A method for preparing an al-plastic film and application thereof in monitoring sodium battery swelling gas

Abstract

The application belongs to the field of sodium ion batteries, and particularly relates to a preparation method of an aluminum plastic film and application thereof in monitoring swelling gas of a sodium battery. First, the application discloses a preparation method of an aluminum plastic film; second, the application provides application of the aluminum plastic film in monitoring swelling gas of a sodium battery. The aluminum plastic film prepared by the application comprises a common aluminum plastic film and a polymer-based functional layer coated on the common aluminum plastic film CPP. The aluminum plastic film prepared by the application is applied to a sodium ion battery. When the sodium ion battery swells, pressure is applied to the polymer-based functional layer. Based on the negative pressure resistance effect, the resistance of the polymer-based functional layer will decrease. After a very small external voltage is applied to the polymer-based functional layer, the swelling gas of the sodium ion battery can be reflected by the increase of the current, so that real-time monitoring can be achieved. The application can not only accurately and timely monitor the swelling gas in the sodium ion battery, but also has simple operation and low cost.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of sodium ion batteries, and particularly relates to a preparation method of an aluminum plastic film and application thereof in monitoring swelling gas of a sodium battery package. BACKGROUND

[0002] With the rapid development of human society and the vigorous development of electric power equipment, it is urgent and critical to develop mature energy storage equipment. Among the many available energy storage technologies, rechargeable ion batteries have attracted much attention in the past few decades because they can successfully convert chemical energy into electrical energy. Among various rechargeable ion batteries, lithium ion batteries and sodium ion batteries occupy an important position, and they have the best overall performance and the most extensive commercial applications. Compared with other rechargeable ion batteries, lithium ion batteries have been successfully commercialized and have penetrated into our daily life with the highest energy-power density. However, due to the supply problem of lithium, sodium has received more and more attention, and sodium ion is considered as the best substitute for lithium ion battery due to its abundant resources and low cost. Sodium and lithium have similar atomic radii and belong to the same alkali metal group, so sodium batteries and lithium ion batteries have similar basic principles and electrochemical characteristics.

[0003] In the application process of sodium ion batteries with ternary materials as the positive electrode, when the battery works abnormally or is charged to above 3.9 volts, a large amount of gas will be generated in the sodium ion battery package, causing the swelling gas phenomenon. This phenomenon will cause the contact between the positive electrode, the separator and the negative electrode in the sodium ion battery to be no longer tight, thereby causing interface problems, and further causing the internal resistance of the battery to increase significantly, which causes the capacity of the battery to decrease significantly, and the cycle performance to decrease significantly. In severe cases, the battery package will have serious volume expansion, thereby affecting the normal use of the entire battery pack; in extreme cases, it will cause fatal safety problems. Therefore, real-time monitoring of the swelling gas condition of the sodium ion battery package is imminent.

[0004] The currently reported battery gas monitoring methods include additional sensors, using negative polarization resistance Rcp monitoring, etc. For example, the invention CN 215869528 U and patent CN 111076655 A both use force-sensitive resistors or pressure sensors fixed on the tab of the battery monomer. When the resistance value changes or the pressure of the pressure sensor changes, it can be fed back to the control system, thereby realizing precise monitoring of the battery gas expansion. However, this method not only greatly increases the cost, but also poses a great challenge to the battery packaging process. Patent CN 106610365 A proposes a lithium battery gas monitoring device, but its essence is a box containing a liquid medium, which occupies a large space and is not suitable for commercial lithium battery monitoring. Patent CN 114487886 A measures the temperature of the battery cell and the negative polarization resistance Rcp value at a specific SOC; based on the obtained Rcp value and the preset rule, the battery cell gas expansion is monitored. However, this method ignores the differences between battery cells and cannot accurately determine the gas expansion. SUMMARY

[0005] To solve the above problems, the present application provides a method for preparing an aluminum-plastic film and its application in monitoring the gas expansion of a sodium battery.

[0006] To solve the above problems, the present application provides an aluminum-plastic film, which comprises a common aluminum-plastic film and a polymer-based functional layer.

[0007] Preferably, the polymer-based functional layer is coated on one side of the CPP layer of the common aluminum-plastic film.

[0008] Preferably, the polymer-based functional layer has a piezoresistive effect.

[0009] Preferably, the components of the polymer-based functional layer include polymer powder, solvent, conductive filler, and nano-inorganic non-conductive filler.

[0010] Preferably, the polymer powder material includes at least one of polyethylene oxide, polyvinylidene fluoride, carboxymethyl cellulose, styrene-butadiene rubber, sodium alginate, and polyacrylic acid.

[0011] Preferably, the solvent includes at least one of deionized water and N-methyl pyrrolidone.

[0012] Preferably, the polymer is polyvinylidene fluoride, and the solvent contains N-methyl pyrrolidone.

[0013] Preferably, the conductive filler includes at least one of conductive carbon black, graphite, carbon nanotubes, graphene, nano-silver powder, nano-iron powder, and indium tin oxide.

[0014] Preferably, the nano-inorganic non-conductive filler includes at least one of nano-aluminum oxide, nano-iron oxide, nano-copper oxide, and nano-silicon dioxide.

[0015] The application also provides a preparation method of the aluminum-plastic film, comprising the following steps:

[0016] The polymer powder is added into the solvent, and after sufficient stirring, the conductive filler and the nano inorganic non-conductive filler are added, and after again sufficient stirring, the polymer-based functional layer slurry is obtained; the polymer-based functional layer slurry is uniformly coated on the CPP side of the ordinary aluminum-plastic film, and after vacuum drying, the polymer-based functional layer is formed on the surface of the ordinary aluminum-plastic film, thereby obtaining the aluminum-plastic film of the application.

[0017] Preferably, the polymer powder and the solvent are used in a weight ratio of 2-5:9-15.

[0018] Preferably, the conductive filler and the nano inorganic non-conductive filler are used in a weight ratio of 20-50:1-5.

[0019] Preferably, the polymer powder and the conductive filler are used in a weight ratio of 2-5:2-5.

[0020] Preferably, the conductive filler is a combination of graphene and SP conductive carbon black.

[0021] Preferably, the mass ratio of graphene to SP conductive carbon black in the combination of graphene and SP conductive carbon black is 3:1-3.

[0022] Preferably, the vacuum drying conditions are: temperature of 60-95℃, air pressure of -95kPa to -70kPa, and drying time of 5-60min.

[0023] Preferably, the thickness of the polymer-based functional layer in the aluminum-plastic film is 5-25μm.

[0024] More preferably, the preparation method of the aluminum-plastic film comprises the following steps:

[0025] 20-50 parts of polymer powder are weighed according to the mass fraction, added into 90-150 parts of solvent, and after sufficient stirring, 20-50 parts of conductive filler and 1-5 parts of nano inorganic non-conductive filler are added, and after again sufficient stirring, the polymer-based functional layer slurry is obtained; the polymer-based functional layer slurry is uniformly coated on the CPP side of the ordinary aluminum-plastic film, and after drying at -95kPa to -70kPa and 60-95℃ for 5-60min, the polymer-based functional layer is formed on the surface of the ordinary aluminum-plastic film, thereby obtaining the aluminum-plastic film of the application.

[0026] Preferably, the conductive filler is a combination of graphene and SP conductive carbon black, and the mass ratio of graphene to SP conductive carbon black in the combination of graphene and SP conductive carbon black is 3:1-3. The thickness of the polymer-based functional layer is 5-25μm.

[0027] In one embodiment of the present application, the polymer powder is modified polyvinylidene fluoride, and the preparation method of the modified polyvinylidene fluoride comprises the following steps:

[0028] After vacuum drying 1-vinyl-3-butyl imidazole tetrafluoroborate and polyvinylidene fluoride (PVDF), the PVDF and 1-vinyl-3-butyl imidazole tetrafluoroborate are added into a Haake mixer for melt blending to obtain a PVDF / 1-vinyl-3-butyl imidazole tetrafluoroborate blend; the PVDF / 1-vinyl-3-butyl imidazole tetrafluoroborate blend is placed in a flat vulcanizing machine for melt hot pressing to obtain a PVDF / 1-vinyl-3-butyl imidazole tetrafluoroborate blend film; the PVDF / 1-vinyl-3-butyl imidazole tetrafluoroborate blend film is vacuum packaged and irradiated under electron beam irradiation; after irradiation, the PVDF / 1-vinyl-3-butyl imidazole tetrafluoroborate blend film is extracted with methanol, dried, and crushed to obtain modified PVDF, i.e., PVDF-g-1-vinyl-3-butyl imidazole tetrafluoroborate. By modifying PVDF with 1-vinyl-3-butyl imidazole tetrafluoroborate, the electrical properties of PVDF are improved, and the piezoelectric and piezoresistive effects of the polymer-based functional layer are optimized.

[0029] Preferably, the PVDF and 1-vinyl-3-butyl imidazole tetrafluoroborate are added into the Haake mixer at a mass ratio of 100:1-10.

[0030] Preferably, the vacuum drying conditions are 40-80℃ for 10-24h.

[0031] Preferably, the melt blending conditions are a temperature of 60-100℃, 10-50rpm for 1-5min of premixing, and 50-100rpm for 5-10min of mixing.

[0032] Preferably, the melt hot pressing conditions are 100-200℃ for 1-5min of hot pressing and 0-20℃ for 1-5min of cold pressing under a pressure of 10-20MPa.

[0033] Preferably, the irradiation conditions are room temperature, an absorbed dose of 30-60kGy, a current of 10-20mA, an acceleration energy of 1-3MeV, and a time of 0.5-1h.

[0034] Preferably, the extraction conditions are 90-120℃ for 48-96h.

[0035] Preferably, the drying conditions are 80-100℃ for 6-18h.

[0036] More preferably, the specific preparation method of the modified polyvinylidene fluoride is as follows:

[0037] Drying 1-vinyl-3-butyl imidazole tetrafluoroborate and PVDF in a vacuum drying oven at 40-80℃ for 10-24h; then adding PVDF and 1-vinyl-3-butyl imidazole tetrafluoroborate in a mass ratio of 100:1-10 into a HAAKE mixer for melt blending, pre-mixing at 60-100℃, 10-50rpm for 1-5min, and mixing at 50-100rpm for 5-10min to obtain a PVDF / 1-vinyl-3-butyl imidazole tetrafluoroborate blend; placing the PVDF / 1-vinyl-3-butyl imidazole tetrafluoroborate blend into a flat vulcanizing machine for melt hot pressing, first hot pressing at 100-200℃ under a pressure of 10-20MPa for 1-5min, and then cold pressing at 0-20℃ for 1-5min to obtain a PVDF / 1-vinyl-3-butyl imidazole tetrafluoroborate blend film; vacuum packaging the PVDF / 1-vinyl-3-butyl imidazole tetrafluoroborate blend film and irradiating it under electron beam irradiation; irradiation conditions: room temperature, absorbed dose 30-60kGy, current 10-20mA, acceleration energy 1-3MeV, and time 0.5-1h; placing the irradiated PVDF / 1-vinyl-3-butyl imidazole tetrafluoroborate blend film into a Soxhlet extractor, extracting it with methanol at 90-120℃ for 48-96h, drying it in a forced air drying oven at 80-100℃ for 6-18h, and crushing it to obtain a modified PVDF, i.e., PVDF-g-1-vinyl-3-butyl imidazole tetrafluoroborate.

[0038] In an embodiment of the present application, the conductive filler is modified, and the step of modifying the conductive filler comprises:

[0039] Mixing p-toluidine, catechol and Tris-HCl, stirring at room temperature, then adding the conductive filler, and performing ultrasonic treatment to obtain reaction solution 1; heating and stirring reaction solution 1, then centrifuging and washing, collecting the precipitate, and drying the precipitate to obtain the modified conductive filler. The modification of the conductive filler improves the distribution of the conductive filler in the polymer-based functional layer, prevents the agglomeration of the conductive filler, and further optimizes the piezoelectric and piezoresistive effects of the polymer-based functional layer.

[0040] Preferably, the p-toluidine, catechol and Tris-HCl are mixed in a ratio of 1-5g:1-5g:100-1000mL.

[0041] Preferably, the concentration of Tris-HCl is 10-50mM, and the pH is 8.0-9.0.

[0042] Preferably, the conductive filler is used in a mass ratio of 1:1-5 with respect to p-toluidine.

[0043] Preferably, the conductive filler is a combination of graphene and SP conductive carbon black.

[0044] Preferably, the mass ratio of graphene and SP conductive carbon black in the combination of graphene and SP conductive carbon black is 3:1-3.

[0045] Preferably, the ultrasonic condition is 20-60KHz frequency, ultrasonic for 10-60min.

[0046] Preferably, the heating and stirring condition is heating and stirring at 40-60℃ for 8-16h.

[0047] Preferably, the drying condition is drying at 40-60℃ for 8-24h.

[0048] More preferably, the specific preparation method of the modified conductive filler is as follows:

[0049] The p-toluidine, catechol and Tris-HCl are mixed in a ratio of 1-5g:1-5g:100-1000mL, stirred at room temperature for 3-5h, the conductive filler is added in a ratio of 1:1-5 of the mass ratio of the conductive filler to p-toluidine, ultrasonic is performed at a frequency of 20-60KHz for 10-60min to obtain reaction liquid 1; the reaction liquid 1 is heated and stirred at 40-60℃ for 8-16h; then centrifugal washing is performed for 3-5 times; the precipitate is collected by filtration, and the precipitate is dried at 40-60℃ for 8-24h to obtain the modified conductive filler.

[0050] The conductive filler is a combination of graphene and SP conductive carbon black, and the mass ratio of graphene and SP conductive carbon black is 3:1-3. The concentration of Tris-HCl is 10-50mM, and the pH is 8.0-9.0.

[0051] The application also provides an application of the aluminum-plastic film in monitoring the swelling gas of the sodium battery package.

[0052] The aluminum-plastic film prepared by the application comprises a general aluminum-plastic film main body and a polymer-based functional layer coated on the surface of the CPP layer of the general aluminum-plastic film. When the aluminum-plastic film is wrapped on the surface of the sodium battery package, when the sodium ion battery package appears swelling gas, the aluminum-plastic film wrapped on the surface of the sodium ion battery package, mainly the polymer-based functional layer on the CPP layer of the aluminum-plastic film, will be pressed. Since the polymer-based functional layer comprises modified PVDF and modified conductive filler, it has a relatively sensitive negative pressure resistance effect. After a very small external voltage is applied to the polymer-based functional layer, the polymer-based functional layer can sensitively reflect the resistance value of the pressure-reduced polymer-based functional layer through the current value of the increased current value. Thus, the swelling gas in the sodium ion battery package can be monitored by monitoring the change of the current of the polymer-based functional layer.

[0053] Compared with the prior art, the present application has the beneficial effects that the present application provides a modification of PVDF, grafts PVDF by 1-vinyl-3-butyl imidazole tetrafluoroborate, improves the piezoelectric effect and negative pressure resistance effect of the prepared polymer-based functional layer. The present application also provides a modification of conductive filler, modifies the conductive filler by aminotoluene, catechol, increases the compatibility between the conductive filler and the polymer matrix, improves the dispersion of the conductive filler in the polymer matrix, and further improves the piezoelectric effect and negative pressure resistance effect of the polymer-based functional layer. The present application also provides an aluminum-plastic film which can be used to monitor the swelling gas of sodium battery package. Based on the negative pressure resistance characteristics of the polymer-based functional layer, the aluminum-plastic film of the present application can quickly and accurately realize the feedback of the internal gas pressure of the sodium ion battery package, monitor the swelling gas of the sodium battery package; it is suitable for the pulp coating system of sodium ion battery, and is suitable for large-scale commercial production; it occupies small volume and does not increase the process difficulty of the battery production system. BRIEF DESCRIPTION OF DRAWINGS

[0054] Figure 1 It is a schematic diagram of the aluminum-plastic film structure.

[0055] Figure 2 It is a schematic diagram of the application of the aluminum-plastic film for monitoring the swelling gas of sodium battery package.

[0056] Figure 3 It is a current-pressure relationship diagram of the polymer-based functional layer under a voltage of 0.1V. DETAILED DESCRIPTION

[0057] The technical solutions of the present application will be described in detail below with reference to the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0058] The experimental methods in the following examples are conventional methods, or according to the conditions suggested by the manufacturer, unless otherwise specified. The materials, reagents, etc. used in the following examples can be obtained from commercial channels, unless otherwise specified.

[0059] Example 1: Preparation of aluminum-plastic film

[0060] A method for preparing an aluminum-plastic film, comprising the following steps:

[0061] The mass fraction 35 parts of PVDF is added into the mass fraction 150 parts of N-methyl pyrrolidone, and is fully stirred and mixed, the mass fraction 20 parts of conductive filler and the mass fraction 1 part of nano silicon dioxide are added, and are fully stirred and mixed, to obtain a polymer-based functional layer slurry; the polymer-based functional layer slurry is uniformly coated on the CPP side of the ordinary aluminum plastic film, and is dried at 90 DEG C under a vacuum degree of-85 kPa for 20 min, to form a polymer-based functional layer on the surface of the ordinary aluminum plastic film, thereby obtaining the aluminum plastic film of the application.

[0062] The conductive filler is a combination of graphene and SP conductive carbon black, and the mass ratio of graphene to SP conductive carbon black in the combination is 3:1; and the obtained polymer-based functional layer is 20 microns thick.

[0063] Example 2: Preparation of aluminum plastic film

[0064] Example 2 and Example 1 differ in that modified PVDF is used to replace PVDF in Example 2, and the modified PVDF is obtained by grafting modification of 1-vinyl-3-butyl imidazole tetrafluoroborate to PVDF. The specific modification steps are as follows:

[0065] The 1-vinyl-3-butyl imidazole tetrafluoroborate and the PVDF are dried in a vacuum drying oven at 60 DEG C for 24 hours; the PVDF and the 1-vinyl-3-butyl imidazole tetrafluoroborate are added to a Haake mixer in a mass ratio of 100:1 for melt blending, and the melt blending conditions are: temperature 90 DEG C, 20 rpm for pre-mixing for 2 min, and 50 rpm for mixing for 5 min, to obtain a PVDF / 1-vinyl-3-butyl imidazole tetrafluoroborate blend; the PVDF / 1-vinyl-3-butyl imidazole tetrafluoroborate blend is placed in a flat vulcanizing machine for melt hot pressing; the melt hot pressing conditions are: under a pressure of 15 MPa, first hot pressing at 200 DEG C for 3 min, and then cold pressing at 20 DEG C for 1 min, to obtain a PVDF / 1-vinyl-3-butyl imidazole tetrafluoroborate blend film; the PVDF / 1-vinyl-3-butyl imidazole tetrafluoroborate blend film is vacuum packaged and irradiated under electron beam; the irradiation conditions are: room temperature, absorbed dose 45 kGy, current 17 mA, acceleration energy 2.5 MeV, and time 1 h; the irradiated PVDF / 1-vinyl-3-butyl imidazole tetrafluoroborate blend film is placed in a Soxhlet extractor, extracted with methanol at 110 DEG C for 72 h, dried in a forced air drying oven at 85 DEG C for 12 h, and then pulverized, to obtain modified PVDF, i.e., PVDF-g-1-vinyl-3-butyl imidazole tetrafluoroborate.

[0066] Example 3: Preparation of aluminum plastic film

[0067] Example 3 differs from Example 2 in that the amount of modified PVDF used in Example 3 is 50 parts. The method of preparing the modified PVDF is the same as that of Example 2.

[0068] Example 4: Preparation of an aluminum-plastic film

[0069] Example 4 differs from Example 3 in that the amount of conductive filler used in Example 4 is 30 parts.

[0070] Example 5: Preparation of an aluminum-plastic film

[0071] Example 5 differs from Example 3 in that the conductive filler used in Example 5 is replaced by a modified conductive filler. The modified conductive filler is obtained by a method of surface in-situ polymerization, and is polymerized and wrapped around the conductive filler by catechol / p-aminotoluene. The specific experimental steps include:

[0072] 0.2 g of p-aminotoluene and 0.2 g of catechol were weighed, added to 100 mL of Tris-HCl, stirred at room temperature for 3 h, heated 0.1 g of conductive filler, and ultrasonically treated at a frequency of 40 KHz for 1 h to obtain a reaction solution 1. The reaction solution 1 was heated and stirred at 60°C for 10 h, then centrifuged and washed 3 times, and the precipitate was collected by filtration and placed in a 60°C oven for drying for 16 h to obtain the modified conductive filler.

[0073] The conductive filler is a combination of graphene and SP conductive carbon black, and the mass ratio of graphene to SP conductive carbon black in the combination of graphene and SP conductive carbon black is 3:1. The concentration of Tris-HCl is 50 mM, and the pH is 8.8.

[0074] Example 6: Preparation of an aluminum-plastic film

[0075] Example 6 differs from Example 4 in that the conductive filler used in Example 6 is replaced by a modified conductive filler. The method of preparing the modified conductive filler is the same as that of Example 5.

[0076] Test Example 1: Piezoelectric performance test of polymer-based functional layer

[0077] The piezoelectric performance of the polymer-based functional layer of Examples 1-6 was tested. The polymer-based functional layer was cut into 2.5 cm x 2.5 cm as a piezoelectric layer, and a copper foil of the same size was prepared as an electrode and assembled on the upper and lower surfaces of the polymer-based functional layer to construct a piezoelectric nanogenerator. Then the piezoelectric nanogenerator was packaged with polyethylene terephthalate, and the output voltage of the nanogenerator was measured by an electrometer. The results are shown in Table 1.

[0078] Table 1 Piezoelectric performance of polymer-based functional layer

[0079]

[0080] Comparing Example 1 and Example 2, it can be seen that the output voltage value of Example 2 is large, indicating that the modification of PVDF improves the electrical properties of PVDF, and enhances the piezoelectric properties of the polymer-based functional layer of Example 2. Comparing Example 2 and Example 3, it can be seen that the output voltage value of Example 3 is large, indicating that increasing the amount of modified PVDF further improves the output voltage value and enhances the piezoelectric properties of the polymer-based functional layer of Example 3.

[0081] Comparing Example 3 and Example 4, it can be seen that the output voltage value of Example 4 is small, indicating that the increase of conductive fillers degrades the piezoelectric properties of the polymer-based functional layer of Example 4. It is possible that too much conductive filler in the polymer matrix easily agglomerates, and the electromechanical coupling effect with the polymer matrix is poor, resulting in a decrease in the output voltage value.

[0082] Comparing Example 3 and Example 5, it can be seen that the output voltage value of Example 5 is large, indicating that the modification of conductive fillers enhances the piezoelectric properties of the polymer-based functional layer of Example 5. Comparing Example 5 and Example 6, it can be seen that the output voltage of Example 6 is large, indicating that the increase of the amount of modified conductive fillers enhances the piezoelectric properties of the polymer-based functional layer of Example 6, unlike Example 4. It is possible that the modified conductive fillers do not agglomerate in the polymer matrix, and they still have good dispersion in the polymer matrix, thereby enhancing the piezoelectric properties of the polymer-based functional layer of Example 6.

[0083] Test Example 2: Piezoresistive properties of the polymer-based functional layer

[0084] The piezoresistive properties of the polymer-based functional layers of Examples 1-6 were tested. The test leads were bonded to the polymer-based functional layer at both ends with conductive silver paste and were packaged and protected with aluminum foil. The leads were connected to a UTD2102CEX oscilloscope, and a universal electronic tester was used to perform load-unload cycles on the experimental samples. The resistance change rate R / R0 of the samples was recorded by the oscilloscope during the compression process, where R represents the resistance value of the polymer-based functional layer under pressure, and R0 represents the initial resistance value of the polymer-based functional layer without pressure. The results are shown in Table 2.

[0085] Table 2 Piezoresistive properties of the polymer-based functional layer

[0086]

[0087] The polymer-based functional layer will exhibit two phenomena under the action of pressure, and the two phenomena coexist, which are negative piezoresistive effect and positive piezoresistive effect. The former is that when the internal conductive path construction speed of the polymer-based functional layer is greater than the destruction speed with the change of pressure, the resistance of the polymer-based functional layer will decrease. The latter is that when the internal conductive path construction speed of the polymer-based functional layer is less than the destruction speed with the change of pressure, the resistance of the polymer-based functional layer will increase.

[0088] Comparing Example 1 and Example 2, it can be seen that the resistance value of Example 1 becomes larger when the pressure is above 0.8 MPa, and the positive piezoresistive effect appears, which may be because part of the formed conductive path is damaged and it is difficult to form a new conductive path. Example 2 shows a negative piezoresistive effect in the pressure range, which shows that after modification of PVDF, the internal conductive path of the polymer-based functional layer may be improved, and thus the sensitivity of the negative piezoresistive effect of the polymer-based functional layer of Example 2 is improved.

[0089] Comparing Example 2 and Example 3, it can be seen that Example 3 shows a negative piezoresistive effect in the pressure range, and the resistance change rate is large, which shows that increasing the amount of modified PVDF improves the sensitivity of the negative piezoresistive effect of the polymer-based functional layer.

[0090] Comparing Example 3 and Example 4, it can be seen that the resistance value of Example 4 remains unchanged when the pressure is above 0.5 MPa, which shows that increasing the amount of conductive filler is not conducive to the piezoresistive effect of the polymer-based functional layer, and reduces the sensitivity of the negative piezoresistive effect, which may be because too much conductive filler agglomerates to form a conductive path that is difficult to damage, thereby reducing the sensitivity of the negative piezoresistive effect.

[0091] Comparing Example 3 and Example 5, it can be seen that the resistance change rate of Example 5 is large, and Example 5 has better sensitivity of the negative piezoresistive effect, which shows that the modified conductive filler enhances the sensitivity of the polymer-based functional layer, which may be because the modified conductive filler has better dispersibility in the polymer matrix and is more sensitive to pressure changes. Comparing Example 5 and Example 6, it can be seen that the resistance change rate of Example 6 is large, and Example 6 has better sensitivity of the negative piezoresistive effect. Unlike Example 4, the increased modified conductive filler in Example 6 does not keep the resistance value of the polymer-based functional layer unchanged, but further improves the piezoresistive effect of the polymer-based functional layer, which may be because the increased amount of modified conductive filler still has good dispersion in the polymer matrix, thereby improving the internal conductive path of the polymer-based functional layer.

[0092] Preferably, Example 6 has a sensitive resistivity change in the range of 0.1-0.8 MPa, and the polymer-based functional layer of Example 6 has better sensitivity of the negative piezoresistive effect.

[0093] Test Example 3: Structure diagram of aluminum-plastic film

[0094] The structure of the aluminum-plastic film prepared by Example 6 is shown in Figure 1 The common aluminum-plastic film 1 and the polymer-based functional layer 2 coated on the common aluminum-plastic film 1 constitute the aluminum-plastic film of the application, which can monitor the swelling gas of the sodium battery.

[0095] Test Example 4: Application of aluminum-plastic film in monitoring the swelling gas of sodium battery

[0096] The aluminum-plastic film prepared in Example 6 was used for a sodium-ion battery pack, a schematic diagram of which is shown in Figure 2 . The common aluminum-plastic film 1 and the polymer-based functional layer 2 coated on the common aluminum-plastic film 1, and the sodium-ion battery pack 3 enclosed therein constitute the application of the aluminum-plastic film of the present application in monitoring the swelling of the sodium-ion battery pack. After a very small voltage is applied, the pressure condition of the sodium-ion battery pack can be monitored in real time through the piezoresistive effect of the polymer-based functional layer 2, and the swelling problem of the battery pack can be found in time.

[0097] Test Example 5: Negative piezoresistive effect test of the polymer-based functional layer

[0098] The negative piezoresistive effect test was performed on the aluminum-plastic film prepared in Example 6, and the current-pressure relationship diagram of the polymer-based functional layer of Example 7 was obtained at a voltage of 0.1 V, as shown in Figure 3 . The corresponding current was detected by applying different pressures to the polymer-based functional layer. Therefore, when the current value increases significantly, it indicates that the battery pack has a swelling phenomenon.

[0099] The above-described examples and / or embodiments are only used to illustrate the preferred examples and / or embodiments for implementing the present application, and do not limit the embodiments of the present application in any form. Any person skilled in the art can make some changes or modifications to other equivalent examples without departing from the scope of the technical means disclosed in the present application, and such changes or modifications should be considered as the same technical or embodiments as the present application.

Claims

1. Application of an aluminum-plastic film in monitoring the swelling gas condition of a sodium battery pack, characterized in that, A polymer-based functional layer is coated on the CPP side of the ordinary aluminum plastic film; the polymer-based functional layer comprises polymer powder; the polymer powder material is modified polyvinylidene fluoride, and the preparation method of the modified polyvinylidene fluoride comprises the following steps: After vacuum drying 1-vinyl-3-butyl imidazole tetrafluoroborate and polyvinylidene fluoride (PVDF), the PVDF and 1-vinyl-3-butyl imidazole tetrafluoroborate are added to a Hake mixer for melt blending to obtain a PVDF / 1-vinyl-3-butyl imidazole tetrafluoroborate blend; the PVDF / 1-vinyl-3-butyl imidazole tetrafluoroborate blend is placed in a flat vulcanizing machine for melt hot pressing to obtain a PVDF / 1-vinyl-3-butyl imidazole tetrafluoroborate blend film; the PVDF / 1-vinyl-3-butyl imidazole tetrafluoroborate blend film is vacuum packaged and irradiated under electron beam irradiation; after irradiation, the PVDF / 1-vinyl-3-butyl imidazole tetrafluoroborate blend film is extracted with methanol, dried, and crushed to obtain modified PVDF, i.e., PVDF-g-1-vinyl-3-butyl imidazole tetrafluoroborate; The polymer-based functional layer further comprises conductive fillers and nano-inorganic non-conductive fillers; The mass ratio of the polyvinylidene fluoride and 1-vinyl-3-butyl imidazole tetrafluoroborate is 100:1-10 to prepare the modified polyvinylidene fluoride.

2. The use of an aluminum-plastic film in monitoring the swelling of a sodium battery pack according to claim 1, characterized in that, The conductive fillers include at least one of conductive carbon black, graphite, carbon nanotubes, graphene, nano-silver powder, nano-iron powder, and indium tin oxide; and the nano-inorganic non-conductive fillers include at least one of nano-aluminum oxide, nano-iron oxide, nano-copper oxide, and nano-silicon dioxide.

3. The use of an aluminum-plastic film in monitoring the swelling of a sodium battery pack according to claim 1, characterized in that, The preparation of the aluminum plastic film comprises the following steps: The polymer powder is added to a solvent, and after sufficient stirring, the conductive fillers and nano-inorganic non-conductive fillers are added, and after again sufficient stirring, a polymer-based functional layer slurry is obtained; the polymer-based functional layer slurry is uniformly coated on the CPP side of the ordinary aluminum plastic film, and after vacuum drying, a polymer-based functional layer is formed on the surface of the ordinary aluminum plastic film to obtain an aluminum plastic film. 4.The application of the aluminum-plastic film in monitoring the swelling gas of the sodium battery pack according to claim 3, characterized in that, The polymer powder and the solvent are used in a weight ratio of 2-5:9-15; the conductive fillers and the nano-inorganic non-conductive fillers are used in a weight ratio of 20-50:1-5; and the polymer powder and the conductive fillers are used in a weight ratio of 2-5:2-5.

5. The use of an aluminum-plastic film in monitoring the swelling of a sodium battery pack according to claim 3, characterized in that, The conductive fillers are a combination of graphene and SP conductive carbon black, and the mass ratio of graphene and SP conductive carbon black in the combination of graphene and SP conductive carbon black is 3:1-3.

6. The use of an aluminum-plastic film in monitoring the swelling of a sodium battery pack according to claim 3, characterized in that, The polymer powder is modified polyvinylidene fluoride, and the solvent contains N-methyl pyrrolidone.

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