Positive electrode for solid-state battery and solid-state battery comprising positive electrode

Abstract

To a positive electrode for improving the energy density and cycle characteristics of a solid-state battery.SOLUTION: A positive electrode includes (i) a high voltage positive electrode active material, (ii) a conductive aid, and (iii) a high voltage stable catholyte that includes a lithium salt, a polymer binder that is a PVdF copolymer, a room temperature ionic liquid, plastic crystals, and optionally a high boiling point solvent, the positive electrode has a density of 2.3 g / cm3 to 3.6 g / cm3. There are also provided a process for preparing the positive electrode and a battery that includes the positive electrode and an article of manufacture that includes the battery.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to the field of solid-state lithium secondary batteries. In particular, the present disclosure relates to a positive electrode comprising a positive electrode active material, a conductive additive, and catholyte, as well as a preparation process thereof, and a solid-state lithium battery including the positive electrode. [Background technology]

[0002] Solid-state batteries (SSBs) based on solid electrolytes using lithium metal anodes and high-voltage cathodes have the potential to offer higher energy density and greater safety than lithium-ion batteries, which have liquid electrolytes based on highly flammable organic solvents. Summary of the Invention [Problem to be solved by the invention]

[0003] The composite cathode of an SSB typically comprises a cathode active material (CAM), a conductive additive such as carbon black, and a solid electrolyte (catholyte). To meet the requirements of high-performance secondary batteries, the catholyte must have high ionic conductivity, high chemical stability, and a wide electrochemical stability range. A large catholyte fraction (30-50 vol%) is required in the composite cathode to provide sufficient ion diffusion, resulting in a relatively low volume fraction of CAM in current SSBs and low energy density. Furthermore, the composite cathode should ideally have good CAM / catholyte contact with minimal voids and the minimum amount of catholyte necessary to ensure sufficient Li-ion movement within the cathode structure.

[0004] To ensure good electrical contact between the electrode components in SSB, a high areal capacity (approximately ≥ 2–3 mAh / cm 2It is necessary to develop an ideally non-porous solid cathode for the SSB (e.g., 1000-150 ... + It must provide sufficient levels of ionic conductivity and be stable against electrolytic oxidation under conditions (e.g., ≥ 4.2 V vs. reference electrode, > 40°C, long exposure times, high surface area, high pressure, etc.).

[0005] Although several SSB configurations are disclosed in the available literature, the stability of known catholytes (such as those containing polyethylene oxide (PEO)) in high voltage composite positive electrodes (e.g., containing lithium nickel manganese cobalt oxide (NMC) as the CAM) is quite limited, especially at high temperatures above 40° C.

[0006] Therefore, there remains a strong need to improve the energy density and cyclability of solid-state batteries by achieving high areal capacity composite cathodes while providing improved stability and enhanced electrochemical performance at high voltages. [Means for solving the problem]

[0007] The inventors have demonstrated a high areal capacity (approximately 3 mAh / cm) suitable for solid-state lithium-based batteries. 2We have developed a high voltage positive electrode that can achieve a high energy density (Energy Density (Energy Density) or higher) of lithium-based batteries, particularly lithium metal solid-state batteries, which are composites including a high voltage positive electrode active material, a conductive additive, and catholyte, the catholyte including a lithium salt, a specific polymer binder, and several types of plasticizers, the plasticizers being (i) room temperature ionic liquids (RTILs), (ii) specific plastic crystals, and (iii) optionally high boiling point solvents. Advantageously, the positive electrodes of the present disclosure have improved electrochemical performance and thus can improve the energy density and cyclability of lithium-based batteries, particularly lithium metal solid-state batteries.

[0008] Thus, a first aspect of the present invention is a positive electrode comprising: i) Lithium cobalt oxide LiCoO2 (LCO), high voltage spinel LiNi 0.5 Mn 1.5 O4(LNMO), Lithium Nickel Manganese Cobalt Oxide LiNi x Mn y Co 1-x-y O2 (where x+y+z=1) (NMC), Lithium manganese iron phosphate LiFe x Mn y PO4 (where x+y=1) (LMFP), and lithium-rich layered oxide Li 1+x TM 1-x O2 (wherein TM is a mixture of at least two transition metals) (LRLO), in particular the transition metals are selected from the group consisting of Mn, Ni, and Co, and combinations thereof; ii) a conductive assistant; and iii) a high voltage stable catholyte; The high voltage stable catholyte includes - a lithium salt selected from the group consisting of LiTFSI, LiBOB, LiDFOB, LiBF4, LiFSI, LiClO4, and combinations thereof; - a polymer binder which is a PVdF copolymer; - a room temperature ionic liquid; - plastic crystals selected from the group consisting of succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, and mixtures thereof; - optionally a high boiling solvent having a boiling point of at least 160°C; Including, Density: 2.3~3.6g / cm 3 , especially 2.8 to 3.2 g / cm 3 The present invention relates to a positive electrode,

[0009] Advantageously, the combination of the above components in catholyte may favor the formation of a robust and stable CAM / catholyte interface.

[0010] Another aspect of the present invention is a process for preparing a positive electrode as described hereinabove and hereinafter, comprising the steps of: i) providing a catholyte formulation comprising a lithium salt, a polymer binder, plastic crystals, an ionic liquid and, optionally, a high boiling point solvent in a suitable solvent; ii) adding a high voltage positive electrode active material, a conductive additive, and optionally an additional amount of a suitable solvent to the catholyte preparation of step (i) with stirring to obtain a positive electrode slurry; iii) casting the positive electrode slurry onto a positive electrode current collector and drying to obtain a positive electrode; iv) calendering the positive electrode to obtain a calendered positive electrode; v) hot pressing the calendared cathode to obtain the final cathode; The present invention relates to a process comprising:

[0011] Another aspect of the present invention is a method for producing a a positive electrode as described hereinabove and hereinafter, a negative electrode; a solid electrolyte disposed between the positive electrode and the negative electrode; The present invention relates to a battery comprising:

[0012] Surprisingly, as can be seen from the Examples and Comparative Examples, high voltage solid state secondary batteries comprising the positive electrodes defined in the present disclosure exhibit surprisingly good electrochemical performance at 60°C.

[0013] Finally, another aspect of the invention relates to an article of manufacture comprising a battery as described herein. [Brief description of the drawings]

[0014] [Figure 1] FIG. 2 shows a preparation scheme of the positive electrode of the present invention. [Diagram 2] FIG. 1 shows the discharge capacity versus cycle number for Li / NMC622 solid coin cells of Example 1 (Ex.1, areal capacity level (LL) is 3.0 mAh / cm2, density (D) is 2.8 g / cm3), Example 2 (Ex.2, LL is 3.0 mAh / cm2, D is 3.0 g / cm3), and Comparative Example (Comp.Ex., LL is 3.0 mAh / cm2, D is 2.8 g / cm3). The cycling conditions were as follows: 60°C, cycle interval 3.0-4.2 V, charge / discharge current 0.05 C / 0.1 C. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] All terms used in the specification of this application are to be understood with their ordinary meaning known in the art unless otherwise specified. Other more specific definition terms used in this application are as follows, and are intended to be applied uniformly throughout the specification and claims, unless a specified definition gives a broader definition.

[0016] It should be noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" are to be construed to cover both the singular and the plural, unless otherwise stated in the specification or clearly contradicted by context.

[0017] All percentages used herein are by weight of all compositions unless otherwise specified.

[0018] The term lithium nickel manganese cobalt oxides (Li-NMC, also abbreviated as LNMC or NMC) as used herein are mixed metal oxides of lithium, nickel, manganese and cobalt. They have the general formula LiNi x Mn y Co z O2, where x+y+z=1. An example of an NMC is LiNi 0.333 Mn 0.333 Co 0.333 O2 (abbreviated as NMC111 or NMC333), LiNi 0.5 Mn 0.3 Co 0.2 O2 (abbreviated as NMC532 or NCM523), LiNi 0.6 Mn 0.2 Co 0.2 O2(NMC622), and LiNi 0.8 Mn 0.1 Co 0.1 O2(NMC811).

[0019] The term "conductive assistant" as used herein refers to a material that is mixed with a positive electrode active material to improve the electronic conductivity of the positive electrode active layer and to reduce the resistance of the positive electrode active layer and the resistance of the interface with the current collector.

[0020] The term "positive electrode active layer" as used herein refers to a layer located on a surface of a positive electrode current collector and comprising a positive electrode active material.

[0021] The term "solid electrolyte" as used herein refers to a solid that includes an electronically insulating material that has Li-ion conductivity and is disposed between the positive and negative electrodes.

[0022] The term "catholyte" as used herein specifically refers to a type of solid electrolyte contained in the positive electrode, and refers to a Li-ion conductor (optionally a mixed ionic and electronic conductor) that is intimately mixed with or surrounds and is in contact with the active positive electrode material. The "catholyte" and "solid electrolyte" in the same cell may be of the same or different compositions.

[0023] The term "plastic crystal" as used herein refers to a crystal composed of weakly interacting molecules with some degree of orientational or conformational freedom. Plastic crystals can be considered a transitional step between true solids and true liquids, and can be thought of as soft matter.

[0024] The term "high boiling point solvent" as used herein refers to a solvent having a boiling point of at least 160°C, especially above 200°C, such as 200°C to 300°C.

[0025] As used herein, the term "high voltage stable catholyte" refers to a catholyte that is stable to high voltages (Li / Li) in such a way that significantly degrades the electrochemical performance of the catholyte when held at high voltages. + This refers to catholyte that does not react (decompose, e.g., undergo electrolytic oxidation) at a potential of 4.2 V or more versus the reference electrode. The electrochemical stability of catholyte is usually expressed as the width of the potential window, i.e., the difference between the oxidation potential and reduction potential of the catholyte.

[0026] The term "high voltage positive electrode active material" as used herein means a material that is capable of withstanding high voltages (Li / Li) in such a manner as to significantly degrade the electrochemical performance of the positive electrode when held at high voltages at 60°C. + This refers to a positive electrode active material that does not react at a voltage of 4.2 V or more versus the reference electrode.

[0027] The term "high voltage" as used herein means Li / Li + This means at least 4.2 V, for example 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0 V or more versus the reference electrode.

[0028] As used herein, the term "chemically compatible" in reference to two or more components of a positive electrode means that the components can be physically exposed to one another without reacting in a manner that would significantly degrade the electrochemical performance of a battery that includes the positive electrode.

[0029] As used herein, the terms "cell" and "battery" may be used interchangeably. The term "solid-state lithium secondary cell (or battery)" may also be abbreviated as "cell," "battery," or "SSB."

[0030] The term "room temperature" refers to a temperature of about 20°C to about 30°C.

[0031] Unless otherwise stated, all materials and agents used in this disclosure are commercially available.

[0032] As previously mentioned, a first aspect relates to a cathode capable of achieving high areal capacity and having a relatively high density suitable for a solid-state lithium-based battery, the cathode including a high voltage active cathode material, a conductive additive, and a high voltage stable catholyte, the catholyte including a lithium salt, certain polymer binders, and some type of plasticizer as described above.

[0033] In one embodiment, the high voltage stable catholyte further comprises a high boiling point solvent having a boiling point of at least 160° C., particularly above 200° C., such as 200° C. to 300° C. In a particular embodiment, the high boiling point solvent is selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC), fluoroethylene carbonate (FEC), sulfolane (SL), and mixtures thereof.

[0034] In another embodiment, optionally in combination with one or more features of the above-described embodiments, the areal capacity of the positive electrode is 0.5 mAh / cm 2 ~10mAh / cm 2 In another embodiment, the areal capacity of the positive electrode is 2.0 mAh / cm 2 ~5.0mAh / cm 2 In another embodiment, the areal capacity of the positive electrode is 2.5 mAh / cm 2 ~3.5mAh / cm 2 , e.g. 3.0mAh / cm 2 It is.

[0035] Catholyte As previously described, the high voltage stable catholyte comprises a lithium salt selected from the group consisting of LiTFSI, LiBOB, LiDFOB, LiBF4, LiFSI, LiClO4, and combinations thereof, a polymer binder which is a PVdF copolymer, a plastic crystal selected from the group consisting of an RTIL, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, and mixtures thereof, and optionally a high boiling point solvent as described above.

[0036] In one embodiment, optionally in combination with one or more features of the above-described embodiments, the plastic crystal is selected from the group consisting of succinonitrile, glutaronitrile, adiponitrile, and any mixture thereof. More specifically, the plastic crystal is succinonitrile, glutaronitrile, or a mixture thereof, and even more specifically, succinonitrile.

[0037] In another embodiment, optionally in combination with one or more features of the above-described embodiments, the plastic crystals are in an amount of 5 wt% to 20 wt% of the total weight of the positive electrode.

[0038] In one embodiment, the catholyte is - a lithium salt selected from the group consisting of LiTFSI, LiBOB, LiDFOB, LiBF4, LiFSI, LiClO4, and combinations thereof; - a polymer binder which is a PVdF copolymer; - RTIL and - plastic crystals selected from the group consisting of succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, and mixtures thereof; - optionally a high boiling point solvent as described above; It consists of:

[0039] The binder holds the components of the positive electrode tightly together and adheres the entire positive electrode to the solid electrolyte.

[0040] The polymer binder must be a polymer that is compatible with the high voltage cathode material and must have thermal stability at high temperatures, such as above 60°C.

[0041] In one embodiment, optionally in combination with one or more features of the embodiments described above, the PVdF copolymer is selected from the group consisting of poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP), poly(vinylidene fluoride-co-chlorotrifluoroethylene) (PVdF-CTFE), poly(vinylidene fluoride-co-trifluoroethylene) (PVdF-TrFE), and mixtures thereof. In particular, the binder is PVdF-HFP.

[0042] In another embodiment, optionally in combination with one or more features of the above-described embodiments, the polymer binder is in an amount of 1 wt % to 7 wt % of the total weight of the positive electrode.

[0043] In another embodiment, optionally in combination with one or more features of the above-described embodiments, the RTIL is selected from the group consisting of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMI-TFSI), 1-methyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide (PMI TFSI), 1,2-dimethyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide (DMPI TFSI), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMI TFSI), 1-methyl-1-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide (PYR TFSI), 13 TFSI), 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (PYR 14 TFSI), 1-methyl-1-propylpiperidinium bis(trifluoromethylsulfonyl)imide (PP 13TFSI), 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMI-FSI), 1-methyl-3-propylimidazolium bis(fluorosulfonyl)imide (PMI FSI), 1,2-dimethyl-3-propylimidazolium bis(fluorosulfonyl)imide (DMPI FSI), 1-butyl-3-methylimidazolium bis(fluorosulfonyl)imide (BMI FSI), 1-methyl-1-propylpyrrolidinium bis(fluorosulfonyl)imide (PYR 13 FSI), 1-butyl-1-methylpyrrolidinium bis(fluorosulfonyl)imide (PYR 14 FSI), 1-methyl-1-propylpiperidinium bis(fluorosulfonyl)imide (PP 13 In another embodiment, the room temperature ionic liquid is selected from the group consisting of PYR 14 It is a TFSI.

[0044] In another embodiment, optionally in combination with one or more features of the above-described embodiments, the RTIL is in an amount of 1 wt% to 20 wt% of the total weight of the positive electrode.

[0045] In another embodiment, optionally in combination with one or more features of the embodiments described above, the combined amount of the RTIL, the plastic crystals, and the optional high boiling point solvent is 1 wt % to 20 wt % of the total weight of the positive electrode.

[0046] In another embodiment, optionally in combination with one or more features of the above-described embodiments, the lithium salt comprises LiBOB, in particular the lithium salt is a mixture of LiBOB and LiTFSI, more particularly the lithium salt consists of LiBOB.

[0047] As mentioned above, the inventors believe that the stabilization of the "CAM / catholyte" interface is achieved by the combined action of the catholyte components. This effect appears to be particularly good when LiBOB is used as the lithium salt.

[0048] The use of LiBOB in solid electrolytes, especially in combination with PVdF copolymers such as PVdF-HFP, has been reported in the literature to have a detrimental effect on the performance of solid-state lithium-based batteries (e.g., T.Lestariningsih, Q.Sabrina, CRRatri, A.Subhan, and S.Priyono, “The Effect of LiBOB Addition on Solid Polymer Electrolyte (SPE) Production based PVdF-HFP / TiO2 / LiTFSI on Ionic Conductivity for Lithium-Ion Battery Applications,” Jurnal Kimia Sains dan Aplikasi, vol.25, no.1, pp.13-19 (2022), and Lestariningsih, Titik et al. “The Effects of LiBOB and LiTFSI Compositions on the Conductivity of PVdF-HFP based Electrolyte Polymer Membrane for Lithium Ion Battery Applications.”International Journal of Scientific & Technology Research 9 (2020) (see 165-169).

[0049] Surprisingly, as shown in the Examples, despite the adverse effects on the properties of the solid electrolyte when partially or totally replacing LiTFSI with LiBOB, the use of LiBOB in the catholyte of the cathode of the present disclosure has an unexpected beneficial effect on the electrochemical performance of the cathode in a solid-state battery.

[0050] In another embodiment, optionally in combination with one or more features of the above-described embodiments, the electrolyte salt is in an amount of 1 wt % to 15 wt % of the total weight of the positive electrode.

[0051] positive electrode In one embodiment, optionally in combination with one or more features of the embodiments described above, the high voltage positive electrode active material is NMC, in particular single crystal NMC.

[0052] The term "single crystal" as used herein refers to ideally monolithic particles between 2-5 μm in size, ideally free of grain boundaries and secondary particles. Single crystal positive electrode active materials are believed to maintain particle integrity during cell cycling. Single crystal NMC materials in powder form are commercially available.

[0053] There are no particular limitations on the conductive assistant, and any of those known to be used in lithium secondary batteries can be used.

[0054] Examples of the conductive additive include, but are not limited to, carbon black, acetylene black, ketjen black, graphite, graphene, carbon nanotubes, carbon nanofibers, vapor grown carbon fibers (VGCF), and combinations thereof.

[0055] In one embodiment, optionally in combination with one or more features of the above-described embodiments, the amount of catholyte in the positive electrode is 0.5 wt% to 30 wt% based on the total weight of the positive electrode active layer.

[0056] In another embodiment, optionally in combination with one or more features of the embodiments described above, in a positive electrode of the present disclosure, the catholyte is in an amount of 5 wt% to 50 wt% based on the total weight of the positive electrode, the high voltage positive electrode active material is in an amount of 50 wt% to 90 wt% of the total weight of the positive electrode, and the conductive additive is in an amount of 0.1 wt% to 5 wt% of the total weight of the positive electrode.

[0057] Process for preparing the positive electrode As previously mentioned, another aspect of the present disclosure is a process for preparing the positive electrode described herein above, comprising: i) providing a catholyte formulation comprising a lithium salt, a polymer binder, plastic crystals, an ionic liquid and, optionally, a high boiling point solvent in a suitable solvent; ii) adding a high voltage positive electrode active material, a conductive additive, and optionally an additional amount of a suitable solvent to the catholyte preparation of step (i) with stirring to obtain a positive electrode slurry; iii) casting the positive electrode slurry onto a positive electrode current collector and drying to obtain a positive electrode; iv) calendering the positive electrode to obtain a calendered positive electrode; v) hot pressing the calendared cathode to obtain the final cathode; The present invention relates to a process comprising:

[0058] In the process of the present disclosure, the lithium salt, the polymer binder, the plastic crystal, the ionic liquid, the optional high boiling point solvent, the positive electrode active material, and the conductive additive are as described above.

[0059] The calendering step can be carried out in a standard calender having at least two rotating cylinders (rolls) by compressing the cathode intermediate between the rolls. The calendering step can be carried out at a temperature of 15° C. to 80° C., for example, 40° C. to 60° C., and a pressure of 20 bar to 70 bar.

[0060] The hot pressing step can be carried out at a temperature between 50° C. and 160° C. and a pressure between 10 bar and 200 bar.

[0061] In one embodiment of the process of the present disclosure, step (i) comprises: - dissolving a lithium salt in a suitable solvent to obtain a first solution; - dissolving the polymer binder in a suitable solvent to obtain a second solution; - mixing the first solution with the second solution and then adding, with stirring, plastic crystals, an ionic liquid and, optionally, a high boiling point solvent to obtain a catholyte preparation; This is carried out by.

[0062] Examples of suitable solvents include, but are not limited to, N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), acetonitrile (ACN), and mixtures thereof.

[0063] The disclosed process ensures small particle sizes and good particle dispersion of the components, making it possible to obtain a cathode with minimal voids, i.e. a substantially non-porous structure with excellent electrical contact between the electrode components, while at the same time allowing the inclusion in the cathode of the amount of catholyte necessary to ensure sufficient Li-ion diffusion between the CAM and the solid electrolyte.

[0064] The disclosed process is easily scalable and can be advantageously carried out by one-pot slurry preparation and casting using a roll-to-roll (R2R) process, which allows for reduced manufacturing costs. In addition, the combination of two post-treatment steps, calendaring and hot pressing, greatly improves the internal contact between the cathode components. Furthermore, the synergistic effect of the catholyte-containing cathode and its preparation process disclosed above makes it possible to provide a solid-state cell with significantly improved cyclability under severe cycling conditions (60° C., cell charging cutoff voltage≧4.2V).

[0065] The positive electrodes obtained by the above process also form part of the present invention.

[0066] solid state secondary battery As mentioned above, another aspect of the present invention relates to a battery, particularly a solid-state secondary battery, including the positive electrode described above, a negative electrode, and a solid electrolyte disposed between the positive electrode and the negative electrode.

[0067] The battery of the present disclosure may optionally contain additional auxiliary materials, as long as they do not adversely affect the electrochemical properties of the battery. The additional auxiliary materials may be contained in or between any of the positive electrode, the negative electrode, and the solid electrolyte.

[0068] In one embodiment, a solid state secondary battery of the present disclosure includes a negative electrode, a solid electrolyte in direct contact with the negative electrode, a positive electrode current collector, a solid positive electrode in direct contact with the positive electrode current collector, and a solid electrolyte in direct contact with the solid positive electrode, wherein the solid positive electrode is disposed between the positive electrode current collector and the solid electrolyte, and the solid electrolyte is disposed between the negative electrode and the positive electrode.

[0069] negative electrode There is no particular limit to the anode material suitable for the present disclosure. Thus, the anode can be made of graphite, silicon, silicon oxide, lithium titanate (LTO), or can be a lithium-based anode. In particular, lithium-based electrode materials known to be used in lithium secondary batteries can be used. Thus, in one embodiment, the anode material is a lithium-based anode. Examples of useful lithium-based anodes include, but are not limited to, lithium metal, lithium metal alloys (e.g., with Mg, Al, Sn, or mixtures thereof), and combinations thereof. In one embodiment, the anode material is Li metal.

[0070] solid electrolyte The solid electrolyte allows for the movement of lithium ions between the positive and negative electrodes and also acts as a physical separator between the positive and negative electrodes.

[0071] Any solid electrolyte known for use in lithium-based secondary batteries can be used, as long as it is a lithium-ion conductive material and meets the requirements such as high stability required for high voltages.

[0072] The solid electrolyte and catholyte disclosed herein may have the same or different compositions, and therefore all of the embodiments described above for catholyte apply independently to the solid electrolyte.

[0073] In one embodiment, optionally in combination with one or more features of the above-described embodiments, the solid electrolyte has the same composition as the catholyte.

[0074] The lithium-based secondary battery of the present disclosure can be obtained by assembling the positive electrode described above, the negative electrode described above, and a solid electrolyte disposed between the positive electrode and the negative electrode. The battery of the present disclosure can also be obtained by stacking multiple layers of the positive electrode, the solid electrolyte, and the negative electrode.

[0075] The lithium secondary battery obtained by the above process also forms part of the present invention.

[0076] It should be noted that in this disclosure, when describing positive electrodes comprising catholyte, batteries comprising the positive electrodes, and processes for preparing the positive electrodes or batteries, each of the embodiments or features defined with respect to any of the mentioned aspects may be considered applicable to any of the other aspects, regardless of whether or not they are explicitly described in relation to the other aspects.

[0077] The SSBs of the present disclosure may be used in multiple energy storage systems, such as consumer electronic devices (e.g., mobile phones, tablets, and laptop computers), drones, electric vertical take-off and landing (eVTOL) aircraft, and electric vehicles, such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), battery electric vehicles (BEVs), mild hybrid electric vehicles (MHEVs), and extended range electric vehicles (E-REVs).

[0078] Throughout the description and claims, the word "comprising" and variations thereof are not intended to exclude other technical features, additives, ingredients, or steps. Furthermore, the term "comprising" encompasses the terms "consisting of" and "consisting essentially of." The products and processes according to the present disclosure may comprise, consist of, and consist essentially of the essential technical features and / or limitations of the present disclosure described herein, as well as any additional and / or optional ingredients, components, steps, or limitations described herein.

[0079] The following examples and figures are provided for illustrative purposes and are not intended to limit the present invention. Moreover, the present invention covers all possible combinations of the specific preferred embodiments described herein.

[0080] Working Example material N-methyl-2-pyrrolidone (NMP) and acetonitrile (ACN) solvents were obtained from Scharlab. Monolithic cathode active material NMC622 (TSC) was purchased from Targray. Lithium bis(oxalato)borate (LiBOB), poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP, pellets), poly(ethylene oxide) (PEO, Mn 4 10 5 g mol -1 ), and succinonitrile (SN, 99% purity) were purchased from Sigma Aldrich. The ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (PYR 14 TFSI, 99.9% purity, and bis(trifluoromethane)sulfonimide lithium salt (LiTFSI, 99.9% purity) were purchased from Solvionic. The conductive additive C-ENERGY Super C45 carbon black was purchased from IMERYS Carbon & Graphite. All chemicals were used as is without further purification. High-purity lithium metal foil (Albemarle) with a thickness of 50 μm was used as is as the anode.

[0081] Experimental Section An NMP-based slurry composed of 74 wt% TSC, 3 wt% C45 carbon black, and 23 wt% catholyte was prepared in a dry room with a dew point below -50°C. The cathode formulations and the functions of each cathode component used in Examples 1 and 2 are shown in Table 1. [Table 1]

[0082] For this purpose, a pre-dissolution of the binder and lithium salt was first performed: the required amount of LIBOB or LITFSI (3.5 wt% of the final cathode) was dissolved in NMP solvent under magnetic stirring (VELP Scientifica stir plate, F203A0178) until the salt was completely dissolved (step A in Figure 1).

[0083] At the same time, a solution of the PVdF-HFP polymer was prepared at 10 wt % in NMP, using mechanical stirring (IKA Eurostar 60 digital) to obtain a polymer solution (3.5 wt % of the final cathode) (Step B in Figure 1).

[0084] In this process, the preparation of catholytes was continued using mechanical stirring. In a beaker, the required amounts of PVdF-HFP solution and LiBOB or LITFSI solution were mixed (first mixing step in Figure 1). Then, SN and PYR 14 TFSI was added directly and the mixture was placed under mechanical stirring (second mixing step in Figure 1). Once the catholyte mixing was complete, 3 wt% of C45 conductive additive and a small amount of NMP to set the desired solid / liquid (S / L) ratio were added (third mixing step in Figure 1). The active material TSC was then added and the mixture was placed under stirring again (final mixing in Figure 1).

[0085] Finally, the well-homogenized cathode slurry was cast onto a carbon-coated aluminum current collector (Gelon) using an automatic film applicator (BEVS1881 / 2) to a thickness of 20 μm (Cast in Figure 1). The electrode was dried in a convection oven (Selecta, Digitronic TFT) at 100 °C for 30 min (Dry in Figure 1).

[0086] The resulting target areal capacity was 3.0 mAh cm -2 (21mg TSC ·cm -2 The positive electrode was compressed at 45 °C by a laboratory hydraulic roll calender (DPM Solutions) (calendering in Figure 1). The calendered positive electrode was then compressed at 3.0 ± 0.2 g cm-3 It was finally hot pressed (Laborpresse, Polystat 200T) at 140 °C and a pressure of 100 bar to reach the target density of 0.01 g / g (hot press in Figure 1).

[0087] A comparative example (Comp.Ex.) consisting of 75 wt% TSC, 5 wt% C45 carbon black, 15 wt% polymer binder PEO, and 5 wt% LiTFSI salt was prepared in a dry room with a dew point below -50 °C using acetonitrile (ACN) as the solvent. First, a 10 wt% solution of PEO in ACN was prepared by mechanical stirring (IKA Eurostar 60 digital), and another solution of LiTFSI salt (5.0 wt% of the final cathode) was prepared separately with magnetic stirring. Once the polymer binder was completely dissolved, the lithium salt solution was added and the mixture was kept under stirring. Then, 5 wt% C45 conductive additive and a small amount of ACN were added to the mixture. The active material TSC (75 wt% of the final cathode) was added to the mixture and kept under stirring again. Finally, following post-treatment steps as in the examples, the well-homogenized cathode slurry was cast onto a carbon-coated aluminum current collector (Gelon) using an automatic film applicator (BEVS1881 / 2). The electrode was then dried at 60°C in a convection oven (Selecta, Digitronic TFT).

[0088] The resulting target areal capacity was 3.0 mAh cm -2 (21 mgTSC cm -2 ) cathode was compressed at 45° C. using a laboratory hydraulic roll calender (DPM Solutions). Finally, the calendered cathode was hot pressed at 50° C. and 100 bar pressure (Laborpresse, Polystat 200T).

[0089] The cathode formulations shown in Table 2 were prepared. [Table 2]

[0090] Preparation of solid coin cells The prepared solid cathode was tested in a lithium metal solid coin cell (2025, Hohsen). Before assembling the coin cell, the cathode was dried under dynamic vacuum (Binder, VD056-230V) in a drying chamber (Drying in Fig. 1). The final cathode, 23.4 wt% PVdF-HFP, 23.4 wt% SN, 15.6 wt% LiTFSI, and 37.5 wt% PYR, was then prepared. 14 A coin cell was assembled using a 200 micron thick solid electrolyte film composed of TFSI and a 50 micron thick Li metal foil. All operations during the cell assembly process were performed under dry room conditions with a dew point below -50°C. After assembly, the cell was kept at 60°C for 3 hours to ensure good electrical contact between all cell components. Then, constant current charge-discharge tests were performed at the same temperature within a cycle range of 3.0-4.2V under a charge-discharge rate of 0.05C / 0.1C using a BaSyTec cell test system (Germany).

[0091] result The electrochemical performance of the solid-state coin cells with different electrodes is shown in Figure 2.

[0092] Coin cell based on the positive electrode of Example 1 (Catholite is PVdF-HFP, PYR 14 The coin cells based on the positive electrodes of Example 2 (based on TFSI, SN, and LiBOB) showed the best performance in terms of discharge capacity and capacity retention. 14 The cells with the comparative cathodes (based on PEO-LiTFSI, SN, and LiTFSI) had lower discharge capacities and similar capacity retention compared to the cells based on the cathode of Example 1. The cells with the comparative cathodes (catholytes based on PEO and LiTFSI) showed adequate discharge capacity on the first cycle but the poorest cyclability due to the poor electrochemical stability of the PEO-LiTFSI catholyte.

[0093] Citation List 1. T. Lestariningsih, Q. Sabrina, C. R. Ratri, A. Subhan, and S. Priyono, ”The Effect of LiBOB Addition on Solid Polymer Electrolyte (SPE) Production based PVdF-HFP / TiO2 / LiTFSI on Ionic Conductivity for Lithium-Ion Battery Applications,” Jurnal Kimia Sains dan Aplikasi, vol. 25, no. 1, pp. 13-19 (2022). 2. Lestariningsih, Titik et al. “The Effects of LiBOB and LiTFSI Compositions on the Conductivity of PVDF-HFP based Electrolyte Polymer Membrane for Lithium Ion Battery Applications.” International Journal of Scientific & Technology Research 9 (2020) 165-169.

Claims

1. A positive electrode, i) Lithium cobalt oxide LiCoO ２ (LCO), high voltage spinel LiNi ０．５ Mn １．５ O ４ (LNMO), Lithium Nickel Manganese Cobalt Oxide (LiNi) ｘ Mn ｙ Co ｚ O ２ (where x+y+z=1) (NMC), lithium manganese iron phosphate LiFe ｘ Mn ｙ P.O. ４ (where x+y=1) (LMFP), and lithium-rich layered oxide Li １＋ｘ T.M. １－ｘ O ２ wherein TM is a mixture of at least two transition metals (LRLO), in particular the transition metals are selected from the group consisting of Mn, Ni, and Co, and combinations thereof; ii) a conductive assistant; and iii) a high voltage stable catholyte; The high voltage stable catholyte comprises: - LiTFSI, LiBOB, LiDFOB, LiBF ４ , LiFSI, LiClO ４ and combinations thereof; a polymer binder which is a PVdF copolymer; - room temperature ionic liquid; - plastic crystals selected from the group consisting of succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile and mixtures thereof; - optionally a high boiling solvent having a boiling point of at least 160°C; and has a density of 2.3 g / cm ３ ~3.6g / cm ３ A positive electrode,

2. The positive electrode has a capacity of 0.5 mAh / cm ２ ~10mAh / cm ２ 2. The positive electrode of claim 1 having an active material areal capacity of

3. 3. The cathode of claim 1 or claim 2, wherein the PVdF copolymer is selected from the group consisting of poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP), poly(vinylidene fluoride-co-chlorotrifluoroethylene) (PVdF-CTFE), poly(vinylidene fluoride-co-trifluoroethylene) (PVdF-TrFE), and mixtures thereof.

4. the polymer binder is in an amount of 1 wt % to 7 wt % of the total weight of the positive electrode; Optionally, the binder is PVdF-HFP. The positive electrode according to any one of claims 1 to 3.

5. The room temperature ionic liquid is 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMI-TFSI), 1-methyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide (PMI TFSI), 1,2-dimethyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide (DMPI TFSI), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMI TFSI), 1-methyl-1-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide (PYR TFSI), １３ TFSI), 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (PYR １４ TFSI), 1-methyl-1-propylpiperidinium bis(trifluoromethylsulfonyl)imide (PP １３ TFSI), 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMI-FSI), 1-methyl-3-propylimidazolium bis(fluorosulfonyl)imide (PMI FSI), 1,2-dimethyl-3-propylimidazolium bis(fluorosulfonyl)imide (DMPI FSI), 1-butyl-3-methylimidazolium bis(fluorosulfonyl)imide (BMI FSI), 1-methyl-1-propylpyrrolidinium bis(fluorosulfonyl)imide (PYR １３ FSI), 1-butyl-1-methylpyrrolidinium bis(fluorosulfonyl)imide (PYR １４ FSI), 1-methyl-1-propylpiperidinium bis(fluorosulfonyl)imide (PP １３ The positive electrode of any one of claims 1 to 4, wherein the positive electrode is selected from the group consisting of: .FSI; and combinations thereof.

6. The room temperature ionic liquid is PYR １４ 6. The positive electrode of claim 5 which is TFSI.

7. 7. The cathode of claim 1, wherein the combined amount of the RTIL, the plastic crystals, and the optional high boiling point solvent is 1 wt % to 20 wt % of the total weight of the cathode.

8. 8. The positive electrode of claim 1, wherein the lithium salt comprises LiBOB, in particular, the lithium salt is a mixture of LiBOB and LiTFSI, more particularly, the lithium salt is LiBOB.

9. The cathode of any one of claims 1 to 8, wherein the electrolyte salt is in an amount of 1 wt% to 15 wt% of the total weight of the cathode.

10. 10. The cathode of claim 1, wherein the high voltage cathode active material is NMC, in particular single crystal NMC.

11. 11. The positive electrode of claim 1, wherein the catholyte is in an amount of 5 wt % to 50 wt % based on the total weight of the positive electrode, the high voltage positive electrode active material is in an amount of 50 wt % to 90 wt % of the total weight of the positive electrode, and the conductive additive is in an amount of 0.1 wt % to 5 wt % of the total weight of the positive electrode.

12. A process for preparing the positive electrode according to any one of claims 1 to 11, comprising the steps of: i) providing a catholyte formulation comprising a lithium salt, a polymer binder, plastic crystals, an ionic liquid and, optionally, a high boiling point solvent in a suitable solvent; ii) adding a high voltage positive electrode active material, a conductive additive, and optionally an additional amount of a suitable solvent to the catholyte preparation solution of step (i) while stirring to obtain a positive electrode slurry; iii) casting the positive electrode slurry onto a positive electrode current collector and drying to obtain a positive electrode; iv) calendering the positive electrode to obtain a calendered positive electrode; v) hot pressing the calendered cathode to obtain a final cathode; The process includes:

13. a positive electrode according to any one of claims 1 to 11; a negative electrode; a solid electrolyte arranged between said positive electrode and said negative electrode; Including batteries.

14. 14. The battery of claim 13, wherein the solid electrolyte and the catholyte have the same composition.

15. 15. An article of manufacture comprising the battery of claim 14.

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