Sodium metal batteries without negative electrodes, separators, and electrical devices

Abstract

This invention relates to the field of battery technology, and particularly to a sodium metal battery without a negative electrode, a separator, and an electrical device. The electrolyte of the sodium metal battery without a negative electrode of this application includes an ether solvent, and the separator includes a base membrane and a molecular sieve layer disposed on at least one side of the base membrane. The pore size of the molecular sieve is 0.45 nm to 0.55 nm, thus improving the cycle performance of the sodium metal battery without a negative electrode. According to simulation calculations, the size of the ether solvent molecular ion pair is smaller than the pore size of the molecular sieve. It can be inferred that the molecular sieve layer intercepts the ether solvent molecular ion pair, reducing the risk of gas generation from the reaction between the low LUMO energy level ether solvent and the sodium metal negative electrode.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a sodium metal battery without a negative electrode, a separator, and an electrical device. Background Technology

[0002] Sodium metal batteries without a negative electrode do not use a negative electrode material. In traditional batteries, an electrochemical reaction occurs between the negative electrode material (such as graphite, silicon carbide, etc.) and the positive electrode material to store or release electrical energy.

[0003] Sodium metal batteries without a negative electrode use foil as the negative electrode. During charging, sodium ions released from the positive electrode material shuttle to the negative electrode and are reduced to sodium metal, which is then deposited on the foil. However, due to the extremely high chemical reactivity of sodium metal, it undergoes side reactions with the electrolyte, affecting the battery's storage performance. Summary of the Invention

[0004] The main objective of this application is to provide a non-negative electrode sodium metal battery, which aims to improve the cycle performance of non-negative electrode sodium metal batteries.

[0005] To achieve the above objectives, this application proposes a sodium metal battery without a negative electrode, which includes a positive electrode, a negative electrode, an electrolyte, and a separator.

[0006] The electrolyte includes ether solvents;

[0007] The diaphragm includes a base membrane and a molecular sieve layer disposed on at least one side of the base membrane, the molecular sieve layer including a molecular sieve with a pore size of 0.45 nm to 0.55 nm.

[0008] The electrolyte of the non-anode sodium metal battery of this application includes an ether solvent, and the separator includes a base membrane and a molecular sieve layer disposed on at least one side of the base membrane. The pore size of the molecular sieve is 0.45 nm to 0.55 nm, thereby improving the cycle performance of the non-anode sodium metal battery.

[0009] Based on simulation calculations, the size of the ether solvent molecular ion pair is smaller than the pore size of the molecular sieve. It can be inferred that the molecular sieve layer intercepts the ether solvent molecular ion pair, reducing the risk of the ether solvent at the low LUMO energy level reacting with the sodium metal at the negative electrode to produce gas.

[0010] Optionally, the molecular sieve layer is disposed on the side of the base membrane facing the negative electrode sheet.

[0011] The molecular sieve layer is located on the side of the base membrane facing the negative electrode, which helps to improve the cycle performance of the sodium metal battery without a negative electrode.

[0012] The closer the molecular sieve layer is to the negative electrode, the smaller the distance between them. This results in fewer ether solvent molecular-ion pairs forming between the molecular sieve layer and the negative electrode, thus reducing the risk of reaction between the ether solvent in these pairs and the sodium metal at the negative electrode. Furthermore, the molecular sieve layer possesses a certain mechanical strength; placing it on the side of the negative electrode after the base membrane has expired can reduce the risk of sodium dendrites piercing the separator.

[0013] Optionally, the area of ​​one side of the molecular sieve layer is larger than the area of ​​one side of the negative electrode sheet;

[0014] The projection of one side surface of the negative electrode sheet is located in the molecular sieve layer.

[0015] The area of ​​one side of the molecular sieve layer refers to the area of ​​the molecular sieve layer facing the negative electrode plate, and the area of ​​the negative electrode plate refers to the area of ​​the negative electrode plate facing the molecular sieve layer. That is, the area of ​​the molecular sieve layer is greater than or equal to the area of ​​the negative electrode plate on the surfaces opposite each other. Furthermore, when the projection of the negative electrode plate's surface is located on the molecular sieve layer, it helps the molecular sieve layer to cover the negative electrode plate and improves the interception of large-sized ether solvent molecular ion pairs by the molecular sieve layer.

[0016] Optionally, the mass of the molecular sieve in the molecular sieve layer is 15 mg / 1540.25 mm. 2 Up to 25mg / 1540.25mm 2 .

[0017] The mass of the molecular sieve in the molecular sieve layer refers to the coating density of the molecular sieve on the base membrane surface, which can be considered as the mass of the molecular sieve per unit area of ​​the molecular sieve layer. Within the aforementioned coating density range, the battery cycle performance is better improved. This indicates that a higher molecular sieve coating density helps reduce the porosity of the molecular sieve layer formed by the accumulation of molecular sieve particles, improves the interception of ether solvent molecular ion pairs by the molecular sieve layer, and reduces the risk of gas generation from the reaction of low-LUMO energy level ether solvents with sodium metal at the negative electrode.

[0018] Optionally, the particle size D50 of the molecular sieve is 3 to 4 micrometers;

[0019] And / or, the thickness of the molecular sieve layer is 10 micrometers to 30 micrometers;

[0020] In one embodiment, the molecular sieve particle size meets the above-mentioned range, resulting in better battery cycle performance. Meeting the above-mentioned range helps reduce the porosity of the molecular sieve layer formed by the accumulation of molecular sieve particles, improving the interception of ether solvent molecular ion pairs by the molecular sieve layer and reducing the risk of gas generation from the reaction of low-LUMO energy level ether solvents with sodium metal at the negative electrode.

[0021] In one embodiment, the thickness of the molecular sieve layer is 10 to 30 micrometers. This helps to improve the interception of ether solvent molecular ion pairs by the molecular sieve layer while reducing internal resistance.

[0022] Optionally, the mass percentage of the ether solvent is 60% to 100% based on the total mass of the electrolyte;

[0023] And / or, the ether solvent includes at least one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol diethyl ether, and ethylene glycol dibutyl ether;

[0024] And / or, the molecular sieve structure includes M m O·xAl2O3·ySiO2, M includes monovalent cations and / or divalent cations, 1≤m≤2, 0<x≤0.3, 0<y≤0.3.

[0025] In one embodiment, the ether solvent accounts for 60% to 100% of the total electrolyte mass. Ether solvents exhibit good compatibility with sodium metal batteries without a negative electrode, and a 60% to 100% ether solvent mass ratio in the electrolyte results in more stable electrochemical performance. Ether solvents can react severely with sodium metal on the negative electrode side, producing gases such as H2, CO, alkenes, and alkanes. This solution employs a molecular sieve layer to intercept ether solvent molecular ion pairs, reducing the risk of gas generation from the reaction between the low-LUMO energy level ether solvent and the negative electrode sodium metal.

[0026] In one embodiment, the ether solvent includes at least one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol diethyl ether, and ethylene glycol dibutyl ether, and the molecular sieve layer helps to intercept solvent molecule ion pairs formed by these ether solvents.

[0027] In one embodiment, the molecular sieve structure includes M m O·xAl2O3·ySiO2, where M is an element including at least one of Na, K, Li, Ca, and Mg.

[0028] Optionally, the molecular sieve comprises Na2O·xAl2O3·ySiO2;

[0029] And / or, the positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, the positive electrode film layer including a positive electrode active material, the positive electrode active material including layered transition metal oxides and / or polyanionic phosphates.

[0030] In one embodiment, the molecular sieve comprises Na2O·xAl2O3·ySiO2, and the sodium-type molecular sieve can conduct sodium ions, thereby realizing the transport of sodium ions.

[0031] In one embodiment, the positive electrode active material comprises layered transition metal oxides and / or polyanionic phosphates.

[0032] Optionally, this application also provides a diaphragm, the diaphragm comprising a base membrane and a molecular sieve layer disposed on at least one side of the base membrane, the molecular sieve layer comprising a molecular sieve having a pore size of 0.45 nm to 0.55 nm.

[0033] Optionally, the mass of the molecular sieve in the molecular sieve layer is 15 mg / 1540.25 mm. 2 Up to 25mg / 1540.25mm 2 ;

[0034] And / or, the particle size D50 of the molecular sieve is 3 to 4 micrometers;

[0035] And / or, the thickness of the molecular sieve layer is 10 micrometers to 30 micrometers.

[0036] Optionally, this application also provides an electrical device comprising a negative electrode-free sodium metal battery as described above.

[0037] This application proposes a negative electrode-free sodium metal battery, comprising a positive electrode, a negative electrode, an electrolyte, and a separator. The electrolyte includes an ether solvent. The separator includes a base membrane and a molecular sieve layer disposed on at least one side of the base membrane. The molecular sieve layer comprises a molecular sieve with a pore size of 0.45 nm to 0.55 nm. The electrolyte in this negative electrode-free sodium metal battery, comprising an ether solvent, and the separator, comprising a base membrane and a molecular sieve layer disposed on at least one side of the base membrane with a pore size of 0.45 nm to 0.55 nm, improve the cycle performance of the negative electrode-free sodium metal battery. Based on simulation calculations, the size of the ether solvent molecular ion pair is smaller than the pore size of the molecular sieve. It can be inferred that the molecular sieve layer intercepts the ether solvent molecular ion pair, reducing the risk of gas generation from the reaction between the low LUMO energy level ether solvent and the negative electrode sodium metal. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0039] Figure 1 The diaphragm is an embodiment of this application;

[0040] Figure 2 The diaphragm and negative electrode sheet are embodiments of this application;

[0041] Figure 3 This is a schematic diagram of a battery cell according to one embodiment of this application;

[0042] Figure 4 yes Figure 3 An exploded view of a battery cell according to an embodiment of this application is shown.

[0043] Figure 5 This is a schematic diagram of a battery module according to one embodiment of this application;

[0044] Figure 6 This is a schematic diagram of a battery pack according to one embodiment of this application;

[0045] Figure 7 yes Figure 6 An exploded view of a battery pack according to one embodiment of this application is shown;

[0046] Figure 8 This is a schematic diagram of an electrical device in which a single battery cell is used as a power source according to one embodiment of this application.

[0047] Explanation of icon numbers:

[0048] 1 Battery pack 5 battery cell 2 Upper box 51 case 3 Lower box 52 Electrode assembly 4 Battery Module 53 cover plate 10 base membrane 30 Negative electrode sheet 20 Molecular sieve layer

[0049] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0050] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0051] The following detailed description, with appropriate reference to the accompanying drawings, discloses the negative electrode-free sodium metal battery, separator, and power supply device of this application. However, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0052] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0053] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0054] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0055] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0056] Conventional ether-based electrolytes react with sodium metal to produce gases such as H2, CO, alkenes, and alkanes. In sodium metal batteries without a negative electrode, this reaction causes battery degradation during cycle life.

[0057] To address the aforementioned issues, this application proposes a negative electrode-free sodium metal battery, comprising a positive electrode, a negative electrode, an electrolyte, and a separator; the electrolyte comprises an ether solvent; the separator comprises a base membrane and a molecular sieve layer disposed on at least one side of the base membrane, the molecular sieve layer comprising a molecular sieve with a pore size of 0.45 nm to 0.55 nm.

[0058] A negative electrode-less metal battery typically refers to a battery where no negative electrode active material layer is actively placed on the negative electrode side during the battery cell manufacturing process. For example, during the manufacturing of the battery cell, a metal layer or a carbonaceous active material layer is not formed at the negative electrode through coating or deposition processes. During the first charge, ions gain electrons on the negative electrode side and deposit on the surface of the negative electrode current collector to form a metallic phase. During discharge, the metal can transform into metal ions and return to the positive electrode, achieving cyclic charging and discharging. Compared to other battery cells, a negative electrode-less metal battery can achieve a higher energy density due to the absence of a negative electrode active material layer.

[0059] The electrolyte of the non-anode sodium metal battery of this application includes an ether solvent, and the separator includes a base membrane and a molecular sieve layer disposed on at least one side of the base membrane. The pore size of the molecular sieve is 0.45 nm to 0.55 nm, thereby improving the cycle performance of the non-anode sodium metal battery.

[0060] Based on simulation calculations, the size of the ether solvent molecular ion pair is smaller than the pore size of the molecular sieve. It can be inferred that the molecular sieve layer intercepts the ether solvent molecular ion pair, reducing the risk of the ether solvent at the low LUMO energy level reacting with the sodium metal at the negative electrode to produce gas.

[0061] like Figure 1 As shown, the diaphragm includes a base membrane 10 and a molecular sieve layer 20 disposed on one side of the base membrane 10.

[0062] The values ​​in the range of 0.45nm to 0.55nm include the minimum and maximum values ​​of this range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, as well as 0.45nm, 0.5nm, 0.55nm, etc., and the range values ​​between any two of the above point values.

[0063] Molecular sieves are a class of inorganic microporous crystalline materials with regular pore structures. For example, molecular sieves include aluminosilicates (e.g., Na2O·xAl2O3·ySiO2, 0<x≤0.3, 0<y≤0.3).

[0064] Testing methods for molecular sieves: Disassemble the battery, remove the separator, peel off the molecular sieve layer, scrape off the material of the molecular sieve layer, and use infrared spectroscopy to test the characteristic absorption peaks of the molecular sieve, or use XRD to test the characteristic diffraction peaks of the molecular sieve, to confirm that the molecular sieve layer contains molecular sieves.

[0065] The steps for testing the pore size of molecular sieves are as follows: First, the molecular sieve sample needs to be degassed, usually by heating it under vacuum at 300°C for 6 hours to remove the physically adsorbed substances on the surface.

[0066] Adsorption experiments: Nitrogen adsorption-desorption experiments were conducted using a surface area and pore size analyzer, such as the V-sorb X800TP series from QuantumCTek. This typically involves measuring the amount of water vapor adsorbed by the molecular sieve at different pressures at liquid nitrogen temperature (approximately -196°C).

[0067] Data analysis: By using adsorption-desorption isotherms and specific analytical methods (such as the BET equation, t-plot method, or SF model) to calculate specific surface area and pore size distribution, the pore size and distribution of the molecular sieve can be determined.

[0068] In one embodiment, the molecular sieve layer is disposed on the side of the base membrane facing the negative electrode sheet.

[0069] The molecular sieve layer is located on the side of the base membrane facing the negative electrode, which helps to improve the cycle performance of the sodium metal battery without a negative electrode.

[0070] The closer the molecular sieve layer is to the negative electrode, the smaller the distance between the molecular sieve layer and the negative electrode, and the fewer ether solvent molecular ion pairs are formed between the molecular sieve layer and the negative electrode. This reduces the risk of ether solvent in the molecular ion pairs between the molecular sieve layer and the negative electrode reacting with the sodium metal of the negative electrode. In addition, the molecular sieve layer has a certain mechanical strength, and placing it on one side of the negative electrode after the base membrane expires can reduce the risk of sodium dendrites piercing the separator.

[0071] In one embodiment, the area of ​​one side of the molecular sieve layer is larger than the area of ​​the other side of the negative electrode sheet; the projection of the surface of the negative electrode sheet is located in the molecular sieve layer.

[0072] The area of ​​one side of the molecular sieve layer refers to the area of ​​the molecular sieve layer facing the negative electrode plate, and the area of ​​the negative electrode plate refers to the area of ​​the negative electrode plate facing the molecular sieve layer. That is, the area of ​​the molecular sieve layer is greater than or equal to the area of ​​the negative electrode plate on the surfaces opposite each other. Furthermore, when the projection of the negative electrode plate's surface is located on the molecular sieve layer, it helps the molecular sieve layer to cover the negative electrode plate and improves the interception of large-sized ether solvent molecular ion pairs by the molecular sieve layer.

[0073] like Figure 2 As shown, a molecular sieve layer 20 is provided on the side of the diaphragm facing the negative electrode 30, and the area of ​​the molecular sieve layer 20 side is larger than the area of ​​the negative electrode 30 side.

[0074] In one embodiment, the mass of the molecular sieve in the molecular sieve layer is 15 mg / 1540.25 mm. 2 Up to 25mg / 1540.25mm2 .

[0075] The mass of the molecular sieve in the molecular sieve layer refers to the coating density of the molecular sieve on the base membrane surface, which can be considered as the mass of the molecular sieve per unit area of ​​the molecular sieve layer. Within the aforementioned coating density range, the battery cycle performance is better improved. This indicates that a higher molecular sieve coating density helps reduce the porosity of the molecular sieve layer formed by the accumulation of molecular sieve particles, improves the interception of ether solvent molecular ion pairs by the molecular sieve layer, and reduces the risk of gas generation from the reaction of low-LUMO energy level ether solvents with sodium metal at the negative electrode.

[0076] Method for testing the mass of molecular sieve in molecular sieve layer: Disassemble the battery, remove the separator, test the area S0 of molecular sieve layer, soak the separator in organic solvent to dissolve the base membrane material, obtain the remaining molecular sieve solid component, and measure its mass as M0. The formula for calculating the mass of molecular sieve in molecular sieve layer is M0 / S0.

[0077] The above 15mg / 1540.25mm 2 Up to 25mg / 1540.25mm 2 In this context, the values ​​include the minimum and maximum values ​​within the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments and 15mg / 1540.25mm. 2 20mg / 1540.25mm 2 25mg / 1540.25mm 2 And so on, as well as the range of values ​​between any two of the above point values.

[0078] In one embodiment, the particle size D50 of the molecular sieve is 3 to 4 micrometers. When the particle size of the molecular sieve meets the above range, the cycle performance of the battery is significantly improved. Meeting the above particle size range helps reduce the porosity of the molecular sieve layer formed by the accumulation of molecular sieve particles, improving the interception of ether solvent molecular ion pairs by the molecular sieve layer and reducing the risk of gas generation from the reaction of low-LUMO energy level ether solvents with sodium metal at the negative electrode.

[0079] D50 is the particle size at which the cumulative particle size distribution percentage of a sample reaches 50%. Physically, it means that 50% of the particles are larger than D50, and 50% are smaller than D50.

[0080] The values ​​in the range of 3 micrometers to 4 micrometers include the minimum and maximum values ​​of this range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, as well as 3 micrometers, 3.5 micrometers, 4 micrometers, etc., and the range values ​​between any two of the above point values.

[0081] Methods for testing the particle size of molecular sieves: Molecular sieves are obtained using the methods described above. The sample is then irradiated with a laser using laser diffraction, and the particle size and distribution are calculated by measuring the intensity distribution of the scattered light.

[0082] Equipment Model: Malvern 2000 (MasterSizer 2000) laser particle size analyzer; Reference Standard Procedure: GB / T19077-2016 / ISO 13320:2009; Specific Test Procedure: Take an appropriate amount of the sample to be tested (the sample concentration should be 8-12% opacity), add 20ml of deionized water, and simultaneously incubate for 5 minutes (53KHz / 120W) to ensure complete dispersion of the sample. Then, measure the sample according to the GB / T19077-2016 / ISO 13320:2009 standard.

[0083] In one embodiment, the thickness of the molecular sieve layer is 10 to 30 micrometers. This helps to improve the interception of ether solvent molecular ion pairs by the molecular sieve layer.

[0084] The thickness of the molecular sieve layer can be measured using a micrometer.

[0085] The values ​​in the range of 10 micrometers to 30 micrometers include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, as well as 10 micrometers, 15 micrometers, 20 micrometers, 25 micrometers, 30 micrometers, etc., and the range values ​​between any two of the above point values.

[0086] In one embodiment, the mass percentage of ether solvent is 60% to 100% of the total electrolyte mass. This 60% to 100% mass percentage of ether solvent indicates good compatibility with sodium metal batteries without a negative electrode, and also contributes to more stable electrochemical performance. Ether solvents can react severely with sodium metal on the negative electrode side, producing gases such as H2, CO, alkenes, and alkanes. This solution employs a molecular sieve layer to intercept ether solvent molecular ion pairs, reducing the risk of gas generation from the reaction between the low-LUMO energy level ether solvent and the sodium metal on the negative electrode.

[0087] Method for determining the mass percentage of ether solvents in electrolyte: Disassemble the battery, remove the electrolyte, dilute the electrolyte to prepare a sample, inject the sample into GC-MS for analysis, obtain a mass spectrum, and confirm the composition of each component based on the mass spectrum and corresponding spectral library search results, confirming the presence of ether solvents in the electrolyte. Prepare standard solutions of different concentration gradients of the target ether solvent. Using the electrolyte as the sample, analyze both the standard solutions and the sample using GC-MS, and calculate the mass of the target substance in the sample based on the standard curve to obtain the concentration of the target substance.

[0088] In one embodiment, the ether solvent includes at least one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol diethyl ether, and ethylene glycol dibutyl ether; the molecular sieve layer helps to intercept solvent molecule ion pairs formed by these ether solvents.

[0089] In one embodiment, the molecular sieve structure includes M m O·xAl2O3·ySiO2, M includes monovalent cations and / or divalent cations, 1≤m≤2, 0<x≤0.3, 0<y≤0.3, and the element M includes at least one of Na, K, Li, Ca, and Mg.

[0090] In one embodiment, the molecular sieve comprises Na2O·xAl2O3·ySiO2; the sodium-type molecular sieve can conduct sodium ions, thereby realizing the transport of sodium ions.

[0091] In one embodiment, the positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector. The positive electrode film layer includes a positive electrode active material, which includes layered transition metal oxides and / or polyanionic phosphates. The chemical formula of the layered transition metal oxide includes NaM1O2 (M1 is a transition metal atom, including one or a combination of elements such as Ti, V, Cr, Mn, Fe, Co, Ni, and Cu, such as NaNi). 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, NaNi 0.20 Fe 0.22 Cu 0.13 Mn 0.45 O2); the chemical formula of polyanionic phosphates includes Na x1 R y1 P m1 O n1 (where 2.5≤x1≤4.5, 1.5≤y1≤3.5, 2.5<m1<4.5, 11.5≤n1≤15.5, and R includes at least one of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Cr, Nb, Mo, In, Ga, Sn, Hf, Ta, W, and Pb), such as Na4Mn3(PO4)2P2O7 and Na3V2(PO4)3.

[0092] In one embodiment, this application also provides a diaphragm, the diaphragm including a base membrane and a molecular sieve layer disposed on at least one side of the base membrane, the molecular sieve layer including a molecular sieve with a pore size of 0.45 nm to 0.55 nm.

[0093] In one embodiment, the mass of the molecular sieve in the molecular sieve layer is 15 mg / 1540.25 mm.2 Up to 25mg / 1540.25mm 2 .

[0094] In one embodiment, the particle size D50 of the molecular sieve is 3 to 4 micrometers.

[0095] In one embodiment, the thickness of the molecular sieve layer is 10 micrometers to 30 micrometers.

[0096] In one embodiment, this application also provides an electrical device, which includes the above-described negative electrode-free sodium metal battery.

[0097] In addition, the following description of the battery (cell battery, battery module, battery pack) and electrical device of this application will be made with appropriate reference to the accompanying drawings.

[0098] In one embodiment of this application, a battery cell is provided.

[0099] Typically, a battery cell includes a positive electrode, a negative electrode, an electrolyte, and a separator. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through. The separator described above is the improved separator of this application.

[0100] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector.

[0101] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0102] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0103] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0104] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0105] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0106] The negative electrode includes the negative current collector.

[0107] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0108] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not specify any particular type of electrolyte; it can be selected according to requirements.

[0109] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0110] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0111] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0112] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0113] In some embodiments, the outer packaging of the battery cell can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the battery cell can also be a flexible package, such as a pouch. The material of the flexible package can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0114] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 3 The example shown is a square-structured battery cell 5.

[0115] In some implementations, refer to Figure 4 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in a single battery cell 5 may be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0116] In some implementations, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0117] Figure 5 This is battery module 4, used as an example. (See reference...) Figure 5 In battery module 4, multiple battery cells 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0118] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0119] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0120] Figure 6 and Figure 7 This is battery pack 1 as an example. (See reference...) Figure 6 and Figure 7The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0121] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0122] As an electrical device, you can choose individual battery cells, battery modules, or battery packs according to your usage requirements.

[0123] Figure 8 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of individual battery cells, a battery pack or battery module can be used.

[0124] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0125] Example

[0126] Example 1

[0127] Molecular sieve pretreatment: The molecular sieve (Na-type molecular sieve with a pore size of 0.5 nm) is processed by a planetary ball mill. After ball milling, the powder is heated in a muffle furnace at 300°C for 24 hours to remove the adsorbed moisture in the molecular sieve. The particle size of the molecular sieve, D50, is 3 micrometers.

[0128] Membrane: Using a polypropylene membrane as the base membrane (12 μm thick), 95 wt% of the above-mentioned molecular sieve was mixed with 5 wt% of polyvinylidene fluoride (PVDF) binder, and then N-methylpyrrolidone was added and stirred to disperse, forming a molecular sieve slurry. The slurry was uniformly coated on one side of the base membrane and then dried in a vacuum oven at 100°C for 24 hours. A pressure of 10 tons was used to eliminate voids between particles. The final molecular sieve layer thickness was 10 micrometers.

[0129] Positive electrode sheet: 98wt% of positive electrode active material (sodium iron pyrophosphate with a particle size D50 of 4μm), 1wt% conductive carbon black (Super-P), and 1wt% binder polyvinylidene fluoride are mixed, then N-methylpyrrolidone is added and stirred to disperse, forming a positive electrode slurry. After stirring, the viscosity of the prepared oil-based slurry is adjusted to 30000-50000 mPa·s. The prepared slurry does not separate into layers. A double-sided coating device is used to coat one side of the positive electrode slurry with a weight of 200mg / 1540.25mm. 2 The coating is applied to Al foil, and after double-sided coating, it is dried, cold-pressed, slit, and the positive electrode sheet is obtained.

[0130] Negative electrode sheet: Weigh 5g of CMC and stir to dissolve in 1000mL of water, then add 5g of single-walled carbon nanotubes, and prepare a slurry after ultrasonic dispersion. Then coat the slurry onto the surface of copper foil, and then transfer it to a vacuum drying oven for complete drying. After that, slit and die-cut to prepare a negative electrode sheet without a negative electrode structure.

[0131] Electrolyte: In an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), ethylene glycol dimethyl ether (DME) is used as the solvent, and a certain amount of sodium hexafluorophosphate is dissolved in the above mixed solvent. The concentration of sodium hexafluorophosphate is controlled at 1mol / L. The mixture is stirred evenly to form the final electrolyte.

[0132] Assembly: The positive electrode, separator (with the molecular sieve layer facing the negative electrode), and negative electrode are assembled in sequence. The separator acts as a separator between the positive and negative electrodes. Tabs are welded to the bare cell, and the bare cell is placed in an aluminum casing. It is then baked at 100°C to remove water, followed by the injection of the electrolyte and sealing, resulting in a non-charged battery. The non-charged battery then undergoes a series of processes including settling, hot and cold pressing, formation, shaping, and capacity testing to obtain a sodium-free negative electrode secondary battery product.

[0133] Example 2, Example 4, Example 5

[0134] Based on Example 1, the thickness of the molecular sieve layer was adjusted.

[0135] Example 3

[0136] Based on Example 1, the thickness of the molecular sieve layer and the solvent of the electrolyte were adjusted (ethylene glycol dimethyl ether (DME) was replaced with a mixture of ethylene glycol dimethyl ether (DME) and ethylene glycol diethyl ether (DEE).

[0137] Example 6

[0138] Based on Example 1, the thickness of the molecular sieve layer was adjusted so that the molecular sieve layer of the diaphragm was positioned facing the positive electrode.

[0139] Example 7

[0140] Based on Example 1, molecular sieve layers are provided on both sides of the diaphragm.

[0141] Examples 8 and 9

[0142] Based on Example 1, the type of positive electrode active material was adjusted, as well as the type of ether solvent or the thickness of the molecular sieve layer.

[0143] Example 10, Example 11

[0144] Based on Example 1, the pore size of the molecular sieve was adjusted.

[0145] Comparative Example 1

[0146] Based on Example 1, the diaphragm does not have a molecular sieve layer.

[0147] Comparative Example 2

[0148] Based on Example 8, the diaphragm does not have a molecular sieve layer.

[0149] Cyclic performance test

[0150] The cycle performance test process is as follows: At 25℃, the prepared battery was left to stand for 30 minutes, then charged to 3.65V with a constant current of 0.33C, and then charged to 0.05C with a constant voltage of 3.65V. After standing for 1 hour, it was discharged to 1.5V with a constant current of 0.33C to obtain the initial capacity (C0). After standing for 1 hour, it was charged to 3.65V with a constant current of 0.33C again, and then charged to 0.05C with a constant voltage of 3.65V. After standing for 1 hour, it was discharged to 1.5V with a constant current of 0.33C to obtain the process capacity (C1). The above steps were repeated for the same battery, and the number of cycles N when the cycle capacity decayed to 80% was recorded.

[0151] Storage gas production volume test

[0152] Before capacity testing, the cell volume (V1) was measured at 25°C using the water displacement method. The battery was charged at 25°C with a constant current of 0.2C to 3.65V, then charged at a constant voltage of 3.65V until the current dropped to 0.05C, and then discharged at a constant current of 0.2C to 1.5V, yielding the discharge capacity before storage (Cd1). This battery was then charged again with a constant current of 0.2C to 3.65V, followed by a constant voltage charge at 3.65V until the current dropped to 0.05C. The battery was then stored in a 60°C constant temperature chamber for 30 days. After removal, the cell volume (V2) was measured at 25°C, and the gas production of the sodium-ion battery was calculated using the following formula:

[0153] Gas production = [Cell volume after storage (V2) - Cell volume before storage (V1)] / Cell capacity (Cd1).

[0154] Table 1. List of Experimental Data

[0155]

[0156]

[0157] In Table 1, with the same positive electrode active material, the positive electrode material includes Na4Fe3(PO4)2(P2O7). The batteries in Examples 1 to 7, 10, and 11 have lower gas production than Comparative Example 1, while the batteries in Examples 1 to 7, 10, and 11 have higher cycle counts than Comparative Example 1. The positive electrode material includes NaNi. 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, the performance of Examples 8 and 9 is better than that of Comparative Example 2. Comparing Examples 3 and 6, the performance of the molecular sieve layer facing the negative electrode is better than that of the layer facing the positive electrode. Comparing Examples 3 and 7, the performance of the molecular sieve layer facing the negative electrode is better than that of the layer on both sides of the base membrane.

[0158] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A sodium metal battery without a negative electrode, characterized in that, The negative electrode-free sodium metal battery includes a positive electrode, a negative electrode, an electrolyte, and a separator; The electrolyte includes ether solvents; The diaphragm includes a base membrane and a molecular sieve layer disposed on at least one side of the base membrane. The molecular sieve layer includes a molecular sieve with a pore size of 0.45 nm to 0.55 nm and a thickness of 10 micrometers to 30 micrometers. The molecular sieve layer is disposed on the side of the base membrane facing the negative electrode sheet.

2. The sodium metal battery without a negative electrode as described in claim 1, characterized in that, The area of ​​one side surface of the molecular sieve layer is larger than the area of ​​one side surface of the negative electrode sheet; The projection of one side surface of the negative electrode sheet is located in the molecular sieve layer.

3. The sodium metal battery without a negative electrode as described in claim 1 or 2, characterized in that, The molecular sieve in the molecular sieve layer has a mass of 15 mg / 1540.25 mm. 2 Up to 25mg / 1540.25mm 2 .

4. The sodium metal battery without a negative electrode as described in claim 1 or 2, characterized in that, The molecular sieve has a particle size D50 of 3 to 4 micrometers.

5. The sodium metal battery without a negative electrode as described in claim 1 or 2, characterized in that, The ether solvent comprises 60% to 100% of the total mass of the electrolyte. And / or, the ether solvent includes at least one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol diethyl ether, and ethylene glycol dibutyl ether; And / or, the molecular sieve structure includes M m O·xAl2O3·ySiO2, M includes monovalent cations and / or divalent cations, 1≤m≤2, 0<x≤0.3, 0<y≤0.

3.

6. The sodium metal battery without a negative electrode as described in claim 1 or 2, characterized in that, The molecular sieve comprises Na2O·xAl2O3·ySiO2, where 0 < x ≤ 0.3 and 0 < y ≤ 0.

3. And / or, the positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, the positive electrode film layer including a positive electrode active material, the positive electrode active material including layered transition metal oxides and / or polyanionic phosphates.

7. An electrical device, characterized in that, The electrical device includes a non-negative electrode sodium metal battery as described in any one of claims 1 to 6.

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