EP3810316A1 - Method for synthesising core-shell silicon-germanium nanoparticles by laser pyrolysis, method for producing an electrode for a lithium battery and associated electrode - Google Patents
Method for synthesising core-shell silicon-germanium nanoparticles by laser pyrolysis, method for producing an electrode for a lithium battery and associated electrodeInfo
- Publication number
- EP3810316A1 EP3810316A1 EP19731771.2A EP19731771A EP3810316A1 EP 3810316 A1 EP3810316 A1 EP 3810316A1 EP 19731771 A EP19731771 A EP 19731771A EP 3810316 A1 EP3810316 A1 EP 3810316A1
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- European Patent Office
- Prior art keywords
- nanoparticles
- silicon
- germanium
- core
- precursor
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- C01B33/027—Preparation by decomposition or reduction of gaseous or vaporised silicon compounds other than silica or silica-containing material
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- C22C1/04—Making non-ferrous alloys by powder metallurgy
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- C22C1/053—Making hard metals based on borides, carbides, nitrides, oxides or silicides; Preparation of the powder mixture used as the starting material therefor with in situ formation of hard compounds
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- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
- C23C16/44—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
- C23C16/4417—Methods specially adapted for coating powder
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- C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
- C23C16/44—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
- C23C16/48—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating by irradiation, e.g. photolysis, radiolysis, particle radiation
- C23C16/483—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating by irradiation, e.g. photolysis, radiolysis, particle radiation using coherent light, UV to IR, e.g. lasers
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- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
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- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/386—Silicon or alloys based on silicon
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- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
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- B22F1/054—Nanosized particles
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- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
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- B22F1/054—Nanosized particles
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- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
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- Y02E60/10—Energy storage using batteries
Definitions
- the invention relates to a process for the synthesis of core-shell nanoparticles by laser pyrolysis, the nanoparticles comprising silicon and germanium.
- a nanoparticle is a particle of solid material whose size is between a few nanometers and a few hundred nanometers, said particle having dimensions of the same order of magnitude in the three directions of space.
- the invention also relates to a method of manufacturing an electrode formed from such nanoparticles for the electrochemical storage of energy.
- the invention finally relates to an associated electrode.
- Silicon represents a very promising material for the manufacture of electrodes, and more particularly of the anodes of lithium-ion batteries.
- the use of silicon nanoparticles in the anodes has made it possible to substantially improve the storage capacity of the batteries.
- two intrinsic drawbacks to silicon remain, limiting the lifespan of this type of battery.
- the first drawback resides in the volume changes of the silicon during its lithiation, a process during which a lithium / silicon alloy is formed in a reversible manner.
- the second drawback associated with silicon is the poor stability of the passivation layer, composed of degradation products of the electrolyte, which forms at the electrolyte / silicon interface during cycling and which, when changing volume, cracks, exhibiting new silicon surfaces. This poor stability has the direct consequence of significantly reducing the performance of the anode and of the battery during cycling, in particular of the retention of the charge capacity.
- Nanoparticles made from silicon-based alloys with metalloids such as germanium, tin or antimony have recently been proposed.
- germanium represents a solution of choice because it easily forms a solid solution with silicon.
- the electrodes based on silicon-germanium alloys are more stable than the anodes based on silicon alone.
- the storage capacity of germanium being lower than that of silicon, the batteries obtained are of lower capacity.
- a solution would consist in developing nanoparticles having a heart-shell type structure in which the heart is in germanium and the shell is in silicon so that silicon remains accessible to lithium.
- Nanowires are synthesized during a preliminary growth step using VLS (Vapor-Liquid-Solid), then annealing is carried out at 850 ° C to allow the migration of part of the silicon at the periphery of the nanowires .
- VLS Very-Liquid-Solid
- annealing is carried out at 850 ° C to allow the migration of part of the silicon at the periphery of the nanowires .
- the stability of the electrodes formed from such nanowires is improved compared to the electrodes formed from silicon-germanium alone and, concomitantly, the capacity is approximately 1100 mAh / g after 300 cycles at 1 C.
- the document Meringher et al., Nanoscale, 2015, 7, 5186, describes a process for the synthesis of nanoparticles of the core-shell type, in which the materials of the core of the nanoparticles (based on silicon and germanium) are very distinct from the shell.
- the process is based on a synthesis of nanoparticles by chemical vapor deposition in a reactor comprising two zones. During a first step, silane and argon are introduced into a first zone of the reactor in order to create a flow of primary silicon particles of approximately 30 nm. In a second step, the flow of primary particles from the first zone is used to synthesize silicon-germanium nanoparticles. To this end, silane and germane are introduced into a second zone of the reactor.
- Nanoparticles therefore have a core composed of a silicon germ on which Si or SiGe is grown.
- the invention overcomes the aforementioned drawbacks and proposes for this purpose a process for synthesizing nanoparticles of the core-shell type by laser pyrolysis, said process comprising the following steps:
- the dilution factor of the silicon precursor in the dilution gas Gt is between 7 and 35;
- the dilution gas is helium
- the silicon precursor is silane (SiH 4 ) and the germanium precursor is germane (GeH 4 );
- the first chamber 1 is under an atmosphere of neutral gas, said neutral gas preferably being argon;
- the silicon precursor is conveyed with a flow d1 and the germanium precursor is conveyed with a flow d2, the ratio d1 / d2 being between 0.19 and 4.27;
- step d) transporting, without return to air, the nanoparticles from said first chamber to a reaction zone of a second chamber of a reactor, and simultaneously conveying a carbon precursor in said second chamber, d) emitting a second beam laser having a fluence of at least 350 W / cm 2 at the second reaction zone so that at the end of step d) the nanoparticles comprise carbon;
- the carbon precursor is ethylene
- the invention also relates to a method for manufacturing an electrode formed from nanoparticles of the core-shell type, said method comprising the following steps:
- step E) removing the solvent from the ink coated on the support of step C), said support being intended to form an electricity collector,
- step E) includes a drying step
- step F comprises, after step F), a drying step to remove all traces of the solvent.
- the invention further relates to an electrode formed of nanoparticles of the core-shell type, the core of which is made of an alloy of silicon and germanium and the shell is made of silicon, the shell coating the heart, the nanoparticles forming an active material of the electrode.
- the nanoparticles are coated with a layer of carbon, said layer of carbon being distributed around the shell.
- FIG. 1 illustrates, schematically, a reactor used for the synthesis of nanoparticles according to the method of the invention, the reactor comprising a first chamber;
- FIG. 2 illustrates a variant of the reactor of Figure 1, comprising a second chamber
- FIG. 3a illustrates the displacement of the diffraction peak (100) of different silicon-germanium alloys, depending on their germanium composition which varies between 0% and 77.4%;
- Figure 3b illustrates the variation of the lattice parameter as a function of the germanium composition relative to the diffraction peaks of Figure 3a;
- Figure 5b illustrates the concentration profiles of Figure 5a in absolute value, in green is shown the profile of germanium and in orange the profile of silicon;
- the invention aims to synthesize by laser pyrolysis nanoparticles of the core-shell type, the core of which is made of an alloy of silicon and germanium and the shell is of silicon.
- the dissociation of the precursors of silicon and germanium is favored in atomic vapors, radicals, molecular species, etc. of each element and rapid agglomeration of said vapors, leading to the formation of an aggregate made of a silicon-germanium alloy whose composition, in terms of Si / Ge ratio, depends on the composition of the mixture M, and - It simultaneously promotes the formation of silicon on the surface, resulting in the formation of core-shell nanoparticles having a silicon shell and a core made of silicon-germanium alloy.
- the electrodes made from these nanoparticles not only significantly improve the capacity of the batteries, but also their stability after several charge / discharge cycles.
- Fluence at the level of reaction zone 5 is an operating parameter which makes it possible to control the crystallinity of the nanoparticles, since this acts directly on the temperature of reaction zone 5.
- This operating parameter is likely to indirectly modify the composition nanoparticles, and, all the more so in the context of the pyrolysis of a mixture of precursors.
- the residence time has an influence on the nucleation kinetics and the growth of nanoparticles.
- the residence time of the precursors in the first chamber 1 depends on the flow conditions of the mixture of precursors in said first chamber 1. These flow conditions can be adjusted by modifying the flow of each of the precursors, but also by diluting them in a gas. adapted. We will come back to this in the next sections.
- a reactor 100 capable of being used for the purposes of carrying out sub-steps a) and b) and therefore for the synthesis of said nanoparticles is described below.
- the reactor 100 comprises a first chamber 1 in which the synthesis of the core and the shell of the nanoparticles takes place.
- the synthesis has takes place in the first chamber 1 by supplying the inlet 1 1 with a continuous flow of the mixture M.
- the first chamber 1 is provided with an inlet 1 1 allowing the introduction of the mixture M.
- the inlet 1 1 is generally in the form of a nozzle d 'injection.
- the input 1 1 is connected to a supply channel 4.
- This channel 4 is connected to a source 9 containing the silicon precursor, a source 10 containing the germanium precursor and a source 8 comprising a transport gas, or alternatively as dilution gas G t .
- the mixture M is therefore in the form of a mixture of gaseous reactants comprising the silicon precursor and the germanium precursor, which are present in said mixture in variable proportions.
- the proportions may vary over the entire range of accessible gas composition. That said, in practice, the silicon precursor is always present in the mixture M even though the respective flow rates of the two precursors can vary.
- the mixture M is produced from gaseous precursors of the silane type, SiH 4 , for silicon and of the germane type, GeH 4 , for germanium.
- gaseous precursors of the silane type, SiH 4 , for silicon and of the germane type, GeH 4 , for germanium can be carried out with other precursors.
- HDMS hexamethyldisilazane
- This precursor being in liquid form, an aerosol generator, for example piezoelectric, may be used to generate droplets of said precursor.
- a confinement gas G c is brought into the first chamber 1 by a conduit 12, part of which surrounds the channel 4, said conduit 12 being moreover connected to a source 14 containing said confinement gas.
- the confinement gas G c is brought simultaneously with the mixture M into the first chamber 1.
- the confinement gas G c makes it possible, on the one hand, to purge the air included in the first chamber in order to maintain this first chamber under an atmosphere of neutral gas and, on the other hand, to avoid any contact between the precursors and the walls of the chamber by confining the reaction in zone 5. In this way, any pollution phenomenon is limited, or even avoided, during the formation of the nanoparticles.
- argon can be used for this purpose.
- the conditions of transport of the precursors in the first chamber 1 are fixed by the gas flow conditions.
- dilution gas By way of nonlimiting example of dilution gas, mention may be made of argon, helium and nitrogen.
- the Si / Ge ratio remains adjustable by modifying the flux of the silicon precursor relative to that of the germanium precursor.
- the gas flow conditions influence the residence time of the gases in the first chamber 1, and consequently the growth kinetics of the nanoparticles.
- the higher the total gas flow the shorter the residence time of the reactants within the reaction zone 5, and the shorter the interaction time of the reactants with the first laser beam 21.
- the lower the total gas flow the longer the interaction time of the precursors with the first laser beam and the longer the residence time in the reaction zone 5. It therefore has an effect on the kinetics of nucleation and, consequently, on the size of the particles.
- the gas flow conditions can be adjusted by modifying the flow of the dilution gas G t in the first chamber 1, so that the total gas flow obtained by summing the gas flows makes it possible to obtain the residence time. wish.
- the gas flow conditions can be adjusted taking into account the dilution factor of the silicon precursor, that is to say the ratio dilution gas flow / silicon precursor flow.
- the dilution factor of the silicon precursor in the dilution gas G t may be between 7 and 35.
- this operating parameter must be correctly determined because the proportion of the dilution gas G t in the mixture M influences the cooling time of the particles, and therefore the temperature of the reaction zone 5.
- the dilution gas G t can accelerate or, on the contrary, delay the dissipation of the energy absorbed by the molecules. Incidentally, this can therefore influence the temperature in the reaction zone 5 and the size of the nanoparticles. For example, a sudden drop in temperature will stop growth, which will lead to the formation of smaller particles.
- helium can advantageously be used as the dilution gas G t , since it allows rapid cooling of the reaction zone 5 by promoting rapid dissipation of the energy absorbed by the molecules.
- the laser pyrolysis of the said mixture M is carried out during step b) to form not only the core but also the shell of the nanoparticles.
- an optical device comprising a laser capable of emitting the first laser beam 21.
- Said optical device is located outside the first chamber 1 of the reactor 100.
- said laser is arranged on one side of the first chamber 1 so as to allow the first laser beam 21 to be illuminated along an axis of propagation intersecting vertically and, in this case, horizontal.
- the first chamber 1 comprises transparent side walls 16, 17 to the first laser beam 21 to allow said laser beam 21 to pass right through it, along a substantially horizontal axis.
- Another respective arrangement of said laser could be provided with respect to the reactor 100.
- this arrangement is particularly practical for making so that the first laser beam 21 is able to interact with said precursors in order to simultaneously form the heart and the shell.
- the laser can be a C0 2 type laser, typically emitting at a wavelength of 10.6 microns. Other types of lasers known to those skilled in the art for their ability to break down certain precursors can be envisaged.
- the first laser beam 21, of circular section, has a size of several millimeters.
- the laser emits at high power. More precisely, the laser can emit a laser beam 21 delivering a maximum continuous power of 2800W, which would make it possible to reach incident powers per unit area of almost 5 kW / cm 2 at most, however closer to 2.5 kW / cm 2 in practice in the reaction zone 5 for a beam diameter of 15 mm for example.
- the fluence acts directly on the temperature of the reaction zone 5 and in this way influences not only the crystallinity of the nanoparticles, and, indirectly, the surface and volume composition of the nanoparticles while retaining nanoparticles of the core-shell type with the desired characteristics. , that is to say whose core is made of an alloy of silicon and germanium and the silicon shell is well delimited from the core.
- the fluence may be at least 100 W / cm 2 .
- the fluence may be at least 200 W / cm 2 .
- the fluence may be at least 300 W / cm 2 . Fluence is the most important control parameter for the temperature of the reaction zone.
- the fluence is to be associated with a given flow rate of the silicon precursor, in particular since this parameter is linked to the energy absorbed and therefore to the density of atoms of the silicon precursor per unit area.
- the fluence could be at least 100 W / cm 2 .
- an additional gas must be supplied, for example dihydrogen ( H 2 ) or ammonia (NH 3 ) to obtain this reducing atmosphere.
- an additional RS tank can be provided comprising such a gas, for example H 2 or NH 3 .
- This additional RS reservoir leads to conduit 4 as for the different sources 8 (dilution gas), 9 (silicon precursor) and 10 (germanium precursor). This is what is shown in Figure 8.
- the core-shell nanoparticles are extracted from the reactor 100 via a channel 15 for recovering these nanoparticles, advantageously comprising collectors equipped with filtering barriers (not shown).
- This recovery channel can advantageously include a lower part 15a of conical shape to assist in the transfer to the nanoparticle collection zone.
- the nanoparticles thus synthesized are collected and form a solid material.
- the invention also relates to a method in which at the end of the step of synthesizing the nanoparticles, the following steps are carried out: c) transporting, without return to air, the nanoparticles from said first chamber 1 to a reaction zone 7 of a second chamber 2 of a reactor 110, and simultaneously convey a carbon precursor in said second chamber 2,
- step d) emitting a second laser beam 41 having a fluence of at least 350 W / cm 2 at the level of the second reaction zone level of said reaction zone 5 so that at the end of step d) the nanoparticles include carbon.
- This method therefore comprises an additional step of interaction with the laser in comparison with the method described above.
- reactor 1 10 there is a reactor 1 10 whose configuration differs from reactor 100.
- the reactor 1 10 comprises a first chamber 1, a second chamber 2 and a communication channel 3 between the two chambers 1, 2.
- the reactor 1 10 is arranged vertically, so that the second bedroom 2 is located above the first bedroom 1.
- the first chamber 1 has the same characteristics as above.
- the second chamber 2 is provided with an inlet 1 1 'for a carbon precursor.
- the first chamber 1 is dedicated to the synthesis of core-silicon-germanium nanoparticles, while the second chamber 2 is dedicated to the introduction of another element, for example carbon.
- the inlet 11 surrounds part of the communication channel 3 extending collinearly with said communication channel so as to allow a radial injection of the carbon precursor.
- core-shell nanoparticles comprising carbon is therefore carried out successively in time and in space.
- the gas flow in the first chamber 1 is sufficient to help transport the nanoparticles to the second chamber 2.
- the communication channel 3 is used to transmit the nanoparticles formed in the first chamber 1 towards the second chamber 2.
- it is advantageously provided with a conical lower part 3a.
- a carbon precursor is brought into the second chamber 2.
- the inlet 11 'of the second chamber 2 forms an end of a supply channel 6 of this precursor, said supply channel 6 being connected to a source 13 for this precursor.
- ethylene, C 2 H can be used as carbon precursor.
- the invention is not limited to the use of this precursor.
- the nanoparticles and the carbon precursor must mix before a second reaction zone 7, said reaction zone being the zone of interaction with a second laser beam 41.
- the flow rate of the carbon precursor must preferably be controlled.
- the carbon precursor is thus brought, with the nanoparticles, into the second reaction zone 7 in order to expose said nanoparticles to carbonaceous species.
- the laser beam 41 is generated by an optical device (not illustrated), comprising a laser arranged on the side of the second chamber 2 so as to allow the second laser beam 41 to be illuminated along an axis of propagation intersecting vertically and, in the case in point, horizontal.
- the second chamber 2 comprises transparent side walls 18, 19 to the second laser beam 41 in order to allow the laser beam 41 to pass right through it, along a substantially horizontal axis.
- the laser of the second chamber 2 can have characteristics similar to the laser of the first chamber 1.
- the second laser may possibly emit a laser beam 41 delivering a higher continuous power than the first laser beam 21.
- an ethylene flow rate equal to 80 sccm will require an incident power per unit area of at least 350 W / cm 2 .
- optical device could be provided in which a set of mirrors would redirect the laser beam 21 coming from the first chamber 1 towards the second chamber 2.
- the latter are extracted from the reactor 110 by means of a channel 15 for recovering these nanoparticles, advantageously comprising collectors equipped with filtering barriers (not shown).
- the nanoparticles thus synthesized are collected and form a solid material.
- First embodiment Synthesis of nanoparticles whose core is made of silicon-germanium alloy and the shell is made of silicon from mixtures M having variable Si / Ge gas ratios.
- the reactor 100 is used, that is to say that shown in FIG. 1.
- silane is used as a precursor of silicon
- germane is used as a precursor of germanium
- helium used here as a transport / dilution gas and argon, used as a containment gas, are introduced with the precursors of silicon and germanium.
- the helium flow is chosen so that the total gas flow is equal to 600 sccm. This flow rate ensures a constant flow of precursors within the reactor 100, knowing that the diameter of the inlet 1 1 (circular orifice) is 2 mm.
- the first chamber 1 is maintained at constant pressure, close to atmospheric pressure.
- the chamber is filled with argon, which prevents unwanted reactions.
- the laser emits a continuous laser beam 21 whose power is 1050 W, with which is associated a certain focusing, making it possible to obtain a surface power of 280 W / cm 2 (fluence) for all the tests carried out.
- the pyrolysis of the said mixture is carried out, for each gas composition mentioned above.
- reaction zone 5 The temperatures in reaction zone 5 are approximately 1900K (Sibat 191), 1690K (Sibat 198), 1480K (Sibat 203) and 1410K (Sibat 193), respectively.
- Nanoparticles are then obtained, the core of which is made of silicon-germanium and the shell mainly of silicon, which are then recovered at the outlet of the recovery channel 15.
- FIG. 3a is illustrated the displacement of the diffraction peak (100) of the nanoparticles as a function of their germanium composition. The measurements were made by X-ray diffraction.
- the nanoparticle has a diameter of about 130 nm in total and has a core of 100 nm in diameter and a shell of about 15 nm in thickness.
- Second embodiment Synthesis of core-shell silicon-germanium nanoparticles with added carbon.
- the reactor 110 is used, that is to say that shown in FIG. 2.
- the nanoparticles formed in the first chamber 1 are then transported, without return to the air, in the second chamber 2 via the communication channel 3 and the inlet 1 1 ’in order to introduce the carbon.
- ethylene initially stored in the source 13, is conveyed to the second chamber 2 via the supply channel 6 and the inlet 1 1 ’.
- the inlet 11 ' with a diameter of 10 mm (circular orifice), is adapted to support an ethylene flow rate of 700 sccm and the continuous production flow of the nanoparticles.
- the second laser delivers a laser beam 41 whose continuous laser power is 1390 W, the absorption of which by the flow of ethylene makes it possible to dissociate the molecules and form carbonaceous species.
- the carbonaceous species thus formed agglomerate around the nanoparticles arriving in the second chamber 2 and thus enrich the shell in silicon with carbon.
- the nanoparticles obtained have a core made of a silicon-germanium alloy and a shell of silicon and are enriched in carbon.
- the invention also relates to a method for manufacturing an electrode formed from nanoparticles of the core-shell type as described above.
- the electrode manufacturing process includes the following steps:
- step E) removing the solvent from the ink coated on the support of step C), said support being intended to form an electricity collector,
- Steps C) to F) are conventional steps for manufacturing an electrode.
- the invention further relates to an electrode formed of nanoparticles of the core-shell type, the core of which is made of an alloy of silicon and germanium and the shell is made of silicon.
- the nanoparticles are such that their core is made of silicon-germanium and that the silicon shell coats the core homogeneously.
- the nanoparticles are such that the core of silicon-germanium alloy is very distinct from the silicon shell.
- the composition of the core is relatively homogeneous in volume throughout the core and up to the zone delimiting the shell, while the shell is mainly made of silicon.
- the shell is mainly made of silicon.
- “predominantly made of silicon” is meant that the shell has a concentration of silicon much higher than that of germanium.
- Such a configuration makes it possible to substantially improve the capacity and the stability of the electrodes produced.
- the nanoparticles have a generally spherical shape.
- the nanoparticles have a diameter of less than 150 nm.
- the size of the nanoparticles plays an important role in the stability of the electrodes made from said nanoparticles. Beyond a threshold particle size, typically of the order of 150 nm, the surface layer of silicon gradually cracks during its lithiation.
- the shell has a thickness of between 5 and 10 nm.
- the nanoparticles can comprise carbon.
- the electrodes made from such nanoparticles have more stable charge capacities over time, in particular during cycling.
- Example of realization of an electrode and characterizations Manufacture of an electrode formed of core-shell nanoparticles whose core is made of a silicon-germanium alloy and the shell is made of silicon, with and without carbon layer and characterizations.
- Electrodes formed from nanoparticles as synthesized in the first and second exemplary embodiments, both having an Si / Ge ratio 1.05, and electrodes were made from silicon material alone.
- the capacity and the retention of the charge capacity of the electrodes obtained during cycling were measured in order to evaluate the performance of such electrodes.
- the samples used to carry out these tests are half-cells, that is to say that their lithium counter-electrode is metallic.
- FIG. 6 illustrates the evolution of the load capacity (full symbols) obtained and the coulombic efficiency (hollow symbols) associated as a function of the number of cycles for particles having a close size.
- Coulombic efficiency is defined here by the ratio between the delithiated capacity of the material over the lithiated capacity of said material, namely the proportion lithiated reversibly within the material. This coulombic efficiency can be determined at each cycle.
- the calculated capacity of the electrodes obtained is 2669 mAh / g, while for nanoparticles comprising, in addition, a layer of carbon, this calculated capacity goes to 2556 mAh / g.
- the results of this study are better than those generally obtained for electrodes formed from silicon-germanium nanoparticles. Indeed, the initial capacity for the silicon-germanium / silicon-based electrode is greater than 2000 mAh / g.
- the capacity retention of the load is important, since it is 87% after 100 cycles.
- Load capacity retention is important, even when speeds as high as 5C are applied. These electrochemical results are better than in the state of the art.
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FR1855612A FR3082768B1 (en) | 2018-06-22 | 2018-06-22 | PROCESS FOR SYNTHESIS OF SILICON-GERMANIUM NANOPARTICLES OF CORE-SHELL TYPE BY LASER PYROLYSIS, PROCESS FOR MANUFACTURING AN ELECTRODE FOR LITHIUM BATTERY AND ASSOCIATED ELECTRODE |
PCT/EP2019/066717 WO2019243637A1 (en) | 2018-06-22 | 2019-06-24 | Method for synthesising core-shell silicon-germanium nanoparticles by laser pyrolysis, method for producing an electrode for a lithium battery and associated electrode |
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