Polymer composite membrane, preparation method for same, and lithium-ion battery including same

1. A polymer composite membrane,

comprising a porous base membrane;

a heat-resistant fiber layer covering at least one side surface of the porous base membrane, wherein materials of the heat-resistant fiber layer contain a first polymeric material and a second polymeric material; the first polymeric material is a heat-resistant polymeric material whose melting point is above 180° C.; and the melting point of the second polymeric material is lower than that of the first polymeric material, and a liquid absorption rate of the second polymeric material in an electrolyte at 25° C. is above 40% and has an error of ±5%; and

a bonding layer formed on an outermost side of at least one side surface of the polymer composite membrane, the bonding layer comprising:

an acrylate crosslinked polymer, a styrene-acrylate crosslinked copolymer and a vinylidene fluoride-hexafluoropropylene copolymer, or

an acrylate crosslinked polymer and a styrene-acrylate crosslinked copolymer, or

an acrylate crosslinked polymer and a vinylidene fluoride-hexafluoropropylene copolymer, and the porosity of the bonding layer is 40% to 65%; and

wherein the glass transition temperature of the acrylate crosslinked polymer is −20° C. to 60° C., the glass transition temperature of the styrene-acrylate crosslinked copolymer is −30° C. to 50° C., and the glass transition temperature of the vinylidene fluoride-hexafluoropropylene copolymer is −65° C. to −40° C.

2. The polymer composite membrane according to claim 1 , wherein a liquid absorption rate of the first polymeric material in an electrolyte at 25° C. is below 5% and has an error of ±5%; and a liquid absorption rate of the second polymeric material in an electrolyte at 25° C. is 40% to 100% and has an error of ±5%.

3. The polymer composite membrane according to claim 1 , wherein the glass transition temperature of the first polymeric material is above 100° C.; and the melting point of the second polymeric material is 100° C. to 150° C.; and optionally, the glass transition temperature of the second polymeric material is below 25° C.

4. The polymer composite membrane according to claim 1 , wherein a weight ratio between the first polymeric material and the second polymeric material in the heat-resistant fiber layer is (0.5 to 10):1.

5. The polymer composite membrane according to claim 1 , wherein

the first polymeric material is selected from one or more of polyetherimide, poly(ether ether ketone), polyether sulfone, polyamide-imide, polyamic acid, and polyvinylpyrrolidone; and

the second polymeric material is selected from one or more of modified polyvinylidene fluoride, polyacrylate, polyphenyl ethylene, and polyethylene oxide.

6. The polymer composite membrane according to claim 5 , wherein the first polymeric material is polyetherimide, and the second polymeric material is polyvinylidene fluoride-hexafluoropropylene.

7. The polymer composite membrane according to claim 1 , wherein the diameter of fiber in the heat-resistant fiber layer is 100 nm to 2000 nm, and the thickness of the heat-resistant fiber layer is 0.5 μm to 30 μm.

8. The polymer composite membrane according to claim 1 , wherein the heat-resistant fiber layer has a porosity of 75% to 93% and a surface density of 0.2 g/m 2 to 15 g/m 2 .

9. The polymer composite membrane according to claim 1 , wherein the porous base membrane is:

a polymer base membrane, which is a polyolefin membrane, or

a ceramic membrane comprising a polymer base membrane and a ceramic layer formed on at least a side surface of the polymer base membrane, wherein the polymer base membrane is a polyolefin membrane,

and the heat-resistant fiber layer is located on a surface on a side of the ceramic membrane on which the ceramic layer is formed.

10. The polymer composite membrane according to claim 9 , wherein the ceramic layer contains ceramic particles and a binder, and a surface density ρ of the ceramic layer at a thickness of 1 μm satisfies 1.8 mg/cm 2 <ρ≤2.7 mg/cm 2 ;

the ceramic particles are selected from one or more of Al 2 O 3 , SiO 2 , BaSO 4 , BaO, TiO 2 , CuO, MgO, Mg(OH) 2 , LiAlO 2 , ZrO 2 , carbon nanotube (CNT), BN, SiC, Si 3 N 4 , WC, B 4 C, AlN, Fe 2 O 3 , BaTiO 3 , MoS 2 , α-V 2 O 5 , PbTiO 3 , TiB 2 , CaSiO 3 , molecular sieve, clay, boehmite, and kaolin, and optionally, an average particle size of the ceramic particles is 200 nm to 800 nm;

the binder is polyacrylate whose glass transition temperature satisfies −40° C. to 0° C.; and

the single-sided thickness of the ceramic layer is 1 μm to 5 μm.

11. The polymer composite membrane according to claim 9 , wherein in the ceramic layer, relative to the ceramic particles of 100 parts by weight, the content of the binder is 2 to 8 parts by weight;

in the ceramic layer, relative to the ceramic particles of 100 parts by weight, a dispersant of 0.3 to 1 part by weight, a thickener of 0.5 to 1.8 parts by weight, and a surface treating agent of 0 to 1.5 parts by weight are further comprised, and the number-average molecular weight of the dispersant is below 50000;

the dispersant is at least one of polyacrylate, aliphatic polyglycol ether, silicates, phosphates, and guar gum;

the thickener is at least one of polyacrylate having a number-average molecular weight of 300000 to 1500000, a polyacrylate copolymer, polyvinylpyrrolidone, a cellulose derivative, and polyacrylamide; and

the surface treating agent is 3-glycidyloxypropyltrimethoxysilane and/or 3-glycidyloxypropyltriethoxysilane.

12. The polymer composite membrane according to claim 1 , wherein

the bonding layer contains the acrylate crosslinked polymer and the styrene-acrylate crosslinked copolymer and does not contain the vinylidene fluoride-hexafluoropropylene copolymer, and a weight ratio of the acrylate crosslinked polymer to the styrene-acrylate crosslinked copolymer is 1:(0.05 to 2); or

the bonding layer contains the acrylate crosslinked polymer and the vinylidene fluoride-hexafluoropropylene copolymer and does not contain the styrene-acrylate crosslinked copolymer, and a weight ratio of the acrylate crosslinked polymer to the vinylidene fluoride-hexafluoropropylene copolymer is 1:(0.3 to 25); or

the bonding layer contains the acrylate crosslinked polymer, the styrene-acrylate crosslinked polymer, and the vinylidene fluoride-hexafluoropropylene copolymer, and a weight ratio between the acrylate crosslinked polymer, the styrene-acrylate crosslinked copolymer and the vinylidene fluoride-hexafluoropropylene copolymer is 1:(0.01 to 2):(0.3 to 5).

13. The polymer composite membrane according to claim 1 , wherein the acrylate crosslinked polymer is:

a mixture of a first acrylate crosslinked polymer and a second acrylate crosslinked polymer and/or a third acrylate crosslinked polymer, or

a second acrylate crosslinked polymer, or

a third acrylate crosslinked polymer;

the first acrylate crosslinked polymer contains a polymethyl methacrylate chain segment of 70 to 80 wt %, a polyethylene acrylate chain segment of 2 to 10 wt %, a polybutyl acrylate chain segment of 10 to 20 wt %, and a polyacrylic acid chain segment of 2 to 10 wt %, the second acrylate crosslinked polymer contains a polymethyl methacrylate chain segment of 30 to 40 wt %, a polyethylene acrylate chain segment of 2 to 10 wt %, a polybutyl acrylate chain segment of 50 to 60 wt %, and a polyacrylic acid chain segment of 2 to 10 wt %, and the third acrylate crosslinked polymer contains a polymethyl methacrylate chain segment of 50 to 80 wt %, a polyethylene acrylate chain segment of 2 to 10 wt %, a polybutyl acrylate chain segment of 15 to 40 wt %, and a polyacrylic acid chain segment of 2 to 10 wt %; the glass transition temperature of the first acrylate crosslinked polymer is 50° C. to 60° C., the glass transition temperature of the second acrylate crosslinked polymer is −20° C. to −5° C., and the glass transition temperature of the third acrylate crosslinked polymer is 30° C. to 50° C.;

the styrene-acrylate crosslinked copolymer contains a polyphenyl ethylene chain segment of 40 to 50 wt %, a polymethyl methacrylate chain segment of 5 to 15 wt %, a polyethylene acrylate chain segment of 2 to 10 wt %, a polybutyl acrylate chain segment of 30 to 40 wt %, and a polyacrylic acid chain segment of 2 to 10 wt %; and the glass transition temperature of the styrene-acrylate crosslinked copolymer is 15° C. to 30° C.; and

the vinylidene fluoride-hexafluoropropylene copolymer contains a vinylidene fluoride chain segment of 80 to 98 wt % and a hexafluoropropylene chain segment of 2 to 20 wt %; and

the glass transition temperature of the vinylidene fluoride-hexafluoropropylene copolymer is −60° C. to −40° C.

14. The polymer composite membrane according to claim 1 , wherein

the bonding layer contains a first acrylate crosslinked polymer, a second acrylate crosslinked polymer and the styrene-acrylate crosslinked copolymer and does not contain the vinylidene fluoride-hexafluoropropylene copolymer, and a weight ratio between the first acrylate crosslinked polymer, the second acrylate crosslinked polymer, and the styrene-acrylate crosslinked copolymer is (5 to 10):1:(10 to 13); or

the bonding layer contains a first acrylate crosslinked polymer, a second acrylate crosslinked polymer, and the vinylidene fluoride-hexafluoropropylene copolymer and does not contain the styrene-acrylate crosslinked copolymer, and a weight ratio between the first acrylate crosslinked polymer, the second acrylate crosslinked polymer, and the vinylidene fluoride-hexafluoropropylene copolymer is (5 to 15):1:(5 to 12); or

the bonding layer contains a second acrylate crosslinked polymer and the vinylidene fluoride-hexafluoropropylene copolymer and does not contain the styrene-acrylate crosslinked copolymer, and a weight ratio between the second acrylate crosslinked polymer and the vinylidene fluoride-hexafluoropropylene copolymer is 1:(15 to 20); or

the bonding layer contains a second acrylate crosslinked polymer, the styrene-acrylate crosslinked copolymer, and the vinylidene fluoride-hexafluoropropylene copolymer, and a weight ratio between the second acrylate crosslinked polymer, the styrene-acrylate crosslinked copolymer, and the vinylidene fluoride-hexafluoropropylene copolymer is 1:(0.5 to 2):(1 to 5); or

the bonding layer contains a third acrylate crosslinked polymer, the styrene-acrylate crosslinked copolymer, and the vinylidene fluoride-hexafluoropropylene copolymer, and a weight ratio between the third acrylate crosslinked polymer, the styrene-acrylate crosslinked polymer, and the vinylidene fluoride-hexafluoropropylene copolymer is 1:(0.5 to 2):(1 to 5); or

the bonding layer contains a first acrylate crosslinked polymer, a second acrylate crosslinked polymer, the styrene-acrylate crosslinked copolymer, and the vinylidene fluoride-hexafluoropropylene copolymer, and a weight ratio between the first acrylate crosslinked polymer, the second acrylate crosslinked polymer, the styrene-acrylate crosslinked copolymer, and the vinylidene fluoride-hexafluoropropylene copolymer is (10 to 15):1:(0.5 to 2):(5 to 10), wherein

the first acrylate crosslinked polymer contains a polymethyl methacrylate chain segment of 70 to 80 wt %, a polyethylene acrylate chain segment of 2 to 10 wt %, a polybutyl acrylate chain segment of 10 to 20 wt %, and a polyacrylic acid chain segment of 2 to 10 wt %, the second acrylate crosslinked polymer contains a polymethyl methacrylate chain segment of 30 to 40 wt %, a polyethylene acrylate chain segment of 2 to 10 wt %, a polybutyl acrylate chain segment of 50 to 60 wt %, and a polyacrylic acid chain segment of 2 to 10 wt %, and the third acrylate crosslinked polymer contains a polymethyl methacrylate chain segment of 50 to 80 wt %, a polyethylene acrylate chain segment of 2 to 10 wt %, a polybutyl acrylate chain segment of 15 to 40 wt %, and a polyacrylic acid chain segment of 2 to 10 wt %; the styrene-acrylate crosslinked copolymer contains a polyphenyl ethylene chain segment of 40 to 50 wt %, a polymethyl methacrylate chain segment of 5 to 15 wt %, a polyethylene acrylate chain segment of 2 to 10 wt %, a polybutyl acrylate chain segment of 30 to 40 wt %, and a polyacrylic acid chain segment of 2 to 10 wt %; the vinylidene fluoride-hexafluoropropylene copolymer contains a vinylidene fluoride chain segment of 80 to 98 wt % and a hexafluoropropylene chain segment of 2 to 20 wt %; and the glass transition temperature of the first acrylate crosslinked polymer is 50° C. to 60° C., the glass transition temperature of the second acrylate crosslinked polymer is −20° C. to −5° C., and the glass transition temperature of the third acrylate crosslinked polymer is 30° C. to 50° C., the glass transition temperature of the styrene-acrylate crosslinked copolymer is 15° C. to 30° C., and the glass transition temperature of the vinylidene fluoride-hexafluoropropylene copolymer is −60° C. to −40° C.

15. The polymer composite membrane according to claim 1 , wherein the bonding layer further contains at least one of an acrylonitrile-acrylate copolymer, a vinyl chloride-propylene copolymer, and a butadiene-styrene copolymer;

when the bonding layer further contains the acrylonitrile-acrylate copolymer, and a weight ratio between the acrylonitrile-acrylate copolymer and the acrylate crosslinked polymer is (0.05 to 2):1;

when the bonding layer further contains the vinyl chloride-propylene copolymer, and a weight ration between the vinyl chloride-propylene copolymer and the acrylate crosslinked polymer is (0.15 to 7):1; and

when the bonding layer further contains the butadiene-styrene copolymer, and a weight ratio between the butadiene-styrene copolymer and the acrylate crosslinked polymer is (0.05 to 2):1.

16. The polymer composite membrane according to claim 1 , wherein the single-sided surface density of the bonding layer is 0.05 mg/cm 2 to 0.9 mg/cm 2 ; and the single-sided thickness of the bonding layer is 0.1 μm to 1 μm.

17. A lithium-ion battery, comprising a positive electrode, a negative electrode, and a battery membrane located between the positive electrode and the negative electrode, wherein the battery membrane is the polymer composite membrane according to claim 1 .

18. A method for preparing a polymer composite membrane, comprising the following steps:

S 1 : providing a porous base membrane;

S 2 : preparing a spinning solution containing a first polymeric material and a second polymeric material, and forming a heat-resistant fiber layer on at least one side surface of the porous base membrane through electrostatic spinning by using the spinning solution, wherein the first polymeric material is a heat-resistant polymeric material whose melting point is above 180° C.; and the melting point of the second polymeric material is lower than that of the first polymeric material, and a liquid absorption rate of the second polymeric material in an electrolyte at 25° C. is above 40% and has an error of ±5%; and

S 3 : forming a bonding layer on at least one side surface of the polymer composite membrane, the bonding layer comprising:

an acrylate crosslinked polymer, a styrene-acrylate crosslinked copolymer and a vinylidene fluoride-hexafluoropropylene copolymer, or

an acrylate crosslinked polymer and a styrene acrylate crosslinked copolymer, or

an acrylate crosslinked polymer and a vinylidene fluoride-hexafluoropropylene copolymer, and the porosity of the bonding layer is 40% to 65%; and

wherein:

the glass transition temperature of the acrylate crosslinked polymer is −20° C. to 60° C., the glass transition temperature of the styrene-acrylate crosslinked copolymer is −30° C. to 50° C., and the glass transition temperature of the vinylidene fluoride-hexafluoropropylene copolymer is −65° C. to −40° C.

a liquid absorption rate of the first polymeric material in an electrolyte at 25° C. is below 5% and has an error of ±5%;

the glass transition temperature of the first polymeric material is above 100° C.;

the melting point of the second polymeric material is 100° C. to 150° C.; and optionally, the glass transition temperature of the second polymeric material is below 25° C.; and

a liquid absorption rate of the second polymeric material in an electrolyte at 25° C. is 40% to 100% and has an error of ±5%.