Aqueous binder for lithium ion battery, preparation method therefor and use thereof

Abstract

An aqueous binder for a lithium ion battery, a preparation method and a use thereof. The binder is an inorganic-organic composite emulsion, comprising a dispersing agent, inorganic nanoparticles, (methyl)acrylate monomers, unsaturated carboxylic acid monomers, vinyl hydrocarbon monomers and optionally copolymers of other copolymerizable monomers, wherein the dispersing agent is a water-soluble cellulose grafted amphiphilic copolymer. When the water-soluble cellulose grafted amphiphilic copolymer is used as the dispersing agent, the agglomeration of the nanoparticles when the binder is formed into a film can be avoided, and at the same time, the effects of toughening and improving the binding strength can be achieved. Meanwhile, the water-soluble cellulose has certain strengthening and toughening properties so that the aqueous binder has an excellent anti-tensile performance. The aqueous binder for a lithium ion battery can be used for lithium ion batteries.

Claims

1. An aqueous binder for a lithium ion battery, wherein the binder is an inorganic-organic composite emulsion comprising a dispersant, inorganic nanoparticles, and copolymers of (methyl)acrylate monomers, unsaturated carboxylic acid monomers, alkenyl-containing monomers and optionally other copolymerizable monomers, wherein the dispersant is a water-soluble cellulose grafted with amphiphilic copolymer; wherein, the alkenyl-containing monomers are selected from any one of vinyl acetate, styrene, -methyl styrene, sodium styrene sulfonate or sodium methyl vinyl sulfonate, or a combination of at least two of them.

2. The aqueous binder of claim 1, wherein the dispersant is in an amount of 0.5-25 wt % of the total mass of solids of the composite emulsion; wherein, the mass ratio of water-soluble cellulose to amphiphilic copolymer is 2/98 to 40/60; wherein, the dispersant has a weight average molecular weight of 100-1,000,000.

3. The aqueous binder of claim 1, wherein the water-soluble cellulose is any one of sodium carboxymethylcellulose, sodium carboxyethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose or hydroxypropylcellulose, or a mixture of at least two of them; wherein, the water-soluble cellulose contains a hydroxyl group capable of grafting, and the hydroxyl group has a mass of 10-20 wt % of the mass of the water-soluble cellulose.

4. The aqueous binder of claim 1, wherein the comonomers of the amphiphilic copolymer comprise hydrophilic monomer, hydrophobic monomer, optionally amphiphilic monomer, and optionally crosslinking monomer; wherein, the mass ratio of the hydrophilic monomer to the hydrophobic monomer is 10/100 to 80/20; wherein, the amphiphilic monomer is added in an amount of 0-40 wt % of the mass of the amphiphilic copolymer; wherein, if present, the crosslinking monomer is added in an amount of 0.01-5 wt % of the mass of the amphiphilic copolymer; wherein, the hydrophilic monomer is selected from any one of fumaric acid, (meth)acrylic acid, itaconic acid, sodium p-styrene sulfonate, sodium vinylsulfonate, sodium allylsulfonate, sodium 2-methylallyl sulfonate, sodium ethyl methacrylate sulfonate, (meth)acrylamide, N-methylol acrylamide, N,N-dimethylacrylamide or 2-acrylamide-2-methylpropanesulfonic acid, or a combination of at least two of them; wherein, the hydrophobic monomer is selected from any one of styrene, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate or 2-ethylhexyl (meth)acrylate, or a combination of at least two of them; wherein, the amphiphilic monomer is selected from any one of lauryl alcohol polyoxyethylene ether (meth)acrylate, stearic acid polyoxyethylene ether (meth)acrylate or nonylphenol polyoxyethylene ether (meth)acrylate, or a combination of at least two of them; wherein, the crosslinking monomer is selected from any one of glycidyl (meth)acrylate, methylene bisacrylamide, divinylbenzene or (ethylene glycol).sub.n di(meth)acrylate, or a combination of at least two of them, wherein n=1-35.

5. The aqueous binder of claim 1, wherein the inorganic nanoparticles are any one of nano-silica, alumina, aluminum silicate, calcium sulfate or wollastonite, or a combination of at least two of them.

6. The aqueous binder of claim 5, the inorganic nanoparticles are surface-modified by a silane coupling agent; wherein, the mass ratio of the silane coupling agent to inorganic nanoparticles is 0.01-0.3/1; wherein, the silane coupling agent is any one of vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(-methoxyethoxy)silane, -methacryloxypropyl trimethoxysilane or -methacryloxypropyltriethoxysilane, or a combination of at least two of them.

7. The aqueous binder of claim 1, wherein the (meth)acrylate monomers are selected from any one of methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, n-pentyl acrylate, isoamyl acrylate, n-hexyl acrylate, isooctyl acrylate, hydroxypropyl acrylate, 2-hydroxyethyl acrylate, lauryl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, n-pentyl methacrylate, n-hexyl methacrylate, isooctyl methacrylate, hydroxypropyl methacrylate or 2-hydroxyethyl methacrylate, or a combination of at least two of them; wherein, the unsaturated carboxylic acid monomers are selected from any one of lithium acrylate, acrylic acid, lithium methacrylate, methacrylic acid, lithium itaconate or itaconic acid, or a combination of at least two of them; wherein, said other copolymerizable monomers are selected from any one of acrylamide, N-methylolacrylamide, N-vinylpyrrolidone, vinylpyridine, vinylimidazole, vinyl acetate, vinyl propionate or vinyl butyrate, or a mixture of at least two of them.

8. The aqueous binder of claim 1, wherein the mass ratio of inorganic nanoparticles to copolymers of (methyl)acrylate monomers, unsaturated carboxylic acid monomers, alkenyl-containing monomers and optionally other copolymerizable monomers is 0.001-6/99.999-94; wherein, the sum of mass of the inorganic nanoparticles and the copolymers of (methyl)acrylate monomers, unsaturated carboxylic acid monomers, alkenyl-containing monomers and optionally other copolymerizable monomers is 25-55 wt % of the mass of the composite emulsion.

9. The aqueous binder of claim 8, wherein the composite emulsion has a core-shell structure, wherein the core-shell structure has more than one shell layer with the inorganic nanoparticles as the cores; wherein an innermost layer of the shell layers has a glass transition temperature lower than that of an outermost layer of the shell layers; wherein the glass transition temperatures of adjacent shell layers differ by 30 to 30 C., and the glass transition temperature of the innermost shell layer is 25 to 30 C.; wherein, the composite emulsion has a glass transition temperature of 30 to 90 C.; wherein, the composite emulsion has a pH of 6-10; wherein, the composite emulsion has a solid content of 25-55 wt %.

10. A method for producing the aqueous binder for a lithium ion battery of claim 1, comprising in-situ polymerizing the dispersant, the inorganic nanoparticles and the (meth)acrylate monomers, the unsaturated carboxylic acid monomers, the alkenyl-containing monomers, and optionally other copolymerizable monomers, to obtain the above aqueous binder; wherein the dispersant is prepared by free radical polymerization of the water-soluble cellulose and comonomers of the amphiphilic copolymer.

11. The method of claim 10, wherein, the mass ratio of the water-soluble cellulose to the amphiphilic copolymer is 2/98 to 40/60; wherein, the comonomers of the amphiphilic copolymer comprise hydrophilic monomer, hydrophobic monomer, optionally amphiphilic monomer, and optionally crosslinking monomer; wherein, the mass ratio of the hydrophilic monomer to the hydrophobic monomer is 10/100 to 80/20; wherein, the amphiphilic monomer is added in an amount of 0-40 wt % of the mass of the amphiphilic copolymer; wherein, the crosslinking monomer, if present, is added in an amount of 0.01-5 wt % of the mass of the amphiphilic copolymer.

12. The method of claim 10, wherein when preparing the dispersant, a chain transfer agent is added in an amount of 0.01-5% of the mass of the comonomers of the amphiphilic copolymer; wherein, the chain transfer agent is selected from any one of dodecyl mercaptan, tert-dodecyl mercaptan or isooctyl thioglycolate, or a combination of at least two of them.

13. The method of claim 10, wherein the dispersant is prepared using a free radical polymerization system, wherein the radical polymerization system is previously neutralized with a 10-20% alkaline compound aqueous solution to a pH of 5-8; wherein, the alkaline compound is any one of lithium hydroxide, sodium hydroxide, potassium hydroxide or sodium bicarbonate, or a combination of at least two of them.

14. The method of claim 10, wherein the water-soluble cellulose contains a hydroxyl group capable of grafting, and the hydroxyl group has a mass fraction of 10-20 wt % of the mass of the water-soluble cellulose.

15. The method of claim 10, wherein the inorganic nanoparticles are surface-modified with a silane coupling agent, and the surface modification method is as follows: the silane coupling agent is added to an alcohol-water solution of the inorganic nanoparticles and the pH of the solution is adjusted to 8-10, and then the mixture was stirred and reacted at 20-70 C. for 3-24 hours to obtain surface-modified inorganic nanoparticles; wherein, the mass ratio of the silane coupling agent to the inorganic nanoparticles is 0.01-0.3/1; wherein, the silane coupling agent is any one of vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(-methoxyethoxy)silane, -methacryloxypropyl trimethoxysilane or -methacryloxypropyltriethoxysilane, or a combination of at least two of them.

16. The method of claim 10, wherein the in-situ polymerization of the dispersant, the inorganic nanoparticles and the (meth)acrylate monomers, the unsaturated carboxylic acid monomers, the alkenyl-containing monomers, and the optionally other copolymerizable monomers includes the following steps: (a) adding the inorganic nanoparticles to an aqueous solution of the dispersant, and after dispersing, adding a portion of the (meth)acrylate monomers, the unsaturated carboxylic acid monomers, the alkenyl-containing monomers, and the optionally other copolymerizable monomers and an initiator; carrying out polymerization under stirring to obtain an inorganic-organic seed composite emulsion; (b) adding an additional portion of the (meth)acrylate monomers, the unsaturated carboxylic acid monomers, the alkenyl-containing monomers, the optionally other copolymerizable monomers and the initiator to the inorganic-organic seed composite emulsion, and carrying out polymerization under stirring to obtain an inorganic-organic composite emulsion.

17. The method of claim 16, wherein step (b) is repeated 1-3 times; wherein, in step (a), the dispersant is in an amount of 1-25% of the total mass of the (meth)acrylate monomers, the unsaturated carboxylic acid monomers, the alkenyl-containing monomers and the optionally other copolymerizable monomers; wherein, in step (a), the mass fraction of the inorganic nanoparticles is 0.1-25 wt % of the solid mass of the dispersant; wherein, in step (a), the dispersion is performed for not less than 20 minutes with an emulsifying and dispersing machine at 300-3,000 rpm to disperse the inorganic nanoparticles; wherein, the polymerization reaction time in step (a) is 3-6 h; wherein, in both step (a) and step (b), the comonomers and the initiator are added and polymerization is performed independently at 30-90 C.; wherein, the initiator is any one of organic peroxide initiator, inorganic peroxide initiator or redox initiator, or a combination of at least two of them; wherein, the organic peroxide initiator is selected from benzoyl peroxide and/or dicumyl peroxide; wherein, the inorganic peroxide initiator is selected from ammonium persulfate, sodium persulfate or potassium persulfate; wherein, the redox initiator is selected from a combination of ammonium persulfate/sodium sulfite, or a combination of ammonium persulfate/sodium bisulfite; wherein, the mass of the initiator is 0.1-2 wt % of the total mass of the (meth)acrylate monomers, the unsaturated carboxylic acid monomers, the alkenyl-containing monomers, and the optionally other copolymerizable monomers; wherein, the mass of the (meth)acrylate monomers, the unsaturated carboxylic acid monomers, the alkenyl-containing monomers and the optionally other copolymerizable monomers in step (b) is 15-85 wt % of the total mass of the (meth)acrylate monomers, the unsaturated carboxylic acid monomers, the alkenyl-containing monomers, and the optionally other copolymerizable monomers.

18. The method of claim 16, wherein the method further comprises: adjusting the pH of the composite emulsion when the polymerization reaction is completed, wherein adjusting the pH of the composite emulsion is to be a pH of 6-10; wherein, this pH adjustment is achieved by alkali neutralization; wherein, the inorganic-organic seed composite emulsion has a glass transition temperature of 30 to 90 C.; wherein, the inorganic-organic composite emulsion has a glass transition temperature of 30 to 90 C.

19. The method of claim 16, wherein the method for preparing the aqueous binder for a lithium ion battery includes the following steps: (1) preparing a the dispersant by free radical polymerization of the water-soluble cellulose and comonomers of the amphiphilic copolymer; (2) adding a silane coupling agent to an alcohol-water mixed solution of the inorganic nanoparticles, adjusting the pH to 8-10 with ammonia, and then stirring and reacting the mixture at 20-70 C. for 3-24 h to obtain surface-modified inorganic nanoparticles; (3) adding the surface-modified inorganic nanoparticles obtained in the step (2) to a deionized water solution containing the dispersant which accounts for 2-15% of the total mass of the (meth)acrylate monomers, the unsaturated carboxylic acid monomers, the alkenyl-containing monomers and the optionally other copolymerizable monomers, carrying out dispersion for not less than 20 minutes with an emulsifying and dispersing machine at 800-3,000 rpm, and then adding a portion of the (meth)acrylate monomers, the unsaturated carboxylic acid monomers, the alkenyl-containing monomers, the optionally other copolymerizable monomers and initiator and carrying out polymerization reaction for 3-6 h under stirring to prepare an inorganic-organic seed composite emulsion; (4) adding an additional portion of the (meth)acrylate monomers, the unsaturated carboxylic acid monomers, the alkenyl-containing monomers, the optionally other copolymerizable monomers and the initiator to the inorganic-organic seed composite emulsion obtained in the step (3) at 60-90 C., and carrying out polymerization reaction under stirring; (5) alkali neutralization to obtain an inorganic-organic composite emulsion having a pH of 6-10, that is, an aqueous binder for a lithium ion battery.

20. A lithium ion battery comprising the aqueous binder of claim 1.

Description

DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a SEM image of the surface-modified nano-silica of Example 1;

(2) FIG. 2 is a DSC chart of the binder of Example 3.

DETAILED DESCRIPTION

(3) The technical solutions of the present disclosure are further explained by specific examples in combination with the drawings hereinafter.

Example 1

(4) Surface Modification of Inorganic Nanoparticles: 20 parts by mass of silica having an average particle size of 50 nm were dispersed in a mixture of ethanol and deionized water, ammonia water was added to adjust pH to 8-10 under stirring at room temperature, and 2 parts by mass of vinyl triethoxysilane were added. Then the mixture was heated to 70 C. and reacted for 1 h before being cooled to room temperature to obtain surface-modified nano-silica.

(5) Preparation of Dispersant: 2.5 parts by mass of hydroxyethyl cellulose were dissolved in 250 parts by mass of deionized water. Then the solution was heated to 75 C., and was previously neutralized with 20% alkaline aqueous solution of lithium hydroxide to pH=5-8. Then 0.6 parts by mass of ammonium persulfate were added therein, and 2 parts by mass of hydrophilic monomer sodium p-styrene sulfonate, 8 parts by mass of methacrylic acid, 10 parts by mass of hydrophobic monomer butyl acrylate, 0.06 parts by mass of crosslinking monomer glycidyl acrylate were added therein.

(6) Inorganic-organic seed composite emulsion: 250 parts by mass of the dispersant solution prepared above and 2 parts by mass of surface-modified silica were added to 50 parts by mass of deionized water. The mixture was emulsified and dispersed at 800 rpm for 30 min. 100 parts by mass of mixed monomers containing 40 w % of methyl methacrylate (MMA), 58 w % of butyl acrylate (BA) and 2 w % of acrylic acid (AA) and 0.6 parts by mass of ammonium persulfate were added under stirring after the temperature was raised to 70 C. Then the mixture was reacted for 6 hours to obtain an inorganic-organic seed composite emulsion.

(7) Inorganic-organic composite emulsion: 50 parts by mass of the inorganic-organic seed composite emulsion were added to 50 parts by mass of deionized water. At 75 C., 100 parts by mass of mixed monomers containing 56.6 w % of methyl methacrylate (MMA), 42.2 w % of butyl acrylate (BA) and 1.2 w % of methacrylic acid (AA) were added, with the mass ratio of core monomer to shell monomer being 1:2 (the mass ratio of core monomer to shell monomer is namely the mass ratio of the seed emulsion to the monomers added subsequently). Then the mixture was polymerized for 6 hours to obtain an inorganic-organic composite emulsion.

(8) The obtained composite emulsion was neutralized with lithium hydroxide solution having a mass fraction of 10%, to obtain an inorganic-organic composite emulsion having a solid content of 40%.

(9) Preparation of Battery Pole Piece

(10) The binder described in the above examples was used in the preparation of silicon-based/graphite composite negative electrode material pole piece.

(11) The silicon-based/graphite composite negative electrode material is preferably prepared by compositing SiOx/C or SiC composite material containing Si and C with natural graphite or artificial graphite.

(12) In the present invention, a silicon-based/graphite composite negative electrode material having a capacity per gram of 480 mAh/g is preferably used.

(13) A suitable amount of deionized water (based on the total solids content being 45%) was added to a mixture of 92.0 w % (mass fraction) of silicon-based composite negative electrode material, 4.0 w % of conductive additive, 2 w % (mass fraction) of thickener sodium carboxymethyl cellulose (denoted as CMC) and 2 w % (mass fraction, based on the solid content) of the aqueous binder of the above examples (denoted as PAA), to prepare a battery pole piece slurry. The uniformly dispersed slurry was passed through a 100-mesh screen, then coated on a 10-m-thick copper foil which was used as a current collector, dried at 120 C. for 5 minutes, and then rolled at a load per length of 1010.sup.4 N/m at room temperature to obtain an electrode pole piece.

Example 2

(14) An aqueous binder was prepared in the same manner as in Example 1, except that sodium carboxymethyl cellulose was used in the preparation of the dispersant.

Example 3

(15) An aqueous binder was prepared in the same manner as in Example 1, except that 10 parts by mass of hydrophilic monomer acrylic acid and 10 parts by mass of the hydrophobic monomer butyl acrylate were used as monomers in the preparation of the dispersant.

Example 4

(16) An aqueous binder was prepared in the same manner as in Example 1, except that 12 parts by mass of hydrophilic monomer sodium p-styrene sulfonate, 18 parts by mass of hydrophilic monomer methacrylic acid, and 20 parts by mass of hydrophobic monomer butyl acrylate were used as monomers in the preparation of the dispersant.

Example 5

(17) Different from Example 2, hydrophilic monomers, that is, 2 parts by mass of sodium styrene sulfonate and 8 parts by mass of methacrylic acid, were replaced with 10 parts by mass of amphiphilic monomer lauryl alcohol polyoxyethylene ether methacrylate.

Example 6

(18) Different from Example 1, the crosslinking monomer was replaced by n=5, (ethylene glycol).sub.5 diacrylate.

Example 7

(19) An aqueous binder was prepared in the same manner as in Example 1, except that the added amount of nano-silica was reduced from 2 parts by mass to 1 part by mass in the preparation of inorganic-organic composite seed emulsion.

Example 8

(20) Different from Example 2, the mass ratio of core monomer to shell monomer is 1:1.

Example 9

(21) Different from Example 2, the mass ratio of core monomer to shell monomer is 4:1.

Comparative Example 1

(22) Commercially available SBR from a company was used as a binder to prepare negative electrode pole piece according to the above examples. SBR binder was surface-carboxyl-modified styrene and butadiene copolymers prepared using a small molecule emulsifier.

Comparative Example 2

(23) Commercially available acrylic resin LA from a company was used as a binder to prepare negative electrode pole piece according to the above examples. LA binder was a water-soluble polyacrylic latex having a linear structure and not containing a emulsifier.

Comparative Example 3

(24) Binder PAA was prepared according to Example 2, with the sole exception that sodium dodecyl sulfonate/alkylphenol polyoxyethylene ether composite emulsifier was used as the dispersing agent to prepare the binder, and a negative electrode pole piece was prepared according to the above examples.

Comparative Example 4

(25) Binder PAA was prepared according to Example 2, with the sole exception that no water-soluble cellulose was contained in the preparation of dispersant, and a binder was prepared. In addition to the above matters, a lithium ion battery was prepared according to Example 1 and evaluated.

Comparative Example 5

(26) Binder PAA was prepared according to Example 2, with the sole exception that no inorganic nanoparticle was contained, and a binder was prepared. In addition to the above matters, a lithium ion battery was prepared according to Example 2 and evaluated.

Comparative Example 6

(27) Comparative Example 6 presents an inorganic-organic composite emulsion having a core-shell structure obtained by Example 1 disclosed in CN1944479A. A lithium ion battery was prepared according to Example 1 and evaluated.

(28) The following performance measurement and evaluation were conducted on the aqueous binders for lithium ion secondary battery prepared by the method of the present disclosure, and relevant pole piece formulas and test evaluation results are shown in Table 1 and Table 2.

(29) (Measurement of Average Particle Size)

(30) Measurements of average particle size and particle size distribution of inorganic-organic composite polymers were conducted by a laser particle analyzer.

(31) (Measurement of Glass Transition Temperature)

(32) Thermal analysis of inorganic-organic composite emulsions were conducted by a DSC thermal analyzer.

(33) (Determination of Peeling Strength)

(34) The electrode pole pieces of examples and comparative examples were cut into strips having a size of 10 cm2 cm. A 1 mm-thick steel plate was bonded to the current collector side with a double-sided adhesive tape, and a transparent adhesive tape was attached to the coating layer side. A tensile test machine was used to peel toward a direction of 180 at a speed of 100 mm/min, and to determine peeling strength.

(35) (Evaluation of Flexibility of Pole Pieces)

(36) A mandril having a diameter =3 mm was placed on the side of current collector of rolled pole pieces of the examples and the comparative examples, and bending test was performed. The state of the pole piece at this time was observed with a light microscope. If the pole piece was intact, it is marked as ; if shedding or cracking occurs, it is marked as x.

(37) (Evaluation of Battery Performance)

(38) Analog batteries were prepared by using the above pole pieces, and the first coulombic efficiency of charge and discharge cycle thereof and the coulombic efficiency and the capacity retention rate after 50 cycles thereof were measured by using a constant current method. After 50 charge and discharge cycles, the ratio of the increased thickness value of pole piece in the state of lithium insertion of the pole piece to the thickness value of the pole piece prior to charging and discharging is recorded as pole piece expansion rate (%).

(39) TABLE-US-00001 TABLE 1 Conductive Binders Active materials additives Amount Amount Amount Type (parts) Type (parts) Type (parts) Example 1 CMC/PAA 2/2 Silicon-based/ 92.0 SP/KS-6 2/2 graphite Example 2 CMC/PAA 2/2 Silicon-based/ 92.0 SP/KS-6 2/2 graphite Example 3 CMC/PAA 2/2 Silicon-based/ 92.0 SP/KS-6 2/2 graphite Example 4 CMC/PAA 2/2 Silicon-based/ 92.0 SP/KS-6 2/2 graphite Example 5 CMC/PAA 2/2 Silicon-based/ 92.0 SP/KS-6 2/2 graphite Example 6 CMC/PAA 2/2 Silicon-based/ 92.0 SP/KS-6 2/2 graphite Example 7 CMC/PAA 2/2 Silicon-based/ 92.0 SP/KS-6 2/2 graphite Example 8 CMC/PAA 2/2 Silicon-based/ 92.0 SP/KS-6 2/2 graphite Example 9 CMC/PAA 2/2 Silicon-based/ 92.0 SP/KS-6 2/2 graphite Comparative CMC/SBR 2/2 Silicon-based/ 92.0 SP/KS-6 2/2 Example 1 graphite Comparative CMC/LA 0.5/3.5 Silicon-based/ 92.0 SP/KS-6 2/2 Example 2 graphite Comparative CMC/PAA 2/2 Silicon-based/ 92.0 SP/KS-6 2/2 Example 3 graphite Comparative CMC/PAA 2/2 Silicon-based/ 92.0 SP/KS-6 2/2 Example 4 graphite Comparative CMC/PAA 2/2 Silicon-based/ 92.0 SP/KS-6 2/2 Example 5 graphite Comparative CMC/PAA 2/2 Silicon-based/ 92.0 SP/KS-6 2/2 Example 6 graphite

(40) Negative electrode pole pieces were prepared according to the formulas in Table 1, and were assembled into lithium-ion batteries.

(41) TABLE-US-00002 TABLE 2 Evaluation Items Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 T.sub.g ( C.) 0.1, 31 2, 32 0.2, 36 5, 40 0.5, 35 1.5, 35 3, 30 Particle size 350.6 280.2 380.3 290.7 260.5 420.1 270.1 (nm) Peeling 3.9 3.6 3.8 4.1 3.5 3.3 3.1 strength (mN/mm) Flexibility of pole piece First 480 480 480 480 480 480 480 discharge capacity (mAh) First 88 88 88 88 88 88 88 coulombic efficiency Capacity 91.1 92.1 91.6 88.9 89.5 88.8 90.1 retention rate after 50 cycles (%) pole piece 47.6 48.2 47.0 49.1 48.1 48.1 49.1 expansion rate after 50 cycles (%)

(42) TABLE-US-00003 TABLE 3 Comparative Comparative Comparative Comparative Comparative Comparative Evaluation Items Example 8 Example 9 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 T.sub.g ( C.) 0.5, 35 3, 35 18 5.1, 28 0.1, 36 5, 34 5, 32 40 Particle size 310.4 380.1 180 5000 260 510.1 270.1 450 (nm) Peeling strength 3.4 3.1 1.1 2.0 5.2 1.1 1.7 2.8 (mN/mm) Flexibility of pole piece First discharge 480 480 480 480 480 480 480 480 capacity (mAh) First coulombic 88 88 88 88 88 88 88 88 efficiency Capacity 89.6 86.7 90.1 74.4 70.1 76.1 85.1 65.1 retention rate after 50 cycles (%) pole piece 48.6 50.2 57 60 65 62.1 58.1 68.1 expansion rate after 50 cycles (%)

(43) As can be seen from Table 2 and Table 3 above, the electrodes using the binders according to Examples 1-9 of the present disclosure show considerably higher adhesive force and have high capacity retention rate after 50 charge and discharge cycles compared to the electrodes using the binders according to Comparative Examples 1-5, and pole piece expansion rates of the electrodes using the binders according to Examples 1-9 are all lower than that of Comparative Examples 1-5. Meantime, it can be seen that Comparative Example 3 has slightly high peeling strength, however low capacity retention rate and high pole piece expansion rate, since the binder is prepared by polymerizing inorganic-organic composite emulsion using small-molecule emulsifier. In Comparative Example 4 and Comparative Example 5, the prepared binders has lower peeling strength and higher pole piece expansion rate, since the water-soluble cellulose and inorganic nanoparticles described in the present disclosure are not contained therein. Comparative Example 6 prepared a binder according to Example 1 disclosed in CN 1944479A and prepared a lithium ion battery, and shows low capacity retention rate and high pole piece expansion rate after 50 charge and discharge cycles.

(44) FIG. 1 is a SEM image of the surface-modified nano-silica prepared in Example 1, showing that the particle size of the surface-modified nano-silica is 60 nm. FIG. 2 is a DSC chart of the binder prepared in Example 3, showing the inorganic-organic composite polymer has a multi-phase structure and double glass transition temperatures.

(45) The applicant states that the present disclosure illustrates the detailed methods of the present disclosure by the above examples, but the present disclosure is not limited to the above detailed methods, that is to say, it does not mean that the present disclosure must be conducted relying on the above detailed methods. Those skilled in the art should understand that any modification to the present disclosure, any equivalent replacement of each raw material of the products of the present disclosure and the addition of auxiliary ingredients, the selection of specific embodiment and the like all fall into the protection scope and the disclosure scope of the present disclosure.