Electrode composition

Abstract

The present invention provides an electrode having a surface layer of a niobium-containing metal oxide disposed on a secondary electrode active material. The niobium-containing metal oxide can be a Nb2O5 polymorph, NbO2, or Nb2O3, or can be a mixed metal oxide such as niobium tungsten oxide, titanium niobium oxide, or niobium molybdenum oxide. Also provided are electrochemical cells including the electrode and the use of the cell at high or low temperatures, for example, in lithium-ion batteries.

Description

[Technical Field]

[0001] Cross-reference of related applications This case relates to and asserts the rights to GB1914983.0, filed on October 16, 2019. Its contents are incorporated herein by reference in their entirety.

[0002] Field of Invention The present invention provides electrodes, electrochemical cells such as lithium-ion batteries containing electrodes, and methods for using electrodes within an electrochemical cell. [Background technology]

[0003] Lithium-ion batteries are widely designed to operate optimally at temperatures between 15°C and 40°C. The main limitations in this operation stem from the materials used in the positive and negative electrodes and the lithium-ion-containing electrolyte. Under these optimal conditions, characteristics related to battery performance, such as specific energy, specific power, cycle life, storage life, and safety, are maximized.

[0004] When the operating temperature of lithium-ion batteries deviates beyond this typical range, their energy, power, cycle life, and safety performance are limited. This variation is typically caused by external factors such as seasonal and climatic conditions. However, temperature variations also arise from the use of batteries intended for applications in portable electronic devices such as mobile phones, laptops, and power tools, as well as in electric vehicles (EVs).

[0005] When such battery-powered devices are used in high-power applications such as fast charging in EVs or fast charging of mobile phone batteries (fully charging the battery in under an hour or partially charging it to over 80% of its capacity in under 30 minutes), the heat generated by the high current (ohmic losses) causes a rapid increase in temperature, limiting the battery's ability to supply sustained power or allow for more charging.

[0006] It is understood that overheating of the battery can cause sudden failures due to thermal runaway, fire, and explosion. A battery management system that controls the charging and discharging of lithium-ion batteries shuts down the operation of the device to prevent rapid temperature changes (Shuai Ma, et al.).

[0007] To overcome this limitation, large thermal management systems are used to maintain the operating temperature of the battery within an optimal temperature range. The weight of these systems typically reduces the range of EVs by 40 - 50 percent.

[0008] A similar reduction in the range of EVs also occurs in low-temperature environments such as below 10°C. In particular, when using an EV in a released state, the range significantly decreases (American Automobile Association, February 2019). At low temperatures, the progress of chemical reactions within the battery becomes slower, and at freezing temperatures, plating of metallic lithium can occur on the surface of the graphite anode (negative electrode).

[0009] Also, at temperatures above 45°C, the interface layer between the electrode material and the electrolyte, called the solid electrolyte interface (SEI), deteriorates, resulting in a shorter cycle life of the cell. Usually, this SEI layer formed on the surface of the anode material is responsible for the stable operation of the lithium-ion battery. When the temperature rises, the SEI layer decomposes, significantly reducing the capacity of the cell, so there is an upper limit of 45°C.

[0010] In light of the above problems, in order to extend the range of EVs and enable optimal battery functions in a wide temperature range for portable battery-powered devices, it is necessary to provide new electrode materials and surfaces for lithium-ion batteries that can operate at high rates and high temperatures.

[0011] In light of the above problems, it is necessary to provide new electrode materials for lithium-ion batteries that can operate at high or low temperatures.

Prior Art Documents

Patent Documents

[0012] [Patent Document 1] U.S. Patent Application Publication No. 2016 / 0351973 [Patent Document 2] U.S. Patent Application Publication No. 2013 / 0266858 [Patent Document 3] European Patent Application Publication No. 3522268 [Patent Document 4] U.S. Patent Application Publication No. 2019 / 0097226 [Patent Document 5] U.S. Patent Application Publication No. 2015 / 0221933 [Patent Document 6] U.S. Patent Application Publication No. 2017 / 0141386 [Non-patent literature]

[0013] [Non-Patent Document 1] Shuai Ma et al., Temperature effect and thermal impact in lithium-ion batteries: A Review, Progress in Natural Science: Materials International, December 2018). [Non-Patent Document 2] Electric Vehicle Range Testing: AAA proprietary research into the effect of ambient temperature and HVAC use on driving range and MPGe, American Automobile Association, February 2019 [Non-Patent Document 3] Griffith et al., Niobium tungsten oxides for high-rate lithium-ion energy storage, Nature, Vol559, pp. 556-559 [Overview of the project] [Means for solving the problem]

[0014] The present invention generally provides electrodes having a niobium-containing metal oxide surface, electrochemical cells including electrodes, and the use of cells at high or low temperatures, for example, in lithium-ion batteries.

[0015] The inventors have established that high energy density can be achieved in lithium-ion cells by using electrode materials having niobium-containing metal oxide surfaces, even when the cells are cycled at high or low temperatures. The cells exhibit excellent capacity retention when repeatedly cycled at high or low temperatures. Furthermore, the cells can be charged and discharged at high C rates at both high and low temperatures. Therefore, lithium-ion cells containing electrodes with niobium-containing metal oxide surfaces have a wider operating temperature range and exhibit improved cycle stability at high or low temperatures compared to typical lithium-ion cells containing graphite electrodes.

[0016] Working electrodes having a niobium-containing metal oxide surface and bulk exhibit favorable lithium diffusion characteristics and therefore show excellent rate characteristics. 1.0V vs. Li + Beyond / Li, SEI formation is minimized, meaning that lithium is not lost through side reactions with the electrolyte.

[0017] A typical lithium-ion cell containing graphite electrodes is 1VvsLi + Operating below / Li, the cells must undergo an initial formation cycle before being sealed. Typically, this formation cycle is performed at a high temperature, e.g., 60°C, to rapidly form the SEI in a single cycle and cause degassing. This adds considerable time and cost to the cell manufacturing process.

[0018] According to the present invention, the niobium-based metal oxide surface minimizes or eliminates SEI formation, which is typically observed on graphite surfaces during the initial formation step of a lithium-ion battery in the first charging cycle.

[0019] Furthermore, for example, in a full cell against LiFePO4, LiN(CF3SO2)2(LiTFSI) can be used as a substitute for the more toxic LiPF6 electrolyte salt commonly used in standard commercial electrolytes. In addition, LiAl alloying potential (≤0.3V vs Li + While avoiding lithium (Li), aluminum can be used as a current collector instead of the more expensive copper.

[0020] Generally, the present invention provides a method for charging and / or discharging an electrochemical cell, wherein the electrochemical cell includes a working electrode having a niobium-containing metal oxide surface, and the temperature of the electrochemical cell is 45°C or higher, for example, 50°C or higher, 55°C or higher, or 60°C or higher.

[0021] Generally, the present invention also provides a method for charging and / or discharging an electrochemical cell, wherein the electrochemical cell includes a working electrode having a niobium-containing metal oxide surface, and the temperature of the electrochemical cell is 10°C or less, for example, 5°C or less, or 0°C or less.

[0022] A first aspect of the present invention provides a method for charging and / or discharging an electrochemical cell, wherein the electrochemical cell includes a working electrode having a niobium-containing metal oxide surface layer disposed on a secondary electrode active material, and the temperature of the electrochemical cell is 45°C or higher, for example, 50°C or higher, 55°C or higher, or 60°C or higher.

[0023] A second aspect of the present invention provides a method for charging and / or discharging an electrochemical cell, wherein the electrochemical cell includes a working electrode having a surface layer of a niobium-containing metal oxide disposed on a secondary electrode active material, and the temperature of the electrochemical cell is 10°C or less, for example, 5°C or less or 0°C or less.

[0024] The electrochemical cell may include a counter electrode and an electrolyte, and optionally, the electrodes may be connectable to or connected to a power source.

[0025] Each embodiment of the method may include charging and / or discharging an electrochemical cell at a C rate of at least 5C, for example, at least 10C, at least 20C, at least 30C, at least 40C, at least 50C, or at least 60C.

[0026] The method may include cycles of charging and discharging an electrochemical cell, or discharging and charging, and the method may include 2 or more cycles, 5 or more cycles, 10 or more cycles, 50 or more cycles, 100 or more cycles, 500 or more cycles, 1000 or more cycles, or 2000 or more cycles.

[0027] The niobium-containing metal oxide layer may have a maximum thickness of 4.5 nm or less.

[0028] A layer of niobium-containing metal oxide can be arranged on particles of the secondary electrode active material. Alternatively, a layer of niobium-containing metal oxide can be arranged on a film of the secondary electrode active material.

[0029] Niobium-containing metal oxides can be selected from different polymorphs of Nb2O5, NbO2, Nb2O3, or combinations thereof.

[0030] Niobium-containing metal oxides can be doped with additional elements such as phosphorus, aluminum, copper, chromium, zirconium, vanadium, and lithium.

[0031] Niobium-containing metal oxides can be selected from niobium tungsten oxide, titanium niobium oxide, niobium molybdenum oxide, or a combination thereof. Niobium vanadium oxide can also be used as a niobium-containing metal oxide.

[0032] The secondary electrode active material can be selected from carbon, silicon, or metal oxides. Lithium and silver can also be used as secondary electrode active materials.

[0033] The secondary electrode active material can be selected from graphite, reduced graphite oxide, or hard carbon.

[0034] The secondary electrode active material can be selected from lithium titanate, titanium tantalum oxide, or tantalum molybdenum oxide. Lithium vanadium oxide, lithium titanium silicate, and lithium vanadium oxide phases can also be used as secondary electrode active materials.

[0035] A third aspect of the present invention provides an electrode, which may be called a working electrode, having a niobium-containing metal oxide surface. The working electrode is suitable for use as an electrode in a lithium-ion battery.

[0036] The working electrode includes a surface layer of niobium-containing metal oxide placed on the secondary electrode active material.

[0037] A layer of niobium-containing metal oxide can be arranged on particles of the secondary electrode active material. Alternatively, a layer of niobium-containing metal oxide can be arranged on a film of the secondary electrode active material.

[0038] The niobium-containing metal oxide can be selected from Nb2O5 polymorphs, NbO2, Nb2O3, or combinations thereof.

[0039] Niobium-containing metal oxides can be doped with additional elements such as phosphorus, aluminum, copper, chromium, zirconium, vanadium, and lithium.

[0040] Niobium-containing metal oxides can be selected from niobium tungsten oxide, titanium niobium oxide, niobium molybdenum oxide, or a combination thereof. Niobium vanadium oxide can also be used as a niobium-containing metal oxide.

[0041] The secondary electrode active material can be selected from carbon, silicon, or metal oxides. Lithium and silver can also be used as secondary electrode active materials.

[0042] The secondary electrode active material can be selected from graphite, reduced graphite oxide, or hard carbon.

[0043] The secondary electrode active material can be selected from lithium titanate, titanium tantalum oxide, and tantalum molybdenum oxide. Lithium vanadium oxide, lithium titanium silicate, and lithium vanadium oxide phases can also be used as secondary electrode active materials.

[0044] A fourth aspect of the present invention provides an electrochemical cell comprising the working electrode of the present invention.

[0045] A fifth aspect of the present invention provides a lithium-ion battery comprising one or more electrochemical cells of the present invention. If there are multiple cells, they may be provided in series or in parallel.

[0046] A sixth aspect of the present invention provides the use of a working electrode having a niobium-containing metal oxide surface layer disposed on a secondary electrode active material in an electrochemical cell, wherein the temperature of the electrochemical cell during charging or discharging is 45°C or higher, for example, 50°C or higher, 55°C or higher, or 60°C or higher.

[0047] A seventh aspect of the present invention provides the use of a working electrode having a niobium-containing metal oxide surface layer disposed on a secondary electrode active material in an electrochemical cell, wherein the temperature of the electrochemical cell during charging or discharging is 10°C or less, for example, 5°C or less, or 0°C or less.

[0048] These and other aspects and embodiments of the present invention will be described in more detail below. [Brief explanation of the drawing]

[0049] [Figure 1] The images show working electrode particles with an intermediate metal oxide layer (top) and without an intermediate metal oxide layer (bottom), both having a niobium-containing metal oxide surface layer. [Figure 2]Figure 2a shows the rate characteristics of NWO(Nb16W5O55) / NMC(LiNi0.6Co0.2Mn0.2O2) cells at cell operating temperatures of 60°C (top), 25°C (center), and 10°C (bottom). Figure 2b shows the long-term cycle characteristics of NWO / NMC cells at 60°C and a 10°C rate. Figure 2c shows the long-term cycle characteristics of NWO / NMC cells at 25°C (top) and 10°C (bottom) under 5°C rate conditions. Figure 2d shows a comparison of the rate characteristics of NWO / LFP cells at temperatures of 60°C (top), 25°C (center), and 10°C (bottom). Figure 2E shows the long-term cycle characteristics of NWO / LFP cells at 10, 25, and 60°C at a 5°C rate. [Figure 3] Figure 3a shows the rate characteristics (top) of a cell containing an anode with a niobium-containing metal oxide surface layer placed on a graphite secondary active material at 65°C, and the rate characteristics (bottom) of a cell containing an anode in which the niobium-containing surface layer dissolves at 65°C. Figure 3b shows the long-term cycle characteristics of a niobium-coated cell (top) and an uncoated cell (bottom) at 65°C. Figure 3c shows the rate characteristics of a niobium-coated cell at 65°C (top) and 25°C (bottom). Figure 3d shows the long-term cycle characteristics of a niobium-coated cell at 65°C (bottom) and 25°C (top). [Figure 4] Figure 4a is a scanning electron microscope image of primary particles of a niobium-based metal oxide used in the preparation of an anode according to an embodiment of the present invention. Figure 4b is a scanning electron microscope image of a niobium-containing metal oxide coated on irregular graphite particles. Figure 4c is a scanning electron microscope image of a niobium-containing metal oxide coated on irregular graphite particles. Figure 4d is a scanning electron microscope image of a niobium-containing metal oxide coated on regular graphite particles. [Figure 5] Figure 5a shows a pouch cell according to an embodiment of the present invention. Figure 5b shows a cylindrical cell according to an embodiment of the present invention. Figure 5c shows an anode electrode according to an embodiment of the present invention coated on a current collector. Figure 5d shows the anode and cathode electrodes of a jelly roll with a separator (left) placed inside a metal can (right) together with an electrolyte to fabricate an electrochemical cell according to an embodiment of the present invention. [Modes for carrying out the invention]

[0050] The present invention generally provides electrodes having a niobium-containing metal oxide surface, electrochemical cells including electrodes, and the use of cells at high or low temperatures, for example, in lithium-ion batteries.

[0051] Electrodes containing niobium tungsten oxide are described in the literature, for example, by Griffith et al. However, the electrochemical properties of niobium tungsten oxide have been tested in a temperature-controlled room at 293 ± 2 K using lithium metal as the counter electrode. Electrochemical properties have not been tested at high or low temperatures.

[0052] Electrodes consisting of an atomically thin coating of aluminum oxide (Al2O3) or titanium oxide (TiO2) on the secondary electrode active material have also been reported (Lee Se-Hee, et al., US9,196,901B2). However, the electrochemical properties of coated electrodes have not been tested at high or low temperatures.

[0053] The inventors have developed an electrochemical cell comprising an electrode having a niobium-containing metal oxide surface that exhibits favorable lithium-ion diffusion characteristics, high volumetric energy density, and high capacity even when cyclically subjected to high or low temperatures.

[0054] The voltage values ​​described herein are Li, as is common in the art. + This is based on / Li.

[0055] The C rate is a measure of the rate at which a battery discharges relative to its maximum capacity. The C rate can be defined as the reciprocal of the number of hours it takes to reach a defined maximum capacity; for example, 10C corresponds to 6 minutes of discharge or charge time. The maximum capacity can be a theoretical maximum or an empirically determined maximum. For example, the theoretical maximum capacity can be defined for one electron transfer per transition metal atom in the electrode active material.

[0056] High charge and discharge rates can also be explained by the (gravimetric) current density relative to the weight of the electrode active material.

[0057] US2017 / 0141386 describes the preparation of a negative electrode containing a layer of LiNbO3 coated on a conductive material (carbon black), rather than on the secondary electrode active material. This contradicts the teaching of coating the secondary electrode active material with a niobium-containing metal oxide.

[0058] US2019 / 0097226 describes the preparation of a niobium-containing positive electrode active material. The material is a single component and is not placed on top of a secondary electrode active material. This contradicts the layered configuration and is a teaching that contradicts the use of niobium in the negative electrode.

[0059] EP3522268 describes a positive electrode containing a layer of lithium niobate on an NMC active material. This is contrary to the instruction to use niobium for the negative electrode.

[0060] US2015 / 0221933 describes a cathode containing an NMC active material having a sintered niobium oxide compound on part of its surface.

[0061] [Working electrode] The present invention provides a working electrode having a niobium-containing metal oxide surface. The working electrode is conductive and can be electrically connected to a counter electrode, for example, in an electrochemical cell.

[0062] The working electrode can be, for example, the anode (negative electrode) or cathode (positive electrode) during the discharge step in a lithium-ion battery. Typically, the working electrode is the anode during the discharge step.

[0063] The working electrode has a niobium-containing metal oxide surface. That is, the surface of the working electrode is terminated with a metal oxide containing niobium (Nb). The niobium-containing metal oxide surface is the active electrode surface of the electrochemical cell. In other words, the niobium-containing metal oxide surface is the surface that comes into contact with the electrolyte in a typical electrochemical cell.

[0064] The working electrode may include a layer of niobium-containing metal oxide disposed on the secondary electrode active material. The layer of niobium-containing metal oxide may be a coating on the secondary electrode active material.

[0065] The thickness of the niobium-containing metal oxide layer is either known or can be determined using standard techniques such as scanning electron microscopy (SEM).

[0066] In one embodiment, the niobium-containing metal oxide layer may have a maximum thickness of 10 μm or less, for example, 5 μm or less, 4 μm or less, 3 μm or less, or 2 μm or less.

[0067] Preferably, the niobium-containing metal oxide layer has a maximum thickness of 5 nm or less, for example, 4.5 nm or less, 4.0 nm or less, 3 nm or less, or 2 nm or less.

[0068] The niobium-containing metal oxide layer may have a minimum thickness of 0.1 nm or more, for example, 0.2 nm or more, 0.3 nm or more, 0.4 nm or more, or 0.5 nm or more.

[0069] The niobium-containing metal oxide can have a thickness within a range selected from the above maximum and minimum amounts. The inventors have found that a thinner coating of the niobium-containing metal oxide is preferable because it reduces impedance compared to thicker layers while maintaining electrode temperature stability and reducing SEI formation.

[0070] The niobium-containing metal oxide layer may be placed directly on the secondary electrode active material, or an intermediate layer of the active material may be present.

[0071] A layer of niobium oxide can be placed on top of the particles of the secondary electrode active material.

[0072] The particle size of the secondary electrode active material is either known or can be determined using standard techniques such as SEM.

[0073] The particles of the secondary electrode active material may have a maximum primary particle size of 100 μm or less, for example, 50 μm or less, 40 μm or less, 30 μm or less, or 20 μm or less.

[0074] The particles of the secondary electrode active material may have a primary particle size of 5 nm or larger, for example, 10 nm or larger, 15 nm or larger, 20 nm or larger, or 25 nm or larger.

[0075] The particles of the secondary electrode active material may have a primary particle size within a range selected from the above-mentioned maximum and minimum amounts. The shape of the particles can be regular or irregular.

[0076] Alternatively, a layer of niobium-containing metal oxide can be placed on a film of secondary electrode active material. The thickness of the film of the secondary electrode active material is not particularly limited.

[0077] Methods for coating films or particles with metal oxides are known and include chemical solution deposition, spin coating, dip coating, chemical vapor deposition, atomic layer deposition, molecular layer deposition, sputtering, and physical vapor deposition.

[0078] Alternatively, a niobium-containing metal oxide surface can exist as a concentration gradient of a single material, comprising a niobium-rich surface layer and a niobium-poor interior.

[0079] The niobium-containing metal oxide can be selected from Nb2O5 polymorphs, NbO2, Nb2O3, or combinations thereof.

[0080] The niobium-containing metal oxide can be doped with additional elements such as phosphorus (P), aluminum (Al), copper (Cu), chromium (Cr), zirconium (Zr), vanadium (V), and lithium (Li).

[0081] The niobium-containing metal oxide can be a lithium conductor such as lithium niobate (LiNbO3), Li3NbO4, LiNbVO, LiNbLaZrO (garnets), LiNbSPO (LISICONs), LiNbAlTiP / LiNbAlGeP (NASICONs), etc.

[0082] The niobium-containing metal oxide can be a mixture of niobium oxide and an additional metal oxide (e.g., an amorphous mixture). Suitable additional metal oxides include titanium oxide, hafnium oxide, tantalum oxide, or aluminum oxide. Vanadium oxide is also a suitable metal oxide.

[0083] The niobium-containing metal oxide can be a compound of niobium oxide and an additional metal oxide (e.g., having a crystal structure). Suitable niobium-containing metal oxides include niobium tungsten oxide (e.g., Nb 16 W5O 55 or Nb 18 W 16 O 93 ), titanium niobium oxide (e.g., TiNb2O7), niobium molybdenum oxide (e.g., Nb2Mo3O 14 ), or combinations thereof. Niobium vanadium oxide can also be used.

[0084] Suitable niobium tungsten oxides include Nb 12 WO 33 , Nb 26 W4O 77 , Nb 14 W3O 44 , Nb 16 W5O 55 , Nb 18 W8O 69 , Nb2WO8, Nb 18 W 16 O 93 , Nb 22W 20 O 115 Nb8W9O 47 Nb 54 W 82 O 381 Nb 20 W 31 O 143 Nb4W7O 31 , or Nb2W 15 O 50 , or a combination thereof.

[0085] The secondary electrode active material is lithium ions (Li + ) is a material that can be reversibly inserted. The secondary electrode active material can be selected from carbon, silicon, or metal oxides. Lithium and silver can also be used as secondary electrode active materials.

[0086] The secondary electrode active material can be selected from graphite, reduced graphite oxide, or hard carbon.

[0087] The secondary electrode active material is lithium titanate (LTO; Li4Ti5O 12 ), titanium tantalum oxide (e.g., TiTa2O7), or tantalum molybdenum oxide (e.g., Ta8W9O 47 ) can be selected from the following. Lithium vanadium oxide (e.g., LiV3O8), lithium titanium silicate, and lithium vanadium oxide phases can also be used as secondary electrode active materials.

[0088] The working electrode may contain a conductive carbon material to improve conductivity. The conductive carbon material may be carbon black, graphite, nanoparticle carbon powder, carbon fibers, and / or carbon nanotubes. The conductive carbon material may be Ketjenblack, Super P carbon, or hard or soft amorphous carbon.

[0089] The working electrode may include a binder to improve the adhesion of the active material to the current-collecting surface. Typical examples of binders include PVDF, PTFE, CMC, PAA, PMMA, PEO, SBR, and copolymers thereof.

[0090] The working electrode is typically fixed to a current collector, such as a copper or aluminum current collector, which may be in the form of a plate.

[0091] The inventors have developed a 2032 type coin cell using ethylene carbonate / dimethyl carbonate containing 1.0 MLiPF6 as the electrolyte, with an electrode configuration of 9:0.5:0.5 active material / carbon / binder for an NMC or LiFePO4 counter electrode, and an active material amount of 8-10 mg / cm³. -2 The electrode area is 1.27 cm². 2 We evaluated working electrodes containing a niobium tungsten oxide (NWO) surface.

[0092] The inventors found that when an NWO / NMC cell is cycled 300 times at 60°C (10C rate), 30.8% of its discharge capacity is lost, while when the cell is cycled at 10°C (5C rate), it shows a capacity loss of 15.5%. When an NWO / LFP cell is cycled 1000 times at 60°C (5C rate), it shows a capacity loss of 18.1%, and when cycled at 10°C (5C rate), it shows a capacity loss of 6.9%.

[0093] [Electrochemical cell] The present invention also provides an electrochemical cell comprising the working electrode of the present invention. The working electrode may be, for example, the anode or cathode during the discharge step in a lithium-ion battery. Typically, the working electrode may be the anode during the discharge step.

[0094] An electrochemical cell typically includes a counter electrode and an electrolyte. An electrochemical cell may also include a current collector plate. An electrochemical cell may be electrically connected to a power source. An electrochemical cell may also be electrically connected to a measuring device, such as an ammeter or voltmeter.

[0095] An electrochemical cell can be a lithium-ion cell. The counter electrode can be, for example, the anode or cathode during the discharge step in a lithium-ion battery. The counter electrode is usually the cathode during the discharge step.

[0096] Suitable cathode materials include lithium-containing or lithium-inserted materials such as lithium metal oxides, where the metal is typically a transition metal such as Co, Fe, Ni, V, or Mn, or a combination thereof. Some examples of cathode materials include lithium cobalt oxide (LiCoO2), lithium nickel manganese cobalt oxide (NMC, LiNiMnCoO2, e.g., LiNi 0.6 Co 0.2 Mn 0.2 This includes O2, lithium vanadium fluorophosphate (LiVPO4F), lithium nickel cobalt aluminum oxide (NCA, LiNiCoAlO2), lithium iron phosphate (LFP, LiFePO4), and manganese-based spinel (e.g., LiMn2O4).

[0097] The counter electrode may contain a conductive carbon material to improve conductivity. The conductive carbon material may be carbon black, graphite, nanoparticle carbon powder, carbon fibers, and / or carbon nanotubes. The conductive carbon material may be Ketjenblack, super P carbon, or hard or soft amorphous carbon.

[0098] The counter electrode may include a binder to improve the adhesion of the active material to the current-collecting surface. Typical examples of binders include PVDF, PTFE, CMC, PAA, PMMA, PEO, SBR, and copolymers thereof.

[0099] The counter electrode is typically fixed to a current collector, such as a copper or aluminum current collector, which may be in the form of a plate.

[0100] Typically, the electrolytes in electrochemical cells are suitable for solubilizing lithium ions. Typically, the electrolyte in charged and discharged cells contains lithium ions.

[0101] Typically, electrolytes contain lithium salts such as LiTFSI (lithium bis(trifluoromethane)sulfonimide), LiPF6, LiBF4, LiClO4, LiTF (lithium triflate), or lithium bis(oxalato)borate (LiBOB).

[0102] The electrolyte can be a liquid electrolyte, such as a liquid at ambient temperature, for example, 25°C. A preferred electrolyte is one that is stable at both high and low temperatures.

[0103] The electrolyte may be a non-aqueous electrolyte. The electrolyte may contain a polar aprotic solvent. The electrolyte may contain an organic solvent. Solvents for dissolving lithium ions are well known in the art.

[0104] Suitable solvents include carbonate solvents, such as propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), chloroethylene carbonate, fluorocarbonate solvents (e.g., fluoroethylene carbonate and trifluoromethylpropylene carbonate), and dialkyl carbonate solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), and ethyl propyl carbonate (EPC).

[0105] Suitable solvents include sulfone solvents. For example, methyl sulfone, ethyl methyl sulfone, methylphenyl sulfone, methyl isopropyl sulfone (MiPS), propyl sulfone, butyl sulfone, tetramethylene sulfone (sulfolane), phenyl vinyl sulfone, allyl methyl sulfone, methyl vinyl sulfone, divinyl sulfone (vinyl sulfone), diphenyl sulfone (phenyl sulfone), dibenzyl sulfone (benzyl sulfone), vinylene sulfone, butadiene sulfone, 4-methoxyphenyl methyl sulfone, 4-chlorophenyl methyl sulfone, 2-chlorophenyl Lophenylmethylsulfone, 3,4-dichlorophenylmethylsulfone, 4-(methylsulfonyl)toluene, 2-(methylsulfonyl)ethanol, 4-bromophenylmethylsulfone, 2-bromophenylmethylsulfone, 4-fluorophenylmethylsulfone, 2-fluorophenylmethylsulfone, 4-aminophenylmethylsulfone, sultones (e.g., 1,3-propanesultone), and sulfone solvents containing ether groups (e.g., 2-methoxyethyl(methyl)sulfone and 2-methoxyethoxyethyl(ethyl)sulfone).

[0106] Suitable solvents also include silicon-containing solvents such as siloxanes or silanes. Examples include hexamethyldisiloxane (HMDS), 1,3-divinyltetramethyldisiloxane, polysiloxanes, and polysiloxane-polyoxyalkylene derivatives. Some examples of silane solvents include methoxytrimethylsilane, ethoxytrimethylsilane, dimethoxydimethylsilane, methyltrimethoxysilane, and 2-(ethoxy)ethoxytrimethylsilane.

[0107] Typically, electrolytes may contain additives to improve performance. For example, vinylene carbonate (VC), vinylethylene carbonate, allyl ethyl carbonate, t-butylene carbonate, vinyl acetate, divinyl adipate, nitrile acrylate, 2-vinylpyridine, maleic anhydride, methyl cinnamate, ethylene carbonate, halogenated ethylene carbonate, α-bromo-γ-butyrolactone, methyl chloroformate, 1,3-propanesultone, ethylene sulfite (ES), propylene sulfite (PS), vinylethylene sulfite (VES), fluoroethylene sulfite (FES), 12-crown-4 ether, carbon dioxide (CO2), sulfur dioxide (SO2), and sulfur trioxide (SO3).

[0108] Electrochemical cells may also include a solid porous membrane placed between the negative and positive electrodes. The solid porous membrane can partially or completely replace the liquid electrolyte. The solid porous membrane may include polymers (e.g., polyethylene, polypropylene, or copolymers thereof), or inorganic materials such as transition metal oxides (e.g., titania, zirconia, yttria, hafnia, or niobia), or typical element metal oxides such as silicon dioxide, which may be in the form of glass fibers.

[0109] Solid nonporous films may contain lithium ion conductors. Examples include LLZO (garnets), LSPO (lisicones), LGPS (thio-lisicones), LATP / LAGP (nasicones), LLTO (perovskites), and phosphide / sulfide glass ceramics.

[0110] 〔method〕 The present invention provides a method for charging and / or discharging an electrochemical cell at high or low temperatures. An electrochemical cell includes a working electrode with a niobium-containing metal oxide surface. Typically, an electrochemical cell also includes a counter electrode and an electrolyte.

[0111] Preferably, the method is a method for charging and / or discharging an electrochemical cell at a high temperature (ambient temperature; higher than about 20°C). For example, the method may be carried out at 30°C or higher, for example, 40°C or higher, 45°C or higher, 50°C or higher, 55°C or higher, or 60°C or higher.

[0112] The inventors have found that a working electrode having a niobium-containing metal oxide surface can be stable up to 600°C. Therefore, the maximum temperature for a method of charging and / or discharging an electrochemical cell at high temperatures is defined by the selection of electrolyte and counter electrode materials. For example, an electrochemical cell comprising a working electrode having a niobium-containing metal oxide surface, a solid ceramic electrolyte, and an LPF counter electrode is expected to be cycled at 300°C.

[0113] Alternatively, this method is a method for charging and / or discharging an electrochemical cell at low temperatures (ambient temperature; below approximately 20°C). For example, this method can be carried out at temperatures below 18°C, e.g., below 15°C, below 10°C, below 5°C, or below 0°C.

[0114] The inventors believe that the lowest temperature for a method of charging and / or discharging an electrochemical cell at low temperatures is defined by the choice of electrolyte. By appropriately selecting the electrolyte, a method of charging and / or discharging an electrochemical cell at low temperatures can be carried out at a minimum temperature of at least -70°C.

[0115] This method requires at least 750mA·g -1 For example, at least 800mA·g -1 This may be a method for charging and / or discharging an electrochemical cell with a current density of at least 800 mA·g. Preferably, the method uses at least 800 mA·g. -1 , 850mA·g -1 , 900mA·g -1 , 950mA·g -1 , 1000mA·g -1 , 1050mA·g -1 , 1100mA·g -1 , 1200mA·g -1 , or 1300mA·g -1This is a method for charging and / or discharging an electrochemical cell at a current density.

[0116] This method may include cycles of charging and discharging, or discharging and charging, an electrochemical cell. This cycle may be repeated multiple times. Therefore, this method may include 2 or more cycles, 5 or more cycles, 10 or more cycles, 50 or more cycles, 100 or more cycles, 500 or more cycles, 1000 or more cycles, or 2000 or more cycles.

[0117] 〔battery〕 The present invention also provides a battery comprising one or more electrochemical cells of the present invention. The battery may be a lithium-ion battery. If there are multiple cells, they can be supplied in series or parallel.

[0118] The battery of the present invention may be supplied to road vehicles such as automobiles, motorcycles, or trucks. Alternatively, the battery of the present invention may be supplied to railway vehicles such as trains or trams. The battery of the present invention may also be supplied to electric bicycles (e-bikes), drones, electric aircraft, and electric or hybrid boats. Similarly, the battery of the present invention may be supplied to power tools such as electric drills or saws, gardening tools such as lawnmowers or trimmers, or household appliances such as toothbrushes or hair dryers.

[0119] The battery of the present invention can be provided for a regenerative braking system. The battery of the present invention can be provided for portable electronic devices such as mobile phones, laptop computers, or tablets. The battery of the present invention can be provided for a power grid management system.

[0120] 〔use〕 The present invention generally provides the use of a working electrode having a niobium-containing metal oxide surface in an electrochemical cell, such as the electrochemical cell described herein. Typically, the temperature of an electrochemical cell during charging or discharging is 45°C or higher, for example, 50°C or higher, 55°C or higher, or 60°C or higher. Alternatively, the temperature of an electrochemical cell during charging or discharging is 10°C or lower, for example, 5°C or lower, or 0°C or lower. The working electrode can be used in the method described herein.

[0121] [Other options] All compatible combinations of the above embodiments are expressly disclosed herein, as each combination is explicitly described individually. Various further aspects and embodiments of the present invention will be apparent to those skilled in the art in consideration of this disclosure.

[0122] As used herein, “and / or” should be interpreted as each of two specific features or components, with or without the other. For example, “A and / or B” should be interpreted as each of the specific disclosures of (i) A, (ii) B, and (iii) A and B, as each is described separately herein.

[0123] Unless otherwise indicated in the context, the above descriptions and definitions of features are not limited to any particular aspect or embodiment of the present invention, but apply equally to all aspects and embodiments described herein. Specific aspects and embodiments of the present invention will be described, for example, with reference to the drawings above.

[0124] 〔experiment〕 The following examples are provided to illustrate the present invention and are not intended to limit the scope of the invention. • Example 1 FriNb 16 W5O 55 [Synthesis] NbO2 (Alfa Aesar, 99+%) or white Nb2O5 (Sigma, 99.9985%) and WO2 (Alfa Aesar, 99.9%) are cotheroxidated in batches of approximately 1 to 5 grams. 16 W5O 55 (NWO) was synthesized. The partially reduced oxide was combined into 0.001 g in a molar ratio of 16:5, manually ground using an agate mortar and pestle, compressed into pellets at 10 MPa, and refrigerated in a platinum crucible at 10 K·min. -1 The NWO powder was heated to 1473K at a certain rate and then allowed to cool naturally in the furnace for approximately 2 hours. Phase purity of the NWO powder was confirmed by X-ray diffraction.

[0125] [Electrode adjustment] NMC-662 was obtained from TargrayUSA. Super P (TIMCAL) and polyvinylidene fluoride (PVdF; Kynar) dispersed in N-methyl-2-pyrrolidone were used as the conductive material and binder, respectively. All slurries consisted of 90% active material, 5% Super P, and 5% PVdF binder, and mixing was performed using a Thinky Mixer 250. The NMC and LFP electrodes were dried in a drying chamber at 80°C for 2 hours, and the NWO electrodes were dried overnight in a 60°C oven under ambient atmosphere. All electrodes were calendered at room temperature, and the electrode filling amount was 8.0–8.3 mg / cm³. 2 (NMC), 8.4~8.7 mg / cm³ 2 (LFP), and 8.8-9.4 mg / cm³ 2 It was the (NWO).

[0126] [Electrochemical property evaluation] All electrochemical measurements were evaluated using a 2032 stainless steel coin cell. The prepared cathode and anode electrodes were dried under vacuum at 100°C for 3 hours, then transferred to an argon-filled glove box (MBraun) without exposure to air. Half-cells and full-cells were assembled in the glove box using LP30 electrolyte (Sigma-Aldrich) containing 1.0 M lithium hexafluorophosphate (LiPF6) in ethylene carbonate (EC):dimethyl carbonate (DMC) (1:1 v / v). After drying under vacuum at 40°C for 2 hours, polyethylene separators (Toray) were used. For electrolyte analysis, glass fiber filters (Whatman, GE) were used as separators. The filters were also dried under vacuum at 150°C in a drying oven (Buchi). Constant current electrochemical tests were performed at various current densities using a galvanostat / potentiostat (BioLogic) in temperature-controlled ovens at 10, 25, and 60°C. The negative-to-positive capacity ratio of all test cells was 1.1–1.2, which is calculated based on the actual capacity of the active material, i.e., 171.3 mAh / g for NWO, 175 mAh / g for NMC, and 165 mAh / g for LFP. The full cell capacity of this test is calculated by the active material mass of the cathode. In the symmetric cell test, two full cells with the same fill weight were operated at 0.2C, and the impedance was measured at 2.0V during the charging step. A scan was performed by applying an amplitude of 10mV at frequencies from 1MHz to 100mHz. The cells were then disassembled in a glove box, and the two symmetric cells were assembled using new LP30 electrolyte. The electrochemical impedance of the symmetric cells was measured again under the same conditions.

[0127] [Evaluation of electrode characteristics] For characterization, the cells were disassembled, rinsed with DMC, and completely dried in a pre-chamber under vacuum. X-ray diffraction patterns of the initial and used electrodes were acquired in transmission mode using an X-ray diffractometer (Empyrean, Panalytical) at ambient temperature with a CuKα source. The lattice constant, phase, and purity of the material were determined by Rietveld analysis using Fullprof software.

[0128] [Thermal stability] The thermal performance stability of NWO / NMC and NWO / LFP cells was tested at 10, 25, and 60°C (Figure 2). In both cells, the discharge capacity of cells tested at different C rates at 60°C (10°C) was relatively higher (lower) compared to 25°C. These phenomena are likely related to the kinetics of charge transfer and diffusion reactions within the cell. The long-term cycle characteristics of NWO / NMC cells were evaluated for 300 cycles under three different conditions: 10°C at 60°C (Figure 2b), and 5°C at 10°C and 25°C (Figure 2c). Cell cycling at 60°C (10°C) resulted in a 30.8% loss of discharge capacity, while at 25°C (5°C) and 10°C (5°C) the capacity losses were 9.2% and 15.5%, respectively. Variable temperature cycling of NWO / LFP cells was performed for 1000 cycles at a 5°C rate. At temperatures of 10, 25, and 60°C (Figure 2e), capacity losses of 6.9%, 7.9%, and 18.1% were observed over 1000 cycles. This suggests that the NWO / LFP combination has superior cycle stability and operating temperature range compared to the NWO / NMC using the electrolytes used here.

[0129] [Example 2] Multiple cells were constructed with different capacities ranging from 0.1 Ah to 5 Ah. The anodes contained small plates, such as platelet-like graphite, with a lithium niobium oxide surface layer. A slurry of 92% active material, 3% conductive material, and 5% binder (PVDF or SBR / CMC) was prepared, mixed, and deposited as a coating on a current collector such as aluminum or copper. This was paired with a cathode containing a lithium metal oxide such as NMC622 or N811 and wound together with a polypropylene or polyethylene separator to obtain a jelly roll (see Figure 5).

[0130] The jelly rolls were placed in a metal can or pouch (Figure 5), filled with an electrolyte containing a lithium salt such as LiPF6, and sealed. The sealed cells were charged using an external power supply in constant current, constant voltage mode to charge the cells to a desired voltage such as 3V or 4.2V, and then discharged to 1V or 0V by constant current.

[0131] For a 1Ah cell, 1C is equivalent to a charge or discharge current of 1A, meaning the cell will be fully charged / discharged in 1 hour. At 2C, the same cell will be charged / discharged in 0.5 hours, and at 0.5C, it will be charged / discharged in 2 hours. Cycle data is generated by varying the C rate or current input to the cell during charging or taken from the cell during discharge.

[0132] [Thermal stability] Figure 3 shows the thermal performance stability of a cell with a capacity of 0.16 Ah. The cell was tested at 65°C against a cell without a lithium niobium oxide surface layer. The discharge rate was 0.5C (155 mhA), and the charge rate was varied between 0.5C and 10C (Figure 3a). Cells with uncoated anodes showed nearly 50% capacity loss at a 10C charge, while cells with anodes having a surface niobium-containing metal oxide layer showed less than 15% capacity loss at 10C. The long-term cycle characteristics of the coated cells were evaluated over 500 cycles under a 12C charge and 0.5C discharge regime (Figure 3b). The uncoated cells showed nearly 50% capacity loss over 500 cycles at 65°C. In contrast, cells with coated anodes showed almost no capacity loss (less than 5%) over 500 cycles at 65°C.

[0133] Figures 3c and 3d show a comparison of cycles at 60°C and 25°C for cells containing lithium niobium-coated anodes. In the cell cycles at the tested C rates, the capacity loss was only 20% (Figure 3c), and the capacity was almost maintained over 400 cycles (Figure 3d). This demonstrates that anode cells coated with niobium-containing metal oxides exhibit superior cycle stability at high temperatures compared to uncoated anode cells.

[0134] [Additional examples] The negative electrode composition constructed an additional cell containing platelet-like graphite with a niobium tungsten oxide surface. The cell also exhibited excellent cycle stability at high temperatures.

Claims

1. A method for charging an electrochemical cell, wherein the electrochemical cell includes a working electrode having a niobium-containing metal oxide surface, the working electrode includes a surface layer of niobium-containing metal oxide disposed on a secondary battery electrode active material, the working electrode is the anode during the discharge of the electrochemical cell, and the niobium-containing metal oxide is Nb ２ O ５ Polymorph, NbO ２ , Nb ２ O ３ A method comprising charging the electrochemical cell at a C-rate of at least 10C, selected from niobium tungsten oxide, titanium niobium oxide, niobium molybdenum oxide, niobium vanadium oxide, or a combination thereof.

2. The method according to claim 1, wherein the temperature of the electrochemical cell is 45°C or higher.

3. The method according to claim 1, wherein the temperature of the electrochemical cell is 10°C or lower.

4. The method according to any one of claims 1 to 3, wherein the niobium-containing metal oxide layer has a maximum thickness of 4.5 nm or less.

5. wherein the niobium-containing metal oxide is Nb ２ O ５ polymorph, NbO ２ , Nb ２ O ３ or a combination thereof, the method according to any one of claims 1 to 4.

6. The method according to any one of claims 1 to 5, wherein the niobium-containing metal oxide is doped with an element selected from phosphorus, aluminum, copper, chromium, zirconium, and vanadium.

7. The method according to any one of claims 1 to 6, wherein the niobium-containing metal oxide is selected from niobium tungsten oxide, titanium niobium oxide, niobium molybdenum oxide, niobium vanadium oxide, or a combination thereof.

8. The method according to claim 7, wherein the niobium-containing metal oxide is niobium tungsten oxide.

9. The niobium-containing metal oxide is Nb １６ W ５ O ５５ The method according to claim 8.

10. The method according to any one of claims 1 to 9, wherein the niobium-containing metal oxide layer is disposed on the particles of the secondary battery electrode active material.

11. The method according to any one of claims 1 to 9, wherein the niobium-containing metal oxide layer is disposed on the film of the secondary battery electrode active material.

12. The method according to any one of claims 1 to 11, wherein the secondary battery electrode active material is selected from carbon, silicon, or a metal oxide.

13. The method according to claim 12, wherein the secondary battery electrode active material is selected from graphite, reduced graphite oxide, or hard carbon.

14. The method according to claim 12, wherein the secondary battery electrode active material is selected from lithium titanate, titanium tantalum oxide, tantalum molybdenum oxide, and lithium vanadium oxide.

15. The electrochemical cell includes a cycle of charging and discharging, or discharging and charging, The method according to any one of claims 1 to 14, comprising two or more cycles.

16. The method according to claim 15, comprising 1,000 cycles or more.

17. An electrochemical cell comprising a working electrode, wherein the working electrode comprises a surface layer of a niobium-containing metal oxide disposed on a secondary battery electrode active material, An electrochemical cell in which the working electrode is an anode during the discharge step of the electrochemical cell, the niobium-containing metal oxide is selected from niobium tungsten oxide, titanium niobium oxide, niobium molybdenum oxide, niobium vanadium oxide, or a combination thereof, and the electrochemical cell is rechargeable at a C rate of at least 5C.

18. The electrochemical cell according to claim 17, wherein the niobium-containing metal oxide layer has a maximum thickness of 45 nm or less.

19. The electrochemical cell according to claim 17 or 18, wherein the niobium-containing metal oxide is doped with an element selected from phosphorus, aluminum, copper, chromium, zirconium, and vanadium.

20. The electrochemical cell according to any one of claims 17 to 19, wherein the niobium-containing metal oxide is niobium tungsten oxide.

21. The niobium-containing metal oxide is Nb １６ W ５ O ５５ The electrochemical cell according to claim 20.

22. The electrochemical cell according to any one of claims 17 to 21, wherein the niobium-containing metal oxide layer is disposed on a film of secondary battery electrode active material.

23. The electrochemical cell according to any one of claims 17 to 21, wherein the layer of niobium-containing metal oxide is arranged on particles of secondary battery electrode active material.

24. The electrochemical cell according to any one of claims 17 to 23, wherein the secondary battery electrode active material is selected from carbon, silicon, or a metal oxide.

25. The electrochemical cell according to claim 24, wherein the secondary battery electrode active material is selected from graphite, reduced graphite oxide, or hard carbon.

26. The electrochemical cell according to claim 25, wherein the secondary battery electrode active material is selected from lithium titanate, titanium tantalum oxide, tantalum molybdenum oxide, and lithium vanadium oxide.

27. The temperature of the electrochemical cell is 45°C or higher, or The electrochemical cell according to any one of claims 17 to 26, wherein the temperature of the electrochemical cell is 10°C or lower.

28. The use of a working electrode having a niobium-containing metal oxide surface, wherein the working electrode includes a surface layer of a niobium-containing metal oxide disposed on a secondary battery electrode active material for use as an anode of an electrochemical cell during charging, and the niobium-containing metal oxide is Nb ２ O ５ Polymorph, NbO ２ , Nb ２ O ３ The use of a working electrode selected from, or a combination thereof, niobium tungsten oxide, titanium niobium oxide, niobium molybdenum oxide, niobium vanadium oxide, or a combination thereof, wherein the electrochemical cell is charged at a C rate of at least 10 C.

29. The temperature of the electrochemical cell during charging or discharging is 45°C or higher, The use of the working electrode according to claim 28, wherein the temperature of the electrochemical cell during charging or discharging is 10°C or less.

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