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 composite phase is a composite of the first phase and the second phase, the determination method comprises the following steps: obtaining a to-be-tested sodium-ion positive electrode material; calculating an energy difference gamma of a minimum energy E1 of the to-be-tested sodium-ion positive electrode material as the first phase and a minimum energy E2 of the to-be-tested sodium-ion positive electrode material as the second phase, the energy difference gamma of the to-be-tested sodium-ion positive electrode material satisfying a formula gamma = E1-E2; and when the energy difference gamma of the to-be-tested sodium-ion positive electrode material satisfies a relationship formula: gamma2<gamma<gamma1, it is determined that the to-be-tested sodium-ion positive electrode material is the composite phase; wherein the value of gamma1 is a critical value of the sodium-ion positive electrode material forming the composite phase and the second phase, and the value of gamma2 is a critical value of the sodium-ion positive electrode material forming the composite phase and the first phase. The determination method of the sodium-ion positive electrode material 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 sodium-ion positive electrode material, 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 abundant resources and low cost, and developing 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 have the characteristics of high specific capacity, structural diversity, adjustable composition and simple preparation, and are one of the most promising sodium-ion positive electrode materials. The common structure of sodium-ion layered oxides can be divided into P(Prismatic, triangular prism)2 phase, O(Octahedral, octahedral)3 phase and composite phase of P2 and O3. The sodium content of the 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 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 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 the 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 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, and 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 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, and the determination method of the sodium-ion positive electrode material can be used to guide the design of a sodium-ion positive electrode material with a composite phase of P2 phase and O3 phase.

[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 the following steps: obtaining a to-be-tested sodium ion positive electrode material; calculating an energy difference γ of a lowest energy E1 of the to-be-tested sodium ion positive electrode material as the first phase and a lowest energy E2 of the to-be-tested sodium ion positive electrode material as the second phase, the energy difference γ of the to-be-tested sodium ion positive electrode material satisfies the formula γ = E1-E2; and when the energy difference γ of the to-be-tested sodium ion positive electrode material satisfies the relationship formula: γ2<γ<γ1, it is determined that the to-be-tested sodium ion positive electrode material is the composite phase; wherein the value of γ1 is a critical value of the sodium ion positive electrode material forming the composite phase and the second phase, and the value of γ2 is a critical value of the sodium ion positive electrode material forming the composite phase and the first phase.

[0005] Further, the determination method of the critical value γ1 of the sodium ion positive electrode material forming the composite phase and the second phase and the critical value γ2 of the sodium ion positive electrode material forming the composite phase and the first phase comprises that 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 method comprises the following steps: selecting a plurality of sodium ion positive electrode materials; calculating an energy difference γ of a lowest energy E1 of each sodium ion positive electrode material as the first phase and a lowest energy E2 of the sodium ion positive electrode material as the second phase, the energy difference γ of each sodium ion positive electrode material satisfies the formula γ = E1-E2; linear fitting according to the energy difference γ of each sodium ion positive electrode material and a proportion Y 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 phase, the second phase is an O3 phase, and the composite phase is a composite of the P2 phase and the O3 phase.

[0008] Further, the chemical general formula of the sodium ion positive electrode material is: Na x A u B v Cw 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; and C is selected from at least one of transition metals such as Mn, Ni, Ti, Co, Fe, Cu, Cr, Zn, V, Zr and Ta.

[0009] Further, the energy difference γ of the lowest energy E1 of the first phase of the to-be-tested sodium-ion positive electrode material and the lowest energy E2 of the second phase of the to-be-tested sodium-ion positive electrode material is calculated, which satisfies the formula γ = E1-E2, comprising: constructing a plurality of first-phase sodium-ion positive electrode material models and a plurality of second-phase sodium-ion positive electrode material models satisfying the chemical formula Na x A u B v C w O2, randomly adjusting the spatial position of the transition metal in the to-be-tested sodium-ion positive electrode material, to construct a plurality of first-phase sodium-ion positive electrode material models and a plurality of second-phase sodium-ion positive electrode material models satisfying the chemical formula; determining the energy of each first-phase sodium-ion positive electrode material model and the energy of each second-phase sodium-ion positive electrode material model according to a preset machine learning algorithm; wherein the preset machine learning algorithm predicts the energy of the sodium-ion material model by identifying the lattice structure of the sodium-ion positive electrode material model; selecting the lowest energy E1 of the plurality of first-phase sodium-ion positive electrode material models and the lowest energy E2 of the plurality of second-phase sodium-ion positive electrode material models; and calculating the energy difference γ of the lowest energy of the first phase of the to-be-tested sodium-ion positive electrode material and the lowest energy of the second phase of the to-be-tested sodium-ion positive electrode material from γ = E1-E2.

[0010] Further, the energy difference γ1 of the sodium-ion positive electrode material when the proportion Y of the first phase is 0 is calculated according to a linear equation, and the energy difference γ2 of the sodium-ion positive electrode material when the proportion Y of the first phase is 1 is calculated according to a linear equation, then when γ2<γ<γ1, the sodium-ion positive electrode material is a composite phase, comprising: calculating the energy difference γ1 = 0.2313 of the sodium-ion positive electrode material when the proportion Y of the first phase is 0 according to the linear equation Y =-1.3758γ+0.3182; calculating the energy difference γ2 =-0.4956 of the sodium-ion positive electrode material when the proportion Y of the first phase is 1; when the energy difference γ of the sodium-ion positive electrode material satisfies the relationship-0.4956<γ<0.2313, the sodium-ion positive electrode material is a composite phase.

[0011] Further, the method further comprises: providing a preset positive electrode material, the preset positive electrode material being a composite phase; calculating a minimum energy E1' when the preset positive electrode material is a first phase and a minimum energy E2' when the preset positive electrode material is a second phase, and calculating an energy difference γ' of the preset positive electrode material according to γ = E1-E2; and calculating a value of Y when γ = γ' according to a linear equation Y = -1.3758γ+0.3182, so as to obtain a proportion of the first phase in the preset positive electrode material.

[0012] The application further provides a sodium-ion positive electrode material, the chemical general formula of the sodium-ion positive electrode material being Na x A u B v C w O2, wherein 0.67

[0013] Further, the energy difference of the sodium-ion positive electrode material is γ, and the proportion of the first phase in the sodium-ion positive electrode material is Y, which satisfies a linear equation Y = -1.3758γ+0.3182.

[0014] The application further provides a positive electrode sheet, the positive electrode sheet comprising a positive electrode current collector and a positive electrode material layer, the positive electrode material layer being arranged on the surface of the positive electrode current collector, and the positive electrode material layer comprising the sodium-ion positive electrode material provided by the application.

[0015] The application further provides a battery, the 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 being arranged in a stack or in a roll; and the negative electrode sheet, the separator and the positive electrode sheet being at least partially immersed in the electrolyte.

[0016] The application further provides an electric device, the electric device comprising a device body and the battery provided by the application, the device body comprising a device positive electrode and a device negative electrode; the positive electrode sheet of the battery being used for electrically connecting the device positive electrode of the device body, the negative electrode sheet of the battery being used for electrically connecting the device negative electrode of the device body, and the battery being used for supplying power to the device body.

[0017] The determination method of the sodium ion positive electrode material provided in the application determines the energy difference γ of the sodium ion positive electrode material to be measured by calculating the minimum energy of the first phase and the minimum energy of the second phase of the sodium ion positive electrode material to be measured. When γ satisfies the relationship formula γ2< γ < γ1, it is determined that 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 sodium ion positive electrode material provided in the embodiment of the 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 a chemical general formula can be constructed, the value of the energy difference γ is calculated, and the size relationship between γ and γ1 and γ2 is judged, so that whether the sodium ion positive electrode material conforming to the chemical general formula is a composite phase can be preliminarily judged. 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 beneficial to saving the time and energy of experimenters, and accordingly reduces the material research cost. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the application, the drawings needed in the embodiments will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0019] Figure 1 The flowchart of the determination method of the sodium ion positive electrode material of an embodiment of the application is shown in the figure.

[0020] Figure 2 The flowchart of the determination method of the sodium ion positive electrode material of another embodiment of the application is shown in the figure.

[0021] Figure 3 The flowchart of the determination method of the sodium ion positive electrode material of another embodiment of the application is shown in the figure.

[0022] Figure 4 The flowchart of the determination method of the sodium ion positive electrode material of another embodiment of the application is shown in the figure.

[0023] Figure 5 The flowchart of the determination method of the proportion of the first phase in the sodium ion positive electrode material of an embodiment of the application is shown in the figure.

[0024] Figure 6 The linear relationship diagram of the energy difference γ of the sodium ion positive electrode material and the proportion Y of the first phase in the sodium ion positive electrode material of an embodiment of the application is shown in the figure.

[0025] Figure 7 A structure schematic diagram of a positive electrode tab of an embodiment of the present application;

[0026] Figure 8 A structure schematic diagram of a positive electrode tab of an embodiment of the present application; Figure 7 A sectional view of the positive electrode tab of the embodiment of the present application along direction A-A;

[0027] Figure 9 A structure schematic diagram of a battery of an embodiment of the present application;

[0028] Figure 10 A sectional view of the battery of the embodiment of the present application along direction B-B; Figure 9

[0029] A structure schematic diagram of a power consuming device of an embodiment of the present application. Figure 11 Legend of reference signs:

[0030] 100-positive electrode tab, 110-positive electrode current collector, 120-positive electrode material layer, 200-battery, 210-electrolyte, 220-negative electrode tab, 230-separator, 300-power consuming device, 310-device body, 311-device positive electrode, 312-device negative electrode.

[0031] DETAILED DESCRIPTION The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative effort belong to the scope of protection of the present application.

[0032] 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, but are not used to describe a specific sequence. In addition, the terms “include” and “have” and any variations thereof are intended to cover the inclusions without exclusivity. 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 other steps or units not listed or can optionally include other steps or units inherent to the process, method, product, or device.

[0033]

[0034] ​Reference to“an embodiment” or“the embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase“in one embodiment” or“in the embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily all directed to the same embodiment, nor are they necessarily all mutually exclusive or alternative embodiments.

[0035] 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 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 have the characteristics of high specific capacity, structural diversity, adjustable composition, and simple preparation, and are one of the most promising sodium-ion positive electrode materials.

[0036] The layered oxides of sodium-ion positive electrode materials form a repeated layer structure through the MO6 octahedron with a common edge. 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 structure of sodium-ion layered oxides can be divided into P2 phase, O3 phase, and a composite phase of P2 and O3. The sodium-ion positive electrode material of the P2 phase has a low sodium content, a large number of sodium ion vacancies, and a large sodium interlayer spacing, which can improve the transmission rate of sodium ions and maintain the integrity of the layered structure, and exhibit good kinetic performance and rate performance. However, the low sodium content limits the capacity of the sodium-ion positive electrode material, so that the sodium-ion positive electrode material of the P2 phase will undergo a violent phase change after deep sodium extraction, resulting in unstable structure of the sodium-ion positive electrode material. The sodium-ion positive electrode material of the O3 phase has a high sodium content, which improves the capacity of the sodium-ion positive electrode material. However, the sodium interlayer spacing is small, which limits the transmission efficiency of sodium ions, so that the sodium-ion positive electrode material of the 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. Designing and synthesizing the composite phase of P2 and O3 can only be achieved through repeated experiments, resulting in a significant increase in the cost of material research.

[0037] See Figure 1 The embodiment of the present 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 the following steps:

[0038] S101, acquire a sodium-ion positive electrode material to be tested.

[0039] Optionally, the sodium-ion positive electrode material to be tested satisfying a certain chemical formula is selected, and a plurality of models of the sodium-ion positive electrode material to be tested satisfying the certain chemical formula are constructed by a Monte Carlo random sampling method.

[0040] 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.

[0041] Optionally, the VESTA (Visualization for Electronic and Structural Analysis) software can be used to construct the plurality of models of the sodium-ion positive electrode material to be tested satisfying the certain chemical formula.

[0042] S102, calculate the energy difference γ of the sodium-ion positive electrode material to be tested when the sodium-ion positive electrode material to be tested is in a first phase and the sodium-ion positive electrode material to be tested is in a second phase, the energy difference γ of the sodium-ion positive electrode material to be tested satisfies the formula γ = E1-E2.

[0043] Optionally, the lattice relaxation of the obtained model of the sodium-ion positive electrode material to be tested is performed by a preset machine learning algorithm, the preset machine learning algorithm is a M3GNet (Materials Graph Neutral Architecture) machine learning potential, to obtain the structure with the lowest energy when the sodium-ion positive electrode material to be tested is in the first phase, calculate the lowest energy E1 of the sodium-ion positive electrode material to be tested when the sodium-ion positive electrode material to be tested is in the first phase, the lowest energy of the first phase is the total energy of the system calculated at 0K of the sodium-ion positive electrode material to be tested; further obtain the structure with the lowest energy when the sodium-ion positive electrode material to be tested is in the second phase, calculate the lowest energy E2 of the sodium-ion positive electrode material to be tested when the sodium-ion positive electrode material to be tested is in the second phase, the lowest energy of the second phase is the total energy of the system calculated at 0K of the sodium-ion positive electrode material to be tested.

[0044] Understandably, the M3GNet machine learning potential is an artificial intelligence (AI) algorithm, which can be used to predict the structure and dynamic characteristics of materials, and can be used to develop a database containing more than 31 million materials that have not been synthesized, and the characteristics of the materials are predicted by the machine learning algorithm.

[0045] It can be understood that according to the principle of energy minimization, the lower the energy is, the more stable it is. When the energy difference γ of the sodium ion positive electrode material is greater than 0 and γ is greater than a certain value, the minimum energy E1 of the sodium ion positive electrode material when it is in the first phase is greater than the minimum energy E2 of the sodium ion positive electrode material when it is in the second phase, then the sodium ion positive electrode material is more inclined to form the second phase; when the energy difference γ of the sodium ion positive electrode material is less than 0 and γ is less than a certain value, the minimum energy E1 of the sodium ion positive electrode material when it is in the first phase is less than the minimum energy E2 of the sodium ion positive electrode material when it is in the second phase, then the sodium ion positive electrode material is more inclined to form the first phase; when the difference between the value of the energy difference γ of the sodium ion positive electrode material and 0 is less than a certain value, the minimum energy of the sodium ion positive electrode material in the first phase and the minimum energy of the sodium ion positive electrode material in the second phase tend to be flat, and the sodium ion positive electrode material is more inclined to form a composite phase.

[0046] S103, when the energy difference γ of the sodium ion positive electrode material to be tested satisfies the relationship: γ2<γ<γ1, it is determined that the sodium ion positive electrode material to be tested is a composite phase; wherein the value of γ1 is the critical value of the sodium ion positive electrode material forming a composite phase and a second phase, and the value of γ2 is the critical value of the sodium ion positive electrode material forming a composite phase and a first phase.

[0047] It can be understood that the value of γ1 is the critical value of the sodium ion positive electrode material forming a composite phase and a second phase, which can be, when γ satisfies γ≥γ1, the sodium ion positive electrode material forms a second phase; when γ<γ1, the sodium ion positive electrode material forms a composite phase.

[0048] It can be understood that the value of γ2 is the critical value of the sodium ion positive electrode material forming a composite phase and a first phase, which can be, when γ satisfies γ≤γ2, the sodium ion positive electrode material forms a first phase; when γ>γ2, the sodium ion positive electrode material forms a composite phase.

[0049] It can be understood that when γ≥γ1, the sodium ion positive electrode material is in the second phase; when γ≤γ2, the sodium ion positive electrode material is in the first phase. When γ2<γ<γ1, the sodium ion positive electrode material is in a composite phase.

[0050] In the embodiment, the method for determining the sodium-ion positive electrode material is to calculate the energy difference γ of the sodium-ion positive electrode material to be tested by calculating the minimum energy of the first phase and the minimum energy of the second phase. When γ satisfies the relationship γ2< γ < γ1, the sodium-ion positive electrode material to be tested is determined to be 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 better overall performance. The method for determining 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. In order to obtain the sodium-ion positive electrode material of the composite phase, a theoretical model of the sodium-ion positive electrode material meeting the chemical general formula can be constructed, and the size relationship between γ and γ1 and γ2 can be judged by calculating the value of the energy difference γ, so as to preliminarily judge whether the sodium-ion positive electrode material meeting the chemical general formula is a composite phase. The determination method provides convenience for the experimenter, can provide reference for the experiment of the experimenter, 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 the experimenter, saves the time and energy of the experimenter, and correspondingly reduces the cost of material research.

[0051] See Figure 1 and Figure 2 In some embodiments, the method for determining the critical value γ1 of the sodium-ion positive electrode material forming a composite phase and a second phase and the critical value γ2 of the sodium-ion positive electrode material forming a composite phase and a first phase comprises:

[0052] S1031, selecting a plurality of sodium-ion positive electrode materials.

[0053] Optionally, a plurality of sodium-ion positive electrode materials meeting different chemical general formulas are selected, and a plurality of models of the sodium-ion positive electrode materials meeting different chemical general formulas are constructed by a Monte Carlo random sampling method.

[0054] 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 meeting different chemical general formulas.

[0055] S1032, calculating the energy difference γ of the minimum energy E1 of each sodium-ion positive electrode material as a first phase and the minimum energy E2 of the sodium-ion positive electrode material as a second phase, and the energy difference γ of each sodium-ion positive electrode material satisfies the formula γ = E1-E2.

[0056] S1033, linear fitting the energy difference γ of each sodium-ion positive electrode material and the proportion Y of the first phase in the sodium-ion positive electrode material, wherein 0 < Y < 1.

[0057] 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.

[0058] It can be understood that the energy difference γ of the sodium ion positive electrode material and the proportion Y of the first phase satisfy the relationship 0 < Y < 1.

[0059] Optionally, the proportion Y of the first phase in the sodium ion positive electrode material can be measured and calculated by XRD (X-ray diffraction) and the like.

[0060] It can be understood that the energy difference γ of the sodium ion positive electrode material is related to the proportion Y of the first phase. When the sodium ion positive electrode material tends to form a composite phase, if the energy difference γ of the sodium ion positive electrode material is positive and gradually increases, the difference between the minimum energy E1 of the sodium ion positive electrode material in the first phase and the minimum energy of the second phase is gradually larger, the minimum energy of the sodium ion positive electrode material in the second phase is lower, the sodium ion positive electrode material tends to form the second phase, and the proportion Y of the first phase in the sodium ion positive electrode material gradually decreases; if the energy difference γ of the sodium ion positive electrode material is negative and gradually decreases, the difference between the minimum energy E1 of the sodium ion positive electrode material in the first phase and the minimum energy of the second phase is gradually larger, the minimum energy of the sodium ion positive electrode material in the first phase is lower, the sodium ion positive electrode material tends to form the first phase, and the proportion Y of the first phase in the sodium ion positive electrode material gradually increases.

[0061] S1034, according to the linear equation, the energy difference γ1 of the sodium ion positive electrode material when the proportion Y of the first phase is 0, and the energy difference γ2 of the sodium ion positive electrode material when the proportion Y of the first phase is 1 are calculated respectively.

[0062] It can be understood that according to the linear equation formed by the energy difference γ of the sodium ion positive electrode material and the proportion Y of the first phase in the sodium ion positive electrode material, when the proportion of the first phase in the sodium ion positive electrode material is 0, the proportion of the second phase in the sodium ion positive electrode material is 1, and at this time, the energy difference of the sodium ion positive electrode material is γ1, in other words, the value of γ1 is the critical value of the sodium ion positive electrode material forming a composite phase and a second phase. When the energy difference γ of the sodium ion positive electrode material satisfies γ ≥ γ1, the sodium ion positive electrode material forms a second phase; when the energy difference γ of the sodium ion positive electrode material satisfies γ < γ1, the sodium ion positive electrode material forms a composite phase.

[0063] It can be understood that, according to the linear equation formed by the energy difference γ of the sodium ion positive electrode material and the proportion Y of the first phase in the sodium ion positive electrode material, when the proportion of the first phase in the sodium ion positive electrode material is 1, the proportion of the second phase in the sodium ion positive electrode material is 0, and the energy difference of the sodium ion positive electrode material is γ2, in other words, the value of γ2 is the critical value of the sodium ion positive electrode material forming a composite phase and a first phase. When the energy difference γ of the sodium ion positive electrode material satisfies γ≤γ2, the sodium ion positive electrode material forms a first phase; when the energy difference γ of the sodium ion positive electrode material satisfies γ>γ2, the sodium ion positive electrode material forms a composite phase.

[0064] In the present embodiment, the determination method of the critical value γ1 of the sodium ion positive electrode material forming a composite phase and a second phase and the critical value γ2 of the sodium ion positive electrode material forming a composite phase and a first phase is that the lowest energy of the first phase and the lowest energy of the second phase of a plurality of sodium ion positive electrode materials are calculated, the energy differences of the plurality of sodium ion positive electrode materials are obtained respectively, the energy difference γ of the plurality of sodium ion positive electrode materials and the proportion of the first phase in the sodium ion positive electrode material are linearly fitted, the energy difference γ1 of the sodium ion positive electrode material is obtained when the proportion Y of the first phase is 0 by calculation, and the energy difference γ2 of the sodium ion positive electrode material is calculated according to the linear equation when the proportion Y of the first phase is 1, so as to obtain the conclusion that the sodium ion positive electrode material is a composite phase when γ2<γ<γ1. The composite phase of the sodium ion positive electrode material can take into account the dual performance of capacity and rate performance, and has relatively optimal overall performance. The determination method of the sodium ion positive electrode material provided in the present embodiment provides scientific guidance for designing and synthesizing a sodium ion positive electrode material of a composite phase. In order to obtain a sodium ion positive electrode material of a composite phase, a theoretical model of a sodium ion positive electrode material conforming to a chemical general formula can be constructed, the value of the energy difference γ is calculated, and the size relationship between γ and γ1 and γ2 is judged respectively, 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 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 the time and energy of experimenters, and accordingly reduces the cost of material research.

[0065] 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

[0066] In the present embodiment, when 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, 0

[0067] In some embodiments, the first phase is a P2 phase, the second phase is an O3 phase, and the composite phase is a composite of the P2 phase and the O3 phase.

[0068] In the present embodiment, the first phase is a P2 single phase, the sodium-ion positive electrode material of the P2 phase has a low sodium content, 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, 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 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 phase, the sodium-ion positive electrode material of the O3 phase has a high sodium content, which improves the capacity of the sodium-ion positive electrode material, but its sodium layer spacing is small, which limits the transmission efficiency of sodium ions, so that the O3 phase sodium-ion positive electrode material exhibits poor kinetic performance and rate performance. The composite phase takes into account the advantages of the P2 phase and the O3 phase, so that the composite phase sodium-ion positive electrode material exhibits high rate performance and high capacity.

[0069] In some embodiments, the chemical general formula of the sodium-ion positive electrode material is: Na x A 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; and C is selected from at least one of transition metals such as Mn, Ni, Ti, Co, Fe, Cu, Cr, Zn, V, Zr, and Ta.

[0070] In the present embodiment, the chemical general formula of the sodium-ion positive electrode material is Na x A u B v Cw 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, and Na 0.67 Mn1O2, etc.

[0071] See Figures 1 to 3 In some embodiments, the energy difference γ of the lowest energy E1 of the sodium-ion positive electrode material under test in the first phase and the lowest energy E2 of the sodium-ion positive electrode material under test in the second phase is calculated, and the formula γ = E1-E2 is satisfied, including:

[0072] S1021, constructing the sodium-ion positive electrode material under test satisfying the chemical formula Na x A u B v C w O2, randomly adjusting the spatial position of the transition metal in the sodium-ion positive electrode material under test to construct a plurality of first-phase sodium-ion positive electrode material models and a plurality of second-phase sodium-ion positive electrode material models satisfying the chemical formula.

[0073] It can be understood that by adjusting the spatial position of the transition metal in the sodium-ion positive electrode material under test through lattice relaxation, a plurality of first-phase sodium-ion positive electrode material models and a plurality of second-phase sodium-ion positive electrode material models can be constructed.

[0074] S1022, determine the energy of the sodium-ion cathode material model of each of the first phase and the energy of the sodium-ion cathode material model of each of the second phase according to a preset machine learning algorithm; wherein the preset machine learning algorithm predicts the energy of the sodium-ion material model by identifying the lattice structure of the sodium-ion cathode material model.

[0075] Optionally, the preset machine learning algorithm is M3GNet (Materials Graph Neutral Architecture) machine learning potential, which is an artificial intelligence (AI) algorithm that can be used to predict the structure and dynamic characteristics of materials and can be used to develop a database containing more than 31 million materials that have not been synthesized, the characteristics of which are predicted by a machine learning algorithm.

[0076] S1023, select the lowest energy E1 in the plurality of first-phase sodium-ion cathode material models and the lowest energy E2 in the plurality of second-phase sodium-ion cathode material models.

[0077] It can be understood that the value of the lowest energy E1 is the lowest value of the energy of the plurality of first-phase sodium-ion cathode material models; the value of the lowest energy E2 is the lowest value of the energy of the plurality of second-phase sodium-ion cathode material.

[0078] S1024, calculate the energy difference γ between the lowest energy of the first phase of the sodium-ion cathode material to be tested and the lowest energy of the second phase of the sodium-ion cathode material to be tested from γ = E1-E2.

[0079] It can be understood that according to the principle of energy minimization, the lower the energy, the more stable it is. When the energy difference γ of the sodium-ion cathode material is greater than 0 and γ is greater than a certain value, the lowest energy E1 of the sodium-ion cathode material when it is in the first phase is greater than the lowest energy E2 of the sodium-ion cathode material when it is in the second phase, then the sodium-ion cathode material is more inclined to form the second phase; when the energy difference γ of the sodium-ion cathode material is less than 0 and γ is less than a certain value, the lowest energy E1 of the sodium-ion cathode material when it is in the first phase is less than the lowest energy E2 of the sodium-ion cathode material when it is in the second phase, then the sodium-ion cathode material is more inclined to form the first phase; when the difference between the value of the energy difference γ of the sodium-ion cathode material and 0 is less than a certain value, the lowest energy of the first phase and the lowest energy of the second phase of the sodium-ion cathode material tend to be flat, and the sodium-ion cathode material is more inclined to form a composite phase.

[0080] In the embodiment, the minimum energy of the sodium ion positive electrode material in the first phase and the minimum energy of the sodium ion positive electrode material in the second phase are calculated by a preset machine learning algorithm, and the energy difference γ of each sodium ion positive electrode material is obtained by the formula γ = E1-E2. The method is simple and easy to operate, and is convenient for experimenters to calculate the energy difference γ of the sodium ion positive electrode material meeting different chemical formulas to preliminarily judge whether the sodium ion positive electrode material is a composite phase. The determination method provides convenience for experimenters and provides reference for experiments of experimenters, reduces the range of sodium ion positive electrode materials that can form a composite phase, reduces the number of experiments and verifications of experimenters, saves the time and energy of experimenters, and accordingly reduces the cost of material research.

[0081] See Figure 2 and Figure 4 In some embodiments, the energy difference γ1 of the sodium ion positive electrode material when the proportion Y of the first phase is 0 is calculated according to a linear equation, the energy difference γ2 of the sodium ion positive electrode material when the proportion Y of the first phase is 1 is calculated according to a linear equation, and when γ2<γ<γ1, the sodium ion positive electrode material is a composite phase, including:

[0082] S1041, according to a linear equation Y =-1.3758γ+0.3182, calculating the energy difference γ1 of the sodium ion positive electrode material when the proportion Y of the first phase is 0; calculating the energy difference γ2 of the sodium ion positive electrode material when the proportion Y of the first phase is 1.

[0083] Understandably, the energy difference γ of the sodium ion positive electrode material and the proportion Y of the first phase in the sodium ion positive electrode material satisfy the linear equation Y =-1.3758γ+0.3182.

[0084] Understandably, when the proportion Y of the first phase is 0, the proportion of the second phase is 1, and the sodium ion positive electrode material is the second phase; when the proportion Y of the first phase is 1, the proportion of the second phase is 0, and the sodium ion positive electrode material is the first phase.

[0085] Understandably, as the energy difference γ of the sodium ion positive electrode material increases, the proportion Y of the first phase gradually decreases. The energy difference γ of the sodium ion positive electrode material continuously increases, the minimum energy of the first phase continuously increases, or the minimum energy of the second phase continuously decreases, according to the principle of energy minimization, the sodium ion positive electrode material is more inclined to form the second phase, and the proportion Y of the first phase continuously decreases.

[0086] It can be understood that Y is the proportion of the first phase, and the value of Y satisfies 0 < Y < 1. The value of Y 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. The sum of the proportion of the first phase and the proportion of the second phase of the sodium ion cathode material is 1, and the proportion of the second phase is 1-Y.

[0087] It can be understood that when the proportion of the first phase Y is 0, the energy difference γ1 of the sodium ion cathode material is 0.2313, and when the energy difference γ of the sodium ion cathode material satisfies γ ≥ 0.2313, the sodium ion cathode material forms the second phase; and when the energy difference γ of the sodium ion cathode material satisfies γ < 0.2313, the sodium ion cathode material forms the composite phase.

[0088] It can be understood that when the proportion of the first phase Y is 1, the energy difference γ2 of the sodium ion cathode material is -0.4956, and when the energy difference γ of the sodium ion cathode material satisfies γ ≤ -0.4956, the sodium ion cathode material forms the first phase; and when the energy difference γ of the sodium ion cathode material satisfies γ > -0.4956, the sodium ion cathode material forms the composite phase.

[0089] S1042, when the energy difference γ of the sodium ion cathode material satisfies the relationship -0.4956 < γ < 0.2313, the sodium ion cathode material is a composite phase.

[0090] In the embodiment, by calculating the energy difference γ of the sodium ion cathode material, when the value of γ satisfies the range -0.4956 < γ < 0.2313, the sodium ion cathode material is a composite phase. When the value of γ satisfies the range γ ≥ 0.2313, the sodium ion cathode material forms the second phase; and when the value of γ satisfies the range γ ≤ -0.4956, the sodium ion cathode material forms the first phase. The determination method of the sodium ion cathode material provided in the embodiment provides scientific guidance for designing and synthesizing a sodium ion cathode material of a composite phase. By calculating the value of the energy difference γ and judging the size relationship between γ and -0.4956 and 0.2313, it can be preliminarily judged whether the sodium ion cathode material of the chemical formula is a composite phase. The determination method provides convenience for experimenters and provides a reference for experiments, narrows the range of sodium ion cathode materials that can form a composite phase, reduces the number of experiments and the number of verifications, saves the time and energy of experimenters, and accordingly reduces the cost of material research.

[0091] Please refer to Figure 5In some embodiments, the determining method further comprises:

[0092] S201, providing a preset positive electrode material, wherein the preset positive electrode material is a composite phase.

[0093] Optionally, the preset positive electrode material is a sodium-ion positive electrode material with a known chemical formula, and the preset positive electrode material is a composite phase.

[0094] S202, calculating the minimum energy E1' when the preset positive electrode material is a first phase and the minimum energy E2' when the preset positive electrode material is a second phase, and calculating the energy difference γ' of the preset positive electrode material according to γ = E1-E2.

[0095] The energy difference γ' of the preset positive electrode material satisfies the relationship -0.4956<γ'<0.2313.

[0096] S203, calculating the value of Y when γ = γ' according to the linear equation Y = -1.3758γ+0.3182, so as to obtain the proportion of the first phase in the preset positive electrode material.

[0097] In the embodiment, when it is verified that the sodium-ion positive electrode material is a composite phase, the proportion of the first phase in the preset positive electrode material can be obtained by calculating the minimum energy E1' when the preset positive electrode material is a first phase and the minimum energy E2' when the preset positive electrode material is a second phase, and calculating the energy difference γ' of the preset positive electrode material according to γ = E1-E2, and further according to the linear equation Y = -1.3758γ+0.3182. The determining method facilitates the experimenter to select a sodium-ion positive electrode material with a suitable proportion of the first phase according to the requirements of capacity and rate performance. The first phase is a P2 single phase, and when the proportion of the first phase is larger, the preset positive electrode material of the composite phase has better rate performance but relatively lower capacity; when the proportion of the first phase is smaller, the preset positive electrode material of the composite phase has higher capacity but relatively poorer rate performance. When the proportion of the first phase is within a reasonable range, the preset positive electrode material of the composite phase has better rate performance and higher capacity. The determining method provides convenience for the experimenter and provides a reference for the experiment of the experimenter, facilitates the experimenter to select a preset positive electrode material with a suitable proportion of the first phase, narrows the range of the preset positive electrode material that can form a suitable proportion of the first phase, reduces the number of experiments and the number of verifications of the experimenter, is conducive to saving the time and energy of the experimenter, and accordingly reduces the cost of material research.

[0098] The embodiment of the application further provides a sodium-ion positive electrode material, wherein the sodium-ion positive electrode material is a composite phase, and the chemical formula of the sodium-ion positive electrode material is Na x A u Bv 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, and an energy difference γ of the sodium-ion positive electrode material satisfies -0.4956 < γ < 0.2313, wherein γ = E1-E2, E1 is the lowest energy when the sodium-ion positive electrode material is in the first phase, and E2 is the lowest energy when the sodium-ion positive electrode material is in the second phase.

[0099] Understandably, the first phase is P2 single phase, the second phase is O3 single phase, and the sodium-ion positive electrode material of the application is a composite phase, so the sodium-ion positive electrode material is a composite of P2 single phase and O3 single phase. The lowest energy of the sodium-ion positive electrode material in the first phase is calculated by means of M3GNet machine learning potential, and the lowest energy of the sodium-ion positive electrode material in the second phase is calculated by means of M3GNet machine learning potential.

[0100] In this embodiment, the sodium-ion positive electrode material is in a composite phase and has a chemical formula of Na x A u B v C w O2, and an energy difference γ of the sodium-ion positive electrode material satisfies -0.4956 < γ < 0.2313, that is, the difference between the lowest energy of the sodium-ion positive electrode material in the first phase and the lowest energy of the sodium-ion positive electrode material in the second phase is within a certain range, and the sodium-ion positive electrode material is a composite of the first phase and the second phase. The sodium-ion positive electrode material in the composite phase takes into account the advantages of the first phase and the second phase, and the sodium-ion positive electrode material in the composite phase exhibits high rate performance and high capacity.

[0101] In some embodiments, the energy difference of the sodium-ion positive electrode material is γ, and the proportion of the first phase in the sodium-ion positive electrode material is Y, which satisfies the linear equation Y = -1.3758γ + 0.3182.

[0102] In this embodiment, the energy difference γ of the sodium-ion positive electrode material in the composite phase and the proportion Y of the first phase satisfy the linear equation Y = -1.3758γ + 0.3182, which facilitates the experimenter to judge the proportion of the first phase and the proportion of the second phase in the composite phase, 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 good rate performance and high capacity.

[0103] The technical solutions of the application will be further described in the following embodiments.

[0104] Embodiments 1 to 8

[0105] 1. Select a plurality of sodium ion positive electrode materials: the chemical general formula of the sodium ion positive electrode materials of Example 1 to Example 8 is respectively: 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 and Na 0.67 Mn 0.6 Ni 0.4 O2, and specific information is shown in Table 1.

[0106] 2. Calculate the lowest energy E1 of each sodium ion positive electrode material as a first phase and the lowest energy E2 of the sodium ion positive electrode material as a second phase, respectively, and calculate the energy difference γ of each sodium ion positive electrode material according to the formula γ = E1-E2, the value of E1, the value of E2 and the value of γ corresponding to each of the sodium ion positive electrode materials of Example 1 to Example 8 are shown in Table 1.

[0107] 3. Measure the proportion Y of the first phase in each of the sodium ion positive electrode materials, the value of Y corresponding to each of the sodium ion positive electrode materials of Example 1 to Example 8 is shown in Table 1, and the proportion of the first phase is the mass proportion of the first phase.

[0108] 4. Linearly fit the energy difference γ of each of the sodium ion positive electrode materials and the proportion Y of the first phase in the sodium ion positive electrode material, wherein 0 < Y < 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, and the linear fitting equation is shown in Figure 6

[0109] ​5. According to the linear equation, the energy difference γ1 of the sodium-ion positive electrode material when the proportion Y of the first phase is 0, and the energy difference γ2 of the sodium-ion positive electrode material when the proportion Y of the first phase is 1, then when γ2 < γ < γ1, the sodium-ion positive electrode material is a composite phase.

[0110] Table 1: The values of E1, E2, γ and Y of the sodium-ion positive electrode materials of Examples 1 to 8

[0111]

[0112] From the data in Table 1, in Examples 1 and 6, the proportion Y of the first phase is 0, so the sodium-ion positive electrode material provided in Example 1 and the sodium-ion positive electrode material provided in Example 6 do not have the first phase (P2 single phase), and both the sodium-ion positive electrode material provided in Example 1 and the sodium-ion positive electrode material provided in Example 6 are the second phase (O3 single phase). In Examples 7 and 8, the proportion Y of the first phase is 1, so the sodium-ion positive electrode material provided in Example 7 and the sodium-ion positive electrode material provided in Example 8 both have the first phase (P2 single phase), and neither the sodium-ion positive electrode material provided in Example 7 nor the sodium-ion positive electrode material provided in Example 8 has the second phase (O3 single phase). The proportion Y of the first phase of the sodium-ion positive electrode materials provided in Examples 2 to 5 satisfies 0 < Y < 1, so the sodium-ion positive electrode materials provided in Examples 2 to 5 are composite phases, i.e. a composite of the first phase and the second phase, and the proportion of the first phase is Y. According to the linear fitting of the energy difference γ of each sodium-ion positive electrode material and the proportion Y of the first phase in the sodium-ion positive electrode material, the linear equation of the fitting is as shown in Figure 6 .

[0113] According to the linear equation as shown in Figure 6 , the energy difference γ of the sodium-ion positive electrode material and the proportion Y of the first phase satisfy the linear equation Y = -1.3758γ + 0.3182, so when the proportion Y of the first phase of the sodium-ion positive electrode material satisfies 0 < Y < 1, the proportion Y of the first phase in the sodium-ion positive electrode material gradually decreases as the energy difference γ increases. Understandably, the energy difference γ of the sodium-ion positive electrode material = E1 - E2, so the energy difference of the sodium-ion positive electrode material is the difference between the lowest energy E1 of the first phase and the lowest energy E2 of the second phase, and when the value of the energy difference is larger, the value of the lowest energy E1 of the first phase is larger or the lowest energy E2 of the second phase is smaller, according to the principle of energy minimization, the sodium-ion positive electrode material is more inclined to form the second phase, so the proportion Y of the first phase in the sodium-ion positive electrode material is smaller.

[0114] A linear equation Y=-1.3758y+0.3182 is obtained by linear fitting of the values obtained in Example 2 to Example 5. When the proportion of the first phase in the sodium ion positive electrode material is 0, the value of the energy difference y1 is 0.2313. When the proportion of the first phase in the sodium ion positive electrode material is 1, the value of the energy difference y2 is-0.4956. When the value of the energy difference y of the sodium ion positive electrode material satisfies the relationship-0.4956

[0115] The determination method of the sodium ion positive electrode material provided in the present application is to calculate the lowest energy E1 of the sodium ion positive electrode material as the first phase, the lowest energy E2 of the sodium ion positive electrode material as the second phase, the energy difference y=E1-E2, and the proportion Y of the first phase of the sodium ion positive electrode material, linear fitting of the energy difference y and the proportion Y of the first phase of the sodium ion positive electrode material satisfying 0

[0116] See Figure 7 and Figure 8The application further provides a positive electrode sheet 100, which comprises a positive electrode current collector 110 and a positive electrode material layer 120 arranged on the surface of the positive electrode current collector 110, wherein the positive electrode material layer 120 comprises the sodium-ion positive electrode material provided by the application.

[0117] It can be understood that 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 two surfaces.

[0118] It can be understood that the positive electrode current collector 110 and the positive electrode material layer 120 are sequentially arranged.

[0119] In the embodiment, the positive electrode material layer 120 comprises the 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 high rate performance and high capacity.

[0120] 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 makes the positive electrode sheet 100 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.

[0121] Please refer to Figure 9 and Figure 10The battery 200 provided by the application comprises an electrolyte 210, a negative electrode sheet 220, a separator 230 and the positive electrode sheet 100 provided by the application, and 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.

[0122] In the embodiment, the battery 200 comprises the positive electrode sheet 100, the positive electrode sheet 100 exhibits high rate performance and high capacity, which is beneficial to improve the rate performance and capacity of the battery 200, so that the battery 200 can have high kinetic performance and high capacity.

[0123] Optionally, the separator 230 is any separator 230 material in the prior art, and the separator 230 comprises one or more of polypropylene (PP), polyethylene (PE) and ceramic separator 230.

[0124] Optionally, the electrolyte 210 comprises an electrolyte salt (such as sodium hexafluorophosphate) and an organic solvent, and the specific types and compositions of the electrolyte salt and the organic solvent are conventional choices in the field of batteries 200, which can be selected according to actual needs.

[0125] Optionally, the battery 200 can be a circular battery 200, a square battery 200 or the like.

[0126] Please refer to Figure 11 The battery 200 provided by the application comprises an electrolyte 210, a negative electrode sheet 220, a separator 230 and the positive electrode sheet 100 provided by the application, and 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.

[0127] In the embodiment, the battery 200 comprises the positive electrode sheet 100, the positive electrode sheet 100 exhibits high rate performance and high capacity, which is beneficial to improve the rate performance and capacity of the battery 200, so that the battery 200 can have high kinetic performance and high capacity.

[0128] Optionally, the power consuming device 300 of the embodiments of the present application can be, but is not limited to, a mobile phone, a tablet computer, a notebook computer, a desktop computer, a smart bracelet, a smart watch, an electronic reader, a game console, and the like portable electronic device. It can also be a vehicle such as a car, a truck, a sedan, a van, a motor car, a high-speed train, an electric automatic car, and the like. In addition, it can also be various household appliances, and the like.

[0129] It can be understood that the power consuming device 300 described in the embodiments 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 of the embodiments of the present application.

[0130] In the present application, the phrase "embodiment" or "embodiments" means that the specific features, structures or characteristics described in connection with the embodiment can be included in at least one embodiment of the present application. The appearance of the phrase in various places in the specification does not necessarily mean the same embodiment, nor is it an independent or alternative embodiment that is not mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in the present application can be combined with other embodiments. In addition, it should also be understood that the features, structures or characteristics described in the embodiments of the present application can be combined with each other without contradiction, to form another embodiment of the present application without departing from the spirit and scope of the present application.

[0131] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and not to limit it. Although the present application has been described in detail with reference to the above preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the present application.

Claims

1. A method of determining a sodium-ion positive electrode material, characterized by, 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 sodium ion positive electrode material to be tested; Calculating the energy difference γ of the minimum energy E1 of the sodium ion positive electrode material to be tested as the first phase and the minimum energy E2 of the sodium ion positive electrode material to be tested as the second phase, the energy difference γ of the sodium ion positive electrode material to be tested satisfies the formula γ=E1-E2; and When the energy difference γ of the sodium ion positive electrode material to be tested satisfies the relationship: γ2<γ<γ1, it is determined that the sodium ion positive electrode material to be tested is a composite phase; wherein the value of γ1 is the critical value of the sodium ion positive electrode material forming a composite phase and a second phase, and the value of γ2 is the critical value of the sodium ion positive electrode material forming a composite phase and a first phase; The determination method of the critical value γ1 of the sodium ion positive electrode material forming a composite phase and a second phase and the critical value γ2 of the sodium ion positive electrode material forming a composite phase and a first phase comprises: Selecting a plurality of sodium ion positive electrode materials; Calculating the energy difference γ of the minimum energy E1 of each sodium ion positive electrode material as the first phase and the minimum energy E2 of the sodium ion positive electrode material as the second phase, the energy difference γ of each sodium ion positive electrode material satisfies the formula γ=E1-E2; According to the energy difference γ of each sodium ion positive electrode material and the proportion Y of the first phase in the sodium ion positive electrode material, linear fitting is performed, wherein 0Y<1; and According to the linear equation, the energy difference γ1 of the sodium ion positive electrode material when the proportion Y of the first phase is 0 is calculated, and the energy difference γ2 of the sodium ion positive electrode material when the proportion Y of the first phase is 1 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 P2 phase, the second phase is O3 phase, and the composite phase is a composite of P2 phase and O3 phase.

4. The determination method according to claim 1, characterized in that, The chemical general formula of the sodium ion positive electrode material is: Na x A u B v C w O2, wherein A is selected from at least one of Mn, Ni, Ti, Co, Fe, Cu, Cr, Zn, V, Zr and Ta transition metals; B is selected from at least one of Mn, Ni, Ti, Co, Fe, Cu, Cr, Zn, V, Zr and Ta transition metals; and C is selected from at least one of Mn, Ni, Ti, Co, Fe, Cu, Cr, Zn, V, Zr and Ta transition metals.

5. The determination method according to claim 2, characterized in that, The calculation of the energy difference γ of the minimum energy E1 of the sodium ion positive electrode material to be tested as the first phase and the minimum energy E2 of the sodium ion positive electrode material to be tested as the second phase satisfies the formula γ=E1-E2, comprising: constructing a sodium-ion positive electrode material satisfying a chemical general formula of Na x A u B v C w O2, randomly adjusting the spatial positions of transition metals in the sodium-ion positive electrode material to be tested, to construct a plurality of first-phase sodium-ion positive electrode material models and a plurality of second-phase sodium-ion positive electrode material models satisfying the chemical general formula. According to a preset machine learning algorithm, the energy of each sodium ion positive electrode material model of the first phase and the energy of each sodium ion positive electrode material model of the second phase are determined; wherein the preset machine learning algorithm predicts the energy of the sodium ion material model by identifying the lattice structure of the sodium ion positive electrode material model; Selecting the minimum energy E1 of the plurality of first phase sodium ion positive electrode material models and the minimum energy E2 of the plurality of second phase sodium ion positive electrode material models; and According to γ=E1-E2, the energy difference γ of the minimum energy of the first phase of the sodium ion positive electrode material to be tested and the minimum energy of the second phase of the sodium ion positive electrode material to be tested is calculated.

6. The determination method of claim 1, wherein, According to the linear equation, the energy difference γ1 of the sodium ion positive electrode material when the proportion Y of the first phase is 0 is calculated, and the energy difference γ2 of the sodium ion positive electrode material when the proportion Y of the first phase is 1 is calculated, when γ2<γ<γ1, the sodium ion positive electrode material is a composite phase, comprising: According to a linear equation Y=-1.3758γ+0.3182, when the proportion Y of the first phase is 0, the energy difference γ1 of the sodium-ion positive electrode material is 0.2313; when the proportion Y of the first phase is 1, the energy difference γ2 of the sodium-ion positive electrode material is -0.4956; When the energy difference γ of the sodium-ion positive electrode material satisfies the relationship -0.4956<γ<0.2313, the sodium-ion positive electrode material is a composite phase.

7. The determination method according to claim 6, characterized in that, The determination method further comprises: providing a preset positive electrode material, the preset positive electrode material being a composite phase; calculating the lowest energy E1' when the preset positive electrode material is a first phase and the lowest energy E2' when the preset positive electrode material is a second phase, and calculating the energy difference γ' of the preset positive electrode material according to γ'=E1'-E2'; According to a linear equation Y=-1.3758γ+0.3182, when γ=γ', the value of Y is calculated, so as to obtain the proportion of the first phase in the preset positive electrode material.

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