Ternary positive electrode material with tantalum-phosphorus coating layer as well as preparation method and application of ternary positive electrode material

Abstract

The invention provides a ternary positive electrode material with a tantalum-phosphorus coating layer as well as a preparation method and application of the ternary positive electrode material. The ternary positive electrode material comprises a high-nickel ternary material core and the tantalum-phosphorus coating layer coating the exterior of the high-nickel ternary material core, and the tantalum-phosphorus coating layer comprises the following components: a tantalum compound, a phosphorus compound and a fast ion conductor Li3PO4. In the ternary positive electrode material, a tantalum-phosphorus coating layer with crack resistance, high ionic conductivity and excellent stability is constructed through synergistic interface modification of a tantalum-containing component and a phosphorus-containing component, and dual functions are synchronously realized: 1, the tantalum-containing component strengthens the near-surface mechanical strength by virtue of a strong Ta-O bond; secondly, residual lithium is converted by utilizing a phosphorus component, a fast ion conductor Li3PO4 is generated in situ, and a fast lithium ion transmission channel is constructed; the high-nickel ternary lithium battery prepared from the ternary positive electrode material shows excellent cycle performance and rate capability under severe working conditions, and is suitable for improving the energy density of the battery in the prior art.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, and relates to ternary cathode materials with tantalum-phosphorus coating, and more particularly to ternary cathode materials with tantalum-phosphorus coating, their preparation methods and applications. Background Technology

[0002] High-nickel layered ternary cathode materials in existing technologies are considered key materials for improving the energy density of lithium-ion batteries due to their high specific capacity. However, their commercial application still faces three inherent challenges. First, when charged to a high voltage state (>4.3V), the highly active Ni on the material surface... 4+ The first step is to catalyze the continuous decomposition of the electrolyte, leading to the dissolution of transition metals, the formation of rock salt phase structures, and the propagation of microcracks in the particles, thereby causing rapid capacity decay. Secondly, the residual Li2CO3 / LiOH on the material surface increases interfacial impedance and undergoes side reactions with the electrolyte, releasing gases such as CO2, increasing battery expansion and safety risks. Finally, during deep charge and discharge, the anisotropic volume change (about 2%) caused by the H2-H3 phase transition will generate stress accumulation inside the secondary particles, thereby promoting the formation of microcracks and electrolyte penetration.

[0003] To address the problems of interfacial instability, residual lithium, and structural mechanical damage faced by high-nickel layered ternary cathode materials, existing technologies have proposed a variety of modification schemes.

[0004] Firstly, single-element coating is used. While single-element coatings (such as Al2O3 and ZrO2 coatings) can physically isolate the electrolyte, their low ionic conductivity leads to a decrease in rate performance, severely hindering the development of Li... + Residual lithium cannot be removed due to migration, and the large difference in thermal expansion coefficients between the coating layer and the substrate during high-temperature cycling can lead to interfacial delamination and accelerate capacity decay. In the field of fast ion conductor coating, the fast ion conductor Li3PO4 coating can improve interfacial ion conduction by converting Li2CO3, but its brittle structure cannot suppress particle cracking caused by mechanical stress. Although niobium-based coating materials (such as LiNbO3) have both ion conduction and structural stability, the scarcity of niobium resources makes the cost too high to be used on a large scale. In addition, tantalum can anchor lattice oxygen and suppress crack propagation due to its ultra-high oxygen binding energy (840kJ / mol), but pure tantalum oxides (such as Ta2O5) lack continuous lithium ion transport channels, which limits the interfacial kinetic performance. Phosphorus can efficiently convert residual lithium to generate an ion-conductive interfacial layer, but the phosphate coating formed has poor resistance to mechanical stress and is difficult to suppress particle damage during cycling.

[0005] For example, CN117401731A discloses a porous alumina-coated ternary cathode material, its preparation method, and its application. The preparation method of the porous alumina-coated ternary cathode material includes: obtaining a high-nickel ternary cathode material; mixing the high-nickel ternary cathode material, a template agent, lithium aluminate, and a solvent to obtain a mixed solution and performing a coating reaction; finally, performing solid-liquid separation, washing, drying, and calcination to obtain the porous alumina-coated ternary cathode material. However, although this porous alumina-coated ternary cathode material can physically isolate the electrolyte, its low ionic conductivity leads to rate performance degradation. Furthermore, the significant difference in thermal expansion coefficients between the coating layer and the substrate during high-temperature cycling can cause interfacial delamination, accelerating capacity decay.

[0006] Secondly, while liquid-phase interface modification and ionic liquid additives such as EMIM-TFSI improve interfacial wettability, their thermal decomposition rate exceeds 40% at high temperatures (>60℃), leading to a sharp drop in stability. In-situ polymerized CEI films, such as polyvinyl carbonate, have poor thickness control precision, and the interfacial impedance increases by 200% when the film thickness is >10nm. Furthermore, the byproducts of the polymerization reaction accelerate the dissolution of transition metals.

[0007] For example, CN115360345A discloses a surface-modified ternary cathode material, its preparation method, and its application, belonging to the field of lithium battery technology. This surface-modified ternary cathode material includes a ternary cathode material and a coating agent, wherein the chemical formula of the ternary cathode material is Li(Ni)₂ x Co y Mn 1-x-y O2, where 0.6 ≤ x ≤ 1, 0 ≤ y ≤ 0.4; the coating agent includes an ionic liquid, wherein the anion of the ionic liquid is TFSI. - PF 6- BF 4- One of the following: the cation of the ionic liquid is either an imidazole salt ion or a pyridinium salt ion; the coating agent is coated onto the surface of the ternary cathode material by spraying. However, in this method for preparing the surface-modified ternary cathode material, the liquid-phase interface modification method has the disadvantage that the ionic liquid coating agent has poor thermal stability and is prone to decomposition at high temperatures, leading to coating layer failure.

[0008] In summary, the existing modification schemes still have significant limitations. They cannot simultaneously achieve mechanical strengthening, residual lithium removal, and ion channel construction, resulting in the high-nickel layered ternary cathode material failing to meet the cycle life and rate performance requirements of practical applications under harsh operating conditions (4.5V / 45℃), which severely restricts the improvement of battery energy density. Therefore, it is crucial to develop and design a novel ternary cathode material and its preparation method and application. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the present invention aims to provide a ternary cathode material with a tantalum-phosphorus coating, its preparation method, and its applications. In the ternary cathode material provided by the present invention, a tantalum-phosphorus coating with crack resistance, high ionic conductivity, and excellent stability is constructed through synergistic interface modification of tantalum-containing and phosphorus-containing components. This tantalum-phosphorus coating simultaneously achieves dual functions: firstly, the tantalum-containing component enhances the near-surface mechanical strength through strong Ta-O bonds; secondly, the phosphorus component converts residual lithium and generates a fast ion conductor, Li3PO4, in situ, constructing a fast lithium-ion transport channel. Therefore, the high-nickel ternary lithium battery prepared using the aforementioned ternary cathode material exhibits excellent cycle performance and rate performance under harsh operating conditions, making it suitable for improving the energy density of batteries in existing technologies.

[0010] To achieve this objective, the present invention adopts the following technical solution:

[0011] In a first aspect, the present invention provides a ternary cathode material having a tantalum-phosphorus coating layer, the ternary cathode material comprising a high-nickel ternary material core and a tantalum-phosphorus coating layer covering the outside of the high-nickel ternary material core;

[0012] The components of the tantalum-phosphorus coating include tantalum compounds, phosphorus compounds, and the fast ion conductor Li3PO4.

[0013] The ternary cathode material provided by this invention includes a tantalum-phosphorus coating layer with dual functions of "mechanical strengthening and enhanced ion transport". The principle of the tantalum-phosphorus coating layer achieving dual functions is as follows: First, the high oxygen binding energy of tantalum element is used to form a tantalum compound with strong Ta-O bonds, which enhances the mechanical strength near the surface and helps to suppress crack propagation; Second, the phosphorus component effectively converts the residual lithium compound to generate the fast ion conductor Li3PO4, thereby constructing a highly efficient ion channel. Therefore, compared with high-nickel ternary lithium batteries directly prepared with a high-nickel ternary material core, the high-nickel ternary lithium batteries prepared with the aforementioned ternary cathode material have a higher capacity retention rate after 120 cycles at room temperature 1C, a higher capacity retention rate after 60 cycles under high temperature and high voltage conditions (4.5V / 45℃), less capacity decay after 100 cycles under high temperature and high voltage conditions (4.5V / 45℃), higher discharge capacity at 2C rate, lower battery gas production when charged to 4.5V, and higher overall battery energy density.

[0014] In summary, the ternary cathode material provided by this invention constructs a tantalum-phosphorus coating layer that combines crack resistance, high ionic conductivity, and excellent stability through synergistic interface modification of tantalum-containing and phosphorus-containing components. This tantalum-phosphorus coating layer simultaneously achieves dual functions: firstly, the tantalum-containing component enhances the near-surface mechanical strength through strong Ta-O bonds; secondly, the phosphorus component converts residual lithium and generates a fast ion conductor, Li3PO4, in situ, thus constructing a fast lithium-ion transport channel. Therefore, the high-nickel ternary lithium battery prepared using this ternary cathode material exhibits excellent cycle performance and rate performance under harsh operating conditions, making it suitable for improving the energy density of batteries in existing technologies.

[0015] Preferably, the components of the tantalum-phosphorus coating include tantalum compounds, phosphorus compounds, and the fast ion conductor Li3PO4.

[0016] Preferably, the thickness of the tantalum-phosphorus coating is 3nm to 10nm, for example, it can be 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm or 10nm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0017] Preferably, the D50 particle size of the high-nickel ternary material core is 3nm~12nm, for example, it can be 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 11nm or 12nm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 8nm~12nm.

[0018] In a second aspect, the present invention provides a method for preparing a ternary cathode material, the method comprising:

[0019] After mixing tantalum source, phosphorus source and high-nickel ternary material, the mixture is then heated and activated in an oxygen-containing atmosphere to obtain the ternary cathode material.

[0020] In the preparation method provided by the present invention, after mixing tantalum source and phosphorus source, an in-situ reaction is triggered in an oxygen-containing atmosphere to achieve uniform coating of tantalum-phosphorus coating. The preparation method has low raw material cost, low energy consumption, is compatible with existing production lines, and can avoid the problem of thickness runaway that is easy to occur in liquid phase method, which is conducive to large-scale promotion and use.

[0021] Preferably, the tantalum source comprises tantalum pentoxide and / or tantalum oxalate.

[0022] Preferably, the phosphorus source includes ammonium dihydrogen phosphate and / or lithium phosphate.

[0023] Preferably, the chemical formula of the high-nickel ternary material is LiNi. x Co yMn2O2, where 0.8≤x<1.0, x+y+z=1.

[0024] In this invention, 0.8 ≤ x < 1.0, for example, it can be 0.80, 0.82, 0.84, 0.86, 0.88, 0.90, 0.92, 0.94, 0.96, 0.98 or 1.00, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0025] Preferably, before mixing, the tantalum source and phosphorus source are ground independently to obtain a tantalum source with a D50 particle size of 0.1μm~1.0μm and a phosphorus source with a D50 particle size of 0.1μm~1.0μm.

[0026] In this invention, a tantalum source with a D50 particle size of 0.1μm to 1.0μm is obtained after grinding. For example, it can be 0.1μm, 0.2μm, 0.3μm, 0.4μm, 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm or 1.0μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0027] In this invention, a phosphorus source with a D50 particle size of 0.1 μm to 1.0 μm is obtained after grinding. For example, it can be 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm or 1.0 μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0028] Preferably, the grinding process is accompanied by drying.

[0029] Preferably, the process further includes a drying pretreatment of the high-nickel ternary material before mixing.

[0030] Preferably, the drying pretreatment temperature is 100℃~150℃ and the time is 8h~16h.

[0031] In this invention, the temperature of the drying pretreatment is 100℃~150℃, for example, it can be 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, 140℃, 145℃ or 150℃, but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0032] In this invention, the drying pretreatment time is 8h to 16h, for example, it can be 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h or 16h, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0033] Preferably, the drying pretreatment is used to remove adsorbed water from the surface of the high-nickel ternary material.

[0034] Preferably, in the mixture, the total mass ratio of the tantalum source and phosphorus source to the high-nickel ternary material is (0.5~5):100, for example, it can be 0.5:100, 1.0:100, 1.5:100, 2.0:100, 2.5:100, 3.0:100, 3.5:100, 4.0:100, 4.5:100 or 5.0:100, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0035] Preferably, the mass ratio of tantalum source to phosphorus source in the mixture is (0.5~2):1, for example, it can be 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1.0:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1 or 2.0:1, but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0036] Preferably, the mixing method includes dry milling, which forms a grayish-white precursor complex after dry milling.

[0037] Preferably, the dry grinding time is 10 min to 20 min, for example, it can be 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min or 20 min, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0038] In the dry grinding process described in this invention, the tantalum source and the phosphorus source are pre-assembled on the surface of the matrix particles in a solid-phase contact form, creating spatial proximity conditions for subsequent interfacial reactions.

[0039] Preferably, during the heating activation process, oxygen is continuously introduced at a rate of 80 mL / min to 120 mL / min, for example, 80 mL / min, 85 mL / min, 90 mL / min, 95 mL / min, 100 mL / min, 105 mL / min, 110 mL / min, 115 mL / min or 120 mL / min, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0040] Preferably, the heating activation includes gradient heating activation, which includes a first heat treatment and a second heat treatment performed sequentially.

[0041] During the first heat treatment process of this invention, ammonium salts are decomposed and organic components are volatilized.

[0042] During the second heat treatment process of this invention, multiple synergistic reactions are triggered: the tantalum source and the phosphorus source react to generate tantalum phosphate and release gaseous byproducts, the residual lithium carbonate and hydrogen phosphate ions are converted into lithium phosphate, and at the same time, the tantalum element anchors the matrix lattice through strong oxygen bonding to form a mechanically reinforcing phase. Finally, a tantalum-phosphorus coating layer that combines the ion conduction network of lithium phosphate and the crack-resistant skeleton of tantalum compound is constructed on the surface of high-nickel ternary material particles.

[0043] Preferably, the first heat treatment includes a first heating and a first heat preservation performed sequentially.

[0044] Preferably, the first heating rate is 5℃ / min to 15℃ / min, for example, it can be 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min, 11℃ / min, 12℃ / min, 13℃ / min, 14℃ / min or 15℃ / min, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable, and the endpoint temperature is the temperature of the first heat preservation.

[0045] Preferably, the temperature of the first heat preservation is 220℃~270℃, and the time is 0.5~1.5h.

[0046] In this invention, the temperature of the first heat preservation is 220℃~270℃, for example, it can be 220℃, 225℃, 230℃, 235℃, 240℃, 245℃, 250℃, 255℃, 260℃, 265℃ or 270℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0047] In this invention, the first heat preservation time is 0.5~1.5h, for example, it can be 0.5h, 0.6h, 0.7h, 0.8h, 0.9h, 1.0h, 1.1h, 1.2h, 1.3h, 1.4h or 1.5h, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0048] Preferably, the second heat treatment includes a second heating and a second holding in sequence.

[0049] Preferably, the second heating rate is 5℃ / min to 15℃ / min, for example, it can be 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min, 11℃ / min, 12℃ / min, 13℃ / min, 14℃ / min or 15℃ / min, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable, and the endpoint temperature is the temperature of the second heat preservation.

[0050] Preferably, the temperature of the second heat preservation is 300℃~500℃, and the time is 2h~6h.

[0051] In this invention, the temperature of the second heat preservation is 300℃~500℃, for example, it can be 300℃, 320℃, 340℃, 360℃, 380℃, 400℃, 420℃, 440℃, 460℃, 480℃ or 500℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0052] In this invention, the second heat preservation time is 2h to 6h, for example, it can be 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h or 6h, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0053] Preferably, the second heat preservation temperature is 320℃~380℃, and the time is 4.5h~5.5h.

[0054] In this invention, the second heat preservation temperature is 320℃~380℃, for example, it can be 320℃, 330℃, 340℃, 350℃, 360℃, 370℃ or 380℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0055] In this invention, the second heat preservation time is 4.5h to 5.5h, for example, it can be 4.5h, 4.6h, 4.7h, 4.8h, 4.9h, 5.0h, 5.1h, 5.2h, 5.3h, 5.4h or 5.5h, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0056] Preferably, the preparation method further includes cooling after heating and activation, wherein oxygen is introduced at a rate of 80 mL / min to 120 mL / min during the cooling process, for example, 80 mL / min, 85 mL / min, 90 mL / min, 95 mL / min, 100 mL / min, 105 mL / min, 110 mL / min, 115 mL / min or 120 mL / min, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0057] Preferably, the cooling method includes natural cooling, and the endpoint temperature of the natural cooling is 10℃~50℃, for example, it can be 10℃, 15℃, 20℃, 25℃, 30℃, 35℃, 40℃, 45℃ or 50℃, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0058] Preferably, the preparation method further includes sieving after cooling.

[0059] Preferably, the sieve used for sieving includes a sieve with a mesh size of 150 to 250 mesh, such as 150 mesh, 160 mesh, 170 mesh, 180 mesh, 190 mesh, 200 mesh, 210 mesh, 220 mesh, 230 mesh, 240 mesh or 250 mesh, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0060] In this invention, the sieving is used to remove sintered agglomerates to obtain a ternary cathode material with good flowability.

[0061] In this invention, the ternary cathode material obtained after sieving is transferred to an argon-protected glove box for sealed storage.

[0062] As a preferred embodiment of the preparation method of the present invention, the preparation method includes:

[0063] (1) Tantalum source and phosphorus source are ground and dried at the same time to obtain tantalum source with D50 particle size of 0.1μm~1.0μm and phosphorus source with D50 particle size of 0.1μm~1.0μm;

[0064] The high-nickel ternary material was pre-treated by drying at 100℃~150℃ for 8h~16h to obtain the dried high-nickel ternary material.

[0065] The tantalum source includes tantalum pentoxide and / or tantalum oxalate; the phosphorus source includes ammonium dihydrogen phosphate and / or lithium phosphate; the chemical formula of the high-nickel ternary material is LiNi. x Co y Mn2O2, where 0.8≤x<1.0, x+y+z=1;

[0066] In the mixture, the mass ratio of tantalum source to phosphorus source is (0.5~2):1, and the total mass of tantalum source and phosphorus source is in the mass ratio of high-nickel ternary material to (0.5~5):100.

[0067] (2) After dry grinding for 10 min to 20 min to mix tantalum source, phosphorus source and high nickel ternary material to form a grayish-white precursor composite, oxygen is continuously introduced at a rate of 80 mL / min to 120 mL / min, and the temperature is raised to 220℃ to 270℃ at a rate of 5℃ / min to 15℃ / min in an oxygen-containing atmosphere and held for 0.5 to 1.5 h, and then the temperature is raised to 320℃ to 380℃ at a rate of 5℃ / min to 15℃ / min and held for 4.5 h to 5.5 h.

[0068] While continuously introducing oxygen at a rate of 80 mL / min to 120 mL / min, the material is naturally cooled to 10°C to 50°C and then sieved through a 150-250 mesh screen to obtain the ternary cathode material.

[0069] Thirdly, the present invention provides a positive electrode sheet, the positive electrode sheet comprising the ternary positive electrode material described in the first aspect.

[0070] Fourthly, the present invention provides a battery comprising the positive electrode plate described in the third aspect.

[0071] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0072] Compared with the prior art, the present invention has the following beneficial effects:

[0073] The ternary cathode material provided by this invention constructs a tantalum-phosphorus coating layer that combines crack resistance, high ionic conductivity, and excellent stability through synergistic interface modification of tantalum-containing and phosphorus-containing components. This tantalum-phosphorus coating layer simultaneously achieves dual functions: firstly, the tantalum-containing component enhances the near-surface mechanical strength through strong Ta-O bonds; secondly, the phosphorus component converts residual lithium and generates a fast ion conductor, Li3PO4, in situ, thus constructing a fast lithium-ion transport channel. Therefore, the high-nickel ternary lithium battery prepared using this ternary cathode material exhibits excellent cycle performance and rate performance under harsh operating conditions, making it suitable for improving the energy density of batteries in existing technologies. Detailed Implementation

[0074] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0075] The "range" disclosed in this invention can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. This type of range definition can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be arbitrarily combined, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for specific parameters, it is understood that ranges of 60~110 and 80~120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0076] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0077] The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0078] Those skilled in the art will understand that the order in which the steps are written in the methods of the various embodiments does not imply a strict execution order. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), meaning that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0079] In this invention, open-ended technical features or solutions described using terms such as "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or exclude additional members. This can be considered as providing both technical features or solutions where "A is composed of a1, a2, and a3" or "A is selected from a1, a2, and a3," and technical features or solutions where "A includes not only a1, a2, and a3, but also other members."

[0080] In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a group consisting of A, B, and "a combination of A and B". "Containing A and / or B" can mean "containing A, containing B, and containing A and B", or "containing A, containing B, or containing A and B", and can be appropriately understood according to the context.

[0081] In this invention, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0082] Example 1

[0083] This embodiment provides a ternary cathode material with a tantalum-phosphorus coating. The ternary cathode material includes a high-nickel ternary material core with a D50 particle size of 8 nm and a tantalum-phosphorus coating with a thickness of 3.5 nm covering the outside of the high-nickel ternary material core.

[0084] The components of the tantalum-phosphorus coating include tantalum compounds, phosphorus compounds, and the fast ion conductor Li3PO4.

[0085] The preparation method of the ternary cathode material is as follows:

[0086] (1) Tantalum source (tantalum pentoxide) and phosphorus source (ammonium dihydrogen phosphate) were ground and dried at the same time to obtain tantalum source with D50 particle size of 0.5 μm and phosphorus source with D50 particle size of 0.5 μm;

[0087] The high-nickel ternary material was pre-treated by drying at 120℃ for 12 hours to obtain the dried high-nickel ternary material.

[0088] The chemical formula of the high-nickel ternary material is LiNi. 0.83 Co 0.11 Mn 0.06 O2;

[0089] (2) After dry grinding for 15 min to mix tantalum source, phosphorus source and high nickel ternary material to form a grayish-white precursor complex, the obtained precursor complex was loaded into a crucible and oxygen was continuously introduced at a rate of 100 mL / min. The temperature was raised to 250 °C at a rate of 10 °C / min in an oxygen-containing atmosphere and held for 1 h. The temperature was then raised to 350 °C at a rate of 10 °C / min and held for 5 h to trigger the reaction of tantalum pentoxide and ammonium dihydrogen phosphate to generate tantalum phosphate. At the same time, the residual lithium carbonate was converted into lithium phosphate.

[0090] While continuing to introduce oxygen at a rate of 100 mL / min, the material is naturally cooled to 25°C and then sieved through a 200-mesh sieve to obtain the ternary cathode material.

[0091] In the mixture, the mass ratio of tantalum source to phosphorus source is 1:1, and the total mass of tantalum source and phosphorus source is in a mass ratio of 1:100 to the mass of high-nickel ternary material.

[0092] Example 2

[0093] This embodiment provides a ternary cathode material with a tantalum-phosphorus coating. The ternary cathode material includes a high-nickel ternary material core with a D50 particle size of 12 nm and a tantalum-phosphorus coating with a thickness of 10 nm covering the high-nickel ternary material core.

[0094] The components of the tantalum-phosphorus coating include tantalum compounds, phosphorus compounds, and the fast ion conductor Li3PO4.

[0095] The preparation method of the ternary cathode material is as follows:

[0096] (1) Tantalum source (tantalum pentoxide) and phosphorus source (ammonium dihydrogen phosphate) were ground and dried at the same time to obtain tantalum source with D50 particle size of 1.0 μm and phosphorus source with D50 particle size of 1.0 μm;

[0097] The high-nickel ternary material was pre-treated by drying at 150℃ for 8 hours to obtain the dried high-nickel ternary material.

[0098] The chemical formula of the high-nickel ternary material is LiNi. 0.83 Co 0.11 Mn 0.06 O2;

[0099] (2) After dry grinding for 20 min to mix tantalum source, phosphorus source and high nickel ternary material to form a grayish-white precursor composite, oxygen is continuously introduced at a rate of 80 mL / min, and the temperature is raised to 270℃ at a rate of 15℃ / min in an oxygen-containing atmosphere and held for 0.5 h, and then raised to 380℃ at a rate of 15℃ / min and held for 4.5 h.

[0100] While continuing to introduce oxygen at a rate of 80 mL / min, the material is naturally cooled to 20°C and then sieved through a 150-mesh sieve to obtain the ternary cathode material.

[0101] In the mixture, the mass ratio of tantalum source to phosphorus source is 0.2:1, and the total mass of tantalum source and phosphorus source is in the mass ratio of high-nickel ternary material to 5:100.

[0102] Example 3

[0103] This embodiment provides a ternary cathode material with a tantalum-phosphorus coating layer. The ternary cathode material includes a high-nickel ternary material core with a D50 particle size of 10 nm and a tantalum-phosphorus coating layer with a thickness of 3 nm covering the high-nickel ternary material core.

[0104] The components of the tantalum-phosphorus coating include tantalum compounds, phosphorus compounds, and the fast ion conductor Li3PO4.

[0105] The preparation method of the ternary cathode material is as follows:

[0106] (1) Tantalum source (tantalum oxalate) and phosphorus source (lithium phosphate) were ground and dried at the same time to obtain tantalum source with D50 particle size of 0.1 μm and phosphorus source with D50 particle size of 0.1 μm;

[0107] The high-nickel ternary material was pre-treated by drying at 100℃ for 16 hours to obtain the dried high-nickel ternary material.

[0108] The chemical formula of the high-nickel ternary material is LiNi. 0.83 Co 0.11 Mn 0.06 O2;

[0109] (2) After dry grinding for 10 min to mix tantalum source, phosphorus source and high nickel ternary material to form a grayish-white precursor composite, oxygen is continuously introduced at a rate of 120 mL / min, and the temperature is raised to 220℃ at a rate of 5℃ / min in an oxygen-containing atmosphere and held for 1.5 h, and then raised to 320℃ at a rate of 5℃ / min and held for 5.5 h.

[0110] While continuing to introduce oxygen at a rate of 120 mL / min, the material is naturally cooled to 10°C and then sieved through a 250-mesh sieve to obtain the ternary cathode material.

[0111] In the mixture, the mass ratio of tantalum source to phosphorus source is 2:1, and the total mass of tantalum source and phosphorus source is in the mass ratio of high-nickel ternary material to 0.5:100.

[0112] Example 4

[0113] This embodiment provides a ternary cathode material with a tantalum-phosphorus coating layer, except that the thickness of the tantalum-phosphorus coating layer is 1 nm.

[0114] In step (2) of the preparation method of the ternary cathode material, the total mass of the tantalum source and phosphorus source is 0.2:100 with the mass ratio of the high-nickel ternary material, and all other steps are the same as in Example 1.

[0115] Example 5

[0116] This embodiment provides a ternary cathode material with a tantalum-phosphorus coating layer, except that the thickness of the tantalum-phosphorus coating layer is 15 nm.

[0117] In step (2) of the preparation method of the ternary cathode material, the total mass of the tantalum source and phosphorus source is in the same ratio as that of the high-nickel ternary material, except that the mass ratio is 8:100.

[0118] Example 6

[0119] This embodiment provides a ternary cathode material with a tantalum-phosphorus coating. Except for step (2) of the cathode material preparation method, in which the mass ratio of tantalum source to phosphorus source is 0.2:1, all other steps are the same as in Example 1.

[0120] Example 7

[0121] This embodiment provides a ternary cathode material with a tantalum-phosphorus coating. Except for step (2) of the cathode material preparation method, in which the mass ratio of tantalum source to phosphorus source is 5:1, all other steps are the same as in Example 1.

[0122] Example 8

[0123] This embodiment provides a ternary cathode material with a tantalum-phosphorus coating. Except for omitting step (1) of the cathode material preparation method, in which the tantalum source (tantalum pentoxide) and the phosphorus source (ammonium dihydrogen phosphate) are ground and dried at the same time, the rest is the same as in Example 1.

[0124] Example 9

[0125] This embodiment provides a ternary cathode material with a tantalum-phosphorus coating. Except for step (2) of the cathode material preparation method, in which oxygen is continuously introduced at a rate of 50 mL / min, the temperature is raised to 250°C at a rate of 10°C / min in an oxygen-containing atmosphere and held for 1 hour, and then raised to 350°C at a rate of 10°C / min and held for 5 hours to trigger the reaction of tantalum pentoxide with ammonium dihydrogen phosphate to generate tantalum phosphate, and the residual lithium carbonate is converted into lithium phosphate, the rest is the same as in Example 1.

[0126] Example 10

[0127] This embodiment provides a ternary cathode material with a tantalum-phosphorus coating. Except for step (2) of the cathode material preparation method, in which oxygen is continuously introduced at a rate of 170 mL / min, the temperature is raised to 250°C at a rate of 10°C / min in an oxygen-containing atmosphere and held for 1 h, and then raised to 350°C at a rate of 10°C / min and held for 5 h to trigger the reaction of tantalum pentoxide with ammonium dihydrogen phosphate to generate tantalum phosphate, and the residual lithium carbonate is converted into lithium phosphate, the rest is the same as in Example 1.

[0128] Example 11

[0129] This embodiment provides a ternary cathode material with a tantalum-phosphorus coating. Except for step (2) of the cathode material preparation method, which omits the step of heating to 250°C at a rate of 10°C / min and holding for 1 hour in an oxygen-containing atmosphere, i.e. directly heating to 350°C at a rate of 10°C / min and holding for 5 hours, the rest is the same as in Example 1.

[0130] Example 12

[0131] This embodiment provides a ternary cathode material with a tantalum-phosphorus coating. Except for step (2) of the cathode material preparation method, in which the temperature is raised to 250°C at a rate of 10°C / min and held for 1 hour, and then raised to 280°C at a rate of 10°C / min and held for 5 hours, the rest is the same as in Example 1.

[0132] Example 13

[0133] This embodiment provides a ternary cathode material with a tantalum-phosphorus coating. Except for step (2) of the cathode material preparation method, in which the temperature is raised to 250°C at a rate of 10°C / min and held for 1 hour, and then raised to 420°C at a rate of 10°C / min and held for 5 hours, the rest is the same as in Example 1.

[0134] Comparative Example 1

[0135] This comparative example provides a ternary cathode material, except that the tantalum-phosphorus coating layer is replaced with a tantalum coating layer consisting only of tantalum compounds;

[0136] Except for omitting the phosphorus source (ammonium dihydrogen phosphate) mixed in step (1) of the preparation method of the positive electrode material, the rest is the same as in Example 1.

[0137] Comparative Example 2

[0138] This comparative example provides a ternary cathode material, except that the tantalum-phosphorus coating is replaced with a phosphorus coating that only includes phosphorus compounds and fast ion conductor Li3PO4;

[0139] Except for omitting the tantalum source (tantalum pentoxide) mixed in step (1) of the preparation method of the positive electrode material, the rest is the same as in Example 1.

[0140] Comparative Example 3

[0141] This comparative example provides a ternary cathode material, which is the LiNi alloy described in Example 1. 0.83 Co 0.11 Mn 0.06 O2 high-nickel ternary materials.

[0142] The residual lithium carbonate content of the ternary cathode materials provided in the above embodiments and comparative examples was tested. The test method was as follows: the residual lithium carbonate content of the ternary cathode materials was detected by titration, as shown in Table 1.

[0143] The microhardness of the ternary cathode materials provided in the above embodiments and comparative examples was tested. The test method was as follows: a nanoindenter was used to apply a maximum load of 5 mN to the surface of a single secondary particle. The total loading-holding-unloading time was set to 30 seconds, and the holding time was 10 seconds to eliminate the creep effect. The microhardness of the ternary cathode material was calculated according to the Oliver-Pharr model based on the obtained load-displacement curve, as shown in Table 1.

[0144] The lithium diffusion coefficient of the ternary cathode materials provided in the above embodiments and comparative examples was tested. The test method was as follows: electrochemical impedance spectroscopy was used, with a test frequency range of 0.01Hz to 100kHz and an amplitude of 5mV. By measuring the impedance spectrum under different SOCs, the charge transfer resistance was obtained by fitting with ZView software, and then the lithium diffusion coefficient of the ternary cathode materials was calculated as shown in Table 1.

[0145] Table 1

[0146]

[0147] The ternary cathode material provided in the above embodiments and comparative examples was used to prepare the cathode sheet. The method for preparing the cathode sheet is as follows: the ternary cathode material, conductive carbon black, and polyvinylidene fluoride were uniformly mixed at a mass ratio of 96.5:2.0:1.5, and N-methylpyrrolidone solvent was added to prepare a slurry with a solid content of 70%. This slurry was coated onto aluminum foil, pre-dried at 85°C, and then vacuum-dried at 120°C for 12 hours. Finally, it was cold-pressed under a pressure of 10 MPa until the compacted density was 3.4 g / cm³. 3 This yields the positive electrode sheet.

[0148] A coin cell was prepared using the obtained positive electrode sheet. The method for preparing the coin cell was as follows: In an argon glove box, the obtained positive electrode sheet was used as the positive electrode, a lithium metal sheet was used as the negative electrode, and a LiPF6 solution was used as the electrolyte (the solute was 1.0 mol / L LiPF6, and the solvent was EC, EMC and DMC in a volume ratio of 1:1:1) to assemble a CR2032 coin cell.

[0149] The obtained CR2032 button cell was subjected to room temperature cycle performance testing. The test method was as follows: the cell was charged at 25°C with a constant current of 0.1C to 4.3V, then charged at a constant voltage until the current dropped to 0.05C. After standing for 5 minutes, it was discharged at a constant current of 0.1C to 3.0V, which constituted one cycle. After completing two formation cycles, it was tested for 120 cycles at a charge / discharge rate of 1C. The capacity retention rate after 120 cycles at 1C at room temperature is shown in Table 2.

[0150] The obtained CR2032 button cell was subjected to high temperature and high voltage cycle performance test. The test method was as follows: the battery was placed in a constant temperature chamber at 45℃ and charged and discharged at a 1C rate in the range of 2.7V~4.5V. After 0.1C activation twice, it was cycled 60 times. The capacity retention rate after 60 cycles under high temperature and high voltage conditions (4.5V / 45℃) is shown in Table 2.

[0151] The obtained CR2032 button cell was subjected to high temperature and high voltage cycle performance test. The test method was as follows: the cell was placed in a constant temperature chamber at 45℃ and cycled at 1C rate at 2.7~4.5V. After activating at 0.1C twice, it was cycled 100 times. The capacity decay rate after 100 cycles under high temperature and high voltage conditions (4.5V / 45℃) is shown in Table 2.

[0152] The CR2032 button cell was tested for discharge capacity at 2C rate. The test method was as follows: at 25℃, it was charged to 4.3V at 0.5C constant current and constant voltage (cutoff current is 0.05C), and after standing for 5 minutes, it was discharged to 2.7V at 2C constant current. The discharge capacity of this process was recorded, and the discharge capacity at 2C rate is shown in Table 3.

[0153] The obtained CR2032 button cell was subjected to a gas production test. The test method was as follows: using an Archimedes principle gas analyzer, the battery was charged at a constant current of 0.1C to 4.5V and then kept constant at that voltage until the current was 0.05C. By measuring the change in the volume of liquid displaced by the battery before and after charging, the volume of gas produced was calculated. Based on the mass of the positive electrode active material, the gas production of the battery when charged to 4.5V was obtained, as shown in Table 3.

[0154] The energy density of the full battery was tested. The test method was as follows: the obtained positive electrode and graphite negative electrode were assembled into a soft-pack full battery with a rated capacity of 2Ah; the battery was charged and discharged at a rate of 0.2C between 3.0V and 4.35V. The energy density (Wh / kg) was calculated by dividing the discharge energy of the first cycle by the total mass of the entire battery (including the casing, tabs, etc.). The energy density of the full battery is shown in Table 3.

[0155] Table 2

[0156]

[0157] Table 3

[0158]

[0159] From Tables 1-3, we can obtain:

[0160] (1) The ternary cathode materials with tantalum-phosphorus coating provided in Examples 1 to 3 of the present invention have high microhardness and large lithium diffusion coefficient;

[0161] In addition, the coin cell prepared with the ternary cathode material has a high capacity retention rate after 120 cycles at 1C at room temperature, a high capacity retention rate after 60 cycles under harsh conditions of 4.5V / 45℃, and a low capacity decay rate after 100 cycles under harsh conditions of 4.5V / 45℃.

[0162] In addition, the coin cell prepared with the ternary cathode material exhibits a high discharge capacity at a 2C rate at room temperature, and the gas production of the battery is low when charged to 4.5V.

[0163] In addition, the full cell prepared with the ternary cathode material exhibits a high energy density;

[0164] (2) By comparing Example 1 with Examples 4 and 5, it can be seen that in the present invention, the thickness of the tantalum-phosphorus coating layer in the ternary cathode material affects the performance of the ternary cathode material, coin cell and soft-pack battery; when the thickness of the tantalum-phosphorus coating layer is 3nm~10nm, the ternary cathode material, coin cell and soft-pack battery exhibit better performance; when the thickness is less than 3nm, the coating layer is discontinuous, it is difficult to form a complete mechanical reinforcement layer and ion transport channel, the residual lithium conversion is incomplete, and the crack resistance and ion conductivity are limited; when the thickness exceeds 10nm, the excessively thick coating layer will increase the ion transport resistance, reduce the charge transfer efficiency, and degrade the performance.

[0165] (3) By comparing Example 1 with Examples 6 and 7, it can be seen that in step (1) of the preparation method of the cathode material in this invention, the mass ratio of tantalum source to phosphorus source will affect the performance of ternary cathode material, coin cell and soft pack battery; when the mass ratio of tantalum source to phosphorus source is (0.5~2):1, ternary cathode material, coin cell and soft pack battery show better performance. This is because when the proportion of tantalum source is too high, the phosphorus component is insufficient, which will lead to incomplete conversion of residual lithium, low generation of fast ion conductor Li3PO4, and imperfect construction of ion transport channel; when the proportion of tantalum source is too low, the tantalum compound will be insufficiently formed, making it difficult to effectively strengthen mechanical strength through strong Ta-O bond, and reducing crack resistance; while the ratio of (0.5~2):1 can achieve tantalum and phosphorus synergy, taking into account both mechanical strengthening and efficient ion transport.

[0166] (4) By comparing Example 1 and Example 8, it can be seen that in the present invention, grinding the tantalum source and phosphorus source separately before mixing is beneficial to improving the performance of ternary cathode material, coin cell and soft pack battery. This is because grinding can reduce the particle size of tantalum source and phosphorus source and increase the specific surface area. On the one hand, it can make it mix more evenly with high nickel ternary material, avoid local coating gaps or excessive thickness, and ensure that the tantalum-phosphorus coating layer is complete and has a uniform thickness. On the other hand, it can increase the reaction contact area of ​​tantalum source and phosphorus source, promote the two to fully react to generate sufficient amount of strong Ta-O bond compound and fast ion conductor Li3PO4, and give full play to the mechanical strengthening and ion transport enhancement effect of tantalum-phosphorus coating layer.

[0167] (5) By comparing Example 1 with Examples 9 and 10, it can be seen that in the present invention, oxygen is continuously introduced at a rate of 80 mL / min to 120 mL / min during the heating activation process, which is beneficial to improving the performance of ternary cathode materials, coin cells and soft-pack cells. This is because introducing oxygen at this rate is beneficial to promoting the full oxidation of tantalum source to form strong Ta-O bonds, ensuring the mechanical strengthening effect of tantalum-phosphorus coating; on the other hand, it is beneficial to promote the efficient reaction of phosphorus source with residual lithium to generate Li3PO4, optimizing the ion transport channel.

[0168] (6) By comparing Example 1 and Example 11, it can be seen that in the present invention, when the heating activation is a gradient heating activation including a first heat treatment and a second heat treatment in sequence, it is beneficial to improve the performance of ternary cathode materials, coin cells and soft-pack batteries. This is because during the first heat treatment, ammonium salts are decomposed and organic components are volatilized; during the second heat treatment, multiple synergistic reactions are triggered: tantalum source and phosphorus source react to generate tantalum phosphate and release gaseous byproducts, residual lithium carbonate and hydrogen phosphate ions are converted into lithium phosphate, and at the same time, tantalum element anchors the matrix lattice through strong oxygen bonding to form a mechanically reinforcing phase, and finally a tantalum-phosphorus coating layer with both lithium phosphate ion conduction network and tantalum compound crack-resistant skeleton is constructed on the surface of high nickel ternary material particles.

[0169] (7) By comparing Example 1 with Examples 12 and 13, it can be seen that the temperature of the second heat treatment in step (2) of the preparation method of the cathode material affects the performance of the ternary cathode material, the coin cell and the soft pack battery. When the temperature of the second heat treatment is 300℃~500℃, the ternary cathode material, the coin cell and the soft pack battery exhibit better performance. This is because 300℃~500℃ can ensure that tantalum phosphorus reacts fully to form a uniform coating layer, while avoiding adverse effects on the performance of the high-nickel ternary material core.

[0170] (8) As can be seen from the comparison between Example 1 and Comparative Example 3, the ternary cathode material provided by the present invention contains a tantalum-phosphorus coating layer with dual functions of "mechanical strengthening and enhanced ion transport". Compared with Comparative Example 3, Example 1 has tantalum compounds with strong Ta-O bonds in the tantalum-phosphorus coating layer, which enhances the mechanical strength near the surface and increases the microhardness of the ternary cathode material by 18.2%, which is beneficial to suppressing crack propagation. As the phosphorus component effectively converts the residual lithium compounds (the residual lithium carbonate content is significantly reduced from 2323 ppm to below 1800 ppm, a reduction of more than 22.5%), a fast ion conductor Li3PO4 is generated, thereby constructing an efficient ion channel and increasing the lithium diffusion coefficient to 1.5 × 10⁻⁶. -8 cm 2 / s or more; therefore, compared with the high-nickel ternary lithium battery directly prepared with a high-nickel ternary material core, the high-nickel ternary lithium battery prepared with the ternary cathode material has an increased capacity retention rate of 120 cycles at room temperature 1C from 83.8% to 95.5%, an increased capacity retention rate of 60 cycles under high temperature and high voltage conditions (4.5V / 45℃) from 57.7% to 74.2%, a capacity decay of <5% after 100 cycles under high temperature and high voltage conditions (4.5V / 45℃), an 8% increase in discharge capacity at 2C rate to 175mAh / g, a 62% reduction in battery gas production when charged to 4.5V, and achieves a full battery energy density >300Wh / kg.

[0171] Furthermore, the ternary cathode material provided by this invention includes a tantalum-phosphorus coating layer with dual functions of "mechanical strengthening and enhanced ion transport". The principle of the tantalum-phosphorus coating layer achieving dual functions is as follows: First, the high oxygen binding energy of tantalum element is used to form a tantalum compound with strong Ta-O bonds, which enhances the mechanical strength near the surface and helps to suppress crack propagation; Second, the phosphorus component effectively converts the residual lithium compound to generate the fast ion conductor Li3PO4, thereby constructing an efficient ion channel. Therefore, compared with high-nickel ternary lithium batteries directly prepared with a high-nickel ternary material core, the high-nickel ternary lithium batteries prepared with the aforementioned ternary cathode material have a higher capacity retention rate after 120 cycles at room temperature 1C, a higher capacity retention rate after 60 cycles under high temperature and high voltage conditions (4.5V / 45℃), less capacity decay after 100 cycles under high temperature and high voltage conditions (4.5V / 45℃), higher discharge capacity at 2C rate, lower battery gas production when charged to 4.5V, and higher overall battery energy density.

[0172] In summary, the ternary cathode material provided by this invention constructs a tantalum-phosphorus coating layer that combines crack resistance, high ionic conductivity, and excellent stability through synergistic interface modification of tantalum-containing and phosphorus-containing components. This tantalum-phosphorus coating layer simultaneously achieves dual functions: firstly, the tantalum-containing component enhances the near-surface mechanical strength through strong Ta-O bonds; secondly, the phosphorus component converts residual lithium and generates a fast ion conductor, Li3PO4, in situ, thus constructing a fast lithium-ion transport channel. Therefore, the high-nickel ternary lithium battery prepared using this ternary cathode material exhibits excellent cycle performance and rate performance under harsh operating conditions, making it suitable for improving the energy density of batteries in existing technologies.

[0173] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A ternary cathode material with a tantalum-phosphorus coating, characterized in that, The ternary cathode material includes a high-nickel ternary material core and a tantalum-phosphorus coating layer covering the outside of the high-nickel ternary material core; The components of the tantalum-phosphorus coating include tantalum compounds, phosphorus compounds, and the fast ion conductor Li3PO4.

2. The ternary cathode material according to claim 1, characterized in that, The thickness of the tantalum-phosphorus coating is 3 nm to 10 nm. Preferably, the D50 particle size of the high-nickel ternary material core is 3nm~12nm.

3. A method for preparing the ternary cathode material according to claim 1 or 2, characterized in that, The preparation method includes: After mixing tantalum source, phosphorus source and high-nickel ternary material, the mixture is then heated and activated in an oxygen-containing atmosphere to obtain the ternary cathode material.

4. The preparation method according to claim 3, characterized in that, The tantalum source includes tantalum pentoxide and / or tantalum oxalate; Preferably, the phosphorus source includes ammonium dihydrogen phosphate and / or lithium phosphate; Preferably, the chemical formula of the high-nickel ternary material is LiNi. x Co y Mn z O2, where 0.8≤x<1.0, x+y+z=1; Preferably, before mixing, the tantalum source and phosphorus source are ground independently to obtain a tantalum source with a D50 particle size of 0.1μm~1.0μm and a phosphorus source with a D50 particle size of 0.1μm~1.0μm.

5. The preparation method according to claim 3, characterized in that, In the mixture, the total mass of the tantalum source and phosphorus source is in the mass ratio of (0.5~5):100 to the high-nickel ternary material; Preferably, the mass ratio of tantalum source to phosphorus source in the mixture is (0.5~2):1; Preferably, the mixing method includes dry milling, which forms a grayish-white precursor complex after dry milling.

6. The preparation method according to claim 3, characterized in that, During the heating and activation process, oxygen is continuously introduced at a rate of 80 mL / min to 120 mL / min; Preferably, the heating activation includes gradient heating activation, which includes a first heat treatment and a second heat treatment performed sequentially. Preferably, the first heat treatment includes a first heating and a first heat holding performed sequentially; Preferably, the first heating rate is 5℃ / min to 15℃ / min, and the final temperature is the temperature of the first heat preservation. Preferably, the temperature of the first heat preservation is 220℃~270℃, and the time is 0.5~1.5h; Preferably, the second heat treatment includes a second heating and a second heat holding performed sequentially; Preferably, the second heating rate is 5℃ / min to 15℃ / min, and the final temperature is the temperature of the second heat preservation. Preferably, the second heat preservation temperature is 300℃~500℃, and the time is 2h~6h; Preferably, the second heat preservation temperature is 320℃~380℃, and the time is 4.5h~5.5h.

7. The preparation method according to claim 3, characterized in that, The preparation method further includes cooling after heating and activation, wherein oxygen is introduced at a rate of 80 mL / min to 120 mL / min during the cooling process; Preferably, the preparation method further includes sieving after cooling.

8. The preparation method according to claim 3, characterized in that, The preparation method includes: (1) Tantalum source and phosphorus source are ground and dried at the same time to obtain tantalum source with D50 particle size of 0.1μm~1.0μm and phosphorus source with D50 particle size of 0.1μm~1.0μm; The high-nickel ternary material was pre-treated by drying at 100℃~150℃ for 8h~16h to obtain the dried high-nickel ternary material. The tantalum source includes tantalum pentoxide and / or tantalum oxalate; the phosphorus source includes ammonium dihydrogen phosphate and / or lithium phosphate; the chemical formula of the high-nickel ternary material is LiNi. x Co y Mn₂O₂, where 0.8 ≤ x < 1.0; In the mixture, the mass ratio of tantalum source to phosphorus source is (0.5~2):1, and the total mass of tantalum source and phosphorus source is in the mass ratio of high-nickel ternary material to (0.5~5):

100. (2) After dry grinding for 10 min to 20 min to mix tantalum source, phosphorus source and high nickel ternary material to form a grayish-white precursor composite, oxygen is continuously introduced at a rate of 80 mL / min to 120 mL / min, and the temperature is raised to 220℃ to 270℃ at a rate of 5℃ / min to 15℃ / min in an oxygen-containing atmosphere and held for 0.5 to 1.5 h, and then the temperature is raised to 320℃ to 380℃ at a rate of 5℃ / min to 15℃ / min and held for 4.5 h to 5.5 h. While continuously introducing oxygen at a rate of 80 mL / min to 120 mL / min, the material is naturally cooled to 10°C to 50°C and then sieved through a 150-250 mesh screen to obtain the ternary cathode material.

9. A positive electrode plate, characterized in that, The positive electrode sheet includes the ternary positive electrode material as described in claim 1 or 2.

10. A battery, characterized in that, The battery includes the positive electrode as described in claim 9.

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