz.

[0167] Comparative Example 1

[0168] The preparation method of the single-crystal cathode material in this comparative example is basically the same as that of the single-crystal cathode material in Example 1, except that:

[0169] In the first calcination treatment, the temperature was 945℃ and the time was 10h.

[0170] In the second calcination process, the temperature was 740℃ and the time was 5 hours.

[0171] In the airflow pulverization process, the grading frequency is 28 Hz, and the induced draft frequency is 50 Hz.

[0172] Comparative Example 2

[0173] The preparation method of the single-crystal cathode material in this comparative example is basically the same as that of the single-crystal cathode material in Example 1, except that:

[0174] In the first calcination treatment, the temperature was 960℃ and the time was 12h.

[0175] In the second calcination process, the temperature was 800℃ and the time was 6 hours.

[0176] In the airflow pulverization process, the grading frequency is 23 Hz, and the induced draft frequency is 50 Hz.

[0177] Comparative Example 3

[0178] The preparation method of the single-crystal cathode material in this comparative example is basically the same as that of the single-crystal cathode material in Example 1, except that:

[0179] In the first calcination treatment, the temperature was 900℃ and the time was 10h;

[0180] In the second calcination process, the temperature was 795℃ and the time was 8 hours.

[0181] In the airflow pulverization process, the grading frequency is 105 Hz, and the induced draft frequency is 50 Hz.

[0182] Comparative Example 4

[0183] The preparation method of the single-crystal cathode material in this comparative example is basically the same as that of the single-crystal cathode material in Example 1, except that:

[0184] The molecular formula of the cathode material precursor is [Ni0.51 Co 0.31 Mn 0.18 [(OH)2, the compound containing doped elements is TiO2, and the ratio of the total molar percentage of metal elements in the positive electrode active material precursor to the molar percentage of Ti element in TiO2 is 1:0.02;

[0185] In the first calcination treatment, the temperature was 985℃ and the time was 16h.

[0186] In the second calcination process, the temperature was 900℃ and the time was 9 hours.

[0187] In the airflow pulverization process, the grading frequency is 27 Hz and the induced draft frequency is 50 Hz.

[0188] Test case

[0189] Batteries were prepared using the single-crystal cathode materials from the examples and comparative examples. The battery preparation process included:

[0190] 1) Preparation of positive electrode sheet

[0191] The single-crystal cathode material, conductive carbon black, and binder polyvinylidene fluoride (PVDF) are thoroughly mixed in N-methylpyrrolidone solvent at a mass percentage ratio of 95:3:24 to obtain a cathode slurry. The cathode slurry is coated onto aluminum foil, and after drying and cold pressing, a cathode sheet containing a cathode active layer with a thickness of 100 μm is obtained.

[0192] 2) Preparation of negative electrode sheet

[0193] Artificial graphite (anode material), styrene-butadiene rubber (binder), and carboxymethyl cellulose (dispersant) are mixed in a mass percentage ratio of 96:2:2 and dispersed in deionized water to form a negative electrode slurry. The negative electrode slurry is coated onto copper foil, and after drying, cold pressing, and slitting, a negative electrode sheet containing a 120 μm thick negative electrode active layer is obtained.

[0194] 3) Assembly of lithium-ion batteries

[0195] The positive electrode sheet and separator from step 1) and the negative electrode sheet from step 2) are stacked in sequence and then wound to obtain an electrode assembly. The electrode assembly is placed in an outer packaging aluminum-plastic film, and after the moisture is removed at 80°C, the above electrolyte is injected. After encapsulation, formation, degassing and shaping, a lithium-ion battery is obtained.

[0196] The electrolyte includes ethylene carbonate (EC), ethyl methyl carbonate (EMC), and LiPF6. The volume ratio of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) is 3 / 7, and the mass percentage of LiPF6 is 12.5%.

[0197] Performance testing

[0198] 1. The single-crystal cathode materials in the examples and comparative examples were subjected to the following tests, and the test results are shown in Table 1;

[0199] 1) Single crystal size of single-crystal cathode material

[0200] Surface morphology images of the single-crystal cathode material were obtained using SEM. The SEM images of the single-crystal cathode material were magnified 2000 times. Figure 1 This is a SEM image of the single-crystal cathode material in Example 2 of the present invention;

[0201] Figure 2 This is a SEM image of the single-crystal cathode material in Example 3 of the present invention; Figure 3 This is a SEM image of the single-crystal cathode material in Example 7 of the present invention. From... Figure 1-3 It can be seen that the single-crystal cathode material has multiple single crystals. 300 test points were taken in the SEM image, and the average particle size of 300 primary particles was measured. The average value was calculated to obtain the single crystal size of the single-crystal cathode material.

[0202] 2) Peak intensity of 104

[0203] XRD was used to test the X-ray diffraction patterns of single-crystal cathode materials. Figure 4 The XRD pattern of the single-crystal cathode material in Example 2 of this invention; Figure 5 The XRD pattern of the single-crystal cathode material in Example 3 of this invention; Figure 6 This is the XRD pattern of the single-crystal cathode material in Example 7 of the present invention. According to... Figure 4-6 Obtain the intensity of the 104 peak of the single-crystal cathode material.

[0204] 3) Dv50

[0205] Using a laser diffraction particle size distribution measuring instrument (Malvern, Master Size 2000), the particle size distribution of the single-crystal cathode material was measured according to the particle size distribution laser diffraction method GB / T19077.1-2016, and then the average particle size corresponding to the median value of the volume distribution was obtained.

[0206] 4) BET

[0207] Take 5g of single-crystal cathode material sample and put it into a long tube with a bulb. First, vacuum it at 200℃ for 2h, and then pass N2 through it for gas adsorption. The amount of adsorbate molecules (N2) adsorbed by the single-crystal cathode material sample is determined according to the pressure or weight change before and after adsorption, so as to obtain the specific surface area of ​​the single-crystal cathode material.

[0208] 5) Compacted density

[0209] Using a compaction density meter, during the compression process at 5T pressure, as the single-crystal cathode material particles move and deform, larger voids are filled, the contact area between the single-crystal cathode material particles increases, generating attractive forces between atoms and enhancing the mechanical wedging effect between particles, thereby forming a compact with a certain density and strength. The compaction density of the single-crystal cathode material is obtained by testing the density of the formed compact.

[0210] 6) Specific capacity

[0211] The single-crystal cathode material, conductive carbon black, and binder polyvinylidene fluoride (PVDF) are thoroughly mixed in N-methylpyrrolidone solvent at a mass percentage ratio of 95:3:24 to obtain a cathode slurry. The cathode slurry is coated onto aluminum foil, and after drying and cold pressing, a cathode sheet containing a cathode active layer with a thickness of 100 μm is obtained.

[0212] At 25°C and atmospheric pressure (0.1 MPa), the positive electrode, separator, and lithium sheet are sequentially stacked in a coin cell to obtain an electrode assembly. The electrode assembly is then placed in an outer aluminum-plastic film, and an electrolyte is injected into the film to obtain a coin cell. The electrolyte includes ethylene carbonate (EC), ethyl methyl carbonate (EMC), and LiPF6. The volume ratio of ethylene carbonate (EC) to ethyl methyl carbonate (EMC) is 3 / 7, and the mass percentage of LiPF6 is 12.5%.

[0213] Charge the battery at a constant current rate of 0.2C until the voltage is the cutoff voltage (4.25V for 8-series, 9-series, 94-series, and 96-series cathode precursor systems, and 4.3V for 7-series cathode precursor systems). Then, charge the battery at a constant voltage rate until the current is less than 0.05C under the cutoff voltage condition. The charging capacity at this time is recorded as the first charge capacity. After resting for 5 minutes, discharge the battery at a constant current rate of 0.2C until the voltage is 2.5V. The discharge capacity at this time is recorded as the battery's first discharge specific capacity A, which is also the initial capacity.

[0214] 2. The following tests were performed on the batteries in the test examples, and the test results are shown in Table 1;

[0215] 1) Capacity retention rate

[0216] At 45°C, the lithium-ion battery in the test case was charged and discharged at 1C. After 300 cycles, the battery's post-cycle capacity Q2 and initial capacity Q1 were recorded. Capacity retention rate = Q2 / Q1 × 100%.

[0217] 2) Weight energy density

[0218] At 25°C, the lithium-ion battery was charged at a constant current of 1C to the cutoff voltage (the cutoff voltage for the 8-series cathode material precursor system, 9-series cathode material precursor system, 94-series cathode material precursor system, and 96-series cathode material precursor system is 4.25V, and the cutoff voltage for the 7-series cathode material precursor system is 4.3V), and then charged at a constant voltage under the cutoff voltage condition until the current is less than 0.05C, and then discharged at 0.5C to 2.8V to obtain the discharge energy E;

[0219] Using an analytical balance, the weight m of a lithium-ion battery is measured, and the gravimetric energy density W = E / m.

[0220] Table 1

[0221]

[0222] As can be seen from Table 1, the cathode material in the embodiments of the present invention has both excellent specific capacity and compaction density, and the battery prepared by the cathode material in the embodiments of the present invention has both excellent cycle performance and energy density.

[0223] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A single-crystal cathode material, characterized in that, The single-crystalline cathode material is a composite metal oxide comprising at least lithium and nickel elements, and in the single-crystalline cathode material, the molar ratio of nickel to lithium is 0.7 - 0.96; The single-crystalline size of the single-crystalline cathode material is a, 2μm ≤ a ≤ 8μm; the single-crystalline size of the single-crystalline cathode material is used to represent the average particle size of the primary particles in the single-crystalline cathode material; In the X-ray diffraction pattern, the single-crystalline cathode material has a 104 peak, the intensity of the 104 peak is b, 60 ≤ b ≤ 120, 15 ≤ b / a ≤ 50; The Dv50 of the single-crystalline cathode material is c, 1.5 ≤ c / a ≤ 3.

5.

2. The single-crystal cathode material according to claim 1, characterized in that, 2.5μm ≤ a ≤ 4μm; and / or, 20 ≤ b / a ≤ 40.

3. The single-crystal cathode material according to claim 1, characterized in that, The specific surface area of ​​the single-crystal cathode material is <0.7m². 2 / g.

4. The single-crystal cathode material according to any one of claims 1-3, characterized in that, The molecular formula of the single-crystal cathode material is Li. 1+a [Ni x Co y Mn z M1 b O2; Where 0.7 ≤ x < 1, 0 < y < 0.3, 0 < z < 0.3, -0.1 < a < 0.2, 0 < b < 0.2, and x + y + z + b = 1, and M1 is a doping element.

5. A method for preparing a single-crystal cathode material according to any one of claims 1-4, characterized in that, Comprising: The single-crystalline cathode material is obtained by successively performing a first calcination treatment and a second calcination treatment on a raw material system comprising a cathode material precursor source and a lithium source; Where the cathode material precursor source at least comprises a cathode material precursor; Based on the total molar content of metal elements in the cathode material precursor source, the molar content of nickel is 0.7 - 0.96; In the first calcination treatment, the first calcination temperature T1 satisfies: T0 + 30°C ≤ T1 ≤ T0 + 80°C, and the first calcination time is t1; In the second calcination treatment, the second calcination temperature T2 satisfies: T0 - 100°C ≤ T2 ≤ T0 - 50°C, the second calcination time is t2, t1 / 2 - 1h ≤ t2 ≤ t1 / 2 + 1h; T0 is the median temperature of the original calcination temperature of the cathode material precursor source.

6. The preparation method according to claim 5, characterized in that, t1 is 10 - 18h.

7. The preparation method according to claim 5 or 6, characterized in that, T0 + 40°C ≤ T1 ≤ T0 + 65°C, t1 is 12 - 16h; T0 - 85°C ≤ T2 ≤ T0 - 60°C, t2 = t1 / 2.

8. A battery, characterized in that, Comprising the single-crystalline cathode material according to any one of claims 1 - 4.

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