Ternary positive electrode precursor material and preparation method and application thereof

Abstract

The invention provides a ternary positive electrode precursor material and a preparation method and application thereof. The ternary positive electrode precursor material sequentially comprises a nickel-cobalt-manganese core, a nickel-cobalt-manganese transition layer and a nickel-cobalt-manganese shell from inside to outside, wherein the surface of the nickel-cobalt-manganese core is coated with the nickel-cobalt-manganese transition layer, and the surface of the nickel-cobalt-manganese transition layer is coated with the nickel-cobalt-manganese shell; wherein the nickel-cobalt-manganese core is also doped with a boron element; the molar content of nickel in the surface, close to the nickel-cobalt-manganese core, of the nickel-cobalt-manganese transition layer is smaller than the molar content of nickel in the nickel-cobalt-manganese core, the molar content of nickel in the nickel-cobalt-manganese transition layer is gradually reduced from inside to outside, and the molar content of nickel in the surface, close to the nickel-cobalt-manganese shell, of the nickel-cobalt-manganese transition layer is larger than or equal to the molar content of nickel in the nickel-cobalt-manganese shell; and the molar content of manganese in the nickel-cobalt-manganese shell is the highest. According to the precursor material, the lithium-nickel mixing phenomenon is inhibited, stress cracking easily caused by sudden change of components between the core and the shell from the core to the shell is relieved, the effect of inhibiting the side reaction of an electrolyte is also achieved, and the cycling stability and safety of the battery are improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of lithium ion electrochemical devices, and relates to a ternary positive electrode precursor material and a preparation method and application thereof. BACKGROUND

[0002] With the wide application of lithium ion batteries in mobile phones, computers, automobiles, energy storage and other fields, people's demand for the safety, energy density and cycle stability performance of the battery is getting higher and higher. The most representative of such batteries is the lithium secondary battery (LIBs) which generates electric energy when lithium ions in the positive electrode and negative electrode change in chemical potential during intercalation and deintercalation. The positive electrode material has a direct dominant effect on the performance of LIBs, so many researchers are committed to realizing the positive electrode material which can reversibly intercalate and deintercalate lithium ions with large capacity, fast charging / discharging speed and long cycle life.

[0003] Ultra-high nickel ternary material (LiNi x Co y Mn z O2, x≥0.9) has become a mainstream technology direction due to its high specific capacity and high voltage platform. However, its commercialization faces two key bottlenecks: 1) poor surface stability: the side reaction of high-activity nickel and electrolyte leads to accelerated cycle decay, and high-temperature oxygen production causes safety hazards; 2) structural stress concentration: microcracks along the grain boundary caused by lithium-nickel mixing and H2-H3 phase transition, electrolyte invasion accelerates the generation of rock salt phase, eventually leading to particle pulverization, resulting in a substantial decrease in capacity.

[0004] The prior art attempts to improve performance through homogeneous doping, surface coating or concentration gradient design, but there are still limitations. CN120149390A mentions a dry coating process to prepare a core-shell lithium ion positive electrode material with an inherent solid-state electrolyte coating layer. The present application can isolate the direct contact between the positive electrode material and the electrolyte through coating modification, reducing side reactions; and the solid-state electrolyte as a support improves the stability of the positive electrode material, but in the long-term cycle process, the core-shell interface is weak and easy to peel off. CN118553890A discloses a ternary positive electrode material having a core-shell structure, including a carbon quantum dot CQDs layer coated titanium-doped low-nickel ternary positive electrode material in the internal core and high-nickel ternary positive electrode material and B2O3 coating layer as the shell. However, the element ratio between the inner core and the outer shell of the core-shell material is significantly different, and this difference leads to significant differences in the micro-morphology of the material, including the size of the primary particles, the pore structure and the accumulation mode of the particles. These differences may cause the separation of the inner core and the outer shell in the cycle use of the material, and then cause the peeling of the positive electrode material. This instability in structure seriously limits the cycle performance of the material, and fails to fundamentally improve its cycle stability, thereby limiting its application potential in high-performance lithium ion batteries.

[0005] Therefore, how to improve the interface stability of the ultra-high nickel positive electrode material and reduce the lithium-nickel mixing degree is a technical problem to be solved at present. SUMMARY

[0006] In view of the deficiencies in the prior art, the purpose of the present application is to provide a ternary positive electrode precursor material, a preparation method and application thereof. The present application performs boron doping in the nickel-cobalt-manganese core with high nickel content, preliminarily inhibits the lithium-nickel mixing phenomenon, and then designs a transition layer with gradually decreasing nickel molar content, which slows down the stress cracking caused by the component mutation between the core and the shell, and at the same time, cooperates with the shell with high manganese content, which plays a role in inhibiting the electrolyte side reaction, improving the cycle stability and safety of the battery.

[0007] To achieve the purpose of the present application, the following technical solutions are adopted:

[0008] In a first aspect, the present application provides a ternary positive electrode precursor material, which comprises a nickel-cobalt-manganese core, a nickel-cobalt-manganese transition layer coated on the surface of the nickel-cobalt-manganese core, and a nickel-cobalt-manganese shell coated on the surface of the nickel-cobalt-manganese transition layer from inside to outside.

[0009] The nickel-cobalt-manganese core is also doped with boron element; the molar content of nickel in the surface of the nickel-cobalt-manganese transition layer close to the nickel-cobalt-manganese core is less than the molar content of nickel in the nickel-cobalt-manganese core, the molar content of nickel gradually decreases from inside to outside of the nickel-cobalt-manganese transition layer, and the molar content of nickel in the surface of the nickel-cobalt-manganese transition layer close to the nickel-cobalt-manganese shell is greater than or equal to the molar content of nickel in the nickel-cobalt-manganese shell; the molar content of manganese in the nickel-cobalt-manganese shell is the highest.

[0010] The present application breaks through the stress concentration bottleneck between the layers of traditional core-shell materials by the three-section structure of core-gradient nickel change transition layer-shell from inside to outside, reduces the volume change rate; adopts a unique core-shell structure design, designs a transition layer with gradually decreasing nickel molar content on the surface of the nickel-cobalt-manganese core with high nickel content, and then slows down the stress cracking caused by the component mutation between the core and the shell, improves the stability during the battery cycle process; at the same time, boron doping is performed in the nickel-cobalt-manganese core with high nickel content, which inhibits Li / Ni mixing to occupy the TM layer tetrahedral site, enhances the TM-O bond energy, improves the Ni 3+ / Ni 2+ oxidation potential, reduces Ni 2+ generation; and cooperates with the shell with high manganese content, which plays a role in inhibiting the electrolyte side reaction; the ternary positive electrode precursor material of the present application improves the cycle stability and safety of the battery after preparing the ternary positive electrode material.

[0011] In the application, the content of nickel in the transition layer gradually decreases from inside to outside, and the content of cobalt and manganese elements also gradually changes synchronously, ensuring the smooth transition of the nickel-cobalt-manganese components in the core-shell; if the content of nickel in the transition layer remains unchanged, there will still be sharp component mutation interfaces (core-transition layer, transition layer-shell), not one. On these two interfaces, the lattice constant will change abruptly, resulting in a huge lattice mismatch stress. The volume change during charging and discharging will produce high stress concentration on such sharp interfaces. These stress concentration points almost inevitably lead to interface cracking. Cracks will preferentially propagate along these weak interfaces. This will make the design of the transition layer and the shell meaningless, and the final performance may not be as good as a uniform high-nickel material.

[0012] The following is a preferred technical solution of the application, but not as a limitation on the technical solutions provided by the application. Through the following preferred technical solution, the technical purpose and beneficial effects of the application can be better achieved and realized.

[0013] Preferably, the molar amount of nickel accounts for ≥90%, such as 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99%, and the molar amount of manganese accounts for ≤5%, such as 1%, 2%, 3%, 4% or 5%, based on the total molar amount of nickel-cobalt-manganese in the nickel-cobalt-manganese core being 100%.

[0014] The application uses an ultra-high nickel nickel-cobalt-manganese ternary positive electrode precursor material in the core, which first ensures high specific capacity and high voltage platform, and then modifies the transition layer and the shell, thereby improving the battery performance.

[0015] Preferably, the doping mass of boron in the nickel-cobalt-manganese core is 0.5% to 2.0%, such as 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% or 2%.

[0016] The application controls the doping mass of boron to be 0.5% to 2.0%, which better plays the stabilizing effect of B-O bond, inhibits Li / Ni mixing, and does not significantly block the lithium ion diffusion channel, achieving the best balance between high capacity and high structural stability.

[0017] Preferably, the molar amount of nickel accounts for ≤70%, such as 50%, 55%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69% or 70%, etc., and the molar amount of manganese accounts for ≥25%, such as 25%, 28%, 30%, 33%, 35%, 38%, 40%, 43%, 45%, 48% or 50%, etc., based on the total molar amount of nickel, cobalt and manganese in the nickel-cobalt-manganese shell being 100%.

[0018] The present application selects a material with a high manganese content, especially a material with a molar amount of manganese ≥25%, in the shell, which is more conducive to building a stable surface crystal structure, significantly reducing the side reaction activity with the electrolyte under high pressure, inhibiting the increase of interface impedance and the dissolution of transition metal ions, thereby greatly improving the cycle stability and thermal safety of the battery.

[0019] In a second aspect, the present application provides a preparation method of the ternary precursor material according to the first aspect, which comprises the following steps:

[0020] S1: The first nickel-cobalt-manganese mixed salt solution, the boron doping source solution, the first precipitant solution and the first complexing agent solution are added in parallel to perform a first co-precipitation reaction to obtain a crystal seed;

[0021] S2: The first nickel-cobalt-manganese mixed salt solution, the second nickel-cobalt-manganese mixed salt solution, the second precipitant solution and the second complexing agent solution are added in parallel to the solution containing the crystal seed to perform a second co-precipitation reaction. During the second co-precipitation reaction, the feeding flow rate of the first nickel-cobalt-manganese mixed salt solution is gradually reduced, and the feeding flow rate of the second nickel-cobalt-manganese mixed salt solution is gradually increased. The second co-precipitation reaction is stopped after the target particle size is reached;

[0022] S3: After the second co-precipitation reaction is completed, the third nickel-cobalt-manganese mixed salt solution, the third precipitant solution and the third complexing agent solution are continuously added in parallel to perform a third co-precipitation reaction to obtain the ternary precursor material;

[0023] Preferably, the molar amount of nickel in the first nickel-cobalt-manganese mixed salt solution accounts for > the molar amount of nickel in the second nickel-cobalt-manganese mixed salt solution > the molar amount of nickel in the third nickel-cobalt-manganese mixed salt solution; and the molar amount of manganese in the third nickel-cobalt-manganese mixed salt solution is the highest.

[0024] It should be noted that the molar amount of nickel, cobalt and manganese in the nickel-cobalt-manganese mixed salt solution of the present application is the molar amount of any one element accounting for 100% of the total molar amount of nickel, cobalt and manganese.

[0025] Meanwhile, in the second co-precipitation reaction process, the feeding flow rate of the nickel-cobalt-manganese mixed salt solution can be adaptively adjusted according to the target nickel content and the target manganese content in the core and the shell, that is, in the process of gradually increasing and gradually decreasing, the nickel-cobalt-manganese content in the outermost surface of the transition layer tends to approach the nickel-cobalt-manganese content in the shell, and the specific feeding flow rate can be adaptively selected and adjusted by a person skilled in the art according to actual needs.

[0026] In the preparation method of the application, a boron-doped seed crystal with high nickel content, that is, a core material, is first prepared, and then in the second co-precipitation reaction process, the transition process of gradually reducing the nickel content with the growth of the particles is realized by synchronously adding the first nickel-cobalt-manganese mixed salt solution and the second nickel-cobalt-manganese mixed salt solution, thereby avoiding the sudden change of the nickel-cobalt-manganese component content; then, by adding the third nickel-cobalt-manganese mixed salt with high manganese content in the third co-precipitation reaction process, a dense shell structure with high manganese content is obtained; thereby, by simply adjusting the raw materials and the feeding flow rate process, a ternary positive electrode precursor material with stable structure and excellent performance is obtained; the preparation process is easy to control and suitable for large-scale production operation.

[0027] Preferably, the concentration of the first nickel-cobalt-manganese mixed salt solution in step S1 is 1 mol / L to 3 mol / L, for example, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, or 3 mol / L, etc.

[0028] Preferably, in the first nickel-cobalt-manganese mixed salt solution in step S1, the molar percentage of nickel is ≥90%, for example, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%, etc., and the molar percentage of manganese is ≤5%, for example, 1%, 2%, 3%, 4%, or 5%, etc.

[0029] Preferably, the concentration of the boron doping source in step S1 is 0.05 mol / L to 0.1 mol / L, for example, 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, 0.08 mol / L, 0.09 mol / L, or 0.1 mol / L, etc.

[0030] Preferably, the reaction temperature of the first co-precipitation reaction in step S1 is 40°C to 80°C, for example, 40°C, 50°C, 60°C, 70°C, or 80°C, etc.

[0031] Preferably, the rotation speed of the first co-precipitation reaction in step S1 is 200 rpm to 500 rpm, for example, 200 rpm, 230 rpm, 250 rpm, 280 rpm, 300 rpm, 330 rpm, 350 rpm, 380 rpm, 400 rpm, 450 rpm, or 500 rpm, etc.

[0032] Preferably, the pH value of the first co-precipitation reaction in step S1 is 11-11.5, such as 11, 11.1, 11.2, 11.3, 11.4, or 11.5, etc.

[0033] Preferably, the median particle size D50 of the seed crystal in step S1 is 2-4 μm, such as 2 μm, 2.3 μm, 2.5 μm, 2.8 μm, 3 μm, 3.3 μm, 3.5 μm, 3.8 μm, or 4 μm, etc.

[0034] In the present application, the median particle size of the seed crystal is controlled, that is, the particle size of the nickel-cobalt-manganese core is controlled, which is preferably 2-4 μm. The core of this size not only provides a solid and appropriately sized substrate for subsequent gradient coating, but also effectively guarantees the processing performance of the electrode sheet, ultimately synergistically improving the volume energy density, rate performance, and long-cycle cycle stability of the battery.

[0035] Preferably, the concentration of the second nickel-cobalt-manganese mixed salt solution in step S2 is 1-3 mol / L, such as 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, or 3 mol / L, etc.

[0036] Preferably, in the second nickel-cobalt-manganese mixed salt solution in step S2, the molar amount of nickel accounts for ≤85%, such as 70%, 73%, 75%, 78%, 80%, 83%, or 85%, etc., and the molar amount of manganese accounts for ≤20%, such as 1%, 5%, 10%, 15%, or 20%, etc.

[0037] Preferably, the reaction temperature of the second co-precipitation reaction in step S2 is 40-80℃, such as 40℃, 50℃, 60℃, 70℃, or 80℃, etc.

[0038] Preferably, the rotation speed of the second co-precipitation reaction in step S2 is 200-500 rpm, such as 200 rpm, 230 rpm, 250 rpm, 280 rpm, 300 rpm, 330 rpm, 350 rpm, 380 rpm, 400 rpm, 450 rpm, or 500 rpm, etc.

[0039] Preferably, the pH value of the second co-precipitation reaction in step S2 is 10-10.5, such as 10, 10.1, 10.2, 10.3, 10.4, or 10.5, etc.

[0040] The application reduces the pH value in the second co-precipitation reaction, so that the pH value of the second co-precipitation reaction is less than that of the first co-precipitation reaction, which helps to fundamentally eliminate the homogeneous nucleation phenomenon in the coating process; and the pH value of the second co-precipitation reaction is controlled to be 10-10.5, so as to ensure that the transition layer and the shell are completely densified and component gradientized through the epitaxial growth mode.

[0041] Preferably, the difference between the target particle size and the median particle size D50 of the crystal seeds in step S2 is 2-3.5 μm, for example, 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm or 3.5 μm, etc.

[0042] It can be understood that the particle size difference in the application is the growth range of the particles in the second co-precipitation reaction process, and the difference between the target particle size and the median particle size D50 of the crystal seeds is 2-3.5 μm, which maintains the gradual change of the nickel-cobalt-manganese components in the transition layer and gives the core-shell structure the characteristics of "long-term protection". It effectively blocks the contact path of the electrolyte and the high-activity core, solves the core pain point of the long-cycle capacity attenuation of high-nickel materials, avoids the loss of energy density and rate performance caused by the over-thickness of the coating layer, and optimizes the comprehensive performance of the product.

[0043] Preferably, the concentration of the third nickel-cobalt-manganese mixed salt solution in step S3 is 1-3 mol / L, for example, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L or 3 mol / L, etc.

[0044] Preferably, in the third nickel-cobalt-manganese mixed salt solution in step S3, the molar amount of nickel accounts for ≤70%, for example, 50%, 55%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69% or 70%, etc., and the molar amount of manganese accounts for ≥25%, for example, 25%, 28%, 30%, 33%, 35%, 38%, 40%, 43%, 45%, 48% or 50%, etc.

[0045] Preferably, the reaction temperature of the third co-precipitation reaction in step S3 is 40-80℃, for example, 40℃, 50℃, 60℃, 70℃ or 80℃, etc.

[0046] Preferably, the third co-precipitation reaction in step S3 has a rotation speed of 200 rpm to 500 rpm, such as 200 rpm, 230 rpm, 250 rpm, 280 rpm, 300 rpm, 330 rpm, 350 rpm, 380 rpm, 400 rpm, 450 rpm, or 500 rpm, etc.

[0047] Preferably, the third co-precipitation reaction in step S3 has a pH value of 10 to 10.5, such as 10, 10.1, 10.2, 10.3, 10.4, or 10.5, etc.

[0048] Preferably, the median particle size D50 of the ternary positive electrode precursor material is 8 μm to 13 μm, such as 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, or 13 μm, etc.

[0049] It should be further noted that in addition to the above-mentioned defined features, the remaining raw material specific substances in the preparation method and further details of preparation are conventional technical solutions, and the conventional details of preparation of the ternary positive electrode precursor co-precipitation are applicable in principle without violating the technical concept of the present application.

[0050] Optionally, the type of salt in the nickel-cobalt-manganese mixed salt solution includes but is not limited to at least one of a chloride salt, a sulfate salt, a nitrate salt, or an acetate salt, etc.

[0051] Optionally, the boron doping source includes but is not limited to a metaborate salt, such as sodium metaborate.

[0052] Optionally, the first precipitant, the second precipitant, and the third precipitant each independently include but are not limited to at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, or sodium bicarbonate, etc.

[0053] Optionally, the mass concentration of the first precipitant solution, the second precipitant solution, and the third precipitant solution is each independently 10% to 30%, such as 10%, 15%, 20%, 25%, or 30%, etc.

[0054] Optionally, the first complexing agent, the second complexing agent, and the third complexing agent each independently include but are not limited to at least one of ammonia, citric acid, or ethylenediaminetetraacetic acid (EDTA), etc.

[0055] Optionally, the mass concentration of the first complexing agent solution, the second complexing agent solution, and the third complexing agent solution is each independently 5% to 20%, such as 5%, 10%, 15%, or 20%, etc.

[0056] In a third aspect, the present application provides a ternary cathode material, which is obtained by mixing and sintering the ternary cathode precursor material prepared according to the first aspect or the second aspect and a substance containing at least a lithium source.

[0057] It can be understood that the present application does not specially limit the specific preparation method of the ternary cathode material, and the method for obtaining the cathode material from the corresponding ternary cathode precursor material within the reasonable range known by the person skilled in the art without violating the technical concept of the present application is applicable in principle.

[0058] Optionally, the lithium source includes, but is not limited to, at least one of lithium hydroxide, lithium carbonate, lithium nitrate or lithium acetate, etc.

[0059] Optionally, the ratio of the total molar amount of nickel, cobalt and manganese in the cathode precursor material to the molar amount of lithium in the lithium source is 1: (1-1.3), for example, 1:1, 1:1.05, 1:1.1, 1:1.15, 1:1.2, 1:1.25 or 1:3, etc., but not limited to the listed values, and other values not listed in this range are also applicable.

[0060] Optionally, the sintering atmosphere is not unique, and the person skilled in the art can adaptively select and adjust according to the actual needs, for example, it can be a protective atmosphere or an oxygen-containing atmosphere, the protective atmosphere includes nitrogen and / or inert gas (argon or helium), and the oxygen-containing atmosphere includes air, oxygen or a mixture of oxygen and non-reactive gas.

[0061] Optionally, the sintering can be one-stage sintering or multi-stage sintering, and the specific sintering process can be adaptively selected and adjusted by the person skilled in the art according to the actual needs.

[0062] Optionally, the sintering temperature is 600-1000℃, for example, 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, 950℃ or 1000℃, etc., but not limited to the listed values, and other values not listed in this range are also applicable.

[0063] In a fourth aspect, the present application provides an electrochemical device, which comprises the ternary cathode material according to the third aspect, and the electrochemical device includes a lithium ion battery.

[0064] In a fifth aspect, the present application further provides an electric device, which comprises the electrochemical device according to the fourth aspect.

[0065] Compared with the prior art, the present application has the following beneficial effects:

[0066] (1) This invention breaks through the bottleneck of interlayer stress concentration in traditional core-shell materials and reduces the volume change rate by adopting a three-segment structure from the inside out: core-gradient nickel transition layer-shell. It adopts a unique core-shell structure design, and designs a transition layer with gradually decreasing nickel molar content on the surface of the high nickel content nickel-cobalt-manganese core, thereby mitigating the stress cracking caused by the sudden change in nickel-cobalt-manganese composition between the core and the shell, and improving the stability during battery cycling. At the same time, boron doping is carried out in the high nickel content nickel-cobalt-manganese core to suppress Li / Ni mixing and occupying tetrahedral sites in the TM layer, enhance the TM-O bond energy, and improve Ni 3+ / Ni 2 + Oxidation potential, reducing Ni 2+ The ternary cathode precursor material of this invention, after being used to prepare the ternary cathode material, improves the cycle stability and safety of the battery. The high manganese content of the outer shell helps to suppress side reactions of the electrolyte.

[0067] (2) In the preparation method of the present invention, boron-doped seed crystals with high nickel content are first prepared, i.e., core material. Then, in the second coprecipitation reaction, the nickel content gradually decreases with particle growth by simultaneously adding the first nickel-cobalt-manganese mixed salt solution and the second nickel-cobalt-manganese mixed salt solution, thus avoiding abrupt changes in the content of nickel-cobalt-manganese components. Then, by adding the third nickel-cobalt-manganese mixed salt with high manganese content in the third coprecipitation reaction, a dense shell structure with high manganese content is obtained. Thus, by simply controlling the added raw materials and feed flow rate, a ternary cathode precursor material with stable structure and excellent performance is obtained. The preparation process is easy to control and suitable for large-scale production operations. Detailed Implementation

[0068] 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.

[0069] 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.

[0070] In this invention, "a combination of at least two" refers to a quantity greater than or equal to two, unless otherwise specified. For example, "any combination of one or at least two" means one or more or more items. It can be understood that when referring to "a combination of at least two," it refers to any suitable combination of multiple items, that is, a combination of "at least two" items carried out in a manner that does not conflict with and enables the implementation of this invention.

[0071] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0072] 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.

[0073] 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.

[0074] 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."

[0075] 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.

[0076] 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.

[0077] In this invention, "optional" means that something is optional, that is, it refers to any one of the two parallel solutions of "having" or "not having". If there are multiple "optional" options in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, then each "optional" option is independent.

[0078] In this invention, "room temperature" generally refers to 4℃~35℃, and can refer to 20℃±5℃. In some embodiments of this invention, room temperature refers to 20℃~30℃.

[0079] Example 1

[0080] This embodiment provides a ternary cathode precursor material, which comprises, from the inside out, a nickel-cobalt-manganese core, a nickel-cobalt-manganese transition layer covering the surface of the nickel-cobalt-manganese core, and a nickel-cobalt-manganese shell covering the surface of the nickel-cobalt-manganese transition layer.

[0081] The nickel-cobalt-manganese core is also doped with boron, with a boron doping mass of 1.0%. The molar ratio of nickel, cobalt, and manganese in the nickel-cobalt-manganese core is 91:6:3. The molar content of nickel in the nickel-cobalt-manganese transition layer gradually decreases from the inside to the outside, and the molar content of nickel in the surface of the nickel-cobalt-manganese transition layer near the nickel-cobalt-manganese outer shell is greater than the molar content of nickel in the nickel-cobalt-manganese outer shell. The molar ratio of nickel, cobalt, and manganese in the nickel-cobalt-manganese outer shell is 70:5:25.

[0082] The preparation method of the ternary cathode precursor material is as follows:

[0083] (1) Prepare a first nickel-cobalt-manganese mixed salt solution with a concentration of 1.5 mol / L and a molar ratio of Ni:Co:Mn of 91:6:3, prepare a sodium metaborate solution with a concentration of 0.1 mol / L, prepare a second nickel-cobalt-manganese mixed salt solution with a concentration of 1.5 mol / L and a molar ratio of Ni:Co:Mn of 75:5:20, prepare a third nickel-cobalt-manganese mixed salt solution with a concentration of 1.5 mol / L and a molar ratio of Ni:Co:Mn of 70:5:25, prepare a sodium hydroxide precipitant solution with a mass concentration of 20%, and prepare an ammonia complexing agent solution with a mass concentration of 15%.

[0084] (2) Pour water into the reactor to half the volume, turn on the stirring to 400 rpm, control the temperature at 50°C, then add precipitant and complexing agent to prepare the base solution, ensure that the pH of the base solution is 11, stir and mix for 30 min, and set aside for later use.

[0085] The first nickel-cobalt-manganese mixed salt solution, sodium metaborate solution, precipitant solution and complexing agent solution were added to the base liquid in parallel to carry out the first coprecipitation reaction. During the first coprecipitation reaction, the reaction temperature was 40℃, the pH was controlled at 11, the ammonia concentration was 0.3mol / L, the rotation speed was 380rpm, and the reaction was stopped when the median particle size D50 was 3μm to obtain seed slurry. After centrifugation and washing of seed slurry, seed crystals were obtained.

[0086] (3) The seed crystals after centrifugation and washing are back-feeded into the reaction vessel containing the bottom liquid. Then, the first nickel-cobalt-manganese mixed salt solution, the second mixed salt solution, the precipitant solution and the complexing agent solution are added to the bottom liquid in parallel to carry out the second coprecipitation reaction. During the reaction, the feed flow rate of the first nickel-cobalt-manganese mixed salt solution gradually decreases and the feed flow rate of the second coprecipitation reaction gradually increases. The reaction temperature is 40℃, the pH is controlled at 10, the ammonia concentration is 0.2mol / L, the rotation speed is 380rpm, and the reaction continues until the median particle size of the particles grows to 3.5μm, so that the molar ratio of nickel, cobalt and manganese on the outer surface of the obtained particles approaches the ratio in the third nickel-cobalt-manganese mixed salt solution, and the second coprecipitation reaction ends.

[0087] (4) After the second coprecipitation reaction is completed, the third nickel-cobalt-manganese mixed salt solution, precipitant solution and complexing agent solution are added in parallel to the reaction slurry after the second coprecipitation reaction to continue the third coprecipitation reaction. The reaction temperature is 40℃, the pH is controlled at 10, the ammonia concentration is 0.2mol / L, the rotation speed is 380rpm, and the reaction is continued until the median particle size D50 of the particles reaches 11.5μm. The third coprecipitation reaction is then completed. Then, the material is aged, washed and dried in sequence to obtain the ternary cathode precursor material.

[0088] Example 2

[0089] This embodiment provides a ternary cathode precursor material, which comprises, from the inside out, a nickel-cobalt-manganese core, a nickel-cobalt-manganese transition layer covering the surface of the nickel-cobalt-manganese core, and a nickel-cobalt-manganese shell covering the surface of the nickel-cobalt-manganese transition layer.

[0090] The nickel-cobalt-manganese core is also doped with boron, with a boron doping mass of 0.5%. The molar ratio of nickel, cobalt, and manganese in the nickel-cobalt-manganese core is 91:6:3. The molar content of nickel in the nickel-cobalt-manganese transition layer gradually decreases from the inside to the outside, and the molar content of nickel in the surface of the nickel-cobalt-manganese transition layer near the nickel-cobalt-manganese outer shell is greater than the molar content of nickel in the nickel-cobalt-manganese outer shell. The molar ratio of nickel, cobalt, and manganese in the nickel-cobalt-manganese outer shell is 70:5:25.

[0091] The preparation method of the ternary cathode precursor material is as follows:

[0092] (1) Prepare a first nickel-cobalt-manganese mixed salt solution with a concentration of 1.5 mol / L and a molar ratio of Ni:Co:Mn of 91:6:3, prepare a sodium metaborate solution with a concentration of 0.05 mol / L, prepare a second nickel-cobalt-manganese mixed salt solution with a concentration of 1.5 mol / L and a molar ratio of Ni:Co:Mn of 75:5:20, prepare a third nickel-cobalt-manganese mixed salt solution with a concentration of 1.5 mol / L and a molar ratio of Ni:Co:Mn of 70:5:25, prepare a sodium hydroxide precipitant solution with a mass concentration of 20%, and prepare an ammonia complexing agent solution with a mass concentration of 15%.

[0093] (2) Pour water into the reactor to half the volume, turn on the stirring to 400 rpm, control the temperature at 50°C, then add precipitant and complexing agent to prepare the base solution, ensure that the pH of the base solution is 11, stir and mix for 30 min, and set aside for later use.

[0094] The first nickel-cobalt-manganese mixed salt solution, sodium metaborate solution, precipitant solution, and complexing agent solution were added concurrently to the base liquid to carry out the first coprecipitation reaction. During the first coprecipitation reaction, the reaction temperature was 60℃, the pH was controlled at 11.5, the ammonia concentration was 0.3mol / L, the rotation speed was 450rpm, and the reaction was stopped when the median particle size D50 was 2μm to obtain seed slurry. After centrifugation and washing of the seed slurry, the seed crystals were obtained.

[0095] (3) The seed crystals after centrifugation and washing are back-feeded into the reaction vessel containing the bottom liquid. Then, the first nickel-cobalt-manganese mixed salt solution, the second mixed salt solution, the precipitant solution and the complexing agent solution are added to the bottom liquid in parallel to carry out the second coprecipitation reaction. During the reaction, the feed flow rate of the first nickel-cobalt-manganese mixed salt solution gradually decreases and the feed flow rate of the second coprecipitation reaction gradually increases. The reaction temperature is 60℃, the pH is controlled at 10.5, the ammonia concentration is 0.2mol / L, the rotation speed is 450rpm, and the reaction continues until the median particle size of the particles grows to 2μm, so that the molar ratio of nickel, cobalt and manganese on the outer surface of the obtained particles approaches the ratio in the third nickel-cobalt-manganese mixed salt solution, and the second coprecipitation reaction ends.

[0096] (4) After the second coprecipitation reaction is completed, the third nickel-cobalt-manganese mixed salt solution, precipitant solution and complexing agent solution are added in parallel to the reaction slurry after the second coprecipitation reaction to continue the third coprecipitation reaction. The reaction temperature is 60℃, the pH is controlled at 10.5, the ammonia concentration is 0.2mol / L, the rotation speed is 450rpm, and the reaction is continued until the median particle size D50 of the particles reaches 8μm. The third coprecipitation reaction is then completed. Then, the material is aged, washed and dried in sequence to obtain the ternary cathode precursor material.

[0097] Example 3

[0098] This embodiment provides a ternary cathode precursor material, which comprises, from the inside out, a nickel-cobalt-manganese core, a nickel-cobalt-manganese transition layer covering the surface of the nickel-cobalt-manganese core, and a nickel-cobalt-manganese shell covering the surface of the nickel-cobalt-manganese transition layer.

[0099] The nickel-cobalt-manganese core is also doped with boron, with a boron doping mass of 2%. The molar ratio of nickel, cobalt, and manganese in the nickel-cobalt-manganese core is 91:6:3. The molar content of nickel in the nickel-cobalt-manganese transition layer gradually decreases from the inside to the outside, and the molar content of nickel in the surface of the nickel-cobalt-manganese transition layer near the nickel-cobalt-manganese outer shell is greater than the molar content of nickel in the nickel-cobalt-manganese outer shell. The molar ratio of nickel, cobalt, and manganese in the nickel-cobalt-manganese outer shell is 70:5:25.

[0100] The preparation method of the ternary cathode precursor material is as follows:

[0101] (1) Prepare a first nickel-cobalt-manganese mixed salt solution with a concentration of 1.5 mol / L and a molar ratio of Ni:Co:Mn of 91:6:3, prepare a sodium metaborate solution with a concentration of 0.08 mol / L, prepare a second nickel-cobalt-manganese mixed salt solution with a concentration of 1.5 mol / L and a molar ratio of Ni:Co:Mn of 75:5:20, prepare a third nickel-cobalt-manganese mixed salt solution with a concentration of 1.5 mol / L and a molar ratio of Ni:Co:Mn of 70:5:25, prepare a sodium hydroxide precipitant solution with a mass concentration of 20%, and prepare an ammonia complexing agent solution with a mass concentration of 15%.

[0102] (2) Pour water into the reactor to half the volume, turn on the stirring to 400 rpm, control the temperature at 50°C, then add precipitant and complexing agent to prepare the base solution, ensure that the pH of the base solution is 11, stir and mix for 30 min, and set aside for later use.

[0103] The first nickel-cobalt-manganese mixed salt solution, sodium metaborate solution, precipitant solution, and complexing agent solution were added concurrently to the base solution to carry out the first coprecipitation reaction. During the first coprecipitation reaction, the reaction temperature was 40℃, the pH was controlled at 11.3, the ammonia concentration was 0.3mol / L, the rotation speed was 300rpm, and the reaction was stopped when the median particle size D50 was 4μm to obtain seed slurry. After centrifugation and washing of the seed slurry, the seed crystals were obtained.

[0104] (3) The seed crystals after centrifugation and washing are back-feeded into the reaction vessel containing the bottom liquid. Then, the first nickel-cobalt-manganese mixed salt solution, the second mixed salt solution, the precipitant solution and the complexing agent solution are added to the bottom liquid in parallel to carry out the second coprecipitation reaction. During the reaction, the feed flow rate of the first nickel-cobalt-manganese mixed salt solution gradually decreases and the feed flow rate of the second coprecipitation reaction gradually increases. The reaction temperature is 40℃, the pH is controlled at 10.3, the ammonia concentration is 0.2mol / L, the rotation speed is 300rpm, and the reaction continues until the median particle size of the particles grows to 2.8μm, so that the molar ratio of nickel, cobalt and manganese on the outer surface of the obtained particles approaches the ratio in the third nickel-cobalt-manganese mixed salt solution, and the second coprecipitation reaction ends.

[0105] (4) After the second coprecipitation reaction is completed, the third nickel-cobalt-manganese mixed salt solution, precipitant solution and complexing agent solution are added in parallel to the reaction slurry after the second coprecipitation reaction to continue the third coprecipitation reaction. The reaction temperature is 40℃, the pH is controlled at 10.3, the ammonia concentration is 0.2mol / L, the rotation speed is 300rpm, and the reaction is continued until the median particle size D50 of the particles reaches 13μm. The third coprecipitation reaction is then completed. Then, the material is aged, washed and dried in sequence to obtain the ternary cathode precursor material.

[0106] Example 4

[0107] The difference between this embodiment and Embodiment 1 is that the molar ratio of nickel, cobalt and manganese in the nickel-cobalt-manganese core is 95:3:2, and the molar ratio of nickel, cobalt and manganese in the nickel-cobalt-manganese shell is 65:5:30.

[0108] In step (1) of the corresponding preparation method, a first nickel-cobalt-manganese mixed salt solution with a concentration of 1.5 mol / L and a molar ratio of Ni:Co:Mn of 95:3:2 is prepared; a sodium metaborate solution with a concentration of 0.1 mol / L is prepared; a second nickel-cobalt-manganese mixed salt solution with a concentration of 1.5 mol / L and a molar ratio of Ni:Co:Mn of 80:10:10 is prepared; and a third nickel-cobalt-manganese mixed salt solution with a concentration of 1.5 mol / L and a molar ratio of Ni:Co:Mn of 65:5:30 is prepared.

[0109] All other conditions remain the same as in Example 1.

[0110] Example 5

[0111] The difference between this embodiment and embodiment 1 is that the molar ratio of Ni:Co:Mn in the second nickel-cobalt-manganese mixed salt solution in step (2) of this embodiment is 88:5:7.

[0112] All other conditions remain the same as in Example 1.

[0113] Example 6

[0114] The difference between this embodiment and embodiment 1 is that the molar ratio of Ni:Co:Mn in the third nickel-cobalt-manganese mixed salt solution in step (2) of this embodiment is 73:5:22.

[0115] All other conditions remain the same as in Example 1.

[0116] Example 7

[0117] The difference between this embodiment and Embodiment 1 is that the boron doping mass in this embodiment is 0.1%.

[0118] In the preparation method, the feed flow rate of sodium metaborate solution is adjusted adaptively.

[0119] All other conditions remain the same as in Example 1.

[0120] Example 8

[0121] The difference between this embodiment and Embodiment 1 is that the boron doping mass in this embodiment is 2.5%.

[0122] In the preparation method, the feed flow rate of sodium metaborate solution is adjusted adaptively.

[0123] All other conditions remain the same as in Example 1.

[0124] Example 9

[0125] The difference between this embodiment and embodiment 1 is that in step (2) of this embodiment, the median particle size D50 of the seed crystal is 5 μm.

[0126] All other conditions remain the same as in Example 1.

[0127] Example 10

[0128] The difference between this embodiment and embodiment 1 is that in step (3) of this embodiment, the reaction continues until the median particle size of the particles grows to 1 μm, at which point the second coprecipitation reaction ends.

[0129] All other conditions remain the same as in Example 1.

[0130] Example 11

[0131] The difference between this embodiment and embodiment 1 is that in step (3) of this embodiment, the reaction continues until the median particle size of the particles grows to 5 μm, at which point the second coprecipitation reaction ends.

[0132] All other conditions remain the same as in Example 1.

[0133] Comparative Example 1

[0134] The difference between this comparative example and Example 1 is that the nickel-cobalt-manganese core of this comparative example is not doped with boron.

[0135] In step (1) of the preparation method, sodium metaborate solution is not prepared, and in step (2), sodium metaborate solution is not added.

[0136] All other conditions remain the same as in Example 1.

[0137] Comparative Example 2

[0138] The difference between this comparative example and Example 1 is that the molar ratio of nickel, cobalt, and manganese in the nickel-cobalt-manganese transition layer of this comparative example is a fixed value of 75:5:20.

[0139] In step (2) of the preparation method, the first nickel-cobalt-manganese mixed salt solution is not added, but only the second nickel-cobalt-manganese mixed salt solution is added.

[0140] All other conditions remain the same as in Example 1.

[0141] Comparative Example 3

[0142] The difference between this comparative example and Example 1 is that in step (1) of this comparative example, the molar ratio of nickel, cobalt and manganese in the third nickel-cobalt-manganese mixed salt solution is 91:6:3, which is the same as the ratio of the core.

[0143] All other conditions remain the same as in Example 1.

[0144] Comparative Example 4

[0145] The difference between this comparative example and Example 1 is that this comparative example does not contain a nickel-cobalt-manganese shell.

[0146] In step (1) of the preparation method, the preparation of the third nickel-cobalt-manganese mixed salt solution is not carried out, nor is the third coprecipitation reaction process in step (3). Instead, the substance after the second coprecipitation reaction is directly aged, washed and dried.

[0147] All other conditions remain the same as in Example 1.

[0148] Battery fabrication and performance testing

[0149] Battery manufacturing

[0150] The ternary cathode precursor materials of the examples and comparative examples were mixed with lithium hydroxide at a molar ratio of 1:1.05. After being sintered at 750°C for 10 hours in an oxygen atmosphere, the materials were taken out, ground and pulverized to obtain the ternary cathode material.

[0151] A positive electrode slurry was prepared according to the ratio of positive electrode material:SP:PVDF=90:5:5, and the solid content of the slurry was 60%. Aluminum foil was placed on a coating machine, and a 150μm coating tool was placed on the aluminum foil. Single crystal slurry was poured in, and the equipment was turned on for coating. After coating, an electrode sheet was obtained. The electrode sheet was placed in a 110℃ oven for drying and then rolled to obtain the positive electrode sheet.

[0152] The positive electrode sheets provided in the examples and comparative examples were cut into circular pieces with a diameter of 15 mm using a stamping machine in a dry environment. In a glove box, a lithium metal sheet was used as the counter electrode, and a Ceglard composite membrane was selected as the separator. Electrolyte was added and assembled to obtain a coin cell. The electrolyte was 1 mol / L LiPF6 and EC:DEC:DMC = 1:1:1 (volume ratio) (where EC is ethylene carbonate; DEC is diethyl carbonate; and DMC is dimethyl carbonate).

[0153] Performance testing

[0154] The performance of the coin cells provided in the examples and comparative examples was tested using the Wuhan Landian CT2001A system: the cells were activated three times at 0.1C rate / 2.7~4.3V, and then the electrochemical performance of the activated coin cells was tested at 2.7~4.3V@0.1C / 1C. The discharge specific capacity at 1C rate and the capacity retention rate after 100 cycles at 1C rate were obtained.

[0155] Thermal stability: Start the ARC adiabatic thermal runaway test (the test sample is heated from room temperature to 45±2ºC in the chamber, and after resting for 90 minutes, the change in battery temperature rise rate is detected. If the temperature rise exceeds 0.2ºC within 10 minutes (i.e., SHR>0.02ºC / min), it is considered that a self-exothermic reaction has occurred inside the battery. Maintain the adiabatic environment until the battery thermal runaway occurs; if the temperature rise does not exceed 0.2℃ within 10 minutes (i.e., SHR≤0.02℃ / min), continue to the next step temperature rise test; each temperature step is 5ºC, and the steps are repeated on each step. The ARC test temperature range is 45℃~300℃, the self-heating start temperature is T1 (temperature rise rate SHR>0.02℃ / min), and the thermal runaway start temperature is T2 (temperature rise rate SHR>1℃ / min).

[0156] The test results are shown in Table 1.

[0157] Table 1

[0158]

[0159] From Table 1, we can obtain:

[0160] In the results of Examples 1-4, the present invention incorporates boron doping into the nickel-cobalt-manganese core, which initially suppresses lithium-nickel mixing. Combined with the three-segment structure of core-gradient nickel transition layer-shell from the inside out, this overcomes the bottleneck of interlayer stress concentration in traditional core-shell materials, reduces volume change rate, and improves battery capacity, cycle stability, and thermal stability. In the results of Examples 1 and 5-6, during the preparation of the precursor material, if the nickel content in the second nickel-cobalt-manganese mixed salt solution or the manganese content in the third nickel-cobalt-manganese mixed salt solution is too low, the components in the transition layer and shell will not transition smoothly, affecting capacity, cycle life, and thermal stability. Furthermore, in the data from Examples 1 and 7-8, the amount of boron doping leads to a worsening of the lithium-nickel mixing effect and affects the synergistic effect of the three-segment structure, also resulting in a decrease in capacity, cycle life, and thermal stability. Meanwhile, Examples 1 and 9-11 show that controlling the growth of particles in the core-gradient nickel transition layer-shell during the preparation process is more beneficial for improving battery performance.

[0161] In the data results of Example 1 and Comparative Examples 1-4, the boron doping in the ternary precursor material, the three-segment structure of the core-gradient nickel transition layer-shell, and the corresponding content rules are all crucial. Without any one of these conditions, it is difficult to achieve simultaneous and significant improvement in capacity, cycle performance, and thermal stability.

[0162] 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 precursor material, characterized in that, The ternary cathode precursor material comprises, from the inside out, a nickel-cobalt-manganese core, a nickel-cobalt-manganese transition layer covering the surface of the nickel-cobalt-manganese core, and a nickel-cobalt-manganese shell covering the surface of the nickel-cobalt-manganese transition layer. The nickel-cobalt-manganese core is also doped with boron; the molar content of nickel in the surface of the nickel-cobalt-manganese transition layer near the nickel-cobalt-manganese core is less than the molar content of nickel in the nickel-cobalt-manganese core, the molar content of nickel in the nickel-cobalt-manganese transition layer gradually decreases from the inside to the outside, and the molar content of nickel in the surface of the nickel-cobalt-manganese transition layer near the nickel-cobalt-manganese outer shell is greater than or equal to the molar content of nickel in the nickel-cobalt-manganese outer shell; the molar content of manganese in the nickel-cobalt-manganese outer shell is the highest.

2. The ternary precursor material according to claim 1, characterized in that, With the total molar amount of nickel, cobalt, and manganese in the nickel-cobalt-manganese core being 100%, the molar amount of nickel is ≥90%, and the molar amount of manganese is ≤5%. Preferably, the boron doping mass in the nickel-cobalt-manganese core is 0.5% to 2%; Preferably, with the total molar amount of nickel, cobalt, and manganese in the nickel-cobalt-manganese shell being 100%, the molar amount of nickel is ≤70%, and the molar amount of manganese is ≥25%.

3. A method for preparing a ternary precursor material as described in claim 1 or 2, characterized in that, The preparation method includes the following steps: S1: The first nickel-cobalt-manganese mixed salt solution, the boron doped source solution, the first precipitant solution and the first complexing agent solution are added in parallel to carry out the first co-precipitation reaction to obtain seed crystals; S2: The first nickel-cobalt-manganese mixed salt solution, the second nickel-cobalt-manganese mixed salt solution, the second precipitant solution, and the second complexing agent solution are added in parallel to the solution containing seed crystals to carry out the second coprecipitation reaction. During the second coprecipitation reaction, the feed flow rate of the first nickel-cobalt-manganese mixed salt solution is gradually reduced, and the feed flow rate of the second nickel-cobalt-manganese mixed salt solution is gradually increased. The second coprecipitation reaction is stopped after the target particle size is reached. S3: After the second coprecipitation reaction is completed, the third nickel-cobalt-manganese mixed salt solution, the third precipitant solution and the third complexing agent solution are added in parallel to carry out the third coprecipitation reaction to obtain the ternary precursor material; Among them, the molar percentage of nickel in the first nickel-cobalt-manganese mixed salt solution is greater than that in the second nickel-cobalt-manganese mixed salt solution, which is greater than that in the third nickel-cobalt-manganese mixed salt solution; the molar percentage of manganese in the third nickel-cobalt-manganese mixed salt solution is the highest.

4. The preparation method according to claim 3, characterized in that, In step S1, the concentration of the first nickel-cobalt-manganese mixed salt solution is 1 mol / L to 3 mol / L; Preferably, in step S1, the first nickel-cobalt-manganese mixed salt solution contains ≥90% nickel and ≤5% manganese. Preferably, the concentration of the boron doping source in step S1 is 0.05 mol / L to 0.1 mol / L; Preferably, in step S1, the reaction temperature of the first coprecipitation reaction is 40℃~80℃, the rotation speed of the first coprecipitation reaction is 200rpm~500rpm, and the pH value of the first coprecipitation reaction is 11~11.

5. Preferably, the median grain size D50 of the seed crystals in step S1 is 2μm~4μm.

5. The preparation method according to claim 3 or 4, characterized in that, In step S2, the concentration of the second nickel-cobalt-manganese mixed salt solution is 1 mol / L to 3 mol / L; Preferably, in step S2, the molar percentage of nickel in the second nickel-cobalt-manganese mixed salt solution is ≤85%, and the molar percentage of manganese is ≤20%. Preferably, in step S2, the reaction temperature of the second coprecipitation reaction is 40℃~80℃, the rotation speed of the second coprecipitation reaction is 200rpm~500rpm, and the pH value of the second coprecipitation reaction is 10~10.

5.

6. The preparation method according to claim 3 or 4, characterized in that, The difference between the target particle size and the median particle size D50 of the seed crystal in step S2 is 2μm~3.5μm.

7. The preparation method according to claim 3, characterized in that, The concentration of the third nickel-cobalt-manganese mixed salt solution in step S3 is 1 mol / L to 3 mol / L; Preferably, in the third nickel-cobalt-manganese mixed salt solution described in step S3, the molar percentage of nickel is ≤70%, and the molar percentage of manganese is ≥25%. Preferably, the reaction temperature of the third coprecipitation reaction in step S3 is 40℃~80℃, the rotation speed of the third coprecipitation reaction is 200rpm~500rpm, and the pH value of the third coprecipitation reaction is 10~10.

5. Preferably, the median particle size D50 of the ternary cathode precursor material is 8 μm to 13 μm.

8. A ternary cathode material, characterized in that, The ternary cathode material is obtained by mixing and sintering a ternary cathode precursor material prepared as described in claim 1 or 2 or by the preparation method described in any one of claims 3-7 with a substance containing at least a lithium source.

9. An electrochemical device, characterized in that, The electrochemical device includes the ternary cathode material as described in claim 8, and the electrochemical device includes a lithium-ion battery.

10. An electrical appliance, characterized in that, The electrical equipment includes the electrochemical device as described in claim 9.

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