Positive electrode active material and low-cost preparation method therefor, secondary battery, and electrical device

Abstract

The present application provides a positive electrode active material and a preparation method therefor, a secondary battery, and an electrical device. The method comprises: mixing pure water, iron phosphate, a lithium source, a carbon source, and an additive and grinding same to obtain a slurry A; spray-drying the slurry A to obtain a dried precursor B; pre-sintering the dried precursor B under a first condition to obtain a sintered product C, parameters of the first condition comprising: a heating rate of 1-20°C / min under a protective atmosphere, a sintering temperature of 400-600°C, and a retention time of 2-5 h; and sintering the sintered product C under a second condition, and then performing grading treatment to obtain a positive electrode active material.

Description

Positive electrode active materials and their low-cost preparation methods, secondary batteries and electrical devices

[0001] Cross-reference to related applications

[0002] This application is based on and claims priority to Chinese Patent Application No. 202411959724.9, filed on December 17, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of battery materials, and in particular to positive electrode active materials and their low-cost preparation methods, secondary batteries and electrical devices. Background Technology

[0004] With the rapid development of the new energy vehicle market, lithium iron phosphate, as a high-performance lithium-ion battery cathode material, has also seen rapid market growth. However, the existing one-step sintering process for lithium iron phosphate has limited room for performance optimization, and adjustments to the conventional roller kiln sintering regime are insufficient to effectively improve and optimize product performance. Currently, the mainstream process involves pretreatment liquid-phase milling, spray drying, and then high-temperature sintering, with limited room for cost reduction. Summary of the Invention

[0005] This application aims to at least partially address one of the technical problems in the related art.

[0006] This application proposes a low-cost preparation method for positive electrode active materials. By utilizing the efficient sintering capability of a rotary kiln, the sintering cycle of positive electrode active materials can be shortened, production capacity can be increased, and the overall preparation cost of positive electrode active materials can be reduced.

[0007] In another aspect, this application proposes a positive electrode active material that can be rapidly prepared using the preparation method provided in this application. This material has the characteristics of producing few byproducts and having potential for improved product performance.

[0008] This application also proposes a secondary battery, which utilizes a positive electrode active material with few byproducts and potential for improved product performance, and is applied in secondary batteries.

[0009] The last aspect of this application proposes an electrical device that applies a positive electrode active material with few byproducts and potential for improved product performance to a secondary battery, and then assembles the resulting secondary battery into the electrical device to improve the performance of the electrical device.

[0010] According to an embodiment of the first aspect of this application, a low-cost method for preparing a positive electrode active material is provided, comprising the following steps:

[0011] Step 1: Mix pure water, iron phosphate, lithium source, carbon source and additives according to stoichiometry and grind to obtain slurry A;

[0012] Step 2: Spray dry the slurry A from Step 1 to obtain precursor dried product B;

[0013] Step 3: Pre-sinter the precursor dried material B from Step 2 under the first condition to obtain sintered material C; the first condition parameters include: heating rate of 1-20℃ / min under a protective atmosphere; sintering temperature of 400-600℃; and residence time of 2-5h.

[0014] Step 4: Sinter the sintered material C from Step 3 under the second condition, and then perform a graded treatment to obtain the positive electrode active material; the second condition parameters include: sintering temperature of 700-800℃ and sintering time of 15-24h.

[0015] In some embodiments, the particle size of slurry A in step one is 0.2-1.2 μm.

[0016] In some embodiments, the moisture content of the precursor dried product B in step two is controlled to be less than 5%;

[0017] And / or; the particle size D50 of the precursor dried product B is 10-60 μm.

[0018] In some embodiments, the precursor dried material B described in step three is subjected to low-temperature sintering and cooling in a continuous rotary kiln;

[0019] And / or; the protective atmosphere includes nitrogen, helium, neon, or argon; its intake volume is 10-100 m³. 3 / h;

[0020] And / or; the oxygen content in the rotary kiln is <10ppm;

[0021] And / or; the pressure inside the rotary kiln is 15-200 Pa;

[0022] And / or; the volume percentage of the precursor dried product B is 5-20%;

[0023] And / or; the feed rate of the precursor dried material B is 50-200 kg / h;

[0024] And / or; the body inclination angle of the rotary kiln relative to the horizontal plane is 0-2°, and the rotation speed is 0-3 r / min to adjust the residence time.

[0025] In some embodiments, the sintered material C in step four is sintered using a roller kiln.

[0026] And / or; the amount of the sintered material C in the pot is 7-28 kg / pot.

[0027] In some embodiments, the lithium source includes at least one of lithium chloride, lithium sulfate, and lithium nitrate.

[0028] In some embodiments, the carbon source includes at least one of glucose, sucrose, polyethylene glycol, and water-soluble phenolic resin.

[0029] In some embodiments, the additive includes at least one of titanium dioxide, magnesium oxide, vanadium pentoxide, cobalt tetroxide, zirconium oxide, and niobium pentoxide.

[0030] The method for preparing the positive electrode active material in this embodiment involves a two-step sintering process. A rotary kiln, with its higher heating efficiency, offers higher production capacity and energy efficiency within the same footprint. The endothermic decomposition reactions of the carbon and lithium sources during the lithium iron phosphate sintering process are pre-sintered in the rotary kiln, resulting in higher energy utilization. The material undergoes decomposition in the rotary kiln to obtain sintered material C. Then, a high-load roller kiln is used to perform high-temperature sintering of sintered material C to finally obtain the lithium iron phosphate product. The roller kiln does not produce a large amount of decomposition reaction, effectively optimizing the atmosphere composition within it. The material undergoes only high-temperature sintering in the roller kiln, completing crystal growth. This significantly increases the sintering rate of the roller kiln, reducing the manufacturing cost of the positive electrode active material. Furthermore, there is room for further increasing the loading capacity of the roller kiln, and the heating cycle can be further shortened, further releasing the roller kiln's production capacity and resulting in superior product performance.

[0031] According to embodiments of the second aspect of this application, a positive electrode active material obtained by the preparation method described in any of the above embodiments is proposed.

[0032] The positive electrode active material of this application embodiment can be rapidly prepared by the preparation method provided in this application. By optimizing the sintering process, the generation of by-products such as iron phosphide that affect product performance can be effectively reduced, thereby further improving the performance of the positive electrode active material.

[0033] According to an embodiment of the third aspect of this application, a secondary battery is provided, which includes the positive electrode active material described in any of the above embodiments.

[0034] The positive electrode active material prepared through the above embodiments, which has excellent performance in all aspects, is applied in secondary batteries.

[0035] An electrical device comprising the secondary battery described in any of the above embodiments is provided according to an embodiment of the fourth aspect of this application.

[0036] The positive electrode active material with excellent performance in all aspects prepared through the above embodiments is applied in secondary batteries, and the resulting secondary batteries are assembled and applied to electrical devices to improve the performance of the electrical devices.

[0037] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0038] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0039] Figure 1 is a flowchart of a method for preparing a positive electrode active material according to an embodiment of this application. Detailed Implementation

[0040] Embodiments of this application are described in detail below. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. Rather, this application includes all variations, modifications, and equivalents falling within the spirit and scope of the appended claims.

[0041] With the rapid development of the new energy vehicle market, battery materials are the core of new energy batteries, and lithium iron phosphate (LFP) materials, as cathode materials, are crucial. The demand for LFP is currently growing rapidly. However, the existing one-step sintering process for LFP has limited room for performance optimization, and adjustments to conventional roller kiln sintering regimes are insufficient to effectively improve and optimize product performance. The current mainstream process involves pretreatment liquid-phase milling, spray drying, and then high-temperature sintering. This process has limited room for cost reduction, necessitating the development of new preparation processes to achieve maximum cost reduction.

[0042] Based on this, the technical solution of this application provides a positive electrode active material and its low-cost preparation method, a secondary battery, and an electrical device. The preparation method for the positive electrode active material can shorten the sintering cycle, increase production capacity, and reduce the overall preparation cost. The positive electrode active material also features few byproducts and potential for performance improvement. Regarding its application, the positive electrode active material can be used in secondary batteries and electrical devices.

[0043] The "range" disclosed in this application is defined by 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 a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, based on the listed ranges of 60-120 and 80-110 for specific parameters, it is expected that ranges of 60-110 and 80-120 are also expected. Furthermore, based on the listed minimum range values ​​1 and 2, and based on the listed maximum range values ​​3, 4, and 5, the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" 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 "0-5" have been listed in this document; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, in response to stating that a parameter is an integer ≥2, it corresponds to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0044] In the description of the embodiments in this application, the term "and / or" is merely a description of 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, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0045] To achieve the above objectives, a low-cost preparation method for a positive electrode active material is proposed according to an embodiment of the first aspect of this application, as shown in Figure 1, comprising the following steps:

[0046] Step 1: Mix pure water, iron phosphate, lithium source, carbon source and additives according to stoichiometry and grind to obtain slurry A;

[0047] Step 2: Spray dry the slurry A from Step 1 to obtain precursor dried product B;

[0048] Step 3: Pre-sinter the dried precursor B from Step 2 under the first condition to obtain sintered product C; the parameters of the first condition include: heating rate of 1-20℃ / min under a protective atmosphere; sintering temperature of 400-600℃; and residence time of 2-5h.

[0049] Step 4: Sinter the sintered material C from Step 3 under the second condition, and then perform a graded treatment to obtain the positive electrode active material; the parameters of the second condition include: sintering temperature of 700-800℃ and sintering time of 15-24h.

[0050] In step one, pure water, iron phosphate, lithium source, carbon source, and additives are mixed according to stoichiometry. For example, the lithium source includes at least one of lithium chloride, lithium sulfate, and lithium nitrate; the carbon source includes at least one of glucose, sucrose, polyethylene glycol, and water-soluble phenolic resin; and the additives include at least one of titanium dioxide, magnesium oxide, vanadium pentoxide, cobalt tetroxide, zirconium oxide, and niobium pentoxide. The stoichiometry of pure water, iron phosphate, lithium source, carbon source, and additives can be determined by referring to the proportions used in conventional lithium iron phosphate preparation processes in this field. This step is readily achievable by those skilled in the art and will not be elaborated further.

[0051] In this process, pure water, iron phosphate, lithium source, carbon source, and additives are mixed and ground to obtain slurry A. In some embodiments, the particle size of slurry A is 0.2-1.2 μm, for example, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, or 1 μm, 1.2 μm, etc. Furthermore, if the particle size of slurry A is too large, such as greater than 1.2 μm, the compaction density of the obtained positive electrode active material is relatively low.

[0052] In step two, the slurry A obtained in step one is spray-dried to obtain precursor dried product B; wherein the moisture content of precursor dried product B is controlled within 5%; and its particle size D50 is 10-60μm.

[0053] The spray drying of slurry A in the example is a conventional technique in this field and will not be described in detail here. The moisture content of the precursor dried material B can be 1%, 2%, 3%, 4%, 5%, etc.; simultaneously, the particle size D50 of the precursor dried material B can be 10μm, 14μm, 16μm, 20μm, 31μm, 35μm, 40μm, 50μm, 60μm, etc. In particular, when the particle size of the precursor dried material B is less than 10μm, the resulting positive electrode active material has a lower carbon content, poorer conductivity, and significantly deteriorated electrochemical performance.

[0054] In step three, the precursor dried material B obtained in step two is pre-sintered under a first condition to obtain sintered material C. In some embodiments, the precursor dried material B obtained in step two is subjected to low-temperature sintering and cooling in a continuous rotary kiln under a protective atmosphere and set conditions to obtain lithium iron phosphate low-temperature sintered material, i.e., sintered material C.

[0055] The pre-sintering process involves: a protective atmosphere, including nitrogen, helium, neon, or argon, being introduced into the rotary kiln at a flow rate of 10-100 m³. 3The oxygen content in the rotary kiln is <10ppm, meeting the conditions for the reduction reaction of lithium iron phosphate. Precursor dried material B is fed into the rotary kiln via a screw feeder and other devices. During this process, the feeding rate of precursor dried material B (determined by the actual volume of the rotary kiln, residence time, and material bulk density) is used to control the material's volume percentage within the rotary kiln. For example, if the feeding rate of precursor dried material B is 50-200 kg / h, the material's volume percentage within the rotary kiln is controlled at 5-20%, and the kiln pressure is 15-200 Pa.

[0056] Then, based on the size and processing capacity of the rotary kiln equipment, the residence time of the precursor dried material B in the rotary kiln is controlled to be 2-5 hours by adjusting the tilt angle (e.g., 0-2°) and rotation speed (e.g., 0-3 r / min) of the rotary kiln body. During the pre-sintering process, the heating rate is 1-20℃ / min, and the sintering temperature is controlled at 400-600℃. The material slides forward with the rotation of the rotary kiln body to complete the heating and decomposition process. The decomposition products enter the kiln cooling section and are cooled and discharged from the furnace by circulating water heat exchange to obtain the lithium iron phosphate intermediate sintered material C.

[0057] For example, the tilt angle of the rotary kiln relative to the horizontal plane is 0°, 1°, 2°, etc., where the tilt angle is the ratio of the height of the kiln body axis to the length of the kiln body; at the same time, the rotation speed of the rotary kiln is 0 r / min, 1 r / min, 2 r / min, 3 r / min, etc.; the embodiments of this application control the residence time of the precursor dried material B in the rotary kiln by adjusting the tilt angle and rotation speed of the rotary kiln. If the tilt angle of the rotary kiln is too large, such as greater than 2°, the residence time of the material in the rotary kiln is difficult to control, the residence time is short, the decomposition is incomplete, and the loss on ignition rate decreases. In response to the rotation speed of the rotary kiln being too large, such as greater than 3 r / min, the material filling rate in the rotary kiln becomes lower, the residence time becomes shorter, the decomposition reaction is incomplete, and the loss on ignition rate decreases.

[0058] Furthermore, the residence time of precursor dried material B in the rotary kiln is 2h, 3h, 4h, 5h, etc. If the residence time of precursor dried material B in the rotary kiln is too short, such as less than 2h, the sintering of precursor dried material B is incomplete, the decomposition reaction is incomplete, and the burn-off rate is reduced. If the residence time of precursor dried material B in the rotary kiln is too long, such as more than 5h, precursor dried material B is overburned, resulting in a lower carbon content and other indicators of the obtained positive electrode active material, which hinders the electrochemical performance, reduces the sintering efficiency, and increases the manufacturing cost.

[0059] The heating rate of precursor dried material B in the rotary kiln can be 1℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 10℃ / min, 11℃ / min, 12℃ / min, 14℃ / min, 15℃ / min, 17℃ / min, 18℃ / min, 20℃ / min, etc. If the heating rate of precursor dried material B in the rotary kiln is too low, such as less than 1℃ / min, the decomposition reaction of precursor dried material B will be slower, the concentration of decomposition reducing gas in the rotary kiln will be lower, the crystal growth effect will be worse, and the compaction density of the obtained positive electrode active material will be lower. In addition, the residence time of precursor dried material B in the rotary kiln will be longer, resulting in lower production capacity of positive electrode active material. When the heating rate in the rotary kiln is too high, such as greater than 20℃ / min, the decomposition reaction of the precursor dried product B is violent. The decomposition reaction overlaps with the crystal growth reaction time, resulting in a decrease in the uniformity of the surface carbon layer of the positive electrode active material and a deterioration in electrochemical performance.

[0060] The sintering temperature of precursor dried material B in the rotary kiln can be 400℃, 450℃, 500℃, 550℃, 600℃, etc. If the sintering temperature of precursor dried material B in the rotary kiln is too low, such as below 400℃, the crystal growth reaction will be interrupted, and the electrochemical performance of the positive electrode active material will deteriorate. If the sintering temperature of precursor dried material B in the rotary kiln is too high, such as above 600℃, the energy consumption of the decomposition reaction of precursor dried material B will increase, and the yield of sintered material C obtained by pre-sintering precursor dried material B under the first condition will decrease.

[0061] The volume percentage of precursor dried material B in the rotary kiln can be 5%, 6%, 8%, 10%, 15%, or 20%, etc. If the volume percentage of precursor dried material B in the rotary kiln is too small, such as less than 5%, the concentration of reducing atmosphere in the rotary kiln will decrease, and the compaction density and electrochemical performance of the positive electrode active material will deteriorate. If the volume percentage of precursor dried material B in the rotary kiln is too large, such as greater than 20%, the decomposition reaction of precursor dried material B will be incomplete, and the electrochemical capacity of the final sintered positive electrode active material will be low.

[0062] The embodiments of this application use a rotary kiln as a pre-sintering device for the precursor dried product B, which has higher heating efficiency and higher production capacity and energy efficiency compared to pusher kilns and roller kilns under the same footprint conditions. This application places the endothermic decomposition reactions of carbon and lithium sources in the lithium iron phosphate sintering process in a rotary kiln, resulting in higher energy utilization. By controlling the material loading, sintering temperature, and residence time in the rotary kiln, the material is made into lithium iron phosphate intermediates with minimal energy, completing most of the material decomposition. No decomposition reaction occurs in the sintered product C during subsequent sintering processes, and its sintering heating cycle can be further shortened by at least 30%. In addition, without the limitation of sagger size, the loading amount of sintered product C can be increased by at least 10%.

[0063] In step four, sintered material C is sintered using a roller kiln. For example, sintered material C is directly fed into the loading bin of the roller kiln via a rotary kiln, and the loading amount of sintered material C is 7-28 kg / bin. The material is heated and cooled at a sintering temperature of 700-800℃ and a sintering time of 15-24 hours, and the secondary sintering is completed to obtain lithium iron phosphate product, i.e., positive electrode active material.

[0064] Depending on the size of the sagger and the different properties of the materials, the loading amount of sinter C can be exemplified as 7kg / sagger, 8kg / sagger, 9kg / sagger, 10kg / sagger, 11kg / sagger, 12kg / sagger, 13kg / sagger, 14kg / sagger, 20kg / sagger, 28kg / sagger, etc.

[0065] The sintering temperature of sintered material C in the roller kiln can be 700℃, 750℃, 800℃, etc. If the sintering temperature of sintered material C in the roller kiln is too low, such as less than 700℃, the compaction density of the positive electrode active material obtained by sintering will be too low. If the sintering temperature of sintered material C in the roller kiln is too high, such as greater than 800℃, the compaction density of the positive electrode active material obtained by sintering will be too high, the capacity will be poor, and the by-products will increase.

[0066] The sintering time of sintered material C in the roller kiln is 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h, etc. If the sintering time of sintered material C in the roller kiln is too short, such as less than 15h, the electrochemical capacity of the sintered positive electrode active material is too low. If the sintering time of sintered material C in the roller kiln is too long, such as more than 24h, the sintered material C is overburned, the compaction density of the sintered positive electrode active material is too high, and the energy consumption of roller kiln sintering increases, thus increasing the cost.

[0067] In some embodiments, the obtained positive electrode active material can be further crushed and demagnetized.

[0068] In the roller kiln sintering process, no decomposition reaction occurs; the material undergoes only high-temperature sintering to complete crystal growth, significantly improving the sintering efficiency. Furthermore, the theoretical heating cycle of the roller kiln can be shortened by at least 30%, and without sagger size limitations, the loading capacity can be increased by at least 10%. In addition, the atmosphere composition within the roller kiln is effectively optimized, resulting in a more stable atmosphere and effectively reducing the generation of byproducts such as iron phosphide that affect product performance, thus allowing for further improvement in product performance.

[0069] The method for preparing the positive electrode active material in this application involves a two-step sintering process. A rotary kiln, with its higher heating efficiency, is used to pre-sinter the carbon and lithium sources involved in the lithium iron phosphate sintering process, resulting in higher energy utilization. The material undergoes a decomposition reaction in the rotary kiln to obtain sintered material C. This sintered material C is then subjected to a high-temperature secondary sintering in a roller kiln with a high loading rate to finally obtain the lithium iron phosphate product. The method described in this application can increase the production capacity of lithium iron phosphate positive electrode active materials by at least 50%, significantly improving production capacity and reducing the manufacturing cost of lithium iron phosphate, thus demonstrating broad application prospects. Furthermore, while related technologies utilize high sintering temperatures to increase the compaction density and electrochemical performance of the positive electrode active material, the decomposition reaction gases can easily lead to a higher proportion of by-products in the positive electrode active material. Compared to related technologies, this application produces fewer by-products in its positive electrode active material, creating better sintering effects and greater flexibility in process adjustment.

[0070] According to embodiments of the second aspect of this application, a positive electrode active material obtained by the preparation method in any of the above embodiments is proposed.

[0071] The positive electrode active material of this application embodiment can be rapidly prepared by the preparation method provided in this application. By optimizing the sintering process, the generation of by-products such as iron phosphide that affect product performance can be effectively reduced, thereby further improving the performance of the positive electrode active material.

[0072] According to an embodiment of the third aspect of this application, a secondary battery is provided, which includes the positive electrode active material of any of the above embodiments.

[0073] The positive electrode active material prepared through the above embodiments has excellent performance in all aspects, with high compaction density, high capacity, and good cycle performance, and can be applied in secondary batteries.

[0074] The secondary battery in the embodiments of this application includes a positive electrode, a negative electrode, an electrolyte, and a separator. The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. The positive electrode film layer includes the positive electrode active material of the first aspect of this application. As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0075] Among them, the positive electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0076] In some embodiments, the positive electrode active material layer in the positive electrode sheet of the present application does not exclude the positive electrode active material provided by the present application. For example, other positive electrode active materials can be positive electrode active materials for batteries well-known in the art. As an example, the positive electrode active material can include at least one of the following materials: As an example, the positive electrode active material can include, but is not limited to, lithium iron phosphate (LiFePO4), lithium manganese phosphate (LiMnPO4), lithium cobalt phosphate (LiCoPO4), lithium iron pyrophosphate (Li2FeP2O7), lithium cobalt oxide (LiCoO2), spinel lithium manganese oxide (LiMn2O4), spinel lithium nickel manganese oxide (LiNi 0.5 Mn 1.5 O4), layered lithium manganese oxide (LiMnO2), lithium nickel oxide (LiNiO2), lithium niobate (LiNbO2), lithium ferrite (LiFeO2), lithium manganate (LiMgO2), lithium calcium oxide (LiCaO2), lithium copper oxide (LiCuO2), lithium zinc oxide (LiZnO2), lithium molybdate (LiMoO2), lithium tantalate (LiTaO2), lithium tungstate (LiWO2), lithium nickel cobalt aluminum oxide (LiNi x Co y Al 1-x-y O2, 0 < x < 1, 0 < y < 1, 0 < x + y < 1, for example LiNi 0.8 Co 0.15 Al 0.05 O2), lithium nickel cobalt manganese oxide (LiNi x Co y Mn 1-x-y O2, 0 < x < 1, 0 < y < 1, 0 < x + y < 1, for example LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co0.1 Mn 0.1 At least one of the following: O2, lithium-rich materials (e.g., lithium-rich nickel-cobalt-manganese oxide), manganese oxide (MnO2), vanadium oxide, sulfur oxide, silicate oxide, and their respective modified compounds. These materials may be used alone or in combination of two or more.

[0077] The modified compounds for the aforementioned positive electrode active materials can be obtained by doping, surface coating, or simultaneous doping and coating of the positive electrode active materials.

[0078] In some embodiments, the positive electrode film layer may include an adhesive. As an example, the adhesive may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0079] In some embodiments, the positive electrode film layer further includes a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0080] In some embodiments, the positive electrode sheet can be prepared by dispersing the components used to prepare the positive electrode sheet, such as the positive active material, conductive agent, binder and any other components of the first aspect of this application, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0081] [Negative electrode plate]

[0082] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer comprising a negative electrode active material. As an example, the negative current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative current collector.

[0083] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0084] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0085] In some embodiments, the negative electrode film layer further includes a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0086] In some embodiments, the negative electrode film layer further includes a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0087] In some embodiments, the negative electrode film layer also includes other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0088] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0089] [Electrolytes]

[0090] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0091] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0092] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0093] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0094] In some embodiments, the electrolyte also includes additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0095] The secondary battery also includes a separator. This application does not have any particular restrictions on the type of separator, and any well-known porous separator with good chemical and mechanical stability can be selected.

[0096] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0097] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0098] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0099] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0100] This application does not impose any particular restrictions on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape.

[0101] An electrical device comprising a secondary battery according to any of the above embodiments is provided according to an embodiment of the fourth aspect of this application.

[0102] The positive electrode active material with few byproducts and potential for improved product performance is applied to secondary batteries, and the resulting secondary batteries are assembled and applied to electrical devices to improve the performance of the electrical devices.

[0103] To facilitate a further understanding of this application, the solutions described below are further described in conjunction with embodiments. Those skilled in the art will understand that the examples described in this application are only a portion of the examples, and any other suitable specific examples are within the scope of this application.

[0104] Example 1

[0105] An embodiment of this application provides a positive electrode active material, the preparation method and specific operating parameters of which are as follows: pure water, iron phosphate, lithium source, carbon source and additives are mixed and ground in proportion to obtain a slurry A with a particle size of 1.2 μm; slurry A is spray-dried to obtain a precursor dried material B with a water content of 5% and a particle size D50 of 25 μm; precursor dried material B is placed in a rotary kiln and pre-sintering parameters are set to obtain sintered material C, wherein the pre-sintering parameters are: feed rate of 200 kg / h, rotation speed of 0.8 r / min, inclination angle of 1°, sintering temperature of 500°C, heating rate of 5°C / min, isothermal time of 1 h, overall residence time of 3.5 h, and filling volume ratio of 15%.

[0106] The sintered material C was placed in a roller kiln and the high-temperature sintering parameters were set as follows: sintering temperature was 785℃, sintering time was 24h, and the amount of material in the kiln was 7kg. After the sintered material C was sintered at high temperature in the roller kiln, it was then subjected to airflow classification treatment to obtain the positive electrode active material.

[0107] Example 2

[0108] The embodiments of this application differ from Embodiment 1 in the following ways: the dried precursor B is placed in a rotary kiln and pre-sintering parameters are set to obtain sintered material C, wherein the pre-sintering parameters are: feed rate of 200 kg / h, rotation speed of 0.8 r / min, inclination angle of 1°, sintering temperature of 600°C, heating rate of 5°C / min, constant temperature time of 1 h, overall residence time of 3.5 h, and filling volume ratio of 15%.

[0109] Example 3

[0110] The embodiments of this application differ from Embodiment 1 in the following ways: the sintered material C is placed in a roller kiln and the high-temperature sintering parameters are set as follows: the sintering temperature is 785°C, the sintering time is 19h, and the loading amount is 14kg.

[0111] Example 4

[0112] The embodiments of this application differ from Embodiment 1 in the following ways: the sintered material C is placed in a roller kiln and the high-temperature sintering parameters are set as follows: the sintering temperature is 700°C, the sintering time is 24 hours, and the loading amount is 7 kg.

[0113] Example 5

[0114] The embodiments of this application differ from Embodiment 1 in the following ways: the sintered material C is placed in a roller kiln and high-temperature sintering parameters are set: the sintering temperature is 800°C, the sintering time is 24 hours, and the loading amount is 7 kg.

[0115] Comparative Example 1

[0116] This comparison provides a positive electrode active material, the preparation method and specific operating parameters of which are as follows: pure water, iron phosphate, lithium source, carbon source and additives are mixed and ground in proportion to obtain a slurry A with a particle size of 1.2 μm; slurry A is spray-dried to obtain a precursor dried product B with a water content of 5% and a particle size D50 of 25 μm.

[0117] The dried material B was placed directly into the roller kiln and the high-temperature sintering parameters were set as follows: sintering temperature was 785℃, sintering time was 24h, and the loading amount was 7kg. After the precursor dried material B was sintered at high temperature in the roller kiln, it was then subjected to airflow classification treatment to obtain the positive electrode active material.

[0118] Comparative Example 2

[0119] This comparative example differs from Example 1 in the following ways: the dried precursor B was placed in a rotary kiln and pre-sintering parameters were set to obtain sinter C. The pre-sintering parameters were: feed rate of 200 kg / h, rotation speed of 0.8 r / min, tilt angle of 1°, sintering temperature of 350°C, heating rate of 5°C / min, isothermal time of 1 h, overall residence time of 3.5 h, and filling volume ratio of 15%.

[0120] Comparative Example 3

[0121] This comparative example differs from Example 1 in the following ways: the dried precursor B is placed in a rotary kiln and pre-sintering parameters are set to obtain sintered material C. The pre-sintering parameters are: feed rate of 200 kg / h, rotation speed of 1 r / min, inclination angle of 1.5°, sintering temperature of 500°C, heating rate of 15°C / min, isothermal time of 0.5 h, overall residence time of 1.5 h, and filling volume ratio of 6%.

[0122] Comparative Example 4

[0123] This comparative example differs from Example 1 in the following ways: the dried precursor B was placed in a rotary kiln and pre-sintering parameters were set to obtain sinter C. The pre-sintering parameters were: feed rate of 120 kg / h, rotation speed of 0.4 r / min, tilt angle of 1°, sintering temperature of 500°C, heating rate of 5°C / min, isothermal time of 3 h, overall residence time of 5.5 h, and filling volume ratio of 15%.

[0124] Comparative Example 5

[0125] This comparative example differs from Example 1 in the following ways: the sintered material C is placed in a roller kiln and high-temperature sintering parameters are set: sintering temperature is 785°C, sintering time is 14h, and the amount of material in the kiln is 7kg.

[0126] Comparative Example 6

[0127] This comparative example differs from Example 1 in the following ways: the dried precursor B is placed in a rotary kiln and pre-sintering parameters are set to obtain sintered material C. The pre-sintering parameters are: feed rate of 50 kg / h, rotation speed of 0.8 r / min, tilt angle of 1°, sintering temperature of 500°C, heating rate of 5°C / min, isothermal time of 1 h, overall residence time of 3.5 h, and filling volume ratio of 4%.

[0128] The sintered material C was placed in a roller kiln and the high-temperature sintering parameters were set as follows: sintering temperature was 785℃, sintering time was 24h, and the amount of material in the kiln was 7kg. After the sintered material C was sintered at high temperature in the roller kiln, it was then subjected to airflow classification treatment to obtain the positive electrode active material.

[0129] Experimental Example

[0130] The positive electrode active materials prepared in the above embodiments and comparative examples were tested for carbon content, specific surface area, powder resistivity and powder compaction density. The corresponding positive electrode active materials in each embodiment and comparative example were used as active materials to prepare battery positive electrodes and assembled into C2032 coin cells for electrical performance testing.

[0131] The carbon content of the positive electrode active materials prepared in the above embodiments and comparative examples was detected using a carbon-sulfur analyzer. The oxygen output was adjusted to 0.04 MPa, 0.3 g of sample was weighed, the "pre-oxygen" and "post-control" switches were turned on, and the flow meter flow rate was adjusted to approximately 100 L / h. The "arc ignition" button was pressed (for 0.2-0.5 seconds) to ignite the sample. Carbon titration was performed, ensuring the endpoint color of the carbon was light blue, and that the endpoint color of the standard sample matched that of the sample. The volume consumed in the titration was recorded.

[0132] The specific surface area of ​​the positive electrode active materials prepared in the above embodiments and comparative examples was determined using the Brunauer-Emmett-Teller method: Samples were weighed and placed in sample tubes, the vacuum pump was turned on, and the samples were heated to 180°C for degassing for 1 hour before being weighed again. The weighed sample tubes were then placed in the analysis station, and liquid nitrogen was added to the Dewar flask. The sample mass was entered into the analysis file, the test parameters were set, and the adsorption and desorption test process began.

[0133] The positive electrode active materials prepared in the above embodiments and comparative examples are placed in a compactor and compacted under specific pressure and time. The samples are then taken out, and the volume and weight after compaction are measured. The compaction density is calculated. The resistivity and compaction density of the powder material are tested using a compacted powder resistivity meter.

[0134] Using the positive electrode active material provided in the embodiments and comparative examples of this application as the active material, a C2032 type coin cell was prepared according to the following steps: The positive electrode active material, conductive agent Super P (manufacturer: Yirui Stone), and binder PVDF (manufacturer: Suwei, model: 5130) were dispersed in N-methylpyrrolidone (NMP) at a mass ratio of 95:2:3, with a solid content of 70%. The mixture was ball-milled to form a uniform positive electrode slurry. The positive electrode slurry was coated onto the rough surface of a clean aluminum foil using a coater, and then placed in a vacuum oven and vacuum-dried at 120°C for 12 hours to obtain an electrode sheet with a compacted density of 3.45 g / cm³. 3 The prepared positive electrode sheet was used, with lithium sheet as the counter electrode and Celgard 2400 as the separator, and assembled into a 2032 button cell in an argon glove box. The electrolyte used in assembling the 2032 button cell was a 1 mol / L LiPF6 solution obtained by dissolving LiPF6 in a mixed solvent of ethyl carbonate (EC) and diethyl carbonate (DMC) (volume ratio EC:DMC = 1:1).

[0135] The button cell battery in this application was tested using the Xinweilan electric tester (model: CT-4008Tn-5V20mA-164). Specifically, this includes:

[0136] 1) First, the prepared C2032 button batteries were left to stand at room temperature for 10 hours, then charged at a constant current rate of 0.1C to the charging cutoff voltage of 4.25V, and then charged at a constant voltage to 0.05mA. After standing for 5 minutes, they were discharged at a constant current rate of 0.1C to the discharge cutoff voltage of 3V to obtain the first discharge capacity at 0.1C.

[0137] 2) Subsequently, constant current and constant voltage charging was performed at 1C until the charging cutoff voltage of 4.25V, and then constant voltage charging was performed to 0.05mA. After standing for 5 minutes, constant current discharge was performed at 1C until the discharge cutoff voltage of 3V to obtain the 1C discharge capacity. All tests were performed at room temperature, which was approximately 25℃. The results are shown in Table 1.

[0138] Table 1. Parameters of each embodiment and comparative example

[0139] As shown in Table 1, comparing Example 2 and Comparative Example 2 reveals that the pre-firing temperature of the rotary kiln has a significant impact on the performance of the positive electrode active material. Increasing the pre-firing temperature has a smaller impact on product performance, but it increases energy consumption. Too low a pre-firing temperature results in lower compaction and reduced capacity. Comparing Comparative Example 6 and Example 1 shows that the material volume ratio in the rotary kiln also significantly affects the performance of the positive electrode active material. A lower material volume ratio in the rotary kiln leads to lower compaction density and reduced capacity. Furthermore, comparing Examples 1-5 and Comparative Examples 3-4 shows that both excessively short residence time and excessively high material volume ratio in the rotary kiln result in incomplete sintering, ultimately leading to poorer performance of the positive electrode active material. Furthermore, this application adopts a rotary kiln for pre-firing followed by roller kiln sintering, which can effectively improve the sintering cycle and the amount of positive electrode active material, and the processing capacity of the roller kiln can be greatly improved. However, as can be seen from the comparison between Example 1 and Comparative Example 5, a sintering cycle that is too short and a sintering temperature that is too high will lead to the deterioration of the electrochemical performance and compaction indicators of the positive electrode active material. Therefore, it is necessary to control the high-temperature sintering conditions.

[0140] In summary, this application provides a low-cost preparation method for positive electrode active materials. By utilizing the efficient sintering capability of a rotary kiln, the sintering cycle of positive electrode active materials can be shortened, production capacity can be increased, and the overall preparation cost of positive electrode active materials can be reduced.

[0141] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0142] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A low cost production method of a positive electrode active material, wherein, Includes the following steps: Step 1: Mix pure water, iron phosphate, lithium source, carbon source and additives according to stoichiometry and grind to obtain slurry A; Step 2: Spray dry the slurry A from Step 1 to obtain precursor dried product B; Step 3: Pre-sinter the dried precursor B from Step 2 under the first condition to obtain sintered product C; The first set of conditions includes: a heating rate of 1-20℃ / min under a protective atmosphere; a sintering temperature of 400-600℃; and a residence time of 2-5h. Step 4: Sinter the sintered material C from Step 3 under the second condition, and then perform a graded treatment to obtain the positive electrode active material; the second condition parameters include: sintering temperature of 700-800℃ and sintering time of 15-24h.

2. The production method according to claim 1, wherein, The particle size of slurry A mentioned in step one is 0.2-1.2 μm.

3. The production method according to claim 1, wherein The moisture content of the precursor dried product B mentioned in step two is controlled to be within 5%; And / or; the particle size D50 of the precursor dried product B is 10-60 μm.

4. The production method according to claim 1, wherein In step three, the precursor dried material B is sintered and cooled at low temperature using a continuous rotary kiln. and / or; the protective atmosphere comprises nitrogen, helium, neon or argon; the amount of gas introduced is 10-100 m 3 / h; And / or; the oxygen content in the rotary kiln is <10ppm; And / or; the pressure inside the rotary kiln is 15-200 Pa; And / or; the volume percentage of the precursor dried product B is 5-20%; And / or; the feed rate of the precursor dried material B is 50-200 kg / h; And / or; the body inclination angle of the rotary kiln relative to the horizontal plane is 0-2°, and the rotation speed is 0-3 r / min to adjust the residence time.

5. The production method according to claim 1, wherein The sintered material C described in step four is sintered using a roller kiln; And / or; the amount of the sintered material C in the pot is 7-28 kg / pot.

6. The method of making according to any one of claims 1-5, wherein, The lithium source includes at least one of lithium chloride, lithium sulfate, and lithium nitrate.

7. The production method according to claim 6, wherein The carbon source includes at least one of glucose, sucrose, polyethylene glycol, and water-soluble phenolic resin.

8. The production method according to claim 6, wherein The additives include at least one of titanium dioxide, magnesium oxide, vanadium pentoxide, cobalt tetroxide, zirconium oxide, and niobium pentoxide.

9. The positive electrode active material obtained by the preparation method according to any one of claims 1-8.

10. A secondary battery comprising the positive electrode active material as described in claim 8.

11. An electrical device, comprising: Includes the secondary battery as described in claim 9.

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