Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
  • H01M4/581—Chalcogenides or intercalation compounds thereof
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/052—Li-accumulators
  • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/36—Accumulators not provided for in groups H01M10/05-H01M10/34
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
  • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries

Definitions

• the present invention relates to electrodes that contain an active material comprising a sulfate group, and to the use of such electrodes, for example in sodium ion battery applications.
• the invention also relates to certain novel materials and to the use of these materials, for example as an electrode material.
• Sodium-ion batteries are analogous in many ways to the lithium-ion batteries that are in common use today; they are both reusable secondary batteries that comprise an anode (negative electrode), a cathode (positive electrode) and an electrolyte material, both are capable of storing power in a compact system by accumulating energy in the chemical bonds of the cathode, and they both charge and discharge via a similar reaction mechanism.
• Na + (or Li + ) ions de-intercalate from the cathode and migrate towards the anode.
• charge balancing electrons pass from the cathode through the external circuit containing the charger and into the anode of the battery. During discharge the same process occurs but in the opposite direction.
• Lithium-ion battery technology has enjoyed a lot of attention in recent years and provides the preferred portable battery for most electronic devices in use today; however lithium is not a cheap metal to source and is too expensive for use in large scale applications.
• sodium-ion battery technology is still in its relative infancy but is seen as advantageous; sodium is much more abundant than lithium and researchers predict this will provide a cheaper and more durable way to store energy into the future, particularly for large scale applications such as storing energy on the electrical grid. Nevertheless a lot of work has yet to be done before sodium-ion batteries are a commercial reality.
• the present invention aims to provide a cost effective electrode that contains an active material that is straightforward to manufacture and easy to handle and store.
• a further object of the present invention is to provide an electrode that has a high initial charge capacity and which is capable of being recharged multiple times without significant loss in charge capacity.
• the present invention provides an electrode containing an active material of the formula:
• A is a single or mixed alkali metal phase comprising one or more of sodium, potassium, lithium mixed with sodium, lithium mixed with potassium, and lithium mixed with both sodium and potassium;
• M is selected from one or more transition metals and/or non-transition metals and/or metalloids
• X is a moiety comprising one or more atoms selected from halogen and OH; and further wherein
• the present invention is directed to an electrode that contains an active material of the formula:
• A is selected from one or more of alkali metals
• M is selected from one or more transition metals and/or non-transition metals and/or metalloids
• X is a moiety comprising one or more atoms selected from halogen and OH and further wherein
• the present invention provides an electrode as described above in which the active material comprises one or more transition metals and/or non-transition metals and/or metalloids (M) selected from titanium, vanadium, niobium, tantalum, hafnium, chromium, molybdenum, tungsten, manganese, iron, osmium, cobalt, nickel, palladium, platinum, copper, silver, gold, zinc, cadmium, aluminium, scandium, yttrium, zirconium, technetium, rhenium, ruthenium, rhodium, iridium, mercury, gallium, indium, tin, lead, bismuth and selenium, magnesium, calcium, beryllium, strontium, barium, boron, silicon, germanium, arsenic, antimony and tellurium;
• M transition metals and/or non-transition metals and/or metalloids
• the moiety X preferably comprises one or more atoms selected from fluorine, chlorine, bromine, iodine and hydroxide.
• M comprises one or more elements selected from nickel, cobalt, manganese and iron.
• the molar ratio of a : b : c is 1 : 1 : 1.5.
• Suitable compounds include those with the general formula: A 2 M 2 (S0 4 )3.
• the molar ratio of a : b : c is 1 : 0.5 : 1.
• suitable compounds include those with the general formula: A 2 M(S0 4 ) 2 .
• Na 2 M(S0 4 ) 2 and Na 2 M 2 (S0 4 ) 3 such as Na 2 Fe(S0 4 ) 2 , Na 2 Fe 2 (S0 4 ) 3 , Na 2 Mn(S0 4 ) 2 and Na 2 Mn 2 (S0 4 ) 3 .
• Electrodes according to the present invention are suitable for use in many different applications, for example energy storage devices, rechargeable batteries, electrochemical devices and electrochromic devices.
• the electrodes according to the invention are used in conjunction with a counter electrode and one or more electrolyte materials.
• the electrolyte materials may be any conventional or known materials and may comprise either aqueous electrolyte(s) or non-aqueous electrolyte(s) or mixtures thereof.
• the active materials of the present invention may be prepared using any known and/or convenient method. For example, using a solution reaction using an aqueous or other solvent. However ideally, the starting materials are intimately admixed in particulate form. This can be achieved using various methods, for example by finely grinding the materials separately using a pestle and mortar or a ball mill, and then mixing them together, or the materials can be admixed whilst they are being finely ground. The grinding and admixing is of sufficient duration to produce a uniformly intermixed and finely ground powder.
• a solvent such as acetone or another material which is easily removed, for example a low boiling liquid, can be used to assist the grinding/admixing process and this is preferably removed prior to a heating step.
• Other known techniques such as high energy ball milling and microwave activation may also be used to help prepare the starting materials, for example to increase their reactivity.
• reaction notably some solution reactions, proceed at room temperature.
• active materials are made by heating the precursor materials, for example in a furnace. This is especially useful when the reaction is a solid state reaction process, i.e. a reaction in which all of the reactants are in solid form and are substantially free of any reaction medium such as a solvent. Where a solvent or other low boiling liquid is used to assist the mixing of the reactants, as described above, it is substantially removed prior to the heating step.
• the heating step typically involves heating the reaction mixture either at a single
• reaction temperature or over a range of temperatures, for example up to at least 25 °C, preferably up to at least 50 °C, further preferably up to at least 150°C, and yet further preferably up to 600°C, although for some reactants a single or a range of reaction temperatures up to 1200 °C may be needed.
• the reaction is performed under atmospheric pressure and under a non-oxidising atmosphere, for example nitrogen, argon or another inert gas, or under vacuum.
• the reaction may also be performed in a sealed reaction vessel.
• the reaction temperature is maintained for between 0.5 and 12 hours, although the exact time will depend on the reactivity of the starting materials. A dwell time of 8 hours has been found to be sufficient for many reactions.
• the conversion of a sodium-ion rich material to a lithium-ion rich material may be effected using an ion exchange process.
• Typical ways to achieve Na to Li ion exchange include:
• Treating the Na-ion rich material with an aqueous solution of lithium salts for example 1 M LiCI in water; and 3. Treating the Na-ion rich material with a non-aqueous solution of lithium salts, for example LiBr in one or more aliphatic alcohols such as hexanol, propanol etc.
• the present invention provides an energy storage device
• a sodium ion and/or lithium ion and/or potassium ion cell for use as one or more of the following: a sodium ion and/or lithium ion and/or potassium ion cell; a sodium metal and/ or lithium metal and/or potassium metal ion cell; a non-aqueous electrolyte sodium ion and/or lithium ion and/or potassium ion cell; and an aqueous electrolyte sodium ion and/or
• the energy storage device may be a battery.
• Figure 1A is the XRD of Na 2 Fe(S0 4 ) 2 (X0176) prepared according to Example 1 ;
• Figure 1 B shows the constant current cycling (Electrode Potential versus Cumulative Specific Capacity of Na 2 Fe(SO 4 ) 2 (X0176) (Example 1);
• Figure 1 C shows the constant current cycling (Discharge Specific Capacity versus Cycle Number) of Na 2 Fe(S0 4 ) 2 (X0176) (Example 1);
• Figure 2A is the XRD for Na 2 Fe(S0 4 ) 2 (X0126) prepared according to Example 2;
• Figure 2B shows the results from EVS testing, Electrode Potential (vs lithium) vs Cathode Specific Potential of Na 2 Fe(S0 4 ) 2 (X0126) (Example 2);
• Figure 2C shows the first cycle data for Differential Capacity versus Electrode Potential for Na 2 Fe(S0 4 ) 2 (X0126) (Example 2);
• Figure 3A is the XRD for Na 2 Fe(S0 4 ) 2 (X0182) prepared according to Example 3;
• Figure 3B shows the constant current cycling (Electrode Potential vs Cumulative Specific Capacity) of Na 2 Fe(S0 4 ) 2 (X0182) (Example 3);
• Figure 3C shows constant current cycling (Discharge Specific Capacity vs Cycle Number) of Na 2 Fe(S0 4 ) 2 (X0182) (Example 3);
• Figure 4A is the XRD for Na 2 Fe(S0 4 ) 2 (X0224) prepared according to Example 4;
• Figure 4B shows the constant current cycling (Electrode Potential vs Cumulative Specific Capacity) of Na 2 Fe(S0 4 ) 2 (X0224) (Example 4);
• Figure 4C shows constant current cycling (Discharge Specific Capacity vs Cycle Number) of Na 2 Fe(S0 4 ) 2 (X0224) (Example 4);
• FIGURE 5A is the XRD of Na 2 Fe(S0 4 ) 2 (X0960) prepared according to Example 5;
• FIGURE 5B shows constant current cycling (Electrode Potential (vs sodium reference) vs Cumulative Specific Capacity of Na 2 Fe(S0 4 ) 2 (X0960) (Example 5);
• FIGURE 5C shows constant current cycling (Differential Capacity vs Electrode Potential (vs sodium reference) of Na 2 Fe(S0 4 ) 2 (X0960) (Example 5);
• FIGURE 6A the XRD of Na 2 Fe(S0 4 ) 2 (X0968) prepared according to Example 6;
• FIGURE 6B shows constant current cycling (Electrode Potential (vs sodium reference) vs Cumulative Specific Capacity of Na 2 Fe(S0 4 ) 2 (X0968) (Example 6);
• FIGURE 6C shows constant current cycling (Differential Capacity vs Electrode Potential (vs sodium reference) of Na 2 Fe(S0 4 ) 2 (X0968) (Example 6);
• FIGURE 7A shows the XRD of Na 2 Fe(S0 4 ) 2 (X0985) prepared according to Example 7;
• FIGURE 7B shows constant current cycling (Electrode Potential (vs sodium reference) vs Cumulative Specific Capacity of Na 2 Fe(S0 4 ) 2 (X0985) (Example 7);
• FIGURE 7C shows constant current cycling (Differential Capacity vs Electrode Potential (vs sodium reference) of Na 2 Fe(S0 4 ) 2 (X0985) (Example 7); DETAILED DESCRIPTION
• Active materials used in the present invention are prepared on a laboratory scale using the following generic method:
• the required amounts of the precursor materials are intimately mixed together.
• the resulting mixture is then heated in a tube furnace or a chamber furnace using either a flowing inert atmosphere (e.g. argon or nitrogen) or an ambient air atmosphere, at a furnace temperature of at least 50 °C until reaction product forms.
• a flowing inert atmosphere e.g. argon or nitrogen
• an ambient air atmosphere at a furnace temperature of at least 50 °C until reaction product forms.
• the reaction product is removed from the furnace and ground into a powder.
• test electrochemical cells containing the active material are constructed as follows:
• the positive electrode is prepared by solvent-casting a slurry of the active material, conductive carbon, binder and solvent.
• the conductive carbon used is Super P (Timcal).
• PVdF co-polymer e.g. Kynar Flex 2801 , Elf Atochem Inc.
• acetone is employed as the solvent.
• the slurry is then cast onto glass and a free-standing electrode film is formed as the solvent evaporates.
• the electrode is then dried further at about 80°C.
• the electrode film contains the following components, expressed in percent by weight: 80% active material, 8% Super P carbon, and 12% Kynar 2801 binder.
• an aluminium current collector may be used to contact the positive electrode.
• the electrolyte comprises one of the following: (i) a 1 M solution of LiPF 6 in ethylene carbonate (EC) and dimethyl carbonate (DMC) in a weight ratio of 1 :1 ; (ii) a 1 M solution of LiPF 6 in ethylene carbonate (EC) and diethyl carbonate (DEC) in a weight ratio of 1 : 1 ; or (iii) a 1 M solution of LiPF 6 in propylene carbonate (PC)
• a glass fibre separator (Whatman, GF/A) or a porous polypropylene separator (e.g. Celgard 2400) wetted by the electrolyte is interposed between the positive and negative electrodes.
• the positive electrode is prepared by solvent-casting a slurry of the active material, conductive carbon, binder and solvent.
• the conductive carbon used is Super P (Timcal).
• PVdF co-polymer e.g. Kynar Flex 2801 , Elf Atochem Inc.
• acetone is employed as the solvent.
• the slurry is then cast onto glass and a free-standing electrode film is formed as the solvent evaporates.
• the electrode is then dried further at about 80°C.
• the electrode film contains the following components, expressed in percent by weight: 80% active material, 8% Super P carbon, and 12% Kynar 2801 binder.
• an aluminium current collector may be used to contact the positive electrode.
• the electrolyte comprises a 0.5 M solution of NaCI0 4 in propylene carbonate (PC).
• a glass fibre separator (Whatman, GF/A) or a porous polypropylene separator wetted by the electrolyte is interposed between the positive and negative electrodes.
• the cells are tested in one of two ways:
• EVS Electrochemical Voltage Spectroscopy
• the Cell #1 12032 shows the constant current cycling data for the Na 2 Fe(S0 4 ) 2 active material (X0176) prepared in accordance with Example 1 described above.
• the Open Circuit Voltage (OCV) of the as-made cell was 3.37 V vs. Li.
• the constant current data were collected using a lithium metal counter electrode at an approximate current density of 0.01 mA/cm 2 between voltage limits of 1.00 and 4.20 V.
• the upper voltage limit was increased by 0.1 V on subsequent cycles.
• the testing was carried out at room temperature. It is shown that sodium ions are extracted from the active material during the initial charging of the cell. A charge equivalent to a material specific capacity of 42 mAh/g is extracted from the active material.
• Figure 2B (Cell#11 1066) for Na 2 Fe(S0 4 ) 2 (X0126) made in Example 2 above, shows the first cycle EVS testing for this material.
• the charge (Na ion extraction) process is equivalent to a specific charge capacity of about 42 mAh/g.
• the subsequent discharge process (Na ion insertion) also demonstrates a specific capacity of 42 mAh/g indicating the excellent coulombic (charge) reversibility of this material.
• the voltage hysteresis between charge and discharge is extremely small, indicating the excellent kinetics of the charge-discharge processes.
• the symmetrical nature of the differential capacity profile shown in Figure 2C confirms the excellent charge-discharge reversibility of this material.
• Figure 3B shows the Electrode Potential vs Cumulative Specific Capacity of Na 2 Fe(S0 4 ) 2 (X0182) made by Example 3 in the voltage range 3.0 - 4.2V vs Li (window opening at 4.5V) in 1 M LiPF 6 in EC/DMC.
• the active material demonstrates a discharge specific capacity of around 46mAh/g (4 th discharge) in the voltage range 3.0 - 4.5 V vs Li and confirms the charge-discharge reversibility of this material.
• Figure 3C shows the constant current cycling (Discharge Specific Capacity vs Cycle number) of Na 2 Fe(S0 4 ) 2 (X0182) made by Example 3 in the voltage range 3.0 - 4.2V vs Li (window opening at 4.6V) in 1 M LiPF 6 in EC/DMC.
• the active material demonstrates a discharge specific capacity of around 46mAh/g (4 th discharge) in the voltage range 3.0 - 4.5 V vs Li.
• Figure 4B shows the constant current cycling of Na 2 Fe(S0 4 ) 2 (X0224) made by Example 4 (Electrode Potential vs Cumulative Specific Capacity) in the voltage range 3.0 - 4.2V vs Li (window opening at 4.5V) in 1 M LiPF 6 in EC/DMC.
• the active material demonstrates a discharge specific capacity of around 45mAh/g (4 th discharge) in the voltage range 3.0 - 4.5 V vs Li and confirms the charge-discharge reversibility of this material.
• Figure 4C shows the constant current cycling (Discharge Specific Capacity vs Cycle number) of Na 2 Fe(S0 4 ) 2 (X0224) made by Example 4 in the voltage range 3.0 - 4.2V vs Li (window opening at 4.6V) in 1 M LiPF 6 in EC/DMC.
• the active material demonstrates a discharge specific capacity of around 45mAh/g (4 th discharge) in the voltage range 3.0 - 4.5 V vs Li.
• Figures 5B and 5C show the Constant current testing of the active material Na 2 Fe(S0 4 ) 2 (X0960) Cell#212012 in the voltage range 2.00 - 4.20 V vs. Na in an electrolyte of 0.5M NaCI0 4 in propylene carbonate.
• the Open Circuit Voltage (OCV) of the as-made cell was 3.17 V vs. Na.
• the constant current data were collected using a sodium metal counter electrode at an approximate current density of 0.02 mA/cm 2 between voltage limits of 2.00 and 4.20 V vs. Na.
• the testing was carried out at 30°C.
• Figure 5B shows the relationship between electrode potential (V versus a Na reference) and cumulative specific capacity (in mAh/g).
• Figure 5C shows the relationship between differential capacity (in C/V) and electrode potential (V versus a Na reference) for the second constant current cycle.
• an active material specific capacity of 88 mAh/g was achieved while during the first discharge process an active material specific capacity of 49 mAh/g was achieved.
• the generally symmetrical nature of the charge-discharge curves indicates the excellent reversibility of the system.
• the level of voltage hysteresis i.e. the voltage difference between the charge and discharge processes
• the symmetrical nature of the differential capacity profile further indicates the reversibility of the ion insertion/extraction reactions.
• Figures 6B and 6C show the Constant current testing of the active material Na 2 Fe(S0 4 ) 2 (X0968) Cell#211083 in the voltage range 2.50 - 4.20 V vs. Na in an electrolyte of 0.5M NaCI0 4 in propylene carbonate.
• the Open Circuit Voltage (OCV) of the as-made cell was 3.14 V vs. Na.
• the constant current data were collected using a sodium metal counter electrode at an approximate current density of 0.02 mA/cm 2 between voltage limits of 2.50 and 4.20 V vs. Na. The testing was carried out at 30°C.
• Figure 6B shows the relationship between electrode potential (V versus a Na reference) and cumulative specific capacity (in mAh/g).
• Figure 6C shows the relationship between differential capacity (in C/V) and electrode potential (V versus a Na reference) for the second constant current cycle.
• an active material specific capacity of 88 mAh/g was achieved while during the first discharge process an active material specific capacity of 60 mAh/g was achieved.
• the generally symmetrical nature of the charge-discharge curves indicates the excellent reversibility of the system.
• the level of voltage hysteresis i.e. the voltage difference between the charge and discharge processes
• the symmetrical nature of the differential capacity profile further indicates the reversibility of the ion insertion/extraction reactions.
• Figures 7B and 7C show the Constant current testing of the active material Na 2 Fe(S0 4 ) 2 (X0985) Cell#212012. in the voltage range 2.50 - 4.20 V vs. Na in an electrolyte of 0.5M NaCI0 4 in propylene carbonate.
• the Open Circuit Voltage (OCV) of the as-made cell was 3.21 V vs. Na.
• the constant current data were collected using a sodium metal counter electrode at an approximate current density of 0.02 mA/cm 2 between voltage limits of 2.50 and 4.20 V vs. Na. The testing was carried out at 30°C.
• Figure 7B shows the relationship between electrode potential (V versus a Na reference) and cumulative specific capacity (in mAh/g).
• Figure 7C shows the relationship between differential capacity (in C/V) and electrode potential (V versus a Na reference) for the second constant current cycle.
• an active material specific capacity of 74 mAh/g was achieved while during the first discharge process an active material specific capacity of 51 mAh/g was achieved.
• the generally symmetrical nature of the charge-discharge curves indicates the excellent reversibility of the system.
• the level of voltage hysteresis i.e. the voltage difference between the charge and discharge processes
• the symmetrical nature of the differential capacity profile further indicates the reversibility of the ion insertion/extraction reactions.

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