Electrode material including lithium transition metal oxide, lithium iron phosphate, further iron-phosphorous compound. and carbon, and lithium battery including the same

Abstract

Electrode materials comprising (a) at least one compound of general formula (I) Li.sub.(1+x)[Ni.sub.aCO.sub.bMn.sub.cM1.sub.d].sub.(1-x)O.sub.2 (I) the integers being defined as follows: x is in the range of from 0.01 to 0.05, a is in the range of from 0.3 to 0.6, b is in the range of from zero to 0.35, c is in the range of from 0.2 to 0.6, d is in the range of from zero to 0.05, a+b+c+d=1 M.sup.1 is at least one metal selected from Ca, Zn, Fe, Ti, Ba, Al, (b) at least one compound of general formula (II) LiFe.sub.(1-x)M2.sub.yPO.sub.4 (II) y is in the range of from zero to 0.8 M.sup.2 is at least one element selected from Ti, Co, Mn, Ni, V, Mg, Nd, Zn and Y, that contains at least one further iron-phosphorous compound, in form of a solid solution in compound (b) or in domains, (c) carbon in electrically conductive modification.

Claims

1. An electrode material, comprising: (a) a component comprising a compound of formula (I):
Li.sub.(1+x)[Ni.sub.aCO.sub.bMn.sub.cM.sup.1.sub.d].sub.(1-x)O.sub.2(I), wherein, in formula (I): x is in the range of from 0.01 to 0.05, a is in the range of from 0.3 to 0.6, b is in the range of from zero to 0.35, c is in the range of from 0.2 to 0.6, d is in the range of from zero to 0.05, a+b+c+d=1, and M.sup.1 is at least one metal selected from the group consisting of Ca, Zn, Fe, Ti, Ba, and Al; (b) a component comprising: a compound of formula (II):
LiFe.sub.(1-y)M.sup.2.sub.yPO.sub.4(II), wherein, in formula (II): y is in the range of from zero to 0.8 M.sup.2 is at least one element selected from the group consisting of Ti, Co, Mn, Ni, V, Mg, Nd, Zn and Y, and a further iron-phosphorus compound, in form of a solid solution in the compound of formula (II) or in domains, wherein said further iron-phosphorus compound is at least one compound selected from the group consisting of Fe.sub.3(PO.sub.4).sub.2 and Fe.sub.2P.sub.2O.sub.7; and (c) carbon in electrically conductive modification, wherein the compound of formula (II) is obtained by reacting a molar excess of Fe with respect to Li or, if M.sup.2 is present, a molar excess of Fe and M.sup.2 with respect to Li, wherein an average particle diameter, D.sub.50, of secondary particles of the component (a) is in a range from 6 m to 16 m, and wherein the component (b) is in the form of agglomerates of primary particles, said agglomerates having an average diameter, D.sub.50, in a range from 1-10 m.

2. The electrode material according to claim 1, wherein, in formula (I): a is in the range of from 0.32 to 0.50, b is in the range of from 0.20 to 0.33, c is in the range of from 0.30 to 0.40, and d is zero.

3. The electrode material according to claim 1, wherein the component (a) is a gradient material.

4. The electrode material according to claim 1, wherein the component (a) has a BET surface area in the range of from 0.2 m.sup.2/g to 10 m.sup.2/g.

5. The electrode material according to claim 1, wherein the component (b) has a BET surface area in the range of from 5 m.sup.2/g to 35 m.sup.2/g.

6. The electrode material according to claim 1, wherein the component (b) has a BET surface area in the range of from 5 m.sup.2/g to 15 m.sup.2/g.

7. The electrode material according to claim 1, wherein, in formula (II), y is not zero and M.sup.2 is Ti, Co, or Mn.

8. The electrode material according to claim 1, wherein the weight ratio of the component (a) to the component (b) is in the range of from 30:70 to 97.5:2.5.

9. The electrode material according to claim 1, wherein the average particle diameter, D.sub.50, of secondary particles of the component (a) is from 7 m to 9 m, and wherein the average diameter, D.sub.50, of the agglomerates of the primary particles of component (b) is from 2 m to 5 m.

10. The electrode material according to claim 1, wherein the further iron-phosphorus compound is in the form of a solid solution in the compound of formula (II).

11. The electrode material according to claim 1, wherein the further iron-phosphorus compound is distributed in grain boundaries.

12. The electrode material according to claim 1, wherein the further iron-phosphorus compound is in domains having an average diameter of 0.1-1 m.

13. The electrode material according to claim 1, wherein the amount of carbon (c) is in the range of 1 to 8% by weight, relative to the component (b).

14. A cathode, comprising: the electrode material according to claim 1; and a binder (d).

15. A battery, comprising: (A) the cathode of claim 14; (B) an anode; and (C) an electrolyte.

16. A method for using a battery according to claim 15, the method comprising: incorporating said battery into an automobile or other mobile appliance.

Description

EXAMPLES

(1) General remarks: % refer to % by weight unless expressly noted otherwise.

(2) LiOH was used as LiOH.H.sub.2O. The amount in the example refers to LiOH without the water. NL: liters under normal conditions (ambient temperature/1 bar).

(3) I. Syntheses of Cathode Active Materials

(4) I.1 Synthesis of Compounds (I)

(5) I.1.1 Synthesis of Compound (I.1)

(6) A precursor Ni.sub.0.33Co.sub.0.33Mn.sub.0.33(OH).sub.2, spherical particles, average particle diameter 10 m, was mixed with finely milled Li.sub.2CO.sub.3. The molar ratio of lithium (Li.sub.2CO.sub.3) to the sum of the transition metals in the Ni.sub.0.33Co.sub.0.33Mn.sub.0.33(OH).sub.2 was 1.11. An amount of 40 g of the mixture so obtained was calcined in a box furnace, in rectangular saggers made from sintered aluminum oxide. The calcination was performed under air, with the heating rate being 3 K/min. The calcination temperature program was as follows: heat to 350 C., keep at 350 C. for 4 hours, heat to 675 C., keep at 675 C. for 4 hours, heat to 900 C., keep at 900 C. for 6 hours, then cool to room temperature. After cooling, the compound of formula (I.1)
Li.sub.1.06[Ni.sub.0.33Co.sub.0.33Mn.sub.0.33].sub.0.94O.sub.2(I.1)
so obtained was grinded in a mortar. The ground compound (1.1) was sieved with a sieve having 32 m mesh size. An amount of 30 g of particles of compound (1.1) with a diameter smaller than 32 m were collected.
I.1.2 Synthesis of Compound (I.2)

(7) A precursor Ni.sub.0.4Co.sub.0.2Mn.sub.0.4(OH).sub.2, spherical particles, average particle diameter 10 m, was mixed with finely milled Li.sub.2CO.sub.3. The molar ratio of lithium (Li.sub.2CO.sub.3) to the sum of the transition metals in the Ni.sub.0.4Co.sub.0.2Mn.sub.0.4(OH).sub.2 was 1.13. An amount of 40 g of the mixture so obtained was calcined in a box furnace, in rectangular saggers made from sintered aluminum oxide. The calcination was performed under air, with the heating rate being 3 K/min. The calcination temperature program was as follows: heat to 350 C., keep at 350 C. for 4 hours, heat to 675 C., keep at 675 C. for 4 hours, heat to 925 C., keep at 925 C. for 6 hours, then cool to room temperature. After cooling, the compound of formula (I.2)
Li.sub.1.07[Ni.sub.0.4Co.sub.0.2Mn.sub.0.4].sub.0.93O.sub.2(I.2)
so obtained was grinded in a mortar. The ground compound (I.2) was sieved with a sieve having 32 m mesh size. An amount of 30 g of particles of compound (I.2) with a diameter smaller than 32 m were collected.
I.2 Synthesis of Components According to Formula (II)
I.2.1 Synthesis of Compound (II.1)

(8) TABLE-US-00001 70.7 g LiOH (2.95 mol) (calculated without water) 280.8 g -FeOOH (3.16 mol) calculated as FeOOH 185.6 g by weight aqueous solution of H.sub.3PO.sub.4 (1.61 mol) 134.2 g H.sub.3PO.sub.3 (98%) 46.6 g starch 46.6 g lactose

(9) A 6-l-reactor equipped with mixer and heater was charged with 4,600 g of H.sub.2O. The water was heated to temperature of 76 C. Then addition of the ingredients was started. First, the LiOH was added and dissolved within 20 min. Due to exothermic reaction the solution temperature rose to 80.5 C. Then, the -FeOOH was added and stirred for another 20 min. Then, H.sub.3PO.sub.4 and H.sub.3PO.sub.3 were added. 20 minutes later, starch and lactose were added in powder form. The temperature of the yellow slurry so obtained was 87 C. Then, 500 g of H.sub.2O were added. The slurry so obtained was stirred for 21 hours at 85 C.

(10) Then, the solid was isolated by spray-drying. The suspension prepared in the above step was spray-dried using N.sub.2 (25 Nm.sup.3/h) as the drying gas, applying the following spray-drying parameters: T.sub.in 295 C.-298 C. T.sub.out 135 C.-143 C. Slurry feed: 724.1 g/h

(11) After spray-drying, 125 g of a yellow spray-powder were obtained.

(12) 60 g of the spray-powder obtained above were calcined in a rotary quartz-bulb. The rotary bulb was rotating with a speed of 10 rpm. The spray-powder sample was heated from ambient temperature to a temperature of 700 C., with a heating rate of 11.33 C./min. Finally, the material was calcined at a temperature of 700 C. for 1 hour under a stream of N.sub.2 flow (16 NL/h). Then, the black material (compound (II.1)) so obtained was cooled down to room temperature. Compound (II.1) of stoichiometry LiFePO.sub.4.0.01 Fe.sub.3(PO.sub.4).sub.2 was sieved to <50 m. It contained about 3.6% by weight of carbon.

(13) I.2.2 Synthesis of a Lithium Iron Phosphate for Comparative Purposes

(14) The following ingredients were used:

(15) TABLE-US-00002 75.6 g LiOH (3.16 mol) 280.8 g -FeOOH (3.16 mol) 182.2 g 85% by weight aqueous solution of H.sub.3PO.sub.4 (1.58 mol) 134.20 g H.sub.3PO.sub.3 (98%) 46.6 g starch 46.6 g lactose

(16) A 6 l reactor equipped with mixer and heater was charged with 4,600 g of H.sub.2O. The water was heated to temperature of 76 C. Then addition of the ingredients was started. First, the LiOHH.sub.2O was added and dissolved within of 20 min. Due to exothermic reaction the solution temperature rose to 80.5 C. Then -FeOOH was added and stirred for another 20 min. Then, H.sub.3PO.sub.4 and H.sub.3PO.sub.3 were added. 20 minutes later, starch and lactose were added in powder form. The temperature of the yellow slurry so obtained was 87 C. Then, 500 g of H.sub.2O were added. The slurry obtained was stirred for more than 21 hours at 85 C.

(17) Then, the solid was isolated by spray-drying. The suspension prepared in the above step was spray-dried using N.sub.2 (25 Nm.sup.3/h) as the drying gas, applying the following spray-drying parameters: T.sub.in 295 C.-298 C. T.sub.out 135 C.-143 C. Slurry feed: 724.1 g/h

(18) After spray-drying, 122 g of a yellow spray-powder were obtained.

(19) 60 g of the spray-powder obtained above were calcined in a rotary quarz-bulb. The rotary bulb was rotating with a speed of 10 rpm. The spray-powder sample was heated from ambient temperature to a temperature of 700 C., with a heating rate of 11.33 C./min. Finally, the material was calcined at a temperature of 700 C. for 1 hour under a stream of N.sub.2 flow (16 NL/h). Then, the black material (compound (II.2)) so obtained was cooled down to room temperature. Comparative compound C-(II.2) of the stoichiometry LiFePO.sub.4 is obtained, without Fe.sub.3(PO.sub.4).sub.2. It was sieved to <50 m. It contained about 3.5% by weight of carbon.

(20) II. Manufacture of Cathodes and Batteries According to the Invention, and of Comparative Cathodes and Batteries

(21) II.1 Manufacture of Cathodes and Batteries According to the Invention

(22) Four mixtures of compounds (a) and (b) were prepared:

(23) 80 g weight of compound (I.1) were blended in a ball-mill with 20 g of compound (II.1) to yield inventive cathode active material CAM.1.

(24) 80 g weight of compound (1.1) were blended in a ball-mill with 20 g of comparative compound C(II.2) to yield comparative cathode active material C-CAM.2.

(25) 80 g weight of compound (I.2) were blended in a ball-mill with 20 g of compound (II.1) to yield inventive cathode active material CAM.3.

(26) 80 g weight of compound (I.2) were blended in a ball-mill with 20 g of comparative compound C(II.2) to yield comparative cathode active material C-CAM.4.

(27) Production of Full Cells:

(28) To produce a cathode (A.1), the following ingredients are blended with one another: 93 g of CAM.1 3 g polyvinylidene difluoride, (d.1) (PVdF), commercially available as Kynar Flex 2801 from Arkema Group, 2.5 g carbon black, (c.1), BET surface area of 62 m.sup.2/g, commercially available as Super C 65L from Timcal, 1.5 g graphite, (c.2), commercially available as KS6 from Timcal.

(29) While stirring, a sufficient amount of N-methylpyrrolidone (NMP) was added and the mixture was stirred with an Ultraturrax until a stiff, lump-free paste had been obtained.

(30) Cathodes are prepared as follows: On a 30 m thick aluminum foil the paste is applied with a 15 m doctor blade. The loading after drying is 2.0 mAh/cm.sup.2. The loaded foil is dried for 16 hours in a vacuum oven at 105 C. After cooling to room temperature in a hood, disc-shaped cathodes are punched out of the foil. The cathode discs are then weighed and introduced into an argon glove box where they are again vacuum-dried. Then, cells with the prepared discs are assembled.

(31) Electrochemical testing was conducted in TC2 cells. The electrolyte (C.1) used was a 1 M solution of LiPF.sub.6 in ethyl methyl carbonate/ethylene carbonate (volume ratio 1:1).

(32) Separator (D.1): glass fiber. Anode (B.1): graphite. Potential range of the cell: 2.50 V-4.525 V.

(33) Inventive electrochemical cell (BAT.1) was obtained.

(34) II.2 Manufacture of Cathodes and Electrochemical Cells According to the Invention, and of Comparative Cathodes and Electrochemical Cells

(35) For comparative purposes, the above experiment was repeated but inventive (CAM.1) was replaced by an equal amount of C-CAM.2.

(36) Comparative electrochemical cell C-(BAT.2) was obtained.

(37) III. Testing of Batteries

(38) Electrochemical cells according to the invention and comparative electrochemical cells are each subjected to the following cycling program: Potential range of the cell: 2.70 V-4.2 V., 0.1 C (first and second cycles), 0.5 C (from the third cycle). 1 C=150 mA/g. Temperature: 60 C., ambient temperature, and 0 C.

(39) Electrochemical cells (BAT.1) according to the invention show an overall better performance compared to comparative electrochemical cells C-(BAT.2). Especially, charging and discharging behaviour are improved. Without wishing to be bound to any theory we assign the improved charging and discharging behaviour to the improved electric conductivity.

(40) The electric conductivity was determined as follows:

(41) Disc-shaped pellets with a diameter of 1.4 cm and a height of 7 mm were formed from (CAM.1). The electric conductivity was measured in accordance with B. J. Ingram et al., J. Electrochem. Soc. 2003, 150, E396.

(42) As a comparison, disc-shaped pellets with a diameter of 1.4 cm and a height of 7 mm were formed from C-(CAM.2).

(43) The electric conductivities were determined at different pressures. The results were as follows, see Table 1. At a pressure of 500 bar, the diameter of the pellets was in the range of from 1 to 2 mm.

(44) TABLE-US-00003 TABLE 1 Results of Conductivity Measurements Pressure Conductivity (bar) (CAM.1) [10.sup.4 S/cm] Conductivity C-(CAM.2) [10.sup.4 S/cm] 100 1.82 0.66 200 2.96 1.14 300 3.89 1.53 400 4.68 1.86 500 5.37 2.12