Abstract
The invention relates to doped nickelate-containing material with the general formula: A.sub.a M.sup.1.sub.v M.sup.2.sub.w M.sup.3.sub.x M.sup.4.sub.y M.sup.5.sub.z O.sub.2- wherein A comprises one or more alkali metals selected from sodium, lithium and potassium; M.sup.1 is nickel in oxidation state 2+, M.sup.2 comprises one or more metals in oxidation state 4+, M.sup.3 comprises one or more metals in oxidation state 2+, M.sup.4 comprises one or more metals in oxidation state 4+, and M.sup.5 comprises one or more metals in oxidation state 3+ wherein 0.4a<0.9, 0<v<0.5, at least one of w and y is >0, x>0, z0, 00.1, and wherein a, v, w, x, y and z are chosen to maintain electroneutrality.
Claims
1. A doped nickelate material with the general formula:
A.sub.aM.sup.1.sub.vM.sup.2.sub.wM.sup.3.sub.xM.sup.4.sub.yM.sup.5.sub.zO.sub.2- wherein A comprises one or more alkali metals selected from sodium, lithium and potassium; M.sup.1 is nickel in oxidation state 2+, M.sup.2 comprises one or more metals in oxidation state 4+, M.sup.3 comprises one or more metals in oxidation state 2+, M.sup.4 comprises one or more metals in oxidation state 4+, and M.sup.5 comprises one or more metals in oxidation state 3+ wherein 0.4a<0.9, 0<v<0.5, at least one of w and y is >0, x>0, z0, 00.1, and wherein a, v, w, x, y and z are chosen to maintain electroneutrality.
2. A doped nickelate material according to claim 1 wherein M.sup.2 comprises one or more metals selected from manganese, titanium and zirconium; M.sup.3 comprises one or more metals selected from magnesium, calcium, copper, zinc and cobalt; M.sup.4 comprises one or more metals selected from manganese, titanium and zirconium; and M.sup.5 comprises one or more metals selected from aluminium, iron, cobalt, molybdenum, chromium, vanadium, scandium and yttrium.
3. A doped nickelate material according to claim 1 selected from one or more of Na.sub.0.67Ni.sub.0.300Mn.sub.0.600Mg.sub.0.033Ti.sub.0.067O.sub.2, Na.sub.0.67Ni.sub.0.267Mn.sub.0.533Mg.sub.0.067Ti.sub.0.133O.sub.2, Na.sub.0.67Ni.sub.0.283Mn.sub.0.567Mg.sub.0.05Ti.sub.0.1O.sub.2, Na.sub.0.67Ni.sub.0.25Mn.sub.0.667Mg.sub.0.083O.sub.2, Na.sub.0.7Ni.sub.0.240Mn.sub.0.533Mg.sub.0.110Ti.sub.0.117O.sub.2, Na.sub.0.6Ni.sub.0.240Mn.sub.0.533Mg.sub.0.060Ti.sub.0.167O.sub.2, Na.sub.0.67Ni.sub.0.240Mn.sub.0.533Mg.sub.0.093Ti.sub.0.133O.sub.2, Na.sub.0.55Ni.sub.0.240Mn.sub.0.533Mg.sub.0.035Ti.sub.0.192O.sub.2, Na.sub.0.67Ni.sub.0.240Mn.sub.0.533Mg.sub.0.043Ti.sub.0.083Fe.sub.0.100O.sub.2 and Na.sub.0.67 Ni.sub.0.240 Mn.sub.0.533 Mg.sub.0.043 Ti.sub.0.083 Al.sub.0.100O.sub.2.
4. A doped nickelate material according to claim 1 comprising a layered P2-type structure.
5. A process for preparing a doped nickelate material according to claim 1 comprising the steps: a) mixing together one or more precursor materials that comprise one or more metals selected from A, M.sup.1, M.sup.2, M.sup.3, M.sup.4 and M.sup.5, in a stoichiometric ratio that corresponds with the amount of the respective one or more metals A, M.sup.1, M.sup.2, M.sup.3, M.sup.4 and M.sup.5 present in the doped nickelate material; and b) heating the resulting mixture in a furnace at a single temperature or over a range of temperatures between 400 C. and 1500 C. until reaction product forms.
6. Use of one or more doped nickelate materials according to claim 1 in an application device selected from an energy storage device, a battery, a rechargeable battery, an electrochemical device, an electrochromic device and a Na-ion cell.
7. A battery comprising one or more doped nickelate materials according to claim 1.
8. An electrode comprising one or more doped nickelate materials according to claim 1.
9. A positive electrode comprising one or more doped nickelate materials according to claim 1.
10. A process for storing electrical charge comprising the use of a device comprising one or more doped nickelate materials according to claim 1.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The present invention will now be described with reference to the following figures in which:
(2) FIG. 1(A) is the XRD profile for the known compound P2-Na.sub.0.67Ni.sub.0.33Mn.sub.0.67O.sub.2 used in Example 1 (comparative example);
(3) FIG. 1(B) shows the cell voltage profile (i.e. Na-ion Cell Voltage [V] versus Cumulative Cathode Specific Capacity [mAh/g]) for the first 4 charge/discharge cycles of the Hard Carbon//Na.sub.0.67Ni.sub.0.33Mn.sub.0.67O.sub.2 cell;
(4) FIG. 1(C) shows the Constant current cycling (CC/CV) of full Na-ion Cell comprising hard carbon (Carbotron P(J) Kureha) and P2-Na.sub.0.67Ni.sub.0.33Mn.sub.0.67O.sub.2 in the voltage range 1.0-4.2V at 30 C. in 0.5M NaClO.sub.4, with propylene carbonate (PC) and glass fibre filter paper (Whatman Grade GF/A) used as a separator;
(5) FIG. 2(A) is the XRD profile for the P2-Target Active Material of the present invention with the formula: P2-Na.sub.0.67Ni.sub.0.3Mn.sub.0.6Mg.sub.0.033Ti.sub.0.067O.sub.2, as made in Example 2;
(6) FIG. 2(B) shows the cell voltage profile (i.e. Na-ion Cell Voltage [V] versus Cumulative Cathode Specific Capacity [mAh/g]) for the first 4 charge/discharge cycles of the Hard Carbon//P2-Na.sub.0.67Ni.sub.0.3Mn.sub.0.6Mg.sub.0.033Ti.sub.0.067O.sub.2 cell;
(7) FIG. 2(C) shows the Constant current cycling (CC/CV) of full Na-ion Cell comprising hard carbon (Carbotron P(J) Kureha) and P2-Na.sub.0.67Ni.sub.0.3Mn.sub.0.6Mg.sub.0.033Ti.sub.0.067O.sub.2 in the voltage range 1.0-4.2V at 30 C. in 0.5M NaClO.sub.4, propylene carbonate (PC) and GF/A;
(8) FIG. 3(A) is the XRD profile for the P2-Target Active Material of the present invention with the formula: P2-Na.sub.0.67Ni.sub.0.267Mn.sub.0.533Mg.sub.0.067Ti.sub.0.133O.sub.2, as made in Example 3;
(9) FIG. 3(B) shows the cell voltage profile (i.e. Na-ion Cell Voltage [V] versus Cumulative Cathode Specific Capacity [mAh/g]) for the first 4 charge/discharge cycles of the Hard Carbon//P2-Na.sub.0.67Ni.sub.0.267Mn.sub.0.533Mg.sub.0.067Ti.sub.0.133O.sub.2 cell;
(10) FIG. 3(C) shows the Constant current cycling (CC/CV) of full Na-ion Cell comprising hard carbon (Carbotron P(J) Kureha) and P2-Na.sub.0.67Ni.sub.0.267Mn.sub.0.533Mg.sub.0.067Ti.sub.0.133O.sub.2 in the voltage range 1.0-4.2V at 30 C. in 0.5M NaClO.sub.4, propylene carbonate (PC) and GF/A;
(11) FIG. 4(A) is the XRD profile for the P2-Target Active Material of the present invention with the formula: P2-Na.sub.0.67Ni.sub.0.25Mn.sub.0.667Mg.sub.0.083O.sub.2, as made in Example 4;
(12) FIG. 4(B) shows the cell voltage profile (i.e. Na-ion Cell Voltage [V] versus Cumulative Cathode Specific Capacity [mAh/g]) for the first 4 charge/discharge cycles of the Hard Carbon//P2-Na.sub.0.67Ni.sub.0.25Mn.sub.0.667Mg.sub.0.83O.sub.2 cell
(13) FIG. 4(C) shows the Constant current cycling (CC/CV) of full Na-ion Cell comprising hard carbon (Carbotron P(J) Kureha) and P2-Na.sub.0.67Ni.sub.0.25Mn.sub.0.667Mg.sub.0.083O.sub.2 in the voltage range 1.0-4.2V at 30 C. in 0.5M NaClO.sub.4, propylene carbonate (PC) and GF/A;
(14) FIG. 5(A) is the XRD profile for the P2-Target Active Material of the present invention with the formula: P2-Na.sub.0.67Ni.sub.0.283Mn.sub.0.567Mg.sub.0.05Ti.sub.0.10O.sub.2, as made in Example 5;
(15) FIG. 5(B) shows the cell voltage profile (i.e. Na-ion Cell Voltage [V] versus Cumulative Cathode Specific Capacity [mAh/g]) for the first 4 charge/discharge cycles of the Hard Carbon//P2-Na.sub.0.67Ni.sub.0.283Mn.sub.0.567Mg.sub.0.05Ti.sub.0.10O.sub.2 cell;
(16) FIG. 5(C) shows the Constant current cycling (CC/CV) of full Na-ion Cell comprising hard carbon (Carbotron P(J) Kureha) and P2-Na.sub.0.67Ni.sub.0.283Mn.sub.0.567Mg.sub.0.05Ti.sub.0.1O.sub.2 in the voltage range 1.0-4.2V at 30 C. in 0.5M NaClO.sub.4, propylene carbonate (PC) and GF/A;
(17) FIG. 6(A) is the XRD profile for the P2-Target Active Material of the present invention with the formula: P2-Na.sub.0.70Ni.sub.0.240Mn.sub.0.533Mg.sub.0.110Ti.sub.0.117O.sub.2, as made in Example 6;
(18) FIG. 6(B) shows the cell voltage profile (i.e. Na-ion Cell Voltage [V] versus Cumulative Cathode Specific Capacity [mAh/g]) for the first 4 charge/discharge cycles of the Hard Carbon//P2-Na.sub.0.70Ni.sub.0.240Mn.sub.0.533Mg.sub.0.110Ti.sub.0.117O.sub.2 cell;
(19) FIG. 6(C) shows the Constant current cycle life profile (cathode specific capacity for discharge versus cycle number) for a full Na-ion Cell comprising hard carbon (Carbotron P(J) Kureha) and P2-Na.sub.0.70Ni.sub.0.240Mn.sub.0.533Mg.sub.0.110Ti.sub.0.117O.sub.2 in the voltage range 1.0-4.3V at 30 C. in 0.5M NaPF.sub.6 in ethylene carbonate/diethyl carbonate/propylene carbonate;
(20) FIG. 7(A) is the XRD profile for the P2-Target Active Material of the present invention with the formula: P2-Na.sub.0.60Ni.sub.0.240Mn.sub.0.533Mg.sub.0.060Ti.sub.0.167O.sub.2, as made in Example 7;
(21) FIG. 7(B) shows the cell voltage profile (i.e. Na-ion Cell Voltage [V] versus Cumulative Cathode Specific Capacity [mAh/g]) for the first 4 charge/discharge cycles of the Hard Carbon//P2-Na.sub.0.60Ni.sub.0.240Mn.sub.0.533Mg.sub.0.060Ti.sub.0.167O.sub.2 cell;
(22) FIG. 7(C) shows the Constant current cycle life profile (Cathode specific Capacity for Discharge versus cycle number) for a full Na-ion Cell comprising hard carbon (Carbotron P(J) Kureha) and P2-Na.sub.0.60Ni.sub.0.240Mn.sub.0.533Mg.sub.0.060Ti.sub.0.167O.sub.2 in the voltage range 1.0-4.3V at 30 C. in 0.5M NaPF.sub.6 in ethylene carbonate/diethyl carbonate/propylene carbonate;
(23) FIG. 8(A) is the XRD profile for the P2-Target Active Material of the present invention with the formula: P2-Na.sub.0.67Ni.sub.0.240Mn.sub.0.533Mg.sub.0.093Ti.sub.0.133O.sub.2, as made in Example 8;
(24) FIG. 8(B) shows the cell voltage profile (i.e. Na-ion Cell Voltage [V] versus Cumulative Cathode Specific Capacity [mAh/g]) for the first 4 charge/discharge cycles of the Hard Carbon//P2-Na.sub.0.67Ni.sub.0.240Mn.sub.0.533Mg.sub.0.093Ti.sub.0.133O.sub.2 cell;
(25) FIG. 8(C) shows the Constant current cycle life profile (Cathode Specific Capacity for Discharge versus cycle number) for a full Na-ion Cell comprising hard carbon (Carbotron P(J) Kureha) and P2-Na.sub.0.67Ni.sub.0.24Mn.sub.0.533Mg.sub.0.093Ti.sub.0.133O.sub.2 in the voltage range 1.0-4.3V at 30 C. in 0.5M NaPF.sub.6 in ethylene carbonate/diethyl carbonate/propylene carbonate;
(26) FIG. 9(A) is the XRD profile for the P2-Target Active Material of the present invention with the formula: P2-Na.sub.0.55Ni.sub.0.240Mn.sub.0.533Mg.sub.0.035Ti.sub.0.192O.sub.2, as made in Example 9;
(27) FIG. 9(B) shows the cell voltage profile (i.e. Na-ion Cell Voltage [V] versus Cumulative Cathode Specific Capacity [mAh/g]) for the first 4 charge/discharge cycles of the Hard Carbon//P2-Na.sub.0.55Ni.sub.0.240Mn.sub.0.533Mg.sub.0.035Ti.sub.0.192O.sub.2 cell;
(28) FIG. 9(C) shows the Constant current cycle life profile (Cathode Specific Capacity for Discharge versus cycle number) for a full Na-ion Cell comprising hard carbon (Carbotron P(J) Kureha) and P2-Na.sub.0.55Ni.sub.0.240Mn.sub.0.533Mg.sub.0.035Ti.sub.0.192O.sub.2 in the voltage range 1.0-4.3V at 30 C. in 0.5M NaPF.sub.6, in ethylene carbonate/diethyl carbonate/propylene carbonate;
(29) FIG. 10(A) is the XRD profile for the P2-Target Active Material of the present invention with the formula: P2-Na.sub.0.67Ni.sub.0.240Mn.sub.0.533Mg.sub.0.043Ti.sub.0.083Fe.sub.0.100O.sub.2, as used in Example 10;
(30) FIG. 10(B) shows the cell voltage profile (i.e. Na-ion Cell Voltage [V] versus Cumulative Cathode Specific Capacity [mAh/g]) for the first 4 charge/discharge cycles of the Hard Carbon//P2-Na.sub.0.67Ni.sub.0.240Mn.sub.0.533Mg.sub.0.043Ti.sub.0.083Fe.sub.0.100O.sub.2 cell;
(31) FIG. 10(C) shows the Constant current cycle life profile (Cathode Specific Capacity for Discharge versus cycle number) for a full Na-ion Cell comprising hard carbon (Carbotron P(J) Kureha) and a Target Active Composition of the formula: P2-Na.sub.0.67Ni.sub.0.240Mn.sub.0.533Mg.sub.0.043Ti.sub.0.083Fe.sub.0.100O.sub.2 in the voltage range 1.0-4.3V at 30 C. in 0.5M NaPF.sub.6, in ethylene carbonate/diethyl carbonate/propylene carbonate;
(32) FIG. 11(A) is the XRD profile for the P2-Target Active Material of the present invention with the formula: P2-Na.sub.0.67Ni.sub.0.240Mn.sub.0.533Mg.sub.0.043Ti.sub.0.03Al.sub.0.100O.sub.2, as used in Example 11;
(33) FIG. 11(B) shows the cell voltage profile (i.e. Na-ion Cell Voltage [V] versus Cumulative Cathode Specific Capacity [mAh/g]) for the first 4 charge/discharge cycles of the Hard Carbon//P2-Na.sub.0.67Ni.sub.0.240Mn.sub.0.533Mg.sub.0.043Ti.sub.0.83Al.sub.0.100O.sub.2 cell;
(34) FIG. 11(C) shows the Constant current cycle life profile (Cathode Specific Capacity for Discharge versus cycle number) for a full Na-ion Cell comprising hard carbon (Carbotron P(J) Kureha) and a P2-Target Active Composition of the present invention with the formula: P2-Na.sub.0.67Ni.sub.0.240Mn.sub.0.533Mg.sub.0.043Ti.sub.0.083Al.sub.0.100O.sub.2 in the voltage range 1.0-4.3V at 30 C. in 0.5M NaPF.sub.6, in ethylene carbonate/diethyl carbonate/propylene carbonate.
DETAILED DESCRIPTION
(35) Any convenient process may be used to make the Target Active Materials of the present invention and a convenient chemical reaction may use the following general method:
(36) General Method:
(37) 1) Intimately mix together the starting materials (i.e. the precursors for the Target Active Material) in the correct stoichiometric ratio for the particular Target Active Material, and press into a pellet; 2) Heat the resulting mixture in a furnace under a suitable atmosphere comprising for example ambient air, or an inert atmosphere (e.g. argon, nitrogen) (the gases may be flowing if desired), at a single temperature or over a range of temperatures between 400 C. and 1500 C. until reaction product forms; and optionally 3) Allow the product to cool before grinding it to a powder.
(38) Table 1 below lists the starting materials and heating conditions used to prepare a known (comparative) composition (Example 1) and the Target Active Materials of the present invention (Examples 2 to 11).
(39) TABLE-US-00001 TABLE 1 Example No. (Sample Furnace No.) Target Composition Starting Materials Conditions 1 P2-Na.sub.0.67Ni.sub.0.33Mn.sub.0.67O.sub.2 0.333 Na.sub.2CO.sub.3 900 C., air, (X1657) (Known material) 0.333 NiCO.sub.3 8 hours 0.667 MnO.sub.2 2 P2-Na.sub.0.67Ni.sub.0.3Mn.sub.0.6Mg.sub.0.033Ti.sub.0.067O.sub.2 0.333 Na.sub.2CO.sub.3 900 C., air, (X1659) General formula: Na.sub.(2/3)Ni.sub.(1/3)xMn.sub.(2/3)yMg.sub.xTi.sub.yO.sub.2, 0.300 NiCO.sub.3 8 hours where x = 1/30 and y = 1/15 0.600 MnO.sub.2 0.033 Mg(OH).sub.2 0.067 TiO.sub.2 3 P2-Na.sub.0.67Ni.sub.0.267Mn.sub.0.533Mg.sub.0.067Ti.sub.0.133O.sub.2 0.333 Na.sub.2CO.sub.3 900 C., air, (X1663) General formula: Na.sub.(2/3)Ni.sub.(1/3)xMn.sub.(2/3)yMg.sub.xTi.sub.yO.sub.2, 0.267 NiCO.sub.3 8 hours where x = 1/15 and y = 2/15 0.533 MnO.sub.2 0.067 Mg(OH).sub.2 0.133 TiO.sub.2 4 P2-Na.sub.0.67Ni.sub.0.25Mn.sub.0.667Mg.sub.0.083O.sub.2 0.333 Na.sub.2CO.sub.3 900 C., air, (X1684) General formula: Na.sub.(2/3)Ni.sub.(1/3)xMn.sub.(2/3)Mg.sub.xO.sub.2, 0.250 NiCO.sub.3 10 hours where x = 1/12 0.667 MnO.sub.2 0.083 Mg(OH).sub.2 5 P2-Na.sub.0.67Ni.sub.0.283Mn.sub.0.567Mg.sub.0.05Ti.sub.0.1O.sub.2 0.333 Na.sub.2CO.sub.3 900 C., air, (X1713) General formula: Na.sub.(2/3)Ni.sub.(1/3)xMn.sub.(2/3)yMg.sub.xTi.sub.yO.sub.2, 0.283 NiCO.sub.3 10 hours where x = 1/20 and y = 1/10 0.567 MnO.sub.2 0.050 Mg(OH).sub.2 0.100 TiO.sub.2 6 P2-Na.sub.0.7Ni.sub.0.240Mn.sub.0.533Mg.sub.0.110Ti.sub.0.117O.sub.2 0.350 Na.sub.2CO.sub.3 900 C., air, (X1919) 0.240 NiCO.sub.3 8 hours 0.533 MnO.sub.2 0.110 Mg(OH).sub.2 0.117 TiO.sub.2 7 P2-Na.sub.0.6Ni.sub.0.240Mn.sub.0.533Mg.sub.0.060Ti.sub.0.167O.sub.2 0.300 Na.sub.2CO.sub.3 900 C., air, (X1921) 0.240 NiCO.sub.3 8 hours 0.533 MnO.sub.2 0.060 Mg(OH).sub.2 0.167 TiO.sub.2 8 P2-Na.sub.0.67Ni.sub.0.240Mn.sub.0.533Mg.sub.0.093Ti.sub.0.133O.sub.2 0.333 Na.sub.2CO.sub.3 900 C., air, (X1922) 0.240 NiCO.sub.3 8 hours 0.533 MnO.sub.2 0.093 Mg(OH).sub.2 0.133 TiO.sub.2 9 P2-Na.sub.0.55Ni.sub.0.240Mn.sub.0.533Mg.sub.0.035Ti.sub.0.192O.sub.2 0.275 Na.sub.2CO.sub.3 900 C., air, (X1923) 0.240 NiCO.sub.3 8 hours 0.533 MnO.sub.2 0.035 Mg(OH).sub.2 0.192 TiO.sub.2 10 P2- 0.333 Na.sub.2CO.sub.3 900 C., air, (X1926) Na.sub.0.67Ni.sub.0.240Mn.sub.0.533Mg.sub.0.043Ti.sub.0.083Fe.sub.0.100O.sub.2 0.240 NiCO.sub.3 8 hours 0.533 MnO.sub.2 0.043 Mg(OH).sub.2 0.083 TiO.sub.2 0.050 Fe.sub.2O.sub.3 11 P2- 0.333 Na.sub.2CO.sub.3 900 C., air, (X1927) Na.sub.0.67Ni.sub.0.240Mn.sub.0.533Mg.sub.0.043Ti.sub.0.083Al.sub.0.100O.sub.2 0.240 NiCO.sub.3 8 hours 0.533 MnO.sub.2 0.043 Mg(OH).sub.2 0.083 TiO.sub.2 0.100 Al(OH).sub.3
Product Analysis Using XRD
(40) Analysis by X-ray diffraction techniques was conducted using a Siemens D5000 powder diffractometer to confirm that the desired target materials had been prepared, 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 lattice parameters of the unit cells.
(41) The general XRD operating conditions used to analyse the materials are as follows:
(42) Slits sizes: 1 mm, 1 mm, 0.1 mm
(43) Range: 20=5-60
(44) X-ray Wavelength=1.5418 (Angstroms) (Cu K)
(45) Speed: 1.0 seconds/step
(46) Increment: 0.025
(47) Electrochemical Results
(48) The target materials were tested using a Na-ion test cell using a hard carbon anode. Cells may be made using the following procedures:
(49) A Na-ion electrochemical test cell containing the active material is constructed as follows:
(50) Generic Procedure to Make a Hard Carbon Na-Ion Cell
(51) 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 is used as the binder, and N-Methyl-2-pyrrolidone (NMP) is employed as the solvent. The slurry is then cast onto aluminium foil and heated until most of the solvent evaporates and an electrode film is formed. The electrode is then dried under dynamic vacuum at about 120 C. The electrode film contains the following components, expressed in percent by weight: 88% active material, 6% Super P carbon, and 6% PVdF binder.
(52) 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 is used as the binder, and N-Methyl-2-pyrrolidone (NMP) is employed as the solvent. The slurry is then cast onto aluminium foil and heated until most of the solvent evaporates and an electrode film is formed. The electrode is then dried further under dynamic vacuum at about 120 C. The electrode film contains the following components, expressed in percent by weight: 89% active material, 2% Super P carbon, and 9% PVdF binder.
(53) Cell Testing
(54) The cells are tested as follows, using Constant Current Cycling techniques.
(55) 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, alkali ions are extracted from the cathode active material. During discharge, alkali ions are re-inserted into the cathode active material.
(56) Discussion of the Results
Example 1: P2-Na0.67Ni0.33Mn0.67O2
(57) FIG. 1(A) shows the X-ray diffraction pattern of the known material Na.sub.0.67Ni.sub.0.33Mn.sub.0.67O.sub.2 (sample number X1657). The pattern shows that this material conforms to a layered P2-type structure.
(58) Referring to FIG. 1(B)-(C):
(59) The data shown in FIG. 1(B)-(C) are derived from the constant current cycling data for a P2-Na.sub.0.67Ni.sub.0.33Mn.sub.0.67O.sub.2 cathode active material in a Na-ion cell (Cell#311044) where this cathode material was coupled with a Hard Carbon (Carbotron P(J)) anode material. The electrolyte used was a 0.5 M solution of NaClO.sub.4 in propylene carbonate (PC). The constant current data were collected at an approximate current density of 0.2 mA/cm.sup.2 between voltage limits of 1.00 and 4.20 V. To ensure that the Na-ion cell was fully charged, the cell was potentiostatically held at 4.2 V at the end of the constant current charging process until the current density dropped to 10% of the constant current value. The testing was carried out at 30 C.
(60) During the cell charging process, sodium ions are extracted from the cathode active material, and inserted into the Hard Carbon anode. During the subsequent discharge process, sodium ions are extracted from the Hard Carbon and re-inserted into the cathode active material.
(61) FIG. 1(B) shows the cell voltage profile (i.e. Na-ion Cell Voltage [V] versus Cumulative Cathode Specific Capacity [mAh/g]) for the first 4 charge/discharge cycles of the Hard Carbon//Na.sub.0.67Ni.sub.0.33Mn.sub.0.67O.sub.2 cell. These data demonstrate that the level of voltage hysteresis (i.e. the voltage difference between the charge and discharge processes) is large indicating the relatively poor kinetic reversibility of the Na-ion extraction-insertion reactions in this cathode material.
(62) FIG. 1(C) shows the constant current cycle life profile, i.e. the relationship between Cathode Specific Capacity for Discharge [mAh/g] and cycle number for the Hard Carbon//P2-Na.sub.0.67Ni.sub.0.33Mn.sub.0.67O.sub.2 cell. For cycle 1 the discharge specific capacity for the cathode is about 127 mAh/g. For cycle 20 the discharge specific capacity for the cathode is about 61 mAh/g. This represents a capacity fade of about 52% over 20 cycles or an average of 2.6% per cycle. The cathode material under test clearly demonstrates relatively poor capacity retention behaviour.
Example 2: P2-Na0.67Ni0.3Mn0.6Mg0.033Ti0.067O2
(63) FIG. 2(A) shows the X-ray diffraction pattern of Na.sub.0.67Ni.sub.0.3Mn.sub.0.6Mg.sub.0.033Ti.sub.0.067O.sub.2 (sample number X1659). The pattern shows that the sample conforms to a layered P2-type structure.
(64) Referring to FIG. 2(B)-(C):
(65) The data shown in FIG. 2(B)-(C) are derived from the constant current cycling data for a P2-Na.sub.0.67Ni.sub.0.30Mn.sub.0.60Mg.sub.0.033Ti.sub.0.067O.sub.2 cathode active material in a Na-ion cell (Cell#311051) where this cathode material was coupled with a Hard Carbon (Carbotron P(J)) anode material. The electrolyte used was a 0.5 M solution of NaClO.sub.4 in propylene carbonate (PC). The constant current data were collected at an approximate current density of 0.2 mA/cm.sup.2 between voltage limits of 1.00 and 4.2 V. To ensure that the Na-ion cell was fully charged, the cell was potentiostatically held at 4.2 V at the end of the constant current charging process until the current density dropped to 10% of the constant current value. The testing was carried out at 30 C.
(66) During the cell charging process, sodium ions are extracted from the cathode active material, and inserted into the Hard Carbon anode. During the subsequent discharge process, sodium ions are extracted from the Hard Carbon and re-inserted into the cathode active material.
(67) FIG. 2(B) shows the cell voltage profile (i.e. Na-ion Cell Voltage [V] versus Cumulative Cathode Specific Capacity [mAh/g]) for the first 4 charge/discharge cycles of the Hard Carbon//P2-Na.sub.0.67Ni.sub.0.30Mn.sub.0.60Mg.sub.0.033Ti.sub.0.067O.sub.2 cell. These data demonstrate that the level of voltage hysteresis (i.e. the voltage difference between the charge and discharge processes) is small, indicating the excellent kinetic reversibility of the Na-ion extraction-insertion reactions. In addition, the generally symmetrical nature of the charge/discharge voltage profile confirms the excellent reversibility of the extraction-insertion reactions.
(68) FIG. 2(C) shows the constant current cycle life profile, i.e. the relationship between Cathode Specific Capacity for Discharge [mAh/g] and cycle number for the Hard Carbon//P2-Na.sub.0.67Ni.sub.0.30Mn.sub.0.60Mg.sub.0.033Ti.sub.0.067O.sub.2 cell. For cycle 1 the discharge specific capacity for the cathode is about 117 mAh/g. For cycle 30 the discharge specific capacity for the cathode is about 106 mAh/g. This represent a capacity fade of about 9.4% over 30 cycles or an average of 0.3% per cycle. The cathode material under test clearly demonstrates excellent capacity retention behaviour.
Example 3: P2-Na0.67Ni0.267Mn0.533Mg0.067Ti0.133O2
(69) FIG. 3(A) shows the X-ray diffraction pattern of Na.sub.0.67Ni.sub.0.267Mn.sub.0.533Mg.sub.0.067Ti.sub.0.133O.sub.2 (sample number X1663). The pattern shows that the sample conforms to a layered P2-type structure.
(70) Referring to FIG. 3(B)-(C):
(71) The data shown in FIG. 3(B)-(C) are derived from the constant current cycling data for a P2-Na.sub.0.67Ni.sub.0.267Mn.sub.0.533Mg.sub.0.067Ti.sub.0.133O.sub.2 cathode active material in a Na-ion cell (Cell#311058) where this cathode material was coupled with a Hard Carbon (Carbotron P(J)) anode material. The electrolyte used was a 0.5 M solution of NaClO.sub.4 in propylene carbonate (PC). The constant current data were collected at an approximate current density of 0.2 mA/cm.sup.2 between voltage limits of 1.00 and 4.2 V. To ensure that the Na-ion cell was fully charged, the cell was potentiostatically held at 4.2 V at the end of the constant current charging process until the current density dropped to 10% of the constant current value. The testing was carried out at 30 C.
(72) During the cell charging process, sodium ions are extracted from the cathode active material, and inserted into the Hard Carbon anode. During the subsequent discharge process, sodium ions are extracted from the Hard Carbon and re-inserted into the cathode active material.
(73) FIG. 3(B) shows the cell voltage profile (i.e. Na-ion Cell Voltage [V] versus Cumulative Cathode Specific Capacity [mAh/g]) for the first 4 charge/discharge cycles of the Hard Carbon//P2-Na.sub.0.67Ni.sub.0.267Mn.sub.0.533Mg.sub.0.067Ti.sub.0.133O.sub.2 cell. These data demonstrate that the level of voltage hysteresis (i.e. the voltage difference between the charge and discharge processes) is small, indicating the excellent kinetic reversibility of the Na-ion extraction-insertion reactions. In addition, the generally symmetrical nature of the charge/discharge voltage profile confirms the excellent reversibility of the extraction-insertion reactions.
(74) FIG. 3(C) shows the constant current cycle life profile, i.e. the relationship between Cathode Specific Capacity for Discharge [mAh/g] and cycle number for the Hard Carbon//P2-Na.sub.0.67Ni.sub.0.267Mn.sub.0.533Mg.sub.0.067Ti.sub.0.133O.sub.2 cell. For cycle 1 the discharge specific capacity for the cathode is about 105 mAh/g. For cycle 30 the discharge specific capacity for the cathode is about 101 mAh/g. This represents a capacity fade of about 3.8% over 30 cycles or an average of 0.13% per cycle. The cathode material under test clearly demonstrates excellent capacity retention behaviour.
Example 4: P2-Na0.67Ni0.25Mn0.667Mg0.083O2
(75) FIG. 4(A) shows the X-ray diffraction pattern of Na.sub.0.67Ni.sub.0.25Mn.sub.0.667Mg.sub.0.083O.sub.2 (sample number X1684). The pattern shows that the sample conforms to a layered P2-type structure.
(76) Referring to FIG. 4(B)-(C):
(77) The data shown in FIG. 4(B)-(C) are derived from the constant current cycling data for a P2-Na.sub.0.67Ni.sub.0.25Mn.sub.0.667Mg.sub.0.083O.sub.2 cathode active material in a Na-ion cell (Cell#312020) where this cathode material was coupled with a Hard Carbon (Carbotron P(J)) anode material. The electrolyte used was a 0.5 M solution of NaClO.sub.4 in propylene carbonate (PC). The constant current data were collected at an approximate current density of 0.2 mA/cm.sup.2 between voltage limits of 1.00 and 4.20 V. To ensure that the Na-ion cell was fully charged, the cell was potentiostatically held at 4.2 V at the end of the constant current charging process until the current density dropped to 10% of the constant current value. The testing was carried out at 30 C.
(78) During the cell charging process, sodium ions are extracted from the cathode active material, and inserted into the Hard Carbon anode. During the subsequent discharge process, sodium ions are extracted from the Hard Carbon and re-inserted into the cathode active material.
(79) FIG. 4(B) shows the cell voltage profile (i.e. Na-ion Cell Voltage [V] versus Cumulative Cathode Specific Capacity [mAh/g]) for the first 4 charge/discharge cycles of the Hard Carbon//P2-Na.sub.0.67Ni.sub.0.25Mn.sub.0.667Mg.sub.0.083O.sub.2 cell. These data demonstrate that the level of voltage hysteresis (i.e. the voltage difference between the charge and discharge processes) is small, indicating the excellent kinetic reversibility of the Na-ion extraction-insertion reactions. In addition, the generally symmetrical nature of the charge/discharge voltage profile confirms the excellent reversibility of the extraction-insertion reactions.
(80) FIG. 4(C) shows the constant current cycle life profile, i.e. the relationship between Cathode Specific Capacity for Discharge [mAh/g] and cycle number for the Hard Carbon//P2-Na.sub.0.67Ni.sub.0.25Mn.sub.0.667Mg.sub.0.083O.sub.2 cell. For cycle 1 the discharge specific capacity for the cathode is about 96 mAh/g. For cycle 30 the discharge specific capacity for the cathode is about 95 mAh/g. This represents a capacity fade of about 1.0% over 30 cycles or an average of 0.03% per cycle. The cathode material under test clearly demonstrates excellent capacity retention behaviour.
Example 5: P2-Na0.67Ni0.283Mn0.567Mg0.05Ti0.1O2
(81) FIG. 5(A) shows the X-ray diffraction pattern of Na.sub.0.67Ni.sub.0.283Mn.sub.0.567Mg.sub.0.05Ti.sub.0.1O.sub.2 (sample number X1713). The pattern shows that the sample conforms to a layered P2-type structure.
(82) Referring to FIG. 5(B)-(C):
(83) The data shown in FIG. 5(B)-(C) are derived from the constant current cycling data for a P2-Na.sub.0.67Ni.sub.0.283Mn.sub.0.567Mg.sub.0.05Ti.sub.0.10O.sub.2 cathode active material in a Na-ion cell (Cell#401018) where this cathode material was coupled with a Hard Carbon (Carbotron P(J)) anode material. The electrolyte used was a 0.5 M solution of NaClO.sub.4 in propylene carbonate (PC). The constant current data were collected at an approximate current density of 0.2 mA/cm.sup.2 between voltage limits of 1.00 and 4.20 V. To ensure that the Na-ion cell was fully charged, the cell was potentiostatically held at 4.2 V at the end of the constant current charging process until the current density dropped to 10% of the constant current value. The testing was carried out at 30 C.
(84) During the cell charging process, sodium ions are extracted from the cathode active material, and inserted into the Hard Carbon anode. During the subsequent discharge process, sodium ions are extracted from the Hard Carbon and re-inserted into the cathode active material.
(85) FIG. 5(B) shows the cell voltage profile (i.e. Na-ion Cell Voltage [V] versus Cumulative Cathode Specific Capacity [mAh/g]) for the first 4 charge/discharge cycles of the Hard Carbon//P2-Na.sub.0.67Ni.sub.0.283Mn.sub.0.567Mg.sub.0.05Ti.sub.0.10O.sub.2 cell. These data demonstrate that the level of voltage hysteresis (i.e. the voltage difference between the charge and discharge processes) is small, indicating the excellent kinetic reversibility of the Na-ion extraction-insertion reactions. In addition, the generally symmetrical nature of the charge/discharge voltage profile confirms the excellent reversibility of the extraction-insertion reactions.
(86) FIG. 5(C) shows the constant current cycle life profile, i.e. the relationship between Cathode Specific Capacity for Discharge [mAh/g] and cycle number for the Hard Carbon//P2-Na.sub.0.67Ni.sub.0.283Mn.sub.0.567Mg.sub.0.05Ti.sub.0.10O.sub.2 cell. For cycle 1 the discharge specific capacity for the cathode is about 97 mAh/g. For cycle 30 the discharge specific capacity for the cathode is about 92 mAh/g. This represents a capacity fade of about 5.2% over 30 cycles or an average of 0.17% per cycle. The cathode material under test clearly demonstrates excellent capacity retention behaviour.
Example 6: P2-Na0.7Ni0.240Mn0.533Mg0.1100Ti0.117O2
(87) FIG. 6(A) shows the X-ray diffraction pattern of Na.sub.0.7Ni.sub.0.24Mn.sub.0.533Mg.sub.0.110Ti.sub.0.117O.sub.2 (sample number X1919). The pattern shows that the sample conforms to a layered P2-type structure.
(88) Referring to FIG. 6(B)-(C).
(89) The data shown in FIG. 6(B)-(C) are derived from the constant current cycling data for a P2-Na.sub.0.70Ni.sub.0.240Mn.sub.0.533Mg.sub.0.110Ti.sub.0.117O.sub.2 cathode active material in a Na-ion cell (Cell#410001) where this cathode material was coupled with a Hard Carbon (Carbotron P(J)) anode material. The electrolyte used was a 0.5 M solution of NaPF.sub.6 in ethylene carbonate/diethyl carbonate/propylene carbonate. The constant current data were collected at an approximate current density of 0.2 mA/cm.sup.2 between voltage limits of 1.00 and 4.30 V. To ensure that the Na-ion cell was fully charged, the cell was potentiostatically held at 4.3 V at the end of the constant current charging process until the current density dropped to 10% of the constant current value. The testing was carried out at 30 C.
(90) During the cell charging process, sodium ions are extracted from the cathode active material, and inserted into the Hard Carbon anode. During the subsequent discharge process, sodium ions are extracted from the Hard Carbon and re-inserted into the cathode active material.
(91) FIG. 6(B) shows the cell voltage profile (i.e. Na-ion Cell Voltage [V] versus Cumulative Cathode Specific Capacity [mAh/g]) for the first 4 charge/discharge cycles of the Hard Carbon//P2-Na.sub.0.70Ni.sub.0.240Mn.sub.0.533Mg.sub.0.110Ti.sub.0.117O.sub.2 cell. These data demonstrate that the level of voltage hysteresis (i.e. the voltage difference between the charge and discharge processes) is small indicating the excellent kinetic reversibility of the Na-ion extraction-insertion reactions in this cathode material.
(92) FIG. 6(C) shows the constant current cycle life profile, i.e. the relationship between Cathode Specific Capacity for Discharge [mAh/g] and cycle number for the Hard Carbon//P2-Na.sub.0.70Ni.sub.0.240Mn.sub.0.533Mg.sub.0.110Ti.sub.0.117O.sub.2 cell. For cycle 1 the discharge specific capacity for the cathode is about 108 mAh/g. For cycle 6 the discharge specific capacity for the cathode is about 108 mAh/g. This represents a capacity fade of about 0% over 4 cycles. The cathode material under test clearly demonstrates excellent capacity retention behaviour.
Example 7: P2-Na0.60Ni0.240Mn0.533Mg0.060Ti0.167O2
(93) FIG. 7(A) shows the X-ray diffraction pattern of Na.sub.0.6Ni.sub.0.24Mn.sub.0.533Mg.sub.0.060Ti.sub.0.167O.sub.2 (sample number X1921). The pattern shows that the sample conforms to a layered P2-type structure.
(94) Referring to FIG. 7(B)-(C).
(95) The data shown in FIG. 7(B)-(C) are derived from the constant current cycling data for a P2-Na.sub.0.60Ni.sub.0.240Mn.sub.0.533Mg.sub.0.060Ti.sub.0.167O.sub.2 cathode active material in a Na-ion cell (Cell#410003) where this cathode material was coupled with a Hard Carbon (Carbotron P(J)) anode material. The electrolyte used was a 0.5 M solution of NaPF.sub.6 in ethylene carbonate/diethyl carbonate/propylene carbonate. The constant current data were collected at an approximate current density of 0.2 mA/cm.sup.2 between voltage limits of 1.00 and 4.30 V. To ensure that the Na-ion cell was fully charged, the cell was potentiostatically held at 4.3 V at the end of the constant current charging process until the current density dropped to 10% of the constant current value. The testing was carried out at 30 C.
(96) During the cell charging process, sodium ions are extracted from the cathode active material, and inserted into the Hard Carbon anode. During the subsequent discharge process, sodium ions are extracted from the Hard Carbon and re-inserted into the cathode active material.
(97) FIG. 7(B) shows the cell voltage profile (i.e. Na-ion Cell Voltage [V] versus Cumulative Cathode Specific Capacity [mAh/g]) for the first 4 charge/discharge cycles of the Hard Carbon//P2-Na.sub.0.60Ni.sub.0.240Mn.sub.0.533Mg.sub.0.060Ti.sub.0.167O.sub.2 cell. These data demonstrate that the level of voltage hysteresis (i.e. the voltage difference between the charge and discharge processes) is small indicating the excellent kinetic reversibility of the Na-ion extraction-insertion reactions in this cathode material.
(98) FIG. 7(C) shows the constant current cycle life profile, i.e. the relationship between Cathode Specific Capacity for Discharge [mAh/g] and cycle number for the Hard Carbon//P2-Na.sub.0.60Ni.sub.0.240Mn.sub.0.533Mg.sub.0.060Ti.sub.0.167O.sub.2 cell. For cycle 1 the discharge specific capacity for the cathode is about 94 mAh/g. For cycle 7 the discharge specific capacity for the cathode is about 91 mAh/g. This represents a capacity fade of about 3% over 7 cycles. The cathode material under test clearly demonstrates good capacity retention behaviour.
Example 8: P2-Na0.67Ni0.240Mn0.533Mg0.093Ti0.133O2
(99) FIG. 8(A) shows the X-ray diffraction pattern of Na.sub.0.67Ni.sub.0.240Mn.sub.0.533Mg.sub.0.093Ti.sub.0.133O.sub.2 (sample number X1922). The pattern shows that the sample conforms to a layered P2-type structure.
(100) Referring to FIG. 8(B)-(C).
(101) The data shown in FIG. 8(B)-(C) are derived from the constant current cycling data for a P2-Na.sub.0.67Ni.sub.0.240Mn.sub.0.533Mg.sub.0.093Ti.sub.0.133O.sub.2 cathode active material in a Na-ion cell (Cell#410004) where this cathode material was coupled with a Hard Carbon (Carbotron P(J)) anode material. The electrolyte used was a 0.5 M solution of NaPF.sub.6 in ethylene carbonate/diethyl carbonate/propylene carbonate. The constant current data were collected at an approximate current density of 0.2 mA/cm.sup.2 between voltage limits of 1.00 and 4.30 V. To ensure that the Na-ion cell was fully charged, the cell was potentiostatically held at 4.3 V at the end of the constant current charging process until the current density dropped to 10% of the constant current value. The testing was carried out at 30 C.
(102) During the cell charging process, sodium ions are extracted from the cathode active material, and inserted into the Hard Carbon anode. During the subsequent discharge process, sodium ions are extracted from the Hard Carbon and re-inserted into the cathode active material.
(103) FIG. 8(B) shows the cell voltage profile (i.e. Na-ion Cell Voltage [V] versus Cumulative Cathode Specific Capacity [mAh/g]) for the first 4 charge/discharge cycles of the Hard Carbon//P2-Na.sub.0.67Ni.sub.0.240Mn.sub.0.533Mg.sub.0.093Ti.sub.0.133O.sub.2 cell. These data demonstrate that the level of voltage hysteresis (i.e. the voltage difference between the charge and discharge processes) is small confirming the excellent kinetic reversibility of the Na-ion extraction-insertion reactions in this cathode material.
(104) FIG. 8(C) shows the constant current cycle life profile, i.e. the relationship between Cathode Specific Capacity for Discharge [mAh/g] and cycle number for the Hard Carbon//P2-Na.sub.0.67Ni.sub.0.240Mn.sub.0.533Mg.sub.0.093Ti.sub.0.133O.sub.2 cell. For cycle 1 the discharge specific capacity for the cathode is about 100 mAh/g. For cycle 5 the discharge specific capacity for the cathode is about 99 mAh/g. This represents a capacity fade of about 1% over 5 cycles. The cathode material under test clearly demonstrates excellent capacity retention behaviour.
Example 9: P2-Na0.55Ni0.240Mn0.533Mg0.035Ti0.192O2
(105) FIG. 9(A) shows the X-ray diffraction pattern of Na.sub.0.55Ni.sub.0.240Mn.sub.0.533Mg.sub.0.035Ti.sub.0.192O.sub.2 (sample number X1923). The pattern shows that the sample conforms to a layered P2-type structure.
(106) Referring to FIG. 9(B)-(C).
(107) The data shown in FIG. 9(B)-(C) are derived from the constant current cycling data for a P2-Na.sub.0.55Ni.sub.0.240Mn.sub.0.533Mg.sub.0.035Ti.sub.0.192O.sub.2 cathode active material in a Na-ion cell (Cell#410005) where this cathode material was coupled with a Hard Carbon (Carbotron P(J)) anode material. The electrolyte used was a 0.5 M solution of NaPF.sub.6 in ethylene carbonate/diethyl carbonate/propylene carbonate. The constant current data were collected at an approximate current density of 0.2 mA/cm.sup.2 between voltage limits of 1.00 and 4.30 V. To ensure that the Na-ion cell was fully charged, the cell was potentiostatically held at 4.3 V at the end of the constant current charging process until the current density dropped to 10% of the constant current value. The testing was carried out at 30 C.
(108) During the cell charging process, sodium ions are extracted from the cathode active material, and inserted into the Hard Carbon anode. During the subsequent discharge process, sodium ions are extracted from the Hard Carbon and re-inserted into the cathode active material.
(109) FIG. 9(B) shows the cell voltage profile (i.e. Na-ion Cell Voltage [V] versus Cumulative Cathode Specific Capacity [mAh/g]) for the first 4 charge/discharge cycles of the Hard Carbon//P2-Na.sub.0.55Ni.sub.0.240Mn.sub.0.533Mg.sub.0.035Ti.sub.0.192O.sub.2 cell. These data demonstrate that the level of voltage hysteresis (i.e. the voltage difference between the charge and discharge processes) is small indicating the excellent kinetic reversibility of the Na-ion extraction-insertion reactions in this cathode material.
(110) FIG. 9(C) shows the constant current cycle life profile, i.e. the relationship between Cathode Specific Capacity for Discharge [mAh/g] and cycle number for the Hard Carbon//P2-Na.sub.0.55Ni.sub.0.240Mn.sub.0.533Mg.sub.0.035Ti.sub.0.192O.sub.2 cell. For cycle 1 the discharge specific capacity for the cathode is about 93 mAh/g. For cycle 4 the discharge specific capacity for the cathode is about 89 mAh/g. This represents a capacity fade of about 4% over 4 cycles. The cathode material under test demonstrates reasonable capacity retention behaviour.
Example 10: P2-Na0.67Ni0.240Mn0.533Mg0.043Ti0.083Fe0.1O2
(111) FIG. 10(A) shows the X-ray diffraction pattern of Na.sub.0.67Ni.sub.0.240Mn.sub.0.533Mg.sub.0.043Ti.sub.0.083Fe.sub.0.1O.sub.2 (sample number X1926). The pattern shows that the sample conforms to a layered P2-type structure.
(112) Referring to FIG. 10(B)-(C).
(113) The data shown in FIG. 10(B)-(C) are derived from the constant current cycling data for a P2-Na.sub.0.67Ni.sub.0.240Mn.sub.0.533Mg.sub.0.043Ti.sub.0.083Fe.sub.0.1O.sub.2 cathode active material in a Na-ion cell (Cell#410006) where this cathode material was coupled with a Hard Carbon (Carbotron P(J)) anode material. The electrolyte used was a 0.5 M solution of NaPF.sub.6 in ethylene carbonate/diethyl carbonate/propylene carbonate. The constant current data were collected at an approximate current density of 0.2 mA/cm.sup.2 between voltage limits of 1.00 and 4.30 V. To ensure that the Na-ion cell was fully charged, the cell was potentiostatically held at 4.3 V at the end of the constant current charging process until the current density dropped to 10% of the constant current value. The testing was carried out at 30 C.
(114) During the cell charging process, sodium ions are extracted from the cathode active material, and inserted into the Hard Carbon anode. During the subsequent discharge process, sodium ions are extracted from the Hard Carbon and re-inserted into the cathode active material.
(115) FIG. 10(B) shows the cell voltage profile (i.e. Na-ion Cell Voltage [V] versus Cumulative Cathode Specific Capacity [mAh/g]) for the first 4 charge/discharge cycles of the Hard Carbon//P2-Na.sub.0.67Ni.sub.0.240Mn.sub.0.533Mg.sub.0.043Ti.sub.0.083Fe.sub.0.1O.sub.2 cell. These data demonstrate that the level of voltage hysteresis (i.e. the voltage difference between the charge and discharge processes) is small indicating the excellent kinetic reversibility of the Na-ion extraction-insertion reactions in this cathode material.
(116) FIG. 10(C) shows the constant current cycle life profile, i.e. the relationship between Cathode Specific Capacity for Discharge [mAh/g] and cycle number for the Hard Carbon//P2-Na.sub.0.67Ni.sub.0.240Mn.sub.0.533Mg.sub.0.043Ti.sub.0.083Fe.sub.0.1O.sub.2 cell. For cycle 1 the discharge specific capacity for the cathode is about 101 mAh/g. For cycle 3 the discharge specific capacity for the cathode is about 97 mAh/g. This represents a capacity fade of about 4% over 3 cycles. The cathode material under test demonstrates reasonable capacity retention behaviour.
Example 11: P2-Na0.67Ni0.240Mn0.533Mg0.043Ti0.083Al0.1O2
(117) FIG. 11(A) shows the X-ray diffraction pattern of Na.sub.0.67Ni.sub.0.240Mn.sub.0.533Mg.sub.0.043Ti.sub.0.083Al.sub.0.1O.sub.2 (sample number X1927). The pattern shows that the sample conforms to a layered P2-type structure.
(118) Referring to FIG. 11(B)-(C).
(119) The data shown in FIG. 11(B)-(C) are derived from the constant current cycling data for a P2-Na.sub.0.67Ni.sub.0.240Mn.sub.0.533Mg.sub.0.043Ti.sub.0.83Al.sub.0.1O.sub.2 cathode active material in a Na-ion cell (Cell#410007) where this cathode material was coupled with a Hard Carbon (Carbotron P(J)) anode material. The electrolyte used was a 0.5 M solution of NaPF.sub.6 in ethylene carbonate/diethyl carbonate/propylene carbonate. The constant current data were collected at an approximate current density of 0.2 mA/cm.sup.2 between voltage limits of 1.00 and 4.30 V. To ensure that the Na-ion cell was fully charged, the cell was potentiostatically held at 4.3 V at the end of the constant current charging process until the current density dropped to 10% of the constant current value. The testing was carried out at 30 C.
(120) During the cell charging process, sodium ions are extracted from the cathode active material, and inserted into the Hard Carbon anode. During the subsequent discharge process, sodium ions are extracted from the Hard Carbon and re-inserted into the cathode active material.
(121) FIG. 11(B) shows the cell voltage profile (i.e. Na-ion Cell Voltage [V] versus Cumulative Cathode Specific Capacity [mAh/g]) for the first 4 charge/discharge cycles of the Hard Carbon//P2-Na.sub.0.67Ni.sub.0.240Mn.sub.0.533Mg.sub.0.043Ti.sub.0.083Al.sub.0.1O.sub.2 cell. These data demonstrate that the level of voltage hysteresis (i.e. the voltage difference between the charge and discharge processes) is small indicating the excellent kinetic reversibility of the Na-ion extraction-insertion reactions in this cathode material.
(122) FIG. 11(C) shows the constant current cycle life profile, i.e. the relationship between Cathode Specific Capacity for Discharge [mAh/g] and cycle number for the Hard Carbon//P2-Na.sub.0.67Ni.sub.0.240Mn.sub.0.533Mg.sub.0.043Ti.sub.0.083Al.sub.0.1O.sub.2 cell. For cycle 1 the discharge specific capacity for the cathode is about 101 mAh/g. For cycle 3 the discharge specific capacity for the cathode is about 97 mAh/g. This represents a capacity fade of about 4% over 3 cycles. The cathode material under test demonstrates reasonable capacity retention behaviour.
