WO2014006600A1

WO2014006600A1 - Molten product containing lithium

Info

Publication number: WO2014006600A1
Application number: PCT/IB2013/055515
Authority: WO
Inventors: Yves Boussant Roux; Arnaud APHECEIXBORDE; Sylvain Petigny; Costana Mihaela IONICA BOUSQUET; Caroline Levy; Benoît WATREMETZ
Original assignee: Saint-Gobain Centre De Recherches Et D'etudes Europeen
Priority date: 2012-07-06
Filing date: 2013-07-05
Publication date: 2014-01-09
Also published as: FR2992955A1

Abstract

A molten polycrystalline product in which the mass content of elements Li, Ti, A and M and C, expressed according to the formula Li x Ti y A a M m C c O 7, is greater than 95%, the contents of the other elements of said product being expressed in the form of the most stable corresponding oxides if said oxides exist, or, alternatively, expressed in elemental form, A being an element chosen from Na, K, H, Mg, Y, P and the mixtures thereof, M being an element chosen from Zr, Al, Ta, Nb, Mn, Hf, Si, Co, Ni, Cr, Fe, V, Cu, Zn, Ga, In, Sn, Sb, and the mixtures thereof, where 1.5 ≤ x ≤ 2.5, 2 ≤ y ≤ 3.4, 0 ≤ a ≤ 0.5, 0 ≤ m ≤ 1.5, and 0.004 < c ≤ 1, x, y, a, m and c being atomic indices, the phase ratio of Li 2 Ti 3 O 7 being greater than 50%.

Description

Lithium-based melted product

Technical area

The invention relates to a lithium-based molten product and a process for producing such a product. This product may in particular be used as electrode material, in particular in a lithium-ion battery.

The invention also relates to such a battery. State of the art

Lithium titanium oxide or "LTO" materials are used in particular for the manufacture of lithium-ion battery anodes.

Among the LTOs, the oxide of structure Li ₄ Ti ₅ 0i ₂ spinel in which the titanium may be optionally partially substituted, and the oxide Li ₂ Ti ₃ 0 ₇ , in which lithium and / or titanium may be optionally partially substituted, the electroneutrality of said oxides being ensured by the oxygen content.

These oxides are generally manufactured by the following methods:

co-precipitation / sol-gel followed by a heat treatment step

sintering, as described in WO2004 / 100292, WO2010 / 1 12103 or WO2009 / 074208.

These complex processes lead to a high cost. There is a need for a process for producing the above-mentioned oxides at reduced cost and in industrial quantities.

Furthermore, WO2010 / 1 12103 describes sintered products of general formula Li ₂ Ti ₃ 0 ₇ in which lithium and / or titanium may be substituted with carbon and / or metal ions.

However, the inventors have found that, for a carbon content of less than 2.5% by weight, the sintered products according to WO2010 / 1 12103 do not make it possible to manufacture a lithium-ion battery having an initial capacity greater than 140 mAh / g. for charging and discharging cycles of 1 C.

There is therefore a need for a new LTO product for manufacturing a lithium-ion battery having an initial capacity greater than that manufactured from the sintered products described in WO2010 / 1 12103. The present invention aims to satisfy these needs. Summary of the invention

According to the invention, this object is achieved by means of a polycrystalline molten product in which the mass content of elements Li, Ti, A, M and C, expressed according to the formula Li _x Ti _y A _has M _m Cc0 ₇ , is greater than 95%, the contents of the other elements of said product being expressed in the form of the most stable corresponding oxides if said oxides exist, or otherwise expressed in elemental form, A being a member selected from Na, K, H, Mg , Y, P and mixtures thereof, M being a member selected from Zr, Al, Ta, Nb, Mn, Hf, Si, Co, Ni, Cr, Fe, V, Cu, Zn, Ga, In, Sn, Sb, and mixtures thereof, with 1.5 <x <2.5, 2 <y <3.4, 0 <a <0.5, 0 <m <1.5, and 0.004 <c <1, x, y, a, m and c being atomic indices, the phase level of Li ₂ Ti ₃ O ₇ being greater than 50%.

In one embodiment, said other elements are in the form of oxides for more than 95%, more than 99%, or even substantially 100% by weight.

Although the manufacture of fusion-solidification products is well known, it is the merit of the inventors to have discovered that this type of process can be used to manufacture, in a simple manner at reduced costs and in industrial quantities, a suitable product. for use in an anode of a lithium-ion battery and making it possible to obtain, in this use and for carbon mass contents of less than 2.5%, an initial capacity greater than 140 mAh / g for charge cycles and discharge of 1 C.

Surprisingly, the inventors have also discovered that a product according to the invention allows, in an unexplained way, to obtain batteries having a stable capacity.

Preferably, a product according to the invention also comprises one, and preferably several, of the following optional characteristics:

- x <2.3 and / or y <3.3 and / or a <0.3 and / or m <1, 3 and / or c <0.9.

- x <2.2 and / or y <3.2 and / or a <0.2 and / or m <0.6 and / or c <0.8.

- x <2.1 and / or y <3.1 and / or a <0.1 and / or m <0.2 and / or c <0.75.

- x≥ 1, 7 and / or y≥ 2.2 and / or a <0.05 and / or m≥ 0.05 and / or c≥ 0.1.

- x≥ 1, 8 and / or y≥ 2,6 and / or a = 0 and / or m≥ 0,10 and / or c≥ 0,2.

- x≥ 1, 9 and / or y≥ 2.9.

Element A is selected from the group consisting of sodium, hydrogen, magnesium, phosphorus and mixtures thereof and / or the element M is selected from group consisting of zirconium, aluminum, tantalum, niobium, manganese, hafnium, silicon, cobalt, chromium, iron and mixtures thereof.

In one embodiment, the sum of the elemental contents Na, K, H, Mg, Y and P, expressed in the elemental form, is less than or equal to 0.4, preferably less than or equal to 0.3, of preferably less than or equal to 0.2, preferably less than or equal to 0.1, preferably less than or equal to 0.05.

In one embodiment, the sum of the elemental contents Na, K, H, Mg, Y and P, expressed in the elemental form, is equal to 0.

In one embodiment, the sum total of Zr, Al, Ta, Nb, Mn, Hf, Si, Co, Ni, Cr, Fe, V, Cu, Zn, Ga, In, Sn and Sb, expressed as the elementary form is greater than 0, preferably greater than or equal to 0.05, preferably greater than or equal to 0.1, even greater than or equal to 0.13, or even greater than or equal to 0.15 and / or lower or equal to 1, 4, preferably less than or equal to 1, 3, preferably less than or equal to 1, 2, preferably less than or equal to 1, 0, preferably less than or equal to 0.8, preferably less than or equal to or equal to 0.6, preferably less than or equal to 0.5, preferably less than or equal to 0.3, preferably less than or equal to 0.2.

In one embodiment, the sum total of Zr, Al, Ta, Nb, Mn, Hf, Si, Co, Ni, Cr, Fe, V, Cu, Zn, Ga, In, Sn and Sb, expressed as the elementary form, is equal to 0.

The phase level of Li ₂ Ti ₃ O ₇ is greater than 55%, greater than 70%, greater than 85%, greater than 95%, greater than 99%, or greater than 99.9%.

The proportion of orthorhombic Li ₂ Ti ₃ O ₇ phase is greater than 50%, greater than 60%, greater than 70%, greater than 80%, greater than 90%, or even greater than 99%.

In one embodiment, the phase level of Li ₄ Ti ₅ O ₁₂ , measured by X-ray diffraction, is less than 5%, preferably less than 3%, preferably less than 1%.

Advantageously, these optional characteristics improve the electrical conductivity properties, making the products particularly well suited, after possible grinding, to the manufacture of anodes for lithium-ion batteries.

The invention also relates to a powder comprising more than 90% by weight, or even more than 95% or even substantially 100% of particles in a product according to the invention.

The invention also relates to a manufacturing method comprising the following steps: a) mixing raw materials so as to form a suitable feedstock to obtain, at the end of step c), a product according to the invention, b) melting the feedstock to obtain a liquid mass, c) cooling until complete solidification of said liquid mass, so as to obtain a molten product,

d) optionally, grinding said molten product,

e) optionally, heat treatment of the molten product at a bearing temperature between the formation temperature of the Li ₂ Ti ₃ O ₇ phase and the melting temperature of the product obtained at the end of step c), during a holding time in upper stage at 5 minutes, and with a temperature descent rate of greater than 500 ° C./s between the bearing temperature and 400 ° C.

By simple adaptation of the composition of the feedstock, fusion-solidification processes, optionally followed by a heat treatment, thus make it possible to manufacture products according to the invention of different sizes and having a phase level of Li ₂ Ti ₃ 0 ₇ greater than 50%, preferably greater than 70%, preferably greater than 90%, more preferably greater than 99%, still more preferably greater than 99.9% or substantially 100%.

Preferably, a manufacturing method according to the invention also comprises one, and preferably several, of the following optional characteristics:

- Carbon and / or carbon precursor is (are) not added in the feedstock in step a), but is (are) added exclusively in the molten liquid during steps b) and / or c).

In step c), in particular if the process does not comprise step e), the cooling rate, or "solidification rate", is greater than 100 ° C./s, preferably greater than 200 ° C. / s, preferably greater than 300 ° C / s and / or less than 10,000 ° C / s, preferably less than 1000 ° C / s, preferably less than 800 ° C / s, preferably less than 600 ° C / s. In one embodiment, particularly if the method comprises a step e), the cooling rate is less than 30 ° C / s, or even less than 20 ° C / s.

In step e), the bearing temperature T _p is greater than the formation temperature of the Li ₂ Ti ₃ O ₇ phase, T _f , and less than the melting temperature T _F of the product obtained in FIG. from step c), the difference (T _p - T _f ) being greater than 10 ° C, preferably greater than 120 ° C and / or the difference (T _F - T _p ) being greater than 10 ° C, preferably greater than 80 ° C.

- At the end of step e), the rate of descent in temperature between the temperature of bearing and 400 ° C is preferably greater than 600 ° C / s, preferably greater than 650 ° C / s, preferably greater than 700 ° C / s.

- The heat treatment in step e) is entirely carried out under a neutral or reducing atmosphere.

The invention also relates to a product that can be obtained by a process according to the invention.

The invention also relates to the use of a molten product according to the invention or manufactured or likely to have been manufactured by a method according to the invention in the manufacture of an anode for lithium-ion battery.

Finally, the invention relates to an anode for a lithium-ion battery, comprising a melted product according to the invention or manufactured or likely to have been manufactured by a method according to the invention, and a lithium-ion battery comprising such anode. The anode may in particular be obtained by shaping a powder according to the invention.

Brief description of the figures

Other objects, aspects, properties and advantages of the present invention will become apparent in the light of the description and examples which follow and on examining the appended drawing in which FIG. 1 represents, schematically and in cross-section, a cell a battery according to the invention.

Definitions

It is appropriate to distinguish a product whose chemical composition is provided by the formula Li _x Ti _y A _to M _m Cc0 ₇ and a phase of formula Li _x Ti _y A _to M _m Cc0 ₇ , in which this formula indicates the crystallographic structure of said phase.

In a product according to the invention, different phases are possible, and in particular one or more phases of formula Li _x TiyA _has M _m Cc0 ₇ .

By "oxide of a most stable element" is meant the oxide of said thermodynamically most stable element at 20 ° C. The International Center for Diffraction Data (ICDD) sheets 034-0393 and 035-0052 make it possible to identify the angular domains of the diffraction peaks corresponding to the phases of lithium-titanium oxide Li ₂ Ti ₃ O ₇ in a form crystallographic orthorhombic and in a hexagonal crystallographic form, respectively.

The "phase rate of Li ₂ Ti ₃ 0 ₇ ", in%, is defined in a product according to the following formula (1):

T = 100 * (H _LT0 237) / (H LT0237 H Secondary Phases) (1) where

Η | _το237 is the sum of the heights of the peak (hk I) = (1 3 0) of the Li ₂ Ti ₃ 0 ₇ phase in orthorhombic crystallographic form, lying at an angle 2Θ substantially equal to 33.3 ° and of the peak (2 2 22) of the phase Li ₂ Ti ₃ 0 ₇ in hexagonal crystallographic form, being at an angle 2Θ substantially equal to 50.46 °, measured on an X-ray diffraction diagram of said product, for example obtained from a device of the D5000 diffractometer type from BRUKER provided with a copper DX tube, without deconvolution treatment, the sample being rotated on itself in order to limit the effects of preferential orientations,

H secondary phases is the sum of the heights of the first minority peak of each secondary phase, measured on the same X diffraction diagram, without deconvolution treatment. The first minority peak of a secondary phase is located on the X-ray diffraction pattern by the corresponding angle 2Θ, on the ICDD record of this secondary phase, at the peak having the greatest height, with the exception of the principal peak on this ICDD record. The secondary phases are the phases detectable by X-ray diffraction other than orthorhombic and hexagonal Li ₂ Ti ₃ O ₇ phases. Among others, Ti0 ₂ rutile, Li ₂ Ti0 ₃ , Li ₄ Ti ₇ 0i ₆ , or Li ₄ Ti ₅ 0i ₂ may be secondary phases identified on the X-ray diffraction pattern, particularly when the product of LT0237 does not have or substantially no element A and / or M.

According to this measurement, the phase ratio of Li ₂ Ti ₃ 0 ₇ thus takes into account phases other than orthorhombic Li ₂ Ti ₃ 0 ₇ phases, the peak (1 3 0) of which is at an angle 2Θ substantially equal to 33. 3 ° is superimposed with that of an orthorhombic Li ₂ Ti ₃ 0 ₇ phase and also takes into account phases other than the hexagonal Li ₂ Ti ₃ 0 ₇ phases, the peak (2 2 22) of which is at a 2Θ angle substantially equal to 50.46 ° is superimposed with that of a phase Li ₂ Ti ₃ 0 ₇ hexagonal. The phase ratio of Li ₂ Ti ₃ O ₇ particularly takes into account the Li ₂ Ti ₃ 0 ₇ phases in which the elements A and / or M are present.

The ratio of the height of the peak (1 3 0) corresponding to this phase to the sum of the peak heights (1 3 0) and the sum of the peak heights (1 3 0) is referred to as the "orthorhombic Li ₂ Ti ₃ O ₇ phase proportion". (2 2 22) corresponding to this phase and to the hexagonal Li ₂ Ti ₃ 0 ₇ phase, the peak heights being measured on said X diffraction pattern.

A "melted product" is a product obtained by melting a feedstock in the form of a liquid mass, and then solidifying said liquid mass.

By "particle" is meant a solid object whose size is less than 10 mm. The size of a particle is classically evaluated by a particle size distribution characterization performed with a laser granulometer. The laser granulometer may be, for example, a Partica LA-950 from the company HORIBA.

By "block" is meant a solid object that is not a particle.

The percentiles or "percentiles" 10 (D ₁₀ ), 50 (D ₅₀ ), 99.5 (D _99.5 ) are the particle sizes corresponding to the percentages by mass of 10%, 50% and 99.5% respectively, on the cumulative particle size distribution curve of the particle sizes of the powder, the particle sizes being ranked in ascending order. For example, 10% by weight of the particles of the powder have a size less than D ₁₀ and 90% of the particles by mass have a size greater than D ₁₀ . Percentiles can be determined using a particle size distribution using a laser granulometer.

The "minimum size of a powder" is the percentile (D ₁₀ ) of said powder.

The "50th percentile" (D ₅₀ ) of said powder is called the "median size of a powder".

The "maximum size of a powder" is the 99.5 percentile (D _99.5 ) of said powder. The term "impurities" refers to the inevitable constituents introduced involuntarily and necessarily with the raw materials or resulting from reactions with these constituents. Impurities are not necessary constituents, but are only tolerated.

By "precursor" of a compound or an element is meant a component capable of supplying said compound or element, respectively, during the implementation of a manufacturing method according to the invention.

Unless otherwise indicated, and in particular in the formula Li _x Ti _y A _a M _m C _c 0 ₇ in which the indices x, y, a, m, c and 7 are atomic indices, all the contents of the constituents according to the invention are mass percentages expressed on the basis of the product.

"Containing a", "comprising a" or "containing a" means "having at least one", unless otherwise indicated.

detailed description Process

An exemplary method according to the invention is now described in detail.

The content and the nature of a product according to the invention depend in particular on the composition of the feedstock prepared in step a).

A feedstock for producing a molten product according to the invention is formed from lithium compounds, optionally of element A and / or M and of titanium, in particular in the form of oxides and / or carbonates and / or hydroxides and / or oxalates and / or nitrates, and / or precursors of lithium, A, M and titanium elements. The composition of the feedstock may be adjusted by the addition of pure oxides or mixtures of oxides and / or precursors, in particular Li ₂ O, Li ₂ CO ₃ , LiOH, oxide (s) ) elements A and / or M, carbonate (s) elements A or M, hydroxide (s) elements A or M or Ti0 ₂ . The use of oxides and / or carbonates and / or hydroxides and / or nitrates and / or oxalates improves the oxygen availability necessary for the phase formation of Li ₂ Ti ₃ O ₇ and its electroneutrality, and is therefore preferred.

Preferably, at least one or all of the titanium elements A and M are introduced into the feedstock in the form of oxides. In a particular embodiment, oxide powders are used to provide the M and titanium elements, and a carbonate powder to provide the lithium element.

Preferably, the compounds providing the elements lithium, titanium, A and M are chosen from Li ₂ CO ₃ , Li ₂ O, LiOH, TiO ₂ , the carbonates of the elements A or M, the hydroxides of the elements A or M, and the oxides of elements A or M.

Preferably, the compounds providing the elements lithium, titanium, A and M together represent more than 90%, preferably more than 99%, in percentages by weight, of the constituents of the feedstock. Preferably, these compounds together with the impurities represent 100% of the constituents of the feedstock.

Preferably, no compound other than those providing the elements lithium, A, M and titanium, or any compound other than Li ₂ 0, Li ₂ CO ₃ , LiOH, oxide (s) of elements A or M, carbonate (s) of elements A or M, hydroxide (s) of elements A or M or Ti0 ₂ is deliberately introduced into the feedstock. In one embodiment, the sum of Li ₂ 0, Li ₂ CO ₃ , oxide (s) of elements A or M, carbonate (s) of elements A or M, hydroxide (s) of elements A or M or TiO ₂ and their precursors represents more than 99% by weight of the feedstock. In particular, preferably, the carbon (and / or a carbon precursor) is not added to the feedstock in step a), but is added to the molten liquid at subsequent steps.

The electrochemical properties of the melted product according to the invention are improved. The amounts of lithium, element A, element M and titanium of the feedstock are found essentially in the manufactured melted product. Part of the constituents, such as for example lithium, which varies according to the melting conditions, can volatilize during the melting step. By his general knowledge, or by simple routine tests, a person skilled in the art knows how to adapt the quantity of these constituents in the starting charge according to the content he wishes to find in the melted products and the melting conditions. implemented.

In order to manufacture a molten product according to the invention, it is preferable in the feedstock that the molar contents li, t, m 'and lithium, titanium, M and A, respectively, in molar percentages on the the sum of the contents li, t, m 'and a' _, comply with the following conditions:

• k-ι. x / y <li / 1 <k ₂ . x / y and / or

• ki. x / m <li / m '<k ₂ . x / m and / or

• ki. x / a <li / a '<k ₂ . x / a

or

- x, y, m and a can take the values defined above, in particular 1, 5 <x <2.5, 2 <y <3.4, 0 <a <0.5 and 0 <m <1 , 5, and

ki is equal to 0.8, preferably equal to 0.9, and

k ₂ is equal to 1, 2, preferably equal to 1, 1.

Of course, these values of k-ι and k ₂ are those to be adopted under established operating conditions, that is to say outside of the transition steps between different compositions and outside the start-up steps. Indeed, if the desired product involves a change in the composition of the feedstock relative to that used to manufacture the previous product, it is necessary to take into account the residues of the previous product in the oven. Those skilled in the art, however, know how to adapt the starting load accordingly.

The granulometries of the powders used can be those commonly encountered in the melting processes. Intimate mixing of the raw materials can be done in a mixer. This mixture is then poured into a melting furnace.

In step b), the feedstock is melted.

All known furnaces are conceivable, such as an induction furnace, a plasma furnace or other types of Heroult furnace, provided that they allow to completely melt the starting charge.

In step b), melting is carried out in a crucible in a heat treatment furnace, preferably in an electric furnace, preferably in an oxygenated environment, for example in air. Electrofusion advantageously allows the manufacture of large quantities of molten product with interesting yields.

For example, it is possible to use a Héroult-type arc furnace comprising two electrodes and whose vessel has a diameter of approximately 0.8 m and can contain around 180 kg of molten liquid. In step b), the energy is preferably greater than 1 100 kWh / T of molten product, preferably greater than 1200 kWh / T. Preferably, the energy is between 1200 kWh / T and 1800 kWh / T, preferably between 1600 kWh / T and 1800 kWh / T. The voltage is for example 130 Volts and the power of 200 kW.

An induction furnace can also be advantageously used.

Preferably, a plasma torch or a heat gun is not used. In particular, processes using a plasma torch or a heat gun do not always make it possible to manufacture melted particles. Even in the case of melting, they generally do not make it possible to manufacture melted particles larger than 200 microns, and at least greater than 500 microns.

After melting, the feedstock is in the form of a liquid mass, which may optionally contain some solid particles, but in an amount insufficient for them to structure said mass. By definition, to maintain its shape, a liquid mass must be contained in a container.

To increase the carbon content in the molten product obtained at the end of step c), carbon and / or a carbon precursor is (are) preferably added to the liquid mass. The introduction of the carbon and / or the precursor of carbon into the liquid mass may be carried out, for example, using a device such as that described in FR 1 208 577, the carbon and / or the precursor of carbon being conveyed (s) and brought into contact with the liquid mass by means of a neutral or reducing gas, preferably neutral, preferably nitrogen. The general environment of the liquid mass may however be neutral, reducing or oxidizing, preferably oxidizing, preferably under air. If the general environment of the liquid mass is oxidizing, the carbon and / or the carbon precursor is preferably added at the end of step b).

The carbon and the carbon precursor may be chosen from the group formed by carbon black, graphite, coke, a resin, a polysaccharide, for example a cellulose, starch or glucose, sucrose and their mixtures . Preferably, the carbon is fed in the form of graphite, carbon black and mixtures thereof.

Preferably, when the steps Ci) and c ₂ ) described below are implemented, the carbon and / or the carbon precursor is not introduced during step b).

Preferably, when the steps Ci ') and c ₂ ') and c ₃ ') described below are implemented, carbon and / or a precursor of carbon is (are) preferably added in the mass. liquid during step b).

In step c), the cooling rate is preferably greater than 100 ° C / s, preferably greater than 200 ° C / s, preferably greater than 300 ° C / s. Advantageously, the phase ratio of Li ₂ Ti ₃ O ₇ is increased and can reach high values without step e). In one embodiment, the cooling rate is greater than 300 ° C / s and less than 10,000 ° C / s, preferably less than 1000 ° C / s, preferably less than 800 ° C / s, preferably less than 600 ° C / s, and the method does not comprise step e).

In step c), the cooling rate may be less than 30 ° C / s, or even less than 20 ° C / s, provided that the method comprises a step e).

In a first embodiment, step c) comprises the following steps:

Ci) dispersion of the liquid mass in the form of liquid droplets,

c ₂ ) solidification of these liquid droplets by contact with a fluid, preferably oxygenated, optionally loaded with carbon particles and / or carbon precursor, so as to obtain molten particles.

By simple adaptation of the composition of the feedstock, conventional dispersion processes, in particular by blowing or atomization, thus make it possible to manufacture, from a liquid mass, particles having a phase content of Li ₂ Ti ₃ 0 ₇ greater than 50%, preferably greater than 60%, preferably greater than 70%, more preferably greater than 90%, more preferably greater than 99%, more preferably greater than 99.9%, or even substantially 100%. The melted product according to the invention, in particular manufactured according to this first embodiment, may be at the end of step c) in the form of particles of size less than 500 μηη, or even less than 200 μηη, or even less than 100 μηη.

In step Ci), a stream of molten liquid, at a temperature preferably greater than the melting temperature of the product according to the invention, preferably greater than 1350 ° C. and preferably less than 1800 ° C., preferably less than 1700 ° C, is dispersed in liquid droplets.

When no element A and M is intentionally added to the feedstock, the temperature of the stream of molten liquid is preferably greater than 1300.degree. C., preferably greater than 1350.degree. C. and preferably less than 1600.degree. C, preferably below 1550 ° C.

The dispersion can result from blowing through the net of the liquid mass.

Depending on the blowing conditions, the melted particles may be spherical or not, hollow or solid. They typically have a size between 0.005 mm and 5 mm.

Any other method of atomizing a liquid mass, known to those skilled in the art, is conceivable.

To increase the carbon content in the molten product obtained at the end of step c), carbon and / or a precursor of carbon is (are) preferably introduced into the molten liquid stream, for example by blowing a gas loaded with carbon particles. This gas can be neutral, reducing or oxidizing.

In step Ci), said liquid mass is brought into contact with a preferably oxygenated fluid, preferably a gas, preferably air and / or water vapor, more preferably with air . The oxygenated fluid preferably has an oxygen content by volume of greater than 20% by volume. This oxygenated fluid preferably serves as a carrier for carbon particles and / or carbon precursors in order to introduce them into the molten liquid.

In step c ₂ ), the liquid droplets are transformed into solid particles by contact with an oxygenated fluid, preferably a gaseous fluid. This oxygenated fluid preferably serves as a carrier for carbon particles and / or carbon precursors.

Preferably, the method is adapted so that, as soon as formed, the droplet of molten liquid is in contact with the oxygenated fluid and / or loaded with particles of carbon and / or carbon precursor, which may be the same or different to that described for step Ci).

More preferably, the dispersion (step C 1) and the solidification (step c ₂ )) are substantially simultaneous, the liquid mass being dispersed by an oxygenated fluid and / or loaded with carbon particles and / or precursor of carbon, preferably gaseous, able to cool and solidify this liquid.

Preferably, the contact with the oxygenated fluid and / or loaded with carbon particles and / or carbon precursor is maintained at least until complete solidification of the droplets.

Air blowing at room temperature is possible.

At the end of step c ₂ ), solid particles are obtained which have a size of between 0.01 μηη and 3 mm, or even between 0.01 μηη and 5 mm, depending on the dispersion conditions.

Dispersion conditions suitable for obtaining particles of sizes of between 0.01 μηη and 3 mm advantageously make it possible to obtain a high phase ratio of Li ₂ Ti ₃ 0 ₇ without resorting to step e).

In a second embodiment, step c) comprises the following steps:

Ci ') pouring the liquid mass into a mold;

c ₂ ') cooling solidification of the liquid mass cast in the mold until a block at least partially solidified;

c ₃ ') demolding the block.

In step Ci '), the liquid mass is cast in a mold capable of withstanding the bath of molten liquid. Preferably, graphite, cast iron, or as defined in US 3,993.1 19 molds are used. In the case of an induction furnace, the turn is considered to constitute a mold. Casting is preferably carried out under air.

To increase the carbon content in the molten product obtained at the end of step c), carbon and / or a carbon precursor is (are) preferably introduced into the jet of molten liquid resulting from casting. of the liquid mass in the mold (step Ci ')), for example by blowing a gas loaded with carbon particles and / or carbon precursor. This gas can be neutral, reducing or oxidizing.

In step c ₂ '), the liquid mass cast in the mold is cooled until an at least partially solidified block is obtained. The use of a mold of the type of those described in US Pat. No. 3,993.1 19 advantageously makes it possible to obtain a high phase ratio of Li ₂ Ti ₃ 0 ₇ without resorting to a step e).

In step c ₃ '), the block is demolded. Preferably, the block is demolded as soon as it has sufficient rigidity to substantially retain its shape.

Preferably, in step Ci ') and / or in step c ₂ ') and / or after step c ₃ '), the said solid mass during solidification is contacted directly or indirectly with an oxygenated fluid, preferably comprising more than 20% by volume of oxygen, preferably a gas, preferably air. This contacting can be performed as soon as casting. In step Ci '), this oxygenated fluid may in particular serve as a vehicle for carbon particles and / or carbon precursor.

To facilitate the contacting of the liquid mass with the oxygenated fluid, it is preferable to unmold the block as quickly as possible, if possible before complete solidification, and then immediately begin the contact with the oxygenated fluid. The solidification then continues in step c ₃ ').

Preferably, the contact with the oxygenated fluid is maintained until complete solidification of the block.

Whatever the embodiment of step c), the introduction of the carbon and / or carbon precursor into the molten liquid can be carried out by any known technique. This introduction can in particular result from contacting a fluid loaded with carbon particles and / or carbon precursor, for example by blowing on the surface or within the liquid mass, for example using of a device as described in FR 1 208 577.

The person skilled in the art can adjust, by simple routine tests, the amount of carbon and / or precursor of carbon in the gas brought into contact with the molten liquid as a function of the composition of the melted product according to the invention sought. . The concentration of carbon or carbon precursor in this gas can be adjusted in particular by means of a Venturi effect proportioner, well known to those skilled in the art.

Preferably, the carbon is introduced in the form of particles. The carbon and the carbon precursor may be selected from the group described above in step b). After complete solidification, a block capable of giving after steps d) and optionally e) a particle powder according to the invention is obtained. In the optional step d), the melted product obtained is crushed and / or ground so as to reduce the size of the pieces, preferably until a powder of melted particles having a median size D _{50 of} less than 50 μηη is obtained. preferably less than 35 μηη, or even less than 30 μηη, or even less than 15 μηη, or even less than 12 μηη, or even less than 5 μηη, or even less than 4 μηη, or even less than 1 μηη, or even less than 0,8 μηη and preferably greater than 0.05 μηη, or even greater than 0.2 μηη, or even greater than 0.5 μηη, or even greater than 1 μηη.

Preferably, if the product is intended to be heat treated during a step e), it is in the form of a powder having a maximum size D _{99.5 of} less than 1 10 μηη, preferably less than 100 μηη , preferably less than 80 μηη, preferably less than 53 μηη, preferably less than 30 μηη, preferably less than 10 μηη, preferably less than 5 μηη, preferably less than 2 μηη. The efficiency of the heat treatment is advantageously improved.

In a preferred embodiment, the powder obtained after grinding has a maximum size D _{99.5 of} less than 5 μηη and a median size of between 0.05 μηη and 1 μηη.

All types of crushers and grinders can be used to reduce the size of pieces. In particular, when a powder of melted particles having a median size D _{50 of} less than 1 μηη is desired, an attrition mill may be used after first grinding in an air jet mill or in a ball mill. .

When powders of melted particles having a median size D ₅₀ greater than 1 μηη are desired, an air jet mill or a ball mill is preferably used.

Step e) is optional, a product according to the invention can thus be an annealed product, that is to say having undergone a heat treatment after solidification, or not.

In step e), the pieces obtained at the end of step c) and / or at the end of step d) can be introduced into an oven to undergo a heat treatment annealing at a temperature of plateau between the temperature of formation of the Li ₂ Ti ₃ O ₇ phase and the melting temperature of the melt product obtained at the end of step c).

Whatever the embodiment considered, other phases than the phase of Li ₂ Ti ₃ 0 ₇ may be present. Advantageously, such a heat treatment makes it possible to increase the phase level of Li ₂ Ti ₃ O ₇ and / or to increase the amount of Li ₂ Ti ₃ O ₇ phase present in an orthorhombic crystallographic form. We can get and phase levels of Li ₂ Ti ₃ 0 ₇ substantially equal to 100%, especially when the cooling rate in step c) is less than 30 ° C / s.

Preferably provided that the bearing temperature remains below the melting temperature T _F of the product obtained after step c) and to increase the rate of Li _x Ti _y phase A _a M _m Cc0 ₇ , the bearing temperature T _p is greater than the formation temperature T _f of said phase, the difference between these temperatures (T _p -T _f ) being preferably greater than 10 ° C, preferably greater than 20 ° C preferably greater than 50 ° C, preferably greater than 100 ° C, preferably greater than 120 ° C. More preferably, provided that the temperature level is still higher than the temperature of forming said phase Li _x Ti _y A _a M _m CC0 _7, _p T bearing temperature is below the melting temperature T _F of the product obtained at the end of step c), the absolute difference between these temperatures (T _F - T _p ) being preferably greater than 10 ° C, preferably greater than 20 ° C, preferably greater than 50 ° C, preferably greater than 80 ° C.

The temperature for forming a phase Li _x Ti _y A _a M _m CC0 ₇ can be determined by X-ray diffraction in temperature.

The melting temperature of a molten product can be determined by differential thermal analysis.

These characteristics advantageously make it possible to increase the phase rate of Li ₂ Ti ₃ 0 ₇ .

When the composition of the desired product is Li _x Ti _y A _a M _m C _c 0 ₇ with 1, 7 <x <2, 1 and 2.9 <x <3, 1 and 0 <a <0, 1 and 0 < m <0.2 and 0.004 <c <1, the bearing temperature is greater than 957 ° C, preferably greater than 967 ° C, preferably greater than 1007 ° C, preferably greater than 1057 ° C, preferably greater than at 1077 ° C and / or preferably below 1290 ° C, preferably below 1280 ° C, preferably below 1250 ° C, preferably below 1220 ° C. A bearing temperature of 1200 ° C is well suited.

The bearing temperature is maintained for a period greater than 5 minutes, preferably greater than 10 minutes, even greater than 1 hour and / or less than 24 hours, preferably less than 15 hours, preferably less than 10 hours, preferably less than 10 hours. at 5 o'clock. The heat treatment is preferably carried out under a neutral or reducing atmosphere, preferably under a neutral atmosphere, preferably under nitrogen. The carbon added during the previous steps is thus preserved.

Preferably, the heat treatment is carried out at atmospheric pressure.

At the end of the temperature step, the temperature is reduced, preferably to room temperature, the rate of descent in temperature being greater than 500 ° C / s, preferably greater than 600 ° C / s, preferably greater than 650 ° C./s, preferably greater than 700 ° C./s, between the stage temperature and 400 ° C. All step e) is carried out entirely in a neutral or reducing atmosphere. The melted particles can be ground after step e), especially if a powder of melted particles having a median size of less than 1 μηη is desired.

If necessary, a granulometric selection is then carried out, according to the intended application, for example by sieving, in particular so that the powder of particles obtained has a median size greater than 0.1 μηη and less than 4 mm. The powder of melted particles may also undergo, especially at the end of step d) or e), an additional step intended to form atomizers, agglomerates or aggregates, in particular when the phase content of Li ₂ Ti ₃ 0 ₇ of the particles melts is greater than 90%, even greater than 99%, even greater than 99.9%, or even substantially equal to 100%. All techniques known to those skilled in the art can be used, including a slurry atomization or granulation.

Product

A product according to the invention, in particular manufactured according to a method according to the invention, may have a composition having one or more of the following characteristics:

Preferably x≥ 1, 6, preferably x≥ 1, 7, preferably x≥ 1, 8, preferably x≥ 1, 9, preferably x≥ 2 and preferably x <2.4, preferably x <2.3, preferably x <2.2 or even x <2.1. In one embodiment 1, 9 <x <2, 1. In one embodiment, x = 2.

Preferably y≥2, 1, preferably y≥2.2, preferably y≥2.2, preferably y≥2.4, preferably y≥2.5, preferably y≥2.6, preferably y≥ 2.7, preferably y≥ 2.8, preferably y≥ 2.9, even y≥ 3.0 and preferably y <3.3, preferably y <3.2, preferably y <3, 1. In one embodiment, 2.9 <y <3.1. In one embodiment, y = 3. Preferably at <0.4, preferably at <0.3, preferably at <0.2, preferably at <0.1 or even at <0.05. In one embodiment, a = 0.

Preferably m> 0, preferably m≥0.05, preferably m≥0.1, or even m≥0.13, or even m ≥0.15 and / or preferably m <1, 4, preferably m <1, 3, preferably m <1, 2, preferably m <1.0, preferably m <0.8, preferably m <0.6, preferably m <0.5, preferably m <0 , 3, preferably m <0.2. In one embodiment, m = 0.

In one embodiment, c ≥ 0.1, preferably c ≥ 0.2, or even c ≥ 0.3 and preferably c <0.9, preferably c <0.8, preferably c <0, 75, preferably c <0.60, preferably c <0.55, preferably c <0.50, or even c <0.40. A low carbon content advantageously makes it possible to increase the amount of Li ₂ Ti ₃ O ₇ for the same volume.

Preferably, the element A is chosen from sodium, hydrogen, magnesium, phosphorus and their mixtures. Preferably the element A is selected from sodium, magnesium and mixtures thereof. Preferably the element A is sodium. In a particular embodiment, more than 80%, preferably more than 85%, preferably more than 90% of the total atomic proportion a of element A, consists of one or two atomic species.

- Preferably, the element M is selected from zirconium, aluminum, tantalum, niobium, manganese, hafnium, silicon, cobalt, chromium, iron and mixtures thereof. These elements significantly improve the number of charge / discharge cycles that a battery comprising an electrode made from a product according to the invention can undergo and / or the electrical capacity of said battery. Preferably, the element M is selected from zirconium, aluminum, tantalum, niobium, chromium, iron and mixtures thereof. In a particular embodiment, more than 80%, preferably more than 85% or even more than 90% of the total atomic proportion m of element M consists of one or two atomic species.

- Preferably, the total mass content of other elements than Li, Ti, A, M and C is less than 3%, preferably less than 2%, preferably less than 1%, preferably less than 0.7%, preferably less than 0.4%, based on the weight of the product. In particular, preferably CaO <0.5%, preferably CaO <0.3%, preferably CaO <0.2%, preferably CaO <0.15%. - Preferably, the total content of elements that can not be expressed in oxide form, and other than carbon C, is less than 1%, preferably less than 0.5%, or even substantially zero, as a percentage by weight on the base of the melted product.

In a particular embodiment:

- 1, 7 <x <2.1, preferably x≥ 1.85, preferably x≥ 1, 9, and

- 2.9 <x≤3.1, and

0 <a <0.1, or even a <0.05, and

- 0 <m <0.2, preferably m≥ 0.05, preferably m≥ 0.1, and

- 0.2 <c <0.75.

In a particular embodiment a = 0 and m = 0.

The determination of the chemical analysis of a melted product according to the invention is carried out as follows. The elemental mass content of each element except oxygen is measured. The oxygen mass content, Q ₀ , is considered as constituting the 100% complement. The elements other than Li, Ti, A, M and C are expressed in the form of their respective most stable oxide if such an oxide exists or in the elementary form in the opposite case. For example, the amount of calcium is expressed as CaO and the amount of chlorine or fluorine is equal to the mass content of Cl or F, respectively. The quantity of oxygen necessary to express the mass contents in the form of the most stable oxides, Q ' ₀ , is subtracted from the mass content of oxygen Q ₀ . Q ₀ -QO, as well as the mass contents of Li, Ti, A, M, and C are converted to the number of moles. The number of moles of Q ₀ -QO is normalized to 7. The number of moles of Li, Ti, A, M, C is multiplied by the factor which allowed said normalization to 7, which makes it possible to determine the indices x, y , a, m and c, respectively, of the formula Li _x Ti _y A _a M _m Cc0 ₇ .

In one embodiment, the product according to the invention may comprise titanium having a valence of less than 4.

In a battery comprising an anode according to the invention, the presence of carbon makes it possible to further improve the initial capacitance of the battery measured after a cycle at a charge and discharge regime of 1 C, but also the capacity of said battery at after 10 cycles at a charging and discharging rate of 1 C.

Without being bound by this theory, the inventors explain the remarkable electrochemical performances of the battery by the presence of a very small amount of Li ₄ Ti ₅ 0i ₂ phase, which appears lower than that of known products of the same composition, and in particular having an identical carbon content.

The carbon may be on the surface and / or inside the product. In particular, it may constitute a layer partially or completely coating a particle with or without carbon. Preferably, however, the carbon is dispersed within the product.

The product may be an annealed product, that is to say having undergone a heat treatment after its solidification.

The phase level of Li ₂ Ti ₃ O ₇ , and more generally the degree of crystallization, are preferably the highest possible. These rates can in particular be increased by increasing the cooling rate during solidification or by the presence of a step e). The cooling rate must not, however, lead to the creation of a glass, that is to say a product mainly of amorphous structure.

Preferably, the phase level of Li ₂ Ti ₃ O ₇ is greater than 55%, greater than 60%, preferably greater than 70%, preferably greater than 90%, preferably greater than 99%, more preferably greater than 99.9% or 100%.

Preferably, the proportion of Li ₂ Ti ₃ O ₇ orthorhombic phase is greater than 50%, preferably greater than 70%, preferably greater than 80%, preferably greater than 90%, or even greater than 95%, or greater than 99%. Elements A and / or M may not be located in the crystalline structure of a Li ₂ Ti ₃ O ₇ phase of said product. It is possible, for example, for the element M to be in the crystalline structure, but also at the grain boundaries.

Preferably, the mass quantity of amorphous phase is less than 80%, less than 70%, less than 60%, less than 50%, less than 40%, less than 30%, less than 20%, less than 10%, less than 5%, less than 3%, less than 2%, or less than 1%, based on the mass of the melt.

The melted product according to the invention may advantageously have various dimensions. It is therefore perfectly suited to industrial manufacturing.

A product according to the invention may in particular be in the form of a particle. The invention also relates to a powder comprising more than 90% by weight, or even more than 95% or even substantially 100% of particles in a product according to the invention. The median size of the powder is preferably greater than 0.1 μηη and / or less than 4 mm, less than 3 mm, less than 2 mm, less than 1 mm, less than 0,5 mm, less than 0,25 mm, less than 0,1 mm.

In a first particular embodiment, the median size of the powder is between 0.05 μηη and 1 μηη, preferably between 0.4 μηη and 0.8 μηη. In a second particular embodiment, the median size of the powder is between 1 μηη and 5 μηη, preferably between 2 μηη and 4 μηη. In a third particular embodiment, the median size of the powder is between 5 μηη and 15 μηη, preferably between 7 μηη and 12 μηη. In a fourth particular embodiment, the median size of the powder is between 15 μηη and 35 μηη, preferably between 20 μηι and 30 μπι.

In one embodiment, the powder according to the invention comprises atomisais, conventionally in the form of granules, and / or aggregates and / or agglomerates of particles according to the invention.

A product according to the invention may also be in the form of a block of which all dimensions are preferably greater than 1 mm, preferably greater than 2 mm, or even greater than 5 cm, or even greater than 15 cm. Preferably, a block of a product according to the invention has a mass greater than 200 g.

A product according to the invention, in particular in the form of a particle, can be coated with a carbon layer.

In one embodiment, the product is not coated with a carbon layer.

In one embodiment, the product is in the form of a powder and more than 50%, preferably more than 70%, preferably more than 90%, preferably more than 95%, preferably more than 99%, Preferably substantially 100% by number, particles of this powder are not covered, even partially, carbon.

A powder according to the invention can advantageously be used to manufacture an anode for lithium-ion batteries. For this purpose, particles according to the invention may be coated with a carbon layer. In particular, the powder of these particles may be mixed in a solvent with binders and a carbon black powder. The mixture obtained is deposited on the surface of the current collector, generally aluminum, for example by scraping with the blade (or "doctor blade" in English) or by a roll-to-roll process (or "roll to roll") , to form the anode. The anode is then dried and / or rolled to evaporate the solvent, obtain good adhesion on the current collector and good contact between the grains of the anode layer.

FIG. 1 represents a cell of a battery 2 consisting of a separator 4, an anode 6, a current collector 12 at the anode, a cathode 8 and a collector current 10 at the cathode, all these organs bathed in an electrolyte.

A battery is conventionally composed of several cells as described above.

Examples

The following examples are provided for illustrative purposes and do not limit the invention. The melted products were manufactured in the following manner.

The following starting raw materials were first intimately mixed in a blender:

for all the examples, a powder comprising more than 99.4% by mass of lithium carbonate Li ₂ CO ₃ , whose median size is less than 10 μηη;

for Example 5, a powder comprising more than 98% by weight of TiO ₂ rutile and, in the form of traces, the Al, Fe, Si, Zr, Nb and Cr elements, whose sieve rejection of 45%; μηη is less than 0.1%;

for Examples 1 to 4, a powder comprising more than 99.5% by weight of anatase TiO ₂ and, in the form of traces, the elements Al, Na, Si, P, Nb, Zr, Cr, Fe and K, whose sieve rejection of 45 μηη is less than 0.1%;

for example 5, a powder comprising more than 90% MnO ₂ and having a median size of between 40 and 50 μηη.

For the products of Examples 3 and 4, the elements K and / or P and / or Zr and / or Al and / or Nb and / or Si and / or Cr and / or Fe result from the presence of these elements, trace state, in the raw materials used.

For each of the examples, the starting load of a mass of 25 kg was poured into a Herault type arc melting furnace. It was then melted following a fusion with a voltage of 130 volts and an applied energy substantially equal to 1800 kWh / T, in order to melt the entire mixture completely and homogeneously. When the melting was complete, the molten liquid was cast to form a net. The temperature of the molten liquid measured during casting was between 1330 ° C and 1370 ° C.

Dry air loaded with graphite particles, at room temperature and at an overpressure of 1 bar, broke the net and dispersed the molten liquid into droplets.

The flow rate of graphite particles, expressed in mass per unit time for blowing dry air, was equal to 10 g / s for the products according to Examples 1, 3, 4 and 5, and 20 g / s for the product. produced according to Example 2.

The blowing cooled these droplets and froze them in the form of melted particles. The particles according to Examples 2, 3 and 5 were sieved and the particle size range 250-500 μηη was characterized.

The particles according to Example 4 were sieved and the particle size range 150- 500 μηη was characterized.

The chemical analyzes and determination of the crystallographic phases of the melted products of the examples were carried out on samples which, after grinding, had a median size of less than 40 μηη.

The chemical analysis was performed by X-ray fluorescence and, for lithium, by "Inductively Coupled Plasma" or ICP.

The carbon content was determined according to ANSI B74.15-1992 (R2007), by the method of "technical resistance furnace", on a sample of crushed product to a maximum size of less than 160 μηη.

The determination of the phase ratio of Li ₂ Ti ₃ 0 ₇ was carried out on the basis of the X-ray diffraction diagrams, acquired with a BRU KER diffractometer D5000 provided with a copper DX tube, the sample being rotated on itself in order to limit the effects of preferential orientations. The diagram was acquired over an angular range 2Θ between 5 ° and 80 °, with a pitch equal to 0.02 °, an acquisition time equal to 1 s / step and a reception slot of 0.6 mm.

With the aid of the EVA software (sold by BRUKER), it is possible to measure the height H _L TO237 of the peak (1 3 0) of the Li ₂ Ti ₃ 0 ₇ phase in orthorhombic crystallographic form, at a angle 2Θ substantially equal to 33.3 °, and the peak (2 2 22) of the phase Li ₂ Ti ₃ 0 ₇ in hexagonal crystallographic form, being at an angle 2Θ substantially equal to 50.46 °; and, for each of the phases secondary, the height H _ps of the first minority peak. We can then calculate the sum of the heights of the first minority peaks H _ph ases side by the sum of _S Hp heights. The phase level of Li ₂ Ti ₃ O ₇ is then calculated according to formula (1).

Thus, if the Li ₂ Ti ₃ O ₇ phase is the only phase present in the X diffraction pattern, the phase level of Li ₂ Ti ₃ O ₇ is equal to 100%.

So, if a diffraction pattern shows:

a height of the peak (1 3 0) of the Li ₂ Ti ₃ O ₇ phase in orthorhombic crystallographic form, being at an angle θ equal to 33.3 ° equal to 15.1 counts / sec, and a height of the peak ( 22 of the Li ₂ Ti ₃ O ₇ phase in hexagonal crystallographic form, being at an angle θ equal to 50.46 ° equal to 81.3 counts / sec. So

Ηι_το237 is equal to 96.4 strokes / sec.

a height of the first minority peak of the TiO ₂ phase in rutile crystallographic form at an angle θ equal to 54.32 ° equal to 28.7 strokes / sec, a height of the first minority peak of the Li ₄ Ti ₅ 0i phase; ₂ being at an angle 2Θ equal to 43.24 ° equal to 40.5 strokes / s. Thus H p _ha his secondary is equal to

69.2 shots / sec

The phase rate of Li ₂ Ti ₃ O ₇ is calculated using formula (1):

T = 100 ^* (96.4) / (96.4 + 69.2) = 58.2%.

The proportion of orthorhombic Li ₂ Ti ₃ O ₇ phase is then equal to 100 ^* (15.1) / (15.1 ⁺ 81.3) = 15.7%.

The X-ray diffraction diagrams of the products of Examples 1 to 5 do not make it possible to highlight the Li ₄ Ti ₅ 0i ₂ phase.

Table 1 below summarizes the results obtained before any annealing heat treatment.

*: Portho denotes the phase proportion of Li ₂ Ti ₃ 0 ₇ orthorombic

Table 1

These examples make it possible to demonstrate the effectiveness of the process according to the invention.

The electrochemical properties of a product powder according to Example 3 and of a powder according to Example 4, having a median size equal to 0.47 μηη and 0.63 μηη, respectively, obtained after crushing, grinding in a jar mill with zirconia cylpebs and then milling in an attritor mill, were measured with a two-electrode cell in Swagelok configuration, the positive electrode comprising a mixture of 85% by weight of the product to be tested and 15% by weight. conductive carbon weight. The negative electrode, serving as a reference electrode, is a metallic lithium film. A solution of ethylene carbonate, dimethyl carbonate and propylene carbonate (1: 3: 1) incorporating 1 M LiPF ₆ is used as the electrolyte. The charge-discharge tests are carried out in galvanostatic mode, at ambient temperature, at a load and discharge rate of 1 C, in the range of voltages 1-2.5V for Li-Li ⁺ , the charging and discharge of C 1 corresponding to 1 mol of Li exchanged per mole of active material Li _x Ti _y a _a m _m CC0 ₇ in 1 hour.

The initial capacity of the battery, measured after a cycle at a charging and discharging rate of 1 C, comprising an anode made from the powder of the product of Example 3 according to the invention and according to Example 4 according to the invention is equal to 162 mAh / g and equal to 157 mAh / g, respectively.

The initial capacity measured after a cycle at a charging and discharging rate of 1 C, on the composition products Li ₂ Ti ₃ 0 ₇ of Examples 3 to 6 described in WO2010 / 1 12103 is equal to 120 mAh / g, 150 mAh / g, 150 mAh / g and 160 mAh / g, respectively.

Table 2 below summarizes the initial capacities measured according to the powders used:

Product powder according to initial capacity after 1

Carbon (% by mass)

the example cycle of 1 C (mAh / g)

3 according to the invention 1, 0 162

3 according to WO2010 / 1 12103 1, 09 120

4 according to WO2010 / 1 12103 1, 25 150

5 according to WO2010 / 1 12103 1, 45 150

4 according to the invention 2.9 157

6 according to WO2010 / 1 12103 3.80 160

Table 2

The batteries comprising an anode made with the product according to Example 3 and Example 4 of WO2010 / 1 12103 having a carbon content equal to 1.09% and 1.25%, respectively, greater than that of the product of example 3 according to the invention, have an initial capacity measured after a cycle at a charging and discharging rate of 1 C, equal to 120 mAh / g and 150 mAh / g, respectively, or 25.9% lower and 7.4% lower, respectively, than that of a battery comprising an anode made with a powder of the melted product of Example 3 according to the invention, which comprises only 1.0% of carbon.

The batteries comprising an anode produced with the product according to Example 5 and Example 6 of WO2010 / 1 12103 having a carbon content equal to 1.45% and 3.80%, respectively, have an initial capacity measured after a cycle at a charging and discharging rate of 1 C, equal to 150 mAh / g and 160 mAh / g, respectively, ie 4.5% lower and substantially identical, respectively, to that of a battery comprising an anode carried out with a powder of the melted product of Example 4 according to the invention.

Thus, for products having an identical carbon mass content, the initial capacity measured after a cycle at a charging and discharging rate of 1 C of a battery comprising an anode made with a melted product according to the invention is much higher. to that of a battery comprising an anode made with a product of the state of the art, for carbon mass contents of less than 2.5%; and substantially the same for higher carbon mass contents. These latter products can however be manufactured simply and economically. As it is now clear, the molten products according to the invention are suitable for use in the manufacture of an anode of a lithium-ion battery having initial capacities and after 1 cycle at a charging and discharging regime of 1 C remarkable. The process according to the invention also makes it possible to manufacture in a simple and economical manner, in industrial quantities, products comprising large quantities of Li ₂ Ti ₃ O ₇ phase.

In particular, this process makes it possible to manufacture particles whose phase content of Li ₂ Ti ₃ 0 ₇ is greater than 99%, greater than 99.9%, or even 100%.

Of course, the present invention is not limited to the described embodiments provided by way of illustrative and non-limiting examples.

In particular, the products according to the invention are not limited to particular shapes or dimensions.

Claims

1. Polycrystalline molten product in which the mass content of elements Li, Ti, A, M and C, expressed according to the formula Li _x Ti _y A _a M _m Cc0 ₇ , is greater than 95%, the contents of the other elements of said product being expressed in the form of the most stable corresponding oxides if said oxides exist, or otherwise, expressed in elementary form, A being an element chosen from Na, K, H, Mg, Y, P and their mixtures, M being an element chosen from Zr, Al, Ta, Nb, Mn, Hf, Si, Co, Ni, Cr, Fe, V, Cu, Zn, Ga, In, Sn, Sb, and their mixtures, with 1.5 < x < 2.5 , 2 < y < 3.4, 0 < a < 0.5, 0 < m < 1.5, and 0.004 < c < 1, x, y, a, m and c being atomic indices, the phase rate of Li ₂ Ti ₃ 0 ₇ being greater than 50%.

2. Product according to the preceding claim, in which x < 2.3 and/or y < 3.3 and/or a < 0.3 and/or m < 1.3 and/or c < 0.9.

3. Product according to the preceding claim, in which x < 2.2 and/or y < 3.2 and/or a < 0.2 and/or m < 0.6 and/or c < 0.8.

4. Product according to the preceding claim, in which x < 2.1 and/or y < 3.1 and/or a < 0.1 and/or m < 0.2 and/or c < 0.75.

5. Product according to any one of the preceding claims, in which x≥ 1.7 and/or y≥ 2.2 and/or a < 0.05 and/or m≥ 0.05 and/or c≥ 0.1 .

6. Product according to the preceding claim, in which x≥ 1.8 and/or y≥ 2.6 and/or c≥ 0.2 and/or a = 0 and/or m≥0.1.

7. Product according to the preceding claim, in which x≥ 1.9 and/or y≥ 2.9.

8. Product according to any one of the preceding claims, in which the element A is chosen from the group formed by sodium, hydrogen, magnesium, phosphorus and their mixtures and/or the element M is chosen from the group formed by zirconium, aluminum, tantalum, niobium, manganese, hafnium, silicon, cobalt, chromium, iron and their mixtures.

9. Product according to any one of the preceding claims, in which the phase content of Li ₂ Ti ₃ 0 ₇ is greater than 70%.

10. Product according to the preceding claim, in which the phase rate of Li ₂ Ti ₃ 0 ₇ is greater than 99%.

1 1 . Product according to the preceding claim, in which the phase rate of Li ₂ Ti ₃ 0 ₇ is greater than 99.9%.

12. Product according to any one of the preceding claims, in which the proportion of orthorhombic Li ₂ Ti ₃ 0 ₇ phase is greater than 50%.

13. Product according to the preceding claim, in which the proportion of orthorhombic Li ₂ Ti ₃ 0 ₇ phase is greater than 90%.

14. Product according to the preceding claim, in which the proportion of orthorhombic Li ₂ Ti ₃ 0 ₇ phase is greater than 99%.

15. Powder comprising more than 90% by weight of particles in a product according to any one of the preceding claims.

16. Manufacturing process comprising the following steps:

a) mixing of raw materials so as to form a starting charge suitable for obtaining, at the end of step c), a product according to any one of claims 1 to 14,

b) melting of the starting charge until a liquid mass is obtained,

c) cooling until complete solidification of said liquid mass, so as to obtain a molten product, the cooling speed being greater than 100°C/s if the process does not include step e) or less than 30°C /s if the process includes a step e),

d) optionally, grinding of said molten product,

e) optionally, heat treatment of the entire molten product under a neutral or reducing atmosphere at a stage temperature between the formation temperature of the Li ₂ Ti ₃ 0 ₇ phase and the melting temperature of the product obtained at the end of step c), for a level holding time greater than 5 minutes, and with a temperature drop speed greater than 500°C/s between the level temperature and 400°C.

17. Method according to the preceding claim comprising a step e), the bearing temperature T _p being higher than the formation temperature of the phase Li _x Ti _y A _a M _m C _c 0 ₇ , T _f , and lower than the temperature of fusion T _F of the product obtained at the outcome of step c), the difference (T _p - T _f ) and/or the difference (T _F - T _p ) being greater than 10°C.

18. Method according to the preceding claim, the difference (T _p - T _f ) being greater than 120°C and/or the difference (T _F - T _p ) being greater than 80°C.

19. Method according to any one of the three preceding claims, in which carbon and/or a carbon precursor is (are) not added in the starting charge in step a), but is (are) (are) added exclusively to the liquid mass during steps b) and/or c).

Anode for a lithium-ion battery, comprising a molten product according to any one of claims 1 to 14 or manufactured or capable of having been manufactured by a process according to any one of claims 16 to 19.

21. Lithium-ion battery comprising an anode according to the preceding claim.