Battery, positive electrode material and preparation method therefor, positive electrode sheet, and electric device

Abstract

A positive electrode active material comprises a substrate and a coating layer provided on the surface of the substrate. The chemical formula of the substrate is Ax1M1y1N1z1O2, wherein the element A comprises at least one of Na and Li, the element M1 comprises at least one transition metal element, the element N1 comprises at least one non-transition metal element, 0.5≤x1≤1, 0≤y1≤1, and 0≤z1≤1. The chemical formula of the coating layer is Ax2M2y2N2z2O2, wherein the element M2 comprises at least one transition metal element, the element N2 comprises at least one non-transition metal element, 0.5≤x2≤1, 0≤y2≤1, and 0≤z2≤1. The greater bond energy among the bond energies between the element M1 and oxygen and between the element N1 and oxygen is the first bond energy; the greater bond energy among the bond energies between the element M2 and oxygen and between the element N2 and oxygen is the second bond energy; and the second bond energy is greater than the first bond energy. The binding force of the metal to oxygen in the coating layer is stronger, such that the reaction between an electrolyte and the coating layer can be effectively reduced, thereby improving the cycle life of a battery.

Description

Batteries, positive electrode materials and their preparation methods, positive electrode sheets and electrical devices

[0001] Related applications

[0002] This application claims priority to Chinese patent application No. 202411035088.0, filed on July 30, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of battery technology, and in particular to a battery, a positive electrode material and its preparation method, a positive electrode sheet and an electrical device. Background Technology

[0004] Side reactions between the cathode material and the electrolyte are one of the important factors affecting the performance of lithium-ion batteries. For example, the surface of the cathode material may undergo an oxidation reaction with the electrolyte, leading to electrolyte decomposition and the formation of a solid electrolyte interphase (CEI) layer. Alternatively, the electrolyte may be oxidized and decomposed to produce gas during cycling, resulting in a lower cycle life, which is detrimental to the health of the battery. Summary of the Invention

[0005] The primary objective of this application is to provide a battery designed to improve battery cycle life.

[0006] To achieve the above objectives, this application proposes a battery comprising a positive electrode sheet, wherein the positive electrode sheet comprises a current collector and a positive electrode coating disposed on the current collector, the positive electrode coating comprises a positive electrode active material, and the positive electrode active material comprises a substrate and a coating layer disposed on the surface of the substrate;

[0007] The chemical formula of the substrate includes A x1 M1 y1 N1 z1 O2, wherein element A includes at least one of Na and Li, element M1 includes at least one transition metal element, element N1 includes at least one non-transition metal element, and 0.5≤x1≤1, 0≤y1≤1, 0≤z1≤1;

[0008] The chemical formula of the coating layer includes A x2 M2 y2 N2 z2 O2, wherein the M2 element includes at least one transition metal element, the N2 element includes at least one non-transition metal element, and 0.5≤x2≤1, 0≤y2≤1, 0≤z2≤1;

[0009] The highest bond energy between M1 and N1 elements and oxygen is the first bond energy, while the highest bond energy between M2 and N2 elements and oxygen is the second bond energy, which is greater than the first bond energy.

[0010] The chemical formula of the coating layer includes A x2 M2 y2 N2 z2 O2, the chemical formula of the substrate includes A x1 M1 y1 N1 z1 The second bond energy of O2 refers to the highest bond energy between oxygen and the transition metal or non-transition metal element in the coating layer's chemical formula, while the first bond energy refers to the highest bond energy between oxygen and the transition metal or non-transition metal element in the substrate's chemical formula. The fact that the second bond energy is greater than the first bond energy indicates that oxygen has a larger bond energy in the coating layer. A larger bond energy signifies a more stable chemical bond, meaning the coating layer is more stable than the substrate. A stable coating layer physically blocks the electrolyte from the substrate, reducing contact between them and minimizing side reactions. Furthermore, the high bond energy between oxygen and transition metal or non-transition metal elements in the coating layer indicates a strong bond between the metal and oxygen. During charging, O is bound, reducing the risk of lattice oxygen in the coating layer turning into oxygen and oxidizing the electrolyte. This effectively reduces the reaction between the electrolyte and the coating layer, improving the material's cycle life and consequently, the battery's cycle life.

[0011] It is also understandable that the coating material also satisfies the extraction and insertion of ions. By coating a stable coating material on the surface of the substrate, this coating material can not only satisfy the extraction and insertion of ions, but also has less impact from the electrolyte. Therefore, the stability of the positive electrode active material will be significantly improved.

[0012] Optionally, at least one of the following conditions must be met:

[0013] Condition A: The difference between the second bond energy and the first bond energy is 0.21 eV to 1.29 eV;

[0014] Condition B: The first bond energy ranges from 1.73 eV to 2.52 eV;

[0015] Condition C: The second bond energy ranges from 2.73 eV to 3.02 eV.

[0016] Understandably, the difference between the second bond energy and the first bond energy within the above range helps the coating layer maintain structural stability, while the substrate can achieve rapid insertion and extraction of ions (such as sodium ions or lithium ions), thus improving the rate performance of the battery.

[0017] Meeting the aforementioned range for the first bond energy can improve the stability of the substrate and enhance the rate performance of the battery. It is understandable that the cathode material undergoes structural changes during battery charging and discharging. Materials with higher metal-oxygen bond energies may exhibit better structural stability, helping to maintain material integrity and reducing volume expansion and contraction during cycling. Therefore, the first bond energy cannot be too small. Simultaneously, since sodium or lithium ions in the cathode material need to cyclically insert and extract within the cathode material structure during battery cycling, excessively high bond energies will restrict ion insertion and extraction, affecting the battery's rate performance. Therefore, the first bond energy also cannot be too small.

[0018] The second bond can meet the above range values, and the coating layer has good stability. It is understood that the metal and the lattice oxygen have strong bonding force. During the reaction with the electrolyte, the structure of the coating layer is difficult to be destroyed, and its lattice oxygen is difficult to be oxidized and released. In this way, the electrolyte is blocked by the coating compound and it is difficult to enter the coating layer, thereby reducing the risk of side reactions between the cathode material and the electrolyte.

[0019] Optionally, at least one of the following conditions must be met:

[0020] Condition A: The transition metal element includes at least one of Ni, Fe, Co, Mn, Cu, and Zn;

[0021] Condition B: The non-transition metal element includes at least one of Li, K, Mg, Ca, Al, Sn, Sb, Te, and Se.

[0022] The transition metal element in this application includes at least one of the above-mentioned elements. Specifically, the bond energy between Ni and oxygen is 1.73 eV, Fe and oxygen is 1.78 eV, Co and oxygen is 1.79 eV, Mn and oxygen is 2.52 eV, Cu and oxygen is 2.02 eV, and Zn and oxygen is 1.94 eV. The bond energy between the metal and oxygen can be calculated using first-principles calculations and DFT theory to determine the energy required to remove an oxygen atom.

[0023] The non-transition metal elements in this application include at least one of the above-mentioned elements. Specifically, the bond energy between Li and oxygen is 0.72 eV, K is 0.34 eV, Mg is 1.87 eV, Ca is 2.14 eV, Al is 2.17 eV, Sn is 2.35 eV, Sb is 2.75 eV, Te is 3.02 eV, and Se is 2.73 eV.

[0024] Optionally, the N2 element includes at least one of Sb, Te, and Se.

[0025] It is understandable that Sb, Te, and Se have large bond energies with oxygen, and including these elements in the chemical formula of the coating layer can improve the stability of the coating layer.

[0026] Optionally, the substrate comprises an O3 phase material, and the coating layer comprises an O3 phase material.

[0027] Understandably, by employing O3 phase coating technology, it is easier to achieve coherent coating of similar materials, resulting in better coating performance.

[0028] It is understandable that O3 phase coating of O3 phase possesses the characteristic of consistent atomic arrangement at the interface between the substrate and the coating layer. When the lattice parameters (such as lattice constants) of two crystals at the interface are very close or identical, their lattices can seamlessly align at the interface, forming a coherent interface. This coherent interface can reduce lattice distortion and stress, thereby improving the mechanical properties and stability of the material. Simultaneously, the coherent interface can promote rapid ion transport, improving the charge / discharge rate and cycle stability of the battery. Furthermore, the presence of a coherent interface can reduce lattice distortion caused by lattice mismatch, which can lead to stress concentration at incoherent interfaces, thus affecting the long-term stability and performance of the material.

[0029] Optionally, the chemical formula of the substrate includes Na. x1 M1 y1 N1 z1 O2, where 0.8 < x1 ≤ 1, y1 + z1 = 1, 0 ≤ y1 ≤ 1, 0 ≤ z1 ≤ 1;

[0030] The chemical formula of the coating layer includes Na. x2 M2 y2 N2 z2 O2, where 0.8 < x2 ≤ 1, y2 + z2 = 1, 0 ≤ y2 ≤ 1, 0 ≤ z2 ≤ 1.

[0031] It is understandable that when the substrate includes the O3 phase, its chemical formula includes Na. x1 M1 y1 N1 z1 O2, wherein 0.8 < x1 ≤ 1, y1 + z1 = 1, 0 ≤ y1 ≤ 1, 0 ≤ z1 ≤ 1; when the coating layer includes the O3 phase, its chemical formula includes Na. x2 M2 y2 N2 z2 O2, where 0.8 < x2 ≤ 1, y2 + z2 = 1, 0 ≤ y2 ≤ 1, 0 ≤ z2 ≤ 1.

[0032] Optionally, at least one of the following conditions must be met:

[0033] Condition A: The volume average particle size D50 of the substrate ranges from 6 μm to 10 μm;

[0034] Condition B: The mass percentage of the coating layer to the total mass of the substrate and the coating layer ranges from 1% to 20%;

[0035] Condition C: The coating thickness ranges from 20 nm to 200 nm;

[0036] Condition D: The substrate includes monocrystalline substrates and / or polycrystalline substrates;

[0037] Condition E: The substrate includes a polycrystalline substrate, and the mass percentage of the coating layer on the surface of the polycrystalline substrate to the total mass of the polycrystalline substrate and the coating layer is in the range of 1% to 2%.

[0038] Condition F: The substrate includes a polycrystalline substrate, and the coating thickness of the coating layer on the surface of the polycrystalline substrate ranges from 5 nm to 20 nm;

[0039] Condition G: The charging voltage range of the battery is 1.5V to 4.3V;

[0040] Condition H: The discharge voltage range of the battery is 4.3V to 1.5V.

[0041] It is understandable that if the volume average particle size D50 of the substrate is too large, the mass transfer will be poor, and if it is too small, the specific surface area will be large, resulting in more reaction interfaces with the electrolyte. Therefore, taking all factors into consideration, the battery performance is better when the volume average particle size D50 of the substrate is within the above range.

[0042] The mass percentage of the coating layer relative to the total mass of the substrate and coating layer ranges from 1% to 20%. It is understandable that for layered cathode materials, such as layered oxide cathode materials in sodium-ion batteries, sodium ions diffuse and migrate along the non-003 crystal planes. The interface of the non-003 crystal planes is affected by electrolyte and transition metal migration and lattice oxygen loss during cycling. This can cause changes such as CEI, spinel phase, and rock salt phase to form on the surface of the non-003 crystal planes. These byproducts slow down the insertion / extraction of sodium ions, ultimately leading to a decline in electrochemical performance. Modifying the non-003 crystal planes is an efficient measure to improve the rate capability and stability of materials. Since it is difficult to control the coating layer to only cover the non-003 crystal planes, within the aforementioned mass percentage range of the coating layer relative to the total mass of the substrate and coating layer, as the percentage increases, the effect of coating the non-003 crystal planes is better, and it is more beneficial to improve the stability of the substrate.

[0043] If the coating thickness meets the above-mentioned range, it can effectively isolate the electrolyte from the substrate and improve the stability of the substrate.

[0044] The substrate includes monocrystalline substrates and / or polycrystalline substrates. That is, the substrate can be monocrystalline, polycrystalline, or a mixture of monocrystalline and polycrystalline. A coating layer is provided on the surface of the monocrystalline and polycrystalline substrates, which can improve the stability of the substrate.

[0045] The mass percentage of the coating layer on the polycrystalline substrate surface to the total mass of the polycrystalline substrate and the coating layer ranges from 1% to 2%. It is understandable that when the coating layer on the polycrystalline substrate surface has a coating amount of 1% to 2%, the cycle stability of the battery is improved better.

[0046] When the coating thickness of the polycrystalline substrate surface coating meets the above-mentioned range, the cycle stability of the battery is improved significantly.

[0047] Because the substrate surface has a coating layer, the stability of the cathode material is improved. As a result, the charging voltage and discharging voltage of the battery can be increased to a wider range, thereby improving the charging and discharging performance of the battery.

[0048] In summary, the coating layer of this application can protect the substrate, reduce its direct contact with the electrolyte, thereby reducing the occurrence of side reactions and improving the chemical stability of the material. During charge and discharge, the cathode material may undergo volume expansion and contraction; the coating layer can limit this volume change, reduce stress concentration, and thus improve the structural stability of the material. The O3 phase coating can optimize the electron and ion transport paths of the cathode material, reduce charge transport resistance, and improve the battery's conductivity and ion diffusion rate. By improving the stability of the cathode material, the coating layer helps the battery operate over a wider voltage range, meaning the battery can operate at higher charging voltages and lower discharging voltages, thereby increasing the battery's energy density and power density. Under high-rate charge and discharge conditions, battery polarization intensifies, leading to performance degradation; the coating layer can reduce electrode surface polarization, improving the battery's rate performance. The coating layer can slow down the degradation of the cathode material during cycling, extending the battery's cycle life. By reducing side reactions and improving material stability, the coating layer helps improve battery safety and reduce the risk of thermal runaway.

[0049] Optionally, this application also provides a positive electrode material, the positive electrode active material comprising a substrate and a coating layer disposed on the surface of the substrate;

[0050] The chemical formula of the substrate includes A x1 M1 y1 N1 z1 O2, wherein element A includes at least one of Na and Li, element M1 includes at least one transition metal element, element N1 includes at least one non-transition metal element, and 0.5≤x1≤1, 0≤y1≤1, 0≤z1≤1;

[0051] The chemical formula of the coating layer includes A x2 M2 y2 N2 z2 O2, wherein the M2 element includes at least one transition metal element, the N2 element includes at least one non-transition metal element, and 0.5≤x2≤1, 0≤y2≤1, 0≤z2≤1;

[0052] The highest bond energy between M1 and N1 elements and oxygen is the first bond energy, while the highest bond energy between M2 and N2 elements and oxygen is the second bond energy, which is greater than the first bond energy.

[0053] Optionally, at least one of the following conditions must be met:

[0054] Condition A: The difference between the second bond energy and the first bond energy is 0.21 eV to 1.29 eV;

[0055] Condition B: The first bond energy ranges from 1.73 eV to 2.52 eV;

[0056] Condition C: The second bond energy ranges from 2.73 eV to 3.02 eV.

[0057] Optionally, at least one of the following conditions must be met:

[0058] Condition A: The transition metal element includes at least one of Ni, Fe, Co, Mn, Cu, and Zn;

[0059] Condition B: The non-transition metal element includes at least one of Li, K, Mg, Ca, Al, Sn, Sb, Te, and Se.

[0060] Optionally, the N2 element includes at least one of Sb, Te, and Se.

[0061] Optionally, the substrate comprises an O3 phase material, and the coating layer comprises an O3 phase material.

[0062] Optionally, the chemical formula of the substrate includes Na. x1 M1 y1 N1 z1 O2, where 0.8 < x1 ≤ 1, y1 + z1 = 1, 0 ≤ y1 ≤ 1, 0 ≤ z1 ≤ 1;

[0063] The chemical formula of the coating layer includes Na. x2 M2 y2 N2 z2 O2, where 0.8 < x2 ≤ 1, y2 + z2 = 1, 0 ≤ y2 ≤ 1, 0 ≤ z2 ≤ 1.

[0064] Optionally, at least one of the following conditions must be met:

[0065] Condition A: The volume average particle size D50 of the substrate ranges from 6 μm to 10 μm;

[0066] Condition B: The mass percentage of the coating layer to the total mass of the substrate and the coating layer ranges from 1% to 20%;

[0067] Condition C: The coating thickness ranges from 20 nm to 200 nm;

[0068] Condition D: The substrate includes monocrystalline substrates and / or polycrystalline substrates;

[0069] Condition E: The substrate includes a polycrystalline substrate, and the mass percentage of the coating layer on the surface of the polycrystalline substrate to the total mass of the polycrystalline substrate and the coating layer is in the range of 1% to 2%.

[0070] Condition F: The substrate includes a polycrystalline substrate, and the coating thickness of the coating layer on the surface of the polycrystalline substrate ranges from 5 nm to 20 nm.

[0071] Optionally, this application also provides a method for preparing a cathode material, comprising:

[0072] Obtain the substrate;

[0073] The coating material source is mixed with the substrate to obtain a mixture;

[0074] The mixture is sintered to obtain a positive electrode material with a coating layer on the surface of the substrate.

[0075] That is, in the process of material preparation, a substrate is obtained. It can be understood that the substrate can be obtained by preparation or by commercial purchase. The coating material source is mixed with the substrate to obtain a mixture. The coating material source refers to the raw material that can form a coating layer. The mixture is sintered to obtain a positive electrode material with a coating layer on the surface of the substrate. That is, during the sintering process, the coating material source forms a coating layer on the surface of the substrate.

[0076] Optionally, the step of obtaining the substrate includes:

[0077] Mix at least two substrate material sources to obtain a hybrid material source;

[0078] The mixed material source is sintered to obtain a substrate.

[0079] That is, when the substrate is obtained by the preparation method, the above method can be used to mix at least two substrate material sources to obtain a mixed material source, wherein the substrate material source refers to the raw material that can form the substrate; the mixed material source is sintered to obtain the substrate, that is, the sintering step can transform the substrate material source into the substrate.

[0080] Optionally, at least one of the following conditions must be met:

[0081] In the step of mixing at least two substrate material sources to obtain a mixed material source, the substrate material sources include a sodium source and a transition metal source;

[0082] In the step of sintering the mixed material source to obtain the substrate, the sintering temperature ranges from 800°C to 1000°C, and the holding time ranges from 6 hours to 24 hours.

[0083] In the step of mixing the coating material source with the substrate to obtain a mixture, the coating material source includes a sodium source, a transition metal source, and a non-transition metal source.

[0084] In the substrate preparation process, the substrate material source includes sodium source and transition metal source. Of course, other elements can also be added as needed, depending on the actual requirements.

[0085] In the process of preparing the substrate, the sintering temperature range for the mixed material source is 800℃ to 1000℃, and the holding time ranges from 6h to 24h.

[0086] In the step of preparing the coating layer, the coating material source includes sodium source, transition metal source and non-transition metal source.

[0087] Optionally, at least one of the following conditions must be met:

[0088] Condition A: The sodium source includes at least one of sodium carbonate, sodium acetate, and sodium hydroxide;

[0089] Condition B: The transition metal source includes at least one of nickel, manganese, iron, and copper sources;

[0090] Condition C: The nickel source includes at least one of nickel oxide, nickel acetate, and nickel carbonate;

[0091] Condition D: The manganese source includes at least one of manganese oxide, manganese acetate, and manganese carbonate;

[0092] Condition E: The iron source includes at least one of iron oxide, iron acetate, and iron carbonate;

[0093] Condition F: The copper source includes at least one of copper oxide, copper acetate, and copper carbonate;

[0094] Condition G: The non-transition metal source includes at least one of antimony source, tellurium source, and selenium source;

[0095] Condition H: The antimony source includes at least one of antimony oxide and antimony acetate;

[0096] Condition I: The tellurium source includes at least one of tellurium oxide and telluric acid;

[0097] Condition J: The selenium source includes at least one of selenium oxide and selenite.

[0098] Optionally, the step of mixing the coating material source with the substrate to obtain a mixture includes:

[0099] The coating material source and the substrate are mixed in a solvent, heated and stirred, and dried to obtain a mixture, wherein the heating temperature range is 60°C to 90°C;

[0100] Alternatively, the coating material source can be ball-milled and mixed with the substrate to obtain a mixture.

[0101] In the step of mixing the coating material source and the substrate, the coating material source and the substrate can be mixed in a solvent, heated and stirred, and dried to obtain a mixture. The heating temperature range is 60°C to 90°C, and the solvent can include solvents such as ethanol and acetone.

[0102] Alternatively, the coating material source and the substrate can be ball-milled to obtain a mixture. Understandably, ball milling is not suitable for spherical polycrystalline materials, as mechanical ball milling can damage the polycrystalline morphology.

[0103] Optionally, in the step of sintering the mixture to obtain a positive electrode material with a coating layer on the surface of the substrate, the sintering temperature ranges from 600°C to 900°C, the holding time ranges from 2h to 24h, and the mass percentage of the coating layer in the total mass of the substrate and the coating layer ranges from 1% to 20%.

[0104] That is, during the process of applying the coating layer to the substrate surface, the sintering temperature ranges from 600℃ to 900℃, and the holding time ranges from 2 hours to 24 hours. In preparing the coating layer material source and the substrate, the amount of coating layer material source can be calculated based on the mass ratio of the coating layer to the substrate, ensuring that the mass percentage of the coating layer in the total mass of the substrate and coating layer ranges from 1% to 20%.

[0105] Optionally, this application also provides a positive electrode sheet, the positive electrode sheet comprising the positive electrode material as described above;

[0106] Alternatively, the positive electrode may comprise a positive electrode material obtained by the method described above for preparing positive electrode materials.

[0107] Optionally, this application also provides an electrical device, which includes the battery as described above.

[0108] The battery of this application includes a positive electrode sheet, which includes a current collector and a positive electrode coating disposed on the current collector. The positive electrode coating includes a positive electrode active material, which includes a substrate and a coating layer disposed on the surface of the substrate. The chemical formula of the substrate includes A. x1 M1 y1 N1 z1 O2, wherein element A includes at least one of Na and Li, element M1 includes at least one transition metal element, element N1 includes at least one non-transition metal element, 0.5≤x1≤1, 0≤y1≤1, 0≤z1≤1; the chemical formula of the coating layer includes A x2 M2 y2 N2 z2 O2, wherein M2 element includes at least one transition metal element, N2 element includes at least one non-transition metal element, 0.5≤x2≤1, 0≤y2≤1, 0≤z2≤1; the highest bond energy between M1 and N1 elements and oxygen is the first bond energy, and the highest bond energy between M2 and N2 elements and oxygen is the second bond energy, and the second bond energy is greater than the first bond energy. The second bond energy refers to the highest bond energy between oxygen and any transition metal or non-transition metal element in the coating layer's chemical formula, while the first bond energy refers to the highest bond energy between oxygen and any transition metal or non-transition metal element in the substrate's chemical formula. The fact that the second bond energy is greater than the first bond energy indicates that oxygen has a higher bond energy in the coating layer. A higher bond energy signifies a more stable chemical bond, meaning the coating layer is more stable than the substrate. A stable coating layer physically blocks the electrolyte from the substrate, reducing contact between them and minimizing side reactions. Furthermore, the high bond energy between oxygen and transition metal or non-transition metal elements in the coating layer indicates a strong bond between the metal and oxygen. During charging, the oxygen is bound, reducing the risk of lattice oxygen in the coating layer turning into oxygen and oxidizing the electrolyte. This effectively reduces the reaction between the electrolyte and the coating layer, improving the material's cycle life and consequently, the battery's cycle life. Attached Figure Description

[0109] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0110] Figure 1 is a schematic diagram of the morphology and structure of the substrate in Embodiment 1 of this application;

[0111] Figure 2 is a schematic diagram of the morphology of the coating layer disposed on the surface of the substrate in Embodiment 1 of this application;

[0112] Figure 3 is a schematic diagram of the cross-sectional morphology of the substrate surface with a coating layer in Embodiment 1 of this application;

[0113] Figure 4 is the energy dispersive spectrum of the substrate surface coated with a coating layer in Embodiment 1 of this application;

[0114] Figure 5 is a graph showing the long-cycle electrochemical performance of Example 1 and Comparative Example 1 of this application;

[0115] Figure 6 is a schematic diagram of a battery cell according to an embodiment of this application;

[0116] Figure 7 is an exploded view of a battery cell according to an embodiment of this application shown in Figure 6;

[0117] Figure 8 is a schematic diagram of a battery module according to one embodiment of this application;

[0118] Figure 9 is a schematic diagram of a battery pack according to an embodiment of this application;

[0119] Figure 10 is an exploded view of a battery pack according to an embodiment of this application, as shown in Figure 9;

[0120] Figure 11 is a schematic diagram of an electrical device in which a single battery cell is used as a power source according to an embodiment of this application.

[0121] Explanation of icon numbers:

[0122] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0123] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0124] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the sodium-supplementing material, its preparation method, positive electrode sheet, electrode assembly, battery, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0125] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0126] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0127] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0128] Unless otherwise specified, all steps in this 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 it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0129] During battery cycling, the electrolyte is oxidized and decomposed to produce gas, resulting in a lower cycle life, which is detrimental to battery health.

[0130] To address the aforementioned problems, this application provides a battery designed to improve its cycle life.

[0131] The battery includes a positive electrode sheet, which includes a current collector and a positive electrode coating disposed on the current collector. The positive electrode coating includes a positive electrode active material, which includes a substrate and a coating layer disposed on the surface of the substrate. The chemical formula of the substrate includes A. x1 M1 y1 N1 z1 O2, wherein element A includes at least one of Na and Li, element M1 includes at least one transition metal element, element N1 includes at least one non-transition metal element, 0.5≤x1≤1, 0≤y1≤1, 0≤z1≤1; the chemical formula of the coating layer includes A x2 M2 y2 N2 z2 O2, wherein M2 element includes at least one transition metal element, N2 element includes at least one non-transition metal element, 0.5≤x2≤1, 0≤y2≤1, 0≤z2≤1; the highest bond energy between M1 and N1 elements and oxygen is the first bond energy, and the highest bond energy between M2 and N2 elements and oxygen is the second bond energy, and the second bond energy is greater than the first bond energy.

[0132] It is understandable that the M1 element includes at least one transition metal element, meaning that M1 can be one transition metal element, two transition metal elements, or more transition metal elements.

[0133] For example, when M1 is two transition metal elements, one of which is represented by M11 and the other by M12, the chemical formula of the substrate includes A. x1 M11 y11 M12 y12 N1 z1 O2, 0≤y11≤1, 0≤y12≤1.

[0134] The M2 element includes at least one transition metal element, meaning that M2 can be one, two, or more transition metal elements.

[0135] For example, when M2 consists of two transition metal elements, one of which is represented by M21 and the other by M22, the chemical formula of the coating layer includes A. x2 M21 y21 M22 y22 N1 z2 O2, 0≤y21≤1, 0≤y22≤1.

[0136] The N1 element includes at least one non-transition metal element, meaning that N1 can be one non-transition metal element, two non-transition metal elements, or more non-transition metal elements.

[0137] For example, when N1 is two non-transition metal elements, one of which is represented by N11 and the other by N12, the chemical formula of the substrate includes A. x1 M1 y1 N11 z11 N12 z12 O2, 0≤z11≤1, 0≤z12≤1.

[0138] The N2 element includes at least one non-transition metal element, meaning that N2 can be one non-transition metal element, two non-transition metal elements, or more non-transition metal elements.

[0139] For example, when N2 consists of two non-transition metal elements, one denoted as N21 and the other as N22, the chemical formula of the coating layer includes A. x2 M2 y2 N21 z21 N22 z22 O2, 0≤z21≤1, 0≤z22≤1.

[0140] The bond energy with oxygen that is the largest among elements M1 and N1 is the first bond energy. For example, if the bond energy between M1 and oxygen is D1 and the bond energy between N1 and oxygen is D2, and D1 > D2, then the bond energy D1 between M1 and oxygen is the first bond energy.

[0141] The bond energy with oxygen in elements M2 and N2 is the second bond energy. For example, the bond energy between M2 and oxygen is D3, and the bond energy between N2 and oxygen is D4. Since D4 > D3, the bond energy D4 between N2 and oxygen is the second bond energy.

[0142] Bond energy, also known as the dissociation energy of a chemical bond, refers to the energy required to break one mole of chemical bonds under standard conditions. In other words, bond energy is the opposite of the energy released when a chemical bond is formed; that is, the energy required to dissociate the chemical bonds in a molecule to make it into independent atoms. Bond energy is an indicator of the strength of a chemical bond; the greater the bond energy, the more stable the chemical bond.

[0143] The chemical formula of the coating layer includes A x2 M2 y2 N2 z2 O2, the chemical formula of the substrate includes A x1 M1 y1 N1 z1The second bond energy of O2 refers to the highest bond energy between oxygen and the transition metal or non-transition metal element in the coating layer's chemical formula, while the first bond energy refers to the highest bond energy between oxygen and the transition metal or non-transition metal element in the substrate's chemical formula. The fact that the second bond energy is greater than the first bond energy indicates that oxygen has a larger bond energy in the coating layer. A larger bond energy signifies a more stable chemical bond, meaning the coating layer is more stable than the substrate. A stable coating layer physically blocks the electrolyte from the substrate, reducing contact between them and minimizing side reactions. Furthermore, the high bond energy between oxygen and transition metal or non-transition metal elements in the coating layer indicates a strong bond between the metal and oxygen. During charging, O is bound, reducing the risk of lattice oxygen in the coating layer turning into oxygen and oxidizing the electrolyte. This effectively reduces the reaction between the electrolyte and the coating layer, improving the material's cycle life and consequently, the battery's cycle life.

[0144] It is also understandable that the coating material also satisfies the extraction and insertion of ions. By coating a stable coating material on the surface of the substrate, this coating material can not only satisfy the extraction and insertion of ions, but also has less impact from the electrolyte. Therefore, the stability of the positive electrode active material will be significantly improved.

[0145] In one embodiment, at least one of the following conditions is satisfied: Condition A: the difference between the second bond energy and the first bond energy is 0.21 eV to 1.29 eV; Condition B: the range of the first bond energy is 1.73 eV to 2.52 eV; Condition C: the range of the second bond energy is 2.73 eV to 3.02 eV.

[0146] Understandably, the difference between the second bond energy and the first bond energy within the above range helps the coating layer maintain structural stability, while the substrate can achieve rapid insertion and extraction of ions (such as sodium ions or lithium ions), thus improving the rate performance of the battery.

[0147] Meeting the aforementioned range for the first bond energy can improve the stability of the substrate and enhance the rate performance of the battery. It is understandable that the cathode material undergoes structural changes during battery charging and discharging. Materials with higher metal-oxygen bond energies may exhibit better structural stability, helping to maintain material integrity and reducing volume expansion and contraction during cycling. Therefore, the first bond energy cannot be too small. Simultaneously, since sodium or lithium ions in the cathode material need to cyclically insert and extract within the cathode material structure during battery cycling, excessively high bond energies will restrict ion insertion and extraction, affecting the battery's rate performance. Therefore, the first bond energy also cannot be too small.

[0148] The second bond can meet the above range values, and the coating layer has good stability. It is understood that the metal and the lattice oxygen have strong bonding force. During the reaction with the electrolyte, the structure of the coating layer is difficult to be destroyed, and its lattice oxygen is difficult to be oxidized and released. In this way, the electrolyte is blocked by the coating compound and it is difficult to enter the coating layer, thereby reducing the risk of side reactions between the cathode material and the electrolyte.

[0149] The values ​​in the range of 0.21eV to 1.29eV include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 0.21eV, 0.27eV, 0.29eV, 1eV, 1.02eV, 1.29eV, etc., as well as the range values ​​between any two of the above point values.

[0150] The values ​​in the range of 1.73eV to 2.52eV include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, as well as 1.73eV, 1.78eV, 1.79eV, 2.52eV, etc., and the range values ​​between any two of the above point values.

[0151] The values ​​in the range of 2.73eV to 3.02eV include the minimum and maximum values ​​of this range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, as well as 2.73eV, 2.75eV, 3.02eV, etc., and the range values ​​between any two of the above point values.

[0152] In one embodiment, at least one of the following conditions is satisfied: Condition A: The transition metal element includes at least one of Ni, Fe, Co, Mn, Cu, and Zn; Condition B: The non-transition metal element includes at least one of Li, K, Mg, Ca, Al, Sn, Sb, Te, and Se.

[0153] The transition metal element in this application includes at least one of the above-mentioned elements. Specifically, the bond energy between Ni and oxygen is 1.73 eV, Fe and oxygen is 1.78 eV, Co and oxygen is 1.79 eV, Mn and oxygen is 2.52 eV, Cu and oxygen is 2.02 eV, and Zn and oxygen is 1.94 eV. The bond energy between the metal and oxygen can be calculated using first-principles calculations and DFT theory to determine the energy required to remove an oxygen atom.

[0154] The non-transition metal elements in this application include at least one of the above-mentioned elements. Specifically, the bond energy between Li and oxygen is 0.72 eV, K is 0.34 eV, Mg is 1.87 eV, Ca is 2.14 eV, Al is 2.17 eV, Sn is 2.35 eV, Sb is 2.75 eV, Te is 3.02 eV, and Se is 2.73 eV.

[0155] In one embodiment, the N2 element includes at least one of Sb, Te, and Se.

[0156] It is understandable that Sb, Te, and Se have large bond energies with oxygen, and including these elements in the chemical formula of the coating layer can improve the stability of the coating layer.

[0157] In one embodiment, the substrate comprises an O3 phase material, and the coating layer comprises an O3 phase material.

[0158] O3 phase materials typically refer to layered oxide materials with an O3-type structure. For example, in sodium-ion cathode materials, sodium ions are located in an octahedral coordination environment of oxygen, forming a so-called O-type (octahedral) stacking configuration. This structure provides a two-dimensional transport channel for the insertion / extraction of sodium ions, which helps to improve the charge and discharge performance of the battery.

[0159] Understandably, by employing O3 phase coating technology, it is easier to achieve coherent coating of similar materials, resulting in better coating performance.

[0160] It is understandable that O3 phase coating of O3 phase possesses the characteristic of consistent atomic arrangement at the interface between the substrate and the coating layer. When the lattice parameters (such as lattice constants) of two crystals at the interface are very close or identical, their lattices can seamlessly align at the interface, forming a coherent interface. This coherent interface can reduce lattice distortion and stress, thereby improving the mechanical properties and stability of the material. Simultaneously, the coherent interface can promote rapid ion transport, improving the charge / discharge rate and cycle stability of the battery. Furthermore, the presence of a coherent interface can reduce lattice distortion caused by lattice mismatch, which can lead to stress concentration at incoherent interfaces, thus affecting the long-term stability and performance of the material.

[0161] For example, the chemical formula of the O3 phase substrate includes Na. x1 M11 y11 M12 y12 M13 y13 M14 y14 N11 z11 N12 z12 N13 z13 N14 z14O2, wherein M11, M12, M13, and M14 are different types of transition metal elements, and N11, N12, N13, and N14 are different types of non-transition metal elements, 0.8 < x1 ≤ 1, 0 ≤ y11 ≤ 1, 0 ≤ y12 ≤ 1, 0 ≤ y13 ≤ 1, 0 ≤ y14 ≤ 1, 0 ≤ z11 ≤ 1, 0 ≤ z12 ≤ 1, 0 ≤ z13 ≤ 1, 0 ≤ z14 ≤ 1. In one embodiment, M11, M12, M13, and M14 are Ni, Fe, Cu, and Mn, respectively, z11 = 0, z12 = 0, z13 = 0, z14 = 0, and the chemical formula of the O3 phase substrate is Na. x Ni a Fe b Cu c Mn d The O2 (0.8 < x ≤ 1, a + b + c + d = 1) substrate has high surface activity, which makes the electrolyte easily oxidized and decomposed to produce gas during cycling, resulting in a low cycle life. This is detrimental to battery health. Therefore, NaNi with low surface activity of O3 phase is selected. e Sb f The O2 (e+f=1) coating material is applied to the surface of the substrate, resulting in better stability of the cathode material system and reducing the likelihood of electrolyte oxidation. Specifically, the coating effectively prevents the reaction between the electrolyte and the substrate, inhibits electrolyte decomposition, reduces the formation of byproducts on the cathode material surface, and improves the battery's cycle performance, rate performance, and stability. Compared to uncoated substrates, the coated substrate exhibits higher cycle stability.

[0162] In one embodiment, the chemical formula of the substrate includes Na. x1 M1 y1 N1 z1 O2, wherein 0.8 < x1 ≤ 1, y1 + z1 = 1, 0 ≤ y1 ≤ 1, 0 ≤ z1 ≤ 1; the chemical formula of the coating layer includes Na. x2 M2 y2 N2 z2 O2, where 0.8 < x2 ≤ 1, y2 + z2 = 1, 0 ≤ y2 ≤ 1, 0 ≤ z2 ≤ 1.

[0163] It is understandable that when the substrate includes the O3 phase, its chemical formula includes Na. x1 M1 y1 N1 z1 O2, wherein 0.8 < x1 ≤ 1, y1 + z1 = 1, 0 ≤ y1 ≤ 1, 0 ≤ z1 ≤ 1; when the coating layer includes the O3 phase, its chemical formula includes Na. x2 M2 y2 N2 z2 O2, where 0.8 < x2 ≤ 1, y2 + z2 = 1, 0 ≤ y2 ≤ 1, 0 ≤ z2 ≤ 1.

[0164] In the above 0.8<x1≤1, the values ​​include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, as well as 0.81, 0.85, 0.90, 0.95, 0.99, 1, etc., and the range values ​​between any two of the above point values.

[0165] In the above 0≤y1≤1, the values ​​include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, etc., as well as the range values ​​between any two of the above point values.

[0166] In the above 0≤z1≤1, the values ​​include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, etc., as well as the range values ​​between any two of the above point values.

[0167] In one embodiment, at least one of the following conditions is satisfied: Condition A: The volume average particle size D50 of the substrate ranges from 6 μm to 10 μm; Condition B: The mass percentage of the coating layer to the total mass of the substrate and the coating layer ranges from 1% to 20%; Condition C: The coating thickness of the coating layer ranges from 20 nm to 200 nm; Condition D: The substrate includes a monocrystalline substrate and / or a polycrystalline substrate; Condition E: The mass percentage of the coating layer on the surface of the polycrystalline substrate to the total mass of the polycrystalline substrate and the coating layer ranges from 1% to 2%; Condition F: The coating thickness of the coating layer on the surface of the polycrystalline substrate ranges from 5 nm to 20 nm; Condition G: The charging voltage of the battery ranges from 1.5 V to 4.3 V; Condition H: The discharging voltage of the battery ranges from 4.3 V to 1.5 V.

[0168] Volume average particle size (Dv50) is the particle size at which the cumulative particle size distribution percentage of a sample reaches 50%. Physically, it means that 50% of the particles are larger than Dv50, and 50% are smaller. Dv50 is also called the median diameter or median particle size.

[0169] It is understandable that if the volume average particle size D50 of the substrate is too large, the mass transfer will be poor, and if it is too small, the specific surface area will be large, resulting in more reaction interfaces with the electrolyte. Therefore, taking all factors into consideration, the battery performance is better when the volume average particle size D50 of the substrate is within the above range.

[0170] The mass percentage of the coating layer relative to the total mass of the substrate and coating layer ranges from 1% to 20%. It is understandable that for layered cathode materials, such as layered oxide cathode materials in sodium-ion batteries, sodium ions diffuse and migrate along the non-003 crystal planes. The interface of the non-003 crystal planes is affected by electrolyte and transition metal migration and lattice oxygen loss during cycling. This can cause changes such as CEI, spinel phase, and rock salt phase to form on the surface of the non-003 crystal planes. These byproducts slow down the insertion / extraction of sodium ions, ultimately leading to a decline in electrochemical performance. Modifying the non-003 crystal planes is an efficient measure to improve the rate capability and stability of materials. Since it is difficult to control the coating layer to only cover the non-003 crystal planes, within the aforementioned mass percentage range of the coating layer relative to the total mass of the substrate and coating layer, as the percentage increases, the effect of coating the non-003 crystal planes is better, and it is more beneficial to improve the stability of the substrate.

[0171] If the coating thickness meets the above-mentioned range, it can effectively isolate the electrolyte from the substrate and improve the stability of the substrate.

[0172] The substrate includes monocrystalline substrates and / or polycrystalline substrates. That is, the substrate can be monocrystalline, polycrystalline, or a mixture of monocrystalline and polycrystalline. A coating layer is provided on the surface of the monocrystalline and polycrystalline substrates, which can improve the stability of the substrate.

[0173] The mass percentage of the coating layer on the polycrystalline substrate surface to the total mass of the polycrystalline substrate and the coating layer ranges from 1% to 2%. It is understandable that when the coating layer on the polycrystalline substrate surface has a coating amount of 1% to 2%, the cycle stability of the battery is improved better.

[0174] When the coating thickness of the polycrystalline substrate surface coating meets the above-mentioned range, the cycle stability of the battery is improved significantly.

[0175] Because the substrate surface has a coating layer, the stability of the cathode material is improved. As a result, the charging voltage and discharging voltage of the battery can be increased to a wider range, thereby improving the charging and discharging performance of the battery.

[0176] In summary, the coating layer of this application can protect the substrate, reduce its direct contact with the electrolyte, thereby reducing the occurrence of side reactions and improving the chemical stability of the material. During charge and discharge, the cathode material may undergo volume expansion and contraction; the coating layer can limit this volume change, reduce stress concentration, and thus improve the structural stability of the material. The O3 phase coating can optimize the electron and ion transport paths of the cathode material, reduce charge transport resistance, and improve the battery's conductivity and ion diffusion rate. By improving the stability of the cathode material, the coating layer helps the battery operate over a wider voltage range, meaning the battery can operate at higher charging voltages and lower discharging voltages, thereby increasing the battery's energy density and power density. Under high-rate charge and discharge conditions, battery polarization intensifies, leading to performance degradation; the coating layer can reduce electrode surface polarization, improving the battery's rate performance. The coating layer can slow down the degradation of the cathode material during cycling, extending the battery's cycle life. By reducing side reactions and improving material stability, the coating layer helps improve battery safety and reduce the risk of thermal runaway.

[0177] The values ​​in the range of 6μm to 10μm include the minimum and maximum values ​​of this range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, as well as 6μm, 7μm, 8μm, 9μm, 10μm, etc., and the range values ​​between any two of the above point values.

[0178] The values ​​in the range of 1% to 20% include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments and 1%, 2%, 5%, 10%, 15%, 20%, etc., as well as the range values ​​between any two of the above point values.

[0179] The values ​​in the range of 20nm to 200nm include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 20nm, 50nm, 80nm, 1000nm, 120nm, 150nm, 170nm, 190nm, 200nm, etc., as well as the range values ​​between any two of the above point values.

[0180] The values ​​in the range of 1% to 2% include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, as well as 1%, 1.5%, 2%, etc., and the range values ​​between any two of the above point values.

[0181] The values ​​in the range of 5nm to 20nm include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 5nm, 8nm, 10nm, 12nm, 15nm, 17nm, 19nm, 20nm, etc., as well as the range values ​​between any two of the above point values.

[0182] The values ​​from 1.5V to 4.3V mentioned above include the minimum and maximum values ​​of this range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 1.5V, 1.7V, 2.0V, 2.5V, 3.0V, 3.5V, 4.0V, 4.3V, etc., as well as the range values ​​between any two of the above point values.

[0183] In one embodiment, this application also provides a positive electrode material, the positive electrode active material comprising a substrate and a coating layer disposed on the surface of the substrate; the chemical formula of the substrate includes A x1 M1 y1 N1 z1 O2, wherein element A includes at least one of Na and Li, element M1 includes at least one transition metal element, element N1 includes at least one non-transition metal element, 0.5≤x1≤1, 0≤y1≤1, 0≤z1≤1; the chemical formula of the coating layer includes A x2 M2 y2 N2 z2 O2, wherein M2 element includes at least one transition metal element, N2 element includes at least one non-transition metal element, 0.5≤x2≤1, 0≤y2≤1, 0≤z2≤1; the highest bond energy between M1 and N1 elements and oxygen is the first bond energy, and the highest bond energy between M2 and N2 elements and oxygen is the second bond energy, and the second bond energy is greater than the first bond energy.

[0184] In one embodiment, at least one of the following conditions is satisfied: the difference between the second bond energy and the first bond energy is 0.21 eV to 1.29 eV; the range of the first bond energy is 1.73 eV to 2.52 eV; and the range of the second bond energy is 2.73 eV to 3.02 eV.

[0185] In one embodiment, at least one of the following conditions is satisfied: the transition metal element includes at least one of Ni, Fe, Co, Mn, Cu, and Zn; and the non-transition metal element includes at least one of Li, K, Mg, Ca, Al, Sn, Sb, Te, and Se.

[0186] In one embodiment, the N2 element includes at least one of Sb, Te, and Se.

[0187] In one embodiment, the substrate comprises an O3 phase material, and the coating layer comprises an O3 phase material.

[0188] In one embodiment, the chemical formula of the substrate includes Na. x1 M1 y1 N1 z1 O2, wherein 0.8 < x1 ≤ 1, y1 + z1 = 1, 0 ≤ y1 ≤ 1, 0 ≤ z1 ≤ 1; the chemical formula of the coating layer includes Na. x2 M2 y2 N2 z2 O2, where 0.8 < x2 ≤ 1, y2 + z2 = 1, 0 ≤ y2 ≤ 1, 0 ≤ z2 ≤ 1.

[0189] In one embodiment, at least one of the following conditions is met: the volume average particle size D50 of the substrate ranges from 6 μm to 10 μm; the mass percentage of the coating layer to the total mass of the substrate and the coating layer ranges from 1% to 20%; the coating thickness of the coating layer ranges from 20 nm to 200 nm; the substrate includes a monocrystalline substrate and / or a polycrystalline substrate; the mass percentage of the coating layer on the surface of the polycrystalline substrate ranges from 1% to 2%; and the coating thickness of the coating layer on the surface of the polycrystalline substrate ranges from 5 nm to 20 nm.

[0190] In one embodiment, this application also provides a method for preparing a positive electrode material, comprising: obtaining a substrate; mixing a coating material source with the substrate to obtain a mixture; and sintering the mixture to obtain a positive electrode material with a coating layer disposed on the surface of the substrate.

[0191] That is, in the process of material preparation, a substrate is obtained. It can be understood that the substrate can be obtained by preparation or by commercial purchase. The coating material source is mixed with the substrate to obtain a mixture. The coating material source refers to the raw material that can form a coating layer. The mixture is sintered to obtain a positive electrode material with a coating layer on the surface of the substrate. That is, during the sintering process, the coating material source forms a coating layer on the surface of the substrate.

[0192] In one embodiment, the step of obtaining the substrate includes: mixing at least two substrate material sources to obtain a mixed material source; and sintering the mixed material source to obtain the substrate.

[0193] That is, when the substrate is obtained by the preparation method, the above method can be used to mix at least two substrate material sources to obtain a mixed material source, wherein the substrate material source refers to the raw material that can form the substrate; the mixed material source is sintered to obtain the substrate, that is, the sintering step can transform the substrate material source into the substrate.

[0194] In one embodiment, at least one of the following conditions is met: in the step of mixing at least two substrate material sources to obtain a mixed material source, the substrate material sources include a sodium source and a transition metal source; in the step of sintering the mixed material source to obtain a substrate, the sintering temperature range is 800°C to 1000°C, and the holding time ranges from 6h to 24h; in the step of mixing a coating material source with a substrate to obtain a mixture, the coating material source includes a sodium source, a transition metal source, and a non-transition metal source.

[0195] In the substrate preparation process, the substrate material source includes sodium source and transition metal source. Of course, other elements can also be added as needed, depending on the actual requirements.

[0196] In the process of preparing the substrate, the sintering temperature range for the mixed material source is 800℃ to 1000℃, and the holding time ranges from 6h to 24h.

[0197] In the step of preparing the coating layer, the coating material source includes sodium source, transition metal source and non-transition metal source.

[0198] In one embodiment, at least one of the following conditions is satisfied: the sodium source includes at least one of sodium carbonate, sodium acetate, and sodium hydroxide; the transition metal source includes at least one of nickel, manganese, iron, and copper; the nickel source includes at least one of nickel oxide, nickel acetate, and nickel carbonate; the manganese source includes at least one of manganese oxide, manganese acetate, and manganese carbonate; the iron source includes at least one of iron oxide, iron acetate, and iron carbonate; the copper source includes at least one of copper oxide, copper acetate, and copper carbonate; the non-transition metal source includes at least one of antimony, tellurium, and selenium; the antimony source includes at least one of antimony oxide and antimony acetate; the tellurium source includes at least one of tellurium oxide and telluric acid; and the selenium source includes at least one of selenium oxide and selenite.

[0199] In one embodiment, the step of mixing the coating material source with the substrate to obtain a mixture includes: mixing the coating material source and the substrate in a solvent, heating and stirring, and drying to obtain a mixture, wherein the heating temperature range is 60°C to 90°C; or, ball milling the coating material source and the substrate to obtain a mixture.

[0200] In the step of mixing the coating material source and the substrate, the coating material source and the substrate can be mixed in a solvent, heated and stirred, and dried to obtain a mixture. The heating temperature range is 60°C to 90°C, and the solvent can include solvents such as ethanol and acetone.

[0201] Alternatively, the coating material source and the substrate can be ball-milled to obtain a mixture. Understandably, ball milling is not suitable for spherical polycrystalline materials, as mechanical ball milling can damage the polycrystalline morphology.

[0202] In one embodiment, in the step of sintering the mixture to obtain a positive electrode material with a coating layer on the surface of the substrate, the sintering temperature ranges from 600°C to 900°C, the holding time ranges from 2h to 24h, and the mass percentage of the coating layer to the total mass of the substrate and the coating layer ranges from 1% to 20%.

[0203] That is, during the process of applying the coating layer to the substrate surface, the sintering temperature ranges from 600℃ to 900℃, and the holding time ranges from 2 hours to 24 hours. In preparing the coating layer material source and the substrate, the amount of coating layer material source can be calculated based on the mass ratio of the coating layer to the substrate, ensuring that the mass percentage of the coating layer in the total mass of the substrate and coating layer ranges from 1% to 20%.

[0204] In one embodiment, this application also provides a positive electrode sheet, which includes the positive electrode material as described above; or, the positive electrode sheet includes the positive electrode material obtained by the method for preparing the positive electrode material as described above.

[0205] In one embodiment, this application also provides an electrical device, which includes a battery as described above.

[0206] In addition, the battery (secondary battery, battery module, battery pack) and power supply device of this application will be described below with appropriate reference to the accompanying drawings.

[0207] In one embodiment of this application, a secondary battery is provided.

[0208] Typically, a secondary battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits between the electrodes while allowing ions to pass through. The separator described above is the improved separator of this application.

[0209] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector.

[0210] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0211] In some embodiments, the positive 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 substrate and a metal layer formed on at least one surface of the polymer substrate. 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 substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0212] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0213] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0214] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0215] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0216] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0217] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0218] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0219] In some embodiments, the negative electrode film layer may optionally 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).

[0220] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0221] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0222] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0223] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not specify any particular type of electrolyte; it can be selected according to requirements.

[0224] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0225] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0226] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0227] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0228] In some embodiments, the diaphragm material can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The diaphragm can be a single-layer film or a multi-layer composite film, without particular limitation. When the diaphragm is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0229] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0230] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0231] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0232] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 6 shows a square battery cell 5 as an example.

[0233] In some embodiments, referring to FIG7, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 may be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0234] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0235] Figure 8 shows a battery module 4 as an example. Referring to Figure 8, in the battery module 4, multiple battery cells 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other arbitrary way. Furthermore, the multiple battery cells 5 can be fixed in place by fasteners.

[0236] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0237] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0238] Figures 9 and 10 show a battery pack 1 as an example. Referring to Figures 9 and 10, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper box 2 and a lower box 3, the upper box 2 covering the lower box 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0239] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0240] As an electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0241] Figure 11 shows an example of an electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0242] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0243] Example

[0244] Example 1

[0245] Preparation of positive electrode active materials

[0246] Substrate preparation: Sodium source (sodium carbonate), nickel source (nickel oxide), manganese source (manganese oxide), iron source (iron oxide), and copper source (copper oxide) were prepared according to the atomic ratio of sodium, nickel, manganese, iron, and copper: 1:0.2:0.44:0.24:0.12. Sodium carbonate, nickel oxide, manganese oxide, iron oxide, and copper oxide were mixed evenly using a ball mill to obtain a mixture. The mixture was then placed in a furnace for high-temperature sintering at 900℃ for 12 hours. After cooling, the substrate material was obtained. The chemical formula of the substrate is O3 phase NaNi. 0.2 Fe 0.24 Cu 0.12 Mn 0.44 O2 has a core volume average particle size D50 of 8 μm.

[0247] Preparation of the coating layer on the substrate surface: Sodium source (sodium carbonate), nickel source (nickel oxide), and antimony source (antimony oxide) were prepared according to an atomic ratio of sodium, nickel, and antimony of 1:0.67:0.33. The substrate material obtained above was mixed with sodium carbonate, nickel oxide, and antimony oxide in alcohol. The coating layer NaNi formed by the substrate material and the mixture of sodium carbonate, nickel oxide, and antimony oxide... 0.67 Sb 0.33 The mass ratio of O2 was 4:1. The mixture was heated and stirred until dry at 80°C to obtain a final product. This product was then sintered at 900°C for 6 hours to obtain a material with a coating layer on the substrate surface. The chemical formula of the coating layer material was O3 phase NaNi. 0.67 Sb 0.33 O2, with a coating thickness of 0.3 μm.

[0248] As shown in Figures 1 to 4, Figure 1 is a schematic diagram of the morphological structure of the substrate prepared in Example 1 obtained by scanning electron microscopy; Figure 2 is a schematic diagram of the morphological structure of the coating layer on the surface of the substrate in Example 1; compared with Figure 1, the particles in Figure 2 have a distinct coating layer. Figure 3 is a schematic diagram of the cross-sectional morphological structure of the coating layer on the surface of the substrate in Example 1. After ion polishing to the electrode cross-section, it can be observed in Figure 3 that the coating layer is attached to the surface of the substrate and the coating layer is relatively thick. Figure 4 shows that the Sb element is mainly distributed on the particle surface, which indicates that the coating layer can be dissolved with the substrate and will not diffuse into the interior of the substrate grains in large quantities. Furthermore, the introduction of Sb can increase the interplanar spacing, making the extraction and insertion of sodium ions easier. As can be seen from Figure 4, the stronger the Sb element signal, the greater the amount. This element content is determined based on the brightness of the received signal; the brighter the area, the greater the amount of this element. The long-cycle electrochemical performance in Figure 5 shows that the coated material has higher capacity and significantly improved stability.

[0249] Positive electrode sheet: The self-made positive electrode material PVDF acetylene black in a mass ratio of 95:2.5:2.5 is dispersed and dissolved in NMP solvent to form a uniformly dispersed slurry. The slurry is then uniformly coated onto an aluminum foil current collector. After drying, cold pressing and slitting, the positive electrode sheet is obtained.

[0250] Negative electrode sheet: Hard carbon, binder PAA, acetylene black = 90:5:5 are thoroughly mixed in NMP solvent to prepare a negative electrode slurry; the negative electrode slurry is uniformly coated on the negative electrode current collector copper foil, and then dried, cold pressed and slit to obtain the negative electrode sheet.

[0251] Separator membrane: Polypropylene membrane is used as the separator membrane.

[0252] Electrolyte: In an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), mix the organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 3 / 7, add 1 mol / L NaPF6 sodium salt dissolved in the organic solvent, and stir until homogeneous.

[0253] Battery Assembly: The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The cells are then wound to obtain a bare cell. Tabs are welded to the bare cell, which is then placed in an aluminum casing and baked at 60°C to remove moisture. Electrolyte is then injected and the casing is sealed, resulting in a non-charged battery. The non-charged battery then undergoes a series of processes including settling, hot and cold pressing, formation, shaping, and capacity testing to obtain the sodium-ion battery product of Example 1.

[0254] Example 2

[0255] Based on Example 1, the percentage of the mass of the coating layer relative to the total mass of the substrate and the coating layer was adjusted.

[0256] Example 3

[0257] Based on Example 1, the percentage of the mass of the coating layer to the total mass of the substrate and the coating layer, as well as the type of substrate source of the substrate, were adjusted.

[0258] Example 4

[0259] Based on Example 1, the type of coating layer was adjusted, and the Sb element was replaced with the Te element.

[0260] Example 5

[0261] Based on Example 1, the type of coating layer was adjusted, and the Sb element was replaced with the Se element.

[0262] Example 6

[0263] Based on Example 1, the type of substrate was adjusted.

[0264] Comparative Example 1

[0265] Based on Example 1, no coating layer is provided on the surface of the substrate.

[0266] Comparative Example 2

[0267] Based on Example 3, no coating layer is provided on the surface of the substrate.

[0268] Test method:

[0269] Ion beam interface polishing is a technique that uses a high-energy ion beam to physically and chemically treat the surface of a material. This method can effectively remove damaged layers, contaminants, and oxide layers from the material surface, thereby obtaining a smooth and clean interface. The operation steps are as follows: the electrode sample is adhered to a baffle plate. Under vacuum conditions and the influence of an electric field, a high-energy argon ion beam bombards the sample, striking the electrode above the baffle plate, ultimately resulting in a smooth interface. The accelerating voltage is 5 kV, the beam spot diameter is 3 mm, and the polishing time is 2 hours. These steps expose the cross-sectional structure of the substrate surface with a coating layer.

[0270] Scanning electron microscopy (SEM): It uses a high-energy electron beam to bombard the sample surface, generating various physical signals to obtain information about the sample's morphology and composition. The high-energy electron beam scans the sample surface; when the electron beam interacts with the sample surface, it excites atoms on the sample surface to emit secondary electrons. These secondary electrons are received by a detector, and the intensity and distribution of the electron signals generate an image of the sample surface's morphology. Simultaneously, elements in the sample are excited and emit characteristic X-rays; by measuring the energy of these X-rays, the types and amounts of elements in the sample can be determined. The operating procedure is as follows: the sample is attached to the stage, placed in the electron microscope chamber, a vacuum is drawn, the electron beam is turned on, and appropriate parameters are set for characterization. Parameters for observing morphology: accelerating voltage 3kV, aperture 30μm, working distance 5mm; parameters for elemental analysis using energy-dispersive spectroscopy (EDS): accelerating voltage 10kV, aperture 60μm, working distance 8.5mm. It is understandable that EDS is a testing mode in scanning electron microscopy, which uses an electron beam to excite the characteristic X-rays of a material to analyze the elements and types of the material. The specific steps are as follows: adjust the working distance to 8.5 mm, the voltage to 10 kV, turn on the EDS probe, select the area to be acquired, and collect the acquisition signal.

[0271] The battery was tested at room temperature. At 25°C, the capacity of the negative electrode was 43mAh.

[0272] Two 0.1C cycles: Perform two complete charge-discharge cycles at a rate of 0.1C. The specific steps are as follows: charge at a rate of 0.1C to 4.3V (the battery's charging cut-off voltage); after reaching 4.3V, continue charging at a current of 0.05C until the battery voltage no longer rises; after constant voltage charging, let it stand for 5 minutes to allow the battery's internal temperature and pressure to stabilize; then discharge at a rate of 0.1C to 1.5V (the battery's discharging cut-off voltage).

[0273] Two cycles at 0.33C: Perform two complete charge-discharge cycles at a rate of 0.33C. The steps are the same as for 0.1C, only the charge-discharge rate is different.

[0274] 1C Long Cycle: Long-term charge-discharge cycle test at a rate of 1C. The procedure is the same as the previous two, but the charge-discharge rate is 1C.

[0275] The formula for calculating the specific capacity of positive electrode active material is: Discharge specific capacity = Discharge capacity / Mass of active material.

[0276] Cyclic retention test steps

[0277] At 25℃, the battery cells are first charged to 4.3V with a constant current of 1C, then further charged to 0.05C with a constant voltage of 4.3V, and finally discharged to 1.5V with a constant current of 1C. This constitutes one charge-discharge cycle, and the discharge capacity of this cycle is the discharge capacity of the first cycle. The battery undergoes multiple charge-discharge cycles in the above manner, and the discharge capacity of the 200th cycle is measured. The capacity retention rate of the battery cells after 200 cycles is calculated using the following formula: Capacity retention rate (%) after 200 cycles = [Discharge capacity of the 200th cycle / Discharge capacity of the first cycle] × 100%.

[0278] Table 1. List of Experimental Data

[0279] As shown in Table 1 above, compared with the uncoated substrate, the capacity retention and specific capacity of the coated material after 200 cycles are improved after the coating layer is applied to the substrate surface. In Example 1, the scheme of this application is adopted, and the coating layer is NaNi 0.67 Sb 0.33 In O2, Sb has the highest bond energy with O. When nickel is oxidized to a high valence state, the bonding force between Sb and oxygen is higher than that between Mn / Cu / Fe / Ni and oxygen in the substrate. In other words, the bond energy between Sb and O is greater than that between metal and O in the substrate. This reduces the risk of lattice oxygen in the coating layer turning into oxygen and oxidizing the electrolyte. It can effectively reduce the reaction between the electrolyte and the coating layer, improve the cycle life of the material, and thus improve the cycle life of the battery.

[0280] The above are merely preferred embodiments of this application and do not limit the scope of the patent application. Any equivalent structural transformations made based on the inventive concept of this application and the contents of the specification and drawings of this application, or direct / indirect applications in other related technical fields, are included within the scope of patent protection of this application.

Claims

1. A battery, wherein, The positive electrode sheet comprises a current collector and a positive electrode coating provided on the current collector, wherein the positive electrode coating comprises a positive electrode active material, and the positive electrode active material comprises a substrate and a coating layer provided on the surface of the substrate. The chemical formula of the substrate includes A x1 M1 y1 N1 z1 O2, wherein the A element includes at least one of Na and Li, the M1 element includes at least one transition metal element, the N1 element includes at least one non-transition metal element, 0.5≤x1≤1, 0≤y1≤1, and 0≤z1≤1. The chemical formula of the coating layer includes A x2 M2 y2 N2 z2 O2, wherein the M2 element includes at least one transition metal element, the N2 element includes at least one non-transition metal element, 0.5≤x2≤1, 0≤y2≤1, and 0≤z2≤1. The maximum bond energy between M1 and N1 and oxygen is a first bond energy, and the maximum bond energy between M2 and N2 and oxygen is a second bond energy, wherein the second bond energy is greater than the first bond energy.

2. The battery of claim 1, wherein, At least one of the following conditions is met: Condition A: the difference between the second bond energy and the first bond energy is 0.21 eV to 1.29 eV; Condition B: the range value of the first bond energy is 1.73 eV to 2.52 eV; Condition C: the range value of the second bond energy is 2.73 eV to 3.02 eV.

3. The battery of claim 1 or 2, wherein, At least one of the following conditions is met: Condition A: the transition metal element comprises at least one of Ni, Fe, Co, Mn, Cu, and Zn; Condition B: the non-transition metal element comprises at least one of Li, K, Mg, Ca, Al, Sn, Sb, Te, and Se.

4. The battery of any one of claims 1 to 3, wherein, The N2 element comprises at least one of Sb, Te, and Se.

5. The battery of any one of claims 1 to 4, wherein, The substrate comprises an O3 phase material, and the coating layer comprises an O3 phase material.

6. The battery of claim 5, wherein, The chemical formula of the substrate includes Na x1 M1 y1 N1 z1 O2, wherein 0.8 < x1 < 1, y1 + z1 = 1, 0 < y1 < 1, 0 < z1 < 1 The chemical formula of the coating layer includes Na x2 M2 y2 N2 z2 O2, wherein 0.8 < x2≤ 1, y2+z2=1, 0≤y2≤1, 0≤z2≤1.

7. The battery of any one of claims 1 to 6, wherein, At least one of the following conditions is met: Condition A: the volume average particle size D50 of the substrate ranges from 6 μm to 10 μm; Condition B: the mass percentage of the coating layer in the total mass of the substrate and the coating layer ranges from 1% to 20%; Condition C: the coating thickness of the coating layer ranges from 20 nm to 200 nm; Condition D: the substrate comprises a single crystal substrate and / or a polycrystalline substrate; Condition E: the substrate comprises a polycrystalline substrate, and the mass percentage of the surface coating layer of the polycrystalline substrate in the total mass of the polycrystalline substrate and the coating layer ranges from 1% to 2%; Condition F: the substrate comprises a polycrystalline substrate, and the coating thickness of the surface coating layer of the polycrystalline substrate ranges from 5 nm to 20 nm; Condition G: the charging voltage of the battery ranges from 1.5 V to 4.3 V; Condition H: the discharging voltage of the battery ranges from 4.3 V to 1.5 V.

8. A positive electrode material, wherein, The positive electrode active material comprises a substrate and a coating layer provided on the surface of the substrate; The chemical formula of the substrate includes A x1 M1 y1 N1 z1 O2, wherein the A element includes at least one of Na and Li, the M1 element includes at least one transition metal element, the N1 element includes at least one non-transition metal element, 0.5≤x1≤1, 0≤y1≤1, and 0≤z1≤1. The chemical formula of the coating layer includes A x2 M2 y2 N2 z2 O2, wherein the M2 element includes at least one transition metal element, the N2 element includes at least one non-transition metal element, 0.5≤x2≤1, 0≤y2≤1, and 0≤z2≤1. The maximum bond energy between M1 and N1 and oxygen is a first bond energy, and the maximum bond energy between M2 and N2 and oxygen is a second bond energy, wherein the second bond energy is greater than the first bond energy.

9. The cathode material of claim 8, wherein, At least one of the following conditions is met: Condition A: the difference between the second bond energy and the first bond energy is 0.21 eV to 1.29 eV; Condition B: the range value of the first bond energy is 1.73 eV to 2.52 eV; Condition C: the range value of the second bond energy is 2.73 eV to 3.02 eV.

10. The positive electrode material of claim 8 or 9, wherein, At least one of the following conditions is met: Condition A: the transition metal element comprises at least one of Ni, Fe, Co, Mn, Cu, and Zn; Condition B: the non-transition metal element comprises at least one of Li, K, Mg, Ca, Al, Sn, Sb, Te, and Se.

11. The cathode material of any one of claims 8 to 10, wherein, The N2 element comprises at least one of Sb, Te, and Se.

12. The cathode material of any one of claims 8 to 11, wherein, The substrate comprises an O3 phase material, and the coating layer comprises an O3 phase material.

13. The cathode material of claim 12, wherein, The chemical formula of the substrate includes Na x1 M1 y1 N1 z1 O2, wherein 0.8 < x1 < 1, y1 + z1 = 1, 0 < y1 < 1, 0 < z1 < 1 The chemical formula of the coating layer includes Na x2 M2 y2 N2 z2 O2, wherein 0.8 y2+z2=1, 0 y2 z2 1.

14. The cathode material of any one of claims 8 to 13, wherein, At least one of the following conditions is met: Condition A: the volume average particle size D50 of the substrate ranges from 6 μm to 10 μm; Condition B: the mass percentage of the coating layer in the total mass of the substrate and the coating layer ranges from 1% to 20%; Condition C: the coating thickness of the coating layer ranges from 20 nm to 200 nm; Condition D: the substrate comprises a single crystal substrate and / or a polycrystalline substrate; Condition E: the substrate comprises a polycrystalline substrate, and the mass percentage of the surface coating layer of the polycrystalline substrate in the total mass of the polycrystalline substrate and the coating layer ranges from 1% to 2%; Condition F: the substrate comprises a polycrystalline substrate, and the coating thickness of the surface coating layer of the polycrystalline substrate ranges from 5 nm to 20 nm.

15. A method of producing a positive electrode material, wherein, Comprising: obtaining a substrate; mixing a coating material source with the substrate to obtain a mixture; sintering the mixture to obtain a positive electrode material with a coating layer on the surface of the substrate.

16. The method of producing a cathode material as claimed in claim 15, wherein, In the step of obtaining a substrate, comprising: mixing at least two substrate material sources to obtain a mixed material source; sintering the mixed material source to obtain a substrate.

17. The method of producing a cathode material as claimed in claim 16, wherein, At least one of the following conditions is met: Condition A: in the step of mixing at least two substrate material sources to obtain a mixed material source, the substrate material source comprises a sodium source and a transition metal source; Condition B: in the step of sintering the mixed material source to obtain a substrate, the sintering temperature ranges from 800°C to 1000°C, and the holding time ranges from 6 h to 24 h; Condition C: in the step of mixing a coating material source with the substrate to obtain a mixture, the coating material source comprises a sodium source, a transition metal source, and a non-transition metal source.

18. The method of producing a cathode material as claimed in claim 17, wherein, At least one of the following conditions is met: Condition A: the sodium source comprises at least one of sodium carbonate, sodium acetate, and sodium hydroxide; Condition B: the transition metal source comprises at least one of a nickel source, a manganese source, an iron source, and a copper source; Condition C: the nickel source comprises at least one of nickel oxide, nickel acetate, and nickel carbonate; Condition D: the manganese source comprises at least one of manganese oxide, manganese acetate, and manganese carbonate; Condition E: the iron source comprises at least one of iron oxide, iron acetate, and iron carbonate; Condition F: the copper source comprises at least one of copper oxide, copper acetate, and copper carbonate; Condition G: the non-transition metal source comprises at least one of an antimony source, a tellurium source, and a selenium source; Condition H: the antimony source comprises at least one of antimony oxide and antimony acetate; Condition I: the tellurium source comprises at least one of tellurium oxide and tellurium acid; Condition J: the selenium source comprises at least one of selenium oxide and selenious acid.

19. The method of producing a cathode material as claimed in claim 15, wherein, In the step of mixing a coating material source with the substrate to obtain a mixture, comprising: mixing the coating material source with the substrate in a solvent, heating and stirring, and drying to obtain a mixture, wherein the heating temperature ranges from 60°C to 90°C; or, mixing the coating material source with the substrate by ball milling to obtain a mixture.

20. The method of producing a cathode material according to any one of claims 15 to 19, wherein, In the step of sintering the mixture to obtain the positive electrode material with the cladding layer on the surface of the substrate, the sintering temperature ranges from 600 to 900 ℃, the holding time ranges from 2 to 24 h, and the mass percentage of the cladding layer in the total mass of the substrate and the cladding layer ranges from 1% to 20%.

21. A positive electrode sheet, wherein, The positive electrode tab comprises the positive electrode material according to any one of claims 8 to 14. Alternatively, the positive electrode tab comprises the positive electrode material obtained by the preparation method of the positive electrode material according to any one of claims 15 to 20.

22. An electrical device, comprising: The electric device comprises the battery according to any one of claims 1 to 7.

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