Conductive polymer artificial SEI film, preparation method thereof, negative electrode material and use thereof

Abstract

The application provides a conductive polymer artificial SEI film and a preparation method and a negative electrode material and an application thereof. The conductive polymer artificial SEI film comprises polyamide and polyphenylacetylene, and the molecular chains of the polyamide and the polyphenylacetylene are intercrossed and entangled. The conductive polymer artificial SEI film is coated on the surface of the negative electrode material by an in-situ polymerization method. The conductive polymer artificial SEI film provided by the application is not easy to break due to the intercrossed and entangled molecular chains of the polyamide and the polyphenylacetylene, and the two form an interpenetrating conductive network structure, thereby forming a lithium ion fast channel with good conductivity. When the conductive polymer artificial SEI film is used as the SEI film on the surface of the negative electrode material, the initial efficiency and the rate performance of the negative electrode material are effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a conductive polymer artificial SEI film, its preparation method, negative electrode material, and its applications. Background Technology

[0002] Graphite and silicon anodes are currently the most important and widely used anode materials for lithium-ion batteries, but they each face different problems during use, limiting their performance. These problems can be solved by designing artificial solid electrolyte (ASEI) films.

[0003] For graphite anode materials, ASEI film can reduce the consumption of active lithium during lithium-ion battery cycling and improve the first-cycle efficiency; for silicon anode materials, ASEI film can suppress the expansion of silicon anode and improve its cycle performance.

[0004] However, ASEI membranes themselves have poor conductivity and often require the addition of additional conductive agents. They also exhibit significant volume changes during cycling, which can lead to fragmentation, detachment from the electrodes, or separation between particles, resulting in loss of electrical contact.

[0005] Chinese invention patent CN110289448A discloses a lithium metal anode with an artificially constructed SEI film. The SEI film constructed by this method has high strength and a certain degree of elasticity, and can move with the fluctuations of the lithium metal surface during charging and discharging, minimizing the "interface spacing" and thus preventing lithium dendrite formation. However, this invention only utilizes physical properties (the strength and elasticity of the SEI film) to suppress lithium dendrites. As the battery cycles, this SEI film will quickly rupture, allowing lithium dendrites to continue growing.

[0006] CN108390030A discloses a surface modification method for SiO2 / C anodes. A lithium-ion conductor buffer layer is deposited on the surface of the SiO2 / C anode using physical vapor deposition (PVD) or atomic layer deposition (ALD). The buffer layer is located between the SiO2 / C anode and the solid electrolyte. The lithium-ion conductor buffer layer is made of Li... 1+x Ti 2-x M x (PO4)3, where 0 ≤ x < 2, M = Al, Ga, In, Sc; or La 2 / 3-x Li 3xTiO3; or LiOH. By adding a lithium-ion conductive buffer layer between the SiO2 / C anode and the solid electrolyte, an artificial SEI film is formed, which suppresses undesirable side reactions at the electrode-electrolyte interface, effectively improving the structural stability of the anode material and reducing the negative impact of SiO2 / C anode volume changes during charge and discharge, thereby improving battery cycle performance. Although the disclosed method is simple and easy to implement and can reduce the lithium ions consumed by the SEI film, this artificial SEI film has poor coating density and is still prone to reacting with the electrolyte and consuming active lithium. Furthermore, it has poor flexibility and poor adhesion to the anode material, making it susceptible to cracking due to anode expansion.

[0007] Therefore, how to obtain an SEI film with good conductivity, a fast lithium-ion channel, and resistance to breakage is an urgent technical problem to be solved. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a conductive polymer artificial SEI film, its preparation method, and its application as a negative electrode material. The conductive polymer artificial SEI film provided by the present invention utilizes the cross-entanglement of polyamide and polyphenylene acetylene molecular chains, which are not easily broken. The two form an interpenetrating conductive network structure, creating a fast lithium-ion channel with good conductivity. When used as an SEI film on the surface of a negative electrode material, it effectively improves the first-efficiency and rate performance of the negative electrode material.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a conductive polymer artificial SEI film, the conductive polymer artificial SEI film comprising polyamide and polyphenylene acetylene, wherein the molecular chains of the polyamide and the molecular chains of the polyphenylene acetylene are intertwined.

[0011] The conductive polymer artificial SEI film provided by this invention forms an interpenetrating conductive network structure through the cross-entanglement of the molecular chains of polyamide and polyphenylene acetylene. This structure is not easily broken and forms a fast lithium-ion channel with good conductivity. When used as an SEI film on the surface of a negative electrode material, it effectively improves the first-efficiency and rate performance of the negative electrode material.

[0012] In this invention, the polyamide and polyphenylene acetylene in the conductive polymer artificial SEI film are not purely physically mixed; their molecular chains interpenetrate each other, forming a good conductive network structure, which enables rapid lithium-ion transport.

[0013] In a second aspect, the present invention provides a method for preparing a conductive polymer artificial SEI film as described in the first aspect, the method comprising the following steps:

[0014] (1) Mix the aqueous monomer solution with the matrix material to obtain a matrix material with surface adsorbed aqueous monomer;

[0015] (2) Mix the matrix material of the surface adsorbed aqueous monomer described in step (1), phenylacetylene and solvent to obtain a mixture slurry, add a catalyst to react and obtain a polyphenylacetylene-coated precursor material;

[0016] (3) React the polyphenylene-coated precursor material described in step (2) with an oil-phase monomer solution to obtain the conductive polymer artificial SEI film.

[0017] The preparation method provided by this invention can realize the in-situ generation of conductive polymer artificial SEI film. Step (1) realizes the adsorption of aqueous monomer by the matrix material. On the surface of the aqueous monomer, a polyphenylene acetylene conductive polymer is obtained through step (2). The oil phase monomer reacts with the aqueous monomer to obtain a polyamide conductive polymer, realizing the interpenetration between the molecular chains of the two polymers, forming a good conductive network and forming a fast lithium ion channel. Combined with the conductivity of the conductive polymer itself, when the matrix material is the negative electrode material, the conductive polymer artificial SEI film serves as the SEI film. That is, a structurally stable, non-crackable, and highly conductive SEI film is obtained on the surface of the negative electrode material by small molecule polymerization and in-situ polymerization, thereby improving the first efficiency and rate performance of the negative electrode material.

[0018] In step (2) of this invention, the catalyst must be added after the mixture slurry is prepared in order to form polyphenylene acetylene on the surface of the aqueous monomer. If it is mixed directly, free polyphenylene acetylene will appear, and the uniform distribution of the conductive network cannot be achieved. In this invention, the aqueous monomer is adsorbed onto the surface of the matrix material first, instead of the oil monomer being adsorbed onto the matrix surface first. Considering the properties of the oil monomer itself, if the oil monomer is added first, the oil monomer will decompose and become ineffective before reacting with the aqueous monomer.

[0019] Preferably, the mass fraction of the aqueous monomer in the aqueous monomer solution in step (1) is 1-5%, for example, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%.

[0020] In this invention, if the mass fraction of the aqueous monomer is too small, it will not be conducive to the formation of lithium-ion fast channels, while if the mass fraction of the aqueous monomer is too large, it will lead to insufficient support of polyamide.

[0021] Preferably, the solvent in the aqueous monomer solution in step (1) includes water.

[0022] Preferably, the preparation process of the aqueous monomer solution in step (1) includes: stirring the aqueous monomer with water for 1 to 5 hours, for example, 1 hour, 2 hours, 3 hours, 4 hours or 5 hours, to obtain the aqueous monomer solution.

[0023] Preferably, the aqueous monomer in step (1) includes a diamine monomer.

[0024] Preferably, the diamine monomer includes any one or a combination of at least two of o-phenylenediamine, m-phenylenediamine, or p-phenylenediamine.

[0025] Preferably, the substrate material in step (1) includes a negative electrode material.

[0026] Preferably, the mixing method in step (1) includes stirring.

[0027] Preferably, the stirring time is 0.5 to 2 hours, for example, 0.5 hours, 1 hour, 1.5 hours or 2 hours.

[0028] Preferably, the mixture after step (1) is filtered.

[0029] Preferably, in step (2), the mass ratio of the matrix material of the surface-adsorbed aqueous monomer to phenylacetylene in step (1) is (95-99.5):(0.5-5), such as 95:5, 96:4, 97:3, 98:2, 99:1 or 99.5:0.5, etc.

[0030] In this invention, adding too much phenylacetylene will result in an excessively thick coating layer, while adding too little will result in incomplete coating.

[0031] Preferably, in the mixture slurry of step (2), the mass ratio of the non-solvent substance to the solvent is 1:(1-2), for example 1:1, 1:1.3, 1:1.5, 1:1.8 or 1:2.

[0032] Preferably, the solvent in step (2) includes an aromatic solvent.

[0033] For example, the aromatic solvent in step (2) includes, but is not limited to, benzene, toluene, or xylene.

[0034] Preferably, the mixing method in step (2) includes ultrasound.

[0035] Preferably, the ultrasound duration is 30 to 90 minutes, such as 30 minutes, 40 minutes, 50 minutes, 60 minutes, 70 minutes, 80 minutes, or 90 minutes.

[0036] Preferably, in step (2), the mixture slurry is heated before adding the catalyst.

[0037] In this invention, the mixture slurry is heated first, and then the catalyst is added, which can better improve the uniformity of the reaction.

[0038] Preferably, the heating temperature is 60 to 100°C, such as 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, or 100°C.

[0039] In this invention, if the heating temperature is too low, it will not be conducive to the evaporation of the solvent, while if the heating temperature is too high, it will cause the reaction process to be too fast and uncontrollable.

[0040] Preferably, the heating time is 1 to 5 hours, such as 1 hour, 2 hours, 3 hours, 4 hours, or 5 hours.

[0041] Preferably, in the heated substance, the mass ratio of the non-solvent to the solvent is 1:(0.1 to 0.25), for example, 1:0.1, 1:0.13, 1:0.15, 1:0.18, 1:0.2, 1:0.23 or 1:0.25, etc.

[0042] Preferably, in step (2), the mass ratio of the catalyst added to phenylacetylene is (0.2-2):100, for example, 0.2:100, 0.3:100, 0.5:100, 0.8:100, 1:100, 1.3:100, 1.5:100, 1.8:100 or 2:100, etc.

[0043] In this invention, adding too much catalyst is not conducive to controlling the reaction process, while adding too little catalyst will affect the degree of polymerization of phenylacetylene.

[0044] Preferably, the catalyst in step (2) comprises any one or a combination of at least two of Zieglar-Natta catalyst, platinum black, chloroplatinic acid, platinum metal halide or non-platinum transition metal complex.

[0045] Preferably, the reaction temperature in step (2) is 25 to 80°C, for example, 25°C, 30°C, 40°C, 50°C, 60°C, 70°C or 80°C.

[0046] Preferably, the reaction time in step (2) is 20 to 120 minutes, such as 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes, 70 minutes, 80 minutes, 90 minutes, 100 minutes, 110 minutes, or 120 minutes.

[0047] Preferably, after the reaction described in step (2) is completed, washing and filtration are performed sequentially.

[0048] Preferably, the mass fraction of the oil phase monomer solution in step (3) is 0.1% to 0.5%, for example, 0.1%, 0.2%, 0.3%, 0.4% or 0.5%.

[0049] In this invention, the mass fraction of the oil phase monomer corresponds to the mass fraction of the aqueous phase monomer. If the mass fraction of the oil phase monomer is too large, the polyamide will be too thick, affecting conductivity. If the mass fraction is too small, the polyamide will be too thin, failing to provide network support.

[0050] Preferably, the oil phase monomer in step (3) includes acyl chloride monomers.

[0051] Preferably, the acyl chloride monomer includes terephthaloyl chloride and / or trimesoyl chloride.

[0052] Preferably, the solvent of the oil phase monomer solution in step (3) includes an alkane solvent.

[0053] For example, alkane solvents include, but are not limited to, n-hexane or isoalkanes.

[0054] Preferably, the preparation of the oil phase monomer solution in step (3) includes: mixing and stirring the oil phase monomer and solvent in the dark for 1 to 5 hours, for example, 1 hour, 2 hours, 3 hours, 4 hours or 5 hours.

[0055] Preferably, the reaction temperature in step (3) is 50 to 80°C, for example, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C.

[0056] Preferably, the reaction time in step (3) is 6 to 12 hours, for example, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours or 12 hours.

[0057] Preferably, the product after the reaction in step (3) is completed is subjected to heat treatment.

[0058] Preferably, the heat treatment temperature is 40 to 90°C, such as 40°C, 50°C, 60°C, 70°C, 80°C, or 90°C.

[0059] Preferably, the heat treatment time is 0.5 to 1 hour, for example, 0.5 hours, 0.8 hours, or 1 hour.

[0060] As a preferred technical solution, the preparation method includes the following steps:

[0061] (1) Stir the aqueous monomer solution with a mass fraction of 1-5% with the matrix material for 0.5-2 hours, filter, and obtain the matrix material with surface adsorbed aqueous monomer;

[0062] (2) The matrix material of the surface adsorbed aqueous monomer described in step (1), phenylacetylene and solvent are mixed to obtain a mixture slurry. The mixture slurry is heated at 60-100℃ for 1-5 hours until the mass ratio of non-solvent to solvent in the heated material is 1:(0.1-0.25). A catalyst is added and the reaction is carried out at 25-80℃ for 20-120 minutes. After washing and filtration, the precursor material coated with polyphenylacetylene is obtained.

[0063] (3) The precursor material coated with polyphenylene acetylene described in step (2) is reacted with an oil phase monomer solution with a mass fraction of 0.1-0.5% at 50-80°C for 6-12 hours and then heat-treated at 40-90°C for 0.5-1 hours to obtain the conductive polymer artificial SEI film.

[0064] In step (2), the mass ratio of the matrix material of the surface-adsorbed aqueous monomer to phenylacetylene in step (1) is (95-99.5):(0.5-5), for example, 95:5, 96:4, 97:3, 98:2, 99:1 or 99.5:0.5, etc.; in step (2), the mass ratio of the catalyst added to phenylacetylene is (0.2-2):100.

[0065] Thirdly, the present invention provides a negative electrode material, wherein the surface of the negative electrode material is coated with a conductive polymer artificial SEI film as described in the first aspect, and the negative electrode material is a matrix material.

[0066] In this invention, when the conductive polymer artificial SEI film is used as the SEI film of the negative electrode material, the negative electrode material serves as the matrix material. This allows for in-situ polymerization on the surface of the negative electrode material to obtain an SEI film with good conductivity, uniform coating, and resistance to breakage, thus compensating for defects and improving the first-pass efficiency. At the same time, the constructed conductive network structure provides a fast lithium-ion transport channel and can also improve the rate efficiency.

[0067] For example, when conductive polymer artificial SEI films are used in graphite anode materials, they can improve the first-efficiency and rate performance, while when used in silicon-based anode materials, they can suppress expansion and prevent cracking failure.

[0068] Fourthly, the present invention also provides a lithium-ion battery, the lithium-ion battery comprising the negative electrode material as described in the third aspect.

[0069] Compared with the prior art, the present invention has the following beneficial effects:

[0070] The conductive polymer artificial SEI film provided by this invention has a cross-entangled molecular chain of polyamide and polyphenylene acetylene, which is not easy to break. The two form an interpenetrating conductive network structure, which constitutes a fast lithium-ion channel with good conductivity. When used as an SEI film on the surface of the negative electrode material, it effectively improves the first efficiency and rate performance of the negative electrode material.

[0071] The preparation method provided by this invention enables in-situ generation of a conductive polymer artificial SEI film. It achieves interpenetration between the molecular chains of two polymers, forming a good conductive network and creating a fast lithium-ion channel. Combined with the inherent conductivity of the conductive polymer, when the matrix material is the negative electrode material, the conductive polymer artificial SEI film serves as the SEI film. This is achieved through small-molecule polymerization and in-situ polymerization on the surface of the negative electrode material, resulting in a structurally stable, non-fracture-prone, and highly conductive SEI film, thereby improving the initial efficiency and rate performance of the negative electrode material. In the battery provided by this invention, when the negative electrode material is graphite, the preparation process of the conductive polymer artificial SEI film involves heating the mixed slurry before reacting it with the catalyst, while simultaneously controlling the mass fraction of the oil phase monomer. The initial efficiency at 0.1C can reach over 94.98%, and the rate performance at 2C / 0.2C can reach over 32.46%. Attached Figure Description

[0072] Figure 1 This is a schematic diagram of the structure of the negative electrode material provided in Example 1 (the surface of the negative electrode material is coated with a conductive polymer artificial SEI film). Detailed Implementation

[0073] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0074] Example 1

[0075] This embodiment provides a conductive polymer artificial SEI film, which is composed of polyamide and polyphenylene acetylene. The molecular chains of the polyamide and the molecular chains of the polyphenylene acetylene are intertwined and wrapped around each other. The conductive polymer artificial SEI film is coated on the surface of the artificial graphite anode material, serving as the SEI film of the artificial graphite anode material.

[0076] The method for preparing the conductive polymer artificial SEI film is as follows:

[0077] (1) Dissolve o-phenylenediamine monomer in pure water at a mass fraction of 3% and stir thoroughly for 4 hours to prepare an o-phenylenediamine aqueous solution. Add artificial graphite anode material into the aqueous solution, stir thoroughly for 2 hours, and then filter to obtain artificial graphite anode material with o-phenylenediamine monomer adsorbed on the surface.

[0078] (2) The substance obtained by filtration in the step (artificial graphite negative electrode material with surface adsorption of o-phenylenediamine monomer) and phenylacetylene are dispersed in 150 parts of toluene solvent at a mass ratio of 98:2 (98 parts of filtered substance and 2 parts of phenylacetylene), and ultrasonicated for 50 min to obtain a mixture slurry.

[0079] (3) Pour the above slurry into a kneading pot, heat it to 85°C, keep it warm for 2 hours, evaporate the slurry into a slurry with 25 parts of residual toluene solvent, add Zieglar-Natta catalyst (mass ratio of catalyst to phenylacetylene is 1:100) to the kneading pot, heat it to 35°C, keep it warm for 90 minutes, knead until the material is basically dry, then wash it repeatedly with toluene solvent 3 times and filter it to obtain the precursor material coated with polyphenylacetylene.

[0080] (4) Dissolve the terephthaloyl chloride oil phase monomer in n-hexane solvent at a mass fraction of 0.3%, protect from light, and stir thoroughly for 5 hours to prepare an oil phase solution. Add the material filtered in step (3) into the oil phase solution, disperse it, transfer it to a kneading pot, heat it to 80°C and knead it for 8 hours until the reaction is complete. At the same time, the material is basically dry. Place the kneaded material in an oven and heat treat it at 55°C for 1 hour to obtain an in-situ polymerized artificial SEI film on the surface of artificial graphite anode material.

[0081] Figure 1 A schematic diagram of the structure of the negative electrode material provided in Example 1 is shown (the surface of the negative electrode material is coated with a conductive polymer artificial SEI film). Figure 1 As can be seen, the two polymers are intertwined, with polyamide providing support and polyphenylene acetylene providing conductive sites and lithium-ion channels, forming a conductive polymer network that coats the surface of the negative electrode material.

[0082] Example 2

[0083] This embodiment provides a conductive polymer artificial SEI film, which is composed of polyamide and polyphenylene acetylene. The molecular chains of the polyamide and the molecular chains of the polyphenylene acetylene are intertwined and wrapped around each other. The conductive polymer artificial SEI film is coated on the surface of the artificial graphite anode material, serving as the SEI film of the artificial graphite anode material.

[0084] The method for preparing the conductive polymer artificial SEI film is as follows:

[0085] (1) Dissolve o-phenylenediamine monomer in pure water at a mass fraction of 1% and stir thoroughly for 2 hours to prepare an o-phenylenediamine aqueous solution. Add artificial graphite anode material into the aqueous solution, stir thoroughly for 1 hour, and then filter to obtain artificial graphite anode material with o-phenylenediamine monomer adsorbed on the surface.

[0086] (2) The substance obtained by filtration in the step (artificial graphite anode material with surface adsorption of o-phenylenediamine monomer) and phenylacetylene are dispersed in 100 parts of toluene solvent at a mass ratio of 99.5:0.5 (99.5 parts of filtered substance and 0.5 parts of phenylacetylene), and ultrasonicated for 50 min to obtain a mixture slurry.

[0087] (3) Pour the above slurry into a kneading pot, heat it to 60°C, keep it warm for 4 hours, evaporate the slurry into a slurry with 15 parts of residual toluene solvent, add chloroplatinic acid catalyst (mass ratio of catalyst to phenylacetylene is 0.6:100) to the kneading pot, heat it to 50°C, keep it warm for 45 minutes, knead until the material is basically dry, then wash it repeatedly with toluene solvent 3 times and filter it to obtain the precursor material coated with polyphenylacetylene.

[0088] (4) Dissolve the terephthaloyl chloride oil phase monomer in n-hexane solvent at a mass fraction of 0.1%, protect from light, and stir thoroughly for 3 hours to prepare an oil phase solution. Add the material filtered in step (3) into the oil phase solution, disperse it, transfer it to a kneading pot, heat it to 45°C and knead it for 6 hours until the reaction is complete. At the same time, the material is basically dry. Place the kneaded material in an oven and heat treat it at 80°C for 1 hour to obtain a conductive polymer artificial SEI film polymerized in situ on the surface of the artificial graphite anode material.

[0089] Example 3

[0090] This embodiment provides a conductive polymer artificial SEI film, which is composed of polyamide and polyphenylene acetylene. The molecular chains of the polyamide and the molecular chains of the polyphenylene acetylene are intertwined and wrapped around each other. The conductive polymer artificial SEI film is coated on the surface of the artificial graphite anode material, serving as the SEI film of the artificial graphite anode material.

[0091] The method for preparing the conductive polymer artificial SEI film is as follows:

[0092] (1) Dissolve p-phenylenediamine monomer in pure water at a mass fraction of 5%, stir thoroughly for 4 hours to prepare a p-phenylenediamine aqueous solution, add artificial graphite anode material into the aqueous solution, stir thoroughly for 2 hours and then filter to obtain artificial graphite anode material with p-phenylenediamine monomer adsorbed on the surface.

[0093] (2) The substance obtained by filtration in the step (artificial graphite negative electrode material with surface adsorption of p-phenylenediamine monomer) and phenylacetylene are dispersed in 200 parts of toluene solvent at a mass ratio of 95:5 (95 parts of filtered substance and 5 parts of phenylacetylene), and ultrasonicated for 90 min to obtain a mixture slurry.

[0094] (3) Pour the above slurry into a kneading pot, heat to 100°C, keep warm for 5 hours, evaporate the slurry into a slurry with 10 parts of residual toluene solvent, add Zieglar-Natta catalyst (mass ratio of catalyst to phenylacetylene is 1.8:100) to the kneading pot, heat to 75°C, keep warm for 50 minutes, knead until the material is basically dry, rinse repeatedly with toluene solvent 3 times and filter to obtain polyphenylacetylene-coated precursor material;

[0095] (4) Dissolve the trimesoyl chloride oil phase monomer in n-hexane solvent at a mass fraction of 0.5%, protect from light, and stir thoroughly for 5 hours to prepare an oil phase solution. Add the material filtered in step (3) into the oil phase solution, disperse it, transfer it to a kneading pot, heat it to 65°C and knead it for 12 hours until the reaction is complete. At the same time, the material is basically dry. Place the kneaded material in an oven and heat treat it at 90°C for 0.5 hours to obtain an in-situ polymerized artificial SEI film on the surface of artificial graphite anode material.

[0096] Example 4

[0097] The difference between this embodiment and embodiment 1 is that in step (3) of this embodiment, a catalyst is directly added to carry out the reaction without heating.

[0098] The remaining preparation methods and parameters are consistent with those in Example 1.

[0099] Example 5

[0100] The difference between this embodiment and Embodiment 1 is that the mass fraction of the oil phase monomer in step (4) of this embodiment is 0.8%.

[0101] The remaining preparation methods and parameters are consistent with those in Example 1.

[0102] Example 6

[0103] The difference between this embodiment and Embodiment 1 is that the substrate material in this embodiment is silicon nano-anode material.

[0104] The remaining preparation methods and parameters are consistent with those in Example 1.

[0105] Example 7

[0106] The difference between this embodiment and Embodiment 1 is that the substrate material in this embodiment is silicon suboxide anode material.

[0107] The remaining preparation methods and parameters are consistent with those in Example 1.

[0108] Comparative Example 1

[0109] The difference between this comparative example and Example 1 is that this comparative example uses pure artificial graphite material without any treatment.

[0110] Comparative Example 2

[0111] The difference between this comparative example and Example 1 is that in the preparation method of this comparative example, steps (2) and (3) are not performed, that is, the polyamide conductive polymer artificial SEI film is directly polymerized in situ on the surface of the artificial graphite material.

[0112] The remaining preparation methods and parameters are consistent with those in Example 1.

[0113] Comparative Example 3

[0114] The difference between this comparative example and Example 1 is that the preparation process of polyamide in steps (1) and (4) of this comparative example is not carried out. Instead, the polyphenylene acetylene conductive polymer artificial SEI film is directly polymerized in situ on the surface of the artificial graphite material.

[0115] The remaining preparation methods and parameters are consistent with those in Example 1.

[0116] Comparative Example 4

[0117] The difference between this comparative example and Example 1 is that steps (2) and (3) of this comparative example are combined, that is, a catalyst is directly added in step (2) to carry out the polymerization reaction of phenylacetylene.

[0118] The remaining preparation methods and parameters are consistent with those in Example 1.

[0119] Comparative Example 5

[0120] The difference between this comparative example and Example 6 is that this comparative example uses pure nano-silicon anode material.

[0121] Comparative Example 6

[0122] The difference between this comparative example and Example 7 is that this comparative example uses pure silicon suboxide anode material.

[0123] Note: The negative electrode materials and various monomers in the above embodiments can be purchased directly and do not need to be prepared separately.

[0124] The negative electrode materials (surface-coated conductive polymer or pure negative electrode material) provided in Examples 1-7 and Comparative Examples 1-6 were used as negative electrode active materials, homogenized and coated together with conductive agent and binder to prepare negative electrode sheets, and coin-type lithium-ion batteries were prepared according to the conventional coin-type battery preparation process.

[0125] The batteries provided in Examples 1-7 and Comparative Examples 1-6 were subjected to electrochemical performance tests. The charge / discharge cutoff voltage was 0-2V, and the batteries were charged and discharged at a constant current of 0.1C. The initial coulombic efficiency was measured, and the rate performance was determined using a capacity ratio of 2C / 0.2C. The test results are shown in Table 1.

[0126] Table 1

[0127]

[0128]

[0129] The data from Examples 1 and 4 show that when the catalyst reacts directly with the mixed slurry without heating, free polyphenylene acetylene will appear, making it impossible to achieve a uniform distribution of the conductive network, and the improvement in first-efficiency and rate performance will not be significant.

[0130] The data results from Examples 1 and 5 show that if the mass fraction of the oil phase monomer is too high, an excessively thick polyamide layer will be formed under the same mass fraction of the aqueous phase monomer, which will reduce the conductivity of the SEI film and thus affect the improvement effect of first-efficiency and rate performance.

[0131] The data results from Example 1 and Comparative Example 1, and Examples 6-7 and Comparative Examples 5-6 show that when the conductive polymer artificial SEI film provided by the present invention is used as the SEI film of the negative electrode material, it effectively improves the first-efficiency and rate performance of the graphite negative electrode material.

[0132] The data from Example 1 and Comparative Examples 2 and 3 show that in-situ polymerization of polyamide or polyphenylacetylene alone cannot improve the first-efficiency and rate performance; on the contrary, it may have a deteriorating effect.

[0133] The data from Example 1 and Comparative Example 4 show that the addition of the catalyst and phenylacetylene together cannot achieve uniform reaction, resulting in uneven SEI film coating and insufficient performance improvement.

[0134] In summary, the conductive polymer artificial SEI film provided by this invention utilizes the cross-entanglement of polyamide and polyphenylene acetylene molecular chains, making it resistant to breakage. The two form an interpenetrating conductive network structure, creating a fast lithium-ion channel with excellent conductivity. When this film is polymerized in situ onto the surface of the negative electrode material as an SEI film, it effectively improves the initial efficiency and rate performance of the negative electrode material. In the battery provided by this invention, when the negative electrode material is graphite, the preparation process of the conductive polymer artificial SEI film involves heating the mixed slurry before reacting it with the catalyst, while simultaneously controlling the mass fraction of the oil phase monomer. The initial efficiency at 0.1C can reach over 94.98%, and the rate performance at 2C / 0.2C can reach over 32.46%.

[0135] The applicant declares that the present invention is illustrated by the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. An electrically conductive polymer artificial SEI film, characterized by, The conductive polymer artificial SEI film comprises polyamide and polyphenylene acetylene, wherein the molecular chains of the polyamide and the molecular chains of the polyphenylene acetylene are intertwined.

2. The method for producing the conductive polymer artificial SEI film according to claim 1, characterized by, The preparation method includes the following steps: (1) Mix the aqueous monomer solution with the matrix material to obtain a matrix material with surface adsorbed aqueous monomer; (2) The matrix material of the surface adsorbed aqueous monomer described in step (1), phenylacetylene and solvent are mixed to obtain a mixture slurry, and a catalyst is added to carry out the reaction to obtain a polyphenylacetylene-coated precursor material; (3) React the polyphenylene acetylene-coated precursor material described in step (2) with an oil-phase monomer solution to obtain the conductive polymer artificial SEI film.

3. The method for producing the conductive polymer artificial SEI film according to claim 2, characterized by, The mass fraction of the aqueous monomer in the aqueous monomer solution in step (1) is 1~5%.

4. The method for producing the conductive polymer artificial SEI film according to claim 2, characterized by, The solvent in the aqueous monomer solution in step (1) includes water.

5. The method for producing the conductive polymer artificial SEI film according to claim 4, characterized by, The preparation process of the aqueous monomer solution in step (1) includes: stirring the aqueous monomer with water for 1 to 5 hours to obtain the aqueous monomer solution.

6. The method for preparing the conductive polymer artificial SEI film according to claim 2, characterized by, The aqueous monomers in step (1) include diamine monomers.

7. The method for producing the conductive polymer artificial SEI film according to claim 6, characterized by, The diamine monomers include any one or a combination of at least two of o-phenylenediamine, m-phenylenediamine, or p-phenylenediamine.

8. The method for preparing the conductive polymer artificial SEI film according to claim 2, characterized in that, The substrate material in step (1) includes the negative electrode material.

9. The method for preparing the conductive polymer artificial SEI film according to claim 2, characterized in that, The mixing method in step (1) includes stirring.

10. The method for producing the conductive polymer artificial SEI film according to claim 9, characterized by, The stirring time is 0.5~2 hours.

11. The method of claim 2, wherein the conductive polymer artificial SEI film is prepared by the steps of: The mixture from step (1) is filtered.

12. The method for preparing the conductive polymer artificial SEI film according to claim 2, characterized in that, In step (2), the mass ratio of the matrix material of the surface-adsorbed aqueous monomer in step (1) to phenylacetylene is (95~99.5):(0.5~5).

13. The method for preparing the conductive polymer artificial SEI film according to claim 2, characterized in that, In step (2), the mass ratio of the non-solvent substance to the solvent in the slurry mixture is 1:(1~2).

14. The method for preparing the conductive polymer artificial SEI film according to claim 2, characterized in that, The solvent in step (2) includes aromatic solvents.

15. The method for preparing a conductive polymer artificial SEI film according to claim 2, characterized in that, The mixing method described in step (2) includes ultrasound.

16. The method of claim 15, wherein the conductive polymer artificial SEI film is prepared by the steps of: The ultrasound duration is 30-90 minutes.

17. The method for preparing a conductive polymer artificial SEI film according to claim 2, characterized in that, In step (2), the mixture slurry is heated before adding the catalyst.

18. The method of claim 17, wherein the conductive polymer artificial SEI film is prepared by the steps of: The heating temperature is 60~100℃.

19. The method of claim 17, wherein the conductive polymer artificial SEI film is prepared by the steps of: The heating time is 1 to 5 hours.

20. The method of claim 17, wherein the conductive polymer artificial SEI film is prepared by the steps of: In the heated substance, the mass ratio of the non-solvent to the solvent is 1:(0.1~0.25).

21. The method of claim 17, wherein the conductive polymer artificial SEI film is prepared by the steps of: In step (2), the mass ratio of the catalyst added to phenylacetylene is (0.2~2):

100.

22. The method of claim 17, wherein the conductive polymer artificial SEI film is prepared by the steps of: The catalyst in step (2) includes any one or a combination of at least two of Zieglar-Natta catalyst, platinum black, chloroplatinic acid, platinum metal halide or non-platinum transition metal complex.

23. The method for preparing the conductive polymer artificial SEI film according to claim 17, characterized in that, The reaction temperature in step (2) is 25~80℃.

24. The method of claim 17, wherein the conductive polymer artificial SEI film is prepared by the steps of: The reaction time in step (2) is 20~120 min.

25. The method for preparing the conductive polymer artificial SEI film according to claim 17, characterized in that, After the reaction described in step (2) is completed, washing and filtration are performed in sequence.

26. The method of claim 2, wherein the conductive polymer artificial SEI film is prepared by the steps of: The mass fraction of the oil phase monomer solution in step (3) is 0.1~0.5%.

27. The method for preparing the conductive polymer artificial SEI film according to claim 2, characterized in that, The oil phase monomers in step (3) include acyl chloride monomers.

28. The method of claim 27, wherein the conductive polymer artificial SEI film is prepared by the steps of: The acyl chloride monomers include terephthaloyl chloride and / or trimesoyl chloride.

29. The method for preparing a conductive polymer artificial SEI film according to claim 2, characterized in that, The solvent for the oil phase monomer solution in step (3) includes alkane solvents.

30. The method of claim 2, wherein the conductive polymer artificial SEI film is prepared by the steps of: The preparation of the oil phase monomer solution in step (3) includes: mixing and stirring the oil phase monomer and solvent in the dark for 1-5 hours.

31. The method of claim 2, wherein the conductive polymer artificial SEI film is prepared by the steps of: The reaction temperature in step (3) is 50~80℃.

32. The method for preparing the conductive polymer artificial SEI film according to claim 2, characterized in that, The reaction time in step (3) is 6 to 12 hours.

33. The method for preparing the conductive polymer artificial SEI film according to claim 2, characterized in that, The product after the reaction in step (3) is completed is subjected to heat treatment.

34. The method of claim 33, wherein the conductive polymer artificial SEI film is prepared by the steps of: The heat treatment temperature is 40~90℃.

35. The method of claim 33, wherein the conductive polymer artificial SEI film is prepared by the steps of: The heat treatment time is 0.5~1h.

36. The method of claim 2, wherein the conductive polymer artificial SEI film is prepared by the steps of: The preparation method includes the following steps: (1) Stir the aqueous monomer solution with a mass fraction of 1-5% with the matrix material for 0.5-2 hours, filter, and obtain the matrix material with surface adsorbed aqueous monomer; (2) Mix the matrix material of the surface adsorbed aqueous monomer described in step (1), phenylacetylene and solvent to obtain a mixture slurry. Heat the mixture slurry at 60~100℃ for 1~5h until the mass ratio of non-solvent to solvent in the heated material is 1:(0.1~0.25). Add catalyst and react at 25~80℃ for 20~120min. Wash and filter to obtain the polyphenylacetylene-coated precursor material. (3) The precursor material coated with polyphenylene acetylene described in step (2) is reacted with an oil phase monomer solution with a mass fraction of 0.1~0.5% at 50~80℃ for 6~12h, and then heat-treated at 40~90℃ for 0.5~1h to obtain the conductive polymer artificial SEI film; In step (2), the mass ratio of the matrix material of the surface adsorbed aqueous monomer in step (1) to phenylacetylene is (95~99.5):(0.5~5); in step (2), the mass ratio of the catalyst added to phenylacetylene is (0.2~2):

100.

37. A negative electrode material, characterized by comprising: The surface of the negative electrode material is coated with the conductive polymer artificial SEI film as described in claim 1, wherein the negative electrode material is a matrix material.

38. A lithium-ion battery, characterized by, The lithium-ion battery includes the negative electrode material as described in claim 37.

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