Coated modified high-nickel ternary positive electrode material, preparation method and lithium ion battery

Abstract

The invention provides a coated modified high-nickel ternary positive electrode material, a preparation method and a lithium ion battery, the coated modified high-nickel ternary positive electrode material comprises a high-nickel ternary matrix and a coating layer containing an oxide solid electrolyte, the coating layer is coated outside the high-nickel ternary matrix and accounts for 1%-3% of the mass of the high-nickel ternary matrix; the oxide solid electrolyte comprises Li < 3x > La < 2 / 3-x > TiO < 3 > (0 lt; x < = 0.16), Li < 7 > La < 3 > Zr < 2 > O < 12 >, Li < 1 + y > Al < y > Ti < 2-y > (PO < 4 >) < 3 > (0 lt; y < = 0.5); the ionic conductivity of the oxide solid electrolyte is greater than or equal to 1 * 10 <-4 > S / cm. The selected oxide solid electrolyte has high ionic conductivity and electronic insulativity, a rapid lithium ion transmission channel can be provided, interface side reaction can be inhibited, the rate capability and the cycling stability of the material can be remarkably improved, and when the oxide solid electrolyte forms a coating layer, the coating layer is not prone to deformation, and the service life of the material is prolonged. The interface bonding strength with a high-nickel ternary matrix can be improved through chemical bonding, the interface impedance can be remarkably reduced, and the dynamic performance of the material is improved.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a coated modified high-nickel ternary positive electrode material, a preparation method and a lithium ion battery. Background Art

[0002] As a core energy storage device, the rapid development of new energy vehicles, portable electronic devices and large-scale energy storage systems has put forward higher requirements on its energy density, cycle life and safety performance. x Co y M z O2 (x>0.8, x+y+z=1, M is at least one of Mn and Al) has become one of the key materials for improving battery energy density due to its high specific capacity (≥200mAh / g) and high operating voltage (3.6-4.3V). However, high-nickel ternary cathode materials are prone to rupture during cycling and have continuous side reactions with the electrolyte, seriously compromising the battery's cycle life and rate performance.

[0003] In order to solve the above problems, many practitioners and researchers have conducted many studies on high-nickel ternary positive electrode materials. The Chinese patent with publication number CN114824214A reported a multi-layer coated high-nickel ternary material. Although it can greatly improve the cycle performance, the multi-layer coating preparation process is complicated, and the improvement of the kinetic performance is not obvious. The Chinese patent with publication number CN108365183A reported a method for improving the structural stability of ternary materials by alumina coating, but the rate performance is poor, and the specific capacity at a 1C discharge rate is only 165mAh / g. The Chinese patent with publication number CN119503908A reported a composite solid electrolyte coated high-nickel ternary positive electrode material, but did not solve the problem of interfacial chemical compatibility, resulting in a capacity retention rate of less than 90% after 100 cycles. The Chinese patent with publication number CN111600014A reported that LATP was coated on LiNi by a liquid phase method. 0.88 Co 0.09 Mn 0.03 Although the method of treating the surface of O2 positive electrode materials has greatly improved the rate performance, it still requires high costs to achieve large-scale production.

[0004] Therefore, it is urgent to develop a modification strategy that takes into account interface stability, high ionic conductivity and structural integrity to break through the application bottleneck of high-nickel ternary materials in high-performance batteries. Summary of the Invention

[0005] The object of the present invention is to provide a coated modified high-nickel ternary positive electrode material, a preparation method and a lithium ion battery to solve the problems in the above-mentioned background technology.

[0006] The technical solution adopted by the present invention includes: a coated and modified high-nickel ternary cathode material, which includes a high-nickel ternary matrix and a coating layer containing an oxide solid electrolyte. The coating layer is coated on the outside of the high-nickel ternary matrix and accounts for 1% to 3% of the mass of the high-nickel ternary matrix.

[0007] Further, the oxide solid electrolyte includes Li 3x La 2 / 3-x TiO3 (0 < x ≤ 0.16), Li7La3Zr2O 12 、Li 1+y Al y Ti 2-y (PO4)3 (0 < y ≤ 0.5) of at least one; the ionic conductivity of the oxide solid electrolyte is ≥ 1×10 -4 S / cm.

[0008] Further, the chemical formula of the high-nickel ternary matrix is LiNi a Co b M c O2, where: M includes at least one of Mn and Al, a > 0.8, a + b + c = 1, a:b:c = (0.8 to 0.95):(0.01 to 0.2):(0.01 to 0.2).

[0009] The technical solution of the present invention also includes: a method for preparing the above-mentioned coated and modified high-nickel ternary cathode material, which includes the steps of:

[0010] Mix the high-nickel ternary precursor and the lithium source, and sinter in segments to obtain the high-nickel ternary matrix;

[0011] Mix the high-nickel ternary matrix and the oxide solid electrolyte in a solvent, add a complexing agent and a pH regulator, and let it stand to obtain a gel system;

[0012] After drying and grinding the gel system, perform annealing treatment to obtain the coated and modified high-nickel ternary cathode material.

[0013] Further, the pH regulator includes ammonia water; after adding the pH regulator, the pH of the system is 8 to 9.

[0014] Further, the complexing agent accounts for 20% to 40% of the volume of the solvent; the solvent includes anhydrous ethanol; the complexing agent includes at least one of citric acid and tartaric acid.

[0015] Further, the conditions for the annealing treatment include: annealing treatment in an inert atmosphere or an oxygen atmosphere, the annealing temperature is 300 to 500 °C, and the annealing time is 2 h to 5 h.

[0016] Furthermore, the ratio of the molar number of lithium element in the lithium source to the total molar number of metal elements in the high-nickel ternary precursor is (1.0-1.1):1.0; the high-nickel ternary precursor includes at least one of cobalt manganese hydroxide, nickel cobalt aluminum hydroxide, nickel cobalt manganese oxide, nickel cobalt aluminum oxide, nickel cobalt manganese carbonate and nickel cobalt aluminum carbonate; the lithium source includes at least one of lithium hydroxide, lithium carbonate and lithium nitrate.

[0017] Furthermore, the staged sintering includes a first stage sintering and a second stage sintering carried out in an oxygen atmosphere; the conditions for the first stage sintering include: a temperature of 400-600°C and a time of 2h-4h; the conditions for the second stage sintering include: a temperature of 700-900°C and a time of 6h-10h; the volume content of oxygen in the oxygen atmosphere is ≥90%.

[0018] The technical solution of the present invention also includes: a lithium-ion battery, the positive electrode of which contains the above-mentioned coated modified high-nickel ternary positive electrode material, and the mass proportion of the coated modified high-nickel ternary positive electrode material in the positive electrode is 70% to 90%.

[0019] The beneficial effects of the present invention include at least:

[0020] (1) The selected oxide solid electrolyte has both high ionic conductivity and electronic insulation, which can not only provide a fast lithium ion transmission channel but also inhibit interface side reactions, and can significantly improve the rate performance and cycle stability of the material. In addition, when forming a coating layer, the oxide solid electrolyte can improve the interface bonding strength with the high nickel ternary matrix through chemical bonding (such as Zr-O-Ni, Ti-O-Ni bonds), which is conducive to the rapid transmission of ions, can significantly reduce the interface impedance, and improve the kinetic performance of the material.

[0021] (2) When preparing the coated modified high-nickel ternary positive electrode material, the oxide solid electrolyte can be uniformly coated on the surface of the high-nickel ternary matrix through the liquid phase dispersion and gelation process (i.e., the sol-gel method). The uniform coating is beneficial to avoid direct contact between the high-nickel ternary matrix and the electrolyte, thereby reducing side reactions to a greater extent and improving the cycle stability of the material.

[0022] (3) The sol-gel method is simple and low-cost, suitable for large-scale production, and the material properties can be flexibly controlled by the sol concentration and coating amount.

[0023] (4) The annealing treatment after gelation is carried out in an oxygen atmosphere, which not only enables the coating layer to be effectively bonded to the high-nickel ternary matrix, but also the oxygen-rich environment eliminates oxygen vacancies on the surface of the high-nickel ternary matrix, reduces its structural defects, inhibits the release of lattice oxygen, improves the structural stability of the material, and ensures the structural integrity of the material during the cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the XRD pattern of the final products prepared in Example 1 and Comparative Example 1 of the present invention;

[0025] Figure 2 It is the SEM image of the final product prepared in Example 2 of the present invention;

[0026] Figure 3 It is the discharge curve of the final products prepared in Example 1 and Comparative Example 1 of the present invention at -20 °C;

[0027] Figure 4 It is the room temperature cycle curve of the final products prepared in Example 2 and Comparative Example 2 of the present invention;

[0028] Figure 5 It is the rate discharge curve of the final products prepared in Example 3 and Comparative Example 3 of the present invention. Detailed implementation manners

[0029] The embodiments of the present invention will be described in detail below.

[0030] In the first aspect of the embodiments of the present invention, a coated and modified high-nickel ternary cathode material is provided. The material includes a high-nickel ternary matrix and a coating layer containing an oxide solid electrolyte. The coating layer is coated on the outside of the high-nickel ternary matrix and accounts for 1% to 3% of the mass of the high-nickel ternary matrix.

[0031] Among them, the oxide solid electrolyte includes Li 3x La 2 / 3-x TiO3 (0 < x ≤ 0.16), Li7La3Zr2O 12 , Li 1+ y Al y Ti 2-y (PO4)3 (0 < y ≤ 0.5) of at least one. The ionic conductivity of the oxide solid electrolyte ≥ 1×10 -4 S / cm. The oxide solid electrolyte selected in this embodiment has both high ionic conductivity and electronic insulation. It can both provide a fast lithium ion transport channel and inhibit interfacial side reactions, and can significantly improve the rate performance and cycle stability of the material. Moreover, when forming the coating layer, the oxide solid electrolyte can improve the interfacial bonding strength with the high-nickel ternary matrix through chemical bonding (such as Zr-O-Ni, Ti-O-Ni bonds) to facilitate the rapid transport of ions and can significantly reduce the interfacial impedance.

[0032] The chemical formula of the high-nickel ternary matrix is LiNi a Co b M cO2, wherein: M includes at least one of Mn and Al, a>0.8, a+b+c=1; the ratio of a, b, and c is preferably a:b:c=(0.8~0.95):(0.01~0.2):(0.01~0.2).

[0033] A second aspect of an embodiment of the present invention provides a method for preparing the above-mentioned coated modified high-nickel ternary positive electrode material, the method comprising the following steps:

[0034] S1. Mix a high-nickel ternary precursor and a lithium source, and sinter them in sections to obtain a high-nickel ternary matrix.

[0035] In this step, the ratio of the molar number of lithium element in the lithium source to the total molar number of metal elements in the high-nickel ternary precursor is (1.0-1.1):1.0, preferably 1.05:1.0; the high-nickel ternary precursor includes at least one of cobalt manganese hydroxide, nickel cobalt aluminum hydroxide, nickel cobalt manganese oxide, nickel cobalt aluminum oxide, nickel cobalt manganese carbonate and nickel cobalt aluminum carbonate; the lithium source includes at least one of lithium hydroxide, lithium carbonate and lithium nitrate.

[0036] In this step, after the high nickel ternary precursor and the lithium source are mixed, they need to be sieved. The mesh size of the sieve is 250 to 300 meshes, and the sieving times are 2 to 3 times.

[0037] In this step, the staged sintering includes a first stage sintering and a second stage sintering carried out in an oxygen atmosphere; the conditions for the first stage sintering include: a temperature of 400-600°C, preferably 600°C, and a time of 2h-4h, preferably 4h; the conditions for the second stage sintering include: a temperature of 700-900°C, preferably 900°C, and a time of 6h-10h, preferably 8h; the heating rate of the first stage sintering and the second stage sintering is 4-8°C / min, preferably 5°C / min; the volume content of oxygen in the oxygen atmosphere is ≥90%.

[0038] S2. Mixing the high nickel ternary matrix and the oxide solid electrolyte in a solvent, adding a complexing agent and a pH adjuster, and allowing to stand to obtain a gel system;

[0039] In this step, the complexing agent accounts for 20% to 40% of the solvent volume; the solvent includes anhydrous ethanol; the complexing agent includes at least one of citric acid and tartaric acid; the pH regulator includes ammonia water; after adding the pH regulator, the system pH is 8 to 9.

[0040] In this step, the mass ratio of the oxide solid electrolyte to the high nickel ternary matrix is 1% to 3%:1, preferably 1.5%:1 or 2.1%:1.

[0041] In this step, to ensure uniform dispersion of the substances, the high-nickel ternary matrix and the oxide solid electrolyte are dispersed in anhydrous ethanol according to the mass ratio and ultrasonically treated for 30 minutes; the purpose of adding ammonia water to adjust the pH is to promote the transformation of sol to gel; standing can be carried out at room temperature until the sol is observed to be completely transformed into gel, which takes about 12 hours.

[0042] S3. Dry and grind the gel system, and then anneal it to obtain a coated modified high-nickel ternary positive electrode material.

[0043] In this step, the annealing conditions include: annealing in an inert atmosphere or an oxygen atmosphere, preferably an oxygen atmosphere, and the volume content of oxygen in the oxygen atmosphere is ≥90%; the annealing temperature is 300-500° C., preferably 350° C., and the annealing time is 2h-5h, preferably 4h.

[0044] In this step, the annealed product needs to be ground and sieved. The mesh size of the sieve is 250-300 meshes and the sieving times are 2-3 times.

[0045] The above method is used to prepare the coated modified high-nickel ternary positive electrode material. Through the liquid phase dispersion and gelation process (i.e., sol-gel method) in step S2, the oxide solid electrolyte can be uniformly coated on the surface of the high-nickel ternary matrix. The uniform coating is beneficial to avoid direct contact between the high-nickel ternary matrix and the electrolyte, thereby reducing side reactions to a greater extent and improving the cyclic stability of the material; when the oxide solid electrolyte forms a coating layer, the interface bonding strength with the high-nickel ternary matrix can be improved by chemical bonding (e.g., Zr-O-Ni, Ti-O-Ni bond) , which is conducive to the rapid transmission of ions, can significantly reduce the interfacial impedance and improve the kinetic properties of the material; the sol-gel process is simple and low-cost, suitable for large-scale production, and the material properties can be flexibly controlled by the sol concentration and coating amount; the annealing treatment after gelation is carried out in an oxygen atmosphere, which not only enables the coating layer to be effectively bonded to the high-nickel ternary matrix, but also the oxygen-rich environment will eliminate the oxygen vacancies on the surface of the high-nickel ternary matrix, reduce its structural defects, inhibit the release of lattice oxygen, improve the structural stability of the material, and ensure the structural integrity of the material during the cycle.

[0046] A third aspect of the present invention provides a lithium-ion battery, including conventional electrolyte lithium-ion batteries and solid-state lithium-ion batteries. The positive electrode of the lithium-ion battery contains the aforementioned coated modified high-nickel ternary positive electrode material, with the coated modified high-nickel ternary positive electrode material comprising 70% to 90% of the positive electrode by mass.

[0047] The present invention is further described below through examples and comparative examples. Unless otherwise specified, the raw materials, reagents, or devices used in the examples and comparative examples can be obtained from conventional commercial sources.

[0048] Example 1: Preparation of coated modified high nickel ternary positive electrode material

[0049] S1, weigh 100g of high nickel ternary precursor Ni 0.92 Co 0.03 Al 0.05 (OH)2, weigh the lithium source LiOH·H2O according to the molar ratio of Li:(Ni+Co+Al) of 1.05:1;

[0050] Use a ball mill to mix the high nickel ternary precursor and lithium source evenly, and then pass through a 150 mesh sieve three times;

[0051] The mixed material was placed in a sagger, placed in a muffle furnace, and sintered in stages under an oxygen atmosphere (oxygen volume content is 100%). The first stage of sintering was: heating to 600°C at 5°C / min and keeping warm for 4 hours; the second stage of sintering was: heating to 900°C at 5°C / min and keeping warm for 8 hours.

[0052] After the segmented sintering is completed, it is naturally cooled to room temperature to obtain the high nickel ternary matrix LiNi 0.92 Co 0.03 Al 0.05 O2.

[0053] S2, weigh 100g high nickel ternary matrix LiNi 0.92 Co 0.03 Al 0.05 O2 and 1.5g oxide solid electrolyte Li7La3Zr2O 12 ;

[0054] The above substances were dispersed in 5 L of anhydrous ethanol and ultrasonicated for 30 min to ensure uniform dispersion of the materials;

[0055] 2 L of citric acid solution was added as a complexing agent, and then ammonia was added to adjust the pH of the system to 8 to promote the transformation of sol to gel;

[0056] The mixture was allowed to stand at room temperature for 12 h to allow the sol to be completely converted into a gel system, and the dried gel was ground into powder using a ball mill.

[0057] S3. After drying the gel system, grind it into powder with a ball mill, place the obtained powder in a sagger, and put it into a sintering furnace for annealing. During the annealing treatment: in an oxygen atmosphere (the volume content of oxygen is 100%), heat it to 350°C at a heating rate of 5°C / min and keep it warm for 4 hours to obtain a coated modified high-nickel ternary positive electrode material.

[0058] The obtained coated modified high nickel ternary cathode material includes: high nickel ternary matrix LiNi 0.92 Co 0.03 Al 0.05O2 and Li7La3Zr2O 12 The coating layer is coated on the outside of the high-nickel ternary matrix and accounts for 1.5% of the mass of the high-nickel ternary matrix.

[0059] Example 2: Preparation of coated modified high nickel ternary positive electrode material

[0060] S1, weigh 100g of high nickel ternary precursor Ni 0.85 Co 0.07 Mn 0.08 (OH)2, weigh the lithium source LiOH·H2O according to the molar ratio of Li:(Ni+Co+Mn) of 1.05:1;

[0061] Use a ball mill to mix the high nickel ternary precursor and lithium source evenly, and then pass through a 150 mesh sieve three times;

[0062] The mixed material was placed in a sagger, placed in a muffle furnace, and sintered in stages under an oxygen atmosphere (oxygen volume content is 100%). The first stage of sintering was: heating to 600°C at 5°C / min and keeping warm for 4 hours; the second stage of sintering was: heating to 900°C at 5°C / min and keeping warm for 8 hours.

[0063] After the segmented sintering is completed, it is naturally cooled to room temperature to obtain the high nickel ternary matrix LiNi 0.85 Co 0.07 Mn 0.08 O2.

[0064] S2, weigh 100g high nickel ternary matrix LiNi 0.85 Co 0.07 Mn 0.08 O2 and 2.1g oxide solid electrolyte Li 1.3 Al 0.3 Ti 1.7 (PO4)3;

[0065] The above substances were dispersed in 5 L of anhydrous ethanol and ultrasonicated for 30 min to ensure uniform dispersion of the materials;

[0066] 2 L of citric acid solution was added as a complexing agent, and then ammonia was added to adjust the pH of the system to 8 to promote the transformation of sol to gel;

[0067] The mixture was allowed to stand at room temperature for 12 h to allow the sol to be completely converted into a gel system, and the dried gel was ground into powder using a ball mill.

[0068] S3. After drying the gel system, grind it into powder with a ball mill, place the obtained powder in a sagger, and put it into a sintering furnace for annealing. During the annealing treatment: in an oxygen atmosphere (the volume content of oxygen is 100%), heat it to 350°C at a heating rate of 5°C / min and keep it warm for 4 hours to obtain a coated modified high-nickel ternary positive electrode material.

[0069] The obtained coated modified high nickel ternary cathode material includes: high nickel ternary matrix LiNi 0.85 Co 0.07 Mn 0.08 O2 and Li 1.3 Al 0.3 Ti 1.7 The (PO4)3 coating layer is coated on the outside of the high-nickel ternary matrix and accounts for 2.1% of the mass of the high-nickel ternary matrix.

[0070] Example 3: Preparation of coated modified high nickel ternary positive electrode material

[0071] S1, weigh 100g of high nickel ternary precursor Ni 0.95 Co 0.02 Mn 0.03 (OH)2, weigh the lithium source LiOH·H2O according to the molar ratio of Li:(Ni+Co+Mn) of 1.05:1;

[0072] Use a ball mill to mix the high nickel ternary precursor and lithium source evenly, and then pass through a 150 mesh sieve three times;

[0073] The mixed material was placed in a sagger, placed in a muffle furnace, and sintered in stages under an oxygen atmosphere (oxygen volume content is 100%). The first stage of sintering was: heating to 600°C at 5°C / min and keeping warm for 4 hours; the second stage of sintering was: heating to 900°C at 5°C / min and keeping warm for 8 hours.

[0074] After the segmented sintering is completed, it is naturally cooled to room temperature to obtain the high nickel ternary matrix LiNi 0.95 Co 0.02 Mn 0.03 O2.

[0075] S2, weigh 100g high nickel ternary matrix LiNi 0.95 Co 0.02 Mn 0.03 O2 and 2.8g oxide solid electrolyte Li 0.33 La 0.56 TiO3;

[0076] The above substances were dispersed in 5 L of anhydrous ethanol and ultrasonicated for 30 min to ensure uniform dispersion of the materials;

[0077] 2 L of citric acid solution was added as a complexing agent, and then ammonia was added to adjust the pH of the system to 8 to promote the transformation of sol to gel;

[0078] The mixture was allowed to stand at room temperature for 12 h to allow the sol to be completely converted into a gel system, and the dried gel was ground into powder using a ball mill.

[0079] S3. After drying the gel system, grind it into powder with a ball mill, place the obtained powder in a sagger, and put it into a sintering furnace for annealing. During the annealing treatment: in an oxygen atmosphere (the volume content of oxygen is 100%), heat it to 350°C at a heating rate of 5°C / min and keep it warm for 4 hours to obtain a coated modified high-nickel ternary positive electrode material.

[0080] The obtained coated modified high nickel ternary cathode material includes: high nickel ternary matrix LiNi 0.95 Co 0.02 Mn 0.03 O2 and Li 0.33 La 0.56 The TiO3 coating layer is coated on the outside of the high-nickel ternary matrix and accounts for 2.8% of the mass of the high-nickel ternary matrix.

[0081] Comparative Example 1: Preparation of high nickel ternary positive electrode material

[0082] S1, weigh 100g of high nickel ternary precursor Ni 0.92 Co 0.03 Al 0.05 (OH)2, weigh the lithium source LiOH·H2O according to the molar ratio of Li:(Ni+Co+Al) of 1.05:1;

[0083] Use a ball mill to mix the high nickel ternary precursor and lithium source evenly, and then pass through a 150 mesh sieve three times;

[0084] The mixed material was placed in a sagger, placed in a muffle furnace, and sintered in stages under an oxygen atmosphere (oxygen volume content is 100%). The first stage of sintering was: heating to 600°C at 5°C / min and keeping warm for 4 hours; the second stage of sintering was: heating to 900°C at 5°C / min and keeping warm for 8 hours.

[0085] After the staged sintering is completed, it is naturally cooled to room temperature to obtain the high nickel ternary positive electrode material LiNi 0.92 Co 0.03 Al 0.05 O2.

[0086] Comparative Example 2: Preparation of coated modified high nickel ternary positive electrode material

[0087] S1, weigh 100g of high nickel ternary precursor Ni 0.85 Co 0.07 Mn0.08 (OH)2, weigh the lithium source LiOH·H2O according to the molar ratio of Li:(Ni+Co+Mn) of 1.05:1;

[0088] Use a ball mill to mix the high nickel ternary precursor and lithium source evenly, and then pass through a 150 mesh sieve three times;

[0089] The mixed material was placed in a sagger, placed in a muffle furnace, and sintered in stages under an oxygen atmosphere (oxygen volume content is 100%). The first stage of sintering was: heating to 600°C at 5°C / min and keeping warm for 4 hours; the second stage of sintering was: heating to 900°C at 5°C / min and keeping warm for 8 hours.

[0090] After the segmented sintering is completed, it is naturally cooled to room temperature to obtain the high nickel ternary matrix LiNi 0.85 Co 0.07 Mn 0.08 O2.

[0091] S2, weigh 100g high nickel ternary matrix LiNi 0.85 Co 0.07 Mn 0.08 O2 and 4.3g oxide solid electrolyte Li 1.3 Al 0.3 Ti 1.7 (PO4)3;

[0092] The above substances were dispersed in 5 L of anhydrous ethanol and ultrasonicated for 30 min to ensure uniform dispersion of the materials;

[0093] 2 L of citric acid solution was added as a complexing agent, and then ammonia was added to adjust the pH of the system to 8 to promote the transformation of sol to gel;

[0094] The mixture was allowed to stand at room temperature for 12 h to allow the sol to be completely converted into a gel system, and the dried gel was ground into powder using a ball mill.

[0095] S3. After drying the gel system, grind it into powder with a ball mill, place the obtained powder in a sagger, and put it into a sintering furnace for annealing. During the annealing treatment: in an oxygen atmosphere (the volume content of oxygen is 100%), heat it to 350°C at a heating rate of 5°C / min and keep it warm for 4 hours to obtain a coated modified high-nickel ternary positive electrode material.

[0096] The obtained coated modified high nickel ternary cathode material includes: high nickel ternary matrix LiNi 0.85 Co 0.07 Mn 0.08 O2 and Li 1.3 Al 0.3 Ti 1.7The (PO4)3 coating layer is coated on the outside of the high-nickel ternary matrix and accounts for 4.3% of the mass of the high-nickel ternary matrix.

[0097] Comparative Example 3: Preparation of high nickel ternary positive electrode material

[0098] S1, weigh 100g of high nickel ternary precursor Ni 0.95 Co 0.02 Mn 0.03 (OH)2, weigh the lithium source LiOH·H2O according to the molar ratio of Li:(Ni+Co+Mn) of 1.05:1;

[0099] Use a ball mill to mix the high nickel ternary precursor and lithium source evenly, and then pass through a 150 mesh sieve three times;

[0100] The mixed material was placed in a sagger, placed in a muffle furnace, and sintered in stages under an oxygen atmosphere (oxygen volume content is 100%). The first stage of sintering was: heating to 600°C at 5°C / min and keeping warm for 4 hours; the second stage of sintering was: heating to 900°C at 5°C / min and keeping warm for 8 hours.

[0101] After the staged sintering is completed, it is naturally cooled to room temperature to obtain the high nickel ternary positive electrode material LiNi 0.95 Co 0.02 Mn 0.03 O2.

[0102] Characterization and testing:

[0103] (1) The crystal structure of the coated modified high nickel ternary positive electrode material prepared in Example 1 and the high nickel ternary positive electrode material prepared in Comparative Example 1 was characterized to obtain the attached Figure 1 XRD pattern of .

[0104] In the attached Figure 1 No impurity phase was observed in the coated modified high-nickel ternary positive electrode material prepared in Example 1, indicating that when the oxide solid electrolyte coats the high-nickel ternary matrix, it will not affect the crystal structure of the high-nickel ternary matrix.

[0105] (2) The micromorphology of the coated modified high nickel ternary positive electrode material prepared in Example 2 was characterized. Figure 2 SEM image of .

[0106] Attachment Figure 2 The surface of the material is shown to be smooth, indicating that the coating layer formed by the oxide solid electrolyte is evenly distributed on the surface of the high-nickel ternary matrix. This can avoid direct contact between the high-nickel ternary matrix and the electrolyte, which is beneficial to reducing the side reactions between the high-nickel ternary matrix and the electrolyte and improving the cycle stability of the material.

[0107] (3) Electrochemical performance test

[0108] ① The final products of Examples 1 to 3 and Comparative Examples 1 to 3 were respectively prepared into button batteries, wherein the mass ratio of the active material (referring to the final products of each Example and Comparative Example), the conductive agent Super P, and the binder PVDF in the positive electrode of the button batteries was 80:10:10; the electrolyte was prepared by dissolving 1M LiPF6 in a mixed solvent, wherein the volume ratio of EC, DEC, and DMC in the mixed solvent was 1:1:1; and a lithium sheet was used as the negative electrode.

[0109] ② The button battery prepared by the final product of Example 1 and Comparative Example 1 was subjected to a low-temperature discharge test at a test temperature of -20°C. Figure 3 The low temperature discharge curve is shown.

[0110] Attachment Figure 3 It shows that the discharge specific capacity of the high-nickel ternary positive electrode material in Comparative Example 1 that has not been coated and modified at -20°C is only 162mAh / g, while the discharge specific capacity of the coated and modified high-nickel ternary positive electrode material prepared in Example 1 at -20°C is 183mAh / g. Not only is the low-temperature discharge specific capacity significantly improved compared with Comparative Example 1, but the discharge platform is also significantly improved.

[0111] ③ The button battery prepared by the final product of Example 2 and Comparative Example 2 was subjected to a room temperature cycle charge and discharge test. The test conditions were: 0.5C charge and 1C discharge. Figure 4 The normal temperature cycle curve is shown.

[0112] Attachment Figure 4 It shows that after the material prepared in comparative example 2 is cycled for 200 cycles, the capacity retention rate is only 88.2%, while after the material prepared in example 2 is cycled for 200 cycles, the capacity retention rate is 92.2%, and its cycle performance is significantly improved.

[0113] ④ The button cell prepared by the final product of Example 3 and Comparative Example 3 was tested for rate performance under the following test conditions: 0.1C, 5C and 10C. Figure 5 The rate discharge curve is shown.

[0114] Attachment Figure 5 It shows that at different rates, the discharge specific capacity of the material prepared in Example 3 is higher than that of the material prepared in Comparative Example 3; at a rate of 5C, the capacity retention rate of the material prepared in Example 3 can reach 82.4%.

[0115] The improvement in the kinetic properties and room temperature cycling stability of the materials prepared in the above Examples 1 to 3 is attributed to the coating of the high-nickel ternary matrix by the oxide solid electrolyte. The preferred high ionic conductivity oxide solid electrolyte of the present invention improves the lithium ion diffusion kinetics of the high-nickel ternary matrix. At the same time, the coating layer containing the oxide solid electrolyte avoids the reaction between the electrolyte and the filter metal in the high-nickel ternary matrix, inhibits the phase change of the high-nickel ternary matrix, and greatly improves the cycling stability.

[0116] It should be understood that the above-described specific embodiments of the present invention are merely illustrative or illustrative of the principles of the present invention and do not constitute limitations of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included within the scope of protection of the present invention. In addition, the appended claims are intended to cover all variations and modifications that fall within the scope and metes and bounds of the claims, or equivalents thereof.

Claims

1. A coated modified high nickel ternary cathode material, characterized in that: It comprises a high-nickel ternary matrix and a coating layer containing an oxide solid electrolyte. The coating layer is coated on the outside of the high-nickel ternary matrix and accounts for 1% to 3% of the mass of the high-nickel ternary matrix.

2. The coated modified high nickel ternary cathode material according to claim 1, characterized in that: The oxide solid electrolyte includes Li 3x La 2 / 3-x TiO3 (0 < x ≤ 0.16), Li7La3Zr2O 12 , Li 1+y Al y Ti 2-y (PO4)3 (0 < y ≤ 0.5); the ionic conductivity of the oxide solid electrolyte is ≥ 1 × 10 -4 S / cm.

3. The coated modified high nickel ternary positive electrode material according to claim 1 or 2, characterized in that: The chemical formula of the high nickel ternary matrix is LiNi a Co b M c O2, wherein: M includes at least one of Mn and Al, a>0.8, a+b+c=1, a:b:c=(0.8~0.95):(0.01~0.2):(0.01~0.2).

4. A method for preparing the coated modified high-nickel ternary cathode material according to any one of claims 1 to 3, characterized in that: Including steps: The high nickel ternary precursor and the lithium source are mixed and sintered in stages to obtain a high nickel ternary matrix; The high nickel ternary matrix and the oxide solid electrolyte are mixed in a solvent, a complexing agent and a pH regulator are added, and the mixture is allowed to stand to obtain a gel system; The gel system is dried, ground, and then annealed to obtain a coated modified high-nickel ternary positive electrode material.

5. The method for preparing a coated modified high nickel ternary cathode material according to claim 4, characterized in that: The pH regulator includes ammonia water; after the pH regulator is added, the pH of the system is 8-9.

6. The method for preparing a coated modified high nickel ternary cathode material according to claim 4, characterized in that: The complexing agent accounts for 20% to 40% of the volume of the solvent; the solvent includes anhydrous ethanol; and the complexing agent includes at least one of citric acid and tartaric acid.

7. The method for preparing a coated modified high nickel ternary cathode material according to claim 4, characterized in that: The annealing conditions include: annealing in an inert atmosphere or an oxygen atmosphere, an annealing temperature of 300-500° C., and an annealing time of 2 hours to 5 hours.

8. The method for preparing a coated modified high nickel ternary cathode material according to claim 4, characterized in that: The ratio of the molar number of lithium element in the lithium source to the total molar number of metal elements in the high-nickel ternary precursor is (1.0-1.1):1.0; the high-nickel ternary precursor includes at least one of cobalt manganese hydroxide, nickel cobalt aluminum hydroxide, nickel cobalt manganese oxide, nickel cobalt aluminum oxide, nickel cobalt manganese carbonate and nickel cobalt aluminum carbonate; the lithium source includes at least one of lithium hydroxide, lithium carbonate and lithium nitrate.

9. The method for preparing a coated modified high-nickel ternary cathode material according to any one of claim 4, characterized in that: The staged sintering includes a first stage sintering and a second stage sintering performed in an oxygen atmosphere; The conditions for the first sintering stage include: temperature of 400-600° C. and time of 2-4 hours; the conditions for the second sintering stage include: temperature of 700-900° C. and time of 6-10 hours; and the volume content of oxygen in the oxygen atmosphere is ≥90%.

10. A lithium ion battery, characterized in that: The positive electrode of the lithium-ion battery contains the coated modified high-nickel ternary positive electrode material according to any one of claims 1 to 3, and the mass proportion of the coated modified high-nickel ternary positive electrode material in the positive electrode is 70% to 90%.

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