Isolating membrane and preparation method thereof, secondary battery and electric device

Abstract

The invention relates to an isolating membrane and a preparation method thereof, a secondary battery and an electric device, the isolating membrane comprises a base membrane and an inorganic oxide arranged in a porous structure of the base membrane, the inorganic oxide comprises one or more of silicon dioxide, titanium dioxide, zirconium dioxide or aluminum oxide, and the average pore size of the isolating membrane is 0.4 nm-1 nm. The inorganic oxide in the porous structure of the base membrane can improve the compactness of the isolating membrane and reduce the porosity of the isolating membrane; meanwhile, the average pore size of the isolating membrane meets the range, and the negative influence of mutual diffusion of other components except active ions in the electrolyte on the performance of the secondary battery can be reduced, so that the cycle performance of the secondary battery can be improved.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, and particularly to a separator, a preparation method thereof, a secondary battery, and an electrical device. Background Art

[0002] The statements herein only provide background information related to the present application and do not necessarily constitute prior art.

[0003] The popularization of consumer electronic products, electric vehicles, etc. has put forward higher requirements for the cycling performance of secondary batteries used in these products. The main function of the separator in the secondary battery is to separate the positive electrode and the negative electrode to prevent direct contact and short circuit between the positive electrode and the negative electrode. At the same time, it is also required that active ions can smoothly pass through the separator during the charge and discharge process of the secondary battery to form a current. The performance of the separator affects the performance of the secondary battery to a certain extent. Therefore, how to improve the separator to enhance the cycling performance of the secondary battery is a technical problem that needs to be solved urgently at present. Summary of the Invention

[0004] The present application provides a separator, a preparation method thereof, a secondary battery, and an electrical device, aiming to enhance the cycling performance of the secondary battery.

[0005] In a first aspect of the present application, a separator is provided, which includes a base film and inorganic oxides disposed in the porous structure of the base film. The inorganic oxides include one or more of silicon dioxide, titanium dioxide, zirconium dioxide, or aluminum oxide, and the average pore size of the separator is 0.4 nm to 1 nm.

[0006] The inorganic oxides in the porous structure of the base film can improve the denseness of the separator and reduce the porosity of the separator; at the same time, the average pore size of the separator meets the above range, which can not only enable the separator to have a certain transmission ability for active ions, but also can inhibit the component diffusion on both sides of the separator to a certain extent, reducing the negative impact of the mutual diffusion of other components in the electrolyte except active ions on the performance of the secondary battery, thereby enhancing the cycling performance of the secondary battery.

[0007] In some embodiments, the separator further includes the inorganic oxides disposed on at least part of the surface of the base film. Thereby, the cycling performance of the secondary battery can be further enhanced.

[0008] In some embodiments, the mass ratio of the inorganic oxides in the separator is 6% to 90%. Thereby, it is beneficial to reduce the porosity of the separator, and at the same time, it is beneficial to balance the ionic conductivity and denseness of the separator, thereby further enhancing the cycling performance of the secondary battery.

[0009] In some embodiments, the air permeability of the separator membrane is ≥4500 s / 100 cc, and the ionic conductivity of the separator membrane is ≥0.1 ms / cm. Thereby, it is beneficial to balance the ionic conductivity and compactness of the separator membrane, thereby further improving the cycling performance of the secondary battery.

[0010] In some embodiments, the air permeability of the separator membrane is 5100 s / 100 cc to 44000 s / 100 cc, and the ionic conductivity of the separator membrane is 0.13 ms / cm to 0.45 ms / cm. Thereby, it is beneficial to further balance the ionic conductivity and compactness of the separator membrane, thereby further improving the cycling performance of the secondary battery.

[0011] In some embodiments, the thickness of the separator membrane is 5 μm to 50 μm. Thereby, it is beneficial to further improve the cycling performance of the secondary battery.

[0012] In some embodiments, the base film includes at least one of a polyolefin-based film, a polyvinyl fluoride-based film, a cellulose-containing nanofiber-based film, and a polyimide-based film.

[0013] In a second aspect of the present application, a method for preparing a separator membrane is provided, including:

[0014] Hydrolyzing a base film in a hydrolysis solution containing an ester compound to obtain a separator membrane, where the ester compound includes one or more of a silicate compound, a titanate compound, a zirconate compound, or an aluminate compound;

[0015] Wherein, the separator membrane includes a base film and inorganic oxides disposed in the porous structure of the base film, the inorganic oxides include one or more of silicon dioxide, titanium dioxide, zirconium dioxide, or aluminum oxide, and the average pore size of the separator membrane is 0.4 nm to 1 nm.

[0016] The inorganic oxides in the porous structure of the base film can improve the compactness of the separator membrane and reduce the porosity of the separator membrane; at the same time, the average pore size of the separator membrane meets the above range, which can not only enable the separator membrane to have a certain transmission ability for active ions, but also can inhibit the component diffusion on both sides of the separator membrane to a certain extent, reducing the negative impact of the mutual diffusion of other components in the electrolyte except active ions on the performance of the secondary battery, thereby improving the cycling performance of the secondary battery. The above types of inorganic oxides are relatively stable, which can not only improve the cycling performance of the secondary battery, but also will not decompose and cause negative impacts on other electrochemical performances of the secondary battery. In addition, the above preparation method is simple and convenient, and is suitable for mass production of separator membranes.

[0017] In some embodiments, the temperature of the hydrolysis treatment is 20°C to 90°C, and the time is 5h to 24h. Thus, it is beneficial to control the degree of hydrolysis of the hydrolysis solution and the mass ratio of the inorganic oxides in the separator membrane, thereby balancing the ionic conductivity and denseness of the separator membrane, and further improving the cycling performance of the secondary battery.

[0018] In some embodiments, the temperature of the hydrolysis treatment is 20°C to 90°C, and the time is 10h to 16h. Thus, it is beneficial to control the degree of hydrolysis of the hydrolysis solution and the mass ratio of the inorganic oxides in the separator membrane, thereby balancing the ionic conductivity and denseness of the separator membrane, and further improving the cycling performance of the secondary battery.

[0019] In some embodiments, the mass ratio of the ester compound in the hydrolysis solution is 10% to 70%. Thus, it is beneficial to control the mass ratio of the inorganic oxides in the separator membrane, balance the ionic conductivity and denseness of the separator membrane, and further improve the cycling performance of the secondary battery.

[0020] In some embodiments, the mass ratio of the ester compound in the hydrolysis solution is 21% to 62%. Thus, it is beneficial to control the mass ratio of the inorganic oxides in the separator membrane, balance the ionic conductivity and denseness of the separator membrane, and further improve the cycling performance of the secondary battery.

[0021] In some embodiments, the silicate ester compound includes tetraethyl orthosilicate and / or tetramethyl orthosilicate. And / or,

[0022] The titanate ester compound includes tetraethyl titanate and / or tetrabutyl titanate; and / or,

[0023] The zirconate ester compound includes tetraethyl zirconate; and / or,

[0024] The aluminate ester compound includes trimethyl aluminate and / or triethyl aluminate.

[0025] In some embodiments, the base film satisfies one or more of the following conditions:

[0026] (1) The average pore size of the base film is 5nm to 100nm;

[0027] (2) The thickness of the base film is 5μm to 20μm;

[0028] (3) The air permeability of the base film is 50s / 100cc to 1200s / 100cc.

[0029] Thus, the cycling performance of the secondary battery can be further improved.

[0030] In some embodiments, the pH value of the hydrolysis solution is 0.5 to 6. Thus, it is beneficial to promote the hydrolysis of the hydrolysis solution to form inorganic oxides, thereby further improving the denseness of the separator and the cycling performance of the secondary battery.

[0031] In some embodiments, the hydrolysis solution further contains a carboxylic acid catalyst, and the mass ratio of the carboxylic acid catalyst in the hydrolysis solution is 5% to 30%. Thus, it is beneficial to promote the hydrolysis reaction of the hydrolysis solution.

[0032] In a third aspect of the present application, there is provided a secondary battery, including at least one of the separator described in the first aspect of the present application and the separator prepared by the preparation method described in the second aspect of the present application.

[0033] The secondary battery of the present application includes at least one of the separator provided by the present application and the separator prepared by the preparation method provided by the present application, and thus has at least the same advantages as the separator or the separator prepared by the preparation method.

[0034] In some embodiments, the secondary battery further includes a positive electrode sheet, a negative electrode sheet, a first electrolyte disposed between the positive electrode sheet and the separator, and a second electrolyte disposed between the negative electrode sheet and the separator.

[0035] In some embodiments, the composition and / or content of the first electrolyte is different from that of the second electrolyte.

[0036] In a fourth aspect of the present application, there is provided an electrical device, including the secondary battery described in the third aspect of the present application.

[0037] The electrical device of the present application includes the secondary battery provided by the present application, and thus has at least the same advantages as the secondary battery.

[0038] Details of one or more embodiments of the present application are set forth in the following drawings and description. Other features, objects, and advantages of the present application will become apparent from the specification, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] To better describe and illustrate the embodiments or examples provided by the present application, one or more drawings may be referred to. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the currently described embodiments or examples, and the currently understood best mode of these applications. Moreover, in all the drawings, the same reference numerals are used to denote the same components. In the drawings:

[0040] Figure 1 It is a schematic diagram of a battery cell according to an embodiment of the present application.

[0041] Figure 2 The Figure 1 exploded view of a battery cell according to an embodiment of the present application shown in the figure.

[0042] Figure 3 Schematic diagram of a battery module according to an embodiment of the present application.

[0043] Figure 4 Schematic diagram of a battery pack according to an embodiment of the present application.

[0044] Figure 5 The Figure 4 exploded view of a battery pack according to an embodiment of the present application shown in the figure.

[0045] Figure 6 Schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of the present application.

[0046] Figure 7 Schematic diagram of the placement position of the separator in the barrier property test method of the present application.

[0047] Figure 8 Scanning electron micrograph of the surface of the base film in Example 1 of the present application.

[0048] Figure 9 Scanning electron micrograph of the surface of the separator in Example 1 of the present application.

[0049] Figure 10 Scanning electron micrograph of the cross-section of the separator in Example 1 of the present application.

[0050] Figure 11 X-ray diffraction pattern of the separator prepared in Example 1 of the present application.

[0051] Explanation of reference numerals:

[0052] 1 Battery pack; 2 Upper box body; 3 Lower box body; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Cover plate; 6 Electrical device; 7 Separator; 8 Iodine-containing dimethyl sulfoxide solution; 9 Iodine-free dimethyl sulfoxide solution; 10 Large bottle; 11 Small bottle. Detailed description of specific embodiments

[0053] Hereinafter, some embodiments of the separator of the present application, its preparation method, secondary battery and electrical device are described in detail with appropriate reference to the drawings. However, there may be cases where non-essential details are omitted. For example, there are cases where the detailed description of well-known matters and the repeated description of actually identical structures are omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0054] The "range" disclosed in this application can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The range defined in this way can include or not include the end values. Any end value can be independently included or not included, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, ranges of 60-110 and 80-120 are understood to be contemplated. In addition, if the minimum range values of 1 and 2 are listed, and if the maximum range values of 3, 4, and 5 are also listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise specified, the numerical range "a-b" represents an abbreviated representation of any real number combination between a and b, where both a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been fully listed herein, and "0-5" is only an abbreviated representation of these numerical combinations. Additionally, when a certain parameter is expressed as an integer ≥2, it is equivalent to listing the parameter as integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For example, when a certain parameter is expressed as an integer selected from "2-10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0055] In this application, terms such as "a plurality of" and "a variety of", unless otherwise specified, mean greater than 2 or equal to 2 in quantity. For example, "one or more" means one or greater than or equal to two.

[0056] If there is no special instruction, all embodiments and optional embodiments of this application can be combined with each other to form a new technical solution.

[0057] Referring to "embodiment" herein means that the specific features, structures, or characteristics described in connection with the embodiment can be included in at least one embodiment or implementation manner of this application. The occurrence of this phrase at various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments. The same understanding applies to "implementation manner" mentioned herein.

[0058] Those skilled in the art can understand that in the methods of various embodiments or examples, the written order of each step does not mean a strict execution order that constitutes any limitation on the implementation process. The detailed execution order of each step should be determined by its function and possible internal logic. If there is no special explanation, all steps of this application can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) carried out sequentially, or may also include steps (b) and (a) carried out sequentially. For example, when it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or may also include steps (a), (c), and (b), or may also include steps (c), (a), and (b), etc.

[0059] In this application, in the open technical features or technical solutions described by words such as "containing", "comprising", "including", etc., without other explanations, additional members other than the listed members are not excluded. It can be regarded as providing both a closed feature or solution composed of the listed members and an open feature or solution that also includes additional members outside the listed members. For example, A includes a1, a2, and a3. Without other explanations, it may also include other members or may not include additional members. It can be regarded as providing both the feature or solution that "A is composed of a1, a2, and a3" and the feature or solution that "A not only includes a1, a2, and a3, but also includes other members". In this application, without other explanations, A (such as B) means that B is a non-limiting example in A, and it can be understood that A is not limited to B.

[0060] In this application, "optionally", "optional", "option" mean that it can be there or not, that is, it refers to any one of the two parallel options of "yes" or "no". If "optional" appears multiple times in a technical solution, without special explanation and without contradiction or mutual restriction relationship, each "optional" is independent of each other.

[0061] Traditional separator membranes mostly have a loose and porous morphology, and substances such as solutes, solvents, and additives in the electrolyte can easily pass through the separator membrane for transmission. However, the transmission of substances other than active ions through the separator membrane may have a negative impact on the cycling performance of the battery. For example, the transmission of anions through the separator membrane will increase the internal polarization of the battery to a certain extent. Some additives are friendly to the positive electrode, but their transmission through the separator membrane to the negative electrode will deteriorate the cycling performance of the battery.

[0062] Based on this, an embodiment of the present application provides a separator, which includes a base film and inorganic oxides disposed in the porous structure of the base film. The inorganic oxides include one or more of silicon dioxide (SiO2), titanium dioxide (TiO2), zirconium dioxide (ZrO2), or aluminum oxide (Al2O3). The average pore size of the separator is 0.4 nm to 1 nm.

[0063] In the above embodiment, the inorganic oxides in the porous structure of the base film can improve the denseness of the separator and reduce the porosity of the separator. At the same time, the average pore size of the separator meets the above range, which can not only enable the separator to have a certain transmission ability for active ions, but also can inhibit the component diffusion on both sides of the separator to a certain extent, reducing the negative impact of the mutual diffusion of other components in the electrolyte except active ions on the performance of the secondary battery, thereby improving the cycle performance of the secondary battery. The above types of inorganic oxides are relatively stable, which can not only improve the cycle performance of the secondary battery, but also will not decompose and cause negative impacts on other electrochemical performances of the secondary battery. It can be understood that the average pore size of the separator includes, but is not limited to: 0.4 nm, 0.5 nm, 0.6 nm, 0.7 nm, 0.8 nm, 0.9 nm, 1 nm.

[0064] Optionally, the type of inorganic oxides in the porous structure of the base film can be determined by measuring the X-ray diffraction pattern of the separator, and the average pore size of the separator can be tested by a BET physical adsorption instrument.

[0065] In some embodiments, the separator further includes inorganic oxides disposed on at least part of the surface of the base film. Thus, the cycle performance of the secondary battery can be further improved.

[0066] In some embodiments, the mass ratio of the inorganic oxides in the separator is 6% to 90%. Controlling the mass ratio of the inorganic oxides in the separator within the above range is beneficial to reducing the porosity of the separator, and at the same time is beneficial to balancing the ionic conductivity and denseness of the separator, thereby further improving the cycle performance of the secondary battery. The mass ratio of the inorganic oxides in the separator includes, but is not limited to: 6%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%. Optionally, the mass ratio of the inorganic oxides in the separator is 6% to 80%.

[0067] Optionally, the mass ratio of the inorganic oxides in the separator can be determined by thermogravimetry or the method of high-temperature sintering plus weighing. Compared with the base film, the inorganic oxides are relatively stable at high temperatures.

[0068] In some embodiments, the air permeability of the separator membrane is ≥4500 s / 100 cc, and the ionic conductivity of the separator membrane is ≥0.1 mS / cm. When the air permeability and ionic conductivity of the separator membrane meet the above ranges, it is beneficial to balance the ionic conductivity and denseness of the separator membrane, thereby further improving the cycling performance of the secondary battery. It can be understood that the air permeability of the separator membrane includes but is not limited to: 4500 s / 100 cc, 5000 s / 100 cc, 6000 s / 100 cc, 7000 s / 100 cc, 8000 s / 100 cc, 9000 s / 100 cc, 10000 s / 100 cc, 11000 s / 100 cc, 12000 s / 100 cc, 13000 s / 100 cc, 14000 s / 100 cc, 15000 s / 100 cc, 20000 s / 100 cc, 25000 s / 100 cc, 30000 s / 100 cc, 35000 s / 100 cc, 40000 s / 100 cc, 45000 s / 100 cc, 50000 s / 100 cc. The ionic conductivity of the separator membrane includes but is not limited to: 0.1 mS / cm, 0.15 mS / cm, 0.2 mS / cm, 0.25 mS / cm, 0.3 mS / cm, 0.35 mS / cm, 0.4 mS / cm, 0.45 mS / cm, 0.5 mS / cm. It should be noted that the ionic conductivity of the separator membrane includes but is not limited to lithium ionic conductivity, sodium ionic conductivity, or potassium ionic conductivity.

[0069] Optionally, the ionic conductivity of the separator membrane can be tested according to the following method: The separator membrane is punched into small round pieces with a diameter of 22 mm. The punched separator membrane and a 20 mm steel sheet are encapsulated in a button cell to assemble a steel-steel symmetric battery. The battery is filled with an electrolyte. The solvent of the electrolyte is EC:EMC:DMC = 1:1:1 (volume ratio), and the concentration of the electrolyte salt is 1 mol / L. The electrochemical alternating current impedance method of a Solartron 1470E CellTest multi-channel electrochemical workstation is used for testing. The test voltage can be 10 mV, and the test frequency can be 0.1 Hz to 100 kHz. A Nyquist diagram is plotted; the obtained Nyquist diagram is analyzed using the equivalent circuit curve fitting method with Zview software, and the intersection of the straight line and the horizontal axis is denoted as R. The ionic conductivity is calculated using the formula λ = d / RS (where λ represents the ionic conductivity, d represents the thickness of the separator membrane, R represents the ionic resistance, and S represents the cross-sectional area of the small round piece). When testing the lithium ionic conductivity of the separator membrane, the corresponding electrolyte salt used is LiFSI (lithium bis(fluorosulfonyl)imide); when testing the sodium ionic conductivity of the separator membrane, the corresponding electrolyte salt used is NaFSI (sodium bis(fluorosulfonyl)imide); when testing the potassium ionic conductivity of the separator membrane, the corresponding electrolyte salt used is KFSI (potassium bis(fluorosulfonyl)imide).

[0070] In some embodiments, the lithium ion conductivity of the separator is ≥ 0.1 mS / cm. Thus, the lithium ion transport ability of the separator can be further improved, thereby further enhancing the cycling performance of the secondary battery. Optionally, the lithium ion conductivity of the separator is 0.12 mS / cm to 0.45 mS / cm.

[0071] In some embodiments, the air permeability of the separator is 5100 s / 100 cc to 44000 s / 100 cc, and the ionic conductivity of the separator is 0.13 mS / cm to 0.45 mS / cm. Thus, it is beneficial to further balance the ionic conductivity and denseness of the separator, thereby further enhancing the cycling performance of the secondary battery.

[0072] In some embodiments, the thickness of the separator is 5 μm to 50 μm. Thus, it is beneficial to further enhance the cycling performance of the secondary battery. It is understood that the thickness of the separator includes but is not limited to: 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm.

[0073] Optionally, the thickness of the separator can be determined using a scanning electron microscope (SEM) (such as ZEISS Sigma 300). For example: taking a photo of the cross-section of the separator using SEM, the thickness of the separator can be measured. Or a lithium battery separator thickness gauge can be used to test the thickness of the separator.

[0074] In some embodiments, the base film includes at least one of a polyolefin-based film, a polyvinyl fluoride-based film, a cellulose-containing nanofiber-based film, and a polyimide-based film.

[0075] In some embodiments, the material of the base film includes one or more of polypropylene (PP), polyethylene (PE), or polyimide (PI).

[0076] In some embodiments, the separator further includes an inorganic coating, and the inorganic coating is provided on at least one surface of the base film. The provided inorganic coating can improve the thermal stability of the separator.

[0077] In some embodiments, the inorganic coating contains an inorganic ceramic material. It is understood that the inorganic ceramic material in the inorganic coating helps to improve the thermal stability of the separator. Optionally, the inorganic ceramic material in the inorganic coating includes one or more of Al2O3, TiO2, or SiO2.

[0078] Another embodiment of the present application provides a method for preparing a separator, including:

[0079] The base film is placed in a hydrolysis solution containing an ester compound for hydrolysis treatment to obtain a separator membrane. The ester compound includes one or more of silicate compounds, titanate compounds, zirconate compounds, or aluminate compounds;

[0080] Among them, the separator membrane includes a base film and inorganic oxides disposed in the porous structure of the base film. The inorganic oxides include one or more of silicon dioxide, titanium dioxide, zirconium dioxide, or aluminum oxide. The average pore size of the separator membrane is 0.4 nm to 1 nm.

[0081] In the above embodiments, the inorganic oxides in the porous structure of the base film can improve the denseness of the separator membrane and reduce the porosity of the separator membrane; at the same time, the average pore size of the separator membrane meets the above range, which can not only enable the separator membrane to have a certain transmission ability for active ions, but also can inhibit the component diffusion on both sides of the separator membrane to a certain extent, reducing the negative impact of the mutual diffusion of other components in the electrolyte except the active ions on the performance of the secondary battery, thereby improving the cycle performance of the secondary battery. The above types of inorganic oxides are relatively stable, which can not only improve the cycle performance of the secondary battery, but also will not decompose and cause negative impacts on other electrochemical performances of the secondary battery. In addition, the above preparation method is simple and convenient, suitable for mass production of separator membranes. It can be understood that the average pore size of the separator membrane includes but is not limited to: 0.4 nm, 0.5 nm, 0.6 nm, 0.7 nm, 0.8 nm, 0.9 nm, 1 nm.

[0082] In some embodiments, the temperature of the hydrolysis treatment is 20°C to 90°C, and the time is 5 h to 24 h. Controlling the hydrolysis temperature and hydrolysis time within the above range is beneficial to controlling the hydrolysis degree of the hydrolysis solution and the mass ratio of the inorganic oxides in the separator membrane, thereby balancing the ionic conductivity and denseness of the separator membrane and further improving the cycle performance of the secondary battery. It can be understood that the hydrolysis temperature includes but is not limited to: 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C; the hydrolysis time includes but is not limited to: 5 h, 8 h, 10 h, 15 h, 20 h, 24 h. Optionally, the temperature of the hydrolysis treatment is 20°C to 90°C, and the time is 10 h to 16 h.

[0083] In some embodiments, the mass ratio of the ester compound in the hydrolysis solution is 10% to 70%. Thereby, it is beneficial to controlling the mass ratio of the inorganic oxides in the separator membrane, balancing the ionic conductivity and denseness of the separator membrane, and further improving the cycle performance of the secondary battery. It can be understood that the mass ratio of the ester compound in the hydrolysis solution includes but is not limited to: 10%, 15%, 20%, 25%, 30%, 32%, 35%, 40%, 45%, 50%, 51%, 55%, 60%, 65%, 70%. Optionally, the mass ratio of the ester compound in the hydrolysis solution is 21% to 62%.

[0084] In some embodiments, the silicate compounds include tetraethyl orthosilicate and / or tetramethyl orthosilicate.

[0085] In some embodiments, the titanate compounds include tetraethyl titanate and / or tetrabutyl titanate.

[0086] In some embodiments, the zirconate compounds include tetraethyl zirconate.

[0087] In some embodiments, the aluminate compounds include trimethyl aluminate and / or triethyl aluminate.

[0088] In some embodiments, the average pore size of the base film is 5 nm to 100 nm. Controlling the average pore size of the base film within the above range enables the mass percentage of the inorganic oxide in the separator membrane to be within a reasonable range, which further facilitates balancing the ionic conductivity and denseness of the separator membrane, thereby further improving the cycling performance of the secondary battery.

[0089] In some embodiments, the thickness of the base film is 5 μm to 20 μm. Thereby, it is beneficial to further improve the cycling performance of the secondary battery. It can be understood that the thickness of the base film includes but is not limited to: 5 μm, 8 μm, 10 μm, 13 μm, 15 μm, 18 μm, 20 μm.

[0090] Optionally, the thickness of the base film can be determined using a scanning electron microscope (SEM) (such as ZEISS Sigma 300). For example: taking a photo of the cross-section of the separator membrane using SEM can measure the thickness of the base film. Or a lithium battery separator thickness gauge can be used to test the thickness of the base film.

[0091] In some embodiments, the air permeability of the base film is 50 s / 100 cc to 1200 s / 100 cc. Controlling the air permeability of the base film within the above range enables the mass percentage of the inorganic oxide in the separator membrane to be within a reasonable range, which further facilitates balancing the ionic conductivity and denseness of the separator membrane, thereby further improving the cycling performance of the secondary battery. The air permeability of the base film includes but is not limited to: 50 s / 100 cc, 100 s / 100 cc, 300 s / 100 cc, 500 s / 100 cc, 700 s / 100 cc, 1000 s / 100 cc, 1300 s / 100 cc, 1500 s / 100 cc, 1800 s / 100 cc, 2000 s / 100 cc. Further, the air permeability of the base film is 100 s / 100 cc to 1000 s / 100 cc.

[0092] In some embodiments, the pH value of the hydrolysis solution is 0.5 to 6. Controlling the pH value of the hydrolysis solution within the above range is conducive to promoting the hydrolysis of the hydrolysis solution to form inorganic oxides, thereby further improving the denseness of the separator and the cycling performance of the secondary battery. It is understandable that the pH value of the hydrolysis solution includes but is not limited to: 0.5, 1, 1.5, 2, 3, 4, 5, 6. Optionally, the pH value of the hydrolysis solution is 1 to 4.

[0093] In some embodiments, the hydrolysis solution further contains a carboxylic acid catalyst, and the mass ratio of the carboxylic acid catalyst in the hydrolysis solution is 5% to 30%. Thereby, it is conducive to promoting the hydrolysis reaction of the hydrolysis solution. It is understandable that the mass ratio of the carboxylic acid catalyst in the hydrolysis solution includes but is not limited to: 5%, 10%, 15%, 20%, 25%, 30%. Optionally, the mass ratio of the carboxylic acid catalyst in the hydrolysis solution is 15% to 20%.

[0094] In some embodiments, the carboxylic acid catalyst includes formic acid and / or acetic acid.

[0095] In some embodiments, an inorganic coating is provided on at least one surface of the base film. The method for preparing the separator includes: a step of forming inorganic oxides in the porous structure of the base film provided with an inorganic coating on at least one surface. The provided inorganic coating can improve the thermal stability of the separator.

[0096] In some embodiments, the solvent in the hydrolysis solution includes water, and for example, it may further include an alcohol solvent. The alcohol solvent may be ethanol, for example.

[0097] In some embodiments, the mass ratio of water in the hydrolysis solution is 2% to 20%. It is understandable that the mass ratio of water in the hydrolysis solution includes but is not limited to: 2%, 5%, 8%, 10%, 12%, 15%, 18%, 20%. Optionally, the mass ratio of water in the hydrolysis solution is 5% to 15%.

[0098] By adjusting the parameter conditions of the preparation method, the separator provided in an embodiment of the present application can be obtained.

[0099] Another embodiment of the present application provides a secondary battery, including at least one of the separator provided in the present application and the separator prepared by the preparation method provided in the present application.

[0100] In some embodiments, the secondary battery further includes a positive electrode plate, a negative electrode plate, a first electrolyte disposed between the positive electrode plate and the separator, and a second electrolyte disposed between the negative electrode plate and the separator. It is understandable that the first electrolyte and the second electrolyte in the present application may be the same or different.

[0101] In some embodiments, the composition and / or content of the first electrolyte is different from that of the second electrolyte. It can be understood that the composition and / or content of the first electrolyte being different from that of the second electrolyte means that the first electrolyte has a different composition from the second electrolyte but the same content; or that the first electrolyte and the second electrolyte have the same composition but different contents; or that the first electrolyte and the second electrolyte have different compositions and contents.

[0102] Another embodiment of the present application further provides an electrical device including the secondary battery of the present application as described above.

[0103] The electrical device of the present application includes the secondary battery provided by the present application, and thus has at least the same advantages as the secondary battery.

[0104] In addition, the secondary battery and the electrical device of the present application will be described below with appropriate reference to the accompanying drawings.

[0105] Generally, a secondary battery includes a positive electrode plate, a negative electrode plate, an electrolyte, and a separator. During the charging and discharging process of the battery, active ions are embedded and extracted back and forth between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate. The separator is disposed between the positive electrode plate and the negative electrode plate, mainly serving to prevent short circuit between the positive and negative electrodes, and at the same time allowing ions to pass through.

[0106] Positive electrode plate

[0107] The positive electrode plate includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector, and the positive electrode active material layer includes a positive electrode active material.

[0108] As a non-limiting example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode active material layer is provided on any one or both of the two opposite surfaces of the positive electrode current collector.

[0109] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil can be used. The composite current collector can include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be obtained by forming a metal material on a polymer material substrate. In the positive electrode current collector, non-limiting examples of the metal material can include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc. In the positive electrode current collector, non-limiting examples of the polymer material substrate can include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE), etc.

[0110] Understandably, during the charge and discharge process of the battery, the insertion and extraction of lithium (Li) and its consumption will occur, and the content of Li in the positive electrode sheet is different when the battery is discharged to different states. In the listing of the positive electrode active materials in this application, unless otherwise specified, the content of Li is the initial state of the material. When the positive electrode active material is applied to the positive electrode sheet in the battery system, after charge and discharge cycles, the content of Li in the positive electrode active material contained in the sheet usually changes. Among them, the content of Li can be measured by molar content, but it is not limited to this. Regarding "the content of Li is the initial state of the material", the initial state of the material refers to the state before being fed into the positive electrode slurry. It can be understood that new materials obtained by appropriate modification based on the listed positive electrode active materials are also within the scope of positive electrode active materials. The aforementioned appropriate modification refers to acceptable modification methods for positive electrode active materials. Non-limiting examples include coating modification.

[0111] In the listing of the positive electrode active materials in this application, the content of oxygen (O) is only the theoretical state value. The release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual content of O will fluctuate. Among them, the content of O can be measured by molar content, but it is not limited to this.

[0112] In some embodiments, the positive electrode active material can be a positive electrode active material well-known in the art for use in batteries. As non-limiting examples, the positive electrode active material can include one or more of the following materials: lithium-containing phosphates with olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other traditional materials that can be used as battery positive electrode active materials can also be used. These positive electrode active materials can be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides can include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds, etc. Non-limiting examples of lithium-containing phosphates with olivine structure can include, but are not limited to, lithium iron phosphate, composites of lithium iron phosphate and carbon, lithium manganese phosphate, composites of lithium manganese phosphate and carbon, lithium manganese iron phosphate, composites of lithium manganese iron phosphate and carbon. Non-limiting examples of lithium cobalt oxide can include LiCoO2; non-limiting examples of lithium nickel oxide can include LiNiO2; non-limiting examples of lithium manganese oxide can include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxide can include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (which can also be abbreviated as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3O2 (which can also be abbreviated as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (which can also be abbreviated as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (which can also be abbreviated as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (which can also be abbreviated as NCM 811 ), etc. Non-limiting examples of lithium nickel cobalt aluminum oxide can include LiNi 0.8 Co 0.15 Al 0.05 O2.

[0113] In some embodiments, the positive electrode active material can be a sodium ion active material. As an example, the sodium ion active material can include one or more of the following materials: sodium transition metal oxides, polyanion-type compounds, and Prussian blue compounds. However, the present application is not limited to these materials, and other conventionally known materials that can be used as the positive electrode active material of a sodium ion battery can also be used.

[0114] As an alternative technical solution of the present application, in the sodium transition metal oxide, the transition metal can include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Non-limiting examples of the sodium transition metal oxide can be Na x MO2, where M can include one or several of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu, and 0 < x ≤ 1.

[0115] As an alternative technical solution of the present application, the polyanion-type compound can be a type of compound having sodium ions, transition metal ions, and tetrahedral (YO4) n- anion units. The transition metal can include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be one or more of P, S, and Si; and n represents the valence state of (YO4) n- .

[0116] The polyanion-type compound can also be a compound having sodium ions, transition metal ions, and tetrahedral (YO4) n-A class of compounds with anionic units and halogen anions. The transition metal can include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be one or more of P, S, and Si, and n represents the valence state of (YO4) n- ; the halogen can be one or more of F, Cl, and Br.

[0117] The polyanionic compound can also be a class of compounds with sodium ions, tetrahedral (YO4) n- anionic units, polyhedral units (ZO y ) m+ and optionally halogen anions. Y can be one or more of P, S, and Si, and n represents the valence state of (YO4) n- ; Z represents a transition metal, which can include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, and m represents the valence state of (ZO y ) m+ ; the halogen can be one or more of F, Cl, and Br.

[0118] The polyanionic compounds can include one or more of NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2(P2O7), NaM’PO4F, and Na3(VO y )2(PO4)2F 3-2y (0 ≤ y ≤ 1). Among them, M’ in NaM’PO4F can include one or more of V, Fe, Mn, and Ni.

[0119] Prussian blue compounds can be a class of compounds with sodium ions, transition metal ions, and cyanide ions (CN - ). The transition metal can include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Non-limiting examples of Prussian blue compounds can be Na a Me b Me’ c (CN)6, where Me and Me’ can each independently be one or more of Ni, Cu, Fe, Mn, Co, and Zn, 0 < a ≤ 2, 0 < b < 1, 0 < c < 1.

[0120] In some embodiments, the positive electrode active material layer may optionally further include an additive. As non-limiting examples, the additive includes one or more of xylene and phenylcyclohexane.

[0121] In some embodiments, the positive electrode active material layer may further optionally include a binder. As a non-limiting example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0122] In some embodiments, the positive electrode active material layer may further optionally include a conductive agent. As a non-limiting example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0123] In some embodiments, the positive electrode sheet can be prepared by the following method: dispersing the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry on at least one surface of the positive electrode current collector, and after processes such as drying and cold pressing, the positive electrode sheet can be obtained. The type of the solvent can be selected from, but not limited to, any one of the foregoing embodiments, such as N-methylpyrrolidone (NMP). The surface of the positive electrode current collector on which the positive electrode slurry is coated can be a single surface of the positive electrode current collector or two surfaces of the positive electrode current collector. The surface of the positive electrode current collector on which the positive electrode slurry is coated can be a single surface of the positive electrode current collector or two surfaces of the positive electrode current collector. The solid content of the positive electrode slurry can be 40 wt% - 80 wt%. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000 mPa·s - 25000 mPa·s. When coating the positive electrode slurry, the coating unit surface density in terms of dry weight (deducting the solvent) can be 15 mg / cm 2 - 35 mg / cm 2 。The compaction density of the positive electrode sheet can be 3.0 g / cm 3 - 3.6 g / cm 3 ,optionally 3.3 g / cm 3 - 3.5 g / cm 3 。

[0124] Negative electrode sheet

[0125] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material.

[0126] As a non-limiting example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode active material layer is provided on any one or both of the two opposite surfaces of the negative electrode current collector.

[0127] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, a copper foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be obtained by forming a metal material on the polymer material substrate. In the negative electrode current collector, non-limiting examples of the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc. In the negative electrode current collector, non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0128] In some embodiments, the negative electrode active material may be a negative electrode active material for a battery well-known in the art. As non-limiting examples, the negative electrode active material may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based materials may include one or more of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based materials may include one or more of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as the negative electrode active material of the battery may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0129] In some embodiments, the negative electrode active material layer may also optionally include additives. The additives may include one or more of vinylene carbonate and acrylonitrile.

[0130] In some embodiments, the negative electrode active material layer may also optionally include a binder. The binder may include one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0131] In some embodiments, the negative electrode active material layer may also optionally include a conductive agent. The conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0132] In some embodiments, the negative electrode active material layer may also optionally include other auxiliaries, such as thickeners (such as sodium carboxymethyl cellulose (CMC-Na)), etc.

[0133] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder, and any other components, are dispersed in a solvent (a non-limiting example of the solvent is deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on at least one surface of the negative electrode current collector, and after processes such as drying and cold pressing, the negative electrode sheet can be obtained. The surface of the negative electrode current collector coated with the negative electrode slurry can be a single surface of the negative electrode current collector or two surfaces of the negative electrode current collector. The solid content of the negative electrode slurry can be 40wt%-60wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000mPa·s - 10000mPa·s. When coating the negative electrode slurry, the coating unit surface density in terms of dry weight (after deducting the solvent) can be 75g / m 2 -220g / m 2 . The compaction density of the negative electrode sheet can be 1.0g / cm 3 -1.8g / cm 3 .

[0134] Electrolyte

[0135] The electrolyte functions to conduct ions between the positive electrode sheet and the negative electrode sheet. The electrolyte includes a first electrolyte and a second electrolyte. The first electrolyte is disposed between the positive electrode sheet and the separator, and the second electrolyte is disposed between the negative electrode sheet and the separator. The present application does not particularly limit the type of the electrolyte, and it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or all-solid-state.

[0136] In some embodiments, the composition and / or content of the first electrolyte is different from that of the second electrolyte. It can be understood that the composition and / or content of the first electrolyte being different from that of the second electrolyte means that the first electrolyte has a different composition from the second electrolyte but the same content; it can also be that the first electrolyte and the second electrolyte have the same composition but different contents; or that the composition and content of the first electrolyte and the second electrolyte are both different.

[0137] In some embodiments, the first electrolyte and / or the second electrolyte adopts an electrolytic solution. The electrolytic solution includes an electrolyte salt and a solvent.

[0138] In some embodiments, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluoro(dioxalato)phosphate (LiDFOP), and lithium tetrafluoro(oxalato)phosphate (LiTFOP).

[0139] In some embodiments, the solvent may include ethylene carbonate (EC, ), propylene carbonate (PC, ), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butenyl carbonate ( ), fluoroethylene carbonate (FEC), methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0140] In some embodiments, the electrolyte may optionally further include additives. For example, the additives may include anode film-forming additives, cathode film-forming additives, and may also include additives that can improve certain battery performances, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature or low-temperature performance of the battery, etc.

[0141] In some embodiments, the additives in the electrolyte may include, but are not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethyl carbonate (TFPC), etc.

[0142] Separator

[0143] The separator of the present application is adopted.

[0144] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be made into an electrode assembly by a winding process or a stacking process.

[0145] In some embodiments, the secondary battery may include an outer package. The outer package can be used to encapsulate the above-mentioned electrode assembly and electrolyte.

[0146] In some embodiments, the outer package of the secondary battery can be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The outer package of the secondary battery can also be a soft package, such as a pouch soft package. The material of the soft package can be plastic. Further, non-limiting examples of the plastic can include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate, etc.

[0147] The secondary battery includes at least one battery cell. The secondary battery can include one or more battery cells.

[0148] In this application, unless otherwise specified, a "battery cell" refers to a basic unit capable of converting chemical energy and electrical energy into each other. Further, generally, it includes at least a positive electrode plate, a negative electrode plate, and an electrolyte. During the charging and discharging process of the battery, active ions are embedded and extracted back and forth between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in conducting active ions between the positive electrode plate and the negative electrode plate.

[0149] This application has no particular limitation on the shape of the battery cell, and it can be cylindrical, square, or any other shape. For example, Figure 1 is a battery cell 5 with a square structure as an example.

[0150] In some embodiments, referring to Figure 2 , the outer package can include a housing 51 and a cover plate 53. Among them, the housing 51 can include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode plate, the negative electrode plate, and the separator can be formed into an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. The number of electrode assemblies 52 included in the battery cell 5 can be one or more, and those skilled in the art can select according to actual needs.

[0151] The secondary battery can be a battery module 4 or a battery pack 1.

[0152] The battery module includes at least one battery cell. The number of battery cells included in the battery module can be one or more, and those skilled in the art can select a suitable number according to the application and capacity of the battery module.

[0153] Figure 3 is a battery module 4 as an example. Referring to Figure 3 , in the battery module 4, a plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other way. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0154] Optionally, the battery module 4 may further include a housing having an accommodation space, and a plurality of battery cells 5 are accommodated in the accommodation space.

[0155] In some embodiments, the above battery modules may also be assembled into a battery pack. The number of battery modules included in the battery pack may be one or more, and those skilled in the art can select a suitable number according to the application and capacity of the battery pack.

[0156] Figure 4 and Figure 5 is a battery pack 1 as an example. Refer to Figure 4 and Figure 5 , in the battery pack 1, a battery box and a plurality of battery modules 4 disposed in the battery box may be included. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0157] In addition, the present application also provides an electrical device, and the electrical device includes the secondary battery provided by the present application. The secondary battery can be used as a power source of the electrical device or as an energy storage unit of the electrical device. The electrical device may include a mobile device, an electric vehicle, an electric train, a ship, a satellite, an energy storage system, etc., but is not limited thereto. Among them, the mobile device may be, for example, a mobile phone, a laptop computer, etc.; the electric vehicle may be, for example, a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc., but is not limited thereto.

[0158] As the electrical device, the secondary battery can be selected according to its usage requirements.

[0159] Figure 6 is an electrical device 6 as an example. The electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the electrical device for the secondary battery, a battery pack or a battery module can be adopted.

[0160] As another example of the device, it may be a mobile phone, a tablet computer, a laptop computer, etc. This device usually requires being thin and light, and a secondary battery can be used as the power source.

[0161] Hereinafter, embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application and should not be construed as a limitation to the present application. For those not specified in the embodiments regarding techniques or conditions, they shall be carried out according to the techniques or conditions described in the literature in the art or according to the product specifications. For the reagents or instruments not specified regarding the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0162] Embodiment 1

[0163] (1) Preparation of Separator Membrane

[0164] A porous polyethylene (PE) membrane with an average pore size of 15 nm and a thickness of 8 μm is selected as the base membrane. Deionized water, ethanol, and acetic acid are mixed into a mixed solution according to a mass ratio of 39:60:1. Tetraethyl orthosilicate is mixed with the mixed solution according to a certain mass ratio to obtain a hydrolysis solution with a pH value less than 6. Among them, the mass proportion of tetraethyl orthosilicate in the hydrolysis solution is 21%. The base membrane is immersed in the hydrolysis solution, and a hydrolysis reaction is carried out at 60 °C for 12 h, and then dried in an oven at 80 °C for 8 h to obtain a separator membrane with a thickness of 9 μm, which is cut into corresponding sizes for standby. Among them, the porous structure of the base membrane is filled with silica.

[0165] (2) Preparation of Positive Electrode Plate

[0166] Lithium manganate LiMn₂O₄, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are fully stirred and mixed evenly in N-methylpyrrolidone solvent according to a weight ratio of 94:3:3, and then coated on both surfaces of the aluminum foil, dried and cold-pressed to obtain a positive electrode plate, which is cut into corresponding sizes for standby.

[0167] (3) Preparation of Negative Electrode Plate

[0168] Graphite, conductive carbon, and styrene-butadiene rubber are fully stirred and mixed evenly in water according to a weight ratio of 94:3:3, and then coated on the copper foil, dried and cold-pressed to obtain a negative electrode plate, which is cut into corresponding sizes for standby.

[0169] (4) Preparation of Lithium-Ion Battery

[0170] The positive electrode plate, separator membrane, and negative electrode plate are assembled into a stacked bare battery cell, and the separator membrane is placed between the positive electrode plate and the negative electrode plate to play a role in isolation. The bare battery cell is placed in an outer package to obtain a dry battery cell. The solvent of the electrolyte is EC:EMC:DMC = 1:1:1 (volume ratio), and the lithium salt is LiFSI with a concentration of 1 mol / L. Each battery cell is injected with 0.3 g of electrolyte, and after injection, it is vacuum-sealed and left to soak to obtain a lithium-ion battery.

[0171] Examples 2 - 17

[0172] They are basically the same as Example 1, except that: the average pore size of the base membrane, the air permeability of the base membrane, the thickness of the base membrane, the type of ester compound, the mass proportion of the ester compound in the hydrolysis solution, and the hydrolysis time are changed.

[0173] The hydrolysis solutions of Examples 1-17 have equal mass, and the mass ratios of deionized water, ethanol, and acetic acid in the hydrolysis solutions are the same. In Examples 1-17, by changing the mass ratio of the mixed solution to the ester compound, the mass percentage of the ester compound in the hydrolysis solution is controlled.

[0174] Comparative Example 1

[0175] It is basically the same as Example 1, except that in this comparative example, the porous PE membrane in Example 1 is directly used as the separator membrane.

[0176] Performance Test

[0177] (1) Average pore size test and air permeability test of the base membrane

[0178] The separator membrane is immersed in a sodium hydroxide solution or a hydrochloric acid solution to allow the inorganic oxides in the separator membrane to react fully with sodium hydroxide or hydrochloric acid (for example, it can react for 3 h at 50 °C), and then the treated separator membrane is washed repeatedly with deionized water and dried to obtain the base membrane; when the inorganic oxide is silica, the separator membrane is immersed in a sodium hydroxide solution; when the inorganic oxide is titanium dioxide, zirconium dioxide, or alumina, the separator membrane is immersed in a hydrochloric acid solution.

[0179] The average pore size of the base membrane is tested using a BET physical adsorption instrument.

[0180] The base membrane is cut into a suitable size, and the air permeability of the base membrane is tested using a Wang Yan type air permeability instrument (Asahi Seiko model EG01-55-1MR). The specific steps are as follows: The base membrane is cut into 60 mm small round piece samples, the samples are installed in the Wang Yan type air permeability instrument to ensure tightness and fixation, and the gas pressure is set to 1.21 kPa, and the time taken for 100 mL of air to pass through is recorded to obtain the air permeability of the base membrane.

[0181] (2) Test of the mass percentage of inorganic oxides in the separator membrane

[0182] The separator membrane with a mass of m1 is heated from room temperature to 600 °C at a heating rate of 5 °C / min in an air atmosphere, held for 3 h, and naturally cooled to room temperature, and the mass of the remaining material is weighed as m2.

[0183] The mass percentage of inorganic oxides in the separator membrane = m2 / m1 × 100%.

[0184] (3) Average pore size test of the separator membrane

[0185] The average pore size of the separator membrane is tested using a BET physical adsorption instrument.

[0186] (4) Air permeability test of the separator membrane

[0187] Cut the separator film into appropriate sizes, and use the Wang Yan-type air permeability meter (Asahi Seiko model EG01-55-1MR) to test the air permeability of the separator film. The specific steps are as follows: Cut the separator film into 60-mm small round piece samples, install the samples in the Wang Yan-type air permeability meter, ensure the sealing and fixation, set the gas pressure to 1.21 kPa, record the time taken for 100 mL of air to pass through, and obtain the air permeability of the separator film.

[0188] (5) Test of the ionic conductivity of the separator film

[0189] Punch the separator film into small round pieces with a diameter of 22 mm, encapsulate the punched separator film and a 20-mm steel sheet in a button cell to assemble a steel-steel symmetric battery. The battery is filled with an electrolyte. The solvent of the electrolyte is EC:EMC:DMC = 1:1:1 (volume ratio), and the lithium salt is LiFSI with a concentration of 1 mol / L. Use the electrochemical impedance spectroscopy method of a Solartron 1470E CellTest multi-channel electrochemical workstation for testing. The test voltage can be 10 mV, and the test frequency can be 0.1 Hz to 100 kHz. Plot a Nyquist diagram; use Zview software to analyze the obtained Nyquist diagram by the equivalent circuit curve fitting method. The intersection of the straight line and the horizontal axis is denoted as R. Calculate the ionic conductivity using the formula λ = d / RS (where λ represents the ionic conductivity, d represents the thickness of the separator film, R represents the ionic resistance, and S represents the cross-sectional area of the small round piece).

[0190] (6) Test of the barrier performance of the separator film

[0191] Cut a separator film of appropriate size and fix it at the mouth of a small bottle. The small bottle contains 2 g of an iodine (I2) dimethyl sulfoxide (DMSO) solution, and the mass fraction of iodine in this solution is 0.2%. The large bottle contains 5 g of a colorless dimethyl sulfoxide solution. The small bottle is placed inside the large bottle and left for a period of time. Test the time for iodine to penetrate through the separator film at the mouth of the small bottle and enter the liquid in the large bottle. The longer the time, the weaker the transmission ability of the separator film for substances other than lithium ions, that is, the stronger the barrier property of the separator film.

[0192] Refer to Figure 7 , a separator film 7 is fixed at the mouth of a small bottle 11. The small bottle 11 contains an iodine-containing dimethyl sulfoxide solution 8, and the large bottle 10 contains 5 g of an iodine-free dimethyl sulfoxide solution 9. The small bottle 11 is placed inside the large bottle 10.

[0193] (7) Test of the cycle life of the battery

[0194] The lithium-ion battery was subjected to a life test in a constant temperature environment of 25°C. The process was as follows: It was left standing for 5 minutes, discharged at 0.5C (75 mA) until 3V, left standing for 5 minutes, then charged at 1 / 3C to 4.3V, and then charged at a constant voltage of 4.3V until the current ≤ 0.05 mA. After standing for 5 minutes, it was discharged at 1 / 3C to 3V. The discharge capacity at this time was the initial discharge capacity, denoted as D0. Subsequently, according to the above process, a cyclic test was carried out in the range of 3V to 4.3V. The capacity value Dn (n = 1, 2, 3…) was recorded weekly. When the capacity Dn ≤ 80% * D0, the number of cyclic weeks n was recorded as the cycle life.

[0195] The preparation process parameters and product parameters of the separator membranes prepared in Examples 1-17 and Comparative Example 1 are shown in Table 1. The performance of the separator membranes and batteries prepared in Examples 1-17 and Comparative Example 1 is shown in Table 2. " / " in Table 1 and Table 2 indicates that this item is not set or this parameter does not exist.

[0196] Table 1

[0197]

[0198] Table 2

[0199]

[0200] Figure 8 This is the scanning electron microscope image of the surface of the base film of Example 1 of this application. Figure 9 This is the scanning electron microscope image of the surface of the separator membrane of Example 1 of this application. Figure 10 This is the scanning electron microscope image of the cross-section of the separator membrane of Example 1 of this application. Figure 11 This is the X-ray diffraction pattern of the separator membrane prepared in Example 1 of this application. It can be seen from Figures 8 - 10 that the compactness of the separator membrane of Example 1 is improved compared to the base film. It can be seen from Figure 11 that the inorganic oxide in the separator membrane of Example 1 is silicon dioxide.

[0201] It can be seen from Table 1 - Table 2 that compared with the separator membrane of Comparative Example 1, the separator membranes prepared in Examples 1-17 have better barrier properties, and the cycle life of the batteries in Examples 1-17 is longer, indicating that the inorganic oxides in the porous structure of the base films in Examples 1-17 reduce the average pore diameter of the separator membranes and effectively improve the cycle performance of the batteries. Combining Table 2 and Figure 10 , the ionic conductivity of the separator membrane prepared in Example 1 is 0.42 mS / cm. This is because there is a nano-scale pore structure in the separator membrane of Example 1, and lithium ions in the electrolyte can be transported through this pore structure.

[0202] The descriptions of the various embodiments above tend to emphasize the differences between the various embodiments. For the similarities or resemblances among them, reference can be made to each other. For the sake of brevity, they will not be elaborated herein.

[0203] It should be noted that the present application is not limited to the above embodiments. The above embodiments are only examples. Embodiments having the same constitution and achieving the same effects as the technical idea within the technical scope of the present application are all included in the technical scope of the present application. In addition, within the scope not departing from the gist of the present application, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways constructed by combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. An isolation film, characterized in that, It includes a base film and inorganic oxides disposed within the porous structure of the base film. The inorganic oxides include one or more of silicon dioxide, titanium dioxide, zirconium dioxide, or aluminum oxide, and the average pore size of the separator membrane is 0.4 nm to 1 nm.

2. The separator film according to claim 1, wherein The separator membrane further includes the inorganic oxides disposed on at least a part of the surface of the base film.

3. The separator film according to claim 1 or 2, characterized in that, The mass ratio of the inorganic oxides in the separator membrane is 6% to 90%.

4. The separator film according to any one of claims 1 to 3, characterized in that, The air permeability of the separator membrane ≥ 4500 s / 100 cc, and the ionic conductivity of the separator membrane ≥ 0.1 ms / cm.

5. The separator film according to any one of claims 1 to 4, characterized in that, The air permeability of the separator membrane is 5100 s / 100 cc to 44000 s / 100 cc, and the ionic conductivity of the separator membrane is 0.13 ms / cm to 0.45 ms / cm.

6. The separator film according to any one of claims 1 to 5, characterized in that, The thickness of the separator membrane is 5 μm to 50 μm.

7. The separator film according to any one of claims 1 to 6, characterized in that, The base film includes at least one of a polyolefin-based film, a polyvinyl fluoride-based film, a cellulose-containing nanofiber-based film, and a polyimide-based film.

8. A method for preparing a separator membrane, characterized in that, It includes: Subject the base film to hydrolysis treatment in a hydrolysis solution containing an ester compound, to obtain a separator membrane. The ester compound includes one or more of a silicate ester compound, a titanate ester compound, a zirconate ester compound, or an aluminate ester compound; Wherein, the separator membrane includes a base film and inorganic oxides disposed within the porous structure of the base film. The inorganic oxides include one or more of silicon dioxide, titanium dioxide, zirconium dioxide, or aluminum oxide, and the average pore size of the separator membrane is 0.4 nm to 1 nm.

9. The preparation method according to claim 8, wherein The temperature of the hydrolysis treatment is 20°C to 90°C, and the time is 5 h to 24 h.

10. The preparation method according to claim 8 or 9, characterized in that, The temperature of the hydrolysis treatment is 20°C to 90°C, and the time is 10 h to 16 h.

11. The preparation method according to any one of claims 8 to 10, characterized in that, The mass ratio of the ester compound in the hydrolysis solution is 10% to 70%.

12. The preparation method according to any one of claims 8 to 11, characterized in that, The mass ratio of the ester compound in the hydrolysis solution is 21% to 62%.

13. The preparation method according to any one of claims 8 to 12, characterized in that, The silicate ester compound includes tetraethyl orthosilicate and / or tetramethyl orthosilicate; and / or, The titanate ester compound includes tetraethyl titanate and / or tetrabutyl titanate; and / or, The zirconate ester compound includes tetraethyl zirconate; and / or, The aluminate ester compound includes trimethyl aluminate and / or triethyl aluminate.

14. The preparation method according to any one of claims 8 to 13, characterized in that, The base film satisfies one or more of the following conditions: (1) The average pore size of the base film is 5 nm to 100 nm; (2) The thickness of the base film is 5 μm to 20 μm; (3) The air permeability of the base film is 50 s / 100 cc to 1200 s / 100 cc.

15. The preparation method according to any one of claims 8 to 14, characterized in that, The pH value of the hydrolysis solution is 0.5 to 6.

16. The preparation method according to any one of claims 8 to 15, characterized in that, The hydrolysis solution further contains a carboxylic acid catalyst, and the mass ratio of the carboxylic acid catalyst in the hydrolysis solution is 5% to 30%.

17. A secondary battery, characterized in that, It includes at least one of the separator membranes described in any one of claims 1 to 7 and the separator membranes prepared by the preparation method described in any one of claims 8 to 16.

18. The secondary battery according to claim 17, characterized in that, The secondary battery further includes a positive electrode plate, a negative electrode plate, a first electrolyte disposed between the positive electrode plate and the separator membrane, and a second electrolyte disposed between the negative electrode plate and the separator membrane.

19. The secondary battery according to claim 18, wherein The composition and / or content of the first electrolyte is different from that of the second electrolyte.

20. An electrical device, characterized in that, A secondary battery comprising any one of claims 17 to 19.

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