Composite cathode material comprising a ceramic oxide electrolyte, a lithium electrode material and a promoter

Abstract

The present invention relates to a solid composite cathode material including a ceramic oxide electrolyte material and a lithium electrode material. By adding lithium halide to the selected electrolyte and cathode materials, it has been found that the electrochemical performance is significantly improved.

Description

Technical Field

[0001] The present invention relates to a solid composite cathode material comprising a ceramic oxide electrolyte material and a lithium electrode material. The present invention further relates to a method for preparing the solid material, an electrochemical cell such as a solid battery comprising the solid material, and the use of the solid material in an electrochemical cell such as a solid battery, particularly as a composite cathode material.

Background Art

[0002] The three main functional components of a lithium-ion battery are the anode, the cathode, and the electrolyte. Although there are many variations, the anode of a conventional lithium-ion battery is typically made from carbon or metallic lithium, the cathode is typically made from transition metal oxides (especially oxides of cobalt, nickel, and / or manganese), and the electrolyte is typically a non-aqueous solvent containing a lithium salt. For example, a mixture of an organic carbonate and lithium hexafluorophosphate is a well-known liquid electrolyte for lithium-ion batteries.

[0003] A major drawback of liquid electrolytes is that the composition, particularly the solvent, is flammable, posing a significant safety risk during normal operation, especially in the event of an accident. Another drawback is inherent to the liquid nature of the electrolyte and is related to the risk of leakage and the increased risk of environmental contamination in the case of spillage or leakage.

[0004] In recent years, efforts have been made to develop solid electrolytes that enable the provision of solid lithium-ion batteries. Such solid batteries significantly reduce EHS (environment, health, and safety) risks. The solid electrolyte functions not only as an electrolyte but also as a separator, and can physically separate the anode material and the cathode material to prevent short circuits.

[0005] Without the fluidity of the liquid, it is difficult to obtain intimate contact between the solid electrolyte and the electrode. The periodic expansion and contraction of the electrode during cycling further deteriorate the mechanical interparticle contact. As a result, in solid lithium batteries, it is common to have a high polarization rate and a low utilization rate of the active material. Therefore, an important key to realizing a solid lithium battery with competitive performance lies in constructing a stable and intimate interface between the electrode and the electrolyte. Direct co-sintering of the electrode and the electrolyte is used as a simple method to obtain good interfacial contact. However, due to the required high-temperature handling (above 600 °C), the mutual diffusion of ions through the interface is promoted, side reactions occur between the electrode and the solid electrolyte, and depending on the material being sintered, it may have an adverse effect on the electrochemical performance. In the art, it has been proposed to mitigate this problem by coating the cathode material with a buffer layer such as Nb, LiNbO2, BaTiO3, etc. before sintering.

[0006] U.S. Patent Application Publication No. 2021 / 0083249 (A1) discloses coating LLZO particles with a lithium carbonate layer added with 2 wt% lithium fluoride and then sintering at 900 °C or higher.

Summary of the Invention

Problems to be Solved by the Invention

[0007] An object of the present invention is to provide an improved composite cathode material, particularly a composite cathode material having improved electrochemical performance such as improved cycle performance. A further object of the present invention is to provide a composite cathode material that can be sintered at a low temperature.

Means for Solving the Problems

[0008] The inventors have found that one or more objects of the present invention can be achieved by providing a composite cathode material comprising a lithium aluminum titanium phosphate (LATP) and / or lithium aluminum germanium phosphate (LAGP) electrolyte material, a lithium nickel-manganese / cobalt oxide (e.g., NMC) cathode material, and a lithium halide. As shown in the attached examples, it has been found that adding a lithium halide to the selected electrolyte and cathode materials strongly improves the electrochemical performance (especially the cycle performance) without sintering the composite cathode material. Further, adding a lithium halide to the selected electrolyte and cathode materials allows these materials to be co-sintered at extremely low temperatures, and surprisingly, a sintered composite cathode material with limited degradation of LATP / LAGP or the cathode material is obtained. In other words, since the thermal stability of the composite cathode material is increased, the composite cathode material reaches the temperature for sintering without degradation. Furthermore, the improved electrochemical performance due to the addition of the lithium halide has been found to be present even after sintering. As shown herein, it has been found that adding a lithium halide in the context of the present invention improves the thermal stability of the composite cathode.

[0009] Accordingly, in a first aspect of the present invention, a ceramic oxide electrolyte material comprising lithium aluminum titanium phosphate (LATP) and / or lithium aluminum germanium phosphate (LAGP); an electrode active material comprising Li, M, and O, wherein M comprises Ni and one or both of Mn and Co; and an accelerator which is LiX [wherein X is a halide]; are provided to form a solid composite cathode composition.

[0010] In another aspect of the present invention, a method for preparing a composite cathode, comprising: a) at least the following precursors: a ceramic oxide electrolyte material comprising lithium aluminum titanium phosphate (LATP) and / or lithium aluminum germanium phosphate (LAGP); An electrode active material containing Li, M, and O, wherein M contains Ni and one or both of Mn and Co; An accelerator which is LiX [wherein X is a halide]; and, Optionally, a carbon-based conductive aid; The step of preparing, b) A step of preparing a substantially homogeneous mixture containing the precursor prepared in step (a), and, c) Optionally, a step of subjecting the mixture of step (b) to sintering, is provided.

[0011] In another aspect of the present invention, an electrode containing the solid composite cathode material described herein in combination with a binder such as a polymer binder is provided.

[0012] In another aspect of the present invention, an electrochemical cell containing the solid composite cathode material described herein is provided.

[0013] In another aspect of the present invention, use of the solid composite cathode material described herein as a cathode for an electrochemical cell is provided.

[0014] In another aspect of the present invention, at least one electrochemical cell containing the solid composite cathode material described herein, for example, a battery containing two or more electrochemical cells according to the present invention, more specifically a lithium ion battery or a lithium metal battery is provided.

[0015] In another aspect of the present invention, a method for manufacturing or operating a fixed application such as a vehicle, a computer, a portable information terminal, a mobile phone, a watch, a camcorder, a digital camera, a thermometer, a calculator, a laptop BIOS, a communication device, a remote car lock, and an energy storage device for a power generation plant by using at least one battery or at least one electrochemical cell containing the solid composite cathode material described herein is provided.

[0016] In another aspect of the present invention, there is provided the use of an electrochemical cell comprising the solid composite cathode material of the present invention in an automobile, a bicycle operated by an electric motor, a robot, an aircraft (e.g., an unmanned aircraft including a drone), a ship, a satellite, or a stationary energy storage device.

[0017] In another aspect of the present invention, there is provided the use of lithium halide for improving electrochemical properties such as the cycle performance of an electrochemical cell comprising a composite cathode material. The composite cathode material comprises a lithium aluminum titanium phosphate (LATP) and / or lithium aluminum germanium phosphate (LAGP) electrolyte material and a lithium nickel-manganese-cobalt oxide (NMC) cathode material.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0019] In the following detailed description, preferred embodiments are described in detail to implement the present invention. The present invention is described with reference to these specific preferred embodiments, but it will be understood that the present invention is not limited to these preferred embodiments. In contrast, the present invention includes numerous alternatives, modifications, and equivalents, as will become apparent in view of the following modes for carrying out the invention.

[0020] The expressions "composite cathode material" and "composite cathode composition" are used interchangeably throughout this specification.

[0021] As used in this application, the expression "sintering" refers to a process of treating a solid material by heat and / or pressure without melting the solid material to its liquefaction point.

[0022] In a first aspect of the present invention, A ceramic oxide electrolyte material comprising lithium aluminum titanium phosphate (LATP) and / or lithium aluminum germanium phosphate (LAGP); An electrode active material comprising Li, M, and O, wherein M comprises Ni and one or both of Mn and Co; and, An accelerator which is LiX [wherein X is a halide]; is provided, a solid composite cathode composition.

[0023] The solid composition of the present invention is preferably a substantially homogeneous mixture. In certain embodiments of the present invention, the solid composition is a substantially homogeneous mixture comprising discrete particles of a ceramic oxide electrolyte material, an electrode active material, and lithium halide optionally sintered. Such a solid comprising discrete particles of a ceramic oxide electrolyte material, an electrode active material, and lithium halide optionally sintered can be obtained by simply dry blending the solid particles of the ceramic oxide electrolyte material, the electrode active material, and the lithium halide, followed by optionally sintering the mixture. It will be understood by those skilled in the art that sintering forms a strong solid-solid interface between the ceramic particles or fuses the ceramic particles, but the resulting solid is still substantially different from a solid in which one compound is coated on another compound. In some embodiments of the present invention, at least the accelerator is distributed substantially homogeneously throughout the composition.

[0024] Lithium aluminum germanium phosphate (LAGP) referred to herein preferably has the formula Li 1+n Aln Ge n (PO4) n [Wherein, 0 < n < 1, preferably 0.2 < n < 0.8, more preferably 0.3 < n < 0.5] is LAGP. According to the present invention, n referred to in this specification is measured by scanning electron microscope (SEM-EDX) analysis using energy-dispersive X-rays.

[0025] The lithium aluminum titanium phosphate (LATP) referred to in this specification is preferably of the formula Li 1+m Al m Ti 2-m (PO4)3 [Wherein, 0 < m < 1, preferably 0.2 < m < 0.8, more preferably 0.3 < m < 0.5] is LATP. According to the present invention, m referred to in this specification is measured by scanning electron microscope (SEM-EDX) analysis using energy-dispersive X-rays.

[0026] The ceramic oxide electrolyte material is preferably lithium aluminum titanium phosphate (LATP), more preferably of the formula Li 1+m Al m Ti 2-m (PO4)3 [Wherein, 0 < m < 1, preferably 0.2 < m < 0.8, more preferably 0.3 < m < 0.5] and contains LATP. According to the present invention, m referred to in this specification is measured by scanning electron microscope (SEM-EDX) analysis using energy-dispersive X-rays.

[0027] The ceramic oxide electrolyte material preferably consists of optionally doped LATP and / or LAGP described herein, and most preferably consists of optionally doped LATP. In some embodiments, LATP and / or LAGP is optionally doped with a dopant selected from the group consisting of tantalum, niobium, aluminum, indium, tin, antimony, bismuth, yttrium, germanium, calcium, strontium, barium, hafnium, or combinations thereof. When doped, the dopant is typically present in an amount of less than 2 wt%, preferably less than 1 wt% (relative to the total weight of LATP and / or LAGP). In embodiments where the ceramic oxide electrolyte material consists of optionally doped LATP and / or LAGP described herein, the solid composite cathode composition preferably does not contain any additional oxide materials other than the electrode active material.

[0028] As will be understood by those skilled in the art, the electrode active material containing Li, M, and O discussed herein is a cathode active material, also referred to as a positive electrode active material. The cathode polarity can be positive or negative depending on the operating mode of the electrochemical cell containing the electrode active material. The electrode active material preferably contains Li, M, and O, where M is Ni with a content x of 55.0 mol% ≤ x ≤ 95.0 mol% relative to M; Mn with a content y of 0.0 mol% ≤ y ≤ 40.0 mol% relative to M; Co with a content z of 0.0 mol% ≤ z ≤ 40.0 mol% relative to M; D with a content a of 0.0 mol% ≤ a ≤ 2.0 mol% relative to M, where D is at least one element other than Li, Ni, Mn, Co, and O; and x + y + z + a is 100.0 mol%, preferably, M is Ni with a content x of 55.0 mol% ≤ x ≤ 80.0 mol% relative to M; Mn with a content y of 10.0 mol% ≤ y ≤ 30.0 mol% relative to M; Co with a content z of 10.0 mol% ≤ z ≤ 30.0 mol% with respect to M; D with a content a of 0.0 mol% ≤ a ≤ 2.0 mol% with respect to M, where D is at least one element other than Li, Ni, Mn, Co, and O; is included, x + y + z + a is 100.0 mol%, More preferably Preferably, M is Ni with a content x of 55.0 mol% ≤ x ≤ 70.0 mol% with respect to M; Mn with a content y of 15.0 mol% ≤ y ≤ 25.0 mol% with respect to M; Co with a content z of 15.0 mol% ≤ z ≤ 25.0 mol% with respect to M; D with a content a of 0.0 mol% ≤ a ≤ 2.0 mol% with respect to M, where D is at least one element other than Li, Ni, Mn, Co, and O; is included, x + y + z + a is 100.0 mol%. In some particularly preferred embodiments, x is about 60 mol%, y is about 20 mol%, and z is about 20 mol%. In some particularly preferred embodiments, a = 0.0 mol%.

[0029] According to the present invention, x, y, z, and a referred to herein are measured by inductively coupled plasma optical emission spectrometry (ICP - OES).

[0030] In a particularly preferred embodiment, the electrode active material described herein is the only electrode active material included in the composite cathode material of the present invention.

[0031] It is particularly preferred that the promoter contains lithium fluoride (LiF). As shown in the attached examples, by combining the selected electrolyte material and electrode active material with LiF, excellent electrochemical results were obtained before and after sintering. In a preferred embodiment of the present invention, the promoter is LiX, where X is a halide, at least more than 50 mol% of X represents F, preferably at least 80 mol% of X represents F, and most preferably X represents F (such that the promoter consists of lithium fluoride (LiF)).

[0032] Typically, the promoter is present in an amount of at least 0.5 wt% (based on the total weight of the composition). For example, the promoter may be present in an amount of at least 0.8 wt%, at least 1.2 wt%, or at least 1.5 wt% (based on the total weight of the composition). As shown in the attached examples, even at such low concentrations, the promoter already significantly improves the electrochemical properties before and after sintering. The inventors have surprisingly found that using a high proportion of the promoter further significantly increases the beneficial effect. Thus, according to a preferred embodiment of the present invention, the promoter is present in an amount of at least 4 wt%, preferably at least 4.5 wt% (based on the total weight of the composition). According to a highly preferred embodiment of the present invention, the promoter is present in an amount of at least 7 wt%, more preferably at least 8 wt% (based on the total weight of the composition). The promoter is preferably present in an amount of less than 25 wt%, preferably less than 20 wt%, and most preferably less than 14 wt% (based on the total weight of the composition).

[0033] In a preferred embodiment of the present invention, the ratio (w / w) of the electrode active material to the ceramic oxide electrolyte material is at least 1:1, preferably at least 1.5:1, more preferably at least 1.8:1, and most preferably at least 2:1. This ratio is preferably less than 8:1, preferably less than 6:1, more preferably less than 3:1, and most preferably less than 2.5:1.

[0034] An optional but highly preferred additional component of the composite cathode material of the present invention is a conductive aid, particularly a carbon-based conductive aid. The inventors have found that when sintering a composite cathode composition containing such a carbon-based conductive aid, the carbon-based conductive aid exhibits significant oxidation (and associated functional loss). The formulations containing the promoter according to the present invention enable sintering at low temperatures, thereby limiting the reactivity between components including carbon oxidation, thus overcoming such problems. The carbon-based conductive aid may be any carbon-rich material, for example, any material containing at least 95% by weight of carbon, preferably any material containing at least 99% by weight of carbon. Examples of suitable materials are graphite, carbon black, carbon fibers, carbon nanotubes, graphene, and combinations thereof. A highly preferred carbon-based conductive aid that has been found by the inventors to exhibit improved electrochemical performance when employed in the solid composite cathode composition of the present invention compared to other carbon-based conductive aids is carbon black. Carbon black is known to those skilled in the art and includes variants such as acetylene black or Super C65.

[0035] In a preferred embodiment, the carbon-based conductive aid described herein is present in the solid composite cathode composition of the present invention in an amount of at least 0.5% by weight, preferably at least 1% by weight, more preferably at least 3% by weight (based on the total weight of the ceramic oxide electrolyte material and the electrode active material). Typically, the carbon-based conductive aid is present in an amount of less than 12% by weight, preferably less than 9% by weight, more preferably less than 7% by weight (based on the total weight of the ceramic oxide electrolyte material and the electrode active material).

[0036] Generally, the total amount of the ceramic oxide electrolyte material, the electrode active material, the promoter, and the optional carbon-based conductive aid is preferably at least 90% by weight, preferably at least 95% by weight, more preferably at least 98% by weight (based on the total weight of the composition). In some embodiments, the solid composite cathode composition consists essentially of a ceramic oxide electrolyte material, an electrode active material, a promoter, and an optional carbon-based conductive aid.

[0037] In a highly preferred embodiment of the present invention, the solid composite cathode composition is sintered. In a particularly preferred embodiment, the material is sintered at a temperature below 600 °C, preferably below 500 °C, more preferably below 450 °C. In a particularly preferred embodiment, the material is sintered at a temperature above 200 °C, preferably above 300 °C, more preferably above 350 °C. In a particularly preferred embodiment, the material is sintered at a temperature in the range of 200 °C to 600 °C, preferably in the range of 300 °C to 500 °C, more preferably in the range of 350 °C to 450 °C. The total time the material is subjected to a temperature above 200 °C is preferably in the range of 5 minutes to 48 hours, preferably in the range of 10 minutes to 24 hours, more preferably in the range of 30 minutes to 10 hours. The sintering is optionally carried out while subjecting the material to an elevated pressure, for example a pressure of at least 0.1 GPa or at least 0.5 GPa. In some embodiments, the sintering is carried out while subjecting the material to an elevated pressure in the range of 1 to 5 GPa, preferably 1 to 3 GPa, in order to achieve high compression while avoiding grain splitting. In any of the embodiments described herein, the solid composite cathode composition is preferably sintered in an inert atmosphere or air, preferably air. Without wishing to be bound by any theory, in view of the degradation of the material at high sintering temperatures, the inventors constructed temperature-time calibration curves at different temperatures, sampled different time points for each curve, obtained the relevant X-ray diffraction spectra of the material at different temperatures and durations, and compared the X-ray diffraction spectrum of the material to be analyzed with the X-ray diffraction spectra recorded for the calibration curves, and believe that the temperature and duration to which the composition was subjected to sintering can be derived from the final product.

[0038] The solid composite cathode composition provided herein preferably has a ratio A of less than 2.3. A = (DC C / 20 ) / (DC 1C ) wherein the ratio A is determined by performing 5 complete discharge cycles in sequence at C / 20, C / 10, C / 5, C / 2, and 1C C-rates in a coin cell, in this order, DC C / 20 is the first discharge capacity expressed in mAh / g obtained at a C-rate of C / 20, DC 1C is the first discharge capacity expressed in mAh / g obtained at a C-rate of 1C. Ratio A is preferably in the range of 1.5 to 2.5, more preferably in the range of 1.5 to 2.2, and most preferably in the range of 1.5 to 1.9. Ratio A is preferably obtained in a coin cell immediately after assembly (without aging), preferably at 2.7 to 4.3 V, preferably 2.9 to 3.1 V, using, for example, a TOYO battery cycler. Ratio A is preferably obtained on a coin cell, and the coin cell is a 90:10 ratio of a solid cathode composition mixed with polyvinylidene fluoride (PVDF) to give a total weight of 400 mg in 1.4 to 1.6 mL of N-methyl-2-pyrrolidone solvent (NMP) solvent, and the resulting slurry is tape cast onto an aluminum foil having a wet thickness of 300 μm using a doctor blade, and the laminate is dried overnight at 80 °C under dynamic vacuum, and then the dried laminate is punched out into a disk having a diameter selected to remain in the range of mAh / cm 2 of 0.3 to 0.45 mAh / cm 2 and the amount of the composite cathode material added corresponds to 2 to 3 mg / cm 2 and the disk is densified at a uniaxial pressure of 0.1 to 0.3 MPa and dried overnight at 120 °C, and then the cell is prepared by assembling with a lithium metal anode and 1M LiPF6 in EC-DMC (ethylene carbonate:dimethyl carbonate 3:7) as the electrolyte.

[0039] In another aspect of the present invention, a method for preparing a composite cathode composition, preferably a method for preparing a composition as previously described herein, comprising: a) at least the following precursors: a ceramic oxide material comprising lithium aluminum titanium phosphate (LATP) and / or lithium aluminum germanium phosphate (LAGP); An electrode active material containing Li, M, and O, where M contains Ni and one or both of Mn and Co; An accelerator that is LiX [where X is a halide]; and, Optionally, a carbon-based conductive aid; The step of preparing, b) The step of preparing a substantially homogeneous mixture containing the precursor prepared in step (a), and, c) Optionally, the step of subjecting the mixture of step (b) to sintering, is provided.

[0040] Preferred embodiments of the composite cathode composition, particularly the identity and (relative) amounts of the ceramic oxide material, electrode active material, accelerator, and carbon-based conductive aid as described herein in the context of the composite cathode composition, are equally applicable to the method for preparing the composite cathode composition described herein.

[0041] Step (b) is preferably a dry blending step and can be carried out using any suitable means known to those skilled in the art, such as a simple mortar and pestle, ribbon mixer, rotating drum, plowshare mixer, paddle mixer, conical screw mixer, etc. Step (b) can also include reducing or grinding the size of one or more of the precursors prepared in step (a) using, for example, a ball mill, hammer mill, pin mill, etc.

[0042] Step (b) can include a first step of mixing a subset of the precursors prepared in step (a) and subsequently adding the remaining precursors prepared in step (a).

[0043] Step (c) includes sintering at a temperature preferably below 600°C, more preferably below 500°C, and even more preferably below 450°C. In a particularly preferred embodiment, the material is sintered at a temperature above 200°C, preferably above 300°C, and more preferably above 350°C. In a particularly preferred embodiment, the material is sintered at a temperature in the range of 200°C to 600°C, preferably 300°C to 500°C, and more preferably 350°C to 450°C. The total time the material is subjected to a temperature above 200°C is preferably in the range of 5 minutes to 48 hours, more preferably 10 minutes to 24 hours, and even more preferably 30 minutes to 10 hours. Sintering is optionally carried out while subjecting the material to an elevated pressure, such as at least 0.1 GPa or at least 0.5 GPa. In some embodiments, sintering is carried out while subjecting the material to an elevated pressure in the range of 1 to 3 GPa, preferably 1 to 5 GPa, in order to ensure sufficient compression while avoiding grain splitting.

[0044] In another aspect of the invention, an electrode comprising the solid composite cathode material of the invention is provided. In a particularly preferred embodiment of the invention, the electrode comprises the solid composite cathode material of the invention in combination with a binder such as a polymer binder. The binder is not particularly limited and can be any suitable polymer binder, such as polyimide (PI), polyvinylidene chloride (PVdC), polyethylene oxide (PEO), polyvinylidene fluoride (PVdF), etc.

[0045] In another aspect of the invention, an electrochemical cell comprising the solid composite cathode material described herein is provided.

[0046] In another aspect of the invention, the use of the solid composite cathode material described herein as a cathode for an electrochemical cell is provided.

[0047] In another aspect of the present invention, there is provided a battery, more specifically a lithium-ion battery or a lithium metal battery, comprising at least one electrochemical cell, for example two or more electrochemical cells according to the present invention, comprising the solid composite cathode material described herein.

[0048] In another aspect of the present invention, there is provided a method for manufacturing or operating fixed applications such as vehicles, computers, personal digital assistants, mobile phones, watches, camcorders, digital cameras, thermometers, calculators, laptop BIOSs, communication devices, remote car locks, and energy storage devices for power plants, by using at least one battery or at least one electrochemical cell comprising the solid composite cathode material described herein.

[0049] In another aspect of the present invention, there is provided the use of an electrochemical cell comprising the solid composite cathode material of the present invention in an automobile, a bicycle operated by an electric motor, a robot, an aircraft (e.g., an unmanned aircraft including a drone), a ship, a satellite, or a stationary energy storage device.

[0050] In another aspect of the present invention, there is provided the use of lithium halide for improving electrochemical properties such as the cycle performance of an electrochemical cell comprising a composite cathode material. The composite cathode material comprises a ceramic oxide electrolyte material containing lithium aluminum titanium phosphate (LATP) and / or lithium aluminum germanium phosphate (LAGP); an electrode active material containing Li, M, and O, where M contains Ni and one or both of Mn and Co; and, optionally, a carbon-based conductive aid. Preferred embodiments of the composite cathode composition, particularly the identity and (relative) amounts of the ceramic oxide material, electrode active material, accelerator, and carbon-based conductive aid as described herein in the context of the composite cathode composition, are equally applicable to the use of the lithium halide described herein.

Examples

[0051] I. Preparation of Composite Cathode Material The composite cathode material according to the present invention was prepared in 2 g batches using the following starting products in the following order: NMC (LiNi 0.6 Mn 0.2 Co 0.2 O2, manufacturer specifications), LiF (99.98% (metal basis)), carbon black (acetylene black - KetjenBlack (registered trademark)) and LATP (Li 1+m Al m Ti 2-m (PO4)3, 0.3 < m < 0.5, by SEM - EDX). Inside a glove box (O2 < 1 ppm, H2O < 1 ppm), appropriate amounts of the starting materials were weighed and mixed using an agate mortar and pestle. The composite material was subjected to heat treatment in a GAF (muffle) furnace under a controlled atmosphere pre - calibrated under similar heating conditions. The sample was heated at a heating rate of 1 °C / min, then held at the sintering temperature (without pressure increase) for 1 hour and cooled back to room temperature. All samples were heated in an open - lid 30 mL alumina (Al2O3) crucible. The transfer time of the sample between the glove box and the furnace was controlled to avoid exposure to ambient conditions. Also, after heat treatment, the sample was transferred to the glove box in the temperature range of 120 - 150 °C to avoid moisture absorption.

[0052] A control material was prepared in the same manner except that it did not contain LiF.

[0053] NMC, LATP and carbon black were always used in a ratio of 65:30:05 (w / w) respectively. LiF was added in amounts of 0, 2, 5 and 10 wt% (based on the total weight of NMC, LATP and carbon black). In other words, LiF was added in ratios of 0:100; 2:100; 5:100 and 10:100 (w / w) (LiF):(NMC + LATP + carbon black) as shown in the following table. Unused NMC (unsintered, pure) was also used as a reference for X - ray diffraction spectra.

[0054]

Table 1

[0055] II. Preparation of Electrodes Slurries of the composite cathode materials of Comparative Examples 1 to 4 and Examples 5 to 10 and polyvinylidene fluoride (PVDF) in a 90:10 ratio were prepared in an amount of 400 mg in 1.4 to 1.6 mL of N-methyl-2-pyrrolidone solvent (NMP). PVDF was dissolved in the NMP solvent for 2 hours using a magnetic stirrer, and then the composite cathode material was added and stirring was continued overnight. The slurry was tape-cast onto an aluminum foil with a wet thickness of 300 μm using a doctor blade. The laminate was dried overnight at 80 °C under dynamic vacuum. The dried laminate was punched into disks, and the area capacity (mAh / cm 2 ) was kept in the range of 0.3 to 0.45 mAh / cm 2 , and the diameter was selected such that the addition amount of the cathode active material corresponded to 2 to 3 mg / cm 2 . The disks were densified under a uniaxial pressure of 0.1 to 0.3 MPa and dried overnight at 120 °C, and then the cells were assembled. All processes were carried out in a drying chamber (dew point of about 37 °C).

[0056] III. Measurement of Electrochemical Properties 2032 coin cells were assembled using the composite cathode disks prepared as described in the previous section, lithium metal anodes, and 1 M LiPF6 in EC-DMC (ethylene carbonate:dimethyl carbonate 3:7) as the electrolyte. The coin cells were charged and discharged at a constant current immediately after cell assembly (without aging) between 2.7 and 4.3 V, together with a cycle performance test using a TOYO battery cycler.

[0057] The cycling protocol consisted of 5 cycles each at C-rates of C / 20, C / 10, C / 5, C / 2, 1C, followed by 100 cycles at C / 10. The capacity values were normalized with respect to the weight of the active material (NMC), and the results were verified with reproducibility. Glass fiber was used as the separator.

[0058] IV. Measurement of X-ray Diffraction Spectrum XRD measurements were carried out using a BRUKER D8 Endeavor X-ray diffractometer equipped with a LYNXEYE XE-T detector, with Co radiation (λ: Kα1 = 1.78897 Å, Kα2 = 1.79285 Å). The samples were measured in the 2θ range of 10° to 130° with a step size of 0.016° and a total time of 19.20 seconds / step. Due to the limited amount of the sample, a silicon holder was used to avoid the amorphous background from the normal holder. Peak comparison was obtained after background subtraction and Kα2 stripping (to avoid the doublets arising from the non-monochromatic source). The peaks considered for comparison were the (101), (012), (006), and (104) of NMC where the crystal structure transition was observed. The intensity was normalized with the (104) peak of NMC at 2θ = 52°.

[0059] V. Results Figure 1 shows the temperature-dependent degradation of the NMC-LATP mixture, as evidenced by the XRD spectra of Comparative Examples 2 and 4. It is observed that the composite cathode material of Comparative Example 4 (treated at 500 °C) shows significant degradation.

[0060] Figure 2 shows the temperature-dependent degradation of the cycle performance of the NMC-LATP mixtures of Comparative Examples 1 to 3. It can be observed that the composite cathode material of Comparative Example 2 (treated at 400 °C) has already significantly deteriorated in performance, and the composite cathode material of Comparative Example 3 (treated at 470 °C) no longer functions.

[0061] Figure 3 shows the improvement effect of lithium fluoride addition on the electrochemical performance of the composite cathode materials of Examples 5 to 7 compared with Comparative Example 1. The electrochemical performance is improved even before sintering, especially at a high C-rate.

[0062] Figure 4 shows the improvement effect of lithium fluoride addition on the electrochemical performance of the composite cathode materials of Examples 8 to 10 compared with Comparative Example 2. The electrochemical performance is particularly improved at a high C-rate and a high LiF addition amount.

Claims

1. A ceramic oxide electrolyte material containing lithium aluminum titanium phosphate (LATP) and / or lithium aluminum germanium phosphate (LAGP); An electrode active material containing Li, M, and O, where M contains Ni and one or both of Mn and Co; and An accelerator which is LiX [where X is a halide]; a solid composite cathode composition containing the same.

2. wherein the ceramic oxide electrolyte material is of the formula Li １＋ｍ Al ｍ Ti ２－ｍ (PO ４ ) ３ [wherein, 0 < m < 1, or 0.2 < m < 0.8, or 0.3 < m < 0.5], the composition according to claim 1 comprising LATP.

3. The electrode active material contains Li, M, and O, and M is Ni with a content x of 55.0 mol% ≤ x ≤ 95.0 mol% with respect to M; Mn with a content y of 0.0 mol% ≤ y ≤ 40.0 mol% with respect to M; Co with a content z of 0.0 mol% ≤ z ≤ 40.0 mol% with respect to M; D with a content a of 0.0 mol% ≤ a ≤ 2.0 mol% with respect to M, where D is at least one element other than Li, Ni, Mn, Co, and O; and x + y + z + a is 100.0 mol%, Or, M is Ni with a content x of 55.0 mol% ≤ x ≤ 80.0 mol% with respect to M; Mn with a content y of 10.0 mol% ≤ y ≤ 30.0 mol% with respect to M; Co with a content z of 10.0 mol% ≤ z ≤ 30.0 mol% with respect to M; D with a content a of 0.0 mol% ≤ a ≤ 2.0 mol% with respect to M, where D is at least one element other than Li, Ni, Mn, Co, and O; and x + y + z + a is 100.0 mol%, the composition according to Claim 1.

4. The composition according to Claim 1, where the accelerator is lithium fluoride.

5. The composition according to Claim 1, where the accelerator is present in an amount of at least 0.5 wt%, or at least 4 wt%, or at least 8 wt% (with respect to the total weight of the composition).

6. The composition according to Claim 1, where the ratio (w / w) of the electrode active material to the ceramic oxide electrolyte material is at least 1:1, or at least 1.5:1, or at least 1.8:

1.

7. The composition according to Claim 1, where the solid further contains a carbon-based conductive aid.

8. The composition according to Claim 7, where the carbon-based conductive aid is selected from the group consisting of graphite, carbon black, carbon fiber, carbon nanotube, graphene, and combinations thereof, or is selected from carbon black.

9. The composition according to claim 7, comprising at least 0.5% by weight, or at least 1% by weight, or at least 3% by weight of the carbon-based conductive aid (relative to the total weight of the ceramic oxide electrolyte material and the electrode active material).

10. The composition according to claim 1, wherein the total amount of the ceramic oxide electrolyte material, the electrode active material, the accelerator, and the optional carbon-based conductive aid is at least 90% by weight, or at least 95% by weight (relative to the total weight of the composition).

11. The composition according to claim 1, wherein the accelerator is substantially homogeneously distributed throughout the composition.

12. The composition according to claim 1, which is sintered, or sintered at a temperature below 600 °C, or sintered at a temperature below 500 °C.

13. A method for preparing a composite cathode composition, or a method for preparing the composition according to any one of claims 1 to 12, comprising: a) preparing at least the following precursors: a ceramic oxide material comprising lithium aluminum titanium phosphate (LATP) and / or lithium aluminum germanium phosphate (LAGP); an electrode active material comprising Li, M, and O, wherein M comprises Ni and one or both of Mn and Co; an accelerator which is LiX [wherein X is a halide]; and optionally, a carbon-based conductive aid; b) preparing a substantially homogeneous mixture comprising the precursors prepared in step (a); and c) optionally, subjecting the mixture of step (b) to sintering.

14. Step (c) is carried out, the temperature during sintering in step (c) is less than 500 °C, or less than 450 °C, or the pressure during sintering is in the range of 1 to 3 GPa. The method according to claim 13.

15. An electrochemical cell comprising the solid material according to any one of claims 1 to 12.

Images