Battery separator including inorganic coating disposed on dense layer formed on support layer, and method for preparing the same

Abstract

A battery separator and a preparation method therefor are provided. The separator includes a lithium ion battery separator substrate and an inorganic coating, the lithium ion battery separator substrate consists of a support layer and a dense layer, and the inorganic coating is coated on the dense layer; the separator has excellent high-temperature resistance, and still has good strength retention and the heat shrinkage rate thereof is no more than 2% after treatment at 300° C. for 1 h, and thus ensures the stability and isolation of the rigid structure of the separator coating at high temperatures; the substrate has a uniform and compact double-layer structure, effectively controls phenomena such as pinholes and filler particles fall-off in a subsequent coating process, and meets the requirements of lithium ion battery separators with respect to heat resistance, porosity and strength, thus having excellent comprehensive performance.

Claims

1. A method of preparing a lithium ion battery separator, comprising: mixing fiber materials of a support layer and a nano layer respectively with water, and then each independently defiberizing, beating and mixing to obtain pulps, and then diluting the pulps with water by a flushing pump to an on-wire concentration; feeding the diluted pulps of the support layer and the nano layer into a double-layer hydraulic inclined wire former, wherein the pulp of the nano layer enters an upper flow channel and the pulp of the support layer enters a lower flow channel, overlapping the pulp in each flow channel in the same area and making papers at the same time, and draining to obtain a wet paper sheet, forming the wet paper sheet for a substrate; drying the wet paper sheet for the substrate to obtain a dry paper sheet for the substrate by a Yankee dryer; calendering the dry paper sheet for the substrate by a metal roller and a soft roller to obtain the substrate; and coating an inorganic coating uniformly on the surface of the nano layer of the substrate, and then drying by hot air to obtain the lithium ion battery separator; wherein, the temperature of the hot air is 80-150° C.; wherein the inorganic coating comprises inorganic particles, dispersants, water-retaining agents and adhesive resins; the inorganic particles are selected from one or more of the group consisting of alumina, silica, boehmite and magnesium hydroxide; the dispersants are ammonium polycarboxylate; the water-retaining agents are sodium carboxymethyl cellulose (CMC); and the adhesive resins are acrylate or styrene-butadiene latex; wherein the inorganic coating comprises 80-85 wt % of the inorganic particles, 1-2 wt % of the dispersants, 2-4 wt % of the water-retaining agents and 10-14 wt % of the adhesive resins; wherein the substrate comprises 50-95 wt % of the support layer and 5-50 wt % of the nano layer, based on a total basis weight; the support layer consists of 30-45 wt % of superfine main fibers, 30-65 wt % of thermoplastic bonded fibers and 5-30 wt % of first nanofibers by weight; the nano layer consists of second nanofibers; wherein the first nanofibers and the second nanofibers are independently selected from one or more of the group consisting of fibrillated poly-p-phenylene terephthalamide (PPTA) nanofibers, fibrillated lyocell nanofibers, fibrillated poly-p-phenylene benzodioxazole (PBO) nanofibers, fibrillated polyacrylonitrile (PAN) nanofibers, polyimide (PI) nanofibers and nanocellulose fibers; wherein a coating weight of the inorganic coating is 3-15 g/m.sup.2.

2. The preparation method according to claim 1, wherein a thickness of the substrate is 10-25 μm; a basis weight of the substrate is 8-17 g/m.sup.2; an average pore size of the substrate is less than 3 μm; and a maximum pore size of the substrate is less than 5 μm.

3. The preparation method according to claim 1, wherein the inorganic particles have a particle size of less than 3 μm; the ammonium polycarboxylate has a viscosity less than 100 mPa.Math.s; the sodium carboxymethyl cellulose has a viscosity between 10 mPa.Math.s and 50 mPa.Math.s; and the adhesive resins have a viscosity less than 1000 mPa.Math.s.

4. The preparation method according to claim 1, wherein the second nanofibers are fibrillated poly-p-phenylene terephthalamide (PPTA) nanofibers and fibrillated lyocell nanofibers; a ratio of the fibrillated poly-p-phenylene terephthalamide (PPTA) nanofibers to fibrillated lyocell nanofibers is 1:(1-4) by weight.

5. The preparation method according to claim 1, wherein a thickness of the separator is less than 30 μm; a basis weight of the separator is 15-29 g/m.sup.2; an average pore size of the separator is less than 0.6 μm; a maximum pore size of the separator is no more than 1.0 μm; and a heat shrinkage rate of the separator is no more than 2% at 300° C.

6. The preparation method according to claim 1, wherein the superfine main fibers have a fiber diameter of 0.1-6 μm; the superfine main fibers have a fiber length of 1-6 mm; the thermoplastic bonded fibers have a fiber diameter of 0.1-8 μm; the thermoplastic bonded fibers have a fiber length of 1-6 mm; and the first nanofibers and the second nanofibers have a beating degree of 60-95° SR.

7. The preparation method according to claim 1, wherein, the solid weight percent concentrations of the pulp of the support layer and the nano layer are both 0.2 wt % before diluting with water; the on-wire concentration of the pulp of the support layer is 0.01-0.05 wt %; the on-wire concentration of the pulp of the nano layer is 0.002-0.05 wt %; the flow rate of the pulp of the support layer is 160-3000 m.sup.3/h; the flow rate of the pulp of the nano layer is 40-750 m.sup.3/h; a drying temperature is 80-130° C.; a calendering temperature is 110-220° C.

8. The preparation method according to claim 1, wherein the superfine main fibers are selected from one or more of the group consisting of stretched polyethylene terephthalate fibers (stretched PET), polyacrylonitrile fibers (PAN), polyamide fibers (PA) and polypropylene fibers (PP); and the thermoplastic bonded fibers are selected from one or more of the group consisting of polyethylene fibers (PE), polypropylene fibers (PP), unstretched polyethylene terephthalate fibers (unstretched PET), PP/PE bi-component fibers, PET/PE bi-component fibers, PET/PP bi-component fibers and PET/co-PET bi-component fibers.

9. The preparation method according to claim 1, wherein, a method for preparing the inorganic coating comprises: according to the composition of the inorganic coating, sequentially adding the dispersants and the water-retaining agents to deionized water and stirring; adding the inorganic particles and dispersing; filtering to obtain a dispersion liquid through a strainer; adding the adhesive resins to the dispersion liquid, and continuing to disperse to obtain a pulp of the inorganic coating.

10. The preparation method according to claim 9, wherein, the inorganic particles are dispersed at 2500 r/min for 30 min; the adhesive resins are uniformly dispersed in the dispersion liquid for 15 min; the strainer is a strainer of 320 mesh; and the pulp of the inorganic coating has a solid content of 40-60%.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) Embodiments of the disclosure are described in detail below with reference to the attached drawing figures, wherein:

(2) FIG. 1 is a schematic diagram of the apparent morphology of a lithium ion battery separator prepared by the disclosure.

(3) FIG. 2 is a schematic structural view of a HYDROFORMER™, a type of double-layer hydraulic inclined wire former, used in the disclosure, wherein A represents a pulp distributor, B represents a rectifying zone, C represents a substrate forming zone, and D represents a formed wet paper sheet of the substrate.

DETAILED DESCRIPTION OF THE DISCLOSURE

(4) The disclosure will be further described below in conjunction with specific embodiments. It should be understood that the embodiments of the disclosure are only used to illustrate the disclosure, and are not intended to limit the scope of the disclosure.

(5) The experimental methods without specific conditions in the following examples are generally performed under conventional conditions or according to the conditions recommended by the manufacturer. Unless otherwise defined, all professional and scientific terms used in the text have the same meaning as familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to the described content can be applied to the method of the disclosure. The preferred implementation methods and materials described herein are for demonstration purposes only.

(6) Preparation of the Lithium Ion Battery Separator Substrate

(7) The following Preparation Examples 1-63 and Comparative Examples 1-11 only disclose examples of using some fiber materials to prepare the substrate, and other fiber materials and combinations thereof given in the disclosure may also be used to prepare the substrate of the disclosure. The schematic structural view of the HYDROFORMER™, a type of double-layer hydraulic inclined wire former, used in Preparation Examples 1-63 of the disclosure is shown in FIG. 2.

Preparation Example 1

(8) A lithium ion battery separator substrate is consisting of a two-layer structure of a support layer and a dense layer, and is prepared by the following method:

(9) Step a: Mixing the fiber materials of the support layer and the dense layer respectively with water in the defibizer according to the formulas shown in Table 1, defiberizing and beating to a solid weight percent concentration of 0.2 wt %, and then diluting by the flushing pump, wherein the fiber material of the support layer is diluted to a solid weight percent concentration of 0.02375 wt % to obtain Pulp 1; the fiber material of the dense layer is diluted to a solid weight percent concentration of 0.005 wt % to obtain Pulp 2.

(10) Step b: Respectively feeding the pulp 1 and the pulp 2 obtained in step a into the HYDROFORMER™, a type of double-layer hydraulic inclined wire former, wherein the pulp 1 enters the lower flow channel at a flow rate of 740 m.sup.3/h, the pulp 2 enters the upper flow channel at a flow rate of 185 m.sup.3/h; after rectification, making papers of the two layers at the same time, and draining to obtain a wet paper sheet for the substrate.

(11) Step c: Drying the wet paper sheet for the substrate obtained in step b to obtain a dry paper sheet for the substrate at a temperature of 120° C. by a Yankee dryer.

(12) Step d: Calendering the dry paper sheet for the substrate obtained in Step c at a temperature of 190° C. by a metal roller and a soft roller to obtain the lithium ion battery separator substrate of the disclosure.

Preparation Examples 2-4, 35-40, 47, 48

(13) A lithium ion battery separator substrate is consisting of a two-layer structure of a support layer and a dense layer. The formulas of the support layer and the dense layer are shown in Table 1. The preparation method is the same as that in Preparation Example 1.

Preparation Example 5

(14) A lithium ion battery separator substrate is consisting of a two-layer structure of a support layer and a dense layer. The formulas of the support layer and the dense layer are shown in Table 1. The separator substrate is prepared by the following method:

(15) Step a: Mixing the fiber materials of the support layer and the dense layer respectively with water in the defibizer according to the formulas shown in Table 1, defiberizing and beating to a solid weight percent concentration of 0.2 wt %, and then diluting by the flushing pump, wherein the fiber material of the support layer is diluted to a solid weight percent concentration of 0.02 wt % to obtain Pulp 1; the fiber material of the dense layer is diluted to a solid weight percent concentration of 0.02 wt % to obtain Pulp 2.

(16) Step b: Respectively feeding the pulp 1 and the pulp 2 obtained in step a into the HYDROFORMER™, a type of double-layer hydraulic inclined wire former, wherein the pulp 1 enters the lower flow channel at a flow rate of 740 m.sup.3/h, the pulp 2 enters the upper flow channel at a flow rate of 185 m.sup.3/h; after rectification, making papers of the two layers at the same time, and draining to obtain a wet paper sheet for the substrate.

(17) Step c: Drying the wet paper sheet for the substrate obtained in step b to obtain a dry paper sheet for the substrate at a temperature of 120° C. by a Yankee dryer.

(18) Step d: Calendering the dry paper sheet for the substrate obtained in Step c at a temperature of 190° C. by a metal roller and a soft roller to obtain the lithium ion battery separator substrate of the present disclosure.

Preparation Examples 6-8, 13-15, 22-28, 41-44, 61-63

(19) A lithium ion battery separator substrate is consisting of a two-layer structure of a support layer and a dense layer. The formulas of the support layer and the dense layer are shown in Table 1. The preparation method is the same as that in Preparation Example 5.

Preparation Example 9

(20) A lithium ion battery separator substrate is consisting of a two-layer structure of a support layer and a dense layer. The formulas of the support layer and the dense layer are shown in Table 1. The separator substrate is prepared by the following method:

(21) Step a: Mixing the fiber materials of the support layer and the dense layer respectively with water in the defibizer according to the formulas shown in Table 1, defiberizing and beating to a solid weight percent concentration of 0.2 wt %, and then diluting by the flushing pump, wherein the fiber material of the support layer is diluted to a solid weight percent concentration of 0.015 wt % to obtain Pulp 1; the fiber material of the dense layer is diluted to a solid weight percent concentration of 0.04 wt % to obtain Pulp 2.

(22) Step b: Respectively feeding the pulp 1 and the pulp 2 obtained in step a to the HYDROFORMER™, a type of double-layer hydraulic inclined wire former, wherein the pulp 1 enters the lower flow channel at a flow rate of 740 m.sup.3/h, the pulp 2 enters the upper flow channel at a flow rate of 185 m.sup.3/h; after rectification, making papers of the two layers at the same time, and draining to obtain a wet paper sheet for the substrate.

(23) Step c: Drying the wet paper sheet for the substrate obtained in step b to obtain a dry paper sheet for the substrate at a temperature of 120° C. by a Yankee dryer.

(24) Step d: Calendering the dry paper sheet for the substrate obtained in Step c at a temperature of 190° C. by a metal roller and a soft roller to obtain the lithium ion battery separator substrate of the disclosure.

Preparation Examples 10-12, 29-34, 45-46

(25) A lithium ion battery separator substrate is consisting of a two-layer structure of a support layer and a dense layer. The formulas of the support layer and the dense layer are shown in Table 1. The preparation method is the same as that in Preparation Example 9.

Preparation Examples 16, 19, 51-52, 55-56

(26) A lithium ion battery separator substrate is consisting of a two-layer structure of a support layer and a dense layer. The formulas of the support layer and the dense layer are shown in Table 1. The separator substrate is prepared by the following method:

(27) Step a and Step b are the same as in Preparation Example 5.

(28) Step c: Drying the wet paper sheet for the substrate obtained in step b to obtain a dry paper sheet for the substrate at a temperature of 90° C. by a Yankee dryer.

(29) Step d: Calendering the dry paper sheet for the substrate obtained in Step c at a temperature of 120° C. by a metal roller and a soft roller to obtain the lithium ion battery separator substrate of the disclosure.

Preparation Examples 17-18, 20-21, 59-60

(30) A lithium ion battery separator substrate is consisting of a two-layer structure of a support layer and a dense layer. The formulas of the support layer and the dense layer are shown in Table 1. The separator substrate is prepared by the following method:

(31) Step a and Step b are the same as in Preparation Example 9.

(32) Step c: Drying the wet paper sheet for the substrate obtained in step b to obtain a dry paper sheet for the substrate at a temperature of 90° C. by a Yankee dryer.

(33) Step d: Calendering the dry paper sheet for the substrate obtained in Step c at a temperature of 120° C. by a metal roller and a soft roller to obtain the lithium ion battery separator substrate of the disclosure.

Preparation Examples 49-50, 53-54, 57-58

(34) A lithium ion battery separator substrate is consisting of a two-layer structure of a support layer and a dense layer. The formulas of the support layer and the dense layer are shown in Table 1. The separator substrate is prepared by the following method:

(35) Step a and Step b are the same as in Preparation Example 1.

(36) Step c: Drying the wet paper sheet for the substrate obtained in step b to obtain a dry paper sheet for the substrate at a temperature of 90° C. by a Yankee dryer.

(37) Step d: Calendering the dry paper sheet for the substrate obtained in Step c at a temperature of 120° C. by a metal roller and a soft roller to obtain the lithium ion battery separator substrate of the disclosure.

Comparative Example 1

(38) A lithium ion battery separator substrate is consisting of a single layer structure. The formula of the single layer is shown in Table 2. The separator substrate is prepared by the following method:

(39) Step a: Mixing the fiber material with water in the defibizer according to the formula shown in Table 2, defiberizing and beating to a solid weight percent concentration of 0.2 wt %, and then diluting the fiber material by the flushing pump to a solid weight percent concentration of 0.02 wt % to obtain a pulp.

(40) Step b: Feeding the pulp obtained in step a to an inclined wire paper machine, wherein the flow rate of the pulp is 925 m.sup.3/h; after rectification, and draining to obtain a wet paper sheet for the substrate.

(41) Step c: Drying the wet paper sheet for the substrate obtained in step b to obtain a dry paper sheet for the substrate at a temperature of 120° C. by a Yankee dryer.

(42) Step d: Calendering the dry paper sheet for the substrate obtained in Step c at a temperature of 190° C. by a metal roller and a soft roller to obtain the single-layer lithium ion battery separator substrate.

Comparative Example 2

(43) A lithium ion battery separator substrate is consisting of a single layer structure. The formula of the single layer is shown in Table 2. The preparation method is the same as that in Comparative Example 1.

Comparative Examples 3-5

(44) A lithium ion battery separator substrate is consisting of a two-layer structure of a support layer and a dense layer. The formulas of the support layer and the dense layer are shown in Table 2. The preparation method is the same as that in Preparation Example 5.

Comparative Examples 6-7

(45) A lithium ion battery separator substrate is consisting of a two-layer structure of a support layer and a dense layer. The formulas of the support layer and the dense layer are shown in Table 2. The preparation method is the same as that in Preparation Example 1.

Comparative Example 8

(46) A lithium ion battery separator substrate is consisting of a two-layer structure of a support layer and a dense layer, and is prepared by the following method:

(47) Step a: Mixing the fiber materials of the support layer and the dense layer respectively with water in the defibizer according to the formulas shown in Table 2, defiberizing and beating to a solid weight percent concentration of 0.2 wt %, and then diluting by the flushing pump, wherein the fiber material of the support layer is diluted to a solid weight percent concentration of 0.0125 wt % to obtain Pulp 1; the fiber material of the dense layer is diluted to a solid weight percent concentration of 0.05 wt % to obtain Pulp 2.

(48) Step b, step c and step d are the same as in Preparation Example 1.

Comparative Examples 9-10

(49) A lithium ion battery separator substrate is consisting of a two-layer structure of a support layer and a dense layer. The formulas of the support layer and the dense layer are shown in Table 2. The separator substrate is prepared by the following method:

(50) Step a and step b are the same as in Preparation Example 5.

(51) Step c: Drying the wet paper sheet for the substrate obtained in step b to obtain a dry paper sheet for the substrate at a temperature of 90° C. by a Yankee dryer.

(52) Step d: Calendering the dry paper sheet for the substrate obtained in Step c at a temperature of 120° C. by a metal roller and a soft roller to obtain the lithium ion battery separator substrate of the disclosure.

Comparative Example 11

(53) The preparing process is performed according to the method diclosed in Chinese Patent CN201410496299.4. It discloses a substrate for separators for lithium secondary batteries which is prepared by the following method: Using a disc mill, mix solvent-spun cellulose fibers 10% by mass, oriented crystalline polyethylene terephthalate (PET) short fibers 50% by mass and unstretched binder polyester fibers 40% by mass together, wherein the solvent-spun cellulose fibers have an average fiber diameter of 10 μm, a fiber length of 4 mm, and a freeness of 97 ml; the oriented crystalline polyethylene terephthalate (PET) short fibers have an average fiber diameter of 2.4 μm and fiber length of 3 mm; unstretched binder polyester fibers have an average fiber diameter of 4.4 μm and fiber length of 3 mm; and then dissociate in the pulp machine water to obtain a uniform papermaking pulp (0.3 mass % concentration) on the basis of agitation using an agitator. The oblique short wire is used as the first layer and the rotary wire is used as the second layer, and the weight ratio of the oblique short wire to the rotary wire is set to 50:50 to laminate the papermaking pulp to obtain a wet sheet. After drying at a Yankee dryer temperature of 130° C., calender by a metal roller and an elastic roller with a surface temperature of 195° C. to obtain a weight per unit area of 8.2 g/m.sup.2 and a thickness of 14.2 μm of the substrate for separators for lithium secondary batteries.

(54) TABLE-US-00001 TABLE 1 Fiber formulation of Preparation Examples 1-63 (wt %) Nanofibers Proportion Thermo- (the first based on Superfine plastic nanofibers or the total main bonded the second basis Preparation Examples fibers fibers nanofibers) weight Preparation Support 45% .sup.a) 40% .sup.d)  15% .sup.i) 95% Example1 layer Dense — — 100% .sup.j)  5% layer Preparation Support 30% .sup.a) 65% .sup.d)  5% .sup.i) 95% Example 2 layer Dense — — 100% .sup.j)  5% layer Preparation Support 65% .sup.a) 30% .sup.d)  5% .sup.i) 95% Example 3 layer Dense — — 100% .sup.j)  5% layer Preparation Support 40% .sup.a) 30% .sup.d)  30% .sup.i) 95% Example 4 layer Dense — — 100% .sup.j)  5% layer Preparation Support 45% .sup.a) 40% .sup.d)  15% .sup.i) 80% Example 5 layer Dense — — 100% .sup.j) 20% layer Preparation Support 30% .sup.a) 65% .sup.d)  5% .sup.i) 80% Example 6 layer Dense — — 100% .sup.j) 20% layer Preparation Support 65% .sup.a) 30% .sup.d)  5% .sup.i) 80% Example 7 layer Dense — — 100% .sup.j) 20% layer Preparation Support 40% .sup.a) 30% .sup.d)  30% .sup.i) 80% Example 8 layer Dense — — 100% .sup.j) 20% layer Preparation Support 45% .sup.a) 40% .sup.d)  15% .sup.i) 60% Example 9 layer Dense — — 100% .sup.j) 40% layer Preparation Support 30% .sup.a) 65% .sup.d)  5% .sup.i) 60% Example 10 layer Dense — — 100% .sup.j) 40% layer Preparation Support 65% .sup.a) 30% .sup.d)  5% .sup.i) 60% Example 11 layer Dense — — 100% .sup.j) 40% layer Preparation Support 40% .sup.a) 30% .sup.d)  30% .sup.i) 60% Example 12 layer Dense — — 100% .sup.j) 40% layer Preparation Support 30% .sup.b) 65% .sup.d)  5% .sup.i) 80% Example 13 layer Dense — — 100% .sup.j) 20% layer Preparation Support 30% .sup.c) 65% .sup.d)  5% .sup.i) 80% Example 14 layer Dense — — 100% .sup.j) 20% layer Preparation Support 10% .sup.a) Example 15 layer 10% .sup.b) 65% .sup.d)  5% .sup.i) 80% 10% .sup.c) Dense — — 100% .sup.j) 20% layer Preparation Support 40% .sup.a) 30% .sup.e)  30% .sup.i) 80% Example 16 layer Dense — — 100% .sup.j) 20% layer Preparation Support 30% .sup.a) 65% .sup.e)  5% .sup.i) 60% Example 17 layer Dense — — 100% .sup.j) 40% layer Preparation Support 40% .sup.a) 30% .sup.e)  30% .sup.i) 60% Example 18 layer Dense — — 100% .sup.j) 40% layer Preparation Support 40% .sup.a) 30% .sup.f)   30% .sup.i) 80% Example 19 layer Dense — — 100% .sup.j) 20% layer Preparation Support 30% .sup.a) 65% .sup.f)   5% .sup.i) 60% Example 20 layer Dense — — 100% .sup.j) 40% layer Preparation Support 40% .sup.a) 30% .sup.f)   30% .sup.i) 60% Example 21 layer Dense — — 100% .sup.j) 40% layer Preparation Support 30% .sup.a) 65% .sup.d)  5% .sup.j) 80% Example 22 layer Dense — — 100% .sup.i) 20% layer Preparation Support 30% .sup.a) 65% .sup.d)  5% .sup.i) 80% Example 23 layer Dense — — 100% .sup.i) 20% layer Preparation Support 30% .sup.a) 65% .sup.d)  5% .sup.i) 80% Example 24 layer Dense — —  50% .sup.i) 20% layer  50% .sup.j) Preparation Support 30% .sup.a) 65% .sup.d)  .sup. 5% .sup.g) 80% Example 25 layer Dense — —  100% .sup.h) 20% layer Preparation Support 45% .sup.b) 40% .sup.d)  15% .sup.i) 80% Example 26 layer Dense — — 100% .sup.j) 20% layer Preparation Support 45% .sup.c) 40% .sup.d)  15% .sup.i) 80% Example 27 layer Dense — — 100% .sup.j) 20% layer Preparation Support 12% .sup.a) 40% .sup.d)  15% .sup.i) 80% Example 28 layer 12% .sup.b) 11% .sup.c) Dense — — 100% .sup.j) 20% layer Preparation Support 30% .sup.b) 65% .sup.d)  5% .sup.i) 60% Example 29 layer Dense — — 100% .sup.j) 40% layer Preparation Support 30% .sup.c) 65% .sup.d)  5% .sup.i) 60% Example 30 layer Dense — — 100% .sup.j) 40% layer Preparation Support 10% .sup.a) 65% .sup.d)  5% .sup.i) 60% Example 31 layer 10% .sup.b) 10% .sup.c) Dense — — 100% .sup.j) 40% layer Preparation Support 45% .sup.b) 40% .sup.d)  15% .sup.i) 60% Example 32 layer Dense — — 100% .sup.j) 40% layer Preparation Support 45% .sup.c) 40% .sup.d)  15% .sup.i) 60% Example 33 layer Dense — — 100% .sup.j) 40% layer Preparation Support 12% .sup.a) 40% .sup.d)  15% .sup.i) 60% Example 34 layer 12% .sup.b) 11% .sup.c) Dense — — 100% .sup.j) 40% layer Preparation Support 30% .sup.b) 65% .sup.d)  5% .sup.i) 95% Example 35 layer Dense — — 100% .sup.j)  5% layer Preparation Support 30% .sup.c) 65% .sup.d)  5% .sup.i) 95% Example 36 layer Dense — — 100% .sup.j)  5% layer Preparation Support 10% .sup.a) 65% .sup.d)  5% .sup.i) 95% Example 37 layer 10% .sup.b) 10% .sup.c) Dense — — 100% .sup.j)  5% layer Preparation Support 45% .sup.b) 40% .sup.d)  15% .sup.i) 95% Example 38 layer Dense — — 100% .sup.j)  5% layer Preparation Support 45% .sup.c) 40% .sup.d)  15% .sup.i) 95% Example 39 layer Dense — — 100% .sup.j)  5% layer Preparation Support 12% .sup.a) 40% .sup.d)  15% .sup.i) 95% Example 40 layer 12% .sup.b) 11% .sup.c) Dense — — 100% .sup.j)  5% layer Preparation Support 45% .sup.a) 40% .sup.d)  15% .sup.j) 80% Example 41 layer Dense — — 100% .sup.i) 20% layer Preparation Support 45% .sup.a) 40% .sup.d) .sup. 15% .sup.g) 80% Example 42 layer Dense — —  100% .sup.h) 20% layer Preparation Support 45% .sup.a) 40% .sup.d)  15% .sup.i) 80% Example 43 layer Dense — — 100% .sup.i) 20% layer Preparation Support 45% .sup.a) 40% .sup.d)  15% .sup.i) 80% Example 44 layer Dense — —  50% .sup.i) 20% layer  50% .sup.j) Preparation Support 30% .sup.a) 65% .sup.d)  5% .sup.i) 60% Example 45 layer Dense — — 100% .sup.i) 40% layer Preparation Support 30% .sup.a) 65% .sup.d)  5% .sup.i) 60% Example 46 layer Dense — —  50% .sup.i) 40% layer  50% .sup.j) Preparation Support 30% .sup.a) 65% .sup.d)  5% .sup.i) 95% Example 47 layer Dense — — 100% .sup.i)  5% layer Preparation Support 30% .sup.a) 65% .sup.d)  5% .sup.i) 95% Example 48 layer Dense — —  50% .sup.i)  5% layer  50% .sup.j) Preparation Support 40% .sup.a) 30% .sup.e)  30% .sup.i) 95% Example 49 layer Dense — — 100% .sup.j)  5% layer Preparation Support 40% .sup.a) 30% .sup.f)   30% .sup.i) 95% Example 50 layer Dense — — 100% .sup.j)  5% layer Preparation Support 30% .sup.a) 65% .sup.e)  5% .sup.i) 80% Example 51 layer Dense — — 100% .sup.j) 20% layer Preparation Support 30% .sup.a) 65% .sup.f)   5% .sup.i) 80% Example 52 layer Dense — — 100% .sup.j) 20% layer Preparation Support 30% .sup.a) 65% .sup.e)  5% .sup.i) 95% Example 53 layer Dense — — 100% .sup.j)  5% layer Preparation Support 30% .sup.a) 65% .sup.f)   5% .sup.i) 95% Example 54 layer Dense — — 100% .sup.j)  5% layer Preparation Support 45% .sup.a) 40% .sup.e)  15% .sup.i) 80% Example 55 layer Dense — — 100% .sup.j) 20% layer Preparation Support 45% .sup.a) 40% .sup.f)   15% .sup.i) 80% Example 56 layer Dense — — 100% .sup.j) 20% layer Preparation Support 45% .sup.a) 40% .sup.e)  15% .sup.i) 95% Example 57 layer Dense — — 100% .sup.j)  5% layer Preparation Support 45% .sup.a) 40% .sup.f)   15% .sup.i) 95% Example 58 layer Dense — — 100% .sup.j)  5% layer Preparation Support 45% .sup.a) 40% .sup.e)  15% .sup.i) 60% Example 59 layer Dense — — 100% .sup.j) 40% layer Preparation Support 45% .sup.a) 40% .sup.f)   15% .sup.i) 60% Example 60 layer Dense — — 100% .sup.j) 40% layer Preparation Support 45% .sup.a) 40% .sup.d)  15% .sup.i) 80% Example 61 layer — —  20% .sup.i) 20% Dense  80% .sup.j) layer Preparation Support 45% .sup.a) 40% .sup.d)  15% .sup.i) 80% Example 62 layer Dense — —  100% .sup.k) 20% layer Preparation Support 45% .sup.a) 40% .sup.d) .sup. 15% .sup.k) 80% Example 63 layer Dense — — 100% .sup.l) 20% layer Note: .sup.a) Stretched PET fiber with a fiber diameter of 2 μm and a fiber length of 3 mm; .sup.b) PAN fiber with a fiber diameter of 2 μm and a fiber length of 3 mm; .sup.c) PA fiber with a fiber diameter of 2 μm and a fiber length of 3 mm; .sup.d) Unstretched PET fiber with a fiber diameter of 4 μm and a fiber length of 3 mm; .sup.e) PET/co-PET bi-component fiber with a fiber diameter of 4 μm and a fiber length of 3 mm; .sup.f) PP/PE bi-component fiber with a fiber diameter of 4 μm and a fiber length of 3 mm; .sup.g) Fibrillated Tencel nanofiber with a beating degree of 70° SR, Lenzing, Austria; .sup.h) Fibrillated PPTA nanofiber with a beating degree of 60° SR, DuPont Kevlar of the United States; .sup.i) Fibrillated Tencel nanofiber with a beating degree of 95° SR, Lenzing, Austria; .sup.j) Fibrillated PPTA nanofiber with a beating degree of 85° SR, DuPont Kevlar of the United States; .sup.k) Fibrillated PBO nanofiber with a beating degree of 85° SR, Japan Toyobo Company; .sup.l) Fibrillated PAN nanofiber with a beating degree of 85° SR.

(55) TABLE-US-00002 TABLE 2 Fiber formulas (wt %) of Comparative Examples 1-10 Proportion Thermo- based on Superfine plastic the total main bonded basis Comparative Examples fibers fibers Nanofibers weight Comparative Single- 50% .sup.a) 50% .sup.b) — 100%  Example 1 layer Comparative Single- 45% .sup.a) 40% .sup.b)  .sup. 15% .sup.e) 100%  Example 2 layer Comparative Support 45% .sup.a) 40% .sup.b)  .sup. 15% .sup.e) 80% Example 3 layer Dense 20% .sup.a) —  80% .sup.f) 20% layer Comparative Support 50% .sup.a) 50% .sup.b) — 80% Example 4 layer Dense — — 100% .sup.f) 20% layer Comparative Support 75% .sup.a) 20% .sup.b)  .sup. 5% .sup.e) 80% Example 5 layer Dense — — 100% .sup.f) 20% layer Comparative Support 30% .sup.a) 30% .sup.b)  .sup. 40% .sup.e) 95% Example 6 layer Dense — — 100% .sup.f)  5% layer Comparative Support 30% .sup.a) 30% .sup.b)  40% .sup.f) 95% Example 7 layer Dense — — 100% .sup.f)  5% layer Comparative Support 45% .sup.a) 40% .sup.b)  .sup. 15% .sup.e) 50% Example 8 layer Dense — — 100% .sup.f) 50% layer Comparative Support 75% .sup.a) 20% .sup.c)  .sup. 5% .sup.e) 80% Example 9 layer Dense — — 100% .sup.f) 20% layer Comparative Support 75% .sup.a) 20% .sup.d)  .sup. 5% .sup.e) 80% Example 10 layer Dense — — 100% .sup.f) 20% layer Note: .sup.a) Stretched PET fiber with a fiber diameter of 2 μm and a fiber length of 3 mm; .sup.b) Unstretched PET fiber with a fiber diameter of 4 μm and a fiber length of 3 mm; .sup.c) PET/co-PET bi-component fiber with a fiber diameter of 4 μm and a fiber length of 3 mm; .sup.d) PP/PE bi-component fiber with a fiber diameter of 4 μm and a fiber length of 3 mm; .sup.e) Fibrillated Tencel nanofiber with a beating degree of 95° SR, Lenzing, Austria; .sup.f) Fibrillated PPTA nanofiber with a beating degree of 85° SR, DuPont Kevlar of the United States.

(56) Note:

(57) a) Stretched PET fiber with a fiber diameter of 2 μm and a fiber length of 3 mm;

(58) b) PAN fiber with a fiber diameter of 2 μm and a fiber length of 3 mm;

(59) c) PA fiber with a fiber diameter of 2 μm and a fiber length of 3 mm;

(60) d) Unstretched PET fiber with a fiber diameter of 4 μm and a fiber length of 3 mm;

(61) e) PET/co-PET bi-component fiber with a fiber diameter of 4 μm and a fiber length of 3 mm;

(62) f) PP/PE bi-component fiber with a fiber diameter of 4 μm and a fiber length of 3 mm;

(63) g) Fibrillated lyocell nanofiber with a beating degree of 70° SR, Lenzing, Austria;

(64) h) Fibrillated PPTA nanofiber with a beating degree of 60° SR, DuPont Kevlar of the United States;

(65) i) Fibrillated lyocell nanofiber with a beating degree of 95° SR, Lenzing, Austria;

(66) j) Fibrillated PPTA nanofiber with a beating degree of 85° SR, DuPont Kevlar of the United States;

(67) k) Fibrillated PBO nanofiber with a beating degree of 85° SR, Japan Toyobo Company; 1) Fibrillated PAN nanofiber with a beating degree of 85° SR.

(68) Note:

(69) a) Stretched PET fiber with a fiber diameter of 2 μm and a fiber length of 3 mm;

(70) b) Unstretched PET fiber with a fiber diameter of 4 μm and a fiber length of 3 mm;

(71) c) PET/co-PET bi-component fiber with a fiber diameter of 4 μm and a fiber length of 3 mm;

(72) d) PP/PE bi-component fiber with a fiber diameter of 4 μm and a fiber length of 3 mm;

(73) e) Fibrillated lyocell nanofiber with a beating degree of 95° SR, Lenzing, Austria;

(74) f) Fibrillated PPTA nanofiber with a beating degree of 85° SR, DuPont Kevlar of the United States.

(75) Preparation of the Lithium Ion Battery Separator

(76) The pulp of the inorganic coating is prepared according to the inorganic coating formulation shown in Table 3.

(77) The method for preparing the pulp of the inorganic coating is: sequentially adding the dispersants and the water-retaining agents to the deionized water and stirring; adding the inorganic particles and dispersing at 2500 r/min for 30 min, and filtering to obtain a dispersion liquid through a strainer of 320 mesh; adding the adhesive resins to the dispersion liquid, and continuing to uniformly disperse for 15 min to obtain the pulp of the inorganic coating, wherein the pulp of the inorganic coating prepared has a solid content of 50 wt %.

(78) TABLE-US-00003 TABLE 3 Formulation of the inorganic coating (wt %) Water- Formu- Inorganic Retaining Adhesive lation particles Dispersants Agents Resins 1 84% alumina 1% ammonium 2% 13% acrylate polycarboxylate CMC 2 84% silica 1% ammonium 2% 13% acrylate polycarboxylate CMC 3 84% boehmite 1% ammonium 2% 13% acrylate polycarboxylate CMC 4 84% 1% ammonium 2% 13% magnesium polycarboxylate CMC styrene- hydroxide butadiene latex 5 80% alumina 2% ammonium 4% 14% acrylate polycarboxylate CMC 6 87% alumina 2% ammonium 0.5% 10.5% acrylate polycarboxylate CMC 7 80% alumina 0.5% ammonium 2.5% 17% acrylate polycarboxylate CMC 8 85% alumina 1.5% ammonium 3.5% 10% acrylate polycarboxylate CMC 9 42% alumina + 1% ammonium 2% 13% acrylate 42% polycarboxylate CMC magnesium hydroxide

(79) The pulp obtained according to formulation 1-9 is respectively coated on the surface of the dense layer of the lithium ion battery separator substrate of Preparation Examples 1-63, with coating weight of 8 g/m.sup.2, and then which is dried by hot air (120° C.) to obtain the lithium ion battery separator of the disclosure. The appearance of the lithium ion battery separator prepared by the disclosure is shown in FIG. 1.

(80) Performance Test of the Lithium Ion Battery Separator

(81) The pulp of the inorganic coating prepared according to the formulation 1 of the inorganic coating was coated on the lithium ion battery separator substrate prepared in Preparation Examples 1-12, 22-25, 41-48, 61-63 and Comparative Examples 1-11 to obtain the lithium ion battery separators corresponding to Examples 1-12, 22-25, 41-48, 61-63 and Comparative Examples 1′-11′, respectively, for performance testing. The test items and methods are as follows:

(82) 1. Basis weight, thickness and tensile strength: measured by TAPPI standard.

(83) 2. Average pore size and maximum pore size: measured using a PMI pore size analyzer.

(84) 3. Heat shrinkage rate

(85) The dimensional stability of the separator at a certain temperature can be characterized by the thermal stability of the separator, usually expressed in heat shrinkage rate. Test of the heat shrinkage rate of the separator as follows:

(86) Cutting the separator into squares with side length Lb, and then respectively placing the separator in an environment of 110° C. and 300° C. for 1 hour, testing the side length L.sub.a of the separator, and calculating the shrinkage rate according to the following formula:
Shrinkage rate (%)=(L.sub.b−L.sub.a)/L.sub.b×100

(87) 4. Separator strength retention

(88) The separator was placed in a 300° C. environment for 1 hour and taken out. The strength retention of the separator was evaluated according to the following criteria:

(89) ◯: Fold the separator 10 times without breaking;

(90) Δ: Fold the separator 2-10 times and break;

(91) x: Fold the separator once and break.

(92) TABLE-US-00004 TABLE 4 Performance test parameters of the lithium ion battery separator of the disclosure Basis Tensile Average Maximum Heat Shrinkage Weight Thickness Strength Pore Size Pore Size Rate % at Strength Parameters g/m.sup.2 μm N/m μm μm 300° C. Retention Example 1 19.9 25.3 1145 0.28 0.86 1.7 Δ Example 2 20.2 25.8 1372 0.36 0.95 1.8 Δ Example 3 20.0 25.9 903 0.34 0.92 1.8 Δ Example 4 20.0 24.5 888 0.25 0.80 1.7 Δ Example 5 20.2 24.7 1042 0.26 0.82 1.2 ∘ Example 6 20.2 25.1 1271 0.28 0.85 1.4 ∘ Example 7 19.9 25.2 843 0.28 0.84 1.3 ∘ Example 8 20.2 23.9 810 0.22 0.68 1.2 ∘ Example 9 19.7 23.8 780 0.20 0.66 1.0 ∘ Example 10 20.2 24.1 985 0.22 0.68 1.0 ∘ Example 11 19.8 24.2 750 0.21 0.67 1.0 ∘ Example 12 20.1 23.3 730 0.16 0.60 0.8 ∘ Example 22 20.1 25.2 1233 0.28 0.86 1.4 Δ Example 23 20.2 25.1 1275 0.28 0.85 1.5 Δ Example 24 20.0 25.3 1254 0.28 0.85 1.4 Δ Example 25 19.8 25.1 1226 0.28 0.87 1.4 ∘ Example 41 19.9 24.6 1018 0.26 0.82 1.2 Δ Example 42 20.2 24.8 1042 0.26 0.83 1.3 ∘ Example 43 20.1 24.7 1032 0.26 0.82 1.4 Δ Example 44 19.8 24.6 1135 0.26 0.82 1.2 Δ Example 45 19.9 24.2 1004 0.21 0.67 1.0 Δ Example 46 20.1 24.3 996 0.21 0.67 1.0 Δ Example 47 20.1 25.9 1387 0.34 0.92 2.0 Δ Example 48 19.8 25.8 1356 0.34 0.93 1.8 Δ Example 61 20.1 24.6 996 0.25 0.81 1.3 ∘ Example 62 20.0 24.7 975 0.26 0.82 1.2 ∘ Example 63 19.9 25.3 970 0.26 0.83 1.2 Δ Note: The lithium ion battery separator of the disclosure has a heat shrinkage rate of zero at 110° C., and shrinkage only begins when it is close to 300° C.

(93) TABLE-US-00005 TABLE 5 Performance test parameters of the lithium ion battery separator Basis Tensile Average Maximum Heat Shrinkage Weight Thickness Strength Pore Size Pore Size Rate % at Strength Parameters g/m.sup.2 μm N/m μm μm 300° C. Retention Comparative 19.8 26.3 1383 0.84 25.3 Melting x Example 1′ Comparative 20.2 25.5 1232 0.65 4.52 5.0 Δ Example 2′ Comparative 20.1 24.8 1178 0.36 2.26 3.5 ∘ Example 3′ Comparative 20.1 25.3 1094 0.34 2.13 1.2 ∘ Example 4′ Comparative 19.9 25.1 514 0.28 0.85 1.2 ∘ Example 5′ Comparative 19.8 23.9 565 0.26 0.82 1.8 Δ Example 6′ Comparative 19.9 23.9 550 0.26 0.83 1.8 Δ Example 7′ Comparative 20.2 23.4 523 0.18 0.62 1.0 ∘ Example 8′ Comparative 19.8 25.1 482 0.28 0.85 1.2 ∘ Example 9′ Comparative 19.9 25.1 673 0.28 0.85 1.2 ∘ Example 10′ Comparative 15.9 20.1 937 0.75 5.54 10.0 Δ Example 11′

(94) It can be seen from Table 4 that the lithium ion battery separators obtained in Examples 1-12, 22-25, 41-48 and 61-63 of the disclosure are consisted of the lithium ion battery separator substrate of the disclosure and an inorganic coating. Compared with the prior art battery separators, the lithium ion battery separator of the disclosure has a heat shrinkage rate of zero at 110° C. with excellent strength retention and excellent heat stability. The heat shrinkage rate at 300° C. for 1 h is no more than 2%, the maximum pore diameter is less than 1 μm, and the strength is greater than 700 N/m.

(95) It can be seen from Table 5 that in Comparative Example 1′, the separator prepared by the single-layer substrate only made of PET fibers has pinholes, wherein the pore size is too large, and melting occurs at 300° C.; in Comparative Example 2′, the separator prepared by the single-layer substrate made of PET fibers and fibrillated lyocell nanofibers has pinholes with too large pore size, the heat shrinkage rate of the separator is 5.0% after treatment at 300° C. for 1 h, and the separator is damaged after folding; in Comparative Example 3′, the separator with double-layer substrate is made by a HYDROFORMER™, a type of double-layer hydraulic inclined wire former, and the dense layer of the separator is added with 20% stretched PET fibers and 70% fibrillated PPTA fibers, so that the separator has a heat shrinkage rate of 3.5% after treatment at 300° C. for 1 hour; in Comparative Example 4′, the support layer does not use nanofibers, which causes the maximum pore diameter of the separator to be too large; in Comparative Examples 5′-10′, the separator strength cannot meet the requirements; in Comparative Example 11′, due to the substrate with large pores, the maximum pore diameter of the separator is too large, and there is no double-layer structure, the heat shrinkage rate is 10.0% after treatment at 300° C. for 1 hour.

(96) In addition, according to the performance test method described above, the disclosure verifies the performance parameters of the lithium ion battery separator, wherein the separator is obtained by respectively coating the inorganic coatings of different formulation compositions (shown in Table 3) on the lithium ion battery separator substrates prepared in Preparation Examples 1-63 of the disclosure. Below, only performance parameters of the lithium ion battery separators (Examples 10, 64-71) are shown, wherein the separators are respectively obtained by coating the pulp of the inorganic coating of the formulation shown in Table 3 on the substrate of Preparation Example 10 as an example. The results are shown in Table 6:

(97) TABLE-US-00006 TABLE 6 Performance test parameters of the lithium ion battery separator Basis Tensile Average Maximum Heat Shrinkage Weight Thickness Strength Pore Size Pore Size Rate % at Strength Parameters g/m.sup.2 μm N/m μm μm 300° C. Retention Example 10 20.2 23.1 985 0.22 0.68 1.0 ∘ (Formulation 1) Example 64 20.3 23.3 954 0.25 0.8 1.0 ∘ (Formulation 2) Example 65 20.1 23.2 934 0.26 0.82 1.0 ∘ (Formulation 3) Example 66 19.8 23.2 958 0.24 0.78 1.0 ∘ (Formulation 4) Example 67 19.9 22.7 1003 0.26 0.82 1.4 ∘ (Formulation 5) Example 68 20.2 22.9 978 0.34 0.92 1.0 ∘ (Formulation 6) Example 69 20.3 23.2 1026 0.24 0.78 1.4 ∘ (Formulation 7) Example 70 20.1 23.3 969 0.36 0.96 1.0 ∘ (Formulation 8) Example 71 20.1 23.3 965 0.23 0.75 1.0 ∘ (Formulation 9)

(98) It should be understood that the disclosure described herein is not limited to specific methodologies, experimental protocols, or reagents, as these may vary. The discussion and examples provided herein are presented to describe specific embodiments and are not intended to limit the scope of the disclosure, which is limited only by the claims.