Carbonate Precursors for Lithium Nickel Manganese Cobalt Oxide Cathode Material and the Method of Making Same

Abstract

A method for producing a M-carbonate precursor of a Li-M oxide cathode material in a continuous reactor, wherein M=NixMnyCozAn, A being a dopant, with x>0, y>0, 0≦z≦0.35, 0≦n≦0.02 and x+y+z+n=1, the method comprising the steps of: —providing a feed solution comprising Ni-, Mn-, Co- and A-ions, and having a molar metal content M″ feed, —providing an ionic solution comprising either one or both of a carbonate and a bicarbonate solution, the ionic solution further comprising either one or both of Na- and K-ions, —providing a slurry comprising seeds comprising M′-ions and having a molar metal content M′ seeds, wherein M′=Nix′Mny′Coz′A′n′, A′ being a dopant, with 0≦x′≦1, 0≦y′≦1, 0≦z′≦1, 0≦n′≦1 and x′+y′+z′+n′=1, and wherein the molar ratio M′ seeds/M″ feed is between 0.001 and 0.1, —mixing the feed solution, the ionic solution and the slurry in the reactor, thereby obtaining a reactive liquid mixture, —precipitating a carbonate onto the seeds in the reactive liquid mixture, thereby obtaining a reacted liquid mixture and the M-carbonate precursor, and —separating the M-carbonate precursor from the reacted liquid mixture.

Claims

1. A method for producing a M-carbonate precursor of a Li-M oxide cathode material in a continuous reactor, wherein M=Ni.sub.xMn.sub.yCo.sub.zA.sub.n, A being a dopant, with x>0, y>0, 0≦z≦0.35, 0≦n≦0.02 and x+y+z+n=1, the method comprising: providing a feed solution comprising Ni-, Mn-, Co- and A-ions, and having a molar metal content M″.sub.feed, providing an ionic solution comprising either one or both of a carbonate and a bicarbonate solution, the ionic solution further comprising either one or both of Na- and K-ions, providing a slurry comprising seeds comprising M′-ions and having a molar metal content M′.sub.seeds, wherein M′=Ni.sub.x′Mn.sub.y′Co.sub.z′A′.sub.n′, A′ being a dopant, with 0≦x′≦1, 0≦y′≦1, 0≦z′≦1, 0≦n′≦1 and x′+y′+z′+n′=1, and wherein the molar ratio M′.sub.seeds/M″.sub.feed is between 0.001 and 0.1, mixing the feed solution, the ionic solution and the slurry in the reactor, thereby obtaining a reactive liquid mixture, precipitating a carbonate onto the seeds in the reactive liquid mixture, thereby obtaining a reacted liquid mixture and the M-carbonate precursor, and separating the M-carbonate precursor from the reacted liquid mixture.

2. The method according to claim 1, wherein the seeds have a median particle size D50 between 0.1 and 3 μm.

3. The method according to claim 1, wherein the M′-ions are present in a water insoluble compound that is selected from the group consisting of M′CO.sub.3, M′(OH).sub.2, M′-oxide and M′OOH.

4. The method according to claim 1, wherein the Ni-, Mn-, Co- and A-ions are present in a water soluble sulfate compound.

5. The method according to claim 1, wherein M′.sub.seeds/M″.sub.feed is between 0.001 and 0.05.

6. The method according to claim 1, wherein A and A′ comprise one or more elements selected from the group consisting of Mg, Al, Ti, Zr, Ca, Ce, Cr, Nb, Sn, Zn and B.

7. The method according to claim 1, wherein the concentration of NH.sub.3 in the reactor is less than 5.0 g/L.

8. The method according to claim 1, wherein M=M′.

9. The method according to claim 1, wherein the solid content in the slurry is between 30 and 300 g/L.

10. The method according to claim 1, wherein the reactor is a continuous stirred tank reactor (CSTR).

11. The method according to claim 5, wherein the median particle size of the M-carbonate precursor is determined by the ratio M′.sub.seeds/M″.sub.feed.

12. The method according to claim 3, wherein the water insoluble compound is either MnCO.sub.3 or TiO.sub.2.

13. The method according to claim 1, wherein the ionic solution further comprises a hydroxide solution, and the ratio OH/CO.sub.3, or OH/HCO.sub.3, or both these ratios are less than 1/10.

14. The method according to claim 1, further comprising the final step of drying and pulverizing the separated M-carbonate precursor, and wherein the ratio M′.sub.seeds/M″.sub.feed is selected to obtain a span <2 of the dried and pulverized M-carbonate precursor.

15. A method for producing a lithium M-oxide cathode material for a rechargeable battery, comprising: providing a M-carbonate precursor by the method according to claim 1, providing a Li precursor compound, mixing the M-carbonate and the Li precursor, and firing the mixture at a temperature between 600 and 1100° C. for at least 1 hr.

16. A method for producing a lithium M-oxide cathode material for a rechargeable battery, comprising: providing a M-carbonate precursor by the method according to claim 4, providing a Li precursor compound, mixing the M-carbonate and the Li precursor, and firing the mixture at a temperature between 600 and 1100° C. for at least 1 hr.

17. A method for producing a lithium M-oxide cathode material for a rechargeable battery, comprising: providing a M-carbonate precursor by the method according to claim 5, providing a Li precursor compound, mixing the M-carbonate and the Li precursor, and firing the mixture at a temperature between 600 and 1100° C. for at least 1 hr.

18. A method for producing a lithium M-oxide cathode material for a rechargeable battery, comprising: providing a M-carbonate precursor by the method according to claim 6, providing a Li precursor compound, mixing the M-carbonate and the Li precursor, and firing the mixture at a temperature between 600 and 1100° C. for at least 1 hr.

19. A method for producing a lithium M-oxide cathode material for a rechargeable battery, comprising: providing a M-carbonate precursor by the method according to claim 8, providing a Li precursor compound, mixing the M-carbonate and the Li precursor, and firing the mixture at a temperature between 600 and 1100° C. for at least 1 hr.

20. A method for producing a lithium M-oxide cathode material for a rechargeable battery, comprising: providing a M-carbonate precursor by the method according to claim 14, providing a Li precursor compound, mixing the M-carbonate and the Li precursor, and firing the mixture at a temperature between 600 and 1100° C. for at least 1 hr.

Description

BRIEF DESCRIPTION OF THE DRAWINGS AND TABLES

[0033] FIG. 1: design of a typical 10 L CSTR reactor.

[0034] FIG. 2: SEM images (500× magnification) of the carbonate precursor in Example 1

[0035] FIG. 3: XRD pattern of the carbonate precursor in Example 1

[0036] FIG. 4: The average particle size (D50) variation before (Comparative Example 1) and after 0.5 wt %, 1.0 wt % and 2 wt % of seeding (Example 1).

[0037] FIG. 5: The average particle size (D50) variation before (Comparative Example 2) and after 1.0 wt % and 5.0 wt % of seeding (Example 2).

DETAILED DESCRIPTION

[0038] In an embodiment of the invention, the carbonate precursor of the present invention is a composite carbonate that contains Ni, Co and Mn atoms, has a general formula of (Ni.sub.xMn.sub.yCo.sub.zA.sub.n)CO.sub.3, with x+y+z+n=1, 0≦x≦1, 0≦y≦1, 0≦z≦0.35, 0≦n≦0.02, A being one or more dopants selected from Mg, Al, Ti, Zr, Ca, Ce, Cr, Nb, Sn, Zn and B. The obtained carbonate precursor has a specific surface area larger than 10 m.sup.2/g. The specific surface area is measured by a standard Brunauer-Emmett-Teller (BET) method and carried out on a Quantachrome® Autosorb instrument. Before the BET measurement, the sample is degassed at 200° C. for 6 hours, to get ride of the moisture completely. The particle size of the carbonate precursor is measured with a Malvern® MasterSizer2000. The tap density (TD) measurement of the carbonate precursor in this invention is carried out by mechanically tapping a graduated measuring cylinder (100 ml) containing the precursor sample (having a mass W, around 60-120 g). After observing the initial powder volume, the measuring cylinder is mechanically tapped for 400 times, so that no further volume (V in cm.sup.3) or mass (W) change is observed. The TD is calculated as TD=W/V. The TD measurement is carried out on an ERWEKA® instrument.

[0039] Next, a method for producing a carbonate precursor according to the present invention is described. The composite carbonate may be obtained by conducting a co-precipitation reaction in a continuous stirred tank reactor (CSTR), by pumping into the reactor a feed solution that contains a Ni salt, a Mn salt and a Co salt and optionally an A salt, a carbonate solution that contains a metal carbonate or a metal bicarbonate, a seed slurry that contains either one of M′CO.sub.3, M′(OH).sub.2, M′-oxide or M′OOH small particles (M′=Ni.sub.x′Mn.sub.y′Co.sub.z′A′.sub.n′, x′+y′+z′+n′=1, 0≦x′≦1, 0≦y′≦1, 0≦z′≦1 and 0≦n′≦1), and optionally a hydroxide solution that contains a metal hydroxide. The composition of M′ is not necessary the same as that of M in this invention. A′ is a dopant that may comprise one or more metals, such as Mg, Al, Ti and Zr. A′ may be equal to A, but may also be different if A is composed of more than one metal. For example if A is a TiMg composition, then A′ may be either Mg, Ti or a MgTi composition, the latter may have the same composition as A but may also have a different composition.

[0040] The feed solution contains a Ni salt, a Mn salt and a Co salt, and optionally an A salt. The kind of Ni salt in the feed solution is not particularly limited, as long as the Ni salt is water-soluble to yield a Ni ion-containing aqueous solution; examples of Ni salts include sulfate salt, chloride salt, nitrate salt and acetate salt of Ni. Also, the kind of Mn salt in the feed solution is not particularly limited, as long as the Mn salt is water-soluble to yield a Mn ion-containing aqueous solution; examples of Mn salts include sulfate salt, chloride salt, nitrate salt and acetate salt of Mn. Similarly, the kind of Co salt in the feed solution is not particularly limited, as long as the Co salt is water-soluble to yield a Co ion-containing aqueous solution; examples of Co salts include sulfate salt, chloride salt, nitrate salt and acetate salt of Co.

[0041] In the carbonate precursor of the present invention, A is a cation dopant different from Ni, Mn and Co, which may be one or more of Mg, Al, Ti, Zr, Ca, Ce, Cr, Nb, Sn, Zn and B. For cation doping (A element), the doping element is dissolved in the feed solution. The corresponding dopant salt in the feed solution is not particularly limited; as long as it is water-soluble to yield a dopant ion-containing aqueous solution; examples of dopant salts include sulfate salt, chloride salt, nitrate salt and acetate salt. The concentration of the dopant salt in the feed solution is determined by its desired content in the final carbonate precursor, and its (optional) presence in the seed slurry.

[0042] In the aqueous feed solution, the content of Ni ions expressed in Ni atoms is preferably 0.1 to 2.0 mol/L and particularly preferably 0.2 to 1.8 mol/L, the content of Mn ions expressed in Mn atoms is preferably 0.1 to 2.0 mol/L and particularly preferably 0.2 to 1.8 mol/L, the content of Co ions expressed in Co atoms is preferably 0.05 to 1.5 mol/L and particularly preferably 0.1 to 1.0 mol/L. The concentration of the Ni ions, Mn ions and Co ion in the feed solution respectively falling within the above described ranges enables to get a balance between the product yield and the physiochemical properties of the obtained carbonate precursor. The total concentration of the anions of Ni, Mn and Co in the feed solution is preferably 1.0 to 3.0 mol/L and particularly preferably 1.5 to 2.5 mol/L. The molar ratios in the feed solution between Ni, Mn and Co atom concentrations falling within the above-described ranges further enhance the electrochemical performance of the final lithium metal oxide.

[0043] The aqueous carbonate solution contains any one or both of a metal carbonate and a metal bicarbonate. The carbonate solution is not particularly limited as long as the metal carbonate is water-soluble to yield a carbonate ion contained aqueous solution; examples of the metal carbonate include: alkaline metal carbonate such as sodium carbonate and potassium carbonate. The bicarbonate solution is not particular limited as long as it is water-soluble to yield a bicarbonate ion contained aqueous solution; examples of the metal bicarbonate include: alkaline metal bicarbonate such as sodium bicarbonate and potassium bicarbonate. Preferably the carbonate solution contains the cheap sodium carbonate, rendering the pH of the reaction solution nearly neutral. In the carbonate solution, the concentration of carbonate or bicarbonate ions is preferably 1.0-4.0 mol/L and particularly preferably 1.5-3.0 mol/L. The concentration of the carbonate or bicarbonate ions falling in that range enables to produce good precursor and a final oxide with excellent electrochemical performances.

[0044] The use of a hydroxide solution is an option in the carbonate precipitation process of this invention. Generally speaking, Na.sub.2CO.sub.3 replaced by a small percentage of NaOH (eg. 0-5 wt %) can further increase the specific surface area of the obtained carbonate precursor, which will benefit the rate performance of the final NMC cathode material. It may be a metal hydroxide aqueous solution. The hydroxide solution is not particularly limited as long as the metal hydroxide is water-soluble to yield a caustic ion containing aqueous solution; examples of the metal hydroxide include: an alkaline metal hydroxide such as lithium, sodium and potassium hydroxide. Preferred among these are lithium hydroxide and sodium hydroxide, rendering the pH of the reaction solution nearly neutral, whilst both are also relatively cheap. In the hydroxide solution, the concentration of hydroxide ions is preferably 5-15 mol/L and particularly preferable 8-10 mol/L. The concentration of the hydroxide ions in that range enables to produce a good precursor and a final oxide with excellent electrochemical performances.

[0045] The seeds of the present invention may be small particles of M′CO.sub.3, M′(OH).sub.2, M′-oxide or M′OOH (M′=Ni.sub.x′Mn.sub.y′Co.sub.z′A′.sub.n′, x′+y′+z′+n′=1, 0≦x′≦1, 0≦y′≦1, 0≦z′≦1 and 0≦n′≦1, M′ can thus be a single metal, bimetal, ternary metal, or even quaternary metal composition). The seeds can be commercial products of M′CO.sub.3, M′(OH).sub.2, M′-oxide or M′OOH with small particle size, with a D50 of 0.1-2 μm. The seeds can also be produced by milling of M′CO.sub.3, M′(OH).sub.2, M′-oxide and M′OOH big particles and decrease its particle size to 0.1-2 μm for D50. The milling technology includes jet mill, ball mill, beads mill or ring mill etc.; with or without a dispersion agent. Then, the obtained small particles are re-dispersed in water to form a homogeneous seed slurry. The solid loading of the seed slurry is preferably in the range of 30-300 g/L, and particularly preferably in the range of 50-200 g/L. It should be emphasized here that the composition of M′ is not necessarily the same as that of M in this invention. In the embodiment where M=M, a quantity of final product MCO.sub.3 is transformed into seed material. It is evident that the seeds used in this invention are water insoluble.

[0046] In one embodiment, the carbonate precursor of the present invention is produced in a continuously stirred tank reactor (CSTR, such as described in http://encyclopedia.che.enqin.umich.edu/Paaes/Reactors/CSTR/CSTR.html) under a certain temperature, pH value and stirring speed. A typical structure and design of a 10 L CSTR reactor is shown in FIG. 1, with a diameter of 200 mm and height of 420 mm. Four baffles are installed in the reactor and a pitched-blade impeller is equipped on ⅓ of the height from the bottom. The dosing tubes are fixed on the baffles at the same height of the impeller. The stirring speed of the impeller is controlled by a motor above the CSTR reactor.

Legend for FIG. 1:

[0047]

TABLE-US-00001 1 Water jacket 2 Overflow 3 Dosing tube 4 Motor 5 Impeller 6 pH senor 7 Baffle 8 Temperature sensor 9 Outlet valve

[0048] In the method for producing a carbonate precursor of the present invention, the different solutions and the seed slurry may be simultaneously or alternately pumped into the reactor; while its content is being maintained at 30 to 95° C., and preferably at 50 to 90° C. The solutions and seed slurry are pumped into a CSTR reactor with a certain flow rate, e.g. R.sub.feed, R.sub.carbonate, R.sub.hydroxide and R.sub.seeds, corresponding to the flow rate of feed solution, carbonate solution, hydroxide solution and seed slurry, respectively. The residence time Re is calculated by dividing the volume of the CSTR reactor (V) by the flow rate sum of the feed, carbonate, hydroxide solution and seed slurry; Re=V/(R.sub.feed+R.sub.carbonate+R.sub.hydroxide+R.sub.seeds). The residence time Re can thus be tuned by adapting the flow rate of feed, carbonate and hydroxide solutions, and the flow rate of the seed slurry. The residence time Re of the present invention is set in the range of 1.5-6.0 hours, and preferably in the range of 2.0 to 4.0 hours. The reaction temperature T is set in the range of 30 to 95° C., and preferably at 50 to 90° C. The stirring speed in the CSTR reactor is set in the range of 500-2000 rpm, and preferably in the range of 800-1500 rpm.

[0049] The amount of the feed and carbonate solution added into the reactor is such that the molar ratio (CO.sub.3/M) of the total number of the carbonate ions to the total number of moles (M) of Ni, Mn, Co and A ions added from the feed solution is preferably 0.9 to 1.2, and particularly preferably 0.95 to 1.15. The ratio (HCO.sub.3/M) of the total number of the moles (HCO.sub.3) present in bicarbonate ions in the reaction to the total number of moles (M) of Ni, Mn and Co ions added from the feed solution is preferably 1.9 to 2.4, and particularly preferably 1.9 to 2.3. The amount of the seeds added into the reactor is such that the molar ratio (M′.sub.seeds/M″.sub.feed) of the total number of moles (M′.sub.seeds) of Ni, Mn, Co and A ions added in the seed slurry to the total number of moles (M″.sub.feed) of Ni, Mn, Co and A ions added from the feed solution is preferably 0.001 to 0.1, and particularly preferably 0.001 to 0.05. When a hydroxide solution is added, the amount of the carbonate/bicarbonate solution and hydroxide solution are such that the ratio OH/CO.sub.3 of the total number of moles OH added in the hydroxide solution to the total number of the moles CO.sub.3 present in the carbonate ion or bicarbonate ions in the reaction is preferably less than 0.1, and particularly preferably less than 0.05. Similarly, OH/HCO.sub.3 is preferably less than 0.1, and particularly preferably less than 0.05.

[0050] The carbonate precipitation process is mainly controlled by the following parameters: [0051] Stirring speed of impeller [0052] Temperature [0053] Residence time [0054] pH [0055] Metal M concentration [0056] CO.sub.3/M molar ratio [0057] OH/CO.sub.3 or OH/HCO.sub.3 molar ratio [0058] M′.sub.seeds/M″.sub.feed molar ratio.

[0059] The carbonate precursors according to the invention can be produced by tuning these parameters in the ranges as described above.

[0060] The carbonate precursor slurry is collected from the overflow of a CSTR reactor and the precursor particles are obtained by a solid-liquid separation process, for example, press filtration or continuous centrifugal filtration. The solid-liquid separation process is considered to be finished when the conductivity of the filter/centrifuge waste water is lower than 20 μS/m. The thus obtained particles are dried at 150° C., pulverized and classified to yield the carbonate precursor of the present invention. The typical scan electron microscopy (SEM) images and XRD pattern of the as-prepared carbonated precursor are shown in FIG. 2 and FIG. 3, respectively. FIG. 2 shows the typical spherical morphology obtained by the method of the invention.

[0061] The (doped) lithium nickel manganese cobalt oxide (NMC(A)) represented by the above-described general formula is produced by mixing the (bi-)carbonate precursor of the present invention with a lithium compound and by sintering the thus obtained mixture. The amount of the lithium compounds added is such that the ratio (Li/M) of the number of moles of the lithium atoms in the lithium compound to the total number of moles (M) of the Ni, Mn, Co and A atoms included in the carbonate precursor is preferably 0.95-1.60, and more preferably 1.00-1.50. The sintering atmosphere is not particularly limited; the sintering may be conducted under air or in an oxygen atmosphere, for example as a multiple stage sintering. The sintering conditions are such that the baking temperature is 600-1100° C., preferably 850 to 1000° C., and the sintering time is 5 hours or more, preferably 10 to 24 hours. After sintering, by appropriately cooling and by pulverizing and classifying where necessary, there can be obtained a (doped) lithium nickel manganese cobalt oxide (NMC(A)) having a BET specific surface area up to 1 m.sup.2/g or more and a tap density up to 1.2 g/cm.sup.3 or more. Such a NMC(A) material is suitable for using as a cathode material in a high rate Li-ion battery for ×EV applications.

[0062] The invention is further illustrated in the following examples:

Comparative Example 1

[0063] Preparation of feed solution: NiSO.sub.4, MnSO.sub.4, CoSO.sub.4 and MgSO.sub.4 are dissolved in deionized water and a transition metal solution is prepared, with a concentration of Ni, Mn, Co and Mg of 0.835 mol/L, 0.835 mol/L, 0.32 mol/L and 0.01 mol/L (Ni:Mn:Co:Mg=41.75:41.75:16:0.5), respectively. For preparing the carbonate solution, Na.sub.2CO.sub.3 is dissolved in deionized water and a 1.65 mol/L Na.sub.2CO.sub.3 solution is obtained. The feed and carbonate solution are pumped into a 10L CSTR reactor. The molar ratio of CO.sub.3: Metal=1.0 and the residence time is set at 3 hours. The feed solution and carbonate solution are continuously pumped into the CSTR reactor set at a precipitation temperature of 90° C., with an impeller stirring speed at 1000 rpm. The obtained carbonate precursor has a value for TD and D50 of 1.7 g/cm.sup.3 and 23.5 μm, respectively. This precursor has a BET value of 132 m.sup.2/g. But the carbonate precipitation process without seeding is unstable and the average particle size (D50) varies continuously during precipitation, which is shown in FIG. 4—left part.

Example 1

[0064] The same precipitation conditions as in Comparative Example 1 are used, but with seeding. For preparing the seed slurry, the seeds are re-dispersed into water to form a homogeneous slurry under stirring with a 200 g/L solid load level. The seeds are prepared by bead milling the big carbonate particles which are produced from the carbonate process without seeding of Comp. Ex. 1 (and hence M=M′), to decrease the median particle size (D50) to 1.0 μm.

[0065] The feed, carbonate solution and the seed slurry are pumped into the 10 L CSTR reactor. The molar ratio of CO.sub.3: Metal=1.0 and the molar ratio of M′.sub.seeds/M″.sub.feed is set at 0.005 (0.5 wt %), 0.01 (1.0 wt %) and 0.02 (2.0 wt %) consecutively, and the residence time is set at 3 hours. The feed solution, carbonate solution and seed slurry are continuously pumped into the CSTR reactor set at a precipitation temperature of 90° C., with an impeller stirring speed at 1000 rpm. The carbonate precursor slurry is collected through the overflow of the reactor. Then, the obtained precursor slurry is solid-liquid separated by a press filter, and washed with deionized water for several times until the conductivity of the filter water is lower than 20 μS/m. The thus obtained carbonate precursor wet cake is dried in an oven at 150° C. for 24 hours. The final obtained carbonate precursor has a composition of (Ni.sub.0.415Mn.sub.0.415Co.sub.0.16Mg.sub.0.005)CO.sub.3. The TD, D50 and BET of these products are compared in Table 1 as shown below.

TABLE-US-00002 TABLE 1 Comparison of TD, D50 and BET for precursors obtained in Comparative Example 1 and Example 1. Particle Seeding D50 TD BET size Example wt % (μm) (g/cm.sup.3) (m.sup.2/g) tunability Morphology Compar- No 22.8 1.56 132 No Spherical ative Example 1 Example 1 0.5 12.5 1.30 141 Yes Spherical Example 1 1.0 7.4 1.21 151 Yes Spherical Example 1 2.0 4.8 1.04 206 Yes Spherical

[0066] FIG. 4 represents in the left part the situation of Comp. Ex.1, and with seeding starting after 4 days, the precipitation process is effectively stabilized and the particle size can be finely tuned by changing the weight ratio of the seed slurry, resulting in the situation shown to the right, corresponding to the data of Example 1.

[0067] Generally speaking, because a very low concentration (≦5 g/L) of a chelating agent (eg. NH.sub.4OH), or even no chelating agent is used in this invention, the nucleation speed is very fast for a typical carbonate precipitation process in a CSTR reactor. This is the reason why the carbon precipitation process is unstable, if seeding is not applied. After small seeds are added into the reactor, in principle, there is no nucleation process taking place in the reactor and the new metal carbonates will only grow on the surface of the seeds as a consequence. Because the carbonate precipitation will only be carried out on the surface of seeds, in principle, the particle size in the reactor after seeding is determined by the molar ratio between M′.sub.seeds/M″.sub.feed, and the quantity and size of the seeds that are added in the reactor. This is the mechanism permitting the seeding process to stabilize the carbonate precipitation process, and also enabling that the particle size after seeding can be tuned, i.e. by changing the quantity of seeds. For example, the particle size can be decreased by increasing the molar ratio M′.sub.seeds/M″.sub.feed. Because more seeds are added in the reactor, this results in less carbonate grow on each seed, and the particle size will decrease as a consequence. However, when increasing the ratio M′.sub.seeds/M″.sub.feed, the span of the PSD of the particles in the slurry and especially in the dried precursor product increases, which is illustrated in Table 2. The data show that the D50 and span change after drying. If the D50 and span of the slurry and dry product are compared, both the D50 and span increase with higher seeding level. This is because the fines are agglomerated on the surface of coarse particles after drying, which results in D50 and span values increasing, especially at high seeding level (where there are more fines). Note that as the metal composition of the seeds and the feed is identical, the ratio M′.sub.seeds/M″.sub.feed corresponds to the weight percentage of the seeds.

TABLE-US-00003 TABLE 2 Comparison of D50 and span for precursors obtained in Comparative Example 1 and Example 1, before and after drying of the slurry. D50 in D50 after Span Seeding M′seeds/ slurry Span in drying after Example wt % M″feed (μm) slurry (μm) drying Comp. No — 22.8 1.28 22.9 1.28 Ex. 1 Ex. 1 0.5 0.005 12.5 1.70 11.7 1.67 Ex. 1 1.0 0.01 7.4 1.54 8.7 1.75 Ex. 1 2.0 0.02 4.8 1.88 5.9 4.24

Comparative Example 2

[0068] Preparation of feed solution: NiSO.sub.4, MnSO.sub.4 and CoSO.sub.4 are dissolved in deionized water and a transition metal solution is prepared, with a concentration of Ni, Mn, Co of 0.44 mol/L, 1.34 mol/L, 0.22 mol/L, resp. (Ni:Mn:Co=22:67:11). For preparing a carbonate solution Na.sub.2CO.sub.3 is dissolved in deionized water and a 1.65 mol/L Na.sub.2CO.sub.3 solution is obtained. For preparing a hydroxide solution NaOH is dissolved in deionized water and a 10 mol/L NaOH solution is obtained. The feed, hydorxide and carbonate solution are pumped into a 10 L CSTR reactor, with flow rates of R.sub.feed=25.7 ml/min, R.sub.NaOH=0.2 ml/min and R.sub.carbonate=29.7 ml/min, respectively. The molar ratio of CO.sub.3: Metal=1.0, and the molar ratio of OH:CO.sub.3=0.04. The residence time is set at 3 hours. The feed and carbonate solution are continuously pumped into the CSTR reactor set at a precipitation temperature of 80° C., with an impeller stirring speed at 1000 rpm. The thus obtained carbonate precursor has a TD and D50 of 1.8 g/cm.sup.3 and 13.4 μm, respectively. This precursor has a BET value of 11.2 m.sup.2/g. But the carbonate precipitation process without seeding is unstable and the median particle size (D50) varies continuously during precipitation, which is shown in FIG. 5—left part.

Example 2

[0069] The same precipitation conditions as in Comparative Example 2 are used, but with seeding. Small seed particles (1.0 μm) are produced by ball milling the big carbonate precursor particles collected under the same precipitation conditions without seeding from a CSTR reactor (Comp. Ex. 2, hence M=M′). For preparing the seed slurry, small size MCO.sub.3 particles (Ni:Mn:Co=22:67:11) are re-dispersed into water to form a homogeneous slurry under stirring with a 150 g/L solid loading level.

[0070] The feed, hydroxide and carbonate solution, and the seed slurry are pumped into the 10 L CSTR reactor, with flow rates of R.sub.feed=25.7 ml/min, R.sub.NaOH=0.2 ml/min and R.sub.carbonate=29.7 ml/min, respectively. The molar ratio of CO.sub.3: Metal=1.0, the molar ratio of OH:CO.sub.3=0.04, and the molar ratio of M′.sub.seeds/M″.sub.feed is set at 0.01 (1 wt %) and 0.05 (5 wt %) consecutively. The residence time is set at 3 hours. The solutions are continuously pumped into the CSTR reactor at a precipitation temperature of 80° C., with an impeller stirring speed at 1000 rpm.

[0071] The carbonate precursor slurry is collected through the overflow of the CSTR reactor. Then, the obtained precursor slurry is solid-liquid separated by a press filter and washed with deionized water for several times until the conductivity of the filter water is lower than 20 μS/m. The thus obtained carbonate precursor wet cake is dried in an oven at 150° C. for 24 hours. The TD, D50 and BET of the obtained carbonate precursor are compared in Table 2 as shown below.

TABLE-US-00004 TABLE 3 Comparison of TD, D50 and BET for precursors obtained in Comparative Example 2 and Example 2. Particle Seeding D50 TD BET size Example wt % (μm) (g/cm.sup.3) (m.sup.2/g) tunability Morphology Compar- No 13.4 1.8 11.2 No Spherical ative Example 2 Example 2 1.0 7.4 1.4 37 Yes Spherical Example 2 5.0 4.2 1.2 41 Yes Spherical

[0072] FIG. 5 represents in the left part the situation of Comp. Ex.2, and with seeding starting after 12 days, the precipitation process is effectively stabilized and the particle size can be finely tuned by changing the weight ratio of the seed slurry, resulting in the situation shown to the right, corresponding to the data of Example 2.

[0073] In Table 4 below, the span before and after drying is given as a function of seeding level, for a precursor product made in nearly the same conditions as the product in Example 2, referred to as Example 2. The results show the same trend as for Example 1.

TABLE-US-00005 TABLE 4 Comparison of D50 and span for a precursor product having the same composition as Example 2, before and after drying of the slurry. D50 in D50 after Span Seeding M′seeds/ slurry Span in drying after Example wt % M″feed (μm) slurry (μm) drying Comp. No — 12.4 1.41 13.2 1.66 Ex. 2′ Ex. 2′ 1.0 0.01 7.2 1.57 7.05 1.87 Ex. 2′ 5.0 0.05 4.1 1.88 5.45 4.58

Example 3

[0074] Preparation of feed solution: NiSO.sub.4, MnSO.sub.4, CoSO.sub.4 are dissolved in deionized water and a transition metal solution is prepared, with a concentration of Ni, Mn, Co of 1.2 mol/L, 0.4 mol/L, 0.4 mol/L, respectively (Ni:Mn:Co=60:20:20). For preparing the carbonate solution Na.sub.2CO.sub.3 is dissolved in deionized water and a 1.65 mol/L Na.sub.2CO.sub.3 solution is obtained.

[0075] The same precipitation conditions as in Example 1 are used, but with M′.sub.seeds/M″.sub.feed=0.04 and MnCO.sub.3 seeding (here Mn=M′≠M). The MnCO.sub.3 seeds are produced by ball milling commercially available MnCO.sub.3 product to 0.5 μm and then dispersing it into water. The solid loading of the seeds slurry is 100 g/L. Before seeding, the particle size of the carbonate precursor in the reactor is continuously fluctuating and the D50 is 24.8 μm. After seeding, the median particle size in the reactor is stabilized at 7.1 μm. The carbonate precursor slurry is collected through the overflow of the CSTR reactor. Then, the obtained precursor slurry is solid-liquid separated by a press filter and washed with deionized water several times until the conductivity of the filter water is lower than 20 μS/m. The thus obtained carbonate precursor wet cake is dried in an oven at 150° C. for 24 hours.

[0076] The BET and TD of the obtained carbonate precursor are 240 m.sup.2/g and 1.1 g/cm.sup.3, respectively.

Example 4

[0077] Preparation of feed solution: NiSO.sub.4, MnSO.sub.4, CoSO.sub.4 are dissolved in deionized water and a transition metal solution is prepared, with a concentration of Ni, Mn, Co of 0.67 mol/L, 0.67 mol/L, 0.67 mol/L, respectively (Ni:Mn:Co=1:1:1). For preparing the carbonate solution Na.sub.2CO.sub.3 is dissolved in deionized water and a 1.65 mol/L Na.sub.2CO.sub.3 solution is obtained. The same precipitation conditions as in Example 1 are used, but with molar ratio of M′.sub.seeds/M″.sub.feed=0.01 of TiO.sub.2 seeding (here M′≠M). TiO.sub.2 nano-particles (D50=250 nm) are dispersed into water to prepare a suspension with a solid loading of 50 g/L. Before seeding, the particle size of the carbonate precursor in the reactor is continuously fluctuating and the D50 is 20.1 μm. After seeding, the median particle size in the reactor is stabilized at 6.8 μm. The carbonate precursor slurry is collected through the overflow of the CSTR reactor. Then, the obtained precursor slurry is solid-liquid separated by a press filter and washed with deionized water several times until the conductivity of the filter water is lower than 20 μS/m. The thus obtained carbonate precursor wet cake is dried in an oven at 150° C. for 24 hours. The BET and TD of the obtained carbonate precursor are 93 m.sup.2/g and 1.3 g/cm.sup.3, respectively. The final obtained carbonate precursor has a composition of (Ni.sub.0.33Mn.sub.0.33Co.sub.0.33Ti.sub.0.01)CO.sub.3.

Example 5

[0078] Preparation of feed solution: NiSO.sub.4, MnSO.sub.4, CoSO.sub.4 are dissolved in deionized water and a transition metal solution is prepared, with a concentration of Ni, Mn, Co of 1.2 mol/L, 0.4 mol/L, 0.4 mol/L, respectively (Ni:Mn:Co=60:20:20). For preparing the sodium bicarbonate solution NaHCO.sub.3 is dissolved in deionized water and a 1.0 mol/L NaHCO.sub.3 solution is obtained. The same precipitation conditions as in Example 1 are used, but the molar ratio of CO.sub.3: Metal=2.05. Small seed particles (1.0 μm) are prepared by ball milling the big carbonate precursor particles collected under the same precipitation conditions without seeding from a CSTR reactor. For preparing the seed slurry, small size MCO.sub.3 particles (Ni:Mn:Co=60:20:20) are re-dispersed into water to form a homogeneous slurry under stirring with a 100 g/L solid loading level. The molar ratio of M′.sub.seeds/M″.sub.feed is set at 0.004 (0.4 wt %) consecutively (here M′=M). The residence time is set at 3 hours. The solutions are continuously pumped into the CSTR reactor at a precipitation temperature of 90° C., with an impeller stirring speed at 1000 rpm. Before seeding, the particle size of the carbonate precursor in the reactor is continuously fluctuating and the D50 is 10.6 μm. After seeding, the median particle size in the reactor is stabilized at 6.5 μm. The carbonate precursor slurry is collected through the overflow of the CSTR reactor. Then, the obtained precursor slurry is solid-liquid separated by a press filter and washed with deionized water several times until the conductivity of the filter water is lower than 20 μS/m. The thus obtained carbonate precursor wet cake is dried in an oven at 150° C. for 24 hours. The BET and TD of the obtained carbonate precursor are 223 m.sup.2/g and 1.1 g/cm.sup.3, respectively.

[0079] In the Examples above no ammonia was added in the CSTR.