ELECTRODE NEGATIVE POREUSE

Abstract

POROUS NEGATIVE ELECTRODE The present invention relates to a Li-free negative electrode made of a solid electrolyte and carbon particles, as well as its preparation and the electrochemical elements comprising them. Figure for abstract: None

Description

Title of the invention: POROUS NEGATIVE ELECTRODE

[0001] The present invention relates to the field of energy storage, and more specifically to accumulators, particularly of the lithium type.

[0002] Lithium-ion rechargeable batteries offer excellent energy and volume densities and now occupy a dominant position in the market for portable electronics, electric and hybrid vehicles, and stationary energy storage systems.

[0003] Solid electrolytes also offer a notable improvement in terms of safety since they present a much lower risk of flammability than liquid electrolytes.

[0004] The operation of lithium batteries is based on the reversible exchange of lithium ions between a positive electrode and a negative electrode, separated by an electrolyte, with lithium being deposited at the negative electrode during charging operation.

[0005] It is therefore desirable to promote the deposition of lithium and to obtain a deposit that is as homogeneous as possible.

[0006] Hitz et al. (Materials Today, Vol. 22, 2019, Pages 50-57) describe all-solid-state batteries with a three-layer "porous-dense-porous" architecture comprising a dense layer between two porous layers of oxide-type electrolyte. However, shaping the oxide-type electrolytes requires a high-temperature sintering step, making their use difficult on an industrial scale. Furthermore, the negative electrodes described therein do not contain carbon.

[0007] Zhao et al. (Nano Energy 62 (2019) 55-63) describe a lithiophilic porous network based on vertical ZnO nanosheets on a Ni foam to guide the homogeneous deposition / removal of Li during cycles, but do not describe the presence of carbon particles or solid electrolyte particles. This technology uses a liquid electrolyte which, during charging, allows the electrolyte to be evacuated from the porosity to make room for the lithium metal. However, this structure is incompatible with a solid electrolyte, which could not be extracted from the porosity and could not return to its initial position as a liquid electrolyte can, thus blocking the discharge process.

[0008] US2017 / 0133662 describes a lithium battery comprising a cathode, a electrolyte and a lithium composite anode comprising a porous composite matrix and lithium metal inserted within the matrix. In particular, a Li / carbon composite anode is described (example 4) but does not mention the presence of a solid electrolyte.

[0009] CN109728291 describes a liquid or any solid battery comprising an electrode A lithium-free negative electrode, meaning a negative electrode that does not contain lithium metal before operation, comprises a metallic substrate and a lithiophilic metal layer to promote uniform lithium deposition, but makes no mention of porosity or the presence of carbon and / or electrolyte. The 2D geometry also limits the efficiency of lithium deposition and does not allow for smoothing of current densities.

[0010] Massive electrodes allow high surface current densities but have the disadvantage of leading to the formation of dendrites and to an inhomogeneous deposition of lithium which ultimately leads to the limitation of the charge.

[0011] Among the configurations considered for improving the energy densities of electrochemical cells, electrochemically active negative electrode materials may contain a metal capable of forming an alloy with lithium. However, these materials exhibit significant volume expansion during lithiation. This expansion will lead to the degradation of the Li-ion cell based on this material at the negative electrode: i) degradation of electrode integrity, leading to decreased electrode utilization; ii) fracture of the electrode-electrolyte interface (or SEI for "Solid Electrolyte Interface"), leading to the continuous formation of degradation products; iii) increased stress on the entire battery and degradation of other components.

[0012] It is therefore desirable to provide a negative electrode whose structure and composition make it possible to increase the quantity and quality of the lithium deposit while avoiding large variations in thickness.

[0013] The invention therefore aims in particular to provide a porous negative electrode characterized in that said electrode comprises: - solid electrolyte particles and - carbon particles.

[0014] Said electrode is suitable for use in an energy storage device.

[0015] The term "negative electrode" refers to the electrode functioning as an anode when the battery is discharging and as a cathode when the battery is charging, the electrode functioning as a cathode, the anode being defined as the electrode where an electrochemical oxidation reaction (electron emission) takes place, while the cathode is the site of reduction.

[0016] The term negative electrode refers to the electrode from which electrons depart and from which cations (Li+) are released during discharge.

[0017] The electrode structure according to the invention thus allows the lithium to be deposited homogeneously within the porous structure while strongly limiting the volumetric variations of the electrode.

[0018] According to one embodiment, the electrode according to the invention does not contain lithium metal before it is put into operation. It can thus be described as a "Li-free" electrode. However, when operating within a charged electrochemical element, it also includes lithium metal or a lithium-rich phase (concentration greater than 80 atomic percent) resulting from the reaction with the lithiophilic compound within its porosity.

[0019] The negative electrode layer generally consists of a conductive support used as a current collector which is coated with the negative electrode according to the invention containing said solid electrolyte particles and said carbon particles.

[0020] It is understood that in “lithium free” systems, a negative electrode is also present (generally initially limited to the current collector only).

[0021] A current collector is understood to be an element such as a pad, plate, sheet or other, made of conductive material, connected to the positive or negative electrode, and ensuring the conduction of the flow of electrons between the electrode and the terminals of the battery.

[0022] The current collector is preferably a two-dimensional conductive support such as a solid or perforated metal strip, for example copper, nickel, steel, stainless steel or aluminum. Said collector at the negative electrode is generally in the form of a copper strip.

[0023] According to one embodiment, said electrode may further contain a binder.

[0024] The term "binder" refers to materials that provide the electrode with cohesion of its various components and mechanical stability on the current collector, and / or that provide the electrode with a certain degree of flexibility for its implementation in the cell. Examples of binders include: polyvinylidene fluoride (PVDF) and its copolymers, polytetrafluoroethylene (PTFE) and its copolymers, polyacrylonitrile (PAN), poly(methyl)- or (butyl)methacrylate, polyvinyl chloride (PVC), poly(vinyl formaldehyde), polyester, sequenced polyetheramides, acrylic acid polymers, methacrylic acid, acrylamide, itaconic acid, sulfonic acid, elastomers, and cellulosic compounds. The elastomer(s) that can be used as a binder can be chosen from styrene-butadiene (SBR), butadiene-acrylonitrile (NBR), hydrogenated butadiene-acrylonitrile (HNBR), and a mixture of several of these.

[0025] According to the invention, the negative electrode is porous:

[0026] Porosity corresponds to the structure of the material having an organized network of channels with very small, variable pore sizes: typically, "porous" according to the invention means a pore size less than Ipm, preferably less than 300 nm. This pore size gives the electrode a particularly large active surface area per unit electrode surface area.

[0027] According to one embodiment, the porosity of the electrode is between 30 and 80%, preferably between 45 and 60%. This porosity allows, in particular, on the one hand, the lithium metal (or the Li-rich phase) to be accommodated within the porosity and, on the other hand, to maintain the mechanical strength of the electrode.

[0028] According to one embodiment, the porosity of the electrode is such that:

[0029] [Math 1] e =a* 485 x C / e

[0030] where C is the surface capacitance of first charge the positive electrode (in mAh / cm2);

[0031] e is the thickness of the negative electrode in the discharged state expressed in pm; and

[0032] e is the porosity of the negative electrode in the discharged state (porosity being defined as the ratio of the difference between the total volume of the electrode (excluding current collector) and the volume of material divided by the volume of the electrode) expressed as %

[0033] and a is a number between 0.8 and 3.

[0034] According to one embodiment, said electrode has an electronic resistance of less than 100 Ohm.cm2, typically less than 50 Ohm.cm2.

[0035] According to one embodiment, said electrode may contain, in addition to carbon particles and solid electrolyte, particles of lithiophilic element, preferably of size less than 200 nm, the quantity of which, expressed in g / cm2, is preferably equal to ak ' CpOSîtive.

[0036] with k between 0.1 x 10⁵ and 2 x 10⁵ g / mAh,

[0037] and CpOSitive represents the total capacity of the positive electrode in mAh / cm2.

[0038] According to one embodiment, said electrode is coated with a layer of lithiophilic metal.

[0039] According to an alternative embodiment, the solid electrolyte particles are coated with a layer of lithiophilic metal.

[0040] The term "lithiophile" defines a material exhibiting an affinity for lithium, (i.e.) its ability to form alloys with lithium.

[0041] According to one embodiment, the lithophile element is chosen from silver, zinc, and magnesium. Typically, the alloys formed by these elements with lithium include LixZny, LixMgy, and LixAgy type alloys, with varying x / y atomic ratios.

[0042] The lithiophilic metal layer mentioned herein coating the solid electrolyte particles or the electrode typically has a thickness that can vary from a few nanometers to less than 100nm, typically about less than 50nm, in particular less than 20 nm, in particular less than 10 nm, more preferably from 2 to 5 nm.

[0043] This layer is lithium conductive, in that it allows the transfer of lithium from the electrolyte layer to the first layer. It can also allow homogenization of the lithium deposit by allowing the formation of local cells: indeed during charging, a potential difference is created in the thickness of the electrode; this potential difference can then allow an electrochemical rebalancing over the thickness of the electrode by oxidation of lithium in the areas of the most positive potentials and a reduction of Li+ in the areas of the most negative potentials.

[0044] According to one embodiment, the coating layer consists exclusively of the lithiophilic material.

[0045] The particles or the electrode may be coated over all or part of their peripheral surface. In one embodiment, they are coated over their entire peripheral surface. The coating layer covers at least 50% of the specific surface area of ​​the electrode, preferably at least 75%, more preferably at least 90%, and even more preferably at least 95%.

[0046] Carbon particles are not limited with respect to their morphology. Examples include spherical particles, particle aggregates, and fibers or nanofibers. In particular, the particles can be chosen from carbon powder particles, such as carbon black particles (for example, type C65), carbon fibers, for example, type VGCF, or carbon nanoparticles, such as carbon nanotubes (CNTs).

[0047] Carbon particles are in particular chosen from among carbon nanoparticles.

[0048] A nanoparticle is understood to be a nano-object of which at least one of the three dimensions is on the nanometric scale, or particles whose nominal (or equivalent) diameter is less than about 100 nm (National Institute for Research and Safety (INRS), Nanomaterials, Paris, June 2008).

[0049] Typically, the carbon content (by weight) of the negative electrodes is between 2 and 30%.

[0050] According to one embodiment, the carbon particles can be in the form of carbon nanotubes (CNTs), and in particular forming porous agglomerates of CNTs (or CNT balls).

[0051] According to one embodiment, the solid electrolyte is of the sulfide type.

[0052] As a sulfide electrolyte, we can mention in particular all the compositions and materials that can be synthesized from at least one of the precursors Li2S and P2S 5 to which other precursors such as LiCl, LiBr, Li2O, SiS2, GeS2, SnS2, ZnS, Li3PO4, ....

[0053] Among these phases, we can notably mention:

[0054] - Li3PS4

[0055] - the set of phases [(Li2S)y(P2S5)iy]0 z) (LiX)z (with X a halogen element; 0 <y<l;0<z<l)

[0056] - argyrodites such as Li6PS5X, with X=C1, Br, I, or Li7P3Sn,

[0057] - LiioGeP2Si2 type thio-phosphates and their derivatives....

[0058] The sulfide electrolyte may be completely or partially crystallized, or amorphous.

[0059] Typically, the electrolyte content (by weight) of the negative electrodes is between 20 and 90%.

[0060] According to one embodiment, the diameter of the solid electrolyte particles is between 0.1 and 5 pm.

[0061] According to another object, the present invention also relates to a method for manufacturing an electrode according to the invention, said method comprising: - The mixture of carbon particles, possibly coated solid electrolyte particles, and a porophore; - The creation of porosity; - And possibly the deposition of said lithiophilic layer.

[0062] The electrode thus formed is then deposited on a current collector, so as to form the negative electrode layer. This deposition can be carried out, for example, by coating.

[0063] Polypropylene carbonate may be cited as a porosity agent. Typically, the content of the porosity agent in the mixture is between 10 and 50% by weight.

[0064] The creation of porosity can then be carried out by applying or adapting known methods, generally depending on the nature of the porosity agent used. Typically, this can be achieved by heat treatment, at a temperature generally above 150°C.

[0065] The coating of the solid electrolyte particles or the electrode by the lithiophilic metal can be carried out by any method allowing the deposition of a thin film, such as: - chemical deposition: sol-gel, spin-coating, vapor deposition, atomic layer deposition (ALD), molecular layer deposition (MLD), or controlled oxidation; and - Physical vapor deposition (PVD): vacuum evaporation, sputtering, pulsed laser deposition, electrohydrodynamic deposition.

[0066] Typically, the layer can be deposited by ALD or PVD.

[0067] ALD consists of exposing the surface of carbon particles successively to different chemical precursors in order to obtain ultra-thin layers.

[0068] The deposition can generally be carried out by ALD, PVD. Typically, the PVD treatment is carried out on a fluidized bed to allow homogeneous deposition, (i.e.) treatment of the particles in all directions.

[0069] According to another object, the present invention also relates to an all-solid electrochemical element comprising a porous negative electrode according to the invention.

[0070] The term "electrochemical element" means an elementary electrochemical cell consisting of the positive electrode / electrolyte / negative electrode assembly, which allows the electrical energy supplied by a chemical reaction to be stored and released in the form of a current.

[0071] Typically such an electrochemical element comprises a negative electrode layer, a positive electrode layer and an electrolytic separation layer, such that solid electrolyte particles are present within all three layers.

[0072] According to one embodiment, the electrochemical element comprises an intermediate layer between the negative electrode and the solid electrolyte layer used as a separator; Typically, this layer contains predominantly fine amorphous carbon powder and a lithiophilic compound forming alloys with lithium.

[0073] Within the framework of the present invention, the positive electrode of the positive electrode layer can be of any known type.

[0074] The term positive electrode refers to the electrode where electrons enter, and where discharged cations (Li+) arrive.

[0075] The positive electrode layer generally consists of a conductive support used as a current collector which is coated with the positive electrode containing the active positive electrode material, solid electrolyte particles and a carbon additive.

[0076] This carbon additive is distributed in the electrode so as to form an electronic percolating network between all the particles of active material and the current collector.

[0077] Typically the positive electrode may also include a binder, such as those previously mentioned for the negative electrode.

[0078] The active material for the positive electrode is not particularly limited. It can be chosen from the following groups or mixtures thereof:

[0079] - a compound (a) of formula LixMi_y_z_wM'yM”zM’”w02 (LM02) where M, M', M” and M”' are chosen from the group consisting of B, Mg, Al, Si, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, W and Mo on the condition that at least M or M' or M'' or M”' is chosen from among Mn, Co, Ni, or Fe; M, M', M” and M”' being different from each other; and 0.8 <x<l,4 ; 0<y<0,5 ; 0<z<0,5 ; 0<w<0,2 et x+y+z+w<2,l ;

[0080] - a compound (b) of formula LixMn2_y_zM'yM"zO4 (LMO), where M' and M" are chosen in the group consisting of B, Mg, Al, Si, Ca, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb and Mo; M' and M" being different from each other, and 1 <x<1,4 ; 0<y<0,6 ; 0<z<0,2 ;

[0081] - a compound (c) of formula LixFei yMyPO4(LFMP) where M is chosen from the group consisting of B, Mg, Al, Si, Ca, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Y, Zr, Nb and Mo; and 0.8 <x<l,2 ; 0<y<0,6 ;

[0082] - a compound (d) of formula LixMni y zM'yM”zP04 (LMP), where M' and M” are different from each other and are chosen from the group consisting of B, Mg, Al, Si, Ca, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb and Mo, with 0.8 <x<l,2 ; 0<y<0,6 ; 0<z<0,2 ;

[0083] - a compound (e) of formula xLi2MnO3; (lx)LiMO2 where M is at least one element chosen from Ni, Co and Mn and x <l.

[0084] - a compound (f) of formula Lii+XMO2 yFy of cubic structure where M represents at minus one element chosen from the group consisting of Na, K, Mg, Ca, B, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Y, Zr, Nb, Mo, Ru, Ag, Sn, Sb, Ta, W, Bi, La, Pr, Eu, Nd and Sm and where 0 < x < 0.5 and 0 < y < 1;

[0085] - Graphite

[0086] - Silicon

[0087] - a titanium niobium oxide TNO having the formula (g):

[0088] LixT ia_yMyNbb_zM ' zO((X+4a+5b) / 2)_c_dXc

[0089] where0 <x<5;0<y<l;0<z<2;l<a<5;l<b<25; 0,25 <a / b<2;0<c< 2 and 0 < d < 2; ay > 0; bz > 0;

[0090] M and M' each represent at least one element chosen from the group consisting of Li, Na, K, Mg, Ca, B, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Y, Zr, Nb, Mo, Ru, Ag, Sn, Sb, Ta, W, Bi, La, Pr, Eu, Nd and Sm;

[0091] X represents at least one element chosen from the group consisting of S, F, Cl and Br.

[0092] The index d represents an oxygen vacancy. The index d can be less than or equal to 0.5.

[0093] Said at least one titanium niobium oxide may be selected from TiNb2O7, Ti2 Nb2O9 and Ti2Nb10O29.

[0094] - a lithia-treated titanium oxide or a titanium oxide capable of being lithia-treated. LTO is chosen among the following oxides:

[0095] h) Lix_aMaTiy_bM'bO4_c_dXc in which 0 <x<3 ; l<y<2,5 ; 0<a<l ; 0<b<l ; 0<c<2 et -2,5<d<2,5 ;

[0096] M represents at least one element chosen from the group consisting of Na, K, Mg, Ca, B, Mn, Fe, Co, Cr, Ni, Al, Cu, Ag, Pr, Y and La;

[0097] M' represents at least one element chosen from the group consisting of B, Mo, Mn, Ce, Sn, Zr, Si, W, V, Ta, Sb, Nb, Ru, Ag, Fe, Co, Ni, Zn, Al, Cr, La, Pr, Bi, Sc, Eu, Sm, Gd, Ti, Ce, Y and Eu;

[0098] X represents at least one element chosen from the group consisting of S, F, Cl and Br;

[0099] The index d represents an oxygen vacancy. The index d can be less than or equal to 0.5.

[0100] i) HxTiyO4 in which 0 <x<l ; 0<y<2, et

[0101] j) a mixture of compounds h) to i).

[0102] Examples of lithia-containing titanium oxides belonging to group h) are spinel Li4Ti5O2, Li2TiO3, Li2TiO7, Li2Ti3O7, LiTi2O4, LiTi2O4, with 0 <x<2 et Li2Na2Ti60i4.

[0103] A preferred LTO compound has the formula LUaMaTisbM'bO^for example Li4Ti50i2 which can also be written Li4 / 3Ti5 / 3O4.

[0104] The positive electrode electronic conductive material is generally chosen from graphite, carbon black, acetylene black, soot, graphene, carbon nanotubes or a mixture thereof.

[0105] The current collector of the positive electrode layer is typically made of aluminum.

[0106] The electrolytic layer (or separator) contains an electrolytic composition, which may comprise one or more electrolytic constituents. Examples of solid electrolyte constituents include sulfur compounds alone or in mixtures with other constituents, such as polymers or gels. Examples include partially or completely crystalline sulfides as well as amorphous sulfides. Examples of these materials may be selected from sulfides of composition A Li2S - B P2S5 (with 0 <A<l,0<B<l et A+B = 1) et leurs dérivés (par exemple avec dopage Lil, LiBr, LiCl, ...) ; les sulfures de structure argyrodite ; ou type LGPS (Lii0GeP2Si2), et ses dérivés. Les matériaux électrolytiques pourront également comprendre des oxysulfures, des oxydes (grenat, phosphate, anti-perovskite, ...), des hydrures, des polymères, des gels ou des liquides ioniques conducteurs des ions lithium.

[0107] Examples of sulfide electrolytic compositions are described in particular in Park, KH, Bai, Q„ Kim, DH, Oh, DY, Zhu, Y., Mo, Y., & Jung, YS (2018). Design Strategies, Practical Considerations, and New Solution Processes of Sulfie Solid Electrolytes for All-Solid-State Batteries. Advanced Energy Materials, 1800035.

[0108] In all-solid type elements, electrolytic compounds may be included in the electrolytic layer, but may also be partly contained within the electrodes.

[0109] The solid electrolyte particles present in the negative electrode and / or the positive electrode and / or the separator layer may be identical or different.

[0110] Typically, the electrochemical element according to the invention is a “lithium free” type battery.

[0111] It is understood that the term "lithium free" defines the fact that the battery does not contain lithium metal when the accumulator is assembled, but that lithium is deposited in metallic form or as a lithium-rich phase and then consumed in a controlled and reversible manner in situ during battery operation. Typically, lithium is deposited within the negative electrode during charging and consumed during discharging.

[0112] According to another object, the present invention also relates to an electrochemical module comprising the stacking of at least two elements according to the invention, each element being electrically connected with one or more other element(s).

[0113] The term “module” therefore refers here to the assembly of several electrochemical elements, said assemblies being able to be in series and / or parallel.

[0114] Another object of the invention is yet another battery comprising one or more modules according to the invention.

[0115] The term “battery” or accumulator means the assembly of several modules according to the invention.

[0116] According to one embodiment, the batteries according to the invention are accumulators whose capacity is greater than 100 mAh, typically 1 to 100Ah. Figures

[0117] [Fig-1] The [Fig. 1] represents a schematic representation of the structure of a electrochemical element according to the invention. Said element comprises a negative electrode layer (1), a positive electrode layer (3), separated by an electrolytic layer (2).

[0118] The negative electrode layer (1) includes a current collector (4) on which is deposited the negative electrode material according to the invention, consisting of solid electrolyte particles (5) and carbon particles (6).

[0119] It is understood that according to embodiments not shown here, the particles (5) or the electrode made up of the particles (5) and (6) can be coated with a lithiophilic metal.

[0120] The separation layer (2) is made up of solid electrolyte particles (7).

[0121] These particles (7) may be identical to the particles (5).

[0122] The positive electrode layer (3) includes a current collector (4') on which is deposited a mixture comprising solid electrolyte particles (9), conductive carbon (8), and active material particles (10).

[0123] It is understood that layers (1) and (3) may include, in addition, binders, which are not shown in [Fig.1]. Example:

[0124] 1- Preparation of the negative electrodes:

[0125] The electrolytes used to illustrate the invention are sulfide-type compounds with the compositions Li3PS4, (Li3PS4)0.8(LiI)0.2, and Li6PS5Cl. The conductive additives were selected from carbon blacks (type C65), VGCF-type fibers, and carbon nanotubes. While carbon nanotubes are usually used dispersed in a solvent, the nanotubes used in these examples are in the form of non-deagglomerated pellets. The solid electrolyte and carbon are mixed with a binder (PTFE), a lithiophilic material such as Zn, Ag, Mg, and Si, and a porophore (polypropylene carbonate). The powders are manually mixed in a glove box using an agate mortar by pounding 500 mg of the mixture for 10 minutes.A quantity of this mixture is placed in a pelletizing mold whose matrix has an internal diameter of 1 cm; the mass of the mixture is equal to the weight of the electrode multiplied by the internal surface area of ​​the matrix. The assembly is compressed at a pressure between 1 and 5 t / cm².

[0126] The lithiophilic material can be used in several forms: either as a fine powder (particles with a size between 30 nm and 200 nm), or the material has been deposited onto the electrolyte powder or onto the carbon powder by PVD. The process used is sputtering with a rotating chamber, allowing movement of the particles and thus obtaining a more homogeneous deposit on the particle surface.

[0127] 2- Realization of the accumulator:

[0128] The positive electrode used in the examples consists of an active NMC material (composition: Li(NiO.33MNiO.33CoO.33)O2), a sulfide electrolyte of composition (Li3PS4)O.8(LiI)O.2, and PTFE. The respective proportions are 74.5%, 25%, and 0.5%. The constituents are mixed for 5 minutes in an agate mortar in a glove box.

[0129] The mass of mixture in mg for the production of the electrode is equal to the desired surface capacitance in mAh / cm2 multiplied by the surface area of ​​the electrode and divided by 150 mAh / g.

[0130] In the pelletizing mold containing the negative electrode pellet, 50 mg of electrolyte (Li3PS4)0.8(LiI)0.2 are added to create the electrolytic layer ensuring electronic isolation between the two electrodes. The assembly is then compressed to 5t / cm². The mass of positive electrode mixture is then added to the surface of the electrolyte layer, and the assembly is compressed again to 5t / cm².

[0131] The pellet thus obtained is then heat-treated at 260°C under argon for 15 min to remove the porophore.

[0132] The assembly is then placed in a sealed electrochemical cell allowing electrical connection with the positive and negative electrodes, while maintaining a mechanical pressure of approximately 50 bar. The cell is then charged at C / 20 to a voltage of 4.3V. The total capacitance of the positive electrode considered in Table 1 corresponds to the charged capacitance of the first charge divided by the surface area of ​​the electrode.

[0133] Due to a partial irreversibility of the capacitance of the positive electrode, the total capacitance cannot be measured during subsequent cycles.

[0134] One way to measure the total capacity after the first cycle is to charge the battery to its maximum nominal voltage (4.3V in our example) at a slow rate (typically C / 20), then disassemble the battery in a glove box and collect a sample of known surface area (if the electrode is double-sided, the surface area is multiplied by 2). Still in the glove box, the electrode sample is placed in a sealed cell of known volume equipped with pressure and temperature sensors and a septum. Using a syringe filled with alkaline water at pH 14, water is introduced into the cell onto the electrode (the electrode must be completely saturated). The metallic lithium in the electrode will then react with the water to form hydrogen. Once the cell pressure has stabilized, the number of moles of hydrogen formed (nH2) can be calculated from the pressure, temperature and volume of the cell.The total surface capacitance of the positive electrode in mAh / cm2 is equal to nH2*53600 / S, where S is the previously considered negative electrode surface area expressed in cm2.

[0135] The porosity of the negative electrode is estimated as follows: a negative electrode is prepared under the conditions described in paragraph 1. Then, a heat treatment is applied at 260°C for 15 minutes under argon. The porosity is then conventionally calculated from the thickness, the mass of the treated electrode, and the composition of the electrode and the density of its components.

[0136] The electronic conductivity of the electrode is checked by placing the treated negative electrode between two 1cm diameter copper discs under a pressure of 50 bar. A current of 1mA is applied and it is verified that the voltage across the copper electrodes is less than 0.13V (which corresponds to a resistance < 100 Ohm.cm2).

[0137] For measuring the swelling of the negative electrode: the electrochemical cell is disassembled and the assembly is placed in a scanning electron microscope with which it is possible to measure the thickness of the negative electrode.

[0138] Examples of the invention and the results obtained are set out in Tables 1, 2 and 3. The comparative examples in Tables 4-6 were prepared using the same procedure as that used for the examples of the invention.

[0139] [Tables 1] No. Example molar composition of the electrolyte % mass of electrolyte before heat treatment than particle diameter electrolyte ( pm ) carbon type % mass of carbon before heat treatment % (weight) binder before heat treatment (% weight) orophore before thermal treatment compound lithi ophile Exl Li3PS4 50 2 pelote CNT 10 10 29.5 Ag Ex2 (Li3PS4)0.8( Lil)o,2 50 1 C65 10 10 29.5 Ag Ex3 Li6PS5Cl 10, 10 pelote 10 95 CNT Ag Ex4 Li6PS5Cl 50 5 VGCF 10 10 29.5 Ag Ex5 Li6PS5Cl 50 5 VGCF 10 10 29.5 Ag Ex6 Li6PS5Cl 50 5 VGCF 10 10 29.5 Ag Ex7 Li6PS5Cl 50 5 14 Ag VGCF 38 38 Li6PS5Cl 50 5 VGCF 10 10 29.5 Ag Ex9 Li6PS5Cl 50 5 VGCF 10 15 24.5 Ag ExlO Li6PS5Cl 40 5 VGCF 10 20 29.5 Ag Ex5 Li6PS5Cl 50 5 VGCF 10 15 Ex 269 Li6PS5Cl 50 2 pellets CNT 2 5 42.5 Ag Ex7 Li6PS5Cl 50 1 pellet CNT 5 10 34.5 Mg Ex8 Li6PS5Cl 50 1 C65 10 10 29.5 Mg Ex9 Li6PS5Cl 40 165 Cl 2015 ZnO Li6PS5Cl 50 1 C65 10 5 34.5 Zn Exyl Li6PS5Cl 20 1 C65 5 10 64.5 Si Exl2 Li6PS5Cl 30 1 C65 10 10 49.5 Si Exl3 Li6PS5Cl 40 1 C65 10 10 39.8 Si Exl4 Li6PS5Cl 60 1 C65 10 10 19 Si Exl5 2 Li6PS5Cl 10 Exte 5 Li6PS5Cl 50 1 CNT pellet 10 5 34.7 Si Exl7 Li6PS5Cl 50 1 CNT pellet 10 5 34.5 Mg Exl8 Li6PS5Cl 50 1 CNT pellet 10 5 34.5 Mg Exl9 10 Li C6PS5 pellet 29.5 Mg

[0140] :

[0141] [Tables2] Example No. Lithiophilic compound (powder or coating on solid or carbon electrolyte) % mass of lithiophilic compound in the electrode before TT k (g / mAh) Negative electrode porosity after TT (*) Thickness (µm) Weight before TT (mg / cm²) Total capacitance of the positive electrode (mAh / cm²) Electronic resistance of the electrode (Ohm.cm²) Ex1 powder 0.5 6E-6 50 43 6 5 0.87 <100 Ex2 powder 0.5 8E-6 47 54 8 5 1.03 <100 Ex3 powder 0.5 8E-6 47 54 8 5 1.03 <100 Ex4 powder 0.5 8E-6 47 54 8 5 1.03 <100 Ex5 powder 0.5 8E-6 47 54 8 5 1.03 <100 Ex6 powder 0.5 8E-6 47 54 8 5 1.03 <100 Ex7 powder 0.5 8E-6 51 55 8 5 1.18 <100 Ex8 powder 0.5 8E-6 47 54 8 5 1.03 <100 Ex9 powder 0.5 8E-6 41 52 8 5 0.89 <100 ExlO powder 0.5 7.5E -6 44 47 7.5 5 0.86 <100 Ex5 coating on ES powder 0.5 8E-6 47 54 8 5 1.03 <100 Ex6 coating on carbon powder 0.5 7.5E -6 59 22 3 2 1.32 <100 Ex7 powder 0.5 6.67E -6 51 28 4 3 0.98 <100 Ex8 powder 0.5 7.5E -6 46 40 6 4 0.97 <100 Ex9 powder 0.5 7.5E -6 47 50 7.5 5 0.97 <100 ExlO powder 0.5 6E-6 51 83 12 10 0.88 <100 Exil powder 0.5 5E-6 78 159 20 20 1.27 <100 Exl2 powder 0.5 6.67E -6 66 50 6.67 5 1.34 <100 Exl3 powder 0.2 3.33E -6 57 35 5 3 1.38 <100 Exl4 powder 1 1.33E -5 42 48 6.67 5 0.83 <100 Exl5 powder 3 3E-6 59 36 5 5 0.87 <100 Exl6 powder 0.3 4.8E -6 49 53 8 5 1.06 <100 Exl7 powder 0.5 8E-6 51 56 8 5 1.18 <100 Exl8 powder 0.5 6E-6 57 47 6 5 1.10 <100 Exl9 powder 0.5 6E-6 58 52 6 5 1.25 <100

[0142] Results:

[0143] [Tables3] No. Exe thickness swelling C*485 / e mAh total / mple min of L of the electro cm3 (expri i outside of negative me by this d eur of the p (%) 'electrode n (Negative porosity (pm) in the charged state) Exl 3.05 7 57 1093 Ex2 0.00 0 45 930 Ex3 0.00 0 45 930 Ex4 0.00 0 45 930 Ex5 0.00 0 45 930 Ex6 0.00 0 45 930 Ex7 0.00 0 44 902 Ex8 0.00 0 45 930 Ex9 2.66 5 47 913 ExlO 3.41 7 51 988 Ex5 0.00 0 45 930 Ex6 0.00 0 45 922 Ex7 0.25 1 52 1072 Ex8 0.57 1 48 974 Ex9 0.75 1 48 981 ExlO 5.59 7 58 1126 Exile 0.00 0 61 1257 Exl2 0.00 0 49 1010 Exl3 0.00 0 41 846 Exl4 4.07 9 51 962 Exl5 3.10 9 67 1278 Exl6 0.00 0 46,948 Exl7 0.00 0 44,898 Exl8 0.00 0 52 1065 Exl9 0.00 0 47,961

[0144] Table 3 shows that for the examples of the invention, electrode swelling is low, or even zero (<10%), and the volumetric capacitance of the negative electrode is greater than 800 mAh / cm³. These characteristics are favorable for obtaining The battery has a high volumetric capacity and a long lifespan. Furthermore, the mechanical strength of the electrodes is suitable for the application.

[0145] Comparative examples:

[0146] [Tables4] No. Example molar composition of the electrolyte % mass electrolyte before TT joint diameter electrolyte (pm) carbon type % mass of carbon before TT % (weight) binder before tTT % (weight) of porophore before thermal treatment olyte 0 2 C65 84.5 5 0 Ag Comp E x2 Li3PS4 60 2 C65 10 10 19.5 Mg Comp E x3 Li6PS5Cl 40 2 C65 10 10 39.5 Ag Comp E x4 Li3PS4 40 2 0 10 Si 49.5

[0147] [Tables5] Example No. Lithiophilic compound (powder or coating on ES or carbon) % mass of lithiophilic compound in the electrode before TT k(g / m Ah) negative electrode porosity after TT (*) thickness (pm) weight before TT (mg / cm²) total capacitance of the positive electrode (mAh / cm²) electronic resistance of the electrode (Ohm.cm²) Comp E x1 powder 10 1.00E -04 11 26 5 5 0.1 1 <50 Comp E x2 powder 0.5 5.00E -06 35 32 5 5 0.4 7 <100 Comp E x3 powder 0.5 7.50E -06 86 159 7.5 5 5.6 1 <100 Comp E x4 powder 0.5 7.50E -06 73 72 7.5 5 2.1 6 >1000

[0148] [Tableauxô] Example No. Minimum thickness of Li outside the electrode (pm) Swelling of the negative electrode (%) C*485 / e Total mAh / cm3 (expressed per cc of negative electrode in the charged state) Comp E x1 21.44 84 95 1065 Comp E x2 12.89 40 76 1116 Comp E x3 0.00 0 15 315 Comp E x4 0.00 34 34 698

[0149] For the comparative examples, the electrode made of carbon alone (comparative example 1) exhibits a very high swelling (95%). The same is true for comparative example No. 2, for which the parameter a is 0.46 (swelling of 76%).

[0150] When the porosity and the number a are too high (comparative example No. 3: porosity = 86% and a = 5.6), the swelling is very low or even zero but the volumetric capacity is low (315mAh / cm3).

[0151] In the case of comparative example 4, the negative electrode does not contain carbon, which results in very poor conductivity on the one hand and strong swelling on the other hand due to poor intercalation of lithium in the porosity.

Claims

Claims

1. Porous negative electrode characterized in that said electrode comprises: - solid electrolyte particles and - carbon particles, such that its porosity e verifies: e = a*Cpositive*485 / e where e is the porosity of the negative electrode in the discharged state (the porosity being defined as the ratio of the difference between the total volume of the electrode (excluding the current collector) and the volume of material divided by the volume of the electrode) expressed in %, CpOsitiVe represents the first charge capacity of the positive electrode in mAh / cm2, e represents the thickness in microns (pm) of said negative electrode in the discharged state and a is a number between 0.8 and 3.

2. Electrode according to the preceding claim 1, such that it contains, in addition to the carbon particles and solid electrolyte, particles of lithiophilic element.

3. An electrode according to any preceding claim, such that said electrode is covered with a layer of lithiophilic metal.

4. Electrode according to claim 1 or 2 such that the solid electrolyte particles are coated with a layer of lithiophilic metal.

5. Electrode according to claim 2, 3 or 4 such that said lithiophilic metal is chosen from silver, zinc and magnesium.

6. Electrode according to any one of the preceding claims, such that the electrode has a porosity of between 30 and 80%, preferably between 45 and 60%.

7. Electrode according to any one of the preceding claims, such that the electrode has a pore size less than Ipm, preferably less than 300 nm.

8. Electrode according to any one of the preceding claims, such that the carbon consists, at least in part, of porous agglomerates of CNT (or CNT balls).

9. Electrode according to any one of the preceding claims such that the solid electrolyte is of the sulfide type.

10. An electrode according to any preceding claim, such that it is a Li-free electrode.

11. A negative electrode layer comprising an electrode according to any preceding claim and a current collector.

12. A method of manufacturing an electrode according to any one of claims 1 to 10, such that it comprises: - Mixing the carbon particles, the optionally coated solid electrolyte particles and a porophoric agent, - Heat treatment of the mixture obtained; - And optionally depositing said lithiophilic layer.

13. An all-solid electrochemical element comprising a porous negative electrode according to any one of claims 1 to 10.

14. An all-solid electrochemical element according to claim 13 further comprising an intermediate layer between the negative electrode layer and the solid electrolyte layer, said intermediate layer comprising predominantly fine amorphous carbon powder and a lithiophilic compound.

15. Electrochemical module comprising the stack of at least two elements according to claim 13, each element being electrically connected with one or more other element(s).

16. A battery comprising one or more modules according to claim 15.

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