A positive electrode material co-modified by niobium and aluminum, and a construction method and application thereof

Abstract

The application discloses a positive electrode material co-modified by niobium and aluminum, a construction method and application thereof. The construction method comprises the following steps: (1) mixing a soluble metal niobium salt, a metal aluminum salt and an alcohol solvent to form a solution A after reaction; (2) adding a positive electrode active material into an anti-solvent to form a suspension B after mixing; (3) mixing the solution A obtained in the step (1) and the suspension B obtained in the step (2) to obtain a uniformly coated powder after reaction under stirring; and (4) calcining the uniformly coated powder obtained in the step (3) to obtain the positive electrode material co-modified by niobium and aluminum. The application constructs an interface co-modified by Nb and Al on the surface of the positive electrode material, and realizes the significant improvement of the performance of the positive electrode material under an extreme environment such as high voltage and the excellent high-voltage stability.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of energy materials, and relates to a positive electrode material co-modified by niobium and aluminum, a construction method and application thereof, in particular to a method for interface regulation of a positive electrode material, and in particular to a method for controllable construction of a composite interface layer containing niobium and aluminum co-modification on the surface of a positive electrode material, and preparation of a lithium ion battery positive electrode material with high stable surface structure and excellent electrochemical performance. BACKGROUND

[0002] The rapid increase in energy density of lithium ion batteries (LIB) has led to its rapid application in the fields of electric vehicles and portable electronic devices. The positive electrode material is a key link to determine the energy density of lithium ion batteries. Among many materials, high-nickel ternary positive electrode material LiNi x Co y Mn 1-x-y O2(x≥0.8) has high energy density and power density, and is considered to be one of the most ideal lithium ion battery positive electrode materials in the next generation. Among them, the capacity of the ternary positive electrode material mainly depends on the content of Ni element, and high Ni content will bring higher specific capacity, but also will make the material have poorer cycle stability. Especially at high cut-off voltage, on the one hand, the positive electrode material in the deep delithiation state has a higher content of high oxidation state Ni 4+ , which will cause serious irreversible side reactions between the material surface and the electrolyte, greatly reduce the structural stability of the positive electrode material, increase the interface impedance, and thus lead to rapid capacity decay; on the other hand, the battery will undergo irreversible structural phase transition and anisotropic volume change during repeated charge and discharge, which will lead to the risk of structural degradation of the positive electrode material such as particle cracking and even crushing.

[0003] Therefore, it is particularly important to modify the interface of high-nickel ternary positive electrode materials. Surface coating is considered as an effective modification strategy. By constructing a uniform and thin buffer layer on the surface of the positive electrode material, the contact reaction between the positive electrode active material and the organic electrolyte can be effectively blocked, which can well stabilize the interface structure. At the same time, lithium ions can be transmitted between the electrolyte and the positive electrode material, without causing a large loss of electrode capacity. However, the current coating methods, such as the solid-phase mixing sintering used in patent CN109950498A and the solvent evaporation used in patent CN108336348A, are difficult to achieve uniform distribution of coated species on the surface of the positive electrode material, and it is even more difficult to accurately control the true state of the surface of the electrode material, resulting in that the corresponding relationship between coating and structure and performance cannot be systematically studied. In order to achieve this goal, it is extremely important to construct a uniform and controllable interface protection layer to regulate the surface state of the positive electrode material, so as to maximize the structural stability and cycle stability of the high-nickel ternary positive electrode material. Although the atomic layer deposition technology can achieve uniform deposition of a single species on the positive electrode material, it has great challenges in the uniform and controllable construction of multiple composite species. At the same time, the method is complicated and the cost is extremely high, so it is difficult to realize large-scale production and application.

[0004] Therefore, based on the above factors, it is of great significance to develop a protection strategy for low-cost, large-batch processing, and uniform and controllable surface regulation of positive electrode materials for lithium-ion battery positive electrode materials. SUMMARY

[0005] The purpose of the present application is to construct a method for constructing a positive electrode material co-modified by niobium and aluminum and its application. By introducing a composite strategy, the interface structure of the positive electrode material is stabilized, thereby improving the cycle life and rate performance of the battery.

[0006] In order to achieve the above technical purpose, the present application adopts the following technical scheme:

[0007] A method for constructing a positive electrode material co-modified by niobium and aluminum, the method comprising the following steps:

[0008] (1) mixing a soluble niobium salt, a metal aluminum salt and an alcohol solvent to form a solution A;

[0009] (2) adding a positive electrode active material to an anti-solvent to form a suspension B;

[0010] (3) mixing the solution A obtained in step (1) with the suspension B obtained in step (2) and reacting under stirring to obtain a uniformly coated powder;

[0011] (4) calcining the powder with the surface uniformly coated obtained in step (3) to obtain the positive electrode material co-modified by niobium and aluminum.

[0012] According to an embodiment of the present application, in step (1), the alcohol solvent includes but is not limited to one or more of ethylene glycol, glycerol, tetraethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, hexaethylene glycol, octaethylene glycol, polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 600, preferably diethylene glycol.

[0013] According to an embodiment of the present application, in step (1), the soluble niobium salt is selected from at least one of soluble metal niobium salts containing metal niobium elements, such as niobium chloride, niobium nitrate, niobium ethoxide, niobium oxalate, etc., and is further preferably niobium ethoxide.

[0014] According to an embodiment of the present application, in step (1), the soluble aluminum salt is selected from at least one of soluble metal aluminum salts containing metal aluminum elements, such as aluminum chloride, aluminum nitrate, aluminum sulfate, aluminum ethoxide, aluminum oxalate, etc., and is further preferably aluminum nitrate.

[0015] According to an embodiment of the present application, in step (1), the concentration of the soluble niobium salt in solution A is 1×10 -4 ~1 mol / L, and is further preferably 1×10 -3 ~0.5 mol / L.

[0016] According to an embodiment of the present application, in step (1), the concentration of the soluble aluminum salt in solution A is 1×10 -4 ~1 mol / L, and is further preferably 1×10 -3 ~0.5 mol / L.

[0017] According to an embodiment of the present application, in step (1), the reaction conditions for forming solution A include that the reaction temperature is room temperature to 50°C, preferably room temperature, and the reaction time is 2h-72h, preferably 12h.

[0018] According to an embodiment of the present application, in step (2), the positive electrode active material includes but is not limited to at least one of lithium ion battery positive electrode materials high-nickel ternary lithium nickel cobalt manganese oxide, lithium nickelate, lithium cobaltate, lithium manganate, lithium-rich manganese-based material, lithium nickel manganate, lithium nickel cobaltate, lithium nickel cobalt aluminate, lithium titanate, lithium iron phosphate, sodium ion battery positive electrode material, potassium ion battery positive electrode material, for example, selected from high-nickel ternary lithium nickel cobalt manganese oxide material.

[0019] According to an embodiment of the present application, in step (2), the concentration of the positive electrode active material is 1×10 -2 ~20 mol / L, and is further preferably 1-15 mol / L.

[0020] According to an embodiment of the present application, in step (2), the anti-solvent includes, but is not limited to, at least one of methanol, ethanol, propanol, acetone, butanone, chloroform, dichloromethane, furfural, acetonitrile, dioxane, ethyl acetate, acetic acid, formic acid, acetic anhydride, acetylacetone, acetaldehyde, tetrahydrofuran, preferably acetone.

[0021] According to an embodiment of the present application, in step (2), the mixing is carried out under stirring.

[0022] According to an embodiment of the present application, in step (3), the method of mixing solution A with suspension B includes: directly pouring, slowly dripping, or dripping by a peristaltic pump to control the dripping speed into solution B; or, directly pouring, slowly dripping, or dripping by a peristaltic pump to control the dripping speed into solution A, preferably slowly dripping solution A into suspension B by a peristaltic pump. Preferably, the dripping speed controlled by the peristaltic pump is between 0.1 ml / min and 30 ml / min.

[0023] According to an embodiment of the present application, in step (3), the stirring temperature is between room temperature and 50°C, preferably room temperature.

[0024] According to an embodiment of the present application, in step (3), the stirring speed is between 100 r / min and 1000 r / min, preferably 600 r / min.

[0025] According to an embodiment of the present application, in step (3), the thickness of the coating layer of the surface uniformly coated powder is between 1 nm and 200 nm.

[0026] According to an embodiment of the present application, in step (4), the calcination atmosphere is at least one of oxygen, air, nitrogen, and argon, preferably oxygen.

[0027] According to an embodiment of the present application, in step (4), the calcination temperature is between 200°C and 900°C, preferably between 500°C and 800°C.

[0028] According to an embodiment of the present application, in step (4), the calcination time is between 1 h and 10 h, preferably between 1 h and 5 h.

[0029] According to an embodiment of the present application, in step (4), the shell structure of the Nb and Al co-modified positive electrode material is a composite interface layer containing niobium and aluminum.

[0030] The present application also provides a Nb and Al co-modified positive electrode material, which is obtained by the above construction method.

[0031] According to an embodiment of the present application, the Nb and Al co-modified positive electrode material is a particle with a core-shell structure.

[0032] According to an embodiment of the present application, the Nb and Al co-modified cathode material comprises a shell structure and a cathode active material, the shell structure is modified on the surface of the cathode active material; the cathode active material has the meaning as described above; the shell structure at least comprises Nb and Al elements.

[0033] Preferably, the shell structure partially or entirely coats the surface of the cathode active material, preferably entirely coats the surface of the cathode active material. Further, the shell structure is continuously and uniformly distributed on the surface of the cathode active material.

[0034] According to an embodiment of the present application, the thickness of the shell structure is 0 nm to 200 nm, for example, 1 nm, 1.5 nm, 5 nm, 10 nm, 50 nm, 100 nm, 150 nm.

[0035] The present application also provides the application of the above-mentioned Nb and Al co-modified cathode material in energy storage batteries, for example, in high-voltage lithium ion batteries.

[0036] Advantages:

[0037] The present application provides a construction method of a Nb and Al co-modified cathode material, which has the advantages of simple process flow, low cost, and suitability for large-scale processing of large quantities of samples, and the non-aqueous solvent environment can ensure the non-destructive modification treatment of the cathode material. The method simultaneously and conveniently introduces different metal elements through the interaction between the precursor solvent, metal salt and anti-solvent, realizes the slow deposition of the Nb and Al-containing coating species on the surface of the cathode particles, and forms a uniform and continuous coating layer. Through further high-temperature calcination process, a cathode material with surface Nb and Al double modification can be obtained. By adjusting the ratio of Nb / Al, the thickness of the coating layer, the calcination temperature and the calcination time, the state of the cathode surface can be effectively controlled, and excellent comprehensive electrochemical performance can be realized.

[0038] The present application constructs a Nb and Al co-modified interface on the surface of the cathode material, and elements Nb and Al simultaneously undergo interface reaction on the surface of the cathode material, thereby creating a unique and more stable surface structure under the driving of high-temperature heat treatment, and finally realizing the significant improvement of the performance of the cathode material under extreme environment such as high voltage, and excellent high-voltage stability.

[0039] The present application can perform large-scale coating treatment of the cathode material under water-free and mild conditions, simultaneously introduce Nb and Al-containing coating layers on the interface of the cathode material, and strengthen the interaction between different coating elements and the layered cathode through calcination treatment, thereby playing a dual role of systematically adjusting the interface stability and cycle stability of the cathode material from the structure. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 Scanning electron microscope (SEM) image of the high-nickel single-crystal cathode material co-modified by Nb and Al interface in Example 1.

[0041] Figure 2 X-ray diffraction (XRD) pattern of the high-nickel single-crystal cathode material co-modified by Nb and Al interface in Example 1.

[0042] Figure 3 Transmission electron microscope (TEM) image of the high-nickel single-crystal cathode material co-modified by Nb and Al interface before calcination in Example 1.

[0043] Figure 4 Transmission electron microscope (TEM) image of the high-nickel single-crystal cathode material co-modified by Nb and Al interface before calcination in Example 1 at high magnification.

[0044] Figure 5 Charge-discharge curve of the high-nickel single-crystal cathode material in Example 1 and Comparative Example 1 at 0.2C rate (4.3V).

[0045] Figure 6 Cycle performance of the high-nickel single-crystal cathode material in Example 1 and Comparative Example 1 at 1C rate (4.3V).

[0046] Figure 7 Cycle performance of the high-nickel single-crystal cathode material in Example 1 and Comparative Examples 1, 2 and 3 at 1C rate (4.5V). DETAILED DESCRIPTION

[0047] The technical solutions of the present application will be further described in detail below in combination with specific examples. It should be understood that the following examples are only illustratively used to explain and describe the present application, and should not be interpreted as limiting the scope of protection of the present application. Any technology realized based on the above description of the present application is covered within the scope of protection intended by the present application.

[0048] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0049] Example 1

[0050] (I) Modification of the cathode material

[0051] 1) Dissolve 0.16 ml of niobium ethoxide and 0.19 g of aluminum nitrate nonahydrate in 10 ml of diethylene glycol, and stir the reaction at room temperature for 12 h to form a precursor solution A;

[0052] 2) Dissolve 10 g of the high-nickel single-crystal cathode LiNi 0.8 Co 0.1Mn 0.1 O2(NCM) particles (particle size 1-10 pm) were dispersed into 40 ml of acetone, and ultrasonic stirring was used to disperse the particles uniformly to form a suspension B;

[0053] 3) Precursor solution A was slowly added dropwise to suspension B by a peristaltic pump at a dropwise speed of 0.1 ml / min-30 ml / min, and stirring was continued at room temperature for 1 h. After centrifugation, washing, and drying, a powder with a uniformly coated surface was obtained;

[0054] 4) The powder with a uniformly coated surface obtained in step 3) was calcined at 750°C in an oxygen atmosphere for 2 h to form a high-nickel single-crystal positive electrode material with Nb and Al double modification.

[0055] (B) Structure and morphology characterization

[0056] The surface morphology of the modified sample was observed by scanning electron microscopy (SEM-8100), Figure 1 showing that the interface-modified positive electrode material maintained the basic single-crystal morphology of the positive electrode material, and there was no enrichment of the modified species on the surface. Powder X-ray diffractometry (D8 Advance, Bruke) was used to analyze the crystal structure of the modified NCM single crystal, and the results are shown in Figure 2 showing that the modified positive electrode material maintained the typical layered structure of the NCM ternary positive electrode, and there were no other impurity peaks, indicating that the interface modification did not destroy the crystal structure of the NCM. Transmission electron microscopy (TEM-2100F) was used to observe the surface state of the coated particles, and the results are shown in Figure 3 showing that a uniform and continuous coating layer was formed on the surface of the positive electrode particles, and Figure 4 further showing that the thickness thereof was about 5 nm.

[0057] (III) Preparation of interface-modified NCM electrode sheet

[0058] The Nb and Al double-modified high-nickel single-crystal positive electrode particles prepared above, 0.24 g, were mixed with conductive additive Super-P 0.03 g, 5% mass concentration of PVDF 0.6 g as a binder, and a small amount of solvent NMP, and a slurry was prepared. The slurry was coated on an aluminum sheet as a current collector, and the coated aluminum sheet was dried to obtain an interface-modified NCM electrode sheet.

[0059] (IV) Assembly of battery

[0060] A battery was assembled in an argon glove box using the above interface-modified NCM electrode sheet as a positive electrode, lithium metal as a negative electrode, polypropylene microporous film (Celgard 2400) as a separator, and 1.15 mol / L LiPF6 as an electrolyte.

[0061] (V) Battery test

[0062] The above battery was tested by constant current charge-discharge test using a blue electric charge-discharge instrument, and was cycled at 1C rate (1C = 200 mA / g), wherein the first three circles were 0.2C activation stage, and the test temperature was 25°C. The specific capacity of the battery and the charge-discharge current were calculated based on the mass of NCM.

[0063] Example 2

[0064] (I) Modification of the positive electrode material

[0065] 1) 0.16 ml of niobium ethoxide and 0.38 g of aluminum nitrate nonahydrate were dissolved in 10 ml of diethylene glycol, and the reaction was stirred at room temperature for 12 h to form precursor solution A;

[0066] 2) 10 g of high-nickel single-crystal positive electrode LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM) particles (particle size 1-10 μm) were dispersed in 40 ml of acetone, and ultrasonic stirring was used to disperse uniformly to form suspension B;

[0067] 3) The precursor solution A was slowly added to the suspension B by peristaltic pump, and stirring was continued at room temperature for 1 h, and the surface uniformly coated powder was obtained after centrifugation, washing and drying;

[0068] 4) The surface uniformly coated powder obtained in step 3) was calcined at 750°C under oxygen atmosphere for 2 h to form a high-nickel single-crystal positive electrode material with Nb and Al double modification.

[0069] (II) Structure and morphology characterization (the specific steps are the same as in Example 1).

[0070] (III) Preparation of interface-modified NCM electrode sheet (the specific steps are the same as in Example 1).

[0071] (IV) Assembly of battery (the specific steps are the same as in Example 1).

[0072] (V) Battery test (the specific steps are the same as in Example 1).

[0073] Example 3

[0074] (I) Modification of the positive electrode material

[0075] 1) 0.16 ml of niobium ethoxide and 0.38 g of aluminum nitrate nonahydrate were dissolved in 10 ml of diethylene glycol, and the reaction was stirred at room temperature for 12 h to form precursor solution A;

[0076] 2) 10 g of high-nickel single-crystal positive electrode LiNi 0.8 Co 0.1 Mn 0.1O2(NCM) particles (particle size 1-10 μm) were dispersed into 40 ml of acetone, and uniformly dispersed by ultrasonic stirring to form a suspension B;

[0077] 3) Precursor solution A was slowly added dropwise into suspension B by peristaltic pump, and stirring was continued at room temperature for 1 h. The uniformly coated powder was obtained by centrifugation, washing, and drying;

[0078] 4) The uniformly coated powder obtained in step 3) was calcined at 750°C under an oxygen atmosphere for 2 h to form a high-nickel single-crystal cathode material with Nb and Al double modification.

[0079] (ii) Structure and morphology characterization (the specific steps are the same as in Example 1).

[0080] (iii) Preparation of an interface-modified NCM electrode sheet (the specific steps are the same as in Example 1).

[0081] (iv) Assembly of a battery (the specific steps are the same as in Example 1).

[0082] (v) Battery testing (the specific steps are the same as in Example 1).

[0083] Example 4

[0084] (i) Modification of a cathode material

[0085] 1) 0.16 ml of niobium ethoxide and 0.19 g of aluminum nitrate nonahydrate were dissolved in 10 ml of diethylene glycol, and stirring was performed at room temperature for 12 h to form a precursor solution A;

[0086] 2) 10 g of high-nickel single-crystal cathode LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM) particles (particle size 1-10 μm) were dispersed into 40 ml of acetone, and uniformly dispersed by ultrasonic stirring to form a suspension B;

[0087] 3) Precursor solution A was slowly added dropwise into suspension B by peristaltic pump, and stirring was continued at room temperature for 1 h. The uniformly coated powder was obtained by centrifugation, washing, and drying;

[0088] 4) The uniformly coated powder obtained in step 3) was calcined at 700°C under an oxygen atmosphere for 2 h to form a high-nickel single-crystal cathode material with Nb and Al double modification.

[0089] (ii) Structure and morphology characterization (the specific steps are the same as in Example 1).

[0090] (iii) Preparation of an interface-modified NCM electrode sheet (the specific steps are the same as in Example 1).

[0091] (iv) Assembling the battery (the specific steps are the same as in Example 1).

[0092] (v) Battery testing (the specific steps are the same as in Example 1).

[0093] Example 5

[0094] (i) Modification of the positive electrode material

[0095] 1) 0.16 ml of niobium ethoxide and 0.19 g of aluminum nitrate nonahydrate were dissolved in 10 ml of diethylene glycol, and the reaction was stirred at room temperature for 12 h to form precursor solution A;

[0096] 2) 10 g of high-nickel single-crystal positive electrode LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM) particles (particle size 1-10 pm) were dispersed in 40 ml of acetone, and ultrasonic stirring was performed to uniformly disperse the particles to form suspension B;

[0097] 3) Precursor solution A was slowly added dropwise to suspension B by using a peristaltic pump, and stirring was continued at room temperature for 1 h, and then surface uniformly coated powder was obtained through centrifugation, washing, and drying;

[0098] 4) The surface uniformly coated powder obtained in step 3) was calcined at 800°C in an oxygen atmosphere for 2 h to form a high-nickel single-crystal positive electrode material with Nb and Al double modification.

[0099] (ii) Structural and morphological characterization (the specific steps are the same as in Example 1).

[0100] (iii) Preparation of an interface-modified NCM electrode sheet (the specific steps are the same as in Example 1).

[0101] (iv) Assembling the battery (the specific steps are the same as in Example 1).

[0102] (v) Battery testing (the specific steps are the same as in Example 1).

[0103] Example 6

[0104] (i) Modification of the positive electrode material

[0105] 1) 0.16 ml of niobium ethoxide and 0.19 g of aluminum nitrate nonahydrate were dissolved in 10 ml of diethylene glycol, and the reaction was stirred at room temperature for 12 h to form precursor solution A;

[0106] 2) 10 g of high-nickel single-crystal positive electrode LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM) particles (particle size 1-10 pm) were dispersed in 40 ml of acetone, and ultrasonic stirring was performed to uniformly disperse the particles to form suspension B;

[0107] 3) The precursor solution A was slowly added dropwise to the suspension B using a peristaltic pump, and the mixture was stirred for 1 hour at room temperature. After centrifugation, washing, and drying, a powder with a uniformly coated surface was obtained.

[0108] 4) The powder with uniform surface coating obtained in step 3) is calcined at 750°C in an oxygen atmosphere for 6 hours to form a high-nickel single crystal cathode material with dual Nb and Al modification.

[0109] (II) Structural and morphological characterization (specific steps are the same as in Example 1).

[0110] (III) Preparation of interface-modified NCM electrode sheets (specific steps are the same as in Example 1).

[0111] (iv) Assemble the battery (the specific steps are the same as in Example 1).

[0112] (v) Battery testing (specific steps are the same as in Example 1).

[0113] Example 7

[0114] (I) Modification of cathode materials

[0115] 1) Dissolve 0.16 ml of niobium ethanol and 0.19 g of aluminum nitrate nonahydrate in 10 ml of diethylene glycol, and stir the mixture at room temperature for 12 h to form precursor solution A;

[0116] 2) 10g of high-nickel single-crystal LiNi cathode 0.8 Co 0.1 Mn 0.1 O2 (NCM) particles (particle size 1-10μm) were dispersed in 40ml of acetone and ultrasonically stirred to form a suspension B.

[0117] 3) The precursor solution A was slowly added dropwise to the suspension B using a peristaltic pump, and the mixture was stirred for 1 hour at room temperature. After centrifugation, washing, and drying, a powder with a uniformly coated surface was obtained.

[0118] 4) The powder with uniform surface coating obtained in step 3) is calcined at 750°C in an oxygen atmosphere for 1 hour to form a high-nickel single crystal cathode material with dual Nb and Al modification.

[0119] (II) Structural and morphological characterization (specific steps are the same as in Example 1).

[0120] (III) Preparation of interface-modified NCM electrode sheets (specific steps are the same as in Example 1).

[0121] (iv) Assemble the battery (the specific steps are the same as in Example 1).

[0122] (v) Battery testing (specific steps are the same as in Example 1).

[0123] Comparative Example 1

[0124] (I) Preparation of cathode materials

[0125] 1) 10g of high-nickel single-crystal LiNi cathode 0.8 Co 0.1 Mn 0.1 O2(NCM) particles (particle size 1-10μm) were dispersed in 40ml of acetone and stirred at room temperature for 1h. After centrifugation, washing and drying, the powder was obtained.

[0126] 2) The dried powder obtained in step 1) is calcined at 750°C in an oxygen atmosphere for 2 hours to obtain unmodified high-nickel single crystal cathode material.

[0127] (II) Structural and morphological characterization (specific steps are the same as in Example 1).

[0128] (III) Preparation of NCM electrode sheet (specific steps are the same as in Example 1).

[0129] (iv) Assemble the battery (the specific steps are the same as in Example 1).

[0130] (v) Battery testing (specific steps are the same as in Example 1).

[0131] Table 1

[0132]

[0133]

[0134] The data in the accompanying drawings and Table 1 demonstrate that the cycle stability of the high-nickel cathode can be maximized without sacrificing its initial charge-discharge capacity by conveniently adjusting the appropriate Nb / Al ratio, coating thickness, and selecting suitable heat treatment temperature and time. This is likely because the simultaneous introduction of an appropriate amount of Nb and Al dual-interface layer is beneficial for stabilizing the interfacial structure of the layered cathode and promoting lithium-ion transport. Insufficient metal salt introduction is insufficient to form a uniform and complete coating layer, while excessive introduction hinders lithium-ion transport. Excessively high heat treatment temperatures and prolonged treatment times are detrimental to the stability of the material's crystal structure, leading to the formation of harmful impurities and significant capacity loss, while also compromising cycle stability. Conversely, low heat treatment temperatures and short treatment times hinder the full conversion of the surface coating layer at the electrode material interface, negatively impacting lithium-ion transport kinetics and thus affecting both capacity and stability.

[0135] Figure 5The charge-discharge curves of the cathode material after condition optimization in Example 1 at a rate of 0.2C (within the range of 3-4.3V) are shown. The high-nickel sample after interface modification exhibits similar charge-discharge curve characteristics to the original sample, and the discharge specific capacity of the modified sample can still reach 190.8mAh / g, indicating that appropriate modification will not cause the initial capacity to decay. Figure 6 The graph shows a comparison of the cycling performance of the modified and unmodified samples in Example 1 at a 1C rate. After 100 cycles, the modified sample showed a significantly improved capacity retention rate of up to 96.4%, demonstrating that the Nb and Al interface co-modification strategy has a clear advantage in improving the cycling stability of the cathode material.

[0136] Comparative Example 2

[0137] (I) Preparation of cathode materials

[0138] 1) Dissolve 0.32 ml of niobium ethanol in 10 ml of diethylene glycol and stir at room temperature for 12 h to form precursor solution A;

[0139] 2) 10g of high-nickel single-crystal LiNi cathode 0.8 Co 0.1 Mn 0.1 O2 (NCM) particles (particle size 1-10μm) were dispersed in 40ml of acetone and ultrasonically stirred to form a suspension B.

[0140] 3) The precursor solution A was slowly added dropwise to the suspension B using a peristaltic pump, and the mixture was stirred for 1 hour at room temperature. After centrifugation, washing, and drying, the processed powder was obtained.

[0141] 4) The dried powder obtained in step 3) is calcined at 750°C in an oxygen atmosphere for 2 hours to form a high-nickel single-crystal cathode material modified with Nb.

[0142] (II) Structural and morphological characterization (specific steps are the same as in Example 1).

[0143] (III) Preparation of interface-modified NCM electrode sheets (specific steps are the same as in Example 1).

[0144] (iv) Assemble the battery (the specific steps are the same as in Example 1).

[0145] (v) Battery testing (specific steps are the same as in Example 1).

[0146] Comparative Example 3

[0147] (I) Preparation of cathode materials

[0148] 1) Dissolve 0.38g of aluminum nitrate nonahydrate in 10ml of diethylene glycol and stir at room temperature for 12h to form precursor solution A;

[0149] 2) 10g of high-nickel single-crystal LiNi cathode 0.8 Co 0.1 Mn 0.1 O2 (NCM) particles (particle size 1-10μm) were dispersed in 40ml of acetone and ultrasonically stirred to form a suspension B.

[0150] 3) The precursor solution A was slowly added dropwise to the suspension B using a peristaltic pump, and the mixture was stirred for 1 hour at room temperature. After centrifugation, washing, and drying, the processed powder was obtained.

[0151] 4) The dried powder obtained in step 3) is calcined at 750°C in an oxygen atmosphere for 2 hours to form a high-nickel single-crystal cathode material modified with Al alone.

[0152] (II) Structural and morphological characterization (specific steps are the same as in Example 1).

[0153] (III) Preparation of interface-modified NCM electrode sheets (specific steps are the same as in Example 1).

[0154] (iv) Assemble the battery (the specific steps are the same as in Example 1).

[0155] (v) Battery testing (specific steps are the same as in Example 1).

[0156] Based on the advantages of cycle stability demonstrated by Example 1 in the 3-4.3V range, its cycle stability under extreme conditions with a high cutoff voltage of 4.5V was further tested and compared with Comparative Example 2 and Comparative Example 3. Figure 7 To test the cycling curves at 1C rate within the voltage range of 3–4.5V, the high-nickel sample co-modified with Nb and Al exhibited excellent high-voltage stability. After 100 cycles, the capacity retention rate remained at 93%, which was much higher than that of Comparative Example 3 (91%), Comparative Example 2 (85%), and Comparative Example 1 (82%). This demonstrates that the strategy of co-modification with Nb and Al creates a more stable interface structure, which is completely different from individual interface modification. This has a significant advantage in improving the cycling stability of cathode materials at high cutoff voltages.

[0157] The exemplary embodiments of the present invention have been described above. However, the scope of protection of this application is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for constructing a positive electrode material co-modified with niobium and aluminum, characterized by, The construction method comprises the following steps: (1) mixing a soluble niobium salt and a soluble aluminum salt with an alcohol solvent to form a solution A; (2) adding a positive electrode active material to an anti-solvent to form a suspension B; (3) mixing the solution A obtained in step (1) with the suspension B obtained in step (2) to form a powder with a uniform surface coating after stirring; (4) calcining the powder with a uniform surface coating obtained in step (3) to obtain a positive electrode material co-modified by niobium and aluminum; the calcination temperature is 200-900 ℃; the calcination time is 1-10 h. The positive electrode material co-modified by niobium and aluminum comprises a shell structure and a positive electrode active material, the shell structure is modified on the surface of the positive electrode active material; the shell structure comprises at least niobium and aluminum elements; the thickness of the shell structure is 1 nm-200 nm.

2. The construction method according to claim 1, characterized in that, In step (1), the alcohol solvent comprises one or more of ethylene glycol, glycerol, tetraethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, hexaethylene glycol, octaethylene glycol, polyethylene glycol 200, polyethylene glycol 400, and polyethylene glycol 600. In step (1), the soluble niobium salt is selected from at least one of soluble metal niobium salts containing a metal niobium element. In step (1), the soluble aluminum salt is selected from at least one of soluble metal aluminum salts containing a metal aluminum element. In step (1), the concentration of the soluble niobium salt in solution A is 1 x 10 -4 1 mol / L. In step (1), the concentration of the soluble aluminum salt in solution A is 1 x 10 -4 1 mol / L. In step (1), the reaction conditions for forming the solution A include a reaction temperature of room temperature to 50 ℃ and a reaction time of 2 h-72 h.

3. The construction method according to claim 1, wherein In step (2), the positive electrode active material comprises at least one of lithium ion battery positive electrode materials, sodium ion battery positive electrode materials, and potassium ion battery positive electrode materials. In step (2), the concentration of the positive electrode active material is 1 x 10 -2 20 mol / L. In step (2), the anti-solvent comprises at least one of methanol, ethanol, propanol, acetone, butanone, chloroform, dichloromethane, furfural, acetonitrile, dioxane, ethyl acetate, acetic acid, formic acid, acetic anhydride, acetylacetone, acetaldehyde, and tetrahydrofuran.

4. The construction method according to claim 3, wherein The lithium ion battery positive electrode material is selected from at least one of high-nickel ternary lithium nickel-cobalt-manganese oxide, lithium nickelate, lithium cobaltate, lithium manganate, lithium-rich manganese-based material, lithium nickel-manganese oxide, lithium nickel-cobalt oxide, lithium nickel-cobalt-aluminum oxide, lithium titanate, and lithium iron phosphate.

5. The construction method according to claim 1, characterized in that, In step (3), the method for mixing the solution A with the suspension B comprises directly pouring, slowly dripping, or dripping into the suspension B at a controlled dripping speed by a peristaltic pump, or directly pouring, slowly dripping, or dripping into the solution A at a controlled dripping speed by a peristaltic pump; the dripping speed controlled by the peristaltic pump is 0.1 ml / min-30 ml / min. In step (3), the stirring temperature is room temperature to 50 ℃. In step (3), the stirring speed is 100 r / min-1000 r / min.

6. The construction method according to claim 1, wherein In step (4), the calcination atmosphere is at least one of oxygen, air, nitrogen, and argon.

7. The construction method according to claim 1, wherein In step (4), the shell structure of the positive electrode material co-modified by niobium and aluminum is a composite interface layer containing niobium and aluminum.

8. A positive electrode material co-modified with Nb and Al, characterized by, The positive electrode material is obtained by the construction method of any one of claims 1-7.

9. The positive electrode material of claim 8, wherein, The Nb and Al co-modified positive electrode material is a particle having a core-shell structure.

10. The positive electrode material of claim 8, wherein, The shell structure coats a surface portion or the entirety of the positive electrode active material.

11. The cathode material of claim 8, wherein, The shell structure is continuously and uniformly distributed on the surface of the positive electrode active material.

12. Use of the Nb and Al co-modified positive electrode material according to any one of claims 8 to 11 in an energy storage battery.

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