A functional current collector and a battery comprising the same

Abstract

The application provides a functional current collector and a battery comprising the same. The functional current collector comprises a base film, and the base film is a polyester composite film. The polyester composite film comprises a polyester and a filler, and the filler is coated by a first silane coupling agent. The filler is an inorganic material or a polymer. The first silane coupling agent has a general structure of (R1O)3-Si-R2-R3. The functional current collector can effectively alleviate the swelling and dissolution of the base layer polyester film, effectively improve the anti-swelling performance of the polyester film, and further effectively improve the electrochemical performance and safety performance of the battery prepared from the functional current collector.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of lithium ion batteries, and particularly relates to a functional current collector and a battery comprising the same. BACKGROUND

[0002] The vigorous development of plastic layer surface metal plating technology provides a new way for large-scale application of new lithium ion battery current collectors. By using an electronically insulating polymer plastic layer as a substrate and depositing a thin layer of metal on the surface thereof, a new type of sandwich structure metalized polymer functional current collector (MPCC, metal layer + polymer layer + metal layer) can be prepared. The MPCC has the dual advantages of polymer plastic and metal, such as light weight, high mechanical strength and elongation, solvent resistance, corrosion resistance, wear resistance, light resistance, electrical conductivity, thermal shrinkage and the like, thereby achieving the purposes of good cycle stability, reducing the thickness of the current collector, improving the energy density and safety.

[0003] The polymer substrate plays an indispensable role in the MPCC and has the characteristics of insulation, thermal shrinkage, melting and ductility difference between the polymer and the metal layer deposited on the surface, which can significantly improve the safety of the battery using the MPCC under mechanical abuse such as needle puncture and extrusion. Among these polymer materials, polyester film has significant advantages, such as high tensile strength, excellent thermal stability, good durability, self-extinguishing and strong flame resistance. In addition, polyester such as PET has good mechanical properties even at a temperature as low as -60℃. Due to the excellent physical and chemical properties of polyester, the low cost due to advanced technology and large-scale production, good heat resistance and the use of evaporation, polyester has become a widely used substrate material in MPCC applications.

[0004] However, due to the presence of a large number of ester bonds in polyester, it is not stable in strong acid and strong alkaline electrolytes and is easily dissolved, swelled or reacted, causing depolymerization of the polyester. If the depolymerized polyester is dissolved in the electrolyte, it will increase the viscosity of the electrolyte, slow down the ion transmission speed and increase the internal resistance of the lithium ion battery. With the increase of the cycle time, the swelling and dissolution reaction of the polyester will cause the chemical bond between the metal layer and the polyester film to gradually age during long-term use, and the interfacial adhesion and peeling strength between the metal layer and the substrate will gradually weaken, thereby causing the cycle capacity to decrease.

[0005] In addition, in the prior art, SiO2 and other nucleating agents are often added to the functional current collector, which will be dissolved and precipitated when immersed in the electrolyte for a long time. This makes the polyester film more prone to swelling and dissolution, and the above phenomenon is particularly obvious after high-temperature cycling. The damage to the polyester film in the functional current collector also accelerates the destruction of the conductive layer, which not only causes the loss of battery capacity, but also causes great safety hazards, which has a great impact on the electrochemical performance and safety performance of the battery using the electrode made of the functional current collector. SUMMARY

[0006] To solve the problems and deficiencies in the prior art, the present application provides a kind of functional current collector and battery comprising it, in the functional current collector, the swelling and dissolution phenomenon of the base layer polyester film can be effectively alleviated, the anti-swelling performance of the polyester film is effectively improved, and the electrochemical performance and safety performance of the battery prepared from the functional current collector are effectively improved.

[0007] According to the first aspect of the application, a functional current collector is provided, comprising a base film, which is a polyester composite film; the polyester composite film comprises polyester and fillers, and the fillers are coated with a first silane coupling agent; the fillers are inorganic materials or polymers; the first silane coupling agent has a general structure of (R1O)3-Si-R2-R3; wherein R1 includes: substituted or unsubstituted C1-C4 alkyl; R2 includes one of the following: substituted or unsubstituted C1-C18 straight-chain alkyl, substituted or unsubstituted C1-C18 branched-chain alkyl, substituted or unsubstituted C2-C18 straight-chain alkenyl with at least one double bond, substituted or unsubstituted C2-C18 branched-chain alkenyl with at least one double bond, substituted or unsubstituted C2-C18 straight-chain alkynyl with at least one triple bond, substituted or unsubstituted C2-C18 branched-chain alkynyl with at least one triple bond, substituted or unsubstituted C3-C18 saturated cyclic alkyl, substituted or unsubstituted C3-C18 at least partially unsaturated cyclic alkyl, substituted or unsubstituted C3-C18 saturated cyclic alkyl without -NH-, and substituted or unsubstituted C3-C18 saturated cyclic alkyl with at least one -NH-; R3 includes one of the following: hydroxyl, amino, vinyl, mercapto, acrylate, epoxy, halogen, and alkali metal.

[0008] In the present application, the fillers are coated with a silane coupling agent containing a specific chemical formula and active groups. The silane coupling agent has active organic groups and silane groups. The active organic groups can react with polymers, and the silane groups can undergo self-polymerization through hydrolysis and condensation, and can connect to inorganic surfaces. Therefore, the silane coupling agent can be coated on the surface of polymers or inorganic materials and effectively connected to the polyester, so that the fillers and the polyester form a uniform inorganic-organic or organic-organic network. When the fillers are inorganic materials, the dispersibility of inorganic material particles in the organic polyester is poor. After the inorganic materials are modified by surface coating with the silane coupling agent, the dispersibility of the inorganic material particles in the polyester is more obviously improved, the roughness of the polyester composite film is reduced, the adhesion between the base film and the primer layer is improved, and the overall structural stability and mechanical properties of the functional current collector are optimized.

[0009] Therefore, the filler coated and modified by the silane coupling agent can be dispersed particularly uniformly in the polyester, and because the filler is coated and modified by the silane coupling agent, the connection between the filler and the polyester is greatly improved, the crystallization temperature and the melting temperature of the polyester composite film can be changed, and the anti-swelling performance of the polyester composite film formed finally can be further improved to avoid the dissolution of the polyester composite film. In addition, the silane coupling agent increases the contact area between the polyester macromolecule and the filler, and enhances the intermolecular adhesion, so that the filler can be effectively fixed to prevent the filler from overflowing into the electrolyte, that is, the precipitation of the filler is greatly reduced, and the safety performance and the electrochemical performance of the battery are not threatened. Finally, because the Si-O bond has a high bond energy (363 kJ / mol), it is relatively stable, and the filler is also fixed, and the heat resistance and high-temperature resistance are very high, so that the thermal stability of the polyester composite film is significantly improved, and the thermal damage is avoided when the polyester composite film is subjected to high temperature and local heat energy, so that the stability and high-temperature cycle performance of the battery based on the functional current collector are improved. In summary, the filler coated and modified by the silane coupling agent in the application is introduced into the preparation of the polyester composite film, so that the thermal stability and the anti-swelling and dissolution performance of the polyester composite film are greatly improved, and therefore the safety performance and the electrochemical performance of the battery can be improved.

[0010] Preferably, R3 includes one of the following: vinyl, amino, mercapto, epoxy, and acrylate.

[0011] Preferably, the thickness of the polyester composite film is 1.0-10 μm. Considering the application requirements of the functional current collector, and taking into account the difficulty and cost of the preparation process, the thickness of the polyester composite film in the above range can better meet the requirements of all aspects.

[0012] Preferably, the inorganic material includes at least one of carbon black, graphite, graphene, aluminum, zinc, aluminum oxide, zinc oxide, iron oxide, silicon dioxide, titanium dioxide, montmorillonite, kaolin, calcium carbonate, and glass fiber; and the polymer includes at least one of polyamide resin, epoxy resin, phenolic resin, polycarbonate resin, polyamide resin, and acrylonitrile-butadiene-styrene copolymer resin.

[0013] Preferably, the preparation of the polyester composite film comprises the following steps: S1. dispersing the filler in a first alcohol solvent, adding a first silane coupling agent thereto, wherein the molar ratio of the filler to the first silane coupling agent is 1:(0.1-0.5), heating to 75-85℃ for 20-50min, then cooling, centrifuging to remove the solvent, and dispersing again in a second alcohol solvent to obtain a solution containing the filler coated with the first silane coupling agent; S2. adding a second silane coupling agent and the solution containing the filler coated with the first silane coupling agent obtained in S1 to a polyester masterbatch, heating to 75-85℃ for 10-30min, and then obtaining the polyester composite film by melt-extrusion-biaxial stretching of the obtained mixture; wherein the molar ratio of the polyester masterbatch: the filler coated with the first silane coupling agent: the second silane coupling agent is 1:(0.1-0.25):(0.01-0.2).

[0014] The polyester composite film prepared by the above steps can fully and uniformly disperse the filler in the polyester composite film, effectively improving the anti-swelling and thermal stability of the polyester composite film. Moreover, the filler is tightly connected to the polyester in the polyester composite film prepared by the above steps, and is not easily precipitated after electrolyte immersion. Therefore, the polyester composite film prepared by the above preparation method has more excellent comprehensive performance, which can further improve the electrochemical performance and safety performance of the battery.

[0015] Preferably, in S1, the first alcohol solvent and the second alcohol solvent independently comprise at least one of methanol and ethanol.

[0016] Preferably, the second silane coupling agent has the general structure (R1O)3-Si-R2-R3; wherein R1 comprises: a substituted or unsubstituted C1-C4 alkyl group; R2 comprises one of: a substituted or unsubstituted C1-C18 linear alkyl group, a substituted or unsubstituted C1-C18 branched alkyl group, a substituted or unsubstituted C2-C18 linear alkenyl group with at least one double bond, a substituted or unsubstituted C2-C18 branched alkenyl group with at least one double bond, a substituted or unsubstituted C2-C18 linear alkynyl group with at least one triple bond, a substituted or unsubstituted C2-C18 branched alkynyl group with at least one triple bond, a substituted or unsubstituted C3-C18 saturated cyclic alkyl group, a substituted or unsubstituted C3-C18 at least partially unsaturated cyclic alkyl group, a substituted or unsubstituted C3-C18 saturated cyclic alkyl group without -NH-, and a substituted or unsubstituted C3-C18 saturated cyclic alkyl group with at least one -NH-; and R3 comprises one of: a hydroxyl group, an amino group, a vinyl group, a mercapto group, an acrylate group, an epoxy group, a halogen group, and an alkali metal group.

[0017] Preferably, the first silane coupling agent and the second silane coupling agent are of the same kind; or, the first silane coupling agent and the second silane coupling agent are of different kinds.

[0018] Preferably, in S1, the first alcohol solvent and the second alcohol solvent independently comprise at least one of methanol and ethanol.

[0019] Preferably, the functional current collector comprises a first protective layer, a first metal layer, a first transition layer, a polyester composite film, a second transition layer, a second metal layer, and a second protective layer in sequence. The transition layer serves to improve the adhesion between the polyester composite film and the metal layer, the metal layer serves to conduct electricity, and the protective layer serves to prevent the metal layer from being chemically corroded or physically damaged. Further, the functional current collector comprises two transition layers, two metal layers, and two protective layers, which can further improve the performance of the functional current collector in all aspects, and make the functional current collector have more excellent mechanical properties, electrical conductivity, and electrolyte resistance.

[0020] Preferably, the first transition layer and the second transition layer independently comprise at least one of aluminum oxide, silicon oxide, titanium oxide, nickel, chromium, titanium, nickel-chromium alloy, nickel-chromium-copper alloy, and silicon-aluminum alloy.

[0021] Preferably, the adhesion between the first transition layer and the first metal layer and between the second transition layer and the second metal layer is 100-900 N / m. The adhesion between the transition layer and the metal layer (conductive layer) affects the relative movement between the metal layer and the polyester film during the deformation of the functional current collector, thereby affecting the deformation and fission behavior of the metal layer and further affecting the effect of the metal layer on the improvement of the safety performance of the battery.

[0022] Preferably, the first metal layer and the second metal layer independently comprise at least one of aluminum, copper, gold, silver, nickel, zinc, or a metal alloy formed by combining at least two of the above metals.

[0023] Preferably, the first protective layer and the second protective layer independently comprise at least one of nickel, chromium, nickel-chromium alloy, nickel-based alloy, copper-based alloy, copper oxide, aluminum oxide, nickel oxide, chromium oxide, cobalt oxide, copper-chromium oxide, graphite, carbon black, carbon nanometer quantum dots, carbon nanotubes, carbon nanofibers, graphene, and graphene oxide.

[0024] Preferably, the thickness of the first transition layer and the second transition layer is independently 5-50 nm.

[0025] Preferably, the thickness of the first metal layer and the second metal layer is independently 400-2000 nm. If the metal layer is too thin, the electrical conductivity is poor; if the metal layer is too thick, the functional current collector prepared is too thick and heavy, which is not conducive to improving the energy density of the battery.

[0026] Preferably, the thickness of the first metal layer and the second metal layer is independently 800-1200nm. The metal layer with the thickness in the range is more conducive to balancing the conductivity and the energy density of the battery.

[0027] Preferably, the preparation method of the first metal layer and the second metal layer comprises one or more of evaporation, magnetron sputtering, chemical plating, electroplating and CVD.

[0028] Preferably, the preparation method of the first metal layer and the second metal layer is electroplating or magnetron sputtering.

[0029] Preferably, the thickness of the first protective layer and the second protective layer is independently 10-100nm.

[0030] Preferably, the thickness of the first protective layer and the second protective layer is independently 20-80nm, and the thickness of the first protective layer and the second protective layer is not more than one-tenth of the thickness of the first metal layer and the second metal layer.

[0031] Preferably, the material of the first protective layer and the second protective layer can be consistent or inconsistent, and the thickness of the first protective layer and the second protective layer can be consistent or inconsistent.

[0032] Preferably, the preparation method of the first protective layer and the second protective layer comprises one or more of physical vapor deposition, chemical vapor deposition, in-situ forming and coating.

[0033] According to the second aspect of the present application, a battery comprising the functional current collector is provided. The battery prepared by using the functional current collector has better thermal stability, and thus the electrochemical performance and safety performance of the battery are effectively improved. DETAILED DESCRIPTION

[0034] In order to make the person skilled in the art better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present application, not all.

[0035] Embodiment 1

[0036] The functional current collector of the present embodiment is prepared according to the following steps:

[0037] S1. The silica particles are ultrasonically dispersed in ethanol, and a first silane coupling agent, vinyltrimethoxysilane (A-171), is added thereto. After stirring and reacting at 80℃ for 30min, the reaction is stopped, and the solution is cooled to room temperature. After removing the solvent by centrifugation, the solution is again dispersed in ethanol to obtain a solution containing silane coupling agent-coated silica (modified silica). The molar ratio of the silica particles to A-171 is 1:0.3.

[0038] S2. Add a second silane coupling agent vinyl trimethoxysilane (A-171) and the solution of silane coupling agent coated filler obtained in S1 to the PET polyester masterbatch, heat to 80°C for 20 min, then melt-extrude and biaxially stretch the resulting mixture to obtain the polyester composite film, which has a thickness of 6 μm; wherein the molar ratio of PET polyester masterbatch: silane coupling agent coated filler: A-171 is 1:0.15:0.1;

[0039] S3. Place the polyester composite film prepared in S2 in a magnetron sputtering machine, and deposit a 5 nm transition layer on each side of the polyester film using a nickel-chromium alloy target as the target material. The specific process conditions are as follows: the nickel-chromium target (purity: 99.99%) is used as the target material, the power is 4 KW, the argon flow rate is 50 mL / min, the film plating vacuum degree is 0.08 Pa, the film plating time is 1 s, and the temperature of the main roller during film plating is 20°C.

[0040] S4. Place the product obtained in S3 in a magnetron sputtering machine, and deposit a 900 nm copper layer (metal layer) on each side. The specific process conditions are as follows: the copper target (purity: 99.99%) is used as the target material, the power is 12.0 KW, the argon flow rate is 70 mL / min, the film plating vacuum degree is 0.1 Pa, the film plating time is 100 s, and the cooling temperature of the main roller during film plating is -5°C.

[0041] S5. Soak the product obtained in S4 in a 0.5 g / L aqueous solution of chromic anhydride (25°C) for 20 s, then clean it in a pure water tank, and then dry it in a 60°C oven to obtain the functional current collector.

[0042] Example 2

[0043] The example is basically the same as Example 1, except that the first and second silane coupling agents added in S1 and S2 are both N-(2-aminoethyl)-3-aminopropyl trimethoxysilane (KH-792). The rest is the same as Example 1.

[0044] Example 3

[0045] The example is basically the same as Example 1, except that the first and second silane coupling agents added in S1 and S2 are both 3-aminopropyl trimethoxysilane (APTMS). The rest is the same as Example 1.

[0046] Example 4

[0047] The example is basically the same as Example 1, except that the first and second silane coupling agents added in S1 and S2 are both 3-mercaptopropyl trimethoxysilane (MPS). The rest is the same as Example 1.

[0048] Example 5

[0049] The embodiment 1 is basically identical, except that in S1 and S2, the first and second silane coupling agents added are both bis(triethoxysilylpropyl) tetrasulfide (TESPT). The rest is identical with the embodiment 1.

[0050] Embodiment 6

[0051] The embodiment 1 is basically identical, except that in S1 and S2, the first and second silane coupling agents added are both 3-(2,3-epoxypropoxy) propyl trimethoxysilane (KH-560). The rest is identical with the embodiment 1.

[0052] Embodiment 7

[0053] The embodiment 1 is basically identical, except that in S1 and S2, the first and second silane coupling agents added are both 3-(methacryloyloxy) propyl trimethoxysilane (KH-570). The rest is identical with the embodiment 1.

[0054] Embodiment 8

[0055] The embodiment 1 is basically identical, except that in S1, the first silane coupling agent added is N-(2-aminoethyl)-3-aminopropyl trimethoxysilane (KH-792), and in S2, the second silane coupling agent added is 3-(2,3-epoxypropoxy) propyl trimethoxysilane (KH-560). The rest is identical with the embodiment 1.

[0056] Embodiment 9

[0057] The embodiment 1 is basically identical, except that in S2, the second silane coupling agent added is 3-(methacryloyloxy) propyl trimethoxysilane (KH-570). The rest is identical with the embodiment 1.

[0058] Embodiment 10

[0059] The embodiment 1 is basically identical, except that in S1, the molar ratio of the silica particles, A-171 is 1:0.05. The rest is identical with the embodiment 1.

[0060] Embodiment 11

[0061] The embodiment 1 is basically identical, except that in S2, the molar ratio of the PET polyester masterbatch, the powder (modified silica), A-171 is 1:0.1:0.1. The rest is identical with the embodiment 1.

[0062] Embodiment 12

[0063] The same as Example 1, except that in S2, the molar ratio of PET polyester masterbatch, powder (modified silica), A-171 is 1:0.2:0.1. The rest is the same as Example 1.

[0064] Example 13

[0065] The same as Example 1, except that in S2, the molar ratio of PET polyester masterbatch, powder (modified silica), A-171 is 1:0.25:0.1. The rest is the same as Example 1.

[0066] Example 14

[0067] The same as Example 1, except that in S2, the molar ratio of PET polyester masterbatch, powder (modified silica), A-171 is 1:0.3:0.1. The rest is the same as Example 1.

[0068] Example 15

[0069] The same as Example 2, except that in S1, epoxy resin is used as filler, and the molar ratio of epoxy resin, KH-792 is also 1:0.3. The rest is the same as Example 2.

[0070] Example 16

[0071] The same as Example 16, except that in S1 and S2, the silane coupling agent added is APTMS. The rest is the same as Example 15.

[0072] Example 17

[0073] The same as Example 15, except that in S1 and S2, the silane coupling agent added is KH-560. The rest is the same as Example 15.

[0074] Example 18

[0075] The same as Example 1, except that in S2, no second silane coupling agent, vinyl trimethoxysilane (A-171) is added. The rest is the same as Example 1.

[0076] Comparative Example 1

[0077] The same as Example 1, except that no modified silica filler is added, and the specific measures are to use a 6 μm polyester film prepared with a polyester masterbatch with a content of 100%. The rest is the same as Example 1.

[0078] Comparative Example 2

[0079] The embodiment 1 is basically identical, except that in S1, the specific operation is as follows: the silica particles are ultrasonically dispersed in ethanol to obtain an unmodified silica solution; in S2, the specific operation is as follows: the PET polyester masterbatch is mixed with the unmodified silica solution, wherein the molar ratio of the PET polyester masterbatch to the unmodified silica is 1:0.15, and then the obtained mixture is subjected to melt-extrusion-biaxial stretching to obtain a polyester composite film with a thickness of 6 μm; the rest is identical with the embodiment 1.

[0080] Test Example

[0081] 1. Experimental construction

[0082] The batteries assembled with the functional current collectors prepared in the above examples and comparative examples are subjected to high-temperature cycle performance test and safety performance test, and the specific test method is as follows:

[0083] Battery assembly:

[0084] For the positive electrode, the positive electrode current collector is an aluminum foil (thickness of 13 μm), and the positive electrode material is LiNi 0.6 Mn 0.2 Co 0.2 O2(NCM622);

[0085] For the negative electrode, the negative electrode current collector is the functional current collector prepared in the above examples and comparative examples, and the negative electrode material is artificial graphite;

[0086] For the separator, an aluminum oxide ceramic coated polyethylene separator (thickness of 25 μm) is used;

[0087] For the electrolyte, a carbonate solution of 1 mol·L -1 LiPF6 is used, and the solvent is a mixture of propylene carbonate, ethylene carbonate and methyl ethyl carbonate with a molar ratio of 1:1:1;

[0088] Using the above materials, a lithium ion battery is assembled.

[0089] (1) High-temperature cycle performance test:

[0090] The test procedure comprises: 1) discharging the battery cell to a discharge termination voltage at 45℃ with I1 current (1 hour discharge current), and standing for 30 min; 2) charging the battery cell to a charge termination voltage with I1 current, and then charging with constant voltage until the charge termination current is reduced to 0.05 times of I1, and standing for 30 min after charging; 3) discharging the battery cell to a discharge termination voltage with I1 current; 4) continuously cycling steps 1)-3) for 500 times, recording the battery capacity at the first time and the 500th time, and calculating the capacity retention rate of the battery, i.e. the battery capacity at the 500th time / battery capacity at the first time x 100%.

[0091] (2) Safety performance test:

[0092] The safety performance of the battery is verified by a needle puncture experiment, and the specific process is as follows: the battery prepared above is placed in a needle puncture experiment device, wherein the diameter of the needle is 3 mm, the needle puncture speed is 10 mm / s, the sampling interval is 100 ms, and the sampling time is 15 min. If the safety performance is qualified, the battery should not explode, catch fire or smoke. Taking 100 batteries as test samples, the safety performance = (the number of batteries with qualified safety performance / 100) x 100%.

[0093] 2. Experimental results

[0094] The high-temperature cycle performance of the functional current collector prepared in the above examples and comparative examples and the safety performance test results of the battery assembled therefrom are shown in Table 1.

[0095] Table 1 High-temperature cycle performance of the functional current collector prepared in the examples and comparative examples and safety performance test results of the battery assembled therefrom

[0096]

[0097]

[0098] As shown in Table 1, the functional current collector provided by the application can effectively improve the thermal stability and anti-swelling and dissolution performance of the polyester composite film, thereby effectively improving the electrochemical performance (such as high-temperature cycle performance) and safety performance of the battery prepared therefrom. For details, refer to the data of Examples 1-18.

[0099] In Comparative Example 1, no modified silica filler is added, and in Comparative Example 2, unmodified silica is added, which both result in the decline of the high-temperature cycle performance and safety performance of the battery. This shows that neither adding no modified silica filler nor adding only unmodified silica can effectively improve the thermal stability and anti-swelling and dissolution performance of the polyester composite film, and thus cannot effectively improve the high-temperature cycle performance and safety performance of the battery prepared therefrom.

[0100] Further observation of Examples 1-9, adding different silane coupling agents to modify the silica particles and the polyester film, can make the battery have good high temperature cycle performance and safety performance, which shows that adding different silane coupling agents to modify the silica particles and the polyester film can effectively improve the thermal stability and anti-swelling and dissolving performance of the polyester composite film, and further improve the high temperature cycle performance and safety performance of the battery prepared therefrom. The battery performance of Example 8 is better than that of Example 9, which shows that the appropriate combination of silane coupling agents in S1 and S2 has better modification effect on the polyester composite film, and thus is more conducive to further optimizing the high temperature cycle performance and safety performance of the battery.

[0101] Comparing Comparative Example 1 and Example 10, the amount of the first silane coupling agent added in Example 10 is too small, which also causes the related performance of the battery to decrease, which shows that controlling the amount of the first silane coupling agent (or the second silane coupling agent) within a certain range is more conducive to the comprehensive modification of the polyester film composite film, improving the comprehensive performance of the polyester composite film, and thus further optimizing the related performance of the battery.

[0102] Comparing Comparative Example 1 and Examples 11-14, the amount of modified silica added in Example 14 is too high, which is not conducive to further improving the high temperature cycle performance and safety performance of the battery, which shows that the amount of modified silica added needs to be within a certain range to improve the overall performance of the polyester composite film and achieve the purpose of further optimizing the battery performance.

[0103] Observing Examples 15-17, it can be seen that when the silica is adjusted to an epoxy resin, a polyester composite film with good performance can also be obtained, and thus the battery prepared therefrom also has good high temperature cycle performance and safety performance.

[0104] Comparing Comparative Example 1 and Example 18, no second silane coupling agent is added in S2 in Example 18, which makes the modification effect on the polyester composite film worse, resulting in a decrease in the high temperature cycle performance and safety performance of the battery.

[0105] The above examples are only used to illustrate the technical solutions of the present application and are not intended to limit the scope of protection of the present application. Although the present application has been described in detail with reference to the above examples, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents, and these modifications or replacements are within the scope of protection of the present application.

Claims

1. A functional current collector characterized by: The base film is a polyester composite film; The polyester composite film comprises polyester, fillers coated with a first silane coupling agent; The fillers are inorganic materials or polymers; The first silane coupling agent has a general structure of (R1O)3-Si-R2-R3; wherein R1 comprises substituted or unsubstituted C1-C4 alkyl; R2 comprises one of the following: substituted or unsubstituted C1-C18 straight-chain alkyl, substituted or unsubstituted C1-C18 branched-chain alkyl, substituted or unsubstituted C2-C18 straight-chain alkenyl with at least one double bond, substituted or unsubstituted C2-C18 branched-chain alkenyl with at least one double bond, substituted or unsubstituted C2-C18 straight-chain alkynyl with at least one triple bond, substituted or unsubstituted C2-C18 branched-chain alkynyl with at least one triple bond, substituted or unsubstituted C3-C18 saturated cyclic alkyl, substituted or unsubstituted C3-C18 at least partially unsaturated cyclic alkyl, substituted or unsubstituted C3-C18 saturated cyclic alkyl without -NH-, and substituted or unsubstituted C3-C18 saturated cyclic alkyl with at least one -NH-; R3 comprises one of the following: hydroxyl, amino, vinyl, mercapto, acrylate, epoxy, halogen, and alkali metal.

2. The functional fluid of claim 1, wherein, R3 comprises one of the following: vinyl, amino, mercapto, and epoxy.

3. The functional fluid of claim 1, wherein: The polyester composite film has a thickness of 1.0-10 μm.

4. The functional current collector of claim 1, wherein: The inorganic materials comprise at least one of carbon black, graphite, graphene, aluminum, zinc, aluminum oxide, zinc oxide, iron oxide, silicon dioxide, titanium dioxide, montmorillonite, kaolin, calcium carbonate, and glass fiber; The polymers comprise at least one of polyamide resin, epoxy resin, phenolic resin, polycarbonate resin, polyamide resin, and acrylonitrile-butadiene-styrene copolymer resin.

5. The functional fluid of claim 1, wherein, The polyester composite film is prepared by the following steps: S1. The fillers are dispersed in a first alcohol solvent, and the first silane coupling agent is added thereto, wherein the molar ratio of the fillers to the first silane coupling agent is 1:(0.1-0.5), and the mixture is heated to 75-85°C for 20-50 min, then cooled, centrifuged to remove the solvent, and dispersed in a second alcohol solvent again to obtain a solution containing the fillers coated with the first silane coupling agent; S2. The second silane coupling agent and the solution containing the fillers coated with the first silane coupling agent obtained in S1 are added to a polyester masterbatch, and the mixture is heated to 75-85°C for 10-30 min, and then the polyester composite film is obtained by melt-extrusion-biaxial stretching; wherein the molar ratio of the polyester masterbatch to the fillers coated with the first silane coupling agent to the second silane coupling agent is 1:(0.1-0.25):(0.01-0.2).

6. The functional fluid of claim 5, wherein: The first silane coupling agent and the second silane coupling agent are the same or different.

7. The functional fluid of any of claims 1-6, wherein: The first protective layer, the first metal layer, the first transition layer, the polyester composite film, the second transition layer, the second metal layer, and the second protective layer are sequentially arranged.

8. The functional fluid of claim 7, wherein: The first transition layer and the second transition layer each independently comprise at least one of aluminum oxide, silicon oxide, titanium oxide, nickel, chromium, titanium, nickel-chromium alloy, nickel-chromium-copper alloy, and silicon-aluminum alloy. The first metal layer and the second metal layer each independently comprise at least one of aluminum, copper, gold, silver, nickel, zinc, or a metal alloy formed by combination of at least two of the above metals. The first protective layer and the second protective layer each independently comprise at least one of nickel, chromium, nickel-chromium alloy, nickel-based alloy, copper-based alloy, copper oxide, aluminum oxide, nickel oxide, chromium oxide, cobalt oxide, copper-chromium oxide, graphite, carbon black, carbon nanometer quantum dot, carbon nanometer tube, carbon nanometer fiber, graphene, and graphene oxide.

9. The functional fluid of claim 8, wherein: The thickness of the first transition layer and the second transition layer is independently 5-50 nm. The thickness of the first metal layer and the second metal layer is independently 400-2000 nm. The thickness of the first protective layer and the second protective layer is independently 10-100 nm.

10. The functional fluid of claim 9, wherein: The thickness of the first metal layer and the second metal layer is independently 800-1200 nm.

11. A battery, characterized by: The functional current collector comprises the functional current collector according to any one of claims 1-10.

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