A method for preparing a dry positive electrode film, a dry positive electrode film, a positive electrode sheet, and a full solid-state battery

Abstract

The application belongs to the technical field of solid-state batteries, and relates to a preparation method of a dry-method positive electrode film, the dry-method positive electrode film, a positive electrode sheet and a full solid-state battery. The preparation method of the dry-method positive electrode film comprises the following steps: mixing a positive electrode active material, a solid-state electrolyte, a conductive agent, a binder and an additive hexafluoropropylene trimer to obtain a mixed block; and repeatedly rolling and folding the mixed block to obtain the dry-method positive electrode film. According to the application, the specific additive hexafluoropropylene trimer is added in the raw material mixing stage, the lithium ion transmission efficiency of the dry-method positive electrode film prepared in this way is high, and the dry-method positive electrode film is suitable for various types of positive electrode active material systems, so that the rate performance of the full solid-state battery is effectively improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solid-state batteries, and relates to a preparation method of a dry-method positive electrode film, the dry-method positive electrode film, a positive electrode sheet and a solid-state battery. BACKGROUND

[0002] With the increasing demand for high-energy-density and high-safety energy storage devices, solid-state batteries are considered as an important development direction of the next generation of power batteries because they can completely solve the safety hazards of flammability and explosiveness of traditional liquid lithium batteries and achieve higher energy density. In the various configurations of solid-state batteries, the positive electrode composed of a solid-state electrolyte and a positive active material is one of the core components, and the internal structure and interface properties thereof directly determine the macroscopic performance of the battery.

[0003] At present, the preparation methods of the solid-state battery positive electrode mainly include a wet method (slurry coating) and a dry method. The wet method process needs to use solvents to disperse the positive active material, the solid-state electrolyte, the conductive agent and the binder, and although the process is mature, it has significant drawbacks: first, most organic solvents can cause serious chemical corrosion to mainstream sulfide solid-state electrolytes, resulting in a decrease in ionic conductivity; second, the subsequent drying process is time-consuming and energy-consuming, and is prone to cause uncontrollable changes in the interface between the solid-state electrolyte and the positive active material. Therefore, the dry-method electrode preparation technology emerges as the times require. The dry-method process does not need to use solvents, directly mixes dry powders such as the solid-state electrolyte, the positive active material, the conductive agent and the binder, forms a self-supporting electrode film through a fibrous binder, and is then compounded onto a current collector. This method is simple, environmentally friendly, and can avoid damage to the solid-state electrolyte by solvents.

[0004] However, the lithium ion transmission efficiency in the composite positive electrode of the solid-state battery prepared by the existing dry method is low, which seriously restricts the rate performance of the battery.

[0005] How to solve the above problems is currently urgently needed to explore. SUMMARY

[0006] In view of the deficiencies in the prior art, the purpose of the present application is to provide a preparation method of a dry-method positive electrode film, the dry-method positive electrode film, a positive electrode sheet and a solid-state battery. In the preparation process of the dry-method positive electrode film of the present application, a liquid additive hexafluoropropylene trimer is added in the raw material mixing stage, and a dry-method positive electrode film capable of effectively improving the rate performance of the solid-state battery is prepared.

[0007] To achieve the purpose of the present application, the following technical solutions are adopted:

[0008] In a first aspect, the present application provides a preparation method of a dry-method positive electrode film, comprising the following steps:

[0009] S1, dry mixing the positive electrode active material, the solid electrolyte, the conductive agent, the binder and the additive hexafluoropropylene terpolymer to obtain a mixed block;

[0010] S2, repeatedly rolling and folding the mixed block to obtain a dry positive electrode film;

[0011] The structural formula of the hexafluoropropylene terpolymer is as follows:

[0012]

[0013] In an embodiment, the rotation speed of the mixing is 3000 rpm-10000 rpm, and the mixing time is 15 min-60 min.

[0014] In an embodiment, the preparation method satisfies at least one of the following conditions:

[0015] (1) the rolling temperature is 80℃-150℃, and (2) the rolling pressure is 10 MPa-15 MPa.

[0016] In a second aspect, the present application provides a dry positive electrode film prepared by the preparation method of the first aspect.

[0017] In an embodiment, in the dry positive electrode film, a buffer layer is formed on at least part of the surface of the positive electrode active material particles.

[0018] In an embodiment, the thickness of the buffer layer is 2 nm-10 nm.

[0019] In an embodiment, the coating rate of the buffer layer on the surface of the positive electrode active material particles is greater than or equal to 65%.

[0020] In an embodiment, the dry positive electrode film does not contain the additive hexafluoropropylene terpolymer.

[0021] In a third aspect, the present application provides a positive electrode tab, which comprises the dry positive electrode film prepared by the preparation method of the first aspect or the dry positive electrode film of the second aspect.

[0022] In a fourth aspect, the present application provides an all-solid-state battery, which comprises the positive electrode tab of the third aspect.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] The present application adds a specific additive hexafluoropropylene terpolymer in the raw material mixing stage, so that the dry positive electrode film prepared thereby has a high lithium ion transmission efficiency and is suitable for various types of positive electrode active material systems, thereby effectively improving the rate performance of the all-solid-state battery. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 EDS spectra of the positive electrode active material particles and the buffer layer of the dry positive electrode film in Example 1. DETAILED DESCRIPTION

[0026] The technical solutions of the present application will be further described below by means of specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations to the present application.

[0027] The "ranges" disclosed in the present application can be defined in the form of lower limit and upper limit, a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of the particular range. The ranges defined in this way can be inclusive or exclusive of the end values, either end value can be independently included or excluded, and can be arbitrarily combined, i.e. any lower limit can be combined with any upper limit to form a range. For example, if the ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that the ranges of 60-110 and 80-120 are also contemplated. In addition, if the minimum range values of 1 and 2 are listed, and if the maximum range values of 3, 4 and 5 are also listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "a-b" represents a shorthand notation for any real combination of integers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed herein, and "0-5" is just a shorthand notation for these numerical combinations. In addition, when it is stated that a parameter is an integer ≥2, it is equivalent to listing the parameter as, for example, integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For example, when it is stated that a parameter is an integer selected from "2-10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9 and 10.

[0028] In the present application, "combination of at least two" means, unless otherwise specified, greater than or equal to 2 in number. For example, "any one or a combination of at least two" means one or greater than or equal to two. It can be understood that, when referring to "combination of at least two", it means a combination of any suitable number of items, i.e. a combination of "at least two" items in a manner that is not conflicting and can implement the present application.

[0029] If not specifically stated, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0030] The term "embodiment" mentioned in the present application means that the specific features, structures or properties described in connection with the embodiment can be included in at least one embodiment or implementation of the present application. The appearance of this phrase at various places in the specification does not necessarily mean the same embodiment, nor is it an independent or alternative embodiment to other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in the present application can be combined with other embodiments.

[0031] Those skilled in the art can understand that in the method of each embodiment, the writing order of each step does not mean a strict execution order, and the detailed execution order of each step should be determined by its function and possible inherent logic. If not specifically stated, all steps of the present application can be performed sequentially or randomly, and can be preferably performed sequentially. For example, the method comprises step (a) and step (b), which means that the method can comprise sequentially performed step (a) and step (b), or sequentially performed step (b) and step (a). For example, the method mentioned can also comprise step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0032] In the present application, the open technical features or technical solutions described by the words such as "include" do not exclude additional members other than the listed members, and can be regarded as providing both the closed features or technical solutions composed of the listed members and the open features or solutions including additional members in addition to the listed members. For example, A includes a1, a2 and a3, and unless otherwise specified, it can also include other members, or it can not include additional members, which can be regarded as providing the technical features or technical solutions of "A is composed of a1, a2 and a3" or "A is selected from a1, a2 and a3", and also providing the technical features or technical solutions of "A includes a1, a2 and a3, and also includes other members".

[0033] In the present application, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more related listed items, and also include any and all combinations of the related listed items, including any two related listed items, any more related listed items, or all related listed items. For example, "A and / or B" indicates a group consisting of A, B and the combination of A and B. Wherein, "including A and / or B" can mean "including A, including B, and including A and B", and can also mean "including A, including B, or including A and B", which can be understood appropriately according to the sentence.

[0034] In the present application, the terms "first", "second", "third", "fourth" and the like in the "first aspect", "second aspect", "third aspect", "fourth aspect" and the like are only for the purpose of description, and cannot be understood as indicating or implying relative importance or quantity, nor can it be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first", "second", "third", "fourth" and the like only serve the purpose of non-exhaustive enumeration description, and should be understood as not constituting a closed limitation on the quantity.

[0035] In the present application, "optional" means optional, that is, any one selected from the two parallel schemes of "yes" or "no". If there are multiple "optional" in a technical solution, unless otherwise specified, and there is no contradiction or mutual restriction, each "optional" is independent.

[0036] In the present application, "room temperature" generally refers to 4℃-35℃, which can refer to 20℃±5℃. In some embodiments of the present application, room temperature refers to 20℃-30℃.

[0037] In a first aspect, the present application provides a preparation method of a dry-method positive electrode film, comprising the following steps:

[0038] S1, mixing the positive electrode active material, the solid-state electrolyte, the conductive agent, the binder and the additive hexafluoropropylene trimer by dry method to obtain a mixed block;

[0039] S2, repeatedly rolling and folding the mixed block to obtain a dry-method positive electrode film;

[0040] The structural formula of the hexafluoropropylene trimer is as follows:

[0041]

[0042] It can be understood that the dry mixing of the present application means that no additional reagent is added except for the mentioned raw materials. The dry mixing includes the mixing process and the fiberization process, which can be pre-mixed at low speed and then mixed and fiberized at high speed, or directly mixed and fiberized. In addition, the present application does not make a detailed limitation on the specific dry preparation process of the positive electrode film layer. Without deviating from the overall technical concept of the present application, any known specific dry preparation details are applicable to the present application; for example, the dry mixing can adopt a conventional mechanical dry mixing method.

[0043] The present application does not specially limit the specific source of the hexafluoropropylene trimer. It can be directly purchased by market means according to the demand, or it can be prepared by a conventional preparation method. The skilled person in the art can make adaptive selection and adjustment according to the actual demand.

[0044] The present application adds a specific additive hexafluoropropylene trimer in the raw material mixing stage, the lithium ion transmission efficiency of the dry method positive electrode film prepared thereby is higher, and is suitable for various types of positive electrode active material system, thereby effectively improving the rate performance of the full solid-state battery.

[0045] Possible reasons, on the one hand, adding a liquid additive in the mixing stage is beneficial to the uniform dispersion of the positive electrode active material, the conductive agent, and the solid-state electrolyte, and the construction of an efficient continuous lithium ion transmission channel in the positive electrode; on the other hand, after adding the hexafluoropropylene trimer, a buffer layer is formed on the surface of the positive electrode active material, the buffer layer can improve the contact between the particles of each raw material, form a more dense and flexible positive electrode film during rolling, and is beneficial to the transmission of lithium ions in the positive electrode film. Moreover, the buffer layer formed by the hexafluoropropylene trimer has ion conductivity, which can further improve the lithium ion conduction between the positive electrode active material and the solid-state electrolyte particles. The above is only a speculation of the possible mechanism of the present application and does not constitute a limitation on the protection scope of the present application.

[0046] In some embodiments, the mass ratio of the positive electrode active material, the solid-state electrolyte, the conductive agent, the binder, and the liquid additive is (70-80):(15-30):(0.1-5):(0.1-1):(0.2-4), for example, 70:15:0.1:0.1:0.2, 75:22.6:2:0.4:0.2, 75:22.6:2:0.4:2, 75:22.6:2:0.4:0.5, 75:22.6:2:0.4:4, 80:30:5:1:4, or 75:20:3:0.5:2.

[0047] In the raw material of the dry method positive electrode film of the present application, the mass ratio of the positive electrode active material, the solid-state electrolyte, the conductive agent, the binder, and the liquid additive is (70-80):(15-30):(0.1-5):(0.1-1):(0.2-4), which further ensures the effective play of other electrochemical properties of the positive electrode sheet and the good synergistic effect with the liquid additive, and better improves the rate performance of the full solid-state battery.

[0048] In some embodiments, the mixing method is mechanical stirring.

[0049] In a specific embodiment, in step S1, the positive electrode active material, the conductive agent, the solid-state electrolyte, the additive, and the binder are put into a shear mixer for mixing.

[0050] In some embodiments, in step S1, the speed of mixing is 3000 rpm to 10000 rpm, for example, it can be 3000 rpm, 5000 rpm, 7000 rpm, 9000 rpm or 10000 rpm, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0051] In some embodiments, in step S1, the mixing time is 15 min to 60 min, for example, it can be 15 min, 20 min, 30 min, 40 min, 50 min or 60 min, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0052] In some embodiments, in step S2, the temperature of rolling is 80°C to 150°C, for example, it can be 80°C, 100°C, 120°C or 150°C, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0053] In some embodiments, in step S2, the pressure of rolling is 10 MPa to 15 MPa, for example, it can be 10 MPa, 11 MPa, 12 MPa, 13 MPa, 14 MPa or 15 MPa, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0054] In some embodiments, in step S2, the mixture is repeatedly rolled and folded to a predetermined thickness to obtain a dry positive electrode film.

[0055] In a specific embodiment, the predetermined thickness is 50 μm to 300 μm, for example, it can be 50 μm, 100 μm, 150 μm, 200 μm, 250 μm or 300 μm, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0056] In some embodiments, the positive electrode active material includes a compound that can reversibly intercalate and deintercalate lithium ions.

[0057] In some embodiments, the positive electrode active material comprises one or more transition metal cations, such as manganese (Mn), nickel (Ni), cobalt (Co), chromium (Cr), iron (Fe), vanadium (V), and combinations thereof.

[0058] In some embodiments, the positive electrode active material is one of a layered oxide, a spinel, and a polyanion. For example, the layered oxide (e.g., a rock-salt layered oxide) comprises one or more lithium-based positive electrode active materials selected from the group consisting of LiCoO2(LCO), LiNi x Mn y Co 1-x-yO2(wherein 0≤x≤1 and 0≤y≤1), LiNi 1-x-y Co x Al y O2(wherein 0≤x≤1 and 0≤y≤1), LiNi x Mn 1-x O2(wherein 0≤x≤1), and Li 1+x MO2(wherein M is one of Mn, Ni, Co and Al and 0≤x≤1). The spinel includes one or more lithium-based positive active materials selected from the group consisting of LiMn2O4(LMO) and LiNi x Mn 1.5 O4. The olivine-type includes one or more lithium-based positive active materials LiMPO4(wherein M is at least one of Fe, Ni, Co and Mn). The polyanion cation includes, for example, phosphates such as LiV2(PO4) 24 and / or silicates such as LiFeSiO4.

[0059] In the dry positive electrode film, the solid-state electrolyte mainly plays a role in constructing an efficient lithium ion transmission channel, and the type of the solid-state electrolyte is not limited in the present application. Illustratively, the solid-state electrolyte can be an inorganic solid-state electrolyte and a polymer solid-state electrolyte, wherein the inorganic solid-state electrolyte includes an oxide solid-state electrolyte, a sulfide solid-state electrolyte and a halide solid-state electrolyte.

[0060] The oxide solid-state electrolyte can include one or more garnet ceramics, LISICON-type oxides, NASICON-type oxides and perovskite-type ceramics. For example, the one or more garnet ceramics can be selected from the group including Li 6.5 La 24 Zr 1.75 Te 0.25 O 12 , Li7La 24 Zr2O 12 , Li 6.2 Ga 0.24 La 2.95 Rb 0.05 Zr2O 12 , Li 6.85 La 2.9 Ca 0.1 Zr 1.75 Nb 0.25 O 12 , Li 6.25 Al 0.25 La 24 Zr2O 12 , Li 6.75 La 24 Zr 1.75 Nb0.25 O 12 Li 6.75 La 24 Zr 1.75 Nb 0.25 O 12 And combinations thereof. One or more LISICON-type oxides may be selected from the group consisting of: Li 14 Zn(GeO4)4, Li24+x(P1-xSix)O4 (where 0 < x < 1), Li24+xGexV1-xO4 (where 0 < x < 1), and combinations thereof. One or more NASICON-type oxides can be derived from LiMM′(PO4). 24 Defined where M and M′ are independently selected from Al, Ge, Ti, Sn, Hf, Zr, and La. For example: in some variants, one or more NASICON-type oxides may be selected from the group consisting of: Li 1+x Al x Ge 2-x (PO4) 24 (LAGP) (where 0 ≤ x ≤ 2), Li 1+x Al x Ti 2-x (PO4) 24 (LATP) (where 0 ≤ x ≤ 2), Li 1+x YxZr 2-x (PO4) 24 (LYZP) (where 0≤x≤2), Li 1.24 Al 0.24 Ti 1.7 (PO4) 24 LiTi2(PO4) 24 LiGeTi(PO4) 24 LiGe2(PO4) 24 LiHf2(PO4) 24 And combinations thereof. One or more perovskite ceramics may be selected from the group consisting of: Li 24.24 La 0.524 TiO 24 LiSr 1.65 Zr 1.24 Ta 1.7 O9、Li 2x-y Sr 1-x Ta y Zr 1-y O 24 (where x = 0.75y and 0.60 < y < 0.75), Li 24 / 8 Sr 7 / 16 Nb 24 / 4 Zr1 / 4 O 24 Li 24-x La (2 / 24-x) TiO 24 (where 0 < x < 0.25) and combinations thereof. In one variant, one or more oxide-based materials may have a value greater than or equal to about 10. -5 S / cm to less than or equal to approximately 10 -1 Ionic conductivity in S / cm.

[0061] Sulfide solid electrolytes may include one or more sulfide-based materials selected from the group consisting of: Li2S-P2S5, Li2S-P2S5-MS x (where M is Si, Ge, and Sn and 0 ≤ x ≤ 2), Li 24.4 Si 0.4 P 0.6 S4, Li 10 GeP2S 11.7 O 0.24 Li 9.6 P 24 S 12 Li7P 24 S 11 Li9P 24 S9O 24 Li 10.245 Si 1.245 P 1.65 S 12 Li 9.81 Sn 0.81 P 2.19 S 12 Li 10 (Si 0.5 Ge 0.5 P2S 12 Li (Ge 0.5 Sn 0.5 P2S 12 Li 10 GeP2S 12 (LGPS), Li6PS5X (where X is Cl, Br, or I), Li7P2S8I, Li 10.245 Ge 1.245 P 1.65 S 12 Li 24.25 Ge 0.25 P 0.75 S4, Li 10 SnP2S 12 Li 10 SiP2S 12 Li 9.54 Si 1.74P 1.44 S 11.7 Cl 0.24 , (1-x)P2S 5-x Li2S (wherein 0.5≤x≤0.7) and combinations thereof. In one variation, one or more of the sulfide-based materials can have an ionic conductivity of greater than or equal to about 10 -7 S / cm to less than or equal to about 1 S / cm.

[0062] The halide solid-state electrolyte includes Li a M b X c N d wherein M includes a base metal element such as one or more combinations of Zr, Hf, In, Sc, Y, La, Ce, Pr, Nb, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and M further includes a doping metal element used in combination with the aforementioned base metal element such as one or more combinations of Nb, Ta, Al, La, Mg, Ca, Ba, Ag; X includes one or more combinations of F, Cl, Br, I; N includes one or more combinations of O, S, and a+mb=c+nd is satisfied, m, n are weighted valences of M and N respectively, 1≤a≤4.

[0063] In some preferred embodiments of the present application, the solid-state electrolyte includes a halide solid-state electrolyte. The halide solid-state electrolyte has high ionic conductivity and is stable in air and is not prone to decomposition and generation of toxic substances compared to sulfide solid-state electrolytes. The halide solid-state electrolyte is not compatible with most liquids and can undergo side reactions, and thus a dry process is very suitable for use in batteries using a halide solid-state electrolyte.

[0064] Exemplarily, the halide solid-state electrolyte particles can be at least one of Li2ZrCl6, Li2ZrCl5F, Li2ZrCl 5.5 O 0.25 , Li3InCl6, Li3YCl6, Li2HfCl6, LiInBr4, Li3InBr6, Li3LaI6, Li3LuCl6, Li3ErCl6.

[0065] The binder improves the binding between the positive electrode active material particles, the conductive agent particles, and the solid-state electrolyte particles.

[0066] The binder includes a fiberizable binder that binds the positive electrode active material, the conductive agent, and the solid-state electrolyte by being transformed from a particulate form to a fibrous form under high shear.

[0067] In some embodiments, the fibrillatable binder includes one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride hexafluoropropylene, polypropylene, polyethylene, polyimide.

[0068] In some embodiments, to further enhance the binding ability of the binder to the positive electrode, the binder further includes at least one of polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymer, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene butadiene rubber, acrylated styrene butadiene rubber, epoxy resin, nylon, etc.

[0069] The conductive agent imparts electrical conductivity to the electrode. The conductive agent can include any electrically conductive material, so long as it does not cause chemical changes.

[0070] The type of conductive agent is not limited in the present application. Exemplarily, the conductive agent includes any one or a combination of at least two of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers. The above are all common conductive agents in the art, which are only examples and are not limiting.

[0071] In a second aspect, the present application provides a dry-method positive electrode film prepared by the preparation method of the first aspect.

[0072] In some embodiments, in the dry-method positive electrode film, a buffer layer is formed on at least part of the surface of the particles of the positive electrode active material. By adding the additive hexafluoropropylene trimer during the preparation stage, a buffer layer is formed on the surface of the particles of the positive electrode active material in the dry-method positive electrode film prepared. The buffer layer can insulate the positive electrode active material and the solid-state electrolyte, preventing side reactions from occurring. The buffer layer can also improve the contact between the positive electrode active material and the solid-state electrolyte, improving the lithium ion transport capacity.

[0073] The present application provides a test method for the coverage rate of the buffer layer as follows:

[0074] The test method for the coverage rate is as follows: scrape off the dry-method positive electrode film powder, wash it with the solvent DMC to remove halides and binders and the like, and perform ion milling (CP) treatment on the remaining positive electrode active material particles to obtain a sample, perform SEM characterization on the sample, and perform F element quantitative analysis by EDS to obtain an EDS test spectrum. The buffer layer contains F elements, which will present a bright image of the buffer layer and a dark image of the positive electrode active material particles. By measuring the length of the bright part and the circumference of the positive electrode active material particles, the coverage rate is calculated.

[0075] The specific calculation formula for the coverage rate is: coverage rate = length of bright part / circumference of particle x 100%.

[0076] And by obtaining multiple coating rate values at different positions, taking the average value, the final coating layer coating rate value is obtained.

[0077] In some embodiments, the thickness of the buffer layer is 2nm-10nm. For example, it can be 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm or 10nm, but is not limited to the listed values, and other unlisted values within the value range are also applicable.

[0078] In some embodiments, the coating rate of the buffer layer on the surface of the positive electrode active material particle is greater than or equal to 65%. For example, it can be 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%.

[0079] The higher the coating rate of the buffer layer, the more conducive to improving the contact between the positive electrode active material and the solid-state electrolyte and improving the lithium ion transmission capacity.

[0080] In some embodiments, the dry positive electrode film does not contain the additive hexafluoropropylene trimer.

[0081] In some embodiments, the mass fraction of the additive in the dry positive electrode film is less than the mass fraction of the additive in the raw material. The raw material refers to the positive electrode active material, the conductive agent, the binder, the solid-state electrolyte and the additive.

[0082] It should be noted that the content of the additive in the dry positive electrode film in the present application is tested as follows: the prepared dry positive electrode film is placed in a vacuum oven, and the temperature of the vacuum oven is set to be greater than the boiling point of the liquid additive, which is 130℃ in the present application. Dry for 6h, compare the weights of the dry positive electrode film before and after the test to determine whether there is still liquid additive in the dry positive electrode film. If the weight does not change before and after the test, it proves that the dry positive electrode film does not contain the additive.

[0083] In a third aspect, the present application provides a positive electrode tab, which comprises the dry positive electrode film prepared by the preparation method of the first aspect or the dry positive electrode film of the second aspect.

[0084] In some embodiments, the positive electrode tab further comprises a current collector; the current collector has the dry positive electrode film compounded on at least one side surface.

[0085] In some embodiments, the positive electrode current collector comprises an electron-conducting metal material, for example, the positive electrode current collector comprises at least one of aluminum, nickel, tin, copper and stainless steel.

[0086] In some embodiments, the positive current collector can adopt a high-purity aluminum foil or aluminum alloy foil with a purity of no less than 99.6% and a thickness of 10-20 μm (e.g., 10 μm, 13 μm, 15 μm, 18 μm, or 20 μm, etc.). In some embodiments, the surface of the aluminum foil can be subjected to an anodization treatment to form a nanoscale aluminum oxide layer, so as to enhance its corrosion resistance and interface bonding force with the positive electrode material. In some embodiments, the aluminum alloy foil can contain trace amounts of titanium (Ti) or silicon (Si) elements, so as to improve the mechanical strength and high-temperature stability. In some embodiments, the aluminum foil can also be a carbon-coated aluminum foil.

[0087] In some embodiments, the composite method in the present application is roll-to-roll lamination.

[0088] In a fourth aspect, the present application provides a full solid-state battery, which comprises the positive electrode sheet as described in the third aspect.

[0089] In some embodiments, the present application provides a full solid-state battery, which comprises the positive electrode sheet as described in the third aspect.

[0090] The positive electrode sheet with the dry-method positive electrode film in the present application in the full solid-state battery has a high lithium ion transmission efficiency, a good solid-solid interface contact, and a significantly improved rate performance.

[0091] In addition to the positive electrode sheet, the full solid-state battery also comprises a negative electrode sheet and a solid-state electrolyte layer between the positive electrode sheet and the negative electrode sheet; the negative electrode sheet and the solid-state electrolyte layer are both conventional technical solutions, and any known raw materials, preparation processes, and structural units suitable for the full solid-state battery are applicable to the present application without deviating from the overall technical concept of the present application.

[0092] In some embodiments, the positive electrode sheet is provided with a positive electrode tab, and the negative electrode sheet is provided with a negative electrode tab.

[0093] In some embodiments, the negative electrode sheet comprises a lithium metal-based negative electrode sheet or a negative electrode sheet comprising a negative electrode current collector and a negative electrode active material layer formed on the surface of the negative electrode current collector, wherein the negative electrode active material layer at least comprises a negative electrode active material and a negative electrode binder; further, the negative electrode active material layer can also have a conductive agent.

[0094] In some embodiments, the negative electrode can be an anode-free lithium metal solid-state battery, and the negative electrode can be made of an Ag-C alloy coated on a copper foil as a negative electrode current collector to form a negative electrode sheet.

[0095] It is understood that the present application does not have a particular limitation on the negative current collector material, as long as it has electrical conductivity without causing chemical changes in the battery. Exemplarily, the negative current collector includes, but is not limited to, any one of copper, nickel, or stainless steel, such as a copper foil.

[0096] It is understood that the present application does not have a particular limitation on the shape of the negative current collector, and exemplarily, the shape of the negative current collector includes, but is not limited to, a metal foil, a metal grid, a metal mesh, and the like.

[0097] It is understood that the negative active material is a compound that reversibly intercalates and deintercalates lithium, and the negative active material in the present application can be any negative active material known in the art. Exemplarily, the negative active material can be selected from at least one of natural graphite, artificial graphite, hard carbon, soft carbon, silicon-based material, titanium-based material, tin-based material, or metallic lithium, and the like.

[0098] It is understood that the present application does not have a particular limitation on the type of the conductive agent, and the same conductive agent or different conductive agents can be selected in the positive electrode sheet and the negative electrode sheet.

[0099] In some embodiments, the conductive agent in the negative electrode sheet includes, but is not limited to, at least one of a carbon-based material, powdered nickel, or other metal particles, or a conductive polymer. For example, natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, channel black, acetylene black, carbon nanotubes, carbon nanofibers, polyaniline, polythiophene, polyacetylene, polypyrrole, or poly(3,4-ethylenedioxythiophene) polystyrene sulfonate, and the like.

[0100] It is understood that the present application does not have a particular limitation on the type of the binder, and a binder capable of binding and maintaining the active material, enhancing the contact between the active material and the conductive agent, and the contact between the active material and the current collector, thereby stabilizing the structure of the electrode sheet, is within the protection scope of the present application, without deviating from the concept of the present application.

[0101] In some embodiments, the binder in the negative electrode sheet includes, but is not limited to, a thermoplastic resin or a thermosetting resin. For example, polytetrafluoroethylene (PTFE), sodium carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR), polyvinylidene fluoride (PVDF), nitrile rubber (NBR), styrene ethylene butylene styrene copolymer (SEBS), styrene butadiene styrene copolymer (SBS), lithium polyacrylate (LiPAA), sodium polyacrylate (NaPAA), sodium alginate, lithium alginate, and the like.

[0102] It is understood that the solid electrolyte layer can be a single-layer structure or a multi-layer laminated structure, which can be adaptively selected and adjusted according to actual needs.

[0103] The technical solutions of the present application are further illustrated below through specific examples.

[0104] Example 1

[0105] The present example provides a preparation method of a dry cathode film, which is as follows:

[0106] The positive electrode active material (LiNi 0.8 Co 0.1 Mn 0.1 O2, a halide solid electrolyte (Li3InCl6), a conductive agent vapor grown carbon fiber (VGCF), a liquid additive (hexafluoropropylene trimer), and a binder (polytetrafluoroethylene, PTFE) are mechanically mixed uniformly at a mass ratio of 75:22.6:2:2:0.4 to obtain a mixed block, and the mixed block is placed in a shear mixer and repeatedly rolled and folded until a uniform and smooth dry cathode film with a preset thickness is obtained, and the thickness is 100 μm. The structural formula of the hexafluoropropylene trimer is . Hereinafter, it is referred to as 6F.

[0107] The present example also provides a dry cathode film prepared by the above method.

[0108] In the dry cathode film, a buffer layer is formed on the surface of the particles of the positive electrode active material. The coating rate of the buffer layer is 82%.

[0109] The present example also provides a positive electrode tab, which comprises an aluminum foil and a dry cathode film compounded on both sides of the aluminum foil.

[0110] The dry cathode film obtained in Example 1 is subjected to SEM test, and DES is used to quantitatively analyze the F element, and the DES energy spectrum is as shown in Figure 1 From Figure 1 it can be seen that the buffer layer will appear as a bright image of the positive electrode active material particles due to the presence of the F element. By measuring the length of the bright part and the circumference of the positive electrode active material particles, the coating rate of the corresponding buffer layer can be calculated according to the calculation formula: coating rate = length of bright part / circumference of particle x 100%.

[0111] Example 2

[0112] The present example provides a preparation method of a dry cathode film, which is as follows:

[0113] The positive electrode active material (LiNi 0.8 Co 0.1 Mn 0.1O2 (NCM811), halide solid electrolyte (Li3InCl6), conductive agent vapor-grown carbon fiber (VGCF), liquid additive (hexafluoropropylene trimer), and binder (polytetrafluoroethylene, PTFE) were mechanically mixed uniformly at a mass ratio of 75:22.6:2:0.2:0.4 to obtain a mixture agglomerate. This agglomerate was then placed in a shear mixer and repeatedly rolled and folded until a uniform and smooth dry-process positive electrode film of a predetermined thickness of 100 μm was obtained. The structural formula of the hexafluoropropylene trimer is... .

[0114] This embodiment also provides a dry cathode film prepared by the above method.

[0115] In the dry-process positive electrode film, a buffer layer is formed on the surface of the positive electrode active material particles. The coverage of the buffer layer is 69%.

[0116] This embodiment also provides a positive electrode sheet, which includes an aluminum foil and a dry-processed positive electrode film laminated on both sides of the aluminum foil.

[0117] Example 3

[0118] This embodiment provides a method for preparing a dry cathode film, the method of which is as follows:

[0119] The positive electrode active material (LiNi) 0.8 Co 0.1 Mn 0.1 O2 (NCM811), halide solid electrolyte (Li3InCl6), conductive agent vapor-grown carbon fiber (VGCF), liquid additive (hexafluoropropylene trimer), and binder (polytetrafluoroethylene, PTFE) were mechanically mixed uniformly at a mass ratio of 75:22.6:2:4:0.4 to obtain a mixture agglomerate. This agglomerate was then placed in a shear mixer and repeatedly rolled and folded until a uniform and smooth dry-process positive electrode film of a predetermined thickness of 100 μm was obtained. The structural formula of hexafluoropropylene trimer is... .

[0120] This embodiment also provides a dry cathode film prepared by the above method.

[0121] In dry-process cathode films, a buffer layer is formed on the surface of the cathode active material particles. The coverage of the buffer layer is 90%.

[0122] This embodiment also provides a positive electrode sheet, which includes an aluminum foil and a dry-processed positive electrode film laminated on both sides of the aluminum foil.

[0123] Example 4

[0124] The present embodiment provides a preparation method of a dry cathode film, which is as follows:

[0125] The positive electrode active material (LiNi 0.8 Co 0.1 Mn 0.1 O2, NCM811), a halide solid electrolyte (Li3InCl6), a conductive agent vapor grown carbon fiber (VGCF), a liquid additive (hexafluoropropylene trimer), and a binder (polytetrafluoroethylene, PTFE) are mechanically mixed uniformly at a mass ratio of 75:22.6:2:0.5:0.4 to obtain a mixed block, and the mixed block is placed in a shearing mixer to repeatedly roll and fold until a uniform and smooth dry cathode film with a preset thickness is obtained, and the thickness is 100 μm. The structural formula of the hexafluoropropylene trimer is .

[0126] The present embodiment also provides a dry cathode film prepared by the above method.

[0127] In the dry cathode film, a buffer layer is formed on the surface of the particles of the positive electrode active material. The coating rate of the buffer layer is 71%.

[0128] The present embodiment also provides a positive electrode tab, which comprises an aluminum foil and a dry cathode film compounded on both sides of the aluminum foil.

[0129] Embodiment 5

[0130] The present embodiment provides a preparation method of a dry cathode film, which is as follows:

[0131] The positive electrode active material (LiNi 0.8 Co 0.1 Mn 0.1 O2, NCM811), a halide solid electrolyte (Li3InCl6), a conductive agent vapor grown carbon fiber (VGCF), a liquid additive (hexafluoropropylene trimer), and a binder (polytetrafluoroethylene, PTFE) are mechanically mixed uniformly at a mass ratio of 75:22.6:2:5:0.4 to obtain a mixed block, and the mixed block is placed in a shearing mixer to repeatedly roll and fold until a uniform and smooth dry cathode film with a preset thickness is obtained, and the thickness is 100 μm. The structural formula of the hexafluoropropylene trimer is .

[0132] The present embodiment also provides a dry cathode film prepared by the above method.

[0133] In the dry cathode film, a buffer layer is formed on the surface of the particles of the positive electrode active material. The coating rate of the buffer layer is 92%.

[0134] The embodiment also provides a positive electrode sheet, which comprises an aluminum foil and a dry positive electrode film compounded on both sides of the aluminum foil.

[0135] Embodiment 6

[0136] The embodiment provides a preparation method of a dry positive electrode film, which comprises the following steps:

[0137] The positive electrode active material (LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), a halide solid-state electrolyte (Li3InCl6), a conductive agent vapor-grown carbon fiber (VGCF), a liquid additive (hexafluoropropylene trimer) and a binder (polytetrafluoroethylene, PTFE) are mechanically mixed uniformly at a mass ratio of 75:22.6:2:8:0.4 to obtain a mixed block, and the mixed block is placed in a shearing mixer to be repeatedly rolled and folded until a dry positive electrode film with a preset thickness is obtained, and the thickness is 100 μm. The structural formula of the hexafluoropropylene trimer is .

[0138] The embodiment also provides a dry positive electrode film prepared by the above method.

[0139] In the dry positive electrode film, a buffer layer is formed on the surface of the particle of the positive electrode active material. The coating rate of the buffer layer is 95%.

[0140] The embodiment also provides a positive electrode sheet, which comprises an aluminum foil and a dry positive electrode film compounded on both sides of the aluminum foil.

[0141] Embodiment 7

[0142] The embodiment provides a preparation method of a dry positive electrode film, which comprises the following steps:

[0143] The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), a halide solid-state electrolyte (Li3InCl6), a conductive agent vapor-grown carbon fiber (VGCF), a liquid additive (hexafluoropropylene trimer) and a binder (polytetrafluoroethylene, PTFE) are mechanically mixed uniformly at a mass ratio of 75:22.6:2:8:0.4 to obtain a mixed block, and the mixed block is placed in a shearing mixer to be repeatedly rolled and folded until a dry positive electrode film with a preset thickness is obtained, and the thickness is 100 μm. The structural formula of the hexafluoropropylene trimer is .

[0144] The embodiment also provides a dry positive electrode film prepared by the above method.

[0145] In the dry-method cathode film, a buffer layer is formed on the surface of the particles of the cathode active material. The coating rate of the buffer layer is 82%.

[0146] The present embodiment also provides a cathode electrode piece, which comprises an aluminum foil and a dry-method cathode film compounded on both sides of the aluminum foil.

[0147] Example 8

[0148] The present embodiment provides a preparation method of a dry-method cathode film, which is as follows:

[0149] The cathode active material LiCoO2 (LCO), the sulfide solid-state electrolyte (Li6PS5Cl), the conductive agent vapor-grown carbon fiber (VGCF), the liquid additive (hexafluoropropylene trimer), and the binder (polytetrafluoroethylene, PTFE) are mechanically mixed uniformly at a mass ratio of 75:22.6:2:2:0.4 to obtain a mixed block, and the mixed block is placed in a shearing mixer to be repeatedly rolled and folded until a uniform and smooth dry-method cathode film with a preset thickness is obtained. The thickness of the dry-method cathode film is 100 μm. The structural formula of the hexafluoropropylene trimer is .

[0150] The present embodiment also provides a dry-method cathode film prepared by the above method.

[0151] In the dry-method cathode film, a buffer layer is formed on the surface of the particles of the cathode active material. The coating rate of the buffer layer is 82%.

[0152] The present embodiment also provides a cathode electrode piece, which comprises an aluminum foil and a dry-method cathode film compounded on both sides of the aluminum foil.

[0153] Comparative Example 1

[0154] The difference between the present comparative example and Example 1 is that the present comparative example does not contain the liquid additive hexafluoropropylene trimer; and the mass ratio of the cathode active material (LiNi 0.8 Co 0.1 Mn 0.1 O2, NCM811), the halide solid-state electrolyte (Li3InCl6), the conductive agent vapor-grown carbon fiber (VGCF), and the binder (polytetrafluoroethylene, PTFE) is 75:22.6:2:0.4.

[0155] The remaining conditions are consistent with those of Example 1.

[0156] Comparative Example 2

[0157] The difference between the present comparative example and Example 7 is that the present comparative example does not contain the liquid additive hexafluoropropylene trimer; and the mass ratio of the corresponding positive active material (LiNi 0.8 Co 0.1 Mn 0.1 O2, NCM811), a sulfide solid electrolyte (Li6PS5Cl), a conductive agent vapor grown carbon fiber (VGCF), and a binder (polytetrafluoroethylene, PTFE) is 75:22.6:2:0.4.

[0158] The remaining conditions are consistent with Example 7.

[0159] Comparative Example 3

[0160] The difference between the present comparative example and Example 8 is that the present comparative example does not contain the liquid additive hexafluoropropylene trimer; and the mass ratio of the corresponding positive active material lithium cobaltate (LiCoO2, LCO), a sulfide solid electrolyte (Li6PS5Cl), a conductive agent vapor grown carbon fiber (VGCF), and a binder (polytetrafluoroethylene, PTFE) is 75:22.6:2:0.4.

[0161] The remaining conditions are consistent with Example 8.

[0162] The positive electrode plates provided in Examples 1-8 and Comparative Examples 1-3 are used to prepare corresponding full solid-state batteries, and the specific applications are as follows.

[0163] Application Example 1

[0164] The present application example provides a full solid-state battery, which comprises the positive electrode plate of Example 1, a negative electrode plate, and a solid-state electrolyte layer between the positive electrode plate and the negative electrode plate.

[0165] The preparation method of the full solid-state battery is as follows:

[0166] (1) providing a positive electrode plate: the positive electrode plate of Example 1;

[0167] (2) providing a negative electrode plate: rolling a carbon layer with a lithium metal sheet to obtain a Li-C composite negative electrode;

[0168] (3) providing a solid-state electrolyte layer: Li6PS5Cl and PTFE are fiberized in a small mixer at a mass ratio of 99:1 at a speed of 1000 r / min, and then rolled to prepare.

[0169] (4) compounding the positive electrode plate, the negative electrode plate, and the solid-state electrolyte layer: stacking the provided positive electrode plate, the solid-state electrolyte layer, and the negative electrode plate, then densifying by isostatic pressing, assembling a 2 cm x 2 cm full solid-state soft pack battery, and testing the electrochemical performance under a test pressure of 2 Mpa.

[0170] Application Examples 2-8 and Comparative Application Examples 1-3

[0171] The difference between the application examples 2-8 and the comparative application examples 1-3 and the application example 1 is that the positive electrode plates of the application examples 2-8 and the comparative application examples 1-3 are respectively used to prepare the all-solid-state batteries.

[0172] The remaining application conditions are consistent with those of the application example 1.

[0173] Performance test

[0174] The all-solid-state batteries of the application examples 1-8 and the comparative application examples 1-3 are tested, and the test conditions include:

[0175] For the batteries of the NCM system, the application examples 1-7 and the comparative application example 1-2: 40℃, 2.5V-4.25V, the fully charged battery is discharged to the cut-off voltage 4.25V at a current of 0.1C in the blue light system, and the capacity obtained by the test is C0; in the normal temperature environment (25℃), the fully charged battery is discharged to the cut-off voltage 4.25V at a current of 1C, and the capacity obtained by the test is C1, and C1 / C0 is the capacity retention rate at 1C, and the test results are shown in Table 1.

[0176] For the batteries of the LCO system, the application example 8 and the comparative application example 3: 40℃, 2.5V-4.2V, the fully charged battery is discharged to the cut-off voltage 4.25V at a current of 0.1C in the blue light system, and the capacity obtained by the test is C0; in the normal temperature environment (25℃), the fully charged battery is discharged to the cut-off voltage 4.25V at a current of 1C, and the capacity obtained by the test is C1, and C1 / C0 is the capacity retention rate at 1C, and the test results are shown in Table 2.

[0177] Table 1

[0178]

[0179] Table 2

[0180]

[0181] As can be seen from the above table, by adding the specific additive hexafluoropropylene trimer in the raw material mixing stage, the lithium ion transmission efficiency of the dry method positive electrode film prepared thereby is higher, and is suitable for various types of positive electrode active material systems, thereby effectively improving the rate performance of the all-solid-state battery.

[0182] The above merely provides a specific implementation of the present application, but the protection scope of the present application is not limited thereto, and those skilled in the art should understand that any changes or replacements within the technical scope disclosed by the present application can be easily thought of by those skilled in the art, and all fall within the protection scope and disclosure scope of the present application.

Claims

1. A dry-process positive electrode film, characterized in that, The dry-process positive electrode film is prepared by the following method, which includes the following steps: S1. Dry mixing of positive electrode active material, solid electrolyte, conductive agent, binder and additive hexafluoropropylene trimer to obtain mixed agglomerates; S2. Repeatedly roll and fold the mixed agglomerate to obtain the dry cathode membrane. In the dry cathode membrane, at least a buffer layer is formed on the surface of the positive electrode active material particles. The buffer layer is formed of hexafluoropropylene trimer. The structural formula of the hexafluoropropylene trimer is shown below: 。 2. The dry-process positive electrode film according to claim 1, characterized in that, The mixing speed is 3000 rpm to 10000 rpm; The mixing time is 15 min to 60 min.

3. The dry-process positive electrode film according to claim 1, characterized in that, At least one of the following conditions must be met: (1) The temperature of the roller pressing is 80℃~150℃; (2) The pressure of the roller is 10MPa~15MPa.

4. The dry-process positive electrode film according to claim 1, characterized in that, The thickness of the buffer layer is 2nm~10nm.

5. The dry-process positive electrode film according to claim 1, characterized in that, The buffer layer on the surface of the positive electrode active material particles has a coating rate of 65% or greater.

6. A positive electrode sheet, characterized in that, The positive electrode includes the dry-process positive electrode film as described in any one of claims 1-5.

7. An all-solid-state battery, characterized in that, The all-solid-state battery includes the positive electrode as described in claim 6.

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