Procédé de préparation d'un matériau actif d'électrode positive du type oxyde métallique lithié comprenant du titane

Abstract

A method for preparing a positive electrode active material for a lithium battery consisting of a lithiated oxide comprising titanium and optionally one or more other metal elements comprising the following successive steps: a) a step of forming a precipitate comprising titanium and the optional other metal element(s) by contacting a titanium coordination complex and, if necessary, at least one salt of the other metal element(s) with an aqueous medium; b) a step of recovering the precipitate thus formed; c) a step of calcining the precipitate in the presence of a lithium source.

Claims

1.-14. (canceled)

15. A method for preparing a positive electrode active material for a lithium battery consisting of a lithiated oxide comprising titanium and optionally one or more other metal elements comprising the following successive steps: a) a step of forming a precipitate comprising titanium and the optional other metal element(s) by contacting a titanium coordination complex and, if necessary, at least one salt of the other metal element(s) with a basic aqueous medium; b) a step of recovering the precipitate thus formed; c) a step of calcining the precipitate in the presence of a lithium source.

16. The preparation method according to claim 15, wherein the optional other metal element(s) is/are selected from transition metal elements, post-transition metal elements and mixtures thereof.

17. The preparation method according to claim 15, wherein the optional further metal element(s) is/are selected from manganese, cobalt, nickel and mixtures thereof.

18. The preparation method according to claim 15, wherein the lithiated oxide comprising titanium is selected from: lamellar oxides of the formula LiTiMO.sub.2, in which M denotes Co, Ni, Mn, Al, Cu, Fe and mixtures thereof; spinel type oxides of the formula LiTiMO.sub.4, in which M denotes Ni, Mn, Co, Cu, Al, Fe and mixtures thereof.

19. The method according to claim 15, wherein the titanium coordination complex comprises at least one ligand comprising at least two groups establishing coordination bonds with titanium.

20. The method according to claim 15, wherein the titanium coordination complex comprises at least one bidentate ligand comprising a carboxylate group and an alcoholate group.

21. The method according to claim 19, wherein the titanium coordination complex further comprises at least one ligand comprising a single group establishing one coordination bond with titanium.

22. The method according to claim 21, wherein the ligand comprising a single group establishing one coordination bond with titanium is a ligand comprising, as the single group establishing one coordination bond with titanium, an —OH group.

23. The method according to claim 15, wherein the coordination complex comprises one or more cations to neutralise, if necessary, the backbone consisting of titanium and its ligands.

24. The method according to claim 15, wherein the coordination complex is a complex of the following formula (I): ##STR00008##

25. The method according to claim 15, wherein the salt(s) of the other metal element(s) is/are nitrates, carbonates, chlorides, or sulphates of the other metal element(s).

26. The method according to claim 15, wherein the step of forming the precipitate is carried out under inert gas.

27. The method according to claim 15, wherein the lithium source is lithium carbonate, lithium hydroxide or lithium acetate.

28. The method according to claim 15, wherein the calcination step is carried out at a temperature ranging from 700° C. to 1000° C. for a duration ranging from 4 hours to 24 hours.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0058] The present invention will be better understood based on the following description and the appended drawings in which:

[0059] FIG. 1 is a graph illustrating, for example 1, the course of the capacitance C (in mAg/h) as a function of the number of cycles N, with curve a) corresponding to that obtained with the button cell comprising the non-titanium-doped material and the curve b) corresponding to that obtained with the button cell comprising the titanium-doped material;

[0060] FIG. 2 is a graph illustrating, for Example 1, the course of the capacitance C (in mAh/g) as a function of the number of cycles N, with curve a) corresponding to the test at 4.3 V and curve b) corresponding to the test at 4.4V;

[0061] FIG. 3 is a graph illustrating, for example 1, the course of the capacitance C (in mAh/g) as a function of the charge/discharge rate applied (indicated by C.sub.rate on the ordinate);

[0062] FIG. 4 is a graph illustrating, for example 2, the course of the capacitance C (in mAg/h) as a function of the number of cycles N, with curve a) corresponding to that obtained for cycling at C/10 and curve b) corresponding to that obtained for cycling at 1 C;

[0063] FIG. 5 is a graph illustrating, for example 2, the course of the capacitance C (in mAh/g) as a function of the charge/discharge rate applied (indicated by C.sub.rate on the ordinate);

[0064] FIG. 6 is a graph illustrating, for example 3, the course of the capacitance C (in mAg/h) as a function of the number of cycles N, with curve a) corresponding to that obtained for cycling at C/10 and curve b) corresponding to that obtained for cycling at 1 C;

[0065] FIG. 7 is a graph illustrating, for example 3, the course of the capacitance C (in mAh/g) as a function of the charge/discharge rate applied (indicated by C.sub.rate on the ordinate).

[0066] FIG. 8 illustrates, for example 4, a graph representing the course of the capacitance C (in mAh/g) as a function of the number of cycles N, with curve a) corresponding to that obtained with the button cell comprising the titanium-doped material and curve b) corresponding to that obtained with the button cell comprising the non-titanium-doped material.

[0067] FIG. 9 is a graph illustrating, for example 4, the course of the capacitance C (in mAh/g) as a function of the charge/discharge rate applied (indicated by the ordinate C.sub.rate), with curve a) corresponding to the 4.9V-3V test of the titanium-doped material and curve b) corresponding to the 4.9V-3V test of the non-titanium-doped material.

[0068] FIG. 10 is a graph illustrating, for example 4, the course of the voltage U (in V) as a function of the capacitance C (in mAh/g).

[0069] FIG. 11 is a graph illustrating, for example 5, the course of the capacitance C (in mAh/g) as a function of the number of cycles N, with curve a) corresponding to that obtained with the button cell comprising the titanium-doped material and curve b) corresponding to that obtained with the button cell comprising the non-titanium-doped material.

[0070] FIG. 12 is a graph illustrating, for example 5, the course of the capacitance C (in mAh/g) as a function of the charge/discharge rate applied (indicated by the ordinate C.sub.rate), with curve a) corresponding to the 4.9V-3V test of the titanium-doped material and curve b) corresponding to the 4.9V-3V test of the non-titanium-doped material.

[0071] FIG. 13 is a graph illustrating, for example 5, the course of the voltage U (in V) as a function of the capacitance C (in mAh/g).

[0072] FIG. 14 illustrates, for example 6, a graph representing the course of the capacitance C (in mAh/g) as a function of the number of cycles N, with curve a) corresponding to that obtained with the button cell comprising the titanium-substituted material and curve b) corresponding to that obtained with the button cell comprising the material without the presence of titanium.

[0073] FIG. 15 illustrates, for example 6, a graph representing the course of the capacitance C (in mAh/g) as a function of the charge/discharge rate applied (indicated by the ordinate C.sub.rate), with curve a) corresponding to the 4.9V-3V test of the titanium-substituted material and curve b) corresponding to the 4.9V-3V test of the material without the presence of titanium.

[0074] FIG. 16 shows a graph illustrating, for example 6, the course of the voltage U (in V) as a function of the capacitance C (in mAh/g).

DETAILED DISCLOSURE OF PARTICULAR EMBODIMENTS

Example 1

[0075] The present example is directed to the preparation of a lamellar oxide of the formula LiNi.sub.0.8Mn.sub.0.08Co.sub.0.1Ti.sub.0.02O.sub.2.

[0076] Firstly, a solution is prepared by dissolving nickel sulphate (169.9 g), manganese sulphate (10.9 g) and cobalt sulphate (22.7 g) in water (392.3 g). To this solution, is added a solution of diammonium bis(lactalo)dihydroxide titanate (9.4 g at 50 mass %) of the following formula:

##STR00002##

[0077] whereby the resulting solution is a 2M equimolar solution (having a volume of approximately 400 mL). A 5M soda solution is prepared separately as well as a dilute ammonia solution (150.2 g of 28 mass % ammonia diluted with 233.1 g of water).

[0078] The three solutions have separate injection circuits allowing the solutions to be pumped into a 5 L co-precipitation reactor, into which 1 L of water and 150 g of 28% ammonia have been previously introduced. The temperature is raised to 50° C. and the content of the reactor is maintained under stirring at 1000 rpm. An auxiliary circuit of inert gas (argon or nitrogen) is used to deoxygenate the solution while maintaining the reactor under an inert atmosphere. The solution containing the metal elements is pumped into the reactor up to 360 mL.

[0079] During the whole operation, the ammonia and soda solution are injected concurrently to maintain a constant pH of 11. Once the metal solution is introduced, the solution is maintained under stirring for 3 hours. The solution is then filtered and the precipitate washed with hot water to remove any sulphate and sodium ions potentially adsorbed on the surface of the material. The mixed hydroxide precipitate of the formula Ni.sub.0.8Mn.sub.0.08Co.sub.0.1Ti.sub.0.02(OH).sub.2 is then dried under vacuum at 80° C. overnight.

[0080] Secondly, the hydroxide of the formula Ni.sub.0.8Mn.sub.0.08Co.sub.0.1Ti.sub.0.02(OH).sub.2 is then mixed with lithium carbonate (3% molar excess relative to the stoichiometry) and then calcined under oxygen at 850° C. for 12 hours to form the compound LiNi.sub.0.8Mn.sub.0.08Co.sub.0.1Ti.sub.0.02O.sub.2.

[0081] The material is then characterised by X-ray diffraction. The X-ray diffraction pattern obtained is characteristic of a lamellar oxide with the space group R-3 m.

[0082] Elemental analyses by ICP and XRF have been carried out on the material, the characterisations yielding the following chemical formulae for the synthesised material: [0083] LiNi.sub.0.79Mn.sub.0.08Co.sub.0.10Ti.sub.0.02O.sub.2 in the case of ICP; [0084] LiNi.sub.0.81Mn.sub.0.07Co.sub.0.10Ti.sub.0.02O.sub.2 in the case of XRF.

[0085] The material has then been characterised electrochemically in a button cell. To do so, the synthesised powder is mixed with a carbon source (SuperP®), PVDF 5130 in N-methyl-2-pyrrolidone (NMP). The mass composition of the mixture represents the following ratio 80/10/10 (material/PVDF/Carbon). The mixture thus formed is coated onto an aluminium foil and left to dry for 24 hours at 60° C. to evaporate the NMP. From this foil thus coated, a 14 mm disk is then cut and dried under vacuum for 48 hours at 80° C. The electrode thus formed is then inserted into a glove box and a button cell is assembled by using lithium metal as the anode, Celgard 2400° as a separator and an electrolyte (1M LiPF.sub.6 in a mixture of EC/PC/DMC carbonate solvents, EC corresponding to ethylene carbonate, PC to propylene carbonate and DMC to dimethyl carbonate).

[0086] Concurrently, a button cell has been made in the same way as above, except that the positive electrode active material is not doped with titanium, this material having the formula LiNi.sub.0.8Mn.sub.0.1Co.sub.0.1O.sub.2. A comparison of the performance of the button cell comprising the titanium-doped material and the button cell comprising the non-titanium-doped material cycled at C/10 between 4.3 V and 2.7 V is set forth in FIG. 1 appended hereto, which is a graph illustrating the course of the capacitance C (in mAg/h) as a function of the number of cycles N, with curve a) corresponding to that obtained with the button cell comprising the non-titanium-doped material and curve b) corresponding to that obtained with the button cell comprising the titanium-doped material.

[0087] It appears that the material with 2% titanium is more stable than the undoped material.

[0088] The titanium-doped material is then evaluated for power, again in the same button cell, the results of the performance obtained at 4.3 V and 4.4 V at 1 C being illustrated in FIG. 2 appended hereto, which illustrates the course of the capacitance C (in mAh/g) as a function of the number of cycles N, with curve a) corresponding to the test at 4.3 V and curve b) corresponding to the test at 4.4 V. A power signature has also been determined, which shows the performance of the material as a function of the charge/discharge rate applied, the results being represented in FIG. 3 appended hereto, which illustrates the course of the capacitance C (in mAh/g) as a function of the charge/discharge rate applied (indicated by the ordinate C.sub.rate), with curve a) corresponding to the 4.3V-2.7V test and curve b) corresponding to the 4.4V-2.7V test.

[0089] The performance achieved by the material is excellent.

Example 2

[0090] This example is directed to the preparation of a lamellar oxide of the formula LiNi.sub.0.9Co.sub.0.05Ti.sub.0.05O.sub.2.

[0091] Firstly, a solution is prepared by dissolving nickel sulphate (191.2 g), cobalt sulphate (11.4 g) in water (380.7 g). To this solution, is added a solution of diammonium bis(lactalo)dihydroxide titanate (23.5 g at 50 mass %) of the following formula:

##STR00003##

[0092] whereby the resulting solution is a 2 M equimolar solution (having a volume of approximately 400 mL). A 5 M soda solution is prepared separately as well as a dilute ammonia solution (150.2 g of 28 mass % ammonia diluted with 233.1 g of water).

[0093] The three solutions have separate injection circuits allowing the solutions to be pumped into a 5 L co-precipitation reactor, into which 1 L of water and 150 g of 28% ammonia have been previously introduced. The temperature is raised to 50° C. and the content of the reactor is maintained under stirring at 1000 rpm. An auxiliary circuit of inert gas (argon or nitrogen) is used to deoxygenate the solution while maintaining the reactor under an inert atmosphere. The solution containing the metal elements is pumped into the reactor up to 360 mL.

[0094] During the whole operation, the ammonia and soda solutions are injected concurrently to maintain a constant pH of 11. Once the metal solution is introduced, the solution is maintained under stirring for 3 hours. The solution is then filtered and the precipitate washed with hot water to remove any sulphate and sodium ions potentially adsorbed on the surface of the material. The mixed hydroxide precipitate of the formula Ni.sub.0.9Co.sub.0.05Ti.sub.0.05(OH).sub.2 is then dried under vacuum at 80° C. overnight.

[0095] Secondly, the hydroxide of the formula Ni.sub.0.9Co.sub.0.05Ti.sub.0.05(OH).sub.2 is then mixed with lithium carbonate (3% molar excess relative to the stoichiometry) and calcined at 850° C. for 12 hours under oxygen to form the compound LiNi.sub.0.9Co.sub.0.05Ti.sub.0.05O.sub.2.

[0096] The material is then characterised by X-ray diffraction. The X-ray diffraction pattern obtained is characteristic of a lamellar oxide with the space group R-3 m.

[0097] Elemental analyses by ICP and XRF have been carried out on the material, the characterisations yielding the following chemical formulae for the synthesised material: [0098] LiNi.sub.0.88Co.sub.0.06Ti.sub.0.06O.sub.2 in case of ICP; and [0099] LiNi.sub.0.88Co.sub.0.06Ti.sub.0.06O.sub.2 in case of XRF.

[0100] The material has then been characterised electrochemically in a button cell. To do so, the synthesised powder is mixed with a carbon source (SuperP®), PVDF 5130 in N-methyl-2-pyrrolidone (NMP). The mass composition of the mixture represents the following ratio 80/10/10 (material/PVDF/Carbon). The mixture thus formed is coated onto an aluminium foil and left to dry for 24 hours at 60° C. to evaporate the NMP. From this foil thus coated, a 14 mm disk is then cut and dried under vacuum for 48 hours at 80° C. The electrode thus formed is then inserted into the glove box and a button cell is assembled by using lithium metal as the anode, Celgard 2400° as a separator and an electrolyte (1M LiPF.sub.6 in a mixture of EC/PC/DMC carbonate solvents, EC corresponding to ethylene carbonate, PC to propylene carbonate and DMC corresponding to dimethyl carbonate).

[0101] The performance of the button cell comprising the titanium-doped material is measured by cycling at C/10 and 1 C, the results being represented in FIG. 4, which is a graph illustrating the course of the capacitance C (in mAg/h) as a function of the number of cycles N, with curve a) corresponding to that obtained for cycling at C/10 and curve b) corresponding to that obtained for cycling at 1 C.

[0102] A power signature has also been determined which shows the performance of the material as a function of the applied charge/discharge rate, the results being represented in FIG. 5 appended hereto, which illustrates the course of the capacitance C (in mAh/g) as a function of the charge/discharge rate applied (indicated by the ordinate C.sub.rate).

[0103] These results highlight an attractive performance.

Example 3

[0104] The present example is directed to the preparation of a lamellar oxide of the formula LiNi.sub.0.8Co.sub.0.1Ti.sub.0.1O.sub.2.

[0105] Firstly, a solution is prepared by dissolving nickel sulphate (169.9 g), cobalt sulphate (22.7 g) in water (361.5 g). To this solution, is added a solution of diammonium bis(lactalo)dihydroxide titanate (47.1 g at 50 mass %) of the following formula:

##STR00004##

[0106] whereby the resulting solution is a 2 M equimolar solution (having a volume of approximately 400 mL). A 5 M soda solution is prepared separately as well as a dilute ammonia solution (150.2 g of 28 mass % ammonia diluted with 233.1 g of water).

[0107] The three solutions have separate injection circuits allowing the solutions to be pumped into a 5 L co-precipitation reactor, into which 1 L of water and 150 g of a 28% ammonia solution have been previously introduced. The temperature is raised to 50° C. and the content of the reactor is maintained under stirring at 1000 rpm. An auxiliary inert gas circuit (argon or nitrogen) is used to deoxygenate the solution while maintaining the reactor under an inert atmosphere. The solution containing the metal elements is pumped into the reactor up to 360 mL.

[0108] During the whole operation, the ammonia and soda solutions are injected concurrently to maintain a constant pH of 11. Once the metal solution is introduced, the solution is maintained under stirring for 3 hours. The solution is then filtered and the precipitate washed with hot water to remove any sulphate and sodium ions potentially adsorbed on the surface of the material. The mixed hydroxide precipitate of the formula Ni.sub.0.8Co.sub.0.1Ti.sub.0.1(OH).sub.2 is then dried under vacuum at 80° C. overnight.

[0109] Secondly, the hydroxide of the formula Ni.sub.0.8Co.sub.0.1Ti.sub.0.1(OH).sub.2 is then mixed with lithium carbonate (3% molar excess relative to the stoichiometry) and calcined under oxygen at 850° C. for 12 hours to form the compound LiNi.sub.0.8Co.sub.0.1Ti.sub.0.1O.sub.2.

[0110] The material is then characterised by X-ray diffraction. The X-ray diffraction pattern obtained is characteristic of a lamellar oxide with the space group R-3 m.

[0111] Elemental analyses by ICP and XRF have been carried out on the material, the characterisations yielding the following chemical formulae for the synthesised material: [0112] LiNi.sub.0.73Co.sub.0.14Ti.sub.0.13O.sub.2 in the case of ICP; and [0113] LiNi.sub.0.73Co.sub.0.14Ti.sub.0.013O.sub.2 in the case of XRF.

[0114] The material has then been characterised electrochemically in a button cell. To do so, the synthesised powder is mixed with a carbon source (SuperP®), PVDF 5130 in N-methyl-2-pyrrolidone (NMP). The mass composition of the mixture represents the following ratio 80/10/10 (material/PVDF/Carbon). The mixture thus formed is coated onto an aluminium foil and left to dry for 24 hours at 60° C. to evaporate the NMP. From this foil thus coated, a 14 mm disk is then cut and dried under vacuum for 48 hours at 80° C. The electrode thus formed is then inserted into the glove box and a button cell is assembled by using lithium metal as the anode, Celgard 2400° as a separator and an electrolyte (1 M LiPF.sub.6 in a mixture of EC/PC/DMC carbonate solvents, EC corresponding to ethylene carbonate, PC to propylene carbonate and DMC corresponding to dimethyl carbonate).

[0115] The performance of the button cell comprising the titanium-doped material is measured by cycling at C/10 and at 1 C, the results being represented in FIG. 6, which is a graph illustrating the course of the capacitance C (in mAg/h) as a function of the number of cycles N, with curve a) corresponding to that obtained for cycling at C/10 and curve b) corresponding to that obtained for cycling at 1 C.

[0116] A power signature has also been determined which shows the performance of the material as a function of the charge/discharge rate applied, the results being represented in FIG. 7 appended hereto, which illustrates the course of the capacitance C (in mAh/g) as a function of different charge/discharge rates (indicated by the ordinate C.sub.rate).

[0117] These results highlight an attractive performance.

Example 4

[0118] The present example is directed to the preparation of a lithiated oxide of spinel type structure having the formula LiNi.sub.0.5Mn.sub.1.48Ti.sub.0.02O.sub.4.

[0119] Firstly, a solution is prepared by dissolving nickel sulphate (53.1 g), manganese sulphate (101.1 g) in water (396.1 g). To this solution, is added a solution of diammonium bis(lactalo)dihydroxide titanate (4.7 g at 50 mass %) of the following formula:

##STR00005##

[0120] whereby the resulting solution is a 2 M equimolar solution (having a volume of approximately 400 mL). A solution comprised of 134.2 g of sodium carbonate and ammonia (31.5 g of 28 mass % ammonia) diluted in water (565 g) is prepared separately.

[0121] The two solutions have separate injection circuits allowing the solutions to be pumped into a 5 L co-precipitation reactor, into which 1 L of water has been previously introduced. The temperature is raised to 50° C. and the content of the reactor is maintained under stirring at 1000 rpm. An auxiliary inert gas circuit (argon or nitrogen) is used to deoxygenate the solution while maintaining the reactor under an inert atmosphere. The solution containing the metal elements is pumped into the reactor up to 360 mL.

[0122] During the whole operation, the solution comprised of sodium carbonate and ammonia is injected concurrently to maintain a constant pH of 7.5. Once the metal solution is introduced, the solution is maintained under stirring overnight. The solution is then filtered and the precipitate washed with hot water to remove any sulphate and sodium ions potentially adsorbed on the surface of the material. The carbonate precipitate of the formula Ni.sub.0.25Mn.sub.0.74Ti.sub.0.01CO.sub.3 is then dried under vacuum at 80° C. overnight.

[0123] Secondly, the carbonate of the formula Ni.sub.0.25Mn.sub.0.74Ti.sub.0.01CO.sub.3 is then mixed with lithium carbonate (3% molar excess relative to the stoichiometry) and calcined under air at 950° C. for 6 hours to form the compound LiNi.sub.0.5Mn.sub.1.48Ti.sub.0.02O.sub.4.

[0124] The material is then characterised by X-ray diffraction. The X-ray diffraction pattern obtained is characteristic of a spinel type material with the space group Fd-3m.

[0125] The material has then been characterised electrochemically in a button cell. To do so, the synthesised powder is mixed with a carbon source (SuperP®), PVDF 8130 in N-methyl-2-pyrrolidone (NMP). The mass composition of the mixture represents the following ratio 90/5/5 (material/PVDF/Carbon). The mixture thus formed is coated onto an aluminium foil and left to dry for 24 hours at 60° C. to evaporate the NMP. From this foil thus coated, a 14 mm disk is then cut and dried under vacuum for 48 hours at 80° C. The electrode thus formed is then inserted into a glove box and a button cell is then assembled by using lithium metal as the anode, Celgard 2400° as a separator and an electrolyte (1M LiPF.sub.6 in a mixture of EC/PC/DMC carbonate solvents, EC corresponding to ethylene carbonate, PC to propylene carbonate and DMC to dimethyl carbonate).

[0126] Concurrently, a button cell has been made in the same way as above, except that the positive electrode active material is not doped with titanium, this material having the formula LiNi.sub.0.5Mn.sub.1.5O.sub.4. A comparison of the performance of the button cell comprising the titanium-doped material and the button cell comprising the non-titanium-doped material is set forth in FIG. 8 appended hereto, which is a graph illustrating the course of the capacitance C (in mAh/g) as a function of the number of cycles N, with curve a) corresponding to that obtained with the button cell comprising the titanium-doped material and curve b) corresponding to that obtained with the button cell comprising the non-titanium-doped material. A power signature of the material is first carried out from C/10 to 15 C over the first 35 cycles (3 cycles at C/10, 5 cycles at C/3, 5 cycles at C, 5 cycles at 3 C, 5 cycles at 5 C, 5 cycles at 10 C, 5 cycles at 15 C) between 4.9 V and 3 V followed by cycling at 1 C over about one hundred cycles. It appears that the material with 1.3% titanium is more stable than the undoped material. This power signature shows the performance of the material as a function of the charge/discharge rate applied. The power behaviour is more clearly illustrated in the FIG. 9 appended hereto, which illustrates the course of the capacitance C (in mAh/g) as a function of the charge/discharge rate applied (indicated by the ordinate C.sub.rate), with curve a) corresponding to the 4.9 V-3 V test of the titanium-doped material and curve b) corresponding to the 4.9 V-3 V test of the non-titanium-doped material.

[0127] Other button cells have been made in the same way as the previous ones and cycled at C/10 over a range of 5.1 V-1.6 V to evaluate the effect of titanium doping on the behaviour of manganese. The results are set forth in FIG. 10 which illustrates the discharge of the material as a function of the measurement potential (curve a) for the doped material and curve b) for the undoped material).

[0128] The performance achieved by the material is excellent.

Example 5

[0129] This example is directed to the preparation of a spinel of the formula LiNi.sub.0.5Mn.sub.1.46Ti.sub.0.04O.sub.4.

[0130] Firstly, a solution is prepared by dissolving nickel sulphate (53.1 g), manganese sulphate (99.7 g) in water (392.3 g). To this solution, is added a solution of diammonium bis(lactalo)dihydroxide titanate (9.4 g at 50 mass %) of the following formula:

##STR00006##

[0131] whereby the resulting solution is a 2 M equimolar solution (having a volume of approximately 400 mL). A solution comprised of 134.2 g of sodium carbonate and ammonia (31.5 g of 28 mass % ammonia) diluted in water (565 g) is prepared separately.

[0132] The two solutions have separate injection circuits allowing the solutions to be pumped into a 5 L co-precipitation reactor, into which 1 L of water has been previously introduced. The temperature is raised to 50° C. and the content of the reactor is maintained under stirring at 1000 rpm. An auxiliary inert gas circuit (argon or nitrogen) is used to deoxygenate the solution while maintaining the reactor under an inert atmosphere. The solution containing the metal elements is pumped into the reactor up to 360 mL.

[0133] During the whole operation, the solution comprised of sodium carbonate and ammonia is injected concurrently to maintain a constant pH of 7.5. Once the metal solution is introduced, the solution is maintained under stirring overnight. The solution is then filtered and the precipitate washed with hot water to remove any sulphate and sodium ions potentially adsorbed on the surface of the material. The carbonate precipitate of the formula Ni.sub.0.25Mn.sub.0.73Ti.sub.0.02CO.sub.3 is then dried under vacuum at 80° C. overnight.

[0134] Secondly, the carbonate of the formula Ni.sub.0.25Mn.sub.0.73Ti.sub.0.02CO.sub.3 is then mixed with lithium carbonate (3% molar excess relative to the stoichiometry) and calcined under air at 950° C. for 6 hours to form the compound of the formula LiNi.sub.0.5Mn.sub.1.46Ti.sub.0.04O.sub.4.

[0135] The material is then characterised by X-ray diffraction. The X-ray diffraction pattern obtained is characteristic of a spinel type material with the space group Fd-3m.

[0136] The material has then been characterised electrochemically in a button cell. To do so, the synthesised powder is mixed with a carbon source (SuperP®), PVDF 8130 in N-methyl-2-pyrrolidone (NMP). The mass composition of the mixture represents the following ratio 90/5/5 (material/PVDF/Carbon). The mixture thus formed is coated onto an aluminium foil and left to dry for 24 hours at 60° C. to evaporate the NMP. From this foil thus coated, a 14 mm disk is then cut and dried under vacuum for 48 hours at 80° C. The electrode thus formed is then inserted into a glove box and a button cell is assembled by using lithium metal as the anode, Celgard 2400° as a separator and an electrolyte (1M LiPF.sub.6 in a mixture of EC/PC/DMC carbonate solvents, EC corresponding to ethylene carbonate, PC to propylene carbonate and DMC to dimethyl carbonate).

[0137] Concurrently, a button cell has been made in the same way as above, except that the positive electrode active material was not doped with titanium, this material having the formula LiNi.sub.0.5Mn.sub.1.5O.sub.4. A comparison of the performance of the button cell comprising the titanium-doped material and the button cell comprising the non-titanium-doped material is set forth in FIG. 11 appended hereto, which is a graph illustrating the course of the capacitance C (in mAh/g) as a function of the number of cycles N, with curve a) corresponding to that obtained with the button cell comprising the titanium-doped material and curve b) corresponding to that obtained with the button cell comprising the non-titanium-doped material. A power signature of the material is first carried out from C/10 to 15 C over the first 35 cycles (3 cycles at C/10, 5 cycles at C/3, 5 cycles at C, 5 cycles at 3 C, 5 cycles at 5 C, 5 cycles at 10 C, 5 cycles at 15 C) between 4.9 V and 3 V followed by cycling at 1 C over about one hundred cycles. It appears that the material with 2.7% titanium is more stable than the undoped material. This power signature shows the performance of the material as a function of the charge/discharge rate applied. The power behaviour is more clearly represented in the FIG. 12 appended hereto, which illustrates the course of the capacitance C (in mAh/g) as a function of the charge/discharge rate applied (indicated by the ordinate C.sub.rate), with curve a) corresponding to the 4.9 V-3 V test of the titanium-doped material and curve b) corresponding to the 4.9 V-3 V test of the non-titanium-doped material.

[0138] Other button cells have been made in the same way as the previous ones and cycled at C/10 over a range of 5.1 V-1.6 V to evaluate the effect of titanium doping on the manganese behaviour. The results are set forth in FIG. 13 in the appendix, which illustrates the discharge of the material as a function of the measurement potential.

[0139] The performance achieved by the material is excellent.

Example 6

[0140] This example is directed to the preparation of a spinel of the formula LiNi.sub.0.5Mn.sub.1.1Ti.sub.0.4O.sub.4.

[0141] Firstly, a solution is prepared by dissolving nickel sulphate (53.1 g), manganese sulphate (75.1 g) in water (323.0 g). To this solution, is added a solution of diammonium bis(lactalo)dihydroxide titanate (94.1 g at 50 mass %) of the following formula:

##STR00007##

[0142] whereby the resulting solution is a 2 M equimolar solution (having a volume of approximately 400 mL). A solution comprised of 134.2 g of sodium carbonate and ammonia (31.5 g of 28 mass % ammonia) diluted in water (565 g) is prepared separately.

[0143] The two solutions have separate injection circuits allowing the solutions to be pumped into a 5 L co-precipitation reactor, into which 1 L of water has been previously introduced. The temperature is raised to 50° C. and the content of the reactor is maintained under stirring at 1000 rpm. An auxiliary inert gas circuit (argon or nitrogen) is used to deoxygenate the solution while maintaining the reactor under an inert atmosphere. The solution containing the metal elements is pumped into the reactor up to 360 mL.

[0144] During the whole operation, the solution comprised of sodium carbonate and ammonia is injected concurrently to maintain a constant pH of 7.5. Once the metal solution is introduced, the solution is maintained under stirring overnight. The solution is then filtered and the precipitate washed with hot water to remove any sulphate and sodium ions potentially adsorbed on the surface of the material. The carbonate precipitate of the formula Ni.sub.0.25Mn.sub.0.55Ti.sub.0.2CO.sub.3 is then dried under vacuum at 80° C. overnight.

[0145] Secondly, the carbonate of the formula Ni.sub.0.25Mn.sub.0.55Ti.sub.0.2CO.sub.3 is then mixed with lithium carbonate (3% molar excess relative to the stoichiometry) and calcined under air at 950° C. for 6 hours to form the compound of the formula LiNi.sub.0.5Mn.sub.1.1Ti.sub.0.4O.sub.4.

[0146] The material is then characterised by X-ray diffraction. The X-ray diffraction pattern obtained is characteristic of a spinel type material with the space group Fd-3m.

[0147] The material has then been characterised electrochemically in a button cell. To do so, the synthesised powder is mixed with a carbon source (SuperP®), PVDF 8130 in N-methyl-2-pyrrolidone (NMP). The mass composition of the mixture represents the following ratio 90/5/5 (material/PVDF/Carbon). The mixture thus formed is coated onto an aluminium foil and left to dry for 24 hours at 60° C. to evaporate the NMP. From this foil thus coated, a 14 mm disk is then cut and dried under vacuum for 48 hours at 80° C. The electrode thus formed is then inserted into a glove box and a button cell is assembled by using lithium metal as the anode, Celgard 2400° as a separator and an electrolyte (1 M LiPF.sub.6 in a mixture of EC/PC/DMC carbonate solvents, EC corresponding to ethylene carbonate, PC to propylene carbonate and DMC to dimethyl carbonate).

[0148] Concurrently, a button cell has been made in the same way as above, except that the positive electrode active material was without titanium, this material having the formula LiNi.sub.0.5Mn.sub.1.5O.sub.4. A comparison of the performance of the button cell comprising the titanium-substituted material and the button cell comprising the material without the presence of titanium is set forth in FIG. 14 appended hereto, which is a graph illustrating the course of the capacitance C (in mAh/g) as a function of the number of cycles N, with curve a) corresponding to that obtained with the button cell comprising the titanium-substituted material and curve b) corresponding to that obtained with the button cell comprising the material without the presence of titanium. A power signature of the material is first carried out from C/10 to 15 C over the first 35 cycles (3 cycles at C/10, 5 cycles at C/3, 5 cycles at C, 5 cycles at 3 C, 5 cycles at 5 C, 5 cycles at 10 C, 5 cycles at 15 C between 4.9 V and 3 V) followed by a cycling at 1 C over about one hundred cycles. It appears that the material with 36% titanium is more stable than the material without titanium. This power signature shows the performance of the material as a function of the charge/discharge rate applied. The power behaviour is more clearly represented in the FIG. 15 appended hereto, which illustrates the course of the capacitance C (in mAh/g) as a function of the charge/discharge rate applied (indicated by the ordinate C.sub.rate), with curve a) corresponding to the 4.9 V-3 V test of the titanium-substituted material and curve b) corresponding to the 4.9 V-3 V test of the material without the presence of titanium.

[0149] Other button cells have been made in the same way as the previous ones and cycled at C/10 over a range of 5.1 V-1.6 V to evaluate the effect of manganese substitution with titanium on the behaviour of the material. The results are set forth in FIG. 16 of the appendix, which illustrates the discharge of the material as a function of the measurement potential.

[0150] The performance achieved by the material is lower than that of the unsubstituted material but in the same orders of magnitude as materials described in scientific journals, such as in P. Strobel et al, «Effect of tetravalent cation on 5 V redox mechanism in LiNi.sub.0.5M.sub.1.5O.sub.4 spinels», Meet. Abstr. MA2010-03 572, 2010. and M. Lin et al, «A strategy to improve cyclic performance of LiNi.sub.0.5M.sub.1.5O.sub.4 in a wide voltage region by Ti-doping», Journal of the Electrochemical Society, 160 (5) A3036-A3040 (2013).