Pre-lithiated cathode precursor, preparation method thereof, cathode material, cathode sheet and battery

Abstract

The application relates to the technical field of batteries, and discloses a pre-lithiated positive electrode precursor, a preparation method thereof, a positive electrode material, a positive electrode sheet and a battery. The preparation method of the pre-lithiated positive electrode precursor comprises the following steps: configuring a mixed metal salt solution containing a nickel source, a manganese source and an M metal source; performing spray pyrolysis treatment on the mixed metal salt solution to obtain a spray pyrolysis precursor; and performing first sintering treatment on the spray pyrolysis precursor after mixing the spray pyrolysis precursor with a first lithium source to obtain the pre-lithiated positive electrode precursor. In the application, lithium elements are introduced into the core of the precursor material through pre-lithiation, the growth of the precursor crystal grains is promoted, the lithium elements have high reactivity, can promote the oxidation and rearrangement of metal ions, help to form a more compact oxide structure, increase the size of the crystal grains and reduce the occurrence of hollowing, so that the tap density of the spray pyrolysis positive electrode precursor is improved.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to a pre-lithiated cathode precursor and its preparation method, cathode material, cathode electrode sheet and battery. Background Technology

[0002] Layered oxide cathode precursors are a key component in the preparation of cathode materials for lithium-ion batteries. These materials are typically composed of transition metals (such as nickel, cobalt, and manganese) and oxygen, which react with lithium salts in subsequent high-temperature solid-state reactions to form layered oxide cathode materials.

[0003] Currently, the mainstream mass production methods for layered oxide cathode precursors mainly include co-precipitation and spray pyrolysis. Co-precipitation involves mixing multiple metal salt solutions with a precipitant solution and controlling the reaction conditions to co-precipitate metal ions, forming a precursor with a layered structure. Spray pyrolysis involves atomizing a metal salt solution and then subjecting it to a pyrolysis reaction in a high-temperature environment to prepare an ultrafine powdered layered oxide cathode precursor.

[0004] Compared to coprecipitation, spray pyrolysis offers advantages such as a shorter process path, fewer key process parameters, lower production costs, and higher sintering reactivity. Compared to coprecipitation precursors of the same composition, spray pyrolysis can sinter single-crystal cathode materials at lower temperatures. It is particularly valuable for precursors that are more sensitive to sintering temperatures, such as cathode precursors with high nickel content.

[0005] However, the cathode precursors prepared by spray pyrolysis have problems such as small particle size and hollowness. These problems will reduce the tap density of the precursor, increase the storage and transportation costs per ton of precursor, and result in low packing density during high-temperature sintering, which limits the increase in production capacity. Summary of the Invention

[0006] In view of the above problems, this application provides a pre-lithiated cathode precursor and its preparation method, cathode material, cathode electrode sheet and battery, aiming to solve the problem of low tap density of spray pyrolysis cathode precursor.

[0007] In a first aspect, embodiments of this application provide a method for preparing a pre-lithiated cathode precursor, comprising the following steps: preparing a mixed metal salt solution of a nickel source, a manganese source, and an M metal source; wherein the M metal source contains at least one of cobalt salt, aluminum salt, zirconium salt, tantalum salt, titanium salt, niobium salt, germanium salt, yttrium salt, tungsten salt, boron salt, cerium salt, and strontium salt; subjecting the mixed metal salt solution to spray pyrolysis treatment to obtain a spray pyrolysis precursor; and mixing the spray pyrolysis precursor with a first lithium source and then performing a first sintering treatment to obtain the pre-lithiated cathode precursor.

[0008] The preparation method of this application involves pre-sintering a spray-pyrolysis precursor with an appropriate amount of lithium source. Through a pre-lithiation process, lithium is introduced into the core of the precursor material, promoting precursor grain growth. Due to the high reactivity of lithium, it promotes the oxidation and rearrangement of metal ions, contributing to the formation of a denser oxide structure. This process increases grain size to some extent and reduces hollowing, thereby significantly improving the tap density of the spray-pyrolysis high-nickel cathode precursor. This improvement not only increases loading density and potting density but also reduces storage and transportation costs, achieving the effect of cost reduction and increased yield. Furthermore, this process causes impurity elements to migrate to the particle surface, allowing for rapid removal of these impurities through simple water washing.

[0009] In some embodiments, the spray pyrolysis step includes: spraying the mixed metal salt solution at a temperature of 500℃ to 1000℃ for 20s to 120s, wherein the atomization flow rate of the mixed metal salt solution is 20L / min to 200L / min, the carrier gas flow rate is 50L / min to 500L / min, and the ratio of the carrier gas flow rate to the atomization flow rate is 2 to 3.

[0010] By adopting the above technical solution, it is helpful to better control the particle size of the spray pyrolysis precursor product and keep it within the ideal target range. The D50 of the obtained spray pyrolysis precursor is...

[0011] 0.5μm~3.5μm, Dmax less than 30μm, specific surface area 4m² 2 / g~16m 2 / g.

[0012] In some embodiments, the molar ratio of lithium in the first lithium source to the total molar ratio of metal elements in the spray pyrolysis precursor is 0.5 to 1; and / or, the temperature of the first sintering treatment is 350°C to 650°C, and the time is 0.5h to 4h.

[0013] By controlling the above process conditions, the growth and aggregation of precursor particles can be promoted, the particle size of the precursor can be increased to the ideal range, and the tap density of the pre-lithiation precursor can be improved.

[0014] Secondly, embodiments of this application provide a pre-lithiated cathode precursor, wherein the chemical formula of the pre-lithiated cathode precursor is Li. a Ni x Mn y M 1-x-y O z, 0.46≤a≤0.98, 0.5≤x≤0.95, y>0, 1≤z≤2; wherein, M includes at least one of Co, Al, Zr, Ta, Ti, Nb, Ge, Y, W, B, Ce, and Sr.

[0015] In this embodiment, lithium is introduced into the core of the precursor material without affecting the precursor activity. The subscript 'a' indicates that each Li... a Ni x Mn y M 1-x-y O z The number of Li atoms in the molecule is a. When the value of a is within the above range, it helps to promote the uniform growth of the cathode precursor particles, which helps to improve the density and stability of the material. The dense crystal structure helps to reduce the hollowing phenomenon, thereby significantly improving the tap density of the spray pyrolysis high-nickel cathode precursor.

[0016] In some embodiments, the pre-lithiated cathode precursor is prepared using the pre-lithiated cathode precursor preparation method as described in the first aspect.

[0017] In some embodiments, the pre-lithiated cathode precursor has at least one of the following (1) to (3):

[0018] (1) The D50 of the pre-lithiated cathode precursor is 0.8 μm to 5 μm;

[0019] (2) The content of S element in the pre-lithiated cathode precursor is less than 200 ppm;

[0020] (3) The Cl content in the pre-lithiated cathode precursor is less than 100 ppm.

[0021] Due to the introduction of lithium, the D50 particle size of the pre-lithiated cathode precursor is larger than that of the spray pyrolysis precursor, and its tap density reaches 1.5 g / cm³. 3 ~2.2g / cm 3 The low content of impurities such as S and Cl in the material helps to form a more uniform and dense crystal structure during the subsequent sintering process, thereby improving the electrochemical performance of the cathode material.

[0022] Thirdly, embodiments of this application provide a cathode material prepared using the pre-lithiation cathode precursor obtained by the preparation method described in the first aspect or the pre-lithiation cathode precursor described in the first aspect, wherein the chemical formula of the cathode material is Li. a1 Ni x1 Mn y1 M 1-x1-y1O2, 1.02≤a1≤1.10, 0.5≤x1≤0.95, 0.01≤y1≤0.4, wherein M includes at least one of Co, Al, Zr, Ta, Ti, Nb, Ge, Y, W, B, Ce, and Sr.

[0023] The cathode material is prepared using a pre-lithiated cathode precursor, either the first or second aspect. Because this pre-lithiated cathode precursor has a high tap density, its particles are tightly packed, and its internal structure is more compact, the resulting cathode material exhibits better energy density. Furthermore, the aforementioned pre-lithiated cathode precursor has a low impurity content, and the cathode material prepared using this precursor demonstrates better structural stability and electrochemical performance.

[0024] In some embodiments, the cathode material has at least one of the following (I) to (III):

[0025] (I) The D50 of the positive electrode material is 2.8 μm to 4.3 μm, and the Dmax is less than 15 μm;

[0026] (II) The specific surface area of ​​the positive electrode material is 0.35 m². 2 / g~0.85m 2 / g;

[0027] (III) The residual lithium mass fraction of the cathode material is 0.02 wt% to 0.06 wt%.

[0028] Fourthly, embodiments of this application provide a method for preparing a cathode material, comprising the following steps: mixing a pre-lithiated cathode precursor with a second lithium source and performing a second sintering treatment to obtain the cathode material.

[0029] Because the pre-lithiated cathode precursor has a high tap density, it exhibits better flowability and plasticity during processing, making the cathode material preparation process smoother and improving production efficiency. Simultaneously, it also helps to prepare cathode material particles with regular morphology and uniform particle size distribution.

[0030] In some embodiments, the molar ratio of lithium in the second lithium source to metal in the spray pyrolysis precursor is 0.06 to 0.66; and / or, the temperature of the second sintering treatment is 700°C to 950°C; and the time is 6 h to 14 h.

[0031] Fifthly, embodiments of this application provide a positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, the positive active material layer comprising the positive electrode material described in the third aspect, or the positive electrode material obtained by the preparation method of the positive electrode material described in the fourth aspect. This improves the quality of the electrode sheet.

[0032] Sixthly, embodiments of this application provide a battery including the positive electrode as described in the fifth aspect. This improves the battery's energy density and charge / discharge efficiency.

[0033] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Detailed Implementation

[0034] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0035] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0036] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0037] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0038] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0039] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0040] Cathode precursors prepared by spray pyrolysis typically have small particle sizes. Furthermore, during spray pyrolysis, the rapid evaporation and decomposition of droplets can lead to the formation of hollow structures within some oxide particles. The combined effect of small particle size and hollowing results in a low tap density in the prepared cathode precursor, which is detrimental to subsequent material processing and the improvement of battery performance.

[0041] Based on this, embodiments of this application provide a method for preparing a pre-lithiated cathode precursor, comprising the following steps: preparing a mixed metal salt solution containing a nickel source, a manganese source, and an M metal source; wherein the M metal source contains at least one of cobalt salt, aluminum salt, zirconium salt, tantalum salt, titanium salt, niobium salt, germanium salt, yttrium salt, tungsten salt, boron salt, cerium salt, and strontium salt; subjecting the mixed metal salt solution to spray pyrolysis treatment to obtain a spray pyrolysis precursor; mixing the spray pyrolysis precursor with a first lithium source and then performing a first sintering treatment, followed by washing with water and drying to obtain the pre-lithiated cathode precursor.

[0042] Pre-lithiation is a technique that introduces lithium elements into the cathode material preparation process in advance. The pre-lithiation technology in this application aims to increase the particle size of the cathode precursor by pre-introducing lithium elements into the core of the precursor material, thereby improving the tap density of the precursor. Tap density refers to the mass per unit volume of powder measured after vibration compaction under specified conditions. For lithium battery cathode materials, a higher tap density means a greater mass of active material per unit volume, which is beneficial for improving the battery's energy density and volumetric capacity.

[0043] Here, nickel source, manganese source, and M metal source refer to compounds used to provide nickel, manganese, and M metal elements, respectively. For example, the nickel source can be selected from at least one of nickel salts, such as nickel nitrate, nickel chloride, nickel sulfate, nickel carbonate, nickel bicarbonate, nickel oxalate, and nickel acetate. The manganese source can be selected from at least one of manganese salts, such as manganese nitrate, manganese chloride, manganese sulfate, manganese carbonate, manganese bicarbonate, manganese oxalate, and manganese acetate. The M metal source can be selected from at least one of nitrates, chlorides, sulfates, manganese carbonate, manganese bicarbonate, manganese oxalate, and manganese acetate containing the M metal element.

[0044] The step of preparing a mixed metal salt solution containing a nickel source, a manganese source, and a metal M source may include: dissolving the nickel salt, manganese salt, and the metal M salt in an aqueous solution according to a predetermined metal element ratio, thereby preparing the mixed metal salt solution. This mixed metal salt solution may be an unsaturated solution, meaning that under specific metal salt and ratio conditions, none of the metal salts reaches its saturation concentration. The main metal elements contained in the mixed metal salt solution include nickel (Ni) and manganese (Mn). In addition, at least one element selected from cobalt (Co), aluminum (Al), zirconium (Zr), tantalum (Ta), titanium (Ti), niobium (Nb), germanium (Ge), yttrium (Y), tungsten (W), boron (B), cerium (Ce), and strontium (Sr) may be added according to actual needs. In some embodiments, the molar percentage of nickel (Ni) in all metal elements exceeds 50%.

[0045] The principle of spray pyrolysis is to spray a solution containing metal salts into a high-temperature environment in the form of a mist. Under these conditions, the solvent evaporates rapidly, and the metal salts undergo thermal decomposition. Subsequently, due to supersaturation, the metal salts transform into a solid state and crystallize, thereby directly forming nanoscale powder. In this embodiment, the spray pyrolysis process can be carried out by passing a mixed metal salt solution into a spray pyrolysis furnace.

[0046] Spray pyrolysis precursors possess small and uniform particle sizes, exhibiting excellent reactivity upon combination with a lithium source. This characteristic enables them to achieve grain boundary fusion and grain growth at relatively low temperatures and in a short time, significantly improving the tap density of the pre-lithiated cathode precursor. Simultaneously, as lithium elements embed into the cathode material's lattice structure and the grains grow further, impurities such as sulfur and chlorine, which were originally present inside the precursor and unable to integrate into the cathode material's lattice, are displaced to the grain surface, becoming easier to remove through water washing. Benefiting from the increased grain size and reduced specific surface area, the resulting pre-lithiated cathode precursor not only exhibits improved flowability but also facilitates moisture evaporation and drying, greatly enhancing its processing performance.

[0047] In some embodiments, the spray pyrolysis process includes: spraying a metal salt solution at a temperature of 500°C to 1000°C for 20 to 120 seconds, wherein the atomization flow rate of the metal salt solution after entering the spray pyrolysis furnace is 20 L / min to 200 L / min, the spray carrier gas is selected from at least one of air or oxygen, the carrier gas flow rate is 50 L / min to 500 L / min, and the ratio of the carrier gas flow rate to the atomization flow rate is 2 to 3.

[0048] As an example, the spray pyrolysis temperature can be a typical but not limiting value such as 500℃, 600℃, 700℃, 800℃, 900℃, or 1000℃, and the spray pyrolysis time can be a typical but not limiting value such as 20s, 40s, 60s, 80s, 100s, or 120s. The pyrolysis temperature affects the evaporation rate of the solvent in the droplets and the rate and extent of the thermal decomposition reaction. The pyrolysis time affects the reaction time of the droplets at high temperatures, thus affecting the phase composition and grain growth of the product. Controlling the spray pyrolysis temperature and time within the above ranges can better promote the crystallization and sintering of the product.

[0049] As an example, the atomization flow rate can be typical but not limiting values ​​such as 20 L / min, 50 L / min, 150 L / min, and 200 L / min. Correspondingly, since the ratio between the carrier gas flow rate and the atomization flow rate is constrained to 2–3, the carrier gas flow rate can be set to typical but not limiting values ​​such as 40 L / min–60 L / min, 100 L / min–150 L / min, 300 L / min–450 L / min, and 400 L / min–600 L / min. The atomization flow rate affects the formation and size distribution of droplets, which in turn affects the particle size and morphology of the product. The carrier gas flow rate, in turn, affects the reaction rate and the crystallinity of the product. By adjusting the atomization flow rate and the carrier gas flow rate to the above ranges, it is helpful to better control the particle size of the product and keep it within the predetermined target range.

[0050] By controlling the process conditions of spray pyrolysis within the above-mentioned range, the D50 particle size of the obtained spray pyrolysis precursor is 0.5 μm to 3.5 μm, the Dmax does not exceed 30 μm, and the specific surface area is 4 m². 2 / g

[0051] ~16m 2 / g. D50 is often used to represent the average particle size of powders. Dmax particle size refers to the largest particle size in the particle size distribution. It is used together with other particle size distribution percentiles such as D10, D50, and D90 to reflect the largest particle size present in a particle sample, and to some extent, the width of the particle size distribution range.

[0052] In some embodiments, the spray pyrolysis products (spray pyrolysis precursors) are separated from the exhaust gas by a cyclone separator and an air classifier. The exhaust gas is then treated by an exhaust gas treatment device and can be reused in a carrier gas recirculation system. Here, the cyclone separator refers to a device that separates the spray pyrolysis products from the gas. The air classifier can classify the material collected by the cyclone separator, separating out fine particles that meet the particle size requirements.

[0053] In the step of mixing the spray pyrolysis precursor with a first lithium source and then performing a first sintering treatment, the first lithium source can be selected from at least one of lithium hydroxide monohydrate, lithium hydroxide, lithium oxide, lithium peroxide, lithium carbonate, and lithium nitrate. As an example, the first lithium source can be a single type of lithium source, such as pure lithium hydroxide or pure lithium carbonate, or a mixture of multiple lithium sources, such as a mixture of lithium hydroxide and lithium carbonate. When multiple lithium sources are used, their mixing ratio is not limited.

[0054] In some embodiments, the ratio of the molar amount of lithium in the first lithium source to the total molar amount of metal elements in the spray pyrolysis precursor is defined as the first lithium ratio, which is 0.5 to 1. Here, the total molar amount of metal elements in the spray pyrolysis precursor refers to the total number of moles of all metal elements (e.g., nickel, manganese, M metal elements, etc.) in the precursor. If the first lithium ratio is too low, it is not conducive to the growth of the pre-lithiated cathode precursor; if the first lithium ratio is too high, it will lead to lithium waste. Therefore, controlling the first lithium ratio at 0.5 to 1 allows for grain boundary fusion and grain growth to be completed quickly at a lower temperature, thereby improving the tap density of the precursor material. As an example, the first lithium ratio can be typical but not limiting values ​​such as 0.5, 0.6, 0.7, 0.8, 0.9, and 1. Since the subsequent water washing and impurity removal process will cause some lithium loss, the final pre-lithiated precursor has the general chemical formula Li. a Ni x Mn y M 1-x-y O z The subscript a of Li in the equation is in the range of 0.46 to 0.98.

[0055] In some embodiments, the temperature of the first sintering treatment is 350°C to 650°C, and the time is 0.5h to 4h. As examples, the temperature of the first sintering treatment can be typical but not limiting values ​​such as 350°C, 450°C, 500°C, 550°C, 600°C, and 650°C, and the time of the first sintering treatment can be typical but not limiting values ​​such as 0.5h, 1.0h, 1.5h, 2.0h, 2.5h, 3.0h, 3.5h, and 4.0h. The sintering atmosphere of the first sintering treatment is not limited; for example, it can be carried out in an air environment. The equipment for the first sintering treatment can be an industrial kiln such as a rotary kiln or a roller kiln.

[0056] Through the aforementioned first sintering process, the spray pyrolysis precursor and an appropriate amount of lithium source can promote particle growth or aggregation during the high-temperature sintering step, thereby increasing the particle size of the final pre-lithiated cathode precursor. Since excessively long sintering times or excessively high sintering temperatures may lead to overly large precursor particles, thus adversely affecting the quality of the precursor, this embodiment of the application, by precisely controlling the temperature and time of the first sintering, can increase the precursor particle size to an ideal range, thereby improving the tap density of the pre-lithiated precursor.

[0057] After the first sintering process, the product is transferred to a water-washing and stirring tank, where water is added and the mixture is stirred. It is then washed, filtered to remove impurities, and dried to obtain the pre-lithiated cathode precursor. During the water washing process, to minimize lithium loss, the mass ratio of water used for washing to the mass ratio of the first sintered product is controlled within the range of 1.25:1 to 3:1. For example, this mass ratio can be typical but not limiting values ​​such as 1.25:1, 1.5:1, 2:1, 2.5:1, and 3:1. The stirring speed during water washing should not be too fast; a stirring speed of 100 rpm to 900 rpm and a stirring time of 3 min to 10 min are recommended.

[0058] Due to limitations in preparation conditions, the raw materials used in the preparation of cathode precursors via spray pyrolysis are mostly transition metal chlorides and transition metal sulfates with high solubility and mild decomposition. These transition metal salts contain a significant amount of impurities such as chlorine and sulfur, which are carried into the spray pyrolysis products and remain in the cathode precursor and cathode material, thus adversely affecting product performance. Therefore, to remove impurities, the industry typically washes the spray pyrolysis cathode precursor with water. However, because the spray pyrolysis oxide precursor has a small particle size, it is prone to agglomeration. Simple water washing cannot quickly remove the impurities and also makes the washed material difficult to dehydrate and dry, resulting in problems such as high moisture content, poor flowability, and easy agglomeration in the spray precursor.

[0059] In this embodiment, the spray pyrolysis precursor obtained by spray pyrolysis is first mixed with an appropriate amount of lithium source and pre-sintered. Then, impurities are removed by water washing and filtration, and finally dried to obtain a pre-lithiated cathode precursor with extremely low impurity content and high tap density.

[0060] In some embodiments, to reduce the content of impurity elements in the material, the moisture content of the material after washing and filtration needs to be controlled below 20,000 ppm. The drying process can be carried out under negative pressure, with a continuous flow of drying gas to remove water vapor from the surface of the material. The drying temperature can be set between 110°C and 130°C.

[0061] The pre-lithiated cathode precursor prepared by the above method has a D50 of 0.8 μm to 5 μm and a tap density of 1.5 g / cm³. 3 ~2.2g / cm 3 Specific surface area is 3m² 2 / g~10m 2 / g. Due to the increase in grain size and the decrease in specific surface area, the pre-lithiated cathode precursor has good flowability, making it easier to dry the moisture in the material, thereby improving the processing performance of the precursor.

[0062] The pre-lithiated cathode precursor prepared by the above method contains magnetic foreign matter such as Fe, Cr, Zn, and Cu within 15 ppm, meaning that the content of any one of these magnetic foreign matter in the pre-lithiated cathode precursor does not exceed 15 ppm. Here, magnetic foreign matter refers to substances that can be attracted or magnetized under the influence of a magnetic field. These substances may be inherently magnetic or become magnetic after being magnetized under the influence of an external magnetic field. In the lithium battery industry, these foreign matter may include transition elements such as iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), and other metallic elements and their alloys. These elements may undergo electrochemical reactions inside the battery, forming dendrites that pierce the battery separator and electrolyte, leading to a series of problems such as battery short circuits and self-discharge.

[0063] The residual lithium mass fraction in the pre-lithiated cathode precursor prepared by the above method is less than 0.02 wt%. Here, residual lithium typically refers to lithium compounds, such as Li₂CO₃, LiHCO₃, and LiOH, that remain on the material surface during the preparation of lithium-ion battery cathode materials due to various reasons. The presence of these residual lithium compounds not only leads to instability in the material structure but also causes a decrease in electrochemical performance and may even trigger battery safety issues. Residual lithium can usually be removed by washing with water, and the mass fraction of residual lithium can be determined by positional titration.

[0064] Secondly, embodiments of this application provide a pre-lithiated cathode precursor, the chemical formula of which is Li. a Ni x Mn y M 1-x-y O z , 0.46≤a≤0.98, 0.5≤x≤0.95, y>0, 1≤z≤2; wherein, M includes at least one of Co, Al, Zr, Ta, Ti, Nb, Ge, Y, W, B, Ce, and Sr.

[0065] The general chemical formula of the pre-lithiated cathode precursor is Li. a Ni x Mn y M 1-x-y Oz In the text, the subscript 'a' indicates each Li a Ni x Mn y M 1-x-y O z The number of Li atoms in the molecule is denoted as 'a', with a value ranging from 0.46 to 0.98. For example, typical but not limiting values ​​for 'a' include 0.46, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, and 0.98. The lithium content significantly influences the crystal structure of the material. Within the aforementioned range, a lithium content promotes uniform growth of the cathode precursor particles, improves the material's density and stability, and reduces hollowing. The subscript 'x' indicates the number of Li atoms per molecule. a Ni x Mn y M 1-x-y O z The number of Ni atoms in the molecule is x, and the value of x ranges from 0.5 to 0.95. For example, typical but not limited values ​​for x include 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, and 0.95. The subscript y indicates each Li atom. a Ni x Mn y M 1-x-y O z The number of Ni atoms in the molecule is y, and the range of y is y > 0. For example, the values ​​of y can be typical but not limited to 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, and 0.95. The subscript z represents each Li... a Ni x Mn y M 1-x-y O zThe number of O atoms in the molecule is z, and the value of y is in the range of 1≤z≤2. As an example, the value of z can be a typical but non-limiting value such as 1.00, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.10, 1.11, 1.12, 1.13, 1.14, 1.15, 1.16, 1.17, 1.18, 1.19, 1.20, 1.21, 1.22, 1.23, 1.24, 1.25, 1.30, 1.35, 1.40, 1.45, 1.50, 1.55, 1.60, 1.65, 1.70, 1.75, 1.80, 1.85, 1.90, 1.95, 2.00. The cathode precursor in this embodiment contains a high proportion of Ni, which imparts a high specific capacity to the material, thereby improving the energy density of the battery. Without the introduction of lithium, the high-nickel cathode precursor might tend to have a smaller particle size to shorten the lithium-ion diffusion path and improve the material's rate performance. The pre-lithiated cathode precursor in this embodiment introduces lithium into the core of the precursor material, promoting grain growth and reducing hollowing through pre-lithiation, thereby improving the tap density of the spray-pyrolyzed high-nickel cathode precursor.

[0066] In some embodiments, the pre-lithiated cathode precursor is prepared using the preparation method of the first aspect.

[0067] In some embodiments, the D50 of the pre-lithiated cathode precursor is 0.8 μm to 5 μm. D50 represents the midpoint of the particle size distribution in the particle population, meaning that particles smaller than D50 account for 50% of the total particle mass or number, and particles larger than D50 also account for 50%. D50 particle size is commonly used to describe the average particle size characteristics of powder or particulate materials. It is one of the important indicators for evaluating particle size distribution. As an example, the D50 of the pre-lithiated cathode precursor can be typical but not limiting values ​​such as 0.8 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, and 5 μm. Due to the introduction of lithium, the D50 particle size of the pre-lithiated cathode precursor is larger than that of the spray pyrolysis precursor, thereby increasing the tap density to 1.5 g / cm³. 3 ~2.2g / cm 3 Its tap density is comparable to that of lithium-mixed precursors prepared by co-precipitation.

[0068] In some embodiments, the sulfur (S) content in the pre-lithiated cathode precursor is less than 200 ppm. Excessive levels of impurities such as sulfur and chlorine in the cathode precursor can disrupt the layered structure of the cathode material, reducing its structural stability and leading to capacity decay and decreased cycle stability. Therefore, it is crucial to strictly control the impurity content of the cathode precursor during its preparation. The sulfur content of less than 200 ppm in the pre-lithiated cathode precursor of this application embodiment helps improve sintering performance, enhances the density and uniformity of the material, and helps maintain particle uniformity and consistency.

[0069] In some embodiments, the chlorine (Cl) content in the pre-lithiated cathode precursor is less than 100 ppm. The presence of chlorine as an impurity, at a concentration of less than 100 ppm, is beneficial for forming a more uniform and dense crystal structure during subsequent heat treatment, thereby improving the electrochemical performance of the cathode material.

[0070] Thirdly, embodiments of this application provide a cathode material, obtained using a pre-lithiation cathode precursor as described in the first or second aspect, wherein the chemical formula of the cathode material is Li. a1 Ni x1 Mn y1 M 1-x1-y1 O2, 1.02≤a1≤1.10, 0.5≤x1≤0.95, 0.01≤y1≤0.4, wherein M includes at least one of Co, Al, Zr, Ta, Ti, Nb, Ge, Y, W, B, Ce, and Sr.

[0071] The cathode material in this embodiment is obtained by using a pre-lithiated cathode precursor, which has a high tap density, meaning the particles are relatively dense. This is beneficial for maintaining structural stability during high-temperature sintering, thereby improving the energy density of the cathode material. Furthermore, the pre-lithiated cathode precursor has a low impurity content, meaning the precursor material has high purity. Therefore, the resulting cathode material has a relatively high active material content, improving the electrochemical performance and structural stability of the cathode material.

[0072] In some embodiments, the D50 of the cathode material is 2.8 μm to 4.3 μm, and the Dmax is less than 15 μm; the specific surface area of ​​the cathode material is 0.35 to 0.85 m². 2 / g; the residual lithium mass fraction of the cathode material is 0.02wt% to 0.06wt%.

[0073] Fourthly, embodiments of this application provide a method for preparing a cathode material, comprising the following steps: mixing a pre-lithiated cathode precursor with a second lithium source and performing a second sintering treatment to obtain the cathode material.

[0074] The second lithium source can be selected from at least one of lithium hydroxide monohydrate, lithium hydroxide, lithium oxide, lithium peroxide, lithium carbonate, and lithium nitrate. The composition of the second lithium source is not affected by the first lithium source; the same lithium source or a different lithium source can be used.

[0075] In some embodiments, the ratio of the molar amount of lithium in the second lithium source to the total molar amount of metal elements in the spray pyrolysis precursor is defined as the second lithium ratio. The second lithium ratio is 0.06 to 0.66. As examples, the second lithium ratio can be typical but not limiting values ​​such as 0.06, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5, 0.6, and 0.66. The value of the second lithium ratio is related to the first lithium ratio. To ensure that the lithium content in the cathode material reaches the desired value, the sum of the first lithium ratio and the second lithium ratio is 1.06 to 1.16. Since the washing step in the preparation process of the pre-lithiated cathode precursor will lose some lithium, the final cathode material Li a1 Ni x1 Mn y1 M 1-x1-y1 The subscript a1 of the Li element in O2 is 1.02 to 1.10.

[0076] In some embodiments, the temperature of the second sintering treatment is 700℃ to 950℃; the sintering time is 6h to 14h. As examples, the sintering temperature can be typical but not limiting values ​​such as 700℃, 750℃, 800℃, 850℃, 900℃, and 950℃, and the sintering time can be typical but not limiting values ​​such as 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, and 14h. The specific sintering temperature and sintering time are related to the nickel content in the cathode material. Generally, when the proportion of nickel in the total molar number of non-lithium metal elements reaches 50% to 80%, a second sintering temperature of 920℃ to 960℃ and a sintering time of 10h to 14h result in better material performance; when the proportion of nickel in the total molar number of non-lithium metal elements reaches more than 80%, a second sintering temperature of 740℃ to 800℃ and a sintering time of 6h to 12h result in better material performance. The sintering atmosphere includes at least one of air or oxygen, and the volume fraction of oxygen therein is 21% or more.

[0077] In some embodiments, after the second sintering treatment, mechanical crushing is required after cooling, including but not limited to jaw crushing, roller crushing, ball milling, etc. At least one sieving process can be performed between the mechanical crushing and air jet milling steps, with a screen mesh size of 200 mesh or more, and the grinding pressure of the air jet milling is 0.2 to 1.0 MPa.

[0078] The cathode material prepared by the above method has a low residual lithium mass fraction, moderate D50 particle size and specific surface area, and good electrochemical performance.

[0079] Fifthly, embodiments of this application provide a positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, the positive active material layer comprising the positive electrode material described in the third aspect, or the positive electrode material obtained by the preparation method of the positive electrode material described in the fourth aspect. This improves the quality of the electrode sheet.

[0080] Sixthly, embodiments of this application provide a battery including the positive electrode as described in the fifth aspect. This improves the battery's energy density and charge / discharge efficiency.

[0081] The following description is based on specific embodiments.

[0082] Example 1

[0083] (1) Preparation of pre-lithiated cathode precursor

[0084] This application provides a pre-lithiated cathode precursor with the chemical formula Li. 0.68 Ni 0.6 Mn 0.1 Co 0.3 O2. The preparation method of this pre-lithiated cathode precursor includes the following steps:

[0085] S1: Weigh out 34.75 kg (120 mol) of nickel nitrate hexahydrate, 5.00 kg (20 mol) of manganese nitrate tetrahydrate, and 17.39 kg (60 mol) of cobalt nitrate hexahydrate in a molar ratio of 6:1:3, dissolve them in 24 L of water to obtain a metal salt solution.

[0086] S2: The metal salt solution is atomized into the spray pyrolysis furnace at a flow rate of 20 L / min. The carrier gas is a mixture of air and oxygen in a 1:1 volume ratio, with a flow rate of 60 L / min. The furnace temperature is set to 770℃, and the pyrolysis time in the furnace is 60 s. The product obtained from the spray pyrolysis is separated from the exhaust gas by a cyclone separator, and the spray pyrolysis precursor Ni is collected. 0.6 Mn 0.1 Co 0.3 O 1.14 .

[0087] S3: Weigh 4.2 kg (56.8 mol) of lithium carbonate and 12 kg (75.89 + 158 mol) of spray pyrolysis precursor according to the first lithium ratio of 0.72. (The "first lithium ratio" is defined as the ratio of the molar amount of lithium element in lithium carbonate to the total molar amount of metal elements in spray pyrolysis precursor). After mixing evenly, perform the first sintering at 550℃ for 3 hours. The sintering atmosphere is dry air with an air flow rate of 20 L / min. The material after the first sintering is crushed, screened, washed, and filtered. After the water content of the solid material is lower than 20,000 ppm, it is transferred to a slightly negative pressure environment and dried at 120℃ for 1 hour to obtain the pre-lithiated cathode precursor. During the water washing process, the mass ratio of water to the first sintering product is 2:1, the water washing speed is 400 rpm, and the water washing time is set to 6 minutes. During the filtration process after water washing, the negative pressure is maintained at -0.8 to -1.0 MPa.

[0088] (2) Preparation of cathode materials

[0089] The chemical formula of the cathode material is Li. 1.06 Ni 0.6 Mn 0.1 Co 0.3 O2. The preparation method of this cathode material includes the following steps:

[0090] The actual first lithium ratio in the pre-lithiated cathode precursor was determined to be 0.68. Therefore, 3.0 kg of lithium carbonate was weighed according to the second lithium ratio of 0.38 and mixed evenly with the above-mentioned pre-lithiated cathode precursor (13.5 kg). (The "second lithium ratio" is defined as the ratio of the molar amount of lithium element in lithium carbonate to the total molar amount of metal elements in the spray pyrolysis precursor). After mixing, a small sample was taken for tap density (TD) testing, and the remainder was poured into a crucible and placed in a high-temperature sintering furnace for a second sintering treatment. The second sintering conditions were set as follows: heating at a rate of 5℃ / min, first heating to 750℃ for 1 h, then heating to 920℃ for 12 h, with a sintering atmosphere of air and oxygen mixed in a volume ratio of 1:2. After sintering, the material was crushed by roller crushing, sieved through a 200-mesh screen, and then crushed by air jet milling at a grinding pressure of 0.40 MPa.

[0091] The impurity content and particle size distribution of the precursor before and after pre-lithiation are shown in Table 1. The tap density (TD) of the mixture of the pre-lithiated cathode precursor and lithium carbonate is 1.89 g / cm³. 3 The TD value is comparable to that of the lithium-co-precipitated precursor; the prepared single-crystal cathode material has a D50 of 3.8 μm, a Dmax of 12 μm, and a specific surface area (BET) of 0.68 m². 2 / g, the residual lithium mass fraction of the cathode material is 0.04wt%, and the impurity content and 0.2C first charge-discharge performance of the cathode material are shown in Table 2.

[0092] Example 2

[0093] The difference between Example 2 and Example 1 is that a metal chloride salt is selected as the raw material for preparing the spray pyrolysis precursor.

[0094] (1) Preparation of pre-lithiated cathode precursor

[0095] The pre-lithiated cathode precursor provided in Example 2 has the chemical formula Li. 0.66 Ni 0.6 Mn 0.1 Co 0.3 O2. The preparation method of this pre-lithiated cathode precursor includes the following steps:

[0096] S1: Weigh out 36.03 kg of nickel chloride hexahydrate, 5.00 kg of manganese chloride tetrahydrate, and 18.03 kg of cobalt chloride hexahydrate in a molar ratio of 6:1:3, dissolve them in 112 L of water to obtain a metal salt solution.

[0097] S2: The metal salt solution is atomized into the spray pyrolysis furnace at a flow rate of 25 L / min. The carrier gas is a mixture of air and oxygen in a 1:1 volume ratio, with a flow rate of 70 L / min. The furnace temperature is set to 800℃, and the pyrolysis time in the furnace is 80 s. The product obtained from the spray pyrolysis is separated from the exhaust gas by a cyclone separator, and the spray pyrolysis precursor Ni is collected. 0.6 Mn 0.1 Co 0.3 O 1.14 .

[0098] S3: Weigh 5.6 kg of lithium carbonate and 16 kg of spray pyrolysis precursor according to the first lithium ratio of 0.72 (wherein, the "first lithium ratio" is defined as the ratio of the molar amount of lithium element in lithium carbonate to the total molar amount of metal elements in spray pyrolysis precursor). After uniform mixing, perform the first sintering at 560℃ for 3 hours. The sintering atmosphere is dry air with an air flow rate of 20 L / min. The material after the first sintering is crushed, screened, washed, and filtered. After the moisture content of the solid material is lower than 20,000 ppm, it is transferred to a slightly negative pressure environment and dried at 120℃ for 1 hour to obtain the pre-lithiated cathode precursor. During the washing process, the mass ratio of water to the first sintering product is 1.5:1, the washing speed is 500 rpm, and the washing time is set to 7 minutes. During the filtration process after washing, the negative pressure is maintained at -0.8 to -1.0 MPa.

[0099] (2) Preparation of cathode materials

[0100] The chemical formula of the cathode material is Li. 1.06 Ni 0.6 Mn 0.1 Co0.3 O2. The preparation method of this cathode material includes the following steps:

[0101] The actual first lithium ratio in the pre-lithiated cathode precursor was determined to be 0.66. Therefore, 4.2 kg of lithium carbonate was weighed according to a second lithium ratio of 0.40 and mixed evenly with the above-mentioned pre-lithiated cathode precursor (18.0 kg). After mixing, a small sample was taken for tap density (TD) testing, and the remainder was poured into a crucible and placed in a high-temperature sintering furnace for a second sintering treatment. The second sintering conditions were set as follows: heating at a rate of 5℃ / min, first heating to 750℃ for 1.5 h, then heating to 925℃ for 12 h, with a sintering atmosphere of air and oxygen mixed in a volume ratio of 1:2. After sintering, the material was crushed by roller crushing, sieved through a 200-mesh screen, and then crushed by an air jet mill at a grinding pressure of 0.45 MPa.

[0102] The impurity content and particle size distribution of the precursor before and after pre-lithiation are shown in Table 1. The tap density (TD) of the mixture of the pre-lithiated cathode precursor and lithium carbonate is 1.92 g / cm³. 3 The TD value is comparable to that of the lithium-mixed co-precipitated precursor; the prepared single-crystal cathode material has a D50 of 3.7 μm, a Dmax of 11 μm, and a specific surface area (BET) of 0.71 m². 2 / g, the residual lithium mass fraction of the cathode material is 0.04wt%, and the impurity content and 0.2C first charge-discharge performance of the cathode material are shown in Table 2.

[0103] Example 3

[0104] The difference between Example 3 and Example 2 is that the first lithium ratio is 0.77, and the pre-lithiated cathode precursor provided in Example 3 has the chemical formula Li. 0.73 Ni 0.6 Mn 0.1 Co 0.3 O2.

[0105] (1) Preparation of pre-lithiated cathode precursor

[0106] The preparation method of the pre-lithiated cathode precursor includes the following steps:

[0107] S1: Weigh out 36.03 kg of nickel chloride hexahydrate, 5.00 kg of manganese chloride tetrahydrate, and 18.03 kg of cobalt chloride hexahydrate in a molar ratio of 6:1:3, dissolve them in 112 L of water to obtain a metal salt solution.

[0108] S2: The metal salt solution is atomized into the spray pyrolysis furnace at a flow rate of 25 L / min. The carrier gas is a mixture of air and oxygen in a 1:1 volume ratio, with a flow rate of 70 L / min. The furnace temperature is set to 800℃, and the pyrolysis time in the furnace is 80 s. The product obtained from the spray pyrolysis is separated from the exhaust gas by a cyclone separator, and the spray pyrolysis precursor Ni is collected. 0.6 Mn 0.1 Co 0.3 O 1.14 .

[0109] S3: Weigh 6.0 kg of lithium carbonate and 16 kg of spray pyrolysis precursor according to the first lithium ratio of 0.77. After mixing evenly, perform the first sintering at 560℃ for 3 hours. The sintering atmosphere is dry air with an air flow rate of 20 L / min. The material after the first sintering is crushed, screened, washed and filtered. After the water content of the solid material is lower than 20,000 ppm, it is transferred to a slightly negative pressure environment and dried at 120℃ for 1 hour to obtain the pre-lithiated cathode precursor. During the water washing process, the mass ratio of water to the first sintering product is 1.5:1, the water washing speed is 500 rpm, and the water washing time is set to 7 minutes. During the filtration process after water washing, the negative pressure is maintained at -0.8 to -1.0 MPa.

[0110] (2) Preparation of cathode materials

[0111] The chemical formula of the cathode material is Li. 1.06 Ni 0.6 Mn 0.1 Co 0.3 O2. The preparation method of this cathode material includes the following steps:

[0112] The actual first lithium ratio in the pre-lithiated cathode precursor was determined to be 0.73. Therefore, 3.64 kg of lithium carbonate was weighed according to a second lithium ratio of 0.33 and mixed evenly with the above-mentioned pre-lithiated cathode precursor (18.8 kg). After mixing, a small sample was taken for TD testing, and the remainder was poured into a crucible and placed in a high-temperature sintering furnace for sintering. The sintering conditions were set as follows: heating at a rate of 5℃ / min, first heating to 750℃ for 1.5 h, then heating to 925℃ for 12 h, and the sintering atmosphere was a mixture of air and oxygen in a volume ratio of 1:2. After sintering, the material was crushed by roller crushing, sieved through a 200-mesh screen, and then crushed by air jet milling at a grinding pressure of 0.45 MPa.

[0113] The impurity content and particle size distribution of the precursor before and after pre-lithiation are shown in Table 1. The TD value of the mixture of pre-lithiation cathode precursor and lithium carbonate is 1.94 g / cm³. 3The TD value is comparable to that of the lithium-mixed co-precipitated precursor; the prepared single-crystal cathode material has a D50 of 3.6 μm, a Dmax of 11 μm, and a BET of 0.70 μm. 2 / g, the residual lithium mass fraction of the single crystal cathode material is 0.04wt%, and the impurity content and 0.2C first charge-discharge performance of the single crystal cathode material are shown in Table 2.

[0114] Example 4

[0115] The difference between Example 4 and Example 2 is that the ratio of nickel, cobalt, and manganese is changed. The pre-lithiated cathode precursor provided in Example 4 has the chemical formula Li. 0.68 Ni 0.8 Mn 0.1 Co 0.1 O2.

[0116] (1) Preparation of pre-lithiated cathode precursor

[0117] The preparation method of the pre-lithiated cathode precursor includes the following steps:

[0118] S1: Weigh 48.04 kg of nickel chloride hexahydrate, 5.00 kg of manganese chloride tetrahydrate, and 6.01 kg of cobalt chloride hexahydrate in a molar ratio of 8:1:1, dissolve them in 53 L of water to obtain a metal salt solution.

[0119] S2: The metal salt solution is atomized by being fed into a spray pyrolysis furnace at a flow rate of 25 L / min. The carrier gas is a mixture of air and oxygen in a 1:1 volume ratio, with a flow rate of 70 L / min. The furnace temperature is set to 790℃, and the pyrolysis time in the furnace is 80 s. The product obtained from the spray pyrolysis is separated from the exhaust gas by a cyclone separator, and the spray pyrolysis precursor Ni is collected. 0.8 Mn 0.1 Co 0.1 O 1.06 .

[0120] S3: Weigh 3.63 kg of lithium hydroxide and 16 kg of spray pyrolysis precursor according to the first lithium ratio of 0.72. After mixing evenly, sinter at 520℃ for 2 hours. The sintering atmosphere is dry air with an air flow rate of 20 L / min. The sintered material is crushed, screened, washed, and filtered. After the moisture content of the solid material is lower than 20,000 ppm, it is transferred to a slightly negative pressure environment and dried at 120℃ for 1 hour to obtain the pre-lithiated cathode precursor. The solid-liquid ratio of the water washing is 1.5:1, the water washing speed is 500 rpm, and the water washing time is set to 7 minutes. During the filtration process after water washing, the negative pressure is maintained at -0.8 to -1.0 MPa.

[0121] (2) Preparation of cathode materials

[0122] The chemical formula of the cathode material is Li. 1.06 Ni 0.8 Mn 0.1 Co 0.1 O2. The preparation method of this cathode material includes the following steps:

[0123] The actual first lithium ratio in the pre-lithiated cathode precursor was determined to be 0.68. Therefore, 2.62 kg of lithium hydroxide was weighed according to a second lithium ratio of 0.38 and mixed evenly with the above-mentioned pre-lithiated cathode precursor (18.0 kg). After mixing, a small sample was taken for TD testing, and the remainder was poured into a crucible and placed in a high-temperature sintering furnace for sintering. The sintering conditions were set as follows: heating at a rate of 5℃ / min, first heating to 600℃ for 1 hour, then heating to 780℃ for 12 hours, with a sintering atmosphere of pure oxygen. After sintering, the material was crushed by roller crushing, sieved through a 200-mesh sieve, and then crushed by an air jet mill at a grinding pressure of 0.78 MPa.

[0124] The impurity content and particle size distribution of the precursor before and after pre-lithiation are shown in Table 1. The TD value of the mixture of pre-lithiation cathode precursor and lithium carbonate is 1.97 g / cm³. 3 The TD value is comparable to that of the lithium-co-precipitated precursor; the prepared single-crystal cathode material has a D50 of 3.6 μm, a Dmax of 13 μm, and a specific surface area BET of 0.65 m². 2 / g, the residual lithium mass fraction of the single crystal cathode material is 0.06wt%, and the impurity content and 0.2C first charge-discharge performance of the single crystal cathode material are shown in Table 2.

[0125] Comparative Example 1

[0126] The difference between Comparative Example 1 and Example 2 is that the precursor was not pre-lithiated. After the spray pyrolysis precursor was prepared, it was directly washed with water to remove impurities. At this time, a longer water washing time is required to effectively remove impurities. Also, since the particle size of the spray pyrolysis precursor is small, the filtration time will be extended accordingly.

[0127] (1) Preparation of spray pyrolysis precursor

[0128] The specific operating steps are as follows:

[0129] S1: Weigh 36.03 kg of nickel chloride hexahydrate, 5.00 kg of manganese chloride tetrahydrate, and 18.03 kg of cobalt chloride hexahydrate in a molar ratio of 6:1:3, dissolve them in 112 L of water to obtain the first reaction solution.

[0130] S2: The first reaction liquid is atomized in the spray pyrolysis furnace at a flow rate of 25 L / min. The spray carrier gas is a mixture of air and oxygen in a volume ratio of 1:1, and the carrier gas flow rate is 70 L / min. The furnace temperature of the spray pyrolysis furnace is set to 800℃, and the pyrolysis time of the material in the pyrolysis furnace is 80 s. The product obtained by spray pyrolysis is separated from the tail gas by a cyclone separator and the spray pyrolysis precursor is collected.

[0131] S3: The spray pyrolysis precursor was poured into pure water at a mass ratio of 1.5:1. The washing speed was 500 rpm and the washing time was 14 h, which is 120 times the washing time of the pre-lithiated cathode precursor. During the filtration process after washing, the negative pressure was maintained at -0.8 to -1.0 MPa. After the water content in the solid material was lower than 20,000 ppm, it was transferred to a slightly negative pressure environment and dried at 120°C for 1 h to obtain the dried spray pyrolysis precursor Ni. 0.6 Mn 0.1 Co 0.3 O 1.14 .

[0132] (2) Preparation of cathode materials

[0133] Preparation of single-crystal cathode material: 9.29 kg of lithium carbonate was weighed according to a lithium ratio of 1.06 and mixed evenly with the above-mentioned spray pyrolysis precursor. After mixing, a small sample was taken for TD testing, and the remainder was poured into a crucible and placed in a high-temperature sintering furnace for sintering. The sintering conditions were set as follows: heating at a rate of 5℃ / min, first sintering at 750℃ for 4 hours, then sintering at 925℃ for 12 hours. The sintering atmosphere was a mixture of air and oxygen in a volume ratio of 1:2. After sintering, the material was crushed by roller crushing, sieved through a 200-mesh screen, and then crushed by air jet milling at a grinding pressure of 0.45 MPa.

[0134] The impurity content and particle size distribution of the precursor were tested and are shown in Table 1; the TD value of the precursor-lithium carbonate mixture was 1.38 g / cm³. 3 The D50 is much smaller than that of the pre-lithiated cathode precursor; the prepared single-crystal cathode material has a D50 of 3.1 μm, a Dmax of 32 μm, and a BET of 0.78 μm. 2 / g, the residual lithium mass fraction of the single crystal cathode material is 0.07wt%, and the impurity content and 0.2C first charge-discharge performance of the single crystal cathode material are shown in Table 2.

[0135] Comparative Example 2

[0136] The difference between Comparative Example 2 and Example 1 is that the first lithium ratio is 0.25, and the resulting pre-lithiated precursor still contains a lot of impurities after washing with water. At the same time, the primary particles are still relatively small, which prolongs the subsequent filtration time.

[0137] (1) Preparation of pre-lithiated cathode precursor

[0138] The preparation method of the pre-lithiated cathode precursor includes the following steps:

[0139] S1: Weigh out 36.03 kg of nickel chloride hexahydrate, 5.00 kg of manganese chloride tetrahydrate, and 18.03 kg of cobalt chloride hexahydrate in a molar ratio of 6:1:3, dissolve them in 112 L of water to obtain a metal salt solution.

[0140] S2: The metal salt solution is atomized into the spray pyrolysis furnace at a flow rate of 25 L / min. The carrier gas is a mixture of air and oxygen in a 1:1 volume ratio, with a flow rate of 70 L / min. The furnace temperature is set to 800℃, and the pyrolysis time in the furnace is 80 s. The product obtained from the spray pyrolysis is separated from the exhaust gas by a cyclone separator, and the spray pyrolysis precursor Ni is collected. 0.6 Mn 0.1 Co 0.3 O 1.14 .

[0141] S3: Weigh 1.95 kg of lithium carbonate and 16 kg of spray pyrolysis precursor according to a lithium metal ratio of 0.25. After mixing evenly, sinter at 560℃ for 3 hours. The sintering atmosphere is dry air with an air flow rate of 20 L / min. The sintered material is crushed, screened, washed, and filtered. After the moisture content of the solid material is lower than 20,000 ppm, it is transferred to a slightly negative pressure environment and dried at 120℃ for 1 hour to obtain the pre-lithiated cathode precursor. The solid-liquid ratio of the water washing is 1.5:1, the water washing speed is 500 rpm, and the water washing time is set to 28 min. During the filtration process after water washing, the negative pressure is maintained at -0.8 to -1.0 MPa.

[0142] (2) Preparation of cathode materials

[0143] The actual first lithium ratio in the pre-lithiated cathode precursor was determined to be 0.23. Therefore, 7.52 kg of lithium carbonate was weighed according to a second lithium ratio of 0.83 and mixed evenly with the pre-lithiated cathode precursor. After mixing, a small sample was taken for TD testing, and the remainder was poured into a crucible and placed in a high-temperature sintering furnace for sintering. The sintering conditions were set as follows: heating at a rate of 5℃ / min, first sintering at 750℃ for 2.5 h, then sintering at 925℃ for 12 h, with a sintering atmosphere of air and oxygen mixed in a volume ratio of 1:2. After sintering, the material was crushed by roller crushing, sieved through a 200-mesh screen, and then crushed by air jet milling at a grinding pressure of 0.45 MPa.

[0144] The impurity content and particle size distribution of the precursor before and after pre-lithiation are shown in Table 1. The TD value of the mixture of pre-lithiated cathode precursor and lithium carbonate is 1.45 g / cm³. 3The values ​​are much smaller than those of the pre-lithiated cathode precursor in Example 2; the prepared single-crystal cathode material has a D50 of 3.6 μm, a Dmax of 12 μm, and a BET of 0.73 μm. 2 / g, the residual lithium mass fraction of the single crystal cathode material is 0.04wt%, and the impurity content and 0.2C first charge-discharge performance of the single crystal cathode material are shown in Table 2.

[0145] Comparative Example 3

[0146] The difference between Comparative Example 3 and Example 2 is that all the lithium salts used to prepare the single-crystal cathode material were added at once during the precursor pre-lithiation, without stepwise lithium addition. At this time, due to the low precursor pre-lithiation temperature and short reaction time, the lithium element could not be completely converted into lattice lithium in the single-crystal cathode material. During the subsequent water washing process, the lithium remaining on the material surface was easily dissolved in the water, causing lithium loss. This resulted in the final cathode material having a lithium deficiency in the lattice, forming structural defects, or even transforming into a spinel or rock salt structure, losing electrochemical activity.

[0147] (1) Preparation of cathode materials

[0148] The chemical formula of the cathode material is Li. 1.06 Ni 0.6 Mn 0.1 Co 0.3 O2. The preparation method of this cathode material includes the following steps:

[0149] S1: Weigh out 36.03 kg of nickel chloride hexahydrate, 5.00 kg of manganese chloride tetrahydrate, and 18.03 kg of cobalt chloride hexahydrate in a molar ratio of 6:1:3, dissolve them in 112 L of water to obtain a metal salt solution.

[0150] S2: The metal salt solution is atomized into the spray pyrolysis furnace at a flow rate of 25 L / min. The spray carrier gas is a mixture of air and oxygen in a volume ratio of 1:1, and the flow rate of the carrier gas is 70 L / min. The furnace temperature of the spray pyrolysis furnace is set to 800℃, and the pyrolysis time of the material in the pyrolysis furnace is 80 s. The product obtained by spray pyrolysis is separated from the tail gas by a cyclone separator, and the spray pyrolysis precursor is collected.

[0151] S3: Weigh 8.26 kg of lithium carbonate and 16 kg of spray pyrolysis precursor according to the first lithium ratio of 1.06. After mixing evenly, sinter at 650℃ for 3 hours. The sintering atmosphere is dry air with an air flow rate of 20 L / min. The sintered material is crushed, screened, washed, and filtered. After the moisture content of the solid material is lower than 20,000 ppm, it is transferred to a slightly negative pressure environment and dried at 120℃ for 1 hour to obtain the pre-lithiated cathode precursor. The solid-liquid ratio of the water washing is 1.5:1, the water washing speed is 500 rpm, and the water washing time is set to 7 minutes. During the filtration process after water washing, the negative pressure is maintained at -0.8 to -1.0 MPa.

[0152] S4: The actual first lithium ratio in the pre-lithiated cathode precursor was determined to be 0.92. A small amount of dried pre-lithiated cathode precursor sample was taken for TD testing, and the remainder was placed in a crucible and sintered in a high-temperature sintering furnace. The sintering conditions were set as follows: heating at a rate of 5℃ / min, first sintering at 750℃ for 1 hour, then sintering at 925℃ for 12 hours, with a sintering atmosphere of air and oxygen mixed in a volume ratio of 1:2. After sintering, the material was crushed by roller crushing, sieved through a 200-mesh screen, and then crushed by an air jet mill at a grinding pressure of 0.45 MPa.

[0153] The impurity content and particle size distribution of the precursor before and after pre-lithiation are shown in Table 1; the TD value of the pre-lithiated cathode precursor is 2.10 g / cm³. 3 The TD value is higher than that of the lithium-mixed precursor after co-precipitation; the prepared single-crystal cathode material has a D50 of 5.6 μm, a Dmax of 26 μm, and a BET of 0.54 μm. 2 / g, the residual lithium mass fraction of the single crystal cathode material is 0.06wt%, the impurity content of the single crystal cathode material and the first charge and discharge performance at 0.2C are shown in Table 2, the first charge and discharge performance is significantly reduced.

[0154] Performance testing

[0155] To verify the progressiveness of the embodiments of this application, the samples of the embodiments and comparative examples were subjected to the following tests:

[0156] 1. Material particle size distribution test

[0157] The Malvern 3000 wet particle size analyzer was used for measurement, referring to the standard procedure: GB / T19077-2016 / ISO13320:2009. The specific test procedure was as follows: Take an appropriate amount of the sample to be tested (the sample concentration should be 8-12% opacity), add 20 ml of NMP, and simultaneously incubate for 5 minutes (53 kHz / 120 W) to ensure complete dispersion of the sample. Then, the sample was measured according to the standard GB / T19077-2016 / ISO13320:2009.

[0158] 2. Tap density test

[0159] The tap density was determined using a tap density meter in accordance with GB / T 5162-2021 "Determination of tap density of metal powder".

[0160] 3. Elemental analysis test

[0161] The Li, other metal element, and impurity content in the cathode material were determined using an inductively coupled plasma atomic emission spectrometer (ICP, instrument model: PE Optima 7000DV). First, an appropriate amount of powder sample was weighed, and approximately 10 mL of aqua regia was added. The sample was then heated at approximately 185°C for 30 to 50 minutes in a plate heater to ensure complete digestion before testing.

[0162] Battery performance test

[0163] Button cells were prepared using the positive electrode materials of Examples 1 to 4 and Comparative Examples 1 to 3: The above-mentioned positive electrode materials, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) were mixed uniformly in a weight ratio of 7:2:1 and coated onto aluminum foil to form electrode sheets, which were then vacuum dried; the areal density of the electrode sheets was designed to be 4–5 mg / cm². -2 In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed uniformly at a volume ratio of 3 / 7. 12.5% ​​LiPF6 lithium salt was added and dissolved in the organic solvent and stirred evenly to form a coin cell for testing.

[0164] The impurity content and particle size distribution data of the spray pyrolysis precursors prepared by the methods of Examples 1-4 and Comparative Examples 1-3 before and after pre-lithiation are shown in Table 1 below. The impurity content was tested using the ICP national standard test method, and the particle size distribution was measured using a Malvern 3000 wet particle size analyzer. The results show that the precursor products after spray drying in the Examples and Comparative Examples have relatively high contents of non-metallic impurities such as S and Cl, and relatively high contents of magnetic foreign metal elements such as Fe, Cr, Cu, and Zn, with little difference in particle size distribution. However, after pre-lithiation and water washing treatment, in Examples 1-4, the contents of impurities such as S and Cl can be significantly reduced, and the contents of magnetic foreign metal elements such as Fe, Cr, Cu, and Zn can be controlled at a low level. Particle size distribution testing shows that the particle size of the pre-lithiated cathode precursor particles has increased to a certain extent. In Comparative Examples 1 and 2, which were either untreated or under-lithiated, the insufficient lithium intercalation and inadequate precursor particle size growth prevented internal impurities from reaching the grain surface, resulting in high levels of impurities such as S and Cl, and metals such as Fe, Cr, Cu, and Zn. In Comparative Example 3, which was over-lithiated, the impurity content and particle size distribution of the pre-lithiated precursor were at the same level as in the examples, but excessive lithium addition would lead to raw material waste and increased costs.

[0165] Table 1

[0166]

[0167] The initial charge and discharge cycle was performed using a constant current / constant voltage charge-constant voltage discharge mode. The charge / discharge voltage range was 2.8–4.4V, the charge rate was 0.2C, the charging cutoff current was 0.05C, and the discharge rate was 0.2C. The nominal capacity at 1C was 200mAh / g. -1 The charging and discharging processes were paused for 5 minutes between each cycle. The impurity content and initial 0.2C charge / discharge performance of the cathode materials prepared by the methods of Examples 1 to 4 and Comparative Examples 1 to 3 are shown in Table 2 below.

[0168] Table 2

[0169]

[0170] As shown in Table 2, the cathode material after complete lithiation of the precursor by high-temperature sintering inherits the impurity content of the precursor. Samples without pre-lithiation treatment or with insufficient pre-lithiation still contain high impurity content. The initial charge-discharge test results show that the samples that have undergone pre-lithiation and water washing have better initial charge-discharge performance than the samples without pre-lithiation treatment or with excessive or insufficient pre-lithiation.

[0171] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for preparing a pre-lithiated cathode precursor, characterized in that, Includes the following steps: Prepare a mixed metal salt solution containing a nickel source, a manganese source, and a metal source M; wherein the metal source M contains at least one of cobalt salt, aluminum salt, zirconium salt, tantalum salt, titanium salt, niobium salt, germanium salt, yttrium salt, tungsten salt, boron salt, cerium salt, and strontium salt; The mixed metal salt solution was subjected to spray pyrolysis to obtain a spray pyrolysis precursor. The spray pyrolysis precursor is mixed with a first lithium source and then subjected to a first sintering treatment. The product of the first sintering is transferred to a water washing and stirring tank, water is added and stirred, and after water washing, filtration to remove impurities and drying, the pre-lithiated cathode precursor is obtained. The molar ratio of lithium element in the first lithium source to the total molar ratio of metal elements in the spray pyrolysis precursor is 0.5~1.

2. The method for preparing the pre-lithiated cathode precursor according to claim 1, characterized in that, The spray pyrolysis treatment step includes: spraying the mixed metal salt solution at a temperature of 500℃~1000℃ for 20s~120s, wherein the atomization flow rate of the mixed metal salt solution is 20L / min~200L / min, the carrier gas flow rate is 50L / min~500L / min, and the ratio of the carrier gas flow rate to the atomization flow rate is 2~3.

3. The method for preparing the pre-lithiated cathode precursor according to claim 1 or 2, characterized in that, The temperature of the first sintering treatment is 350℃~650℃, and the time is 0.5h~4h.

4. A pre-lithiated cathode precursor, characterized in that, The chemical formula of the pre-lithiated cathode precursor is Li. a Ni x Mn y M 1-x-y O z , 0.46≤a≤0.98, 0.5≤x≤0.95, y>0, 1≤z≤2; wherein, M includes at least one of Co, Al, Zr, Ta, Ti, Nb, Ge, Y, W, B, Ce, and Sr, and the pre-lithiated cathode precursor is prepared by the preparation method of the pre-lithiated cathode precursor as described in any one of claims 1 to 3.

5. The pre-lithiated cathode precursor according to claim 4, characterized in that, The pre-lithiated cathode precursor has at least one of the following (1) to (3): (1) The D50 of the pre-lithiated cathode precursor is 0.8 μm to 5 μm; (2) The content of sulfur in the pre-lithiated cathode precursor is less than 200 ppm; (3) The Cl content in the pre-lithiated cathode precursor is less than 100 ppm.

6. A positive electrode material, characterized in that, The pre-lithiated cathode precursor prepared by any one of the preparation methods described in claims 1 to 3, or prepared by the pre-lithiated cathode precursor described in claim 4 or 5, wherein the cathode material has the chemical formula Li. a1 Ni x1 Mn y1 M 1-x1-y1 O2, 1.02≤a1≤1.10, 0.5≤x1≤0.95, 0.01≤y1≤0.4, wherein M includes at least one of Co, Al, Zr, Ta, Ti, Nb, Ge, Y, W, B, Ce, and Sr.

7. The cathode material according to claim 6, characterized in that, The cathode material has at least one of the following (I) to (III): (I) The D50 of the positive electrode material is 2.8 μm to 4.3 μm; (II) The specific surface area of ​​the positive electrode material is 0.35~0.85m². 2 / g; (III) The residual lithium content of the cathode material is 0.02wt%~0.06wt%.

8. A method for preparing the cathode material as described in claim 6 or 7, characterized in that, The process includes the following steps: mixing a pre-lithiated cathode precursor with a second lithium source and performing a second sintering process to obtain the cathode material.

9. The method for preparing the cathode material according to claim 8, characterized in that, The molar ratio of lithium in the second lithium source to the total molar ratio of metal elements in the spray pyrolysis precursor is 0.06~0.66; and / or, The second sintering treatment is performed at a temperature of 700℃ to 950℃ for 6 hours to 14 hours.

10. A positive electrode plate, characterized in that, The positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one side surface of the positive current collector. The positive active material layer includes the positive electrode material as described in claim 6 or 7, or the positive electrode material obtained by the preparation method of the positive electrode material as described in claim 8 or 9.

11. A battery, characterized in that, Includes the positive electrode sheet as described in claim 10.

Images