Positive electrode active material and preparation method thereof, battery monomer, battery device and electric device

Abstract

The invention relates to a positive active material and a preparation method thereof, a battery monomer, a battery device and a power utilization device. The battery monomer comprises a positive pole piece; the positive electrode plate comprises a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector, the positive electrode film layer comprises a positive electrode active material with the following chemical formula: NaxM11-yM2yO2F, x is greater than or equal to 2 and less than or equal to 2.5, y is greater than or equal to 0 and less than 0.4, M1 comprises one or more of Mn, Ni, Co and Fe, M2 comprises one or more of Mg, Al, Ti, Zn, Zr, Cu, Nb and W, and the pH value of the positive electrode active material is 10-13. The positive electrode active material provided by the invention is stable in structure, and the cycle performance of the battery monomer can be improved.

Description

Technical Field

[0001] This disclosure relates to the field of batteries, specifically to a positive electrode active material and its preparation method, a battery cell, a battery device, and an electrical device. Background Technology

[0002] Commonly used positive electrode active materials in sodium batteries include oxides, polyanionic compounds, and Prussian blue compounds. Research on oxide-based positive electrode active materials is extensive; however, the existing categories of oxide-based positive electrode active materials have limited chemical compositions, and the inherent structural instability of layered oxide materials reduces the structural stability of the positive electrode active material and the cycle performance of individual battery cells. Therefore, developing cost-effective and high-performance positive electrode active materials is an urgent problem to be solved. Summary of the Invention

[0003] This disclosure provides a positive electrode active material and its preparation method, a battery cell, a battery device, and an electrical device, which can obtain a structurally stable positive electrode active material and improve the cycle performance of the battery cell.

[0004] In a first aspect, this disclosure provides a battery cell, including a positive electrode sheet; the positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, the positive electrode film layer including a positive electrode active material having the following chemical formula: Na x M 1 1-y M 2 y O2F, 2≤x≤2.5, 0≤y<0.4, M 1 Includes one or more of Mn, Ni, Co, and Fe, M 2 It includes one or more of Mg, Al, Ti, Zn, Zr, Cu, Nb and W, and the pH of the positive electrode active material is 10-13.

[0005] This disclosure discloses an embodiment in which fluorine is added to layered oxide-based cathode active materials, replacing some of the oxygen in the cathode active material with fluorine. The stronger electronegativity of fluorine enhances the bond strength between transition metals and non-metals, altering the electronic states of the metals and crystals. Replacing some oxygen with fluorine also changes the valence state of anions, regulating the structure and chemical properties of the cathode active material, and reducing irreversible oxidation processes of anions. This improves the structural stability of the cathode active material, reduces capacity decay caused by irreversible structural transformations, enhances the cycle performance of individual battery cells, and improves the processing performance of the cathode slurry and battery device.

[0006] In some embodiments, the content of free alkaline substances on the surface of the positive electrode active material is 0.5%-2%; the free alkaline substances include CO3.2- and / or OH - This can reduce side reactions between the positive electrode active material and the electrolyte, reduce gas production, improve the reliability of the battery cell, and also enable the positive electrode active material to have higher interfacial stability, which is conducive to further improving the capacity and cycle performance of the battery cell, as well as improving the processing performance of the positive electrode slurry and battery device.

[0007] In some embodiments, the positive electrode active material has a secondary particle morphology formed by the aggregation of multiple primary particles.

[0008] In some embodiments, the volumetric particle size distribution Dv50 of the positive electrode active material is 2-10 μm. Therefore, the positive electrode active material can possess high capacity and high compaction density, as well as good ion transport capability.

[0009] In some embodiments, the average particle size of the primary particles constituting the positive electrode active material is 1-3 μm.

[0010] By controlling the average particle size of primary particles within the aforementioned range, the relationship between the structural stability, cycle performance, and capacity of the positive electrode active material can be balanced.

[0011] In some embodiments, the positive electrode active material includes Na2MnO2F, Na2NiO2F, Na2CoO2F, Na2FeO2F, and Na2MnO2F. 0.9 Al 0.1 O2F, Na2Mn 0.9 Mg 0.1 O2F, Na2Mn 0.9 Ti 0.1 O2F, Na2Ni 0.9 Al 0.1 O2F, Na2Ni 0.9 Mg 0.1 O2F, Na2Ni 0.9 Ti 0.1 O2F, Na2Mn 0.9 Zn 0.1 O2F, Na2Mn 0.9 Zr 0.1 O2F, Na2Mn 0.9 Cu 0.1 O2F, Na2Mn 0.9 Nb 0.1 O2F, Na2Mn 0.9 W 0.1 O2F, Na2Ni 0.9 Zn 0.1 O2F, Na2Ni 0.9 Zr 0.1 O2F, Na2Ni 0.9Cu 0.1 O2F, Na2Ni 0.9 Nb 0.1 O2F, Na2Ni 0.9 W 0.1 O2F, Na2Co 0.9 Zn 0.1 O2F, Na2Co 0.9 Zr 0.1 O2F, Na2Co 0.9 Cu 0.1 O2F, Na2Co 0.9 Nb 0.1 O2F, Na2Co 0.9 W 0.1 O2F, Na2Fe 0.9 Zn 0.1 O2F, Na2FeO .9 Zr 0.1 O2F, Na2Fe 0.9 Cu 0.1 O2F, Na2Fe 0.9 Nb 0.1 O2F and Na2Fe 0.9 W 0.1 One or more of O2F.

[0012] In some embodiments, the positive electrode active material is an O3-type layered oxide.

[0013] Secondly, this disclosure provides a method for preparing a positive electrode active material, comprising the following steps: providing a pH adjuster, M... 1 Source and optional M 2 A mixed aqueous solution of the source, the pH of which is 10-13, M 1 The source includes one or more of nickel, cobalt, manganese, and iron sources; M 2 The source includes one or more of copper, magnesium, aluminum, titanium, zinc, zirconium, niobium and tungsten sources; the mixed aqueous solution is reacted to obtain a precursor; the obtained precursor is mixed with sodium and fluorine sources and then sintered to obtain a positive electrode active material.

[0014] In some embodiments, in the step of reacting the mixed aqueous solution to obtain the precursor, the volumetric particle size distribution Dv50 of the obtained precursor is 4-12 μm.

[0015] In some embodiments, the specific surface area of ​​the obtained precursor is 10-16 m². 2 / g. When the specific surface area of ​​the precursor is within the above range, the positive electrode active material can provide more ion adsorption sites, which can further improve the transport rate of active ions in the positive electrode film and the electrolyte wettability, thus giving the positive electrode active material better electrochemical performance.

[0016] In some embodiments, the step of mixing the obtained precursor with a sodium source and a fluorine source and then sintering it to obtain a positive electrode active material includes: the mixing ratio of the sodium source and the precursor is based on the ratio of Na to M in the precursor. 1 The elements are mixed in a molar ratio of (2-2.5):1.

[0017] In some embodiments, the fluorine source content is 0.5%-1.7% based on the total mass of the sodium source and the precursor mixture as 100%.

[0018] By setting the fluorine source content within the aforementioned range, the doping amount of fluorine in the positive electrode active material can be adjusted. This allows for further utilization of fluorine's stronger electronegativity to enhance the bond strength between transition metals and non-metals, thereby altering the electronic states of the metal and crystal. Furthermore, setting the fluorine source content within this range can also further adjust the valence state of anions, modulate the structure and chemical properties of the positive electrode active material, and reduce irreversible anion oxidation processes. This, in turn, improves the structural stability of the positive electrode active material and enhances the cycle performance of the battery cell.

[0019] In some embodiments, the pH adjuster includes one or more of ammonia, sodium hydroxide, sodium carbonate, sodium bicarbonate, sodium oxalate, and sodium acetate.

[0020] In some embodiments, the manganese source includes one or more of manganese sulfate, manganese oxalate, manganese acetate, and manganese chloride.

[0021] In some embodiments, in the step of reacting the mixed aqueous solution to obtain the precursor, the reaction time is 50-70 h.

[0022] In some embodiments, in the step of reacting the mixed aqueous solution to obtain the precursor, the reaction temperature is 40-70°C.

[0023] In some embodiments, in the step of reacting the mixed aqueous solution to obtain the precursor, the stirring speed of the reaction is 500-1500 r / min.

[0024] By limiting one or more of the reaction time, temperature, or stirring speed within the above range, the volume particle size distribution and specific surface area of ​​the precursor can be precisely adjusted, further improving the structural stability of the cathode active material and the cycle performance of the battery cell.

[0025] In some embodiments, in the step of reacting the mixed aqueous solution to obtain the precursor, the reaction is carried out under a protective gas atmosphere. Conducting the above reaction under a protective gas atmosphere can remove dissolved oxygen from the mixed aqueous solution, thereby further reducing the content of free alkaline substances on the surface of the positive electrode active material.

[0026] In some embodiments, the step of reacting the mixed aqueous solution to obtain the precursor further includes: filtering and drying the precursor obtained from the reaction.

[0027] In some embodiments, the drying temperature is 90-160°C.

[0028] In some embodiments, the drying process takes 6-30 hours.

[0029] By limiting the temperature or time of the drying process within the above range, moisture in the precursor can be removed, thereby allowing for more precise control of the amount of precursor added.

[0030] In some embodiments, the moisture content in the dried precursor is 0.1%-0.2%.

[0031] In some embodiments, the sodium source includes one or more of sodium hydroxide, sodium carbonate, sodium bicarbonate, sodium acetate, and sodium oxalate.

[0032] In some embodiments, the fluorine source includes one or more of fluorine-containing inorganic salts and fluorine-containing organic compounds.

[0033] In some embodiments, the fluorine-containing inorganic salt includes one or more of sodium fluoride, ammonium fluoride, potassium fluoride, and calcium fluoride.

[0034] In some embodiments, the fluorinated organic compound includes one or more of polyvinylidene fluoride and polytetrafluoroethylene.

[0035] In some embodiments, in the step of mixing the obtained precursor with a sodium source and a fluorine source and then sintering it to obtain a positive electrode active material, the sintering temperature is 800-1000℃.

[0036] In some embodiments, the holding time for sintering is 10-14 hours.

[0037] In some embodiments, the heating rate of the sintering process is 1-10 °C / min.

[0038] In some embodiments, the sintering pressure is 0-20 Pa.

[0039] By controlling the sintering temperature, holding time, or heating rate within the above range, the size of the primary particles can be controlled within a suitable range, thereby improving the stability, cycle performance, and capacity of the positive electrode active material.

[0040] In some embodiments, the sintering atmosphere is an oxygen-containing atmosphere. Sintering in an oxygen-containing atmosphere can stabilize the surface structure of the material, allowing the surface sodium, which has become unstable due to washing, to react with oxygen and become stable again. This can help repair surface defects, reduce vacancies, and thus improve the cycle performance of the battery cell.

[0041] Thirdly, this disclosure provides a positive electrode active material, which is prepared by the preparation method of the second aspect of this disclosure.

[0042] Fourthly, this disclosure provides a battery device including a battery cell according to the first aspect of this disclosure.

[0043] Fifthly, this disclosure provides an electrical device, including the battery device of the fourth aspect of this disclosure. Attached Figure Description

[0044] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the embodiments of this disclosure will be briefly described below. Obviously, the drawings described below are merely some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on the drawings without any creative effort.

[0045] Figure 1 This is a schematic diagram of one embodiment of the battery cell disclosed herein.

[0046] Figure 2 This is a schematic diagram of one embodiment of an electrical device that uses the battery device disclosed herein as a power source.

[0047] The attached figures may not be drawn to scale. The reference numerals are explained as follows: 5. Battery cell. Detailed Implementation

[0048] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the positive electrode active material, its preparation method, battery cell, battery device, and power-consuming device of this disclosure. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this disclosure and are not intended to limit the subject matter of the claims.

[0049] The "range" disclosed in this disclosure is defined by a lower limit and an upper limit, whereby a given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the 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, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this disclosure, 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 article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0050] Unless otherwise specified, all embodiments and optional embodiments of this disclosure may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the content of this disclosure.

[0051] Unless otherwise specified, all technical features and optional technical features of this disclosure can be combined to form new technical solutions, and such technical solutions should be considered as included in the content of this disclosure.

[0052] Unless otherwise specified, all steps in this disclosure may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0053] In this disclosure, the terms "multiple" or "a variety" refer to two or more kinds.

[0054] Unless otherwise stated, the test temperature for all parameters mentioned in this disclosure is 25°C.

[0055] The battery apparatus mentioned in the embodiments of this disclosure may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells connected in series, parallel, or mixed connections via a busbar.

[0056] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells. As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form a single module. As an example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0057] In some embodiments, the battery device may be a battery pack, which may include a housing and one or more individual battery cell assemblies housed within the housing. As an example, the individual battery cell assembly may be a battery module, which can be housed within the housing by securing the battery module to the housing. Alternatively, as an example, the individual battery cell assembly may be housed within the housing by directly securing multiple individual battery cells to the housing.

[0058] A single battery cell is the smallest unit that makes up a battery device, and it can independently perform the functions of charging and discharging. A single battery cell can be cylindrical, cuboid, or other shapes, and the embodiments disclosed herein are not limited to this. Figure 1 The example shown is a rectangular battery cell 5.

[0059] In this embodiment of the disclosure, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0060] The battery cells provided in the embodiments of this disclosure include sodium-ion battery cells, sodium metal battery cells, and sodium metal battery cells without negative electrodes, etc., and the embodiments of this disclosure are not limited to these.

[0061] A sodium-metal-free negative electrode battery cell typically refers to a battery cell in which a negative electrode film layer is not actively formed on the negative electrode side during the battery cell manufacturing process. For example, during the battery cell manufacturing process, a negative electrode film layer of carbonaceous active material is not formed at the negative electrode through processes such as coating or deposition. During the first charge, ions gain electrons on the negative electrode side and deposit on the surface of the negative electrode current collector to form a metallic phase. During discharge, the metal can be converted into metal ions and return to the positive electrode, achieving cyclic charging and discharging. Compared with other battery cells, sodium-metal-free negative electrode battery cells can achieve higher energy density because they do not have a negative electrode film layer. In some embodiments, to improve the performance of the battery cell, some conventional materials that can be used as negative electrode active materials, such as carbon materials, can also be placed on the negative electrode side of the sodium-metal-free negative electrode battery cell. Although these materials have a certain capacity, because their content is small and they are not used as the main negative electrode active materials in the battery cell, the battery cell constructed in this way can still be regarded as a sodium-metal-free negative electrode battery cell.

[0062] The CB value of a sodium metal battery cell without a negative electrode is typically very small; for example, in some embodiments, the CB value of a sodium metal battery cell without a negative electrode can be less than or equal to 0.1. The CB value is the capacity per unit area of ​​the negative electrode divided by the capacity per unit area of ​​the positive electrode in the battery cell. Because a sodium metal battery cell without a negative electrode contains little or no negative electrode active material, the capacity per unit area of ​​the negative electrode is small, and therefore the CB value is very small, typically less than or equal to 0.1.

[0063] Taking a sodium metal battery cell without a negative electrode as an example, the negative electrode sheet may include a negative current collector but does not include a sodium metal layer. During the cyclic charging and discharging process of a sodium metal battery cell without a negative electrode, the sodium at the positive electrode will be deposited and stripped off in the form of sodium metal on the negative electrode side.

[0064] A single battery cell includes an electrode assembly and an electrolyte. The electrode assembly can be a wound structure or a stacked structure, and the embodiments disclosed herein are not limited to this.

[0065] In some embodiments, the electrode assembly is a wound structure. The positive electrode and the negative electrode are wound into a wound structure.

[0066] In some embodiments, the electrode assembly has a stacked structure.

[0067] As an example, multiple positive and negative electrode sheets can be set, with multiple positive and multiple negative electrode sheets stacked alternately. As an example, multiple positive electrode sheets can be set, and negative electrode sheets are folded to form multiple stacked folded segments, with a positive electrode sheet sandwiched between adjacent folded segments.

[0068] As an example, both the positive and negative electrode sheets are folded to form multiple stacked folded segments.

[0069] As an example, multiple separators can be provided, each positioned between any adjacent positive or negative electrode plates.

[0070] As an example, the separator can be continuously installed between any adjacent positive or negative electrode plates by folding or rolling.

[0071] In some embodiments, the electrode assembly may be cylindrical, flat, or polygonal, etc.

[0072] In some embodiments, the electrode assembly has tabs that allow current to be drawn from the electrode assembly. The tabs include a positive tab and a negative tab.

[0073] The battery cell also includes an outer packaging, which encapsulates the electrode components and electrolyte. The outer packaging can be a rigid shell, such as a hard plastic shell, aluminum shell, or steel shell. It can also be a flexible package, such as a pouch. The material of the flexible package can be plastic, such as one or more of aluminum-plastic film, polypropylene, polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0074] In some embodiments, the number of electrode components contained in a single battery cell can be one or more, and can be adjusted as needed.

[0075] In some embodiments, individual battery cells can be assembled into a battery module, and the number of individual battery cells contained in the battery module can be multiple, the specific number of which can be adjusted according to the application and capacity of the battery module.

[0076] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0077] The battery device mentioned in the embodiments of this disclosure can be a single physical module comprising one or more battery cells to provide higher voltage and capacity. For example, the battery device mentioned in this disclosure can include battery cells, battery modules, or battery packs.

[0078] The industrial production equipment for oxide-based cathode active materials in sodium batteries is basically the same as that for ternary lithium-ion batteries, which are already in mass production. Furthermore, research on oxide-based cathode active materials is extensive. However, layered oxide-based cathode active materials inherently suffer from poor structural stability. During charge and discharge, the insertion and extraction of sodium ions—for example, after extraction, the re-insertion of sodium ions occupies a certain number of transition metal vacancies, leading to the mixing of transition metal and sodium. This causes irreversible structural collapse, preventing sodium ions from being extracted again, resulting in capacity loss of the cathode active material and deterioration of the battery cell's cycle performance. During charge and discharge, inactive substances (e.g., water and carbon dioxide) may insert into the lattice containing sodium ions, and oxygen ions may easily extract from the lattice, also causing irreversible structural collapse and hindering sodium ion diffusion channels. These factors hinder the commercialization of layered oxide-based cathode active materials.

[0079] Furthermore, when sodium ion extraction exceeds a certain capacity limit, layered oxide cathode active materials suffer severe capacity decay. Therefore, the capacity decay of NaMO2 (where M is a transition metal) materials is related to the irreversible structural transformation at the end of complete sodium extraction, as well as to transition metal migration and possible H2O / CO2 insertion into the sodium layer. At this point, the diffusion channels for sodium ions may be blocked, potentially leading to a reduction in the degree of intercalation from a kinetic perspective. Currently, NaMO2 cathode active materials, such as NaNi... x Fe y Mn z O2(x+y+z=1) or NaNi x Fe y Mn z Cu (1-x-y-z) O2 exhibits low cycle stability, possibly due to reduced crystal structure stability, large volume changes, and, in particular, irreversible anion redox activity during charging.

[0080] In view of the above problems, this disclosure provides a battery cell including a positive electrode sheet; the positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, the positive electrode film layer including a positive electrode active material having the following chemical formula: Na x M 1 1-y M 2 y O2F, 2≤x≤2.5, 0≤y<0.4, M 1 Includes one or more of Mn, Ni, Co, and Fe, M 2 It includes one or more of Mg, Al, Ti, Zn, Zr, Cu, Nb and W, and the pH of the positive electrode active material is 10-13.

[0081] This disclosure discloses an embodiment in which fluorine is added to layered oxide-based cathode active materials, replacing some of the oxygen in the cathode active material with fluorine. The stronger electronegativity of fluorine enhances the bond strength between transition metals and non-metals, altering the electronic states of the metals and crystals. Replacing some oxygen with fluorine also changes the valence state of anions, regulating the structure and chemical properties of the cathode active material, and reducing irreversible oxidation processes of anions. This improves the structural stability of the cathode active material, reduces capacity decay caused by irreversible structural transformations, enhances the cycle performance of individual battery cells, and improves the processing performance of the cathode slurry and battery device.

[0082] The pH of the positive electrode active material can be tested according to GB / T 9724-2007. Specifically: at 25℃, prepare a solution by mixing the positive electrode active material sample with deionized water at a mass ratio of 1:9, seal the solution, stir it on a magnetic stirrer for 30 minutes, and then let it stand for 90 minutes before filtering. The pH of the filtrate is measured with a pH meter (such as pHS-3C), which is the pH of the positive electrode active material.

[0083] In some embodiments, the content of free alkaline substances on the surface of the positive electrode active material can be 0.5%-2%. Optionally, it can be 1%-2%.

[0084] When the content of free alkaline substances on the surface of the positive electrode active material is within the above range, it can reduce the side reactions between the positive electrode active material and the electrolyte, reduce gas production, improve the reliability of the battery cell, and also enable the positive electrode active material to have higher interfacial stability. This is beneficial to further improve the capacity and cycle performance of the battery cell, and also beneficial to improve the processing performance of the positive electrode slurry and battery device.

[0085] The content of free alkaline substances can be detected by chemical titration or potentiometric titration. The content of free alkaline substances on the surface varies slightly depending on the type of positive electrode active material.

[0086] In some embodiments, the free alkaline substance may include CO3. 2- and / or OH - .

[0087] In some embodiments, the positive electrode active material can be a secondary particle morphology formed by the aggregation of multiple primary particles.

[0088] In some embodiments, the average particle size of the primary particles constituting the positive electrode active material can be 1-3 μm, for example, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm, 3 μm, or optionally 1.2-1.9 μm or 1.4-1.6 μm.

[0089] Primary particles refer to non-agglomerated particles. The size of primary particles is closely related to the electrochemical performance of the cathode active material. Generally, the larger the primary particle size, the more stable the structure of the cathode active material and the better its cycle performance, but the lower its capacity.

[0090] By controlling the average particle size of primary particles within the aforementioned range, the relationship between the structural stability, cycle performance, and capacity of the positive electrode active material can be balanced.

[0091] In some embodiments, the volumetric particle size distribution Dv50 of the positive electrode active material can be 2-10 μm, for example, it can be 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or any combination of two of the above values. It can be selected as 3-6 μm or 3.5-4.5 μm.

[0092] When the volumetric particle size distribution Dv50 of the positive electrode active material is within the above range, it can have high capacity and high compaction density, as well as good ion transport capability.

[0093] In some embodiments, the positive electrode active material may include Na2MnO2F, Na2NiO2F, Na2CoO2F, Na2FeO2F, or Na2MnO2F. 0.9 Al 0.1 O2F, Na2Mn 0.9 Mg 0.1 O2F, Na2Mn 0.9 Ti 0.1 O2F, Na2Ni 0.9 Al 0.1 O2F, Na2Ni 0.9 Mg 0.1 O2F, Na2Ni 0.9 Ti 0.1 O2F, Na2Mn 0.9 Zn 0.1 O2F, Na2Mn 0.9 Zr 0.1 O2F, Na2Mn 0.9 Cu 0.1 O2F, Na2Mn 0.9 Nb 0.1 O2F, Na2Mn 0.9 W0.1 O2F, Na2Ni 0.9 Zn 0.1 O2F, Na2Ni 0.9 Zr 0.1 O2F, Na2Ni 0.9 Cu 0.1 O2F, Na2Ni 0.9 Nb 0.1 O2F, Na2Ni 0.9 W 0.1 O2F, Na2Co 0.9 Zn 0.1 O2F, Na2Co 0.9 Zr 0.1 O2F, Na2Co 0.9 Cu 0.1 O2F, Na2Co 0.9 Nb 0.1 O2F, Na2Co 0.9 W 0.1 O2F, Na2Fe 0.9 Zn 0.1 O2F, Na2FeO .9 Zr 0.1 O2F, Na2Fe 0.9 Cu 0.1 O2F, Na2Fe 0.9 Nb 0.1 O2F and Na2Fe 0.9 W 0.1 One or more of O2F.

[0094] In some embodiments, the positive electrode active material may be an O3-type layered oxide.

[0095] [Preparation method of positive electrode active material]

[0096] This disclosure also provides a method for preparing a positive electrode active material, including the following steps:

[0097] Provides pH adjusters, M 1 Source and optional M 2 A mixed aqueous solution of the source, the pH of which is 10-13, M 1 The source includes one or more of nickel, cobalt, manganese, and iron sources, M 2 The source includes one or more of the following: copper source, magnesium source, aluminum source, titanium source, zinc source, zirconium source, niobium source, and tungsten source;

[0098] The mixed aqueous solution was reacted to obtain the precursor;

[0099] The obtained precursor was mixed with sodium and fluorine sources and then sintered to obtain the positive electrode active material.

[0100] This disclosure embodiment adjusts the pH adjuster, M... 1 Source and optional M 2 The pH of the mixed aqueous solution of the source can yield precursors with suitable particle size and specific surface area. By adding a fluorine source during the sintering process, fluorine replaces some of the oxygen in the positive electrode active material. The stronger electronegativity of fluorine enhances the bond strength between transition metals and non-metals, altering the electronic state of the metal and crystal. Replacing some oxygen with fluorine also changes the valence state of anions, regulating the structure and chemical properties of the positive electrode active material, and reducing irreversible oxidation of anions, resulting in a structurally stable positive electrode active material, thereby improving its cycle performance. The positive electrode active material prepared by the method of this disclosure has a suitable pH range and a low content of surface-free alkaline substances, thus stabilizing the crystal structure of the positive electrode active material and enabling the battery cell to have good cycle performance.

[0101] Adjusting the pH of a mixed aqueous solution can precipitate precursors. Different pH values ​​in the mixed aqueous solution will yield precursors with different morphologies.

[0102] In some embodiments, the pH of the mixed aqueous solution can be 10.8-12.2, for example, 10.8, 11, 11.2, 11.5, 11.8, 12, 12.2, or any range of two of the above values. This allows for the preparation of precursors with suitable particle size and specific surface area.

[0103] In some embodiments, a pH adjuster, M is provided. 1 Source and optional M 2 In the step of preparing the mixed aqueous solution of the source, a pH adjuster and M can be added. 1 Source and optional M 2 Alternatively, M can be prepared as an aqueous solution separately before mixing. 1 Source and optional M 2 The source is first dissolved in water, and then a pH adjuster is added.

[0104] pH adjusters can be used to reduce the solubility of metal ions in mixed aqueous solutions, making M... 1 Source and optional M 2 Metal ions in the source can precipitate as hydroxides. Furthermore, pH adjusters can be used to regulate the rate of precipitate formation during the reaction. In the embodiments of this disclosure, the pH of the mixed aqueous solution is the pH of the solution after the reaction has stabilized.

[0105] In some embodiments, M 1 M in the aqueous solution of the source 1 The molar concentration of the element can be 2-5 mol / L.

[0106] By using pH adjuster, M 1 Source and optional M 2 Preparing the sources into solutions separately before mixing them helps to improve M. 1 Source and optional M 2 The conversion rate of the source makes the reaction more complete and is also beneficial for industrial production.

[0107] In some embodiments, in the step of reacting the mixed aqueous solution to obtain the precursor, the volumetric particle size distribution Dv50 of the obtained precursor can be 4-12 μm, for example, it can be 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, or any range of two of the above values.

[0108] In some embodiments, the specific surface area of ​​the obtained precursor can be 10-16 m². 2 / g.

[0109] Specific surface area refers to the total area per unit mass of material. If the specific surface area of ​​the precursor is within the aforementioned range, the positive electrode active material can provide more ion adsorption sites, further improving the transport rate of active ions in the positive electrode film and electrolyte wettability, thus giving the positive electrode active material superior electrochemical performance. Specific surface area can be measured according to the methods and instruments specified in GB / T19587-2017.

[0110] In some embodiments, the step of mixing the obtained precursor with a sodium source and a fluorine source and then sintering it to obtain a positive electrode active material includes: the mixing ratio of the sodium source and the precursor is based on the ratio of Na to M in the precursor. 1 The elements are mixed in a molar ratio of (2-2.5):1.

[0111] In some embodiments, the mass content of the fluorine source can be 0.5%-1.7% based on the total mass of the sodium source and the precursor mixture as 100%.

[0112] By setting the fluorine source content within the aforementioned range, the doping amount of fluorine in the positive electrode active material can be adjusted. This allows for further utilization of fluorine's stronger electronegativity to enhance the bond strength between transition metals and non-metals, thereby altering the electronic states of the metal and crystal. Furthermore, setting the fluorine source content within this range can also further adjust the valence state of anions, modulate the structure and chemical properties of the positive electrode active material, and reduce irreversible anion oxidation processes. This, in turn, improves the structural stability of the positive electrode active material and enhances the cycle performance of the battery cell.

[0113] In some embodiments, the pH adjuster may include one or more of ammonia, sodium hydroxide, sodium carbonate, sodium bicarbonate, sodium oxalate, and sodium acetate.

[0114] In some embodiments, the mass concentration of ammonia water can be 10%-40%.

[0115] In this embodiment, the pH adjuster can be a mixed aqueous solution of ammonia and sodium hydroxide, a mixed aqueous solution of ammonia and sodium carbonate, or an aqueous solution of sodium hydroxide and sodium carbonate. The ammonia in the pH adjuster can act as a complexing agent. Exemplarily, the molar concentration of sodium carbonate in the pH adjuster can be 3-8 mol / L, or the molar concentration of sodium hydroxide in the pH adjuster can be 3-8 mol / L.

[0116] In some embodiments, M 1 The source may include M 1 The corresponding salt, such as M 1 carbonates, M 1 Acetate, M 1 sulfates, M 1 nitrates and M 1 Oxalate. M 2 The source may include M 2 The corresponding salt, such as M 2 carbonates, M 2 Acetate, M 2 sulfates, M 2 nitrates and M 2 Oxalate.

[0117] In some embodiments, M 1 The source may include a manganese source.

[0118] Manganese is abundant and inexpensive on Earth, and using manganese as a source can improve the cost-effectiveness of positive electrode active materials.

[0119] In some embodiments, the manganese source may include one or more of manganese sulfate, manganese oxalate, manganese acetate, and manganese chloride.

[0120] In some embodiments, the purity of the manganese source is greater than 95%.

[0121] In some embodiments, the reaction time for the step of reacting the mixed aqueous solution to obtain the precursor can be 50-70 hours.

[0122] In some embodiments, the reaction temperature in the step of reacting the mixed aqueous solution to obtain the precursor can be 40-70°C.

[0123] In some embodiments, in the step of reacting the mixed aqueous solution to obtain the precursor, the stirring speed of the reaction can be 500-1500 r / min.

[0124] By limiting one or more of the reaction time, temperature, or stirring speed within the above range, the volume particle size distribution and specific surface area of ​​the precursor can be precisely adjusted, further improving the structural stability of the cathode active material and the cycle performance of the battery cell.

[0125] In some embodiments, the step of reacting the mixed aqueous solution to obtain the precursor can be carried out under a protective gas atmosphere.

[0126] The above reaction is carried out under a protective gas atmosphere, which can remove dissolved oxygen from the mixed aqueous solution, thereby further reducing the content of free alkaline substances on the surface of the positive electrode active material.

[0127] In some embodiments, the protective gas may include one or more of nitrogen and argon.

[0128] In some embodiments, the step of reacting the mixed aqueous solution to obtain the precursor may further include: filtering and drying the precursor obtained from the reaction.

[0129] Filtration methods include, but are not limited to, vacuum filtration and pressure filtration. During filtration, the precursor can also be washed, using methods including, but not limited to, water washing or alcohol washing. Filtration and washing can improve the purity of the precursor.

[0130] In some embodiments, the drying temperature can be 90-160°C.

[0131] In some embodiments, the drying time can be 6-30 hours.

[0132] By limiting the temperature or time of the drying process within the above range, moisture in the precursor can be removed, thereby allowing for more precise control of the amount of precursor added.

[0133] In some embodiments, the moisture content in the dried precursor may be 0.1%-0.2%.

[0134] The drying equipment in the embodiments of this disclosure includes, but is not limited to, disc dryers, tunnel dryers, etc.

[0135] The precursors obtained by the preparation method of the present disclosure have high purity.

[0136] In some embodiments, the purity of the precursor is greater than 99%.

[0137] In some embodiments, in the step of mixing the obtained precursor with a sodium source and a fluorine source and then sintering it to obtain the positive electrode active material, the mixing equipment used can affect the uniformity of the mixture to some extent. For example, a high-speed mixer or a plow mixer can be used for dry mixing, and the mixing time can be 1-3 hours. The criterion for judging the uniformity of the mixture is that no white spots appear in the material upon visual inspection.

[0138] In some embodiments, the sodium source may include one or more of sodium hydroxide, sodium carbonate, sodium bicarbonate, sodium acetate, and sodium oxalate.

[0139] In some embodiments, the purity of the sodium source is greater than 95%.

[0140] In some embodiments, the fluorine source may include one or more of fluorine-containing inorganic salts and fluorine-containing organic compounds.

[0141] In some embodiments, the fluoride-containing inorganic salt may include one or more of sodium fluoride, ammonium fluoride, potassium fluoride, and calcium fluoride.

[0142] In some embodiments, fluorinated organic compounds may include one or more of polyvinylidene fluoride and polytetrafluoroethylene.

[0143] In some embodiments, the sintering temperature can be 800-1000℃ in the step of mixing the obtained precursor with a sodium source and a fluorine source to obtain a positive electrode active material.

[0144] In some embodiments, the holding time for sintering can be 10-14 hours.

[0145] In some embodiments, the heating rate of the sintering process can be 1-10℃ / min, and optionally 2-4℃ / min.

[0146] By controlling the sintering temperature, holding time, or heating rate within the above range, the size of the primary particles can be controlled within a suitable range, thereby improving the stability, cycle performance, and capacity of the positive electrode active material.

[0147] In some embodiments, the pressure of the sintering process can be 0-20 Pa.

[0148] The sintering pressure is the pressure displayed on the pressure gauge of the sintering apparatus. When the sintering pressure is within the above range, it allows for good air intake and exhaust during the sintering process, thereby further reducing the content of free alkaline substances on the surface of the positive electrode active material, improving the structural stability of the positive electrode active material, and enhancing the cycle performance of the battery cell.

[0149] In some embodiments, the sintering atmosphere can be an oxygen-containing atmosphere. Sintering in an oxygen-containing atmosphere can stabilize the surface structure of the material, allowing the surface sodium, which has become unstable due to washing, to react with oxygen and become stable again. This can help repair surface defects, reduce vacancies, and thus improve the cycle performance of the battery cell.

[0150] In some embodiments, the volume fraction of oxygen in the oxygen-containing atmosphere can be 40%-100%, for example, 40%, 50%, 60%, 70%, 80%, 90%, 100%, or any range of two of the above values. 50%-90% is an option.

[0151] By setting the volume fraction of oxygen in the oxygen-containing atmosphere within the above range, the positive electrode active material can better maintain its original layered structure, which can further stabilize the structure of the positive electrode active material, increase its capacity, and thus further improve the cycle performance of the battery cell. It can also further reduce the content of carbonate and hydroxide ions on the surface of the positive electrode active material.

[0152] Understandably, the sintering atmosphere may also contain inert gases, such as one or more of nitrogen, helium, and argon. Of course, the sintering atmosphere may also contain air, for example, a mixture of air and oxygen, which can reduce production costs.

[0153] In some embodiments, the sintering apparatus may include a mullite sagger; alternatively, the mullite sagger may include a graphite sagger or a corundum sagger.

[0154] In some embodiments, sintering can be performed using a roller kiln.

[0155] Typically, the sintered material is a hard, grayish-black block, so it needs to be pulverized to obtain the positive electrode active material. Pulverization methods include, but are not limited to, ball milling, water milling, air jet milling, or roller milling.

[0156] In some embodiments, the preparation method may further include packaging the pulverized positive electrode active material after demagnetization and sieving.

[0157] For example, sieving can include, but is not limited to, sieving and vibrating sieving. Demagnetization can remove small amounts of metallic impurities such as Fe, Cr, and Zn from the positive electrode active material.

[0158] The method for preparing the positive electrode active material in this embodiment is simple to operate and conforms to the relevant process equipment for ternary layered oxide positive electrode active materials that have been commercialized on a large scale. This brings great potential for the large-scale commercialization of positive electrode active materials for sodium batteries.

[0159] Unless otherwise specified, all raw materials used in the above preparation methods can be obtained commercially.

[0160] [Positive electrode plate]

[0161] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector. The positive electrode film layer includes the positive electrode active material described in the present disclosure embodiment or the positive electrode active material prepared by the preparation method described in the present disclosure embodiment.

[0162] In some embodiments, the content of positive electrode active material in the positive electrode film layer is 85%-95%, optionally 88%-90%, based on the total mass of the positive electrode film layer as 100%.

[0163] The compaction density of the positive electrode active material in the positive electrode film layer is 2.8-3.2 g / cm³. 3 .

[0164] In some embodiments, compaction density has a meaning known in the art and can be determined using methods already known in the art, for example, by means of an electronic pressure testing machine, referring to GB / T 24533-2009. In this embodiment, the compaction density is measured at a pressure of 3 tons.

[0165] The positive current collector has two surfaces opposite each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0166] The positive electrode film layer may also include other positive electrode active materials known in the art, such as, but not limited to, one or more of fluorides, sulfides, phosphates, pyrophosphates, metal-organic frameworks / metal hexacyanides, and organic compounds. These other positive electrode active materials may be used alone or in combination of two or more. As an example, other positive electrode active materials may include NaCoO2, Na... 2 / 3 [Cu 1 / 3 Mn 2 / 3 O2, Na 2 / 3 [Fe 1 / 3 Mn 2 / 3 O2, Na 2 / 3 [Li 1 / 3Ni 2 / 3 O2, Na[Ni 0.5 Co 0.5 O2, Na 7 / 9 [Cu 2 / 9 Fe 1 / 9 Mn 2 / 3 O2, Na 2 / 3 [Li 1 / 3 Mn 1 / 2 Ti1 / 6 O2, Na[Ni 0.5 Fe 0.5 O2, Na[Co 0.5 Fe 0.5 O2, Na[Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, Na[Cu 1 / 9 Ni 2 / 9 Fe 1 / 3 Mn 1 / 3 One or more of O2.

[0167] In some embodiments, the positive electrode film layer may further include a positive electrode conductive agent. As an example, the positive electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0168] In some embodiments, the positive electrode film layer may further include a positive electrode binder. As an example, the positive electrode binder may include, but is not limited to, one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resins, styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0169] In some embodiments, the positive current collector may be a metal foil, a conductive polymer material, a carbon material, or a composite current collector. For example, as a metal foil, pure metals, alloys, or surface-treated metals may be used, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver. The composite current collector may include a polymer substrate and a metal material layer formed on at least one surface of the polymer substrate. As an example, the metal material may include, but is not limited to, one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymer substrate may include, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE). The composite current collector may be formed by forming a metal material on a polymer substrate.

[0170] The positive electrode film is typically formed by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is usually formed by dispersing positive electrode active materials, positive electrode conductive agents, positive electrode binders, and any other components in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP), but is not limited to this.

[0171] [Negative electrode plate]

[0172] The structure and composition of the negative electrode can be selected according to the type of battery cell, and the embodiments disclosed herein are not limited in this regard.

[0173] In some embodiments, the negative electrode sheet may include a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector and comprising a negative electrode active material. For example, the negative current collector has two surfaces opposite each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative current collector.

[0174] The negative electrode active material can be any negative electrode active material known in the art for use in battery cells. 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, mesophase microcarbon spheres, silicon-based materials, and tin-based materials. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, this disclosure is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for battery cells may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0175] In some embodiments, the negative electrode film layer may further include a negative electrode conductive agent. As an example, the negative electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0176] In some embodiments, the negative electrode film layer may further include a negative electrode binder. As an example, the negative electrode binder may include, but is not limited to, one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0177] In some embodiments, the negative electrode film layer may also include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0178] The negative electrode film is typically formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, negative electrode conductive agent, negative electrode binder, and other optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0179] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet may also include a conductive undercoat layer (e.g., composed of a conductive agent and an adhesive) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector; in some embodiments, the negative electrode sheet may also include a protective layer covering the surface of the negative electrode film layer.

[0180] In some embodiments, the negative electrode sheet may include a negative current collector and a metal layer disposed on at least one surface of the negative current collector, wherein the metal material in the metal layer may include one or more of elemental sodium and sodium alloy.

[0181] Sodium alloys can be alloys formed from metallic sodium with other metallic or non-metallic elements. For example, other metallic elements in a sodium alloy may include one or more of tin, zinc, aluminum, magnesium, silver, gold, gallium, indium, and platinum, while non-metallic elements may include one or more of boron, carbon, and silicon.

[0182] In some embodiments, the negative electrode sheet may be a sodium sheet (foil) or a sodium alloy sheet (foil).

[0183] In some embodiments, the negative electrode may include a negative current collector and does not include a metal layer, thereby assembling a sodium metal battery cell without a negative electrode.

[0184] In some embodiments, the negative electrode current collector may include a metal foil, a conductive polymer material, a carbon material, or a composite current collector. Examples of metal foils include pure metals, alloys, and surface-treated metals, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver. The composite current collector may include a polymer substrate and a metal material layer formed on at least one surface of the polymer substrate. Examples of metal materials include, but are not limited to, one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, aluminum, aluminum alloys, silver, and silver alloys. Examples of polymer materials include, but are not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE). The composite current collector can be formed by forming a metal material on a polymer substrate.

[0185] In some embodiments, the negative electrode can be made of foamed metal. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon, etc. When foamed metal is used as the negative electrode sheet, the surface of the foamed metal may or may not contain a negative electrode active material.

[0186] As an example, negative electrode active materials can be filled or / and deposited within the negative electrode current collector.

[0187] In some embodiments, the positive current collector can be made of aluminum, and the negative current collector can be made of copper.

[0188] [Electrolytes]

[0189] Each battery cell includes an electrolyte, which acts as a conductor of ions between the positive and negative electrodes. This disclosure does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte may include one or more selected from solid electrolytes, gel electrolytes, and liquid electrolytes (i.e., electrolyte solutions).

[0190] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0191] The type of electrolyte salt is not specifically limited and can be selected according to actual needs. In some embodiments, as an example, the electrolyte salt may include, but is not limited to, one or more of NaPF6, NaClO4, NaBCl4, NaSO3CF3, and Na(CH3)C6H4SO3.

[0192] There are no specific restrictions on the type of solvent; it can be selected according to actual needs.

[0193] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate (PPC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE). Ether solvents may also be selected. Ether solvents may include one or more of the following: ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyltetrahydrofuran, diphenyl ether, and crown ether.

[0194] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve the overcharge / fast charge performance of individual battery cells, additives that improve the high-temperature performance of individual battery cells, additives that improve the low-temperature performance of individual battery cells, etc.

[0195] The gel electrolyte includes a polymer as a backbone network and can be used in conjunction with an ionic liquid—sodium salt.

[0196] Solid electrolytes include polymer solid electrolytes, inorganic solid electrolytes, and composite solid electrolytes.

[0197] As an example, the polymers of polymeric solid electrolytes may include polyethers (polyoxyethylene), polysiloxanes, polycarbonates, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, monoionic polymers, polyionic liquids, cellulose, etc.

[0198] As an example, inorganic solid electrolytes can be one or more of the following: oxide solid electrolytes (crystalline perovskite, sodium superconducting ion conductor, garnet, amorphous NaPON thin film), sulfide solid electrolytes (crystalline sodium superconducting ion conductor, amorphous sulfide), halide solid electrolytes, nitride solid electrolytes, and hydride solid electrolytes.

[0199] As an example, composite solid electrolytes are formed by adding inorganic solid electrolyte fillers to polymer solid electrolytes.

[0200] [Isolation membrane]

[0201] In some embodiments, the electrode assembly further includes a separator disposed between the positive and negative electrodes. This disclosure does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0202] As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramics. 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. The separator can be a single component located between the positive and negative electrodes, or it can be attached to the surfaces of the positive and negative electrodes. An inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating can also be applied to the surface of the separator.

[0203] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is disposed between the positive and negative electrodes, serving both to transport ions and to isolate the positive and negative electrodes.

[0204] Methods for preparing battery cells are well known. In some embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form a battery cell. As an example, the positive electrode, separator, and negative electrode can be formed into an electrode assembly through a winding process and / or a stacking process. The electrode assembly is placed in an outer packaging, dried, and then injected with the electrolyte. After vacuum sealing, settling, and formation processes, a battery cell is obtained.

[0205] [Electrical appliances]

[0206] This disclosure also provides an electrical device, which includes the battery device provided in this disclosure. The battery device can be used as the power source for the electrical device or as the energy storage unit of the electrical device. The electrical device can be, but is not limited to, mobile devices (e.g., mobile phones, tablets, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and spacecraft (e.g., airplanes, rockets, space shuttles, and spacecraft), energy storage systems, etc.

[0207] Electrical devices can choose the type of battery device according to their usage needs, such as individual battery cells, battery modules, or battery packs. Figure 2 This is a schematic diagram illustrating an example of an electrical device. This device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used as the power source.

[0208] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0209] Example

[0210] The following examples describe the contents of this disclosure in more detail. These examples are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of this disclosure. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the examples are commercially available.

[0211] Test section

[0212] (1) Initial discharge capacity, initial efficiency, and cycle capacity retention

[0213] The positive electrode active material is mixed with conductive agent Super P and binder polyvinylidene fluoride (PVDF) at a mass ratio of 90:5:5. A slurry of the positive electrode active material is prepared using a degassing machine. The solid content of the slurry is adjusted to 41% using N-methylpyrrolidone (NMP). The slurry is then coated onto aluminum foil using an automatic coating machine. After drying in a vacuum drying oven at 150°C for 2 hours, the foil is rolled by a roller press and punched by a slicing machine to form the positive electrode sheet.

[0214] A sodium metal sheet is used as the negative electrode, a glass fiber membrane as the separator, and a 1.5 mol / L sodium hexafluorophosphate (NaPF6) solution in a 1:1:1 volume ratio of ethylene carbonate (EC), propylene carbonate (PC), and dimethyl carbonate (DMC) as the electrolyte. The positive electrode, negative electrode, electrode shell, separator, and gasket are assembled into a coin cell inside a glove box.

[0215] The coin cells were subjected to charge-discharge tests on the Blue Electric testing system. After the obtained coin cells were left to stand for 4 hours, they were charged at 0.1C constant current to 3.9V at 25℃ to obtain the first charge capacity of the coin cells. They were then discharged at 0.1C constant current to 2.5V to obtain the first discharge capacity of the coin cells.

[0216] The initial discharge capacity (mAh / g) of the positive electrode active material = the initial discharge capacity of the coin cell / the mass of the positive electrode active material.

[0217] Initial efficiency = (initial discharge capacity / initial charge capacity) × 100%.

[0218] At 25°C, the coin cell was charged at a constant current of 1C to 3.9V, and then discharged at a constant current of 1C to 2.5V to obtain the initial discharge capacity of the coin cell. The coin cell was then subjected to a cyclic charge-discharge test using the above method, and the discharge capacity after each cycle was recorded. The capacity retention rate of the coin cell after 30 cycles = discharge capacity of the coin cell after 30 cycles / initial discharge capacity of the coin cell.

[0219] (2) Specific surface area test of precursor

[0220] The specific surface area of ​​solid materials was determined according to GB / T 19587-2017 by the gas adsorption BET method. The test was conducted using a Bestar dynamic adsorption-desorption surface analyzer with a sample mass of 6g and pretreatment conditions of 120℃ for 120min.

[0221] (3) Particle size test of precursor

[0222] Referring to GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method, the Malvern 3000 particle size analyzer was used to test the sample. The sample mass was 1g, the material was ultrasonically dispersed, and the refractive index was set to 1.

[0223] (4) pH test

[0224] The test was conducted according to GB / T 9724-2007. At 25℃, a 100 g / L solution of the positive electrode active material was prepared, and the pH of the filtrate was measured using a pH meter (pHS-3C). This pH value is the pH of the positive electrode active material.

[0225] (5) Content of free alkaline substances

[0226] Weigh 10.000g of the prepared positive electrode active material, add it to 100mL of deionized water, stir for 30min, and then filter. Transfer 60mL of the filtrate to a 250mL Erlenmeyer flask, add 10 drops of indicator (methyl orange and phenolphthalein) and shake well; the solution will turn purple. Then titrate with 0.5mol / L hydrochloric acid as a standard solution to calculate the free alkaline substances (OH-) in the sample. - CO3 2- The content of ).

[0227] Example 1

[0228] 3 mol / L M 1 A 1:1 molar ratio of source manganese sulfate aqueous solution and 3 mol / L sodium hydroxide aqueous solution (pH adjuster) was slowly added to a 500L reactor. The reactants occupied 1 / 3 of the reactor volume. The reaction was carried out at 60℃ with stirring at 600 rpm / min. Ammonia was added to adjust the pH to 11.2. Nitrogen gas was purged during this process to remove dissolved oxygen from the aqueous solution. The reaction was stopped after 60 hours when the volumetric particle size distribution (Dv50) of the material in the reactor reached 5 μm. At this point, the specific surface area of ​​the precursor was 12.5 m². 2 / g. The slurry in the reactor was transferred to a filter press for filtration and washing for 30 minutes. Then, the washed material was placed in a disc dryer and dried at 150°C for 30 hours to obtain the manganese hydroxide precursor.

[0229] Sodium hydroxide and manganese hydroxide precursors were added to a high-speed mixer at a sodium to manganese molar ratio of 2:1. Sodium fluoride was used as the fluorine source. The total mass of the mixed sodium hydroxide and manganese hydroxide precursors was 100%, and the sodium fluoride content was 1.5%. The high-speed mixer was operated at a low speed of 10Hz for 10 minutes and a high speed of 45Hz for 30 minutes. The mixture was considered uniform when no white spots were visually observed. The mixed material was transferred to a mullite crucible and sintered in a roller kiln under a sintering atmosphere of 90% oxygen and 10% air. The temperature was increased to 900℃ at a rate of 2℃ / min and sintered for 10 hours. After sintering, the material was coarsely crushed by roller crushers and then fed into an air jet mill to pulverize it into a particle size distribution (Dv50) of 5 μm, yielding the Na₂MnO₂F positive electrode active material.

[0230] Example 2

[0231] Except for the total mass of the mixture of sodium hydroxide and manganese hydroxide precursors being 100%, and the mass content of sodium fluoride as the fluorine source being 1%, the rest of the preparation process is the same as in Example 1.

[0232] Example 3

[0233] Except for the total mass of the mixture of sodium hydroxide and manganese hydroxide precursors being 100%, and the mass content of sodium fluoride as the fluorine source being 0.5%, the rest of the preparation process is the same as in Example 1.

[0234] Example 4

[0235] Except for the total mass of the mixture of sodium hydroxide and manganese hydroxide precursors being 100%, and the mass content of sodium fluoride as the fluorine source being 0.05%, the rest of the preparation process is the same as in Example 1.

[0236] Example 5

[0237] Except for the total mass of the mixture of sodium hydroxide and manganese hydroxide precursors being 100%, and the mass content of sodium fluoride as the fluorine source being 3%, the rest of the preparation process is the same as in Example 1.

[0238] Comparative Example 1

[0239] Except for the absence of a fluorine source in the preparation of the positive electrode active material, the rest of the preparation process is the same as in Example 1.

[0240] The test results of Examples 1-5 and Comparative Example 1 are shown in Table 1.

[0241] Table 1

[0242]

[0243] As shown in Table 1, the cycle performance of the battery cell is poor when the surface of the positive electrode active material does not contain fluorine. Adding fluorine can improve the structural stability of the positive electrode active material and improve the cycle performance of the battery cell.

[0244] Example 6

[0245] Except M 1 Except for the source being nickel carbonate, the rest of the preparation process is the same as in Example 1.

[0246] Example 7

[0247] Except M 1 The source is cobalt nitrate, M 2 The source is ZnO. Except for the addition amount of ZnO source according to the molar ratio of ZnO to cobalt nitrate of 1:9, the rest of the preparation process is the same as in Example 1.

[0248] The test results for Examples 1 and 6-7 are shown in Table 2.

[0249] Table 2

[0250]

[0251]

[0252] As can be seen from the test results in Table 2, M 1 Source and M 2 The initial discharge capacity, initial efficiency, and capacity retention rate after 30 cycles vary slightly depending on the type and amount of the source.

[0253] Example 8

[0254] Except for adjusting the pH of the mixed aqueous solution to 10 with ammonia, the preparation process was the same as in Example 1. The reaction time was 60 hours, and the reaction was stopped when the particle size distribution (Dv50) of the material in the reactor reached 4 μm. At this point, the specific surface area of ​​the precursor was 14.5 m². 2 / g.

[0255] Example 9

[0256] Except for adjusting the pH of the mixed aqueous solution to 13 with ammonia, the preparation process was the same as in Example 1. The reaction time was 60 hours, and the reaction was stopped when the particle size distribution (Dv50) of the material in the reactor reached 6 μm. At this point, the specific surface area of ​​the precursor was 11.5 m². 2 / g.

[0257] Comparative Example 2

[0258] Except for adjusting the pH of the mixed aqueous solution to 9 with ammonia, the preparation process was the same as in Example 1. The reaction time was 60 hours, and the reaction was stopped when the particle size distribution Dv50 of the material in the reactor reached 3.5 μm. At this point, the specific surface area of ​​the precursor was 15 m². 2 / g.

[0259] Comparative Example 3

[0260] Except for adjusting the pH of the mixed aqueous solution to 13.5 with ammonia, the preparation process was the same as in Example 1. The reaction time was 60 hours, and the reaction was stopped when the particle size distribution (Dv50) of the material in the reactor reached 6.5 μm. At this point, the specific surface area of ​​the precursor was 11 m². 2 / g.

[0261] The test results of Examples 1, 8-9 and Comparative Examples 2-3 are shown in Table 3.

[0262] Table 3

[0263]

[0264]

[0265] Examples 1, 8-9, and Comparative Examples 2-3 show that as the pH of the mixed aqueous solution increases, the volumetric particle size distribution (Dv50) of the precursor gradually increases, while the specific surface area gradually decreases. When the pH of the mixed solution is in the range of 10-13, the structural stability of the positive electrode active material can be improved, thereby enhancing the cycle performance of the battery cell.

[0266] Example 10

[0267] Except for heating to 930°C at a rate of 2°C / min and then sintering for 10 hours, the rest of the preparation process is the same as in Example 1.

[0268] Example 11

[0269] Except for heating to 1100℃ at a rate of 2℃ / min and then sintering for 10h, the rest of the preparation process is the same as in Example 1.

[0270] Example 12

[0271] Except for the sintering atmosphere being a mixture of 70% oxygen and 30% air, the rest of the preparation process is the same as in Example 1.

[0272] Example 13

[0273] Except for the sintering atmosphere being a mixture of 50% oxygen and 50% air, the rest of the preparation process is the same as in Example 1.

[0274] Example 14

[0275] Except for the sintering atmosphere being air, the rest of the preparation process is the same as in Example 1.

[0276] The test results for Examples 1, 10-14 are shown in Table 4.

[0277] Table 4

[0278]

[0279]

[0280] As shown in Table 4, the average particle size of the primary particles gradually increases with the increase of sintering temperature, and the initial discharge capacity, initial efficiency, and capacity retention rate after 30 cycles are slightly different.

[0281] The test results in Table 4 also show that as the oxygen content increases, the carbonate content on the surface of the positive electrode active material gradually decreases. By adjusting the oxygen content in the sintering atmosphere, the battery cell can have good cycle performance.

[0282] Although this disclosure has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this disclosure. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This disclosure is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, comprising a positive electrode sheet, characterized in that, The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, the positive electrode film layer comprising a positive electrode active material having the following chemical formula: Na x M 1 1-y M 2 y O2F, 2≤x≤2.5, 0≤y<0.4, M 1 Including Mn, Ni, Co and Fe One or more of them, M 2 Including one or more of Mg, Al, Ti, Zn, Zr, Cu, Nb, and W; The pH of the positive electrode active material is 10-13.

2. The battery cell according to claim 1, characterized in that, The content of free alkaline substances on the surface of the positive electrode active material is 0.5%-2%; The free alkaline substances include CO3. 2- and / or OH - .

3. The battery cell according to claim 1 or 2, characterized in that, The positive electrode active material has a secondary particle morphology formed by the aggregation of multiple primary particles.

4. The battery cell according to claim 3, characterized in that, The volumetric particle size distribution Dv50 of the positive electrode active material is 2-10 μm; and / or, The average particle size of the primary particles constituting the positive electrode active material is 1-3 μm.

5. The battery cell according to any one of claims 1-4, characterized in that, The positive electrode active material includes Na2MnO2F, Na2NiO2F, Na2CoO2F, Na2FeO2F, Na2Mn 0.9 Al 0.1 O2F, Na2Mn 0.9 Mg 0.1 O2F, Na2Mn 0.9 Ti 0.1 O2F, Na2Ni 0.9 Al 0.1 O2F, Na2Ni 0.9 Mg 0.1 O2F, Na2Ni 0.9 Ti 0.1 O2F, Na2Mn 0.9 Zn 0.1 O2F, Na2Mn 0.9 Zr 0.1 O2F, Na2Mn 0.9 Cu 0.1 O2F, Na2Mn 0.9 Nb 0.1 O2F, Na2Mn 0.9 W 0.1 O2F, Na2Ni 0.9 Zn 0.1 O2F, Na2Ni 0.9 Zr 0.1 O2F, Na2Ni 0.9 Cu 0.1 O2F, Na2Ni 0.9 Nb 0.1 O2F, Na2Ni 0.9 W 0.1 O2F, Na2Co 0.9 Zn 0.1 O2F, Na2Co 0.9 Zr 0.1 O2F, Na2Co 0.9 Cu 0.1 O2F, Na2Co 0.9 Nb 0.1 O2F, Na2Co 0.9 W 0.1 O2F, Na2Fe 0.9 Zn 0.1 O2F, Na2Fe0 .9 Zr 0.1 O2F, Na2Fe 0.9 Cu 0.1 O2F, Na2Fe 0.9 Nb 0.1 O2F and Na2Fe 0.9 W 0.1 One or more of O2F.

6. The battery cell according to any one of claims 1-5, characterized in that, The positive electrode active material is an O3-type layered oxide.

7. A method for preparing a positive electrode active material, comprising the following steps: Provides pH adjusters, M 1 Source and optional M 2 A mixed aqueous solution of the source, wherein the pH of the mixed aqueous solution is 10-13, wherein M 1 The source includes one or more of nickel, cobalt, manganese, and iron sources, wherein M 2 The source includes one or more of the following: copper source, magnesium source, aluminum source, titanium source, zinc source, zirconium source, niobium source, and tungsten source; The mixed aqueous solution was reacted to obtain the precursor; The obtained precursor was mixed with sodium and fluorine sources and then sintered to obtain the positive electrode active material.

8. The preparation method according to claim 7, characterized in that, In the step of reacting the mixed aqueous solution to obtain the precursor, the volumetric particle size distribution Dv50 of the obtained precursor is 4-12 μm; and / or, The specific surface area of ​​the obtained precursor is 10⁻¹⁶ m². 2 / g.

9. The preparation method according to claim 7 or 8, characterized in that, The step of mixing the obtained precursor with a sodium source and a fluorine source and then sintering it to obtain the positive electrode active material includes: the mixing ratio of the sodium source and the precursor is based on the ratio of Na to M in the precursor. 1 The elements are mixed in a molar ratio of (2-2.5):1; and / or, With the total mass of the sodium source and the precursor being 100%, the mass content of the fluorine source is 0.5%-1.7%.

10. The preparation method according to any one of claims 7-9, characterized in that, The pH adjuster includes one or more of ammonia, sodium hydroxide, sodium carbonate, sodium bicarbonate, sodium oxalate, and sodium acetate.

11. The preparation method according to any one of claims 7-10, characterized in that, The manganese source includes one or more of manganese sulfate, manganese oxalate, manganese acetate, and manganese chloride.

12. The preparation method according to any one of claims 7-11, characterized in that, The step of reacting the mixed aqueous solution to obtain the precursor satisfies one or more of the following conditions (1)-(4): (1) The reaction time is 50-70 hours; (2) The reaction temperature is 40-70℃; (3) The stirring speed of the reaction is 500-1500 r / min; (4) The reaction is carried out under a protective gas atmosphere.

13. The preparation method according to any one of claims 7-12, characterized in that, The step of reacting the mixed aqueous solution to obtain the precursor further includes: filtering and drying the precursor obtained from the reaction, wherein the drying process satisfies one or more of the following conditions (1)-(3): (1) The drying temperature is 90-160℃; (2) The drying process takes 6-30 hours; (3) The moisture content in the dried precursor is 0.1%-0.2%.

14. The preparation method according to any one of claims 7-13, characterized in that, The sodium source includes one or more of sodium hydroxide, sodium carbonate, sodium bicarbonate, sodium acetate, and sodium oxalate; and / or, The fluorine source includes one or more of fluorine-containing inorganic salts and fluorine-containing organic compounds.

15. The preparation method according to claim 14, characterized in that, The fluorine-containing inorganic salt includes one or more of sodium fluoride, ammonium fluoride, potassium fluoride, and calcium fluoride; and / or, The fluorinated organic compounds include one or more of polyvinylidene fluoride and polytetrafluoroethylene.

16. The preparation method according to any one of claims 7-15, characterized in that, In the step of sintering the obtained precursor with sodium and fluorine sources to obtain the positive electrode active material, the sintering process satisfies one or more of the following conditions (1)-(5): (1) The sintering temperature is 800-1000℃; (2) The holding time for the sintering treatment is 10-14 hours; (3) The heating rate of the sintering treatment is 1-10℃ / min; (4) The pressure of the sintering treatment is 0-20 Pa; (5) The atmosphere for the sintering process is an oxygen-containing atmosphere.

17. A positive electrode active material, characterized in that, It is prepared by the preparation method according to any one of claims 7-16.

18. A battery device, characterized in that, Includes the battery cell described in any one of claims 1-6.

19. An electrical appliance, characterized in that, Includes the battery device as described in claim 18.

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