Patent Application
20140158933
The invention relates to a lithium-based fused product, and a method for producing said product. This product can notably be used as electrode material, notably in a lithium-ion battery.
The invention also relates to such a battery.
A family of crystalline phases of formula (Li1−aAa)1+x(G1−bJb)y[(XO4)1−dDd]zEe is known, in which:
The products rich in (Li1−aAa)1+x(G1−bJb)y[(XO4)1−dDd]zEe phases notably include products obtained by solid-phase sintering or by mild chemistry and fused products.
The products obtained by solid-phase sintering or by mild chemistry can have a very high percentage of (Li1−aAa)1+x(G1−bJb)y[(XO4)1−dDd]zEe phases relative to the total crystalline phases. However, these products are much more expensive to produce than the fused products.
Fused products are described for example in WO2005/062404 or in the article “Melt casting LiFePO4”, Journal of the Electrochemical Society, 157 (4) A453-A462 (2010), M. Gauthier et al. In contrast to sintered products, fused products can be manufactured industrially, at reduced cost, but are less rich in (Li1−aAa)1+x(G1−bJb)y[(XO4)1−dDd]zEe phases.
Fused products can be produced by rapidly cooling a mass of molten liquid so as to create a mainly amorphous structure, and then carrying out a thermal treatment of crystallization. This gives a vitroceramic. Such methods are described in particular in EP 2 295 385, WO 2011/049034 or WO 2010/114104. The article “Lithium ion conductive glass-ceramics semi mix with Li3Fe2(PO4)3 and YAG laser-induced local crystallization in lithium phosphate ion glasses” by Nagamine et al., Solid State Ionics 179 (2008) 508-515 describes the possibility of drawing patterns of crystals by means of laser technology.
According to these methods, quenching typically leads to a product consisting, to more than 90 wt %, of amorphous phase.
Moreover, lithium is a natural flux, which sublimes if the melting point is too high. For producing these fused products, the melting point is therefore determined conventionally as being as close as possible to the melting point of the raw materials of the starting charge.
Lithium-ion batteries, which are manufactured in large quantities, can incorporate products rich in (Li1−aAa)1+x(G1−bJb)y[(XO4)1−dDd]zEe phases, notably for manufacturing cathodes thereof. Their performance as well as their service lives depend, among other things, on the richness in (Li1−aAa)1+x(G1−bJb)y[(XO4)1−dDd]zEe phases of the product used.
There is therefore a need for a product rich in (Li1−aAa)1+x(G1−bJb)y[(XO4)1−dDd]zEe phases, suitable as electrode material and that can be manufactured in industrial quantities and at reduced cost.
One aim of the invention is to meet this need, at least partially.
According to the invention, this aim is achieved by means of a product whose crystalline part consists, to more than 99.3 wt %, of one and the same phase (Li1−aAa)1+x(G1−bJb)y[(XO4)1−dDd]zEe, called “LAGJXODE phase” (in the interests of clarity). This product is remarkable in that it is fused, i.e. it is obtained by fusion and then solidification.
Although the manufacture of fused products having a LAGJXODE phase is well known, the inventors have discovered a method which, surprisingly, makes it possible to produce a fused product very rich in LAGJXODE phase, as will be seen in more detail in the rest of the description.
Advantageously, a product according to the invention can therefore be produced at reduced cost and in industrial quantities.
“Same phase (Li1−aAa)1+x(G1−bJb)y[(XO4)1−dDd]zEe” or “LAGJXODE phase” means a defined crystalline phase of formula (Li1−aAa)1+x(G1−bJb)y[(XO4)1−dDd]zEe, with a, b, d, e, x, y, z, A, G, J, X, D and E fixed. Thus, for example, a product comprising 90% of a first phase (Li1−aAa)1+x(G1−bJb)y[(XO4)1−dDd]zEe, with a=a1, b=b1, d=d1, e=e1, x=x1, y=y1, z=z1, A=A1, G=G1, J=J1, X=X1, D=D1 and E=E1, and 9.5% of a second phase (Li1−aAa)1+x(G1−bJb)y[(XO4)1−dDd]zEe, with a=a2, b=b2, d=d2, e=e2, x=x2, y=y2, z=z2, A=A2, G=G2, J=J2, X=X2, D=D2 and E=E2, such that a1≠a2 and/or b1≠b2 and/or d1≠d2 and/or e1≠e2 and/or x1≠x2 and/or y1≠y2 and/or z1≠z2 and/or A1≠A2 and/or G1≠G2 and/or J1≠J2 and/or X1≠X2 and/or D1≠D2 and/or E1≠E2, does not conform to the present invention.
Preferably, a product according to the invention further comprises one, and preferably several, of the following optional characteristics:
Advantageously, these optional characteristics improve the electrochemical performance, making the products particularly suitable, after optional grinding, for producing cathodes for lithium-ion batteries.
A product according to the invention can be in the form of a block with all its dimensions preferably greater than 1 mm, preferably greater than 2 mm, preferably greater than 1 cm, preferably greater than 5 cm, more preferably greater than 15 cm. Preferably, a block according to the invention has a weight greater than 200 g.
The invention also relates to a powder of a fused product according to the invention. The median size of the powder is preferably greater than 0.05 μm and/or less than 100 μm.
In a particular embodiment, the median size of the powder is between 0.05 μm and 5 μm, preferably between 0.05 μm and 2 μm, preferably between 0.05 μm and 0.2 μm. In a particular embodiment, the median size of the powder is between 5 μm and 20 μm, preferably between 7 μm and 15 μm.
More than 50%, preferably more than 70%, preferably more than 90%, preferably more than 95%, preferably more than 99%, preferably approximately 100% by number, of the particles can be covered at least partially, preferably completely, with carbon or with a precursor of carbon.
The invention also relates to a first method for producing a fused product according to the invention, comprising the following steps:
Preferably and remarkably, in step b), fusion takes place in a neutral environment or one containing oxygen, preferably under air. This facilitates carrying out of the fusion process.
Preferably, in step c), the cooling rate until complete solidification of the liquid mass is less than 1000 K/s, or even less than 800 K/s, or even less than 500 K/s.
The invention also relates to a second method for producing a fused product according to the invention, in which the crystalline part has, to more than 99.3 wt %, one and the same phase (Li1−aAa)1+x(Fe1−bJb)y[(PO4)1−dDd]z, said method comprising the following steps:
Advantageously, this second method of production makes it possible to produce a fused product comprising less than 30%, preferably less than 20%, preferably less than 10%, preferably less than 5%, preferably less than 1% of (Li1−aAa)1+x(Fe1−bJb)y[(PO4)1−dDd]z phases in which the iron has a valence greater than or equal to 3, and in particular a small amount of Li3Fe2(PO4)3. Advantageously, a low content of phases in which the iron has a valence greater than or equal to 3 improves the electrochemical performance of the battery comprising the fused product according to the invention.
Preferably and remarkably, in step b′), fusion takes place in a neutral environment or one containing oxygen, preferably under air. This facilitates carrying out of the fusion process.
This second method is also remarkable in the sense that it makes it possible to obtain a fused product (Li1−aAa)1+x(Fe1−bJb)y[(PO4)1−dD]z according to the invention without a step of thermal treatment after the fusion step (in contrast to the first method of production according to the invention that comprises a step e)).
In one embodiment, in step a) or in step a′), the raw materials can be in the solid and/or liquid state, preferably solid.
In one embodiment, one or more raw materials can be supplied in the form of a gas, notably for supplying the element chlorine Cl or the element fluorine F, in step b) or b′).
The methods of the invention can be used for producing particles or blocks. They can be adapted so that the fused product has one or more of the optional characteristics mentioned above.
The invention also relates to a product produced or that can have been produced by a method according to the invention.
The invention also relates to the use of a fused product according to the invention or produced or that can have been produced by a method according to the invention in the production of a cathode for lithium-ion batteries.
The invention finally relates to a cathode for lithium-ion batteries comprising a fused product according to the invention or produced or that can have been produced by a method according to the invention, and a lithium-ion battery comprising such a cathode.
The cathode can be obtained in particular by forming a powder according to the invention.
Other aims, aspects, properties and advantages of the present invention will become even clearer from the description and examples given below and on examining the appended drawing, in which
T=100*(ALAGJXODE)/(ALAGJXODE+ASecondary phases) (1)
where
An example of the first method according to the invention is now described in detail.
In step a), a starting charge for producing a fused product according to the invention is formed from the constituents lithium, A, G, J, D, X and E, or from compounds of these constituents, notably for compounds of oxides and/or of carbonates and/or of hydroxides and/or of oxalates and/or of nitrates and/or of phosphates and/or of metals and/or of chlorides and/or of fluorides and/or of sulfides and/or of ammonia compounds. Preferably, these compounds are selected from the phosphates, the carbonates and the oxides. These compounds can preferably be selected from Li2O, Li2CO3, LiOH, LiH2PO4, Li3PO4, LiF, Na2CO3, NaOH, KOH, Fe, Fe2O3, Fe3O4, FeO, FePO4,n.H2O with 0≦n≦6, Co3O4, CoO, V2O5, Nb2O5, Y2O3, B2O3, TiO2, Cu2O, CuO, Cr2O3, NH4H2PO4, (NH4)2HPO4, H3PO4, P2O5, SiO2, Al2O3, MoO, MnO, Mn2O3, MnO2, Mn3O4, MgO, MgCO3, NiO. Preferably, these compounds are selected from Li2O, Li2CO3, Li3PO4, Na2CO3, Fe2O3, Fe3O4, FeO, FePO4,n.H2O with 0≦n≦6, Co3O4, CoO, V2O4, Nb2O5, Y2O3, B2O3, TiO2, Cu2O, CuO, Cr2O3, NH4H2PO4, (NH4)2HPO4, H3PO4, P2O5, SiO2, Al2O3, MoO, MnO, Mn2O3, MnO2, Mn3O4, MgO, MgCO3, NiO.
In one embodiment, the element F is supplied in the form of a gas.
In one embodiment, the element Cl is supplied in the form of a gas.
Preferably, the compounds of the constituents lithium, A, G, J, D, X and E represent together more than 90%, more than 95%, more than 98%, preferably more than 99%, in percentages by weight, of the constituents of the starting charge. Preferably these compounds represent, together with the impurities, 100% of the constituents of the starting charge.
Preferably, no compound other than those supplying the constituents lithium, A, G, J, D, X and E is introduced deliberately in the starting charge, the other constituents present thus being impurities.
The constituents lithium A, G, J, D, X and E of the starting charge are essentially present in the fused product produced. A proportion of these constituents, for example manganese and/or lithium, variable depending on the fusion conditions, may however evaporate during the fusion step. A person skilled in the art knows how to adapt the composition of the starting charge accordingly, so as to obtain, at the end of step e), a fused product according to the invention.
In one embodiment, the starting charge comprises less than 10%, less than 5%, less than 1%, or even no oxide(s) of silicon and/or of aluminum and/or of niobium and/or of boron and/or of germanium and/or of gallium and/or of antimony and/or of bismuth. These elements may however be present in the starting charge in a form other than an oxide.
The granulometries of the powders used can be those commonly encountered in the fusion techniques.
An intimate mixture of the raw materials can be produced in a mixer. This mixture is then poured into a melting furnace.
In step b), the starting charge is melted until a liquid mass is obtained, at a temperature Tlm greater than the melting point Tm of the fused product obtained at the end of step e), preferably in an arc furnace. Electric melting in fact makes it possible to produce large amounts of fused product at high yields.
It is possible for example to use an arc furnace of the Héroult type comprising two electrodes, and with a tank with a diameter of about 0.8 m, which can contain about 180 kg of molten liquid.
However, all the known furnaces are conceivable, such as an induction furnace, a plasma furnace or other types of Héroult furnace, provided that they allow the starting charge to be melted completely.
In particular, for a fused LiFePO4 product, power between 400 and 1200 kWh/T is very suitable.
Crucible melting can also be carried out in a heat treatment furnace, preferably in an electric furnace, preferably in a neutral or reducing environment.
An arc furnace or an induction furnace is preferably used.
Without this always being applicable, it is possible to increase the quality of mixing by bubbling with a neutral gas as mentioned in FR 1 208 577. The quality of mixing of the molten liquid can in particular be improved by bubbling with nitrogen. The flow rate and/or the temperature of said gas is preferably adjusted so that the temperature of the liquid mass is not affected much by this addition of gas.
The inventors found that, surprisingly, in the first method according to the invention, the environment in the fusion step b) has little influence on the fused product obtained at the end of step e). It is therefore possible to carry out the fusion step b) in a neutral or oxidizing environment, preferably under air. The carrying out of the method is advantageously simplified thereby.
Preferably, when G is not the element Fe, heating is carried out in such a way that the temperature of the molten liquid mass Tlm is less than Tm+300° C., preferably less than Tm+150° C., and/or greater than Tm+20° C., preferably greater than ve Tm+50° C.
At the end of step b), the starting charge is in the form of a liquid mass, which can optionally contain some solid particles, but in an insufficient amount to produce structuring of said mass. By definition, to preserve its shape, a liquid mass must be held in a container.
In a first embodiment, step c) comprises the following operations:
By simple adaptation of the composition of the starting charge, conventional methods of dispersion, in particular by blowing or spraying, thus make it possible to produce, from a molten liquid mass, particles of various sizes in a fused product according to the invention.
In operation c1), a fine stream of the molten liquid is dispersed into liquid droplets. Dispersion can result from blowing through the fine stream of the liquid mass. However, any other method of atomization of a liquid mass, known by a person skilled in the art, is conceivable.
In operation c1), said liquid mass is brought into contact with a fluid, preferably a neutral fluid or an oxygen-containing fluid, preferably an oxygen-containing fluid, preferably a fluid having at least 20 vol % of oxygen, preferably gaseous, more preferably with air.
In operation c2), the liquid droplets are transformed into solid particles by contact with a fluid, preferably a neutral fluid or an oxygen-containing fluid, preferably an oxygen-containing fluid, preferably a fluid having at least 20 vol % of oxygen, preferably gaseous, more preferably with air.
Preferably, the fluid employed is the same for both operations c1) and c2).
Preferably, the method is arranged so that as soon as it is formed, the droplet of molten liquid is in contact with the fluid. More preferably, dispersion (operation c1)) and solidification (operation c2)) are roughly simultaneous, the liquid mass being dispersed by a fluid, preferably a gas, that is able to cool and solidify said liquid.
Preferably, contact with the fluid is maintained at least until complete solidification of the droplets.
Blowing with air at room temperature is possible.
At the end of operation c2), solid particles are preferably obtained that have a size between 0.01 μm and 5 mm, or even between 0.01 μm and 3 mm, depending on the dispersion conditions.
At the end of step c2), the fused product according to the invention can be in the form of particles smaller than 50 μm. Grinding of said particles can then be optional, for manufacture of a cathode.
In a second embodiment, step c) comprises the following operations:
In operation c1′), the liquid mass is poured into a mold that is able to withstand the molten liquid mass. It is preferable to use molds made of graphite, of cast iron, or as defined in U.S. Pat. No. 3,993,119. In the case of an induction furnace, the winding is considered to constitute a mold. Casting is preferably carried out under air.
In step c2′), the liquid mass cast in the mold is cooled until an at least partly solidified block is obtained.
The cooling rate of the molten liquid during solidification is always less than 1000 K/s, or even less than 500 K/s, or even less than 100 K/s.
In one embodiment, during solidification, the liquid mass is brought into contact with a neutral fluid or an oxygen-containing fluid, preferably an oxygen-containing fluid, preferably a fluid having at least 20 vol % of oxygen, preferably gaseous, more preferably with air. Generally, said liquid mass and/or block can be brought into contact with said oxygen-containing fluid in operation c1′) and/or in operation c2′) and/or in operation c3′) and/or after operation c3′).
This bringing in contact can therefore be carried out once casting takes place. However, it is preferable only to begin this bringing in contact after casting. For practical reasons, bringing in contact with the fluid preferably only begins after mold release.
In step c3′), the block is removed from the mold.
In step d), optional, the fused product, in the form of particles or blocks, is crushed and/or ground. All types of crushers and grinding mills can be used. Preferably, an air jet mill or a ball mill is used.
In one embodiment, the method comprises a step d).
The fused product is preferably ground so as to obtain a powder having a maximum size D99.5 less than 100 μm, preferably less than 80 μm, preferably less than 50 μm, preferably less than 30 μm, preferably less than 10 μm, preferably less than 5 μm, preferably less than 1 μm.
The fused product, optionally after grinding, preferably undergoes an operation of granulometric selection depending on the intended applications, for example by sieving.
Whatever embodiment is considered, impurities derived from the raw materials may be present.
In particular, the elements Ba, Sr, Yb, Ce, Ca; and Si, S, Na, K, Nb, Y, B, Ti, Cu, Cr, Mg, Al may be found as impurities, when the LAGJXODE phase is required not to contain these elements.
Preferably, the total content of impurities by weight is less than 2%, preferably less than 1%, preferably less than 0.7%. More preferably,
In step e), the fused product undergoes a thermal treatment of crystallization, which advantageously makes it possible to reduce the amount of amorphous phase and increase the amount of LAGJXODE phase.
In step e), preferably the plateau temperature of the thermal treatment is greater than Tm−700° C., preferably greater than Tm−600° C., preferably greater than Tm−530° C., preferably greater than Tm−480° C., preferably greater than Tm−430° C., preferably greater than Tm−380° C., preferably greater than Tm−330° C., and/or preferably less than Tm−80° C., preferably less than Tm−130° C., preferably less than Tm−180° C., preferably less than Tm−230° C. For example, for a LiFePO4 fused product, the temperature of the thermal treatment is greater than 500° C., preferably greater than 550° C., preferably greater than 600° C., preferably greater than 650° C., and less than 930° C., preferably less than 900° C., preferably less than 850° C., preferably less than 800° C., preferably less than 750° C.
Preferably, the holding time at the plateau is more than 2 hours and/or less than 24 hours, preferably less than 15 hours, preferably less than 10 hours. A plateau temperature of 700° C. maintained for 5 hours is very suitable.
The reducing environment can be created with a gas stream such as a CO/CO2 mixture or a N2/H2 mixture. However, any method making it possible to generate a reducing environment known from the prior art can be used.
Preferably, the particles are annealed in a reducing environment created with a gas.
In step f), optional, the annealed fused particles can be ground and/or can undergo an operation of granulometric selection depending on the intended applications, for example by sieving, in particular so that the particles obtained constitute a powder having a median size greater than 0.05 μm and/or less than 100 μm.
In a particular embodiment, the median size of the powder is between 0.05 μm and 5 μm, preferably between 0.05 μm and 2 μm, preferably between 0.05 μm and 0.2 μm. In a particular embodiment, the median size of the powder is between 5 μm and 20 μm, preferably between 7 μm and 15 μm.
In a further step, more than 50% by number of the particles of the fused product from the powder obtained at the end of step e) or f) can be coated, at least partially, with carbon or with a precursor of carbon.
In one embodiment, said particles of the fused product coated with carbon or with a precursor of carbon represent more than 70%, more than 90%, more than 95%, more than 99%, approximately 100% by number of the particles of the powder, which advantageously makes it possible to improve their electrical conductivity, and therefore the performance of the battery comprising a cathode formed from said powder.
The deposition of carbon or of precursor of carbon is carried out conventionally by pyrolysis. Other methods can also be used, for example those described in EP 1 325 525 and EP 1 325 526.
An example of the second method according to the invention is now described in detail.
All the characteristics described above for step a) of the first method according to the invention are also applicable to step a′).
Almost all the constituents lithium, A, Fe, J, D, P and E of the starting charge are present in the fused product manufactured. A proportion of these constituents, for example manganese and/or lithium, variable depending on the fusion conditions, may however evaporate during the fusion step. A person skilled in the art knows how to adapt the composition of the starting charge accordingly so as to obtain, at the end of step c′), a fused product according to the invention.
In one embodiment, in step a′), preferably more than 99%, preferably substantially 100 wt % of the element Fe is supplied by FePO4,n.H2O with 0≦n≦6.
In one embodiment, in step a′), preferably more than 5%, or even more than 15%, or even more than 25 wt % of the element Fe is supplied by Fe2O3.
In one embodiment, in step a′), preferably more than 99%, preferably substantially 100 wt % of the element Fe is supplied by FeO.
In one embodiment, in step a′), preferably more than 10%, or even more than 15%, or even more than 25 wt % of the element Fe is supplied by Fe3O4.
In step b′), the starting charge is melted until a liquid mass is obtained, at a temperature Tlm greater than the melting point Tm of the fused product obtained at the end of step e), the temperature Tm being such that:
The inventors found that, surprisingly, it is possible, in the conditions described above, to obtain, at the end of step c′), fused products having a proportion of phase (Li1−aAa)1+x(Fe1−bJb)y[(PO4)1−dDd]z greater than 99.3%, without having recourse to a thermal treatment such as that in step e) of the first method according to the invention.
It is nevertheless possible to perform a step of thermal treatment, as defined in step e) of the first method according to the invention after step d′) of the second method according to the invention.
As with step b), it is possible for example to use an arc furnace of the Héroult type comprising two electrodes and with a tank with a diameter of about 0.8 m, which can contain about 180 kg of molten liquid. However, all the known furnaces are conceivable, such as an induction furnace, a plasma furnace or other types of Héroult furnace, provided that they make it possible to melt the starting charge completely.
Crucible melting can also be carried out in a heat treatment furnace, preferably in an electric furnace, preferably in a neutral or reducing environment.
An arc furnace or an induction furnace is preferably used.
A power between 400 and 1200 kWh/T is very suitable, notably for a LiFePO4 fused product.
Without this always being applicable, it is possible to increase the quality of mixing by bubbling with a neutral gas as mentioned in FR 1 208 577. The quality of mixing of the molten liquid can in particular be improved by bubbling with nitrogen. The flow rate and/or the temperature of said gas are adjusted so that the temperature of the liquid mass is not affected much by this addition of gas.
The inventors found that, surprisingly, in a second method according to the invention, the environment in the fusion step b′) has little influence on the fused product obtained at the end of step c′). This simplifies the carrying out of the method advantageously, and the fusion step b′) can be carried out in a neutral or oxidizing environment, preferably under air.
At the end of step b′), the starting charge is in the form of a liquid mass, which can optionally contain some solid particles, but in an insufficient amount to produce structuring of said mass. By definition, to preserve its shape, a liquid mass must be held in a container.
All the characteristics described above for step c) of the first method according to the invention are also applicable to step c′).
All the characteristics described above for step d) of the first method according to the invention are also applicable to step d′).
The fused products according to the invention can advantageously have various sizes, and the method of production is not limited to the production of submicron powders. It is therefore perfectly suitable for industrial manufacture.
They can be coated with a layer of carbon or with a layer of a precursor of carbon.
In a preferred embodiment, they are not coated with a layer of carbon. Advantageously, this extends the range of possible uses.
The proportion of LAGJXODE phase, and more generally the degree of crystallization, are preferably as high as possible. These proportions can in particular be increased by reducing the cooling rate during solidification.
Moreover, a powder according to the invention can advantageously be used for making a cathode for lithium-ion batteries. For this purpose, the powder according to the invention can be mixed, in a solvent, with binders and powdered carbon black. The mixture obtained is deposited on the surface of the current collector, generally of aluminum, for example by scraping with a blade (or “doctor blade”) or by a roll-to-roll technique, to form the cathode. The cathode is then dried and/or hot rolled to evaporate the solvent, obtain good adhesion on the current collector and good contact between the grains of the cathode layer.
A battery is conventionally composed of several parts as described above.
The following examples are given for purposes of illustration and do not limit the invention.
The fused products were produced as follows.
The following starting raw materials were first mixed intimately in a mixer:
For examples 1 to 6, the starting charge, weighing 4 kg, was poured into a melting arc furnace of the Héroult type. It was then fused following melting at a voltage of 120 V, instantaneous power of 48 kW, and power applied approximately equal to 800 kWh/T, in order to fuse the whole starting charge completely and homogeneously. Fusion was carried out under air.
For the product according to example 1, not according to the invention, after fusion of the starting charge, the mass of molten liquid was at a measured temperature Tlm of 1200° C. In step c), the liquid mass was then poured so as to form a fine stream.
Blowing with dry compressed air, at room temperature and at a pressure of 8 bar, broke up the fine stream, dispersing the molten liquid into droplets.
Blowing cooled these droplets and solidified them in the form of fused particles. The cooling rate was between 300 K/s and 800 K/s.
Depending on the conditions of blowing, the fused particles can be spherical or nonspherical, hollow or solid. Their size is between 0.005 mm and 5 mm.
For the product according to example 2, produced by the second method according to the invention, in step b′), after fusion of the starting charge, the measured temperature Tlm of the molten liquid was 1300° C. The liquid mass was then poured, under air, into cast-iron molds as defined in U.S. Pat. No. 3,993,119, in such a way that the thickness of the casting was equal to 5 mm. The cooling rate was less than 500 K/s.
For example 3, produced by the first method according to the invention, steps a) to c) are identical to those carried out for the product according to example 1 (not according to the invention). In step d), 100 g of the fused product according to example 1 was ground in a vibratory disk mill RS100 marketed by the company Retsch, so as to obtain a powder having a median size equal to 11 μm. In step e), this powder was placed in an alumina box. This box was put in a Nabertherm HT 16/17 electric furnace, and connected to a system for circulation of a gas 96 vol % N2-4 vol % H2, to create a reducing environment in said box during thermal treatment. The powder was heated in this reducing environment for 5 hours at 700° C., the rate of temperature increase being 100° C./h and the rate of temperature decrease being 100° C./h. After cooling, a powder of product according to example 3 was recovered in the box.
For the product according to example 4, produced by the second method according to the invention, in step b′), after fusion of the starting charge, the measured temperature Tlm of the molten liquid was 1275° C. In step c′), the liquid mass was then poured so as to form a fine stream. Blowing with dry compressed air, at room temperature and at a pressure of 8 bar, broke up the fine stream and dispersed the molten liquid into droplets. Blowing cooled these droplets and solidified them in the form of fused particles. The cooling rate was between 300 K/s and 800 K/s.
For the products according to examples 5 and 6, produced by the second method according to the invention, in step b′), after fusion of the starting charge, the measured temperature Tlm of the molten liquid was 1260° C. and 1320° C., respectively. Step c′) is identical to that of the product of example 4.
Chemical analyses and phase determination were carried out on samples, which had, after grinding, a median size less than 40 μm.
Chemical analysis was carried out by X-ray fluorescence and by “Inductively Coupled Plasma” or “ICP” for lithium and the impurities.
The proportion of LAGJXODE phase was determined from X-ray diffraction patterns, acquired with a D5000 diffractometer from the company BRUKER equipped with a copper DX tube.
Using the EVA software (marketed by the company BRUKER) and after subtracting the continuous background (background 0.8), it is possible to measure the area ALAGJXODE (without deconvolution treatment) of the main peak or main multiplet of diffraction of the LAGJXODE and, for each of the secondary phases, the area Aps (without deconvolution treatment) of the peak of highest intensity that is not superposed or the multiplet of highest intensity that is not superposed. The total area Asecondary phases can then be calculated as the sum of the areas Aps. The proportion of LAGJXODE phase is then calculated from formula (1).
Thus, if the LAGJXODE phase is the only phase present in the X-ray diffraction pattern, the proportion of LAGJXODE phase is equal to 100%.
The amount by weight of amorphous phase was determined from X-ray diffraction patterns, obtained from an instrument of the D8 Discover diffractometer type from the company BRUKER equipped with a copper DX tube and a 2D, GADDS, counter, also marketed by the company BRUKER, with an incident angle of 7°.
Acquisition of the diffraction patterns is performed using this equipment, over an angular domain 2θ between 14° and 80°, in a window of 19° and with a counting time of 72 s/window. The sample is rotated about its own axis in order to limit the preferential orientations and obtain average data.
The patterns obtained are processed using the EVA software as follows:
100×[1−(area of the peaks of Patt2/area of the peaks of Patt1)]
The products in examples 1 to 6 did not comprise amorphous phase, according to the method described above.
The results obtained are summarized in Tables 1 and 2:
These examples demonstrate the effectiveness of the methods according to the invention.
Comparison of the results of the fusions in examples 1 and 2 shows that a fused product having a proportion of (Li1−aAa)1+x(G1−bJb)y[(XO4)1−dDd]zEe phase greater than 99.3% is not obtained if the element Fe is supplied by FePO4,2H2O with a temperature of the liquid mass, Tlm, equal to 1200° C., and without step e) of thermal treatment. In contrast, the product in example 2, prepared by the second method according to the invention, with the element Fe supplied to approximately 100% of its weight by FePO4,2H2O in step a′) and with a temperature of the liquid mass Tlm equal to 1300° C. in step b′), has a proportion of (Li1−aAa)1+x(G1−bJb)y[(XO4)1−dDd]zEe phase greater than 99.9%.
Comparison of the results of the fusions in examples 1 and 4 shows that a product having a proportion of (Li1−aAa)1+x(G1−bJb)y[(XO4)1−dDd]zEe phase greater than 99.3% is obtained if the element Fe is supplied by FePO4,2H2O with a temperature of the liquid mass, Tlm, equal to 1300° C., and without step e) of thermal treatment, step c) for the product according to example 1 and step c′) for the product according to example 4 being identical. The product according to example 4 has a proportion of (Li1−aAa)1+x(G1−bJb)y[(XO4)1−dDd]zEe phase greater than 99.9%.
Comparison of the products in examples 1 and 3 shows that a product having a proportion of Li1.08Fe0.93PO4 phase greater than 99.9% can be obtained by the first method according to the invention comprising a step of thermal treatment e).
As is now clear, the method according to the invention makes it possible to produce, simply and economically, in industrial quantities, fused products whose crystalline part comprises more than 99.3% of LAGJXODE phase.
The size of these products can be reduced, for example by grinding in the form of powders if use thereof so requires. These products can also be obtained directly in the form of particles.
Of course, the present invention is not limited to the embodiments described, which are supplied as illustrative, nonlimiting examples.
In particular, the products according to the invention are not limited to particular shapes or dimensions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1156634 | Jul 2011 | FR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IB2012/053634 | 7/16/2012 | WO | 00 | 2/20/2014 |
