Fluorine-based lubricant, electrode, and secondary battery

Abstract

In the present disclosure, the problem is solved by providing a fluorine-based lubricant which is used in an active material layer containing an active material and a sulfide solid electrolyte, and which is solid at 25 DEG C.

Description

Technical Field

[0001] This disclosure relates to fluorinated lubricants, electrodes, and secondary batteries. Background Technology

[0002] Lithium-ion secondary batteries and similar batteries have electrodes comprising a current collector and an active material layer. For example, Patent Document 1 discloses a negative electrode composite layer for an all-solid-state lithium-ion secondary battery, comprising porous silicon particles as the negative electrode active material and a sulfide-based solid electrolyte. Patent Document 2 discloses an electrolyte (electrolyte) comprising an alkali metal salt dissolved in a non-aqueous solvent containing a perfluoroether as the active material layer. Patent Document 3 discloses an electrode having a compound containing a perfluoropolyether group on its surface.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2020-170605

[0006] Patent Document 2: Japanese Patent Application Publication No. 2018-200866

[0007] Patent Document 3: Japanese Patent Application Publication No. 2018-147887 Summary of the Invention

[0008] In an active material layer containing active materials and a sulfide solid electrolyte, the active materials expand and contract during charging and discharging. If the volume change of the active material layer is large, there is a possibility that the active material particles may peel off from each other, potentially leading to electrode delamination. If electrode delamination occurs, there is a possibility of increased battery resistance and decreased battery performance. In particular, active materials containing Si (Si-based active materials) are effective for achieving high energy density in batteries, but on the other hand, the large volume changes caused by charging and discharging can easily lead to the aforementioned performance degradation.

[0009] This disclosure is made in view of the above-mentioned circumstances, and its main purpose is to provide a fluorine-based lubricant capable of inhibiting electrode stripping.

[0010] [1] A fluorinated lubricant used in an active material layer of an electrolyte containing active material and sulfide solid electrolyte, which is solid at 25°C.

[0011] [2] The fluorine-based lubricant according to [1] has a melting point below 120°C.

[0012] [3] The fluorinated lubricant according to [1] or [2] has a fluorinated polyether structure.

[0013] [4] An electrode having an active material layer and a current collector, wherein the active material layer contains a Si-based active material, a sulfide solid electrolyte and a fluorine-based lubricant, wherein the fluorine-based lubricant is any one of [1] to [3].

[0014] [5] According to the electrode described in [4], the above-mentioned Si-based active material is combined with the above-mentioned fluorine-based lubricant, which is a solid.

[0015] [6] The electrode according to [4] or [5], wherein the ratio of the above-mentioned fluorine-based lubricant to the above-mentioned Si-based active material is 4% to 12% by weight.

[0016] [7] A secondary battery comprising any one of the electrodes described in [4] to [6].

[0017] In this disclosure, the effect of providing a fluorinated lubricant that can suppress electrode stripping is achieved. Attached Figure Description

[0018] Figure 1 This is a schematic cross-sectional view illustrating a secondary battery in this disclosure. Detailed Implementation

[0019] The following provides a detailed description of the fluorinated lubricant, electrodes, and secondary battery disclosed herein. In this disclosure, "fluorinated lubricant" refers to a lubricant containing fluorine (F).

[0020] A. Fluorine-based lubricants

[0021] The fluorinated lubricant in this disclosure is used in an active material layer containing an active material and a sulfide solid electrolyte, and is solid at 25°C. The active material, the sulfide solid electrolyte, and the active material layer are described below.

[0022] As mentioned above, active materials expand and contract with charging and discharging, especially Si-based active materials, which exhibit large volume changes. Therefore, electrodes using active materials may experience delamination. However, it is presumed that the fluorine-based lubricant in this disclosure can penetrate the gaps formed at the interfaces between the active materials, thus suppressing electrode delamination (repairing delamination).

[0023] Fluorine-based lubricants have melting points of, for example, above 38°C, above 50°C, above 65°C, or above 80°C. On the other hand, fluorine-based lubricants have melting points of, for example, below 200°C, below 150°C, or below 100°C.

[0024] It is believed that fluorinated lubricants, by possessing the aforementioned melting point, can, even if the active materials peel off from each other due to expansion and contraction, undergo phase transition to liquid form using the heat generated during battery charging and discharging or by heating the battery. This allows them to function as a lubricant between the active materials, repairing the peeling and suppressing an increase in battery resistance. In particular, the melting point of fluorinated lubricants is preferably in the range of 60°C to 120°C. Here, the melting point of fluorinated lubricants can be determined using differential scanning calorimetry (DSC) to find the temperature corresponding to the maximum value in the heat of fusion curve when the temperature is increased at a rate of 5°C / minute.

[0025] Fluorinated lubricants typically contain at least one of a fluoroalkyl group and a fluoroalkylene group. The fluoroalkyl group can be a functional group in which all hydrogen atoms in the alkyl group are replaced by fluorine (perfluoroalkyl), or a functional group in which some hydrogen atoms in the alkyl group are replaced by fluorine. The number of carbon atoms in the fluoroalkyl group is, for example, 1 to 10, and can be 1 to 5. Conversely, the number of carbon atoms in the fluoroalkylene group is, for example, 1 to 20, and can be 1 to 15.

[0026] Furthermore, fluorinated lubricants can have either a straight-chain or branched-chain structure. They may or may not have ether bonds in their main chain. The terminal functional groups at the ends of fluorinated lubricants are not particularly limited. Examples of terminal functional groups include fluorinated groups, hydrogen groups, hydroxyl groups, aldehyde groups, carboxylic acid groups, C1-10 alkyl ester groups, amide groups (which may have one or more substituents), and amino groups (which may have one or more substituents).

[0027] As an example of a fluorinated lubricant, a carboxylic acid compound containing at least one of a fluoroalkyl group and a fluoroalkylene group can be cited. The number of carbon atoms of the fluoroalkyl group and the fluoroalkylene group are as described above. In addition, the above-mentioned carboxylic acid compound may have one carboxyl group, two carboxyl groups, or three or more carboxyl groups. As examples of carboxylic acid compounds, the following compounds can be cited.

[0028] HOOC-(CF2)2-COOH

[0029] HOOC-(CF2)3-COOH

[0030] HOOC-(CF2)4-COOH

[0031] HOOC-CF2O(CF2)2OCF2-COOH

[0032] CF3 (CF2) 10 -COOH

[0033] CF3 (CF2) 12 -COOH

[0034] Other examples of fluorinated lubricants include alcohol compounds containing at least one of a fluoroalkyl group and a fluoroalkylene group. The number of carbon atoms in the fluoroalkyl and fluoroalkylene groups is as described above. Furthermore, the aforementioned alcohol compounds may have one hydroxyl group, two hydroxyl groups, or three or more hydroxyl groups. Examples of alcohol compounds include the following compounds.

[0035] HO-CH2(CF2)2CH2-OH

[0036] HO-CH2(CF2)3CH2-OH

[0037] HO-CH2(CF2)4CH2-OH

[0038] HO-CH2CF2O(CF2)2OCF2CH2-OH

[0039] CF3 (CF2) 13 -OH

[0040] Other examples of fluorinated lubricants include fluoroalkanes. The number of carbon atoms in fluoroalkanes is, for example, 10 to 20. Examples of fluoroalkanes include the following compounds.

[0041] CF3 (CF2) 11 CF3

[0042] CF3 (CF2) 14 CF3

[0043] CF3 (CF2) 18 CF3

[0044] Other examples of fluorinated lubricants include ester compounds containing at least one of a fluoroalkyl group and a fluoroalkylene group. The number of carbon atoms in the fluoroalkyl and fluoroalkylene groups is as described above. Preferably, the fluoroalkylene group has 8 to 15 carbon atoms. The ester compounds described above may have one ester group, two ester groups, or three or more ester groups. Examples of ester compounds include the following compounds.

[0045] CH3OOC-(CF2) 10 -COOCH3

[0046] CF3 (CF2) 12 -COOCH3

[0047] In addition, as a fluorinated lubricant, for example, compounds having a fluorinated polyether structure (FPE structure) can be cited. Compounds having a fluorinated polyether structure (FPE structure) have the structure represented by the following formula (1).

[0048] E1-Rf1-RF-O-Rf2-E2 (1)

[0049] [In formula (1), Rf1 and Rf2 are each independently a C1-16 divalent alkylene group that can be substituted with one or more fluorine atoms.]

[0050] E1 and E2 are each independently a monovalent group selected from fluorine, hydrogen, hydroxyl, aldehyde, carboxylic acid, C1-10 alkyl ester, amide (which may have one or more substituents), and amino (which may have one or more substituents).

[0051] RF stands for -(AO) n - indicates a group (A contains a carbon chain as the main chain and has at least one fluorine atom bonded to the aforementioned carbon chain).

[0052] The carbon chain of A described above preferably has 1, 2, 3, or 4 carbon atoms. A may or may not have hydrogen atoms. Additionally, A may have -CF. 3-x H x (0≤x≤3) as a side chain. Considering that it is a solid at 25°C, -(CH2CF2CF2O) is preferred as the RF. n - A number where n is 1 or higher.

[0053] Among the above-mentioned compounds, those with fluorinated polyether structures are preferred from the perspectives of electrochemical stability and low volatility at high temperatures.

[0054] B. Electrode

[0055] The electrode in this disclosure is an electrode having an active material layer and a current collector. The active material layer contains an active material and a fluorinated lubricant, and the fluorinated lubricant is the aforementioned fluorinated lubricant.

[0056] According to this disclosure, since the active material layer in the electrode contains the aforementioned fluorine-based lubricant, it becomes an electrode that can suppress peeling.

[0057] 1. Active substance layer

[0058] The electrode in this disclosure has an active material layer and a current collector. Furthermore, the active material layer contains an active material, a sulfide solid electrolyte, and a fluorine-based lubricant.

[0059] (1) Active substances

[0060] Examples of active materials include, for example, carbon-based active materials, oxide active materials, and metal active materials. Examples of carbon-based active materials include, for example, graphite. Examples of oxide active materials include, for example, lithium titanate. Examples of metal active materials include, for example, Si-based active materials. Among these, Si-based active materials are preferred. Si-based active materials contain at least Si. Examples of Si-based active materials include, for example, elemental Si, Si alloys, and Si oxides. Si alloys preferably contain Si as a main component. The proportion of Si in the Si alloy is, for example, 50 at% or more, 70 at% or more, or 90 at% or more. Examples of Si alloys include, for example, Si-Li alloys, Si-Al alloys, Si-Sn alloys, Si-In alloys, Si-Ag alloys, Si-Pb alloys, Si-Sb alloys, Si-Bi alloys, Si-Mg alloys, Si-Ca alloys, Si-Ge alloys, Si-Pb alloys, etc. Si alloys can be two-component alloys or multi-component alloys with three or more components. Si alloys can be Si-Li based alloys. Additionally, SiO can be cited as an example of a Si oxide.

[0061] As for the shape of an active substance, for example, particulate matter can be cited. The average particle size (D) of the active substance... 50 For example, the range is 10 nm to 50 μm. It should be noted that the average particle size (D...) 50 The cumulative 50% particle size in the volumetric particle size distribution measured using a laser diffraction particle size distribution measuring device refers to the particle size distribution of a volumetric reference.

[0062] The proportion of active substances in the active substance layer is, for example, 50% to 99% by weight.

[0063] (2) Sulfide solid electrolytes

[0064] Sulfide solid electrolytes are typically electrolytes containing sulfur (S) as the main anionic element. Sulfide solid electrolytes preferably contain, for example, Li, X (X being at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, In), and S. Furthermore, sulfide solid electrolytes may further contain at least one of O and a halogen.

[0065] Examples of sulfide solid electrolytes include, for example, Li₂S-P₂S₅, Li₂S-P₂S₅-LiI, Li₂S-P₂S₅-GeS₂, Li₂S-P₂S₅-Li₂O, Li₂S-P₂S₅-Li₂O-LiI, Li₂S-P₂S₅-LiBr, Li₂S-SiS₂, Li₂S-SiS₂-LiI, Li₂S-SiS₂-LiBr, Li₂S-SiS₂-LiCl, Li₂S-SiS₂-B₂S₃-LiI, Li₂S-SiS₂-P₂S₅-LiI, Li₂S-B₂S₃, and Li₂S-P₂S₅-Z. m S n (Where m and n are positive numbers. Z is any one of Ge, Zn, and Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (Where x and y are positive numbers. M is any one of P, Si, Ge, B, Al, Ga, and In).

[0066] Sulfide solid electrolytes can be either glass (amorphous) or glass-ceramic. Additionally, the average particle size (D) of sulfide solid electrolytes... 50 For example, it can range from 0.01μm to 10μm.

[0067] The proportion (by weight) of sulfide solid electrolyte in the active material layer is, for example, 10% to 50% by weight.

[0068] (3) Fluorine-based lubricants

[0069] The melting point and types of fluorinated lubricants are the same as those described in "A. Fluorinated Lubricants", so the details are omitted here.

[0070] In the active material layer, the ratio of fluorinated lubricant to active material is, for example, 4% by weight or more, 6% by weight or more, or 8% by weight or more. On the other hand, the above ratio is, for example, 12% by weight or less, or 10% by weight or less.

[0071] Furthermore, in the active material layer, it is preferable to combine the active material with a solid fluorinated lubricant. For example, an active material that has undergone physical mixing such as mechanical grinding and a solid fluorinated lubricant can be used as the active material material. Whether the active material and the solid fluorinated lubricant are combined can be confirmed by microscopic observation such as SEM (scanning electron microscopy) and TEM (transmission electron microscopy). It is believed that by combining the active material with the solid fluorinated lubricant, the interface between the active materials can be formed better, and in particular, the resistance during the initial charge and discharge can be suppressed.

[0072] (4) Active substance layer

[0073] In addition to the active material, sulfide solid electrolyte and fluorine-based lubricant mentioned above, the active material layer may also contain at least one of conductive additives and binders.

[0074] Carbon materials can be cited as examples of conductive additives. Examples of carbon materials include particulate carbon materials such as acetylene black (AB) and Ketjen black (KB), as well as fibrous carbon materials such as carbon fibers, carbon nanotubes (CNTs) and carbon nanofibers (CNFs).

[0075] Examples of adhesives include rubber-based adhesives such as butadiene rubber (BR), acrylate butadiene rubber (ABR), and styrene butadiene rubber (SBR), as well as fluorinated adhesives such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE).

[0076] The thickness of the active material layer is not particularly limited, for example, it can be 0.1 μm to 1000 μm. The active material layer can be either a positive or negative electrode active material layer. That is, the electrode in this disclosure can be either a positive or negative electrode.

[0077] 2. Current collector

[0078] A current collector is a component that has the function of collecting electrons from the aforementioned active material layer. A current collector can be a positive current collector or a negative current collector. Examples of materials for current collectors include metals such as aluminum, copper, SUS, and nickel. Examples of shapes for current collectors include foil and mesh.

[0079] 3. Electrodes

[0080] The electrodes in this disclosure are typically used in secondary batteries. Secondary batteries are described below.

[0081] B. Secondary battery

[0082] Figure 1 This is a schematic cross-sectional view illustrating a secondary battery in this disclosure. Figure 1 The secondary battery 100 shown includes: a positive electrode 10A having a positive current collector 1a and a positive active material layer 2a; a negative electrode 10B having a negative current collector 1b and a negative active material layer 2b; and an electrolyte layer 11 disposed between the positive electrode 10A and the negative electrode 10B. The secondary battery 100 includes the aforementioned electrodes. Specifically, at least one of the positive electrode 10A and the negative electrode 10B in the secondary battery 100 is the electrode described in "A. Electrode" above.

[0083] According to this disclosure, since the secondary battery contains the aforementioned electrodes (electrodes that can suppress stripping), it becomes a secondary battery that can suppress the increase in resistance caused by electrode stripping.

[0084] 1. Positive electrode

[0085] Secondary batteries typically have a positive electrode. Furthermore, the positive electrode typically has a positive current collector and a positive active material layer disposed on the electrolyte layer side of the positive current collector. The positive electrode in a secondary battery is preferably the electrode described above. On the other hand, when the positive electrode in this disclosure is not the electrode described above, the negative electrode in this disclosure is typically the electrode described above. In this case, any existing positive electrode can be used.

[0086] 2. Negative electrode

[0087] Secondary batteries typically have a negative electrode. Furthermore, the negative electrode typically has a negative current collector and a negative active material layer disposed on the electrolyte layer side of the negative current collector. The negative electrode in a secondary battery is preferably the electrode described above. On the other hand, when the negative electrode in this disclosure is not the electrode described above, the positive electrode in this disclosure is typically the electrode described above. In this case, any existing negative electrode can be used.

[0088] 3. Electrolyte layer

[0089] Secondary batteries typically have an electrolyte layer disposed between the positive electrode and the negative electrode. More specifically, the electrolyte layer is typically disposed between the positive electrode active material layer and the negative electrode active material layer. The electrolyte layer preferably contains the aforementioned sulfide solid electrolyte. That is, the electrolyte layer is preferably a solid electrolyte layer.

[0090] 4. Secondary battery

[0091] The secondary battery disclosed herein is typically a lithium-ion secondary battery. Alternatively, the secondary battery is preferably an all-solid-state battery containing a sulfide solid electrolyte as the solid electrolyte.

[0092] Furthermore, secondary batteries can be used as power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), battery electric vehicles (BEVs), gasoline-powered vehicles, and diesel-powered vehicles. They are particularly preferred for use as power sources for driving hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or battery electric vehicles (BEVs). Additionally, secondary batteries can be used as power sources for mobile bodies other than vehicles (e.g., railways, ships, and aircraft), and also as power sources for electrical products such as information processing devices.

[0093] It should be noted that this disclosure is not limited to the embodiments described above. The embodiments described above are illustrative, and any structure that has substantially the same structure and achieves the same effect as the technical concept described in the scope of the patent claims in this disclosure is included within the technical scope of this disclosure.

[0094] Example

[0095] [Synthetic Example 1] (Synthesis of Compound 1-1)

[0096] In a nitrogen-purified reaction vessel, 15.4 g of cesium fluoride, 290 mL of diethylene glycol dimethyl ether, and 107.0 g of methyl 2,2,3-trifluoro-3-oxopropionate were added and stirred at 5°C for 10 minutes in an ice bath. Then, 526.0 g of 2,2,3,3-tetrafluorooxetane was added dropwise through a dropping funnel at 5°C for 20 minutes in an ice bath, and the mixture was stirred for 2 hours. Afterward, the ice bath was removed, and the mixture was stirred for 50 hours to obtain a reaction solution. 60 mL of methanol was added dropwise to the obtained reaction solution over 20 minutes, and the mixture was stirred for 24 hours. Then, volatile components were distilled off from the reaction solution under reduced pressure. Subsequently, 80 g of hexafluorom-xylene and 40 g of water were added for separation and washing. 5 g of magnesium sulfate was added to the extracted organic layer and dried to obtain a treated solution. By distilling off volatile components from the obtained treated solution, compound 1-1 (a compound with an FPE structure) was obtained.

[0097]

[0098] [Comparative Example 1]

[0099] Add conductive additives, binders, sulfide solid electrolytes, and positive electrode active materials (LiNi) to organic solvents. 0.8 Co 0.15 Mn 0.05 O2) is mixed using an ultrasonic homogenizer. This yields a positive electrode slurry. The positive electrode slurry is coated onto a positive current collector (Al foil) and dried to fabricate a positive electrode with a positive current collector and a layer of positive active material. It should be noted that butyl butyrate is used as the organic solvent, VGCF as the conductive additive, PVDF as the binder, and 10LiI-15LiBr-75Li3PS4 as the sulfide solid electrolyte. The same materials are used in the subsequent steps.

[0100] Next, conductive additives, binders, sulfide solid electrolytes, and negative electrode active material (Si particles) are added to an organic solvent and mixed using an ultrasonic homogenizer. This yields a negative electrode slurry. The negative electrode slurry is then coated onto a negative electrode current collector (Cu foil) and dried to create a negative electrode with a negative electrode current collector and a layer of negative electrode active material.

[0101] Next, a binder and a sulfide solid electrolyte are added to an organic solvent and kneaded using an ultrasonic homogenizer. This yields a solid electrolyte layer slurry. The resulting solid electrolyte slurry is then coated onto a transfer foil (Al foil) and dried to create a transfer part with a solid electrolyte layer and a transfer foil.

[0102] The aforementioned positive electrode, negative electrode, and transfer component are formed into a strip. Then, the positive electrode and transfer component are overlapped with the solid electrolyte layer and the positive electrode active material layer facing each other, and rolled at 165°C and a pressure of 50 kN / cm. The transfer foil of the transfer component is then peeled off to fabricate the positive electrode side structure. Conversely, the transfer component and negative electrode are overlapped with the solid electrolyte layer and the negative electrode active material layer facing each other, and rolled at 25°C and a pressure of 50 kN / cm. The transfer foil of the transfer component is then peeled off to fabricate the negative electrode side structure.

[0103] The negative electrode and positive electrode structures were punched into circles with diameters of 13.00 mm and 11.28 mm, respectively. A sulfide solid electrolyte was added to the solid electrolyte layer of the negative electrode structure, and the layers were pressed using a uniaxial press. Subsequently, the positive electrode and negative electrode structures were overlapped with their solid electrolyte layers facing each other to obtain a laminate. Current-carrying tabs were installed on the laminate, and the laminate was sealed within an aluminum laminate using a vacuum sealing machine. This resulted in the fabrication of an evaluation battery (all-solid-state battery).

[0104] [Examples 1-3]

[0105] In the preparation of the negative electrode slurry, a fluorinated lubricant (compound 1-1 having an FPE structure) was added to an organic solvent. Otherwise, an evaluation battery was prepared in the same manner as in Comparative Example 1. It should be noted that the fluorinated lubricant was added in the amount (wt%) of the fluorinated lubricant to the negative electrode active material (Si particles) as shown in Table 1. It should be noted that the melting point of the fluorinated lubricant used was 66°C.

[0106] [Example 4]

[0107] Si particles and solid fluorine-based lubricant were weighed according to the proportions in Table 1 and mixed in a mortar to prepare a composite. The composite was used in the preparation of the negative electrode slurry. Otherwise, an evaluation battery was prepared in the same manner as in Comparative Example 1.

[0108] [evaluate]

[0109] (Peel strength test)

[0110] Peel strength was measured using a Micro Auto Graph. First, the negative electrode structures of Comparative Example 1 and Examples 1-4, pressed in a roller press with a linear pressure of 2.5 kN / cm, were punched at a diameter of Φ14.5. Next, double-sided adhesive tape was applied to the sample stage of the Micro Auto Graph, with the current collector foil side of the punched negative electrode structure facing down and attached to the upper part of the layer, with the coated side facing up. Additionally, double-sided adhesive tape at a diameter of Φ11.28 was applied to the terminal side of the Micro Auto Graph. Then, the terminals were moved downwards to the negative electrode structure, and the pressure at contact was increased to 50 N / cm. 2 Subsequently, the negative pressure during upward movement was measured, and the maximum value was taken as the peel strength.

[0111] (Battery performance test)

[0112] The resistance change rate of the evaluation batteries prepared in Comparative Example 1 and Examples 1-3 was measured as follows. First, 100 charge-discharge cycles (cycle test) were performed at 25°C, 2C, and SOC 93%-10%, after which the resistance value (resistance value before heating) was measured. Then, each evaluation battery after the cycle test was heated at 100°C for 6 hours, and after returning to room temperature, the resistance value (resistance value after heating) was measured. The resistance change rate was calculated from the resistance value before heating and the resistance value after heating. The results are shown in Table 1. It should be noted that when the resistance change rate becomes negative, it indicates that the resistance increased after heating, and when the resistance change rate becomes positive, it indicates that the resistance decreased after heating.

[0113] In addition, the evaluation batteries of Examples 2 and 4 were initially charged to 3.7V and then initially discharged at a 5C rate. The initial resistance value was calculated from the voltage drop after 5 seconds of initial discharge and compared. The results are shown in Table 1.

[0114] [Table 1]

[0115]

[0116] As shown in Table 1, the peel strength of any of Examples 1-4 was higher than that of Comparative Example 1, confirming that the electrode of this disclosure can suppress peeling. Furthermore, it is inferred that batteries using the electrode of this disclosure can suppress the increase in battery resistance. Additionally, compared to Comparative Example 1, Examples 1-3 showed a decrease in resistance value (increased resistance change rate) after heating following the cycling test. It is believed that the fluorine-based lubricant, which becomes liquid upon heating, fills the interparticle spaces, maintaining and restoring a good electronic conduction path, thereby reducing the resistance value. Furthermore, regarding the initial resistance, Example 4 was better than Example 2. It is inferred that by combining the Si-based active material with the fluorine-based lubricant, a good electronic conduction path was formed.

[0117] Symbol Explanation

[0118] 1. Current collector

[0119] 2. Active Material Layer

[0120] 10 ···Electrode

[0121] 11 ···Electrolyte layer

[0122] 100... Secondary batteries

Claims

1. A fluorinated lubricant used in an active material layer of an electrolyte containing active material and a sulfide solid electrolyte, wherein the active material is solid at 25°C.

2. The fluorine-based lubricant according to claim 1 has a melting point below 120°C.

3. The fluorinated lubricant according to claim 1, wherein it has a fluorinated polyether structure.

4. An electrode having an active material layer and a current collector, The active material layer contains active materials, sulfide solid electrolytes, and fluorine-based lubricants. The fluorinated lubricant is any one of the fluorinated lubricants according to claims 1 to 3.

5. The electrode according to claim 4, wherein, The active material is compounded with the solid fluorine-based lubricant.

6. The electrode according to claim 4, wherein, The ratio of the fluorinated lubricant to the active substance is 4% to 12% by weight.

7. A secondary battery comprising the electrode as described in claim 4.

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