Negative-electrode-free sodium metal battery, diaphragm and electric device

Abstract

The invention relates to the technical field of batteries, in particular to a negative-electrode-free sodium metal battery, a diaphragm and an electric device. The electrolyte of the negative-electrode-free sodium metal battery comprises the ether solvent, the diaphragm comprises the base membrane and the molecular sieve layer arranged on at least one side of the base membrane, the pore diameter of the molecular sieve is 0.45 nm to 0.55 nm, and the cycle performance of the negative-electrode-free sodium metal battery is improved. According to simulation calculation, the size of an ether solvent molecular ion pair is smaller than the aperture of the molecular sieve, the molecular sieve layer can be speculated to intercept the ether solvent molecular ion pair, and the risk of gas production by reaction of an ether solvent with a low LUMO energy level in the ether solvent molecular ion pair and negative electrode sodium metal is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a sodium metal battery without negative electrode, a separator and an electric device. BACKGROUND

[0002] The sodium metal battery without negative electrode does not use negative electrode materials. In a conventional battery, an electrochemical reaction occurs between the negative electrode material (such as graphite, silicon-carbon, etc.) and the positive electrode material to store or release electrical energy.

[0003] The sodium metal battery without negative electrode uses a foil as the negative electrode. During the charging process, sodium ions released from the positive electrode material shuttle to the negative electrode and are reduced to sodium metal to be deposited on the foil. Since sodium metal has extremely high chemical activity, it will react with the electrolyte, affecting the storage performance of the battery. SUMMARY

[0004] The main purpose of the present application is to provide a sodium metal battery without negative electrode, aiming to improve the cycle performance of the sodium metal battery without negative electrode.

[0005] To achieve the above purpose, the present application provides a sodium metal battery without negative electrode, which comprises a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator.

[0006] The electrolyte comprises an ether solvent.

[0007] The separator comprises a base film and a molecular sieve layer arranged on at least one side of the base film, the molecular sieve layer comprising a molecular sieve, and the pore size of the molecular sieve being 0.45-0.55 nm.

[0008] The electrolyte of the sodium metal battery without negative electrode of the present application comprises an ether solvent, the separator comprises a base film and a molecular sieve layer arranged on at least one side of the base film, and the pore size of the molecular sieve is 0.45-0.55 nm. The cycle performance of the sodium metal battery without negative electrode is improved.

[0009] According to the simulation calculation, 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 reaction between the ether solvent with low LUMO energy level in the ether solvent molecular ion pair and the negative sodium metal to produce gas.

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

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

[0012] The closer the molecular sieve layer is to the negative electrode sheet, the smaller the distance between the molecular sieve layer and the negative electrode sheet, and the fewer the number of ether solvent molecular ion pairs formed between the molecular sieve layer and the negative electrode sheet, thereby reducing the risk of reaction between the ether solvent in the ether solvent molecular ion pair and the negative electrode sodium metal.

[0013] Optionally, the area of one side of the molecular sieve layer is greater than the area of one side of the negative electrode sheet.

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

[0015] The area of one side of the molecular sieve layer refers to the area of the side of the molecular sieve layer facing the negative electrode sheet, and the area of one side of the negative electrode sheet refers to the area of the side of the negative electrode sheet facing the molecular sieve layer, i.e., the surface opposite the molecular sieve layer and the negative electrode sheet. The area of the molecular sieve layer is greater than or equal to the area of the negative electrode sheet, and when the projection of the surface of one side of the negative electrode sheet is located on the molecular sieve layer, it helps the molecular sieve layer to cover the negative electrode sheet and improve the interception of the molecular sieve layer for large-size ether solvent molecular ion pairs.

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

[0017] The mass of the molecular sieve in the molecular sieve layer refers to the coating density of the molecular sieve on the surface of the base film, which can be considered as the mass of the molecular sieve per unit area in the molecular sieve layer. The coating density of the molecular sieve is in the above range, and the battery cycle performance is improved. It is shown that a higher coating density of the molecular sieve helps to reduce the voids of the molecular sieve layer formed by the accumulation of molecular sieve particles, improve the interception of the molecular sieve layer for ether solvent molecular ion pairs, and reduce the risk of reaction between ether solvents with low LUMO energy levels in the ether solvent molecular ion pairs and the negative electrode sodium metal.

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

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

[0020] In an embodiment, the particle size of the molecular sieve meets the above range, and the cycle performance of the battery is improved. The particle size of the molecular sieve meets the above range, which helps to reduce the voids of the molecular sieve layer formed by the accumulation of molecular sieve particles, improve the interception of the molecular sieve layer for ether solvent molecular ion pairs, and reduce the risk of reaction between ether solvents with low LUMO energy levels in the ether solvent molecular ion pairs and the negative electrode sodium metal.

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

[0022] Optionally, the mass percentage of the ether solvent in the total mass of the electrolyte is 60% to 100%.

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

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

[0025] In an embodiment, the mass percentage of the ether solvent in the total mass of the electrolyte is 60% to 100%, and the ether solvent has good compatibility with the negative electrode-free sodium metal battery. The mass percentage of the ether solvent in the electrolyte is 60% to 100%, and the electrochemical performance of the battery is more stable. The ether solvent will react seriously with the sodium metal on the negative electrode side to produce H2, CO, olefins and alkanes, etc. The present application uses a molecular sieve layer to intercept the ether solvent molecule ion pair, reducing the risk of gas production by the ether solvent with low LUMO energy level in the ether solvent molecule ion pair reacting with the negative electrode sodium metal.

[0026] In an embodiment, the ether solvent includes at least one of dimethyl ether of ethylene glycol, diethyl glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethyl ether of ethylene glycol, dibutyl ether of ethylene glycol. The above-mentioned molecular sieve layer helps to intercept the solvent molecule ion pair formed by these ether solvents.

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

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

[0029] And / or, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector, the positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes a layered transition metal oxide and / or a polyanion phosphate.

[0030] In an embodiment, the molecular sieve includes Na2O·xAl2O3·ySiO2, and the sodium-type molecular sieve can conduct sodium ions to achieve the transmission of sodium ions.

[0031] In an embodiment, the positive active material comprises a layered transition metal oxide and / or a polyanionic phosphate.

[0032] Optionally, the application further provides a separator, the separator comprising a base film and a molecular sieve layer provided on at least one side of the base film, the molecular sieve layer comprising a molecular sieve, the 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 / 15 40.25 mm 2 to 25 mg / 15 40.25 mm 2 ;

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

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

[0036] Optionally, the application further provides a power utilization device, the power utilization device comprising the negative electrode-free sodium metal battery as described.

[0037] The negative electrode-free sodium metal battery provided by the application comprises a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator; the electrolyte comprises an ether solvent; the separator comprises a base film and a molecular sieve layer provided on at least one side of the base film, the molecular sieve layer comprising a molecular sieve, the molecular sieve having a pore size of 0.45 nm to 0.55 nm. The electrolyte of the negative electrode-free sodium metal battery of the application comprises an ether solvent, the separator comprises a base film and a molecular sieve layer provided on at least one side of the base film, and the molecular sieve has a pore size of 0.45 nm to 0.55 nm. The cycle performance of the negative electrode-free sodium metal battery is improved. According to simulation calculation, 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 reaction of the ether solvent with low LUMO energy level in the ether solvent molecular ion pair and the negative electrode sodium metal to produce gas. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained according to the structures shown in the drawings without creative labor for those skilled in the art.

[0039] FIG. 1 The separator of an embodiment of the application;

[0040] FIG. 2 The separator and the negative electrode sheet of an embodiment of the application;

[0041] FIG. 3 is a schematic view of a battery cell according to an embodiment of the present application;

[0042] FIG. 4 is a schematic view of a battery module according to an embodiment of the present application; FIG. 3 is an exploded view of a battery cell according to an embodiment of the present application;

[0043] FIG. 5 is a schematic view of a battery module according to an embodiment of the present application;

[0044] FIG. 6 is a schematic view of a battery pack according to an embodiment of the present application;

[0045] FIG. 7 is an exploded view of a battery pack according to an embodiment of the present application; FIG. 6

[0046] is a schematic view of an electric device using a battery cell according to an embodiment of the present application as a power source. FIG. 8 BRIEF DESCRIPTION OF DRAWINGS

[0047]

[0048] Reference Signs Name Reference Signs Name 1 Battery pack 5 Battery cell 2 Upper case 51 Housing 3 Lower case 52 Electrode assembly 4 Battery module 53 Cover plate 10 Base film 30 Negative electrode sheet 20 Molecular sieve layer

[0049] The object, features and advantages of the present application will become more apparent from the following detailed description made with reference to the accompanying drawings. DETAILED DESCRIPTION

[0050] The technical solutions in the embodiments of the present application will be apparently and completely described with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0051] Hereinafter, the anode-free sodium metal battery, the separator and the electric device according to the present application are specifically disclosed with appropriate reference to the drawings. However, there are cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of matters well known in the art, repeated descriptions of substantially the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0052] ​The ranges disclosed herein are intended to be "open" ranges, i.e., the upper and lower limits of the range are not included. The ranges are also intended to include any and all sub-ranges of the same, wherein each sub-range is inclusive of the end values. For example, if a range is from 1 to 10, then the range includes any and all sub-ranges between (and including) the minimum of 1 and the maximum of 10, that is, any of 1 to 3, 4 to 6, 7 to 9, and 10 to 10, etc. Also, it is specifically intended that the minimum and maximum values of the ranges are included in the ranges. For example, if a parameter is from 1 to 5, it is intended that the parameter can be the minimum of 1 and the maximum of 5, and any and all sub-ranges between (and including) the minimum of 1 and the maximum of 5, e.g., 1 to 3, 4 to 5, and 3 to 5, etc.

[0053] All embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, if not specifically stated otherwise.

[0054] All technical features and optional technical features of the present application can be combined with each other to form new technical solutions, if not specifically stated otherwise.

[0055] All steps of the present application can be performed in sequence or randomly, preferably in sequence, if not specifically stated otherwise. For example, the method comprises steps (a) and (b) means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method can further comprise step (c) means that step (c) can be added to the method in any sequence, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0056] The conventional ether-based electrolyte reacts with sodium metal to produce H2, CO, olefins and alkanes, etc. In the negative electrode-free sodium metal battery, the above reaction will cause the cycle decay of the battery.

[0057] To solve the above problems, the application provides a negative electrode-free sodium metal battery, which comprises a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator; the electrolyte comprises an ether solvent; the separator comprises a base film and a molecular sieve layer arranged on at least one side of the base film, and the molecular sieve layer comprises a molecular sieve with a pore size of 0.45-0.55 nm.

[0058] The negative electrode-free metal battery generally refers to that no negative active material layer is actively arranged on the negative electrode side during the manufacturing process of the battery, for example, no metal layer is arranged on the negative electrode by coating or deposition or other processes during the manufacturing process of the battery cell to form a negative active material layer from a carbon active material layer. During the first charging, ions obtain electrons on the negative electrode side and deposit on the surface of the negative electrode current collector to form a metal phase, and during the discharging, the metal can be converted into metal ions to return to the positive electrode to realize the cyclic charging and discharging. Compared with other battery cells, the negative electrode-free metal battery has no negative active material layer, and thus a higher energy density can be obtained.

[0059] The electrolyte of the negative electrode-free sodium metal battery of the application comprises an ether solvent, the separator comprises a base film and a molecular sieve layer arranged on at least one side of the base film, and the molecular sieve has a pore size of 0.45-0.55 nm, and the cycle performance of the negative electrode-free sodium metal battery is improved.

[0060] According to the simulation calculation, the size of the ether solvent molecular ion pair is smaller than the pore size of the molecular sieve, and it can be speculated that the molecular sieve layer intercepts the ether solvent molecular ion pair, thereby reducing the risk of reaction of the ether solvent with low LUMO energy level in the ether solvent molecular ion pair and the negative sodium metal to produce gas.

[0061] As shown in FIG. 1, the separator comprises a base film 10 and a molecular sieve layer 20 arranged on one side of the base film 10. FIG. 1

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

[0063] The molecular sieve is a kind of inorganic microporous crystal material with regular pore structure, for example, the molecular sieve comprises a silicoaluminate (for example, Na2O·xAl2O3·ySiO2, 0

[0064] The test method of the molecular sieve is as follows: the battery is disassembled, the separator is taken out, the molecular sieve layer is peeled off, the material of the molecular sieve layer is scraped, and the characteristic absorption peak of the molecular sieve is tested by infrared spectroscopy or the characteristic diffraction peak of the molecular sieve is tested by XRD to confirm that the molecular sieve layer comprises the molecular sieve.

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

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

[0067] Data analysis: The specific surface area and pore size distribution are calculated using the adsorption-desorption isotherm using a specific analytical method (such as the BET equation, t-plot method, or SF model) to determine the pore size and distribution of the molecular sieve.

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

[0069] The molecular sieve layer is arranged on the side of the base membrane facing the negative electrode plate, which helps to improve the cycle performance of the negative electrode-free sodium metal battery.

[0070] The closer the molecular sieve layer is to the negative electrode, the smaller the distance between them. This reduces the number of ether solvent molecular ion pairs formed between the molecular sieve layer and the negative electrode, thereby reducing the risk of the ether solvent in the ether solvent molecular ion pairs between the molecular sieve layer and the negative electrode reacting with the negative electrode sodium metal. Furthermore, the molecular sieve layer has a certain mechanical strength. Placing it on the side of the base membrane that extends beyond the negative electrode can reduce the risk of sodium dendrites piercing the diaphragm.

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

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

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

[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 surface of the base film, which can be considered as the mass of the molecular sieve per unit area in the molecular sieve layer. The coating density of the molecular sieve is in the above range, and the cycle performance of the battery is improved better. It is illustrated that the higher the coating density of the molecular sieve is, the smaller the voids of the molecular sieve layer formed by the accumulation of the molecular sieve particles are, the interception of the molecular sieve layer to the ion pair of the ether solvent molecules is improved, and the risk of the reaction of the ether solvent with the negative sodium metal to produce gas is reduced.

[0076] The test method of the mass of the molecular sieve in the molecular sieve layer is as follows: the battery is disassembled, the separator is taken out, the area S0 of the molecular sieve layer is tested, the separator is soaked in an organic solvent, the base film material is dissolved, the remaining solid components of the molecular sieve are obtained, the mass is measured as M0, and the calculation formula of the mass of the molecular sieve in the molecular sieve layer is M0 / S0.

[0077] The above 15 mg / 15 40.25 mm 2 to 25 mg / 15 40.25 mm 2 The value includes the minimum value and the maximum value in the range, and every value between the minimum value and the maximum value, and specific examples include but are not limited to the point values in the embodiments and 15 mg / 15 40.25 mm 2 , 20 mg / 15 40.25 mm 2 , 25 mg / 15 40.25 mm 2 , etc., and the range value between any two point values.

[0078] In an embodiment, the particle size D50 of the molecular sieve is 3 microns to 4 microns; the particle size of the molecular sieve meets the above range value, and the cycle performance of the battery is improved better. The particle size of the molecular sieve meets the above range, which is helpful to reduce the voids of the molecular sieve layer formed by the accumulation of the molecular sieve particles, improve the interception of the molecular sieve layer to the ion pair of the ether solvent molecules, and reduce the risk of the reaction of the ether solvent with the negative sodium metal to produce gas.

[0079] D50, the particle size corresponding to the cumulative particle size distribution percentage of 50% of a sample. Its physical meaning is that the particles with a particle size greater than it account for 50%, and the particles with a particle size less than it also account for 50%.

[0080] The above 3 microns to 4 microns, the value includes the minimum value and the maximum value in the range, and every value between the minimum value and the maximum value, and specific examples include but are not limited to the point values in the embodiments and 3 microns, 3.5 microns, 4 microns, etc., and the range value between any two point values.

[0081] The test method of the particle size of the molecular sieve is as follows: the molecular sieve is obtained by the above method, laser diffraction method is used to irradiate the sample with laser, and the particle size and distribution are calculated by measuring the intensity distribution of scattered light.

[0082] Device model: MasterSizer 2000 laser particle size analyzer, reference standard process: GB / T19077-2016 / ISO 13320:2009, specific test process: take an appropriate amount of sample to be tested (the sample concentration is guaranteed to be 8-12% obscuration), add 20ml deionized water, and simultaneously super 5min (53KHz / 120W), ensure that the sample is completely dispersed, then measure the sample according to the GB / T19077-2016 / ISO 13320:2009 standard.

[0083] In an embodiment, the thickness of the molecular sieve layer is 10 microns to 30 microns. It helps to improve the interception of the ether solvent molecular ion pair by the molecular sieve layer.

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

[0085] In the above 10 microns to 30 microns, the values include the minimum and maximum values of the range, and every value between such minimum and maximum values, specific examples include but are not limited to the point values in the embodiments and 10 microns, 15 microns, 20 microns, 25 microns, 30 microns, etc., and the range values between any two point values.

[0086] In an embodiment, the mass percentage of the ether solvent is 60% to 100% based on the total mass of the electrolyte. The mass percentage of the ether solvent in the total mass of the electrolyte is 60% to 100%, the compatibility of the ether solvent with the anode-free sodium metal battery is better, the mass percentage of the ether solvent in the mass of the electrolyte is 60% to 100%, and the electrochemical performance of the battery is more stable. The ether solvent will react seriously with the sodium metal on the negative side to produce H2, CO, olefins and alkanes, etc. The molecular sieve layer is used to intercept the ether solvent molecular ion pair, and reduce the risk of gas production by the ether solvent with low LUMO energy level in the ether solvent molecular ion pair reacting with the negative sodium metal.

[0087] The test method of the mass percentage of the ether solvent in the electrolyte is as follows: disassemble the battery, take out the electrolyte, dilute the electrolyte to prepare a sample to be tested, inject the sample into the GC-MS for analysis, obtain the mass spectrum, confirm the substances of each component according to the mass spectrum of the measured component and the corresponding spectral library retrieval result, and confirm that the electrolyte includes the ether solvent. The standard solution of different concentration gradients of the above-mentioned ether solvent target substance is configured, the electrolyte to be tested is taken as the sample to be tested, the standard solution and the sample to be tested are analyzed by GC-MS respectively, and the mass of the target substance in the sample to be tested is calculated according to the standard curve, so as to obtain the concentration of the target substance.

[0088] In an 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 the solvent molecular ion pairs formed by the ether solvent.

[0089] In an embodiment, the molecular sieve structure formula 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 M elements include at least one of Na, K, Li, Ca, and Mg.

[0090] In an embodiment, the molecular sieve includes Na2O·xAl2O3·ySiO2; the sodium type molecular sieve can conduct sodium ions to achieve the transmission of sodium ions.

[0091] In an embodiment, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes a layered transition metal oxide and / or a polyanion phosphate. The chemical formula of the layered transition metal oxide includes NaM1O2 (M1 is a transition metal atom, including one or a combination of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, etc., 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 the polyanion phosphate includes Na x1 R y1 P m1 O n1 (wherein, 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 an embodiment, the application also provides a separator, which includes a base film and a molecular sieve layer arranged on at least one side of the base film, and the molecular sieve layer includes a molecular sieve, and the pore size of the molecular sieve is 0.45 nm to 0.55 nm.

[0093] In an embodiment, the mass of the molecular sieve in the molecular sieve layer is 15 mg / 1540.25 mm2 to 25 mg / 15 40.25 mm 2 .

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

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

[0096] In an embodiment, the application further provides a power utilization device, which comprises the negative electrode-free sodium metal battery as described above.

[0097] In addition, the battery (battery cell, battery module, battery pack) and the power utilization device of the application are described below with appropriate reference to the accompanying drawings.

[0098] In an embodiment of the application, a battery cell is provided.

[0099] Generally, the battery cell comprises a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. The electrolyte plays a role of conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly plays a role of preventing the short circuit of the positive and negative electrodes, and can also allow ions to pass through. The separator is the improved separator as described above.

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

[0101] As an example, the positive electrode current collector has two opposite surfaces in the thickness direction thereof, and the positive electrode film layer is arranged on any one or both of the two opposite surfaces of the positive electrode current collector.

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

[0103] In some embodiments, the positive electrode film layer can also optionally comprise a binder. As an example, the binder can comprise 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 fluorine-containing acrylic ester resin.

[0104] In some embodiments, the positive electrode film layer can further optionally include a conductive agent. As an example, the conductive agent can include at least one of super-P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

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

[0106] The negative electrode tab includes a negative electrode current collector.

[0107] In some embodiments, the negative electrode current collector can employ a metal foil or a composite current collector. For example, as the metal foil, a copper foil can be employed. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can 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 base layer (e.g., a base layer of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0108] The electrolyte serves to conduct ions between the positive electrode tab and the negative electrode tab. The type of the electrolyte is not specifically limited in the present application, and can be selected as needed.

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

[0110] In some embodiments, the electrolyte solution can further optionally include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can further include an additive capable of improving certain properties of the battery, such as an additive for improving overcharge performance of the battery, an additive for improving high-temperature or low-temperature performance of the battery, etc.

[0111] In some embodiments, the positive electrode tab, the negative electrode tab, and the separator can be made into an electrode assembly through a winding process or a stacking process.

[0112] In some embodiments, the battery cell can include an outer package. The outer package can be used to package the above-mentioned electrode assembly and the electrolyte.

[0113] In some embodiments, the outer package of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the battery cell can also be a soft package, such as a pouch soft package. The material of the soft package can be plastic, and as plastic, polypropylene, polybutylene terephthalate, polybutylene succinate, etc. can be listed.

[0114] The shape of the battery cell is not particularly limited in the present application, and it can be cylindrical, square, or any other shape. For example, FIG. 3 is a square structure battery cell 5 as an example.

[0115] In some embodiments, referring to FIG. 4 , the outer package can include a shell 51 and a cover plate 53. Among them, the shell 51 can include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate are enclosed to form a containing cavity. The shell 51 has an opening communicating with the containing cavity, and the cover plate 53 can be provided on the opening to close the containing cavity. The positive electrode sheet, the negative electrode sheet, and the separator can form an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is packaged in the containing cavity. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and the person skilled in the art can select according to the specific actual demand.

[0116] In some embodiments, the battery cell pool can be assembled into a battery module, and the number of battery cells contained in the battery module can be one or more, and the specific number can be selected by the person skilled in the art according to the application and capacity of the battery module.

[0117] FIG. 5 is a battery module 4 as an example. Referring to FIG. 5 , in the battery module 4, a plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, it can also be arranged in other arbitrary ways. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0118] Optionally, the battery module 4 can also include a housing having a containing space, and the plurality of battery cells 5 are contained in the containing space.

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

[0120] FIG. 6 and FIG. 7 is a battery pack 1 as an example. Referring to FIG. 6 and FIG. 7In the battery pack 1, a battery case and a plurality of battery modules 4 disposed in the battery case can be included. The battery case includes an upper case 2 and a lower case 3, and the upper case 2 is capable of being disposed on the lower case 3 and forms an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery case in any manner.

[0121] In addition, the present application also provides a power consuming device including at least one of the secondary battery, the battery module, or the battery pack provided by the present application. The secondary battery, the battery module, or the battery pack can be used as a power source of the power consuming device, or can be used as an energy storage unit of the power consuming device. The power consuming device can include a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto.

[0122] As the power consuming device, the battery cell, the battery module, or the battery pack can be selected according to the use requirement thereof.

[0123] FIG. 8 The power consuming device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirement of high power and high energy density of the battery cell for the power consuming device, the battery pack or the battery module can be used.

[0124] The power consuming device as another example can be a mobile phone, a tablet computer, a notebook computer, etc. The device usually requires thinning, and the battery cell can be used as a power source.

[0125] Embodiment

[0126] Embodiment 1

[0127] Molecular sieve pretreatment: The molecular sieve (Na type molecular sieve, pore size 0.5 nm) is treated by a planetary ball mill, and after the ball milling is completed, the powder is heated at a temperature of 300°C for 24 hours in a muffle furnace to remove the water adsorbed in the molecular sieve. The particle size of the molecular sieve is D50 of 3 microns.

[0128] Separator: A polypropylene film is used as a base film (thickness of 12 microns), 95wt% of the above-mentioned molecular sieve is mixed with 5wt% of a binder polyvinylidene fluoride, then N-methyl pyrrolidone is added for stirring and dispersion to prepare a molecular sieve slurry. The slurry is uniformly coated on one side of the base film, and then dried in a 100°C vacuum oven for 24 hours to eliminate the gap between the particles with a pressure of 10 tons. The final thickness of the molecular sieve layer is 10 microns.

[0129] Positive electrode sheet: 98wt% of positive electrode active material (sodium iron pyrophosphate with a particle size D50 of 4μm), 1wt% of conductive agent conductive carbon black (Super-P), 1wt% of binder polyvinylidene fluoride were mixed, then N-methyl pyrrolidone was added to stir and disperse to prepare a positive electrode slurry. After the prepared oil-based slurry was stirred, the slurry viscosity was adjusted to 30,000-50,000 mPa.s, and the prepared slurry was not layered. The positive electrode slurry was single-sided coated by a double-sided coating device with a weight of 200mg / 1540.25mm 2 The coated Al foil was dried, cold-pressed, cut, and a positive electrode sheet was prepared.

[0130] Negative electrode sheet: 5g of CMC was stirred and dissolved in 1000mL of water, then 5g of single-walled carbon nanotubes was added and dispersed by ultrasonic to prepare a slurry. The slurry was coated on the surface of a copper foil, then transferred to a vacuum drying oven for complete drying, and then cut 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 was used as a solvent, then a certain amount of sodium hexafluorophosphate was dissolved in the above mixed solvent, the concentration of sodium hexafluorophosphate was controlled to be 1mol / L, and the mixture was stirred uniformly to form the final use electrolyte.

[0132] Assembly: The positive electrode sheet, the separator (with the molecular sieve layer facing the negative electrode side), and the negative electrode sheet were assembled in order, with the separator between the positive and negative electrode sheets to play a role of isolation. The bare cell was welded with tabs, and the bare cell was loaded into an aluminum shell and baked at 100℃ to remove water. Then the electrolyte was injected and sealed to obtain a non-charged battery. The non-charged battery was sequentially subjected to standing, hot and cold pressing, formation, shaping, capacity testing, and other processes to obtain a negative electrode-free sodium secondary battery product.

[0133] Example 2, Example 4, Example 5

[0134] On the basis of Example 1, the thickness of the molecular sieve layer was adjusted.

[0135] Example 3

[0136] On the basis of Example 1, the thickness of the molecular sieve layer was adjusted, and the solvent of the electrolyte was replaced by a mixture of ethylene glycol dimethyl ether DME and ethylene glycol diethyl ether DEE.

[0137] Example 6

[0138] On the basis of Example 1, the thickness of the molecular sieve layer was adjusted, and the molecular sieve layer of the separator was arranged to face the positive electrode.

[0139] Example 7

[0140] On the basis of Example 1, a molecular sieve layer is arranged on both sides of the separator.

[0141] Example 8 and Example 9

[0142] On the basis of Example 1, the type of positive electrode active material is adjusted, and the type of ether solvent or the thickness of the molecular sieve layer is adjusted.

[0143] Example 10, Example 11

[0144] On the basis of Example 1, the pore size of the molecular sieve is adjusted.

[0145] Comparative Example 1

[0146] On the basis of Example 1, the separator is not provided with a molecular sieve layer.

[0147] Comparative Example 2

[0148] On the basis of Example 8, the separator is not provided with a molecular sieve layer.

[0149] Cycle performance test

[0150] The cycle performance test process is as follows: at 25°C, the prepared battery is rested for 30 min, then charged to 3.65V at a constant current of 0.33C, then charged at a constant voltage of 3.65V until the current drops to 0.05C, rested for 1h, then discharged to 1.5V at a constant current of 0.33C, to obtain the initial capacity (C0); after resting for 1h, again charged to 3.65V at a constant current of 0.33C, then charged at a constant voltage of 3.65V until the current drops to 0.05C, rested for 1h, then discharged to 1.5V at a constant current of 0.33C, to obtain the process capacity (C1), and the above steps are repeated for the same battery, and the cycle number N when the cycle capacity decays to 80% is recorded at the same time.

[0151] Storage gas production volume test

[0152] Before testing the capacity, the volume of the cell (V1) is tested by the drainage method at 25°C, the battery is charged to 3.65V at a constant current of 0.2C at 25°C, then charged at a constant voltage of 3.65V until the current drops to 0.05C, then discharged to 1.5V at a constant current of 0.2C, to obtain the discharge capacity before storage (Cd1); then the battery is again charged to 3.65V at a constant current of 0.2C, then charged at a constant voltage of 3.65V until the current drops to 0.05C. Then the battery is placed in a constant temperature oven at 60°C for 30 days, after taking out, the battery is placed at 25°C to test the volume of the cell after storage (V2), and the gas production of the sodium ion battery is calculated according to the following formula:

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

[0154] Table 1: Experimental data list

[0155]

[0156]

[0157] In Table 1, with the same positive active material, the positive active material includes Na4Fe3(PO4)2(P2O7), the battery of Examples 1 to 7, Example 10, and Example 11 has less gas production than Comparative Example 1, and the battery of Examples 1 to 7, Example 10, and Example 11 has more cycle times than Comparative Example 1. The positive active material includes NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, the performance of Example 8 and Example 9 is better than that of Comparative Example 2. Comparing Example 3 and Example 6, when the molecular sieve layer is arranged towards the negative electrode, the performance is better than when the molecular sieve layer is arranged towards the positive electrode. Comparing Example 3 and Example 7, when the molecular sieve layer is arranged towards the negative electrode, the performance is better than when the molecular sieve layer is arranged on both sides of the base film.

[0158] The above merely describes the preferred embodiments of the present application, and does not limit the patent scope of the present application. Any equivalent structural transformation, direct / indirect application in other related technical fields, or the like, which is made under the inventive concept of the present application, and based on the content of the present application specification and drawings, is included in the patent protection scope of the present application.

Claims

1. A negative electrode-free sodium metal battery, characterized in that: The negative electrode-free sodium metal battery comprises a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator; The electrolyte includes an ether solvent; The diaphragm includes a base membrane and a molecular sieve layer provided on at least one side of the base membrane. The molecular sieve layer includes a molecular sieve, and the pore size of the molecular sieve is 0.45 nm to 0.55 nm.

2. The negative electrode-free sodium metal battery according to claim 1, wherein The molecular sieve layer is arranged on a side of the base film facing the negative electrode plate.

3. The negative electrode-free sodium metal battery according to claim 1 or 2, 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 plate; The projection of one side surface of the negative electrode plate is located on the molecular sieve layer.

4. The negative electrode-free sodium metal battery according to any one of claims 1 to 3, characterized in that The mass of the molecular sieve in the molecular sieve layer is 15 mg / 1540.25 mm 2 Up to 25mg / 1540.25mm 2 .

5. The negative electrode-free sodium metal battery according to any one of claims 1 to 4, characterized in that The particle size D50 of the molecular sieve is 3 microns to 4 microns; And / or, the thickness of the molecular sieve layer is 10 microns to 30 microns.

6. The negative electrode-free sodium metal battery according to any one of claims 1 to 5, characterized in that The mass percentage of the ether solvent is 60% to 100% based on 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 structural formula 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.

7. The negative electrode-free sodium metal battery according to any one of claims 1 to 6, wherein: The molecular sieve includes Na2O·xAl2O3·ySiO2; And / or, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer provided on at least one side of the positive electrode current collector, the positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes a layered transition metal oxide and / or a polyanion phosphate.

8. A diaphragm, characterized in that: The diaphragm includes a base membrane and a molecular sieve layer provided on at least one side of the base membrane. The molecular sieve layer includes a molecular sieve, and the pore size of the molecular sieve is 0.45 nm to 0.55 nm.

9. The diaphragm according to claim 8, wherein The mass of the molecular sieve in the molecular sieve layer is 15 mg / 1540.25 mm 2 Up to 25mg / 1540.25mm 2 ; and / or, the particle size D50 of the molecular sieve is 3 μm to 4 μm; And / or, the thickness of the molecular sieve layer is 10 microns to 30 microns.

10. An electrical device, characterized in that: The electrical device comprises the negative electrode-free sodium metal battery according to any one of claims 1 to 7.

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