Multifunctional Polymer Binder for Negative Electrode and Its Preparation Method

Abstract

Disclosed is a method for preparing a negative electrode for a lithium-ion battery, comprising the following steps: mixing a silicon / graphite / carbon material, one or more linear polymers, one or more conductive polymers, one or more self-healing polymers, and one or more rubber polymers to produce a slurry; coating the slurry on a metal member; drying the metal member coated with the slurry to form a negative electrode. Also disclosed are a negative electrode and a lithium-ion battery. Also disclosed is a multifunctional polymer binder, which comprises one or more linear polymers, one or more conductive polymers, one or more self-healing polymers, and one or more rubber polymers.

Description

[0001] Related Applications

[0002] This application claims priority to Australian Provisional Patent Application No. 2019904719, filed on December 13, 2019, the content of which is hereby incorporated by reference into this application. Technical Field

[0003] The present invention generally relates to electrochemical cells, particularly batteries. In specific embodiments, the present invention relates to electrodes for batteries, such as lithium-ion batteries, i.e., lithium-ion battery cells, and methods of manufacturing the electrodes and batteries. More specifically, example embodiments relate to methods of manufacturing anodes and lithium-ion batteries, and / or methods of preparing components or materials for anodes and lithium-ion batteries. In addition, a multifunctional polymer binder is also disclosed. Background Art

[0004] Any discussion of the prior art throughout the specification should not be considered an admission that such prior art is well known or forms part of the common general knowledge in the art.

[0005] Lithium-ion-based battery cells are attractive energy sources for various applications, in part because of their ability to provide relatively high energy and long cycle life. The performance characteristics of a lithium-ion battery (LIB), such as the total energy capacity, depend on the types of anode and cathode used in the LIB. In the field of anode materials for lithium-ion batteries, silicon with a theoretical capacity of up to 4200 mAh / g is considered a promising candidate for the next generation of LIB anode materials, e.g., to replace graphite. However, during the lithiation and delithiation processes, silicon typically undergoes a large volume change (about 300%), resulting in the rupture and pulverization of the active material, subsequent disintegration of the anode, and a rapid decline in capacity.

[0006] Some methods involving nanostructured silicon (nanosilicon) can alleviate the volume expansion of silicon to some extent. However, the known synthetic processes involving nanosilicon are relatively complex, expensive, and difficult to industrialize.

[0007] To achieve improvements in the performance of silicon-based anodes in LIBs, particularly high-energy LIBs, important problems that need to be addressed may include: (a) the uniform distribution of silicon particles in a conductive matrix; (b) the ability to prepare silicon secondary particles on a large scale to achieve high weight energy density, high volume energy density, and high first Coulomb efficiency; and (c) excellent mechanical properties of the anode.

[0008] The Chinese patent application CN108807861A of Amperex Nanjing Co., Ltd. discloses a method for manufacturing an anode for a lithium-ion battery, including the steps of grinding a mixture of nano-silicon, one or more carbonaceous materials (paragraph

[0028] ), and one or more solvents, wherein the mixture remains as a wet slurry during grinding; carbonizing the mixture at a carbonization temperature to produce silicon material coated with carbon (Si@C); grinding a second mixture of Si@C material, one or more second carbonaceous materials, and one or more second solvents, wherein the second mixture remains as a second wet slurry during grinding; carbonizing the second mixture at a second carbonization temperature to produce Si@C / carbon material; and forming an anode from the Si@C / carbon material. Although CN'861 describes the silicon as "nano-silicon", the silicon used is about 3 - 4 μm.

[0009] More specifically, that of CN’861 Figure 1 shows a silicon-carbon composite material formed by irregularly shaped secondary particles obtained by the method described in CN’861. Figure 1 shows particles surrounded by a continuous amorphous carbon protective layer, inside which are multiple secondary particles composed of silicon material. The particles also contain conductive additives, such as carbon nanotubes, which are uniformly dispersed throughout the mixture. The silicon material and the conductive filler are each surrounded by amorphous carbon filler, and then the amorphous carbon filler is in turn surrounded by a continuous amorphous carbon protective layer.

[0010] Zhou et al. ("Preparation and characterisation of core-shell structure Si / C composite with multiple carbon phases as anode materials for lithium ion batteries", 2016, J. Alloys and Compounds, vol. 658, pp. 91 - 97) disclose an anode for a lithium-ion battery including modified spherical graphite / silicon / flaky graphite / disordered carbon. The active material is prepared by mixing nano-silicon, flaky graphite, and citric acid and then carbonizing to obtain Si@CFG, adding modified spherical graphite (i.e., graphite and a second carbonaceous material) containing a coal tar pitch layer and performing a second carbonization step, thus obtaining Si@CFG / spherical graphite / carbon material. Zhou et al. apparently do not teach that the second mixing step includes grinding. Therefore, the anode structure and integrity are relatively rough. Zhou et al. further teach silicon particles that are not directly coated with carbon, which makes them prone to swelling and side reactions, resulting in lower conductivity.

[0011] Eom and Cao ("Effect of anode binders on low-temperature performance of Automotive Li-ion Battery", Journal of Power Sources, vol. 441, 30 November 2019, p. 227178) studied the effects of styrene-butadiene rubber (SBR) / sodium carboxymethyl cellulose (CMC) and polyvinylidene fluoride (PVdF) binders in the anode on the low-temperature performance and recyclability of automotive lithium-ion batteries. The applicant believes that those skilled in the art will understand from the teachings of this document that using PVdF in combination with other components (e.g., carboxymethyl cellulose (CMC), CP, and SHP) is the next logical step to increase the number of cycles. Those skilled in the art would not expect to use styrene-butadiene rubber (SBR) to increase the number of cycles.

[0012] Wu and Li ("Distribution uniformity of water-based binders in Si anodes and the distribution effects on cell performance", ACS Sustainable Chem. Eng., 8, 17, 13 April 2020, pp. 6868-6876) reported and discussed the concentration distribution of binders, CMC, and the composite of SBR and CMC in dry silicon anodes, and the effects of their distribution on the electrochemical performance of the constructed batteries. When preparing silicon electrodes with a single binder CMC, the binder was uniformly distributed in the dry / thickness direction of the electrode sheet. However, when CMC was combined with SBR, the distribution of the binder became non-uniform; this is because the contained SBR is prone to migrate with the solvent during drying and eventually accumulate on the upper surface of the electrode. The non-uniform distribution of SBR weakens the adhesion strength of the electrode sheet on the current collector, thereby increasing the impedance of the fabricated anode and reducing the capacity, rate performance, and cycle life of the constructed lithium-ion battery. The applicant infers that those skilled in the art would not seek a mixed phase or different structure. Instead, the skilled person would seek to use miscible or compatible polymers that would be relatively uniformly distributed throughout the composition. This citation clearly teaches that using SBR results in a bilayer structure, and SBR does not form integrally and interact with other components in the said structure. Therefore, those skilled in the art will understand that using SBR does not provide any advantages in the composition. Summary of the Invention

[0013] An object of the present invention is to overcome or improve at least one drawback of the prior art, or to provide a useful alternative.

[0014] It is an object of a particularly preferred form of the present invention to provide a new or improved method for manufacturing a negative electrode and / or a lithium-ion battery, and / or a method for preparing a component or material for a negative electrode and / or a lithium-ion battery.

[0015] Another particularly preferred form of the present invention aims to provide a new or improved multifunctional polymer binder, which can be used as part of a negative electrode to improve the performance of the negative electrode, for example.

[0016] Unless the context clearly requires otherwise, throughout the specification and claims, the words "comprise", "comprising", etc. shall be construed in an inclusive sense rather than an exclusive or exhaustive sense; that is, it is meant "including but not limited to".

[0017] Although the present invention will be described with reference to specific examples, those skilled in the art will understand that the present invention can be implemented in many other forms.

[0018] The present invention is provided to introduce some concepts in a simplified form, which will be further described below. The present invention is not intended to identify the key features or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter.

[0019] According to a first aspect of the present invention, there is provided a method for manufacturing a negative electrode for a lithium-ion battery, the method comprising the following steps:

[0020] Mixing a silicon / graphite / carbon material, one or more linear polymers, one or more conductive polymers, one or more self-healing polymers, and one or more rubber polymers to produce a slurry;

[0021] Coating the slurry onto a metal member; and

[0022] Drying the metal member coated with the slurry to form a negative electrode.

[0023] In one embodiment, the method for manufacturing a negative electrode for a lithium-ion battery comprises the following steps:

[0024] Mixing a silicon / graphite / carbon material with a multifunctional polymer binder comprising one or more linear polymers, one or more conductive polymers, one or more self-healing polymers, and one or more rubber polymers to produce a slurry;

[0025] Coating the slurry onto a metal member; and

[0026] Drying the metal member coated with the slurry to form a negative electrode.

[0027] In one embodiment, the silicon / graphite / carbon material is a Si@C / graphite / carbon material.

[0028] In one embodiment, the metal member is a metal foil, a metal strip, or a metal grid.

[0029] In one embodiment, the metal member is a copper foil.

[0030] In one embodiment, first, the one or more linear polymers, the one or more conductive polymers, the one or more self-healing polymers, and the one or more rubber polymers are mixed together, wherein:

[0031] The one or more linear polymers have a weight percentage equal to or about 15 wt% to about 70 wt%;

[0032] The one or more conductive polymers have a weight percentage equal to or about 1 wt% to about 30 wt%;

[0033] The one or more self-healing polymers have a weight percentage equal to or about 5 wt% to about 20 wt%;

[0034] The one or more rubber polymers have a weight percentage equal to or about 10 wt% to about 40 wt%; and

[0035] wherein the total weight percentage of the one or more linear polymers, the one or more conductive polymers, the one or more self-healing polymers, and the one or more rubber polymers is 100 wt%.

[0036] In one embodiment, first, the one or more linear polymers, the one or more conductive polymers, the one or more self-healing polymers, and the one or more rubber polymers are mixed together, wherein:

[0037] The weight percentage of the one or more linear polymers is about 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, or 70 wt%;

[0038] The weight percentage of the one or more conductive polymers is about 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 7.5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, or 30 wt%;

[0039] The weight percentage of said one or more self-healing polymers is about 5 wt%, 7.5 wt%, 10 wt%, 15 wt% or 20 wt%;

[0040] The weight percentage of said one or more rubber polymers is about 10 wt%, 15 wt%, 20 wt%, 30 wt%, 35 wt% or 40 wt%; and

[0041] Wherein, the total weight percentage of said one or more linear polymers, said one or more conductive polymers, said one or more self-healing polymers and said one or more rubber polymers is 100 wt%.

[0042] In one embodiment, first mix said one or more linear polymers, said one or more conductive polymers, said one or more self-healing polymers and said one or more rubber polymers together, wherein:

[0043] The weight percentage of said one or more linear polymers is about 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt%, 30 wt%, 31 wt%, 32 wt%, 33 wt%, 34 wt%, 35 wt%, 36 wt%, 37 wt%, 38 wt%, 39 wt%, 40 wt%, 41 wt%, 42 wt%, 43 wt%, 44 wt%, 45 wt%, 46 wt%, 47 wt%, 48 wt%, 49 wt%, 50 wt%, 51 wt%, 52 wt%, 53 wt%, 54 wt%, 55 wt%, 56 wt%, 57 wt%, 58 wt%, 59 wt%, 60 wt%, 61 wt%, 62 wt%, 63 wt%, 64 wt%, 65 wt%, 66 wt%, 67 wt%, 68 wt%, 69 wt% or 70 wt%;

[0044] The weight percentage of said one or more conductive polymers is about 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt% or 30 wt%;

[0045] The weight percentage of the one or more self-healing polymers is about 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt% or 20 wt%;

[0046] The weight percentage of the one or more rubber polymers is about 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%, 26, 27 wt%, 28 wt%, 29 wt%, 30 wt%, 31 wt%, 32 wt%, 33 wt%, 34 wt%, 35 wt%, 36 wt%, 37 wt%, 38 wt%, 39 wt% or 40 wt%; and

[0047] wherein the total weight percentage of the one or more linear polymers, the one or more conductive polymers, the one or more self-healing polymers and the one or more rubber polymers is 100 wt%.

[0048] In one embodiment, the one or more linear polymers, the one or more conductive polymers, the one or more self-healing polymers and the one or more rubber polymers are first mixed together at a mass ratio of about 15 - 70:1 - 30:5 - 20:10 - 40 (linear polymer:conductive polymer:self-healing polymer:rubber polymer), wherein the total mass ratio of the one or more linear polymers, one or more conductive polymers, one or more self-healing polymers and one or more rubber polymers is 100.

[0049] In one embodiment, the one or more linear polymers, the one or more conductive polymers, the one or more self-healing polymers, and the one or more rubber polymers are first mixed together at a mass ratio of about 20-50:1-20:5-20:10-30, 30-50:5-15:5-15:15-30, 30-40:5-10:5-10:20-30, 40-70:10-20:10-20:10-20, 30-40:10:10:30, 40-50:10-15:10-15:30-40, or 40-45:10-15:10-15:30-35 (linear polymer:conductive polymer:self-healing polymer:rubber polymer), wherein the total mass ratio of the one or more linear polymers, one or more conductive polymers, one or more self-healing polymers, and one or more rubber polymers is 100.

[0050] In one embodiment, the one or more linear polymers, the one or more conductive polymers, the one or more self-healing polymers, and the one or more rubber polymers are first mixed together at a mass ratio of about 40:10:10:10:30 (linear polymer:conductive polymer:self-healing polymer:rubber polymer). In one embodiment, citric acid is used instead of the conductive polymer. In one embodiment, the one or more linear polymers, citric acid, the one or more self-healing polymers, and the one or more rubber polymers are first mixed together at a mass ratio of about 40:10:10:10:30 (linear polymer:citric acid:self-healing polymer:rubber polymer).

[0051] In one embodiment, the one or more linear polymers are selected from linear polymers of hydroxyl, amino, or carboxyl groups.

[0052] In one embodiment, the one or more conductive polymers are selected from conductive polymers of amino or sulfonic acid groups.

[0053] In one embodiment, the one or more self-healing polymers are selected from self-healing polymers of ureido groups.

[0054] In one embodiment, the one or more linear polymers are selected from the group consisting of sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), lithium polyacrylate (LiPAA), polyvinyl alcohol (PVA), sodium alginate (SA), 2-pentenoic acid, 2-methylacrylic acid, and chitosan (CS).

[0055] In one embodiment, the one or more conductive polymers are selected from the group consisting of polyaniline (PANI), sodium poly[9,9-bis(3-propionic acid)fluorene] (PFCOONa), poly[(l-pyrenemethyl)methacrylate-co-methacrylic acid] (PPyMAA), polypyrrole (PPY), and 3,4-ethylenedioxythiophene / polystyrene-4-sulfonate (PEDOT:PSS).

[0056] In one embodiment, citric acid drives the crosslinking of the polymer elements. This crosslinking occurs after the binder is fully mixed with the active material and the conductive material, coated on the current collector, and then dried. Heating of the slurry triggers the crosslinking of the binder elements, thereby generating a 3D structure and ensuring that SBR does not migrate to the electrode surface.

[0057] In one embodiment, the one or more self-healing polymers are selected from the group consisting of ureido-pyrimidinone (UPy), ureido-oligo-amidoamine (UOAA), dopamine methacrylamide (DMA), and dopamine (DA).

[0058] In one embodiment, the one or more self-healing polymers are ureido-oligo-amidoamine (UOAA).

[0059] In one embodiment, the one or more rubber polymers are selected from the group consisting of styrene-butadiene rubber (SBR), chloroprene rubber, nitrile rubber, butyl silicone rubber, and polysulfide rubber.

[0060] In one embodiment, the method further includes mixing a conductive agent into the slurry.

[0061] In one embodiment, the conductive agent is selected from the group consisting of carbon black, carbon nanotubes, graphene, functionalized graphene flakes, nanofibers of carbon, and mixtures thereof.

[0062] In one embodiment, the silicon / graphite / carbon material, the conductive agent, and the combined mixture of the one or more linear polymers, the one or more conductive polymers, the one or more self-healing polymers, and the one or more rubber polymers are mixed together at a mass ratio of equal to or about 80-96:1-10:3-10 (silicon / graphite / carbon material:conductive agent:polymer combined mixture).

[0063] In one embodiment, the silicon / graphite / carbon material, the conductive agent, and the mixed combination of the one or more linear polymers, the one or more conductive polymers, the one or more self-healing polymers, and the one or more rubber polymers are mixed together at a mass ratio of about 80:10:10, about 85:10:5, about 85:9:6, about 85:8:7, about 85:7:8, about 85:6:9, about 85:5:10, about 90:7:3, about 90:6:4, about 90:5:5, about 90:4:6, about 90:3:7, about 90:2:8, about 90:1:9, about 95:2:3, about 95:1:4, or about 96:1:3 (silicon / graphite / carbon material:conductive agent:mixed combination of polymers).

[0064] In one embodiment, considering the increased conductivity provided by the binder of the present invention, 0 wt% of conductive carbon can be added, and then the ratio can be 96% active material:4% binder material, 97:3, 98:2, or 99:1.

[0065] In some embodiments, the multifunctional polymer binder has sufficient conductivity such that it does not require a conductive agent. In some embodiments, the silicon / graphite / carbon material, the mixed combination of the one or more linear polymers, the one or more conductive polymers, the one or more self-healing polymers, and the one or more rubber polymers are mixed together at a mass ratio of about 80 - 99:1 - 20, 85 - 99:1 - 15, 90 - 99:1 - 10, 95 - 99:1 - 5, 96:4, 97:3, 98:2, or 99:1 (silicon / graphite / carbon material:mixed combination of polymers).

[0066] In one embodiment, the one or more linear polymers are sodium carboxymethyl cellulose (CMC); the one or more conductive polymers are polypyrrole (PPY); the one or more self-healing polymers are dopamine (DA); and the one or more rubber polymers are styrene-butadiene rubber (SBR).

[0067] In one embodiment, the one or more linear polymers are sodium carboxymethyl cellulose (CMC); and / or the one or more conductive polymers are polypyrrole (PPY); and / or the one or more self-healing polymers are dopamine (DA); and / or the one or more rubber polymers are styrene-butadiene rubber (SBR).

[0068] According to a second aspect of the present invention, there is provided a multifunctional polymer binder comprising:

[0069] One or more linear polymers;

[0070] One or more conductive polymers;

[0071] One or more self - healing polymers, and

[0072] One or more rubber polymers.

[0073] In a particularly preferred embodiment, the multifunctional polymer adhesive comprises 30% CMC, 10% PAA, 10% citric acid, 10% PEDOT - PSS, 10% SHP and 30% SBR.

[0074] In one embodiment, the one or more linear polymers have a weight percentage equal to or about 15 wt% to about 70 wt%;

[0075] The one or more conductive polymers have a weight percentage equal to or about 1 wt% to about 30 wt%;

[0076] The one or more self - healing polymers have a weight percentage equal to or about 5 wt% to about 20 wt%;

[0077] The one or more rubber polymers have a weight percentage equal to or about 10 wt% to about 40 wt%; and

[0078] Wherein the total weight percentage of the adhesive is 100 wt%.

[0079] In one embodiment, the weight percentage of the one or more linear polymers is about 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt% or 70 wt%;

[0080] The weight percentage of the one or more conductive polymers is about 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 7.5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt% or 30 wt%;

[0081] The weight percentage of the one or more self - healing polymers is about 5 wt%, 7.5 wt%, 10 wt%, 15 wt% or 20 wt%;

[0082] The weight percentage of the one or more rubber polymers is about 10 wt%, 15 wt%, 20 wt%, 30 wt%, 35 wt% or 40 wt%; and

[0083] Wherein the total weight percentage of the adhesive is 100 wt%.

[0084] In one embodiment, the weight percentage of the one or more linear polymers is about 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt%, 30 wt%, 31 wt%, 32 wt%, 33 wt%, 34 wt%, 35 wt%, 36 wt%, 37 wt%, 38 wt%, 39 wt%, 40 wt%, 41 wt%, 42 wt%, 43 wt%, 44 wt%, 45 wt%, 46 wt%, 47 wt%, 48 wt%, 49 wt%, 50 wt%, 51 wt%, 52 wt%, 53 wt%, 54 wt%, 55 wt%, 56 wt%, 57 wt%, 58 wt%, 59 wt%, 60 wt%, 61 wt%, 62 wt%, 63 wt%, 64 wt%, 65 wt%, 66 wt%, 67 wt%, 68 wt%, 69 wt% or 70 wt%;

[0085] The weight percentage of the one or more conductive polymers is about 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt% or 30 wt%;

[0086] The weight percentage of the one or more self-healing polymers is about 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%; and

[0087] The weight percentage of the one or more rubber polymers is about 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt%, 30 wt%, 31 wt%, 32 wt%, 33 wt%, 34 wt%, 35 wt%, 36 wt%, 37 wt%, 38 wt%, 39 wt% or 40 wt%;

[0088] The total weight percentage of the binder is 100 wt%.

[0089] In one embodiment, the one or more linear polymers, the one or more conductive polymers, the one or more self-healing polymers, and the one or more rubber polymers are mixed together at a mass ratio (linear polymer:conductive polymer:self-healing polymer:rubber polymer) of about 15 - 70:1 - 30:5 - 20:10 - 40, wherein the total mass ratio of the one or more linear polymers, one or more conductive polymers, one or more self-healing polymers, and one or more rubber polymers is 100.

[0090] In one embodiment, the one or more linear polymers, the one or more conductive polymers, the one or more self-healing polymers, and the one or more rubber polymers are mixed together at a mass ratio (linear polymer:conductive polymer:self-healing polymer:rubber polymer) of about 20 - 50:1 - 20:5 - 20:10 - 30, 30 - 50:5 - 15:5 - 15:15 - 30, 30 - 40:5 - 10:5 - 10:20 - 30, 40 - 70:10 - 20:10 - 20:10 - 20, 30 - 40:10:10:30, 40 - 50:10 - 15:10 - 15:30 - 40, or 40 - 45:10 - 15:10 - 15:30 - 35, wherein the total mass ratio of the one or more linear polymers, one or more conductive polymers, one or more self-healing polymers, and one or more rubber polymers is 100.

[0091] In one embodiment, the multifunctional polymeric binder further comprises an acid. Suitable acids can be selected from the group consisting of organic acids, inorganic acids, sulfonic acids, carboxylic acids, halo-carboxylic acids, vinylogous carboxylic acids, and combinations thereof. Suitable acids can be selected from the group consisting of hydrofluoric acid (HF), hydrochloric acid (HCl), hydrobromic acid (HBr), hydroiodic acid (HI), hypochlorous acid (HClO), chlorous acid (HClO2), chloric acid (HClO3), perchloric acid (HClO4), and the corresponding compounds of bromine and iodine, sulfuric acid (H2SO4), fluorosulfuric acid (HSO3F), nitric acid (HNO3), phosphoric acid (H3PO4), fluoroantimonic acid (HSbF6), fluoroboric acid (HBF4), hexafluorophosphoric acid (HPF6), chromic acid (H2CrO4), boric acid (H3BO3), methanesulfonic acid (CH3SO3H), ethanesulfonic acid (CH3CH2SO3H), benzenesulfonic acid (C6H5SO3H), p-toluenesulfonic acid (CH3C6H4SO3H), trifluoromethanesulfonic acid (CF3SO3H), polystyrenesulfonic acid, acetic acid (CH3COOH), citric acid (C6H8O7), formic acid (HCOOH), gluconic acid, lactic acid, oxalic acid, tartaric acid, fluoroacetic acid, trifluoroacetic acid, chloroacetic acid, dichloroacetic acid, trichloroacetic acid, ascorbic acid, and combinations thereof.

[0092] In a preferred embodiment, the acid is an organic acid. In some embodiments, the organic acid is selected from the group consisting of lactic acid, acetic acid, gluconic acid, formic acid, citric acid, oxalic acid, uric acid, malic acid, tartaric acid, and combinations thereof. In a preferred embodiment, the organic acid is citric acid.

[0093] Citric acid is a triprotic acid with pKa values of approximately 2.92, 4.28, and 5.21 at 25 °C. As will be understood by those skilled in the art, any acid with a pKa approximately equal to any of the pKa values of citric acid can be suitable for use in the present invention.

[0094] In one embodiment, the acid is added to the multifunctional polymer binder of the present invention in an amount of about 1 wt% to 30 wt%, 1 wt% to 25 wt%, 3 wt% to 20 wt%, 5 wt% to 15 wt%, and preferably 10 wt%. In this embodiment, the total weight percentage of the one or more linear polymers, the one or more conductive polymers, the one or more self-healing polymers, the one or more rubber polymers, and the acid is 100 wt%. In other embodiments, the total mass ratio of the one or more linear polymers, the one or more conductive polymers, the one or more self-healing polymers, the one or more rubber polymers to the acid is 100. Advantageously, in some embodiments, adding an acid, preferably an organic acid such as citric acid, can improve the distribution of the binder of the present invention in the entire silicon / graphite / carbon material of the fabricated negative electrode by initiating crosslinking of the one or more linear polymers, the one or more conductive polymers, the one or more self-healing polymers, and the one or more rubber polymers when the slurry is heated, which prevents or improves the migration of the rubber polymer to the electrode surface, thereby providing a more uniform three-dimensional structure.

[0095] In one embodiment, the one or more linear polymers are selected from linear polymers of hydroxyl, amino, or carboxyl groups.

[0096] In one embodiment, the one or more conductive polymers are selected from conductive polymers of imino or sulfonic acid groups.

[0097] In one embodiment, the one or more self-healing polymers are selected from self-healing polymers of ureido groups.

[0098] In one embodiment, the one or more linear polymers are selected from the group consisting of sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), lithium polyacrylate (LiPAA), polyvinyl alcohol (PVA), sodium alginate (SA), 2-pentenoic acid, 2-methylacrylic acid, and chitosan (CS).

[0099] In one embodiment, the one or more conductive polymers are selected from the group consisting of polyaniline (PANI), poly[9,9-bis(3-propionic acid)fluorene]sodium (PFCOONa), poly[(l-pyrenemethyl)methacrylate-co-methylacrylic acid] (PPyMAA), polypyrrole (PPY), and 3,4-ethylenedioxythiophene / polystyrene-4-sulfonate (PEDOT:PSS).

[0100] In one embodiment, the one or more self-healing polymers are selected from the group consisting of ureido-pyrimidinone (UPy), ureido-oligo-amidoamine (UOAA), dopamine methacrylamide (DMA), and dopamine (DA). In one embodiment, the one or more self-healing polymers are ureido-oligo-amidoamine (UOAA).

[0101] In one embodiment, the one or more rubber polymers are selected from the group consisting of styrene-butadiene rubber (SBR), chloroprene rubber, nitrile rubber, butyl silicone rubber, and polysulfide rubber.

[0102] According to a third aspect of the present invention, there is provided a method for preparing a multifunctional polymer adhesive, the method comprising mixing one or more linear polymers, one or more conductive polymers, one or more self-healing polymers, and one or more rubber polymers together.

[0103] According to a fourth aspect of the present invention, there is provided a method for manufacturing a negative electrode for a lithium-ion battery, the method comprising the steps of: mixing a silicon / graphite / carbon material and a multifunctional polymer adhesive (such as comprising one or more linear polymers, one or more conductive polymers, one or more self-healing polymers, and one or more rubber polymers) to obtain a slurry; coating the slurry onto a metal member; and drying the metal member coated with the slurry to form a negative electrode.

[0104] According to a fifth aspect of the present invention, there is provided a negative electrode for a lithium-ion battery prepared by any method disclosed herein. In another aspect, there is provided a negative electrode for a lithium-ion battery, the negative electrode comprising a Si@C / graphite / carbon material.

[0105] According to a sixth aspect of the present invention, there is provided a lithium-ion battery, comprising: a negative electrode prepared by any one of the methods disclosed herein; a cathode; and an electrolyte and / or a separator located between the negative electrode and the cathode.

[0106] In another example, the Si@C / graphite / carbon material is mixed with one or more polymer adhesives to manufacture a negative electrode. In another example, the negative electrode is formed by: mixing the Si@C / graphite / carbon material and the one or more polymer adhesives to produce a slurry; coating the slurry onto a metal member; and drying the metal member coated with the slurry to form a negative electrode. In yet another example, the metal member is a metal foil, a metal strip, or a metal grid. In another example, a conductive agent is mixed into the slurry.

[0107] According to a seventh aspect of the present invention, there is provided a kit, comprising: an emulsion (part 1) comprising a mixture of a silicon / graphite / carbon material, one or more linear polymers, one or more conductive polymers, one or more self-healing polymers, and optionally a conductive agent; and an emulsion (part 2) comprising one or more rubber polymers.

[0108] In some embodiments, the emulsion (part 1) further comprises an acid, preferably an organic acid such as citric acid. In yet another embodiment, the emulsion (part 1) comprises one or more linear polymers selected from carboxymethyl cellulose (CMC) and polyacrylic acid (PAA), one or more self-leading polymers selected from urea-oligomeric-amidoamine (UOAA), dopamine (DA), and combinations thereof, one or more conductive polymers selected from PEDOT:PSS, and citric acid. In certain embodiments, the emulsion (part 2) comprises one or more rubber polymers selected from styrene butadiene rubber (SBR).

[0109] In some embodiments, the emulsion (part 1) and the emulsion (part 2) are each independently an aqueous emulsion or a non-aqueous emulsion. In certain embodiments, the emulsion (part 1) and the emulsion (part 2) are each independently dispersed in a suitable solvent. In some embodiments, the solvent may be one or more of ethylene glycol (EG), 1-pentanol, propylene glycol, polyacrylic acid, toluene, xylene, quinoline, pyridine, and tetrahydrofuran (THF), diethyl ether, diisopropyl ether, methyl ethyl ether, dioxane, methanol, ethanol, 1-propanol, isopropanol, n-butanol, tert-butanol, ethyl acetate, dimethylacetamide (DMA), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), pentane, n-hexane, cyclohexane, acetonitrile, acetone, chloroform, dichloromethane, carbon tetrachloride, or mixtures or analogs thereof. In some embodiments, the solvent is selected from the group consisting of water, polar solvents, and combinations thereof. In certain embodiments, the polar solvents are selected from the group consisting of acetic acid, n-butanol, isopropanol, n-propanol, ethanol, methanol, acetone, formic acid, dimethyl sulfoxide, dimethylformamide, acetonitrile, dichloromethane, tetrahydrofuran, ethyl acetate, and combinations thereof.

[0110] In a preferred embodiment, the emulsion (part 1) is an aqueous emulsion and the emulsion (part 2) is a non-aqueous emulsion.

[0111] The following descriptive portion will make other aspects, features, and advantages more apparent in conjunction with the accompanying drawings, which are part of this disclosure and illustrate, by way of example, the principles of various embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0112] A preferred embodiment of the present invention will now be described, which is given only by way of example of at least one non-limiting embodiment and is described in conjunction with the accompanying drawings.

[0113] Figure 1 It is an exemplary representation of an embodiment of the Si@C / G / C structure obtained by the present invention.

[0114] Figure 2 An example lithium-ion battery, i.e., a lithium-ion battery cell, is shown, which includes a negative electrode manufactured according to one of the example methods disclosed herein.

[0115] Figure 3(a) shows the cycling performance of an example negative electrode (labeled Si@C / G / C-1), and Figure 3(b) shows the cycling performance of an example electrode (labeled Si / G-1); both use a standard industrial CMC / SBR binder. The average reversible discharge capacity (i.e., specific capacity) of the Si@C / G / C-1 negative electrode after 400 cycles is 522.17 mAh / g. The first CE is 80.56%, the CE exceeds 99.0% after 25 cycles, and 72.6% of the capacity remains after 400 cycles. The average discharge capacity of the Si / C / G-1 negative electrode after 400 cycles is 510.17 mAh / g, and the capacity retention rate is 70.67%. This result proves that the double carbon coating (e.g., as used in Example 1) is beneficial to the electrochemical performance of the negative electrode.

[0116] Figure 4 It shows a flow chart of an example method for producing a multifunctional polymer binder.

[0117] Figure 5 It shows a flow chart of an example method for manufacturing a negative electrode for a lithium-ion battery. Step 1010 includes mixing silicon / graphite / carbon materials, one or more linear polymers, one or more conductive polymers, one or more self-healing polymers, and one or more rubber polymers to produce a slurry.

[0118] Figure 6 It shows a flow chart of an example method for manufacturing a negative electrode for a lithium-ion battery with a binder.

[0119] Figure 7(a) shows the cycling performance of an example negative electrode (Example 2, labeled Si@C / G / C-5 negative electrode) using an LSCR binder. The average reversible discharge capacity of the Si@C / G / C-5 negative electrode after 250 cycles is about 525.7 mAh / g. The CE exceeds 99.0% after 13 cycles, 95.35% of the capacity can be retained after 100 cycles, and 89.2% of the capacity can be retained after 250 cycles. The electrochemical performance is improved compared to the Si@C / G / C-1 negative electrode (Example 1) using a standard CMC:SBR binder.

[0120] Figure 7(b) shows the cycling performance of an exemplary negative electrode using LSCR binder (Example 2, labeled as Si@C / G / C-5 negative electrode) after 400 cycles. 82.8% of the capacity was retained after 400 cycles, which represents an improvement in electrochemical performance compared to the Si@C / G / C-1 negative electrode (Example 1) using LSCR binder after 400 cycles.

[0121] Figure 8 The cycling performance of Si@C / G / C-5.1 using various binders at 0.3C (200 mA / g) is shown. The preparation method of the Si@C / G / C-5.1 negative electrode is the same as that of Si@C / G / C-1 (Example 1), except that new graphite (natural graphite) was used in the composite material. Si@C / G / C-5.1 using LSCR binder (#1) can maintain 88.0% of its capacity after 100 cycles, which is higher than 72.8% of Si@C / G / C-5.1 using LSC (without SBR) binder (#2), higher than 68.4% of Si@C / G / C-5.1 using CMC+SBR binder (#3), and higher than 63.4% of Si@C / G / C-5.1 using CMC binder (#4). The results demonstrate that this binder of the present invention is beneficial for the capacity retention of Si / C composite negative electrodes.

[0122] Figure 9 The rate performance of Si@C / G / C-5.1 using various binders at 0.3C (200 mA / g) is shown. The preparation method of the Si@C / G / C-5.1 negative electrode is the same as that of Si@C / G / C-1 (Example 1), except that new graphite (natural graphite) was used in the composite material. Si@C / G / C-5.1 using LSCR binder (#1) provides specific capacities of 606, 581, 559, 522, 376, 241 mAh / g at 0.15C, 0.3C, 0.45C, 0.75C, 1.5C, 3C respectively, which is superior to the electrodes using LSC binder (#2), CMC+SBR binder (#3), and CMC binder (#4), while the electrode using CMC binder (#4) has the lowest capacities of 234, 146 mAh / g at 1.5C and 3C respectively.

[0123] Figure 10 SEM images of fresh and 100-cycle Si@C / G / C-5.1 negative electrodes using different binders were compared. Figure 10 Among them, (a) and (b) are fresh and 100-cycle Si@C / G / C-5.1 negative electrodes using CMC binder; (c) and (d) use CMC+SBR binder; (e) and (f) use LSC binder; (g) and (h) use LSCR binder.Figure 10 Among them, (b) and (d) show obvious microcracks on the entire electrode surface, while no obvious cracks are observed after 100 cycles when using the LSCR adhesive, indicating better electrode integrity after 100 charge / discharge cycles.

[0124] Figure 11 Shows the viscosities of different adhesives used in Example 3. Specifically, it compares the viscosities of different adhesives. The SBR adhesive has the lowest viscosity, while the LSCR adhesive has the highest viscosity. This result indicates that the LSCR adhesive is beneficial for withstanding the stress caused by volume changes during cycling and maintaining the integrity of the negative electrode. Detailed implementation manners

[0125] To more precisely understand the subject matter of one or more embodiments, the following manners are described by way of example only. In the drawings incorporated to describe the features of the exemplary embodiments, like reference numerals are used to identify like parts throughout the drawings.

[0126] To achieve a high-performance negative electrode, such as a negative electrode formed of silicon / carbon / graphite materials, for example, to replace the known graphite negative electrode in LIBs, the present inventors have solved the problems related to the following: (a) achieving uniform distribution of silicon particles in a conductive matrix such as graphite and carbon; (b) large-scale preparation of silicon secondary particles to achieve high weight energy density, high volume energy density, and high initial Coulomb efficiency; and / or (c) excellent mechanical properties of the negative electrode. In one specific example, a long cycle life of the negative electrode is achieved by using a viscous, elastic, conductive, and self-healing polymer adhesive.

[0127] The mention of Si / C / G and Si@C / G / C refers to "silicon / carbon / graphite" materials formed of or based on the components silicon (Si), carbon (C), and graphite (G). The mention of Si@C refers to silicon particles coated with carbon (i.e., silicon coated or covered with a carbon material). For example, in the Si@C material, a carbon shell or carbon layer covers the silicon core, which avoids direct contact between the silicon surface and the electrolyte. Specifically, the mention of Si@C / G / C refers to a material formed of or based on the components Si@C material, graphite (G), and carbon (C).

[0128] A multifunctional polymer adhesive is provided, which comprises a mixture of one or more linear polymers, one or more conductive polymers, one or more self-healing polymers, and one or more rubber polymers.

[0129] In additional exemplary embodiments, one or more binders can be additionally used in manufacturing the negative electrode, such as one or more polymeric binders or multifunctional polymeric binders. The performance of the negative electrode, such as the mechanical properties and stability of the negative electrode, can be further improved according to the type and content ratio of one or more binders.

[0130] In one example, the fabricated negative electrode including the Si@C / G / C material and the multifunctional polymeric binder has an average reversible discharge capacity of about 525.7 mAh / g after 250 cycles. The Coulombic efficiency (CE) exceeds 99.0% after 13 cycles, 95.35% of the capacity can be retained after 100 cycles, and 82.8% of the capacity can be retained after 400 cycles.

[0131] In another exemplary embodiment, a method of manufacturing a negative electrode for a lithium-ion battery is provided. In one non-limiting example, the method includes mixing a silicon / graphite / carbon material (such as a Si@C / G / C material) and one or more binders, such as a multifunctional polymeric binder mixture, where the one or more binders include: (a) a linear polymer; (b) a conductive polymer; (c) a self-healing polymer; (d) a rubber polymer, wherein the different polymers used are within a specific weight range.

[0132] The self-healing polymer has the ability to convert physical energy into chemical and / or physical responses to repair damage to the system. The self-healing polymer responds to external or internal stimuli to restore the initial material properties. As will be understood by those skilled in the art, any suitable self-healing polymer capable of restoring and responding to external stimuli (such as scratches, cracking, etc.) to repair damage can be used in the present invention.

[0133] In one embodiment, one or more self-healing polymers for use in the present invention are selected from the group consisting of ureido-pyrimidinone (UPy), ureido-oligo-amidoamine (UOAA), dopamine methacrylamide (DMA), and dopamine (DA) and mixtures thereof. Other self-healing polymers are known to those skilled in the art and are incorporated herein by reference, for example, those described by Chao Wang et al., “Self-healing chemistry enables the stable operation of silicon microparticle anodes for high-energy lithium-ion batteries,” Nature Chemistry, 2013, pp 1042-1048 (‘Self-healing chemistry enables the stable operation of silicon microparticle anodes for high-energy lithium-ion batteries’, Nature Chemistry, 2013, pp 1042-1048) (DOI: 10.1038 / NCHEM.1802).

[0134] In a preferred embodiment, the one or more self-healing polymers are ureido-oligo-amidoamine (UOAA).

[0135] Experiment

[0136] a) Fabrication of the anode for a lithium-ion battery

[0137] Examples of anodes for lithium-ion batteries comprising a silicon / graphite / carbon material, such as a Si / C / G material or a Si@C / G / C material, are fabricated by pyrolysis, sintering, or preferably carbonizing a mixture of silicon carbide particles, one or more carbonaceous materials, and graphite.

[0138] In one particular example, the micro-silicon (micro-Si) has an average particle size equal to or of about 2 μm to about 120 μm. Preferably, the average particle size of the micro-silicon is about 2, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, or 120 μm. Most preferably, the average particle size of the micro-silicon is about 4-5 μm.

[0139] Nano - Si is prepared by sand - grinding or ball - milling (high - energy) micro - Si in the presence of at least one solvent and keeping the mixture as a wet slurry during the grinding of micro - Si. The average particle size of the obtained nano - Si is equal to or about 50 nm to about 500 nm. Preferably, the average particle size of nano - Si is about 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, 400, 410, 420, 430, 440, 450, 460, 470, 480, 490 or 500 nm. Most preferably, the average particle size of nano - Si is about 100 nm, for example, about 50 - 150, 60 - 140, 70 - 130, 80 - 120, 90 - 110 nm.

[0140] Micro - Si is crushed into nano - Si by grinding in one or more solvents, preferably by sand - grinding. The solvents can be ethylene glycol (EG), 1 - pentanol, propylene glycol, polyacrylic acid, toluene, xylene, quinoline, pyridine, and tetrahydrofuran (THF), diethyl ether, diisopropyl ether, methyl ethyl ether, dioxane, methanol, ethanol, 1 - propanol, isopropyl alcohol, n - butanol, tert - butanol, ethyl acetate, dimethylacetamide (DMA), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), pentane, n - hexane, cyclohexane, acetonitrile, acetone, chloroform, dichloromethane, carbon tetrachloride or their mixtures or analogues. In this step, sand - grinding or high - energy ball - milling is required because grinding micro - Si requires extremely high grinding energy. During the wet - grinding process, the slurry is deliberately not allowed to dry, so as to avoid the agglomeration of silicon particles.

[0141] Nano - Si obtained from micro - Si as described above is obtained for standby, or commercially available nano - Si can be used. The average particle size of the nano - Si used is preferably equal to or about 50 nm to about 500 nm. The average particle size of the nano - Si used can be about 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, 400, 410, 420, 430, 440, 450, 460, 470, 480, 490 or 500 nm. Most preferably, the average particle size of the nano - Si used is about 100 nm, for example, about 50 - 150, 60 - 140, 70 - 130, 80 - 120, 90 - 110 nm.

[0142] Obtain one or more carbonaceous materials for later use. For example, the one or more carbonaceous materials can be functionalized graphene flakes, carbon nanotubes (CNT), reduced graphene oxide (rGO), pyrolytic carbon derived from precursors such as glucose, sucrose, or citric acid (CA), pitch, polyacrylonitrile (PAN), polyvinyl chloride (PVC), poly(diallyldimethylammonium chloride) (PDDA), poly(sodium 4-styrenesulfonate) (PSS), polydopamine (PDA), polypyrrole (PPy), or phenolic resin.

[0143] Obtain graphite for later use, and the graphite can be natural graphite and / or synthetic graphite. For natural graphite, spherical shape is preferred, while for synthetic graphite, flaky shape is preferred. For example, graphite microspheres with an average size equal to or about 1 μm to about 20 μm can be used. Preferably, the average size of the graphite microspheres is about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 μm. Most preferably, the graphite microspheres have an average size of about 8 - 20 μm.

[0144] Method steps for further non - limiting examples of manufacturing an anode for a lithium - ion battery are provided below. A representative method for preparing a Si@C / G / C material is provided below, and the Si@C / G / C material will be mixed with a binder as described herein, such as a multifunctional polymer binder mixture.

[0145] Step 1 Weigh nanosilicon and at least one carbonaceous material at a mass ratio (nanosilicon: carbonaceous material) equal to or about 40:60 to about 70:30. Preferably, the mass ratio (nanosilicon: carbonaceous material) is about 40:60, about 50:50, about 60:40, or about 70:30. More preferably, the ratio is about 40:60, 41:59, 42:58, 43:57, 44:56, 45:55, 46:54, 47:53, 48:52, 49:51, about 50:50, 51:49, 52:48, 53:47, 54:46, 55:45, 56:44, 57:43, 58:42, 59:41, about 60:40, 61:39, 62:38, 63:37, 64:36, 65:35, 66:34, 67:33, 68:32, 69:31, or about 70:30. Most preferably, the mass ratio (nanosilicon: carbonaceous material) is about 50:50.

[0146] Step 2: Mix nano-silicon and one or more carbonaceous materials thoroughly by grinding, preferably wet ball milling. During wet ball milling, use one or more solvents, which may include, for example, toluene, xylene, quinoline, pyridine, tetrahydrofuran (THF), ether, diisopropyl ether, methyl ethyl ether, dioxane, methanol, ethanol, 1-propanol, isopropyl alcohol, n-butanol, tert-butanol, ethyl acetate, dimethylacetamide (DMA), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), pentane, n-hexane, cyclohexane, acetonitrile, acetone, chloroform, dichloromethane, carbon tetrachloride, ethylene glycol (EG), propylene glycol, polyacrylic acid, or mixtures thereof.

[0147] The volume of the one or more solvents required should be just sufficient to submerge the solid powder, keeping the mixture as a wet slurry during grinding by wet ball milling, rather than as a dilute liquid or in a viscous state. Sealing is required throughout the grinding process to avoid solvent evaporation. The speed of ball milling is preferably about 400 rpm, although the speed of ball milling can be about 300 to about 600 rpm, such as about 300, 325, 350, 375, 400, 425, 450, 475, 500, 525, 550, 575, or about 600 rpm. The duration of ball milling is preferably about 6 hours, although the duration of ball milling can be about 3 to about 24 hours, such as about 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, or 24 hours. The ball:weight ratio is preferably about 20:1, although the ball:weight ratio can be about 10:1 to 40:1, such as about 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1, or about 50:1.

[0148] Step 3: Dry the mixture (wet slurry) under vacuum at a drying temperature in an oven for a period of time (drying time) to produce a dry powder. For example, the temperature can be equal to or about 70 °C to about 150 °C. Preferably, the temperature is about 70 °C, 80 °C, 90 °C, 100 °C, 110 °C, 120 °C, 130 °C, 140 °C, or 150 °C. Most preferably, the temperature is about 80 °C. The drying time can be equal to or about 2 hours to about 18 hours. Preferably, the drying time is about 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 hours. Most preferably, the drying time is about 12 hours.

[0149] Step 4: Then, the dried material (i.e., dried powder) is carbonized, for example, in a tubular furnace under a flowing inert gas (preferably argon or nitrogen), and the resulting Si@C material (i.e., silicon particles coated with a carbon material) is collected. Preferably, the carbonization process, which is characterized by high-temperature carbonization, includes the following steps:

[0150] The dried powder is heated to a holding temperature of about 400 °C (or optionally equal to or in the range of about 300 °C to about 500 °C), increasing by about 5 °C per minute (or optionally equal to or in the range of about 2 °C to about 5 °C per minute).

[0151] The dried powder at the holding temperature is maintained at about 400 °C (or optionally equal to or in the range of about 300 °C to about 500 °C) for about 3 hours (or optionally equal to or in the range of about 2 hours to about 5 hours).

[0152] The dried powder is further heated to a carbonization temperature of about 1000 °C (or optionally equal to or in the range of about 900 °C to about 1200 °C carbonization temperature range, for example, the carbonization temperature can be about 900 °C, 950 °C, 1000 °C, 1050 °C, 1100 °C, 1150 °C or 1200 °C) at about 8 °C per minute (or optionally equal to or in the range of about 5 °C to about 10 °C per minute).

[0153] The dried powder is maintained at the carbonization temperature for about 5 hours (or optionally equal to or in the range of about 3 hours to about 8 hours), and then

[0154] The resulting Si@C material is naturally cooled to room temperature, during which the gas flow rate of argon (or nitrogen) remains stable.

[0155] Step 5 : Thereafter, the Si@C material, graphite, and one or more second carbonaceous materials are weighed in a mass ratio equal to or in the range of about 10 - 30:40 - 80:10 - 30 (Si@C material:graphite:second carbonaceous material). Preferably, the mass ratio (Si@C material:graphite:second carbonaceous material) is about 10:80:10, about 10:70:20, about 10:60:30, about 20:70:10, about 20:60:20, about 20:50:30, about 30:60:10, about 30:50:20, or about 30:40:30. Most preferably, the mass ratio (Si@C material:graphite:second carbonaceous material) is about 20:60:20. The one or more second carbonaceous materials used in this step are preferably the same as the one or more carbonaceous materials used previously, but different types of one or more second carbonaceous materials can be used.

[0156] Step 6: Through grinding, preferably wet ball milling, the obtained Si@C material, graphite, and one or more second carbonaceous materials are thoroughly mixed to form a second mixture. In this step, the Si@C material and graphite are integrated and further coated with the one or more second carbonaceous materials (used for the second time). One or more second solvents are used during the grinding process, and the one or more second solvents can be one or more of toluene, xylene, quinoline, pyridine, tetrahydrofuran, ether, diisopropyl ether, methyl ethyl ether, dioxane, methanol, ethanol, 1-propanol, isopropyl alcohol, n-butanol, tert-butanol, ethyl acetate, dimethylacetamide (DMA), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), pentane, n-hexane, cyclohexane, acetonitrile, acetone, chloroform, dichloromethane, carbon tetrachloride, ethylene glycol (EG), propylene glycol, polyacrylic acid, or a mixture thereof.

[0157] The one or more second solvents are preferably the same as the one or more solvents used previously, but can be different solvents. The volume of the one or more second solvents required should be just sufficient to submerge the solid powder, keeping the second mixture as a second wet slurry during wet ball milling, rather than as a diluting liquid or in a viscous state. Sealing is required throughout the grinding process to avoid solvent evaporation. The rate of the ball milling is preferably about 400 rpm, although the speed of the ball milling can be about 300 to about 600 rpm. The duration of the ball milling is preferably about 24 hours, although the duration of the ball milling can be about 12 to about 48 hours. The ball:weight ratio is preferably about 20:1, although the ball:weight ratio can be about 10:1 to 40:1.

[0158] Step 7 : The obtained second mixture (second wet slurry) is vacuum dried in an oven at a second drying temperature for a second drying time to prepare a dried crude Si@C / G / C material powder. For example, the temperature can be equal to or about 70 °C to about 150 °C. Preferably, the temperature is about 70 °C, 80 °C, 90 °C, 100 °C, 110 °C, 120 °C, 130 °C, 140 °C, or 150 °C. Most preferably, the temperature is about 80 °C. The drying time can be equal to or about 6 hours to about 18 hours. Preferably, the drying time is about 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 hours. Most preferably, the drying time is about 12 hours.

[0159] Step 8 : Then the dried crude Si@C / G / C material (powder) is carbonized, for example, in a tube furnace under a flowing inert gas (preferably argon or nitrogen), and the obtained Si@C / G / C material is collected. Preferably, the carbonization process, characterized by high-temperature carbonization, includes the following steps:

[0160] Heat the dry coarse Si@C / G / C powder to a second holding temperature of about 400 °C (or optionally equal to or about 300 °C to about 500 °C), increasing by about 5 °C per minute (or optionally equal to or about 2 °C to about 5 °C per minute).

[0161] Hold the Si@C / G / C powder at the second holding temperature of about 400 °C (or optionally equal to or about 300 °C to about 500 °C) for about 3 hours (or optionally equal to or about 2 hours to about 5 hours).

[0162] Further heat the Si@C / G / C powder to a second carbonization temperature of about 1000 °C (or optionally equal to or a second carbonization temperature range of about 900 °C to about 1200 °C, for example, the second carbonization temperature can be about 900 °C, 950 °C, 1000 °C, 1050 °C, 1100 °C, 1150 °C or 1200 °C), increasing at an increment of about 8 °C per minute (or optionally equal to or about 5 °C to about 10 °C per minute), wherein the second carbonization temperature can be the same as or different from the carbonization temperature, and the second carbonization temperature range can be the same as or different from the carbonization temperature range.

[0163] Hold the Si@C / G / C powder at the second carbonization temperature for about 5 hours (or optionally equal to or about 3 hours to about 8 hours), and then naturally cool the obtained Si@C / G / C material to room temperature, during which the gas flow rate of argon remains stable.

[0164] Step 9 : After final grinding, preferably by dry ball milling, the final Si@C / G / C material is obtained. The speed of the dry ball milling is preferably about 400 rpm, although the speed of the dry ball milling can be about 300 rpm to about 500 rpm. The duration of the dry ball milling is preferably about 24 hours, although the duration of the ball milling can be about 12 to about 48 hours. Sufficient time and speed are required to make the obtained material uniform, and the ball milling jar should be filled with an inert gas such as argon, helium, nitrogen, etc.

[0165] Step 10: The Si@C / G / C material exhibits a micron-scale hierarchical structure, where carbon-coated silicon nanoparticles are uniformly distributed on the graphite matrix, and there is a second carbon coating on the entire structure to form a uniform conductive network. To form an anode for a lithium-ion battery, the Si@C / G / C material, one or more polymeric binders (e.g., CMC+SBR), and a conductive agent (e.g., carbon black) are mixed in proportion (e.g., 8:1:1), uniformly stirred in distilled water to form a uniform slurry, and then coated on a clean and flat metal member (e.g., copper foil). For example, a copper foil coated with the Si@C / G / C slurry as discussed is obtained. The copper foil coated with the Si@C / G / C slurry is heated and dried under vacuum for about 12 hours, and then the dried copper foil coated with Si@C / G / C is cut and pressed to form an Si@C / G / C anode for a lithium-ion battery. An exemplary representation of the resulting Si@C / G / C structure is as Figure 1 shown.

[0166] b) Example of a lithium-ion battery (LIB)

[0167] Reference Figure 2 , shows an example of a lithium-ion battery - lithium-ion battery 300 (i.e., a lithium-ion battery cell), which includes an anode manufactured according to one of the example methods disclosed herein.

[0168] Figure 2 Shows a coin-to-coin type lithium-ion battery 300, which has a first component 312 and a second component 314, which are made of a conductive material and can be used as electrical contacts. However, it should be noted that the battery 300 can be constructed according to any lithium-ion battery configuration known in the art. Inside the first component 312, or attached to the first component 312, is the anode 316 manufactured according to this embodiment, and inside the second component 314, or attached to the second component 314 is the cathode 320, and the separator 318 is located between the anode 316 and the cathode 320.

[0169] The insulator 322 ensures that the anode 316 is only conductively connected to the first component 312, while the cathode 20 is only conductively connected to the second component 314. Thus, the conductive contact with the first component 312 and the second component 314 forms a closed circuit and allows current to flow due to the electrochemical reaction between the anode 316 and the cathode 320. The coin-to-coin lithium-ion battery configuration, as well as other electrode and component configurations, are well known in the art, and it is obvious to those skilled in the art that the anode of the present invention can be easily configured into any type of lithium-ion battery.

[0170] In an example of a lithium-ion battery configuration using an electrolyte, various electrolytes can be used. Non-limiting examples of electrolytes include ethylene carbonate (EC) / ethyl methyl carbonate (EMC) / ethyl propionate (EP) / fluoroethylene carbonate (FEC) in a mixture of 1.15 M LiPF6 in a weight ratio of 27:35:27:10 (ethylene carbonate (EC):ethyl methyl carbonate (EMC)):ethyl propionate (EP):fluoroethylene carbonate (FEC)), and additives such as propylene sulfate (PS) and adiponitrile (AND).

[0171] The following examples provide a more detailed discussion, which is only intended to illustrate and not to limit the scope of the present invention.

[0172] For the following negative electrode examples, the negative electrode is formed of the materials / powders prepared in each example into a solid electrode. The electrodes are manufactured using a slurry coating and drying method. To form the negative electrode, a mixture of an active material (e.g., Si@C / G / C, Si / C / G, Si / G, etc.), sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) (i.e., one or more polymer binders) and carbon black (as a conductive agent) is mixed in a ratio equal to or about 80-96:1-10:3-10, uniformly stirred in distilled water to form a uniform slurry, and coated on a clean and flat copper foil to obtain a copper foil coated with the slurry. The copper foil coated with the slurry is heated and dried under vacuum for about 12 hours, and then the copper foil coated with the dried active material is cut and pressed to form a negative electrode for use in a lithium-ion battery example.

[0173] The prepared negative electrode is assembled into a lithium-ion battery (i.e., a lithium-ion battery cell) as a button-type half CR2032 battery. On a Neware TM battery test system, a constant current charge and discharge test is carried out at a constant current density of 200 mA / g within a voltage window of 10 mV to 1.5 V (vs Li+ / Li). The electrolyte used includes ethylene carbonate (EC) / ethyl methyl carbonate (EMC) / ethyl propionate (EP) / fluoroethylene carbonate (FEC) in a mixture of 1.15 M LiPF6 in a weight ratio of 27:35:27:10 (ethylene carbonate (EC):ethyl methyl carbonate (EMC)):ethyl propionate (EP):fluoroethylene carbonate (FEC)), and additives such as propylene sulfate (PS) and adiponitrile (AND).

[0174] Synthesis of Urea-Oligo-Amidoamine Self-Healing Polymer

[0175] Urea - oligo - amidoamine (UOAA) can be obtained using any synthetic route known or devised by those skilled in the art. In some embodiments, UOAA can be synthesized using the method described by Cordier et al., “Self - healing and thermoreversible rubber from supermolecules assembly”, Nature, 2008, pp 977 - 980 (doi:10.1038 / nature06669), which is incorporated herein by reference. In an exemplary synthesis, UOAA can be formed by condensing 1016 (3 - 5% monocarboxylic acid, 78 - 82% dicarboxylic acid, 16 - 19% tricarboxylic acid and polyacids) with diethylenetriamine at 160 °C under nitrogen for 24 hours to form oligo - amidoamine. After removing the unreacted amines (by chloroform / water solvent extraction), as determined by NMR, the [C H 2 - CONH] / [C H 2 - NH2] ratio of the oligo - amidoamine is 1.8. Then the oligo - amidoamine is reacted with urea at 135 - 160 °C under nitrogen for 7.5 hours, followed by extracting ammonia and unreacted urea by vacuum stripping and washing with water. The resulting urea - oligo - amidoamine is dried under vacuum and pressed into a steel mold with an area of 100 cm 2 and a thickness of 2 mm at 120 °C. It is swollen with dodecane at 60 °C for 24 hours.

[0176] Example 1

[0177] In an exemplary embodiment, a negative electrode (Example 1) was prepared, labeled as the Si@C / G / C - 1 negative electrode. The Si@C / G / C - 1 negative electrode was prepared using 5.0 g of nanosilicon obtained by sand milling and 5.0 g of pitch, which were mixed together with 50 mL of THF (tetrahydrofuran) as a solvent by wet ball milling.

[0178] The volume of the THF solvent covered the solid powder, and during wet ball milling, the mixture remained a wet slurry during grinding, rather than a diluted liquid or a viscous state. It was sealed during wet ball milling to avoid THF evaporation. The ball - milling speed was 400 rpm, and the ball - milling time was 48 hours. The ball:weight ratio was approximately 20:1. The resulting slurry was dried under vacuum in an oven at a temperature of 80 °C overnight for about 12 hours.

[0179] Then, the dried powder was carbonized in a tubular furnace under flowing argon. During the carbonization process, the dried powder was first heated at an increment of 5 °C per minute to a holding temperature of 400 °C. The dried powder at the holding temperature was maintained at 400 °C for 3 hours. Then, the dried powder was further heated at an increment of 8 °C per minute to a final temperature of 1000 °C. The dried powder at the final temperature was maintained at 1000 °C for 5 hours, and then the obtained Si@C material was allowed to cool naturally to room temperature, during which the gas flow rate of argon was kept stable. The obtained Si@C material was collected.

[0180] Then, 5.0 g of the obtained Si@C material, 15.0 g of graphite, and 5.0 g of pitch were subjected to wet ball milling together with THF (50 mF) as a solvent. The volume of the THF solvent submerged the solid powder mixture, and the mixture was maintained as a wet slurry rather than a diluted solution or a viscous state during the grinding process by wet ball milling. The milling process was sealed to avoid evaporation of the THF solvent. The ball milling speed was 400 rpm, and the ball milling time was about 48 hours. The ball-to-weight ratio was about 20:1. The obtained slurry was vacuum dried in an oven at a temperature of 80 °C for a drying time of about 12 hours.

[0181] Then, the collected dried coarse SiC / G / C powder was carbonized in a tubular furnace under flowing argon (second carbonization step). During the further carbonization process, the dried coarse Si@C / G / C powder was first heated at an increment of 5 °C per minute to a holding temperature of 400 °C. The Si@C / G / C powder at the holding temperature was maintained at 400 °C for 3 hours. Then, the Si@C / G / C powder was further heated at an increment of 8 °C per minute to a final temperature of 1000 °C. The Si@C / G / C powder at the final temperature was maintained at 1000 °C for 5 hours, and then the obtained Si@C / G / C material was allowed to cool naturally to room temperature, during which the gas flow rate of argon was kept stable. The obtained Si@C / G / C powder was collected.

[0182] The Si@C / G / C powder was dry ball milled into a uniform state, and the obtained Si@C / G / C material (powder) was collected. The dry ball milling rate was 400 rpm, the dry ball milling duration was about 24 hours, and the ball milling tank was filled with argon.

[0183] Figure 3 shows the cycling performance of the obtained Si@C / G / C-1 negative electrode. Referring to Figure 3, the average reversible discharge capacity (i.e., specific capacity) of the Si@C / G / C-1 negative electrode after 400 cycles was 522.17 mAh / g. The initial Coulombic efficiency (CE) was 80.56%, the CE exceeded 99.0% after 25 cycles, and 72.6% of the capacity was still retained after 400 cycles. For example, this is compared with that of CN108807861A (discussed above). Figure 5This is advantageous compared to the latter, which achieved a capacity retention rate of 83% after 200 cycles.

[0184] c) Multifunctional polymer binder

[0185] Multifunctional binders, especially relatively low-cost multifunctional polymer binders, have been designed and synthesized. The multifunctional polymer binder has a 3D (three-dimensional) network structure, improved conductivity, and self-healing properties. In one application example of the negative electrode for a lithium-ion battery, using the multifunctional polymer binder as part of the negative electrode helps to solve the problems of relatively poor conductivity and large volume expansion of the negative electrode (such as a silicon-based negative electrode), which can lead to rapid capacity decay. Those skilled in the art will understand that the multifunctional polymer binder can also be applied to various other application examples.

[0186] Reference Figure 4 , which shows a method 900 for preparing a multifunctional polymer binder. Method 900 includes mixing one or more linear polymers 910, one or more conductive polymers 920, one or more self-healing polymers 930, and one or more rubber polymers 940 together to prepare a multifunctional polymer binder 950.

[0187] The composition of an example of a multifunctional polymer binder includes:

[0188] One or more linear polymers having a weight percentage equal to or about 15 wt% to about 70 wt%; preferably, the weight percentage of the one or more linear polymers is about 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, or 70 wt%; in a preferred example, the weight percentage of the one or more linear polymers is about 30 - 50 wt%, more preferably 35 - 45 wt%;

[0189] One or more conductive polymers having a weight percentage equal to or about 1 wt% to about 30 wt%. Preferably, the weight percentage of the one or more conductive polymers is about 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 7.5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, or 30 wt%. In a preferred example, the weight percentage of the one or more conductive polymers is about 10 wt%;

[0190] One or more self - healing polymers having a weight percentage equal to or about 5 wt% to about 20 wt%; preferably, the weight percentage of the one or more self - healing polymers is about 5 wt%, 7.5 wt%, 10 wt%, 15 wt% or 20 wt%. In a preferred example, the weight percentage of the one or more self - healing polymers is about 5 - 10 wt%; or

[0191] One or more rubber polymers having a weight percentage equal to or about 10 wt% to about 40 wt%. Preferably, the weight percentage of the one or more rubber polymers is about 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt% or 40 wt%. In a preferred example, the weight percentage of the one or more rubber polymers is about 30 to 40 wt%.

[0192] Surprisingly, the inventors found that the multifunctional adhesives described herein, when mixed with silicon / graphite / carbon materials (e.g., Si@C / G / C) to fabricate an anode for a lithium - ion battery, increase at least one of the cycle life (cycling performance) of the silicon - containing anode and the Coulombic efficiency of the resulting lithium - ion battery.

[0193] Without being bound by any one theory, the inventors believe that the increase in cycle life and Coulombic efficiency is because the multifunctional polymer adhesive of the present invention is substantially uniformly distributed throughout the silicon / graphite / carbon materials of the fabricated anode. Without being bound by any one theory, the inventors believe that the multifunctional polymer adhesive is miscible or compatible with the silicon / graphite / carbon materials in the fabricated anode, resulting in a substantially uniform distribution and avoiding SBR migration.

[0194] In a specific example, linear polymers of hydroxyl, amine or carboxyl groups, conductive polymers of imino or sulfonic acid groups, and self - healing polymer cross - links of ureido groups form a 3D network composed of rigid and flexible chains, thereby improving the desired mechanical properties and adhesion of the anode.

[0195] Without being bound by any one theory, the inventors also found that in some embodiments, adding an acid, preferably an organic acid, more preferably citric acid, can improve the distribution of the adhesive described herein throughout the silicon / graphite / carbon materials in the prepared anode by triggering the cross - linking of one or more linear polymers, one or more conductive polymers, one or more self - healing polymers and one or more rubber polymers when heating the slurry. The cross - linked multifunctional polymer adhesive can prevent or improve the migration of the rubber polymer to the electrode surface, thereby providing a more uniform three - dimensional structure.

[0196] Preferred linear polymers include, for example, sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), lithium polyacrylate (LiPAA), polyvinyl alcohol (PVA), sodium alginate (SA), 2-pentenoic acid, 2-methylacrylic acid, or chitosan (CS).

[0197] Preferred conductive polymers include, for example, polyaniline (PANI), poly[9,9-bis(3-propionic acid)fluorene]sodium (PFCOONa), poly[(1-pyrenylmethyl)methacrylate-co-methylacrylic acid] (PPyMAA), polypyrrole (PPY), or 3,4-ethylenedioxythiophene / polystyrene-4-sulfonate (PEDOT:PSS).

[0198] Preferred self-healing polymers include, for example, ureido-pyrimidinone (UPy), ureido-oligo-amidoamine (UOAA), dopamine methacrylamide (DMA), and dopamine (DA). In a preferred embodiment, the self-healing polymer is ureido-oligo-amidoamine (UOAA).

[0199] Preferred rubber polymers include, for example, styrene-butadiene rubber (SBR), chloroprene rubber, nitrile rubber, butyl silicone rubber, or polysulfide rubber. In a preferred embodiment, the rubber polymer is styrene-butadiene rubber (SBR) and its derivatives.

[0200] In some embodiments, the one or more linear polymers have a weight-average molecular weight of from 1000 to 1,000,000 daltons. In some embodiments, the weight-average molecular weight is from 20,000 to 1,000,000 daltons. In some embodiments, the weight-average molecular weight is from 20,000 to 600,000 daltons. In some embodiments, the weight-average molecular weight is from 50,000 to 600,000 daltons. In some embodiments, the weight-average molecular weight is from 100,000 to 600,000 daltons. In some embodiments, the weight-average molecular weight is from 500,000 to 550,000 daltons. In some embodiments, the weight-average molecular weight is 520,000 daltons. In some embodiments, the weight-average molecular weight is from 50,000 to 150,000 daltons. In some embodiments, the number-average molecular weight is from 100,000 to 200,000 daltons.

[0201] In some embodiments, the one or more conductive polymers have a weight average molecular weight of from 20,000 to 1,000,000 Daltons. In some embodiments, the weight average molecular weight is from 20,000 to 600,000 Daltons. In some embodiments, the weight average molecular weight is from 50,000 to 600,000 Daltons. In some embodiments, the weight average molecular weight is from 100,000 to 600,000 Daltons. In some embodiments, the weight average molecular weight is from 500,000 to 550,000 Daltons. In some embodiments, the weight average molecular weight is 520,000 Daltons. In some embodiments, the weight average molecular weight is from 50,000 to 150,000 Daltons. In some embodiments, the number average molecular weight is from 100,000 to 200,000 Daltons.

[0202] In some embodiments, the one or more self-healing polymers have a weight average molecular weight of from 20,000 to 1,000,000 Daltons. In some embodiments, the weight average molecular weight is from 20,000 to 600,000 Daltons. In some embodiments, the weight average molecular weight is from 50,000 to 600,000 Daltons. In some embodiments, the weight average molecular weight is from 100,000 to 600,000 Daltons. In some embodiments, the weight average molecular weight is from 500,000 to 550,000 Daltons. In some embodiments, the weight average molecular weight is 520,000 Daltons. In some embodiments, the weight average molecular weight is from 50,000 to 150,000 Daltons. In some embodiments, the number average molecular weight is from 100,000 to 200,000 Daltons.

[0203] In some embodiments, the one or more rubber polymers have a weight average molecular weight of from 20,000 to 1,000,000 Daltons. In some embodiments, the weight average molecular weight is from 20,000 to 600,000 Daltons. In some embodiments, the weight average molecular weight is from 50,000 to 600,000 Daltons. In some embodiments, the weight average molecular weight is from 100,000 to 600,000 Daltons. In some embodiments, the weight average molecular weight is from 500,000 to 550,000 Daltons. In some embodiments, the weight average molecular weight is 520,000 Daltons. In some embodiments, the weight average molecular weight is from 50,000 to 150,000 Daltons. In some embodiments, the number average molecular weight is from 100,000 to 200,000 Daltons.

[0204] In certain embodiments, the one or more linear polymers, one or more conductive polymers, one or more self-healing polymers, and / or one or more rubber polymers are block copolymers. In certain embodiments, the one or more linear polymers, one or more conductive polymers, one or more self-healing polymers, and / or one or more rubber polymers are random copolymers.

[0205] d) Preparation of the negative electrode using an adhesive for a lithium-ion battery

[0206] In yet another exemplary embodiment, examples of the negative electrode for a lithium-ion battery further include a multifunctional adhesive, such as, as disclosed herein, preferably a multifunctional polymer adhesive.

[0207] By improving the electrode structure, the electrochemical performance of the previously prepared negative electrode material is further improved. The multifunctional adhesive as disclosed herein can be used as part of the negative electrode. The multifunctional adhesive has a 3D (three-dimensional) network structure, improved conductivity, and self-healing properties, solving the problems of relatively poor conductivity and large volume expansion of the silicon-based negative electrode for a lithium-ion battery (LIB), which lead to the problem of rapid capacity decay.

[0208] Reference Figure 5 , a method 1000 for preparing a negative electrode for a lithium-ion battery is shown. Step 1010 includes mixing a silicon / graphite / carbon material, one or more linear polymers, one or more conductive polymers, one or more self-healing polymers, and one or more rubber polymers to produce a slurry. The silicon / graphite / carbon material can be an example as previously disclosed, such as Si@C / G / C or Si / C / G powder material, or can be a mixture of raw silicon (Si), graphite (G), and carbon (C) (active materials). Optionally, step 1010 can also include mixing a conductive agent as part of the slurry. The conductive agent can be, for example, carbon black, carbon nanotubes, graphene, functionalized graphene flakes, nanofibers, or a mixture thereof as a conductive slurry. Step 1020 includes coating the slurry onto a metal member, such as a metal foil, metal strip, or metal grid. Step 1030 includes drying the metal member coated with the slurry to form a negative electrode.

[0209] Provided below and with reference to Figure 6 , yet another non-limiting example method 1100 for preparing a negative electrode for a lithium-ion battery that includes a multifunctional polymer adhesive.

[0210] Step 1110: Weigh one or more linear polymers, one or more conductive polymers, one or more self-healing polymers, and one or more rubber polymers according to the weight percentages and mass ratios (linear polymer:conductive polymer:self-healing polymer:rubber polymer) described herein.

[0211] Step 1120 : Uniformly mix the active material silicon / graphite / carbon material (which can be, for example, Si@C / G / C or Si / C / G powder as previously disclosed examples, or can be a mixture of raw silicon (Si), graphite (G), and carbon (C)) with a conductive agent (such as functionalized graphene flakes, carbon black, carbon nanotubes, nanofibers, or a mixture thereof as a conductive paste) and a multifunctional polymer binder in a mass ratio (active material:conductive agent:multifunctional polymer binder) equal to or about 80 - 96:1 - 10:3 - 10. Preferably, the mass ratio (active material:conductive agent:multifunctional polymer binder) is about 80:10:10, about 85:10:5, about 85:9:6, about 85:8:7, about 85:7:8, about 85:6:9, about 85:5:10, about 90:7:3, about 90:6:4, about 90:5:5, about 90:4:6, about 90:3:7, about 90:2:8, about 90:1:9, about 95:2:3, about 95:1:4, or about 96:1:3. Most preferably, the mass ratio (active material:conductive agent:multifunctional polymer binder) is about 80:10:10.

[0212] In some embodiments, the multifunctional polymer binder has sufficient conductivity such that it does not require a conductive agent. In some embodiments, the mixed combination of the one or more linear polymers, the one or more conductive polymers, the one or more self-healing polymers, and the one or more rubber polymers is mixed with the silicon / graphite / carbon material in a mass ratio (silicon / graphite / carbon material:mixed combination of polymers) equal to or about 80 - 99:1 - 20, 85 - 99:1 - 15, 90 - 99:1 - 10, 95 - 99:1 - 5, 96:4, 97:3, 98:2, or 99:1.

[0213] The mixing time can be equal to or about 2 hours to about 5 hours. Preferably, the mixing time is about 2 hours, 3 hours, 4 hours, or 5 hours. Most preferably, the mixing time is about 2 hours.

[0214] Step 1130: The resulting slurry is coated onto a metal component, such as a metal foil, metal strip, or metal grid, preferably a copper component provided as a copper foil, which should be kept clean and flat. Other metal components can be made of, for example, nickel, zinc, aluminum, gold, or silver. Any suitable technique such as dip coating, spraying, spin coating, adhesion, and combinations thereof can be used to coat the resulting slurry. Those skilled in the art should understand that the coating of the electrode can be of any suitable thickness to provide sufficient conductive contact.

[0215] Step 1140 : The metal component (such as a copper foil) coated with the negative electrode material slurry is dried in a vacuum oven at a specified drying temperature for a specified drying time. For example, the drying temperature can be equal to or about 100 °C to about 180 °C. Preferably, the temperature is about 100 °C, 110 °C, 120 °C, 130 °C, 140 °C, 150 °C, 160 °C, 170 °C, or 180 °C. Most preferably, the temperature is about 100 °C. The drying time can be equal to or about 10 hours to about 18 hours. Preferably, the drying time is about 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, or 18 hours. Most preferably, the drying time is about 12 hours.

[0216] Step 1150 : Then the prepared dried composite is compacted and then used as the negative electrode of an assembled lithium-ion battery (i.e., a lithium-ion battery cell). In certain embodiments, the thickness of the resulting coating is about 10 nm to 500 microns, about 100 nm to 500 microns, about 300 nm to 500 microns, about 10 to 500 microns, about 50 to 500 microns, about 100 to 500 microns, about 200 to 500 microns. In certain embodiments, the thickness of the coating is less than about 500 microns, 400 microns, 300 microns, 200 microns, or 100 microns. In some embodiments, the coating has a thickness of about 0.5 mm to about 5 mm, about 0.5 mm to about 3 mm, about 0.5 mm to about 2 mm, preferably about 1 mm.

[0217] e) Negative electrode with a multifunctional polymer binder

[0218] The following examples provide a more detailed discussion, which is only intended to illustrate and not limit the scope of the present invention.

[0219] Example 2

[0220] In an exemplary embodiment, a negative electrode (Example 2) was prepared and labeled as the Si@C / G / C-5 negative electrode (with a multifunctional polymer binder).

[0221] The preparation method of the Si@C / G / C-5 negative electrode is the same as that of the Si@C / G / C-1 negative electrode (Example 1), except that the Si@C / G / C-1 negative electrode (Example 1) uses a binder including CMC (a linear polymer) and SBR (a rubber polymer), while the Si@C / G / C-5 negative electrode uses a multifunctional polymer binder including CMC (a linear polymer), PPY (a conductive polymer), DA and / or UOAA (a self-healing polymer), and SBR (a rubber polymer) (Example 2). The conditions for preparing the negative electrode are the same.

[0222] The Si@C / G / C-5 negative electrode was prepared with a mass ratio of polymers (CMC:PPY:DA / UOAA:SBR) of 40:20:20:20. The conductive agent used is a carbon black sold by TIMCAL Graphite&Carbon of Switzerland under the trade name Super P TM Then, the active material, conductive agent, and multifunctional polymer binder were mixed at a mass ratio of 80:10:10 (Si@C / G / C: conductive agent: multifunctional polymer binder) for 2 hours. The resulting slurry was coated onto a copper foil (the copper foil was kept clean and flat). The copper foil coated with the slurry of the negative electrode material was dried in a vacuum oven at a drying temperature of 100 °C for 12 hours. Then the prepared dry composite material was compacted and used as the negative electrode of the assembled lithium-ion battery.

[0223] Figure 7(a) shows the cycling performance of an exemplary negative electrode using an LSCR binder (Example 2, which is labeled as the Si@C / G / C-5 negative electrode). The average reversible discharge capacity of the Si@C / G / C-5 negative electrode after 250 cycles was approximately 525.7 mAh / g. The CE exceeded 99.0% after 13 cycles, 95.35% of the capacity was retained after 100 cycles, and 89.2% of the capacity was retained after 250 cycles. Compared with the Si@C / G / C-1 negative electrode (Example 1) using a standard CMC:SBR binder, the electrochemical performance was improved.

[0224] Figure 7(b) shows the cycling performance of an exemplary negative electrode using an LSCR binder (which is labeled as the Si@C / G / C-5 negative electrode) after 400 cycles. 82.8% of the capacity was retained after 400 cycles, which represents an improvement in electrochemical performance compared to the Si@C / G / C-1 negative electrode (Example 1) using an LSCR binder after 400 cycles.

[0225] Example 3

[0226] In an exemplary embodiment, a negative electrode (Example 3) was prepared and labeled as the Si@C / G / C-5.1 negative electrode. This example was similar to Example 2, but natural graphite (preferably purified spherical natural graphite) was used.

[0227] The preparation method of the Si@C / G / C-5.1 negative electrode was the same as that of the Si@C / G / C-1 negative electrode (Example 1), except that the Si@C / G / C-1 negative electrode (Example 1) used a binder including CMC (a linear polymer) and SBR (a rubber polymer), while the Si@C / G / C-5 negative electrode (Example 3) used a multifunctional polymer binder (also known as LSCR linear self-healing composite rubber) including CMC (a linear polymer), PPY (a conductive polymer), DA and / or UOAA (a self-healing polymer), and SBR (a rubber polymer). The comparative example used a linear self-healing composite material without rubber (LSC, which included CMC (linear polymer), PPY (conductive polymer), DA and / or UOAA (self-healing polymer)) in combination with the Si@C / G / C-5 negative electrode (Example 2). Other conditions for preparing the negative electrode were the same.

[0228] The LSCR Si@C / G / C-5.1 negative electrode was prepared with a mass ratio of polymers (CMC:PPY:DA / UOAA:SBR) of 40:20:20:20. The conductive agent used was a carbon black sold by TIMCAL Graphite&Carbon of Switzerland under the trade name Super P TM Then, the active material, conductive agent, and multifunctional polymer binder were mixed at a mass ratio of 80:10:10 (Si@C / G / C:conductive agent:multifunctional polymer binder) for 2 hours. The resulting slurry was coated onto a copper foil (the copper foil was kept clean and flat). The copper foil coated with the slurry of the negative electrode material was dried in a vacuum oven at a drying temperature of 100 °C for 12 hours. Then, the prepared dried composite material was compacted and used as the negative electrode of the assembled lithium-ion battery.

[0229] Alternative formulations of the multifunctional polymer binder (LCSR binder) used to prepare the LSCR Si@C / G / C-5 and LSCR Si@C / G / C-5.1 negative electrodes in Examples 2 and 3 were: weight percentage (one or more linear polymers:one or more conductive polymers:one or more self-healing polymers:one or more rubber polymers:acid) of 40:10:10:30:10 and (CMC+PAA:PEDOT+PSS:UOAA:SBR:citric acid) 40:10:10:30:10.

[0230] Figure 8The cycling performance of Si@C / G / C-5.1 using various binders at 0.3C (200 mA / g) is shown. Si@C / G / C-5 using the LSCR binder (#1) can maintain 88.0% of its capacity after 100 cycles, which is higher than 72.8% of Si@C / G / C-5 using the LSC (without SBR) binder (#2), higher than 68.4% of Si@C / G / C-5 using the CMC+SBR binder (#3), and higher than 63.4% of Si@C / G / C-5 using the CMC binder (#4). The results indicate that the multifunctional polymer binder is beneficial for the capacity retention of the Si / G / C composite anode.

[0231] Figure 9 The rate performance of Si@C / G / C-5.1 using various binders at 0.3C (200 mA / g) is shown. At 0.15C, 0.3C, 0.45C, 0.75C, 1.5C, and 3C, Si@C / G / C-5 using the LSCR binder (#1) can provide specific capacities of 606, 581, 559, 522, 376, and 241 mAh / g, respectively, which is better than the electrodes using the LSC binder (#2), CMC+SBR binder (#3), and CMC binder (#4), while the electrode using the CMC binder (#4) has the lowest capacities at 1.5C and 3C, which are 234 and 146 mAh / g, respectively. The inventors surprisingly found that, compared with the standard industrial CMC:SBR binder (i.e., used with Si@C / G / C; Example 2), for the same dual-carbon-coated anode (Si@C / G / C), using the LSCR binder of the present invention has an improved capacity retention. This indicates that the beneficial effects of the LSCR binder of the present invention include improved cycling performance and Coulombic efficiency of the resulting lithium-ion battery.

[0232] Figure 10 The comparison of scanning electron microscope (SEM) images of the Si@C / G / C-5 anode using different binders for the pristine and 100th cycles is shown. (a) and (b) refer to the Si@C / G / C-5 anode using the CMC binder for the pristine and 100th cycles; (c) and (d) the CMC+SBR binder; (e) and (f) the LSC binder; (g) and (h) the LSCR binder. Figure 10 Among them, (b) and (d) show obvious microcracks on the entire electrode surface, while no obvious cracks are observed after 100 cycles in the case of using the LSCR binder, indicating better electrode integrity after 100 charge / discharge cycles, thus providing improved cycle life and / or Coulombic efficiency.

[0233] Figure 11Shows a comparison of the viscosities of the different binders used, with the SBR binder having the lowest viscosity and the LSCR binder having the highest viscosity. This result indicates that the LSCR binder is beneficial for withstanding the stress caused by volume changes during cycling and maintaining the integrity of the negative electrode.

[0234] Alternative embodiments can also be said to broadly include the parts, elements, steps, and / or features mentioned or pointed out herein, either individually or in any combination of two or more parts, elements, steps, and / or features, and where specific objects having known equivalents in the fields related to the present invention are concerned, such known equivalents are considered to be incorporated herein as if individually listed.

[0235] Although the preferred embodiments have been described in detail, it should be understood that many modifications, changes, substitutions, or alterations will be obvious to those skilled in the art without departing from the scope of the present invention.

Claims

1. A method for preparing a negative electrode for a lithium-ion battery, comprising the following steps: Mixing a silicon / graphite / carbon material, one or more linear polymers, one or more conductive polymers, one or more self-healing polymers, one or more rubber polymers, and a conductive agent to produce a slurry; Coating the slurry onto a metal member; and Drying the metal member coated with the slurry to form a negative electrode, wherein the one or more linear polymers are sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), and combinations thereof; the one or more conductive polymers are polypyrrole (PPY), PEDOT:PSS, and combinations thereof; the one or more self-healing polymers are dopamine (DA), urea-oligo-aminoamides (UOAA), and combinations thereof; the one or more rubber polymers are styrene-butadiene rubber (SBR); and the conductive agent is selected from the group consisting of carbon black, carbon nanotubes, graphene, functionalized graphene flakes, nanofibers, and mixtures thereof.

2. The method according to claim 1, wherein the silicon / graphite / carbon material is a Si@C / graphite / carbon material.

3. The method according to claim 1, wherein the metal member is a metal foil, a metal strip, or a metal grid.

4. The method according to any one of claims 1 to 3, wherein, First, the one or more linear polymers, the one or more conductive polymers, the one or more self-healing polymers, the conductive agent, and the one or more rubber polymers are mixed together to produce the slurry, wherein: the one or more linear polymers have a weight percentage equal to or of 15 wt% to 70 wt%; the one or more conductive polymers have a weight percentage equal to or of 1 wt% to 30 wt%; the one or more self-healing polymers have a weight percentage equal to or of 5 wt% to 20 wt%; the one or more rubber polymers have a weight percentage equal to or of 10 wt% to 40 wt%; the conductive agent has a weight percentage equal to or of 1 wt% to 10 wt%; wherein the total weight percentage of the one or more linear polymers, the one or more conductive polymers, the one or more self-healing polymers, the conductive agent, and the one or more rubber polymers is 100 wt%.

5. The method according to any one of claims 1-4, wherein the slurry further comprises an acid.

6. The method according to claim 5, wherein The acid is an organic acid.

7. The method according to any one of claims 1 - 6, wherein, The silicon / graphite / carbon material, the conductive agent, and the mixed combination of the one or more linear polymers, the one or more conductive polymers, the one or more self-healing polymers, and the one or more rubber polymers are mixed together at a mass ratio (silicon / graphite / carbon material:conductive agent:polymer mixed combination) equal to or in the range of 80-96:1-10:3-10.

8. The method according to any one of claims 1-7, wherein, Mix the silicon / graphite / carbon material and the mixed combination of the one or more linear polymers, the one or more conductive polymers, the one or more self-healing polymers, and the one or more rubber polymers together at a mass ratio of 80-99:1-20 (silicon / graphite / carbon material: mixed combination of polymers).

9. A multifunctional polymer binder for use in the negative electrode of a lithium-ion battery, the multifunctional polymer binder comprising: One or more linear polymers; One or more conductive polymers; One or more self-healing polymers, A conductive agent, and One or more rubber polymers, wherein The one or more linear polymers are sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), and combinations thereof; The one or more conductive polymers are polypyrrole (PPY), PEDOT:PSS, and combinations thereof; The one or more self-healing polymers are dopamine (DA), urea-oligo-amidoamine (UOAA), and combinations thereof; The one or more rubber polymers are styrene-butadiene rubber (SBR); and The conductive agent is selected from the group consisting of carbon black, carbon nanotubes, graphene, functionalized graphene flakes, nanofibers, and mixtures thereof.

10. The multifunctional polymer binder according to claim 9, wherein: The one or more linear polymers have a weight percentage equal to or of 15 wt% to 70 wt%; The one or more conductive polymers have a weight percentage equal to or of 1 wt% to 30 wt%; The one or more self-healing polymers have a weight percentage equal to or of 5 wt% to 20 wt%; The conductive agent has a weight percentage equal to or of 1 wt% to 10 wt%; and The one or more rubber polymers have a weight percentage equal to or of 10 wt% to 40 wt%, wherein the total weight percentage of the binder is 100 wt%.

11. The multifunctional polymer binder according to claim 9 or 10, the multifunctional polymer binder further comprising an acid.

12. The multifunctional polymeric adhesive according to claim 11, wherein, The acid is an organic acid.

13. A method for producing a multifunctional polymer binder for use in the negative electrode of a lithium-ion battery, which comprises mixing one or more linear polymers, one or more conductive polymers, one or more self-healing polymers, a conductive agent, and one or more rubber polymers together, wherein: The one or more linear polymers are sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), and combinations thereof; The one or more conductive polymers are polypyrrole (PPY), PEDOT:PSS, and combinations thereof; The one or more self-healing polymers are dopamine (DA), urea-oligo-amidoamine (UOAA), and combinations thereof; The one or more rubber polymers are styrene-butadiene rubber (SBR); and The conductive agent is selected from the group consisting of carbon black, carbon nanotubes, graphene, functionalized graphene flakes, nanofibers, and mixtures thereof.

14. A kit, comprising: A first part emulsion containing a mixture of a silicon / graphite / carbon material, one or more linear polymers, one or more conductive polymers, one or more self-healing polymers, and a conductive agent; and A second part emulsion containing one or more rubber polymers, wherein: The one or more linear polymers are sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), and combinations thereof; The one or more conductive polymers are polypyrrole (PPY), PEDOT:PSS, and combinations thereof; The one or more self-healing polymers are dopamine (DA), urea-oligo-aminoamides (UOAA), and combinations thereof; The one or more rubber polymers are styrene-butadiene rubber (SBR); and The conductive agent is selected from the group consisting of carbon black, carbon nanotubes, graphene, functionalized graphene flakes, nanofibers, and mixtures thereof.

15. The kit according to claim 14, wherein, The first part emulsion further contains an acid.

16. The kit according to claim 15, wherein, The acid is an organic acid.

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