CN116190561A - Battery monomer of sodium ion battery, sodium ion battery and power utilization device - Google Patents

Battery monomer of sodium ion battery, sodium ion battery and power utilization device Download PDF

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CN116190561A
CN116190561A CN202310479148.7A CN202310479148A CN116190561A CN 116190561 A CN116190561 A CN 116190561A CN 202310479148 A CN202310479148 A CN 202310479148A CN 116190561 A CN116190561 A CN 116190561A
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transition metal
metal oxide
ion battery
sodium ion
battery
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CN116190561B (en
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唐正
叶永煌
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Chemical Kinetics & Catalysis (AREA)
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  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Inorganic Chemistry (AREA)
  • Composite Materials (AREA)
  • Manufacturing & Machinery (AREA)
  • Secondary Cells (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The embodiment of the application discloses a battery monomer of a sodium ion battery sodium ion battery and power utilization device. The battery cell comprises a positive electrode plate, wherein the positive electrode plate comprises a positive electrode active material, and the positive electrode active material comprises octahedral transition metal oxide and prismatic transition metal oxide; cut-off voltage V of sodium ion battery 1 The method meets the following conditions: 3.95 V is less than or equal to V 1 And less than or equal to 4.15 and V. The battery monomer has higher energy density and good cycle performance.

Description

Battery monomer of sodium ion battery, sodium ion battery and power utilization device
Technical Field
The present application relates to the field of batteries, and more particularly, to a battery cell of a sodium ion battery, and an electric device.
Background
In recent years, lithium ion batteries have been widely used in energy storage power systems such as hydraulic power, thermal power, wind power and solar power stations, and in various fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc., and have been greatly developed. However, lithium resources are limited in reserves and unevenly distributed, which becomes a big problem to limit the development of lithium ion batteries.
The sodium element and the lithium element are in the same main group, have similar physicochemical properties, and have abundant sodium resources and wide distribution, so that the sodium ion battery has a larger competitive advantage than the lithium ion battery. However, sodium ion batteries generally do not combine a high energy density with good cycle performance. Therefore, how to improve the energy density and the cycle performance of the sodium ion battery at the same time is a technical problem to be solved.
Disclosure of Invention
The present application has been made in view of the above-described problems, and an object thereof is to provide a battery cell of a sodium ion battery, and an electric device. The battery monomer has higher energy density and good cycle performance.
In a first aspect, a battery cell of a sodium ion battery is provided, the battery cell comprising a positive electrode sheet comprising a positive electrode active material comprising an octahedral transition metal oxide and a prismatic transition metal oxide; cut-off voltage V of charging of the sodium ion battery 1 The method meets the following conditions: 3.95 V is less than or equal to V 1 ≤4.15 V。
In embodiments of the present application, the positive electrode active material of the sodium ion battery includes two different structures of transition metal oxides. The octahedral transition metal oxide has higher sodium content, can contribute higher capacity, has higher ionic conductivity and more stable structure, and can contribute good cycle performance. In the sodium ion battery, the charge cut-off voltage V of the sodium ion battery is controlled 1 The positive electrode active material obtained by compounding the two materials can exert higher capacity of the octahedral transition metal oxide, has a stable structure of the prismatic transition metal oxide, and can enable the sodium-ion battery to have good cycle performance. Because ofThe charge cut-off voltage V of the sodium ion battery is controlled by compounding two materials 1 The sodium ion battery can have higher energy density and good cycle performance at the same time when meeting the range.
In some embodiments, the sodium ion battery has a discharge cut-off voltage V 2 The method meets the following conditions: 1.50 V is less than or equal to V 2 ≤2.00 V。
In the embodiment of the application, the discharge cut-off voltage V of the sodium ion battery is controlled 2 The method meets the above range, and can reduce the over-discharge probability of the sodium ion battery, thereby improving the conditions of gas generation in the battery and reduction of the copper current collector, being beneficial to maintaining the stability of the internal structure of the battery and improving the cycle performance of the battery.
In some embodiments, the sodium ion battery has a charge cutoff voltage V 1 Is configured to be according to the load m of the octahedral transition metal oxide on the positive electrode sheet 1 But is set.
In some embodiments, the loading 154.025 mm of the octahedral transition metal oxide is at least one of 2 /g≤m 1 ≤1386.225 mm 2 In the case of/g, the charge cut-off voltage V of the sodium-ion battery 1 The method meets the following conditions: 3.95 V is less than or equal to V 1 ≤4.1 V。
In some embodiments, the sodium ion battery has a discharge cut-off voltage V 2 Is configured to be according to the octahedron type loading m of transition metal oxide 1 But is set.
In some embodiments, the loading 154.025 mm of the octahedral transition metal oxide is at least one of 2 /g≤m 1 ≤1386.225 mm 2 In the case of/g, the discharge cut-off voltage V of the sodium-ion battery 2 The method meets the following conditions: 1.5 V is less than or equal to V 2 ≤1.8 V。
In the embodiment of the application, the load m of the octahedral transition metal oxide capable of contributing to higher capacity on the positive electrode plate can be calculated 1 Configuration of the charging cut-off voltage V of a sodium ion battery 1 Cut-off voltage of discharge V 2 Is not limited in terms of the range of (a). Octahedral transition through positive electrode active materialMetal oxide loading m 1 Setting the charge cut-off voltage V of the sodium ion battery 1 Cut-off voltage of discharge V 2 The range ensures that the octahedral transition metal oxide contributes higher capacity in the voltage range, improves the energy density of the sodium ion battery, and has a relatively stable structure, thereby further improving the stability of the positive electrode active material in the charge and discharge process and ensuring that the sodium ion battery has good cycle performance.
In some embodiments, the sodium ion battery has a charge cutoff voltage V 1 Is configured to be based on the loading ratio m of the octahedral transition metal oxide and the prismatic transition metal oxide on the positive electrode sheet 1 /m 2 But is set.
In some embodiments, the loading ratio between the octahedral transition metal oxide and the prismatic transition metal oxide is 1/9.ltoreq.m 1 /m 2 Under the condition of less than or equal to 9, the charge cut-off voltage V of the sodium ion battery 1 The method meets the following conditions: 3.95 V is less than or equal to V 1 ≤4.15 V。
In some embodiments, the sodium ion battery has a discharge cut-off voltage V 2 Configured to be based on a loading ratio m of the octahedral transition metal oxide and the prismatic transition metal oxide on the positive electrode sheet 1 /m 2 But is set.
In some embodiments, the mass ratio between the octahedral transition metal oxide and the prismatic transition metal oxide is 1/9.ltoreq.m 1 /m 2 At a discharge cut-off voltage V of 9 or less 2 The method meets the following conditions: 1.5 V is less than or equal to V 2 ≤1.8 V。
In the embodiment of the application, the charge cut-off voltage V of the sodium ion battery can also be configured according to the loading ratio of the octahedral transition metal oxide and the prismatic transition metal oxide in the positive electrode active material on the positive electrode plate 1 Cut-off voltage of discharge V 2 Is not limited in terms of the range of (a). By the mass of octahedral transition metal oxide and the loading ratio m of prismatic transition metal oxide in the positive electrode active material 1 /m 2 To set the charge cut-off voltage V of the sodium ion battery 1 Cut-off voltage of discharge V 2 The range ensures that the octahedral transition metal oxide contributes higher capacity in the voltage range, improves the energy density of the sodium ion battery, and has a relatively stable structure, thereby further improving the stability of the positive electrode active material in the charge and discharge process and ensuring that the sodium ion battery has good cycle performance.
In some embodiments, the octahedral transition metal oxide has an average volume particle diameter that satisfies: 7. dv50 of μm or less 1 Less than or equal to 20 mu m; the average volume particle diameter of the prismatic transition metal oxide satisfies the following conditions: 5. dv50 of μm or less 2 ≤10 μm。
In some embodiments, the octahedral transition metal oxide has a specific surface area that satisfies: 0.3 m is m 2 /g≤BET 1 ≤2.0 m 2 /g; the specific surface area of the prismatic transition metal oxide satisfies: 2.0 m is m 2 /g≤BET 2 ≤5.0 m 2 /g。
In the embodiment of the application, the average volume particle diameter and the specific surface area of two different transition metal oxides are controlled within the ranges, so that the powder compaction density of the positive electrode material is improved, and the energy density of the sodium ion battery is further improved.
In a second aspect, there is provided a sodium ion battery comprising the cell of any of the embodiments of the first aspect.
In a third aspect, there is provided an electrical device comprising a battery cell according to any of the embodiments of the first aspect, and/or a battery according to any of the embodiments of the second aspect.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments of the present application will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present application, and that other drawings may be obtained according to the drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic diagram of a sodium ion battery cell according to an embodiment of the present application.
Fig. 2 is a schematic diagram of a sodium ion battery module according to an embodiment of the present application.
Fig. 3 is a schematic diagram of a sodium ion battery according to an embodiment of the present application.
Fig. 4 is another schematic diagram of a sodium ion battery according to an embodiment of the present application.
Detailed Description
Hereinafter, embodiments of a battery cell of a sodium ion battery, and an electric device of the present application are specifically disclosed with reference to the drawings as appropriate. However, unnecessary detailed description may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of the actual same structure may be omitted. This is to avoid that the following description becomes unnecessarily lengthy, facilitating the understanding of those skilled in the art. Furthermore, the drawings and the following description are provided for a full understanding of the present application by those skilled in the art, and are not intended to limit the subject matter recited in the claims.
The "range" disclosed herein is defined in terms of lower and upper limits, with a given range being defined by the selection of a lower and an upper limit, the selected lower and upper limits defining the boundaries of the particular range. Ranges that are defined in this way can be inclusive or exclusive of the endpoints, and any combination can be made, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3,4 and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise indicated, the numerical range "a-b" represents a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed throughout, and "0-5" is simply a shorthand representation of a combination of these values. When a certain parameter is expressed as an integer of 2 or more, it is disclosed that the parameter is, for example, an integer of 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12 or the like.
In the description of the present application, it should be noted that the number of the substrates, unless otherwise indicated, the meaning of "a plurality" is two or more; the terms "upper," "lower," "left," "right," "inner," "outer," and the like indicate an orientation or positional relationship merely for convenience of description and to simplify the description, and do not indicate or imply that the devices or elements being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus are not to be construed as limiting the present application. Furthermore, the terms "first," "second," "third," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
Reference herein to "comprising" and "including" means open ended, as well as closed ended, unless otherwise noted. For example, the terms "comprising" and "comprises" may mean that other components not listed may be included or included, or that only listed components may be included or included.
The term "or" is inclusive in this application, unless otherwise specified. For example, the phrase "a or B" means "a, B, or both a and B. More specifically, either of the following conditions satisfies the condition "a or B": a is true (or present) and B is false (or absent); a is false (or absent) and B is true (or present); or both A and B are true (or present).
All steps of the present application may be performed sequentially or randomly, preferably sequentially, unless otherwise indicated. For example, the method comprises steps (a) and (b), meaning that the method may comprise steps (a) and (b) performed sequentially, or may comprise steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), may include steps (a), (c) and (b), may include steps (c), (a) and (b), and the like.
All embodiments and alternative embodiments of the present application may be combined with each other to form new solutions, unless specifically stated otherwise.
All technical features and optional technical features of the present application may be combined with each other to form new technical solutions, unless specified otherwise.
Unless otherwise indicated, the following terms have the following meanings. Any undefined terms have their art-recognized meanings.
As mentioned, the "sodium metal battery" refers to a sodium ion battery in which the anode active material includes metallic sodium.
As mentioned above, "octahedral transition metal oxide" refers to an O3 type layered transition metal oxide. Layered transition metal oxides are a class of transition metal oxides in which the transition metal layers are formed by co-extensive octahedra and sodium ions are located between the transition metal layers. In the O3 type layered transition metal oxide, O represents the position of sodium ion (O represents octahedron), and the number 3 represents the stacking mode of oxygen is ABCABC type. For example, na 0.95 Mn 0.33 Fe 0.33 Ni 0.33 O 2 。
As mentioned, the term "prismatic transition metal oxide" refers to a layered transition metal oxide of the P2 type. In the P2 type layered transition metal oxide, P represents a position where a sodium ion is located (P represents a prism), and numeral 2 represents a stacking mode of oxygen in ABAB type. For example, na 2/3 Mg 1/4 Mn 3/4 O 2 。
Typically, the battery cell includes a positive electrode tab, a negative electrode tab, an electrolyte, and a separator. In the charge and discharge process of the battery cell, active ions are inserted and extracted back and forth between the positive pole piece and the negative pole piece. The electrolyte plays a role in ion conduction between the positive electrode plate and the negative electrode plate. The isolating piece is arranged between the positive pole piece and the negative pole piece, mainly plays a role in preventing the positive pole piece and the negative pole piece from being short-circuited, and can enable active ions to pass through. In some embodiments, the above-described battery cells are also referred to as secondary batteries.
In the charging process of the sodium ion battery, sodium ions are separated from the positive electrode active material, move and are embedded into the negative electrode active material; and sodium ions are extracted from the negative electrode active material, moved and embedded in the positive electrode active material during discharge.
It should be understood that the "intercalation" process described herein refers to a process in which sodium ions are intercalated into the positive electrode active material and the negative electrode active material due to an electrochemical reaction, and the "deintercalation" process described herein refers to a process in which sodium ions are deintercalated into the positive electrode active material and the negative electrode active material due to an electrochemical reaction.
Similar to lithium ion batteries, the positive electrode material is one of the key factors restricting the performance of sodium ion batteries. Among various cathode materials that have been widely studied, transition metal oxide cathode materials having a layered structure have been attracting attention due to their high theoretical capacity and energy density.
Layered transition metal oxides are largely divided into two classes, namely octahedral transition metal oxides and prismatic transition metal oxides, depending on the location of sodium ions in the crystalline structure. According to the stacking mode of oxygen in the crystal structure, the octahedral transition metal oxide is mainly O3-type transition metal oxide, and the prismatic transition metal oxide is mainly P2-type transition metal oxide. Wherein O represents octahedron, P represents prism, and the number represents stacking mode of oxide layer. In the O3 type transition metal oxide, the oxygen stacking mode is abcab type, whereas in the P2 type transition metal oxide, the oxygen stacking mode is ABAB type.
Due to the different environments in which sodium ions are located in different transition metal oxides, the stability and dynamics of the layered structure are affected differently by the sodium ions, and therefore, the material shows different electrochemical properties.
Generally, octahedral transition metal oxides have a higher sodium content, have a higher theoretical capacity, and can contribute higher energy density to the battery than prismatic transition metal oxides. However, the octahedral transition metal oxide undergoes a series of phase changes during charge and discharge, and the capacity retention rate is inferior to that of the prismatic transition metal oxide. The prismatic transition metal oxide has good structural stability, low ion diffusion barrier, high ion conductivity and excellent cycle performance and rate performance.
In some examples, the capacity and cycle performance of a sodium ion battery may be simultaneously enhanced by preparing a transition metal oxide having both an O3 phase and a P2 phase as a positive electrode material of the sodium ion battery. However, the structural collapse of the O3 phase of the composite phase material is unavoidable in the normal charge-discharge voltage range of the sodium ion battery, and the respective advantages of the two materials are difficult to develop.
In view of this, the present application provides a battery cell of a sodium ion battery, which includes a positive electrode sheet including a positive electrode active material including an octahedral type transition metal and a prismatic type transition metal oxide. Wherein, the charge cut-off voltage V of the sodium ion battery 1 The method meets the following conditions: 3.95 V is less than or equal to V 1 ≤4.15 V。
Specifically, the charge cut-off voltage V of the sodium ion battery 1 May be 3.95V, 4.00V, 4.05V, 4.10V, 4.15V, or a range of values thereof within the range obtained by combining any two of the values described above.
According to the battery monomer of the sodium ion battery, provided by the embodiment of the application, the transition metal oxides with two different structures are compounded to serve as the positive electrode material, and the charge cut-off voltage of the sodium ion battery is controlled within the range, so that the high energy density of the octahedral transition metal oxide and the good cycle performance of the prismatic transition metal oxide can be simultaneously exerted, and the sodium ion battery with the high energy density and the good cycle performance can be obtained.
In one embodiment, the discharge cut-off voltage V of the sodium ion battery 2 The method meets the following conditions: 1.50 V is less than or equal to V 2 ≤2.00 V。
Specifically, the discharge cut-off voltage V of the sodium ion battery 2 May be 1.50V, 1.55V, 1.60V, 1.65V, 1.70V, 1.75V, 1.80V, 1.85V, 1.90V, 1.95V, 2.00V, or ranges of values thereof within the ranges stated as being obtained by combining any two of the above values.
In the embodiment of the application, through controlling the discharge cut-off voltage of sodium ions, the problems of gas production in the battery and reduction of the negative electrode current collector caused by overdischarge in the sodium ion discharging process can be effectively solved, and the stability of the internal structure of the sodium ion battery is facilitated, so that the sodium ion battery can fully discharge and provide higher capacity, and meanwhile, the cycle performance of the sodium ion battery is further improved.
In combination with control of the charge cut-off voltage of the sodium ion battery, the embodiment of the application can exert good cycle performance of the prismatic transition metal oxide while exerting high capacity of the octahedral transition metal oxide by controlling the charge and discharge cut-off voltage of the sodium ion battery in the proper range, so that the sodium ion battery has higher energy density and good cycle performance.
In one embodiment, the charge cut-off voltage V of the sodium ion battery 1 Configured to be in accordance with the loading m of the octahedral transition metal oxide 1 But is set.
In one embodiment, the loading m of the octahedral transition metal oxide 1 Satisfy 154.025 mm 2 /g≤m 1 ≤1386.225 mm 2 In the case of/g, the charge cut-off voltage V of the sodium-ion battery 1 The method meets the following conditions: 3.95 V is less than or equal to V 1 ≤4.15 V。
In one embodiment, the discharge cut-off voltage V of the sodium ion battery 2 Configured to be in accordance with the loading m of the octahedral transition metal oxide 1 But is set.
In one embodiment, the loading m of the octahedral transition metal oxide 1 Satisfy 154.025 mm 2 /g≤m 1 ≤1386.225 mm 2 In the case of/g, the discharge cut-off voltage V of the sodium-ion battery 2 The method meets the following conditions: 1.5 V is less than or equal to V 2 ≤1.8 V。
In one embodiment, the charge cut-off voltage V of the sodium ion battery 1 Is configured to be based on the loading ratio m of the octahedral transition metal oxide and the prismatic transition metal oxide on the positive electrode sheet 1 /m 2 But is set.
In one embodiment of the present invention, in one embodiment,loading ratio m of octahedral transition metal oxide and prismatic transition metal oxide 1 /m 2 Satisfy 1/9.ltoreq.m 1 /m 2 Under the condition of less than or equal to 9, the charge cut-off voltage V of the sodium ion battery 1 The method meets the following conditions: 3.95 V is less than or equal to V 1 ≤4.15 V。
Discharge cut-off voltage V of sodium ion battery 2 Is configured to be based on the loading ratio m of the octahedral transition metal oxide and the prismatic transition metal oxide on the positive electrode sheet 1 /m 2 But is set.
In one embodiment, the loading ratio m of the octahedral transition metal oxide and the prismatic transition metal oxide 1 /m 2 Satisfy 1/9.ltoreq.m 1 /m 2 Under the condition of less than or equal to 9, the discharge cut-off voltage V of the sodium ion battery 2 The method meets the following conditions: 1.5 V is less than or equal to V 2 ≤1.8 V。
In the embodiment of the application, the load m of the octahedral transition metal oxide on the positive electrode plate in the positive electrode active material can be controlled 1 Mass m of octahedral transition metal oxide 1 And the loading ratio m of prismatic transition metal oxide on positive electrode plate 1 /m 2 To set the charge cut-off voltage V of the sodium ion battery 1 Cut-off voltage of discharge V 2 The range enables the octahedral transition metal oxide to contribute higher capacity in the voltage range, improve the energy density of the sodium ion battery and have a relatively stable structure; the positive electrode active material comprising prismatic transition metal oxide has high capacity and good stability, and further improves the structural stability of the positive electrode active material and the stability of the internal structure of the battery in the charge and discharge process, so that the sodium ion battery has good cycle performance.
In one embodiment, the octahedral transition metal oxide has an average volume particle diameter satisfying: 7. dv50 of μm or less 1 Less than or equal to 20 mu m; the average volume particle diameter of the prismatic transition metal oxide satisfies: 5. dv50 of μm or less 2 ≤10 μm。
In particular, the average volume of octahedral transition metal oxidesProduct particle diameter Dv50 1 May be 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, or a range of values thereof within a range obtained by combining any two of the above values. Average volume particle diameter Dv50 of prismatic transition metal oxide 2 May be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or a range of values thereof within the range obtained by combining any two values described above.
In one embodiment, the specific surface area of the octahedral transition metal oxide satisfies: 0.3 cm 2 /g≤BET 1 ≤2.0 cm 2 /g; the specific surface area of the prismatic transition metal oxide satisfies: 2.0 cm 2 /g≤BET 2 ≤5.0 cm 2 /g。
Specifically, the specific surface area BET of the octahedral transition metal oxide 1 May be 0.3. 0.3 cm 2 /g、0.4 cm 2 /g、0.5 cm 2 /g、0.6 cm 2 /g、0.7 cm 2 /g、0.8 cm 2 /g、0.9 cm 2 /g、1.0 cm 2 /g、1.1 cm 2 /g、1.2 cm 2 /g、1.3 cm 2 /g、1.4 cm 2 /g、1.5 cm 2 /g、1.6 cm 2 /g、1.7 cm 2 /g、1.8 cm 2 /g、1.9 cm 2 /g、2.0 cm 2 /g, or a range of values thereof, within the range obtained by combining any two values described above. Specific surface area BET of prismatic transition metal oxide 2 May be 2.0. 2.0 cm 2 /g、2.5 cm 2 /g、3.0 cm 2 /g、3.5 cm 2 /g、4.0 cm 2 /g、4.5 cm 2 /g、5.0 cm 2 /g, or a range of values thereof, within the range obtained by combining any two values described above.
Next, the electrode material, the positive electrode sheet, the negative electrode sheet, the separator, the electrolyte, and the like in the sodium ion battery will be described in detail.
[ Positive electrode sheet ]
The positive pole piece comprises a positive current collector and a positive film layer arranged on at least one surface of the positive current collector, wherein the positive film layer comprises a positive active material.
As an example, the positive electrode current collector has two surfaces opposite in the thickness direction thereof, and the positive electrode film layer may be disposed on either or both of the two surfaces opposite to the positive electrode current collector.
Alternatively, the positive electrode current collector may employ a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
In the embodiments of the present application, the positive electrode active material includes an octahedral type transition metal oxide and a prismatic type transition metal oxide. Wherein the octahedral transition metal oxide includes but is not limited to Na 0.95 Mn 0.33 Fe 0.33 Ni 0.33 O 2 . Prismatic transition metal oxides include, but are not limited to, na 2/3 Mg 1/4 Mn 3/4 O 2 。
Alternatively, the positive electrode active material may also include a positive electrode active material for sodium ion batteries, as known in the art. For example, the positive electrode active material may further include one or more of a polyanion-type compound and a prussian blue-type compound. As an example, the polyanionic compound may be a type of compound having sodium ions, transition metal ions, and tetrahedral anion units, for example, sodium iron phosphate (NaFePO 4 ) Sodium vanadium phosphate (Na) 3 V 2 (PO 4 ) 3 ) Etc. Prussian blue compounds may be a class of compounds having sodium ions, transition metal ions, and cyanide ions. However, the present application is not limited to these materials, and other materials that can be used as the positive electrode active material of the sodium ion battery may be used. These positive electrode active materials may be used alone or in combination of two or moreTwo or more materials are used in combination.
Optionally, the positive electrode film layer further optionally includes a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluoroacrylate resin.
Optionally, the positive electrode film layer includes a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
In some embodiments, the positive electrode sheet may be prepared by: dispersing the above components for preparing the positive electrode sheet, such as a positive electrode active material, a conductive agent, a binder and any other components, in a solvent (such as NMP) to form a positive electrode slurry; and (3) coating the positive electrode slurry on a positive electrode current collector, and obtaining a positive electrode plate after the procedures of drying, cold pressing and the like.
[ negative electrode sheet ]
The negative electrode tab typically includes a negative electrode current collector, or includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material.
In some embodiments, the sodium-ion battery is a sodium-metal battery, i.e., the negative electrode tab of the sodium-ion battery is a negative current collector. In other words, the negative current collector directly acts as the negative electrode tab of the battery, which type of sodium ion battery may also be referred to as a "non-negative battery". In the charging process, sodium ions separated from the positive pole piece are deposited on the negative pole current collector to form a sodium metal negative pole, wherein sodium metal is a negative pole active material in the sodium metal negative pole. In other embodiments, a conductive film layer may be provided on the negative current collector for normal use of the negative electrode tab or to facilitate deposition of sodium metal on the negative current collector.
As an example, the anode current collector has two surfaces opposing in its own thickness direction, and the anode film layer may be provided on either one or both of the two surfaces opposing the anode current collector.
Alternatively, the negative electrode current collector may employ a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
Alternatively, the negative active material may employ a negative active material for a sodium ion battery, which is well known in the art. For example, the anode active material may include at least one of the following materials: natural graphite, artificial graphite, mesophase micro carbon spheres (MCMB), hard carbon, and soft carbon. For another example, in a sodium metal battery, the anode active material may include at least one of the following materials: sodium metal, carbon-based materials or metals deposited with sodium metal, alloy materials, composite materials containing sodium metal, alloy materials containing sodium metal, and the like. However, the present application is not limited to these materials, and other materials that can be used as the negative electrode active material of the sodium ion battery may be used. These negative electrode active materials may be used alone, or two or more materials may be used in combination.
The above-described negative electrode tab may be prepared according to a conventional method in the art. For example, a copper foil or a copper foil having a conductive film layer provided on at least one surface of the copper foil may be used as the negative electrode tab. The conductive film layer may be disposed on at least one surface of the negative electrode current collector by physical vapor deposition (Physical Vapor Deposition, PVD), spin coating, electroplating, chemical vapor deposition (Chemical Vapor Deposition, CVD), or the like.
[ electrolyte ]
The electrolyte plays a role in ion conduction between the positive electrode plate and the negative electrode plate. The type of electrolyte is not particularly limited in this application, and may be selected according to the need. For example, the electrolyte may be liquid, gel, or all solid.
In some embodiments, the electrolyte is an electrolyte. The electrolyte includes an electrolyte salt and a solvent.
Optionally, the electrolyte salt comprises NaPF 6 、NaBCl 4 、NaSO 3 CF 3 Na (CH) 3 )C 6 H 4 SO 3 Etc.
Alternatively, the solvent comprises a carbonate or ether solvent. The carbonate solvents include cyclic Ethylene Carbonate (EC), propylene Carbonate (PC), fluoroethylene carbonate (FEC), chain dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), and the like; the ether solvent comprises ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, tetrahydrofuran, 1, 3-dioxane, etc.
Optionally, the electrolyte further optionally includes an additive. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives capable of improving certain properties of the battery, such as additives that improve the overcharge performance of the battery, additives that improve the high or low temperature performance of the battery, and the like.
[ spacer ]
In some embodiments, a separator is also included in the sodium ion battery. The kind of the separator is not particularly limited in the present application, and for example, the separator may be a separator film. The isolating film may be any known porous isolating film with excellent chemical and mechanical stability.
Optionally, the material of the isolating film may be at least one selected from glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. When the separator is a multilayer composite film, the materials of the respective layers may be the same or different, and are not particularly limited.
In some embodiments, the positive electrode tab, the negative electrode tab, and the separator may be manufactured into an electrode assembly through a winding process or a lamination process.
In some embodiments, the battery cell may include an outer package. The outer package may be used to encapsulate the electrode assembly and electrolyte described above.
In some embodiments, the exterior packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, or the like. The outer package of the battery cell may also be a pouch, such as a pouch-type pouch. The material of the flexible bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.
The shape of the battery cell is not particularly limited in this application, and may be cylindrical, square, or any other shape. For example, fig. 1 is a cell 100 of a sodium ion battery of square structure as one example.
Fig. 2 is a battery module 200 of a sodium ion battery as one example. Referring to fig. 2, in the battery module 200, a plurality of battery cells 100 may be sequentially arranged in the longitudinal direction of the battery module 200. Of course, the arrangement may be performed in any other way. The plurality of battery cells 100 may be further fixed by fasteners.
Alternatively, in one embodiment, the battery module 200 may further include a case having a receiving space in which the plurality of battery cells 100 are received.
Optionally, in one embodiment, the battery modules 200 may be further assembled into a sodium ion battery, and the number of the battery modules 200 contained in the sodium ion battery may be one or more, and a specific number may be selected by those skilled in the art according to the application and capacity of the battery.
Fig. 3 and 4 are sodium ion batteries 300 as one example. Referring to fig. 3 and 4, a battery case and a plurality of battery modules 200 disposed in the battery case may be included in the sodium ion battery 300. The battery case includes an upper case 301 and a lower case 302, the upper case 301 being capable of being covered with the lower case 302 and forming a closed space for accommodating the battery module 200. The plurality of battery modules 200 may be arranged in the battery case in any manner.
It should be appreciated that in other embodiments, the sodium-ion battery 300 described above is also referred to as a sodium-ion battery pack. The battery cell 100 may be first assembled into the battery module 200, and the sodium ion battery 300 is assembled from the battery module 200. The sodium ion battery 300 may be directly formed from the battery cells 100, and the intermediate form of the battery module 200 may be omitted.
In addition, the application also provides an electric device, which comprises at least one of the battery cell 100 of the sodium ion battery, the battery module 200 of the sodium ion battery or the sodium ion battery 300. The battery cell 100, the battery module 200, or the sodium ion battery 300 may be used as a power source of an electric device, or may be used as an energy storage unit of the electric device. The power utilization device may include, but is not limited to, mobile devices (e.g., cell phones, notebook computers, etc.), electric vehicles (e.g., electric only vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, and the like.
As the power consumption device, the number of the battery cells 100, the battery modules 200, or the sodium ion battery 300 may be selected according to the use requirements thereof.
As an example, an electric device. The electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle or the like. In order to meet the high power and high energy density requirements of the secondary battery by the power consumption device, the sodium ion battery 300 or the battery module 200 may be employed.
As another example, the device may be a cell phone, tablet computer, notebook computer, or the like. The device is generally required to be thin and lightweight, and may employ the battery cell 100 as a power source.
Hereinafter, embodiments of the present application are described. The embodiments described below are exemplary only for the purpose of illustrating the present application and are not to be construed as limiting the present application. The examples are not to be construed as limiting the specific techniques or conditions described in the literature in this field or as per the specifications of the product. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
Examples and comparative examples
Example 1
(1) Preparation of positive electrode plate
Octahedral transition metal oxide Na 0.95 Mn 0.33 Fe 0.33 Ni 0.33 O 2 Prismatic transition metal oxide Na 2/ 3 Mg 1/4 Mn 3/4 O 2 And (3) fully and uniformly stirring conductive carbon black (Super P) and a binder PVDF in a proper amount of NMP according to a mass ratio of 27:63:5:5 to form positive electrode slurry, coating the positive electrode slurry on a positive electrode current collector aluminum foil, and drying and cold pressing to obtain a positive electrode plate.
(2) Preparation of negative electrode plate
And uniformly mixing the anode active material hard carbon, the adhesive Styrene Butadiene Rubber (SBR) and the conductive carbon black in a proper amount of deionized water according to a mass ratio of 90:5:5 to form anode slurry, coating the anode slurry on an anode current collector copper foil, and drying and cold pressing to obtain an anode pole piece.
(3) Assembly of battery cells
Sequentially stacking the positive electrode plate, the glass fiber film and the negative electrode plate, winding to form an electrode assembly, loading the electrode assembly into a packaging shell, and adding NaPF with the concentration of 1 mol/L 6 And (3) packaging, forming, standing and the like the electrolyte to obtain the sodium metal battery.
In example 1, the charge cut-off voltage of the sodium ion battery: v (V) 1 =4.1V, discharge cut-off voltage: v (V) 2 =1.5V. On the positive electrode sheet of the sodium ion battery, the loading amount of the octahedral transition metal oxide is as follows: m is m 1 =1078.175 mm 2 Load of prismatic transition metal oxide/g: m is m 2 =462.075 mm 2 Load ratio/g: m is m 1 /m 2 =7/3. Wherein the octahedral transition metal oxide has an average volume particle diameter D V 50 1 =7μm, specific surface area BET 1 =1.5 m 2 /g; average volume particle diameter D of prismatic transition metal oxide V 50 2 =5 μm, specific surface area BET 2 =3 m 2 /g。
Example 2
The sodium ion battery of example 2 has a charge cutoff voltage V compared to example 1 1 =3.95 V。
Example 3
The sodium ion battery of example 3 has a charge cutoff voltage V compared to example 1 1 =4.15 V。
Example 4
Discharge cut-off voltage V of sodium ion Battery of example 4 compared to example 1 2 =1.8 V。
Example 5
Discharge cut-off voltage V of sodium ion Battery of example 5 compared to example 1 2 =2 V。
Example 6
In comparison with example 1, m on the positive electrode sheet of the sodium ion battery of example 6 1 =308.05 mm 2 /g，m 2 =1232.2 mm 2 /g，m 1 /m 2 =1/4。
Example 7
In comparison with example 1, m on the positive electrode sheet of the sodium ion battery of example 7 1 =770.125 mm 2 /g，m 2 =770.125 mm 2 /g，m 1 /m 2 =1。
Example 8
In comparison with example 1, m on the positive electrode sheet of the sodium ion battery of example 8 1 =154.025 mm 2 /g，m 2 =1386.225 mm 2 /g，m 1 /m 2 =1/9。
Example 9
In comparison with example 1, m on the positive electrode sheet of the sodium ion battery of example 9 1 =1386.225 mm 2 /g，m 2 =154.025 mm 2 /g，m 1 /m 2 =9。
Example 10
In the sodium ion battery of example 10, the positive electrode active material further includes Prussian blue compound Na as compared with example 1 2 Fe[Fe(CN) 6 ]. In this example, the octahedral overvoltage on the positive electrode sheet Loading m of transition metal oxide 1 =1078.175 mm 2 Load m of prismatic transition metal oxide 2 =308.05 mm 2 /g，Na 2 Fe[Fe(CN) 6 ]Load m of (2) 3 =154.025 mm 2 /g，m 1 /m 2 =7/2。
Example 11
In the positive electrode active material of the sodium-ion battery of example 11, D compared with example 1 V 50 1 =15 μm。
Example 12
In the positive electrode active material of the sodium-ion battery of example 12, D compared with example 1 V 50 1 =20 μm。
Example 13
In the positive electrode active material of the sodium-ion battery of example 13, D is as compared with example 1 V 50 1 =10 μm，D V 50 2 =7 μm。
Example 14
In the positive electrode active material of the sodium-ion battery of example 14, D compared with example 1 V 50 1 =10 μm，D V 50 2 =10 μm。
Example 15
In the positive electrode active material of the sodium-ion battery of example 15, compared with example 1, BET 1 =0.3 m 2 /g，BET 2 =5 m 2 /g。
Example 16
In the positive electrode active material of the sodium-ion battery of example 16, compared with example 1, BET 1 =2 m 2 /g，BET 2 =5 m 2 /g。
Example 17
In the positive electrode active material of the sodium-ion battery of example 17, compared with example 1, BET 1 =1.5 m 2 /g，BET 2 =2 m 2 /g。
Example 18
In the positive electrode active material of the sodium-ion battery of example 18, compared with example 1, BET 1 =1.5 m 2 /g，BET 2 =5 m 2 /g。
Example 19
In example 19, as compared with example 1, na was used 0.94 Mn 0.35 Ni 0.28 Fe 0.33 Cu 0.04 O 2 As octahedral transition metal oxide, na 2/3 [Ni 1/3 Mn 2/3 ]O 2 As a prismatic transition metal oxide.
Comparative example 1
In the sodium ion battery of comparative example 1, the positive electrode material includes only octahedral transition metal oxide Na as compared with example 1 0.95 Mn 0.33 Fe 0.33 Ni 0.33 O 2 。
Comparative example 2
Charge cutoff voltage of sodium ion battery in comparative example 2 compared to example 1: v (V) 1 =4.2 V。
Comparative example 3
Charge cutoff voltage of sodium ion battery in comparative example 3 compared to example 1: v (V) 1 =4.2V, and discharge cutoff voltage: v (V) 2 =1.3 V。
The sodium metal battery performance test results of examples 1-19 and comparative examples 1-3 are detailed in Table 2.
TABLE 1 product parameters for examples 1-19 and comparative examples 1-3
Figure SMS_1
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Figure SMS_2
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Figure SMS_3
In Table 1, V 1 Representing the charge cutoff voltage of the sodium ion battery; v (V) 2 Represents the discharge cut-off voltage of the sodium ion battery; m is m 1 Representing the loading capacity of octahedral transition metal oxide on the positive electrode plate of the sodium ion battery; m is m 2 Representing the positive pole piece of the sodium ion batteryA loading of prismatic transition metal oxide; d (D) V 50 1 Represents the average volume particle diameter of the octahedral transition metal oxide; d (D) V 50 2 Represents the average volume particle diameter of the prismatic transition metal oxide; BET (BET) 1 Represents the specific surface area of the octahedral transition metal oxide; BET (BET) 2 The specific surface area of the prismatic transition metal oxide is shown. It should be understood that the subscripts "1", "2" of the above characters are for distinction only and do not represent any other meaning.
The sodium metal battery performance test results of examples 1-19 and comparative examples 1-3 are detailed in Table 2.
Table 2 results of battery performance tests for different examples and comparative examples
Figure SMS_4
As can be seen from table 2, the energy density and cycle performance of the sodium ion batteries of all examples are superior to those of the comparative examples.
The parameters and properties of the examples and comparative examples were analyzed as follows in combination with tables 1 and 2.
As can be seen from a comparison of example 1 and comparative example 1, the positive electrode active material in example 1 was a positive electrode active material obtained by compounding an octahedral transition metal oxide and a prismatic transition metal oxide, whereas in comparative example 1 only an octahedral transition metal oxide was used as the positive electrode active material. The cycle performance of comparative example 1 is far inferior to that of example 1, and it is demonstrated that the octahedral transition metal oxide has a higher sodium content and can provide a certain energy density, but it alone cannot provide a support for long-term cycle as a positive electrode active material. Thus, it was demonstrated that the combination of the octahedral transition metal oxide and the prismatic transition metal oxide contributes to a sodium-ion battery having both high energy density and good cycle performance.
As can be seen from comparison of example 1 and comparative examples 2 to 3, the sodium ion battery in example 1 was controlled in the range of 3.95. 3.95V to 4.15. 4.15V in charge cutoff voltage, and exhibited high energy density and excellent cycle performance. While comparative examples 2 to 3 did not control the charge cutoff voltage within the above range, the energy density and cycle performance of the sodium ion battery were inferior to those of example 1, although the same positive electrode active material was used. Under the condition of compounding two transition metal oxides, the charge cut-off voltage of the sodium ion battery is controlled, so that the respective advantages of the two materials are brought into play, and the sodium ion battery has higher energy density and good cycle performance. The above effects cannot be achieved by compounding only two materials.
According to the data of examples 1 and 4-5, it is known that controlling the discharge cut-off voltage of the sodium ion battery has a significant effect on the cycle performance of the battery, on the basis of controlling the charge cut-off voltage.
According to the embodiments 6-9, under the condition that other conditions are the same, the loading amount of the octahedral transition metal oxide on the positive electrode plate is increased, so that the energy density of sodium ions is improved; the load of the prismatic transition metal oxide is increased, and the cycle performance of the sodium ion battery is improved. Thus, an appropriate voltage range can be set according to the loading of the octahedral transition metal oxide, or the ratio of the loading of the two transition metal oxides. So that the sodium ion battery has high energy density and good cycle performance.
Next, a method for testing physical and chemical parameters and performance parameters according to the embodiment of the present application will be described.
BET test method
Test methods reference standard GB/T19587-2004 determination of solid substance specific surface area by gas adsorption BET method.
Taking the sample to be measured 8 g-15 g, loading the sample into a sample tube, and recording the initial mass of the sample to be measured. The weighed sample to be tested is loaded into the apparatus NOVA2000 e. Then degassing is started, and the sample to be tested is heated to 200 o After C, 2 h is held. The mass of the sample to be tested after degassing is then recorded. The degassed sample to be tested is then reloaded into the apparatus and is poured into liquid nitrogen for the BET test. Setting nitrogen pressure at 0.08-0.12 MPa and heating temperature at 40% o C-350 o C. After the test is completed, the specific surface area is read from the test results.
2. Method for testing average volume particle size
The average volume particle size of the material can be tested using a malvern 2000 (MasterSizer 2000) laser particle sizer. Taking a proper amount of a sample to be detected (the concentration of the sample is ensured to be 8-12% of the shading degree), adding 20ml of deionized water, simultaneously exceeding 5 minutes (53 KHz/120W) to ensure that the sample is completely dispersed, and then measuring the sample according to the GB/T19077-2016/ISO 13320:2009 standard.
3. Method for testing battery energy density
At 25 o C. Under normal pressure, the sodium ion battery is charged to 3.65V at a constant current of 0.2C, then is charged to a current of less than or equal to 0.05C at a constant voltage of 3.65V, and then is kept stand for 5min, and the charging capacity at the moment, namely the primary charging capacity, is recorded; then, the discharge capacity was recorded by constant current discharge of 0.2. 0.2C until the voltage was 1.5. 1.5V or less. Energy density = discharge capacity/mass of active material. Wherein the active materials refer to a positive electrode active material and a negative electrode active material. The results of the sodium ion battery energy density tests of the examples and comparative examples of the present application are detailed in table 2.
4. Method for testing battery cycle performance
Under normal temperature, the battery charge-discharge voltage interval is kept to be 1.5V-4.15V, and the cycle number of the battery is reduced to 80% when the recording capacity retention rate is cycled under the current density of 1C. The results of the sodium ion battery cycle number test of the examples and comparative examples of the present application are detailed in table 2.
While the present application has been described with reference to a preferred embodiment, various modifications may be made and equivalents may be substituted for elements thereof without departing from the scope of the present application. In particular, the technical features mentioned in the respective embodiments may be combined in any manner as long as there is no structural conflict. The present application is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions falling within the scope of the claims.

Claims (14)

1. A battery cell of a sodium ion battery, characterized in that the battery cell comprises a positive electrode sheet comprising a positive electrode active material comprising an octahedral transition metal oxide and a prismatic transition metal oxide;
cut-off voltage V of charging of the sodium ion battery 1 The method meets the following conditions: 3.95 V is less than or equal to V 1 ≤4.15 V。
2. The battery cell according to claim 1, wherein the sodium ion battery has a discharge cut-off voltage V 2 The method meets the following conditions: 1.50 V is less than or equal to V 2 ≤2.00 V。
3. The battery cell of claim 1, wherein the sodium ion battery has a charge cutoff voltage V 1 Configured to be in accordance with the capacity m of the octahedral transition metal oxide on the positive electrode sheet 1 But is set.
4. The battery cell according to claim 3, wherein the loading m of the octahedral transition metal oxide 1 Satisfy 154.025 mm 2 /g≤m 1 ≤1386.225 mm 2 In the case of/g, the charge cut-off voltage V of the sodium-ion battery 1 The method meets the following conditions: 3.95 V is less than or equal to V 1 ≤4.15 V。
5. The battery cell according to claim 2, wherein the sodium ion battery has a discharge cut-off voltage V 2 Is configured to be according to the load m of the octahedral transition metal oxide on the positive electrode sheet 1 But is set.
6. The battery cell according to claim 5, wherein the loading m of the octahedral transition metal oxide 1 Satisfy 154.025 mm 2 /g≤m 1 ≤1386.225 mm 2 In the case of/g, the discharge cut-off voltage V of the sodium-ion battery 2 The method meets the following conditions: 1.5 V is less than or equal to V 2 ≤1.8 V。
7. The battery cell of claim 1, wherein the sodium ion battery has a charge cutoff voltage V 1 Configured to be based on a loading ratio m of the octahedral transition metal oxide and the prismatic transition metal oxide on the positive electrode sheet 1 /m 2 But is set.
8. The battery cell according to claim 7, wherein the loading ratio m of the octahedral transition metal oxide and the prismatic transition metal oxide 1 /m 2 Satisfy 1/9.ltoreq.m 1 /m 2 Under the condition of less than or equal to 9, the charge cut-off voltage V of the sodium ion battery 1 The method meets the following conditions: 3.95 V is less than or equal to V 1 ≤4.15 V。
9. The battery cell according to claim 2, wherein the sodium ion battery has a discharge cut-off voltage V 2 Is configured to be based on the loading ratio m of the octahedral transition metal oxide and the prismatic transition metal oxide on the positive electrode sheet 1 /m 2 But is set.
10. The battery cell according to claim 9, wherein the loading ratio m of the octahedral transition metal oxide and the prismatic transition metal oxide 1 /m 2 Satisfy 1/9.ltoreq.m 1 /m 2 At a discharge cut-off voltage V of 9 or less 2 The method meets the following conditions: 1.5 V is less than or equal to V 2 ≤1.8 V。
11. The battery cell according to any one of claims 1 to 10, wherein the octahedral transition metal oxide has an average volume particle diameter satisfying: 7. dv50 of μm or less 1 Less than or equal to 20 mu m; the average volume particle diameter of the prismatic transition metal oxide satisfies the following conditions: 5. dv50 of μm or less 2 ≤10 μm。
12. According to any one of claims 1 to 10The battery cell of any one of the claims, wherein the octahedral transition metal oxide has a specific surface area that satisfies: 0.3 m is m 2 /g≤BET 1 ≤2.0 m 2 /g; the specific surface area of the prismatic transition metal oxide satisfies: 2.0 m is m 2 /g≤BET 2 ≤5.0 m 2 /g。
13. A sodium ion battery, characterized in that it comprises a battery cell according to any one of claims 1-12.
14. An electrical device, characterized in that it comprises a battery cell according to any one of claims 1-12 and/or a sodium-ion battery according to claim 13.
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