Sodium-ion positive electrode material and determination method, positive electrode sheet, battery and electric device

Abstract

The application relates to a sodium ion positive electrode material and a determination method, a positive electrode sheet, a battery and an electric device. The sodium ion positive electrode material has a first phase, a second phase and a composite phase. The method comprises the following steps: obtaining a to-be-tested sodium ion positive electrode material; the to-be-tested sodium ion positive electrode material comprises sodium elements and transition metal elements; the actual sodium ion potential Y1 and the actual cation potential X1 of the to-be-tested sodium ion positive electrode material are calculated; the value of the theoretical sodium ion potential Y when X=X1 is calculated according to the equation Y=0.4065X+1.572; the difference value d between the actual sodium ion potential and the theoretical sodium ion potential is calculated according to d=Y1-Y; when d satisfies d2 The determination method is used for guiding the design of the sodium ion positive electrode material with the composite phase.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a sodium-ion positive electrode material and a determination method, a positive electrode sheet, a battery and an electric device. BACKGROUND

[0002] With the continuous development of battery technology, sodium-ion batteries are becoming more and more popular due to their abundant resources and low cost, and the development of sodium-ion positive electrode materials with high performance has become a key task in the current research and development of sodium-ion batteries. Among them, sodium-ion layered oxides have a periodic layered structure and two-dimensional ion channels, making them one of the most promising sodium-ion positive electrode materials, with high specific capacity, diverse structure, adjustable composition, and simple preparation. The common structure of sodium-ion layered oxides can be divided into P(Prismatic, three-prismatic)2 phase, O(Octahedral, octahedral)3 phase and composite phase of P2 and O3. The sodium content of P2 phase sodium-ion positive electrode material is low, has more sodium ion vacancies, has a large sodium layer spacing, can improve the transmission rate of sodium ions and maintain the integrity of the layered structure, and shows good kinetic performance and rate performance, but the low sodium content limits the capacity of the sodium-ion positive electrode material, so that the P2 phase sodium-ion positive electrode material will produce a sharp phase change after deep sodium removal, resulting in unstable structure of the sodium-ion positive electrode material; the sodium content of O3 phase sodium-ion positive electrode material is high, which improves the capacity of the sodium-ion positive electrode material, but the sodium layer spacing is small, which limits the transmission efficiency of sodium ions, so that the O3 phase sodium-ion positive electrode material shows poor kinetic performance and rate performance. Therefore, in order to balance the dual performance of capacity and rate performance, the composite phase of P2 and O3 has become a research hotspot in recent years, and the composite phase of P2 and O3 has better overall performance than P2 single phase and O3 single phase. However, there is currently a lack of clear guidance for the design and synthesis of such materials, and the design and synthesis of P2 and O3 composite phases can only be achieved through repeated experiments, resulting in a sharp increase in material research costs. SUMMARY

[0003] In view of this, the present application provides a sodium-ion positive electrode material and a determination method, a positive electrode sheet, a battery and an electric device. The determination method of the sodium-ion positive electrode material can guide the design of a sodium-ion positive electrode material with a composite phase of P2 phase and O3 phase through the difference d between the actual sodium-ion potential and the theoretical sodium-ion potential of the sodium-ion positive electrode material.

[0004] The application provides a determination method of a sodium ion positive electrode material, the sodium ion positive electrode material has a first phase, a second phase and a composite phase, the composite phase is a composite of the first phase and the second phase; the determination method comprises: obtaining a to-be-tested sodium ion positive electrode material; wherein the to-be-tested sodium ion positive electrode material comprises sodium elements and transition metal elements; calculating actual sodium ion potential Y1 and actual cation potential X1 of the to-be-tested sodium ion positive electrode material; calculating the value of theoretical sodium ion potential Y of the to-be-tested sodium ion positive electrode material when X=X1 according to the equation Y=0.4065X+1.572 of the to-be-tested sodium ion positive electrode material; calculating the difference d between the actual sodium ion potential and the theoretical sodium ion potential of the to-be-tested sodium ion positive electrode material according to d=Y1-Y; and when the difference d between the actual sodium ion potential and the theoretical sodium ion potential of the to-be-tested sodium ion positive electrode material satisfies the relationship d2

[0005] Further, the determination method of the critical value d1 of the sodium ion positive electrode material forming the composite phase and the second phase and the critical value d2 of the sodium ion positive electrode material forming the composite phase and the first phase comprises: selecting a plurality of sodium ion positive electrode materials; calculating the actual sodium ion potential Y1 and the actual cation potential X1 of each sodium ion positive electrode material; calculating the value of the theoretical sodium ion potential Y of the sodium ion positive electrode material when X=X1 according to the equation Y=0.4065X+1.572 of the sodium ion positive electrode material; calculating the difference between the actual sodium ion potential and the theoretical sodium ion potential of each sodium ion positive electrode material according to d=Y1-Y; performing linear equation fitting on d of the plurality of sodium ion positive electrode materials and the proportion Z of the first phase in the sodium ion positive electrode material, wherein 0

[0006] Further, in the case that the sodium ion positive electrode material is the composite phase, the chemical general formula of the sodium ion positive electrode material is: Na x A u B v C w O2, wherein 0.67

[0007] Further, the first phase is a P2 single phase, the second phase is an O3 single phase, and the composite phase is a composite of the P2 single phase and the O3 single phase.

[0008] Further, the calculating the actual sodium ion potential Y1 and the actual cation potential X1 of the sodium ion positive electrode material to be tested comprises: calculating the actual sodium ion potential Y1 of the sodium ion positive electrode material to be tested according to the formula Y1 = x / R Na calculating the actual sodium ion potential Y1 of the sodium ion positive electrode material to be tested, wherein x is the stoichiometric number of sodium elements, R Na is the ionic radius of sodium ions, and calculating the actual cation potential X1 of the sodium ion positive electrode material to be tested according to the actual sodium ion potential Y1.

[0009] Further, the calculating the actual cation potential X1 of the sodium ion positive electrode material to be tested according to the actual sodium ion potential Y1 comprises: calculating the actual cation potential X1 of the sodium ion positive electrode material to be tested according to the formula X1 = Y2 * Y1 / Y3, wherein Y2 is the weighted average ion potential of transition metals, Y1 is the actual sodium ion potential, and Y3 is the oxygen anion potential.

[0010] Further, the weighted average ion potential Y2 of the transition metals satisfies the formula Y2 = ∑wni / Rni, wherein ni is the valence of each transition metal A, B, and C in the chemical formula, wn is the stoichiometric number of each transition metal A, B, and C in the chemical formula when the valence is ni, and Rn is the ionic radius of each transition metal A, B, and C in the chemical formula.

[0011] Further, the oxygen anion potential Y3 satisfies the formula Y3 = 2 / R O , wherein R O is the ionic radius of oxygen ions.

[0012] Further, the calculating the difference d1 between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material when the proportion Z of the first phase is 0 and the calculating the difference d2 between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material when the proportion Z of the first phase is 1 according to the linear equation comprises: calculating the difference d1 = 0.2508 between the actual cation potential and the theoretical cation potential of the sodium ion positive electrode material when the proportion Z of the first phase is 0 according to the formula Z = (-9.151d) + 2.2954; calculating the difference d2 = 0.1416 between the actual cation potential and the theoretical cation potential of the sodium ion positive electrode material when the proportion Z of the first phase is 1; and when 0.1416 < d < 0.2508, the sodium ion positive electrode material is a composite phase.

[0013] The application also provides a sodium ion positive electrode material, which is a composite phase and has a chemical formula of Nax A u B v C w O2, wherein 0.67 < x < 1, 0 < u < 1, 0 < v < 1, 0 < w < 1, and u + v + w = 1, A, B and C are transition metal elements, a difference between an actual sodium ion potential and a theoretical sodium ion potential of the sodium ion positive electrode material is d, d satisfies a relationship of 0.1416 < d < 0.2508.

[0014] Further, a difference between an actual sodium ion potential and a theoretical sodium ion potential of the sodium ion positive electrode material is d, a proportion of the first phase in the sodium ion positive electrode material is Z, and Z satisfies a relationship of Z = (-9.151d) + 2.2954.

[0015] The application further provides a positive electrode sheet, comprising a positive electrode current collector and a positive electrode material layer, the positive electrode material layer is arranged on the surface of the positive electrode current collector, and the positive electrode material layer comprises the sodium ion positive electrode material provided by the application.

[0016] The application further provides a battery, comprising an electrolyte, a negative electrode sheet, a separator and the positive electrode sheet provided by the application, the negative electrode sheet, the separator and the positive electrode sheet are sequentially stacked or wound; the negative electrode sheet, the separator and the positive electrode sheet are at least partially immersed in the electrolyte.

[0017] The application further provides a power utilization device, comprising a power utilization device body and the battery provided by the application, the power utilization device body comprises a device positive electrode and a device negative electrode; the positive electrode sheet of the battery is used for electrically connecting the device positive electrode of the power utilization device body, the negative electrode sheet of the battery is used for electrically connecting the device negative electrode of the power utilization device body, and the battery pack is used for supplying power to the power utilization device body.

[0018] In the method for determining sodium-ion cathode materials provided in this application, the actual sodium-ion potential and the actual cation potential are calculated, and according to the equation Y = 0.4065X + 1.572, the difference d between the actual sodium-ion potential and the theoretical sodium-ion potential of the sodium-ion cathode material to be tested when X = X1 is calculated. When d satisfies d2 < d < d1, the sodium-ion cathode material to be tested is a composite phase. The sodium-ion cathode material of the composite phase can take into account both capacity and rate performance, and has better overall performance. The method for determining sodium-ion cathode materials provided in this application provides scientific guidance for designing and synthesizing composite phase sodium-ion cathode materials. In order to obtain a composite phase sodium-ion cathode material, a theoretical model of the sodium-ion cathode material to be tested that conforms to the general chemical formula can be constructed. By calculating the value of the difference d between the actual sodium-ion potential and the theoretical sodium-ion potential of the sodium-ion cathode material to be tested, and then judging the relationship between d and d1 and d2 respectively, it can be preliminarily determined whether the sodium-ion cathode material to be tested that conforms to the general chemical formula is a composite phase. The aforementioned determination method provides convenience for experimenters, serves as a reference for their experiments, narrows down the range of sodium-ion cathode materials that can form composite phases, reduces the number of experiments and verifications required by experimenters, saves experimenters' time and energy, and correspondingly reduces the cost of materials research. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the implementation will be briefly introduced below. Obviously, the drawings described below are some implementations of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a flowchart illustrating a method for determining a sodium-ion cathode material according to an embodiment of this application.

[0021] Figure 2 This is a flowchart illustrating a method for determining a sodium-ion cathode material according to another embodiment of this application.

[0022] Figure 3 This is a linear relationship graph between the theoretical cation potential X and the theoretical sodium ion potential Y of a sodium ion cathode material according to an embodiment of this application.

[0023] Figure 4 This is a flowchart illustrating a method for determining a sodium-ion cathode material according to another embodiment of this application.

[0024] Figure 5 This is a flowchart illustrating a method for determining a sodium-ion cathode material according to another embodiment of this application.

[0025] Figure 6A flowchart of a method for determining a sodium-ion positive electrode material according to another embodiment of the present application;

[0026] Figure 7 A linear relationship diagram of a difference d between an actual sodium-ion potential and a theoretical sodium-ion potential of a sodium-ion positive electrode material according to an embodiment of the present application and a proportion Z of a first phase in the sodium-ion positive electrode material;

[0027] Figure 8 A structural diagram of a positive electrode sheet according to an embodiment of the present application;

[0028] Figure 9 A structural diagram of a positive electrode sheet according to an embodiment of the present application along Figure 8 a direction of A-A;

[0029] Figure 10 A structural diagram of a battery according to an embodiment of the present application;

[0030] Figure 11 A structural diagram of a battery according to an embodiment of the present application along Figure 10 a direction of B-B;

[0031] Figure 12 A structural diagram of a power consumption device according to an embodiment of the present application.

[0032] Explanation of reference signs:

[0033] 100 - positive electrode sheet, 110 - positive electrode current collector, 120 - positive electrode material layer, 200 - battery, 210 - electrolyte, 220 - negative electrode sheet, 230 - separator, 300 - power consumption device, 310 - device body, 311 - device positive electrode, 312 - device negative electrode. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0035] The terms "first", "second", and the like in the specification and claims of the present application and the above drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device including a series of steps or units is not limited to the listed steps or units, but can optionally include steps or units not listed or can optionally include other steps or units inherent to the process, method, product, or device.

[0036] Reference herein to "an embodiment" or "an implementation" means that a particular feature, structure, or characteristic described in connection with the embodiment or implementation can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another. As will be apparent to those of ordinary skill in the art, embodiments described herein can be combined with other embodiments.

[0037] With the continuous development of battery technology, sodium-ion batteries are becoming more and more popular due to abundant resources and low cost, and the development of sodium-ion cathode materials with high performance has become a key task in the current research and development of sodium-ion batteries. Among them, sodium-ion layered oxides have a periodic layered structure and two-dimensional ion channels, making them have the characteristics of high specific capacity, structural diversity, adjustable composition, and simple preparation, and are one of the most promising sodium-ion cathode materials.

[0038] The layered oxides of sodium-ion cathode materials form a repeated layer structure through the common edge of MO6 octahedron, and the sodium ions form two coordination environments with oxygen between the layers formed by the MO6 octahedron, which are P (Prismatic, triangular prism) phase and O (Octahedral, octahedron) phase. In these layer structures, the common structures of sodium-ion layered oxides can be divided into P2 phase, O3 phase and composite phase of P2 and O3. The sodium-ion cathode material of P2 phase has a low sodium content, has more sodium ion vacancies, has a large sodium interlayer spacing, can improve the transmission rate of sodium ions and maintain the integrity of the layered structure, and exhibits good kinetic performance and rate performance. However, the low sodium content limits the capacity of the sodium-ion cathode material, so that the sodium-ion cathode material of P2 phase will produce a sharp phase change after deep sodium extraction, resulting in unstable structure of the sodium-ion cathode material; the sodium-ion cathode material of O3 phase has a high sodium content, which improves the capacity of the sodium-ion cathode material, but its sodium interlayer spacing is small, which limits the transmission efficiency of sodium ions, so that the sodium-ion cathode material of O3 phase exhibits poor kinetic performance and rate performance. Therefore, in order to balance the dual performance of capacity and rate performance, the composite phase of P2 and O3 has become a research hotspot in recent years. The composite phase of P2 and O3 has better overall performance than the P2 single phase and the O3 single phase. However, there is currently a lack of clear guidance for the design and synthesis of such materials, and the design and synthesis of P2 and O3 composite phases can only be achieved through repeated experiments, resulting in a sharp increase in the cost of material research.

[0039] See Figure 1 The application provides a determination method of a sodium-ion cathode material, the sodium-ion cathode material has a first phase, a second phase and a composite phase, and the composite phase is a composite of the first phase and the second phase.

[0040] Understandably, the sodium ion positive electrode material is a layered oxide, the first phase is a P2 single phase, the second phase is an O3 single phase, and the composite phase is a composite of the P2 phase and the O3 phase. The sodium ion positive electrode material includes alkali metal layers (O-Na-O) and transition metal layers (O-M-O) arranged alternately. In the first phase (P2 single phase), the layer spacing of the alkali metal layer (O-Na-O) is larger, and the layer spacing of the transition metal layer (O-M-O) is smaller; in the second phase (O3 single phase), the layer spacing of the alkali metal layer (O-Na-O) is smaller, and the layer spacing between the transition metal layers (O-M-O) is larger.

[0041] The determination method includes:

[0042] S101, obtaining a sodium ion positive electrode material to be tested; wherein the sodium ion positive electrode material to be tested includes sodium elements and transition metal elements.

[0043] Understandably, the sodium ion positive electrode material to be tested satisfies a certain chemical formula and includes sodium elements and transition metal elements, and a model of the sodium ion positive electrode material to be tested satisfying a certain chemical formula can be constructed by a Monte Carlo random sampling method.

[0044] Understandably, the Monte Carlo method is also called a statistical simulation method or a statistical test method, which is a determination method for determining unknown characteristic quantities by sampling survey method to obtain statistical values. The problem to be solved by the Monte Carlo method is that the definition of the probability distribution is known, and the random sample of the probability distribution is obtained by sampling, and the characteristics of the probability distribution are analyzed by the obtained random sample.

[0045] Optionally, a VESTA (Visualization for Electronic and Structural Analysis) software can be used to construct a plurality of models of the sodium ion positive electrode material to be tested satisfying a certain chemical formula.

[0046] S102, calculating an actual sodium ion potential Y1 and an actual cation potential X1 of the sodium ion positive electrode material to be tested.

[0047] Understandably, the ion potential refers to the ratio of the charge number of the ion to the ion radius. The actual sodium ion potential Y1 of the sodium ion positive electrode material to be tested is the ratio of the charge number of the sodium ion to the sodium ion radius.

[0048] It can be understood that the actual cation potential of the to-be-tested sodium-ion positive electrode material normalizes the weighted average ion potential of the transition metal, the sodium ion potential and the oxygen anion potential in the to-be-tested sodium-ion positive electrode material to describe the electron cloud density and polarization degree of the cation, and reflects the interaction between the alkali metal layer (O-Na-O) and the transition metal layer (O-M-O) in the layered oxide of the to-be-tested sodium-ion positive electrode material. The greater the value of the actual cation potential X1 of the to-be-tested sodium-ion positive electrode material, the stronger the interaction force of M-O in the transition metal layer (O-M-O) of the to-be-tested sodium-ion positive electrode material, which reduces the interlayer spacing of the transition metal layer (O-M-O), and the to-be-tested sodium-ion positive electrode material is more inclined to form a first phase (P2 single phase); the smaller the value of the actual cation potential X1 of the to-be-tested sodium-ion positive electrode material, the weaker the interaction force of M-O in the transition metal layer (O-M-O) of the to-be-tested sodium-ion positive electrode material, and the larger the interlayer spacing of the transition metal layer (O-M-O), and the to-be-tested sodium-ion positive electrode material is more inclined to form a second phase (O3 single phase).

[0049] S103, according to the equation Y=0.4065X+1.572 of the to-be-tested sodium-ion positive electrode material, the value of the theoretical sodium ion potential Y of the to-be-tested sodium-ion positive electrode material when X=X1.

[0050] It can be understood that the equation of the to-be-tested sodium-ion positive electrode material is derived from "Zhao, Chenglong, et al. Rational design of layered oxide materials for sodium-ion batteries. Science 370.6517 (2020): 708-711". As shown in Figure 2 The linear relationship diagram of the theoretical cation potential X and the theoretical sodium ion potential Y of the to-be-tested sodium-ion positive electrode material is shown.

[0051] It can be understood that the theoretical sodium ion potential and the theoretical cation potential of the to-be-tested sodium-ion positive electrode material satisfy a linear relationship. Taking the theoretical cation potential of the sodium-ion positive electrode material as the X axis and the theoretical sodium ion potential of the sodium-ion positive electrode material as the Y axis, the theoretical sodium ion potential increases with the increase of the theoretical cation potential, and the theoretical sodium ion potential decreases with the decrease of the theoretical cation potential.

[0052] S104, according to d=Y1-Y, the difference d between the actual sodium ion potential and the theoretical sodium ion potential of the to-be-tested sodium-ion positive electrode material is calculated.

[0053] It can be understood that the actual cation potential of the sodium ion positive electrode material to be tested is taken as the x-axis coordinate, and the actual sodium ion potential is taken as the y-axis coordinate. The point A formed by the actual cation potential and the actual sodium ion potential of the sodium ion positive electrode material to be tested in the coordinate system is (X1, Y1). The value of d is the distance from the point A to the linear equation Y = 0.4065X + 1.572 in the direction parallel to the Y-axis.

[0054] It can be understood that when the value of d is greater than 0, the point A is located above the linear equation. When the actual cation potential of the sodium ion positive electrode material to be tested is equal to the theoretical cation potential, the actual sodium ion potential of the sodium ion positive electrode material to be tested is greater than the theoretical sodium ion potential of the sodium ion positive electrode material to be tested. In other words, when the actual sodium ion potential of the sodium ion positive electrode material to be tested is equal to the theoretical sodium ion potential, the actual cation potential of the sodium ion positive electrode material to be tested is less than the theoretical cation potential. When the value of d is less than 0, the point A is located below the linear equation. When the actual cation potential of the sodium ion positive electrode material to be tested is equal to the theoretical cation potential, the actual sodium ion potential of the sodium ion positive electrode material to be tested is less than the theoretical sodium ion potential of the sodium ion positive electrode material to be tested. In other words, when the actual sodium ion potential of the sodium ion positive electrode material to be tested is equal to the theoretical sodium ion potential, the actual cation potential of the sodium ion positive electrode material to be tested is greater than the theoretical cation potential. When the value of d is equal to 0, the point A is located on the linear equation. The actual sodium ion potential of the sodium ion positive electrode material to be tested is equal to the theoretical sodium ion potential, and the actual cation potential of the sodium ion positive electrode material to be tested is equal to the theoretical cation potential.

[0055] S105, when the difference d between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material to be tested satisfies the relationship d2 < d < d1, it is determined that the sodium ion positive electrode material to be tested is a composite phase; wherein the value of d1 is the critical value of the sodium ion positive electrode material forming a composite phase and a second phase, and the value of d2 is the critical value of the sodium ion positive electrode material forming a composite phase and a first phase.

[0056] It can be understood that the value of d1 is the critical value of the sodium ion positive electrode material forming a composite phase and a second phase. When d satisfies d ≥ d1, the sodium ion positive electrode material to be tested forms a second phase; when d < d1, the sodium ion positive electrode material to be tested forms a composite phase.

[0057] It can be understood that the value of d2 is the critical value of the sodium ion positive electrode material forming a composite phase and a first phase. When d satisfies d ≤ d2, the sodium ion positive electrode material to be tested forms a first phase; when d > d2, the sodium ion positive electrode material to be tested forms a composite phase.

[0058] In the embodiment, the determination method of the sodium ion positive electrode material is to calculate the actual sodium ion potential and the actual cation potential, and according to the equation Y=0.4065X+1.572, calculate the difference d between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material to be measured when X=X1. When d satisfies d2

[0059] See Figures 1 to 3 In some embodiments, the determination method of the critical value d1 of the sodium ion positive electrode material forming a composite phase and a second phase and the critical value d2 of the sodium ion positive electrode material forming a composite phase and a first phase includes:

[0060] S1051, selecting a plurality of sodium ion positive electrode materials.

[0061] Optionally, a plurality of sodium ion positive electrode materials satisfying different chemical formulas are selected, and a plurality of models of the sodium ion positive electrode materials satisfying different chemical formulas are constructed by a Monte Carlo random sampling method.

[0062] Optionally, the VESTA (Visualization for Electronic and Structural Analysis) software can be used to construct a plurality of models of the plurality of sodium ion positive electrode materials satisfying different chemical formulas.

[0063] S1052, calculating the actual sodium ion potential Y1 and the actual cation potential X1 of each sodium ion positive electrode material.

[0064] S1053, according to the equation Y=0.4065X+1.572 of the sodium ion positive electrode material, calculating the value of the theoretical sodium ion potential Y of the sodium ion positive electrode material when X=X1.

[0065] S1054, calculating a difference between the actual sodium ion potential and the theoretical sodium ion potential of each sodium ion positive electrode material according to d=Y1-Y.

[0066] S1055, performing linear equation fitting on the d of the plurality of sodium ion positive electrode materials and the proportion Z of the first phase in the sodium ion positive electrode material, wherein 0

[0067] It can be understood that the energy difference γ of the sodium ion positive electrode material with the proportion Z of the first phase satisfying the relationship 0

[0068] Optionally, the proportion Z of the first phase in the sodium ion positive electrode material can be measured and calculated by XRD (X-ray diffraction) and the like.

[0069] It can be understood that the value of the difference d between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material is related to the proportion Z of the first phase. When the sodium ion positive electrode material tends to form a composite phase, when the value of d is greater than 0 and the value of d is large, when the actual sodium ion potential of the sodium ion positive electrode material is equal to the theoretical sodium ion potential, the actual cation potential of the sodium ion positive electrode material is less than the theoretical cation potential, and the difference between the two is large, the value of the actual cation potential of the sodium ion positive electrode material is small, the interaction force between M-O in the transition metal layer (O-M-O) of the sodium ion positive electrode material is weaker, the interlayer spacing of the transition metal layer (O-M-O) is larger, and the sodium ion positive electrode material tends to form a second phase (O3 single phase). When the value of d is greater than 0 and the value of d is small, when the actual sodium ion potential of the sodium ion positive electrode material is equal to the theoretical sodium ion potential, the actual cation potential of the sodium ion positive electrode material is less than the theoretical cation potential, but the difference between the two is small, the interaction force between M-O in the transition metal layer (O-M-O) of the sodium ion positive electrode material is moderate, which is conducive to the formation of a composite phase. When the value of d is less than 0, when the actual sodium ion potential of the sodium ion positive electrode material is equal to the theoretical sodium ion potential, the actual cation potential of the sodium ion positive electrode material is greater than the theoretical cation potential, then the interaction force between M-O in the transition metal layer (O-M-O) of the sodium ion positive electrode material is stronger, which reduces the interlayer spacing of the transition metal layer (O-M-O), and the sodium ion positive electrode material tends to form a first phase (P2 single phase).

[0070] S1056, according to the linear equation, respectively calculating the difference d1 between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material when the proportion Z of the first phase is 0, and the difference d2 between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material when the proportion Z of the first phase is 1, then when d2

[0071] It can be understood that the proportion of the first phase can be, but is not limited to, the volume proportion or the mass proportion of the first phase in the sodium ion positive electrode material.

[0072] It can be understood that the value of the difference d between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material and the proportion Z of the first phase in the sodium ion positive electrode material satisfy a linear relationship. When the proportion Z of the first phase is 0, the proportion of the second phase in the sodium ion positive electrode material is 1, and at this time, the difference between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material is d1. In other words, the value of d1 is the critical value of the formation of the composite phase and the second phase of the sodium ion positive electrode material. When the value of the difference d between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material satisfies d≥d1, the sodium ion positive electrode material forms the second phase; when the value of the difference d between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material satisfies d<d1, the sodium ion positive electrode material forms the composite phase.

[0073] It can be understood that when the proportion Z of the first phase is 1, the proportion of the second phase in the sodium ion positive electrode material is 0, and at this time, the difference between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material is d2. In other words, the value of d2 is the critical value of the formation of the composite phase and the first phase of the sodium ion positive electrode material. When the value of the difference d between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material satisfies d≤d2, the sodium ion positive electrode material forms the first phase; when the value of the difference d between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material satisfies d>d2, the sodium ion positive electrode material forms the composite phase.

[0074] It can be understood that when d satisfies d≥d1, the sodium ion positive electrode material forms the second phase; when d satisfies d≤d2, the sodium ion positive electrode material forms the first phase; when d satisfies d2<d<d1, the sodium ion positive electrode material is the composite phase.

[0075] In the embodiment, by linear fitting the value of d and the proportion Z of the first phase in the sodium ion positive electrode material, the difference d1 between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material when the proportion Z of the first phase is 0 is obtained, the difference d2 between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material when the proportion Z of the first phase is 1 is calculated according to the linear equation, so as to obtain the critical value d1 of the sodium ion positive electrode material forming the composite phase and the second phase and the critical value d2 of the sodium ion positive electrode material forming the composite phase and the first phase. So that when the d of the sodium ion positive electrode material to be measured satisfies the relationship d2 < d < d1, the sodium ion positive electrode material to be measured is a composite phase. The sodium ion positive electrode material of the composite phase can balance the dual performance of capacity and rate performance, and has relatively optimal overall performance. The determination method of the critical value d1 of the sodium ion positive electrode material forming the composite phase and the second phase and the critical value d2 of the sodium ion positive electrode material forming the composite phase and the first phase provided in the embodiment of the present application provides scientific guidance for designing and synthesizing the sodium ion positive electrode material of the composite phase. In order to obtain the sodium ion positive electrode material of the composite phase, a theoretical model of the sodium ion positive electrode material conforming to the chemical general formula can be constructed, the value of the difference d between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material is calculated, and then the size relationship between d and d1 and d2 is judged, so as to preliminarily judge whether the sodium ion positive electrode material conforming to the chemical general formula is a composite phase. The determination method provides convenience for experimenters, can provide reference for experiments of experimenters, narrows the range of the sodium ion positive electrode material that can form a composite phase, reduces the number of experiments and the number of verifications of experimenters, is conducive to saving time and energy of experimenters, and accordingly reduces the cost of material research.

[0076] In some embodiments, in the case that the sodium ion positive electrode material is a composite phase, the chemical general formula of the sodium ion positive electrode material is: Na x A u B v C w O2, wherein 0.67 < x ≤ 1, 0 < u ≤ 1, 0 ≤ v < 1, 0 ≤ w < 1, and u + v + w = 1, A, B and C are transition metal elements. Among them, u, v and w are not zero at the same time.

[0077] In the embodiment, the sodium ion positive electrode material is a composite phase, and the sodium ion positive electrode material of the composite phase satisfies the chemical general formula Na x A u B v C w O2, wherein u, v and w are not zero at the same time, and the sodium ion positive electrode material of the composite phase has relatively optimal kinetic performance and rate performance.

[0078] In some embodiments, the chemical general formula of the sodium ion positive electrode material is: Na xA u B v C w O2, wherein A is selected from at least one of transition metals such as Mn, Ni, Ti, Co, Fe, Cu, Cr, Zn, V, Zr and Ta; B is selected from at least one of transition metals such as Mn, Ni, Ti, Co, Fe, Cu, Cr, Zn, V, Zr and Ta; C is selected from at least one of transition metals such as Mn, Ni, Ti, Co, Fe, Cu, Cr, Zn, V, Zr and Ta.

[0079] In the present embodiment, the chemical general formula of the sodium-ion positive electrode material is Na x A u B v C w O2, the sodium-ion positive electrode material can be but is not limited to Na 0.85 Mn 0.5 Ni 0.4 Ti 0.1 O2, Na 0.85 Mn 0.5 Ni 0.4 Co 0.1 O2, Na 0.85 Mn 0.5 Ni 0.4 Fe 0.1 O2, Na- 0.85 Mn 0.5 Ni 0.4 Cu 0.1 O2, Na 0.85 Mn 0.5 Ni 0.5 O2, Na 0.95 Mn 0.5 Ni 0.5 O2, Na 0.67 Mn 0.5 Ni 0.5 O2, Na 0.67 Mn 0.6 Ni 0.4 O2, Na 0.85 Mn 0.6 Ni 0.4 O2, and Na 0.67 MnO2, etc.

[0080] Optionally, the first phase is a P2 single phase, the second phase is an O3 single phase, and the composite phase is a composite of the P2 phase and the O3 phase.

[0081] In the embodiment, the first phase is a P2 single phase, the sodium content of the sodium ion positive electrode material of the P2 single phase is low, there are more sodium ion vacancies, the layer spacing of the alkali metal layer (O-Na-O) is large, which can improve the transmission rate of sodium ions and maintain the integrity of the layered structure, so that the sodium ion positive electrode material exhibits good kinetic performance and rate performance, but the low sodium content limits the capacity of the sodium ion positive electrode material, so that the P2 single phase sodium ion positive electrode material will produce a violent phase change after deep sodium removal, resulting in unstable structure of the sodium ion positive electrode material. The second phase is an O3 single phase, the sodium content of the O3 single phase sodium ion positive electrode material is high, which improves the capacity of the sodium ion positive electrode material, but the layer spacing of the alkali metal layer (O-Na-O) is small, which limits the transmission efficiency of sodium ions, so that the O3 single phase sodium ion positive electrode material exhibits poor kinetic performance and rate performance. The composite phase takes into account the advantages of the P2 single phase and the O3 single phase, so that the sodium ion positive electrode material of the composite phase exhibits high rate performance and high capacity when applied to the positive electrode sheet 100.

[0082] See Figure 4 In some embodiments, the actual sodium ion potential Y1 and the actual cation potential X1 of the to-be-tested sodium ion positive electrode material are calculated, including:

[0083] S1021, according to the formula Y1=x / R Na The actual sodium ion potential Y1 of the to-be-tested sodium ion positive electrode material is calculated, wherein x is the stoichiometric number of sodium elements, R Na is the ionic radius of sodium ions.

[0084] It can be understood that in some embodiments, if the to-be-tested sodium ion positive electrode material satisfies the chemical formula Na 0.85 Mn 0.5 Ni 0.4 Ti 0.1 O2, then in the to-be-tested sodium ion positive electrode material, the stoichiometric number x of the sodium element is 0.85. In other embodiments, if the to-be-tested sodium ion positive electrode material satisfies the chemical formula Na 0.67 Mn 0.5 Ni 0.5 O2, then in the to-be-tested sodium ion positive electrode material, the stoichiometric number x of the sodium element is 0.67.

[0085] S1022, according to the actual sodium ion potential Y1, the actual cation potential X1 of the to-be-tested sodium ion positive electrode material is calculated.

[0086] In the embodiment, the actual sodium ion potential Y1 of the to-be-tested sodium ion positive electrode material is calculated by the formula Y1=x / R NaCalculate the actual sodium ion potential Y1 of the sodium ion cathode material to be tested, so as to further calculate the actual cation potential of the sodium ion cathode material to be tested.

[0087] Please see Figure 4 and Figure 5 In some embodiments, calculating the actual cation potential X1 of each sodium ion cathode material based on the actual sodium ion potential Y1 includes:

[0088] S10221, calculate the actual cation potential X1 of the sodium ion cathode material to be tested according to X1=Y2×Y1 / Y3, where Y2 is the weighted average ion potential of the transition metal, Y1 is the actual sodium ion potential, and Y3 is the oxygen anion potential.

[0089] In this embodiment, the actual cation potential X1 of the sodium ion cathode material to be tested satisfies the formula X1=Y2×Y1 / Y3. The actual cation potential of the sodium ion cathode material to be tested is normalized to the weighted average ion potential of the transition metal, sodium ion potential and oxygen anion potential in the sodium ion cathode material to be tested, so as to describe the electron cloud density and polarization degree of the cation, and reflect the interaction between the alkali metal layer (O-Na-O) and the transition metal layer (OMO) in the layered oxide of the sodium ion cathode material. The larger the actual cation potential X1 of the sodium ion cathode material, the stronger the interaction force of MO in the transition metal layer (OMO) of the sodium ion cathode material, which reduces the interlayer spacing of the transition metal layer (OMO), and the sodium ion cathode material under test is more likely to form the first phase (P2 single phase); the smaller the actual cation potential X1 of the sodium ion cathode material, the weaker the interaction force of MO in the transition metal layer (OMO) of the sodium ion cathode material, which increases the interlayer spacing of the transition metal layer (OMO), and the sodium ion cathode material under test is more likely to form the second phase (O3 single phase).

[0090] In some embodiments, the weighted average ionic potential Y2 of the transition metals satisfies the formula Y2=∑wini / , where ni is the valence state of each transition metal A, B, and C in the general chemical formula, wi is the stoichiometric coefficient of each transition metal A, B, and C in the general chemical formula when the valence state is ni, and Ri is the ionic radius of each transition metal A, B, and C in the general chemical formula.

[0091] Understandably, in some embodiments, if the sodium ion cathode material to be tested satisfies the general chemical formula Na- 0.85 Mn 0.5 Ni 0.4 Ti 0.1 O2, then in the sodium ion cathode material to be tested, the Mn element exists in two valence states, Mn 4+ The stoichiometric coefficient of Mn is 0.45.3+ the stoichiometric number of Mn is 0.05, Ni 2+ the stoichiometric number of Ti is 0.4, Ni 4+ the stoichiometric number of O2 is 0.1.

[0092] In the embodiment, the weighted average ion potential Y2 of the transition metal satisfies the formula Y2 = ∑wini / , and the weighted average ion potential of the transition metal can be obtained by summing the ion potential of the transition metal. In some embodiments, the transition metal A, B or C has two or three valence states, and the weighted average ion potential Y2 of the transition metal is calculated according to the formula Y2 = ∑wini / , where w represents the weight of the transition metal, i represents the ion potential of the transition metal, and n represents the number of the transition metal. 0.85 Mn 0.5 Ni 0.4 Ti 0.1 For example, the stoichiometric number of O2 is 0.5, and there are two valence states of Mn, Mn 4+ the stoichiometric number of Mn is 0.45, and Mn 2+ the stoichiometric number of O2 is 0.05. For example, the stoichiometric number of O2 is 0.5, and there are two valence states of Mn, Mn 0.85 Mn 0.5 Ni 0.4 Fe 0.1 For example, the stoichiometric number of O2 is 0.4, and there are two valence states of Ni, Ni 2+ the stoichiometric number of Ni is 0.35, and Ni 3+ the stoichiometric number of O2 is 0.05. In the embodiment, the weighted average ion potential Y2 of each sodium ion positive electrode material is calculated according to the formula Y2 = ∑wini / , so as to further calculate the actual cation potential of the sodium ion positive electrode material.

[0093] In some embodiments, the oxygen anion potential Y3 satisfies the formula Y3 = 2 / R O , where R O is the ionic radius of the oxygen ion.

[0094] In the embodiment, the oxygen anion potential Y3 of each sodium ion positive electrode material is calculated according to the formula Y3 = 2 / R O , so as to further calculate the actual cation potential of the sodium ion positive electrode material.

[0095] Please refer to Figure 6 In some embodiments, when the difference d2 between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material is calculated according to the linear equation when the proportion Z of the first phase is 0, and the difference d1 between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material is calculated according to the linear equation when the proportion Z of the first phase is 1, then when d2 < d < d1, the sodium ion positive electrode material is a composite phase, including:

[0096] S10561, according to the formula Z = (-9.151d) + 2.2954, the difference d1 between the actual cation potential and the theoretical cation potential of the sodium-ion positive electrode material when the proportion Z of the first phase is 0 is 0.2508; the difference d2 between the actual cation potential and the theoretical cation potential of the sodium-ion positive electrode material when the proportion Z of the first phase is 1 is 0.1416.

[0097] Understandably, the difference d between the actual cation potential and the theoretical cation potential of the sodium-ion positive electrode material and the proportion Z of the first phase satisfy the linear relationship Z = (-9.151d) + 2.2954.

[0098] Understandably, Z is the proportion of the first phase, the value of Z satisfies 0 < Z < 1, and the value of Z can be, but is not limited to, 0.01, 0.05, 0.079, 0.123, 0.13, 0.24, 0.35, 0.379, 0.39, 0.45, 0.455, 0.55, 0.69, 0.75, 0.79, 0.85, 0.89, 0.92, 0.93 and 0.99, etc. The sum of the proportion of the first phase and the proportion of the second phase of the sodium-ion positive electrode material is 1, and the proportion of the second phase is 1-Z.

[0099] Understandably, when the proportion Z of the first phase is 0, the difference d1 between the actual cation potential and the theoretical cation potential of the sodium-ion positive electrode material is 0.2508, then the difference d between the actual cation potential and the theoretical cation potential of the sodium-ion positive electrode material satisfies d ≥ 0.2508, the sodium-ion positive electrode material forms a second phase; when the difference d between the actual cation potential and the theoretical cation potential of the sodium-ion positive electrode material satisfies d < 0.2508, the sodium-ion positive electrode material forms a composite phase.

[0100] Understandably, when the proportion Z of the first phase is 1, the difference d2 between the actual cation potential and the theoretical cation potential of the sodium-ion positive electrode material is 0.1416, then when the difference d between the actual cation potential and the theoretical cation potential of the sodium-ion positive electrode material satisfies d ≤ 0.1416, the sodium-ion positive electrode material forms a first phase; when the difference d between the actual cation potential and the theoretical cation potential of the sodium-ion positive electrode material satisfies d > 0.1416, the sodium-ion positive electrode material forms a composite phase.

[0101] S10562, when 0.1416 < d < 0.2508, the sodium-ion positive electrode material is a composite phase.

[0102] In the embodiment, when the value of d satisfies the range 0.1416 < d < 0.2508, the sodium ion positive electrode material is a composite phase. When the value of d satisfies the range d ≥ 0.2508, the sodium ion positive electrode material forms a second phase; and when the value of d satisfies the range d ≤ 0.1416, the sodium ion positive electrode material forms a first phase. The determination method of the sodium ion positive electrode material provided in the embodiment provides scientific guidance for designing and synthesizing the sodium ion positive electrode material of the composite phase. By calculating the difference d between the actual cation potential and the theoretical cation potential of the sodium ion positive electrode material, the size relationship between d and 0.1416 and 0.2508 is determined, and it can be preliminarily determined whether the sodium ion positive electrode material of the chemical formula is a composite phase. The determination method provides convenience for experimenters, provides a reference for experiments of experimenters, narrows the range of sodium ion positive electrode materials that can form a composite phase, reduces the number of experiments and the number of verifications of experimenters, is conducive to saving time and energy of experimenters, and accordingly reduces the cost of material research.

[0103] The application further provides a sodium ion positive electrode material, the sodium ion positive electrode material being a composite phase, and the chemical formula of the sodium ion positive electrode material being Na x A u B v C w O2, wherein 0.67 < x ≤ 1, 0 < u ≤ 1, 0 ≤ v < 1, 0 ≤ w < 1, and u + v + w = 1, A, B and C are transition metal elements, the difference d between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material of the composite phase satisfies the relationship 0.1416 < d < 0.2508. In other words, wherein d satisfies the relationship d = Y1-Y, Y1 is the actual sodium ion potential of the sodium ion positive electrode material, and Y is the theoretical sodium ion potential of the sodium ion positive electrode material.

[0104] It can be understood that the composite phase is a composite of P2 single phase and O3 single phase.

[0105] In the embodiment, the sodium ion positive electrode material is a composite phase and the chemical formula is Na x A u B v C wO2, the difference d between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material satisfies the relationship 0.1416 < d < 0.2508, that is, when the difference between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material is within a reasonable range, the sodium ion positive electrode material tends to form a composite material. The sodium ion potential of the sodium ion positive electrode material and the cation potential are linearly related, that is, when the difference between the actual cation potential and the theoretical cation potential of the sodium ion positive electrode material is within a reasonable range, the sodium ion positive electrode material tends to form a composite phase. The sodium ion positive electrode material of the composite phase takes into account the advantages of the first phase and the second phase, so that the sodium ion positive electrode material of the composite phase exhibits higher rate performance and higher capacity.

[0106] In some embodiments, the proportion of the first phase in the sodium ion positive electrode material is Z, and d and Z satisfy the relationship Z = (-9.151d) + 2.2954.

[0107] In this embodiment, the difference d between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material and the proportion Z of the first phase in the sodium ion positive electrode material satisfy the relationship Z = (-9.151d) + 2.2954, which facilitates the preliminary judgment of the proportion of the first phase and the proportion of the second phase in the composite phase by the experimenter, so as to obtain a sodium ion positive electrode material with a suitable proportion of the first phase, and then obtain a sodium ion positive electrode material with higher rate performance and higher capacity.

[0108] The technical solutions of the present application will be further described in the following multiple embodiments.

[0109] Embodiments 1 to 8

[0110] 1. Select a plurality of sodium ion positive electrode materials: the chemical general formula of the sodium ion positive electrode material in embodiments 1 to 8 is respectively: 0.85 Mn 0.5 Ni 0.4 Ti 0.1 O2, Na 0.85 Mn 0.5 Ni 0.4 Fe 0.1 O2, Na 0.85 Mn 0.5 Ni 0.4 Cu 0.1 O2, Na 0.85 Mn 0.5 Ni 0.5 O2, Na 0.85 Mn 0.6 Ni 0.4 O2, Na 0.95 Mn 0.5 Ni 0.5O2, Na 0.67 Mn 0.5 Ni 0.5 O2, and Na 0.67 Mn 0.6 Ni 0.4 O2, and Na, as shown in Table 1.

[0111] 2. Calculate the actual sodium ion potential Y1 and the actual cation potential X1 of each of the sodium ion positive electrode materials, the values of the actual sodium ion potential Y1 and the actual cation potential X1 of each of the sodium ion positive electrode materials of Example 1 to Example 8 are shown in Table 1.

[0112] 3. Calculate the value of the theoretical sodium ion potential Y of the sodium ion positive electrode material according to the equation Y = 0.4065X + 1.572 when X = X1, the values of the theoretical sodium ion potential Y of each of the sodium ion positive electrode materials of Example 1 to Example 8 are shown in Table 1.

[0113] 4. Calculate the difference between the actual sodium ion potential and the theoretical sodium ion potential of each of the sodium ion positive electrode materials according to d = Y1-Y, the values of the difference d between the actual sodium ion potential and the theoretical sodium ion potential of each of the sodium ion positive electrode materials of Example 1 to Example 8 are shown in Table 1.

[0114] 5. Linear equation fitting is performed according to d and the proportion Z of the first phase in the sodium ion positive electrode material, wherein 0 < Z < 1, the first phase is P2 single phase, the second phase is O3 single phase, and the composite phase is the composite of the P2 single phase and the O3 single phase, the fitting linear equation is as shown in the following formula: Figure 7 The proportion of the first phase is the mass proportion of the first phase.

[0115] 6. According to the linear equation, the difference d1 between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material is calculated when the proportion Z of the first phase is 0, and the difference d2 between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material is calculated according to the linear equation when the proportion Z of the first phase is 1, then when d2 < d < d1, the sodium ion positive electrode material is a composite phase.

[0116]

[0117] From the data in Table 1, in Example 1 and Example 6, the proportion Z of the first phase is 0, so the sodium ion positive electrode material provided by Example 1 and the sodium ion positive electrode material provided by Example 6 do not have the first phase (P2 single phase), and the sodium ion positive electrode material provided by Example 1 and the sodium ion positive electrode material provided by Example 6 are both the second phase (O3 single phase). In Example 7 and Example 8, the proportion Z of the first phase is 1, so the sodium ion positive electrode material provided by Example 7 and the sodium ion positive electrode material provided by Example 8 both have the first phase (P2 single phase), and the sodium ion positive electrode material provided by Example 7 and the sodium ion positive electrode material provided by Example 8 do not have the second phase (O3 single phase). The proportion Z of the first phase of the sodium ion positive electrode material provided by Example 2 to Example 5 satisfies 0 < Z < 1, so the sodium ion positive electrode material provided by Example 2 to Example 5 is a composite phase, that is, a composite of the first phase and the second phase, and the proportion of the first phase is Z. According to the linear fitting of the difference d between the actual sodium ion potential and the theoretical sodium ion potential of each sodium ion positive electrode material and the proportion Z of the first phase in the sodium ion positive electrode material, the linear equation is as shown in Figure 7

[0118] According to the linear equation as shown in Figure 7 , the difference d between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material and the proportion Z of the first phase satisfy the linear equation Z = (-9.151d) + 2.2954, so it can be known that when the proportion Z of the first phase of the sodium ion positive electrode material satisfies 0 < Z < 1, the proportion Z of the first phase in the sodium ion positive electrode material gradually decreases with the increase of the difference d between the actual sodium ion potential and the theoretical sodium ion potential. When the proportion of the first phase in the sodium ion positive electrode material is 0, the difference d1 between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material is calculated to be 0.2508. When the proportion of the first phase in the sodium ion positive electrode material is 1, the difference d2 between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material is calculated to be 0.1416. Therefore, when the value of the difference d between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material satisfies the relationship 0.1416 < d < 0.2508, the sodium ion positive electrode material is a composite phase. When the value of the difference d between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material satisfies the relationship d ≥ 0.2508, the sodium ion positive electrode material is O3 single phase. When the value of the difference d between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material satisfies the relationship d ≤ 0.1416, the sodium ion positive electrode material is P2 single phase.

[0119] ​It can be understood that when the value of the difference d between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material satisfies the relationship formula d≥0.2508, the value of d is greater than 0 and the value of d is large, when the actual sodium ion potential of the sodium ion positive electrode material is equal to the theoretical sodium ion potential, the actual cation potential of the sodium ion positive electrode material is less than the theoretical cation potential, and the difference between the two is large, the value of the actual cation potential of the sodium ion positive electrode material is small, the interaction force between M-O in the transition metal layer (O-M-O) of the sodium ion positive electrode material is weaker, the interlayer spacing of the transition metal layer (O-M-O) is larger, and the sodium ion positive electrode material is more inclined to form a second phase (O3 single phase), and the value of d is greater than or equal to 0.2508, at this time, the sodium ion positive electrode material is a second phase (O3 single phase).

[0120] It can be understood that when the value of the difference d between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material satisfies the relationship formula 0.1416

[0121] It can be understood that when the value of the difference d between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material satisfies the relationship formula d<0, when the actual sodium ion potential of the sodium ion positive electrode material is equal to the theoretical sodium ion potential, the actual cation potential of the sodium ion positive electrode material is greater than the theoretical cation potential, then the interaction force between M-O in the transition metal layer (O-M-O) of the sodium ion positive electrode material is stronger, the interlayer spacing of the transition metal layer (O-M-O) is reduced, and the sodium ion positive electrode material is more inclined to form a first phase (P2 single phase), at this time, the sodium ion positive electrode material is a first phase (P2 single phase). In addition, due to the error in the experiment, when d satisfies the relationship formula 0≤d≤0.1416, the sodium ion positive electrode material is also a first phase (P2 single phase).

[0122] The application provides a determination method of a sodium ion positive electrode material. The actual sodium ion potential, the actual cation potential, the theoretical sodium ion potential, the difference d between the actual sodium ion potential and the theoretical sodium ion potential, and the proportion Z of the first phase in the sodium ion positive electrode material of the sodium ion positive electrode material satisfying different chemical formulas are calculated. The difference d between the actual sodium ion potential and the theoretical sodium ion potential and the proportion Z of the first phase in the sodium ion positive electrode material of the sodium ion positive electrode material satisfying 0

[0123] Please refer to Figure 8 and Figure 9 An embodiment of the application further provides a positive electrode sheet 100, which comprises a positive electrode current collector 110 and a positive electrode material layer 120, wherein the positive electrode material layer 120 is arranged on the surface of the positive electrode current collector 110, and the positive electrode material layer 120 comprises the sodium ion positive electrode material provided by the application.

[0124] Understandably, the positive electrode material layer 120 is arranged on the surface of the positive electrode current collector 110, which can be arranged on the entire surface of one surface of the positive electrode current collector 110 or part of the surface of one surface, or arranged on the entire surface of two surfaces of the positive electrode current collector 110 or part of the surface of the two surfaces.

[0125] It can be understood that the positive electrode current collector 110 and the positive electrode material layer 120 are sequentially stacked.

[0126] In the embodiment, the positive electrode material layer 120 comprises a sodium-ion positive electrode material provided by the application, the sodium-ion positive electrode material is a composite phase, and the composite phase takes into account the advantages of the first phase and the second phase, so that the sodium-ion positive electrode material and the positive electrode sheet 100 exhibit higher rate performance and higher capacity.

[0127] Optionally, the positive electrode material layer 120 further comprises a binder and a conductive agent, the binder is used to bond and maintain the positive electrode material layer 120, enhance the electronic contact between the positive electrode material layer 120 and the positive electrode current collector 110, and better stabilize the structure of the positive electrode sheet 100. The binder comprises one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylonitrile (PAN), polyacrylic acid (PAA), etc. The conductive agent enables the positive electrode sheet 100 to have good charge and discharge performance, reduces the contact resistance of the positive electrode sheet 100, accelerates the moving rate of electrons, and thus improves the charge and discharge efficiency of the positive electrode sheet 100. The conductive agent comprises one or more of acetylene black, conductive carbon black, carbon nanotubes, carbon fibers, graphene, etc.

[0128] Please refer to Figure 10 and Figure 11 , an embodiment of the application further provides a battery 200, the battery 200 comprises: an electrolyte 210, a negative electrode sheet 220, a separator 230, and a positive electrode sheet 100 provided by the application, the negative electrode sheet 220, the separator 230, and the positive electrode sheet 100 are sequentially stacked or wound; the negative electrode sheet 220, the separator 230, and the positive electrode sheet 100 are at least partially immersed in the electrolyte 210. In other words, the negative electrode sheet 220 is at least partially immersed in the electrolyte 210; the separator 230 is located on one side of the negative electrode sheet 220 and is at least partially immersed in the electrolyte 210, and the positive electrode sheet 100 is arranged on the side of the separator 230 away from the negative electrode sheet 220 and is at least partially immersed in the electrolyte 210.

[0129] In the embodiment, the battery 200 comprises the positive electrode sheet 100, the positive electrode sheet 100 exhibits higher rate performance and higher capacity, which is conducive to improving the rate performance and capacity of the battery 200, so that the battery 200 can have both higher kinetic performance and higher capacity.

[0130] Optionally, the separator 230 is any separator 230 material in the prior art, including one or more of polypropylene (PP), polyethylene (PE), ceramic separator 230.

[0131] Optionally, the electrolyte 210 includes electrolyte salt (such as sodium hexafluorophosphate, etc.) and organic solvent, wherein the specific types and compositions of electrolyte salt and organic solvent are conventional choices in the field of battery 200, which can be selected according to actual needs.

[0132] Optionally, the battery 200 can be a circular battery 200, a square battery 200, etc.

[0133] Please refer to Figure 12 An embodiment of the present application also provides a power consuming device 300, which comprises a power consuming device 300 body and the battery 200 provided by the present application, the power consuming device 300 body comprises a device positive electrode 311 and a device negative electrode 312; the positive electrode sheet 100 of the battery 200 is used for electrically connecting the device positive electrode 311 of the power consuming device 300 body, the negative electrode sheet 220 of the battery 200 is used for electrically connecting the device negative electrode 312 of the power consuming device 300 body, and the battery 200 is used for supplying power to the power consuming device 300 body.

[0134] In the embodiment, the power consuming device 300 comprises the battery 200 provided by the embodiment of the present application, the battery 200 has higher rate performance and higher capacity, and the battery 200 can provide stable power supply for the device body 310, so that the power consuming device 300 can normally and stably work.

[0135] Optionally, the power consuming device 300 of the embodiment of the present application can be, but is not limited to, a portable electronic device such as a mobile phone, a tablet computer, a notebook computer, a desktop computer, a smart bracelet, a smart watch, an electronic reader, a game console, etc. It can also be a vehicle such as a car, a truck, a sedan, a truck, a motor car, a high-speed train, an electric automatic car, etc. In addition, it can also be various household appliances, etc.

[0136] It can be understood that the power consuming device 300 in the embodiment is only one form of the power consuming device 300 to which the battery 200 is applied, and should not be understood as a limitation on the power consuming device 300 provided by the present application, nor should it be understood as a limitation on the power consuming device 300 provided by each embodiment of the present application.

[0137] In this application, the terms "embodiment" and "implementation" mean that a specific feature, structure, or characteristic described in connection with an embodiment can be included in at least one embodiment of this application. The appearance of these phrases in various locations throughout the specification does not necessarily refer to the same embodiment, nor are they independent or alternative embodiments mutually exclusive with other embodiments. Those skilled in the art will understand, explicitly and implicitly, that the embodiments described in this application can be combined with other embodiments. Furthermore, it should be understood that the features, structures, or characteristics described in the various embodiments of this application can be arbitrarily combined to form another embodiment that does not depart from the spirit and scope of the technical solution of this application, provided there is no contradiction between them.

[0138] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the above preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of this application should not depart from the spirit and scope of the technical solutions of this application.

Claims

1. A method of determining a sodium-ion cathode material, characterized by, The sodium ion positive electrode material has a first phase, a second phase, and a composite phase, and the composite phase is a composite of the first phase and the second phase; the determination method comprises: Obtaining a to-be-tested sodium ion positive electrode material; wherein the to-be-tested sodium ion positive electrode material comprises sodium elements and transition metal elements; Calculating the actual sodium ion potential Y1 and the actual cation potential X1 of the to-be-tested sodium ion positive electrode material; According to the equation Y=0.4065X+1.572 of the to-be-tested sodium ion positive electrode material, when X=X1, the value of the theoretical sodium ion potential Y of the to-be-tested sodium ion positive electrode material is calculated; According to d=Y1-Y, the difference d between the actual sodium ion potential and the theoretical sodium ion potential of the to-be-tested sodium ion positive electrode material is calculated; and When the difference d between the actual sodium ion potential and the theoretical sodium ion potential of the to-be-tested sodium ion positive electrode material satisfies the relationship d2 The determination method of the critical value d1 of the sodium ion positive electrode material forming the composite phase and the second phase and the critical value d2 of the sodium ion positive electrode material forming the composite phase and the first phase comprises: Selecting a plurality of sodium ion positive electrode materials; Calculating the actual sodium ion potential Y1 and the actual cation potential X1 of each sodium ion positive electrode material; According to the equation Y=0.4065X+1.572 of the sodium ion positive electrode material, when X=X1, the value of the theoretical sodium ion potential Y of the sodium ion positive electrode material is calculated; According to d=Y1-Y, the difference d between the actual sodium ion potential and the theoretical sodium ion potential of each sodium ion positive electrode material is calculated; Linear equation fitting is performed on the d of the plurality of sodium ion positive electrode materials and the proportion Z of the first phase in the sodium ion positive electrode material, wherein 0 According to the linear equation, when the proportion Z of the first phase is 0, the difference d1 between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material is calculated, and according to the linear equation, when the proportion Z of the first phase is 1, the difference d2 between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material is calculated.

2. The determination method according to claim 1, characterized in that, In the case that the sodium ion positive electrode material is a composite phase, the chemical general formula of the sodium ion positive electrode material is: Na x A u B v C w O2, wherein 0.67 x≤1, 0 u≤1, 0 v w =1, and A, B and C are all transition metal elements.

3. The determination method according to claim 1, characterized in that, The first phase is a P2 single phase, the second phase is an O3 single phase, and the composite phase is a composite of the P2 single phase and the O3 single phase.

4. The determination method according to claim 1, characterized in that, The calculation of the actual sodium ion potential Y1 and the actual cation potential X1 of the to-be-tested sodium ion positive electrode material comprises: According to the formula Y1=x / R Na The actual sodium ion potential Y1 of the sodium ion positive electrode material to be measured is calculated, wherein x is the stoichiometric number of sodium elements, R Na is the ionic radius of sodium ions; and According to the actual sodium ion potential Y1, the actual cation potential X1 of the to-be-tested sodium ion positive electrode material is calculated.

5. The determination method according to claim 4, characterized in that, The calculation of the actual sodium ion potential Y1 of the to-be-tested sodium ion positive electrode material comprises: According to X1=Y2×Y1 / Y3, the actual cation potential X1 of the to-be-tested sodium ion positive electrode material is calculated, wherein Y2 is the weighted average ion potential of the transition metal, Y1 is the actual sodium ion potential, and Y3 is the oxygen anion potential.

6. The determination method according to claim 5, characterized in that, The weighted average ionic potential Y2 of the transition metal satisfies the formula Y2= , where ni is the valence state of each transition metal A, B, and C in the general formula, wi is the stoichiometric coefficient of each transition metal A, B, and C in the general formula when the valence state is ni, and Ri is the ionic radius of each transition metal A, B, and C in the general formula.

7. The determination method according to claim 5, characterized in that, The oxygen anion potential Y3 satisfies the formula Y3 = 2 / R O where R O is the ionic radius of the oxygen ion.

8. The determination method of claim 1, wherein, The difference d1 between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material when the proportion Z of the first phase is 0 is calculated according to the linear equation, and the difference d2 between the actual sodium ion potential and the theoretical sodium ion potential of the sodium ion positive electrode material when the proportion Z of the first phase is 1 is calculated according to the linear equation, comprising: According to the formula Z= (-9.151d) + 2.2954, the difference d1 between the actual cation potential and the theoretical cation potential of the sodium ion positive electrode material when the proportion Z of the first phase is 0 is calculated to be 0.2508; and the difference d2 between the actual cation potential and the theoretical cation potential of the sodium ion positive electrode material when the proportion Z of the first phase is 1 is calculated to be 0.1416; When 0.1416 < d < 0.2508, the sodium ion positive electrode material is a composite phase.

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