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

Abstract

The invention discloses a positive electrode active material and a preparation method thereof, a positive electrode plate, a battery and a power utilization device, the positive electrode active material comprises a positive electrode active material body and a coating layer formed on at least part of the surface of the positive electrode active material body, the coating layer comprises CeaZrbLcO2-gamma, L comprises at least one of Y, La, Pr, Tb, Nd, Sc, Al, Cu, Mn, Co, Ni, Fe or Sr, 0.4 < = a < = 0.9, 0.1 < = b < = 0.6, 0 < = c < = 0.1, 0 < = gamma < = 0.2, 0 < = gamma < = 0.2, and 0 < = gamma < = 0.2. A + b + c = 1, and gamma is more than 0 and less than or equal to 0.4. The positive electrode active material can reduce the gas production of the battery and improve the cycle performance of the battery.

Description

Technical Field

[0001] The present application belongs to the field of batteries, and specifically relates to a positive electrode active material and a preparation method thereof, a positive electrode sheet, a battery and an electrical device. Background Art

[0002] Secondary batteries are widely used in energy storage systems such as hydropower, thermal, wind, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. As battery applications expand, the performance requirements for secondary batteries are becoming increasingly stringent. Existing batteries produce excessive gas, which affects their cycle performance. Summary of the Invention

[0003] In view of the technical problems existing in the background technology, the present application provides a positive electrode active material, aiming to reduce the gas production of the battery containing the positive electrode active material and improve the cycle performance of the battery.

[0004] In order to achieve the above-mentioned object, the present application provides a positive electrode active material in the first aspect, comprising a positive electrode active material body and a coating layer formed on at least a portion of the surface of the positive electrode active material body, wherein the coating layer comprises Ce a Zr b L c O 2-γ , wherein L includes at least one of Y, La, Pr, Tb, Nd, Sc, Al, Cu, Mn, Co, Ni, Fe or Sr, 0.4≤a≤0.9, 0.1≤b≤0.6, 0≤c≤0.1, a+b+c=1, 0<γ≤0.4.

[0005] The present application at least includes the following beneficial effects: In the positive electrode active material of the present application, a layer containing Ce is provided on at least a portion of the surface of the positive electrode active material body. a Zr b L c O 2-γ The coating layer, Ce a Zr b L c O 2-γ It can absorb the active oxygen generated by the positive electrode active material during the cycle, reduce the generation of battery gas, and thus improve the cycle performance of the battery.

[0006] In some embodiments, a / b = 0.8-8. This can reduce the generation of battery gas, thereby improving the cycle performance of the battery.

[0007] In some embodiments, a / b = 0.8-4. This can reduce the generation of battery gas and improve the cycle performance of the battery.

[0008] In some embodiments, 0.02≤c≤0.05, thereby reducing the generation of battery gas and improving the cycle performance of the battery.

[0009] In some embodiments, the ratio of the mass of the coating layer to the mass of the positive electrode active material body is (0.1-20):100, thereby reducing the generation of battery gas and improving the cycle performance of the battery.

[0010] In some embodiments, the ratio of the mass of the coating layer to the mass of the positive electrode active material body is (0.5-5): 100. This can reduce the generation of battery gas and thus improve the cycle performance of the battery.

[0011] In some embodiments, the cathode active material comprises Na x M y N 1-y O 2-z F z , where M includes at least one of Cu, Ni, Fe, Co, V, Y, Ta, Mn, Ti, Zr, Sb, Nb, Mg, Mo, Zn, Cr, W, Bi, Sn, Ge, Al, Ca, Sc, or Sr, and N includes at least one of Si, P, B, S, or Se, and 0.6≤x≤1, 0≤y≤1, and 0≤z≤0.05. This can reduce the generation of battery gas and thus improve the cycle performance of the battery.

[0012] In some embodiments, the cathode active material comprises Na x Ni m Fe n Mn q D p O 2-z F z , where D includes at least one of Cu or Zn, 0.6≤x≤1, 0.2≤m≤0.5, 0.2≤n≤0.4, 0.2≤q≤0.6, 0≤p≤0.15, 0≤z≤0.05, and m+n+p+q=1. This can reduce battery gas generation and improve battery cycle performance.

[0013] In some embodiments, the volume average particle size Dv50 of the cathode active material is 1 μm to 20 μm, thereby reducing the generation of battery gas and improving the cycle performance of the battery.

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

[0015] A coating layer is formed on at least a portion of the surface of the positive electrode active material body, wherein the coating layer includes Ce aZr b L c O 2-γ , wherein L includes at least one of Y, La, Pr, Tb, Nd, Sc, Al, Cu, Mn, Co, Ni, Fe or Sr, 0.4≤a≤0.9, 0.1≤b≤0.6, 0≤c≤0.1, a+b+c=1, 0<γ≤0.4.

[0016] Therefore, the positive electrode active material prepared in this application is provided with Ce on at least part of the surface of the positive electrode active material body. a Zr b L c O 2-γ The coating layer, Ce a Zr b L c O 2-γ It can absorb the active oxygen generated by the positive electrode active material during the cycle, reduce the generation of battery gas, and thus improve the cycle performance of the battery.

[0017] In some embodiments, comprising:

[0018] The positive electrode active material body and Ce with a volume average particle size Dv50 of 20nm-100nm a Zr b L c O 2-γ The particles are mixed and stirred to make Ce a Zr b L c O 2-γ The particles are coated on at least a portion of the surface of the cathode active material body and calcined to obtain the cathode active material. This can reduce the generation of battery gas and thus improve the cycle performance of the battery.

[0019] In some embodiments, the calcination temperature is 200° C.-500° C. This can reduce the generation of battery gas and thus improve the cycle performance of the battery.

[0020] In some embodiments, the Ce a Zr b L c O 2-γ The particles were prepared by the following method:

[0021] Dissolve a soluble Ce salt and a soluble Zr salt in water, mix, adjust the pH to alkaline, and filter to obtain a solid;

[0022] The solid is sintered to obtain Ce a Zr b L c O 2-γParticles. This can reduce the generation of battery gas and improve the cycle performance of the battery.

[0023] In some embodiments, the sintering temperature is 500° C.-1500° C. This can reduce the generation of battery gas, thereby improving the cycle performance of the battery.

[0024] In some embodiments, the cathode active material comprises Na x M y N 1-y O 2-z F z , where M includes at least one of Cu, Ni, Fe, Co, V, Y, Ta, Mn, Ti, Zr, Sb, Nb, Mg, Mo, Zn, Cr, W, Bi, Sn, Ge, Al, Ca, Sc, or Sr, and N includes at least one of Si, P, B, S, or Se, and 0.6≤x≤1, 0≤y≤1, and 0≤z≤0.05. This can reduce the generation of battery gas and thus improve the cycle performance of the battery.

[0025] In some embodiments, the cathode active material comprises Na x Ni m Fe n Mn q D p O 2-z F z , where D includes at least one of Cu or Zn, 0.6≤x≤1, 0.2≤m≤0.5, 0.2≤n≤0.4, 0.2≤q≤0.6, 0≤p≤0.15, 0≤z≤0.05, and m+n+p+q=1. This can reduce battery gas generation and improve battery cycle performance.

[0026] In the third aspect of the present application, the present application proposes a positive electrode plate, comprising the positive electrode active material described in the first aspect of the present application or the positive electrode active material prepared by the method described in the second aspect of the present application.

[0027] In a fourth aspect of the present application, the present application provides a battery comprising the positive electrode sheet described in the third aspect of the present application, thereby having low gas production and excellent cycle performance.

[0028] In the fifth aspect of the present application, the present application proposes an electrical device comprising the battery described in the fourth aspect of the present application.

[0029] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0031] Figure 1 Schematic diagram of the structure of the positive electrode active material according to one embodiment of the present application.

[0032] Figure 2 Schematic diagram of a battery according to one embodiment of the present application.

[0033] Figure 3 yes Figure 2 An exploded view of a battery according to an embodiment of the present application is shown.

[0034] Figure 4 Schematic diagram of a battery module according to one embodiment of the present application.

[0035] Figure 5 Schematic diagram of a battery pack according to one embodiment of the present application.

[0036] Figure 6 yes Figure 5 An exploded view of a battery pack according to an embodiment of the present application is shown.

[0037] Figure 7 Schematic diagram of an electrical device using a battery as a power source according to one embodiment of the present application.

[0038] Figure 8 This is a scanning electron microscope image of the positive electrode active material prepared in Example 1 of the present application.

[0039] Description of reference numerals:

[0040] 100 positive electrode active material body; 200 coating layer; 1 battery cell; 11 shell; 12 electrode assembly; 13 cover plate; 2 battery module; 3 battery pack; 31 upper box; 32 lower box. DETAILED DESCRIPTION

[0041] The following embodiments of the technical solution of the present application are described in detail. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only used as examples and are not intended to limit the scope of protection of the present application.

[0042] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present 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 herein may be combined with other embodiments.

[0043] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and 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 form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0044] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0045] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0046] Unless otherwise specified, all steps of the present application 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 may include steps (b) and (a) performed sequentially. For example, the method may further 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 may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0047] Currently, judging by market developments, the application of secondary batteries is becoming increasingly widespread. They are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power stations, but are also widely used in electric vehicles such as electric bicycles, electric motorcycles, and electric vehicles, as well as in military equipment and aerospace, among other fields.

[0048] In secondary batteries, when the cathode active material is highly depleted of Li / Na, highly active oxygen (O2 or O2 - ). This reactive oxygen species, upon contact with the electrolyte, not only causes electrolyte oxidation, resulting in gas production and interface deterioration, but also releases a significant amount of heat, increasing the risk of thermal runaway. Furthermore, due to its combustion-supporting properties, its presence can further increase the risk of thermal runaway. Therefore, suppressing the release of reactive oxygen species on the surface of the cathode active material is essential.

[0049] CeO2 has a cubic fluorite structure and has a certain amount of oxygen vacancies due to its own oxygen defects, which is generally expressed as CeO 2-γ , mainly using Ce 3+ and Ce 4+ The oxidation reaction between them is used to store oxygen. The specific reaction is as follows:

[0050] CeO 2-γ +O2→CeO2

[0051] Therefore, coating the surface of the cathode active material with a cerium-based oxygen storage material to inhibit oxygen loss from the cathode active material is a good option. However, since CeO2 mainly stores oxygen through its own oxygen vacancies, its ability to absorb active oxygen is limited. Under conditions where the cathode active material is highly depleted of Li / Na, the active oxygen on the surface is not completely absorbed, and gas will still be generated, resulting in a deterioration in the cycle performance of the battery containing the cathode active material.

[0052] In the positive electrode active material of the present application, a layer containing Ce is provided on at least a portion of the surface of the positive electrode active material body. a Zr b L c O 2-γ The coating layer, Ce a Zr b L c O 2-γ There are many oxygen vacancies in the battery, which can fully absorb the active oxygen generated by the positive electrode active material during the cycle, reduce the generation of battery gas, and thus improve the cycle performance of the battery.

[0053] The positive electrode active materials disclosed in the embodiments of the present application are suitable for lithium-ion batteries and sodium-ion batteries, and the batteries 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, electric tools, battery cars, electric cars, ships, spacecraft, and the like. 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, and the like, and spacecraft may include airplanes, rockets, space shuttles, and spacecraft, and the like.

[0054] The first aspect of this application proposes a positive electrode active material, see Figure 1 The positive electrode active material includes a positive electrode active material body 100 and a coating layer 200 formed on at least a portion of the surface of the positive electrode active material body 100, wherein the coating layer 200 includes Ce a Zr b L c O 2-γ , wherein L includes at least one of Y, La, Pr, Tb, Nd, Sc, Al, Cu, Mn, Co, Ni, Fe or Sr, 0.4≤a≤0.9, 0.1≤b≤0.6, 0≤c≤0.1, a+b+c=1, 0<γ≤0.4.

[0055] For example, 0.4≤a≤0.8, 0.5≤a≤0.8, 0.6≤a≤0.7, etc.; 0.1≤b≤0.5, 0.2≤b≤0.4, 0.3≤b≤0.4, etc.; 0≤c≤0.09, 0.01≤c≤0.08, 0.02≤c≤0.07, 0.03≤c≤0.06, 0.04≤c≤0.05, etc.; 0.01≤γ≤0.4, 0.05≤γ≤0.35, 0.1≤γ≤0.3, 0.15≤γ≤0.25, 0.2≤γ≤0.25, etc.

[0056] In the present application, a layer containing Ce is provided on at least a portion of the surface of the positive electrode active material body 100. a Zr b L c O 2-γ The coating layer 200, CeO 2-γ It is a cubic fluorite structure. Due to its own oxygen defects, it has a certain oxygen vacancy and has a certain oxygen storage capacity. 2-γ Medium doped Zr, Zr with smaller ion radius 4+ (0.084nm) replaced Ce with a larger ionic radius 4+ (0.097nm), will cause CeO 2-γThe lattice distortion can form more defects on the one hand, increase the number of oxygen vacancies (oxygen storage capacity), and on the other hand compensate for the Ce 4+ To Ce 3+ The volume expansion caused by the change reduces the activation energy of oxygen ion diffusion, which is beneficial to the migration and diffusion of bulk oxygen and improves Ce a Zr b L c O 2-γ stability, redox performance and oxygen storage capacity; further controlling the amount a and b of Ce and Zr can effectively improve Ce a Zr b L c O 2-γ Stability and oxygen storage capacity, and can reduce the lattice distortion caused by excessive Zr content, reduce Ce a Zr b L c O 2-γ The probability of the unit cell changing from cubic phase to tetragonal phase, thus maintaining Ce a Zr b L c O 2-γ Active oxygen migration ability within the crystal improves Ce a Zr b L c O 2-γ The storage and release capacity of the crystal. When the positive electrode active material body 100 is charged to a high voltage state, active oxygen (O2 or O2 - ) is generated, and when the active oxygen passes through the coating layer 200, it will be a Zr b L c O 2-γ The sufficient oxygen vacancies in the electrolyte can be absorbed, reducing the migration of active oxygen to the electrolyte and oxidizing the electrolyte to produce gas. In summary, the positive electrode active material proposed in this application can reduce battery gas production and improve the cycle performance of the battery.

[0057] In addition, the presence of the coating layer 200 can also reduce the side reaction between the positive electrode active material body 100 and the electrolyte, thereby improving the cycle performance of the battery.

[0058] It can be understood that in the embodiment of the present application, the "positive electrode active material body 100" refers to a material that can provide active metal ions (such as lithium ions, sodium ions, etc.), that is, a common positive electrode active material. In order to distinguish it from the positive electrode active material containing the coating layer 200, the "positive electrode active material body 100" is used in the embodiment of the present application.

[0059] In some embodiments of the present application, a / b=0.8-8. For example, the value of a / b can be 0.8-7.9, 1-7, 2-6, 3-5, 4-5, etc. Specifically, since c is relatively small or even 0, Ce a Zr b L c O 2-γ The main elements in addition to O are Ce and Zr. The larger the a / b value, the higher the Ce content and the lower the Zr content. Conversely, the smaller the a / b value, the higher the Zr content. In the embodiment of the present application, the a / b value is controlled within the above range, Ce and Zr will form a solid solution, the lattice defects will increase, the oxygen storage capacity will be enhanced, and the Ce content caused by the low Zr ratio (the a / b value is too large) can be reduced. a Zr b L c O 2-γ The improvement in oxygen storage capacity is not significant, which is enough to increase Ce a Zr b L c O 2-γ and can reduce the formation of phase separation of Ce and Zr solid solution due to excessive lattice distortion caused by too high a Zr ratio (too small a / b value), reduce the reduction of crystal defects caused by too small a / b value, and reduce the oxygen storage capacity. In addition, it can also reduce the association of oxygen vacancy defects caused by too high a Zr ratio (too small a / b value), resulting in a reduction in oxygen vacancies. In summary, controlling the value of a / b within the above range can reduce the generation of battery gas, thereby improving the cycle performance of the battery. In other embodiments of the present application, a / b = 0.8-4.

[0060] In some embodiments of the present application, 0≤c≤0.1, for example, 0≤c≤0.09, 0.01≤c≤0.08, 0.02≤c≤0.07, 0.03≤c≤0.06, 0.04≤c≤0.05, etc. Specifically, in Ce a Zr b O 2-γ Further doping at least one of the rare earth elements or transition elements mentioned above and controlling the doping amount c within the above range can further increase Ce a Zr b L c O 2-γ The oxygen vacancies in the crystal can be reduced, and the oxygen vacancies caused by excessive doping of the above elements can be reduced, which can reduce the generation of battery gas and thus improve the cycle performance of the battery. In other embodiments of the present application, 0.02≤c≤0.05.

[0061] In some embodiments of the present application, the mass ratio of the coating layer 200 to the mass of the positive electrode active material body 100 is (0.1-20):100. For example, the mass ratio of the coating layer 200 to the mass of the positive electrode active material body 100 can be (0.1-19.9):100, (1-19):100, (2-18):100, (3-17):100, (4-16):100, (5-15):100, (6-14):100, (7-13):100, (8-12):100, (10-11):1 00. Specifically, the ratio of the mass of the coating layer 200 to the mass of the positive electrode active material body 100 is controlled within the above range. On the one hand, it is sufficient to form an oxygen storage coating layer 200 on at least a portion of the surface of the positive electrode active material body 100, and the coating layer 200 is sufficient to absorb the active oxygen generated by the positive electrode active material body 100, reducing battery gas production and improving battery cycle performance; on the other hand, it can reduce the excessive thickness of the coating layer 200 caused by excessive mass of the coating layer 200, so that the migration path of active metal ions (such as lithium ions or sodium ions) is not too large, so that the battery has excellent electrochemical performance. In other embodiments of the present application, the ratio of the mass of the coating layer 200 to the mass of the positive electrode active material body 100 is (0.5-5):100.

[0062] It is understood that the “ratio of the mass of the coating layer 200 to the mass of the positive electrode active material body 100” is a well-known definition in the art and can be measured using methods well-known in the art, for example:

[0063] The ratio of the coating element content to the cathode material content can be obtained by measuring the ratio using an inductively coupled plasma emission spectrometer (ICP):

[0064] The coating layer is Ce a Zr b L c O 2-γ , the molecular weight is M1, and the main component of the positive electrode active material is Na x M y N 1-y O 2-z F z , the molecular weight is M2, the dissolved mass during ICP test is 0.2g (subject to actual dissolution), and the output value is the mass ratio of the tested element, Ce a Zr b L c O 2-γ The concentration of Ce in ICP test is Ce1, Na x M y N 1-y O 2-z F zThe concentration of element M in the ICP test is M 11 Assuming the coating mass is L, the mass of the cathode active material is 0.2-L, then Ce1 / M 11 =[(L / M1)x] / [(0.2-L) / M2y], the value of L can be calculated.

[0065] The ratio of the mass of the coating layer to the mass of the positive electrode active material body = L / (0.2-L).

[0066] In some embodiments of the present application, the positive electrode active material body 100 includes Na x M y N 1-y O 2-z F z , wherein M includes at least one of Cu, Ni, Fe, Co, V, Y, Ta, Mn, Ti, Zr, Sb, Nb, Mg, Mo, Zn, Cr, W, Bi, Sn, Ge, Al, Ca, Sc or Sr, N includes at least one of Si, P, B, S or Se, 0.6≤x≤1, 0≤y≤1, and 0≤z≤0.05. For example, 0.6≤x≤0.99, 0.65≤x≤0.95, 0.7≤x≤0.9, 0.75≤x≤0.85, 0.7≤x≤0.8, etc.; 0≤y≤0.9, 0.1≤y≤0.8, 0.2≤y≤0.7, 0.3≤y≤0.6, 0.4≤y≤0.5, etc.; 0≤z≤0.04, 0.01≤z≤0.04, 0.02≤z≤0.03, etc. By using the above-mentioned positive electrode active material body 100, the obtained sodium ion battery produces less gas and has excellent cycle performance.

[0067] In some embodiments of the present application, the positive electrode active material body 100 includes Na x Ni m Fe n Mn q D p O 2-z F z, wherein D includes at least one of Cu or Zn, 0.6≤x≤1, 0.2≤m≤0.5, 0.2≤n≤0.4, 0.2≤q≤0.6, 0≤p≤0.15, 0≤z≤0.05, and m+n+p+q=1. For example, 0.6≤x≤0.99, 0.65≤x≤0.95, 0.7≤x≤0.9, 0.75≤x≤0.85, 0.7≤x≤0.8, etc.; 0.2≤m≤0.5, 0.3≤m≤0.5, 0.3≤m≤0.4, 0.4≤m≤0.5, etc.; 0.2≤n≤0.4, 0.3≤n≤0.4, 0.2≤n≤0.3, etc.; 0.2≤q≤0.5, 0 .3≤q≤0.5, 0.3≤q≤0.4, etc.; 0≤p≤0.14, 0.01≤p≤0.13, 0.03≤p≤0.1, 0.05≤p≤0.08, etc.; 0≤z≤0.04, 0.01≤z≤0.04, 0.02≤z≤0.03, etc. Therefore, the use of the above-mentioned positive electrode active material body 100 can reduce the generation of battery gas and thus improve the cycle performance of the battery.

[0068] In some embodiments of the present application, when the battery is a sodium ion battery, the positive electrode active material body 100 may further include a positive electrode active material for sodium ion batteries known in the art.

[0069] As an example, the positive electrode active material body 100 may also include at least one of the following materials: a polyanion compound, a Prussian blue-based sodium compound, and their respective modified compounds. However, this application is not limited to these materials; other conventional materials that can be used as battery positive electrode active materials may also be used. The modified compounds of the above materials may be modified by doping and / or surface coating.

[0070] In some embodiments, the polyanionic compound may be a compound having sodium ions, transition metal ions and tetrahedral (YO4) n- A class of compounds with anionic units. Among them, the transition metal may include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y may include at least one of P, S, and Si; n represents (YO4) n- valence.

[0071] In some embodiments, the polyanionic compound can also be a compound having sodium ions, transition metal ions, tetrahedral (YO4) n- A class of compounds of anion units and halogen anions. The transition metal may include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y may include at least one of P, S, and Si, and n represents (YO4) n-The halogen may include at least one of F, Cl, and Br.

[0072] In some embodiments, the polyanionic compound may also be a compound having sodium ions, tetrahedral (YO4) n- Anion unit, polyhedron unit (ZO y ) m+ and an optional halogen anion. M may include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce, Y may include at least one of P, S and Si, and n represents (YO4) n- valence state, Z represents a transition metal, m represents (ZO y ) m+ The halogen may include at least one of F, Cl, and Br.

[0073] As an example, the polyanionic compound may satisfy the chemical formula NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2(P2O7), NaM'PO4F (M' includes at least one of V, Fe, Mn and Ni) and Na3(VO y )2(PO4)2F 3-2y At least one of (0≤y≤1).

[0074] In some embodiments, the Prussian blue compound may be a compound having sodium ions, transition metal ions and cyanide ions (CN - The transition metal may include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce.

[0075] As an example, a Prussian blue-like compound may satisfy the chemical formula Na a Me b Me' c (CN)6, wherein Me and Me' each independently include at least one of Ni, Cu, Fe, Mn, Co, and Zn, 0<a≤2, 0<b<1, and 0<c<1.

[0076] The battery's charge and discharge processes involve the intercalation and deintercalation of Na, leading to different molar Na contents at different discharge states. The molar Na contents listed in this application for the positive electrode active material 100 are those in their initial state, i.e., before addition. Once the positive electrode active material 100 is used in a battery system and undergoes charge and discharge cycles, the molar Na content will change.

[0077] In the enumeration of the positive electrode active material body 100 for sodium ion batteries in this application, the molar content of O is only a theoretical value. Lattice oxygen release will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.

[0078] In some embodiments, when the secondary battery is a lithium-ion battery, the positive electrode active material body 100 may be a positive electrode active material for lithium-ion batteries known in the art.

[0079] As an example, the positive electrode active material body 100 may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.8 Co 0.15 Al 0.05 O2) and its modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0080] The battery's charge and discharge processes involve the intercalation and deintercalation of Li, leading to different molar Li contents at different discharge states. The molar Li contents listed in this application for the positive electrode active material 100 refer to the material's initial state, i.e., before addition. Once the positive electrode active material 100 is used in a battery system, the molar Li content will change after charge and discharge cycles.

[0081] In the examples of the positive electrode active material body 100 for lithium-ion batteries in this application, the molar content of O is only a theoretical value. Oxygen release from the lattice will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.

[0082] In some embodiments of the present application, the volume average particle size Dv50 of the positive electrode active material body 100 is 1 μm-20 μm. For example, the volume average particle size Dv50 of the positive electrode active material body 100 can be 1 μm-19 μm, 2 μm-18 μm, 3 μm-17 μm, 4 μm-16 μm, 5 μm-15 μm, 6 μm-14 μm, 7 μm-13 μm, 8 μm-12 μm, 9 μm-10 μm, etc. When the volume average particle size Dv50 of the positive electrode active material body 100 is controlled within the above range, the transmission efficiency of the active metal ions is high, the battery produces less gas, and the cycle performance is excellent.

[0083] It is understood that the “volume average particle size Dv50 of the positive electrode active material body 100” is a well-known definition in the art and can be measured by methods well-known in the art. For example, it can be measured by the following method:

[0084] According to the standard GB / T 19077-2016, the volume average particle size Dv50 of the positive electrode active material can be obtained by testing the positive electrode active material body using a laser particle size analyzer (such as Malvern Master Sizer3000).

[0085] In some embodiments of the present application, the crystal type of the positive electrode active material body 100 may include single crystal and polycrystalline, and the morphology may include spherical, flaky and irregular shapes; the positive electrode active material body 100 may be a mixed phase structure of one or more of O3, P3 and P2.

[0086] In a second aspect of the present application, the present application proposes a method for preparing a positive electrode active material, comprising:

[0087] S100: forming a coating layer on at least a portion of the surface of the positive electrode active material body, wherein the coating layer includes Ce a Zr b L c O 2-γ, wherein L includes at least one of Y, La, Pr, Tb, Nd, Sc, Al, Cu, Mn, Co, Ni, Fe or Sr, 0.4≤a≤0.9, 0.1≤b≤0.6, 0≤c≤0.1, a+b+c=1, 0<γ≤0.4.

[0088] Therefore, the positive electrode active material prepared in this application is provided with Ce on at least part of the surface of the positive electrode active material body. a Zr b L c O 2-γ When the cathode active material is charged to a high voltage state, active oxygen (O2 or O2 - ) is generated, and when the active oxygen passes through the coating layer, it will be a Zr b L c O 2-γ It absorbs oxygen defects in the electrolyte, reduces the migration of active oxygen to the electrolyte, and then oxidizes the electrolyte to produce gas.

[0089] In some implementations of the present application, step S100 includes:

[0090] S101: The cathode active material and Ce with a volume average particle size Dv50 of 20nm-100nm are mixed. a Zr b L c O 2-γ The particles are mixed and stirred to make Ce a Zr b L c O 2-γ The particles are coated on at least a portion of the surface of the cathode active material body, and the cathode active material is obtained by calcining.

[0091] For example, Ce a Zr b L c O 2-γ The volume average particle size Dv50 of the particles can be 20nm-99nm, 30nm-90nm, 40nm-80nm, 50nm-70nm, etc. Specifically, Ce a Zr b L c O 2-γ The volume average particle size Dv50 of the particles is controlled within the above range, Ce a Zr b L c O 2-γ When the particles are mixed with the cathode active material, it may be beneficial to the nano-scale Ce a Zr b L c O2-γ The particles are formed on the surface of the positive electrode active material under the action of shear force, centrifugal force and impact force, which may be conducive to the formation of a uniform coating layer, which can effectively absorb the active oxygen generated by the positive electrode active material during the cycle, thereby reducing the generation of battery gas and improving the cycle performance of the battery.

[0092] In some embodiments of the present application, the calcination temperature is 200°C-500°C, for example, the calcination temperature can be 200°C-490°C, 250°C-450°C, 300°C-400°C, 350°C-400°C, etc. Therefore, controlling the calcination temperature within the above range may be beneficial to the production of Ce a Zr b L c O 2-γ The coating layer is tightly coated on the surface of the positive electrode active material layer, which may enhance the bonding strength between the coating layer and the positive electrode active material layer, effectively absorb the active oxygen generated by the positive electrode active material layer during the cycle, thereby reducing the generation of battery gas and improving the cycle performance of the battery.

[0093] In some embodiments of the present application, the Ce a Zr b L c O 2-γ The particles were prepared by the following method:

[0094] S1001: dissolving a soluble Ce salt and a soluble Zr salt in water, mixing, adjusting the pH value to alkaline, and filtering to obtain a solid;

[0095] S1002: Sintering the solid to obtain Ce a Zr b L c O 2-γ particles.

[0096] Thus, the Ce prepared by the above method a Zr b L c O 2-γ The particles are uniform and may be more easily coated on the surface of the positive electrode active material to form a uniform coating layer, which can effectively absorb the active oxygen generated by the positive electrode active material during the cycle, thereby reducing the generation of battery gas and improving the cycle performance of the battery.

[0097] Understandably, when Ce a Zr b L c O 2-γWhen the element L exists in the particles, that is, c>0, in step S1001, the soluble L salt is also dissolved in water and mixed with the aqueous solution of the soluble Ce salt and the soluble Zr salt before the subsequent operations are performed.

[0098] In some embodiments of the present application, the sintering temperature is 500°C-1500°C. For example, the sintering temperature can be 500°C-1400°C, 600°C-1300°C, 700°C-1200°C, 800°C-1100°C, 900°C-1000°C, etc. Controlling the sintering temperature within the above range may be beneficial to the generation of nano-scale Ce. a Zr b L c O 2-γ particles, which is beneficial for nanoscale Ce a Zr b L c O 2-γ The particles may be formed on the surface of the positive electrode active material under the action of shear force, centrifugal force and impact force, which may be conducive to the formation of a uniform coating layer, which can effectively absorb the active oxygen generated by the positive electrode active material during the cycle, thereby reducing the generation of battery gas and improving the cycle performance of the battery.

[0099] In some embodiments of the present application, the cathode active material includes Na x M y N 1-y O 2-z F z , wherein M includes at least one of Cu, Ni, Fe, Co, V, Y, Ta, Mn, Ti, Zr, Sb, Nb, Mg, Mo, Zn, Cr, W, Bi, Sn, Ge, Al, Ca, Sc or Sr, N includes at least one of Si, P, B, S or Se, 0.6≤x≤1, 0≤y≤1, and 0≤z≤0.05. For example, 0.6≤x≤0.99, 0.65≤x≤0.95, 0.7≤x≤0.9, 0.75≤x≤0.85, 0.7≤x≤0.8, etc.; 0≤y≤0.9, 0.1≤y≤0.8, 0.2≤y≤0.7, 0.3≤y≤0.6, 0.4≤y≤0.5, etc.; 0≤z≤0.04, 0.01≤z≤0.04, 0.02≤z≤0.03, etc. By using the above-mentioned positive electrode active material body, the obtained sodium ion battery produces less gas and has excellent cycle performance.

[0100] In some embodiments of the present application, the cathode active material includes Na x Ni m Fe n Mn q D p O2-z F z , wherein D includes at least one of Cu or Zn, 0.6≤x≤1, 0.2≤m≤0.5, 0.2≤n≤0.4, 0.2≤q≤0.6, 0≤p≤0.15, 0≤z≤0.05, m+n+p+q=1. For example, 0.6≤x≤0.99, 0.65≤x≤0.95, 0.7≤x≤0.9, 0.75≤x≤0.85, 0.7≤x≤0.8, etc.; 0.2≤m≤0.5, 0.3≤m≤0.5, 0.3≤m≤0.4, 0.4≤m≤0.5, etc.; 0.2≤n≤0.4, 0.3≤n≤0.4, 0.2≤n≤0.3, etc.; 0.2 ≤q≤0.5, 0.3≤q≤0.5, 0.3≤q≤0.4, etc.; 0≤p≤0.14, 0.01≤p≤0.13, 0.03≤p≤0.1, 0.05≤p≤0.08, etc.; 0≤z≤0.04, 0.01≤z≤0.04, 0.02≤z≤0.03, etc., thereby reducing the generation of battery gas and improving the cycle performance of the battery.

[0101] The third aspect of the present application provides a positive electrode plate, which includes the positive electrode active material described in the first aspect of the present application or the positive electrode active material prepared by the method described in the second aspect of the present application.

[0102] In some embodiments of the present application, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer is provided on at least one side of the positive electrode current collector, and the positive electrode active material layer includes the positive electrode active material.

[0103] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is provided on either or both of the two facing surfaces of the positive electrode current collector.

[0104] In some embodiments of the present application, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0105] In some embodiments of the present application, the positive electrode active material layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0106] In some embodiments of the present application, the positive electrode active material layer may further optionally include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0107] In some embodiments of the present application, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0108] In a fourth aspect of the present application, the present application provides a battery comprising the positive electrode sheet described in the third aspect of the present application. Thus, the battery produces less gas and has excellent cycle performance.

[0109] Typically, a battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active metal ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0110] In some embodiments of the present application, the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer provided on at least one side of the negative electrode current collector.

[0111] As an example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active material layer is provided on either or both of the two facing surfaces of the negative electrode current collector.

[0112] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0113] In some embodiments, the negative electrode active material may adopt the negative electrode active material for batteries known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials and titanates, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides and tin alloys. When the battery is a lithium-ion battery, the titanate includes lithium titanate, and when the battery is a sodium-ion battery, the titanate includes sodium titanate. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0114] In some embodiments, the negative electrode active material layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0115] In some embodiments, the negative electrode active material layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0116] In some embodiments, the negative electrode active material layer may further optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0117] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0118] The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or solid.

[0119] In some embodiments of the present application, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0120] In some embodiments of the present application, when the battery is a lithium ion battery, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate or lithium tetrafluorooxalatophosphate.

[0121] In some embodiments of the present application, when the battery is a sodium ion battery, the electrolyte salt may include at least one of sodium hexafluorophosphate, sodium difluorooxalatoborate, sodium tetrafluoroborate, sodium bisoxalatoborate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethylsulfonate or sodium bis(trifluoromethylsulfonyl)imide.

[0122] In some embodiments of the present application, the solvent may include at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, ethylene glycol dimethyl ether, methyl ethyl sulfone or diethyl sulfone.

[0123] In some embodiments of the present application, 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 properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0124] The present application has no particular limitation on the type of isolation membrane, and any known isolation membrane with a porous structure having good chemical stability and mechanical stability can be selected.

[0125] In some embodiments, the material of the separator may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, or polyvinylidene fluoride. The separator may 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 may be the same or different, without particular limitation.

[0126] The battery of the present application includes a battery cell form, a battery module form and a battery pack form. The battery cell, battery module and battery pack of the present application are described below with reference to the accompanying drawings as appropriate.

[0127] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0128] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0129] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery may also be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0130] The present application has no particular restrictions on the shape of the battery cell, which can be cylindrical, square or any other shape. For example, Figure 2 The battery cell 1 is a square structure as an example.

[0131] In some embodiments, reference Figure 3 The outer packaging may include a shell 11 and a cover plate 13. The shell 11 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 11 has an opening connected to the receiving cavity, and the cover plate 13 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 12 through a winding process or a lamination process. The electrode assembly 12 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 12. The number of electrode assemblies 12 contained in the battery cell 1 can be one or more, and those skilled in the art can select according to specific actual needs.

[0132] In some embodiments, battery cells may be assembled into a battery module. The battery module may contain one or more battery cells. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0133] Figure 4 2 is an example of a battery module. Figure 4 In the battery module 2, the plurality of battery cells 1 may be arranged in sequence along the length direction of the battery module 2. Of course, they may also be arranged in any other manner. The plurality of battery cells 1 may further be fixed by fasteners.

[0134] Optionally, the battery module 2 may further include a housing having an accommodation space, and the plurality of battery cells 1 are accommodated in the accommodation space.

[0135] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0136] Figure 5 and Figure 6 The battery pack 3 is used as an example. Figure 5 and Figure 6 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 31 and a lower box body 32. The upper box body 31 can cover the lower box body 32 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.

[0137] In addition, the present application also provides an electric device, which includes the secondary battery provided by the present application. The battery cell, battery module, or battery pack can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as 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 satellites, energy storage systems, etc., but is not limited thereto.

[0138] As the electrical device, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

[0139] Figure 7 This is an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery, a battery pack or battery module can be used.

[0140] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0141] 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.

[0142] Example 1

[0143] Preparation of positive electrode active materials:

[0144] (1) Positive electrode active material NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 Preparation of O2: First, NiO, Mn2O3, Fe2O3 and Na2CO3 are mixed evenly in the ratio of Na:Ni:Fe:Mn=1.03:1 / 3:1 / 3:1 / 3 (molar ratio), and then the mixture is placed in a sagger in a box furnace, and the temperature of the box furnace is raised to 900℃ at a heating rate of 5℃ / min, and maintained at this temperature for 15h, and then the program is terminated and naturally cooled to room temperature. The cooled material is crushed to obtain NaNi 1 / 3 Fe 1 / 3Mn 1 / 3 O2.

[0145] (2) Ce 0.485 Zr 0.485 Y 0.03 Preparation of O2: According to the ratio of metal atoms in the chemical formula of the oxygen storage material, a mixed solution is prepared using single metal nitrates such as Ce(NO3)3·6H2O, Y(NO3)3·6H2O and ZrO(NO3)2. The solution is placed in a water bath preheated to 100°C, and then 0.5 mol / L ammonia solution is gradually added dropwise, and the pH is adjusted to 10. The resulting precipitate is allowed to stand at room temperature, filtered and filtered, and then washed with deionized water three times, and then dried at 100°C for 12 hours. The resulting powder is calcined at 700°C for 7 hours in a nitrogen or argon atmosphere to obtain the coating agent Ce. 0.485 Zr 0.485 Y 0.03 O2.

[0146] (3) Preparation of positive electrode active material: First, take 5g of the above synthesized Ce 0.485 Zr 0.485 Y 0.03 O2 and 1kgNaNi 1 / 3Fe 1 / 3 Mn 1 / 3 O2 positive electrode material, the two are mixed evenly through a mechanical fusion machine. During the mixing process, the coating agent will be evenly dispersed on the surface of the material under the action of shear force. The mixing program is: 1000rpm / 5min+2000rpm / 10min. Then the mixture is placed in a sagger in a box furnace, and the temperature of the box furnace is raised to 300℃ at a heating rate of 5℃ / min and maintained at this temperature for 3h, then the program is ended and naturally cooled to room temperature. The cooled material is crushed to obtain 0.5wt% Ce 0.485 Zr 0.485 Y 0.03 O2-coated NaN i1 / 3 Fe1 / 3 Mn 1 / 3 O2 positive electrode active material.

[0147] 1. Preparation of positive electrode sheet

[0148] The prepared positive electrode active material was mixed with the conductive agent carbon black Super P, the binder PVDF and the solvent NMP in a mass ratio of 90:5:5:100 and stirred evenly to obtain a positive electrode slurry; the positive electrode slurry was then evenly coated on one surface of the positive electrode collector (aluminum foil), and then dried, cold pressed and cut to obtain a positive electrode sheet.

[0149] 2. Preparation of negative electrode sheet

[0150] The negative electrode material hard carbon, conductive agent carbon black Super P, binder CMC and solvent water are mixed and stirred in a mass ratio of 8:1:1:10 to obtain a negative electrode slurry; the negative electrode slurry is then evenly coated on one surface of the negative electrode collector (copper foil); and then dried, cold pressed and cut to obtain a negative electrode sheet.

[0151] 3. Preparation of electrolyte

[0152] Sodium hexafluorophosphate (NaPF6) was dissolved in the solvent EC / DEC (1:1, v / v) to obtain a NaPF6 electrolyte with a concentration of 1 mol / L.

[0153] 4. Isolation film

[0154] Polyethylene film was selected as the separator.

[0155] 5. Preparation of secondary batteries

[0156] The positive electrode sheet, separator and negative electrode sheet obtained above are cut into square shapes according to a mold and arranged in sequence, so that the separator is placed between the positive electrode sheet and the negative electrode sheet to play an isolating role. Then, they are dried, injected with liquid and packaged. After standing, a sodium ion battery is obtained.

[0157] The preparation methods of the sodium ion batteries of Examples 2-9 and Comparative Examples 1-4 are the same as those of Example 1, except that the process of preparing the positive electrode sheet is different. The positive electrode active material of Comparative Example 1 does not have a coating layer of Ce. 0.485 Zr 0.485 Y 0.03 O2, as shown in Table 1.

[0158] Table 1

[0159]

[0160]

[0161] Scanning electron microscopy was performed on the positive electrode active material prepared in Example 1, and the Figure 8 , Figure 8 It can be seen that the surface of the positive electrode active material is evenly coated with Ce a Zr b L c O 2-γ Small particles can reduce battery gas production and improve battery cycle performance.

[0162] The batteries of Examples 1-9 and Comparative Examples 1-4 were tested for 200 cycles of capacity retention and volume expansion rate. The test results are shown in Table 2.

[0163] (1) 200-cycle capacity retention rate

[0164] The cycling performance test process is as follows: At 25°C, a single-layer sodium-ion battery stack is charged to 4.0V at a rate of 0.1C, then discharged to 1.5V at a rate of 0.1C. This process is repeated once to complete the battery activation. After activation is completed, the sodium-ion stacked battery is charged to 4.0V at a rate of 1C, and then discharged to 1.5V at a rate of 1C. At this time, the initial cycle capacity is obtained. The above 1C charge and discharge system is repeated 200 times. The 200-cycle capacity retention rate is obtained by dividing the 200-cycle discharge capacity by the initial 1C discharge capacity.

[0165] (2) Volume expansion rate test

[0166] The test was conducted according to the 200-cycle capacity retention process. In order to increase the gas production and improve the test accuracy, the cycle temperature was changed to 45°C. Other conditions were consistent with the cycle performance test process.

[0167] The volume expansion rate of the battery cell can be calculated by testing the volume of the single-layer laminate soft package before and after the cycle using the water displacement method. Volume expansion rate = (volume after cycle - volume before cycle) / volume before cycle × 100%.

[0168] Table 2

[0169]

[0170]

[0171] Conclusion: By comparing Examples 1-9 of the present application with Comparative Examples 1-4, it can be seen that the capacity retention rate of the batteries of Examples 1-9 of the present application is above 90%, and the volume expansion rate is below 30. Compared with the examples, Comparative Example 1 does not add a coating layer, the coating material of Comparative Example 2 is not doped with Zr, and a and b of Comparative Examples 3 and 4 are not within the scope of the present application. The battery cycle performance is significantly reduced, and the gas production is significantly increased. It can be seen that the positive electrode active material of the present application, Ce in the coating layer a Zr b Lc O 2-γ It can absorb the active oxygen generated by the positive electrode active material, reduce battery gas production, and improve the battery's cycle performance.

[0172] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A positive electrode active material, characterized in that The invention comprises a positive electrode active material body and a coating layer formed on at least a part of the surface of the positive electrode active material body, wherein the coating layer comprises Ce a Zr b L c O 2-γ , wherein L includes at least one of Y, La, Pr, Tb, Nd, Sc, Al, Cu, Mn, Co, Ni, Fe or Sr, 0.4≤a≤0.9, 0.1≤b≤0.6, 0≤c≤0.1, a+b+c=1, 0≤γ≤0.

4.

2. The positive electrode active material according to claim 1, characterized in that a / b=0.8-8.

3. The positive electrode active material according to claim 1 or 2, characterized in that a / b=0.8-4.

4. The positive electrode active material according to any one of claims 1 to 3, characterized in that 0.02≤c≤0.05。 5. The positive electrode active material according to any one of claims 1 to 4, characterized in that The ratio of the mass of the coating layer to the mass of the positive electrode active material body is (0.1-20):

100.

6. The positive electrode active material according to any one of claims 1 to 5, characterized in that The ratio of the mass of the coating layer to the mass of the positive electrode active material body is (0.5-5):

100.

7. The positive electrode active material according to any one of claims 1 to 6, characterized in that The positive electrode active material includes Na x M y N 1-y O 2-z F z , wherein M includes at least one of Cu, Ni, Fe, Co, V, Y, Ta, Mn, Ti, Zr, Sb, Nb, Mg, Mo, Zn, Cr, W, Bi, Sn, Ge, Al, Ca, Sc or Sr, N includes at least one of Si, P, B, S or Se, 0.6≤x≤1, 0≤y≤1, and 0≤z≤0.

05.

8. The positive electrode active material according to any one of claims 1 to 7, characterized in that The positive electrode active material includes Na x Ni m Fe n Mn q D p O 2-z F z , wherein D includes at least one of Cu or Zn, 0.6≤x≤1, 0.2≤m≤0.5, 0.2≤n≤0.4, 0.2≤q≤0.6, 0≤p≤0.15, 0≤z≤0.05, m+n+p+q=1.

9. The positive electrode active material according to any one of claims 1 to 8, characterized in that The volume average particle size Dv50 of the positive electrode active material body is 1 μm-20 μm.

10. A method for preparing a positive electrode active material, characterized in that: include: A coating layer is formed on at least a portion of the surface of the positive electrode active material body, wherein the coating layer includes Ce a Zr b L c O 2-γ , wherein L includes at least one of Y, La, Pr, Tb, Nd, Sc, Al, Cu, Mn, Co, Ni, Fe or Sr, 0.4≤a≤0.9, 0.1≤b≤0.6, 0≤c≤0.1, a+b+c=1, 0≤γ≤0.

4.

11. The method according to claim 10, characterized in that include: The positive electrode active material body and Ce with a volume average particle size Dv50 of 20nm-100nm a Zr b L c O 2-γ The particles are mixed and stirred to make Ce a Zr b L c O 2-γ The particles are coated on at least a portion of the surface of the cathode active material body, and the cathode active material is obtained by calcining.

12. The method according to claim 10 or 11, characterized in that The Ce a Zr b L c O 2-γ The particles were prepared by the following method: Dissolve soluble Ce salt and soluble Zr salt in water, mix, adjust pH to alkaline, and filter to obtain solid; The solid is sintered to obtain Ce a Zr b L c O 2-γ particles.

13. The method according to claim 12, characterized in that The sintering temperature is 500°C-1500°C.

14. The method according to any one of claims 10 to 13, characterized in that The positive electrode active material includes Na x M y N 1-y O 2-z F z , wherein M includes at least one of Cu, Ni, Fe, Co, V, Y, Ta, Mn, Ti, Zr, Sb, Nb, Mg, Mo, Zn, Cr, W, Bi, Sn, Ge, Al, Ca, Sc or Sr, N includes at least one of Si, P, B, S or Se, 0.6≤x≤1, 0≤y≤1, and 0≤z≤0.

05.

15. The method according to any one of claims 10 to 14, characterized in that The positive electrode active material includes Na x Ni m Fe n Mn q D p O 2-z F z , wherein D includes at least one of Cu or Zn, 0.6≤x≤1, 0.2≤m≤0.5, 0.2≤n≤0.4, 0.2≤q≤0.6, 0≤p≤0.15, 0≤z≤0.05, m+n+p+q=1.

16. A positive electrode plate, characterized in that: The invention comprises the positive electrode active material according to any one of claims 1 to 9 or the positive electrode active material prepared by the method according to any one of claims 10 to 15.

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

18. An electrical device, characterized in that: Including the battery according to claim 17.

Images