METHOD FOR SYNTHESISING SPHERICAL MATERIAL PARTICLES

Abstract

A method for synthesising spherical material particles carried out in a continuous reactor. An intake tube is supplied with a solution A including at least one transition metal sulfate and the other intake tube being supplied with a solution B comprising hydroxide or a carbonate. The method includes delivering solutions A and B to a reaction tube at a flow rate d.sub.A and d.sub.B, and recovering the precipitated precursor at the outlet of the reaction tube. The length of the reaction tube and the delivery flow rates d.sub.A and d.sub.B are configured such that the residence time in the reaction tube is less than or equal to 10 seconds, wherein the pH in the reaction tube is 7 to 12 and wherein the regime in the reaction tube is a laminar regime.

Claims

1. Method for synthesising spherical material particles, said method being carried out in a continuous reactor, said continuous reactor being formed by a reaction tube, said reaction tube being supplied by two intake tubes, the reaction tube having a length L, one of the two intake tubes being supplied with a solution A comprising at least one transition metal sulfate chosen from among nickel (Ni), aluminium (Al), magnesium (Mg), titanium (Ti), copper (Cu), zinc (Zn), iron (Fe), manganese (Mn) and cobalt (Co), the other intake tube being supplied with a solution B comprising a hydroxide or a carbonate and optionally a chelating agent, said method comprising the following steps: a) delivering solutions A and B to the reaction tube of the continuous reactor at a flow rate of d.sub.A and d.sub.B respectively, resulting in the precipitation of a precursor in the reaction tube, and b) recovering said precipitated precursor at the outlet of the reaction tube, wherein the length L of the reaction tube and the delivery flow rates d.sub.A and d.sub.B are configured such that the residence time in the reaction tube is less than or equal to 10 seconds, wherein the pH in the reaction tube is 7 to 12 and wherein the regime in the reaction tube is a laminar regime.

2. Synthesis method according to claim 1, wherein the residence time in the reaction tube is between 1 millisecond and 10 seconds, the residence time in the reaction tube is preferably less than or equal to 5 seconds, the residence time in the reaction tube is more preferably still less than or equal to 1 second.

3. Synthesis method according to claim 1, wherein the length L of the reaction tube is at least 1 mm.

4. Synthesis method according to claim 1, wherein the inner diameter of each intake tube and the reaction tube is at least 0.5 mm, the inner diameter of each intake tube is preferably greater than 1 mm, the inner diameter of each intake tube and the reaction tube is more preferably still between 1 and 1.5 mm.

5. Synthesis method according to claim 1, wherein the temperature in the reaction tube is between 20? C. and 70? C., preferably between 25? C. and 50? C.

6. Synthesis method according to claim 1, wherein the solution A comprises at least three transition metal sulfates chosen from among nickel (Ni), aluminium (Al), manganese (Mn) and cobalt (Co).

7. Synthesis method according to claim 1, wherein the hydroxide is chosen from the group made up of sodium hydroxide, potassium hydroxide, 8-hydroxyquinoline, ammonia, lithium hydroxide and mixtures thereof, the hydroxide is preferably sodium hydroxide.

8. Synthesis method according to claim 1, wherein the carbonate is chosen from the group made up of ammonium bicarbonate, sodium carbonate, potassium carbonate, lithium carbonate and mixtures thereof, the carbonate is preferably sodium carbonate.

9. Synthesis method according to claim 1, wherein each solution A and B is delivered by means of a peristaltic pump.

10. Synthesis method according to claim 1, wherein the delivery flow rates d.sub.A and d.sub.B are each at least 0.01 m/min.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0050] FIG. 1 is a diagram of a T-shaped continuous reactor used in the synthesis method according to the invention.

[0051] FIG. 2 combines two charts (A and B) relating to the chemical classification and purity of a precursor precipitated using the synthesis method according to the invention. Figure a) shows the result of an X-ray diffractogram performed on said precursor. The x-axis represents 26 in degrees and the y-axis is the intensity in arbitrary units. Figure b) shows the result of a thermogravimetric analysis carried out on 30 mg of sample of said precursor. The x-axis shows the temperature in ? C. and the y-axis shows the mass of the sample as a percentage. The double arrow indicates the loss of mass obtained at 640? C. (?35.5%).

[0052] FIG. 3 is a series of images (A and B) obtained by scanning electron microscopy of aggregates of a precursor precipitated according to the synthesis method according to the invention. The white bar shows the scale for each image.

[0053] FIG. 4 shows the distribution of the size of the aggregates of a sample of a precursor precipitated using the synthesis method according to the invention in volume (FIG. 4A) and in number (FIG. 4B). In FIG. 4A, the x-axis shows the size of the aggregates in micrometres and the y-axis shows the volume occupied by the aggregates as a percentage. In FIG. 4B, the x-axis shows the size of the aggregates in micrometres and the y-axis shows the number of aggregates as a percentage.

[0054] FIG. 5 shows the thermal cycle used to synthesise a positive electrode active material from a precursor obtained using the synthesis method according to the invention. In this figure, A represents the starting conditions corresponding to room temperature (25? C.). The temperature is then increased at a rate of 3.5? C./min until it reaches 400? C. B corresponds to decarbonization, where the temperature is maintained at 400? C. for 2 hours. The temperature is then increased at a rate of 3.5? C./min until it reaches 900? C. C corresponds to crystallization, where the temperature is maintained at 900? C. for 12 hours. The temperature is then decreased at a rate of 2? C. per minute, returning to room temperature at D.

[0055] FIG. 6 shows an X-ray diffractogram performed on a positive electrode active material obtained from a precursor obtained using the synthesis method according to the invention. The x-axis represents 26 in degrees and the y-axis is the intensity in arbitrary units. The inset shows an improved view of the diffractogram for the values 30? to 80? of 2?. The hollow circles represent the observed intensity values. The black lines in the hollow circles represent the expected theoretical values. The black line at the bottom represents the difference between the observed values and the expected vales (an absence of peak corresponds to no observed difference). The vertical black lines above the black line represent the position of the Bragg reflections.

[0056] FIG. 7 is a series of images (A and B) obtained by scanning electron microscopy of aggregates of a positive electrode active material obtained from a precursor precipitated using the synthesis method according to the invention. The white bar shows the scale on each image.

[0057] FIG. 8 shows the evolution in discharged capacity (mAh.g.sup.?1) as a function of the number of cycles of a 2032 button cell comprising a positive electrode active material obtained from a precursor precipitated using the synthesis method according to the invention.

[0058] FIG. 9 shows an X-ray diffractogram performed on two precursors obtained by comparative synthesis methods where the delivery flow rates of the solutions A and B were 4 ml/min and where the length of the reaction tube of the microfluidic reactor was 1 metre (curve 1) or 2 metres (curve 2). The x-axis represents 20 in degrees and the y-axis is the intensity in arbitrary units. The origin of the y-axis of curve 2 has been moved to make the figure easier to read.

[0059] FIG. 10 shows two images obtained by scanning electron microscopy of aggregates of precursors precipitated using a comparative synthesis method where the delivery flow rates of the solutions A and B were 4 ml/min and where the length of the reaction tube of the microfluidic reactor was 1 metre (FIG. 10A) or 2 metres (FIG. 10B). The white bar shows the scale on each image.

[0060] FIG. 11 shows the result of an X-ray diffractogram performed on a precursor Ni.sub.0.25Mn.sub.0.75CO.sub.3 obtained according to the method of the invention. The x-axis represents 20 in degrees and the y-axis is the intensity in arbitrary units.

[0061] FIG. 12 is a series of images (A and B) obtained by scanning electron microscopy of aggregates of a precursor Ni.sub.0.25Mn.sub.0.75CO.sub.3 obtained according to the method of the invention. The white bar shows the scale for each image.

[0062] FIG. 13 shows the result of an X-ray diffractogram performed on a precursor Ni.sub.1/3Mn.sub.1/3Co.sub.1/3CO.sub.3 obtained according to the method of the invention. The x-axis represents 20 in degrees and the y-axis is the intensity in arbitrary units.

[0063] FIG. 14 is a series of images (A and B) obtained by scanning electron microscopy of aggregates of a precursor Ni.sub.1/3Mn.sub.1/3Co.sub.1/3CO.sub.3 obtained according to the method of the invention. The white bar shows the scale for each image.

[0064] FIG. 15 shows the result of an X-ray diffractogram performed on a precursor Ni.sub.1/3Mn.sub.1/3Co.sub.1/3CO.sub.3 obtained according to a method in which the regime in the reaction tube is turbulent. The x-axis represents 20 in degrees and the y-axis is the intensity in arbitrary units.

[0065] FIG. 16 is a series of images (A, B and C) obtained by scanning electron microscopy of aggregates of a precursor Ni.sub.1/3Mn.sub.1/3Co.sub.1/3CO.sub.3 obtained according to a method in which the regime in the reaction tube is turbulent. The white bar shows the scale for each image.

EXAMPLES

1. T-Shaped Continuous Reactor

[0066] The continuous reactor 1 used in the invention is shown in FIG. 1. This figure shows the T-shaped continuous reactor made up of two intake tubes 3 facing each other, each supplied with a solution (A or B) joining at an intersection leading into a reaction tube 5 perpendicular to the direction of the intake tubes 3 at the intersection. A counter-flow is thus achieved at the intersection of the two intake tubes 3. The solution A contains the transition metal sulfates and the solution B comprises a hydroxide or a carbonate as well as a complexing agent. The solutions A and B are delivered to the reactor 1 thanks to peristaltic pumps 7. The precursor precipitates in the reaction tube, which leads into a tank 9 where the precipitated precursor is recovered.

2. Carbonate Precursor Ni.SUB.0.2.Mn.SUB.0.5.Co.SUB.0.3.CO.SUB.3

[0067] The inventors first of all synthesized a carbonate precursor rich in manganese, the composition of which is Ni.sub.0.2Mn.sub.0.5Co.sub.0.3CO.sub.3.

a. Preparing Starting Solutions

[0068] To do so, a solution A of 250 mL of transition metal sulfates was prepared by weighing 26.29 g of NiSO.sub.4.Math.6H.sub.2O, 42.26 g of MnSO.sub.4.Math.H.sub.2O and 42.17 g of CoSO.sub.4.Math.7H.sub.2O. These sulfates were dissolved in distilled water then placed in a volumetric flask of 250 mL filled to the mark. The Ni/Mn/Co molar ratio is 2/5/3. The concentration of this solution is 2 mol/l. A solution B of 250 mL containing sodium carbonate and a complexing agent (NH.sub.4OH) was prepared by dissolving 47.69 g of Na.sub.2CO.sub.3 and 11.26 g of NH.sub.4OH in distilled water then placed in a volumetric flask of 250 mL filled to the mark. The concentration of Na.sub.2CO.sub.3 is 1.8 mol/L and the concentration of NH.sub.4OH is 0.36 mol/L.

b. Synthesis Conditions

[0069] The sampling flow rate for the solution containing the transition metals was 20 mL/min while the sampling flow rate for the solution containing the carbonate was 12 mL/min. The pH of the solution containing the precipitate was 7.8. The discharge tube from the reactor was 10 cm long and had an inner diameter of 1.39 mm. Under these conditions, the residence time in the discharge tube from the reactor was 0.3 s and the regime of the fluid in the reactor was laminar. The precipitate was not sampled for the first 30 seconds of the reaction, then sampled for 60 seconds. It is then washed by centrifugation with distilled water (until the wash water has been neutralized) and dried in an oven at 70? C. for 1 night.

[0070] The mass of transition metal carbonate recovered after drying was 2.56 g, in line with the expected theoretical quantity (2.53 g). This shows that the reaction yield is close to 100%.

c. Analysis of the Precipitate

[0071] An X-ray diffractogram (XRD) was performed and the result is shown in FIG. 2A. This diffractogram shows that all the lines are indexable in the R-3c space group, the lattice parameters of which are: a=b=4.778(3) ?, c=15.424(9) ?. This diffractogram therefore confirms that a carbonate without any crystallized impurities has been obtained. In addition, a thermogravimetric analysis was performed on around 30 mg of powder in air at a temperature of 25? C. up to 700? C. with an increase rate of 10? C./min. The result is shown in FIG. 2B and also confirms that a carbonate without any crystallized impurities has been obtained as the experimental mass loss (?35.5%) is equivalent to the expected theoretical mass loss (?37.6%).

[0072] Chemical analysis was carried out using inductively coupled plasma optical emission spectroscopy (ICP-OES) to determine the chemical composition of the precipitate:

TABLE-US-00003 TABLE 3 Ni Mn Co Experimental 0.17 ? 0.01 0.53 ? 0.02 0.30 ? 0.01 Theory 0.2 0.5 0.3

[0073] The experimental composition is in line with the expected theoretical composition.

[0074] The morphology of the aggregates was verified by scanning electron microscopy (SEM), the results of which are shown in FIG. 3. The observed aggregates have a diameter of around 6 micrometres. This value and the homogeneity were verified by laser granulometry analysis, the results of which are shown in FIG. 4. The volume distribution 50 (D50) of the precipitate is 6.3 ?m, in line with the observations carried out using SEM.

d. Preparing an Active Material and Electrochemical Performance

[0075] The inventors then mixed the precursor Ni.sub.0.2Mn.sub.0.5Co.sub.0.3CO.sub.3 with Li.sub.2CO.sub.3 in order to synthesize a positive electrode active material for a battery with the formula:

##STR00001##

[0076] For this, 2 g of Ni.sub.0.2Mn.sub.0.5Co.sub.0.3CO.sub.3 were mixed in an agate mortar with 0.8980 g of Li.sub.2CO.sub.3 (with an excess of 5% by mass in order to prevent any lithium loss during the calcination of the material at high temperature) for at least 5 min until a homogeneous coloured mixture was obtained. The mixture is then positioned in a gold crucible and placed in a tube furnace in order to undergo heat treatment at high temperature in air, the thermal cycle of which is shown in FIG. 5.

[0077] An XRD is performed on the active material. The results are shown in FIG. 6 and confirm that a lamellar oxide has been obtained, the X-ray diffraction pattern of which can be indexed in the space group R-3m with the lattice parameters a=b=2.8470(1) ? et c=14.2171(9) ?. The material obtained after synthesis is pure, no crystallized secondary phase was observed. The lattice parameters obtained after refinement using the Le Bail method are in line with those obtained for this same compound from a precursor synthesized by co-precipitation (a=b=2.8492(3) ? and c=14.219(3) ?). The Le Bail method is described in particular in the document Petricek, V., Dusek, M. & Palatinus, L. (2014). Z. Kristallogr. 229(5), 345-352.

[0078] The chemical composition was verified by ICP-OES, the results of which are shown in the following table

TABLE-US-00004 TABLE 4 Li Ni Mn Co Carbonate 1.18 ? 0.03 0.137 ? 0.004 0.435 ? 0.013 0.247 ? 0.007 Oxide 1.15 0.144 0.450 0.255 Theoretical 1.15 0.17 0.425 0.255

[0079] The last line of table 2 corresponds to the expected composition for a lithium oxide considering the Ni/Mn/Co ratio of 2/5/3. The carbonate (1st line in the table) and the oxide (2nd line in the table) obtained have a very slight deviation from the expected composition (last line in the table) for a lithium oxide considering the Ni/Mn/Co ratio of 2/5/3. The materials obtained are therefore ideal for use as an active material in a battery cathode.

[0080] SEM images shown in FIG. 7 show the morphology of the aggregates of the material obtained. As with the precursor, spherical aggregates of the order of 6 ?m were obtained.

[0081] An electrode composed of 92% obtained active material, 4% carbon black and 4% polyvinylidene fluoride (92/4/4 in % by mass) was prepared. To do this, a solution of polyvinylidene fluoride dissolved in N-Methyl-2-pyrrolidone (5% by mass) was initially prepared. The active material and carbon black were then suspended in this solution and the required quantity of N-Methyl-2-pyrrolidone was added to obtain a dry matter content of around 30 to 40%. The mixture was left under magnetic stirring for 1 hour. The resulting ink was coated onto an aluminium strip (coating thickness of 150 ?m) by the method known as Doctor Blade using the Elcometer? 4340 applicator.

[0082] The electrode was finally placed in an oven at 80? C. to evaporate the solvent. Electrodes with a diameter of 16 mm were die-cut and then calendered at a uniaxial pressure of 5 tonnes. Finally, these electrodes were dried at 80? C. in a vacuum for 12 hours before being stored in a glove box under a controlled argon atmosphere. The grammage was 4 mg of active material per cm.sup.2. Electrochemical tests were then carried out in CR2032 button cells in the presence of Li with 2 Celgard? 2400 separators. The electrolyte used is a mixture of fluoroethylene carbonate (FEC) and dimethyl carbonate (DMC) (30/70 in % by mass) in which 1M lithium hexafluorophosphate (LiPF.sub.6) is dissolved. Successive charge and discharge cycles were carried out at a C/10 regime (i.e. 10 hours to fully charge or discharge the cell). The evolution in discharged capacity as a function of the number of cycles is shown in FIG. 8. This figure shows that the capacity remains stable around 200 mAh/g during the first 30 cycles of cells tested.

e. Influence of the Residence Time in the Reactor

[0083] The inventors tested longer residence times in the discharge tube from the reactor (greater than 10 seconds) and their impact on the morphology and homogeneity of the precursors obtained.

[0084] To do this, the initial solutions A and B from example 2.a. were used. Two different reactors were then used (1 and 2), wherein the reactor 1 had a discharge tube length of 1 metre and the reactor 2 had a discharge tube length of 2 metres. Each reactor 1 and 2 had an inner diameter of 1.39 mm. In each case, the sampling flow rate for the solutions A and B was 4 mL/min. The residence time for the discharge tube from the reactor 1 was 11.4 seconds and the residence time in the discharge tube from the reactor 2 was 22.8 seconds. The regime of the fluid in the reactor was laminar. The pH of each solution containing the precipitate was 8.

[0085] An X-ray diffractogram (XRD) was performed on the precipitate obtained and the result is shown in FIG. 9. This diffractogram shows that all the lines are indexable in the R-3c space group, the lattice parameters of which are: a=b=4.778(3) ?, c=15.424(9) ?. This diffractogram confirms that a carbonate without any crystallized impurities has been obtained.

[0086] The chemical composition was verified by ICP-OES, the results of which are shown in the following table

TABLE-US-00005 TABLE 5 Ni Mn Co Reactor 1 0.18 ? 0.01 0.51 ? 0.02 0.31 ? 0.01 Reactor 2 0.18 ? 0.01 0.51 ? 0.02 0.31 ? 0.01 Theoretical 0.2 0.5 0.3

[0087] The experimental composition obtained with each reactor is in line with the expected theoretical composition.

[0088] The morphology of the aggregates was verified by scanning electron microscopy, the results of which are shown in FIG. 10. In each case, the aggregates observed were partially spherical with a high degree of heterogeneity in the shape and size of the aggregates. In addition, the size of the aggregates was of the order of 1 ?m at best. A residence time of more than 10 seconds in the discharge tube therefore diminishes the properties of the precursor obtained, which no longer has the diameter and homogeneity of the precursors obtained with the synthesis method according to the invention.

3. Carbonate Precursor Ni.SUB.0.25.Mn.SUB.0.75.CO.SUB.3

[0089] The inventors subsequently synthesized a carbonate precursor rich in manganese, the composition of which is Ni.sub.0.25Mn.sub.0.75CO.sub.3.

a. Preparing Starting Solutions

[0090] To do so, a solution of 50 mL of transition metal sulfates was prepared by weighing 6.57 g of NiSO.sub.4.6H.sub.2O and 12.68 g of MnSO.sub.4.Math.H.sub.2O. These Sulfates were dissolved in distilled water then placed in a volumetric flask of 50 mL filled to the mark. The Ni/Mn/Co molar ratio was ?:?:?. The concentration of this solution is 2 mol/L. A solution of 50 mL containing sodium carbonate and a complexing agent (NH.sub.4OH) was prepared by weighing 10.60 g of Na.sub.2CO.sub.3 and 2.25 g of NH.sub.4OH. Na.sub.2CO.sub.3 was dissolved in distilled water in the presence of NH.sub.4OH then placed in a volumetric flask of 50 mL filled to the mark. The concentration of Na.sub.2CO.sub.3 is 2 mol/L and the concentration of NH.sub.4OH is 0.36 mol/L.

b. Synthesis Conditions

[0091] The solutions were injected into the mixer/reactor system by means of peristaltic pumps. The sampling flow rate for the solution containing the transition metals was set at 5 mL/min (Qa) and the sampling flow rate for the solution containing the carbonate was set at 5 mL/min (Qb) (so Qa=Qb). The reactor was 10 cm long and had an inner diameter of 1.39 mm. Under these conditions, the residence time in the reactor was 0.91 s and the regime of the fluid in the reactor was laminar. In order to ensure the homogeneity of the precipitate that is recovered, the precipitate was not recovered for the first 30 seconds of the reaction, then it was sampled under the aforementioned conditions for 60 seconds. The pH of the solution containing the precipitate was 8.7. The precipitate was then washed by centrifugation with distilled water (until the wash water had been neutralized) and dried in an oven at 70? C. for 1 night.

[0092] The mass of transition metal carbonate recovered after drying was 2.33 g, in line with the expected theoretical quantity (2.37 g). This shows that the reaction yield is close to 100%. 2.33 g of carbonates Ni.sub.0.25Mn.sub.0.75CO.sub.3 were therefore produced in 60 seconds. This constitutes a production of 140 g/h for a 0.15 mL reactor compared with 16 g in a 500 mL batch reactor over 6 h used in the prior art.

c. Analysis of the Precipitate

[0093] An X-ray diffractogram (XRD) was performed and the result is shown in FIG. 11. This diffractogram confirms that a carbonate without any crystallized impurities has been obtained.

[0094] Chemical analysis was carried out using inductively coupled plasma optical emission spectroscopy (ICP-OES) to determine the chemical composition of the precipitate:

TABLE-US-00006 TABLE 6 Ni Mn Experimental 0.24 0.76 Theory 0.25 0.75

[0095] The experimental composition is in line with the expected theoretical composition.

[0096] The morphology of the aggregates was verified by scanning electron microscopy (SEM), the results of which are shown in FIG. 12. The observed aggregates have a diameter of around 4 micrometres.

[0097] All of these characteristics (XRD, ICP-OES, SEM) demonstrate that a transition metal carbonate with controlled composition and morphology has been obtained.

4. Carbonate Precursors Ni.SUB.1/3.Mn.SUB.1/3.Co.SUB.1/3.CO.SUB.3

[0098] The inventors subsequently synthesized a carbonate precursor, the composition of which is Ni.sub.1/3Mn.sub.1/3Co.sub.1/3CO.sub.3.

A. Preparing Starting Solutions

[0099] To do so, a solution of 50 mL of transition metal sulfates was prepared by weighing 8.67 g of NiSO.sub.4.Math.6H.sub.2O, 5.58 g of MnSO.sub.4.Math.H.sub.2O and 9.28 g of CoSO.sub.4.Math.7H.sub.2O. These sulfates were dissolved in distilled water then placed in a volumetric flask of 50 mL filled to the mark. The Ni/Mn/Co molar ratio is ?:?:?. The concentration of this solution is 2 mol/L. A solution of 50 mL containing sodium carbonate and a complexing agent (NH.sub.4OH) was prepared by weighing 10.60 g of Na.sub.2CO.sub.3 and 2.25 g of NH.sub.4OH. Na.sub.2CO.sub.3 was dissolved in distilled water in the presence of NH.sub.4OH then placed in a volumetric flask of 50 mL filled to the mark. The concentration of Na.sub.2CO.sub.3 is 2 mol/L and the concentration of NH.sub.4OH is 0.36 mol/L.

b. Synthesis Conditions

[0100] The solutions were injected into the mixer/reactor system by means of peristaltic pumps. The sampling flow rate for the solution containing the transition metals was set at 15 mL/min (Qa) and the sampling flow rate for the solution containing the carbonate was set at 15 mL/min (Qb) (so Qa=Qb). The reactor was 10 cm long and had an inner diameter of 1.39 mm. Under these conditions, the residence time in the reactor was 0.3 s and the regime of the fluid in the reactor was laminar. In order to ensure the homogeneity of the precipitate that is recovered, the precipitate was not recovered for the first 30 seconds of the reaction, then it was sampled under the aforementioned conditions for 60 seconds. The pH of the solution containing the precipitate was 7.3. The precipitate was then washed by centrifugation with distilled water (until the wash water had been neutralized) and dried in an oven at 70? C. for 1 night.

[0101] The mass of transition metal carbonate recovered after drying was 2.24 g, in line with the expected theoretical quantity (2.27 g). This shows that the reaction yield is close to 100%. 2.24 g of carbonates Ni.sub.1/3Mn.sub.1/3Co.sub.1/3CO.sub.3 were therefore produced in 60 seconds. This constitutes a production of 136 g/h for a 0.15 mL reactor compared with 16 g in a 500 mL batch reactor over 6 h used in the prior art.

c. Analysis of the Precipitate

[0102] An X-ray diffractogram (XRD) was performed and the result is shown in FIG. 13. This diffractogram indicates that a carbonate with a slight presence of oxyhydroxide has been obtained.

[0103] Chemical analysis was carried out using inductively coupled plasma optical emission spectroscopy (ICP-OES) to determine the chemical composition of the precipitate:

TABLE-US-00007 TABLE 7 Ni Mn Co Experimental 0.33 0.33 0.33 Theory 0.33 0.33 0.33

[0104] The experimental composition is in line with the expected theoretical composition.

[0105] The morphology of the aggregates was verified by scanning electron microscopy (SEM), the results of which are shown in FIG. 14. The observed aggregates have a diameter of around 5 micrometres.

[0106] All of these characteristics (XRD, ICP-OES, SEM) demonstrate that a transition metal carbonate with controlled composition and morphology has been obtained.

d. Influence of the Regime in the Reaction Tube

[0107] The inventors tested the influence of the regime in the reaction tube with regard to obtaining the precursor Ni.sub.1/3Mn.sub.1/3Co.sub.1/3CO.sub.3.

[0108] To do this, a 50 mL solution of metal sulfates was prepared with an Ni/Mn/Co molar ratio of ?:?:?, and a concentration of 0.1 mol/L. A 50 mL solution containing 0.2 mol/L ammonium bicarbonate was also prepared.

[0109] The solutions were injected into the mixer/reactor system by means of peristaltic pumps. The sampling flow rate for the solution containing the transition metals was set at 50 mL/min (Qa) and the sampling flow rate for the solution containing the carbonate was set at 50 mL/min (Qb) (so Qa=Qb). The reactor was 10 cm long and had an inner diameter of 1.39 mm. Under these conditions, the regime of the fluid in the reactor was laminar. In order to ensure the homogeneity of the precipitate that is recovered, the precipitate was not recovered for the first 30 seconds of the reaction, then it was sampled under the aforementioned conditions for 60 seconds. The pH of the solution containing the precipitate was 7.5. The precipitate was then washed by centrifugation with distilled water (until the wash water had been neutralized) and dried in an oven at 70? C. for 1 night.

[0110] An X-ray diffractogram (XRD) was performed and the result is shown in FIG. 15. This diffractogram shows that no crystallized phase has precipitated, and it has therefore not been possible to obtain a carbonate with an Ni.sub.1/3Mn.sub.1/3Co.sub.1/3CO.sub.3 composition using this method.

[0111] The morphology of the aggregates was verified by scanning electron microscopy (SEM), the results of which are shown in FIG. 16. This figure clearly shows that no sphericity has been obtained, and demonstrates that an intermediate regime does not produce a carbonate with an Ni.sub.1/3Mn.sub.1/3Co.sub.1/3CO.sub.3 composition.