Positive electrode material of sodium-ion battery and preparation method therefor, positive electrode sheet, battery and electric device

Abstract

The present application belongs to the technical field of batteries. Provided are a positive electrode material of a sodium-ion battery and a preparation method therefor, a positive electrode sheet, a battery and an electric device. The positive electrode material of a sodium-ion battery comprises: a sodium-containing positive electrode material substrate and a modification layer formed on at least part of the surface of the sodium-containing positive electrode material substrate, wherein the modification layer comprises a sodium-metal oxide salt and a carbon material, the sodium-metal oxide salt comprising an assistant metal element, phosphorus and boron.

Description

Sodium ion battery positive electrode material and preparation method thereof, positive electrode sheet, battery and power-consuming device Technical Field

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

[0002] Secondary batteries, represented by sodium-ion batteries, have been applied in a variety of fields, including electric vehicles and energy storage power systems (such as hydropower, thermal power, wind power, and solar power stations). Compared with lithium-ion batteries, sodium-ion batteries have significant advantages in raw material costs, especially for cathode materials, which account for a large proportion of the cost. The reserves of sodium salts, which are the main components of sodium-ion cathode materials, are more abundant, making the cost of sodium-ion cathode materials lower than that of lithium batteries. However, the poor electrochemical performance of sodium-ion batteries in terms of capacity, rate performance, and stability has limited their practical application.

[0003] Summary of the Invention

[0004] In response to the above-mentioned problems, the purpose of this application is to provide a sodium ion battery positive electrode material and its preparation method, a positive electrode sheet, a battery, and an electrical device. The battery prepared with the sodium ion battery positive electrode material has the characteristics of high battery capacity and good cycle stability.

[0005] In a first aspect, the present application provides a sodium-ion battery positive electrode material, comprising: a sodium-containing positive electrode material matrix, and a modified layer formed on at least a portion of the surface of the sodium-containing positive electrode material matrix; wherein the modified layer comprises a metal oxide sodium salt and a carbon material, and the metal oxide sodium salt has a metal promoter element, a phosphorus element, and a boron element.

[0006] In the sodium-ion battery positive electrode material of the present application, a composite material containing a sodium salt of a metal oxide and a carbon material is used as a modification layer on the surface of the sodium-containing positive electrode material substrate, which not only reduces the residual alkali content of the substrate, but also the modification layer can reduce the direct contact between the electrolyte and the substrate, inhibit the generation of by-products and metal dissolution during battery operation, and improve the cycle stability of the battery. On the other hand, it can promote ion conduction, reduce battery impedance, and improve the battery rate performance.

[0007] In some embodiments of the present application, the chemical formula of the metal oxide sodium salt is: Na x M y (PO4) m (BO3) n (SO3) p , wherein M represents an auxiliary metal element, 1≤x≤6, 0.3≤y≤4, 0<m≤4, 0.3<n≤9, 0≤p≤2.

[0008] In some embodiments of the present application, the auxiliary metal element includes one or more of Li, Ni, Co, Ca, Mn, Fe, Cu, V, Cr, Mo, or Zn. This can further improve the conductivity and cycle stability of the battery.

[0009] In some embodiments of the present application, the atomic molar ratio of phosphorus to boron in the sodium salt of the metal oxide is 1:(1-3), thereby improving the overall performance of the battery.

[0010] In some embodiments of the present application, the carbon material includes amorphous carbon.

[0011] In some embodiments of the present application, the thickness of the modified layer is 7 nm to 13 nm, thereby improving the cycle stability of the battery while also enabling the battery to have a higher rate performance.

[0012] In some embodiments of the present application, the ratio of the mass of the modified layer to the mass of the sodium-containing positive electrode material matrix is ​​(0.4-3): 100. This can increase the gram capacity of the positive electrode material while isolating the electrolyte, promote the transmission of sodium ions, and improve the rate performance of the material.

[0013] In some embodiments of the present application, the sodium-containing positive electrode material matrix includes a sodium-containing transition metal oxide; the chemical formula of the sodium-containing transition metal oxide is Na r Mn a Fe b M' c O 2-d+e Q d ; wherein, M' includes one or more of Cu, Ni, Li, Zr, K, La, Ce, Sr, Sb, Nb, Mg, Ca, Mo, Zn, Cr, W, Bi, Sn, Ge or Al; Q includes one or more of F, Cl and N; a>0, b>0, c≥0, and a+b+c=1, r≥0.66, 0≤d≤0.1, -0.1≤e≤0.

[0014] In some embodiments of the present application, the average particle size Dv50 of the sodium-containing positive electrode material matrix is ​​3 μm to 8 μm.

[0015] In some embodiments of the present application, the specific surface area of ​​the sodium-containing positive electrode material matrix is ​​0.5 m 2 / g~2m 2 / g.

[0016] In a second aspect, the present application provides a method for preparing the sodium ion battery positive electrode material, comprising: mixing and sintering a modification layer raw material including a first raw material and an organic phosphorus source with a sodium-containing positive electrode material matrix; wherein the first raw material includes a metal-co-source and an organic boron source, or the first raw material includes a metal-co-source borate.

[0017] In the preparation method of the present application, the organic matter (such as an organic phosphorus source) in the raw material of the modification layer is carbonized at high temperature during the sintering process. On the one hand, it can neutralize and remove the residual alkali on the surface of the sodium-containing positive electrode material to form a sodium salt of a metal oxide. On the other hand, the organic matter can directly form a carbon material after sintering. The raw materials of this preparation method are simple, and problems such as the complicated mixing process caused by the separate use of different element sources (such as an inorganic phosphorus source and an organic carbon source) can be avoided. In addition, the preparation method of the present application can also form a thinner modification layer, which can protect the positive electrode material while enabling the positive electrode material to have both high rate performance and cycle stability.

[0018] In some embodiments of the present application, the co-metal source includes one or more of a co-metal carboxylate, a co-metal carbonate, a co-metal bicarbonate, or a co-metal oxalate.

[0019] In some embodiments of the present application, the organic boron source includes one or more of 2-cyanophenylboronic acid, 3-phenoxyphenylboronic acid, 3-methylthiophenylboronic acid or 4-boronbenzenesulfonic acid.

[0020] In some embodiments of the present application, the organic phosphorus source includes one or more of a small molecule organic compound containing a phosphoric acid group or a polymer containing a phosphoric acid group.

[0021] Optionally, the small molecule organic compound containing a phosphoric acid group includes one or more of amino trimethylene phosphonic acid, ethylenediamine tetramethylene phosphonic acid, diethylenetriamine penta methylene phosphonic acid, dihexamethylenetriamine penta methylene phosphonic acid, hydroxy ethylidene diphosphonic acid or 2-phospho-1,2,4-tricarboxylic acid butane.

[0022] Optionally, the polymer containing a phosphoric acid group includes an acrylic acid-acrylate-phosphonic acid-sulfonate tetrapolymer.

[0023] In some embodiments of the present application, the sintering temperature is 600° C. to 1200° C. Thus, while promoting the reaction between the organic phosphorus source and the boron source and the residual alkali in the matrix, the organic matter has a relatively suitable degree of carbonization, thereby making the prepared positive electrode material have a high rate performance.

[0024] In some embodiments of the present application, the sintering time is 8 hours to 48 hours.

[0025] In some embodiments of the present application, the mixing is performed in the presence of a solvent, thereby improving the dispersion uniformity between the raw materials.

[0026] In a third aspect, the present application provides a positive electrode sheet comprising the sodium ion battery positive electrode material described in the first aspect of the present application or the sodium ion battery positive electrode material prepared by the method described in the second aspect of the present application.

[0027] In a fourth aspect, the present application provides a battery comprising the positive electrode sheet described in the third aspect of the present application.

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

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

[0030] Various other advantages and benefits will become apparent to those skilled in the art by reading the detailed description of the preferred embodiment below. The accompanying drawings are only for the purpose of illustrating the preferred embodiment and are not to be considered as limiting the present application. In the accompanying drawings:

[0031] FIG1 is a schematic diagram of a battery cell according to an embodiment of the present application;

[0032] FIG2 is an exploded view of a battery cell according to an embodiment of the present application shown in FIG1 ;

[0033] FIG3 is a schematic diagram of a battery module according to an embodiment of the present application;

[0034] FIG4 is a schematic diagram of a battery pack according to an embodiment of the present application;

[0035] FIG5 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG4 ;

[0036] FIG6 is a schematic diagram of an electrical device using a battery as a power source according to an embodiment of the present application.

[0037] Explanation of reference numerals: 1: battery pack; 2: upper case; 3: lower case; 4: battery module; 5: battery cell; 51: housing; 52: electrode assembly; 53: top cover assembly. DETAILED DESCRIPTION

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

[0039] In this application, references to "embodiments" mean that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of such phrases in various locations in the specification does not necessarily refer to the same embodiment, nor do they represent independent or alternative embodiments that are mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described in this application may be combined with other embodiments.

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

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

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

[0043] Unless otherwise specified, in this application, the terms "plurality" and "multiple" refer to more than two. "Above" and "below" are inclusive of the number itself. For example, "two or more" includes two itself, such as two, three, four, or more.

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

[0045] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used in this application are for the purpose of describing specific embodiments only and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and any variations thereof are intended to cover non-exclusive inclusions. Unless otherwise specified, the terms used in this application have the well-known meanings commonly understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the examples of this application).

[0046] Research on sodium-ion batteries has developed rapidly in recent years. Although the performance of sodium-ion battery cathode materials is similar to that of lithium-ion battery cathode materials, their interfaces are more sensitive to electrolytes during storage and use. In the current sodium battery field, sodium-ion cathode materials (especially layered transition metal oxides) have serious residual alkali on the surface. These residual alkalis will react with H2O and CO2 in the air, accelerate the dissolution of metals in the liquid electrolyte, and cause damage to the cathode materials. The presence of residual alkali will also affect the performance of the battery cell, including making the battery cell more likely to produce gas (such as CO2, CO, H2, etc.) during the cycle, which may lead to battery cell failure. In addition, the interfacial impedance of sodium-ion cathode materials is large, resulting in a decrease in the electrochemical performance of the battery. Therefore, it is necessary to modify the sodium-ion cathode materials.

[0047] Accordingly, the first aspect of the present application provides a sodium ion battery positive electrode material, comprising: a sodium-containing positive electrode material matrix, and a modified layer formed on at least a portion of the surface of the sodium-containing positive electrode material matrix; wherein the modified layer comprises a metal oxide sodium salt and a carbon material, and the metal oxide sodium salt has a metal promoter element, a phosphorus element (P) and a boron element (B).

[0048] In the sodium-ion battery positive electrode material of the present application, a composite material containing a sodium salt of a metal oxide and a carbon material is used as a modified layer on the surface of the sodium-containing positive electrode material substrate, which not only achieves a reduction in the residual alkali content of the substrate, but also the modified layer can reduce the direct contact between the electrolyte and the substrate, inhibit the production of by-products and metal dissolution during battery operation, and improve the cycle stability of the battery. On the other hand, it can promote ion conduction, reduce battery impedance, and improve the rate performance of the battery. Specifically, in the modified layer of the present application, the introduction of a metal-assisted element into the sodium salt of the metal oxide helps promote electron transport and stabilizes the structure of the positive electrode material. Boron and phosphorus elements can respectively promote the improvement of the electronic conductivity and ionic conductivity of the modified layer. In addition, the introduction of carbon material into the modified layer can enhance the electronic conductivity of the battery and isolate the side reactions of the electrolyte.

[0049] In this application, "sodium salt of metal oxide" refers to a complex formed between elements including sodium, oxygen, co-metal elements, boron, and phosphorus. Each element in the complex can exist in the form of multiple components. Due to the differences in the distribution ratio of each component of the modification layer raw materials, the alkali content on the substrate surface, and the preparation conditions, these components may include, but are not limited to, co-metal oxides (such as ZnO), metal oxygenates (such as sodium phosphate, sodium borate, etc.), phosphorus oxides (such as P2O5), boron oxides (such as B2O3), etc. It can be understood that the net charge of the sodium salt of metal oxide is zero.

[0050] In the present application, the sodium salt of metal oxide may optionally include sulfur. The sulfur may come from raw materials for the modification layer, such as organic boric acid or organic phosphorus having a sulfonic acid group.

[0051] In some embodiments, the chemical formula of the metal oxide sodium salt is: Na x M y (PO4) m (BO3) n (SO3) p , wherein M represents a metalloid element, 1≤x≤6, 0.3≤y≤4, 0<m≤4, 0.3<n≤9, 0≤p≤2. Alternatively, 1≤x≤3, 0.3≤y≤3, 0.3≤m≤1, 0.3<n≤2, 0≤p≤1.

[0052] In this application, the co-metal element in the sodium salt of a metal oxide refers to a metal element other than Na, such as one or more transition metal elements, alkali metal elements other than Na, alkaline earth metal elements, etc. In some embodiments, the co-metal element includes one or more of Li, Ni, Co, Ca, Mn, Fe, Cu, V, Cr, Mo, or Zn. This can further improve the conductivity and cycle stability of the battery. Furthermore, the co-metal element includes one or more of Zn, Li, Co, Fe, Cu, or Mn.

[0053] In the present application, the atomic molar ratio of phosphorus to boron in the metal oxide sodium salt can be 1:(0.5-5), for example, 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:4, 1:5, etc. In some embodiments, the atomic molar ratio of phosphorus to boron in the metal oxide sodium salt is 1:(1-3). This is beneficial to the balanced electronic and ionic conductivity of the modified layer and improves the overall performance of the battery.

[0054] It is understood that when the chemical formula of the metal oxide sodium salt is Na x M y (PO4) m(BO3) n (SO3) p When the atomic mole ratio of phosphorus and boron is m to n.

[0055] In the present application, the carbon material can enhance the electronic conductivity of the battery and isolate side reactions between the positive electrode material and the electrolyte. In some embodiments, the carbon material comprises amorphous carbon. In particular, the carbon material can be formed by sintering organic matter from the raw materials of the modification layer, such as an organic phosphorus source or an organic boron source.

[0056] In some embodiments, the carbon material may be optionally doped with nitrogen. The nitrogen may generally come from a raw material for the modification layer, such as, but not limited to, an organic phosphorus source containing nitrogen.

[0057] In the present application, the thickness of the modified layer can be, for example, 2 nm to 20 nm, such as 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, 20 nm, etc. Furthermore, the thickness of the modified layer is 7 nm to 13 nm. This ensures that the battery has both high rate performance and cycling stability.

[0058] In the present application, the modification layer elements can be analyzed by X-ray energy dispersive spectroscopy (EDS) and the thickness of the modification layer can be measured by transmission electron microscopy (TEM).

[0059] In some embodiments, the modification layer is a mixture of a sodium salt of a metal oxide and a carbon material.

[0060] In the present application, the ratio of the mass of the modified layer to the mass of the sodium-containing positive electrode material matrix can generally be (0.1-5):100, for example, 0.2:100, 0.3:100, 0.4:100, 0.5:100, 0.6:100, 0.7:100, 0.8:100, 0.9:100, 1:100, 1.5:100, 1.8:100, 2:100, 3:100, 4:100, 5:100, etc. The mass of the modified layer can be determined according to the amount of raw materials added to the modified layer.

[0061] In some embodiments, the mass ratio of the modified layer to the sodium-containing positive electrode material matrix is ​​(0.4-3):100. This can reduce the problem of residual alkaline residue in the matrix caused by too low a modification amount, while also reducing the low specific capacity caused by too high a modification amount. Therefore, controlling the mass of the modified layer within the above range can increase the specific capacity of the positive electrode material while isolating the electrolyte, promote the transport of sodium ions, and improve rate performance.

[0062] The present application does not particularly limit the matrix of the sodium-containing positive electrode material, and can be various sodium ion positive electrode materials well known in the art, for example, can include one or more of layered oxides, Prussian blue compounds, and polyanionic compounds. In addition, the present application is particularly suitable for improving the electrochemical performance of sodium-containing positive electrode materials with a high residual alkali content. From this perspective, optionally, the sodium-containing positive electrode material is a layered oxide, and the layered oxide generally includes a sodium-containing transition metal oxide.

[0063] In some embodiments, the sodium-containing positive electrode material matrix includes a sodium-containing transition metal oxide, the chemical formula of which is Na r Mn a Fe b M' c O 2-d+e Q d , wherein M' includes one or more of Cu, Ni, Li, Zr, K, La, Ce, Sr, Sb, Nb, Mg, Ca, Mo, Zn, Cr, W, Bi, Sn, Ge and Al; Q includes one or more of F, Cl and N; a>0, b>0, c≥0, and a+b+c=1, r≥0.66, 0≤d≤0.1, -0.1≤e≤0. Specific examples of the sodium-containing positive electrode material matrix include, but are not limited to, Na 0.67 Mn 0.92 Cu 0.04 Fe 0.04 O2. In the list of positive electrode materials in this application, the molar content of Na refers to the initial state of the material, that is, the state before the material is added. It is understood that when the positive electrode material is used in a battery system, the molar content of Na will change after charge and discharge cycles. The molar content of O is only a theoretical value. Lattice oxygen release will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.

[0064] In some embodiments, the average particle size Dv50 of the sodium-containing positive electrode material matrix is ​​3 μm to 8 μm, for example, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, etc.

[0065] In the present application, the Dv50 of the sodium-containing positive electrode material matrix can be measured using a Malvern laser particle size analyzer.

[0066] In some embodiments, the specific surface area of ​​the sodium-containing positive electrode material matrix is ​​0.5 m 2 / g~2m 2 / g, for example 0.5m 2 / g, 0.6m 2 / g, 0.7m 2 / g, 0.8m2 / g, 0.9m 2 / g、1m 2 / g, 1.2m 2 / g, 1.5m 2 / g, 2m 2 / g, etc. Thus, the cycle and rate performance of the material can be improved. Optionally, the specific surface area of ​​the sodium-containing positive electrode material matrix is ​​0.7m 2 / g~1.5m 2 / g.

[0067] In the present application, a flow method gas adsorption type specific surface area measuring device can be used to measure the specific surface area of ​​the sodium-containing positive electrode material matrix.

[0068] The second aspect of the present application provides a method for preparing the sodium ion battery positive electrode material described in the first aspect of the present application, comprising: mixing and sintering a modification layer raw material including a first raw material and an organic phosphorus source with a sodium-containing positive electrode material matrix; wherein the first raw material includes a metal-co-source and an organic boron source, or the first raw material includes a metal-co-source borate.

[0069] In the preparation method of the present application, the organic matter in the raw material of the modification layer is carbonized at high temperature during the sintering process. On the one hand, it can neutralize and remove the residual alkali on the surface of the sodium-containing positive electrode material to form a sodium salt of a metal oxide, and on the other hand, it can form a carbon material. The raw materials provided by this preparation method are simple, which can avoid the problems such as the complicated mixing process caused by the separate use of different element sources (such as inorganic phosphorus sources and organic carbon sources). In addition, the preparation method of the present application can also form a thinner modification layer, which can protect the positive electrode material while making the positive electrode material have both high rate performance and cycle stability.

[0070] In the present application, the co-metal source can generally be selected from various compounds that can be converted into co-metal oxides during sintering. For example, the co-metal source can include a soluble salt of the co-metal.

[0071] In some embodiments, the co-metal source includes one or more of a co-metal carboxylate, a co-metal carbonate, a co-metal bicarbonate, or a co-metal oxalate. As an example, the co-metal source is zinc acetate.

[0072] In the present application, the organic boron source can be selected from various organic compounds containing boric acid groups, such as aromatic compounds containing boric acid groups. In addition to boric acid groups, the organic compound can also optionally have one or more groups such as sulfonic acid groups, cyano groups, and aryloxy groups. The number of boric acid groups in the structure of the organic boron source can be one or more.

[0073] In some embodiments, the organic boron source includes one or more of 2-cyanophenylboronic acid, 3-phenoxyphenylboronic acid, 3-methylthiophenylboronic acid, or 4-boronbenzenesulfonic acid.

[0074] In the present application, the organic phosphorus source can be selected from various organic substances containing phosphoric acid groups, for example, small molecule organic substances containing phosphoric acid groups, or polymers containing phosphoric acid groups.

[0075] The structure of the small molecule organic compound containing a phosphate group may include one or more phosphate groups. In some embodiments, the small molecule organic compound containing a phosphate group includes one or more of aminotrimethylphosphonic acid (ATMP, CAS: 6419-19-8), ethylenediaminetetramethylenephosphonic acid (EDTMP), diethylenetriaminepentamethylphosphonic acid (DTPMPA), dihexamethylenetriaminepentamethylenephosphonic acid (BHMTPMPA), hydroxyethylidenediphosphonic acid (HEDP) or 2-phospho-1,2,4-tricarboxylic acid butane (PBTCA).

[0076] The phosphoric acid group-containing polymer is, for example, a multi-component copolymer formed by copolymerizing a phosphoric acid-containing monomer with other monomers. As an example, the phosphoric acid group-containing multi-component copolymer includes an acrylic acid-acrylate-phosphonic acid-sulfonate tetrapolymer, such as the product KR-241 purchased from Shandong Kairui Chemical Co., Ltd. The structural formula of KR-241 is as follows:

[0077] In the present application, the sintering conditions can be selected according to the type of the modification layer raw material, as long as the organic matter therein reacts with the residual alkali of the matrix and the carbon chain is pyrolyzed or decomposed to form a carbon material.

[0078] In some embodiments, the sintering temperature may be 600° C. to 1200° C., for example, 600° C., 650° C., 700° C., 750° C., 800° C., 900° C., 1000° C., 1100° C., 1200° C., etc. Thus, while promoting the reaction between the raw materials and the residual alkali in the matrix, the prepared positive electrode material has a higher capacity.

[0079] In some embodiments, the sintering time may be 8 h to 48 h, for example, 8 h, 9 h, 10 h, 11 h, 12 h, 15 h, 18 h, 20 h, 24 h, 30 h, 35 h, 40 h, 45 h, 48 h, etc.

[0080] In the present application, the sintering may generally be performed in nitrogen and / or an inert atmosphere (such as argon).

[0081] In the present application, the components are mixed uniformly by mixing, which may include solid-solid mixing (e.g., in a mixer) or solid-liquid mixing, e.g., uniform dispersion of the components in the presence of a solvent.

[0082] In some embodiments, the mixing is carried out in the presence of a solvent. The solvent can be selected based on the type of raw materials, as long as it can dissolve at least some of the components. As some examples, the solvent includes one or more of ethanol, propanol, ethyl acetate, methanol, acetone, acetonitrile, dioxane, tetrahydrofuran, or formamide.

[0083] In the present application, the sodium content of the sodium-containing positive electrode material matrix can be, for example, 0.1wt% to 0.5wt%. The sodium content refers to the ratio of the sodium content in the sodium-containing alkaline substance on the surface of the matrix to the matrix, and the sodium-containing alkaline substance is mainly sodium carbonate, sodium hydroxide, sodium oxide, etc. Unless otherwise specified, the sodium content can be measured by the following method: take a certain mass of sodium-containing positive electrode material, add it to a certain volume of water, ultrasonicate for 15min to 30min to dissolve the sodium-containing alkaline substance in the water, and measure the sodium ion content in the solution by inductively coupled plasma emission spectrometry (ICP). The mass percentage of sodium content in the sodium-containing positive electrode material matrix is ​​the sodium content.

[0084] In the present application, the amount of the modified layer raw material can be selected based on the residual sodium content of the sodium-containing positive electrode material. As some examples, the amount of the organic phosphorus source can be determined based on the molar amount of the impurity sodium and its reaction percentage, and the amount of the first raw material can be determined based on the molecular formula of the sodium salt of the metal oxide. In the method of the present application, the impurity sodium reaction percentage can be controlled to be no less than 30%, optionally above 80%, and further optionally 100%.

[0085] In some specific embodiments, the method for preparing the sodium ion positive electrode material comprises the following steps:

[0086] The sodium-containing positive electrode material matrix, the metal-promoting borate and a solvent are first mixed to obtain a first mixed solution;

[0087] performing a second mixing of the first mixed solution and the organic phosphorus source to obtain a second mixed solution;

[0088] removing the solvent (e.g., evaporating at elevated temperature) to obtain a reaction precursor salt;

[0089] The reaction precursor salt is sintered.

[0090] In this embodiment, the mass ratio of the sodium-containing positive electrode material matrix, the metal-aiding borate, and the organic phosphorus source can be, for example, 100:(0.05-5):(0.02-4).

[0091] In this embodiment, the amount of the solvent used is such that the concentration of the sodium-containing positive electrode material matrix in the first mixed solution can be, for example, 0.06 g / mL to 5 g / mL.

[0092] In this embodiment, the first mixing can be performed at room temperature under stirring conditions. The second mixing can be performed at a temperature of 40° C. to 120° C. under stirring conditions.

[0093] In other specific embodiments, the preparation of the sodium ion positive electrode material includes the following steps:

[0094] performing a third mixing of the solvent, the sodium-containing positive electrode material matrix, the auxiliary metal source, the organic boron source, and the organic phosphorus source to obtain a third mixed solution;

[0095] removing the solvent (e.g., evaporating at elevated temperature) to obtain a reaction precursor salt;

[0096] The reaction precursor salt is sintered.

[0097] In this embodiment, the mass ratio of the sodium-containing positive electrode material matrix, the auxiliary metal source, the organic boron source and the organic phosphorus source can be, for example, 100:(0.2-3):(0.05-3):(0.02-4).

[0098] In this embodiment, the amount of the solvent used is such that the concentration of the sodium-containing positive electrode material matrix in the third mixed solution can be, for example, 0.04 g / mL to 3 g / mL.

[0099] In this embodiment, the temperature of the third mixing may be 60° C. to 120° C., and the third mixing may be performed under stirring conditions.

[0100] In the preparation method of this application, infrared spectroscopy was used to measure the functional groups on the material surface, indicating the presence of PO, OPO, MO, and BO. X-ray photoelectron spectroscopy confirmed that the modified layer contained characteristic spectra of OP, MO, and BO. This indicates that the modified layer raw materials reacted with the residual alkali in the positive electrode material to form a sodium metal oxide salt. The relative content of each element in the sodium metal oxide salt can be measured using inductively coupled plasma emission spectrometry (ICP).

[0101] The third aspect of the present application provides a positive electrode plate, comprising the sodium ion battery positive electrode material described in the first aspect of the present application or the sodium ion battery positive electrode material prepared by the method described in the second aspect of the present application.

[0102] In some embodiments, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector, and the positive electrode film layer contains the sodium ion battery positive electrode material.

[0103] In the present application, the positive electrode current collector may be, for example, a metal foil or a composite current collector. The metal foil may be, for example, aluminum foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one side of the polymer base layer. The metal layer may be made of, but is not limited to, aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The polymer material of the polymer base layer may be, for example, polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), and the like.

[0104] In some embodiments, the sodium ion battery positive electrode material is used as the positive electrode active material in the positive electrode film layer. In addition to the positive electrode material, the positive electrode film layer may optionally contain a conductive agent and / or a binder. As an example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers; the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, or fluorine-containing acrylate resin.

[0105] The present application does not particularly limit the preparation method of the positive electrode sheet, and the preparation method can refer to existing methods. For example, the positive electrode slurry is coated on the positive electrode current collector, dried, and cold pressed to form the positive electrode sheet. The positive electrode slurry can be formed by dispersing the components such as the sodium ion battery positive electrode material, an optional conductive agent, and an optional binder in a solvent (e.g., N-methylpyrrolidone) and stirring them uniformly.

[0106] In addition, the positive electrode sheet of the present application does not exclude other additional functional layers in addition to the positive electrode film layer. For example, the positive electrode sheet may also include a conductive primer layer (e.g., composed of a conductive agent and a binder) disposed between the positive electrode current collector and the positive electrode film layer. For another example, the positive electrode sheet may also include a protective layer covering the surface of the positive electrode film layer.

[0107] The fourth aspect of the present application provides a battery, comprising the positive electrode sheet described in the third aspect of the present application.

[0108] In the present application, the battery may be a secondary battery. It is understood that the secondary battery may be a sodium ion battery. In some embodiments, the secondary battery further comprises a negative electrode sheet, a separator, and an electrolyte. During the battery charge and discharge process, active ions are intercalated and released back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte acts as an ion conductor between the positive electrode sheet and the negative electrode sheet. The separator is disposed between the positive electrode sheet and the negative electrode sheet to prevent a short circuit between the positive and negative electrodes while allowing ions to pass through.

[0109] [Negative electrode]

[0110] In some embodiments, the negative electrode sheet may include a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode material.

[0111] In some embodiments, the negative electrode current collector may include a metal foil or a composite current collector. The metal foil is, for example, copper foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one side of the polymer base layer. The material of the metal layer includes, but is not limited to, copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, silver alloys, etc., and the polymer material of the polymer base layer includes, but is not limited to, polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0112] In the present application, the negative electrode material may include negative electrode active materials for secondary batteries well known in the art. For example, the negative electrode active material includes one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may include one or more of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may include one or more of elemental tin, tin oxides, and tin alloys.

[0113] In some embodiments, the negative electrode film layer may further optionally include a binder. The binder may include, for example, one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), carboxymethyl cellulose (CMC), or carboxymethyl chitosan (CMCS).

[0114] In some embodiments, the negative electrode film layer may optionally include a conductive agent. For example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.

[0115] In some embodiments, the negative electrode film layer may further optionally contain other additives, such as a thickener. Specific examples of thickeners include, but are not limited to, sodium carboxymethyl cellulose (CMC-Na).

[0116] The present application does not particularly limit the preparation method of the negative electrode sheet, and the negative electrode sheet can be prepared by referring to existing methods. For example, the negative electrode components, such as the negative electrode material, conductive agent, and binder, are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry; the negative electrode slurry is then coated on a negative electrode current collector, and the negative electrode sheet is obtained by drying and cold pressing.

[0117] [Electrolyte]

[0118] In this application, the electrolyte can be selected with reference to existing secondary batteries. In some embodiments, the electrolyte comprises an organic solvent, a sodium salt, and an optional additive. The sodium salt includes, but is not limited to, one or more of NaPF6, NaClO4, NaBCl4, NaSO3CF3, or Na(CH3)C6H4SO3. The organic solvent includes, but is not limited to, one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) or diethyl sulfone (ESE).

[0119] In some embodiments, the additives in the electrolyte may include negative electrode film-forming additives and positive electrode film-forming additives; they may also include additives that can improve certain performance of the battery, such as additives that improve the overcharge performance of the battery, additives that improve the high temperature or low temperature performance of the battery, etc. As an example, the additives may include, but are not limited to, one or more of vinylene carbonate (VC), vinyl ethylene carbonate (VEC), vinyl sulfate (DTD), propylene sulfate, vinyl sulfite (ES), 1,3-propane sultone (PS), 1,3-propene sultone (PST), sulfonate cyclic quaternary ammonium salt, succinic anhydride, succinonitrile (SN), adiponitrile (AND), tris(trimethylsilyl) phosphate (TMSP) or tris(trimethylsilyl) borate (TMSB).

[0120] [Isolation film]

[0121] In the present application, the isolation membrane is arranged between the positive electrode plate and the negative electrode plate, and mainly plays the role of preventing the positive and negative electrodes from short-circuiting, while allowing active ions to pass through. The present application has no particular restrictions on the type of isolation membrane, and various porous structure isolation membranes well known in the art can be selected. In some embodiments, the material of the isolation membrane may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. In addition, the isolation membrane can be a single-layer film or a multi-layer composite film. When the isolation membrane is a multi-layer composite film, the materials of each layer are the same or different.

[0122] In some embodiments, a ceramic coating and / or a metal oxide coating is further provided on the isolation membrane.

[0123] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0124] In some embodiments, the battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte. In some embodiments, the outer packaging may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging may be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0125] The battery of the present application may include a battery cell form, a battery module form, and a battery pack form. The battery cell, battery module, and battery pack of the present application will be described below with reference to the accompanying drawings as appropriate.

[0126] The present application has no particular limitation on the shape of the battery, which can be cylindrical, square, or any other shape. For example, FIG1 shows a battery cell 5 of a square structure as an example.

[0127] In some embodiments, referring to Figure 2, the outer packaging may include a shell 51 and a top cover assembly 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the top cover assembly 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell can be one or more, and those skilled in the art can select according to specific actual needs.

[0128] In some embodiments, battery cells may be assembled into a battery module. The battery module may contain one or more battery cells. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0129] Figure 3 shows an example battery module 4. Referring to Figure 3 , within the battery module 4, multiple battery cells 5 may be arranged sequentially along the length of the module 4. Of course, they may also be arranged in any other manner. Furthermore, the multiple cells may be secured together using fasteners.

[0130] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0131] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0132] Figures 4 and 5 illustrate an example battery pack 1. Referring to Figures 4 and 5 , the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be placed over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0133] The fifth aspect of the present application provides an electrical device, comprising the battery described in the fourth aspect of the present application. The battery can be used as a power source for the electrical device or as an energy storage unit for the electrical device.

[0134] Electrical devices may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited to these.

[0135] As an electrical device, a battery cell, battery module or battery pack can be selected according to its usage requirements.

[0136] Figure 6 shows an example of an electric device. This device can be a pure electric vehicle, hybrid electric vehicle, plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the battery, a battery pack or battery module can be used.

[0137] As another example, an electric device may be a mobile phone, a tablet computer, a laptop computer, etc. Such an electric device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0138] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0139] Example 1

[0140] 1) Preparation of sodium-containing positive electrode materials

[0141] MnO, CuO, Fe2O3 and Na2CO3 were mixed uniformly according to the molar ratio of Mn / Cu / Fe / Na of 0.92:0.04:0.04:0.85, and then placed in a sagger in a box furnace and sintered at 800℃ for 36h. After sintering and cooling to room temperature, the chemical formula of Na 0.67 Mn 0.92 Cu 0.04 Fe 0.04 The sodium-containing positive electrode material of O2 was measured to have a sodium content of 0.15wt%, a Dv50 of 5μm, and a BET specific surface area of ​​1.5m 2 / g.

[0142] 2) Preparation of positive electrode materials for sodium ion batteries

[0143] 100 g of sodium-containing positive electrode material and 0.78 g of zinc borate (CAS: 10361-94-1, the same below) were added to 50 mL of ethanol and stirred at 800 rpm for 20 min at room temperature to obtain a dispersion;

[0144] The dispersion was heated to 50°C, 0.22 g of aminotrimethylphosphonic acid (ATMP) was added to the dispersion and stirred for 30 minutes, and the temperature was further raised to 80°C, and the reaction was stirred until the solvent was completely evaporated to obtain the reaction precursor salt;

[0145] The reaction precursor salt is placed in a muffle furnace and sintered at 600 ° C for 24 hours to form NaZn (PO4) on the sodium-containing positive electrode material. 1 / 3 (BO3)@C, thereby obtaining the positive electrode material for sodium ion batteries.

[0146] Examples 2-9

[0147] Sodium ion battery positive electrode materials were prepared according to the method of Example 1. However, in Examples 2-9, the amounts of zinc borate and ATMP were adjusted, and the amount of ethanol was controlled to maintain a raw material concentration of 2 g / mL in the dispersion. Different modified layers were formed on the sodium-containing positive electrode materials to obtain sodium ion battery positive electrode materials. The specific amounts of raw materials used are shown in Table 1.

[0148] Example 10

[0149] 1) Preparation of sodium-containing positive electrode materials

[0150] Same as Example 1.

[0151] 2) Preparation of positive electrode materials for sodium ion batteries

[0152] 100 g of sodium-containing positive electrode material was mixed with 0.46 g of zinc borate, added to 50 mL of ethanol, and stirred at 1000 rpm at room temperature for 20 min to obtain a dispersion;

[0153] The dispersion was heated to 50°C, 0.67 g of copolymer KR-241 was added to the dispersion and stirred for 40 minutes, and then the temperature was raised to 80°C and stirred to react until the solvent was completely evaporated to obtain the reaction precursor salt;

[0154] The reaction precursor salt was placed in a muffle furnace and sintered at 1000 ° C for 24 h to form Na on the sodium-containing positive electrode material. 5 / 3 Zn(PO4) 1 / 3 (BO3)(SO3) 1 / 3 @C, thereby obtaining the positive electrode material for sodium ion batteries.

[0155] Examples 11-13

[0156] Sodium ion battery cathode materials were prepared according to the method of Example 10, except that the amount of zinc borate was adjusted and the amount of ethanol was controlled to adjust the raw material concentration in the dispersion to 2 g / mL. Different modified layers were formed on the sodium-containing cathode materials to produce sodium ion battery cathode materials. The specific raw material amounts are shown in Table 1.

[0157] Example 14

[0158] 1) Preparation of sodium-containing positive electrode materials

[0159] Same as Example 1.

[0160] 2) Preparation of positive electrode materials for sodium ion batteries

[0161] 100 g of sodium-containing cathode material, 0.22 g of ATMP, 1.22 g of zinc acetate, and 0.97 g of 2-cyanophenylboronic acid were mixed and added to 60 mL of ethanol. The mixture was stirred at 1000 rpm at 50°C for 60 min, and then the temperature was raised to 80°C and stirred for reaction until the solvent was completely evaporated to obtain a reaction precursor salt.

[0162] The reaction precursor salt is placed in a muffle furnace and sintered at 900 ° C for 24 hours to form NaZn (PO4) on the sodium-containing positive electrode material. 1 / 3 (BO3)@C, thereby preparing the positive electrode material for sodium ion batteries.

[0163] Examples 15-16

[0164] Sodium ion battery cathode materials were prepared according to the method of Example 14, except that the amounts of zinc acetate and 2-cyanophenylboronic acid were adjusted, and the amount of ethanol was controlled to adjust the raw material concentration in the dispersion to 1.8 g / mL, forming different modified layers to obtain sodium ion battery cathode materials. The specific raw material amounts are shown in Table 1.

[0165] Example 17

[0166] 1) Preparation of sodium-containing positive electrode materials

[0167] Same as Example 1.

[0168] 2) Preparation of positive electrode materials for sodium ion batteries

[0169] 100 g of sodium-containing cathode material, 0.22 g of ATMP, 1.62 g of zinc acetate, and 0.89 g of sodium 4-boron benzene sulfonate were mixed and added to 60 mL of ethanol. The mixture was stirred at 1000 rpm at 50°C for 50 min to obtain a dispersion. The mixture was then heated to 80°C and stirred for reaction until the solvent was completely evaporated to obtain a reaction precursor salt.

[0170] The reaction precursor salt was placed in a muffle furnace and sintered at 900 ° C for 24 h to form NaZn on the sodium-containing positive electrode material. 4 / 3 (PO4) 1 / 3 (BO3) 2 / 3 (SO3) 2 / 3 @C, thereby obtaining the positive electrode material for sodium ion batteries.

[0171] Comparative Example 1

[0172] The sodium-containing positive electrode material prepared in Example 1 was used as a comparison sample.

[0173] Comparative Example 2

[0174] The sodium ion battery cathode material was prepared according to the method of Example 1, except that ATMP was replaced with phosphoric acid (concentration 0.3 mol / L), and the amount of zinc borate was adjusted accordingly to form NaZn(PO4) on the sodium-containing cathode material. 1 / 3 (BO3), thereby obtaining a positive electrode material for a sodium ion battery. The specific amounts of raw materials used are shown in Table 1.

[0175] Comparative Example 3

[0176] 1) Preparation of sodium-containing positive electrode materials

[0177] Same as Example 1.

[0178] 2) Preparation of positive electrode materials for sodium ion batteries

[0179] 100 g of sodium-containing positive electrode material, 1.13 g of zinc acetate and phosphoric acid (concentration 0.3 mol / L, H3PO4 mass 0.60 g) were mixed and added to 60 mL of ethanol. The mixture was stirred at 1000 rpm at 50 ° C for 60 min to obtain a dispersion. The temperature was further raised to 80 ° C and stirred for reaction until the solvent was completely evaporated to obtain a reaction precursor salt.

[0180] The reaction precursor salt is placed in a muffle furnace and sintered at 900°C for 24 hours to form NaZn(PO4) on the sodium-containing positive electrode material, thereby obtaining a sodium ion battery positive electrode material.

[0181] Test section

[0182] 1. Characterization of cathode materials

[0183] (1) Elemental analysis test

[0184] Take a small amount of cathode material powder sample and add aqua regia diluted by half. Use microwave digestion (high temperature and high pressure ~200℃) for 6 hours to remove the residue (carbon material) and obtain a digestion solution. Take a certain amount of digestion solution and analyze the sodium salt element content by inductively coupled plasma emission spectrometry (ICP).

[0185] (2) Thickness of the modified layer

[0186] The sample was evenly dispersed in an ethanol solution, ultrasonicated for 5 minutes, and then allowed to stand. The supernatant was dropped onto a carbon-coated copper mesh and baked with an infrared lamp for 15 minutes. The thickness of the modified layer and the distribution of EDS elements in the modified layer were observed using a high-resolution transmission scanning microscope (HR-TEM TalosF200).

[0187] (3) Particle size (Dv50) test

[0188] The particle size test was performed using a Malvern laser particle size analyzer, and the reference standard was GB / T19077-2016.

[0189] Pretreatment: Add an appropriate amount of the sample to be tested and water into a beaker, and add a dispersant (sodium hexametaphosphate) and disperse by ultrasonication to ensure that the sample is completely dispersed in the dispersant.

[0190] (4) Specific surface area test

[0191] The specific surface area was tested using a specific surface area tester F-Sorb 1400CES in accordance with GB / T 19587-2017.

[0192] Pretreatment: Take a certain amount of powder and degas it at 80℃ under nitrogen atmosphere for 12h.

[0193] 2. Performance Testing

[0194] (1) Preparation of sodium ion batteries

[0195] 1) Preparation of positive electrode sheet

[0196] The positive electrode materials prepared in the example and the comparative example were respectively mixed with a conductive agent (SuperP), a binder (PVDF) and a solvent NMP at a mass ratio of 95:5:5:100 and stirred uniformly to obtain a positive electrode slurry.

[0197] The positive electrode slurry is evenly coated on one surface of the positive electrode collector (aluminum foil), and then dried, cold pressed, and cut to obtain the positive electrode sheet.

[0198] 2) Preparation of negative electrode sheet

[0199] The negative electrode material hard carbon, the conductive agent carbon black SuperP, the binder CMC and the solvent water are mixed and stirred in a mass ratio of 8:1:1:10 to obtain a negative electrode slurry; the negative electrode slurry is then evenly coated on one surface of the negative electrode current collector (copper foil); and then dried, cold pressed and cut to obtain a negative electrode sheet;

[0200] 3) Preparation of electrolyte

[0201] Sodium hexafluorophosphate (NaPF6) was dissolved in the solvent EC / DEC (1:1, v / v) to obtain a NaPF6 electrolyte with a concentration of 1 mol / L.

[0202] 4) The positive electrode sheet, separator (porous polyethylene film), and negative electrode sheet obtained above are cut into discs and arranged in order, so that the separator is placed between the positive electrode sheet and the negative electrode sheet to play an isolating role. The separator is infiltrated with the above electrolyte and compacted to obtain a button-type sodium ion battery.

[0203] (2) Battery performance test

[0204] 1) Rate performance test

[0205] The rate performance test process is as follows: at 25°C, in the voltage range of 1.5V to 4.2V, the battery is charged at 0.33C and discharged at a rate of 2C to obtain the capacity of the material at a rate of 2C. The designed nominal capacity of the battery cell is 72Ah.

[0206] 2) 1000-cycle capacity retention rate

[0207] The cycle performance test process is as follows: At 25°C, the battery is charged to 4.2V at a rate of 0.1C, then discharged to 1.5V at a rate of 0.1C. This process is repeated once to complete the battery activation. After activation is complete, the battery is charged to 4.2V at a rate of 0.5C, and then discharged to 1.5V at a rate of 0.5C. At this time, the initial cycle capacity is obtained. The above 0.5C charge and discharge system is repeated 1000 times. The 1000-cycle capacity retention rate is obtained by dividing the 1000-cycle discharge capacity by the initial 0.5C discharge capacity.

[0208] 3) Internal pressure expansion force test

[0209] The internal pressure expansion force was tested using an air-guide oil pipe device (Vtest-P1000 internal pressure test device).

[0210] The battery was placed on the electrochemical test channel, and the internal expansion force was monitored by a pressure gauge connected to the silicone oil tube, and the gas production during the electrochemical cycle was recorded; the pressure gauge value was read after 5 cycles of 1 / 3C charge and discharge, charging to 97% of the upper limit voltage, and 1000 cycles.

[0211] The results are shown in Table 2.

[0212] Table 1

[0213] Table 2 Note: “Modification amount” refers to the mass percentage of the total amount of modification layer raw materials to the sodium-containing positive electrode material; n(B) / n(P) represents the atomic molar ratio of B to P.

[0214] Combining Tables 1 and 2, it can be seen that the batteries prepared from the sodium ion battery positive electrode materials of Examples 1-17 have higher 2C capacity, capacity retention rate and lower internal pressure expansion force. Compared with the unmodified sodium-containing positive electrode material (Comparative Example 1), the positive electrode materials of Examples 1-17 co-modified with sodium salts of metal oxides containing P, B and Zn and carbon materials have higher conductivity, stability and higher safety. Although Comparative Examples 2-3 also have a modified layer, which can also reduce the residual alkali content and alleviate the internal pressure expansion force compared with Comparative Example 1, the modified layer of Comparative Example 2 does not contain carbon, and the 2C capacity of the battery is low; the modified layer of Comparative Example 3 does not contain C and B, and the capacity retention rate and 2C capacity of the battery are not high.

[0215] In summary, the sodium ion battery positive electrode material of the present application can improve the rate performance and cycle stability of the battery, and inhibit the generation of gas in the battery, effectively reducing the internal pressure expansion force.

[0216] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A sodium ion battery positive electrode material, wherein: include: A sodium-containing positive electrode material matrix, and a modified layer formed on at least a portion of the surface of the sodium-containing positive electrode material matrix; wherein the modified layer comprises a metal oxide sodium salt and a carbon material, and the metal oxide sodium salt has a metal promoter element, a phosphorus element and a boron element.

2. The sodium ion battery positive electrode material according to claim 1, wherein The chemical formula of the metal oxide sodium salt is: Na x M y (PO4) m (BO3) n (SO3) p , wherein M represents an auxiliary metal element, 1≤x≤6, 0.3≤y≤4, 0<m≤4, 0.3<n≤9, 0≤p≤2.

3. The sodium ion battery positive electrode material according to claim 1 or 2, wherein The auxiliary metal element includes one or more of Li, Ni, Co, Ca, Mn, Fe, Cu, V, Cr, Mo or Zn.

4. The sodium ion battery positive electrode material according to any one of claims 1 to 3, wherein In the metal oxide sodium salt, the atomic molar ratio of phosphorus element to boron element is 1:(1-3).

5. The sodium ion battery positive electrode material according to any one of claims 1 to 4, wherein The carbon material includes amorphous carbon.

6. The sodium ion battery positive electrode material according to any one of claims 1 to 5, wherein The thickness of the modified layer is 7nm-13nm.

7. The sodium ion battery positive electrode material according to any one of claims 1 to 6, wherein: The ratio of the mass of the modified layer to the mass of the sodium-containing positive electrode material matrix is ​​(0.4-3):

100.

8. The sodium ion battery positive electrode material according to any one of claims 1 to 7, wherein The sodium-containing positive electrode material matrix includes a sodium-containing transition metal oxide; the chemical formula of the sodium-containing transition metal oxide is Na r Mn a Fe b M' c O 2- d+e Q d ; Wherein, M' includes one or more of Cu, Ni, Li, Zr, K, La, Ce, Sr, Sb, Nb, Mg, Ca, Mo, Zn, Cr, W, Bi, Sn, Ge or Al; Q includes one or more of F, Cl and N; a>0, b>0, c≥0, and a+b+c=1, r≥0.66, 0≤d≤0.1, -0.1≤e≤0.

9. The sodium ion battery positive electrode material according to any one of claims 1 to 8, wherein The sodium-containing positive electrode material matrix satisfies one or two of the following conditions: The average particle size Dv50 is 3 μm to 8 μm; The specific surface area is 0.5m 2 / g~2m 2 / g.

10. A method for preparing the sodium ion battery positive electrode material according to any one of claims 1 to 9, wherein: include: The modification layer raw material including the first raw material and the organic phosphorus source is mixed and sintered with the sodium-containing positive electrode material matrix; wherein the first raw material includes an auxiliary metal source and an organic boron source, or the first raw material includes a borate of an auxiliary metal.

11. The method according to claim 10, wherein: The co-metal source includes one or more of a co-metal carboxylate, a co-metal carbonate, a co-metal bicarbonate or a co-metal oxalate; and / or, The organic boron source includes one or more of 2-cyanophenylboronic acid, 3-phenoxyphenylboronic acid, 3-methylthiophenylboronic acid or 4-borobenzenesulfonic acid.

12. The method according to claim 10 or 11, wherein: The organic phosphorus source includes one or more of small molecule organic matter containing phosphoric acid groups or polymers containing phosphoric acid groups.

13. The method according to claim 12, wherein: The small molecule organic compound containing a phosphoric acid group includes one or more of aminotris(methylene)phosphonic acid, ethylenediaminetetra(methylene)phosphonic acid, diethylenetriaminepenta(methylene)phosphonic acid, dihexamethylenetriaminepentamethylenephosphonic acid, hydroxyethylidenediphosphonic acid or 2-phospho-1,2,4-tricarboxylic acid butane; and / or, The polymer containing phosphoric acid group includes acrylic acid-acrylate-phosphonic acid-sulfonate tetrapolymer.

14. The method according to any one of claims 10 to 13, wherein: The sintering temperature is 600°C to 1200°C; and / or, The sintering time is 8h to 48h.

15. The method according to any one of claims 10 to 14, wherein: The mixing is carried out in the presence of a solvent.

16. A positive electrode sheet, wherein: A sodium ion battery positive electrode material comprising the sodium ion battery positive electrode material according to any one of claims 1 to 9 or a sodium ion battery positive electrode material prepared by the method according to any one of claims 10 to 15.

17. A battery, wherein: Including the positive electrode sheet as described in claim 16.

18. An electrical device, wherein: Comprising the battery of claim 17.

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