A coated composite, electrode sheet, and battery

Abstract

This invention relates to the field of battery technology, specifically to a coated composite material and electrodes and batteries comprising the coated composite material. The coated composite material has a core-shell structure, wherein the core is garnet-type lithium lanthanum zirconium oxide particles, and the shell is a vinylidene fluoride-hexafluoropropylene copolymer. The coated composite material of this invention has a hydrophobic outer shell, which effectively isolates moisture and carbon dioxide from the air, reducing the formation of lithium hydroxide and lithium carbonate, thereby improving the stability of the coated composite material in air. Furthermore, the coated composite material does not gel with PVDF when used in N-methyl solvents. The electrodes comprising the coated composite material of this invention exhibit higher stability and excellent lithium-ion conductivity. Batteries derived from the electrodes of this invention have better cycle performance.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically to a coated composite material and electrodes and batteries comprising the coated composite material. Background Technology

[0002] Oxide solid electrolyte materials, as a class of ceramic materials with high ionic conductivity, have broad application prospects in lithium-ion batteries, especially solid-state batteries. They mainly include perovskite-type oxides such as lithium lanthanum titanium oxide (LLTO), and Nascon-structured oxides such as lithium aluminum titanium phosphate (LATP), lithium titanium germanium phosphate (LAGP), and garnet-structured lithium lanthanum zirconium oxide (LLZO)-based solid electrolytes. Among these, LLTO and LATP or LAGP exhibit excellent chemical stability, but poor interfacial stability with the negative electrode lithium metal. LLZO-based solid electrolytes, on the other hand, not only have excellent lithium stability but also achieve room-temperature ionic conductivity up to 10⁻⁶. -3 S·cm -1 LLZO exhibits excellent electrochemical performance in batteries. However, the surface of LLZO-based solid electrolytes is highly reactive, reacting with moisture and carbon dioxide in the air to form lithium hydroxide and lithium carbonate, leading to lithium dissolution and a decrease in surface ionic conductivity. Furthermore, when used in NMP, DMF, DMAc, and other N-methyl solvents, LLZO reacts with PVDF groups to undergo gelation, severely impacting its use in lithium-ion and solid-state batteries.

[0003] The main solution to the problem of poor stability of LLZO-based solid electrolytes in air is to coat their surface with a protective layer. For example, Chinese patent application number CN 112290082 A coats the surface of the LLZO-based solid electrolyte with a layer of lithium salt-doped polyethylene oxide and polycarbonate-based ion-conducting polymer. However, this method, due to the introduction of lithium salt, makes the surface more susceptible to water absorption and the formation of lithium hydroxide, and does not solve the problem of poor stability of LLZO-based solid electrolytes in air.

[0004] Therefore, it is very important to invent an LLZO-based solid electrolyte that is stable in air and does not gel with PVDF when used in N-methyl solvents. Summary of the Invention

[0005] The purpose of this invention is to overcome the aforementioned problems in the prior art and provide a coated composite material, as well as an electrode and a battery comprising the coated composite material. The coated composite material of this invention has a hydrophobic outer shell, which effectively isolates moisture and carbon dioxide in the air, reducing the formation of lithium hydroxide and lithium carbonate, thereby improving the stability of the coated composite material in air. Furthermore, the coated composite material does not gel with PVDF when used in N-methyl solvents. The electrode comprising the coated composite material of this invention has higher stability and excellent lithium-ion conductivity. The battery obtained from the electrode of this invention has better cycle performance.

[0006] The first aspect of the present invention provides a coated composite material having a core-shell structure, wherein the core is a garnet-type lithium lanthanum zirconium oxide particle and the shell is a vinylidene fluoride-hexafluoropropylene copolymer.

[0007] A second aspect of the present invention provides an electrode comprising a current collector and at least one coating layer applied to one or both surfaces of the current collector, the coating layer comprising the encapsulated composite material described in the first aspect.

[0008] A third party to this invention provides a battery comprising the electrode plates described in the second aspect, wherein the electrode plates are positive and / or negative.

[0009] By employing the above technical solution, the present invention has at least the following advantages compared with the prior art:

[0010] (1) The coated composite material of the present invention has good stability in air;

[0011] (2) The coated composite material of the present invention does not gel with PVDF when used in N-methyl solvents;

[0012] (3) The electrode sheet of the present invention, which includes a coated composite material, has higher stability;

[0013] (4) The electrode of the present invention, including the coated composite material, has good lithium-ion conductivity;

[0014] (5) The battery of the present invention, including the coated composite material, has good cycle performance.

[0015] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0016] Figure 1 The diagram shown is a schematic diagram of the core-shell structure of the encapsulated composite material provided by the present invention.

[0017] Figure 2 The image shows a negative electrode sheet comprising two coating layers according to an embodiment of the present invention.

[0018] Figure 3 The image shown is a cross-sectional SEM image of a negative electrode sheet including two coating layers according to an embodiment of the present invention. Detailed Implementation

[0019] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0020] The inventors of this invention have discovered that improving the stability of garnet-type lithium lanthanum zirconium oxide particles in air can improve the stability of the electrode, thereby improving the cycle performance of the battery.

[0021] Through further in-depth research, the inventors of this invention discovered that, in order to improve the stability of garnet-structured lithium lanthanum zirconium oxide particles in air, a hydrophobic outer shell can be coated onto the surface of the garnet-structured lithium lanthanum zirconium oxide particles, enabling them to isolate moisture and carbon dioxide from the air. Extensive research further revealed that coating the surface of garnet-structured lithium lanthanum zirconium oxide particles with a shell of vinylidene fluoride-hexafluoropropylene copolymer effectively isolates moisture and carbon dioxide from the air, thereby improving the stability of the garnet-structured lithium lanthanum zirconium oxide particles in air. Simultaneously, the vinylidene fluoride-hexafluoropropylene copolymer can absorb electrolyte and exhibit lithium-ion conductivity, thereby further improving the lithium-ion conductivity of the electrode and the cycle performance of the battery.

[0022] To achieve the above objectives, the first aspect of the present invention provides a coated composite material having a core-shell structure, wherein the core is a garnet-type lithium lanthanum zirconium oxide particle, and the shell is a vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP).

[0023] In this invention, by coating garnet-type lithium lanthanum zirconium oxide particles with a vinylidene fluoride-hexafluoropropylene copolymer, the coated composite material achieves better stability than existing technologies. To further improve the effect, one or more of the technical features can be further optimized.

[0024] The coated composite material has a core-shell structure, such as Figure 1 As shown, the core 1 of the coated composite material is a garnet-type lithium lanthanum zirconium oxide particle, and the shell 2 of the coated composite material is a vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP). The core 1 of the coated composite material is surrounded by the shell 2, forming a coated composite material with a core-shell structure.

[0025] The garnet-type lithium lanthanum zirconium oxide particles indicate that the lithium lanthanum zirconium oxide particles are ion conductors with a garnet-type structure.

[0026] In one example, the chemical formula of the garnet-type lithium lanthanum zirconium oxide particles is Li. 7-x La3Zr 2-x M x O 12 Where M is one of Ta, Nb, Hf, Al, Si, Ga, Ge, Sc, Ti, V, Y, and Sn, and x is 0-0.6. When x is 0, it indicates that the garnet-type lithium lanthanum zirconium oxide particles are unmodified garnet-type lithium lanthanum zirconium oxide particles; when x is not 0, it indicates that the garnet-type lithium lanthanum zirconium oxide particles are modified garnet-type lithium lanthanum zirconium oxide particles. In this invention, the garnet-type lithium lanthanum zirconium oxide particles represent modified and / or unmodified garnet-type lithium lanthanum zirconium oxide particles.

[0027] According to one specific embodiment, based on the total weight of the coated composite material, the core content is 80-99 wt% (e.g., 80 wt%, 85 wt%, 90 wt%, 95 wt%, 99 wt%), and the shell content is 1-20 wt% (e.g., 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%).

[0028] In one example, based on the total weight of the coated composite material, the core content is 85-97 wt% and the shell content is 3-15 wt%.

[0029] In one example, based on the total weight of the coated composite material, the core content is 90-95 wt% and the shell content is 5-10 wt%.

[0030] The shell of the coated composite material is a vinylidene fluoride-hexafluoropropylene (PVDF-HFP) copolymer. The vinylidene fluoride-hexafluoropropylene (PVDF-HFP) copolymer represents a BAB block copolymer, wherein A is vinylidene fluoride (PVDF) and B is hexafluoropropylene (HFP).

[0031] The PVDF-HFP copolymer is hydrophobic, and the shell formed by it, which coats the surface of the garnet-type lithium lanthanum zirconium oxide particles, can effectively isolate moisture and carbon dioxide in the air, reduce the formation of lithium hydroxide and lithium carbonate, and thus improve the stability of the coated composite material in air. At the same time, after swelling in the electrolyte, the PVDF-HFP copolymer also exhibits excellent lithium-ion conductivity, thereby improving the conductivity of the electrode and the cycle performance of the battery.

[0032] According to one specific embodiment, the content of hexafluoropropylene is 3-25 wt% (e.g., 3 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%), based on the total weight of the vinylidene fluoride-hexafluoropropylene copolymer. It is understood that in the PVDF-HFP copolymer, the sum of the PVDF content and the HFP content is 100%.

[0033] In one example, the content of hexafluoropropylene is 10-20 wt%, based on the total weight of the vinylidene fluoride-hexafluoropropylene copolymer.

[0034] In one example, the median particle size D of the garnet-type lithium lanthanum zirconium oxide particles is... 50 The range is 0.3-5μm (e.g., 0.3μm, 0.5μm, 1μm, 2μm, 3μm, 4μm, 5μm).

[0035] In one example, the median particle size D of the garnet-type lithium lanthanum zirconium oxide particles is... 50 It is 0.5-1μm.

[0036] In one example, the coated composite material can be prepared by contacting garnet-type lithium lanthanum zirconium oxide particles with an organic solvent to form a first solution; contacting a PVDF-HFP copolymer with an organic solvent to form a second solution; contacting the first solution with the second solution to form a first slurry; and evaporating the solvent in the first slurry by a drying method (e.g., spray drying) to obtain the coated composite material.

[0037] The organic solvent may be selected from one or more of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl isobutyl ketone, butyl acetate, isophorone, triethyl phosphate, and acetone.

[0038] The PVDF-HFP copolymer can be obtained commercially or prepared using conventional processes.

[0039] In one example, the median particle size D of the coated composite material 50 The range is 0.3-5μm (e.g., 0.3μm, 0.5μm, 1μm, 2μm, 3μm, 4μm, 5μm).

[0040] In one example, the median particle size D of the coated composite material 50 It ranges from 0.5 to 2 μm.

[0041] A second aspect of the present invention provides an electrode comprising a current collector and at least one coating layer applied to one or both surfaces of the current collector, the coating layer comprising the encapsulated composite material described in the first aspect.

[0042] The coated composite material exhibits good stability in air and does not gel with PVDF when used in N-methyl solvents, resulting in better stability of the prepared coating slurry and thus improving the stability of the electrode. At the same time, the coated composite material demonstrates excellent lithium-ion conductivity in electrolyte, thereby enhancing the lithium-ion conductivity of the electrode.

[0043] The current collector can be a conventional current collector in the art. For example, the current collector is a positive current collector and / or a negative current collector.

[0044] In one example, the positive current collector is an aluminum foil.

[0045] In one example, the negative current collector is a copper foil.

[0046] The electrode may include a current collector and at least one (e.g., one, two, or three) coating applied to one or both sides of the current collector surface.

[0047] According to one specific embodiment, the electrode includes a current collector and a coating applied to one or both sides of the current collector.

[0048] The thickness of the coating can be designed and adjusted according to the required battery size.

[0049] In one example where the electrode includes a coating, the coating is a mixed layer containing an active material and the coated composite material.

[0050] In an example where the electrode comprises a coating layer, the weight ratio of the coated composite material to the active material in the hybrid layer is (0.01-0.07):1 (e.g., 0.01:1, 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.07:1).

[0051] In one example where the electrode comprises a coating layer, the weight ratio of the coated composite material to the active material in the hybrid layer is (0.02-0.05):1.

[0052] In one example where the electrode comprises a coating layer, the hybrid layer further contains a conductive agent and a binder.

[0053] In an example where the electrode comprises a coating layer, the content of the coated composite material is 0.09–5.82 wt% (e.g., 0.09 wt%, 0.1 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 5.5 wt%, 5.82 wt%) based on the total weight of the mixed layer, the content of the active material is 90–97 wt% (e.g., 90 wt%, 91 wt%, 92 wt%, 93 wt%, 94 wt%, 95 wt%, 96 wt%, 97 wt%), the content of the conductive agent is 0.5–3 wt% (0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%), and the content of the binder is 0.5–3 wt% (0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%).

[0054] In one example where the electrode comprises a coating layer, the content of the coated composite material is 0.19–4.85 wt%, the content of the active material is 93–97 wt%, the content of the conductive agent is 1–2 wt%, and the content of the binder is 1–2 wt%, based on the total weight of the mixed layer.

[0055] In one example where the electrode includes a coating layer, the electrode can be prepared by coating a mixed layer slurry onto one or both sides of the current collector to obtain an electrode including a coating layer.

[0056] In this invention, the mixed layer slurry can be prepared by contacting an active substance slurry with a first slurry or a coated composite material obtained in the first aspect of this invention.

[0057] In this invention, the active material slurry can be a conventional active material slurry in the art. For example, the active material slurry is a positive electrode active material slurry and / or a negative electrode active material slurry. When the positive electrode active material slurry comes into contact with the first slurry or the coated composite material, the resulting mixed layer slurry no longer gels and has strong stability, thereby expanding the range of applications of the first slurry or the coated composite material in alkaline slurries.

[0058] In one example, the positive electrode active material slurry includes a positive electrode active material, a conductive agent, and a binder.

[0059] In one example, the positive electrode active material is selected from one or more of lithium iron phosphate, lithium vanadium phosphate, lithium cobalt oxide, ternary materials, and lithium manganese oxide.

[0060] In one example, the negative electrode active material slurry includes a negative electrode active material, a conductive agent, a binder, and a dispersant.

[0061] In one example, the negative electrode active material is selected from carbon-based materials and / or silicon-based materials.

[0062] In one example, the carbon-based material is selected from one or more of natural graphite, artificial graphite, mesophase carbon fiber, mesophase carbon microspheres, and soft carbon.

[0063] In one example, the conductive agent is selected from one or more of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotubes, metal powder, and carbon fiber.

[0064] In one example, the adhesive is selected from one or more of sodium methylcellulose, styrene-butadiene rubber (SBR), styrene-butadiene latex, polyvinylidene fluoride (PVDF), polytetrafluoroethylene, and polyethylene oxide.

[0065] In one example, the dispersant is carboxymethyl cellulose.

[0066] In one example, the electrode including a coating layer is a positive electrode.

[0067] According to another specific embodiment, the electrode includes a current collector and two coatings applied to one or both sides of the current collector.

[0068] In one example, the coating comprises a first coating and a second coating disposed sequentially from the surface of the current collector outwards.

[0069] The coating comprises a first coating and a second coating sequentially disposed from the surface of the current collector outwards, indicating that the coating comprises a first coating and a second coating, wherein the first coating is applied to one or both sides of the surface of the current collector, and the second coating is applied to the surface of the first coating.

[0070] In one instance, the thickness of the first coating is designed and adjusted according to the required battery size.

[0071] In one example, the thickness of the second coating is 2.5–40 μm (e.g., 2.5 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm). The thickness of the second coating represents the total thickness of the second coating in the battery. For example, when the negative electrode or positive electrode in the battery includes the second coating, the thickness of the second coating is the thickness of the second coating in the negative electrode or positive electrode; when both the positive electrode and the negative electrode in the battery include the second coating, the thickness of the second coating represents the sum of the thickness of the second coating in the positive electrode and the thickness of the second coating in the negative electrode.

[0072] In one example, the thickness of the second coating is 5 to 30 μm.

[0073] In one example where the electrode comprises two coating layers, the first coating contains an active material and the second coating contains the encapsulated composite material.

[0074] In one example where the electrode comprises two coating layers, the first coating is an active material layer and the second coating is an encapsulated composite material layer.

[0075] The active material layer can be a conventional active material layer in the art, for example, the active material layer includes an active material, a conductive agent, a binder, and a dispersant.

[0076] The coated composite material layer may include the coated composite material.

[0077] The coated composite material layer may also include an oil-based binder to enhance adhesion, such as PVDF homopolymer or polytetrafluoroethylene. The PVDF homopolymer is a CC block homopolymer, wherein C is vinylidene fluoride (PVDF).

[0078] In one example where the electrode comprises two coating layers, the content of the active material is 90–97 wt% (90 wt%, 91 wt%, 92 wt%, 93 wt%, 94 wt%, 95 wt%, 96 wt%, 97 wt%) based on the total weight of the active material layers, the content of the conductive agent is 0.5–3 wt% (0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%), the content of the binder is 0.5–3 wt% (0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%), and the content of the dispersant is 0–4 wt% (0 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%).

[0079] When the content of the dispersant is 0 wt%, it means that there is no dispersant in the active material layer.

[0080] In one example where the electrode comprises two coating layers, the content of the active material is 93-97 wt%, the content of the conductive agent is 1-2 wt%, the content of the binder is 1-2 wt%, and the content of the dispersant is 0.5-3 wt%, based on the total weight of the active material layers.

[0081] In one example where the electrode comprises two coating layers, the content of the coated composite material is 95-99.5 wt% (e.g., 95 wt%, 96 wt%, 97 wt%, 98 wt%, 99 wt%, 99.5 wt%) based on the total weight of the coated composite material layers, and the content of the oil-based binder is 0.5-5 wt% (e.g., 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%).

[0082] In one example where the electrode comprises two coating layers, the content of the coated composite material is 96-99 wt% and the content of the oil-based binder is 1-4 wt%, based on the total weight of the coated composite material layers.

[0083] In another example where the electrode comprises two coating layers, the first coating is a mixed layer containing an active material and the coated composite material, and the second coating is a coated composite material layer.

[0084] In an example where the electrode comprises two coating layers, the weight ratio of the coated composite material to the active material in the hybrid layer is (0.01-0.07):1 (e.g., 0.01:1, 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.07:1).

[0085] In one example where the electrode comprises two coating layers, the weight ratio of the coated composite material to the active material in the hybrid layer is (0.02-0.05):1.

[0086] In one example where the electrode comprises two coating layers, the hybrid layer further contains a conductive agent and a binder.

[0087] In an example where the electrode comprises two coating layers, the content of the coated composite material is 0.09–5.82 wt% (e.g., 0.09 wt%, 0.1 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 5.5 wt%, 5.82 wt%) based on the total weight of the mixed layers, the content of the active material is 90–97 wt% (e.g., 90 wt%, 91 wt%, 92 wt%, 93 wt%, 94 wt%, 95 wt%, 96 wt%, 97 wt%), the content of the conductive agent is 0.5–3 wt% (0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%), and the content of the binder is 0.5–3 wt% (0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%).

[0088] In one example where the electrode comprises two coating layers, the content of the coated composite material is 0.19–4.85 wt%, the content of the active material is 93–97 wt%, the content of the conductive agent is 1–2 wt%, and the content of the binder is 1–2 wt%, based on the total weight of the mixed layers.

[0089] In one instance, the composition of the hybrid layer in the electrode comprising one coating layer may be the same as or different from that in the electrode comprising two coating layers.

[0090] In one example where the electrode comprises two coating layers, the electrode can be prepared by coating the mixed layer slurry or the active material slurry onto one or both sides of the current collector to form a first coating layer, and coating the surface of the first coating layer with an encapsulated composite material slurry to form a second coating layer.

[0091] In this invention, the coated composite material slurry can be prepared by contacting the first slurry obtained in the first aspect of this invention with a solution comprising PVDF homopolymer and N-methylpyrrolidone (NMP) (PVDF / NMP solution).

[0092] In one example, the content of the PVDF homopolymer is 3 to 10 wt% (e.g., 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%), based on the total weight of the PVDF / NMP solution.

[0093] In one example, the first coating is a hybrid layer, the second coating is a coated composite material layer, and the electrode is a positive electrode.

[0094] In one example, the first coating is an active material layer, and the second coating is a coated composite material layer. The electrode is a negative electrode.

[0095] The electrode of the present invention improves the stability of the electrode in air and the lithium-ion conductivity of the electrode by including the coating composite material described in the present invention.

[0096] A third party to this invention provides a battery comprising the electrode plates described in the second aspect, wherein the electrode plates are positive and / or negative.

[0097] The materials and preparation methods for the battery, excluding the positive and / or negative electrode sheets, can be carried out in accordance with the methods in this field, all of which can achieve good cycle performance.

[0098] In one example, the battery is a lithium-ion battery.

[0099] In one example, the battery is a semi-solid-state battery.

[0100] According to one specific embodiment, the battery includes a positive electrode, a negative electrode, an electrolyte, and a separator.

[0101] The electrolyte can be a conventional electrolyte in the art, which can be obtained commercially or prepared by conventional preparation processes.

[0102] The separator can be a conventional separator in the art, which can be commercially available or prepared using conventional manufacturing processes. The separator can separate the positive electrode and the negative electrode, thus functioning as an isolation layer.

[0103] The electrode can be a positive electrode and / or a negative electrode.

[0104] In an example where the battery includes a separator, the positive electrode and / or the negative electrode includes a second coating with a thickness of 5-40 μm (5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm). The thickness of the second coating represents the total thickness of the second coating in the battery.

[0105] In one example where the battery includes a separator, the thickness of the second coating is 5-14 μm.

[0106] According to another specific embodiment, the battery does not include a separator, and the positive electrode and the negative electrode are in contact. The positive electrode and / or the negative electrode include a second coating present on the contact surface. The second coating is an encapsulated composite material layer, and the thickness of the second coating is not less than 15 μm.

[0107] The contact between the positive electrode and the negative electrode means that the surfaces of the positive current collector of the positive electrode and the negative current collector of the negative electrode are, in sequence, the positive current collector, a coating applied to the surface of the positive current collector, a coating applied to the surface of the negative current collector, and the negative current collector, wherein the coating applied to the surface of the positive current collector is in contact with the coating applied to the surface of the negative current collector. The coating applied to the surface of the positive current collector and / or the coating applied to the surface of the negative current collector includes a second coating. When the coating applied to the surface of the positive current collector includes a second coating, the second coating is in contact with the coating applied to the surface of the negative current collector; when the coating applied to the surface of the negative current collector includes a second coating, the second coating is in contact with the coating applied to the surface of the positive current collector; when both the coating applied to the surface of the positive current collector and the coating applied to the surface of the negative current collector include a second coating, the second coating in the positive electrode is in contact with the second coating in the negative electrode.

[0108] When the thickness of the second coating is not less than 15 μm, the positive electrode and / or the negative electrode include a second coating present on the contact surface. This second coating serves the same function as the separator, i.e., separating the positive and negative electrode. The thickness of the second coating represents the total thickness of the second coating in the battery.

[0109] In one example where the battery does not include a separator, the thickness of the second coating is 15-40 μm (15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm).

[0110] The battery of the present invention has improved conductivity and cycle performance because it contains the electrode sheet described in the present invention.

[0111] The present invention will be described in detail below through embodiments. The embodiments described herein are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0112] The following examples illustrate the coated composite material, negative electrode, and positive electrode of the present invention.

[0113] The unmodified garnet-type lithium lanthanum zirconium oxide particles and PVDF-HFP copolymer used in the examples were both commercially available.

[0114] Unmodified garnet-type lithium lanthanum zirconium oxide particles, D 50 =0.6μm, purchased from Tianjin Guoan Mengguli;

[0115] The PVDF-HFP copolymers were purchased from Arkema, and their models were: 2500 (HFP content 20wt%), 2751 (HFP content 15wt%), 2801 (HFP content 10wt%), and LBG (HFP content 3wt%).

[0116] It should be noted that in the examples, DMC is used as an organic solvent to form a first solution and a second solution with the unmodified garnet-type lithium lanthanum zirconium oxide particles and the PVDF-HFP copolymer, respectively. Therefore, the amount of DMC is adjusted according to the amount of modified and / or unmodified garnet-type lithium lanthanum zirconium oxide particles and the PVDF-HFP copolymer. DMC, as an organic solvent, only acts as a solvent; its amount does not affect the performance of the prepared coated composite material.

[0117] Example 1

[0118] (1) Preparation and fabrication of coated composite materials:

[0119] 1) Ingredient preparation:

[0120] A total of 95 parts by weight of unmodified garnet-type lithium lanthanum zirconium oxide particles;

[0121] 2500 in total, 5 parts by weight;

[0122] Organic solvent: DMC, of ​​which the first part is 155 parts by weight, the second part is 45 parts by weight, and the total is 200 parts by weight;

[0123] Zirconium beads, with a median particle size D 50 =1.5mm, totaling 40 parts by weight.

[0124] 2) Preparation of coated composite materials:

[0125] Unmodified garnet-type lithium lanthanum zirconium oxide particles were added to a first portion of DMC to form a first solution. Zirconium beads were then added and dispersed in a vacuum degassing machine. A second solution was formed from 2500 and a second portion of DMC. This second solution was added to the first solution and dispersed again, then filtered to obtain a first slurry. The first slurry was spray-dried to evaporate the organic solvent, yielding a 2500-coated composite material. The median particle size D of the coated composite material was... 50 The thickness is 0.8-1.2 μm, denoted as LLZO / 2500-5.

[0126] (2) Preparation and fabrication of the negative electrode:

[0127] 1) Ingredient preparation

[0128] Negative electrode current collector: copper foil (6μm thick);

[0129] First coating (active material layer): Negative electrode active material: 94 parts by weight of graphite; Conductive agent: 1.5 parts by weight of conductive carbon black, 0.5 parts by weight of carbon nanotubes; Binder: 2 parts by weight of SBR; Dispersant: 2 parts by weight of carboxymethyl cellulose;

[0130] Second coating (coated composite material layer): 98 parts by weight of coated composite material; oily binder: 33.3 parts by weight of PVDF / NMP solution (of which, PVDF is 2 parts by weight).

[0131] 2) Preparation of negative electrode sheet

[0132] (a) A negative electrode active material, conductive agent, binder, dispersant, and 100 parts by weight of water are thoroughly mixed to form a negative electrode active material slurry. This slurry is then coated onto both sides of the negative electrode current collector to form an active material layer. The slurry is then dried at 100°C and rolled under 40 tons of pressure to a compaction density of 1.67 g / cm³. 3 A negative electrode sheet including an active material layer was obtained, with an areal density of 7.8 mg / cm³. 3 .

[0133] (b) The coated composite material is redispersed in NMP (100 parts by weight) and then PVDF / NMP solution is added and mixed evenly to form a coated composite material slurry. This slurry is then coated onto the surface of the active material layer in the negative electrode sheet of (a) to form a coated composite material layer (20 μm thick) to obtain a negative electrode sheet with two coating layers.

[0134] (3) Preparation of positive electrode sheet

[0135] 1) Preparation of the positive electrode components:

[0136] Positive current collector: aluminum foil (10μm thick);

[0137] One layer of coating (hybrid layer): Positive electrode active material: NCM811 (Hunan Shanshan Energy Technology Co., Ltd. 4.2V NCM811) 94 parts by weight; Coated composite material 3 parts by weight; Conductive agent: conductive carbon black 1.5 parts by weight; Binder: PVDF 1.5 parts by weight.

[0138] 2) Preparation process

[0139] The positive electrode active material, coated composite material, conductive agent, binder, and NMP (60 parts by weight) were thoroughly mixed to form a positive electrode mixed layer slurry, which was then coated on both sides of the positive electrode current collector. The slurry was then dried at 120°C and rolled under 40 tons of pressure to achieve a compaction density of 3.0–4.2 g / cm³. 3 This yields a positive electrode sheet containing a coating layer.

[0140] Example 2

[0141] (1) Preparation of coated composite materials

[0142] The preparation of the coated composite material was carried out in accordance with the composition and preparation method described in Example 1.

[0143] (2) Preparation and manufacturing method of negative electrode sheet:

[0144] 1) Ingredient preparation

[0145] Negative electrode current collector: copper foil (6μm thick);

[0146] First coating (mixed layer): Negative electrode active material: 94 parts by weight of graphite; 3 parts by weight of coated composite material; Conductive agent: 1.5 parts by weight of conductive carbon black; Binder: 1.5 parts by weight of SBR.

[0147] Second coating (coated composite material layer): 98 parts by weight of coated composite material; oily binder: 33.3 parts by weight of PVDF / NMP solution (of which, PVDF is 2 parts by weight).

[0148] 2) Preparation of negative electrode sheet

[0149] (a) A negative electrode active material, a coated composite material, a conductive agent, a binder, and 100 parts by weight of water are thoroughly mixed to form a negative electrode active material slurry. This slurry is then coated onto both sides of the negative electrode current collector to form a mixed layer. The mixture is then dried at 100°C and rolled under 40 tons of pressure to a compaction density of 1.67 g / cm³. 3 A negative electrode sheet including an active material layer was obtained, with an areal density of 7.8 mg / cm³. 3 .

[0150] (b) The coated composite material is redispersed in NMP (100 parts by weight) and then PVDF / NMP solution is added and mixed evenly to form a coated composite material slurry. This slurry is then coated onto the surface of the active material layer in the negative electrode sheet of (a) to form a coated composite material layer (20 μm thick) to obtain a negative electrode sheet with two coating layers.

[0151] (4) Preparation of positive electrode sheet

[0152] The preparation of the positive electrode sheet was carried out in accordance with the composition and preparation method described in Example 1.

[0153] Example 3

[0154] (1) Preparation of coated composite materials

[0155] The preparation of the coated composite material was carried out in accordance with the composition and preparation method described in Example 1.

[0156] (2) Preparation and fabrication of negative electrode components

[0157] 1) Preparation of the negative electrode components:

[0158] Negative electrode current collector: copper foil (6μm thick);

[0159] Coating (hybrid layer): Negative electrode active material: 94 parts by weight of graphite; 3 parts by weight of coated composite material; Conductive agent: 1.5 parts by weight of conductive carbon black; Binder: 1.5 parts by weight of SBR.

[0160] The negative electrode active material, coated composite material, conductive agent, binder, and 100 parts by weight of water were thoroughly mixed to form a negative electrode active material slurry. This slurry was then coated onto both sides of the negative electrode current collector to form a mixed layer. The mixture was then dried at 100°C and rolled under 40 tons of pressure to achieve a compaction density of 1.67 g / cm³. 3 The resulting negative electrode has an areal density of 7.8 mg / cm³. 3 .

[0161] (4) Preparation of positive electrode sheet

[0162] The preparation of the positive electrode sheet was carried out in accordance with the composition and preparation method described in Example 1.

[0163] Example 4

[0164] The experiment was conducted in accordance with Example 1, except that the amounts of unmodified garnet-type lithium lanthanum zirconium oxide particles and PVDF-HFP copolymer were varied, as detailed in Table 1.

[0165] The resulting coated composite material is designated as LLZO / 2500-10.

[0166] Example 5

[0167] The experiment was conducted in accordance with Example 1, except that the amounts of unmodified garnet-type lithium lanthanum zirconium oxide particles and PVDF-HFP copolymer were varied, as detailed in Table 1.

[0168] The resulting coated composite material is designated as LLZO / 2500-15.

[0169] Example 6

[0170] The procedure was carried out in accordance with Example 1, except that the type of PVDF-HFP copolymer was changed to 2751, as detailed in Table 1.

[0171] The resulting coated composite material is designated as LLZO / 2751-5.

[0172] Example 7

[0173] The procedure was carried out in accordance with Example 4, except that the type of PVDF-HFP copolymer was changed to 2751, as detailed in Table 1.

[0174] The resulting coated composite material is designated as LLZO / 2751-10.

[0175] Example 8

[0176] The procedure was carried out in accordance with Example 5, except that the type of PVDF-HFP copolymer was changed to 2751, as detailed in Table 1.

[0177] The resulting coated composite material is designated as LLZO / 2751-15.

[0178] Example 9

[0179] The procedure was carried out in accordance with Example 1, except that the type of PVDF-HFP copolymer was changed to 2801, as detailed in Table 1.

[0180] The resulting coated composite material is designated as LLZO / 2801-5.

[0181] Example 10

[0182] The procedure was carried out in accordance with Example 4, except that the type of PVDF-HFP copolymer was changed to 2801, as detailed in Table 1.

[0183] The resulting coated composite material is designated as LLZO / 2801-10.

[0184] Example 11

[0185] The procedure was carried out in accordance with Example 5, except that the type of PVDF-HFP copolymer was changed to 2801, as detailed in Table 1.

[0186] The resulting coated composite material is designated as LLZO / 2801-15.

[0187] Example 12

[0188] The procedure was carried out in accordance with Example 4, except that the unmodified garnet-type lithium lanthanum zirconium oxide particles were replaced with niobium-Nb-doped modified garnet-type lithium lanthanum zirconium oxide particles (LLZNO,Li). 6.4 La3Zr 1.4 Nb 0.6 O 12 ).

[0189] The resulting coated composite material is designated as LLZNO / 2500-10.

[0190] Example 13

[0191] The procedure was carried out in accordance with Example 1, except that the type of PVDF-HFP copolymer was changed to LBG, as detailed in Table 1.

[0192] The resulting coated composite material is designated as LLZO / LBG-5.

[0193] Example 14

[0194] The procedure was carried out in accordance with Example 4, except that the type of PVDF-HFP copolymer was changed to LBG, as detailed in Table 1.

[0195] The resulting coated composite material is designated as LLZO / LBG-10.

[0196] Table 1

[0197]

[0198]

[0199]

[0200] Comparative Example 1

[0201] The procedure was carried out in accordance with Example 1, except that the coated composite material in the negative and positive electrodes was replaced with the same weight parts of unmodified garnet-type lithium lanthanum zirconium oxide particles, denoted as LLZO.

[0202] Comparative Example 2

[0203] The procedure was carried out in accordance with Example 9, except that the unmodified garnet-type lithium lanthanum zirconium oxide particles were replaced with Al2O3 particles (with a median particle size D). 50 =0.6μm), and the coated composite material in the negative electrode and positive electrode is replaced with the same weight of Al2O3 particles. It is denoted as Al2O3 / 2801-5.

[0204] Comparative Example 3

[0205] The procedure was carried out in accordance with Example 1, except that no coated composite material was added to either the negative or positive electrode. (This is recorded as blank.)

[0206] Comparative Example 4

[0207] (1) Preparation of ingredients

[0208] Unmodified garnet-type lithium lanthanum zirconium oxide particles, D 50 =0.6μm, 110 parts by weight;

[0209] 13 parts by weight of polyoxyethylene polymer PEO;

[0210] 4.71 parts by weight of lithium bis(trifluoromethanesulfonyl)imide;

[0211] 868 parts by weight of acetonitrile.

[0212] (2) Preparation of LLZO-based solid electrolyte with a layer of lithium salt-doped polyethylene oxide and polycarbonate-based ion-conducting polymer coated on the surface.

[0213] a) Dissolve polyoxyethylene polymer (PEO) and lithium bis(trifluoromethanesulfonylimide) in acetonitrile to prepare an ion-conducting polymer solution with a concentration of 2%.

[0214] b) Calculate and weigh the amount of LLZO powder and ion-conducting polymer solution based on a coating thickness of 50nm. Add the LLZO powder to the ion-conducting polymer solution and disperse it by ultrasonication to obtain a uniform slurry.

[0215] c) The slurry was dried using a closed-loop centrifugal spray dryer to form an ion-conductive polymer coating layer with a thickness of 50 nm on the LLZO surface, denoted as LLZO / PEO.

[0216] The spray drying operating conditions are as follows: the atomizing disc speed is 5000 rpm, the atmosphere is argon, and the spray drying outlet temperature is equal to the solvent boiling point temperature.

[0217] Preparation Example

[0218] The first slurry or coated composite material obtained in the examples and the comparative examples were used to prepare electrodes and batteries, respectively, in the following manner.

[0219] (1) Preparation of negative electrode

[0220] The negative electrode sheets obtained from the above embodiments and comparative examples were used respectively.

[0221] (2) Preparation of positive electrode

[0222] The positive electrode sheets obtained from the above-described embodiments and comparative examples were used respectively.

[0223] (3) Preparation of lithium-ion batteries

[0224] A lithium-ion battery is prepared using the negative electrode from step (1), the positive electrode from step (2), and the electrolyte (LBC445B33 electrolyte from Shenzhen Xinzhoubang Technology Co., Ltd.).

[0225] Test case

[0226] The electrodes of the examples and comparative examples, as well as the resulting batteries, were subjected to the following tests:

[0227] (1) Negative electrode sheet

[0228] A negative electrode sheet comprising two coating layers, wherein the first coating is an active material layer and the second coating is a coated composite material layer, such as... Figure 2 and Figure 3 As shown. Figure 3 The surfaces of the central current collector are composed of active material layers, and the surfaces of the active material layers are coated with composite material layers.

[0229] (2) Air stability test

[0230] The water content of the coated composite material was tested after it was exposed to air for 5 hours. The water content was characterized using an S-300 fully automated Karl Fischer water analyzer.

[0231] (3) Conductivity test

[0232] The first slurry, including the coated composite material, is coated on one side of the copper foil surface. After drying, it is cut into a circular piece with a diameter of 1.2 cm, placed in a fixture with steel sheets on both sides, and then wetted with a small amount of electrolyte before testing the AC impedance.

[0233] The resistance was tested by AC impedance using the Chenhua electrochemical workstation, and then the lithium-ion conductivity of the coating was calculated by formula (1).

[0234] σ=t / R×S (1)

[0235] Where: σ is the ionic conductivity (S / cm), t is the coating thickness (cm), R is the in-plane resistance perpendicular to the coating surface (Ω), and S is the effective coating area (cm²). 2 ).

[0236] (4) Cyclic performance test

[0237] The cycle performance of lithium-ion batteries was tested in accordance with GB / T 18287-2013 standard. The cycle test conditions were: 25℃, 0.5C / 0.5C charge and discharge (upper limit voltage set to 4.2V, lower limit voltage 2.75V), and the number of cycles when the battery capacity decreased to 80% was recorded.

[0238] The results are recorded in Table 2.

[0239] Table 2

[0240]

[0241]

[0242] *The positive electrode slurry in Comparative Example 1 gelled and could not be used to prepare a battery, therefore no battery data is available.

[0243] # Since there is no coated composite material in Comparative Example 3, there is no data on water content and conductivity.

[0244] As shown in the examples and Comparative Example 1, after coating the LLZO surface, the water absorption of the coated composite material is significantly reduced, and the stability of the positive electrode slurry containing the coated composite material and the slurry containing the coated composite material is significantly improved. Compared with Comparative Example 2, the ionic conductivity of the coating using the coated composite material is higher than that of ordinary ceramics, and the cycle performance of the battery made from it is also better. Comparing the examples with the blank battery without the added coated composite material (Comparative Example 3), it can be seen that the battery with the added coated composite material has a significant performance improvement. PVDF-HFP coated LLZO and PE coated LLZO (Comparative Example 4) show that there is a huge advantage in terms of water absorption resistance, resulting in the battery using PVDF-HFP coated LLZO having significantly better cycle performance than the battery using PEO-Li coated LLZO.

[0245] As can be seen from Table 2, and through the comparative examples and embodiments, the water absorption of the coated composite material in the embodiments is significantly reduced, the electrical conductivity is increased, and it does not gel with PVDF when used in nitrogen-methyl solvent. This indicates that by using vinylidene fluoride-hexafluoropropylene copolymer to coat the garnet-type lithium lanthanum zirconium oxide particles, the stability of the coated composite material in air is improved, and the cycle performance of the battery including the coated composite material is improved.

[0246] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. An electrode sheet, characterized in that, The electrode comprises a positive electrode and a negative electrode. The positive electrode comprises a positive current collector and a coating layer applied to one or both sides of the current collector. The coating layer is a mixed layer containing an active material and a coated composite material. The negative electrode comprises a negative current collector and a first coating layer and a second coating layer sequentially disposed from the surface of the negative current collector outwards. The first coating layer is an active material layer, and the second coating layer is a coated composite material layer. The coated composite material layer comprises a coated composite material. The coated composite material has a core-shell structure, wherein the core is a garnet-type lithium lanthanum zirconium oxide particle, and the shell is a vinylidene fluoride-hexafluoropropylene copolymer. Based on the total weight of the vinylidene fluoride-hexafluoropropylene copolymer, the content of hexafluoropropylene is 10-20 wt%. The chemical formula of the garnet-type lithium lanthanum zirconium oxide particles is Li. 7-x La3Zr 2-x M x O 12 M is one of Ta, Nb, Hf, Al, Si, Ga, Ge, Sc, Ti, V, Y and Sn, and x is 0-0.6, and x is not 0.

2. The electrode according to claim 1, wherein, Based on the total weight of the coated composite material, the core content is 80-99 wt% and the shell content is 1-20 wt%.

3. The electrode according to claim 1, wherein, In the coating, the weight ratio of the encapsulated composite material to the active substance is (0.01-0.07):

1.

4. The electrode according to claim 1, wherein, Based on the total weight of the active material layer, the content of the active material is 90-97 wt%; based on the total weight of the coated composite material layer, the content of the coated composite material is 95-99.5 wt%.

5. A battery, characterized in that, The battery includes the electrode as described in any one of claims 1-4.

6. The battery according to claim 5, wherein, The battery does not include a separator, and the positive electrode and the negative electrode are in contact. The positive electrode and / or the negative electrode include a second coating on the contact surface. The second coating is an encapsulated composite material layer, and the thickness of the second coating is not less than 15 μm.

7. The battery according to claim 5, wherein, The battery includes a separator, and the thickness of the second coating is 15-40 μm.

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