A modified high-nickel cathode material with a stable interface and its preparation method, and a lithium-ion battery.

Abstract

This invention provides a modified high-nickel cathode material with a stable interface, comprising a high-nickel cathode material matrix and a coating layer. The surface of the matrix includes a lithium-containing rock salt phase, which is doped with high-valence metal A ions with strong metal-oxygen bonds, and the lithium-nickel mixture on the surface is higher than that in the bulk phase. The coating layer is a homogeneous mixture of carbon and oxides of high-valence metal A ions, with the valence state of the high-valence metal A ions not lower than +3. This modified high-nickel cathode material is obtained by uniformly coating a nickel cathode material with a metal-organic salt and then subjecting it to short-time heat treatment in an inert atmosphere. The synergistic effect of carbon reduction and strong M-O bonds clamps the oxygen vacancy content, constructing a stable surface, mitigating phase transitions during charge and discharge, improving the lithium-ion diffusion rate under deep delithiation conditions, suppressing the generation of interfacial side reactions, and the carbon coating layer improves the electronic conductivity of the material. Therefore, the electrochemical cycle stability, rate performance, and safety of the cathode material are improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery cathode material technology, and specifically relates to a high-nickel cathode material with an efficient and stable interface structure and its construction method. Background Technology

[0002] Lithium-ion batteries have gradually become the most important rechargeable batteries due to their high energy density, superior safety performance, and excellent cycle life. Currently, lithium-ion batteries are widely used in mobile electronic devices such as mobile phones, tablets, and laptops. Furthermore, with the increasing demand for clean transportation, new energy hybrid electric vehicles (HEVs) and pure electric vehicles (EVs) are developing rapidly, leading to explosive growth in their core lithium-ion power batteries. To enable electric vehicles to approach or even reach the performance levels of gasoline vehicles and meet consumer demands for long-distance driving, fast charging, and safety, it is crucial to develop lithium-ion batteries with higher energy density, stronger rate performance, longer cycle life, and greater safety.

[0003] Cathode materials are one of the most critical components of lithium-ion batteries, accounting for approximately 40% of their cost and being a major factor limiting their performance. Nickel-based layered transition metal oxides have attracted widespread attention due to their high energy density, excellent cycle stability, and economic efficiency, and are gradually being developed towards high-nickel and ultra-high-nickel materials to achieve even higher energy densities. While high-nickel and ultra-high-nickel cathode materials exhibit increased specific capacity with increasing nickel content, they also face more severe electrochemical performance degradation and safety issues. One of the main reasons for these problems is the interfacial side reactions between the cathode material and the electrolyte. These side reactions, leading to metal element dissolution, the formation of a cathode solid electrolyte interphase (CEI), and changes and destruction of the surface crystal structure, hinder the transport of lithium ions and electrons within the cathode material and at the interface, exacerbating structural instability and ultimately affecting the electrochemical cycle stability of the cathode material.

[0004] Currently, the main methods to enhance the interfacial stability of high-nickel cathode materials are element doping and surface coating, thereby improving their electrochemical performance. Specifically, doping with elements that form strong metal-oxygen bonds (MO bonds) can improve the structural stability of the crystal lattice; a uniform surface coating can prevent direct contact between the cathode material surface and the electrolyte, reducing interfacial side reactions; and coating with substances possessing high electron transport rates can also effectively improve the overall electronic conductivity of the cathode material.

[0005] CN111994967A discloses a method for producing a high-nickel ternary lithium-ion cathode material doped with an organic titanium source. The method involves secondary sintering of the high-nickel cathode material-organic titanium source gel under an oxidizing atmosphere to achieve surface coating and doping of titanium, thereby increasing the lattice stability of the material and improving its cycle stability.

[0006] CN106910874B discloses a method for simultaneously achieving surface coating and surface doping of high-nickel materials. The method involves mixing a precursor with tetrabutyl titanate, followed by a titanium dioxide coating layer formed on the precursor surface through the hydrolysis of tetrabutyl titanate. In the subsequent lithium mixing-high-temperature sintering process, a high-nickel cathode material with surface Li₂TiO₃ coating and surface Ti doping is formed. The synergistic effect of these two processes effectively suppresses interfacial reactions, improves structural stability, and enhances the electrochemical performance of the material. While the synergistic effect of surface doping and coating can effectively improve the interfacial stability of the material, it often affects electron conduction at the interface.

[0007] CN110429275A discloses a method for achieving carbon coating on the surface of ternary cathode materials in an organic liquid phase system using an organic carbon source in a low-temperature thermal reducing atmosphere. This method improves the electronic conductivity of the material and enhances its cycle stability and rate performance. However, the increase in coating material leads to a decrease in its discharge specific capacity under low current. This is because the secondary sintering process in an argon atmosphere creates a micro-reducing environment, where carbon captures oxygen from the cathode material lattice, resulting in an increase in the degree of oxygen vacancies and lithium-nickel mixing. The particle surface undergoes a phase transformation from layered to spinel phase to inert rock salt phase, affecting the insertion and extraction of lithium ions.

[0008] Therefore, simultaneously improving the electronic conductivity and lithium-ion transport rate at the interface while suppressing the generation of oxygen vacancies to achieve the construction of an efficient and stable interface is the key to improving the performance of high-nickel cathode materials, especially ultra-high-nickel cathode materials. Summary of the Invention

[0009] To address the aforementioned technical problems, the present invention aims to provide a modified high-nickel cathode material with a stable interface, its preparation method, and a lithium-ion battery.

[0010] To achieve the above objectives, the present invention proposes the following solution:

[0011] This invention provides a modified high-nickel cathode material with a stable interface, comprising a matrix and a coating layer covering the matrix. The matrix is ​​a high-nickel cathode material, the surface of the matrix includes a lithium-containing rock salt phase, the surface of the matrix is ​​doped with high-valence metal A ions with strong metal-oxygen bonds, and the lithium-nickel mixture on the surface of the matrix is ​​higher than that in the bulk phase. The valence state of the high-valence metal A ions is not lower than +3. The coating layer is a homogeneous mixture of carbon and oxides of high-valence metal A.

[0012] Preferably, the high-valence metal A is one or more of Mn, Ti, Mo, Cr, and W.

[0013] Preferably, the doping depth of the high-valence metal A ions is within 100 nm.

[0014] Optionally, the surface of the substrate may further include one or both of a layered and spinel phase with a high lithium-ion transport rate.

[0015] Preferably, the thickness of the coating layer is 1~200 nm.

[0016] Preferably, the chemical formula of the matrix is ​​LiNi. x M 1-x O2, where 0.9≤x≤1, and M is one or more of the rare earth elements Co, Mn, Al, Mg, Ti, Zr, Mo, Cr, B, and O2.

[0017] As a general inventive concept, this invention also provides a method for preparing a modified high-nickel cathode material with a stable interface, comprising:

[0018] S1. A soluble organometallic salt is coated on the surface of a high-nickel cathode material; the metal in the organometallic salt is one or more of Mn, Ti, Mo, Cr, and W;

[0019] S2. The high-nickel cathode material coated with organometallic salt is subjected to short-term heat treatment under a protective atmosphere to obtain the cathode material.

[0020] Preferably, step S1 includes:

[0021] (1) Dissolve the organometallic salt in an organic solvent to obtain an organometallic salt solution;

[0022] (2) Disperse the high-nickel cathode material in the metal-organic salt solution to form a uniformly dispersed suspension;

[0023] (3) The suspension is heated and stirred to remove the solvent, and a high-nickel cathode material coated with metal-organic salt is obtained.

[0024] Preferably, the organometallic salt has the general chemical formula M. m (C a H b O c X d ) n The metallic element M is one or more of the elements Mn, Ti, Mo, Cr, and W, (C a H b O c X d ) n It is an anionic group containing one or more of the functional groups selected from -OH, -CHO, -COOH, -NO2, -SO3H, -NH2, and RCO-.

[0025] Preferably, the high-nickel cathode material has the chemical formula LiNi. xM 1-x O2, where 0.9≤x≤1, and M is one or more of the rare earth elements Co, Mn, Al, Mg, Ti, Zr, Mo, Cr, B, and O2.

[0026] Preferably, in step S2, the temperature of the heat treatment is 300–650°C.

[0027] Preferably, in step S2, the heat treatment holding time is 1 to 3 hours.

[0028] Preferably, in step S2, the heating rate during the heat treatment is 5–20 °C / min; and the protective atmosphere is nitrogen and / or an inert atmosphere.

[0029] Preferably, the organic solvent is one or more of methanol, ethanol, propanol, ethylene glycol, formamide, acetonitrile, and acetone.

[0030] Preferably, the molar ratio of the metal in the organometallic salt to the high-nickel cathode material is 0.01% to 2%.

[0031] As a general inventive concept, the present invention also provides a lithium-ion battery, including the aforementioned modified high-nickel cathode material with a stable interface or the modified high-nickel cathode material with a stable interface prepared by the aforementioned preparation method.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. In the modified high-nickel cathode material of the present invention, the surface of the high-nickel cathode material matrix has a uniform composite coating layer of carbon and metal oxides, which can effectively suppress side reactions at the electrolyte interface, reduce gas production, and effectively improve the electronic conductivity of the material. Simultaneously, the surface of this matrix has high-valence metal element doping characteristics with high lithium conductivity and strong MO bonds, which can provide sufficient positive charge balance even under high lithium-nickel mixing conditions, enough to bind lattice oxygen and achieve the effect of clamping oxygen vacancies. This effectively improves the stability of the surface lithium-conducting rock salt phase, avoids the formation of inert rock salt phase, and improves the surface ionic conductivity of the material. Therefore, the modified high-nickel cathode material of the present invention has excellent structural stability, cycle performance, rate performance, and safety.

[0034] 2. Typically, carbon coating requires an inert atmosphere. The micro-reducing environment generated by pyrolysis induces oxygen precipitation in the crystal lattice, creating oxygen vacancies and promoting a phase transition from layered to inert rock salt phase on the particle surface. The modified high-nickel cathode material preparation method of this invention can efficiently construct a stable interface structure. It introduces high-valence metal doping with strong MO bonds while simultaneously coating with carbon. The strong MO bonds of the doped high-valence metal element can suppress the generation of oxygen vacancies, thus achieving the purpose of controlling oxygen vacancies. Subsequent reduction transforms the material into a lithium-containing phase instead of an inert rock salt phase. This ingeniously overcomes the problem of oxygen precipitation caused by lithium-nickel mixing under the micro-reducing environment of pyrolysis carbon, achieving the construction of a stable interface. This simultaneously improves the interface's ion and electron transport performance and strengthens the surface structure. Furthermore, the metal-organic salt achieves uniform coating on the material surface through liquid-phase coating and in-situ pyrolysis. Compared with solid-phase mixing and aqueous systems, the organic system can achieve uniform coating of the modified material while suppressing Li... + / H + The displacement reaction effectively avoids problems such as lithium deposition and oxygen evolution that occur when processing in aqueous solutions, thus protecting the basic properties of high-nickel cathode materials from damage.

[0035] 3. The preparation method of the modified high-nickel cathode material of the present invention is simple to operate and can achieve multi-dimensional modification such as stable interface construction, element doping, and surface coating in one step. Compared with the traditional multi-step modification method, the process flow is greatly shortened. In addition, the organic solvent used is easy to volatilize, the reaction time is short, and it can be recycled and reused, reducing costs. Attached Figure Description

[0036] 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, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 The images show the XRD patterns and refined XRD Rietveld images of lithium nickelate prepared in Examples 1-2, where (a) is the XRD pattern and (b) is the refined XRD Rietveld image.

[0038] Figure 2 SEM images of lithium nickelate prepared in Examples 1-2;

[0039] Figure 3 HRTEM images of lithium nickelate prepared in Examples 1-2;

[0040] Figure 4 EELS images of lithium nickelate prepared in Examples 1-2;

[0041] Figure 5 The lithium-ion transport rate diagrams are for lithium nickelate prepared in Examples 1-2;

[0042] Figure 6 The paramagnetic resonance spectra of lithium nickelate prepared in Examples 1-2 are shown.

[0043] Figure 7 The graph shows the cycling performance of lithium nickelate prepared in Examples 1-2 at a current density of 1C.

[0044] Figure 8 The XRD pattern and the refined XRD Rietveld pattern of lithium nickelate prepared in Comparative Example 1 are shown, where (a) is the XRD pattern and (b) is the refined XRD Rietveld pattern.

[0045] Figure 9 SEM image of lithium nickelate prepared in Comparative Example 1;

[0046] Figure 10 HRTEM image of lithium nickelate prepared in Comparative Example 1;

[0047] Figure 11 The lithium-ion transport rate diagram is for lithium nickelate prepared in Comparative Example 1.

[0048] Figure 12 The paramagnetic resonance spectrum of lithium nickelate prepared in Comparative Example 1 is shown.

[0049] Figure 13 The cycling performance of lithium nickelate prepared in Comparative Example 1 at a current density of 1C is shown in the figure.

[0050] Figure 14 Here is an HRTEM image of lithium nickelate prepared in Comparative Example 4;

[0051] Figure 15 The image shows the HRTEM image of the high-nickel cathode material prepared in Comparative Example 5. Detailed Implementation

[0052] This invention provides a modified high-nickel cathode material with a stable interface, comprising a substrate and a coating layer covering the substrate. The substrate is a high-nickel cathode material, and its surface mainly comprises a lithium-containing rock salt phase. The surface of the substrate is doped with high-valence metal A ions with strong metal-oxygen bonds, and the lithium-nickel mixture on the surface of the substrate is higher than that in the bulk phase (i.e., in the substrate, the lithium-nickel mixture on its surface is higher than the average lithium-nickel mixture of the entire substrate). The valence state of the high-valence metal A ions is not lower than +3. The coating layer is a homogeneous mixture of carbon and oxides of high-valence metal A, such as +3, +4, +5, and +6 valence metals. In this embodiment, the surface of the substrate refers to the surface layer of the substrate, while the coating layer is located outside this position.

[0053] The highly efficient and stable interface characteristics of this modified high-nickel cathode material include: (1) a high lithium-ion transport rate; (2) the presence of high-valence ion doping with strong metal-oxygen bonds, forming a clamping effect on oxygen vacancies; and (3) the presence of a uniform carbon and metal oxide coating layer. By synergistically clamping oxygen vacancies through carbon reduction and strong MO bonds, a stable surface is constructed, mitigating phase transitions during charge and discharge, increasing the lithium-ion diffusion rate under deep delithiation conditions, suppressing the generation of interfacial side reactions, and the carbon coating layer can improve the electronic conductivity of the material. Therefore, the electrochemical cycle stability, rate performance, and safety of the cathode material are improved.

[0054] In some preferred embodiments, the high-valence metal A is one or more of Mn, Ti, Mo, Cr, and W.

[0055] In some optional embodiments, the surface of the substrate further includes one or both of a layered and spinel phase with a high lithium-ion transport rate.

[0056] In some preferred embodiments, the doping depth of the high-valence metal A ions is within 100 nm, for example, it can be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 809 nm, 90 nm, 100 nm, etc.

[0057] In some preferred embodiments, the thickness of the coating layer is 1~200 nm, such as 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, etc.

[0058] In some preferred embodiments, the chemical formula of the high-nickel cathode material is LiNi. x M 1-x O2, where 0.9≤x≤1, and M is one or more of the rare earth elements Co, Mn, Al, Mg, Ti, Zr, Mo, Cr, B, and O2.

[0059] As a general inventive concept, this invention also provides a method for preparing a modified high-nickel cathode material with a stable interface, comprising:

[0060] S1. A soluble organometallic salt is coated on the surface of a high-nickel cathode material; the metal in the organometallic salt is one or more of Mn, Ti, Mo, Cr, and W;

[0061] S2. The high-nickel cathode material coated with organometallic salt is subjected to short-term heat treatment under a protective atmosphere to obtain the cathode material.

[0062] In some preferred embodiments, step S1 includes:

[0063] (1) Dissolve the organometallic salt in an organic solvent to obtain an organometallic salt solution;

[0064] (2) Disperse the high-nickel cathode material in the metal-organic salt solution to form a uniformly dispersed suspension;

[0065] (3) The suspension is heated and stirred to evaporate and remove the solvent, thereby obtaining a high-nickel cathode material coated with a metal-organic salt.

[0066] In some preferred embodiments, the general chemical formula of the organometallic salt is M. m (C a H b O c X d ) n The metallic element M is one or more of the elements with high valence states, such as Mn, Ti, Mo, Cr, and W. (C a H b O c X d ) n It is an anionic group containing one or more of the functional groups selected from -OH, -CHO, -COOH, -NO2, -SO3H, -NH2, and RCO-.

[0067] In some preferred embodiments, the chemical formula of the high-nickel cathode material is LiNi. x M 1-x O2, where 0.9≤x≤1, and M is one or more of the rare earth elements Co, Mn, Al, Mg, Ti, Zr, Mo, Cr, B, and O2.

[0068] In some preferred embodiments, in step S2, the temperature of the heat treatment is 300 to 650°C, for example, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, etc.

[0069] In some preferred embodiments, in step S2, the heat treatment holding time is 1 to 3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, etc.

[0070] In some preferred embodiments, during step S2, the heating rate during the heat treatment is 5 to 20°C / min, for example, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min, 12°C / min, 14°C / min, 16°C / min, 18°C / min, 20°C / min, etc.

[0071] In some embodiments, in step S2, the protective atmosphere is nitrogen and / or an inert atmosphere, such as argon or helium.

[0072] In some preferred embodiments, the organic solvent is one or more of methanol, ethanol, propanol, ethylene glycol, formamide, acetonitrile, and acetone.

[0073] In some preferred embodiments, the molar ratio of the metal in the organometallic salt to the high-nickel cathode material is 0.01% to 2%, for example, 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, etc.

[0074] In some embodiments, step (3) may further include: drying the solid obtained by heating and evaporating to remove the solvent.

[0075] Some embodiments also provide lithium-ion batteries, including the aforementioned modified high-nickel cathode material with a stable interface or the modified high-nickel cathode material with a stable interface prepared by the aforementioned preparation method.

[0076] To facilitate understanding of the present invention, the invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0077] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0078] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0079] The high-purity argon gas used in the following examples has a purity of 99.99%.

[0080] Example 1-1

[0081] A method for constructing an efficient and stable interface structure for ultra-high nickel cathode materials, specifically including the following steps:

[0082] (1) A certain amount of tetrabutyl titanate was dissolved in 1 mL of anhydrous ethanol to obtain a mixed solution, wherein the molar ratio of titanium to lithium nickelate in tetrabutyl titanate was 0.5%;

[0083] (2) Disperse 1g of lithium nickelate cathode material in the mixed solution to form a suspension;

[0084] (3) The suspension in step (2) is stirred and evaporated at 60°C to obtain lithium nickelate cathode material uniformly coated with tetrabutyl titanate.

[0085] (4) The lithium nickelate cathode material uniformly coated with tetrabutyl titanate is heated to 500°C in high-purity argon at a heating rate of 5°C / min and held for 2 hours, and then cooled in the furnace to obtain a lithium nickelate cathode material with a high efficiency and stable interface.

[0086] Examples 1-2

[0087] The only difference from Example 1-1 is that in step (1), the molar ratio of titanium to lithium nickelate in tetrabutyl titanate is 1%.

[0088] The materials obtained in Examples 1-2 were characterized, and the XRD patterns and Rietveld refinement images are shown below. Figure 1 As shown, the SEM image is as follows: Figure 2 As shown, the HRTEM image is as follows Figure 3 As shown, the EELS diagram is as follows Figure 4 As shown in the figure, the lithium-ion transport rate diagram is as follows: Figure 5 As shown, the EPR oxygen vacancy test results are as follows: Figure 6 As shown, the calculated concentration of oxygen vacancies is 2.055 × 10⁻⁶. -7 mol / L, cycle performance graph as shown Figure 7 As shown.

[0089] Examples 1-3

[0090] The only difference from Example 1-1 is that in step (1), the molar ratio of titanium to lithium nickelate in tetrabutyl titanate is 1.5%.

[0091] Examples 1-4

[0092] The only difference from Example 1-1 is that in step (1), the molar ratio of titanium to lithium nickelate in tetrabutyl titanate is 2%.

[0093] The effects of different amounts of tetrabutyl titanate on the electrochemical performance of lithium nickelate cathode materials are detailed in Table 1.

[0094] Comparative Example 1

[0095] The difference from Examples 1-2 is that no organometallic salt is added, but lithium nickelate is simply dispersed in anhydrous ethanol and treated in the same way.

[0096] The cathode materials obtained in Examples 1-1, 1-2, 1-3, 1-4, and Comparative Example 1 were assembled into coin cell half-cells. These half-cells were then subjected to a voltage range of 2.8–4.3 V and a voltage rating of 0.1 C (1 C = 200 mA g). -1 After two activation cycles, it was cycled 100 times at a current density of 1C. Rate performance was then tested at a current density of 5C.

[0097] The obtained material was characterized, and the XRD patterns and Rietveld refinement images are shown below. Figure 8 As shown, the SEM image is as follows: Figure 9 As shown, the HRTEM image is as follows Figure 10 As shown in the figure, the lithium-ion transport rate diagram is as follows: Figure 11 As shown, the EPR oxygen vacancy test results are as follows: Figure 12 As shown, the calculated concentration of oxygen vacancies is 2.635 × 10⁻⁶. -7 mol / L, cycle performance graph as shown Figure 13 As shown.

[0098] contrast Figure 1 and Figure 8 It can be seen that the construction of the efficient and stable interface in Examples 1-2 did not significantly affect the phase composition of the main lithium nickel oxide cathode material, but it did slightly increase the degree of lithium-nickel mixing. (Comparison) Figure 2 and Figure 9 It can be seen that the surface of lithium nickelate in Comparative Example 1 is relatively smooth, while the surface of lithium nickelate in Examples 1-2 has obvious nanoparticles, which are the coating layer formed by the decomposition products of tetrabutyl titanate. Figure 3 and Figure 10 It can be seen that in Comparative Example 1, lithium nickelate has a layered structure from the surface to the interior, while in Examples 1-2, lithium nickelate is divided into three regions from the surface to the interior. Region I is a coating layer composed of TiO2 and C, Region II is a rock salt phase, and Region III is the layered structure of the lithium nickelate material, forming a triple-structured surface containing a carbon coating layer, a rock salt phase, and a layered structure. Figure 4 It can be seen that the materials obtained in Examples 1-2 exhibit Li1s peaks from the surface to the interior, indicating that the rock salt phase formed on the material surface is a lithium-containing rock salt phase rather than an electrochemically inert NiO-like rock salt phase. Although the characterization results show that the surface forms a lithium-conducting rock salt phase, since the surface is located in the transition region between the matrix material and the coating material, and it is difficult to control the phase transformation from layered to spinel phase to lithium-conducting rock salt phase to be exactly complete, it is speculated that its surface may also contain layered and spinel phases with high lithium-ion transport rates. (Comparison) Figure 5 and Figure 11 It can be seen that lithium nickelate in Examples 1-2 exhibits a faster lithium-ion transport rate. The main reason for this is the formation of a lithium-conducting rock salt phase on its surface, which effectively improves the lithium-ion transport rate. (Comparison) Figure 6 and Figure 12 The calculation results show that, compared to Comparative Example 1, the oxygen vacancy concentration of the lithium nickelate material in Examples 1-2 is significantly reduced. However, according to existing research, surface coating of high-nickel materials with carbon leads to an increase in the lattice oxygen vacancy concentration. Analysis reveals that the reason for the significantly reduced oxygen vacancy concentration in the lithium nickelate material in Examples 1-2 is that some high-valence metal elements, Ti, are incorporated into the lattice to form strong Ti-O bonds, providing sufficient positive charge balance to bind lattice oxygen, effectively suppressing the generation of oxygen vacancies and thus clamping them. (Comparison) Figure 7 and Figure 13 It can be seen that the cycle performance of lithium nickelate is significantly improved in Example 1.

[0099] Table 1. Electrochemical performance of the cathode materials prepared in each embodiment and Comparative Example 1

[0100]

[0101] As can be seen from Table 1, compared with Comparative Example 1, the rate performance and cycle performance of the batteries in Examples 1-2 were significantly improved. Based on the previous analysis, the reason for this phenomenon may be that, on the one hand, the lithium-conducting phase formed on the surface improved the ion transport performance, and on the other hand, the carbon coating layer formed on the surface improved the electron transport performance, thereby effectively improving the rate performance of the material. At the same time, although the lithium-nickel mixing on the surface is improved, the Ti part is incorporated into the substrate surface layer, forming a strong Ti-O bond, which can provide sufficient positive charge balance to bind lattice oxygen, effectively suppress the generation of oxygen vacancies, form a clamping effect on oxygen vacancies, and improve the interfacial stability of the surface. The composite coating layer of carbon and titanium dioxide formed on the surface can also effectively reduce the side reactions between the cathode material and the electrolyte.

[0102] Example 2-1

[0103] A method for constructing an efficient and stable interface structure for ultra-high nickel cathode materials, specifically including the following steps:

[0104] (1) A certain amount of zinc citrate was dissolved in 1 mL of anhydrous ethanol to obtain a mixed solution, wherein the zinc in the zinc citrate reacts with LiNi 0.90 Co 0.06 Mn 0.04 The molar ratio of O2 is 0.5%;

[0105] (2) Add 1g LiNi 0.90 Co 0.06 Mn 0.04 O2 is dispersed in the mixed solution to form a suspension;

[0106] (3) The suspension in step (2) was stirred and evaporated at a constant temperature of 80°C to obtain LiNi uniformly coated with zinc citrate. 0.90 Co 0.06 Mn 0.04 O2 ultra-high nickel cathode material;

[0107] (4) The LiNi uniformly coated with zinc citrate 0.90 Co 0.06 Mn 0.04 O2 ultra-high nickel cathode material was heated to 300℃ in high-purity argon at a heating rate of 10℃ / min and held at that temperature for 3 hours, followed by furnace cooling to obtain LiNi with a highly efficient and stable interface. 0.90 Co 0.06 Mn 0.04 O2 ultra-high nickel cathode material.

[0108] Example 2-2

[0109] The only difference between this embodiment and Embodiment 2-1 is that, in step (1), the zinc in zinc citrate reacts with LiNi. 0.90 Co 0.06 Mn 0.04 The molar ratio of O2 is 1%.

[0110] Example 2-3

[0111] The only difference between this embodiment and Embodiment 2-1 is that, in step (1), the zinc in zinc citrate reacts with LiNi. 0.90 Co 0.06 Mn 0.04 The molar ratio of O2 is 1.5%.

[0112] Examples 2-4

[0113] The only difference between this embodiment and Embodiment 2-1 is that, in step (1), the zinc in zinc citrate reacts with LiNi. 0.90 Co 0.06 Mn 0.04 The molar ratio of O2 is 2%.

[0114] The effect of different amounts of zinc citrate on LiNi 0.90 Co 0.06 Mn 0.04 The effects of O2 on the electrochemical performance of ultra-high nickel cathode materials are detailed in Table 2.

[0115] Comparative Example 2-1

[0116] The difference from Example 2-1 is that the organometallic salt zinc citrate is not added, but lithium nickelate is simply dispersed in anhydrous ethanol and treated in the same way.

[0117] Comparative Example 2-2

[0118] The difference from Examples 2-3 is that the organometallic salt is replaced with citric acid and the same treatment is performed, and the molar ratio of citric acid to lithium nickelate is 1.5%.

[0119] The cathode materials obtained in Examples 2-1, 2-2, 2-3, 2-4, and Comparative Examples 2-1 and 2-2 were assembled into coin cell half-cells. These half-cells were then subjected to a voltage range of 2.8-4.3V and a voltage rating of 0.1C (1C = 200 mA g). -1 After two activation cycles, it was cycled 100 times at a current density of 1C. Rate performance was then tested at a current density of 5C.

[0120] Table 2 Electrochemical performance of the cathode materials prepared in each embodiment and Comparative Example 2

[0121]

[0122] Example 3-1

[0123] A method for constructing an efficient and stable interface structure for ultra-high nickel cathode materials, specifically including the following steps:

[0124] (1) Dissolve manganese gluconate in 1 mL of anhydrous ethanol to obtain a mixed solution, wherein manganese reacts with LiNi 0.95 Co 0.01 Mn 0.04 The molar ratio of O2 was 5%;

[0125] (2) Add 1g LiNi 0.95 Co 0.01 Mn 0.04 O2 is dispersed in the mixed solution to form a suspension;

[0126] (3) The suspension in step (2) is stirred and evaporated at a constant temperature of 70°C to obtain LiNi uniformly coated with organometallic compounds. 0.95 Co 0.01 Mn 0.04 O2 ultra-high nickel cathode material;

[0127] (4) LiNi uniformly coated with the aforementioned organometallic compound 0.95 Co 0.01 Mn 0.04 O2 ultra-high nickel cathode material was heated to 650℃ in high-purity argon at a heating rate of 20℃ / min and held at that temperature for 1 hour, followed by furnace cooling to obtain LiNi with a highly efficient and stable interface. 0.95 Co 0.01 Mn 0.04 O2 ultra-high nickel cathode material.

[0128] Example 3-2

[0129] The only difference between this embodiment and embodiment 3-1 is that step (1) is different. In this embodiment, step (1) specifically involves dissolving molybdenum dialkyldithiocarbamate in 1 mL of anhydrous ethanol to obtain a mixed solution, wherein molybdenum and LiNi 0.95 Co 0.01 Mn 0.04 The molar ratio of O2 is 2%.

[0130] Example 3-3

[0131] The only difference between this embodiment and embodiment 3-1 is that step (1) is different. In this embodiment, step (1) specifically involves dissolving chromium pyridinecarboxylate in 1 mL of anhydrous ethanol to obtain a mixed solution, wherein chromium and LiNi 0.95 Co 0.01 Mn 0.04 The molar ratio of O2 is 3%.

[0132] Examples 3-4

[0133] The only difference between this embodiment and embodiment 3-1 is that step (1) is different. In this embodiment, step (1) is specifically: dissolving tungsten isopropoxide in 1 mL of anhydrous ethanol to obtain a mixed solution, wherein tungsten and LiNi 0.95 Co 0.01 Mn 0.04 The molar ratio of O2 is 1%.

[0134] Different organometallic compounds for LiNi 0.95 Co 0.01 Mn 0.04 The effects of O2 on the electrochemical performance of ultra-high nickel cathode materials are detailed in Table 3.

[0135] Comparative Example 3

[0136] The difference from Example 3-1 is that no organometallic compound is added, but only LiNi is used. 0.95 Co 0.01 Mn 0.04 O2 was dispersed in anhydrous ethanol and treated in the same way.

[0137] The cathode materials obtained in Examples 3-1, 3-2, 3-3, 3-4, and Comparative Example 3 were assembled into coin cell half-cells. These half-cells were then subjected to a voltage range of 2.8–4.3 V and a voltage rating of 0.1 C (1 C = 200 mA g). -1 After two activation cycles, it was cycled 100 times at a current density of 1C. Rate performance was then tested at a current density of 5C.

[0138] Table 3 Electrochemical performance of the cathode materials prepared in each embodiment and Comparative Example 3

[0139]

[0140] Comparative Example 4

[0141] The only difference between this comparative example and Examples 1-2 is that, in step (4), the heat preservation time is 4 hours.

[0142] The HRTEM image of the obtained lithium nickelate is shown below. Figure 14 As shown, the obtained lithium nickelate was assembled into a coin cell using conventional methods. It was then subjected to a voltage range of 2.8–4.3 V and a 0.1C (1C = 200 mA g) temperature. -1 After two activation cycles, it was cycled 100 times at a current density of 1C. Rate performance was then tested at a current density of 5C, and the electrochemical performance is shown in Table 4.

[0143] Comparing the data in Tables 1 and 4, it can be seen that the batteries assembled with the cathode materials of Examples 1-2 have significantly better cycle performance and rate performance than Comparative Example 4. Furthermore, considering the comparison... Figure 4 and Figure 14 It can be seen that, Figure 14 The lattice distortion of the cathode material is significantly greater than that of the cathode material. Figure 4 The stronger effect is likely due to the excessive reduction of elements, which forms a NiO-like phase that is inert for lithium-ion transport. The arrangement and lattice distortion of the NiO-like phase are significantly stronger.

[0144] Table 4 Electrochemical performance of the cathode material prepared in Comparative Example 4

[0145]

[0146] Comparative Example 5

[0147] A method for modifying an ultra-high nickel cathode material specifically includes the following steps:

[0148] (1) Zinc citrate and LiNi 0.90 Co 0.06 Mn 0.04 O2 is used for grinding and mixing, in which zinc in zinc citrate reacts with LiNi 0.90 Co 0.06 Mn 0.04 The molar ratio of O2 is 1%;

[0149] (2) The obtained mixture was heated to 300°C in high-purity argon at a heating rate of 10°C / min and held for 3 hours. It was then cooled in the furnace to obtain the modified ultra-high nickel cathode material.

[0150] HRTEM images of the obtained modified high-nickel cathode material are shown below. Figure 15 As shown, from Figure 15It can be seen that the coating layer is unevenly distributed on the material surface, and agglomeration of the coating material is found on the surface of the cathode material. Analysis shows that this may be due to the unevenness of the coating layer formed by solid-phase grinding.

[0151] Table 5 Electrochemical performance of the cathode material prepared in Comparative Example 5

[0152]

[0153] In summary, the lithium nickelate cathode material with a highly efficient and stable interface prepared by this invention has significantly improved cycle stability and rate performance, which is a simple and effective strategy for improving ultra-high nickel materials.

[0154] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A modified high-nickel cathode material with a stable interface, characterized in that, The device comprises a substrate and a coating layer covering the substrate. The substrate is a high-nickel cathode material. The surface of the substrate includes a lithium-containing rock salt phase. The surface of the substrate is doped with high-valence metal A ions with strong metal-oxygen bonds, and the lithium-nickel mixture on the surface of the substrate is higher than that in the bulk phase. The valence state of the high-valence metal A ions is not lower than +3. The coating layer is a homogeneous mixture of carbon and oxides of high-valence metal A. The high-valence metal A is one or more of Mn, Ti, Mo, Cr, and W. The doping depth of the high-valence metal A ions is within 100 nm. The surface of the substrate also includes one or more of layered and spinel phases with high lithium-ion transport rates.

2. The modified high-nickel cathode material with a stable interface as described in claim 1, characterized in that, The thickness of the coating layer is 1~200 nm; The chemical formula of the matrix is ​​LiNi x M 1-x O2, where 0.9≤x≤1, and M is one or more of the rare earth elements Co, Mn, Al, Mg, Ti, Zr, Mo, Cr, B, and O2.

3. A method for preparing a modified high-nickel cathode material with a stable interface as described in claim 1 or 2, characterized in that, include: S1. A soluble organometallic salt is coated on the surface of a high-nickel cathode material; the metal in the organometallic salt is one or more of Mn, Ti, Mo, Cr, and W; S2. The high-nickel cathode material coated with organometallic salt is subjected to short-term heat treatment under a protective atmosphere to obtain the cathode material.

4. The method for preparing the modified high-nickel cathode material with a stable interface as described in claim 3, characterized in that, Step S1 includes: (1) Dissolve the organometallic salt in an organic solvent to obtain an organometallic salt solution; (2) Disperse the high-nickel cathode material in the metal-organic salt solution to form a uniformly dispersed suspension; (3) The suspension is heated and stirred to remove the solvent, and a high-nickel cathode material coated with metal-organic salt is obtained.

5. The method for preparing the modified high-nickel cathode material with a stable interface as described in claim 3, characterized in that, The general chemical formula of the organometallic salt is M. m (C a H b O c X d ) n The metallic element M is one or more of Mn, Ti, Mo, Cr, and W, (C a H b O c X d ) n It is an anionic group containing one or more of the functional groups selected from -OH, -CHO, -COOH, -NO2, -SO3H, -NH2, and RCO-. The chemical formula of the high-nickel cathode material is LiNi. x M 1-x O2, where 0.9≤x≤1, and M is one or more of the rare earth elements Co, Mn, Al, Mg, Ti, Zr, Mo, Cr, B, and O2.

6. The method for preparing the modified high-nickel cathode material with a stable interface as described in claim 3 or 4, characterized in that, In step S2, the temperature of the heat treatment is 300–650°C; In step S2, the heat treatment holding time is 1 to 3 hours; In step S2, the heating rate during the heat treatment is 5–20 °C / min; In step S2, the protective atmosphere is nitrogen and / or an inert atmosphere.

7. The method for preparing the modified high-nickel cathode material with a stable interface as described in claim 4, characterized in that, The organic solvent is one or more of methanol, ethanol, propanol, ethylene glycol, formamide, acetonitrile, and acetone.

8. The method for preparing the modified high-nickel cathode material with a stable interface according to claim 3 or 4, characterized in that, The molar ratio of the metal in the organometallic salt to the high-nickel cathode material is 0.01% to 2%.

9. A lithium-ion battery, characterized in that, This includes the modified high-nickel cathode material with a stable interface as described in claim 1 or 2, or the modified high-nickel cathode material with a stable interface prepared by the preparation method described in any one of claims 3 to 8.

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