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

Abstract

The invention discloses a positive active material and a preparation method thereof, a positive pole piece, a battery and an electric device. The positive electrode active material comprises a layered transition metal oxide, the layered transition metal oxide comprises a first phase, the positive electrode active material comprises a main strong peak and a secondary strong peak in an area with a 2 theta angle of 15-18 degrees in an X-ray diffraction pattern obtained by taking a CuK alpha ray as a radiation source, the main strong peak corresponds to the first phase, and the secondary strong peak corresponds to the second phase. The ratio of the peak intensity of the main strong peak to the peak intensity of the secondary strong peak is greater than or equal to 9, and the Dv50 particle size of the positive electrode active material is greater than or equal to 30 microns. The positive electrode active material is relatively pure in phase state and relatively large in particle size, so that side reaction between the positive electrode active material and an electrolyte is reduced, and gas production of a battery cell is inhibited.

Description

Technical Field

[0001] The present application belongs to the field of battery technology, and specifically relates to positive electrode active materials and preparation methods thereof, positive electrode sheets, batteries and electrical devices. Background Art

[0002] Secondary batteries are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but are also widely used in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. With the development of today's society, people's requirements for batteries are becoming increasingly higher.

[0003] Public content

[0004] In view of the technical problems existing in the background technology, the present application provides a positive electrode active material, which aims to reduce its side reactions with the electrolyte and inhibit gas production in the battery cell.

[0005] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a positive electrode active material, which includes a layered transition metal oxide, wherein the layered transition metal oxide includes a first phase, and the positive electrode active material includes a main strong peak and a secondary strong peak in the region of 2θ angle of 15° to 18° in the X-ray diffraction pattern obtained with CuKα rays as the radiation source, wherein the main strong peak corresponds to the first phase, the ratio of the peak intensity of the main strong peak to the peak intensity of the secondary strong peak is ≥9, and the Dv50 particle size of the positive electrode active material is ≥30μm.

[0006] The positive electrode active material of the first aspect of the present application has at least the following beneficial effects: the particles of the positive electrode active material have a relatively large particle size, which can effectively reduce the specific surface area in contact with the electrolyte, thereby reducing the side reaction between the layered transition metal oxide and the electrolyte and suppressing gas production in the battery cell; and, by ensuring that the peak intensity ratio of the main strong peak to the secondary strong peak in the XRD spectrum of the positive electrode active material meets the given conditions, the positive electrode active material can be phase-pure, which can reduce the risk of increased side reactions or the risk of affecting the performance of the positive electrode active material due to the introduction of excessive impurities or impurities. Thus, the side reaction between the positive electrode active material and the electrolyte can be effectively reduced, and gas production in the battery cell can be suppressed.

[0007] In some embodiments of the present application, the 2θ angle of the main strong peak is 16° to 16.5°.

[0008] In some embodiments of the present application, the layered transition metal oxide comprises alternating sodium ion layers and transition metal layers, with the interlayer spacing between two adjacent transition metal layers perpendicular to the (001) crystal plane being 0.530 nm to 0.545 nm. This allows for both high specific capacity and initial charge capacity while suppressing gassing in the battery cell.

[0009] In some embodiments of the present application, the first phase includes an O3 phase, which is beneficial for further improving the energy density of the battery.

[0010] In some embodiments of the present application, the ratio of the peak intensity of the main strong peak to the peak intensity of the secondary strong peak is ≥ 12. This can further make the phase state of the positive electrode active material purer.

[0011] In some embodiments of the present application, the Dv50 particle size of the positive electrode active material is 50 μm to 100 μm, which is beneficial for further suppressing gas generation in the battery cell.

[0012] In some embodiments of the present application, the layered transition metal oxide includes: Na x Mn a M1 b1 O 2-e+δ F e , 0.8≤x≤1.2, a+b1=1, a>0, b1>0, 0≤e≤0.2, -0.1≤δ≤0.1, M1 contains one or more of the following elements: Li, B, Mg, Al, Si, K, Ca, Ti, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Nb, Mo, In, Sn, Sb, La, Ce, Ta, W, Bi. This is conducive to achieving a high specific capacity of the positive electrode active material, a high first coulombic efficiency, and low cell gassing.

[0013] In some embodiments of the present application, the layered transition metal oxide includes: Na x Mn a Ni c Fe d M2 b2 O 2-e+δ F e , 0.8≤x≤1.2, a+c+d+b2=1, a≥0.3, c≥0.2, d≥0.2, 0≤b2≤0.2, 0≤e≤0.1, -0.1≤δ≤0.1, M2 contains one or more of the following elements: Li, B, Mg, Al, Si, K, Ca, Ti, Co, Cu, Zn, Ga, Y, Zr, Nb, Mo, In, Sn, Sb, La, Ce, Ta, W, Bi. This helps to balance the specific capacity and cycle stability of the positive electrode active material while suppressing gassing of the battery cell.

[0014] A second aspect of the present application provides a method for preparing a positive electrode active material, comprising:

[0015] mixing a first alkali metal source and a transition metal source and performing a first calcination;

[0016] mixing a second alkali metal source with the first calcined product and performing a second calcination to obtain a positive electrode active material,

[0017] The alkali metal elements in the first alkali metal source and the second alkali metal source are the same; the positive electrode active material includes a layered transition metal oxide, the layered transition metal oxide includes a first phase, and the positive electrode active material includes a main strong peak and a secondary strong peak in the region of 2θ angle of 15° to 18° in an X-ray diffraction pattern obtained using CuKα rays as a radiation source, the main strong peak corresponds to the first phase, the ratio of the peak intensity of the main strong peak to the peak intensity of the secondary strong peak is ≥9, and the Dv50 particle size of the positive electrode active material is ≥30μm.

[0018] The method for preparing a positive electrode active material according to the second aspect of the present application has the following beneficial effects: not only is it highly universal, but it is also advantageous for obtaining a positive electrode active material whose Dv50 particle size and phase state meet the requirements of a given range without adding a nucleating additive or flux. The particle size of the positive electrode active material is relatively large, which can effectively reduce its specific surface area in contact with the electrolyte, thereby reducing the side reaction between the layered transition metal oxide and the electrolyte and suppressing gas production in the battery cell. Moreover, the peak intensity ratio of the main strong peak and the secondary strong peak in the XRD spectrum of the positive electrode active material meets the given conditions, and can also reduce the risk of increased side reactions or the risk of affecting the performance of the positive electrode active material due to the introduction of too many miscellaneous phases or impurities. Thus, the side reaction between the positive electrode active material and the electrolyte can be effectively reduced, and gas production in the battery cell can be suppressed.

[0019] In some embodiments of the present application, the first alkali metal source and the second alkali metal source each independently include a sodium source.

[0020] In some embodiments of the present application, the first calcination satisfies at least one of the following conditions: the calcination temperature is 1100° C. to 1400° C., the time is 10 h to 30 h, and the calcination atmosphere is an oxygen-containing atmosphere.

[0021] In some embodiments of the present application, the temperature of the first calcination is 1150° C. to 1300° C. This can further reduce the loss of alkali metal elements in the layered transition metal oxide phase during the first calcination process while obtaining a large-particle positive electrode active material.

[0022] In some embodiments of the present application, the second calcination satisfies at least one of the following conditions: a calcination temperature of 700°C to 1000°C, a calcination time of 5 hours to 30 hours, and an oxygen-containing atmosphere. This reduces energy consumption while maintaining a large particle size and primary phase structure, compensating for the loss of alkali metal elements in the layered transition metal oxide bulk phase and improving phase purity.

[0023] In some embodiments of the present application, the layered transition metal oxide includes Nax Mn a M1 b1 O 2-e+δ F e , 0.8≤x≤1, a+b1=1, a>0, b1>0, 0≤e≤0.2, -0.1≤δ≤0.1, M1 comprises one or more of the following elements: Li, B, Mg, Al, Si, K, Ca, Ti, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Nb, Mo, In, Sn, Sb, La, Ce, Ta, W, Bi, wherein: based on the total molar number of Mn and M1, the relative molar amount of sodium in the first alkali metal source is 1.05 mol to 1.2 mol; and / or the relative molar amount of sodium in the second alkali metal source is 0.05 mol to 0.25 mol.

[0024] In some embodiments of the present application, the layered transition metal oxide includes Na x Mn a Ni c Fe d M2 b2 O 2-e+δ F e , 0.8≤x≤1, a+c+d+b2=1, a≥0.3, c≥0.2, d≥0.2, 0≤b2≤0.2, 0≤e≤0.1, -0.1≤δ≤0.1, M2 comprises one or more of the following elements: Li, B, Mg, Al, Si, K, Ca, Ti, Co, Cu, Zn, Ga, Y, Zr, Nb, Mo, In, Sn, Sb, La, Ce, Ta, W, Bi, wherein: based on the total molar number of Mn, Ni, Fe, and M2, the relative molar amount of sodium in the first alkali metal source is 1.05 mol to 1.2 mol; and / or the relative molar amount of sodium in the second alkali metal source is 0.05 mol to 0.25 mol.

[0025] The third aspect of the present application provides a positive electrode plate, which includes: the positive electrode active material of the first aspect of the present application, and / or the positive electrode active material prepared by the method of the second aspect of the present application.

[0026] The fourth aspect of the present application provides a battery, which includes: the positive electrode plate of the third aspect of the present application.

[0027] The fifth aspect of the present application provides an electrical device, which includes: the battery described in the fourth aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0029] Figure 1 It is a schematic structural diagram of a battery according to one embodiment of the present application.

[0030] Figure 2 It is a schematic structural diagram of a battery module according to one embodiment of the present application.

[0031] Figure 3 It is a schematic structural diagram of a battery pack according to one embodiment of the present application.

[0032] Figure 4 yes Figure 3 Exploded diagram of .

[0033] Figure 5 It is a schematic diagram of an embodiment of an electrical device using a battery as a power source of the present application.

[0034] Figure 6 This is the X-ray diffraction pattern of the positive electrode active material prepared in Example 1 of the present application.

[0035] Figure 7 This is the X-ray diffraction pattern of the positive electrode active material prepared in Comparative Example 1 of the present application.

[0036] Description of reference numerals:

[0037] 1: Battery; 2: Battery module; 3: Battery pack; 4: Upper case; 5: Lower case. DETAILED DESCRIPTION

[0038] The present application will be further described below in conjunction with specific embodiments. It should be understood that these specific embodiments are only used to illustrate the present application and are not used to limit the scope of the present application.

[0039] References to "embodiments" in this application mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described in this application may be combined with other embodiments.

[0040] " Scope " disclosed in the present application is limited in the form of lower limit and / or upper limit, and given range is limited by selecting a lower limit and / or an upper limit, and the selected lower limit and / or the rear upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form the scope of not clearly recording, and any lower limit can be combined with other lower limits to form the scope of not clearly recording, and any upper limit can be combined with any other upper limit to form the scope of not clearly recording. In addition, each separately disclosed point or single numerical value itself can be used as lower limit or upper limit and any other point or single numerical value combination or with other lower limit or upper limit combination to form the scope of not clearly recording.

[0041] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0042] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of this application.

[0043] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps S1 and S2, which means that the method may include steps S1 and S2 performed sequentially, or may include steps S2 and S1 performed sequentially. For example, the method may further include step S3, which means that step S3 may be added to the method in any order, for example, the method may include steps S1, S2, and S3, or may include steps S1, S3, and S2, or may include steps S3, S1, and S2, etc.

[0044] Unless otherwise specified, the term "and / or" in this application simply describes an association between related objects, indicating that three possible relationships exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Furthermore, the character " / " in this document generally indicates that the related objects are in an "or" relationship.

[0045] In this application, the terms "plurality" and "multiple" refer to two or more.

[0046] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used in this application are for the purpose of describing specific embodiments only and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and any variations thereof are intended to cover non-exclusive inclusions. Unless otherwise specified, the terms used in this application have the well-known meanings commonly understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the examples of this application).

[0047] With the continuous advancement of green environmental protection, the application of batteries has penetrated into all aspects of life, including vehicles, electronic equipment, energy storage devices, etc. However, as the application of batteries continues to expand, people's requirements for batteries are also getting higher and higher. Taking sodium-ion batteries as an example, sodium-ion batteries currently used as secondary batteries mainly rely on the movement of sodium ions between the positive and negative electrodes to work. Commonly used positive electrode active materials for sodium-ion batteries include sodium-ion layered transition metal oxides. Among them, sodium-ion layered transition metal oxides have strong surface activity under high voltage and are prone to side reactions with the electrolyte to produce a large amount of gas, causing the internal gas pressure of the battery cell to increase, affecting the normal operation of the battery cell.

[0048] To address the above issues, the present application proposes a positive electrode active material comprising a layered transition metal oxide, the layered transition metal oxide comprising a first phase. In an X-ray diffraction pattern obtained using CuKα radiation as a radiation source, the positive electrode active material includes a primary peak and a secondary peak in the 2θ angle region of 15° to 18°, wherein the primary peak corresponds to the first phase, and the ratio of the peak intensity of the primary peak to the peak intensity of the secondary peak is ≥9. The positive electrode active material has a Dv50 particle size ≥30μm. The positive electrode active material has a relatively pure phase and a large particle size, which helps reduce side reactions with the electrolyte and thereby suppress gas production in the battery cell.

[0049] The positive electrode active material disclosed in the embodiments of the present application is suitable for secondary batteries, and the battery disclosed in the embodiments of the present application can be used in electrical devices that use batteries as power sources or various energy storage systems that use batteries as energy storage elements. Electrical devices may include but are not limited to mobile phones, tablets, laptops, electric toys, power tools, battery cars, electric cars, ships, spacecraft, etc. Among them, electric toys may include fixed or mobile electric toys, for example, game consoles, electric car toys, electric ship toys and electric airplane toys, etc., and spacecraft may include airplanes, rockets, space shuttles and spacecraft, etc.

[0050] The first aspect of the present application provides a positive electrode active material, which includes a layered transition metal oxide, the layered transition metal oxide includes a first phase, and the positive electrode active material includes a main strong peak and a secondary strong peak in the region of 2θ angle of 15° to 18° in an X-ray diffraction pattern obtained using CuKα rays as a radiation source, the main strong peak corresponds to the first phase, the ratio of the peak intensity of the main strong peak to the peak intensity of the secondary strong peak is ≥9, and the Dv50 particle size of the positive electrode active material is ≥30μm.

[0051] For example, in the X-ray diffraction (XRD) pattern of the positive electrode active material, the ratio of the peak intensity of the main strong peak to the peak intensity of the secondary strong peak can be ≥9, ≥10, ≥12, ≥13, ≥15, ≥20, etc.; the Dv50 particle size of the positive electrode active material can be 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, 70μm, 80μm, 70μm, 100μm, etc., or can be a range consisting of any of the above values. Wherein, D v The 50 particle size refers to the particle size corresponding to the cumulative volume distribution percentage reaching 50%. The elemental composition, XRD analysis, and Dv50 particle size of the positive electrode active material can all be obtained using conventional methods and instruments in the art. Considering that side reactions of the positive electrode active material are concentrated on the surface of its particles and layered transition metal oxide, the specific surface area of ​​the positive electrode active material can be reduced by increasing its particle size, thereby reducing its contact area with the electrolyte. However, the current method of increasing the size of metal oxide particles is usually to add nucleating additives or co-solvents, which easily introduce elements or components that have a negative effect on the performance of the positive electrode active material. By simultaneously controlling the phase purity and particle size of the positive electrode active material, the specific surface area of ​​the positive electrode active material can be reduced, reducing its contact area with the electrolyte, thereby effectively reducing the potential side reactions between the layered transition metal oxide and the electrolyte, and also reducing the risk of increased side reactions or the risk of affecting the performance of the positive electrode active material due to the introduction of excessive impurities. This can effectively suppress gassing in the battery cell.

[0052] The positive electrode active material of the first aspect of the present application has at least the following beneficial effects: the particles of the positive electrode active material have a relatively large particle size, which can effectively reduce the specific surface area in contact with the electrolyte, thereby reducing the side reaction between the layered transition metal oxide and the electrolyte and suppressing gas production in the battery cell; and, by ensuring that the peak intensity ratio of the main strong peak to the secondary strong peak in the XRD spectrum of the positive electrode active material meets the given conditions, the positive electrode active material can be phase-pure, which can reduce the risk of increased side reactions or the risk of affecting the performance of the positive electrode active material due to the introduction of excessive impurities or impurities. Thus, the side reaction between the positive electrode active material and the electrolyte can be effectively reduced, and gas production in the battery cell can be suppressed.

[0053] In some embodiments, the analysis method of the elemental composition of the positive electrode active material may include, but is not limited to, one or more of X-ray photoelectron spectroscopy analysis (XPS), EDS energy spectrum analysis, inductively coupled plasma emission spectrometry (ICP) testing, etc. For example, the ICP test can refer to EPA6010D-2014 "Inductively Coupled Plasma Atomic Emission Spectrometry". After the sample to be tested is chemically treated and digested into a solution, it is atomized into a plasma and excited to produce characteristic spectral lines of the elements. The element content is qualitatively and quantitatively analyzed based on the wavelength and intensity of the spectral lines (which are proportional to the concentration).

[0054] In some embodiments, when performing XRD testing on the positive electrode active material, the following method can be used: CuKα radiation is used as the radiation source, and the radiation wavelength is The scanning 2θ angle range can be 5° to 60°, and the scanning rate can be 4° / min. The peak intensity ratio of the main strong peak and the secondary strong peak is judged based on the diffraction peaks in the obtained XRD spectrum, and the matching relationship between the phase corresponding to the main strong peak and the layered transition metal oxide is judged in combination with the standard card. In addition, the elemental composition of the phase in the positive electrode active material can also be obtained by ion polishing the cross-section of the sample to be tested and performing elemental analysis on the particles of different phases.

[0055] In some embodiments, the D of the positive electrode active material v The particle size can be determined using a laser particle size analyzer (Malvern Master Size 2000) in accordance with the GB / T 19077-2016 / ISO 13320:2009 standard. The specific testing process includes taking an appropriate amount of the sample to be tested (ensuring a sample concentration of 8%-12% obscuration), adding 20ml of deionized water, and ultrasonicating for 5 minutes (53KHz / 120W) to ensure complete dispersion of the sample. The sample is then measured in accordance with the GB / T 19077-2016 / ISO 13320:2009 standard.

[0056] Furthermore, the positive electrode active material of the first aspect of the present application may optionally satisfy one or more of the following conditions in addition to satisfying the above conditions.

[0057] In some embodiments of the present application, the 2θ angle of the main peak is 16-16.5°. This indicates that the bulk phase of the resulting positive electrode active material has a high alkali metal content and a high specific charge capacity. For example, the 2θ angle of the main peak corresponds to a high sodium content in the bulk phase of the sodium-ion layered transition metal oxide within a given range.

[0058] In some embodiments of the present application, the layered transition metal oxide may include alternating sodium ion layers and transition metal layers, and the interlayer spacing between two adjacent transition metal layers in a direction perpendicular to the (001) crystal plane may be 0.530 nm to 0.545 nm.

[0059] Exemplarily, the interlayer spacing between two adjacent transition metal layers in the direction perpendicular to the (001) crystal plane can be 0.530nm, 0.532nm, 0.534nm, 0.536nm, 0.538nm, 0.540nm, 0.542nm, 0.544nm, 0.545nm, etc., or can be a range consisting of any of the above values. The interlayer spacing can also be obtained by XRD testing. After performing XRD testing on the positive electrode active material, the interlayer spacing of the selected crystal plane can be obtained by the angle corresponding to the selected crystal plane, according to the Bragg equation 2d·sinθ=λ, and each unit cell of the selected crystal plane contains three transition metal layers, and then the interlayer spacing of the two adjacent transition metal layers in the corresponding phase in the direction perpendicular to the (001) crystal plane is obtained. The interlayer spacing of sodium ion layered transition metal oxides is related to their sodium content. In the positive electrode active material, the content of layered transition metal oxides is relatively high, and the layered transition metal oxides whose interlayer spacing meets the given range also have a relatively high initial sodium content. This can make the positive electrode active material have a higher specific capacity and first charge capacity. Using it in positive electrode sheets and batteries is conducive to exerting higher capacity and improving the energy density of the battery.

[0060] In some embodiments of the present application, the first phase may include an O3 phase. In sodium-ion batteries, the initial sodium content and specific capacity of layered transition metal oxides in the O3 phase are relatively high. Using the O3 phase as the primary phase of the positive electrode active material can further improve the battery's energy density. The presence of the O3 phase can also be confirmed by XRD characterization.

[0061] In some embodiments, in a sodium ion battery, the layered transition metal oxide may include sodium manganese oxide, and the first phase of the sodium manganese oxide may include an O 3 phase.

[0062] In some embodiments of the present application, the ratio of the peak intensity of the main strong peak to the peak intensity of the secondary strong peak can be ≥12, thereby further making the phase state of the positive electrode active material purer, thereby further reducing the risk of increased side reactions due to impurities or the risk of affecting the performance of the positive electrode active material. On this basis, the interlayer spacing between two adjacent transition metal layers in the layered transition metal oxide in the direction perpendicular to the (001) crystal plane can be 0.530nm to 0.545nm, and / or the first phase can be an O3 phase, thereby further taking into account the specific capacity of the positive electrode active material on the basis of suppressing gas production of the battery cell, thereby improving the energy density of the battery.

[0063] In some embodiments of the present application, the Dv50 particle size of the positive electrode active material may be 50 μm to 100 μm. For example, it may be 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, etc. This helps to further reduce the specific surface area of ​​the positive electrode active material, reduce the side reactions that may occur when the layered transition metal oxide contacts the electrolyte, and further help to suppress gassing of the battery cell.

[0064] In some embodiments of the present application, the layered transition metal oxide may include: Na x Mn a M1 b1 O 2-e+δ F e , 0.8≤x≤1.2, a+b1=1, a>0, b1>0, 0≤e≤0.2, -0.1≤δ≤0.1, M1 contains one or more of the following elements: Li, B, Mg, Al, Si, K, Ca, Ti, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Nb, Mo, In, Sn, Sb, La, Ce, Ta, W, Bi.

[0065] For example, the value of x can be 0.8, 0.85, 0.9, 0.95, 1, 1.05, 1.1, 1.15, 1.2, etc.; the value of a can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.95, etc.; the value of b1 can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.95, etc.; the value of δ can be -0.1, -0.08, -0.05, -0.02, 0, 0.02, 0.05, 0.08, 0.1, etc.; the value of e can be 0.01, 0.02, 0.05, 0.08, 0.1, 0.12, 0.15, 0.18, 0.2, etc. Among them, Na can be analyzed by ICP test and EDS analysis of electron microscope. x Mn a M1 b1 O 2-e+δ F e The elemental composition of Na x Mn a M1 b1 O 2-e+δ F eThe sodium ion content in the cathode is relatively high, and the interlayer spacing is small. The content of the phase that meets the range of 0.530nm to 0.545nm is relatively high. Controlling the content of each element to meet the given range is beneficial to taking into account the high specific capacity, high first coulomb efficiency and low gas production of the positive electrode active material. Optionally, M1 can include Ni and / or Fe. Fe and Ni are active metal elements, which are beneficial to provide charge compensation in the process of sodium insertion and extraction, further increasing Na x Mn a M1 b1 O 2-e+δ F e The specific capacity of the battery is improved, thereby increasing the energy density of the battery.

[0066] In some embodiments of the present application, the layered transition metal oxide may include: Na x Mn a Ni c Fe d M2 b2 O 2-e+δ F e , 0.8≤x≤1.2, a+c+d+b2=1, a≥0.3, c≥0.2, d≥0.2, 0≤b2≤0.2, 0≤e≤0.1, -0.1≤δ≤0.1, M2 contains one or more of the following elements: Li, B, Mg, Al, Si, K, Ca, Ti, Co, Cu, Zn, Ga, Y, Zr, Nb, Mo, In, Sn, Sb, La, Ce, Ta, W, Bi.

[0067] For example, the value of a can be 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, etc.; the value of c can be 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, etc.; the value of d can be 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, etc.; the value of e can be 0.01, 0.02, 0.05, 0.08, 0.1, etc. Optionally, the values ​​of c and d can be independently 0.2 to 0.35. By further doping Fe and Ni and controlling the element contents of Fe, Ni and Mn to meet the given range, Fe and Ni can be used to further provide charge compensation in the process of sodium insertion and extraction, and increase Na x Mn a Ni c Fe d M2 b2 O 2-e+δ F eThe specific capacity is improved, and the risk of loss or side reaction of Fe and Ni due to the easy activation of adjacent oxygen is reduced, while taking into account the cycle stability of the positive electrode active material. In addition, controlling the fluorine doping amount to meet the given range is also beneficial to reduce the risk of impurity phase formation when the fluorine doping amount is high, resulting in a decrease in specific capacity. Therefore, by controlling the Na x Mn a Ni c Fe d M2 b2 O 2-e+δ F e The content of each element in the positive electrode satisfies the given range, which is beneficial to further improve the specific capacity and cycle stability of the positive electrode active material.

[0068] It should be noted that in the positive electrode sheet, battery or electrical device, as the battery undergoes processes such as formation and circulation, sodium ions will be consumed, so the measured sodium content x in the positive electrode active material will be less than 1; in addition, the battery will be accompanied by the deintercalation and consumption of Na during the charge and discharge process, and the molar content of Na is different when the battery is discharged to different states. In the enumeration of positive electrode active materials in this application, the molar content of Na is the initial state of the material, that is, the state before feeding. The positive electrode active material is used in the battery system, and the molar content of Na will change after the charge and discharge cycle. In addition, during the preparation process of the positive electrode active material, due to different control of the process such as oxygen content or factors such as lattice oxygen release, the oxygen content will also vary. In the enumeration of positive electrode active materials in this application, the molar content of oxygen is only a theoretical state value, and the actual molar content of oxygen will fluctuate.

[0069] In some embodiments of the present application, Na x Mn a M1 b1 O 2-e+δ F e The interlayer spacing between two adjacent transition metal layers in the direction perpendicular to the (001) crystal plane can be 0.530nm to 0.545nm, and the first phase can be an O3 phase; or, Na x Mn a Ni c Fe d M2 b2 O 2-e+δ F e The interlayer spacing between two adjacent transition metal layers in the direction perpendicular to the (001) crystal plane can be 0.530nm to 0.545nm, and the first phase can be an O3 phase. This can suppress gas production in the battery cell while further increasing the specific capacity of the positive electrode active material.

[0070] In some embodiments of the present application, the pH value of the positive electrode active material may be ≤12.5. The pH value can be tested by the following method: take 2g of the positive electrode active material sample and place it in a beaker, add 18mL of deionized water and stir vigorously for 1 minute, let it stand for 30 minutes, and then test the pH of the supernatant with a pH meter. When the positive electrode active material meets the given conditions, gel is not easily formed during the coating process when preparing the positive electrode sheet, which is further conducive to the utilization of its specific capacity.

[0071] Based on the same inventive concept, in order to obtain the positive electrode active material with a relatively pure phase and large particle size according to the first aspect of the present application, a method for preparing the positive electrode active material is also proposed:

[0072] At present, when preparing large-particle metal oxides, it is usually achieved by adding nucleating additives or fluxes. When this method is used to prepare positive electrode active materials, it is very easy to introduce elements or components that have a negative effect on the performance of the positive electrode active materials, and the universality is poor. In order to reduce the impurities and foreign phases introduced during the preparation process, it is expected to obtain positive electrode active materials with a relatively pure phase and a larger particle size without adding nucleating additives or fluxes. Generally, layered transition metal oxides can be obtained by mixing and calcining an alkali metal source and a transition metal source. In attempts to increase the particle size of the positive electrode active material by regulating the calcination temperature, although the particle size of the positive electrode active material becomes larger after increasing the calcination temperature, the loss of the bulk alkali metal element is relatively serious, which not only easily produces foreign phases, but also easily leads to a significant decrease in the specific capacity of the positive electrode active material.

[0073] To address this problem, the present application solves this problem by mixing an alkali metal source and a transition metal source, calcining them, and then adding an alkali metal source and calcining them again. Specifically, a first alkali metal source and a transition metal source are mixed and calcined for a first time; a second alkali metal source is mixed with the first calcined product and calcined for a second time to obtain a positive electrode active material that meets the range given in the first aspect of the present application, wherein the alkali metal elements in the first alkali metal source and the second alkali metal source are the same. In this method, the particle size of the positive electrode active material can be regulated by the first calcination, and the loss of the bulk alkali metal element during the first calcination process can be compensated by the second calcination, thereby facilitating the production of a positive electrode active material whose Dv50 particle size and phase state both meet the given range without adding nucleating additives or fluxes.

[0074] That is, the second aspect of the present application provides a method for preparing a positive electrode active material, which comprises:

[0075] mixing a first alkali metal source and a transition metal source and performing a first calcination;

[0076] mixing a second alkali metal source with the first calcined product and performing a second calcination to obtain a positive electrode active material,

[0077] The alkali metal elements in the first alkali metal source and the second alkali metal source are the same; the positive electrode active material includes a layered transition metal oxide, the layered transition metal oxide includes at least a first phase, and the positive electrode active material has a main strong peak and a secondary strong peak in the region of 2θ angle of 15° to 18° in an X-ray diffraction pattern obtained using CuKα rays as a radiation source, the main strong peak corresponds to the first phase, the ratio of the peak intensity of the main strong peak to the peak intensity of the secondary strong peak is ≥9, and the Dv50 particle size of the positive electrode active material is ≥30μm.

[0078] In this method, the purpose of the first calcination is mainly to form a layered transition metal oxide whose particle size meets the requirements of the given range, and the purpose of the second calcination is mainly to increase the content of bulk alkali metal elements in the layered transition metal oxide while maintaining a large particle size, so as to make up for the loss of alkali metal elements in the first calcination process. As the content of bulk alkali metal elements in the layered transition metal oxide increases, it is also beneficial to reduce the interlayer spacing between two adjacent transition metal element layers in the layered transition metal oxide, and to improve the specific capacity and phase purity of the layered transition metal oxide, which is beneficial to obtain a positive electrode active material whose Dv50 particle size and phase state meet the given range without adding nucleating additives or fluxes.

[0079] The method for preparing a positive electrode active material according to the second aspect of the present application has the following beneficial effects: the method is not only highly universal, but also advantageously allows for obtaining a positive electrode active material whose Dv50 particle size and phase state meet the requirements of a given range without adding a nucleating additive or flux. The particle size of the positive electrode active material is relatively large, which can effectively reduce its specific surface area in contact with the electrolyte, thereby reducing the side reaction between the layered transition metal oxide and the electrolyte and suppressing gas production in the battery cell. Furthermore, the peak intensity ratio of the main strong peak and the secondary strong peak in the XRD spectrum of the positive electrode active material satisfies the given conditions, and can also reduce the risk of increased side reactions or the risk of affecting the performance of the positive electrode active material due to the introduction of too many miscellaneous phases or impurities. Thus, the side reaction between the positive electrode active material and the electrolyte can be effectively reduced, and gas production in the battery cell can be suppressed.

[0080] It is understandable that the first alkali metal source and the second alkali metal source may be the same or different, as long as the two can provide the same type of alkali metal elements. Exemplarily, taking the first alkali metal source and the second alkali metal source as sodium sources, the sodium sources used in the first calcination and the second calcination may be NaOH or Na2CO3, or the sodium source used in the first calcination may be NaOH, and the sodium source used in the second calcination may be Na2CO3. In addition, the types and ratios of the first alkali metal source, the second alkali metal source, and the transition metal element source can be flexibly selected according to the composition of the expected positive electrode active material to be obtained, and are not particularly limited here. Exemplarily, the first alkali metal source, the second alkali metal source, and the transition metal element source can be independently distributed and include but are not limited to one or more of hydroxides, carbonates, bicarbonates, halides, oxides, metals, etc.

[0081] In some embodiments of the present application, the temperature of the second calcination can be lower than the temperature of the first calcination, which is not only easy to operate and has low energy consumption, but also can compensate for the loss of alkali metal elements in the layered transition metal oxide phase and improve the phase purity while maintaining large particle size and main phase structure.

[0082] In some embodiments of the present application, the first alkali metal source and the second alkali metal source may each independently include a sodium source. The sodium source may include, but is not limited to, one or more common sodium sources such as sodium hydroxide, sodium halide, sodium salt, sodium oxide, and sodium metal, and may include, but is not limited to, one or more of NaOH, NaF, NaCl, NaBr, NaI, NaHCO3, Na2CO3, Na2O2, Na2O, and Na. The positive electrode active material prepared using a sodium source as the alkali metal source can be used in sodium ion batteries.

[0083] In some embodiments of the present application, the first calcination may satisfy at least one of the following conditions: the calcination temperature may be 1100° C. to 1400° C., the time may be 10 h to 30 h, and the calcination atmosphere may be an oxygen-containing atmosphere.

[0084] For example, in the first calcination, the calcination temperature can be 1100°C, 1150°C, 1200°C, 1250°C, 1300°C, 1350°C, 1400°C, etc.; the calcination time can be 10h, 12h, 15h, 18h, 20h, 22h, 25h, 28h, 30h, etc.; the calcination atmosphere can include but is not limited to air atmosphere, oxygen atmosphere, a mixed atmosphere of oxygen and nitrogen or an inert gas, etc., and air atmosphere can be selected. Increasing the calcination temperature or extending the calcination time are both beneficial to increasing the particle size of the calcined product. By controlling the conditions of the first calcination to meet the given range, it is beneficial to obtain a layered transition metal oxide with a Dv50 particle size of more than 30μm, and it is also beneficial for the layered transition metal oxide to form an O3 phase. At the same time, it is also beneficial to take into account the calcination efficiency and reduce the loss of alkali metal elements in the layered transition metal oxide phase during the first calcination process.

[0085] In some embodiments of the present application, the temperature of the first calcination can be 1150°C to 1300°C, for example, 1150°C to 1250°C, thereby further reducing the loss of alkali metal elements in the layered transition metal oxide phase during the first calcination process on the basis of obtaining a large-particle positive electrode active material.

[0086] In some embodiments of the present application, the second calcination may satisfy at least one of the following conditions: the calcination temperature may be 700° C. to 1000° C., the time may be 5 h to 30 h, and the calcination atmosphere may be an oxygen-containing atmosphere.

[0087] For example, in the second calcination, the calcination temperature can be 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C, etc.; the calcination time can be 5 hours, 10 hours, 12 hours, 15 hours, 18 hours, 20 hours, 22 hours, 25 hours, 28 hours, 30 hours, etc.; the calcination atmosphere can include but is not limited to air atmosphere, oxygen atmosphere, a mixed atmosphere of oxygen and nitrogen or an inert gas, etc., and air atmosphere can be selected. Controlling the conditions of the second calcination to meet the given range can not only reduce energy consumption, but also compensate for the loss of alkali metal elements in the layered transition metal oxide phase and improve phase purity while maintaining large particle size and main phase structure.

[0088] In some embodiments of the present application, the layered transition metal oxide may include Na x Mn a M1 b1 O 2-e+δ F e, 0.8≤x≤1, a+b1=1, a>0, b1>0, 0≤e≤0.2, -0.1≤δ≤0.1, M1 may include one or more of the following elements: Li, B, Mg, Al, Si, K, Ca, Ti, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Nb, Mo, In, Sn, Sb, La, Ce, Ta, W, Bi, wherein: based on the total molar number of Mn and M1, the relative molar amount of sodium in the first alkali metal source may be 1.05 mol to 1.2 mol; and / or, the relative molar amount of sodium in the second alkali metal source may be 0.05 mol to 0.25 mol.

[0089] For example, the first alkali metal source can be a first sodium source, the second alkali metal source can be a second sodium source, and in the first calcination, the molar ratio of the manganese source to the M1 source can be based on the Na x Mn a M1 b1 O 2-e+δ F e The stoichiometric ratio is determined based on the total molar number of Mn and M1 and the molar amount of Na. The relative molar amount of sodium in the first sodium source can be 1.05 mol, 1.08 mol, 1.1 mol, 1.12 mol, 1.15 mol, 1.18 mol, 1.2 mol, etc. The relative molar amount of sodium in the second sodium source can be 0.05 mol, 0.08 mol, 0.1 mol, 0.12 mol, 0.15 mol, 0.18 mol, 0.2 mol, 0.25 mol, etc. The sodium source is easily volatilized and lost during the high temperature calcination process. Based on Na x Mn a M1 b1 O 2-e+δ F e The elemental composition of the first sodium source and the second sodium source is such that the relative molar amounts of the first sodium source and the second sodium source both meet the given ranges. This is beneficial for increasing the bulk sodium content in the layered transition metal oxide obtained by the first calcination on the basis of forming large particle size, thereby increasing the phase content of the interlayer spacing between two adjacent transition metal layers in the layered transition metal oxide to meet the physical content of 0.530nm to 0.545nm. It can also further increase the bulk sodium content in the layered transition metal oxide during the second calcination process, further increasing the phase content of the interlayer spacing between two adjacent transition metal layers in the layered transition metal oxide to meet the physical content of 0.530nm to 0.545nm, and obtaining a positive active material with a relatively pure phase. In this way, the phase state and particle size of the positive active material can meet the given requirements while further taking into account a higher specific capacity, a higher first coulombic efficiency, and a lower gas production of the battery cell.

[0090] In some embodiments of the present application, the layered transition metal oxide may include Nax Mn a Ni c Fe d M2 b2 O 2-e+δ F e , 0.8≤x≤1, a+c+d+b2=1, a≥0.3, c≥0.2, d≥0.2, 0≤b2≤0.2, 0≤e≤0.1, -0.1≤δ≤0.1, M2 may include one or more of the following elements: Li, B, Mg, Al, Si, K, Ca, Ti, Co, Cu, Zn, Ga, Y, Zr, Nb, Mo, In, Sn, Sb, La, Ce, Ta, W, Bi, wherein: based on the total molar number of Mn, Ni, Fe, and M2, the relative molar amount of sodium in the first alkali metal source may be 1.05 mol to 1.2 mol; and / or, the relative molar amount of sodium in the second alkali metal source may be 0.05 mol to 0.25 mol.

[0091] For example, the first alkali metal source can be a first sodium source, the second alkali metal source can be a second sodium source, and in the first calcination, the molar ratio of the manganese source, the Ni source, the Fe source and the M2 source can be based on the Na x Mn a Ni c Fe d M2 b2 O 2-e+δ F e The stoichiometric ratio is determined based on the total molar number of Mn and M1, and based on the molar amount of Na, the relative molar amount of sodium in the first sodium source can be 1.05 mol, 1.08 mol, 1.1 mol, 1.12 mol, 1.15 mol, 1.18 mol, 1.2 mol, etc., and the relative molar amount of sodium in the second sodium source can be 0.05 mol, 0.08 mol, 0.1 mol, 0.12 mol, 0.15 mol, 0.18 mol, 0.2 mol, 0.25 mol, etc. Ensuring that the first sodium source and the second sodium source meet the given dosage is beneficial for further increasing the bulk sodium content in the layered transition metal oxide obtained on the basis of forming large particle size, and increasing the phase content of the interlayer spacing between two adjacent transition metal layers in the layered transition metal oxide to meet 0.530 nm to 0.545 nm, thereby obtaining a positive electrode active material with a relatively pure phase. Therefore, on the basis of ensuring that the phase state and particle size of the positive electrode active material meet the given requirements, higher specific capacity, higher cycle stability and lower cell gas production can be further taken into account.

[0092] In addition, it should be noted that the method for preparing the positive electrode active material in the second aspect of the present application and the positive electrode active material in the first aspect of the present application are based on the same inventive concept. The characteristics and effects described for the positive electrode active material in the first aspect of the present application are also applicable to the method for preparing the positive electrode active material in the second aspect of the present application, and will not be repeated here.

[0093] The third aspect of the present application provides a positive electrode plate, which includes: the positive electrode active material of the first aspect of the present application, or the positive electrode active material prepared by the method of the second aspect of the present application.

[0094] In a battery, a positive electrode sheet generally includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode active material.

[0095] The positive electrode current collector may be a conventional metal foil or a composite current collector (a metal material may be disposed on a polymer substrate to form a composite current collector). As an example, the positive electrode current collector may include at least one of copper foil, aluminum foil, nickel foil, stainless steel foil, stainless steel mesh, and carbon-coated aluminum foil.

[0096] The positive electrode active material layer may also optionally include at least one of a binder, a conductive agent, and other optional auxiliary agents. Among them, the binder, conductive agent, and auxiliary agent can all be conventionally selected in the art. For example, the conductive agent can include but is not limited to one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The binder can include but is not limited to one or more of styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB). These materials can all be obtained through commercial channels.

[0097] The fourth aspect of the present application provides a battery, which includes: the positive electrode plate of the third aspect of the present application.

[0098] A battery is a battery that can be recharged to activate the active materials after discharge and continue to be used.

[0099] It will be appreciated that the battery proposed in this application may comprise a sodium ion battery.

[0100] Typically, a battery consists of a positive electrode, a negative electrode, a separator, and an electrolyte. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The separator is placed between the positive and negative electrodes to isolate them. The electrolyte conducts ions between the positive and negative electrodes.

[0101] [Negative electrode]

[0102] In a battery, the negative electrode plate typically includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material. The negative electrode current collector can be a conventional metal foil or a composite current collector (for example, a metal material disposed on a polymer substrate to form a composite current collector). As an example, the negative electrode current collector can be copper foil. The negative electrode active material layer typically also optionally includes a binder and a conductive agent. The conductive agent is used to improve the conductivity of the negative electrode active material layer, and the binder is used to firmly bond the negative electrode active material and the binder to the negative electrode current collector. This application does not specifically limit the types of conductive and binder agents used in the negative electrode plate; they can be selected based on actual needs. As examples, the conductive agent may include, but is not limited to, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. As examples, the binder may include, but is not limited to, at least one of styrene-butadiene rubber (SBR), styrene-butadiene rubber (SBCs), water-based acrylic resin, and carboxymethyl cellulose (CMC).

[0103] The negative electrode active material layer may also optionally include a thickener, such as carboxymethyl cellulose (CMC), etc. However, the present application is not limited thereto, and the present application may also use other materials that can be used as thickeners for sodium ion battery negative electrode sheets.

[0104] In some embodiments of the present application, the battery of the fourth aspect of the present application may be a sodium metal battery. In this case, the negative electrode active material may include, but is not limited to, metallic sodium. For example, the negative electrode active material may also be an alloy of metallic sodium and various other metal or non-metal elements.

[0105] In some embodiments of the present application, the battery of the fourth aspect of the present application can also be a negative electrode-free sodium metal battery. In this case, the negative electrode is composed of only a metal foil current collector, and there is no sodium metal on its surface. During the cycle, only the sodium in the positive electrode is used, and it is precipitated and stripped in the form of sodium metal on the negative electrode side.

[0106] [Electrolyte]

[0107] The electrolyte solution may include an electrolyte salt and a solvent.

[0108] As an example, taking a sodium ion battery as an example, the electrolyte salt may be a sodium salt, and the sodium salt may include but is not limited to at least one of sodium hexafluorophosphate, sodium difluorooxalatoborate, sodium tetrafluoroborate, sodium bisoxalatoborate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethylsulfonate and sodium bis(trifluoromethylsulfonyl)imide.

[0109] As an example, the solvent may include, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene 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), ethyl methyl sulfone (EMS) and diethyl sulfone (ESE).

[0110] In some embodiments, the electrolyte may further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, or additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature performance.

[0111] [Isolation film]

[0112] As the above-mentioned isolation membrane, the present application has no special restrictions and any known porous structure isolation membrane with electrochemical stability and mechanical stability can be selected according to actual needs, for example, it can include but is not limited to a single-layer or multi-layer film containing at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.

[0113] The embodiment of the present application has no particular limitation on the shape of the battery, which can be cylindrical, square or any other shape. Figure 1 The battery 1 is a square structure as an example.

[0114] In some embodiments, the battery may include an outer packaging for encapsulating the positive electrode sheet, the negative electrode sheet, and the electrolyte.

[0115] In some embodiments, the outer packaging may include a housing and a cover. The housing may include a bottom plate and side plates connected to the bottom plate, with the bottom plate and side plates enclosing a receiving cavity. The housing may have an opening communicating with the receiving cavity, and the cover may be positioned over the opening to seal the receiving cavity.

[0116] The positive electrode sheet, negative electrode sheet, and separator can be wound or laminated to form an electrode assembly. The electrode assembly is encapsulated in the housing. The number of electrode assemblies in a battery can include one or more, which can be adjusted according to needs.

[0117] In some embodiments, the outer packaging of the battery may include a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell.

[0118] The outer packaging of the battery may also include a soft bag, such as a bag-type soft bag. The material of the soft bag may be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0119] In some embodiments, the battery may be either a single battery cell or a battery module or battery pack assembled from battery cells. The battery module or battery pack may contain multiple batteries, and the specific number may be adjusted according to the application and capacity of the battery module.

[0120] Figure 2 2 is an example of a battery module. Figure 2 In the battery module 2, the multiple batteries 1 can be arranged in sequence along the length of the battery module 2. Of course, they can also be arranged in any other manner. The multiple batteries 1 can further be fixed by fasteners. The battery module 2 can also include a housing having a storage space, and the multiple batteries 1 are accommodated in the storage space. In some embodiments, the above-mentioned battery modules 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.

[0121] Figure 3 and 4 The battery pack 3 is used as an example. Figure 3 and 4 The battery pack 3 may include a battery box and multiple battery modules 2 disposed in the battery box. The battery box includes an upper box body 4 and a lower box body 5. The upper box body 4 can cover the lower box body 5 and form an enclosed space for accommodating the battery modules 2. The multiple battery modules 2 can be arranged in the battery box in any manner.

[0122] The fifth aspect of the present application provides an electrical device, which includes: the battery of the fourth aspect of the present application.

[0123] Specifically, the battery can serve as a power source or an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks), electric trains, ships, satellites, and energy storage systems.

[0124] Figure 5 This is an example of an electrical device. This device includes a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. Another example of an electrical device may include a mobile phone, a tablet computer, or a laptop computer. These devices are typically required to be lightweight and thin, and may use batteries as a power source.

[0125] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0126] Example 1

[0127] (1) Preparation of batteries

[0128] (1) Preparation of positive electrode active materials for sodium ion batteries

[0129] A first calcined sample was prepared by weighing NaCO, MnO, NiO, FeO, CuO, and ZnO in a molar ratio of Na:Mn:Ni:Fe:Cu:Zn of 1.1:0.4:0.25:0.25:0.05:0.05. Based on the total molar amounts of Mn, Ni, Fe, Cu, and Zn in the first calcined sample, a corresponding amount of NaCO was weighed, with a relative molar content of sodium of 0.05 mol. The first calcined sample was pre-ground in an agate mortar and then ball-milled in a planetary ball mill for 1 hour to obtain precursor mixture I. The obtained precursor mixture II is evenly placed in an open crucible, and then the first calcination is carried out in a muffle furnace: the temperature is increased from room temperature to 1200°C at a heating rate of 5°C / min, and the temperature is kept constant at 1200°C for 20 hours. The atmosphere used is dehumidified air without carbon dioxide. After the first calcination is completed and the temperature is naturally cooled, the obtained powder and the aforementioned spare Na2CO3 are pre-ground in an agate mortar and added to a planetary ball mill for ball milling for 1 hour to obtain a precursor mixture II. The obtained precursor mixture II is evenly placed in an open crucible, and then the second calcination is carried out in a muffle furnace: the temperature is increased from room temperature to 850°C at a heating rate of 5°C / min, and the temperature is kept constant at 850°C for 10 hours. The atmosphere used is dehumidified air without carbon dioxide. After cooling naturally, the layered oxide positive electrode active material Na is obtained. 0.89 Mn 0.4 Ni 0.25 Fe 0.25 Cu 0.05 Zn 0.05 O2, where the elemental composition was tested by inductively coupled plasma optical emission spectrometry.

[0130] (2) Preparation of half-cell

[0131] (2-1) Preparation of positive electrode sheet

[0132] The prepared positive electrode active material, conductive agent carbon black (Super P), and binder polyvinylidene fluoride (PVDF) were thoroughly stirred and mixed in an appropriate amount of solvent NMP at a mass ratio of 80:15:5 to form a uniform positive electrode slurry; the positive electrode slurry was evenly coated on the surface of the positive electrode current collector aluminum foil, and after drying and cold pressing, it was punched into a disc with a diameter of 14 mm to obtain a positive electrode sheet.

[0133] (2-2) Preparation of negative electrode sheet: The negative electrode sheet is made of metal sodium sheet.

[0134] (2-3) Preparation of electrolyte: Ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in equal volumes to obtain an organic solvent. NaClO4 was then dissolved in the organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0135] (2-4) Isolation membrane: A porous polyethylene membrane is used as the isolation membrane.

[0136] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive electrode sheet and the negative electrode sheet to serve as an isolation. The prepared electrolyte is added to complete the preparation of the button half-cell.

[0137] (3) Preparation of full battery

[0138] (3-1) Preparation of positive electrode sheet

[0139] The prepared positive electrode active material, conductive agent carbon black (Super P), and binder polyvinylidene fluoride (PVDF) were fully stirred and mixed in an appropriate amount of solvent NMP at a mass ratio of 80:15:5 to form a uniform positive electrode slurry; the positive electrode slurry was evenly coated on the single side surface of the positive electrode current collector aluminum foil with a coating surface density of 10 mg / cm 2 After drying and cold pressing, it is punched into an area of ​​80cm 2 The positive electrode.

[0140] (3-2) Preparation of negative electrode sheet: Hard carbon material, conductive agent carbon black (Super P), and sodium carboxymethyl cellulose were thoroughly stirred and mixed in an appropriate amount of deionized water at a mass ratio of 90:5:5 to form a uniform negative electrode slurry; the negative electrode slurry was evenly coated on one side of the negative electrode current collector copper foil with a coating surface density of 5 mg / cm 2 After drying and cold pressing, it is punched into an area of ​​85cm 2 The negative electrode.

[0141] (3-3) Preparation of electrolyte: Ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in equal volumes to obtain an organic solvent. NaPF6 was then dissolved in the organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0142] (3-4) Isolation membrane: A porous polyethylene membrane is used as the isolation membrane.

[0143] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an isolating role. The prepared electrolyte is added, and the laminated battery is obtained after vacuum sealing with aluminum-plastic film.

[0144] Examples 2 to 13 and Comparative Examples 1 to 3

[0145] The differences between Examples 2 to 13 and Comparative Examples 1 to 3 and the Examples are shown in Table 1. The main differences are: when preparing the positive electrode active material, the amount of Na2CO3 used as a sodium source in the first calcination and / or the second calcination process is different (calculated as sodium in Na2CO3), and / or the temperature and time conditions of the first calcination and / or the second calcination are different, and / or whether the second calcination is performed, and / or the type of transition metal source used and the ratio of transition metal elements are different, and the elemental composition or stoichiometric ratio of the obtained positive electrode active material is different (see Table 1 for details).

[0146] Test method:

[0147] (1) Elemental composition test by inductively coupled plasma optical emission spectrometry

[0148] The instrument standard refers to EPA 6010D-2014, Inductively Coupled Plasma Atomic Emission Spectrometry. The sample is chemically treated and dissolved into a solution. This solution is then atomized and injected into the plasma, where it is excited to produce characteristic elemental spectral lines. The wavelength and intensity of these spectral lines (which are proportional to concentration) are used to qualitatively and quantitatively analyze the elemental content.

[0149] (2) Interlayer spacing test of positive electrode active materials

[0150] In a dry room or glove box, grind the sample to be tested in an agate mortar and pass it through a 350 mesh sieve. Take an appropriate amount of the sieved sample and place it in the middle of the groove of the sample holder so that the loose sample powder is slightly higher than the plane of the sample holder. Take a glass slide and gently press the sample surface until the sample surface is flattened and aligned with the frame plane, and scrape off the excess powder. After the sample is prepared, use a Brucker D8A_A25 X-ray powder diffractometer from BruckerAxS, Germany, with CuK α The ray is the radiation source, and the wavelength of the ray is The 2θ angle range is 5° to 60°, and the scanning rate is 4° / min. After the test is completed, the angle corresponding to the 003 crystal plane is measured. Generally, the 2θ angle peak is within 15° to 17°. According to the Bragg equation 2d·sinθ=λ, and each unit cell of the 003 crystal plane contains three transition metal layers, the interlayer spacing d of the 003 crystal plane can be obtained. 003 , through d 003 That is, the interlayer spacing between adjacent transition metal layers in the direction perpendicular to the (001) crystal plane can be obtained.

[0151] (3) Dv50 particle size test of the prepared positive electrode active material

[0152] Equipment model: Malvern 2000 (MasterSizer 2000) laser particle size analyzer, reference standard process: GB / T19077-2016 / ISO 13320:2009, specific test process: Take an appropriate amount of the sample to be tested (the sample concentration is sufficient to ensure 8-12% obscuration), add 20ml of deionized water, and ultrasonicate for 5min (53KHz / 120W) to ensure that the sample is completely dispersed. Then, the sample is measured according to GB / T19077-2016 / ISO 13320:2009 standard.

[0153] (4) Discharge specific capacity test

[0154] At 25°C, the prepared positive electrode active material was prepared into a button half-cell, which was then charged to 4.2 V at a constant current density of 10 mA / g, and then discharged to 2.2 V at a constant current density of 10 mA / g to obtain the discharge specific capacity C0 of the button cell.

[0155] (5) Gas production test after 50 cycles

[0156] At 25°C, for the prepared stacked full battery, the initial volume V0 of the battery was tested by the water drainage method. Then, after 50 cycles in the voltage range of 1.5 to 4.2 V at a current density of 50 mA / g, the battery volume V1 at this time was tested by the water drainage method, and the gas production was V1-V0.

[0157] The above-mentioned related tests were carried out on Examples 1 to 13 and Comparative Examples 1 to 3. The test results are shown in Table 1. Figure 6 and Figure 7 .

[0158]

[0159] Results and Conclusions:

[0160] Combining Examples 1 to 13, Comparative Examples 1 to 3, and Table 1, it can be seen that the gas production of the positive electrode active materials prepared in the above-mentioned embodiments of the present application is significantly reduced during use. Combining the test results of the Dv50 particle size and XRD test of Examples 1 to 13 and Comparative Examples 1 to 3, it can be seen that the positive electrode active materials prepared in the above-mentioned embodiments generally have a larger particle size, and the 2θ angle peak in the XRD spectrum is in the region of 15° to 18°, and the peak intensity ratio of the main strong peak to the secondary strong peak is generally above 9. Taking Example 1 and Comparative Example 1 as examples, Figure 6 is the XRD pattern of the positive electrode active material prepared in Example 1, Figure 7The XRD pattern of the positive electrode active material prepared in Comparative Example 1 shows that the positive electrode active material prepared in Example 1 is relatively pure in phase, and the peak intensity ratio of the main strong peak to the secondary strong peak is significantly improved compared to Comparative Example 1. This shows, to a certain extent, that increasing the particle size and phase purity of the positive electrode active material is beneficial to suppressing gas production in the battery cell. In addition, in combination with the various examples and comparative examples, it can be seen that increasing the Dv50 particle size of the positive electrode active material or the peak intensity ratio of the main strong peak to the secondary strong peak has a positive effect on suppressing gas production in the battery cell. In combination with Example 12 and other examples, it can be seen that the sodium content of the positive electrode active material in the region of 16° to 16.5° corresponding to the 2θ angle peak of the main strong peak is relatively high, and the corresponding specific capacity is also high. Furthermore, in combination with Comparative Examples 1, 3 and the various embodiments, it can be seen that the second calcination with a sodium source is beneficial to improving the same purity of the positive electrode active material; in combination with Comparative Example 2 and the various embodiments, it can be seen that increasing the temperature of the first calcination is beneficial to increasing the particle size of the positive electrode active material, and the overall particle size of the positive electrode active material particles can be optionally controlled during the first calcination process.

[0161] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A positive electrode active material, characterized in that The positive electrode active material includes a layered transition metal oxide, which includes a first phase. In an X-ray diffraction pattern obtained using CuKα rays as a radiation source, the positive electrode active material includes a main strong peak and a secondary strong peak in a region with a 2θ angle of 15° to 18°, the main strong peak corresponds to the first phase, the ratio of the peak intensity of the main strong peak to the peak intensity of the secondary strong peak is ≥9, and the Dv50 particle size of the positive electrode active material is ≥30 μm.

2. The positive electrode active material according to claim 1, characterized in that The 2θ angle of the main strong peak is 16° to 16.5°.

3. The positive electrode active material according to claim 1 or 2, characterized in that The layered transition metal oxide comprises sodium ion layers and transition metal layers that are alternated in sequence, and the interlayer spacing between two adjacent transition metal layers in a direction perpendicular to the (001) crystal plane is 0.530 nm to 0.545 nm.

4. The positive electrode active material according to any one of claims 1 to 3, characterized in that The first phase includes an O3 phase.

5. The positive electrode active material according to any one of claims 1 to 4, characterized in that The ratio of the peak intensity of the main strong peak to the peak intensity of the secondary strong peak is ≥12.

6. The positive electrode active material according to any one of claims 1 to 5, characterized in that The Dv50 particle size of the positive electrode active material is 50 μm to 100 μm.

7. The positive electrode active material according to any one of claims 1 to 6, characterized in that The layered transition metal oxide includes: Na x Mn a M1 b1 O 2-e+δ F e , 0.8≤x≤1.2, a+b1=1, a>0, b1>0, 0≤e≤0.2, -0.1≤δ≤0.1, M1 contains one or more of the following elements: Li, B, Mg, Al, Si, K, Ca, Ti, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Nb, Mo, In, Sn, Sb, La, Ce, Ta, W, Bi.

8. The positive electrode active material according to any one of claims 1 to 7, characterized in that The layered transition metal oxide includes: Na x Mn a Ni c Fe d M2 b2 O 2-e+δ F e , 0.8≤x≤1.2, a+c+d+b2=1, a≥0.3, c≥0.2, d≥0.2, 0≤b2≤0.2, 0≤e≤0.1, -0.1≤δ≤0.1, M2 contains one or more of the following elements: Li, B, Mg, Al, Si, K, Ca, Ti, Co, Cu, Zn, Ga, Y, Zr, Nb, Mo, In, Sn, Sb, La, Ce, Ta, W, Bi.

9. A method for preparing a positive electrode active material, characterized in that: include: mixing a first alkali metal source and a transition metal source and performing a first calcination; mixing a second alkali metal source with the first calcined product and performing a second calcination to obtain a positive electrode active material, The alkali metal elements in the first alkali metal source and the second alkali metal source are the same; the positive electrode active material includes a layered transition metal oxide, the layered transition metal oxide includes a first phase, and the positive electrode active material includes a main strong peak and a secondary strong peak in the region of 2θ angle of 15° to 18° in an X-ray diffraction pattern obtained using CuKα rays as a radiation source, the main strong peak corresponds to the first phase, the ratio of the peak intensity of the main strong peak to the peak intensity of the secondary strong peak is ≥9, and the Dv50 particle size of the positive electrode active material is ≥30μm.

10. The method according to claim 9, characterized in that The first alkali metal source and the second alkali metal source each independently include a sodium source.

11. The method according to claim 9 or 10, characterized in that The first calcination satisfies at least one of the following conditions: the calcination temperature is 1100° C. to 1400° C., the time is 10 h to 30 h, and the calcination atmosphere is an oxygen-containing atmosphere.

12. The method according to any one of claims 9 to 11, characterized in that The temperature of the first calcination is 1150°C to 1300°C.

13. The method according to any one of claims 9 to 12, characterized in that The second calcination satisfies at least one of the following conditions: the calcination temperature is 700° C. to 1000° C., the time is 5 hours to 30 hours, and the calcination atmosphere is an oxygen-containing atmosphere.

14. The method according to any one of claims 9 to 13, characterized in that The layered transition metal oxide includes Na x Mn a M1 b1 O 2-e+δ F e , 0.8≤x≤1, a+b1=1, a>0, b1>0, 0≤e≤0.2, -0.1≤δ≤0.1, M1 contains one or more of the following elements: Li, B, Mg, Al, Si, K, Ca, Ti, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Nb, Mo, In, Sn, Sb, La, Ce, Ta, W, Bi, wherein: Based on the total molar number of Mn and M1, the relative molar amount of sodium in the first alkali metal source is 1.05 mol to 1.2 mol; and / or the relative molar amount of sodium in the second alkali metal source is 0.05 mol to 0.25 mol.

15. The method according to any one of claims 9 to 14, characterized in that The layered transition metal oxide includes Na x Mn a Ni c Fe d M2 b2 O 2-e+δ F e , 0.8≤x≤1, a+c+d+b2=1, a≥0.3, c≥0.2, d≥0.2, 0≤b2≤0.2, 0≤e≤0.1, -0.1≤δ≤0.1, M2 comprises one or more of the following elements: Li, B, Mg, Al, Si, K, Ca, Ti, Co, Cu, Zn, Ga, Y, Zr, Nb, Mo, In, Sn, Sb, La, Ce, Ta, W, Bi, wherein: Based on the total molar number of Mn, Ni, Fe, and M2, the relative molar amount of sodium in the first alkali metal source is 1.05 mol to 1.2 mol; and / or the relative molar amount of sodium in the second alkali metal source is 0.05 mol to 0.25 mol.

16. A positive electrode plate, characterized in that: include: The positive electrode active material according to any one of claims 1 to 8, and / or the positive electrode active material prepared by the method according to any one of claims 9 to 15.

17. A battery, characterized in that: include: The positive electrode sheet according to claim 16.

18. An electrical device, characterized in that: include: The battery according to claim 17.

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