CN112886143B - Multilayer structure composite diaphragm, preparation method thereof, secondary battery and electric equipment - Google Patents
Multilayer structure composite diaphragm, preparation method thereof, secondary battery and electric equipment Download PDFInfo
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- CN112886143B CN112886143B CN202110326143.1A CN202110326143A CN112886143B CN 112886143 B CN112886143 B CN 112886143B CN 202110326143 A CN202110326143 A CN 202110326143A CN 112886143 B CN112886143 B CN 112886143B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract
The application relates to the field of battery diaphragms, and discloses a multilayer-structure composite diaphragm, a preparation method thereof, a secondary battery and electric equipment, wherein the multilayer-structure composite diaphragm comprises a porous polymer base film, nano oxide particles and a dot-shaped polymer coating; the nano oxide particles are completely embedded into the pores of the porous polymer-based membrane and are attached to the filamentous structure of the porous polymer-based membrane; the two sides of the porous polymer base membrane are provided with point-shaped polymer coating layers. According to the application, the nano-scale oxide particles are introduced by using an atomic layer deposition technology on the porous polymer base film, so that all the oxide particles with better consistency are embedded into the pore diameter of the base film, the stability of the diaphragm at high temperature is improved on the basis of not influencing the original lithium ion channel of the diaphragm, and the wettability of the diaphragm to electrolyte can be enhanced. In addition, the two surfaces of the battery are provided with the point-shaped polymer coatings, so that the battery is more suitable for the existing lithium ion production scene, and the cycle performance of the battery is improved.
Description
Technical Field
The application relates to the technical field of battery diaphragms, in particular to a multilayer structure composite diaphragm, a preparation method thereof, a secondary battery and electric equipment.
Background
Lithium ion batteries have the advantages of high energy density, long cycle life, and the like, and are widely used in portable electronic devices and electric vehicles. In recent years, lithium batteries have been developed rapidly, and safety and durability have become the primary concerns.
The diaphragm of Polyethylene (PE), polypropylene (PP) and its composite layer is one of the mainstream diaphragms used by domestic power battery manufacturers to improve the safety performance of the battery. However, such a separator has two major problems, namely, a problem of shrinkage at high temperature and a problem of poor wettability with a lithium salt electrolyte. When the battery works at a higher temperature, the polymer-based diaphragm can generate a thermal contraction phenomenon, so that the positive and negative pole pieces are contacted, and the internal short circuit and even explosion of the battery occur. And due to the hydrophobicity and the lower surface energy of the material of the diaphragm, the polymer diaphragms have poor wettability to electrolyte, so that the process time is prolonged and the cycle life of the battery is reduced.
The polymer diaphragm with the water-based ceramic coating layer is a mainstream method for solving the problems, and the polymer diaphragm is simple and controllable in process and low in cost. On one hand, the thermal stability of the diaphragm at high temperature can be further improved, and on the other hand, the wettability of the diaphragm can be improved to a certain extent by the ceramic particles.
However, the separator having the water-based ceramic coating layer is generally coated with a conventional binder, and the adhesion effect of the coating layer is limited, and there is a risk of powder falling during the operation inside the battery. Once the ceramic coating falls off, on one hand, the thickness of the diaphragm is not uniform, the consistency of internal current is poor, and the performance of the battery is influenced; on the other hand, ceramic particles fall off, the thermal stability of the diaphragm is reduced, and the safety performance at high temperature is also affected.
In view of this, the present application is specifically made.
Disclosure of Invention
The application discloses a multilayer structure composite diaphragm and a preparation method thereof, a lithium ion battery and application, which can relieve the problems of high-temperature thermal shrinkage, poor wettability to electrolyte and serious powder falling of the diaphragm with a ceramic coating layer of a polymer base film for the conventional lithium battery, and are more suitable for the conventional lithium ion production scene, and the cycle performance of the battery is improved.
In order to achieve the purpose, the application provides the following technical scheme:
in a first aspect, the present application provides a multilayer structure composite separator comprising a porous polymer-based membrane, nano-oxide particles, and dot-shaped polymer coating layers; the particle size of the nano oxide particles is 10-50nm, the pore size of the porous polymer-based membrane is in the range of 0.05-0.3 μm, and the nano oxide particles are embedded in the pores of the porous polymer-based membrane and attached to the filamentous structures of the porous polymer-based membrane; the dot-shaped polymer coating layers are arranged on two sides of the porous polymer base membrane.
Further, the porous polymer-based membrane includes polyethylene, polypropylene, polyamide, polyimide, or a composite membrane thereof.
Further, the thickness of the porous polymer-based membrane is 1 to 100 μm.
Further, the nano-oxide particles include Al 2 O 3 、TiO 2 、SiO 2 、ZrO 2 、ITO、In 2 O 3 、SnO 2 、HfO 2 、Ta 2 O 5 、Y 2 O 3 、MgO、La 2 O 3 One or more of ZnO and NiO.
Further, the dot-shaped polymer coating comprises a PVDF material; the thickness of the dot-shaped polymer coating is 1-5 mu m.
In a second aspect, the present application provides a method for preparing a composite separator having a multilayer structure, comprising the steps of:
depositing nano oxide particles on a filamentous structure of the porous polymer base membrane through an atomic layer deposition process, and completely embedding the nano oxide particles into holes of the porous polymer base membrane to obtain the porous polymer base membrane on which the nano oxide particles are deposited;
and (3) dot-coating polymer coatings on two surfaces of the porous polymer-based membrane after the nano oxide particles are deposited to obtain the multilayer-structure composite diaphragm.
Further, the process parameters of the atomic layer deposition process include:
the temperature of the precursor is 30-100 ℃; the vacuum degree of the reaction chamber is 20-100Pa; the temperature of the base material is 80-110 ℃.
Further, the polymer coating is applied in a spot-like manner by spraying.
In a third aspect, the present application provides a secondary battery comprising the aforementioned multilayer-structure composite separator or the multilayer-structure composite separator obtained by the aforementioned production method.
In a fourth aspect, the present application provides an electric device including the aforementioned secondary battery. The electric equipment can be portable electronic equipment or an electric automobile.
By adopting the technical scheme of the application, the beneficial effects are as follows:
the diaphragm of the application not only provides firm support for the porous polymer base membrane through the introduction of the nano-scale oxide particles, but also increases the stability of the original porous polymer base membrane, and increases the ionic conductivity, so that the safety and the durability of the lithium ion battery at high temperature are improved to a certain extent. And a point-shaped polymer coating is added outside the porous polymer base membrane-nano oxide particle structure, so that the application scene of the diaphragm can be more fit with the production scene of the existing lithium ion battery, and the rate capability and the cycle performance of the battery are improved to a certain extent.
According to the application, the nano-scale oxide particles are introduced by using an atomic layer deposition technology on the porous polymer base film, so that all the oxide particles with better consistency are embedded into the pore diameter of the base film, the stability of the diaphragm at high temperature is improved on the basis of not influencing the original lithium ion channel of the diaphragm, and the wettability of the diaphragm to electrolyte can be enhanced.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
It should be noted that: in the present application, all embodiments and preferred methods mentioned herein can be combined with each other to form new solutions, if not specifically stated. In the present application, all the technical features mentioned herein as well as preferred features may be combined with each other to form new technical solutions, if not specifically stated. In the present application, the percentage (%) or parts refers to the weight percentage or parts relative to the composition, unless otherwise specified. In the present application, the components referred to or the preferred components thereof may be combined with each other to form new embodiments, if not specifically stated. In this application, unless otherwise stated, the numerical range "a-b" represents a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "6 to 22" indicates that all real numbers between "6 to 22" have been listed herein, and "6 to 22" is only a shorthand representation of the combination of these numbers. The "ranges" disclosed herein may be in the form of lower limits and upper limits, and may be one or more lower limits and one or more upper limits, respectively. In the present application, the individual reactions or process steps may be performed sequentially or in sequence, unless otherwise indicated. Preferably, the reaction processes herein are carried out sequentially.
Unless otherwise defined, technical and scientific terms used herein have the same meaning as is familiar to those skilled in the art. In addition, any methods or materials similar or equivalent to those described herein can also be used in the present application.
According to a first aspect of the present application, there is provided a multi-layered structure composite separator including a porous polymer-based film, nano-oxide particles, and a dot-shaped polymer coating layer; the particle size of the nanometer oxide particles is 10-50nm, the aperture range of the porous polymer basement membrane is 0.05-0.3 mu m, and the nanometer oxide particles are completely embedded into the pores of the porous polymer basement membrane and attached to the filiform structure of the porous polymer basement membrane; the two sides of the porous polymer base membrane are provided with point-shaped polymer coating layers.
The diaphragm is a multilayer diaphragm structure of a point-shaped polymer coating, a porous polymer base membrane, nano oxide particles and a point-shaped polymer coating.
Porous polymer-based membranes
The porous polymer-based membrane may be a commonly used battery separator material, including but not limited to: polyethylene (PE), polypropylene (PP), polyamide (PA), polyimide (PI) or composite films thereof, and the like.
Preferably, the thickness of the porous polymer-based membrane is between 1-100 μm (e.g., 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100 μm).
Nano-oxide particles
The particle size of the nano oxide particles is 10-50nm, and the pore diameter range of the porous polymer-based membrane is 0.05-0.3 mu m. The particle size of the oxide particles is far smaller than the pore diameter of the porous polymer-based membrane, and the oxide particles are required to be completely embedded into the pores of the porous polymer-based membrane and attached to the filamentous structures of the polymer-based membrane. It should be noted that the oxide particles are required to be completely embedded in the pores of the porous polymer-based film, which means that the nano oxide particles are completely embedded in the base film and do not form another layer of adhesion on the surface of the base film, thereby not only ensuring that the thickness of the original base film is not affected, but also ensuring that the number of pores is not affected.
The oxide particles are not limited and include, but are not limited to: alumina (Al) 2 O 3 ) Titanium oxide (TiO) 2 ) Silicon oxide (SiO) 2 ) Zirconium oxide (ZrO) 2 ) Indium Tin Oxide (ITO) and tin oxide (In) 2 O 3 ) Indium oxide (SnO) 2 ) Hafnium oxide (HfO) 2 ) Tantalum oxide (Ta) 2 O 5 ) Yttrium oxide (Y) 2 O 3 ) Magnesium oxide (MgO), lanthanum oxide (La) 2 O 3 ) Zinc oxide (ZnO), nickel oxide (NiO), etc.
The particle size of the particles can be controlled between 10 nm and 50nm through an atomic layer deposition technology, and the situation that the lithium ion transmission channel is blocked because the particles are filled into the polymer base film is guaranteed.
Through the introduction of the nano oxide particles, a firm supporting effect is provided, and the shrinkage performance of the polymer-based film at high temperature can be further stabilized. Meanwhile, the nano-scale oxide particles are introduced, so that the wettability of the diaphragm to the electrolyte can be improved, the electrolyte can be soaked into the aperture of the polymer-based membrane and can be kept on the particles of the diaphragm functional layer, and a better liquid channel is provided for lithium ion transmission.
Dot-shaped polymer coating
The application arranges point-shaped polymer coatings on two sides of a porous polymer base membrane introduced with nano oxide particles, wherein the point-shaped polymer coatings are in point shapes and can be obtained by coating polymers on two sides of the porous polymer base membrane in a point manner, and finally a multilayer diaphragm structure of the point-shaped polymer coatings, the porous polymer base membrane and the nano oxide particles and the point-shaped polymer coatings is formed.
The material of the dot-shaped polymer coating is not limited, and includes but is not limited to PVDF material. The thickness of the dot-shaped polymer coating is within 1-5 μm (e.g. 1, 2, 3, 4, 5 μm).
The polymer coating in the outside selects the punctiform form, avoids on the one hand to cover the diaphragm gas permeability that polymer coating leads to and reduces by a wide margin comprehensively, and on the other hand has also guaranteed that the pole piece of making can have certain hardness after the hot pressing, and the manipulator of being convenient for snatchs, improves production efficiency, to the multiplying power performance of battery, circulation performance, also have certain promotion simultaneously.
The diaphragm that this application provided is the multilayer diaphragm structure of punctiform polymer coating-polymer base film + nanometer oxide granule-punctiform polymer coating, and oxide particle diameter is less than porous polymer base film's aperture far away, and oxide granule need all imbed in porous polymer base film aperture to adhere to on filiform polymer base film, on not influencing the original lithium ion channel basis of diaphragm, improve the stability of diaphragm under the high temperature, can also strengthen the infiltration nature of diaphragm to electrolyte. In addition, the two surfaces of the polymer base film and the nano oxide particle structure are provided with the point-shaped polymer coating, so that the transmission channel of the original base film is not blocked, the application is more suitable for the existing lithium ion production scene, and the application is convenient to be directly applied to commercial lithium ion batteries.
According to a second aspect of the present application, there is provided a method of manufacturing a multilayer structure composite separator, including the steps of:
s1: depositing nano oxide particles on a filamentous structure of the porous polymer base membrane through an atomic layer deposition process, and completely embedding the nano oxide particles into holes of the porous polymer base membrane to obtain the porous polymer base membrane on which the nano oxide particles are deposited;
s2: and (3) dot-coating polymer coatings on two surfaces of the porous polymer-based membrane after the nano oxide particles are deposited to obtain the multilayer-structure composite diaphragm.
The oxide particles form a functional layer inside the porous polymer-based film by Atomic Layer Deposition (ALD). The oxide particles are fully embedded in the porous polymer-based membrane by atomic layer deposition technique ALD. ALD has obvious advantages in film formation uniformity, particle size control and the like, and the preparation method can completely avoid the binder required by preparing nano oxide particles.
Nanometer-scale oxide particles embedded in the diaphragm with higher consistency can be prepared by special Atomic Layer Deposition (ALD).
The Atomic Layer Deposition (ALD) technology can further refine oxide powder particles in the process, and embed nanoscale oxide powder particles in the base film to be deposited on the filamentous structure of the polymer base film to form a firmly combined functional layer. The size, uniformity, and quantity of the oxide particles can be controlled by varying various factors such as the precursor temperature, the vacuum level of the reaction chamber, the substrate temperature, and the like. The uniformity of the oxide particles can ensure the uniformity of particle embedding, and prevent large particles from blocking or small particles from being unable to attach. The quantity of the nano-scale oxide particles is controlled to promote a certain supporting effect under the condition of not influencing the porosity of the diaphragm.
In a preferred embodiment, the process parameters of the atomic layer deposition process include:
the temperature of the precursor is 30-100 ℃, the vacuum degree of the reaction chamber is 20-100Pa, and the temperature of the base material is 80-110 ℃.
Besides the structure of the porous polymer base membrane and the nano oxide particles, the polymer coating can be sprayed in a dot mode through a conventional water system diaphragm spraying process to form a multi-layer diaphragm structure of the dot polymer coating-the polymer base membrane + the nano oxide particles-the dot polymer coating.
Preferably, a method for preparing a typical composite separator having a multilayer structure comprises the following steps:
using porous PE filmBase film, preparation of TiO using atomic deposition technique ALD 2 And a functional layer. The precursor used is tetraisopropyl titanate TTIP and deionized water H 2 And (O). TTIP precursor is stored in a chamber with the temperature of 60-80 ℃, and deionized water is stored in a chamber with the temperature of 20-50 ℃. And the temperatures of the transmission pipelines are respectively set to be 80-110 ℃ and 60-80 ℃. Both sides of the PE membrane need to be at stable O before ALD deposition 2 Plasma surface treatment is carried out under the flow rate. In ALD processing, 5 pulses, N, are used in a cycle 2 ，TTIP，N 2 ，H 2 O，N 2 . And the amount of oxide deposited can be controlled by controlling the number of cycles. Preferably the number of cycles is 50-150;
obtaining PE basal membrane and TiO 2 And after the diaphragm of the functional layer is coated with the PVDF coating in a dot-shaped manner by a conventional spraying process, so that the diaphragm with the multilayer structure is obtained.
According to a third aspect of the present application, there is provided a secondary battery including the foregoing multilayer-structure composite separator or the multilayer-structure composite separator produced by the foregoing production method.
The separator with the multilayer structure prepared by the method can be directly applied to the existing commercial secondary batteries, such as lithium ion batteries, lithium metal batteries and the like, and the matched positive electrode materials include but are not limited to: one or more of lithium cobaltate, lithium manganate, lithium iron phosphate and lithium nickel cobalt manganese ternary materials are mixed. The negative electrode material that can be matched includes but is not limited to one or more of conventional artificial graphite, natural graphite, silicon carbon and the like. Lithium-containing cathodes may be collocated including, but not limited to: lithium metal, lithium metal transition nitride, lithium metal layered oxide, and the like.
According to a fourth aspect of the present application, there is provided an electric device including the secondary battery of the third aspect of the present application, wherein the electric device may be, for example, a portable electronic device or an electric car.
The third and fourth aspects have the same advantages as the first and second aspects, and are not described in detail herein.
The present application is further illustrated by the following examples. The materials in the examples are prepared according to known methods or are directly commercially available, unless otherwise specified.
Example 1
Preparation of TiO using ALD 2 Functional layer:
preparing TiO by using a porous PE film with the thickness of 12 mu m as a base film and using an atomic deposition technology ALD 2 And a functional layer. The precursor used is titanium tetraisopropyl ester TTIP and deionized water H 2 And O. The TTIP precursor was stored in an 80 ℃ chamber and deionized water was stored in a 35 ℃ chamber. While the temperatures of their transfer pipes were set at 100 c and 70 c, respectively. Both sides of the PE membrane need to be at stable O before ALD deposition can take place 2 Plasma surface treatment is carried out under the flow rate. In ALD process, 5 pulses, N, are used in a cycle 2 ，TTIP，N 2 ，H 2 O，N 2 . And the amount of oxide deposited can be controlled by controlling the number of cycles. The present embodiment sets the number of cycles to 100 cycles.
By taking SEM images before and after the diaphragm is used for preparing the functional layer, the diaphragm PE base film with the aperture of about 0.1-0.2 mu m and the particle size of nano oxide particles of about 10-30nm is obtained.
Obtaining PE basal membrane and TiO 2 And (3) after the diaphragm of the functional layer is coated with the PVDF coating in a dot manner by a conventional spraying process, so that the diaphragm with the multilayer structure is obtained.
Preparation of a conventional lithium battery:
lithium iron phosphate (LiFePO) coated with graphite 4 ) Stacking and placing the positive plate serving as the positive material, the prepared diaphragm plate and the negative plate serving as the graphite negative material in sequence from bottom to top to form a lamination, and then placing the lamination on a punching machine for punching to obtain C/LiFePO 4 A battery.
Thermal shrinkage test:
a100 mm X100 mm separator was kept at 130 ℃ for 1 hour, and the change in length in the MD and TD directions was measured after taking out.
Performance of the battery at high temperature:
the experiment is carried out in a constant temperature box at 60 ℃, constant current and constant voltage charging is carried out firstly, the constant current and constant voltage charging at 0.2 ℃ is carried out until the voltage reaches 3.8V, the current is cut off at 0.05C, then constant current discharging is carried out, the constant current discharging is carried out until the voltage reaches 2.0V, the cycle is carried out for 100 times, and the discharging capacity at each time is recorded.
Example 2
Preparation of TiO using ALD 2 Functional layer:
preparing TiO by using a porous PP film with the thickness of 12 mu m as a base film and using an atomic deposition technology ALD 2 And a functional layer. The precursor used is titanium tetraisopropyl ester TTIP and deionized water H 2 And O. The TTIP precursor was stored in an 80 ℃ chamber and deionized water was stored in a 35 ℃ chamber. While the temperatures of the transfer pipes thereof were set to 100 c and 70 c, respectively. Both sides of the PE membrane need to be at stable O before ALD deposition can take place 2 Plasma surface treatment is carried out under the flow rate. In ALD processing, 5 pulses, N, are used in a cycle 2 ，TTIP，N 2 ，H 2 O，N 2 . While the amount of oxide deposited can be controlled by controlling the number of cycles. The present embodiment sets the number of cycles to 200 cycles.
By taking SEM images before and after the diaphragm is used for preparing the functional layer, the aperture of the PE-based membrane of the diaphragm is about 0.1-0.2 mu m, and the particle size of nano oxide particles is about 30-50nm.
Obtaining PE base film and TiO 2 And (3) after the diaphragm of the functional layer is coated with the PVDF coating in a dot manner by a conventional spraying process, so that the diaphragm with the multilayer structure is obtained.
Preparation of a conventional lithium battery:
and (2) stacking and placing a positive plate taking a ternary material (NCM 523) containing lithium, cobalt, nickel and manganese as a positive electrode material, the prepared diaphragm plate and a negative plate taking graphite as a negative electrode material in sequence from bottom to top to form a lamination, and then placing the lamination on a punching machine for punching to obtain the C/NCM523 battery.
And (3) thermal shrinkage test:
a100 mm X100 mm separator was kept at 130 ℃ for 1 hour, and the change in length in the MD and TD directions was measured after taking out.
Performance of the battery at high temperature:
the experiment is carried out in a constant temperature box with the temperature of 60 ℃, constant current and constant voltage charging is firstly carried out, constant current and constant voltage charging at 0.2 ℃ is carried out until the voltage reaches 4.25V, the current is cut off at 0.05C, then constant current discharging is carried out, discharging at 0.2C is carried out until the voltage reaches 2.5V, the circulation is carried out for 100 times, and the discharge capacity at each time is recorded.
Example 3
Preparation of Al using ALD 2 O 3 Functional layer:
preparing Al by using a porous PE film with the thickness of 12 mu m as a base film and using atomic deposition technology ALD 2 O 3 And a functional layer. The precursor is Al (OH) 3 And deionized water H 2 O。Al(OH) 3 The precursor was stored in an 80 ℃ chamber and deionized water was stored in a 35 ℃ chamber. While the temperatures of their transfer pipes were set at 100 c and 70 c, respectively. Both sides of the PE membrane need to be at stable O before ALD deposition 2 Plasma surface treatment is carried out under the flow rate. In ALD process, 5 pulses, N, are used in a cycle 2 ，Al(OH) 3 ，N 2 ，H 2 O，N 2 . While the amount of oxide deposited can be controlled by controlling the number of cycles. The number of cycles set in this example is 100 cycles.
By shooting SEM images before and after the functional layer is prepared by the diaphragm, the aperture of the PE base membrane of the diaphragm is about 0.1-0.2 mu m, and the grain diameter of nano oxide particles is about 10-30nm.
Obtaining PE basal membrane and Al 2 O 3 And (3) after the diaphragm of the functional layer is coated with the PVDF coating in a dot manner by a conventional spraying process, so that the diaphragm with the multilayer structure is obtained.
Preparation of a conventional lithium battery:
lithium iron phosphate (LiFePO) coated with graphite 4 ) Stacking and placing the positive plate serving as the positive material, the prepared diaphragm plate and the negative plate serving as the graphite negative material in sequence from bottom to top to form a lamination, and then placing the lamination on a punching machine for punching to obtain C/LiFePO 4 A battery.
Thermal shrinkage test:
a100 mm X100 mm separator was kept at 130 ℃ for 1 hour, and the change in length in the MD and TD directions was measured after taking out.
Performance of the battery at high temperature:
the experiment is carried out in a constant temperature box at 60 ℃, constant current and constant voltage charging is carried out firstly, the constant current and constant voltage charging at 0.2 ℃ is carried out until the voltage reaches 3.8V, the current is cut off at 0.05C, then constant current discharging is carried out, the constant current discharging is carried out until the voltage reaches 2.0V, the cycle is carried out for 100 times, and the discharging capacity at each time is recorded.
Comparative example 1
A porous polymer-based membrane, which is a PE separator, having a thickness of 12 μm.
The pore size of the PE-based film is about 0.1-0.2 μm by taking SEM images of the PE-based film.
Comparative example 2
Preparation of TiO using ALD 2 Functional layer:
preparing TiO by using a porous PE film with the thickness of 12 mu m as a base film and using an atomic deposition technology ALD 2 And a functional layer. The precursor used is tetraisopropyl titanate TTIP and deionized water H 2 And O. The TTIP precursor was stored in a 120 ℃ chamber and the deionized water was stored in a 100 ℃ chamber. While the temperatures of their transfer pipes were set to 200 c and 150 c, respectively. Both sides of the PE membrane need to be at stable O before ALD deposition 2 Plasma surface treatment is carried out under the flow rate. In ALD processing, 5 pulses, N, are used in a cycle 2 ，TTIP，N 2 ，H 2 O，N 2 . While the amount of oxide deposited can be controlled by controlling the number of cycles. The present embodiment sets the number of cycles to 300 cycles.
By taking SEM images before and after the diaphragm is used for preparing the functional layer, the diaphragm PE base film is obtained, wherein the aperture is about 0.1-0.2 mu m, and the particle size of nano oxide particles is about 100-150nm.
Obtaining PE base film and TiO 2 And (3) after the diaphragm of the functional layer is coated with the PVDF coating in a dot manner by a conventional spraying process, so that the diaphragm with the multilayer structure is obtained.
Preparation of a conventional lithium battery:
lithium iron phosphate (LiFePO) coated with graphite 4 ) Stacking and placing the positive plate serving as the positive material, the prepared diaphragm plate and the negative plate serving as the graphite negative material in sequence from bottom to top to form a lamination, and then placing the lamination on a punching machine for punching to obtain C/LiFePO 4 A battery.
Thermal shrinkage test:
a100 mm X100 mm separator was kept at 130 ℃ for 1 hour, and the change in length in the MD and TD directions was measured after taking out.
Performance of the battery at high temperature:
the experiment is carried out in a constant temperature box at 60 ℃, constant current and constant voltage charging is carried out firstly, the constant current and constant voltage charging at 0.2 ℃ is carried out until the voltage reaches 3.8V, the current is cut off at 0.05C, then constant current discharging is carried out, the constant current discharging is carried out until the voltage reaches 2.0V, the cycle is carried out for 100 times, and the discharging capacity at each time is recorded.
The test results of the examples and comparative examples are shown in table 1:
TABLE 1
As can be seen from Table 1, the diaphragm of the structure of the present application has a low thermal shrinkage at high temperature, and the performance at high temperature is superior to that of a common PE diaphragm. In addition, with the composite separator of the multilayer structure obtained by the preparation process in comparative example 2, the particle size of the obtained nano-oxide particles is located outside the porous polymer-based membrane and is not embedded in the pore structure of the porous polymer-based membrane, and thus, each performance of comparative example 2 is poor.
It will be apparent to those skilled in the art that various changes and modifications can be made in the embodiments of the present application without departing from the spirit and scope of the application. Thus, if such modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is intended to include such modifications and variations as well.
Claims (9)
1. A multilayer structure composite membrane is characterized by comprising a porous polymer-based membrane, nano oxide particles and a point-shaped polymer coating; the particle size of the nano oxide particles is 10-50nm, the pore size of the porous polymer-based membrane is in the range of 0.05-0.3 μm, and the nano oxide particles are embedded in the pores of the porous polymer-based membrane and attached to the filamentous structures of the porous polymer-based membrane; the dot-shaped polymer coating layers are arranged on two sides of the porous polymer base film;
depositing nano oxide particles on a filamentous structure of the porous polymer base membrane through an atomic layer deposition process, and completely embedding the nano oxide particles into holes of the porous polymer base membrane to obtain the porous polymer base membrane on which the nano oxide particles are deposited;
wherein the process parameters of the atomic layer deposition process comprise:
the temperature of the precursor is 30-100 ℃; the vacuum degree of the reaction chamber is 20-100Pa; the temperature of the base material is 80-110 ℃.
2. The multi-layered structure composite separator according to claim 1, wherein the porous polymer-based membrane comprises polyethylene, polypropylene, polyamide, polyimide, or a composite membrane thereof.
3. The multi-layered structure composite separator according to claim 1, wherein the thickness of the porous polymer-based membrane is 1 to 100 μm.
4. The multi-layered structure composite separator according to claim 1, wherein said nano-oxide particles comprise Al 2 O 3 、TiO 2 、SiO 2 、ZrO 2 、ITO、In 2 O 3 、SnO 2 、HfO 2 、Ta 2 O 5 、Y 2 O 3 、MgO、La 2 O 3 One or more of ZnO and NiO.
5. The multi-layer structure composite membrane of any one of claims 1-4, wherein the dot-shaped polymer coating comprises a PVDF material; the thickness of the dot-shaped polymer coating is 1-5 mu m.
6. A method for preparing a multilayer structure composite separator as claimed in any one of claims 1 to 5, comprising the steps of:
and (3) coating polymer coatings on two surfaces of the porous polymer-based membrane on which the nano oxide particles are deposited in a dotted manner to obtain the multilayer-structure composite membrane.
7. The method according to claim 6, wherein the polymer coating is applied in dots by spraying.
8. A secondary battery comprising the multilayer structure composite separator according to any one of claims 1 to 5 or the multilayer structure composite separator produced by the production method according to claim 6 or 7.
9. An electric device comprising the secondary battery according to claim 8.
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| CN105226219A (en) * | 2015-09-11 | 2016-01-06 | 江西先材纳米纤维科技有限公司 | Compound many curved hole membrane material that zirconia particles is filled and its preparation method and application |
| CN106960933A (en) * | 2015-12-02 | 2017-07-18 | Sk新技术株式会社 | Heat resistance and the excellent secondary cell barrier film of closing property |
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| JP5384631B2 (en) * | 2008-08-25 | 2014-01-08 | エルジー・ケム・リミテッド | Separator provided with porous coating layer, method for producing the same, and electrochemical device provided with the same |
| CN102891275A (en) * | 2011-07-20 | 2013-01-23 | 上海纳米技术及应用国家工程研究中心有限公司 | Modified microporous diaphragm and its preparation method and use |
| CN203932169U (en) * | 2014-05-30 | 2014-11-05 | 东莞市卓高电子科技有限公司 | Environmental protection breathable type battery inner septum |
| CN111092192A (en) * | 2019-12-27 | 2020-05-01 | 武汉中兴创新材料技术有限公司 | Polymer coating diaphragm and lithium ion battery |
| CN111384345A (en) * | 2020-03-20 | 2020-07-07 | 中航锂电技术研究院有限公司 | Diaphragm, preparation method and lithium ion battery comprising diaphragm |
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| CN105226219A (en) * | 2015-09-11 | 2016-01-06 | 江西先材纳米纤维科技有限公司 | Compound many curved hole membrane material that zirconia particles is filled and its preparation method and application |
| CN106960933A (en) * | 2015-12-02 | 2017-07-18 | Sk新技术株式会社 | Heat resistance and the excellent secondary cell barrier film of closing property |
| CN207558902U (en) * | 2017-09-12 | 2018-06-29 | 乳源东阳光氟树脂有限公司 | A kind of composite lithium battery membrane |
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