Anode slurry and method for preparing the same

Abstract

The present invention provides a method for preparing an anode slurry used in a lithium ion battery. The method includes the following steps: providing at least one anode active material, at least one conductive agent, at least one monomer or a prepolymer and at least one solvent. Mixing the anode active material, the conductive agent and the monomer or the prepolymer with the solvent; dispersing uniformly to form a mixture. Adding an initiator into the mixture; polymerizing the monomer or the prepolymer at a certain temperature; and yielding the anode slurry. Besides, the present invention also provides an anode slurry prepared by the above method, and an anode plate prepared by the anode slurry, and a lithium ion battery including the anode plate.

Claims

1. A method for preparing an anode slurry used in a lithium ion battery, comprising: providing at least one anode active material, at least one conductive agent, at least one monomer or prepolymer, and at least one solvent; mixing the anode active material, the conductive agent and the monomer or prepolymer with the solvent, dispersing uniformly to form a dispersion; and adding an initiator into the dispersion and therefore inducing a polymerization of the monomer or the prepolymer, thereby yielding an anode slurry; the monomer is at least one selected from the group consisting of acrylic acid, methacrylic acid and itaconic acid; the prepolymer is selected from at least one of acrylic prepolymers, methacrylic acid prepolymer, and itaconic acid prepolymer; wherein said polymerization of the monomer or prepolymer is induced prior to coating onto a current collector.

2. The method of claim 1, wherein the anode active material comprises silicon, which is at least one selected from the group consisting of silicon powder, nano-silicon particles, and silicon-carbon composite.

3. The method of claim 2, wherein an average particle diameter of the silicon powder or the nano-silicon particles is between 20 nm and 2000 nm.

4. The method of claim 2, wherein an average particle diameter of the silicon-carbon composite is between 1 m and 100 m.

5. The method of claim 1, wherein a BET specific surface area of the anode active material is from 1 cm.sup.2/g to 100 cm.sup.2/g.

6. The method of claim 1, wherein an initial coulombic efficiency of the anode active material is greater than 50%.

7. The method of claim 1, wherein the solvent is water and/or organic solvent, the organic solvent is alcoholic solvent or ketone solvent.

8. The method of claim 7, wherein the organic solvent is at least one selected from methanol, ethanol and acetone.

9. The method of claim 1, wherein the conductive agent is at least one selected from the group consisting of carbon power, carbon fiber, conductive carbon black, carbon nanotube, flaky graphite and graphene; a mass of the conductive agent accounts for 0.1% to 5% of the total mass of the anode slurry.

10. The method of claim 1, wherein the initiator is at least one selected from the group consisting of sodium persulfate, potassium persulfate and ammonium persulfate; a mass of the initiator accounts for 0.1% to 5% of the total mass of the anode slurry.

11. The method of claim 1, wherein a mass of the anode active material accounts for 5% to 50% of the total mass of the anode slurry.

12. The method of claim 1, wherein a mass of the monomer or prepolymer accounts for 5% to 50% of the total mass of the anode slurry.

13. The method of claim 1, wherein a mass of the solvent accounts for 20% to 85% of the total mass of the anode slurry.

14. The method of claim 1, wherein a temperature of polymerization is between 30 C. to 120 C.

15. The method of claim 14, wherein the temperature of polymerization is between 50 C. to 100 C.

16. The method of claim 14, wherein the temperature of polymerization is between 65 C. to 85 C.

17. The method of claim 1, wherein a reaction time of the polymerization is between 1 to 10 hours.

18. The method of claim 17, wherein the reaction time of the polymerization is between 2 to 6 hours.

19. The method of claim 17, wherein the reaction time of the polymerization is between 2 to 4 hours.

20. The method of claim 1, wherein a viscosity of the anode slurry prepared above is 1000 to 8000 mPa.Math.s.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The FIGURE illustrates the cycling performance test results of the button batteries prepared in embodiment 1 and embodiment 2 of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(2) The present invention will now be described more specifically with reference to the following embodiments. It is to be noted that the following descriptions of preferred embodiments of this invention are presented herein for purpose of illustration and description only. It is not intended to be exhaustive or to be limited to the precise form disclosed. In the embodiments below, a Ketjenblack conductive agent EC600JD is provided by AkzoNobel, and a silicon-carbon anode composite is provided by Shenzhen BTR new energy materials Inc.

Embodiment 1

(3) Mixing 10 g nano-silicon powder, 1 g Ketjenblack conductive agent (EC600JD) and 9 g acrylic acid with 30 g water, wherein the average diameter D.sub.50 of the nano-silicon powder being 200 nm. After stirring and ultrasonic dispersing treatment, a 1.sup.st mixture is obtained. Next, dissolving 1.5 g sodium persulfate (abbr. as SPS) into 10 g water to obtain a 2.sup.nd mixture, wherein the SPS acting as an initiator. Finally, adding the 2.sup.nd mixture into the 1.sup.st mixture, stirring at 70 C. for 3 hours, and yielding anode slurry of the lithium batteries.

Embodiment 2

(4) Mixing 10 g nano-silicon powder, 1 g Ketjenblack conductive agent (EC600JD) and 9 g acrylic acid with 30 g water, wherein the D.sub.50 of the nano-silicon powder being 100 nm. After stirring and ultrasonic dispersing treatment, a 1.sup.st mixture is obtained. Next, dissolving 1 g ammonium persulfate (abbr. as APS) into 10 g water to obtain a 2.sup.nd mixture, wherein the SPS acting as initiator. Finally, adding the 2.sup.nd mixture into the 1.sup.st mixture, stirring at 75 C. for 4 hours, and yielding anode slurry of lithium batteries.

Embodiment 3

(5) Mixing 5 g nano-silicon powder, 0.5 g Super P conductive agent and 7 g acrylic acid with 40 g water, after stirring and ultrasonic dispersing treatment, a 1.sup.st mixture is obtained. Next, dissolving 1 g APS into 10 g water to obtain a 2.sup.nd mixture, wherein the APS acting as initiator. Finally, adding the 2.sup.nd mixture into the 1.sup.st mixture, stirring at 100 C. for 2 hours, and yielding anode slurry of lithium batteries.

Embodiment 4

(6) Mixing 8 g nano-silicon powder, 0.5 g Super P conductive agent and 7 g acrylic acid with 25 g water, after stirring and ultrasonic dispersing treatment, a 1.sup.st mixture is obtained. Next, dissolving 1 g SPS into 10 g water to obtain a 2.sup.nd mixture, wherein the SPS acting as initiator. Finally, adding the 2.sup.nd mixture into the 1.sup.st mixture, stirring at 60 C. for 4 hours, and yielding anode slurry of lithium batteries.

Embodiment 5

(7) Mixing 15 g nano-silicon powder, 0.5 g Super P conductive agent and 7 g acrylic acid with 25 g water, after stirring and ultrasonic dispersing treatment, a 1.sup.st mixture is obtained. Next, dissolving 0.5 g SPS into 10 g water to obtain a 2.sup.nd mixture, wherein the SPS acting as initiator. Finally, adding the 2.sup.nd mixture into the 1.sup.st mixture, stirring at 60 C. for 9 hours, and yielding anode slurry of lithium batteries.

Embodiment 6

(8) Mixing 10 g silicon-carbon anode composite, 1 g Super P conductive agent and 7 g acrylic acid with 25 g water, wherein the D.sub.50 of the silicon-carbon anode composite being 10 m. After stirring and ultrasonic dispersing treatment, a 1.sup.st mixture is obtained. Next, dissolving 0.5 g SPS into 10 g water to obtain a 2.sup.nd mixture, wherein the SPS acting as initiator. Finally, adding the 2.sup.nd mixture into the 1.sup.st mixture, stirring at 60 C. for 6 hours, and yielding anode slurry of lithium batteries.

Embodiment 7

(9) Mixing 15 g silicon-carbon anode composite, 1 g Super P conductive agent and 7 g acrylic acid with 25 g water, after stirring and ultrasonic dispersing treatment, a 1.sup.st mixture is obtained. Next, dissolving 0.5 g SPS into 10 g water to obtain a 2.sup.nd mixture, wherein the SPS acting as initiator. Finally, adding the 2.sup.nd mixture into the 1.sup.st mixture, stirring at 90 C. for 4 hours, and yielding anode slurry of lithium batteries.

Embodiment 8

(10) Mixing 20 g silicon-carbon anode composite, 2 g Super P conductive agent and 7 g acrylic acid with 45 g water, after stirring and ultrasonic dispersing treatment, a 1.sup.st mixture is obtained. Next, dissolving 1 g SPS into 10 g water to obtain a 2.sup.nd mixture, wherein the SPS acting as initiator. Finally, adding the 2.sup.nd mixture into the 1.sup.st mixture, stirring at 60 C. for 4 hours, and yielding anode slurry of lithium batteries.

Embodiment 9

(11) Mixing 20 g silicon-carbon anode composite, 0.5 g Super P conductive agent and 7 g acrylic acid with 45 g water, after stirring and ultrasonic dispersing treatment, a 1.sup.st mixture is obtained. Next, dissolving 0.5 g SPS into 10 g water to obtain a 2.sup.nd mixture, wherein the SPS acting as initiator. Finally, adding the 2.sup.nd mixture into the 1.sup.st mixture, stirring at 95 C. for 4 hours, and yielding anode slurry of lithium batteries.

Embodiment 10

(12) Mixing 20 g silicon-carbon anode composite, 0.5 g Ketjenblack conductive agent (EC600JD) and 7 g acrylic acid with 45 g water, after stirring and ultrasonic dispersing treatment, a 1.sup.st mixture is obtained. Next, dissolving 0.5 g SPS into 10 g water to obtain a 2.sup.nd mixture, wherein the SPS acting as initiator. Finally, adding the 2.sup.nd mixture into the 1.sup.st mixture, stirring at 70 C. for 4 hours, and yielding anode slurry of lithium batteries.

Embodiment 11

(13) Mixing 20 g silicon-carbon anode composite, 0.5 g Ketjenblack conductive agent (EC600JD) and 7 g acrylic acid with 45 g water, after stirring and ultrasonic dispersing treatment, a 1.sup.st mixture is obtained. Next, dissolving 0.5 g SPS into 10 g water to obtain a 2.sup.nd mixture, wherein the SPS acting as initiator. Finally, adding the 2.sup.nd mixture into the 1.sup.st mixture, stirring at 60 C. for 8 hours, and yielding anode slurry of lithium batteries.

Embodiment 12

(14) Mixing 20 g silicon-carbon anode composite, 0.5 g Ketjenblack conductive agent (EC600JD) and 7 g acrylic acid with 45 g water, after stirring and ultrasonic dispersing treatment, a 1.sup.st mixture is obtained. Next, dissolving 2 g SPS into 10 g water to obtain a 2.sup.nd mixture, wherein the SPS acting as initiator. Finally, adding the 2.sup.nd mixture into the 1.sup.st mixture, stirring at 90 C. for 2 hours, and yielding lithium battery anode slurry.

Embodiment 13

(15) Mixing 25 g silicon-carbon anode composite, 0.5 g Ketjenblack conductive agent (EC600JD) and 7 g acrylic acid with 45 g water, after stirring and ultrasonic dispersing treatment, a 1.sup.st mixture is obtained. Next, dissolving 2 g SPS into 10 g water to obtain a 2.sup.nd mixture, wherein the SPS acting as initiator. Finally, adding the 2.sup.nd mixture into the 1.sup.st mixture, stirring at 100 C. for 2 hours, and yielding lithium battery anode slurry.

Embodiment 14

(16) Mixing 25 g silicon-carbon anode composite, 0.5 g Ketjenblack conductive agent (EC600JD) and 7 g acrylic acid with 20 g water and 25 g ethanol, after stirring and ultrasonic dispersing treatment, a 1.sup.st mixture is obtained. Next, dissolving 2 g SPS into 10 g water to obtain a 2.sup.nd mixture, wherein the SPS acting as initiator. Finally, adding the 2.sup.nd mixture into the 1.sup.st mixture, stirring at 110 C. for 2 hours, and yielding lithium battery anode slurry.

Embodiment 15

(17) Mixing 25 g silicon-carbon anode composite, 0.5 g Ketjenblack conductive agent (EC600JD) and 7 g acrylic acid with 60 g water, after stirring and ultrasonic dispersing treatment, a 1.sup.st mixture is obtained. Next, dissolving 2 g SPS into 10 g water to obtain a 2.sup.nd mixture, wherein the SPS acting as initiator. Finally, adding the 2.sup.nd mixture into the 1.sup.st mixture, stirring at 70 C. for 2 hours, and yielding lithium battery anode slurry.

Embodiment 16

(18) Mixing 25 g silicon-carbon anode composite, 0.5 g Ketjenblack conductive agent (EC600JD) and 7 g acrylic acid with 20 g water and 25 g ethanol, after stirring and ultrasonic dispersing treatment, a 1.sup.st mixture is obtained. Next, dissolving 2 g SPS into 10 g water to obtain a 2.sup.nd mixture, wherein the SPS acting as initiator. Finally, adding the 2.sup.nd mixture into the 1.sup.st mixture, stirring at 70 C. for 2 hours, and yielding lithium battery anode slurry.

Embodiment 17

(19) Mixing 25 g silicon-carbon anode composite, 0.5 g Ketjenblack conductive agent (EC600JD) and 7 g itaconic acid (abbr. as ITA) with 40 g water, after stirring and ultrasonic dispersing treatment, a 1.sup.st mixture is obtained. Next, dissolving 2 g SPS into 10 g water to obtain a 2.sup.nd mixture, wherein the SPS acting as initiator. Finally, adding the 2.sup.nd mixture into the 1.sup.st mixture, stirring at 50 C. for 10 hours, and yielding lithium battery anode slurry.

Embodiment 18

(20) Mixing 25 g silicon-carbon anode composite, 0.5 g Ketjenblack conductive agent (EC600JD) and 7 g ITA with 40 g water, after stirring and ultrasonic dispersing treatment, a 1.sup.st mixture is obtained. Next, dissolving 2 g SPS into 10 g water to obtain a 2.sup.nd mixture, wherein the SPS acting as initiator. Finally, adding the 2.sup.nd mixture into the 1.sup.st mixture, stirring at 80 C. for 2 hours, and yielding lithium battery anode slurry.

Embodiment 19

(21) Mixing 25 g silicon-carbon anode composite, 0.5 g Ketjenblack conductive agent (EC600JD) and 7 g methacrylic acid (abbr. as MAA) with 40 g water, after stirring and ultrasonic dispersing treatment, a 1.sup.st mixture is obtained. Next, dissolving 2 g SPS into 10 g water to obtain a 2.sup.nd mixture, wherein the SPS acting as initiator. Finally, adding the 2.sup.nd mixture into the 1.sup.st mixture, stirring at 65 C. for 2 hours, and yielding lithium battery anode slurry.

(22) Button Batteries were prepared by the following method: first, coating the silicon-containing anode slurry onto a copper foil uniformly, wherein the silicon-containing anode slurry is prepared in any of the embodiments 1-19; Then, vacuum-drying and rolling the coated copper foil to form an anode plate, which is going to be used as cathode. Next, a solution of LiPF.sub.6 in EC, DMC and EMC mixed solvent system is used as electrolyte, wherein a concentration of LiPF.sub.6 in the solution is 1 mol/L, and a volume ratio of EC, DMC and EMC is 1:1:1. Polypropylene microporous membrane is used as the separator. Finally, the above components are assembled into a button battery.

(23) The cycling performance is tested by performing the charge-discharge processes under constant current, wherein the charge-discharge current remains at 0.2 mA, and the charge-discharge voltage is limited within 0.01V to 1.8V. The FIGURE illustrates the cycling performance test results of the button batteries prepared in embodiment 1 and embodiment 2 of the present invention. As shown in the FIGURE, capacity of the lithium batteries prepared in embodiments 1 and 2 reaches 1500 mAh/g to 2000 mAh/g, and the charge-discharge cycle is quite stable. The reason for the improvement above is that, the anode slurries used in the lithium batteries are prepared by silicon (or silicon-carbon) coated with poly acrylic acid through in-situ polymerization. In this way, the silicon (or silicon-carbon) powder is uniformly coated by polymers, thus the volume expansion of silicon is effectively inhibited. Therefore, the silicon powder and the conductive agent maintain good contact with the current collector. All these make the silicon (or silicon-carbon) anode more stable during the charge-discharge processes. Similarly, the anode slurries of embodiments 3-13 also prepared with a material of acrylic acid.

(24) The cycling performance of the batteries in embodiments 14, 15 and 19 is similar to that in embodiments 1 and 2, wherein the anode slurries are prepared by silicon coated with poly(methacrylic acid) by in-situ polymerization, wherein the methacrylic acid includes carboxyl groups. Meanwhile, the cycling performance of the batteries in embodiments 16-18 is also similar to that in embodiments 1 and 2, wherein the anode slurries are prepared by silicon coated with poly (itaconic acid) by in-situ polymerization. As we all know, the itaconic acid is also named as methylene succinic acid, which includes carboxyl groups. That is, the carboxyl groups in acrylic acid, methacrylic acid and itaconic acid enable the in-situ polymerizations taking place, and the silicon powders are uniformly coated by the products during the polymerization reaction.

(25) It will be understood that the above particular embodiments are shown and described by way of illustration only. The principles and the features of the present disclosure may be employed in various and numerous embodiments thereof without departing from the scope of the disclosure. The above-described embodiments illustrate the scope of the disclosure but do not restrict the scope of the disclosure.