Modified positive electrode material and preparation method thereof, positive electrode plate and electrochemical device

Abstract

The invention relates to the technical field of positive electrode materials, in particular to a modified positive electrode material, a preparation method thereof, a positive electrode plate and an electrochemical device. The modified positive electrode material comprises a high-nickel ternary positive electrode material and lanthanum nickel oxide coated on the surface of the high-nickel ternary positive electrode material, the high-nickel ternary positive electrode material is LiNixCoyMnzO2, x is greater than or equal to 0.6, and x + y + z = 1. The modified positive electrode material provided by the invention has excellent ionic conductivity, electronic conductivity and capacity retention rate, and the first efficiency and the specific capacity are effectively improved. In addition, the raw material lanthanum and nickel compounds of the lanthanum-nickel oxide are relatively low in cost, so that the cost of the positive electrode material is not greatly increased, and the application prospect is good.

Description

Technical Field

[0001] This invention relates to the field of cathode material technology, and in particular to a modified cathode material and its preparation method, cathode sheet, and electrochemical device. Background Technology

[0002] LiNi ternary cathode material x Co y Mn z O2(x+y+z=1) belongs to the α-NaFeO2 type layered structure. (Spatial point group). Among them, high-nickel ternary cathode materials (x≥0.6) have attracted much attention due to their high reversible capacity, excellent rate performance, and low price, and are one of the most promising cathode materials for future lithium-ion batteries.

[0003] Currently, LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811) high-nickel ternary lithium-ion batteries have achieved commercial application and are rapidly expanding their market share in the power battery field, with system energy densities reaching 180-200 Wh / kg. However, NCM811 cathode materials are still insufficient to meet the ever-increasing energy density demands of power batteries. Compared to traditional gasoline vehicles, driving range is the biggest bottleneck restricting the development of electric vehicles. To further improve the energy density of NCM lithium-ion batteries, it is necessary to further increase the nickel content in the NCM cathode material. Therefore, 9-series NCM high-nickel ternary cathode materials, such as LiNi... 0.9 Co 0.05 Mn 0.05 The development of O2 (NCM90) has garnered significant attention. However, the extremely high nickel content, while improving material capacity, also brings many problems, such as decreased capacity retention and gas generation. Surface coating is an effective method to improve the capacity retention of electrode materials. The coated material usually protects the cathode material from electrolyte corrosion but also hinders the diffusion of lithium ions at the electrode-electrolyte interface, and may even affect the electronic conductivity of the cathode. In other words, while existing coating materials can improve capacity retention to some extent, they usually cause a decrease in conductivity. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a modified cathode material, its preparation method, a cathode electrode, and an electrochemical device. The modified cathode material provided by this invention possesses excellent ionic conductivity, electronic conductivity, and capacity retention, and its initial efficiency and specific capacity are effectively improved.

[0005] In a first aspect, the present invention provides a modified cathode material, the modified cathode material comprising a high-nickel ternary cathode material and a lanthanum-nickel oxide coating on the surface of the high-nickel ternary cathode material, wherein the high-nickel ternary cathode material is LiNi. x Co y Mn z O2, where x≥0.6, y>0, z>0, x+y+z=1.

[0006] The value of x can be 0.6, 0.7, 0.8, 0.9, etc.

[0007] The modified cathode material provided by this invention, by coating the surface of a high-nickel ternary cathode material with lanthanum nickel oxide, exhibits high ionic conductivity, high electronic conductivity, and excellent capacity retention, while effectively improving initial efficiency and specific capacity. Specifically:

[0008] The modified cathode material provided by this invention features a high-nickel ternary cathode material with high specific capacity. Coating the surface of the high-nickel ternary cathode material with lanthanum nickel oxide can protect it from electrolyte corrosion and maintain its capacity well. Furthermore, the lanthanum nickel oxide coating on the surface of the high-nickel ternary cathode material does not affect the diffusion of lithium ions between the electrode and the electrolyte, resulting in a modified cathode material with excellent ionic and electronic conductivity, thereby effectively improving the battery's initial efficiency and specific capacity.

[0009] In a preferred embodiment of the present invention, the lanthanum nickel oxide is selected from La3Ni2O7. The present invention effectively improves the ionic conductivity, electronic conductivity, capacity retention, first-efficiency, and specific capacity of a high-nickel ternary cathode material by coating the surface of the material with La3Ni2O7.

[0010] As a preferred embodiment of the present invention, x ≥ 0.9 and x + y + z = 1.

[0011] In a preferred embodiment of the present invention, x = 0.9, y = z = 0.05, meaning that the high-nickel ternary cathode material in the modified cathode material provided by the present invention is LiNi. 0.9 Co 0.05 Mn 0.05 O2(NCM90), this invention effectively improves the ionic conductivity, electronic conductivity, capacity retention, first-efficiency and specific capacity of NCM90 cathode material by coating the surface of NCM90 cathode material with lanthanum nickel oxide.

[0012] As a preferred embodiment of the present invention, with the total molar sum of the lanthanum nickel oxide and the high-nickel ternary cathode material being 100, the molar ratio of the lanthanum nickel oxide to the high-nickel ternary cathode material is (0.8-3.5):(99.2-96.5), for example 0.8:99.2, 1:99, 2:98, 3:97, 3.5:96.5, etc., preferably (0.8-3):(99.2-97), and more preferably (0.8-1):(99.2-99).

[0013] When the molar ratio of lanthanum nickel oxide to high-nickel ternary cathode material is within this range, the modified cathode material provided by this invention has a better effect on improving the specific capacity and rate performance.

[0014] As a preferred embodiment of the present invention, the molar ratio of the lanthanum nickel oxide to the high-nickel ternary cathode material is 1:99. The modified cathode material obtained at this time has excellent ionic conductivity, electronic conductivity and capacity retention, and the first-efficiency and specific capacity are effectively improved, while the cost is low.

[0015] If the lanthanum nickel oxide coating is too low, the effect on improving conductivity will be poor; if the coating is too high, it may lead to a decrease in conductivity and ion diffusion rate, as well as a reduction in the initial capacity of the electrode, while increasing the cost.

[0016] Secondly, the present invention provides a method for preparing the modified cathode material described in the first aspect. The preparation method provided by the present invention is a commonly used method in the field for preparing coated cathode materials. The present invention does not impose too many limitations on the preparation method. Any preparation method that can obtain the modified cathode material of the present invention is applicable to the present invention.

[0017] Specifically, the preparation method of the present invention includes: mixing a high-nickel ternary cathode material or its preparation raw materials with a lanthanum source and a nickel source, and carrying out a solid-phase reaction to obtain the modified cathode material.

[0018] The preparation method provided by this invention uses low-cost coating materials and readily available raw materials. The preparation method is simple and easy to implement. It can effectively control production costs while improving the ionic and electronic conductivity of the cathode material. It is suitable for mass production and has good application prospects.

[0019] As a preferred embodiment of the present invention, the preparation method includes: mixing a high-nickel ternary cathode material with a lanthanum source and a nickel source, and carrying out a solid-phase reaction to obtain the modified cathode material.

[0020] The present invention controls the amount of lanthanum source and nickel source so that the molar ratio of the prepared lanthanum nickel oxide to the high-nickel ternary cathode material is (0.8-3.5):(99.2-96.5), preferably (0.8-3):(99.2-97).

[0021] As a preferred embodiment of the present invention, the preparation method includes: mixing a lithium source, a precursor of a high-nickel ternary cathode material with a lanthanum source and a nickel source, and carrying out a solid-phase reaction to obtain the modified cathode material.

[0022] This invention controls the amounts of lanthanum and nickel sources to achieve a molar ratio of lanthanum-nickel oxide to the precursor of the high-nickel ternary cathode material of (0.8-3.5):(99.2-96.5), preferably (0.8-3):(99.2-97). This invention does not impose excessive limitations on the preparation method of the high-nickel ternary cathode material precursor; the preparation method is a commonly used method in the art, and the raw materials are conventionally available.

[0023] The preparation method provided by this invention can directly modify high-nickel ternary cathode materials or modify them during the lithiation process.

[0024] As a preferred embodiment of the present invention, the molar ratio of lithium element in the lithium source to the precursor of the high-nickel ternary cathode material is 1.02-1.05:1, such as 1.02:1, 1.03:1, 1.04:1, 1.05:1, etc., that is, the lithium source needs to be slightly excessive so that the precursor can react fully.

[0025] As a preferred embodiment of the present invention, the mixing is either direct mixing or mixing in a solvent. Direct mixing can be achieved by grinding and mixing evenly in a mortar. The present invention does not impose excessive limitations on the solvent; any solvent capable of dissolving the raw materials is suitable for the present invention, such as DMF, ethanol, etc.

[0026] In the preparation method provided by the present invention, a solid-phase reaction can be used directly, or the mixture can be dissolved in a solvent first, i.e., ion exchange can be performed first, and then a solid-phase reaction can be performed.

[0027] As a preferred embodiment of the present invention, the mixing time in the solvent is 3-8 hours, for example, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, etc. A mixing time within this range results in the prepared modified cathode material exhibiting excellent conductivity, initial specific capacity, and capacity retention.

[0028] As a preferred embodiment of the present invention, the preparation method further includes adding a carbon source for mixing when mixing in a solvent. When the present invention mixes in a solvent and adds a carbon source, the prepared modified cathode material exhibits higher initial specific capacity and capacity retention.

[0029] In a preferred embodiment of the present invention, the mixture is dried in a solvent, followed by a solid-phase reaction. Specifically, the present invention dissolves each raw material in a solvent, mixes and stirs them evenly, then dries them, and then performs a solid-phase reaction to obtain the modified cathode material.

[0030] As a preferred embodiment of the present invention, the solid-phase reaction is carried out in oxygen.

[0031] As a preferred embodiment of the present invention, the solid-phase reaction temperature is 450-800℃, such as 450℃, 500℃, 600℃, 700℃, 800℃, etc. When the reaction temperature is within this range, the components can react fully, resulting in a modified cathode material with excellent performance.

[0032] In a preferred embodiment of the present invention, the solid-phase reaction time is 5-24 hours, such as 5 hours, 10 hours, 15 hours, 20 hours, 24 hours, etc. When the reaction time is within this range, the components can react fully, resulting in a modified cathode material with excellent performance.

[0033] As a preferred embodiment of the present invention, the lanthanum source is selected from any one or more of lanthanum oxide, lanthanum carbonate, lanthanum nitrate, lanthanum oxalate, or lanthanum acetate.

[0034] As a preferred embodiment of the present invention, the nickel source is selected from any one or more of nickel oxide, nickel carbonate, nickel nitrate, nickel oxalate, or nickel acetate.

[0035] The lanthanum and nickel sources used in this invention are low-cost and will not lead to a significant increase in the cost of cathode materials, thus showing good application prospects.

[0036] As a preferred embodiment of the present invention, the carbon source is selected from any one or more of citric acid, oxalic acid, or glucose.

[0037] As a preferred embodiment of the present invention, the lithium source is selected from any one or more of lithium acetate, lithium carbonate, lithium hydroxide, or lithium dihydrogen phosphate.

[0038] Thirdly, the present invention provides a positive electrode sheet, the positive electrode sheet comprising the modified positive electrode material described in the first aspect.

[0039] Fourthly, the present invention provides an electrochemical device comprising the modified positive electrode material described in the first aspect or the positive electrode sheet described in the third aspect.

[0040] The technical solution provided by the embodiments of the present invention has the following advantages compared with the prior art:

[0041] The modified cathode material provided by this invention possesses excellent ionic conductivity, electronic conductivity, and capacity retention, while effectively improving initial efficiency and specific capacity. Furthermore, the raw materials for lanthanum-nickel oxide, lanthanum and nickel compounds, are relatively inexpensive, thus avoiding a significant increase in the cost of the cathode material and demonstrating promising application prospects. Attached Figure Description

[0042] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 The image shows the XRD pattern of the modified cathode material prepared in Example 1 of this invention.

[0045] Figure 2 The image shows a comparison of the first rings of the modified cathode material prepared in Example 1 of this invention and the unmodified high-nickel ternary cathode material in Comparative Example 1.

[0046] Figure 3 The diagram shows the cycling process of the modified cathode material prepared in Example 1 of this invention and the unmodified high-nickel ternary cathode material in Comparative Example 1. Detailed Implementation

[0047] To better understand the above-mentioned objectives, features, and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0048] Many specific details are set forth in the following description in order to provide a full understanding of the invention, but the invention may also be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of the invention, and not all embodiments.

[0049] Example 1

[0050] This embodiment provides a modified cathode material and its preparation method. The modified cathode material includes a high-nickel ternary cathode material and La3Ni2O7 coated on the surface of the high-nickel ternary cathode material. The high-nickel ternary cathode material is LiNi. 0.9 Co 0.05 Mn 0.05O2(NCM90), wherein the molar ratio of La3Ni2O7 to the high-nickel ternary cathode material is 1:99;

[0051] The preparation method includes the following steps:

[0052] (1) Place nickel nitrate and lanthanum nitrate in DMF at a molar ratio of 2:3 and stir until homogeneous. Add citric acid to the above solution to convert nitrate into citrate.

[0053] (2) A certain amount of P-NCM90 (so that the final molar ratio of La3Ni2O7 to P-NCM90 is 1:99) was added to the above citrate solution, stirred at room temperature for 5 h, and the resulting solution was dried in air at 80 °C to obtain solid powder.

[0054] (3) The obtained solid powder was heated to 675°C for 5 hours in flowing oxygen at a heating rate of 5°C / min to obtain the modified cathode material.

[0055] Example 2

[0056] This embodiment provides a modified cathode material and its preparation method. The modified cathode material includes a high-nickel ternary cathode material and La3Ni2O7 coated on the surface of the high-nickel ternary cathode material. The high-nickel ternary cathode material is LiNi. 0.9 Co 0.05 Mn 0.05 O2(NCM90), wherein the molar ratio of La3Ni2O7 to the high-nickel ternary cathode material is 1:99;

[0057] The preparation method includes the following steps:

[0058] (1) Place nickel oxide and lanthanum oxide in a nitric acid / DMF solution at a molar ratio of 4:3, wherein the number of moles of nitric acid is the same as the sum of the number of moles of nickel and lanthanum. Stir well and add citric acid to convert nitrate into citrate.

[0059] (2) A certain amount of P-NCM90 (so that the final molar ratio of La3Ni2O7 to P-NCM90 is 1:99) was added to the above citrate solution, stirred at room temperature for 5 h, and the resulting solution was dried in air at 80 °C to obtain solid powder.

[0060] (3) The obtained solid powder was heat-treated in flowing oxygen at a heating rate of 5℃ / min to 675℃ for 5h to obtain the modified cathode material.

[0061] Example 3

[0062] This embodiment provides a modified cathode material and its preparation method. The modified cathode material includes a high-nickel ternary cathode material and La3Ni2O7 coated on the surface of the high-nickel ternary cathode material. The high-nickel ternary cathode material is LiNi. 0.9 Co 0.05 Mn 0.05 O2(NCM90), wherein the molar ratio of La3Ni2O7 to the high-nickel ternary cathode material is 1:99;

[0063] The preparation method includes the following steps:

[0064] (1) Place nickel carbonate and lanthanum carbonate in DMF at a molar ratio of 4:3 and stir until homogeneous. Add citric acid to the above solution to convert nitrate into citrate.

[0065] (2) A certain amount of P-NCM90 (so that the final molar ratio of La3Ni2O7 to P-NCM90 is 1:99) was added to the above citrate solution, stirred at room temperature for 5 h, and the resulting solution was dried in air at 80 °C to obtain solid powder.

[0066] (3) The obtained solid powder was heat-treated in flowing oxygen at a heating rate of 5℃ / min to 675℃ for 5h.

[0067] Example 4

[0068] This embodiment provides a modified cathode material and its preparation method. The modified cathode material includes a high-nickel ternary cathode material and La3Ni2O7 coated on the surface of the high-nickel ternary cathode material. The high-nickel ternary cathode material is LiNi. 0.9 Co 0.05 Mn 0.05 O2(NCM90), wherein the molar ratio of La3Ni2O7 to the high-nickel ternary cathode material is 1:99;

[0069] The preparation method includes the following steps:

[0070] (1) Place nickel nitrate and lanthanum nitrate in DMF at a molar ratio of 2:3 and stir until homogeneous;

[0071] (2) A certain amount of P-NCM90 (so that the final molar ratio of La3Ni2O7 to P-NCM90 is 1:99) was added to the above nitrate solution, stirred at room temperature for 5 hours, and the resulting solution was dried in air at 80°C to obtain solid powder.

[0072] (3) The obtained solid powder was heat-treated in flowing oxygen at a heating rate of 5℃ / min to 675℃ for 5h to obtain the modified cathode material.

[0073] Example 5

[0074] This embodiment provides a modified cathode material and its preparation method. The modified cathode material includes a high-nickel ternary cathode material and La3Ni2O7 coated on the surface of the high-nickel ternary cathode material. The high-nickel ternary cathode material is LiNi. 0.9 Co 0.05 Mn 0.05 O2(NCM90), wherein the molar ratio of La3Ni2O7 to the high-nickel ternary cathode material is 1:99;

[0075] The preparation method includes the following steps:

[0076] Nickel nitrate and lanthanum nitrate were mixed evenly in a mortar with a molar ratio of 2:3 and a certain amount of P-NCM90 (so that the final molar ratio of La3Ni2O7 to P-NCM90 was 1:99). The mixture was then heat-treated to 675°C for 5 hours under an oxygen atmosphere at a heating rate of 5°C / min to obtain the modified cathode material.

[0077] Example 6

[0078] This embodiment provides a modified cathode material and its preparation method. The modified cathode material includes a high-nickel ternary cathode material and La3Ni2O7 coated on the surface of the high-nickel ternary cathode material. The high-nickel ternary cathode material is LiNi. 0.9 Co 0.05 Mn 0.05 O2(NCM90), wherein the molar ratio of La3Ni2O7 to the high-nickel ternary cathode material is 1:99;

[0079] The preparation method includes the following steps:

[0080] Nickel nitrate and lanthanum nitrate were mixed uniformly with a certain amount of P-NCM90 precursor (so that the final molar ratio of La3Ni2O7 to P-NCM90 precursor was 1:99) and LiOH·H2O (2% excess compared with the precursor) at a molar ratio of 2:3. The mixture was then heated to 500℃ for 5 h in an oxygen atmosphere, and then heated to 750℃ at a heating rate of 5℃ / min and held for 15 h to obtain the modified cathode material.

[0081] Example 7

[0082] This embodiment provides a modified cathode material and its preparation method. The preparation method is the same as that in Example 6, except that in this embodiment, LiOH·H2O is in 5% excess compared to the precursor.

[0083] Example 8

[0084] This embodiment provides a modified cathode material and its preparation method. The preparation method is the same as that in Example 1. The difference between Example 1 and Example 1 is that the molar ratio of La3Ni2O7 to high-nickel ternary cathode material in this embodiment is 0.8:99.2.

[0085] Example 9

[0086] This embodiment provides a modified cathode material and its preparation method. The preparation method is the same as that in Example 1. The difference between Example 1 and Example 1 is that the molar ratio of La3Ni2O7 to high-nickel ternary cathode material in this embodiment is 0.5:99.5.

[0087] Example 10

[0088] This embodiment provides a modified cathode material and its preparation method. The preparation method is the same as that in Example 1. The difference between Example 1 and Example 1 is that the molar ratio of La3Ni2O7 to high-nickel ternary cathode material in this embodiment is 3:97.

[0089] Example 11

[0090] This embodiment provides a modified cathode material and its preparation method. The preparation method is the same as that in Example 1. The difference between Example 1 and Example 1 is that the molar ratio of La3Ni2O7 to high-nickel ternary cathode material in this embodiment is 3.5:96.5.

[0091] Example 12

[0092] This embodiment provides a modified cathode material and its preparation method. The preparation method is the same as that in Example 1. The difference between Example 1 and Example 1 is that the molar ratio of La3Ni2O7 to high-nickel ternary cathode material in this embodiment is 5:95.

[0093] Example 13

[0094] This embodiment provides a modified cathode material and its preparation method. The preparation method is the same as in Example 1, except that the high-nickel ternary cathode material in this embodiment is LiNi. 0.6 Co 0.2 Mn 0.2 O2.

[0095] Comparative Example 1

[0096] This comparative example provides a cathode material NCM90 and its preparation method. The difference from Example 1 is that the cathode material is not coated or modified in this comparative example.

[0097] Performance Test 1

[0098] The modified cathode material prepared in Example 1 was subjected to XRD testing. Figure 1 The image shows the XRD pattern of the modified cathode material prepared in Example 1.

[0099] Performance Test 2

[0100] The electronic conductivity, ionic conductivity, specific capacity, and capacity retention of the cathode materials provided in the examples and comparative examples were tested.

[0101] The modified cathode material provided in the examples and the cathode material provided in the comparative examples were used to assemble batteries respectively:

[0102] (1) Preparation of the positive electrode: First, wipe the glass plate with an alcohol swab. After wiping it clean, gently pick up a piece of aluminum foil (current collector) with flat-tipped tweezers and place it on the glass plate. Wipe both sides until the aluminum surface is smooth and free of bubbles. Blow the residual alcohol on the aluminum foil with a syringe and fix the aluminum to the glass plate with high-temperature tape for coating. Weigh an appropriate amount of PVDF (5wt%) into a glass bottle and dissolve it fully in NMP (95wt%). Stir magnetically for 24 hours until uniform and use it as a binder. Weigh the positive electrode material, SuperP and PVDF in a mass ratio of 80:10:10. First, grind the positive electrode material and SuperP in an agate mortar for 20 minutes. Then, use a pipette to measure an appropriate amount of binder and drop it into the ground material. Grind quickly and evenly. Use a spatula to scrape the electrode slurry and place it on one side of the aluminum foil. Use a 100mm thick coater to coat the slurry evenly on the current collector. Finally, the coated electrode sheets are dried in a vacuum drying oven at 80°C for 10 hours, then removed and rolled twice on a roller press. They are then cut into 12mm diameter rounds using a slicer, weighed using a high-precision electronic balance, placed in sealed bags, labeled, and stored in a glove box for future battery assembly.

[0103] (2) Preparation of negative electrode sheet: In this experiment, a lithium sheet with a diameter of 16 mm and a thickness of 1 mm was directly used as the negative electrode.

[0104] (3) Electrolyte: 1.2M LIPF6 in EC:EMC = 3:7wt%.

[0105] (4) Diaphragm: Cut into PP diaphragms with a diameter of 18mm.

[0106] The testing method is as follows:

[0107] 1. Electronic conductivity: Electronic conductivity was tested using the four-probe method;

[0108] 2. Ionic conductivity: Ionic conductivity was tested using the Gitt method.

[0109] 3. Constant current charge and discharge test: Under the charge and discharge voltage, the test battery is activated at 0.1C for two cycles, and then cycled at 1C.

[0110] The test results are shown in Table 1 and Figure 2-3 As shown, Figure 2 The image shows a comparison of the first layer of the modified cathode material prepared in Example 1 and the unmodified high-nickel ternary cathode material in Comparative Example 1. Figure 3 The images show the cycling diagrams of the modified cathode material prepared in Example 1 and the unmodified high-nickel ternary cathode material in Comparative Example 1.

[0111] Table 1

[0112] project <![CDATA[Conductivity / S cm -1 > <![CDATA[Ionic diffusion coefficient (cm 2 / s)]]> First-round specific capacity mAh / g Capacity retention Example 1 <![CDATA[2.681×10 -4 ]]> <![CDATA[2.88×10 -10 ]]> 213.53 94.4％ Example 2 <![CDATA[1.248×10 -4 ]]> <![CDATA[2.56×10 -10 ]]> 210.35 91.23％ Example 3 <![CDATA[8.371×10 -5 ]]> <![CDATA[2.35×10 -10 ]]> 201.46 90.35％ Example 4 <![CDATA[4.561×10 -5 ]]> <![CDATA[2.48×10 -10 ]]> 195.33 89.86％ Example 5 <![CDATA[8.086×10 -5 ]]> <![CDATA[1.82×10 -10 ]]> 196.52 82.23％ Example 6 <![CDATA[9.072×10 -6 ]]> <![CDATA[2.12×10 -10 ]]> 195.20 90.12％ Example 7 <![CDATA[8.223×10 -5 ]]> <![CDATA[2.10×10 -10 ]]> 198.26 80.11％ Example 8 <![CDATA[9.487×10 -5 ]]> <![CDATA[2.23×10 -10 ]]> 195.45 84.24％ Example 9 <![CDATA[7.067×10 -5 ]]> <![CDATA[1.95×10 -10 ]]> 190.22 82.13％ Example 10 <![CDATA[5.894×10 -5 ]]> <![CDATA[1.92×10 -10 ]]> 196.52 87.37％ Example 11 <![CDATA[3.358×10 -5 ]]> <![CDATA[1.87×10 -10 ]]> 195.24 85.75％ Example 12 <![CDATA[1.354×10 -5 ]]> <![CDATA[1.85×10 -10 ]]> 193.20 84.62％ Example 13 <![CDATA[9.784×10 -5 ]]> <![CDATA[2.01×10 -10 ]]> 162.51 90.24％ Comparative Example 1 <![CDATA[7.067×10 -5 ]]> <![CDATA[1.93×10 -10 ]]> 208.54 79.7％％

[0113] From Table 1 and Figure 2-3 It is known that the modified cathode material prepared by this invention can improve the ionic conductivity, electronic conductivity, specific capacity and first-time efficiency of the cathode material, and the raw materials for preparing the modified coating material La3Ni2O7, lanthanum source and nickel source, are inexpensive and have low cost.

[0114] A comparison between Example 1 and Comparative Example 1 reveals that the modified cathode material in Example 1 achieves a first-cycle discharge specific capacity of 213.53 mAh / g, while the unmodified high-nickel ternary cathode material in Comparative Example 1 achieves 208.54 mAh / g, representing an improvement of nearly 5 mAh / g. The first-cycle efficiency of the modified cathode material in Example 1 is 85.21%, compared to 78.29% in Comparative Example 1, demonstrating a significant improvement. The ionic conductivity of the modified cathode material in Example 1 is 2.88 × 10⁻⁶. -10 cm 2 / s, which is nearly 50% higher than that of the unmodified cathode material; the electronic conductivity of the modified cathode material in Example 1 is 2.681 × 10 -4 S cm -1 The modified cathode material showed a 2.8-fold improvement over the unmodified cathode material. The capacity retention rate of the modified cathode material in Example 1 was 94.4%, while that in Comparative Example 1 was 79.7%, indicating a significant improvement in cycle performance.

[0115] A comparison of Examples 1 and 4 shows that adding a carbon source (citric acid) during mixing in a solvent results in a modified cathode material with better performance. A comparison of Examples 1 and 5 shows that mixing in a solvent results in a modified cathode material with better performance than direct mixing.

[0116] A comparison of Examples 1, 8-12, and Comparative Example 1 reveals that the best performance is achieved when the molar ratio of La3Ni2O7 to the high-nickel ternary cathode material is 1:99. When the coating amount is too small (Example 9), the performance improvement effect on the cathode material is not significant; conversely, when the coating amount is too large (Example 12), it leads to a decrease in performance.

[0117] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0118] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A modified cathode material, characterized in that, The modified cathode material includes a high-nickel ternary cathode material and a lanthanum nickel oxide coating on the surface of the high-nickel ternary cathode material, wherein the high-nickel ternary cathode material is LiNi. x Co y Mn z O2, where x≥0.6, y>0, z>0, x+y+z=1.

2. The modified cathode material according to claim 1, characterized in that, The lanthanum nickel oxide is selected from La3Ni2O7.

3. The modified cathode material according to claim 1 or 2, characterized in that, The x ≥ 0.

9.

4. The modified cathode material according to claim 1 or 2, characterized in that, The molar ratio of the lanthanum nickel oxide to the high-nickel ternary cathode material is (0.8-3.5):(99.2-96.5).

5. The method for preparing the modified cathode material according to any one of claims 1-4, characterized in that, The preparation method includes: mixing a high-nickel ternary cathode material or its preparation raw materials with a lanthanum source and a nickel source, and carrying out a solid-phase reaction to obtain the modified cathode material.

6. The preparation method according to claim 5, characterized in that, The mixing is either direct mixing or mixing in a solvent; And / or, the solid-phase reaction is carried out in oxygen; And / or, the temperature of the solid-phase reaction is 450-800℃; And / or, the solid-phase reaction time is 5-24 h.

7. The preparation method according to claim 6, characterized in that, The mixing time in the solvent is 3-8 hours; And / or, when mixed in a solvent, the preparation method further includes adding a carbon source for mixing; And / or, the mixture is dried in a solvent and then subjected to a solid-phase reaction.

8. The preparation method according to claim 7, characterized in that, The lanthanum source is selected from any one or more of lanthanum oxide, lanthanum carbonate, lanthanum nitrate, lanthanum oxalate, or lanthanum acetate; And / or, the nickel source is selected from any one or more of nickel oxide, nickel carbonate, nickel nitrate, nickel oxalate, or nickel acetate; And / or, the carbon source is selected from any one or more of citric acid, oxalic acid, or glucose.

9. A positive electrode sheet, characterized in that, The positive electrode sheet comprises the modified positive electrode material according to any one of claims 1-4.

10. An electrochemical device, characterized in that, The electrochemical device includes the modified cathode material according to any one of claims 1-4 or the cathode sheet according to claim 9.

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