CN120497419A - Sodium ion battery using PTFE/PE asymmetric composite membrane - Google Patents
Sodium ion battery using PTFE/PE asymmetric composite membraneInfo
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- CN120497419A CN120497419A CN202510986172.9A CN202510986172A CN120497419A CN 120497419 A CN120497419 A CN 120497419A CN 202510986172 A CN202510986172 A CN 202510986172A CN 120497419 A CN120497419 A CN 120497419A
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Abstract
本申请提供一种应用PTFE/PE非对称复合隔膜的钠离子电池，属于钠离子电池技术领域。包括硬碳正极、钠金属负极、电解液和隔膜，所述隔膜为PTFE/PE非对称复合隔膜，PTFE/PE非对称复合隔膜包括聚乙烯基底层和亲水改性聚四氟乙烯功能层，所述亲水改性聚四氟乙烯功能层的接触角＜60˚，孔隙率≥60%。本申请钠离子电池中的隔膜可以有效抑制枝晶的生长，阻止枝晶穿透。
This application provides a sodium-ion battery utilizing a PTFE/PE asymmetric composite diaphragm, belonging to the technical field of sodium-ion batteries. The battery comprises a hard carbon positive electrode, a sodium metal negative electrode, an electrolyte, and a diaphragm. The diaphragm is a PTFE/PE asymmetric composite diaphragm, comprising a polyethylene base layer and a hydrophilically modified polytetrafluoroethylene functional layer. The hydrophilically modified polytetrafluoroethylene functional layer has a contact angle of less than 60° and a porosity of ≥60%. The diaphragm in the sodium-ion battery of this application can effectively inhibit the growth of dendrites and prevent dendrite penetration.
Description
Technical Field
The application relates to a sodium ion battery applying PTFE/PE asymmetric composite membrane, belonging to the technical field of sodium ion batteries.
Background
Sodium ion batteries are receiving great attention as an energy storage technology with great potential due to the abundance of sodium resources and low cost. However, the sodium negative electrode is easy to generate dendrite and dead sodium in the circulating process, so that the capacity of the battery is quickly attenuated and potential safety hazard is caused, and the method becomes a key bottleneck for restricting commercialization of the battery. The separator, as a critical component inside the battery, plays an important role in regulating sodium ion transport and interfacial stability, in addition to providing mechanical support and electrical insulation. The existing commercial Polyethylene (PE) diaphragm has certain mechanical stability and ion channel capacity, but has limited lyophilic property, so that electrolyte is easy to be unevenly distributed at an interface, further uneven deposition of sodium metal is induced, problems of dendrite, dead sodium and the like are generated, and stable operation of a battery under a fast-charge working condition is severely restricted. To overcome this bottleneck, material selection and interface design are important to study.
Polytetrafluoroethylene (PTFE) films present unique advantages as a highly crystalline, highly chemically resistant fluoropolymer material. First, PTFE has an extremely low dielectric constant (about 2.0), its intrinsically low polarizability makes it difficult to respond to an applied electric field, so that an "electric field buffer layer" can be formed near the sodium-metal interface, effectively smoothing the interfacial electric field distribution, reducing electrodeposition non-uniformity caused by local electric field concentration, promoting uniform deposition of sodium ions, and inhibiting dendrite germination. Secondly, the high chemical stability of PTFE ensures that the PTFE keeps the structural integrity in a strongly reduced sodium metal environment, and ensures the long-term stability of the diaphragm. Furthermore, by surface hydrophilic modification, the wettability and electrolyte holding capacity of the PTFE film are remarkably improved, the distribution of interface electrolytes is optimized, the formation of a uniform and compact Solid Electrolyte Interface (SEI) film is promoted, and the interface polarization and dendrite risks are further reduced. In addition, the excellent mechanical toughness and porous structure of PTFE facilitates the construction of stable ion transport channels and mechanical protective layers, creating physical constraints on sodium deposition, preventing dendrite penetration. Compared with other hydrophilic polymer materials, PTFE has obvious advantages in the aspects of electrochemical inertia, thermal stability and industrial feasibility, so that PTFE becomes an ideal material for constructing a high-performance sodium ion battery composite membrane.
Disclosure of Invention
In view of the above, the present application provides a sodium ion battery using a PTFE/PE asymmetric composite membrane, which is constructed by disposing a hydrophilically modified Polytetrafluoroethylene (PTFE) membrane near a sodium metal side. By utilizing the remarkable advantages of the electrolyte and the electrolyte, on the basis of keeping the mechanical stability of the whole diaphragm, the maintainability and the wettability of the electrolyte at the interface of the cathode are remarkably improved, the electric field distribution and the sodium ion deposition behavior of the interface are effectively regulated and controlled, the generation of sodium dendrite is remarkably inhibited, the rate capability and the cycling stability of the battery are improved, and the excellent quick charge adaptability is shown.
Specifically, the application is realized by the following scheme:
A sodium ion battery applying PTFE/PE asymmetric composite membrane comprises a hard carbon anode, a sodium metal cathode, electrolyte and a membrane, wherein the membrane is a PTFE/PE asymmetric composite membrane, the PTFE/PE asymmetric composite membrane comprises a Polyethylene (PE) substrate layer and a hydrophilic modified Polytetrafluoroethylene (PTFE) functional layer, the contact angle of the hydrophilic modified polytetrafluoroethylene functional layer is less than 60 degrees, and the porosity is more than or equal to 60 percent.
According to the application, the PTFE/PE asymmetric composite membrane is used as a membrane of a sodium ion battery, an ion channel is ensured by a PE layer (positive electrode side), an interface is regulated and controlled by a hydrophilic PTFE layer (negative electrode side), PTFE is assembled in a sodium ion negative electrode oriented mode, and the performance is improved by combining the low dielectric property (about 2.0) of PTFE and the mechanical stability of PE through the following mechanism:
1. Interface regulation and control, namely, the PTFE layer is difficult to respond to fluctuation of an external electric field because of extremely low polarizability, and an electric field buffer layer is constructed on the surface of sodium metal by utilizing a synergistic mechanism to adsorb electrolyte to effectively homogenize near-interface electric field distribution and induce more uniform deposition of sodium ions.
2. Wetting enhancement, namely improving the wettability of the hydrophilic modified PTFE on the ether electrolyte and reducing interface impedance.
3. Dendrite inhibition-the composite structure forms a physical barrier preventing dendrite penetration.
Further, as preferable:
the polyethylene base layer has a thickness of 10-30 [ mu ] m.
The thickness of the hydrophilic modified polytetrafluoroethylene functional layer is 10-50 mu m, and the aperture is 0.1-0.5 mu m. The hydrophilic modified polytetrafluoroethylene functional layer is obtained by performing plasma hydrophilic modification treatment on polytetrafluoroethylene.
The electrolyte is an ether electrolyte, and is a solution obtained by dissolving sodium salt in ethylene glycol dimethyl ether (G2), diethylene glycol dimethyl ether (DG) and triethylene glycol dimethyl ether (TG), wherein the concentration of the sodium salt is 0.5-2M.
More preferably:
The sodium salt is any one of NaPF 6, naFSI or NaTFSI.
The concentration of the sodium salt is 1-1.5M.
The hydrophilic modified polytetrafluoroethylene functional layer of the PTFE/PE asymmetric composite membrane faces to the sodium metal negative electrode assembly.
The assembling method of the sodium ion battery using the PTFE/PE asymmetric composite membrane comprises the following steps:
firstly, pulping hard carbon, a conductive agent and a binder according to mass ratio, coating copper foil, and drying cut pieces to obtain a hard carbon anode;
Step two, in an argon glove box, a hard carbon positive electrode is arranged in a battery positive electrode shell, a PTFE/PE asymmetric composite membrane is covered, and a hydrophilic modified polytetrafluoroethylene functional layer is assembled facing a negative electrode;
step three, slowly dripping an ether electrolyte, and infiltrating the PTFE/PE asymmetric composite membrane;
And fourthly, putting a sodium sheet as a sodium ion negative electrode, packaging and standing to obtain the sodium ion battery.
In the first step, the first step is to perform,
The conductive agent is SuperP.
The binder is PVDF.
In the third step, the mass ratio of the hard carbon to the conductive agent to the binder is 8:0.5-1.5:0.5-1.5, and the preferable mass ratio is 8:1-1.2:1-1.2, and the addition amount of the ether electrolyte is 100-150 mu L.
And fourthly, standing at room temperature (25+/-5 ℃) for 12-24 hours.
The beneficial effects of the invention are as follows:
1) The hydrophilic modification obviously enhances the wetting capability of the PTFE membrane to ether electrolyte ethylene glycol dimethyl ether (G2), especially can keep local electrolyte concentration on one side of sodium metal, slows down the phenomena of drying or polarization, and compared with a natural lyophile PE membrane with uneven pore distribution and easy collapse, the modified PTFE can stably hold electrolyte, ensures the transmission continuity of sodium ions and reduces interface impedance.
2) In the construction of an interface structure, the hydrophilic modified PTFE is not completely inert any more, and can participate in interface induction of SEI formation, so that the surface of metal sodium is promoted to form thinner, denser and low-impedance SEI, and rapid deintercalation and deposition of sodium ions under high multiplying power are facilitated. When the deposition behavior and the electric field distribution are regulated, the high mechanical stability and the surface uniformity of the modified PTFE film can create a uniform electric field environment at the sodium end, and the low dielectric property of the modified PTFE film is matched with the uniform electric field environment to reduce dendrite and dead sodium phenomena, and meanwhile, the composite film combines the PE uniform ion flow distribution and the PTFE to reduce the high-rate polarization characteristic and delay the formation of sodium dendrite.
3) The constructed modified PTFE/PE composite gradient membrane structure maintains a good ion channel at the positive electrode side by PE, and the negative electrode side stabilizes an interface and wets electrolyte by the modified PTFE, compared with the traditional single-layer PE membrane, the composite membrane can still maintain higher specific capacity output under the condition of 5C and other high multiplying power, realizes the synergistic effect of a rapid sodium ion channel and an interface buffer protection layer under high multiplying power, shows excellent rapid charging adaptability and cycle stability, is suitable for the construction of high-performance sodium ion batteries, and is particularly suitable for the construction of a battery system adopting an ether electrolyte system and a hard carbon-sodium structure.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments or the description of the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.
Figure 1 is an assembly sequence of the PTFE/PE composite separator of the present application,
In the figure, the reference numeral is 1. Metallic sodium sheet, 2.PTFE functional layer, 3.PE basal layer, 4. Hard carbon sheet;
FIG. 2 is a graph showing the long cycling stability of sodium ion batteries constructed with different membranes under 0.3C charge and discharge conditions;
FIG. 3 is a graph showing the long cycling stability of sodium ion batteries constructed with different membranes under 5C charge and discharge conditions;
Fig. 4 is a graph showing the rate performance test of sodium ion batteries constructed with different separators.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects to be solved by the present application more clear, the technical solutions in the embodiments of the present application will be further described in detail below with reference to the accompanying drawings in the embodiments of the present application, and it should be understood that the specific embodiments described herein are only for explaining the present application and are not intended to limit the technical solutions of the present application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
Example 1
The sodium ion battery assembly method of this embodiment is as follows:
(1) Preparation of hard carbon pole piece
The preparation method comprises the steps of weighing hard carbon powder, a conductive agent (SuperP) and a binder (polyvinylidene fluoride, PVDF), taking a proper amount of N-methylpyrrolidone (NMP) solvent, and preparing the PVDF into a solvent with the weight percentage of 6% for later use.
Slurry preparation the hard carbon powder, superP and PVDF are mixed according to the mass ratio of 8:1:1, and stirred for at least 3 times by a refiner until a uniform slurry is formed.
And (3) coating and drying, namely uniformly coating the slurry on a copper foil current collector by using a small heating coating dryer, controlling the thickness range of a scraper to be 100-200 mu m, placing the copper foil current collector in a vacuum drying oven, and pre-drying the copper foil current collector for 12 hours at 80 ℃.
And cutting the electrode slice into a wafer with the diameter of 12mm by using a slicing machine.
And finally drying, namely placing the cut pole piece in a vacuum box, and further drying for 6 hours at 80 ℃ to remove residual solvent, wherein the obtained hard carbon pole piece 4 is ready for use and is reserved for battery assembly.
(2) Preparation of electrolyte
The electrolyte solvent system selects ethylene glycol dimethyl ether (G2), and sodium hexafluorophosphate (NaPF 6) is adopted as sodium salt. In a dry glove box, the sodium salt is added into a solvent, and the solution is fully mixed by using magnetic stirring until the solution is transparent, so that the electrolyte with the concentration of the sodium salt of 1M is obtained for standby.
The whole process was completed in a glove box (H 2O<0.01ppm,O2 <0.01 ppm) to prevent contamination of the electrolyte with moisture or oxygen.
(3) Assembly of button cell
A dried hard carbon sheet 4, a metal sodium sheet 1 (diameter 14mm, thickness about 50 um), a PTFE/PE asymmetric composite membrane formed by a PTFE functional layer 2 and a PE base layer 3, an electrolyte, and the like were prepared. The cell assembly was performed in an argon (Ar) atmosphere glove box, maintaining the water oxygen content in the environment below 0.01ppm.
Assembling:
(1) Placing a hard carbon pole piece 4 at the bottom of a stainless steel positive electrode shell, and weighing the mass of an active substance;
(2) The membrane was placed and a PTFE/PE asymmetric composite membrane was used with the hydrophilic PTFE functional layer 2 facing the sodium metal sheet 1 side.
(3) A measured amount of electrolyte (typically 100-150 μl) is added dropwise, wetting the separator.
(4) The metallic sodium sheet 1 was placed over the PTFE/PE asymmetric composite membrane ensuring good contact. At this time, the positional relationship among the metal sodium sheet 1, the PTFE functional layer 2, the PE base layer 3, and the hard carbon sheet 4 is shown in fig. 1.
(5) And placing the gasket and the spring piece, assembling the cathode shell, and pressing and packaging to form the CR2032 button cell.
(6) After assembly, the battery is kept stand for more than 12 hours, so that electrolyte infiltration and interface stabilization are promoted.
Example 2
This example is the same as the setup of example 1, except that the mass ratios of hard carbon powder, superP and PVDF are shown in table 1.
TABLE 1 influence of different hard carbon Pole pieces composition (mass ratio)
。
As can be seen from the results of Table 1, when SuperP is insufficient (e.g., 0.5 part of SEQ ID NO: 1 in Table 1), the conductive agent cannot form a continuous network, electron transport between hard carbon particles is hindered, and kinetic polarization is deteriorated. When PVDF is excessive (e.g., 1.5 parts of nos. 1, 2, 3, 5, 10 in table 1), the binder plugs the pores, the ion transport channels decrease, and the interfacial resistance increases. When PVDF is not critical enough (as shown by the numbers 4 and 7 in the table 1), the binding force is close to the material limit, and SuperP is excessive (as shown by the number 7 in the table 1), the porosity is extruded instead, the binding is invalid after electrolyte is soaked, the electrode structure collapses in the later period of circulation, the active substance is separated from the current collector, and the visible copper foil of the disassembled battery is exposed. When SuperP/PVDF is too small (such as 9:0.5:0.5 of serial number 12), the two-component critical is insufficient, high-proportion hard carbon particles cannot be effectively coated, the contact resistance among the particles is increased rapidly, the utilization rate of active substances is low, the mechanical strength is weak, and the electrode is pulverized and falls off (obvious cracks are observed by SEM) when the charge and discharge volume is changed.
Therefore, the mass ratio of the hard carbon powder to SuperP to PVDF can be selected to be 8:0.5-1.5:0.5-1.5, and the effect of the hard carbon powder to the PVDF is superior to that of a conventional pure PE membrane system (the capacity retention rate of 0.3C of the conventional system is less than or equal to 75 percent, and the rate capacity of 5C is less than or equal to 120 mAh/g). And preferably hard carbon powder, superP and PVDF in a mass ratio=8:1 to 1.2:1 to 1.2.
Example 3
This example is the same as example 1 except that sodium salt NaPF6 in the electrolyte is replaced with sodium fluorosulfonyl imide (NaFSI) or sodium bis (trifluoromethanesulfonyl) imide (NaTFSI).
The results show that NaFSI strong nucleophilic corrosion to sodium metal causes SEI local damage and coulombic efficiency collapse (< 90%), while the bulky anions of NaTFSI cause an increase in electrolyte viscosity of 20%, ion migration resistance induces concentration polarization, and dendrite density increases by 30%. However, both the sodium salt of the embodiment 1 and the sodium salt of the embodiment 3 realize that under the synergistic effect of the PTFE/PE asymmetric composite membrane, all sodium salt systems (NaPF 6/NaFSI/NaTFSI) are obviously superior to the conventional pure PE membrane systems, wherein the minimum 0.3C cycle retention rate (75%) is greater than 70% of that of the conventional PE membrane, the minimum 5C multiplying power capacity (135 mAh/g) is higher than 120mAh/g of that of the conventional PE membrane, the NaPF 6 is selected for the optimal sodium salt because of the optimal comprehensive performance (5C capacity 210mAh/g and coulombic efficiency 99.2%), and NaFSI and NaTFSI are suitable for scenes with low requirements on cost sensitivity and multiplying power (the required acceptance cycle life is shortened by 15% -20%). Thus, in the ether electrolyte systems presented in this document, sodium salts may be employed as NaPF 6, naFSI or NaTFSI, and most preferably as NaPF 6.
Example 4
This example was identical to the setup of example 1, except that the sodium salt concentration in the electrolyte was replaced by 0.5M, 1.5M, 2M, respectively, from 1M.
The results show that when the sodium salt concentration is 0.5M, insufficient carriers result in 30% increase in internal resistance and 30% decrease in 2C capacity, and when the sodium salt concentration is 2M, high viscosity deteriorates separator wettability, and the desolvation energy barrier increases result in 40% decrease in 5C capacity. Under the synergistic effect of the PTFE/PE asymmetric composite membrane, however, the concentration system (0.5-2M) is obviously superior to the conventional pure PE membrane system in that the minimum 0.3C cycle retention rate (82%) is more than 70% of the conventional PE membrane, the minimum 5C multiplying power capacity (126 mAh/g) is more than 120mAh/g of the conventional PE membrane, the comprehensive performance of the concentration interval of 1-1.5M is optimal, and the optimal solution can be realized in ether solvents when the concentration of sodium salt is controlled to be 1-1.5M, so that the ionic conductivity is ensured, and the interfacial reaction dynamics is maintained through the synergistic effect of anions and solvents, so that the electric field regulation advantage of the PTFE/PE membrane is fully exerted. Therefore, in the ether electrolyte system provided by the scheme, the concentration of sodium salt can be controlled to be 0.5-2M, and the optimal concentration is 1-1.5M.
Comparative example 1
The comparative example is the same as example 1, except that the solvent system of the electrolyte adopts a carbonate system of 1MNaPF 6 dissolved in EC/DMC/EMC (3:5:2 volume ratio), and the result shows that the strong solvation characteristic of the carbonate leads to the rise of the desolvation energy barrier of sodium ions, causes interfacial kinetics retardation, and the formed SEI film is loose and porous and continuously cracked and regenerated, so that dendrites grow rapidly (short circuit rate is more than 40% after 100 circles of 5C circulation), and meanwhile, the capacity retention rate of 0.3C is suddenly reduced to below 75%, which is far lower than ether G2.
Comparative example 2
This comparative example was the same as example 1 except that a pure PE separator was used as the separator.
The result shows that when PE is used as a diaphragm, the uneven distribution of interface electrolyte is caused by insufficient lyophilic, so that the deposition of sodium is uneven, and the polarization is aggravated under high multiplying power, so that sodium dendrite penetrates through the diaphragm.
Comparative example 3
This comparative example was the same as example 1 except that a pure GF membrane was used as the membrane.
The results show that when GF is used as a membrane, GF mechanical strength is insufficient and pore size is too large to restrict dendrite growth.
The comparison of the long cycle performance of comparative examples 2 and 3 and example 1 is shown in fig. 2 and 3 (the arrow pointing to the left indicates the trend of the specific capacity of different membranes with the number of cycles, the arrow pointing to the right indicates the trend of the coulomb efficiency of different membranes with the number of cycles), the long cycle stability of different membranes under the charge and discharge conditions of 0.3C and 5C is respectively shown, the result shows that the PTFE/PE asymmetric composite membrane is excellent under the conditions of low multiplying power and high multiplying power, the specific capacity retention rate exceeds 85% after 700 cycles, the coulomb efficiency is still more than 80% after 1500 cycles, and the pure PE membrane, the pure GF membrane and the PE/PTFE composite membrane which are sequentially exchanged are obviously inferior in color due to the defects of insufficient lyophilic, poor mechanical strength or structural design on the aspects of the cycle stability and high multiplying power adaptability, and the advantages of regulating the interface electric field and enhancing the wettability of the PTFE/PE asymmetric composite membrane, combining with the PE substrate layer to maintain ion channels, synergistically inhibiting dendrites and optimizing the electrolyte distribution to improve the battery performance are verified. The rate performance results of the PE/PTFE membrane shown in the figure 4 show that the PE/PTFE membrane has the highest specific capacity in the full rate interval, good performance at the high rate of 5C, rapid recovery of the specific capacity after the reduction of the specific capacity to 0.1C, excellent rate adaptability, obvious reduction of the specific capacity of the PE membrane along with the rate improvement, serious attenuation at 5C, limited low rate recovery, high rate polarization aggravation caused by poor lyophile, lowest specific capacity of the GF membrane, abrupt reduction at the high rate due to insufficient mechanical strength and large aperture, failure of restraining dendrites, and easy damage of an electrode structure. The specific capacity of the PTFE/PE asymmetric composite membrane is close to a theoretical value of more than 330mAh/g at a low rate of 0.1C, the performance attenuation amplitude is small in a wide rate range, the specific capacity of the pure PE membrane is about 300mAh/g at 0.1C, the specific capacity of the pure PE membrane is suddenly reduced to below 120mAh/g at 5C, and the specific capacity of the pure GF membrane is rapidly attenuated to below 100mAh/g at more than 1C, so that the PTFE/PE asymmetric composite membrane is verified to be under the synergistic effect of 'PE substrate ion channel + hydrophilic PTFE functional layer interface buffering', uniform electric field with low dielectric characteristics, enhanced electrolyte infiltration, excellent rapid charging adaptability is shown at the wide rate, and support is provided for high-performance sodium ion battery application.
Comparative example 4
The comparative example was the same as example 1 except that the order of the PTFE/PE asymmetric composite membrane was changed to PE/PTFE asymmetric composite membrane, and at this time, the PE membrane was oriented to the side of the metal sodium sheet. The PTFE functional layer is not facing the negative electrode, its low dielectric constant advantage fails, and the poor wettability of the PE substrate layer exacerbates polarization.
The application adopts Land CT2001 of Wuhan City blue electric electronic Co., ltd to test the constant current charge and discharge performance.
In summary, the invention provides a PTFE/PE asymmetric composite membrane for a sodium ion battery and a configuration design for inhibiting dendrites, wherein hydrophilic modification obviously enhances the wetting capability of a PTFE membrane to an ether electrolyte (such as G2), especially can keep local electrolyte concentration on one side of sodium metal, slows down drying or polarization phenomenon, and compared with a natural lyophile PE membrane with uneven pore distribution and easy collapse, the modified PTFE can stably hold the electrolyte, ensure sodium ion transmission continuity and reduce interface impedance. In the construction of an interface structure, the hydrophilic modified PTFE is not completely inert any more, and can participate in interface induction of SEI formation, so that the surface of metal sodium is promoted to form thinner, denser and low-impedance SEI, and rapid deintercalation and deposition of sodium ions under high multiplying power are facilitated. When the deposition behavior and the electric field distribution are regulated, the high mechanical stability and the surface uniformity of the modified PTFE film can create a uniform electric field environment at the sodium end, and the low dielectric property of the modified PTFE film is matched with the uniform electric field environment to reduce dendrite and dead sodium phenomena, and meanwhile, the composite film combines the PE uniform ion flow distribution and the PTFE to reduce the high-rate polarization characteristic and delay the formation of sodium dendrite. In addition, the constructed modified PTFE/PE composite gradient membrane structure maintains a good ion channel by PE on the positive electrode side, and the negative electrode side stabilizes an interface and wets electrolyte by the modified PTFE, so that the synergistic effect of a rapid sodium ion channel and an interface buffer protection layer under high multiplying power is realized.
In the description of the present specification, technical terms such as "implementation method", "exemplary embodiment", etc., mean that the specific technical feature, material property, or structural design described is fully included in at least one specific implementation of the technology of the present patent. It is to be noted, in particular, that the schematic descriptions of technical features may differ in different embodiments, and do not necessarily correspond to exactly the same technical implementation path. Those skilled in the art will appreciate that the features disclosed in the specification may be applied in any single or multiple embodiments, creatively in combination, by suitable technical means.
Claims (10)
1. A sodium ion battery applying PTFE/PE asymmetric composite membrane comprises a hard carbon anode, a sodium metal cathode, electrolyte and a membrane, and is characterized in that the membrane is PTFE/PE asymmetric composite membrane, the PTFE/PE asymmetric composite membrane comprises a polyethylene base layer and a hydrophilic modified polytetrafluoroethylene functional layer, the contact angle of the hydrophilic modified polytetrafluoroethylene functional layer is less than 60 degrees, and the porosity is more than or equal to 60%.
2. The sodium ion battery using the PTFE/PE asymmetric composite membrane according to claim 1, wherein the polyethylene substrate layer is 10-30 μm thick, the hydrophilic modified polytetrafluoroethylene functional layer is 10-50 μm thick, and the pore diameter is 0.1-0.5 μm.
3. The sodium ion battery using the PTFE/PE asymmetric composite membrane according to claim 1, wherein the electrolyte is an ether electrolyte, and the concentration of sodium salt is 0.5-2M, wherein the sodium salt is a solution obtained by dissolving sodium salt in ethylene glycol dimethyl ether, diethylene glycol dimethyl ether and triethylene glycol dimethyl ether.
4. A sodium ion battery employing a PTFE/PE asymmetric composite membrane as claimed in claim 3, wherein the sodium salt is any one of NaPF 6, naFSI or NaTFSI.
5. The sodium ion battery using the PTFE/PE asymmetric composite membrane according to claim 1, wherein the concentration of sodium salt is 1-1.5M.
6. The sodium ion battery using the PTFE/PE asymmetric composite membrane as claimed in claim 1, wherein the hydrophilic modified polytetrafluoroethylene functional layer of the PTFE/PE asymmetric composite membrane is assembled facing the sodium metal negative electrode.
7. The sodium ion battery using the PTFE/PE asymmetric composite membrane according to any one of claims 1 to 6, wherein the assembling method of the sodium ion battery is as follows:
firstly, pulping hard carbon, a conductive agent and a binder according to mass ratio, coating copper foil, and drying cut pieces to obtain a hard carbon anode;
Step two, in an argon glove box, a hard carbon positive electrode is arranged in a battery positive electrode shell, a PTFE/PE asymmetric composite membrane is covered, and a hydrophilic modified polytetrafluoroethylene functional layer is assembled facing a negative electrode;
step three, slowly dripping an ether electrolyte, and infiltrating the PTFE/PE asymmetric composite membrane;
and fourthly, putting a sodium sheet as a negative electrode, packaging and standing to obtain the sodium ion battery.
8. The sodium ion battery using PTFE/PE asymmetric composite membrane according to claim 7, wherein the conductive agent is SuperP and the binder is PVDF.
9. The sodium ion battery using the PTFE/PE asymmetric composite membrane according to claim 7, wherein the mass ratio of the hard carbon to the conductive agent to the binder is 8:0.5-1.5:0.5-1.5.
10. The sodium ion battery using the PTFE/PE asymmetric composite membrane according to claim 7, wherein in the third step, the addition amount of the ether electrolyte is 100-150 mu L.
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| CN106415913A (en) * | 2014-05-26 | 2017-02-15 | 日本戈尔有限公司 | Rechargeable battery and separator used therein |
| CN118946689A (en) * | 2022-04-21 | 2024-11-12 | 株式会社Lg化学 | Separator and electrochemical conversion cell including the same |
| CN120016083A (en) * | 2025-04-17 | 2025-05-16 | 合肥综合性国家科学中心能源研究院(安徽省能源实验室) | A composite diaphragm for aqueous zinc ion battery and preparation method thereof |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106415913A (en) * | 2014-05-26 | 2017-02-15 | 日本戈尔有限公司 | Rechargeable battery and separator used therein |
| CN118946689A (en) * | 2022-04-21 | 2024-11-12 | 株式会社Lg化学 | Separator and electrochemical conversion cell including the same |
| CN120016083A (en) * | 2025-04-17 | 2025-05-16 | 合肥综合性国家科学中心能源研究院(安徽省能源实验室) | A composite diaphragm for aqueous zinc ion battery and preparation method thereof |
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