WO2014183656A1

WO2014183656A1 - Separator and method for preparing the same

Info

Publication number: WO2014183656A1
Application number: PCT/CN2014/077572
Authority: WO
Inventors: Xiaofang Chen; Weifeng Miao
Original assignee: Shenzhen Byd Auto R&D Company Limited; Byd Company Limited
Priority date: 2013-05-15
Filing date: 2014-05-15
Publication date: 2014-11-20
Also published as: CN104157810B; CN104157810A

Abstract

A separator and a method for preparing the separator are provided. The separator includes a polymer substrate,a ceramic layer provided on the polymer substrate and an infiltration part formed between the polymer substrate and the ceramic layer. The polymer substrate contains a base polymer and a first curing resin. The infiltration part has at least a portion infiltrated into the polymer substrate. Each of the infiltration part and the ceramic layer independently contains ceramic particles and a second curing resin.A battery including the separator is also provided.

Description

SEPARATOR AND METHOD FOR PREPARING THE SAME

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and benefits of Chinese Patent Application No. 201310179600.4, filed with the State Intellectual Property Office of P. R. China on May 15, 2013, the entire content of which is incorporated herein by reference.

FIELD

The present disclosure relates to batteries, and more particularly to a separator, a method for preparing the separator and a lithium ion battery including the separator.

BACKGROUND

A separator for a lithium ion secondary battery is generally made of thin and porous insulating materials, which not only has high permeability to ions and good mechanical strength, but also has long term stability to various chemical substances and chemical solvents. Therefore, positive and negative electrodes of the battery are separated due to the insulation of the separator, and a short circuit caused by the contact of the positive and negative electrodes is prevented. Meanwhile, with the porous structure of the separator, lithium ions may pass the separator easily, then the lithium ion conduction between the positive and negative electrodes may be ensured.

When the temperature of the interior of the battery is increased to some extent, the separator would be melted, which causes a close of the porous structure. Then the current may be cut off and the battery stops working. In this way, the safety of the battery is ensured. The separator has a great influence on the life of the battery, especially a high power battery which the voltage cannot be interrupted when a large amount of energy is obtained in a short time and the current has relatively high density, and which requires to achieve battery performances by optimizing functions of the positive and negative electrodes.

Therefore, the separator of the high power battery should be as thin as possible. A plurality of lithium dendrites may be formed when the lithium ion battery is under a large current condition, which may break the separator and cause a short circuit in the battery. Then it requires the separator to have excellent high temperature stability, in which condition the high power battery with stable and excellent performances can be obtained. Currently, the separator mainly consists of organic polymer films. Typically the organic polymer film includes three film layers, i.e., polyethylene (PE) film, polypropylene (PP) film, and polypropylene/polyethylene/polypropylene film. One disadvantage of these organic polyolefin films is the polymer generally has relatively lower melting point and relatively lower thermal stability, for example, PE has a melting point of 130°C, and PP has a melting point of 180°C. Worse still, the polymer has relatively lower chemical stability in the lithium ion battery system. Therefore, these polyolefin films may be corroded gradually during the contact with the graphite inserted with lithium.

A modified separator contains a heat resistant ceramic layer coated on the surface of the separator. The heat resistant ceramic layer contains ceramic particles, a binder and a solvent. The solvent may be an organic solvent which has good wettability with the porous flexible substrate. The disclosed solvent includes at least one selected from N- methyl pyrrolidone, N,N-methyl acrylamide, Ν,Ν-dimethylformamide and dimethylformamide, in order to improve the stability, heat stability and safety of the separator. For example, US patent application No. US2005084761 also discloses a separator for a battery and a method for preparing the separator. The method includes: applying to a sheetlike flexible substrate having a multiplicity of openings and a coating on and in said substrate, the material of said substrate being selected from woven or non-woven electrically nonconductive fibers of polymers and/or natural fibers and said coating being a porous electrically insulating ceramic coating. The coating is applied on and in said substrate by spraying a suspension on and in said substrate and heating the applied suspension, in which the suspension is cured on and in said substrate. The suspension contains a solvent of at least one oxide of metal, where the metal is selected from Al, Zr, Si, Ti and/or Y and the solvent may be an alcohol or a mixture of alcohol and aliphatic hydrocarbon. A tackifier may also be added to the suspension in order to enhance the adhesion between inorganic component and the polymer fiber substrate.

As to improving the binding between the coating layer and the substrate and the acting force between the ceramic particles, also disclosed is a separator, comprising a substrate and a slurry layer on two sides of the substrate respectively. The slurry layer contains ceramic particles, silane coupling agent and binder. The binder is at least one selected from a group consisting of: aqueous polyurethane, aqueous vinisol, aqueous unsaturated polyester and aqueous epoxy resin. The ceramic particles are made of at least one selected from a group consisting of: BaTi0₃, A1₂0₃, Ti0₂, Si0₂ and Zr0₂. However, the coating prepared according to this method has a quite poor adhesion to the sheetlike flexible substrate. The ceramic layer and the substrate are bond only via the binder dispersed in the ceramic layer, thus the binding strength therebetween is quite low. Therefore, particles of the coating layer are easy to fall off during the processing of the separator, preparing the electrode and the charging-discharging process of the battery. Further, the separator prepared according said method has reduced high temperature resistance. In addition, the fallen ceramic particles may cause uniformity on the performances of the separator, which has a great influence on the consistency of the battery performances. Further, the transfer resistance of lithium ions in the electrolyte may be increased, which is harmful to rapid charging/discharging process. It also possible that the lithium ions transfer to the surfaces of the positive and negative electrodes, which affects the insertion and leaving of lithium ions. Worse still, pinholes may be formed on the separator, which may cause a short circuit between the positive and negative electrodes. Then the performance of the battery may be significantly affected, and the practical use of the battery can be limited. SUMMARY

Embodiments of the present disclosure seek to solve at least one of the problems existing in the prior art to at least some extent, or to provide a consumer with a useful commercial choice.

Embodiments of one broad aspect of the present disclosure provide a separator. The separator may contain: a polymer substrate containing a base polymer and a first curing resin, and a ceramic layer provided on the polymer substrate, and an infiltration part formed between the polymer substrate and the ceramic layer and having at least a portion infiltrated into the polymer substrate. In some embodiments, each of the infiltration part and the ceramic layer may independently contain ceramic particles and a second curing resin.

In some embodiments, the first curing resin may be obtainable by a cross-linking of a first self-initiated UV curing resin. In some embodiments, the second curing resin may be obtainable by a cross-linking of a second self-initiated UV curing resin.

With the separator according to embodiments of the present disclosure, problems, such as poor adhesion between the substrate and the coatings, falling of the coatings and influences on the performances of a battery containing the separator, may be solved. Accordingly, the separator according to embodiments of the present disclosure has excellent high temperature resistance, which is easier to wind to form an electrode, easier to prepare and to apply in practical use. In addition, the ceramic layer is not easy to fall off from the polymer substrate, and the binding between the ceramic layer and the polymer substrate may be improved.

In some embodiments, the first self-initiated UV curing resin may be the same as the second self-initiated UV curing resin. Then the consistency of the separator may be optimized, which may further increase the strength of the separator.

In some embodiments, the first self-initiated UV curing resin may be different from the second self-initiated UV curing resin.

The ceramic layer of the separator according to embodiments of the present disclosure has good thermal resistance and uniform structure, which is aesthetic in appearance and resistant to high temperature and chemical substances, i.e. the ceramic layer may prevent the polymer substrate from corroding by electrolyte.

Further, the first curing resin and the second curing resin may be used to bind the ceramic particles and the polymer substrate, which facilitate to form an integral structure with the polymer substrate and the ceramic layer. Therefore, on the one hand, the binding between the ceramic particles and the polymer substrate may be improved. The ceramic particles may be received in a network- structure formed by the first and second curing resins, then they may not fall off easily. In this way, the thermal resistance of the separator may not be affected. On the other hand, an electrolyte system surrounding the separator may not be affected, and because of the rapid transfer of lithium ions, positive and negative electrodes of a battery containing the separator, the insertion and leave of the lithium ions may not be affected. Then, the separator may obtain excellent thermal resistance and safety.

Even further, a cross-linking structure formed by the cross-linking of the first and second self-initiated UV curing resins may improve the wettability of the separator with regard to the electrolyte, which may further enhance the performance for transmitting the lithium ions. Also, the resistance to electrolyte of the separator may be improved, and the separator may obtain better stability. Thus the thermal resistance and stability of the battery containing the separator may be both improved.

Additionally, the ceramic layer is a thermal resistant layer, also referred as thermal resistant layer. The thermal resistant layer may be more uniform and thinner, which may covers the polymer substrate more completely and no leakage source may be formed on the polymer substrate. Then the ceramic layer may obtain optimized thermal resistance. The first and second self-initiated UV curing resin of the separator according to embodiments of the present disclosure may be cured without heating, by which not only resources are saved, but also the shrinking of the polymer substrate caused by the rather high curing temperature may be avoided, the porosity of the separator may be reduced, and the influence on the ion transmitting may be reduced. Meanwhile, the first and second self-initiated UV curing resin are safe and non-toxic, have no residue and have well compatibility with the polymer substrate, which may have no bad influence on the polymer substrate. Thus, the subsequent infiltration transferring and volatilization generally occurred in a conventional separator may be avoided.

Embodiments of another broad aspect of the present disclosure provide a method for preparing a separator. The method may include steps of: forming a polymer substrate by mixing a base polymer and a first self-initiated UV curing resin; providing a ceramic slurry containing ceramic particles, a second self-initiated UV curing resin and a solvent on the polymer substrate; and subjecting the first and second self-initiated UV curing resins to cross-linking by curing with UV.

In some embodiments, a first curing resin may be formed by cross-linking of the first self-initiated UV curing resin. In some embodiments, a second curing resin may be formed by cross-linking of the second self-initiated UV curing resin. In some embodiments, the solvent may be an organic solvent capable of dissolving or swelling the polymer substrate.

According to embodiments of the present disclosure, the separator prepared by the method may obtain the above-described properties. In some embodiments, the solvent may be capable of dissolving or swelling the polymer substrate, thus the ceramic slurry may infiltrate into the polymer substrate, and then form an infiltration part on the surface of the polymer substrate and a ceramic layer formed on the infiltration part. The infiltration part may act as a transition layer between the polymer substrate and the ceramic layer, i.e. disposed on the surface of polymer substrate and at least partially infiltrate into the interior of the polymer substrate but below the ceramic layer (such as pores in the surface of the polymer substrate). The second self-initiated UV curing resin in the transition layer (i.e. the infiltration part) and in the ceramic layer may be subjected to cross-linking by curing with UV, thus the ceramic layer and the polymer substrate may form an integral structure, and the binding between the ceramic layer and the polymer substrate may be improved.

Embodiments of a further broad aspect of the present disclosure provide a lithium ion battery. The lithium ion battery may contain: a shell; a core provided in the shell; a cover plate configured to seal the shell; and an electrolyte received in the shell. In some embodiments, the core contains a positive electrode, a negative electrode, and the separator disposed between the positive and negative electrodes.

According to embodiments of the present disclosure, the battery has excellent safety and cycling performances.

Additional aspects and advantages of embodiments of present disclosure will be given in part in the following descriptions, become apparent in part from the following descriptions, or be learned from the practice of the embodiments of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects and advantages of embodiments of the present disclosure will become apparent and more readily appreciated from the following descriptions made with reference to the accompanying drawings, in which:

Fig. 1 is a flow chart showing a method for preparing a separator according to embodiments of the present disclosure.

DETAILED DESCRIPTION

Reference will be made in detail to embodiments of the present disclosure. The embodiments described herein with reference to drawings are explanatory, illustrative, and used to generally understand the present disclosure. The embodiments shall not be construed to limit the present disclosure.

In addition, terms such as "first" and "second" are used herein for purposes of description and are not intended to indicate or imply relative importance or significance.

Further, a structure in which a first feature is "on" a second feature may include an embodiment in which the first feature directly contacts the second feature, and may also include an embodiment in which an additional feature is formed between the first feature and the second feature so that the first feature does not directly contact the second feature.

For the purpose of the present description and of the following claims, the definitions of the numerical ranges always include the extremes unless otherwise specified.

For the aim of the present description and of the following claims, the term "comprising" also includes the terms "essentially consisting of or "consisting of.

According to a first aspect of embodiments of the present disclosure, a separator is provided. The separator may contain: a polymer substrate containing a base polymer and a first curing resin, a ceramic layer provided on the polymer substrate, and an infiltration part formed between the polymer substrate and the ceramic layer. In some embodiments, the infiltration part may have at least a portion infiltrated into the polymer substrate. In some embodiments, each of the infiltration part and the ceramic layer may independently contain ceramic particles and a second curing resin.

The separator according to embodiments of the present disclosure may have excellent high temperature resistance and corrosion resistance to electrolyte, and the ceramic layer is not easy to fall from the polymer substrate. In addition, the separator may be easier to wind to form an electrode, easier to prepare, and easier to apply in practical use. Further, with the separator, the transmitting of lithium ions in a battery containing the separator may be enhanced.

In some embodiments, the first curing resin is obtainable by a cross-linking of a first self-initiated UV curing resin, and the second curing resin is obtainable by a cross-linking of a second self-initiated UV curing resin. Then the binding between the ceramic layer and the polymer substrate may be improved, and the separator may obtain better high temperature resistance.

In some embodiments, the separator may include two ceramic layers provided on two sides of the polymer substrate, and two infiltration parts each of which may be independently formed between the ceramic layer and the corresponding side of the polymer substrate.

Although the number of surfaces where the ceramic layer is formed on has been described above with embodiments, it is appreciated that there are no specific limits on the number of the ceramic layers. In other words, the ceramic layer may be formed on at least one side of the polymer substrate.

In some embodiments, the ceramic layer may have a thickness of about 0.1-1 μπι. It is appreciated that, the thickness of the ceramic layer may indicate the thickness of the ceramic layer formed at one side of the polymer substrate.

In some embodiments, the infiltration part may have a thickness of about 0.01-0.1 μπι. In some embodiments, the infiltration part may have a thickness of about 0.05-0.1 μπι. It is appreciated that, the thickness of the infiltration part may refer to the thickness of the infiltration part formed at one side of the polymer substrate.

In some embodiments, the first curing resin may be the same with the second curing resin. In some embodiments, the first and second self-initiated UV curing resins may be the same. Then the compatibility of the separator may be improved. In the specification, the term "self-initiated UV curing resin" may refer to a resin which may be self-initiated and optical active, which may also be cross-linked by curing with UV irradiation, without the addition photo initiator.

In some embodiments, each of the first and second self-initiated UV curing resins may independently contain an optical active structure.

In some embodiments, each of the first and second self-initiated UV curing resins may independently contain at least one selected from a group consisting of: a resin containing a quaternary carbon-containing dicarbonyl, a resin containing a cinnamoyl group, ethylene acrylate, α,β-unsaturated ethylene carboxylate, N-alkyl maleimide, unsaturated polyesteramide urea, coumarin modified resin, anacardol and acrylate hyperbranched polymer. In an embodiment, the unsaturated polyesteramide urea may contain a chain segment of urea bond. In an embodiment, the anacardol may include a phenol containing a long carbon chain formed on the meta position.

In some embodiments, the resin containing a quaternary carbon-containing dicarbonyl is obtainable by reacting a β-dicarbonyl compound with acrylate. In an embodiment, the reacting may be obtained by an addition reaction between the β-dicarbonyl compound and the double bond in the acrylate.

In some embodiments, the β-dicarbonyl compound may have a -CO-CHR-CO- group, and the acrylate is a multi- functionality acrylate.

In some embodiments, the β-dicarbonyl compound may contain at least one selected from a group consisting of: ethyl acetoacetate, methyl acetoacetate, acetylacetone and malonate. In some embodiments, the acrylate may be a multiple functional acrylate. The acrylate may be at least one selected from a group consisting of: epoxy acrylate, polyester acrylate, polyurethane acrylate and polysiloxane acrylate.

According to embodiments of the present disclosure, the resin containing a quaternary carbon-containing dicarbonyl may become unstable after absorbing the optical energy, and the acetyl group may be separated from the resin and active free radiacals may be generated. Then a polymerization may be initiated. The first and second self-initiated UV curing resins have improved performances, which have better compatibility and action with the polymer substrate, thus the separator may be provided with better application use. The curing of the first and second self-initiated UV curing resins may be represented with the following formula:

In some embodiments, the resin containing a cinnamoyl group is at least one selected from cinnamic acid modified polysiloxane and cinnamic acid modified polyvinyl alcohol. Under the UV condition, the cinnamoyl group may be subjected to a cross-linking represented with the following formula:

in which "-" represents the main chain segment of the modified resin. The resin containing a cinnamoyl group has excellent performances, and may have better compatibility and action with the polymer substrate, thus the separator may be provided with better application use.

In some embodiments, the N-alkyl maleimide may be an N-alkyl substituted maleimide. In some embodiments, the N-alkyl substituted maleimide (and therefore the N-alkyl maleimide) may be at least one selected from a group consisting of: N-methyl maleimide, N-ethyl maleimide, N-tert-butyl maleimide, N-hexyl maleimide, N-cyclohexyl maleimide, N-hydroxylpentyl maleimide, N-hydroxyl ethyl maleimide, N-phenyl maleimide and N-(diethyl carbonate) maleimide. The applicants have found that, the N-alkyl maleimide may reach an excited triplet state which offers the N-alkyl maleimide rather strong hydrogen abstraction capability. Then the N-alkyl maleimide may abstract active hydrogen from structures like ether bonds, primary alcohols and secondary alcohols and form active free radicals which are capable of initiating the polymerization. The N-alkyl maleimide has excellent performances, and may have better compatibility and action with the polymer substrate, thus the separator may be provided with better application use.

In some embodiments, the α,β-ethylene carboxylate and the ethylene acrylate may have the similar structure. In some embodiments, the α,β-ethylene carboxylate may be at least one selected from a group consisting of: ethylene tiglate, ethylene cinnamate, diethylene maleate, mono(ethylene) fumarate and diethylene fumarate. The applicants have found that, under the UV irradiation, the α,β-ethylene carboxylate may split and rearrange, by which active free radicals may be generated and the polymerization may be initiated. The α,β-ethylene carboxylate has excellent performances, and may have better compatibility and action with the polymer substrate, thus the separator may be provided with better application use.

The ceramic particles may be adopted as those well known in the art. In some embodiments, the ceramic particle may have an average particle diameter of about 10-1000 nm and a specific surface area of about 1-4000 m²/g. In some embodiments, the ceramic particle may have an average particle diameter of about 50-500 nm and a specific surface area of about 5-50 m²/g. The applicants have found that, the ceramic particles have optimized lipophilicity, which are hard to dissolve in organic electrolyte. In addition, the ceramic particles may be easy to disperse uniformly in the porous polymer substrate. Then the performances of the separator and the battery may be optimized.

In some embodiments, the ceramic particle may be at least one selected from a group consisting of: metal oxide, metal sulfate, metal silicate, metal carbonate and metal titanate. In some embodiments, the metal may be at least one selected from a group consisting of: Al, Zr, Mg, Ca, Ti, Si, Ba and Zn. In an embodiment, the ceramic particle may be at least one selected from a group consisting of: Ca oxide, Mg oxide, Al oxide, Zr oxide, Zn oxide and Ti oxide. In an embodiment, the ceramic particle may be at least one inorganic salt selected from a group consisting of: caoline, asbestos, magnesium silicate, calcium silicate, aluminum silicate, calcium carbonate, barium sulfate and barium titanate. The ceramic particle may be commercially available.

The base polymer may be made from any polymers which may be used for the separator and well known to a person skilled in the art. In some embodiments, the base polymer may contain at least one selected from a group consisting of: polypropylene, polyethylene terephthalate, polyimide and the polyethylene.

There are no particular limits to the process for preparing the polymer substrate. In some embodiments, the polymer substrate may be prepared by: mixing the base polymer and the first self-initiated UV curing resin, and subjecting the first self-initiated UV curing resin to cross-linking to form a first curing resin by a spinning method.

In some embodiments, the polymer substrate may have a porosity of about 40-95% and a thickness of about 10-40 μπι.

According to another aspect of the present disclosure, a method for preparing a separator is provided. The method may include steps of: forming a preliminary polymer substrate by mixing a base polymer and a first self-initiated UV curing resin; providing a ceramic slurry containing ceramic particles, a second self-initiated UV curing resin and a solvent on the preliminary polymer substrate; and subjecting the first and second self-initiated UV curing resins to cross-linking by curing with UV. In some embodiments, the solvent may be an organic solvent capable of dissolving or swelling the polymer substrate.

In some embodiments, after providing the ceramic slurry on the preliminary polymer substrate, at least a part of the ceramic slurry may infiltrate into the preliminary polymer substrate. In some embodiments, with the curing step, both the first and second self-initiated UV curing resins may be cured, and first and second curing resins may be formed respectively. After the curing step, the preliminary polymer substrate may turn to a polymer substrate which contains the base polymer and the first curing resin. According to the method of the present disclosure, the obtained separator may include the polymer substrate, a ceramic layer formed on the polymer substrate and an infiltration part formed between the polymer substrate and the ceramic layer. At least a portion of the infiltration part may infiltrate into the polymer substrate. Each of the infiltration part and the ceramic layer may independently contain ceramic particles and the second curing resin.

According to embodiments of the present disclosure, the method for preparing the separator may include the followings steps S100-300.

In the step SI 00, a preliminary polymer substrate is provided. In some embodiments, the preliminary polymer substrate may be provided by mixing a base polymer and a first self-initiated UV curing resin.

There are no particular limits for the mixing process in the present disclosure. In some embodiments, based on the total weight of the base polymer, the amount of the first self-initiated UV curing resin may be about 1-5 wt%. There are particular limits to the method for obtaining the preliminary polymer substrate, in some embodiments, the method may include biaxial tension. In some embodiments, the preliminary polymer substrate may be obtained by a spinning method.

In some embodiments, in the step S200, a ceramic slurry is provided on the preliminary polymer substrate. In some embodiments, the ceramic slurry may contain ceramic particles, a second self-initiated UV curing resin and a solvent.

There are no particular limits for providing the ceramic slurry on the preliminary polymer substrate, which may be any conventional method in the art. In some embodiments, the method for providing the ceramic slurry on the preliminary polymer substrate may include: printing, rolling, applying slurry, immersing, spraying and coating, without limits.

In some embodiments, the step S200 may include providing the ceramic slurry onto a surface of the preliminary polymer substrate and resting said preliminary polymer substrate for about 1-10 min. In the step S200, at least a part of the ceramic slurry may infiltrate into the preliminary polymer substrate. With the following curing step, the ceramic slurry formed on the polymer substrate may become the ceramic layer, and the part of the ceramic slurry which infiltrates into the polymer substrate may become the infiltration part.

In some embodiments, the step S200 may include immersing the preliminary polymer substrate into the ceramic slurry with a temperature of about 50-120°C for about 1-10 min. In the step S200, at least a part of the ceramic slurry may infiltrate into the preliminary polymer substrate. With the following curing step, the ceramic slurry formed on the polymer substrate may become the ceramic layer, and the part of the ceramic slurry which infiltrates into the preliminary polymer substrate may become the infiltration part.

With the immersing method and the above-mentioned temperature as well as the immersing time which facilitate the dissolving and swelling of the preliminary polymer substrate in the solvent, the ceramic slurry may infiltrate into the preliminary polymer substrate and forming a transitional layer (i.e. the infiltration part between the polymer substrate and the ceramic layer) more conveniently.

In some embodiments, the ceramic slurry provided on one side of the polymer substrate may have a thickness of about 0.15-1.2 μηι.

In some embodiments, based on 1 weight part of the second self-initiated UV curing resin, the amount of the ceramic particles may be about 1-20 weight parts, and the amount of the solvent may be about 30-50 weight parts. In some embodiments, based on 1 weight part of the second self-initiated UV curing resin, the amount of the ceramic particles may be about 6-11 weight parts, and the amount of the solvent may be about 38-48 weight parts.

In some embodiments, the ceramic slurry may further contain other modifying additives. In some embodiments, the additives are added to disperse the ceramic particles into the ceramic slurry more uniformly. By way of example and without limits, in an embodiment, the ceramic slurry may further contain a dispersant.

In some embodiments, the solvent may be an organic solvent which is capable of dissolving or swelling the base polymer. In some embodiments, the solvent may be at least one selected from a group consisting of: aliphatic hydrocarbon, aromatic hydrocarbon and chlorinated hydrocarbon.

It is known that, different solvent may have different dissolving and swelling effects on the polymer substrate. In some embodiments, the base polymer may be polyethylene, and the solvent may be at least one selected from a group consisting of: toluene, xylene, pentyl acetate, trichloroethylene and carbon tetrachloride.

In some embodiments, the base polymer may be polypropylene, and the solvent may be at least one selected from a group consisting of: benzene, para-xylene, heptane, tetrachloronaphthalene, tetrahydrofuran, decalin and tetrahydronaphthalene.

In some embodiments, the base polymer may be polyethylene terephthalate, and the solvent may be at least one selected from a group consisting of: trifluoroacetic acid, phenol, chloro-phenol and a mixture containing phenol and trichloroethane.

With the base polymer and solvent mentioned above, the method may be further simplified and the properties of the prepared separator may be further improved.

In the step S300, the first and second self-initiated UV curing resins are subjected to cross-linking. In some embodiments, the first and second self-initiated UV curing resins are subjected to cross-linking by curing with UV.

In some embodiments, the curing may be performed for about 1-5 min and the UV may have a wave length of about 200-380 nm. In some embodiments, the curing may be performed at the room temperature. In some embodiments, the curing may be performed under vacuum. Then the solvent volatilized may be removed in time, then the method may be further simplified and the prepared separator may be further improved.

According to a further aspect of the present disclosure, a battery is provided. The battery may include: a shell; a core provided in the shell; a cover plate configured to seal the shell; and an electrolyte received in the shell. The core may include a positive electrode, a negative electrode and the above-identified separator.

The battery according to embodiments of the present disclosure has the above mentioned separator. There are no particular limits for the structure and connecting relationship with other elements in the battery, such as the positive and negative electrodes, electrolyte and shell.

In some embodiments, the negative electrode may be one which is well known in the art. In an embodiment, the negative electrode may include a negative current collector and a negative material layer coated on the negative current collector. There are no particular limits to the negative material layer in the present disclosure, which may be adopted as any known negative material layer to those skilled in the art. The negative material layer may contain a negative active substance and a binder. The negative active substance may be known to those skilled in the art, for example, which may be selected from metal lithium, lithium alloy, carbon material, silicon alloy, phosphorized iron. In an embodiment, the carbon material may be non-graphite carbon, graphite or the carbon obtained by high-temperature oxidation of polymer material containing polyacetylenes. In another embodiment, the carbon may be selected from hydrolytic carbon, coke, sintering product of organic polymers and active carbon. The sintering product of organic polymer may be a product by sintering and carbonizing phenol formaldehyde resin, and epoxy resin, etc.

The binder may be any conventional binder used in the negative electrode of the battery. In some embodiments, the binder may be at least one selected from a group consisting of: poly( vinyl alcohol), poly(tetrafluoroethylene), hydroxymethyl cellulose (CMC) and styrene butadiene rubber (SBR). In some embodiments, based on the total weight of the negative active substance, the content of the binder may be 0.5-8 wt%. In some embodiments, based on the total weight of the negative active substance, the content of the binder may be 2-5 wt%.

In some embodiments, the negative material layer may alternatively contain a conducting agent which is well known to those skilled in the art. The conducting agent may be used to increase the conducting property of the electrode and reduce the inner resistance of the battery. The content and type of the conducting agent may be known to those skilled in the art. For example, based on the total weight of the negative material layer, the content of the conducting agent may be about 0.1-12 wt%. The conducting agent may be at least one selected from a group consisting of: conducting carbon black, nickel powders and copper powders.

The positive electrode may be known to those skilled in the art, which generally include a positive current collector and positive material layer coated on the positive current collector. There are no particular limits to the positive material layer in the present disclosure. The positive material layer may contain a positive active substance, a binder, and a conducting agent. The positive active substance may be any positive material which may be commercially available and selected from LiFeP0₄, Li₃V₂(P04)3, LiMn₂0₄, LiMn0₂, LiNi0₂, LiCo0₂, LiVP0₄F, LiFe0₂ and a compound represented by Lii _{+ x}Li -_y-_zM_yN_z02, in which -0.1<x≤0.2, 0<y≤l, 0<z≤l, 0<y+z≤1.0, and L, M and N may be respectively at least one selected from a group consisting of Co, Mn, Ni, Al, Mg, Ga and 3d transitional metal.

The binder may be any well-known binder in the art, for example and without limits, the binder may be at least one selected from polyvinylidene difluoride, poly(tetrafluoroethylene) and styrene butadiene rubber. In some embodiments, based on the total weight of the positive active substance, the content of the binder may be 0.01-8 wt%. In some embodiments, based on the total weight of the positive active substance, the content of the binder may be 1-5 wt%. It is to be noted that, the binder mentioned in this paragraph may refer to the binder used in the positive electrode.

The conducting agent may be any conventional conducting agent in the art. In some embodiments, the conducting agent may be at least one selected from a group consisting of: graphite, carbon fiber, carbon black, metal powders and metal fiber. In some embodiments, based on the total weight of the positive electrode, the content of the conducting agent may be 0.1-20 wt%. In some embodiments, based on the total weight of the positive electrode, the content of the conducting agent may be 2-10 wt%.

In some embodiments, the positive current collector may be selected from Al foil, Cu foil, steel strip plated with Ni and steel strip with punched holes.

The method for preparing the positive electrode is known to those skilled in the art. In some embodiments, the method for preparing the positive electrode may include the following steps. First, the positive active substance, the binder and the conducting agent for the positive electrode are mixed with a solvent to form a positive material slurry. Then the positive material slurry is coated on the positive current collector. Finally, the positive current collector coated with the positive material slurry is dried, pressed into plates, and cut into required shapes.

In some embodiments, the amount of the solvent is known to those skilled in the art, which can be adjusted flexibly according to the viscosity of the slurry and the operation requirements, provided the amount of the slurry ensures the slurry may be coated successfully on the conducting substrate. In some embodiments, the amount of the slurry may ensure that the content of the positive active substance in the slurry may be 40-90 wt%. In some embodiments, the amount of the slurry may ensure that the content of the positive active substance in the slurry may be 50-85 wt%.

The solvent may be any conventional solvent known to those skilled in the art. In some embodiments, the solvent may be at least one selected a group consisting of: N- methyl pyrrolidone ( MP), dimethylformamide (DMF), diethylformamide (DEF), dimethyl Sulfoxide (DMSO), tetrahydrofuran (TUF), water and alcohols.

In some embodiments, the drying may be performed at 120°C for a time of 5 h.

In some embodiments, the electrolyte may be a non-hydrolysis electrolyte which contains a lithium salt as the electrolyte material and a non-aqueous solvent. The non-aqueous solvent may be any conventional non-aqueous solvent known to those skilled in the art, which may be at least one selected from a group consisting of: LiPF₆, L1CIO₄, L1BF₄, LiAsF₆, LiSiF₆, LiB(C6H₅)₄, LiCl, LiBr, L1AICI₄, LiC(S0₂CF₃)₃, LiCH₃S0₃ and LiN(S0₂CF₃)₂. In some embodiments, the non-aqueous solvent may be selected from linear and cyclic acid esters. In some embodiments, the linear acid ester may be at least one selected from a group consisting of: dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC) methyl propyl carbonate (MPC), dipropyl carbonate (DPC) and other organic linear esters containing sulfur, fluorine and unsaturated bond. In some embodiments, the cyclic acid ester may be at least one selected from a group consisting of: ethylene carbonate (EC), proylene carbonate (PC), vinylene carbonate (VC), γ-butyrolactone (γ-BL), sulfur lactone and other organic cyclic esters containing sulfur, fluorine and unsaturated bond.

In some embodiments, based on the non-aqueous electrolyte, the concentration of the electrolyte material, i.e. the lithium salt, may be 0.1-2 mol/L. In some embodiments, based on the non-aqueous electrolyte, the concentration of the electrolyte material, i.e. the lithium salt, may be 0.8- 1.2 mol/L.

The core may be any conventional core which is known to those skilled in the art. In some embodiments, the core may be prepared by winding or stacking the positive electrode, the separator and the negative electrode in turn. The winding and stacking step are both known to those skilled in the art.

The method for preparing the battery may be known to those with ordinary skill in the art. In some embodiments, the method may include the following steps. First, the core is positioned in the shell. Then the electrolyte is filled in the shell, and the shell is sealed with the cover plate. The sealing method, the amount of the electrolyte, and other conditions for preparing the battery are all known to those skilled in the art.

It will be understood that the features mentioned above and those still to be explained hereinafter may be used not only in the particular combination specified but also in other combinations or on their own, without departing from the scope of the present invention.

Some illustrative and non-limiting examples are provided hereunder for a better understanding of the present invention and for its practical embodiment. Embodiment 1

The present embodiment provides a separator and a method for preparing the separator.

Step 1) Preparing preliminary polymer substrate

Polyethylene and 1 wt% of unsaturated polyesteramide urea (0.04 mol% of urea) were mixed to prepare a preliminary polymer substrate via a spinning method. The preliminary polymer substrate had a thickness of 35 μπι and a porosity of 50%.

Step 2) Proving ceramic slurry on preliminary polymer substrate

1 weight part of the unsaturated polyesteramide urea (0.04 mol% of urea), 39 weight parts of toluene, and 10 weight parts of A1₂0₃ were mixed and stirred form a uniform mixture, then the mixture was milled with a ball mill until particle of the A1₂0₃ had an average particle diameter of 200 nm and a specific surface area of 10 m²/g. Then a ceramic slurry was obtained, which was subsequently heated to 80°C.

The preliminary polymer substrate was immersed into the ceramic slurry for 10 min, during which the ceramic slurry was adhered on two sides of the preliminary polymer substrate. The ceramic slurry formed on one side of the preliminary polymer substrate had a thickness of 0.86 μπι.

Step 3) Curing The preliminary polymer substrate formed with the ceramic slurry was irradiated with a 100 W high pressure mercury lamp under conditions of: a UV having wavelength of 330 nm, an irradiating distance of 10 cm, an irradiating time of 2 min. A separator SI was obtained. With the curing step, a ceramic layer was formed on the polymer substrate and an infiltration part was formed between the ceramic layer and the polymer substrate, in which the ceramic layer had a thickness of 0.6 μπι and the infiltration part had a thickness of 0.05 μπι.

Embodiment 2

Step 1) Preparing preliminary polymer substrate

Polyethylene and 4.5 wt% of ethylene acrylate were mixed to prepare a preliminary polymer substrate via a spinning method. The preliminary polymer substrate had a thickness of 35 μπι and a porosity of 63%.

Step 2) Proving ceramic slurry on preliminary polymer substrate

1 weight part of the ethylene acrylate, 41 weight parts of carbon tetrachloride, and 10 weight parts of MgO were mixed and stirred form a uniform mixture, then the mixture was milled with a ball mill until particle of the MgO had an average particle diameter of 60 nm and a specific surface area of 43 m²/g. Then a ceramic slurry was obtained, which was subsequently heated to 70°C.

The preliminary polymer substrate was immersed into the ceramic slurry for 10 min, during which the ceramic slurry was adhered on two sides of the preliminary polymer substrate. The ceramic slurry formed on one side of the preliminary polymer substrate had a thickness of 0.8 μπι.

Step 3) Curing

The preliminary polymer substrate formed with the ceramic slurry was irradiated with a 100 W high pressure mercury lamp under conditions of: a UV having wavelength of 254 nm, an irradiating distance of 10 cm, an irradiating time of 4 min. A separator S2 was obtained. With the curing step, a ceramic layer was formed on the polymer substrate and an infiltration part was formed between the ceramic layer and the polymer substrate, in which the ceramic layer had a thickness of 0.56 μπι and the infiltration part had a thickness of 0.05 μπι. Embodiment 3

The present embodiment provides a separator and a method for preparing the separator. Step 1) Preparing preliminary polymer substrate

Polyproylene and 2.98 wt% of cashew nut shell liquid were mixed to prepare a preliminary polymer substrate via a spinning method. The preliminary polymer substrate had a thickness of 26 μπι and a porosity of 71%.

Step 2) Proving ceramic slurry on preliminary polymer substrate

1 weight part of the cashew nut shell liquid, 42.5 weight parts of benzene, and 8 weight parts of ZnSC"4 were mixed and stirred form a uniform mixture, then the mixture was milled with a ball mill until particle of the ZnS0₄ had an average particle diameter of 110 nm and a specific surface area of 23 m²/g. Then a ceramic slurry was obtained, which was subsequently heated to 110°C.

The polymer substrate was immersed into the ceramic slurry for 8 min, during which the ceramic slurry was adhered on two sides of the preliminary polymer substrate. The ceramic slurry formed on one side of the preliminary polymer substrate had a thickness of 0.92 μπι.

Step 3) Curing

The polymer substrate formed with the ceramic slurry was irradiated with a 100 W high pressure mercury lamp under conditions of: a UV having wavelength of 253.7 nm, an irradiating distance of 10 cm, an irradiating time of 3 min. A separator S3 was obtained. With the curing step, a ceramic layer was formed on the polymer substrate and an infiltration part was formed between the ceramic layer and the polymer substrate, in which the ceramic layer had a thickness of 0.73 μπι and the infiltration part had a thickness of 0.08 μπι.

Embodiment 4

Step 1) Preparing preliminary polymer substrate

Polyproylene and 2.6 wt% of ethylene cronate were mixed to prepare a preliminary polymer substrate via a spinning method. The preliminary polymer substrate had a thickness of 23 μπι and a porosity of 73%.

Step 2) Proving ceramic slurry on preliminary polymer substrate

1 weight part of the ethylene cronate, 44 weight parts of para-xylene, and 8 weight parts of ZnC"2 were mixed and stirred form a uniform mixture, then the mixture was milled with a ball mill until particle of the Zn0₂ had an average particle diameter of 90 nm and a specific surface area of 35 m²/g. Then a ceramic slurry was obtained, which was subsequently heated to 100°C. The preliminary polymer substrate was immersed into the ceramic slurry for 8 min, during which the ceramic slurry was adhered on two sides of the preliminary polymer substrate. The ceramic slurry formed on one side of the preliminary polymer substrate had a thickness of 0.86 μιη.

Step 3) Curing

The preliminary polymer substrate formed with the ceramic slurry was irradiated with a 100 W high pressure mercury lamp under conditions of: a UV having wavelength of 313 nm, an irradiating distance of 10 cm, an irradiating time of 3 min. A separator S4 was obtained. With the curing step, a ceramic layer was formed on the polymer substrate and an infiltration part was formed between the ceramic layer and the polymer substrate, in which the ceramic layer had a thickness of 0.67 μπι and the infiltration part had a thickness of 0.07 μπι.

Embodiment 5

Step 1) Preparing preliminary polymer substrate

Polyethylene terephthalate and 1.3 wt% of TMDAC containing a quaternary carbon-containing dicarbonyl were mixed to prepare a polymer substrate via a spinning method. The preliminary polymer substrate had a thickness of 13 μπι and a porosity of 86%. The TMDAC was a product of an addition reaction between tri(hyroxyl methyl) propane triacrylate and acetylacetone.

Step 2) Proving ceramic slurry on preliminary polymer substrate

1 weight part of the TMDAC, 47 weight parts of phenol, and 6 weight parts of BaTi0₃ were mixed and stirred form a uniform mixture, then the mixture was milled with a ball mill until particle of the BaTi0₃ had an average particle diameter of 55 nm and a specific surface area of 46 m²/g. Then a ceramic slurry was obtained, which was subsequently heated to 70°C.

The preliminary polymer substrate was immersed into the ceramic slurry for 2 min, during which the ceramic slurry was adhered on two sides of the preliminary polymer substrate. The ceramic slurry formed on one side of the preliminary polymer substrate had a thickness of 0.55 μπι.

Step 3) Curing

The preliminary polymer substrate formed with the ceramic slurry was irradiated with a 100 W high pressure mercury lamp under conditions of: a UV having wavelength of 290 nm, an irradiating distance of 10 cm, an irradiating time of 4 min. A separator S5 was obtained. With the curing step, a ceramic layer was formed on the polymer substrate and an infiltration part was formed between the ceramic layer and the polymer substrate, in which the ceramic layer had a thickness of 0.32 μπι and the infiltration part had a thickness of 0.03 μπι.

Embodiment 6

Step 1) Preparing preliminary polymer substrate

Polyethylene terephthalate and 2 wt% of cinnamic acid modified polysiloxane were mixed to prepare a preliminary polymer substrate via a spinning method. The preliminary polymer substrate had a thickness of 21 μπι and a porosity of 77%.

Step 2) Proving ceramic slurry on preliminary polymer substrate

1 weight part of the cinnamic acid modified polysiloxane, 36 weight parts of chloro-phenol, and 8 weight parts of ZnO were mixed and stirred form a uniform mixture, then the mixture was milled with a ball mill until particle of the ZnO had an average particle diameter of 90 nm and a specific surface area of 35 m²/g. Then a ceramic slurry was obtained, which was subsequently heated to 50°C.

The preliminary polymer substrate was immersed into the ceramic slurry for 5 min, during which the ceramic slurry was adhered on two sides of the preliminary polymer substrate. The ceramic slurry formed on one side of the preliminary polymer substrate had a thickness of 0.63 μπι.

Step 3) Curing

The preliminary polymer substrate formed with the ceramic slurry was irradiated with a 100 W high pressure mercury lamp under conditions of: a UV having wavelength of 365 nm, an irradiating distance of 10 cm, an irradiating time of 3 min. A separator S6 was obtained. With the curing step, a ceramic layer was formed on the polymer substrate and an infiltration part was formed between the ceramic layer and the polymer substrate, in which the ceramic layer had a thickness of 0.47 μπι and the infiltration part had a thickness of 0.45 μπι.

Embodiment 7 The present embodiment provides a separator and a method for preparing the separator.

Step 1) Preparing preliminary polymer substrate

Polyethylene terephthalate and 1.9 wt% of coumarin modified iso-octyl acrylate were mixed to prepare a preliminary polymer substrate via a spinning method. The preliminary polymer substrate had a thickness of 20 μπι and a porosity of 79%.

Step 2) Proving ceramic slurry on preliminary polymer substrate

1 weight part of the coumarin modified iso-octyl acrylate, 38 weight parts of chloro-phenol, and 9 weight parts of BaS0₄ were mixed and stirred form a uniform mixture, then the mixture was milled with a ball mill until particle of the BaS0₄ had an average particle diameter of 100 nm and a specific surface area of 33 m²/g. Then a ceramic slurry was obtained, which was subsequently heated to 50°C.

The preliminary polymer substrate was immersed into the ceramic slurry for 4 min, during which the ceramic slurry was adhered on two sides of the preliminary polymer substrate. The ceramic slurry formed on one side of the preliminary polymer substrate had a thickness of 0.69 μπι.

Step 3) Curing

The preliminary polymer substrate formed with the ceramic slurry was irradiated with a 100 W high pressure mercury lamp under conditions of: a UV having wavelength of 324 nm, an irradiating distance of 10 cm, an irradiating time of 3 min. A separator S7 was obtained. With the curing step, a ceramic layer was formed on the polymer substrate and an infiltration part was formed between the ceramic layer and the polymer substrate, in which the ceramic layer had a thickness of 0.48 μπι and the infiltration part had a thickness of 0.056 μπι.

Embodiment 8

The present embodiment included substantially the same steps as those described in Embodiment 1, with the difference that:

in the step 2), the preliminary polymer substrate was immersed into the ceramic slurry for 5 min, during which the ceramic slurry formed on one side of the preliminary polymer substrate had a thickness of 0.66 μπι.; and

in the step 3), a separator S8 was obtained. With the curing step, a ceramic layer was formed on the polymer substrate and an infiltration part was formed between the ceramic layer and the polymer substrate, in which the ceramic layer had a thickness of 0.45 μπι and the infiltration part had a thickness of 0.02 μπι. Embodiment 9

in the step 2), a ceramic slurry was obtained, which was subsequently heated to 120°C; the preliminary polymer substrate was immersed into the ceramic slurry for 10 min, during which the ceramic slurry formed on one side of the preliminary polymer substrate had a thickness of 0.98 μπι.; and

in the step 3), a separator S9 was obtained. With the curing step, a ceramic layer was formed on the polymer substrate and an infiltration part was formed between the ceramic layer and the polymer substrate, in which the ceramic layer had a thickness of 0.75 μπι and the infiltration part had a thickness of 0.09 μπι.

Comparative Embodiment 1

The present comparative embodiment provides a separator and a method for preparing the separator.

Step 1) Preparing preliminary polymer substrate

A preliminary polymer substrate was prepared using polyethylene via a spinning method. The preliminary polymer substrate had a thickness of 35 μπι and a porosity of 50%.

Step 2) Proving ceramic slurry on preliminary polymer substrate

1 weight part of the epoxy resin, 39 weight parts of methyl pyrrolidone, and 10 weight parts of A1₂0₃ were mixed and stirred form a uniform mixture, then the mixture was milled with a ball mill until particle of the A1₂0₃ had an average particle diameter of 200 nm and a specific surface area of 10 m²/g. Then a ceramic slurry was obtained.

The preliminary polymer substrate was immersed into the ceramic slurry for 5 min, during which the ceramic slurry was adhered on two sides of the preliminary polymer substrate. The ceramic slurry formed on one side of the preliminary polymer substrate had a thickness of 0.88 μπι. Step 3) Drying

The preliminary polymer substrate formed with the ceramic slurry was dried at 120°C for 20 min. A separator DS1 was obtained. The separator DS1 had a ceramic layer, and the ceramic layer had a thickness of 0.79 μιη.

Comparative Embodiment 2

Step 1) Preparing polyethylene substrate

A polyethylene substrate having a thickness 35 μιη of and a porosity of 50% was provided.

Step 2) Proving ceramic solution on polyethylene substrate

Triethoxy acrylate, triethoxy diacrylate, aliphatic polyurethane diacrylate and ethoxidized tri(hydoxyl methyl) propane triacrylat with a weight ratio of 2: 15:6: 1 were mixed to form a photosensitive monomer mixture, then the photosensitive monomer mixture was dissolved in a solvent together with a photoinitiator, and then subjected to magnetic stirring to obtain a monomer blend. The photoinitiator contained benzoin dimethyl ether and hydroxyl cyclohexyl phenyl methanone with a weight ratio of 1 :2. The monomer blend was added with nano A1₂0₃ and subjected to ultrasonic oscillating to obtain a ceramic solution.

The ceramic solution was applied on a surface of the polyethylene substrate.

Step 3) Curing

The polyethylene substrate applied with the ceramic solution was irradiated with UV. A separator DS2 was obtained. The separator DS2 had a ceramic layer, and the ceramic layer had a thickness of 0.79 μιη. Embodiments 10-18 and Comparative Embodiments 3-4

The present embodiments respectively provide lithium ion rechargeable batteries prepared by independently using the separators S1-S9 and DS1-DS2. Each of these batteries was prepared with the following steps.

Firstly, the positive electrode was made by LiCo0₂, the negative electrode was made by graphite, the electrolyte was lmol/L of LiPF₆, and the solvent was a mixture solution of EC, PC and DEC with a volume ratio of EC/PC/DEC=30/20/50. The separator was placed between the positive and negative electrodes, then the separator and the positive and negative electrodes were wound into a plate, and then cut into proper size. The cut plate was disposed within a shell containing the electrolyte, and finally the shell was sealed with a cover plate. Then a lithium ion rechargeable battery was obtained.

By using the separators S1-S9 and DS1-DS2 described in the above embodiments, lithium ion rechargeable batteries SS1-SS9 and DSS1-DSS2 were obtained.

TEST

1) Separator

The thickness of the separator was measured with a contact type thickness measuring meter with an accuracy of 0.01 μπι.

The average pore diameter of the separator was measured with a scanning electron microscopy.

The porosity of the separator was measured with a mercury intrusion porosimeter.

The separators S1-S9 and DS1-DS2 were all tested, and the results were recorded in Table 1.

Table 1

2) Battery

2.1) Cycling Performance of Battery

The lithium ion rechargeable battery was subjected to a 1C/2C charging/discharging cycle test at 60°C. The residual ratio of capacity after the cycle test was performed for 100 times, 200 times and 300 times were recorded respectively. The lithium ion rechargeable batteries SS1-SS9 and DSS1-DSS2 were tested, and the results were recorded in Table 2.

Table 2

2.2) Safety of Battery

The lithium ion rechargeable battery was subjected to a high temperature resisting test by placing the battery in a sealed drying oven.

The lithium ion rechargeable batteries SS1-SS9 and DSS1-DSS2 were tested, and the results were recorded in Table 3. In the Table 3, "OK" means that the battery tested satisfies the safety requirement, "NG" means that a fire or an explosion have been caused, and "150°C/2hr" means that the battery has been baked for 2 h at 150°C.

Table 3

150°C/lhr 150°C/2hr 160°C/lhr 160°C/2hr

SSI OK OK OK OK

SS2 OK OK OK OK

SS3 OK OK OK NG

SS4 OK OK OK NG

SS5 OK OK OK OK

SS6 OK OK OK OK

SS7 OK OK OK OK

SS8 OK OK OK NG

SS9 OK OK OK NG

DSS1 OK OK NG NG

DSS2 OK OK NG NG From the Tables shown above, it can be concluded that, the separator according to embodiments of the present disclosure may be thinner and have improved thermal resistance. Further, the heat resistance layer (i.e. the ceramic layer) may not easy to fall from the polymer substrate, and the separator may be easier to wind and to apply into practical use. Accordingly, the method for preparing the separator may be simplified. In addition, the battery including the separator may have improved cycling performances and thermal stability.

Reference throughout this specification to "an embodiment," "some embodiments," "one embodiment", "another example," "an example," "a specific example," or "some examples," means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present disclosure. Thus, the appearances of the phrases such as "in some embodiments," "in one embodiment", "in an embodiment", "in another example," "in an example," "in a specific example," or "in some examples," in various places throughout this specification are not necessarily referring to the same embodiment or example of the present disclosure. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

Although explanatory embodiments have been shown and described, it would be appreciated by those skilled in the art that the above embodiments can not be construed to limit the present disclosure, and changes, alternatives, and modifications can be made in the embodiments without departing from spirit, principles and scope of the present disclosure.

Claims

What is claimed is:

1. A separator comprising:

a polymer substrate containing a base polymer and a first curing resin,

a ceramic layer provided on the polymer substrate, and

an infiltration part formed between the polymer substrate and the ceramic layer and having at least a portion infiltrated into the polymer substrate, wherein each of the infiltration part and the ceramic layer independently comprises ceramic particles and a second curing resin.

2. The separator according to claim 1, wherein the first curing resin is obtainable by a cross-linking of a first self-initiated UV curing resin, and the second curing resin is obtainable by a cross-linking of a second self-initiated UV curing resin.

3. The separator according to claim 1 or 2, wherein the separator comprises

two ceramic layers provided on two sides of the polymer substrate; and

two infiltration parts each of which is independently formed between the ceramic layer and the corresponding side of the polymer substrate.

4. The separator according to any of claims 1-3, wherein the ceramic layer has a thickness of about 0.1-1 μπι, and the infiltration part has a thickness of about 0.01-0.1 μπι.

5. The separator according to any of claims 2-4, wherein the first self-initiated UV curing resin is the same as the second self-initiated UV curing resin, and each of the first and second self-initiated UV curing resins independently contains an optical active structure.

6. The separator according to any of claims 2-5, wherein each of the first and second self-initiated UV curing resins independently comprises at least one selected from a group consisting of: ethylene acrylate, α,β-unsaturated ethylene carboxylate, N-alkyl maleimide, unsaturated polyesteramide urea, coumarin modified resin, anacardol, acrylate hyperbranched polymer, a resin containing a quaternary carbon-containing dicarbonyl, and a resin containing a cinnamoyl group.

7. The separator according to claim 6, wherein the resin containing a quaternary carbon-containing dicarbonyl is obtainable by reacting a β-dicarbonyl compound with acrylate.

8. The separator according to claim 7, wherein the β-dicarbonyl compound has a -CO-CHR-CO- group, and the acrylate is a multi-functionality acrylate.

9. The separator according to claim 8, wherein the β-dicarbonyl compound comprises at least one selected from a group consisting of: ethyl acetoacetate, methyl acetoacetate, acetylacetone and malonate; and the acrylate comprises at least one selected from a group consisting of: epoxy acrylate, polyester acrylate, polyurethane acrylate and polysiloxane acrylate.

10. The separator according to claim 6, wherein the resin containing a cinnamoyl group comprises at least one selected from cinnamic acid modified polysiloxane and cinnamic acid modified polyvinyl alcohol.

11. The separator according to claim 6, wherein the N-alkyl maleimide comprises at least one selected from a group consisting of: N-methyl maleimide, N-ethyl maleimide, N-tert butyl maleimide, N-hexyl maleimide, N-cyclohexyl maleimide, N-hydroxylpentyl maleimide, N-hydroxylethyl maleimide, N-phenyl maleimide and N-(diethyl carbonate) maleimide.

12. The separator according to claim 6, wherein the α,β-ethylene carboxylate comprises at least one selected from a group consisting of: ethylene tiglate, ethylene cinnamate, diethylene maleate, mono(ethylene) fumarate and diethylene fumarate.

13. The separator according to any of claims 1-12, wherein the ceramic particle has an average particle diameter of about 10-1000 nm and a specific surface area of about 1-4000 m²/g.

14. The separator according to claim 13, wherein the ceramic particle has an average particle diameter of about 50-500 nm and a specific surface area of about 5-50 m²/g.

15. The separator according to any of claims 1-14, wherein the ceramic particle comprises at least one selected from a group consisting of: metal oxide, metal sulfate, metal silicate, metal carbonate and metal titanate, and the metal comprises at least one selected from a group consisting of: Al, Zr, Mg, Ca, Ti, Si, Ba and Zn.

16. The separator according to any of claims 1-15, wherein the polymer substrate has a porosity of about 40-95% and a thickness of about 10-40 μπι.

17. A method for preparing a separator, comprising steps of:

forming a preliminary polymer substrate by mixing a base polymer and a first self-initiated UV curing resin;

providing a ceramic slurry containing ceramic particles, a second self-initiated UV curing resin and a solvent on the preliminary polymer substrate, wherein the solvent is an organic solvent capable of dissolving or swelling the polymer substrate; and

subjecting the first and second self-initiated UV curing resins to cross-linking by curing with UV.

18. The method according to claim 17, wherein providing the ceramic slurry on the preliminary polymer substrate comprises providing the ceramic slurry onto a surface of the preliminary polymer substrate and resting said preliminary polymer substrate for about 1-10 min.

19. The method according to claim 17, wherein providing the ceramic slurry on the preliminary polymer substrate comprises immersing the preliminary polymer substrate into the ceramic slurry with a temperature of about 50-120°C for about 1-10 min.

20. The method according to any of claims 17-19, wherein the solvent comprises at least one selected from a group consisting of: aliphatic hydrocarbon, aromatic hydrocarbon and chlorinated hydrocarbon.

21. The method according to any of claims 17-20, wherein the base polymer comprises polyethylene; and the solvent comprises at least one selected from a group consisting of: toluene, xylene, pentyl acetate, trichloroethylene and carbon tetrachloride.

22. The method according to any of claims 17-20, wherein the base polymer comprises polypropylene; and the solvent comprises at least one selected from a group consisting of: benzene, para-xylene, heptane, tetrachloronaphthalene, tetrahydrofuran, decalin and tetrahydronaphthalene.

23. The method according to any of claims 17-20, wherein the base polymer comprises polyethylene terephthalate; and the solvent comprises at least one selected from a group consisting of: trifluoroacetic acid, phenol, chloro-phenol and a mixture of phenol and trichloroethane.

24. The method according to any of claims 17-23, wherein the curing is performed for about 1-5 min and the UV has a wave length of about 200-380 nm.

25. The method according to any of claims 17-24, wherein based on the total weight of the base polymer, the amount of the first self-initiated UV curing resin is about 1-5 wt%.

26. The method according to any of claims 17-25, wherein the ceramic slurry provided on one side of the preliminary polymer substrate has a thickness of about 0.15-1.2 μπι.

27. The method according to any of claims 17-26, wherein based on 1 weight part of the second self-initiated UV curing resin, the amount of the ceramic particles is about 1-20 weight parts, and the amount of the solvent is about 30-50 weight parts.

28. A lithium ion battery comprising:

a shell;

a core provided in the shell;

a cover plate configured to seal the shell; and

an electrolyte received in the shell, wherein the core comprises a positive electrode, a negative electrode, and a separator according to any of claims 1-16 disposed between the positive and negative electrodes.