WO2017097266A1

WO2017097266A1 - Power cell diaphragm, preparation method therefor, and power cell comprising same

Info

Publication number: WO2017097266A1
Application number: PCT/CN2016/109543
Authority: WO
Inventors: 王彦红; 杨重科; 秦兴权
Original assignee: 北京新能源汽车股份有限公司
Priority date: 2015-12-11
Filing date: 2016-12-12
Publication date: 2017-06-15
Also published as: CN105355824B; CN105355824A

Abstract

The present invention provides a power cell diaphragm, a preparation method therefor, and a power cell comprising same. The power cell diaphragm comprises: a diaphragm body, having a first surface and a second surface opposite to the first surface; and a first modified layer located on the first surface, and/or a second modified layer located on the second surface. The first modified layer and the second modified layer comprise a base material and phase change capsules dispersed in the base material separately, the phase change capsules being of a core-shell structure, shell layers of the phase change capsules comprising polymers and ceramic particles dispersed in the polymers, and core layers of the phase change capsules comprising phase change materials.

Description

Power battery separator, preparation method thereof and power battery including the same

Related application

Priority is claimed on Japanese Patent Application No. 201510921142.6, the entire disclosure of which is hereby incorporated by reference.

Technical field

The present invention relates to the field of power battery technology, and in particular to a power battery separator, a method of manufacturing the same, and a power battery including the same.

Background technique

The safety of the power battery system directly affects the safety of the electric vehicle. For the safety study of the power battery system, it can be controlled from the system, module and battery level to ensure its safety to the greatest extent. The safety of the battery level is the root of the entire battery system, especially the power battery diaphragm. Whether the current can be effectively cut off in the event of thermal runaway plays an important role in preventing the occurrence of safety accidents.

Currently, commercially available lithium ion power batteries employ a polyolefin-based separator material having a microporous structure, such as a single layer or a multilayer film of polyethylene (PE) and polypropylene (PP). Since the polyolefin microporous membrane has a closed cell function, the microporous structure will self-close at a certain temperature to cut off the current. However, since the separator raw material itself has a low melting point temperature (PE melting point is about 130 ° C, PP melting point is about 160 ° C), its closed cell temperature is not higher than the melting point temperature. Moreover, the fact that the closed cells mean that the diaphragm itself has undergone severe shrinkage cannot prevent further occurrence of short circuit of the battery. Therefore, the closed-cell function of the polyolefin-based separator cannot prevent the occurrence of a short circuit when the internal temperature of the battery is high or the heat is out of control, which is bound to cause a safety accident.

For the above reasons, it is necessary to modify the polyolefin-based separator so that it can still prevent short-circuiting even when the internal temperature of the battery is high or the heat is out of control.

Summary of the invention

The main object of the present invention is to provide a power battery separator, a preparation method thereof, and a power battery including the same, to solve the problem that the polyolefin-based separator in the prior art is prone to functional failure when the internal temperature of the battery is high or the heat is out of control. problem.

In order to achieve the above object, according to an aspect of the invention, a power battery separator includes: a diaphragm body having a first surface and a second surface opposite to the first surface; and a first on the first surface a modified layer, and/or a second modified layer on the second surface; the first modified layer and the second modified layer respectively comprise a substrate and a phase change capsule dispersed in the substrate; wherein the phase change capsule The core-shell structure includes a polymer and a ceramic particle dispersed in the polymer in the shell layer of the phase change capsule, and the phase change capsule includes a phase change material in the core layer.

Further, the phase change capsules in the first modified layer and the second modified layer each independently comprise 0.5 to 3 parts of ceramic particles, 6 to 10 parts of phase change material, and 2 to 6 parts by weight. polymer.

Further, the core layer of the phase change capsule further includes a flame retardant, wherein the flame retardant is 0.5 to 2 parts by weight.

Further, the flame retardant is chlorinated paraffin.

Further, the ceramic particles are silica particles, wherein the ceramic particles have a particle diameter of 400 nm; the phase change material is selected from the group consisting of phase change paraffins and/or C ₁₂ - C ₂₅ alkane mixtures, wherein the phase change paraffins have a melting point of 25 ～ 62 ° C paraffin, C ₁₂ - C ₂₅ alkane selected from one or more of C ₁₂ H ₂₆ , C ₁₈ H ₃₈ , C ₁₅ H ₃₂ and C ₂₅ H ₅₂ ; the synthetic monomer of the polymer is selected from benzene At least one of ethylene, methyl methacrylate and butyl acrylate, the crosslinking agent for the synthetic polymer is selected from the group consisting of divinylbenzene or ethylene glycol dimethacrylate.

Further, the substrate is formed by curing a binder, wherein the binder is selected from a PTFE binder or an SBR binder.

Further, the diaphragm body is a polyolefin separator, wherein the polyolefin membrane is selected from the group consisting of a PP/PE double layer composite membrane or a PP/PE/PP three layer composite membrane.

According to another aspect of the present invention, there is provided a method of producing a power battery separator comprising the steps of: preparing a Pickering emulsion comprising ceramic particles, a phase change material, a synthetic monomer of a polymer, a crosslinking agent, and an initiator; The synthetic monomer in the Pickering emulsion is polymerized to form a polymer, and then the emulsion is dried to obtain a phase change capsule; the phase change capsule and the binder for forming the substrate are mixed to form a liquid to be solidified; Coating on the first surface and/or the second surface of the membrane body, after curing treatment, forming a first modified layer and/or a second modified layer, thereby obtaining a power battery separator.

Further, the step of preparing the Pickering emulsion comprises: dispersing the ceramic particles in water to form an aqueous phase; mixing the phase change material, the synthetic monomer, the crosslinking agent and the initiator, heating to a molten state to form an oil phase; After mixing the phases with the oil phase, it is stirred to form a Pickering emulsion.

Further, before the synthesis of the synthetic monomer in the Pickering emulsion, the step of adding an emulsifier to the Pickering emulsion, wherein the emulsifier is selected from the group consisting of a fatty acid salt, a rosin acid salt, an alkyl sulfate salt, an alkyl sulfonate, is also included. Or an alkylaryl sulfonate.

Further, the fatty acid salt is sodium stearate, the rosin acid salt is disproportionated sodium sulphate, the alkyl sulfate salt is sodium lauryl sulfate, and the alkyl sulfonate is sodium hexadecyl sulfonate.

Further, the step of mixing the phase change material, the synthetic monomer, the crosslinking agent, and the initiator further includes a process of adding a flame retardant.

Further, in the process of polymerizing the synthetic monomer in the Pickering emulsion, the polymerization time is 8 to 10 hours, and the polymerization temperature is 50 to 85 °C.

According to still another aspect of the present invention, there is provided a power battery comprising a battery separator, wherein the battery separator is the above-described power battery separator.

In the above power battery separator provided by the present invention, a modified layer is coated on the surface of the separator body, and the modified layer includes a substrate and a phase change capsule dispersed in the substrate. Among them, the phase change capsule has a core-shell structure, and the shell layer includes a polymer and ceramic particles dispersed in the polymer, and the core layer includes a phase change material. The phase change material can absorb heat during charging and discharging of the power battery to reduce the internal temperature of the high-power battery and at the same time act as a thermal buffer to prevent functional failure of the diaphragm body which is prone to sudden temperature rise. At the same time, the ceramic particles have high high temperature resistance, which can effectively improve the high temperature resistance of the battery separator, and make it more resistant to potential oxidation during the long-term charge and discharge cycle. At the same time, the ceramic particles can also prevent the excessive shrinkage of the diaphragm body when the internal temperature of the battery is high or the heat is out of control, so that it can maintain the shrinkable function after cutting off the current and preventing the short circuit. Both of the above factors can improve the thermal performance of the diaphragm, which is beneficial to prevent diaphragm failure caused by high temperature or thermal runaway, and improve the safety of the power battery.

detailed description

It should be noted that the embodiments in the present application and the features in the embodiments may be combined with each other without conflict. The invention will be described in detail below with reference to the embodiments.

As described in the background art, the polyolefin-based separator of the prior art cannot function to prevent short-circuiting under the condition that the internal temperature of the battery is high or the heat is out of control, and the functional failure is liable to occur. In order to solve this problem, the present invention provides a power battery separator including: a diaphragm body having a first surface and a second surface opposite to the first surface; and a first modified layer on the first surface, And/or a second modified layer on the second surface; a first modified layer, The second modified layer respectively comprises a substrate and a phase change capsule dispersed in the substrate; wherein the phase change capsule has a core-shell structure, and the shell of the phase change capsule comprises a polymer and ceramic particles dispersed in the polymer, the phase The phase change material is included in the core layer of the capsule.

In the above power battery separator provided by the present invention, a modified layer is coated on the surface of the separator body, and the modified layer includes a substrate and a phase change capsule dispersed in the substrate. Among them, the phase change capsule has a core-shell structure, and the shell layer includes a polymer and ceramic particles dispersed in the polymer, and the core layer includes a phase change material (ie, a thermal phase transition material). The phase change material can absorb heat during charging and discharging of the power battery to reduce the internal temperature of the high-power battery and at the same time act as a thermal buffer to prevent functional failure of the diaphragm body which is prone to sudden temperature rise. At the same time, the ceramic particles have high high temperature resistance, which can effectively improve the high temperature resistance of the battery separator, and make it more resistant to potential oxidation during the long-term charge and discharge cycle. At the same time, the ceramic particles can also prevent the excessive shrinkage of the diaphragm body when the internal temperature of the battery is high or the heat is out of control, so that it can maintain the shrinkable function after cutting off the current and preventing the short circuit. Both of the above factors can improve the thermal performance of the diaphragm, which is beneficial to prevent diaphragm failure caused by high temperature or thermal runaway, and improve the service life of the power battery. Further, dispersing the ceramic particles in the shell polymer of the phase change capsule enables it to be more stably present on the surface of the diaphragm body. Coating the phase change material inside the shell polymer is also beneficial to improve the stability of the phase change material. In short, the phase change capsule having the above special structure can exert more stable heat absorption, heat buffering and high temperature resistance, thereby further improving the stability of the battery separator, improving the safety of the power battery, and reducing the safety hazard during high power charging and discharging. .

In the above-mentioned power battery separator provided by the present invention, the phase change capsule in the modified layer can effectively improve the high temperature resistance and thermal buffering property of the separator at a high temperature condition as long as it has the above-described core-shell structure and contains the above-mentioned several materials. Or maintain the diaphragm function under thermal runaway conditions. In a preferred embodiment, the phase change capsules in the first modified layer and the second modified layer each independently comprise 0.5 to 3 parts of ceramic particles and 6 to 10 parts of phase change. Materials and 2 to 6 parts of polymer. The relationship between the amounts of the components in the phase change capsule is controlled within the above range, and the phase change capsule can have a more stable core-shell structure to improve the stability of the battery separator. At the same time, it is beneficial to balance the functions of the components, so that the high temperature resistance and thermal buffering performance of the separator are higher, and the safety of the power battery is improved.

In the above-described power battery separator, the phase change capsule can effectively improve the high temperature resistance and thermal cushioning performance of the separator and improve the service life thereof as long as it has the above-described core-shell structure and contains the above-mentioned several materials. In a preferred embodiment, the phase change capsule further comprises a flame retardant in the core layer. The addition of a flame retardant can improve the flame retardant performance of the battery separator, so that it can exert a certain flame retarding effect even when the heat is out of control. Among them, the flame retardant is 0.5 to 2 parts by weight. More preferably, the flame retardant includes, but is not limited to, chlorinated paraffin. Chlorinated paraffin has higher compatibility with phase change materials, and it is beneficial to improve the stability of phase change capsules.

Those skilled in the art can be selected from a particular class of materials in accordance with the teachings of the present invention. Preferably, the ceramic particles include, but are not limited to, silica particles. Silica particles have good high temperature resistance. Preferably, silica The particles are surface-modified silica particles, which have higher compatibility with the polymer, can further improve the stability of the phase change capsule, thereby improving the overall thermal performance of the battery separator. The above surface modification method may employ a conventional process in the art. Specifically, the modification process is as follows: silica is super-dispersed in ethanol, γ-aminopropyltriethoxysilane is added, and stirred at room temperature for 5 hours. The temperature was raised to 80 ° C and condensed and refluxed for 2 h. The precipitated particles were separated by centrifugation, washed with ethanol, and dried to obtain modified silica particles. More preferably, the ceramic particles have a particle diameter of 400 nm.

Preferably, the phase change the phase change material is selected from a mixture of paraffin and / or C ₁₂ ~ C ₂₅ alkane, wherein the melting point of the phase change paraffin paraffin of 25 ~ 62 ℃, C ₁₂ ~ C ₂₅ alkane is selected from C ₁₂ H ₂₆ , one or more of C ₁₈ H ₃₈ , C ₁₅ H ₃₂ and C ₂₅ H ₅₂ . The above phase change materials all have good thermal phase transition properties and have high endothermic values during phase transition. At the same time, these phase change materials have good compatibility with the shell layer, and can form a stable interface with them, thereby facilitating further improvement of the thermal properties of the phase change capsule. In summary, the use of several phase change materials described above can further improve the high temperature resistance, heat absorption and thermal buffering properties of the separator.

Preferably, the synthetic monomer of the polymer includes, but is not limited to, at least one of styrene, methyl methacrylate and butyl acrylate; the crosslinking agent of the synthetic polymer is selected from divinyl benzene or dimethacrylate B Glycol ester. These kinds of synthetic monomers and cross-linking agents are selected, and the polymer obtained after polymerization has high thermal stability. Moreover, it has good compatibility with the ceramic particles and the internal phase change material, so that the ceramic particles can be more uniformly dispersed in the polymer while the phase change material is more stably coated inside the polymer. In addition, the polymer formed by the polymerization of these synthetic monomers has better compatibility with the substrate in the modified layer, which is beneficial to improve the dispersion performance of the phase change capsule in the substrate, thereby making the thermal properties of the separator different positions. More stable and uniform to further improve the performance and safety of the diaphragm. Preferably, the synthetic monomer is styrene and divinylbenzene, more preferably the weight ratio of styrene to divinylbenzene is 3:1.

In the above modified layer, the substrate to be used may be stably covered on the surface of the separator body. In a preferred embodiment, the substrate is cured from a binder, wherein the binder is selected from the group consisting of a PTFE binder or an SBR binder. After the phase change material is dispersed in the binder using a binder, it is coated on the surface of the separator body to form the modified layer by curing. This is advantageous in improving the processability of the modified layer and better controlling the thickness of the modified layer. With the above several kinds of binders, the formed substrate has better thermal stability, and it has better compatibility with the phase change capsule, thereby further improving the thermal performance of the separator and improving the safety of use thereof.

In the above power battery separator, the diaphragm body used may be a battery separator commonly used in the art. In a preferred embodiment, the membrane body is selected from the group consisting of polyolefin membranes, wherein the polyolefin membrane is selected from the group consisting of PP/PE double layer composite membranes or PP/PE/PP three layer composite membranes.

In addition, the present invention also provides a method for preparing a power battery separator, comprising the steps of: preparing a Pickering emulsion containing ceramic particles, a phase change material, a synthetic monomer of a polymer, a crosslinking agent, and an initiator; and making a Pickering emulsion The synthetic monomer is polymerized to form a polymer, and the emulsion is dried to obtain a phase change capsule; the phase change capsule and the binder for forming the substrate are mixed to form a liquid to be solidified; and the liquid to be solidified is coated On the first surface and/or the second surface of the diaphragm body, after the curing treatment, a first modified layer and/or a second modified layer are formed, thereby obtaining a power battery separator.

In the above preparation method provided by the present invention, a Pickering emulsion containing ceramic particles, a phase change material, a synthetic monomer of a polymer, and an initiator is prepared; after the synthesis monomer in the Pickering emulsion is polymerized to form a polymer, A phase change capsule having a core-shell structure is produced. Wherein the shell layer comprises a polymer and ceramic particles dispersed in the polymer, and the core layer comprises a phase change material. After mixing the phase change capsule and the binder for forming the substrate, coating on the first surface and/or the second surface of the diaphragm body, after curing, forming a first modification on the surface of the diaphragm body Layer and / or second modified layer.

In the power battery separator prepared by the above method, the phase change material can absorb heat during charging and discharging of the power battery to reduce the internal temperature of the high-power battery and at the same time function as a heat buffer to prevent the diaphragm body from being swelled when the temperature rises. The function that occurred is invalid. At the same time, the ceramic particles have high high temperature resistance, which can effectively improve the high temperature resistance of the battery separator, and make it more resistant to potential oxidation during the long-term charge and discharge cycle. At the same time, the ceramic particles can also prevent the excessive shrinkage of the diaphragm body when the internal temperature of the battery is high or the heat is out of control, so that it can maintain the shrinkable function after cutting off the current and preventing the short circuit. Both of the above factors can improve the thermal performance of the diaphragm, and help prevent the diaphragm failure caused by high temperature or thermal runaway, and improve the safety of the use of the power battery. Further, dispersing the ceramic particles in the shell polymer of the phase change capsule enables it to be more stably present on the surface of the diaphragm body. Coating the phase change material inside the shell polymer is also beneficial to improve the stability of the phase change material. In short, the phase change capsule having the above special structure can exert more stable heat absorption, heat buffering and high temperature resistance, thereby further improving the stability of the battery separator and improving the safety of the power battery.

In the above preparation method, the preparation process of the Pickering emulsion may be a conventional process in the art. In a preferred embodiment, the step of preparing the Pickering emulsion comprises: dispersing the ceramic particles in water to form an aqueous phase; mixing the phase change material, the synthetic monomer, the crosslinking agent and the initiator, and heating to a molten state, An oil phase is formed; the aqueous phase and the oil phase are mixed and stirred to form a Pickering emulsion.

The ceramic particles are dispersed in water to form an aqueous phase, and then mixed with an oil phase containing a phase change material, a synthetic monomer, a crosslinking agent, and an initiator, and then a Pickering emulsion can be formed under stirring. At this time, the ceramic particles are distributed at the water-oil interface, and during the later polymerization, they are dispersed in the polymer to form a shell layer of the phase change capsule. Preferably, the mixture is subjected to high-speed stirring after mixing the aqueous phase and the oil phase (stirring speed is not less than 5000 rar/min). More preferably, make Pickering Emulsion Prior to the polymerization of the synthetic monomer, a step of adding an emulsifier to the Pickering emulsion is also included. The addition of the polymeric surfactant can make the Pickering emulsion more stable, thereby facilitating the stability of the late polymerization process, thereby improving the dimensional uniformity and structural integrity of the phase change capsule. Preferably, the emulsifier is selected from the group consisting of a fatty acid salt, a rosinate salt, an alkyl sulfate, an alkyl sulfonate or an alkyl aryl sulfonate; more preferably, the fatty acid salt is sodium stearate and the rosin acid salt is disproportionated. Sodium rosinate, the alkyl sulfate is sodium lauryl sulfate, and the alkyl sulfonate is sodium hexadecyl sulfonate.

In the above preparation method, as long as the above-mentioned several materials are contained in the Pickering emulsion, a phase change capsule excellent in high temperature resistance, heat absorption, and heat cushioning property can be obtained. In a preferred embodiment, a flame retardant is further added to the step of mixing the phase change material, the synthesis monomer, and the initiator.

In addition, in the polymerization process, the selected initiator may be selected according to the type of the synthetic monomer, for example, azobisisobutyronitrile, dibenzoyl peroxide or the like may be selected. Preferably, when styrene is used as the synthetic monomer, when divinylbenzene is used as the crosslinking agent, azobisisobutyronitrile is used as the initiator.

In a preferred embodiment, during the polymerization of the synthetic monomer in the Pickering emulsion, the polymerization time is 8 to 10 hours, and the polymerization temperature is 50 to 85 °C. Polymerization under the above process conditions can improve the structural integrity and dimensional uniformity of the phase change capsule.

In addition, in the process of mixing the phase change capsule and the binder for forming the substrate to form the liquid to be solidified, those skilled in the art can select the ratio of the two according to the specific process and requirements. More preferably, the weight ratio of the phase change capsule to the binder is 1:10.

According to another aspect of the present invention, there is also provided a power battery comprising a battery separator, wherein the battery separator is the above-described power battery separator of the present invention.

The above-mentioned power battery separator of the invention has good heat absorption properties and thermal buffering properties due to the unique core-shell structure and material composition of the phase change capsule. This enables the diaphragm to absorb heat during charging and discharging of the power battery to reduce the internal temperature of the high-power battery while preventing the functional failure of the diaphragm body which is prone to sudden temperature rise. At the same time, the separator also has good high temperature resistance, making it more resistant to potential oxidation during long-term charge and discharge cycles. It is also possible to prevent excessive shrinkage of the diaphragm body in the case where the internal temperature of the battery is high or thermal runaway, so that the shrinkage function is maintained after the current is cut off and the short circuit is prevented. Both of the above factors can improve the thermal performance of the diaphragm, which is beneficial to prevent diaphragm failure caused by high temperature or thermal runaway, and improve the safety of the power battery. Further, dispersing the ceramic particles in the shell polymer of the phase change capsule enables it to be more stably present on the surface of the diaphragm body. Coating the phase change material inside the shell polymer is also beneficial to improve the stability of the phase change material. In short, a phase change capsule having the above special structure can be issued It has more stable heat absorption, heat buffering and high temperature resistance, which further improves the stability of the battery separator and improves the safety of the power battery.

The present application is further described in detail below with reference to the specific embodiments, which are not to be construed as limiting the scope of the claims.

Example 1

Silica surface treatment: 1 g of silica particles were ultrasonically dispersed in 50 mL of ethanol, and 1 g of γ-aminopropyltriethoxysilane was added thereto, and stirred at room temperature for 5 hours. The temperature was raised to 80 ° C and condensed and refluxed for 2 h. Separate by centrifugation, wash with ethanol, and dry for use.

1 g of the surface-treated silica particles having an average particle diameter of 400 nm were dispersed in 100 g of water, and the temperature was raised to 70 ° C, and the mixed liquid was used as an aqueous phase.

10 g of paraffin wax having a melting point of 52 ° C, 3 g of styrene, 1 g of divinylbenzene, 0.5 g of chlorinated paraffin, and 1 g of azobisisobutyronitrile were mixed, and the temperature was raised to 70 ° C to form an oil phase in a molten state.

After mixing the oil phase and the water phase, high-speed stirring was carried out for 10 minutes, and the stirring speed was not less than 5000 rar/min. Get a Pickering lotion.

The emulsifier 1 g SDS was added to the emulsion, and the mixture was stirred at 80 ° C for 8 h to obtain a phase change capsule.

After mixing 2 g of the phase change capsule with 20 g of the binder PTFE, both sides of the PP/PE/PP three-layer composite separator were coated, and after curing, a power battery separator was obtained.

Example 2

0.5 g of the surface-treated silica particles having an average particle diameter of 400 nm (treatment method as in Example 1) were dispersed in 100 g of water, and the temperature was raised to 70 ° C, and the mixed liquid was used as an aqueous phase.

6 g of paraffin wax having a melting point of 52 ° C, 1 g of styrene, 1 g of divinylbenzene, 1 g of chlorinated paraffin, and 0.06 g of azobisisobutyronitrile were mixed and heated to 70 ° C to form an oil phase in a molten state. .

A phase change capsule was obtained by adding 1 g of SDS to the emulsion and incubating at 70 ° C for 10 h at a constant temperature.

Example 3

8 g of paraffin wax having a melting point of 52 ° C, 3 g of styrene, 0.2 g of divinylbenzene, 0.5 g of chlorinated paraffin, and 0.08 g of azobisisobutyronitrile were mixed and heated to 70 ° C to form a molten oil. phase.

2 g of SDS was added to the emulsion, and polymerization was carried out at 70 ° C for 8 h at a constant temperature to obtain a phase change capsule.

After mixing 2 g of the phase change capsule with 20 g of the binder PTFE, both sides of the PP/PE double-layer composite separator were coated, and after solidification, a power battery separator was obtained.

Example 4

3 g of the surface-treated silica particles having an average particle diameter of 400 nm (treatment method as in Example 1) were dispersed in 100 g of water, and the temperature was raised to 70 ° C, and the mixed liquid was used as an aqueous phase.

10 g of paraffin wax having a melting point of 52 ° C, 4 g of butyl acrylate, 2 g of ethylene glycol dimethacrylate, 2 g of chlorinated paraffin, 1 g of azobisisobutyronitrile were mixed, and the temperature was raised to 70 ° C to form a molten state. Oil phase.

Comparative example 1

The traditional PP/PE double-layer composite diaphragm is used as the power battery separator.

Comparative example 2

The traditional PP/PE/PP three-layer composite diaphragm is used as the power battery separator.

Comparative example 3

8 g of paraffin wax having a melting point of 52 ° C, 2 g of styrene, 1 g of divinylbenzene, and 1 g of azobisisobutyronitrile were mixed, and the temperature was raised to 70 ° C to form an oil phase in a molten state.

2 g of emulsifier SDS was added to 86 g of water to form an aqueous phase.

After the oil phase and the water phase were mixed, high-speed stirring was carried out for 10 minutes, and the stirring speed was not less than 5000 rar/min to obtain an emulsion.

The emulsion was thermopolymerized at 70 ° C for 7 h, and after drying, a phase change capsule was obtained.

After mixing 2 g of the phase change capsule with the binder PTFE, both sides of the PP/PE/PP three-layer composite separator were coated, and after curing, a power battery separator was obtained.

Comparative example 4

After mixing 1 g of silica particles having a particle diameter of 400 nm with a binder PTFE, both sides of the PP/PE/PP three-layer composite separator were coated, and after curing, a power battery separator was obtained.

testing method

The power battery separators prepared in Examples 1 to 4 and Comparative Examples 1 to 4 were subjected to test comparison. The test method is as follows:

1. Fix the diaphragm on the experimental metal frame (fixed with polyimide high temperature tape).

2. Place in an oven at 200 ° C and start timing.

3. Observe the change of the inner membrane of the oven. When the membrane begins to become transparent, record time 1.

4. When the film is blown, record time 2. The test results are shown in Table 1:

Table 1

From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects:

In the above power battery separator provided by the present invention, a modified layer is coated on the surface of the separator body, and the modified layer includes a substrate and a phase change capsule dispersed in the substrate. Among them, the phase change capsule has a core-shell structure, and the shell layer includes a polymer and ceramic particles dispersed in the polymer, and the core layer includes a phase change material. The phase change material can absorb heat during charging and discharging of the power battery to reduce the internal temperature of the high-power battery and at the same time act as a thermal buffer to prevent functional failure of the diaphragm body which is prone to sudden temperature rise. At the same time, the ceramic particles have high high temperature resistance, which can effectively improve the high temperature resistance of the battery separator, and make it more resistant to potential oxidation during the long-term charge and discharge cycle. At the same time, the ceramic particles can also prevent the excessive shrinkage of the diaphragm body when the internal temperature of the battery is high or the heat is out of control, so that it can maintain the shrinkable function after cutting off the current and preventing the short circuit. Both of the above factors can improve the thermal performance of the diaphragm, which is beneficial to prevent diaphragm failure caused by high temperature or thermal runaway, and improve the safety of the power battery. Further, dispersing the ceramic particles in the shell polymer of the phase change capsule enables it to be more stably present on the surface of the diaphragm body. Coating the phase change material inside the shell polymer is also beneficial to improve the stability of the phase change material. In short, the phase change capsule having the above special structure can exert more stable heat absorption, heat buffering and high temperature resistance, thereby further improving the stability of the battery separator, improving the safety of the power battery, and reducing the safety hazard during high power charging and discharging. .

The above description is only the preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes can be made to the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and scope of the present invention are intended to be included within the scope of the present invention.

Claims

A power battery separator, comprising:

a diaphragm body having a first surface and a second surface opposite the first surface;

a first modified layer on the first surface, and/or a second modified layer on the second surface; the first modified layer and the second modified layer respectively comprise a substrate And a phase change capsule dispersed in the substrate;

Wherein, the phase change capsule has a core-shell structure; the shell layer of the phase change capsule comprises a polymer and ceramic particles dispersed in the polymer, and the phase change capsule comprises a phase change material in the core layer.
The power battery separator according to claim 1, wherein the phase change capsules in the first modified layer and the second modified layer each independently comprise 0.5 to 3 parts by weight. The ceramic particles, 6 to 10 parts of the phase change material, and 2 to 6 parts of the polymer.
The power battery separator according to claim 1 or 2, wherein the core layer of the phase change capsule further comprises a flame retardant.
The power battery separator according to claim 3, wherein the flame retardant is 0.5 to 2 parts by weight.
The power battery separator according to claim 3 or 4, wherein the flame retardant is chlorinated paraffin.
The power battery separator according to any one of claims 1 to 5, wherein the ceramic particles are silica particles.
The power battery separator according to claim 6, wherein the ceramic particles have a particle diameter of 400 nm.
The battery separator 1 to 7 according to any one of the preceding claims, wherein said phase change material is selected from a phase change alkane mixture 12 ~ C 25 paraffin and / or C.
The power battery separator according to claim 8, wherein the phase change paraffin is a paraffin wax having a melting point of 25 to 62 ° C, and the C 12 - C 25 alkane is selected from the group consisting of C 12 H 26 and C 18 H 38 . One or more of C 15 H 32 and C 25 H 52 .
The power battery separator according to any one of claims 1 to 9, wherein the synthetic monomer of the polymer is at least one selected from the group consisting of styrene, methyl methacrylate and butyl acrylate, and is synthesized. The crosslinking agent of the polymer is selected from the group consisting of divinylbenzene or ethylene glycol dimethacrylate.
The power battery separator according to any one of claims 1 to 10, wherein the substrate is cured by an adhesive.
The power battery separator according to claim 11, wherein the binder is selected from the group consisting of a PTFE binder or an SBR binder.
The power battery separator according to any one of claims 1 to 12, wherein the diaphragm body is a polyolefin separator.
The power battery separator according to claim 13, wherein the polyolefin separator is selected from the group consisting of a PP/PE double-layer composite separator or a PP/PE/PP three-layer composite separator.
A method of manufacturing a power battery separator according to any one of claims 1 to 14, comprising the steps of:

Preparing a Pickering emulsion containing ceramic particles, a phase change material, a synthetic monomer of a polymer, a crosslinking agent, and an initiator;

After the synthetic monomer in the Pickering emulsion is polymerized to form the polymer, the emulsion is dried to obtain a phase change capsule;

Mixing the phase change capsule with a binder for forming a substrate to form a liquid to be solidified;

Coating the liquid to be solidified on the first surface and/or the second surface of the diaphragm body, and after curing, forming a first modified layer and/or a second modified layer, thereby obtaining the power battery Diaphragm.
The method according to claim 15, wherein the step of preparing the Pickering emulsion comprises:

Dispersing the ceramic particles in water to form an aqueous phase;

Mixing the phase change material, the synthetic monomer, the crosslinking agent and the initiator, and heating to a molten state to form an oil phase;

The aqueous phase and the oil phase are mixed and stirred to form the Pickering emulsion.
The method according to claim 15 or 16, wherein the step of adding the emulsifier to the Pickering emulsion before the polymerization of the synthetic monomer in the Pickering emulsion is further included.
The process according to claim 17, wherein the emulsifier is selected from the group consisting of a fatty acid salt, a rosinate salt, an alkyl sulfate salt, an alkyl sulfonate salt or an alkyl aryl sulfonate.
The preparation method according to claim 18, wherein the fatty acid salt is sodium stearate, the rosin acid salt is disproportionated sodium sulphate, and the alkyl sulfate is sodium lauryl sulfate. The alkyl sulfonate is sodium cetyl sulfonate.
The preparation method according to any one of claims 16 to 19, wherein the step of mixing the phase change material, the synthetic monomer, the crosslinking agent, and the initiator further comprises The process of adding a flame retardant.
The preparation method according to any one of claims 15 to 20, wherein in the process of polymerizing the synthetic monomer in the Pickering emulsion, the polymerization time is 8 to 10 hours, and the polymerization temperature is 50 to 85. °C.
A power battery, comprising a battery separator, characterized in that the battery separator is the power battery separator according to any one of claims 1 to 14.