Multi-functionally Modified Polymer Binder for Lithium Ion Batteries and Use Thereof in Electrochemical Energy Storage Devices

Abstract

A multi-functionally modified polymer binder for lithium ion batteries, which is prepared by a free radical graft copolymerization or a Michael addition reaction, with a biomass polymer or a synthetic polymer as a substrate, and a hydrophilic monomer and a lipophilic monomer as functionally modifying monomers. The binder presents a three-dimensional network body with a multi-branch structure, provides more active cites for contacting with the electrode active materials, improves uniformity and flatness in the formation of films from electrode slurry, enhances the binding strength between the electrode active materials, the conductive agents and the current collector, has high elasticity and binding strength, and is applicable in water/organic solvent. Use of the binder in positive electrodes and negative electrodes can facilitate the conduction of electrons/ions during charging and discharging, reduce the electrochemical interface impedance of the electrodes, and largely improve high-rate performances and cycling stabilities of positive and negative electrode materials for lithium batteries. Moreover, raw materials of the binder can be obtained from wide variety of sources, which significantly reduces the cost. Accordingly, the binder has a promising market potential.

Claims

1. A multi-functionally modified polymer binder for lithium ion batteries, characterized in that, the binder is prepared by a free radical graft copolymerization or a Michael addition reaction, with a biomass polymer or a synthetic polymer as a substrate, and a hydrophilic monomer and a lipophilic monomer as functionally modifying monomers; the binder has a molecular weight of 10000-1500000, a solids content of 1-50 wt % and a viscosity of 1-50000 mPa.Math.s; the biomass polymer is selected from one or more of arabic gum, cyclodextrin, cellulose derivative, xanthan gum, pectin, gelatin, starch, and sesbania gum; the synthetic polymer is selected from one or more of polyethyleneimine, polyethylene glycol and polyhydroxy polybutadiene; the hydrophilic monomer is selected from at least one of monomers having a structure of CH.sub.2CR.sub.1R.sub.2, wherein R.sub.1 is selected from H, CH.sub.3 and CH.sub.2CH.sub.3, and R.sub.2 is selected from COOH, COOM and CONH.sub.2, wherein M is selected from Li, Na or K; the lipophilic monomer is selected from at least one of monomers having a structure of CH.sub.2CR.sub.3R.sub.4, wherein R.sub.3 is selected from H, CH.sub.3 and CH.sub.2CH.sub.3, and R.sub.4 is selected from at least one of CN, OCOCH.sub.3, CONHCH.sub.3, CON(CH.sub.3).sub.2, CHCH.sub.2, Ph-R.sub.5 and COOR.sub.6, wherein R.sub.5 is H or any substituent other than H, and R.sub.6 is selected from at least one of C.sub.1-C.sub.8 alkyl groups; a weight ratio of the biomass polymer or the synthetic polymer, the hydrophilic monomer and the lipophilic monomer is 1:0-100:0-100.

2. The multi-functionally modified polymer binder for lithium ion batteries according to claim 1, characterized in that, the weight ratio of the biomass polymer or the synthetic polymer, the hydrophilic monomer and the lipophilic monomer is 1:0.01-20:0.01-20.

3. The multi-functionally modified polymer binder for lithium ion batteries according to claim 1 or 2, characterized in that, the free radical graft copolymerization refers to a free radical polymerization or copolymerization grafting reaction of the biomass polymer or the synthetic polymer with one or more of the hydrophilic monomers and the lipophilic monomers which is initiated by a initiator; the initiator is selected from (NH.sub.4).sub.2S.sub.2O.sub.8, Na.sub.2S.sub.2O.sub.8, K.sub.2S.sub.2O.sub.8, (NH.sub.4).sub.2S.sub.2O.sub.8/NaHSO.sub.3, (NH.sub.4).sub.2S.sub.2O.sub.8/Na.sub.2SO.sub.3, Na.sub.2S.sub.2O.sub.8/NaHSO.sub.3, Na.sub.2S.sub.2O.sub.8/Na.sub.2SO.sub.3, K.sub.2S.sub.2O.sub.8/NaHSO.sub.3, K.sub.2S.sub.2O.sub.8/Na.sub.2SO.sub.3, Ce(NH.sub.4).sub.2(NO.sub.3).sub.6, and 2,2-azobis[2-methylpropionamidine] dihydrochloride; an amount of the initiator is 0.01-5 wt % of a total weight of the monomers.

4. The multi-functionally modified polymer binder for lithium ion batteries according to claim 1 or 2, characterized in that, the Michael addition reaction refers to a Michael addition reaction of the biomass polymer or the synthetic polymer with one or more of the hydrophilic monomers and the lipophilic monomers through a base catalyst; an amount of the base catalyst is 0.01-5 wt % of a total weight of the monomers.

5. The multi-functionally modified polymer binder for lithium ion batteries according to claim 1 or 2, characterized in that, the cellulose derivative is selected from one or more of sodium carboxymethyl cellulose, sodium hydroxyethyl cellulose, and hydroxypropyl methylcellulose.

6. A preparation method of the multi-functionally modified polymer binder for lithium ion batteries according to claim 1, characterized in that, it comprises the following steps: (1) dissolving the biomass polymer or the synthetic polymer in deionized water, and thoroughly stirring under a protective gas atmosphere for 0.5-2.5 hours to remove oxygen and obtain a solution which is uniform and shows high dispersity; a stirring rate is 100-500 rpm; (2) adding the initiator or the base catalyst to the solution obtained in step (1), thoroughly stirring to obtain a mixing solution; adding the hydrophilic monomer and the lipophilic monomer to the mixing solution, stirring to allow reaction at 40-90 C. for 1-4 hours to obtain the multi-functionally modified polymer binder for lithium ion batteries; water-solubility and oil-solubility of the binder is regulated by adjusting a mass ratio of the hydrophilic monomer and the lipophilic monomer; the amount of the initiator or the base catalyst is 0.01-5 wt % of the total weight of the monomers; the weight ratio of the biomass polymer or the synthetic polymer, the hydrophilic monomer and the lipophilic monomer is 1:0-100:0-100; the initiator is selected from (NH.sub.4).sub.2S.sub.2O.sub.8, Na.sub.2S.sub.2O.sub.8, K.sub.2S.sub.2O.sub.8, (NH.sub.4).sub.2S.sub.2O.sub.8/NaHSO.sub.3, (NH.sub.4).sub.2S.sub.2O.sub.8/Na.sub.2SO.sub.3, Na.sub.2S.sub.2O.sub.8/NaHSO.sub.3, Na.sub.2S.sub.2O.sub.8/Na.sub.2SO.sub.3, K.sub.2S.sub.2O.sub.8/NaHSO.sub.3, K.sub.2S.sub.2O.sub.8/Na.sub.2SO.sub.3, Ce(NH.sub.4).sub.2(NO.sub.3).sub.6, and 2,2-azobis[2-methylpropionamidine] dihydrochloride; the base catalyst is selected from one or more of LiOH, NaOH, LiOH/carbamide and NaOH/carbamide.

7. Use of the multi-functionally modified polymer binder for lithium ion batteries of claim 1 in lithium ion battery positive electrode, characterized in that, the lithium ion battery positive electrode comprises a current collector and a lithium ion battery positive electrode slurry supported on the current collector; the lithium ion battery positive electrode slurry comprises a positive electrode active material, a conductive agent, the multi-functionally modified polymer binder for lithium ion batteries of claim 1, and a solvent; a weight ratio of the positive electrode active material, the conductive agent and the multi-functionally modified polymer binder for lithium ion batteries is 70-95:1-20:2.5-10; the solvent is water or an organic solvent; the positive electrode active material is selected from one or more of lithium iron phosphate, lithium cobaltate, lithium manganate and a ternary material; the conductive agent is acetylene black; the current collector is an aluminum foil; a solids content of the lithium ion battery positive electrode slurry is 30-75 wt %, and a viscosity of the lithium ion battery positive electrode slurry is 3000-8000 mPa.Math.s.

8. Use of the multi-functionally modified polymer binder for lithium ion batteries of claim 1 in lithium ion battery negative electrode, characterized in that, the lithium ion battery negative electrode comprises a current collector and a lithium ion battery negative electrode slurry supported on the current collector; the lithium ion battery negative electrode slurry comprises a negative electrode active material, a conductive agent, the multi-functionally modified polymer binder for lithium ion batteries of claim 1, and a solvent; a weight ratio of the negative electrode active material, the conductive agent and the multi-functionally modified polymer binder for lithium ion batteries is 70-95:1-20:2.5-10; the solvent is water or an organic solvent; the negative electrode active material is selected from one or more of a silicon-based material, lithium titanate or graphite; the conductive agent is acetylene black; the current collector is a copper foil.

9. Use of the multi-functionally modified polymer binder for lithium ion batteries of claim 1 in electrochemical energy storage device, characterized in that, the electrochemical energy storage device is a supercapacitor or a solar cell.

10. A lithium ion battery, the battery comprising a battery case, an electrode core and an electrolyte, and the electrode core and the electrolyte being sealed in the battery case, characterized in that, the electrode core contains electrodes which comprise a multi-functionally modified polymer binder for lithium ion batteries, and a separator between the electrodes.

Description

DESCRIPTION OF THE DRAWINGS

[0031] FIG. 1 is an infrared spectrogram comparing the multi-functionally modified polymer binders prepared with sodium carboxymethyl cellulose under various reaction systems according to embodiments 1 and 2 of the present invention.

[0032] FIG. 2 is an infrared spectrogram comparing the multi-functionally modified polymer binders prepared with sodium carboxymethyl cellulose under various reaction systems according to embodiment 3 of the present invention.

[0033] FIG. 3 is an infrared spectrogram comparing the multi-functionally modified polymer binders prepared with arabic gum under various reaction systems according to embodiments 10 and 13 of the present invention.

[0034] FIG. 4 is an infrared spectrogram comparing the multi-functionally modified polymer binders prepared with various polymer substrates under various reaction systems according to embodiments 16 to 18 of the present invention.

[0035] FIG. 5 is an infrared spectrogram comparing the multi-functionally modified polymer binders prepared with various polymer substrates under various reaction systems according to embodiments 19 to 20 of the present invention.

[0036] FIG. 6 is an infrared spectrogram comparing the multi-functionally modified polymer binders prepared with arabic gum and a base catalyst according to embodiment 15 of the present invention.

[0037] FIG. 7 is an infrared spectrogram comparing the multi-functionally modified polymer binders prepared with a base catalyst according to embodiments 9 and 21 of the present invention.

[0038] FIG. 8 shows a comparison of the multi-functionally modified polymer binders of embodiments 6, 10 and 13 in peel strength towards aluminum foil.

[0039] FIG. 9 shows a comparison of the multi-functionally modified polymer binders of embodiments 6, 7 and 10 in peel strength towards various electrode materials (positive electrode: LFP; negative electrode: Si and graphite). Coating thickness parameters: 100 m for positive electrode-LFP, 80 m for negative electrode-Si, and 50 m for graphite.

[0040] FIG. 10 shows voltage-specific capacity curves during initial charging and discharging of lithium iron phosphate and a comparative electrode as disclosed in embodiment 22.

[0041] FIG. 11 shows electrochemical impedance curves of lithium iron phosphate and a comparative electrode as disclosed in embodiment 23.

[0042] FIG. 12 is a cyclic voltammogram comparing a ternary material and a comparative electrode as disclosed in embodiment 24 under a scan rate of 0.2 mV/s.

[0043] FIG. 13 shows charging and discharging curves of a ternary material and a comparative electrode as disclosed in embodiment 25 at various rates.

[0044] FIG. 14 shows charging and discharging curves of a graphite negative electrode material of embodiment 26 at a rate of 0.2C.

[0045] FIG. 15 shows charging and discharging curves of a silicon-based material and a comparative electrode as disclosed in embodiment 7 at a current density of 400 mA/g.

[0046] FIG. 16 shows a comparison in coating flatness of the binders of embodiments 6, 7 and 10 and comparative example 1 with various electrode materials (positive electrode: LFP; negative electrode: Si and graphite).

[0047] Coating thickness parameters: 100 m for positive electrode-LFP, 80 m for negative electrode-Si, and 50 m for graphite.

[0048] Sodium carboxymethyl cellulose is abbreviated as CMC; arabic gum is denoted as Acacia; xanthan gum is abbreviated as XG; pectin is denoted as Pectin; gelatin is denoted as Gelatin; polyethyleneimine is abbreviated as PEI; cyclodextrin is denoted as Cyclodextrin.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0049] The following embodiments are for further describing this invention rather than limiting the invention.

[0050] Sodium carboxymethyl cellulose is abbreviated as CMC; arabic gum is denoted as Acacia; xanthan gum is abbreviated as XG; pectin is denoted as Pectin; gelatin is denoted as Gelatin; polyethyleneimine is abbreviated as PEI; cyclodextrin is denoted as Cyclodextrin. Acrylic acid is abbreviated as AA; acrylonitrile is abbreviated as AN; acrylamide is abbreviated as AM; methyl methacrylate is abbreviated as MMA; styrene is abbreviated as St.

[0051] Preparation of electrodes comprising the active materials: mixing an electrode material, a conductive agent and the binder according to a certain ratio, grinding the mixture to obtain a slurry and coating an aluminum foil (positive electrode) or a copper foil (negative electrode) with the slurry. A thickness of nano silicone powders was 80 m (copper foil substrate), a thickness of graphite (copper foil substrate) was 50 m, and a thickness of lithium iron phosphate was 100 m (aluminum foil substrate).

[0052] Preparation of an electrode comprising only the binder: coating an aluminum foil with a 2 wt % binder with a coating thickness of 200 m.

[0053] Peel strength measurement: cutting the electrode to obtain a segment having a width of 15 mm, and performing a measurement on the segment using a peel strength testing device (Shenzhen, Kaiqiangli, 180 peel tester) with a peeling rate of 20 mm/min; the results are listed in a table.

Embodiment 1

[0054] (1) First dissolving 1 g of sodium carboxymethyl cellulose in 50 ml of deionized water (DI-Water) in advance, and thoroughly stirring for 0.5-2.5 hours under an argon atmosphere to remove oxygen and obtain a solution which was uniform and showed high dispersity with a stirring rate of 100-500 rpm;

[0055] (2) adding 0.1 g of (NH.sub.4).sub.2S.sub.2O.sub.8 as an initiator to the solution obtained in step (1), thoroughly stirring to obtain a mixing solution; adding 2.5 g of acrylic acid as an monomer to the mixing solution, adjusting a reaction temperature to 55 C. and keeping stirring to allow reaction for 2.5 hours with the temperature held constant to obtain a transparent and uniform glue solution which was the multi-functionally modified polymer binder for lithium ion batteries. See table 1, the binder had a solids content of 6.5 wt % and a viscosity of 164.5 mPa.Math.s. See FIG. 1 for the infrared spectrogram.

Embodiment 2

[0056] Embodiment 2 was different from embodiment 1 in that: the monomers added were 2.5 g of acrylic acid and 0.84 g of acrylonitrile, and the initiators used were 0.1 g of (NH.sub.4).sub.2S.sub.2O.sub.8 and 0.03 g of NaHSO.sub.3. Eventually a light white and slightly transparent emulsion (the multi-functionally modified polymer binder) was obtained. See table 1, the binder had a solids content of 8 wt % and a viscosity of 432.1 mPa.Math.s. See FIG. 1 for the infrared spectrogram.

Embodiment 3

[0057] Embodiment 3 was different from embodiment 1 in that: the monomers added were 2.5 g of acrylic acid, 0.84 g of acrylonitrile and 1 g of acrylamide, the initiators used were 0.1 g of (NH.sub.4).sub.2S.sub.2O.sub.8 and 0.03 g of NaHSO.sub.3, and the reaction temperature was 60 C. Eventually a transparent and slightly white emulsion (the multi-functionally modified polymer binder) was obtained. See table 1, the binder had a solids content of 9.6 wt % and a viscosity of 1377.4 mPa.Math.s. See FIG. 2 for the infrared spectrogram.

Embodiment 4

[0058] Embodiment 4 was different from embodiment 1 in that: the monomers added were 2.5 g of acrylic acid and 2.49 g of acrylamide, and the initiators used were 0.1 g of (NH.sub.4).sub.2S.sub.2O.sub.8 and 0.03 g of NaHSO.sub.3. Eventually a transparent glue solution (the multi-functionally modified polymer binder) was obtained. See table 1, the binder had a solids content of 10.7 wt % and a viscosity of 1481.3 mPa.Math.s.

Embodiment 5

[0059] Embodiment 5 was different from embodiment 1 in that: the monomers added were 2.5 g of acrylic acid and 3.47 g of methyl methacrylate, and the initiators used were 0.1 g of (NH.sub.4).sub.2S.sub.2O.sub.8 and 0.03 g of NaHSO.sub.3. Eventually a bright white emulsion (the multi-functionally modified polymer binder) was obtained. See table 1, the binder had a solids content of 12.3 wt % and a viscosity of 215.8 mPa.Math.s.

Embodiment 6

[0060] Embodiment 6 was different from embodiment 1 in that: the monomers added were 7.2 g of acrylic acid and 0.53 g of acrylonitrile, and the initiators used were 0.1 g of (NH.sub.4).sub.2S.sub.2O.sub.8 and 0.03 g of NaHSO.sub.3. Eventually a transparent, slightly white and viscous solution (the multi-functionally modified polymer binder) was obtained. See table 1, the binder had a solids content of 14.9 wt % and a viscosity of 10381 mPa.Math.s. See FIG. 8 for the peel strength thereof towards aluminum foil.

Embodiment 7

[0061] Embodiment 7 was different from embodiment 1 in that: the monomers added were 7.2 g of acrylic acid, 0.53 g of acrylonitrile and 0.71 g of acrylamide, and the initiators used were 0.1 g of (NH.sub.4).sub.2S.sub.2O.sub.8 and 0.03 g of NaHSO.sub.3. Eventually a transparent, slightly white and viscous solution (the multi-functionally modified polymer binder) was obtained. See table 1, the binder had a solids content of 15.9 wt % and a viscosity of 12531 mPa.Math.s.

Embodiment 8

[0062] Embodiment 8 was different from embodiment 1 in that: the monomers added were 3.6 g of acrylic acid and 3 g of styrene, and the initiators used were 0.1 g of (NH.sub.4).sub.2S.sub.2O.sub.8 and 0.03 g of NaHSO.sub.3. Eventually a transparent solution (the multi-functionally modified polymer binder) was obtained. See table 1, the binder had a solids content of 13.2 wt % and a viscosity of 44.2 mPa.Math.s.

Embodiment 9

[0063] Embodiment 9 was different from embodiment 1 in that: the monomer added was 6.63 g of acrylonitrile, and the initiator was replaced with a catalyst, and the catalyst used is 1 ml of 20 wt % NaOH. Eventually a white and uniform emulsion (the multi-functionally modified polymer binder) was obtained. See table 1, the binder had a solids content of 13.2 wt % and a viscosity of 2536.5 mPa.Math.s. See FIG. 7 for the infrared spectrogram.

Comparative Example 1

[0064] Comparative example 1 was different from embodiment 2 in that the polymer substrate was chitosan, a marine polysaccharide polymer. Eventually a white emulsion was obtained, with a solids content of 8.0 wt % and a viscosity of 6.47 mPa.Math.s (see table 1).

[0065] The binders obtained in embodiments 1-9 and comparative example 1 were characterized. The data are shown in table 1 and FIGS. 1-2.

TABLE-US-00001 TABLE 1 Monomers V APS AA AN AM MMA St S/S Color mPa .Math. s APF N mN/mm CMC Solution/ Transparent 1802.7 0.025 2 Water E1 2.5 Solution/ Transparent 164.5 0.030 2 Water E2 2.5 0.84 Emulsion/ Light white 432.1 0.057 4 Water E3 2.5 0.84 1 Emulsion/ Transparent 1377.4 0.077 5 Water E4 2.5 2.49 Solution/ Transparent 1481.3 0.035 2 Water E5 2.5 3.47 Emulsion/ White 215.8 0.090 6 Water E6 7.2 0.53 Solution/ Transparent 10381 1.05 70 Water E7 7.2 0.53 0.71 Solution/ Transparent 12531 0.066 4 Water E8 3.6 3 Solution/ Transparent 44.2 >1.166 >78 NMP *E9 6.63 Emulsion/ White 2536.5 0.156 11 Water C1 2.5 0.84 Emulsion White 6.47 0.027 2 *The product in Embodiment 9 was prepared by a Michael addition reaction of CMC with a base catalyst S/S: Solubility/Solvent V: Viscosity APF: Average peel force APS: Average peel strength

[0066] The average peel strength in table 1 was determined by the following steps. Preparing an electrode comprising only the binder by directly coating an aluminum foil with 2 wt % binder with a coating thickness of 200 Measuring the peel strength by cutting the electrode to obtain a segment having a width of 15 mm, and performing a measurement on the segment using a peel strength testing device (Shenzhen, Kaiqiangli, 180 peel tester) with a peeling rate of 20 mm/min. The results are listed in a table.

[0067] Conclusion from table 1 and FIGS. 1 to 2: The multi-functionally modified CMC-based polymer binder showed high water-solubility (embodiments 1 to 7) or oil-solubility (embodiment 8), largely improved peel strength towards the current collector, and improved comprehensive performances. Compared with the unmodified CMC binder, the multi-functionally modified CMC-based polymer binder obtained in embodiments 6, 8 and 9 had been greatly improved in the binding properties. Moreover, the acrylic acid-modified polymer binder had obtained a high water-solubility of polyacrylic acid or salts thereof and showed a lower viscosity (embodiment 1). The polymer binders modified with acrylic acid and acrylonitrile had obtained both the high water-solubility (of polyacrylic acid or salts thereof) and good binding performance (of polyacrylonitrile), and showed improved peel strengths (embodiments 2 and 6). The polymer binders modified with acrylic acid, acrylonitrile and acrylamide, had showed well-balanced properties of water-solubility, binding performance and flexibility, and improved comprehensive performances (embodiments 3 and 7). The polymer binder modified with acrylic acid and styrene, can be applied in an organic solvent by regulating its water-solubility and oil-solubility through adjusting the ratio of the hydrophilic monomer and the lipophilic monomer (embodiment 8). It is noteworthy that, compared with modified marine polysaccharide polymers (see CN105576247A, e.g. CTS-PAA-PAN), under identical reaction conditions, the binder showed a doubled peel strength (comparing the binders of embodiment 2 and comparative example 1).

Embodiment 10

[0068] Embodiment 10 was different from embodiment 1 in that: sodium carboxymethyl cellulose was replaced with arabic gum, and 2.5 g of acrylic acid was replaced with 5 g of acrylic acid. Eventually a transparent and uniform glue solution (the multi-functionally modified polymer binder) was obtained. See table 2, the binder had a solids content of 10.7 wt % and a viscosity of 23159 mPa.Math.s. See FIG. 3 for the infrared spectrogram. See FIG. 8 for the peel strength thereof towards aluminum foil.

Embodiment 10*

[0069] The transparent and uniform glue solution in embodiment 10 was neutralized with LiOH to a pH of 6 to 7, so as to obtain a multi-functionally modified polymer binder. See table 2, the binder had a solids content of 11.5 wt % and a viscosity of 24581 mPa.Math.s.

Embodiment 11

[0070] Embodiment 11 was different from embodiment 10 in that: the monomer added was 3.18 g of acrylonitrile, and the initiators used were 0.1 g of (NH.sub.4).sub.2S.sub.2O.sub.8 and 0.03 g of NaHSO.sub.3. Eventually a white emulsion (the multi-functionally modified polymer binder) was obtained. See table 2, the binder had a solids content of 7.7 wt % and a viscosity of 13.2 mPa.Math.s.

Embodiment 12

[0071] Embodiment 12 was different from embodiment 10 in that: the monomer added was 4.26 g of acrylamide, and the initiators used were 0.1 g of (NH.sub.4).sub.2S.sub.2O.sub.8 and 0.03 g of NaHSO.sub.3. Eventually a transparent and slightly white solution (the multi-functionally modified polymer binder) was obtained. See table 2, the binder had a solids content of 9.5 wt % and a viscosity of 21.5 mPa.Math.s.

Embodiment 13

[0072] Embodiment 13 was different from embodiment 10 in that: the monomers added were 2.5 g of acrylic acid and 0.84 g of acrylonitrile, the initiators used were 0.1 g of (NH.sub.4).sub.2S.sub.2O.sub.8 and 0.03 g of NaHSO.sub.3, and the reaction temperature was 60 C. Eventually a white emulsion (the multi-functionally modified polymer binder) was obtained. See table 2, the binder had a solids content of 8 wt % and a viscosity of 1.86 mPa.Math.s. See FIG. 3 for the infrared spectrogram. See FIG. 8 for the peel strength thereof towards aluminum foil.

Embodiment 14

[0073] Embodiment 14 was different from embodiment 10 in that: the monomers added were 4 g of acrylic acid and 1 g of acrylonitrile, and the initiators used were 0.1 g of (NH.sub.4).sub.2S.sub.2O.sub.8 and 0.03 g of NaHSO.sub.3. Eventually a white emulsion (the multi-functionally modified polymer binder) was obtained. See table 2, the binder had a solids content of 10.7 wt % and a viscosity of 4.8 mPa.Math.s.

Embodiment 15

[0074] Embodiment 15 was different from embodiment 10 in that: the monomer added was 6.63 g of acrylonitrile, and the initiator was replaced with a catalyst, and the catalyst used is 1 ml of 20 wt % NaOH. Eventually a white and uniform emulsion (the multi-functionally modified polymer binder) was obtained. See table 2, the binder had a solids content of 13.2 wt % and a viscosity of 5.6 mPa.Math.s. See FIG. 6 for the infrared spectrogram.

[0075] The binders obtained in embodiments 10-15 were characterized. The data are shown in table 2 and FIG. 3.

TABLE-US-00002 TABLE 2 Monomers V APS AA AN AM S/S Color mPa .Math. s APF N mN/mm E10 5 Solution/ Transparent 23159 >0.9 >60 Water E10* 5 Solution/ Transparent 18581 >0.813 >54 Water E11 3.18 Emulsion/ White 13.2 >1.3 >86 Water E12 4.26 Solution/ Transparent 21.5 0.04 2 Water E13 2.5 0.84 Emulsion/ White 1.9 >1.2 >80 Water E14 4 1 Emulsion/ Transparent 4.8 >0.9 >60 Water E15** 6.63 Emulsion/ White 5.6 >1.5 >90 Water PVDF Solution/ Transparent 0.539 36 NMP The binder of embodiment 10* is an Acacia-PAA-COOLi binder prepared by neutralizing the glue solution of embodiment 10 with LiOH. **The product in Embodiment 15 was prepared by a Michael addition reaction of Acacia with a base catalyst. S/S: Solubility/Solvent V: Viscosity APF: Average peel force APS: Average peel strength

[0076] The average peel strength in table 2 was determined by the following steps.

[0077] Preparing an electrode comprising only the binder by directly coating an aluminum foil with 2 wt % binder with a coating thickness of 200 Measuring the peel strength by cutting the electrode to obtain a segment having a width of 15 mm, and performing a measurement on the segment using a peel strength testing device (Shenzhen, Kaiqiangli, 180 peel tester) with a peeling rate of 20 mm/min. The results are listed in a table.

[0078] Conclusion from table 2 and FIG. 3: The multi-functionally modified polymer binder showed high water-solubility, largely improved peel strength towards the current collector, and improved comprehensive performances. Except the binder of embodiment 12, other multi-functionally modified polymer binders of embodiments 11 to 16 showed binding strengths higher than that of the current commercial PVDF system. It is noteworthy that, the Acacia-PAA-COOLi binder, which was prepared by neutralizing the grafted polyacrylic acid, showed a higher solubility and a low viscosity, but its peel strength decreased (see embodiments 10 and 10*). FIG. 8 shows a comparison of the multi-functionally modified polymer binders of embodiments 6, 10 and 13 in peel strength towards aluminum foil. As can be seen from the figure, dually-modified CMC (embodiment 6) showed a peel strength of 70 mN/mm towards aluminum foil, while that of unmodified CMC was 2 mN/mm. Singly-modified arabic gum (embodiment 10) and dually-modified arabic gum respectively showed peel strengths of 60 mN/mm and 80 mN/mm towards aluminum foil. Parallel experiments showed that PVDF had a peel strength of 36 mN/mm towards aluminum foil. As can be seen from above, through functional modification of polymers, the invention has significantly improved the peel strength of the binder towards aluminum foil. Accordingly, it is a promising binder for lithium ion batteries.

Embodiment 16

[0079] Embodiment 16 was different from embodiment 1 in that: the polymer substrate used was xanthan gum, the monomers added were 3.6 g of acrylic acid and 0.53 g of acrylonitrile, and the initiators used were 0.1 g of (NH.sub.4).sub.2S.sub.2O.sub.8 and 0.03 g of NaHSO.sub.3. Eventually a white emulsion (the multi-functionally modified polymer binder) was obtained. See table 3, the binder had a solids content of 9.3 wt % and a viscosity of 3621.4 mPa.Math.s. See FIG. 4 for the infrared spectrogram.

Embodiment 17

[0080] Embodiment 17 was different from embodiment 1 in that: the polymer substrate used was pectin, the monomers added were 3.6 g of acrylic acid and 0.53 g of acrylonitrile, and the initiators used were 0.1 g of (NH.sub.4).sub.2S.sub.2O.sub.8 and 0.03 g of NaHSO.sub.3. Eventually a white, uniform and viscous solution (the multi-functionally modified polymer binder) was obtained. See table 3, the binder had a solids content of 9.3 wt % and a viscosity of 215.1 mPa.Math.s. See FIG. 4 for the infrared spectrogram.

Embodiment 18

[0081] Embodiment 18 was different from embodiment 1 in that: the polymer substrate used was gelatin, the monomers added were 3.6 g of acrylic acid and 0.53 g of acrylonitrile, and the initiators used were 0.1 g of (NH.sub.4).sub.2S.sub.2O.sub.8 and 0.03 g of NaHSO.sub.3. Eventually a product with separated layers was obtained (the multi-functionally modified polymer binder). See table 3, the binder had a solids content of 9.3 wt % and a viscosity of 250.6 mPa.Math.s. See FIG. 4 for the infrared spectrogram.

Embodiment 19

[0082] Embodiment 19 was different from embodiment 1 in that: the polymer substrate used was polyethyleneimine (PEI), the monomers added were 3.6 g of acrylic acid and 0.53 g of acrylonitrile, and the initiators used were 0.1 g of (NH.sub.4).sub.2S.sub.2O.sub.8 and 0.03 g of NaHSO.sub.3. Eventually a yellow and uniform solution (the multi-functionally modified polymer binder) was obtained. See table 3, the binder had a solids content of 9.3 wt % and a viscosity of 2.43 mPa.Math.s. See FIG. 5 for the infrared spectrogram.

Embodiment 20

[0083] Embodiment 20 was different from embodiment 1 in that: the polymer substrate used was cyclodextrin, the monomers added were 3.6 g of acrylic acid and 0.53 g of acrylonitrile, and the initiators used were 0.1 g of (NH.sub.4).sub.2S.sub.2O.sub.8 and 0.03 g of NaHSO.sub.3. Eventually a transparent and uniform solution (the multi-functionally modified polymer binder) was obtained. See table 3, the binder had a solids content of 9.3 wt % and a viscosity of 219.4 mPa.Math.s. See FIG. 5 for the infrared spectrogram.

Embodiment 21

[0084] Embodiment 21 was different from embodiment 1 in that: the polymer substrate used was xanthan gum, the monomer added was 6.63 g of acrylonitrile, and the catalyst used is 1 ml of 20 wt % NaOH. Eventually a white emulsion (the multi-functionally modified polymer binder) was obtained. See table 3, the binder had a solids content of 13.2 wt % and a viscosity of 5613.8 mPa.Math.s. See FIG. 7 for the infrared spectrogram.

[0085] The binders obtained in embodiments 16-21 were characterized. The data are shown in table 3 and FIGS. 4, 5 and 7.

TABLE-US-00003 TABLE 3 Monomers V APS AA AN S/S Color mPa .Math. s APF N mN/mm XG 3.6 0.53 Colloidal White 3621.4 0.04 2 emulsion *XG 6.63 Colloidal White 5613.8 0.15 10 emulsion Pectin 3.6 0.53 Viscous White 215.1 >1.0 >66 solution Gelatin 3.6 0.53 Emulsion White 250.6 0.32 21 PEI 3.6 0.53 Solution/Water Yellow 2.4 0.28 19 Cyclodextrin 7.2 0.53 Solution/Water Transparent 219.4 >0.9 >58 *XG: The product in Embodiment 21 was prepared by a Michael addition reaction of xanthan gum with a base catalyst. S/S: Solubility/Solvent V: Viscosity APF: Average peel force APS: Average peel strength

[0086] The average peel strength in table 3 was determined by the following steps. Preparing an electrode comprising only the binder by directly coating an aluminum foil with 2 wt % binder with a coating thickness of 200 m. Measuring the peel strength by cutting the electrode to obtain a segment having a width of 15 mm, and performing a measurement on the segment using a peel strength testing device (Shenzhen, Kaiqiangli, 180 peel tester) with a peeling rate of 20 mm/min. The results are listed in a table.

[0087] Conclusion from table 3: The multi-functionally modified polymer binder showed high water-solubility and binding strength, largely improved peel strength towards the current collector, and improved comprehensive performances, and thus can be used as a novel binder for lithium ion batteries.

Embodiment 22

[0088] Lithium iron phosphate was used as a positive electrode material, and the transparent, slightly white and viscous solution as prepared in embodiment 6 was used as the multi-functionally modified polymer water-based binder for lithium ion batteries (this binder was selected for performance test since it showed the highest peel strength).

[0089] 1. Preparation of Test Electrodes

[0090] As an example of the lithium ion battery positive electrode of the present invention, the lithium ion battery positive electrode comprises a current collector and a lithium ion battery positive electrode slurry supported on the current collector; the lithium ion battery positive electrode slurry comprises a positive electrode active material, a conductive agent, the solution prepared in embodiment 6 (which is transparent, slightly white and viscous, as the multi-functionally modified polymer water-based binder), and a solvent; a weight ratio of the positive electrode active material, the conductive agent and the binder is 90:5:5; the solvent is water. The positive electrode active material is lithium iron phosphate (LiFePO.sub.4, LFP); the conductive agent is acetylene black; the current collector is an aluminum foil current collector; a solids content of the lithium ion battery positive electrode slurry is 45 wt %, and a viscosity of the lithium ion battery positive electrode slurry is 3000 mPa.Math.s.

[0091] LFP and the conductive agent were mixed and stirred until uniform dispersion; then the transparent, slightly white and viscous solution prepared in embodiment 6 was added into the mixture as a water-based binder, stirred well, and a proper quantity of water was added to adjust the viscosity, so as to obtain an LFP electrode slurry; the slurry was coated onto an aluminum foil which was then vacuum-dried at 90 C. so as to obtain the LFP positive electrode. The vacuum-dried electrode was cut and weighed, and then installed into a 2025 battery case, with a lithium sheet as the counter electrode, a polyethylene film as the separator and 1 M LiPF.sub.6 EC/DMC/DEC (v/v/v=1/1) as the electrolyte, to assemble a battery which was then subjected to a constant current charge-discharge test.

[0092] 2. Preparation of Comparative Electrodes

[0093] The comparative electrodes were prepared by the same method wherein PVDF and the modified marine polysaccharide polymer CTS-PAA-PAN of comparative example 1 were used as the binders.

[0094] 3. Electrochemical Test

[0095] An electrochemical test was performed on the test electrodes and the comparative electrodes to determine the charging and discharging performances.

[0096] 4. Result Analysis

[0097] FIG. 10 shows voltage-specific capacity curves of the test electrodes and the comparative electrodes of the present embodiment at a charging and discharging current density of 0.2C. As can be seen from the figure, the LFP battery prepared with the multi-functionally modified polymer binder CMC-PAA-PAN showed a longer discharge plateau than those with PVDF and the modified marine polysaccharide polymer CTS-PAA-PAN binders, indicating that the battery with CMC-PAA-PAN experienced less polarization during discharging, and suggesting that the multi-functionally modified polymer binder had improved the conductive performance of the electrode system and the overall electrochemical performance of the battery.

Embodiment 23

[0098] Lithium iron phosphate was used as a positive electrode material, and the products as prepared in embodiments 6 and 13 were respectively used as the multi-functionally modified polymer water-based binder for lithium ion batteries (this binder was selected for performance test since it showed the highest peel strength).

[0099] 1. Preparation of Test Electrodes

[0100] As an example of the lithium ion battery positive electrode of the present invention, the lithium ion battery positive electrode comprises a current collector and a lithium ion battery positive electrode slurry supported on the current collector; the lithium ion battery positive electrode slurry comprises a positive electrode active material, a conductive agent, the product prepared in embodiment 6 or 13 (as the multi-functionally modified polymer water-based binder), and a solvent; a weight ratio of the positive electrode active material, the conductive agent and the binder is 90:5:5; the solvent is water. The positive electrode active material is lithium iron phosphate (LiFePO.sub.4, LFP); the conductive agent is acetylene black; the current collector is an aluminum foil current collector; a solids content of the lithium ion battery positive electrode slurry is 45 wt %, and a viscosity of the lithium ion battery positive electrode slurry is 3000 mPa.Math.s.

[0101] LFP and the conductive agent were mixed and stirred until uniform dispersion; then the transparent, slightly white and viscous solution prepared in embodiment 6 or 13 was added into the mixture as a water-based binder, stirred well, and a proper quantity of water was added to adjust the viscosity, so as to obtain an LFP electrode slurry; the slurry was coated onto an aluminum foil which was then vacuum-dried at 90 C. so as to obtain the LFP positive electrode. The vacuum-dried electrode was cut and weighed, and then installed into a 2025 battery case, with a lithium sheet as the counter electrode, a polyethylene film as the separator and 1 M LiPF.sub.6 EC/DMC/DEC (v/v/v=1/1) as the electrolyte, to assemble a battery which was then subjected to an electrochemical performance test.

[0102] 2. Preparation of Comparative Electrodes

[0103] The comparative electrodes were prepared by the same method wherein PVDF and the modified marine polysaccharide polymer CTS-PAA-PAN of comparative example 1 were used as the binders.

[0104] 3. Electrochemical Test

[0105] An electrochemical test was performed on the test electrodes and the comparative electrodes to determine the electrochemical Impedance.

[0106] 4. Result Analysis

[0107] FIG. 11 shows electrochemical impedance curves of the test electrodes and the comparative electrodes of the present embodiment under perturbation of 5 mv. As can be seen from the figure, the LFP battery prepared with the multi-functionally modified polymer binder (CMC-PAA-PAN or Acacia-PAA-PAN) showed a electrochemical impedance lower than those with PVDF and the modified marine polysaccharide polymer CTS-PAA-PAN binders, indicating that the battery experienced less polarization during charging and discharging, and suggesting that the multi-functionally modified polymer binder (CMC-PAA-PAN or Acacia-PAA-PAN) had improved the electron/ion conducting performance of the battery system, facilitated charging and discharging at high rate, and improved the overall electrochemical performance of the battery.

Embodiment 24

[0108] A ternary material (LiNi.sub.1/3Mn.sub.1/3Co.sub.1/3O.sub.2, NMC) was used as a positive electrode material, and the transparent, slightly white and viscous solution as prepared in embodiment 6 was used as the multi-functionally modified polymer water-based binder for lithium ion batteries (this binder was selected for performance test since it showed the highest peel strength).

[0109] 1. Preparation of Test Electrodes

[0110] As an example of the lithium ion battery positive electrode of the present invention, the lithium ion battery positive electrode comprises a current collector and a lithium ion battery positive electrode slurry supported on the current collector; the lithium ion battery positive electrode slurry comprises a positive electrode active material, a conductive agent, the solution prepared in embodiment 6 (which is transparent, slightly white and viscous, as the multi-functionally modified polymer water-based binder), and a solvent; a weight ratio of the positive electrode active material, the conductive agent and the binder is 85:9:6; the solvent is water. The positive electrode active material is the ternary material (LiNi.sub.1/3Mn.sub.1/3Co.sub.1/3O.sub.2, NMC); the conductive agent is acetylene black; the current collector is an aluminum foil current collector; a solids content of the lithium ion battery positive electrode slurry is 45 wt %, and a viscosity of the lithium ion battery positive electrode slurry is 3000 mPa.Math.s.

[0111] NMC and the conductive agent were mixed and stirred until uniform dispersion; then the transparent, slightly white and viscous solution prepared in embodiment 6 was added into the mixture as a water-based binder, stirred well, and a proper quantity of water was added to adjust the viscosity, so as to obtain an NMC electrode slurry; the slurry was coated onto an aluminum foil which was then vacuum-dried at 90 C. so as to obtain the NMC positive electrode. The vacuum-dried electrode was cut and weighed, and then installed into a 2025 battery case, with a lithium sheet as the counter electrode, a polyethylene film as the separator and 1 M LiPF.sub.6 EC/DMC/DEC (v/v/v=1/1) as the electrolyte, to assemble a battery which was then subjected to an electrochemical performance test.

[0112] 2. Preparation of Comparative Electrodes

[0113] The comparative electrodes were prepared by the same method wherein PVDF and the modified marine polysaccharide polymer CTS-PAA-PAN of comparative example 1 were used as the binders.

[0114] 3. Electrochemical Test

[0115] An electrochemical test was performed on the test electrodes and the comparative electrodes to determine the charging and discharging performances.

[0116] 4. Result Analysis

[0117] FIG. 12 is a cyclic voltammogram of the test electrode and the comparative electrode under a scan rate of 0.2 mV/s. As can be seen from the figure, the curve of the NMC battery, which was prepared with the multi-functionally modified polymer binder CMC-PAA-PAN, was generally consistent with the curve of the PVDF system, and showed a voltage interval between the oxidation and reduction peaks commensurate with that of the PVDF system while smaller than that of the CTS-PAA-PAN system, indicating that the NMC electrode with the CMC-PAA-PAN binder exhibited lower polarization and high electrochemical performance, and further, the multi-functionally modified polymer binder showed high electrochemical stability under the working voltage.

Embodiment 25

[0118] A ternary material (LiNi.sub.1/3Mn.sub.1/3Co.sub.1/3O.sub.2, NMC) was used as a positive electrode material, and the transparent solution as prepared in embodiment 7 was used as the multi-functionally modified polymer water-based binder for lithium ion batteries.

[0119] 1. Preparation of Test Electrodes

[0120] As an example of the lithium ion battery positive electrode of the present invention, the lithium ion battery positive electrode comprises a current collector and a lithium ion battery positive electrode slurry supported on the current collector; the lithium ion battery positive electrode slurry comprises a positive electrode active material, a conductive agent, the transparent solution prepared in embodiment 7 (as the multi-functionally modified polymer water-based binder), and a solvent; a weight ratio of the positive electrode active material, the conductive agent and the binder is 85:9:6; the solvent is water. The positive electrode active material is the ternary material (LiNi.sub.1/3Mn.sub.1/3Co.sub.1/3O.sub.2, NMC); the conductive agent is acetylene black; the current collector is an aluminum foil current collector; a solids content of the lithium ion battery positive electrode slurry is 45 wt %, and a viscosity of the lithium ion battery positive electrode slurry is 3000 mPa.Math.s.

[0121] NMC and the conductive agent were mixed and stirred until uniform dispersion; then the transparent solution prepared in embodiment 7 was added into the mixture as a water-based binder, stirred well, and a proper quantity of water was added to adjust the viscosity, so as to obtain an NMC electrode slurry; the slurry was coated onto an aluminum foil which was then vacuum-dried at 90 C. so as to obtain the NMC positive electrode. The vacuum-dried electrode was cut and weighed, and then installed into a 2025 battery case, with a lithium sheet as the counter electrode, a polyethylene film as the separator and 1 M LiPF.sub.6 EC/DMC/DEC (v/v/v=1/1) as the electrolyte, to assemble a battery which was then subjected to an electrochemical performance test.

[0122] 2. Electrochemical Test

[0123] An electrochemical test was performed on the test electrodes to determine the rate performance.

[0124] 3. Result Analysis

[0125] FIG. 13 shows charging and discharging curves of the test electrode of the present embodiment at various rates (0.1C-0.2C-0.5C-1C-2C-5C-0.2C). As can be seen from the figure, the NMC electrode, which was prepared with the multi-functionally modified polymer binder CMC-PAA-PAA-PAM, exhibited a high rate performance. The electrode showed a discharging specific capacity of 80.8mAh/g at a rate of 5C; after charging and discharging at a high rate (5C), the capacity at a rate of 0.2C did not decrease much but remains almost the same, indicating that the NMC electrode with the CMC-PAA-PAN-PAM binder exhibited lower polarization and excellent high rate performance.

Embodiment 26

[0126] Graphite was used as a negative electrode material, and the white emulsion as prepared in embodiment 10 was used as the water-based binder.

[0127] 1. Preparation of Test Electrodes

[0128] As an example of the lithium ion battery negative electrode of the present invention, the lithium ion battery negative electrode comprises a current collector and a lithium ion battery negative electrode slurry supported on the current collector; the lithium ion battery negative electrode slurry comprises a negative electrode active material, a conductive agent, the white emulsion prepared in embodiment 10 (as the binder), and a solvent; a weight ratio of the negative electrode active material, the conductive agent and the binder is 90:5:5; the solvent is water. The negative electrode active material is graphite; the conductive agent is acetylene black; the current collector is a copper foil current collector; a solids content of the lithium ion battery negative electrode slurry is 45 wt %, and a viscosity of the lithium ion battery negative electrode slurry is 3000 mPa.Math.s.

[0129] Graphite and the conductive agent were mixed and stirred until uniform dispersion; then the white emulsion prepared in embodiment 10 was added into the mixture as a water-based binder, stirred well, and a proper quantity of water was added to adjust the viscosity, so as to obtain a graphite electrode slurry; the slurry was coated onto a copper foil which was then vacuum-dried at 60 C. so as to obtain the graphite negative electrode. The vacuum-dried electrode was cut and weighed, and then installed into a 2025 battery case, with a lithium sheet as the counter electrode, a polyethylene film as the separator and 1 M LiPF.sub.6 EC/DMC/DEC (v/v/v=1/1) as the electrolyte, to assemble a battery which was then subjected to a constant current charge-discharge test.

[0130] 2. Electrochemical Test

[0131] An electrochemical test was performed on the test electrodes to determine the charging and discharging performances.

[0132] 3. Result Analysis

[0133] FIG. 14 shows charging and discharging curves of the test electrode of the present embodiment at a rate of 0.2C. As can be seen from the figure, the graphite electrode which was prepared with the multi-functionally modified polymer (Acacia-PAA) binder, exhibited excellent cyclic performance and had an initial coulombic efficiency of up to 99.18%. Compared with the binder system with polyvinyl alcohol as the binder and comprising polystyrene (CN 105261759A), the electrode of the present embodiment showed a higher initial coulombic efficiency. After 24 charging-discharging cycles, the electrode still exhibited a charging specific capacity of 326 mAh/g and a coulombic efficiency of 97.93%, indicating that it had excellent cyclic performance and electrochemical stability.

Embodiment 27

[0134] A silicone-based material was used as a negative electrode material, and the white emulsion as prepared in embodiment 10 was used as the water-based binder.

[0135] 1. Preparation of Test Electrodes

[0136] As an example of the lithium ion battery negative electrode of the present invention, the lithium ion battery negative electrode comprises a current collector and a lithium ion battery negative electrode slurry supported on the current collector; the lithium ion battery negative electrode slurry comprises a negative electrode active material, a conductive agent, the white emulsion prepared in embodiment 10 (as the binder), and a solvent; a weight ratio of the negative electrode active material, the conductive agent and the binder is 70:20:10; the solvent is water. The negative electrode active material is a silicone-based material; the conductive agent is acetylene black; the current collector is a copper foil current collector; a solids content of the lithium ion battery negative electrode slurry is 45 wt %, and a viscosity of the lithium ion battery negative electrode slurry is 3000 mPa.Math.s.

[0137] The silicone-based material and the conductive agent were mixed and stirred until uniform dispersion; then the white emulsion prepared in embodiment 10 was added into the mixture as a water-based binder, stirred well, and a proper quantity of water was added to adjust the viscosity, so as to obtain a Silicone-based electrode slurry; the slurry was coated onto a copper foil which was then vacuum-dried at 60 C. so as to obtain the silicone-based negative electrode. The vacuum-dried electrode was cut and weighed, and then installed into a 2025 battery case, with a lithium sheet as the counter electrode, a polyethylene film as the separator and 1 M LiPF.sub.6 EC/DMC/DEC (v/v/v=1/1) as the electrolyte, to assemble a battery which was then subjected to a constant current charge-discharge test.

[0138] 2. Preparation of Comparative Electrodes

[0139] The comparative electrodes were prepared by the same method wherein CMC and the modified marine polysaccharide polymer CTS-PAA-PAN of comparative example 1 were used as the binders.

[0140] 3. Electrochemical Test

[0141] An electrochemical test was performed on the test electrode and the comparative electrodes to determine the charging and discharging cyclic stability.

[0142] 4. Result Analysis

[0143] FIG. 15 shows cyclic performance test curves of the test electrode and the comparative electrodes at a charging and discharging current density of 400 mA/g, and table 4 shows a comparison between the initial coulombic efficiencies and the coulombic efficiencies of the 33.sup.th cycle. As can be seen from the table, the Silicone-based negative electrode, which was prepared with the multi-functionally modified polymer (Acacia-PAA) binder, showed initial charge-discharge efficiency and charging specific capacity higher than those of the CMC system and the CTS-PAA-PAN system, up to 83.2% and 4195mAh/g, exhibiting excellent electrochemical performance. After 33 charging-discharging cycles, the binder showed a charging specific capacity much higher than those of the CMC system and the CTS-PAA-PAN system, and a coulombic efficiency higher than those of the CMC system and the CTS-PAA-PAN system, exhibiting excellent electrochemical performance. It is indicated that, Acacia-PAA could not only enhance the binding strength between the electrode active material, the conductive agent and the current collector, but also greatly increase the cyclic stability and ion conduction rate of the silicone-based material, and thereby it could effectively extend battery life.

[0144] See table 4 for a comparison of the silicone-based negative materials with different binders in the coulombic efficiencies at a current density of 400 mA/g.

TABLE-US-00004 TABLE 4 Binder Initial coulombic efficiency (%) 33.sup.th coulombic efficiency (%) E10 83.2 98.1 CMC 81.3 98.0 C1 80.4 97.9

Embodiment 28

[0145] Electrodes were prepared, with graphite or a silicone-based material as the negative electrode material, lithium iron phosphate as the positive electrode material, and the glue solution prepared in embodiment 6, 7 or 10 (CMC-PAA-PAN, CMC-PAA-PAN-PAM, and Acacia-PAA) as the water-based binder. Peel strengths of different electrodes were measured.

[0146] 1. Preparation of Test Electrodes

[0147] The graphite electrode was prepared according to embodiment 26. The silicone-based electrode was prepared according to embodiment 27. The LFP-based electrode was prepared according to embodiment 22.

[0148] 2. Preparation of Comparative Electrodes

[0149] The comparative electrodes were prepared by the same method wherein CMC, PVDF and CTS-PAA-PAN were used as the binders.

[0150] 3. Peel Strength Measurement

[0151] A peel strength measurement was performed on the test electrodes and the comparative electrodes.

[0152] 4. Result Analysis

[0153] Table 5 (FIG. 9) shows the comparison between the test electrodes (with the binders in embodiments 6, 7 and 10) and the comparative electrodes (with PVDF, CMC and CTS-PAA-PAN as the binders) in the peel strength. As can be seen from the table, the lithium iron phosphate positive electrode with the multi-functionally modified polymer binder CMC-PAA-PAN, exhibited a peel strength higher than those of the CMC and the CTS-PAA-PAN systems (about 33 times higher) and compare favorably to that of the PVDF system, suggesting promising application and development potential. The graphite negative electrode with the multi-functionally modified polymer binder Acacia-PAA, exhibited a relatively high peel strength, which is about 20 times higher than those of the binder system with polyvinyl alcohol as the binder and comprising polystyrene (CN 105261759A). In addition, the silicone-based negative electrodes with the multi-functionally modified polymer binders CMC-PAA-PAN, CMC-PAA-PAN-PAM and Acacia-PAA, exhibited relatively high peel strengths and binding strengths which prevents the materials from break off during charging and discharging and thereby improves the cyclic stability of the battery. The multi-functionally modified polymer binders of the present invention exhibit excellent water-solubility, enhance the binding strength between the electrode active materials, the conductive agents and the current collector, and improve the overall performances of the binders.

TABLE-US-00005 TABLE 5 Average peel Electrode Binder strength (mN/mm) Nano silicone powder CMC-PAA-PAN 39 Nano silicone powder CMC-PAA-PAN-PAM 52 Nano silicone powder Acacia-PAA 35 Graphite Acacia-PAA 141 Lithium iron phosphate CMC-PAA-PAN 66 Lithium iron phosphate CMC 2 Lithium iron phosphate PVDF 75 Lithium iron phosphate CTS-PAA-PAN 2

[0154] The average peel strength in table 5 was determined by the following steps. Preparing an electrode comprising the binder by coating an aluminum foil (positive electrode) or a copper foil (negative electrode) with a thickness of 80 m for nano silicone powder (copper foil substrate), 50 m for graphite (copper foil substrate) and 100 m for lithium iron phosphate (aluminum foil substrate). Measuring the peel strength by cutting the electrode to obtain a segment having a width of 15 mm, and performing a measurement on the segment using a peel strength testing device (Shenzhen, Kaiqiangli, 180 peel tester) with a peeling rate of 20 mm/min. The results are listed in a table.

Embodiment 29

[0155] Electrodes were prepared, with graphite or a silicone-based material as the negative electrode material, lithium iron phosphate or a ternary material as the positive electrode material, and the binder CMC-PAA-PAN or Acacia-PAA prepared in embodiment 6 or 10 as the binder. Comparative electrodes were prepared with CTS-PAA-PAN of embodiment 1 as the binders. Flatness of the electrodes were observed for comparison.

[0156] 1. Preparation of Test Electrodes

[0157] The graphite electrode was prepared according to embodiment 26.

[0158] The silicone-based electrode was prepared according to embodiment 27.

[0159] The LFP-based electrode was prepared according to embodiment 22.

[0160] The NCM electrode was prepared according to embodiment 24.

[0161] 2. Electrode Flatness Test

[0162] Flatness of the electrodes were observed for comparison.

[0163] 3. Result Analysis

[0164] FIG. 16 shows a comparison in flatness of the electrodes of the present embodiment. As can be seen from the figure, the graphite and silicone-based negative electrodes with the multi-functionally modified polymer binder Acacia-PAA, and the lithium iron phosphate and ternary material positive electrodes with the multi-functionally modified polymer binder CMC-PAA-PAN, all exhibited uniform and excellent flatness, which can improve the cyclic stability of the battery, suggesting promising application and development potentials. In addition, the lithium iron phosphate electrode with CMC-PAA-PAN showed uniformity and flatness better than those of the CTS-PAA-PAN system, without graininess or discontinuity, which can improve the electrochemical stability of the battery during charging and discharging and thereby extend battery life.