Patent Application
20150037679
The present invention relates to electrodes that contain an active material comprising a metallate group, and to the use of such electrodes, for example in sodium and lithium 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. When a sodium-ion (or lithium-ion battery) is charging, Na+ (or Li+) ions de-intercalate and migrate towards the anode. Meanwhile 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. Once a circuit is completed electrons pass back from the anode to the cathode and the Na+ (or Li+) ions travel back to the anode.
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. By contrast 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.
From the prior art, for example in the Journal of Solid State Chemistry 180 (2007) 1060-1067, L. Viciu et al disclosed the synthesis, structure and basic magnetic properties of Na2Co2TeO6 and Na3Co2SbO6. Also in Dalton Trans 2012, 41, 572, Elena A. Zvereva et al disclosed the preparation, crystal structure and magnetic properties of Li3Ni2SbO6. Neither of these documents discusses the use of such compounds as electrode materials in sodium- or lithium-ion batteries.
In a first aspect, 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.
Therefore, the present invention provides an electrode that contains an active material of the formula:
In a preferred embodiment of an electrode of the above formula, one or more of a, b, x and y are integers, i.e. whole numbers. In an alternative embodiment, one or more of a, b, x and y are non-integers, i.e. fractions.
Preferably M comprises one or more transition metals and/or one or more non-transition metals and/or one or more metalloids selected from titanium, vanadium, chromium, molybdenum, tungsten, manganese, iron, osmium, cobalt, nickel, palladium, platinum, copper, silver, gold, zinc, cadmium, magnesium, calcium, beryllium, strontium, barium, aluminium and boron, and particularly preferred is an electrode containing an active material wherein M is selected from one or more of copper, nickel, cobalt, manganese, titanium, aluminium, vanadium, magnesium and iron.
The term “metalloids” as used herein is intended to refer to elements which have both metal and non-metal characteristics, for example boron.
We have found it advantageous that the electrode contains an active material wherein at least one of the one or more transition metals has an oxidation state of +2 and at least one of the one or more non-transition metals has an oxidation state of +2.
Other suitable electrodes contain an active material wherein at least one of the one or more transition metals has an oxidation state of either +2 or +3 and at least one of the one or more non-transition metals has an oxidation state of +3.
Preferred electrodes contain an active material of the formula: AaMbSbxOy, wherein A is one or more alkali metals selected from lithium, sodium and potassium and M is one or more metals selected from cobalt, nickel, manganese, titanium, iron, copper, aluminium, vanadium and magnesium.
Alternative preferred electrodes contain an active material of the formula: AaMbTexOy, wherein A is one or more alkali metals selected from lithium, sodium and potassium and M is one or more metals selected from cobalt, nickel, manganese, titanium, iron, copper, aluminium, vanadium and magnesium.
As described above it is typical that a may be in the range 0<a≦6; b may be in the range: 0<b≦4; x may be in the range 0<x≦1 and y may be in the range 2≦y≦10. Preferably, however, a may be in the range 0<a≦5; b may be in the range 0≦b≦3; 0.5≦x≦1; and y may be in the range 2≦y≦9. Alternatively, a may be in the range 0<a≦5; b may be in the range 0<b≦2; x may be in the range 0<x≦1; and 2≦y≦8. As mentioned above, one or more of a, b, x and y may be integers or non-integers.
Extremely beneficial electrochemical results are expected for electrodes that contain one or more active materials: Na3Ni2SbO6, Na3Ni1.5Mg0.5SbO6, Na3Co2SbO6, Na3Co1.5Mg0.5SbO6, Na3Mn2SbO6, Na3Fe2SbO6, Na3Cu2SbO6, Na2AlMnSbO6, Na2AlNiSbO6, Na2VMgSbO6, NaCoSbO4, NaNiSbO4, NaMnSbO4, Na4FeSbO6, Na0.8CO0.6Sb0.4O2, Na0.8Ni0.6Sb0.4O4, Na2Ni2TeO6, Na2Co2TeO6, Na2Mn2TeO6, Na2Fe2TeO6, Na3Ni2-z,MgzSbO6 (0≦z≦0.75), Li3Ni1.5Mg0.5SbO6, Li3Ni2SbO6, Li3Mn2SbO6, Li3Fe2SbO6, Li3Ni1.5Mg0.5SbO6, Li3Cu2SbO6, Li3Co2SbO6, Li2Co2TeO6, Li2Ni2TeO6, Li2Mn2TeO6, LiCoSbO4, LiNiSbat, LiMnSbO4, Li3CuSbO5, Na4NiTeO6, Na2NiSbO5, Li2NiSbO5, Na4Fe3SbO9, Li4Fe3SbO9, Na2Fe3SbO8, Na5NiSbO6, Li5NiSbO6, Na4MnSbO6, Li4MnSbO6, Na3MnTeO6, Li3MnTeO6, Na3FeTeO6, Li3FeTeO6, Na4Fe1-z(Ni0.5Ti0.5)zSbO6 (0≦z≦1), Na4Fe0.5Ni0.25Ti0.25SbO6, Li4Fe1-z(Ni0.51Ti0.5)zSbO6 (0≦z≦1), Li4Fe0.5Ni0.25Ti0.25SbO6, Na4Fe1-z(Ni0.5Mn0.5)zSbO6 (0≦z≦1), Na4Fe0.5Ni0.25Mn0.25)zSbO6, Li4Fe1-z(Ni0.5Mn0.5)zSbO6 (0≦z≦1), Li4Fe0.5Ni0.25Mn0.25SbO6, Na5-zNi1-zFezSbO6 (0≦z≦1), Na4.5Ni0.5Fe0.5SbO6, Li5-zNi1-zFezSbO6 (0≦z≦1), Li4.5Ni0.5Fe0.5SbO6, Na3Ni1.75Zn0.25SbO6, Na3Ni1.75Cu0.25SbO6, Na3Ni1.50Mn0.50SbO6, Li4FeSbO6 and Li4NiTeO6.
It is convenient to use an electrode according to the present invention in an energy storage device, particularly an energy storage device for use as one or more of the following: a sodium and/or lithium ion and/or potassium cell, a sodium and/or lithium and/or potassium metal ion cell, a non-aqueous electrolyte sodium and/or lithium and/or potassium ion cell, an aqueous electrolyte sodium and/or lithium and/or potassium ion cell.
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.
Advantageously, 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.
In a second aspect, the present invention provides a novel material of the formula: A3Ni2-zMgzSbO6, wherein A is one or more alkali metals selected from lithium, sodium and potassium and z is in the range 0<z<2.
In a third aspect, the present invention provides a novel material of the formula:
Na3Mn2SbO6.
In a third aspect, the present invention provides a novel material of the formula:
Na3Fe2SbO6.
The active materials of the present invention may be prepared using any known and/or convenient method. For example, the precursor materials may be heated in a furnace so as to facilitate a solid state reaction process. Further, 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:
1. Mixing the sodium-ion rich material with an excess of a lithium-ion material e.g. LiNO3, heating to above the melting point of LiNO3 (264° C.), cooling and then washing to remove the excess LiNO3;
2. Treating the Na-ion rich material with an aqueous solution of lithium salts, for example 1M LiCl 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 will now be described with reference to the following drawings in which:
Active materials used in the present invention are prepared on a laboratory scale using the following generic method:
Generic Synthesis 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 between 400° C. and 1200° C. until reaction product forms. When cool, the reaction product is removed from the furnace and ground into a powder.
Using the above method, active materials used in the present invention were prepared as summarised below in Examples 1 to 40
Product Analysis using XRD
All of the product materials were analysed by X-ray diffraction techniques using a Siemens D5000 powder diffractometer to confirm that the desired target materials had been prepared and to establish the phase purity of the product material and to determine the types of impurities present. From this information it is possible to determine the unit cell lattice parameters.
The general operating conditions used to obtain the XRD spectra are as follows:
Slits sizes: 1 mm, 1 mm, 0.1 mm
Range: 20=5°-60°
X-ray Wavelength=1.5418 Å) (Cu Kα)
Speed: 0.5 or 1.0 second/step
Increment: 0.015° or 0.025°
Electrochemical Results
The target materials were tested in a lithium metal anode test electrochemical cell to determine their specific capacity and also to establish whether they have the potential to undergo charge and discharge cycles. A lithium metal anode test electrochemical cell containing the active material is constructed as follows:
Generic Procedure to Make A Lithium Metal Test Electrochemical Cell
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.) is used as the binder, and 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. Optionally, an aluminium current collector may be used to contact the positive electrode. Metallic lithium on a copper current collector may be employed as the negative electrode. The electrolyte comprises one of the following: (i) a 1 M solution of LiPF6 in ethylene carbonate (EC) and dimethyl carbonate (DMC) in a weight ratio of 1:1; (ii) a 1 M solution of LiPF6 in ethylene carbonate (EC) and diethyl carbonate (DEC) in a weight ratio of 1:1; or (iii) a 1 M solution of LiPF6 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.
Generic Procedure to Make a Hard Carbon Na-ion Cell
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.) is used as the binder, and 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. Optionally, an aluminium current collector may be used to contact the positive electrode.
The negative electrode is prepared by solvent-casting a slurry of the hard carbon active material (Carbotron P/J, supplied by Kureha), conductive carbon, binder and solvent. The conductive carbon used is Super P (Timcal). PVdF co-polymer (e.g. Kynar Flex 2801, Elf Atochem Inc.) is used as the binder, and 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: 84% active material, 4% Super P carbon, and 12% Kynar 2801 binder. Optionally, a copper current collector may be used to contact the negative electrode.
Generic Procedure to Make a Graphite Li-ion Cell
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.) is used as the binder, and 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. Optionally, an aluminium current collector may be used to contact the positive electrode.
The negative electrode is prepared by solvent-casting a slurry of the graphite active material (Crystalline Graphite, supplied by Conoco Inc.), conductive carbon, binder and solvent. The conductive carbon used is Super P (Timcal). PVdF co-polymer (e.g. Kynar Flex 2801, Elf Atochem Inc.) is used as the binder, and 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: 92% active material, 2% Super P carbon, and 6% Kynar 2801 binder. Optionally, a copper current collector may be used to contact the negative electrode.
Cell Testing
The cells are tested as follows using Constant Current Cycling techniques.
The cell is cycled at a given current density between pre-set voltage limits. A commercial battery cycler from Maccor Inc. (Tulsa, Okla., USA) is used. On charge, sodium (lithium) ions are extracted from the active material. During discharge, sodium (lithium) ions are re-inserted into the active material.
Results:
Na3Ni2SbO6 Prepared according to Example 1.
Referring to
Na3Cu2SbO6 Prepared according to Example 22.
Referring to
Na2Ni2TeO6 Prepared according to Example 28.
Referring to
It is expected from thermodynamic considerations that the sodium extracted from the Na2Ni2TeO6 active material during the initial charging process, enters the electrolyte, and would then be displacement ‘plated’ onto the lithium metal anode (i.e. releasing more lithium into the electrolyte). Therefore, during the subsequent discharging of the cell, it is assumed that a mix of lithium and sodium ions is re-inserted into the active material. The re-insertion process corresponds to 43 mAh/g; indicating the reversibility of the ion extraction-insertion processes. The generally symmetrical nature of the charge-discharge curves further indicates the excellent reversibility of the system. In addition, the level of voltage hysteresis (i.e. the voltage difference between the charge and discharge processes) is extremely small, indicating the excellent kinetics of the extraction-insertion reactions. This is an important property that is useful for producing a high rate active material.
Li3Ni2SbO6 Prepared according to Example 19.
Referring to
Na3Ni1.5Mg0.5SbO6 Prepared according to Example 34C.
Referring to
To fully charge the cell the Na-ion cell was potentiostatically held at 4.2 V at the end of the constant current charging process. The testing was carried out at room temperature. It is shown that sodium ions are extracted from the cathode active material, Na3Ni1.6Mg0.6SbO6, and inserted into the Hard Carbon anode during the initial charging of the cell. During the subsequent discharge process, sodium ions are extracted from the Hard Carbon and re-inserted into the Na3Ni1.6Mg0.5SbO6 cathode active material. The first discharge process corresponds to a specific capacity for the cathode of 91 mAh/g, indicating the reversibility of the sodium ion extraction-insertion processes. The generally symmetrical nature of the charge-discharge curves further indicates the excellent reversibility of the system. In addition, the level of voltage hysteresis (i.e. the voltage difference between the charge and discharge processes) is extremely small, indicating the excellent kinetics of the extraction-insertion reactions. This is an important property that is useful for producing a high rate active material.
Li3Ni1.5Mg0.5SbO6 Prepared according to Example 17.
Referring to
Na3Ni1.76Zn0.26SbO6 Prepared According to Example 35.
Na3Ni1.75Cu0.25SbO6 Prepared According to Example 36.
Na3Ni1.25Mg0.75SbO6 Prepared According to Example 34d.
During the subsequent discharge process, sodium ions are extracted from the Hard Carbon and re-inserted into the cathode active material. The initial cathode specific capacity (cycle 1) is 83 mAh/g. The Na-ion cell cycles more than 40 times with low capacity fade.
Na3Ni1.50Mn0.50SbO6 Prepared According to Example 37.
Li4FeSbO6 Prepared According to Example 38.
Li4NiTeO6 Prepared According to Example 39
Na4NiTeO6 Prepared According to Example 40.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1205170.2 | Mar 2012 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2013/050736 | 3/21/2013 | WO | 00 |
