Method of manufacturing an electrode, electrode and energy storage device

Abstract

A semi-dry method of manufacturing an electrode (E) is disclosed comprising: a) providing a conductive metal substrate, preferably a copper or aluminium laminate; b) providing an electrode formulation (EF) in the form of a cohesive solid material, 5 the electrode formulation (EF) comprising: F1) at least the following functional ingredients: an electrode active material for anode or cathode, a binder and a plasticizer, and F2) a solvent in an amount equal to or lower than 25% by weight based on the total weight of the functional ingredients; 0 c) coating at least a first face of the conductive metal substrate with the electrode formulation (EF); and d) compressing the coated conductive metal substrate. An electrode formulation (EF), a method of manufacturing the electrode formulation (EF) in the form of a self-supporting film, an electrode composition 5 and an energy storage device comprising the electrode composition are also disclosed.

Description

[0001] Method of manufacturing an electrode, electrode and energy storage device

[0002] DESCRIPTION

[0003] Field of the invention

[0004] The present invention generally relates to the field of electrical energy storage in rechargeable secondary batteries, in particular of the Li-ion type. More specifically, the invention relates to method of manufacturing an electrode for energy storage devices by a technique which minimizes the use of solvents.

[0005] The invention also relates to an electrode formulation in the form of a cohesive solid material, to a method of manufacturing an electrode formulation in the form of a self-supporting film, to an electrode composition and to an energy storage device in particular a Li-ion secondary battery, comprising at least one such electrode composition.

[0006] Background

[0007] Energy storage devices, such as Li-ion batteries, comprise at least one negative electrode or anode coupled to a first metal current collector, i.e. a copper current collector, a positive electrode or cathode coupled to a second current collector, i.e. an aluminum current collector, a separator and an electrolyte. In Li-ion batteries, the electrolyte consists of a lithium salt, generally lithium hexafluorophosphate, mixed with a solvent that is a mixture of organic carbonates, which are selected to optimize ion transportation and dissociation.

[0008] During operation, electrical contact is made to the electrodes, allowing electrons to flow through the device to provide electrical power, and lithium ions to move through the electrolyte from one electrode to the other.

[0009] Rechargeable, or secondary, batteries are more advantageous than primary batteries (which are not rechargeable) because the associated chemical reactions taking place at the positive and negative electrodes of the battery are reversible. The electrodes of the secondary battery can be regenerated multiple times by application of an electrical charge.

[0010] The electrodes generally comprise at least one current collector on which is deposited, in the form of a thin layer, an electrode formulation comprising an electrode active material, i.e. a material which exhibits electrochemical activity for example toward lithium, a binder, and optionally one or more electronically conductive additives such as carbon black.

[0011] The main purpose of using a binder is to form stable networks of the solid components of the electrodes, that is to say, the active materials and the conductive agents (cohesion). In addition, the binder must ensure close contact between the composite electrode and the current collector (adhesion).

[0012] On the other hand, the main purpose of using electronically conductive additives is that of enhancing the electrical conductivity of the electrode.

[0013] In the Applicant's experience, the positive and negative electrodes can be manufactured by so-called “wet” or “dry” production techniques.

[0014] In the first case, a dispersion (slurry) comprising an electrode formulation, at least one solvent and at least one binder is formed and applied to at least one surface of a current-collecting metal foil to form a layer which is dried to remove the solvent and then calendered to uniform thickness.

[0015] In the context of this wet production technology, however, the application of the active material as a dispersion on the metal current collector foil can cause certain drawbacks resulting from the drying process during which the solvent of the dispersion is evaporated.

[0016] Indeed, the removal of the solvent is a relatively slow and energy-intensive operation, which leads to increased production time and costs.

[0017] Moreover, in some cases, the solvent can be toxic, so evaporating large quantities thereof may trigger undesirable environmental problems.

[0018] In terms of the end product, the removal of the solvent in a wet process during the drying process often leads to migration of the binder to the surface of the electrode. Though minimal migration can be acceptable in some cases, it is problematic in others. For high electrode thickness the migration is exacerbated, leading to delamination of the coated layer from the current collector, thus poor electrode performance.

[0019] On the other hand, “dry” production techniques that have been proposed generally include high shear mixing involving a fibrillizable binder, use of sacrificial binders to be removed upon processing of the electrode, dry powder spraying, electrostatic spray deposition, cold plasma deposition, sputtering deposition, powder printing. In some, a fibrillization promoter is incorporated into the binder and the resulting formulation undergoes high shear mixing to fibrillate the binder, thereby generating a web-like structure that can better hold the materials together and support the active material.

[0020] While “dry” manufacturing processes may eliminate some of the challenges posed by the addition and / or removal of solvents (often harmful), problems remain.

[0021] For example, current “dry” fabrication techniques utilize not only the active electrode material but many other ingredients such as fibrillization promoters, conductive additives and binders. Since many of these components are not involved in the electrochemical reactions that generate electrical energy, they can negatively affect certain performance characteristics (e.g., capacity and energy density) of the battery, as they effectively lower the amount of active material that can be contained in a given volume.

[0022] A need exists, therefore, for compositions and processes that address at least some of the problems associated with existing approaches.

[0023] Related art

[0024] CN116315140A discloses an interface-free laminated semi-solid battery and a preparation method thereof. According to this method, before the electrolyte is injected, the binder materials with the same melting temperature are used on the cathode electrode, the anode electrode and a diaphragm, so that the materials can be subjected to hot pressing at the same melting temperature, and the structures are fused together to form a flat laminated board and form an interface- free battery. Although the battery components are fully fused, the method allows plasticizers to be added to the mixed material of each battery component, thereby injecting electrolyte within the structure. After the plasticizer is extracted, a gap is formed in the position where the plasticizer is located, and the remaining gap can be filled with the electrolyte in the method, so that an interface-free semi-solid battery is formed. of the invention

[0025] In a first aspect, the present invention relates to a method of manufacturing an electrode aiming at minimizing the use of solvent to reduce both costs and energy consumption. Within the framework of the present document, such a method of manufacturing will also be referred to as a “semi-dry” method of manufacturing.

[0026] More specifically, according to this first aspect the present invention relates to a method of manufacturing an electrode comprising: a) providing a conductive metal substrate; b) providing an electrode formulation in the form of a cohesive solid material, the electrode formulation comprising:

[0027] F1 ) at least the following functional ingredients:

[0028] - an electrode active material for anode or cathode,

[0029] - a binder,

[0030] - a plasticizer,

[0031] - optionally, a conductive additive,

[0032] - optionally, a processability adjuvant; and

[0033] F2) a solvent in an amount equal to or lower than 25% by weight based on the total weight of said functional ingredients; c) coating the conductive metal substrate with the electrode formulation; and d) compressing the coated conductive metal substrate.

[0034] In a second aspect, the present invention relates to an electrode formulation in the form of a cohesive solid material, the electrode formulation comprising:

[0035] F1 ) at least the following functional ingredients:

[0036] - an electrode active material for anode or cathode,

[0037] - a binder,

[0038] - a plasticizer,

[0039] - optionally, a conductive additive,

[0040] - optionally, a processability adjuvant; and F2) a solvent in an amount equal to or lower than 25% by weight based on the total weight of said functional ingredients.

[0041] In a third aspect, the present invention relates to a method of manufacturing an electrode formulation as disclosed herein in the form of a self-supporting film, the method comprising: a) providing an electrode formulation in the form of a cohesive solid material as disclosed herein; b) feeding the electrode formulation in the form of a cohesive solid material to a first shaping device, preferably a calendering device, to obtain a self-supporting film of the electrode formulation.

[0042] In a fourth aspect, the present invention relates to an electrode composition in the form of a cohesive solid material comprising the following functional ingredients:

[0043] - an electrode active material for anode or cathode,

[0044] - a water-soluble binder or a non water-soluble binder,

[0045] - a plasticizer,

[0046] - optionally, a conductive additive, and

[0047] - optionally, a processability adjuvant.

[0048] In a fifth aspect, the present invention relates to an energy storage device comprising the electrode composition as disclosed herein.

[0049] The applicant has found that the “semi-dry” method disclosed herein allows to minimize the use of solvents thereby reducing both costs and energy consumption, yet achieving an electrode formulation showing remarkable flexibility, exhibiting no signs of cracking or wrinkling when subjected to bending or folding.

[0050] In particular and as will be illustrated in better detail hereinbelow, the use of the plasticizers disclosed herein, in particular of glycerol, allows to eliminate the need for either chemical or thermal binder activation. This not only streamlines the manufacturing method but also results in a reduction in both time and energy consumption for the production of electrodes, particularly for Li-ion batteries. The Applicant observed that the plasticizer, in particular glycerol, used in the electrode formulation effectively bonds all electrode materials together and to the current collector providing an electrode formulation having the required mechanical and electrical characteristics.

[0051] Further, the Applicant observed that the plasticizer, in particular glycerol, used in the electrode formulation remains within the electrode materials forming an integral component thereof and achieving the advantageous technical effect of providing flexibility to the electrode formulation.

[0052] Finally, the Applicant observed that the binder and plasticizer, in particular sodium carboxy-methylcellulose (Na-CMC) and glycerol, used in the electrode formulation even though are not involved in the electrochemical reactions that generate electrical energy do not negatively affect the performance characteristics (e.g., capacity and energy density) of the battery.

[0053] Detailed description of preferred embodiments of the invention

[0054] In the context of this description and subsequent claims, the clause “cohesive solid material” is used to indicate a composite solid material provided with suitable cohesion characteristics among its components, in this case the electrode active material, the conductive additive (if present), the binder and the plasticizer.

[0055] Within the framework of this definition, a “cohesive solid material” may be a solid smooth continuous mass or a mass formed by granules sticked together in a cohesive manner.

[0056] In the context of this description and subsequent claims, the clause “functional ingredients” is used to indicate the ingredients of the electrode formulation disclosed herein except any solvent(s) used in the manufacturing methods.

[0057] Within the framework of this definition, a “functional ingredient” may thus be any ingredient used to manufacture an electrode and which remains within the final electrode composition, such as an electrode active material for anode or cathode, a binder, a plasticizer, a conductive additive, a processability adjuvant and a filler.

[0058] In the context of this description and subsequent claims, the clause “electrode formulation” is used to indicate an intermediate product in the manufacture of the electrode, that is, a semi-finished product obtained before carrying out the drying operations required to reduce the solvent content down to those negligible values as are required to subsequently manufacture an energy storage device, such as a secondary battery.

[0059] In the context of this description and subsequent claims, the clause “electrode composition” is used to indicate a cohesive solid material comprising the functional ingredients as defined herein, that is, a solid product obtained after carrying out the drying operations and, as such, including those negligible amounts of the solvent as are required to subsequently manufacture an energy storage device, such as a secondary battery.

[0060] In the context of this description and subsequent claims, the term “processability adjuvant” is used to indicate an additive which helps the processability of the active material, in particular of the cathode active material, in a semi-dry process. The term is general for including any agent which creates connections among dry components. The processability adjuvant also acts as a lubricant or compressibility modifier of the dry mixtures obtained in the manufacturing methods as disclosed herein.

[0061] In the context of this description and subsequent claims, the term “calendering device” is used to indicate a shaping device including at least two counter-rotating rolls configured to compact the material fed to the device and reduce the thickness of said material to a desired value.

[0062] In the context of this description and subsequent claims, all the numerical entities indicating quantities, parameters, percentages, and so on are to be considered preceded in every circumstance by the term “about” unless indicated otherwise. Furthermore, all ranges of numerical entities are to be understood as including extremes, unless otherwise indicated, and include all possible combinations of maximum and minimum numerical values and all possible intermediate ranges, in addition to those specifically indicated below.

[0063] The present invention may include, in one or more of its aspects, one or more of the preferred features outlined below, which can be combined with one another as preferred according to the application requirements.

[0064] In preferred embodiments, providing the electrode formulation in the form of a cohesive solid material comprises:

[0065] - mixing the binder and the plasticizer, to form a gel-like material; - mixing the electrode active material and said gel-like material to obtain a pastelike mixture;

[0066] - adding the solvent to the paste-like mixture while stirring to obtain the electrode formulation.

[0067] In preferred embodiments, providing the electrode formulation in the form of a cohesive solid material comprises:

[0068] - mixing the binder and the plasticizer, to form a gel-like material;

[0069] - separately mixing the electrode active material and the conductive additive obtain a dry mixture;

[0070] - mixing the dry mixture and said gel-like material to obtain a paste-like mixture;

[0071] - adding the solvent to the paste-like mixture while stirring to obtain the electrode formulation.

[0072] In preferred embodiments, the electrode active material is an electrode active material for a cathode.

[0073] Preferably, separately mixing the electrode active material and the conductive additive to obtain a dry mixture comprises mixing the cathode active material, the conductive additive and processability adjuvant.

[0074] In preferred embodiments, providing the electrode formulation in the form of a cohesive solid material comprises:

[0075] - mixing the binder, the electrode active material and optionally the conductive additive to obtain a first dry mixture;

[0076] - mixing the plasticizer and the first dry mixture to obtain a paste-like mixture;

[0077] - adding the solvent to the paste-like mixture while stirring to obtain the electrode formulation.

[0078] In preferred embodiments, mixing the plasticizer and the first dry mixture to obtain a paste-like mixture and adding the solvent to the paste-like mixture while stirring to obtain the electrode formulation are carried out in a mixing extruder.

[0079] In these embodiments, the electrode formulation thereby obtained is in sheet form which advantageously facilitates the preparation of an electrode formulation in the form of a self-supporting film which will in turn facilitate the manufacture of an electrode as will be explained in better detail hereinafter.

[0080] In preferred embodiments, providing the electrode formulation in the form of a cohesive solid material comprises:

[0081] - mixing the binder, the electrode active material and optionally the conductive additive to obtain a dry mixture;

[0082] - mixing the plasticizer and at least a first portion of the solvent to obtain a plasticizer solution;

[0083] - mixing the dry mixture and the plasticizer solution to obtain the electrode formulation.

[0084] In this preferred embodiment, the method preferably further comprises adding at least a second portion of the solvent while mixing the first paste-like mixture and the plasticizer solution.

[0085] In preferred embodiments, mixing the dry mixture and the plasticizer solution to obtain the electrode formulation is carried out in a mixing extruder.

[0086] In these embodiments as well, the electrode formulation thereby obtained is in sheet form which advantageously facilitates the preparation of an electrode formulation in the form of a self-supporting film as illustrated above.

[0087] In preferred embodiments, the method of the invention may further comprise drying the electrode formulation in sheet form to suitably reduce the amount of solvent in the electrode formulation.

[0088] In this way, the dried electrode formulation thereby obtained advantageously possesses mechanical properties which allow an easier preparation of an electrode formulation in the form of a self-supporting film which will in turn facilitate the manufacture of an electrode as will be explained in better detail hereinafter.

[0089] Preferably, the electrode formulation in sheet form has a thickness equal to or higher than 200 micron and equal to or lower than 400 micron.

[0090] Preferably, the electrode formulation obtained by means of the manufacturing method disclosed herein comprises:

[0091] F1 ) at least the following functional ingredients:

[0092] 45-98% by weight of electrode active material,

[0093] 1 -50% by weight of binder,

[0094] 1 -40% by weight plasticizer,

[0095] 0-20% by weight of conductive additive,

[0096] - optionally, 1 -40% of processability adjuvant based on the total weight of the functional ingredients F1 ); and

[0097] F2) a solvent in an amount equal to or greater than 5% by weight and equal to or lower than 25% by weight based on the total weight of the functional ingredients F1 ).

[0098] Preferably, the electrode composition according to the invention has the following composition in % by weight based on the total weight of the functional ingredients:

[0099] 45-98% of electrode active material,

[0100] 1 -50% of binder,

[0101] 1 -40% of plasticizer,

[0102] 0-20% of conductive additive, and optionally, 1 -40% of processability adjuvant.

[0103] Preferably, the electrode active material for anode is anyone of graphite, soft carbons, hard carbons, N-doped carbons, silicon, silicon oxide, lithium titanate Li4TisOi2 (LTO), titanium dioxide, TiO2, or mixtures thereof if compatible.

[0104] Preferably, the electrode active material for cathode is anyone of lithium cobalt oxide, UCOO2 (LCO), lithium Manganese Dioxide, LiMnO2, lithium nickel manganese cobalt oxides, LiNixMnyCoi-x-y02 (NMC), lithium iron phosphate, LiFePCh (LFP), lithium nickel cobalt aluminium oxide, LiNiCoAI02 (NCA), or mixtures thereof if compatible.

[0105] Preferably, the electrode formulation or the electrode composition disclosed herein comprises an amount of electrode active material equal to or greater than 45% by weight, more preferably equal to or greater than 50% by weight, even more preferably equal to or greater than 55% by weight, even more preferably equal to or greater than 60% by weight, even more preferably equal to or greater than 65% by weight, even more preferably equal to or greater than 70% by weight, even more preferably equal to or greater than 75% by weight, even more preferably equal to or greater than 80% by weight, based on the total weight of the functional ingredients.

[0106] Preferably, the electrode formulation or the electrode composition disclosed herein comprises an amount of electrode active material equal to or lower than 98% by weight, more preferably equal to or lower than 95% by weight, even more preferably equal to or lower than 90% by weight, even more preferably equal to or lower than 85% by weight, based on the total weight of the functional ingredients.

[0107] Preferably, the conductive additive is any one of carbon black (CB), conductive graphite (CG), single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), graphene, vapor-grown carbon fibers, or mixtures thereof if compatible.

[0108] Preferably, the electrode formulation or the electrode composition disclosed herein comprises an amount of conductive additive equal to or greater than 1 % by weight, more preferably equal to or greater than 2% by weight, even more preferably equal to or greater than 3% by weight, even more preferably equal to or greater than 4% by weight, even more preferably equal to or greater than 5% by weight, even more preferably equal to or greater than 10% by weight, based on the total weight of the functional ingredients.

[0109] Preferably, the electrode formulation or the electrode composition disclosed herein comprises an amount of conductive additive equal to or lower than 20% by weight, more preferably equal to or lower than 15% by weight, even more preferably equal to or lower than 10% by weight, even more preferably equal to or lower than 5% by weight, based on the total weight of the functional ingredients.

[0110] Preferably, the binder is a water-soluble binder, such as anyone of sodium carboxymethyl cellulose (Na-CMC), polyvinyl Alcohol (PVA), polyethylene Oxide (PEO), polyvinyl Pyrrolidone (PVP), polyacrylic Acid (PAA), sodium alginate, styrene-butadiene Rubber (SBR), or mixtures thereof if compatible.

[0111] In preferred embodiments, the binder is a carboxymethyl cellulose, preferably, sodium carboxymethyl cellulose (Na-CMC).

[0112] Within the framework of the present invention, water-soluble binders achieve the advantage of being non-toxic thereby strongly reducing and substantially eliminating the concerns related to environmental issues of the manufacturing method mentioned above.

[0113] In alternative embodiments, the binder may be a non water-soluble binder, such as polyvinylidene fluoride (PVDF).

[0114] Preferably, the electrode formulation or the electrode composition disclosed herein comprises an amount of binder equal to or greater than 1% by weight, more preferably equal to or greater than 2% by weight, even more preferably equal to or greater than 3% by weight, even more preferably equal to or greater than 4% by weight, even more preferably equal to or greater than 5% by weight, even more preferably equal to or greater than 10% by weight, based on the total weight of the functional ingredients.

[0115] Preferably, the electrode formulation or the electrode composition disclosed herein comprises an amount of binder equal to or lower than 50% by weight, more preferably equal to or lower than 45% by weight, even more preferably equal to or lower than 40% by weight, even more preferably equal to or lower than 35% by weight, even more preferably equal to or lower than 30% by weight, even more preferably equal to or lower than 25% by weight, even more preferably equal to or lower than 20% by weight, even more preferably equal to or lower than 15% by weight, even more preferably equal to or lower than 10% by weight, based on the total weight of the functional ingredients.

[0116] Preferably, the plasticizer is a plasticizer compatible with a water-soluble binder and is any one of glycerol, sorbitol, triacetin, propylene glycol, polyethylene glycol (PEG), diethylene glycol (DEG), triethyl Citrate (TEC), or mixtures thereof if compatible.

[0117] Advantageously, this kind of plasticizers achieves the advantage of being nontoxic thereby strongly reducing and substantially eliminating the concerns related to environmental issues of the manufacturing method mentioned above. In particularly preferred embodiments, the plasticizer is glycerol.

[0118] Within the framework of the present invention and as mentioned above, the Applicant found that glycerol is particularly effective in eliminating the need for either chemical or thermal binder activation. This not only streamlines the manufacturing method but also results in a reduction in both time and energy consumption for the production of electrodes, particularly for Li-ion batteries.

[0119] The Applicant also experimentally observed, as will be better illustrated below, that glycerol effectively bonds all electrode materials together and to the current collector providing an electrode formulation having the required mechanical and electrical characteristics.

[0120] Further, the Applicant observed that glycerol remains within the electrode materials forming an integral component thereof and achieving the advantageous technical effect of providing flexibility to the electrode formulation without requiring solvent removal from the formulation.

[0121] This feature turns out to be particularly beneficial in the manufacture of the electrode formulation, and more particularly, when the electrode is in the form of a self-supporting film.

[0122] Finally, the Applicant also experimentally observed, as will be better illustrated below, that sodium carboxy-methyl-cellulose (Na-CMC) and glycerol, although being components of the electrode formulation which are not involved in the electrochemical reactions that generate electrical energy, do not negatively affect in a substantial way the electrical performance characteristics of the electrode formulation, such as capacity and energy density of a battery including the same.

[0123] In alternative embodiments, the plasticizer is a plasticizer compatible with a non water-soluble binder and is anyone of dibutyl phthalate (DBP), naphthenic oils, triethyl citrate (TEC), diisononyl phthalate (DINP), epoxidized soybean oil (ESO), or mixtures thereof if compatible.

[0124] Preferably, the electrode formulation or the electrode composition disclosed herein comprises an amount of plasticizer equal to or greater than 1 % by weight, more preferably equal to or greater than 5% by weight, even more preferably equal to or greater than 10% by weight, even more preferably equal to or greater than 15% by weight, even more preferably equal to or greater than 20% by weight, even more preferably equal to or greater than 25% by weight, based on the total weight of the functional ingredients.

[0125] Preferably, the electrode formulation or the electrode composition disclosed herein comprises an amount of plasticizer equal to or lower than 40% by weight, even more preferably equal to or lower than 35% by weight, even more preferably equal to or lower than 30% by weight, even more preferably equal to or lower than 25% by weight, even more preferably equal to or lower than 20% by weight, even more preferably equal to or lower than 15% by weight, even more preferably equal to or lower than 10% by weight, based on the total weight of the functional ingredients.

[0126] Preferably, the solvent is anyone of water, dimethylformamide (DMF), N,N- Dimethylacetamide (DMAc), dimethyl Sulfoxide (DMSO), N-Methyl-2-pyrrolidone (NMP), cyrene™, toluene, xylene, or mixtures thereof if compatible.

[0127] In particularly preferred embodiments, the solvent is water.

[0128] Advantageously, water as a solvent achieves the advantage of being non-toxic thereby strongly reducing and substantially eliminating the concerns related to environmental issues of the manufacturing method as a whole.

[0129] Preferably, the electrode formulation disclosed herein comprises an amount of solvent equal to or greater than 5% by weight, more preferably equal to or greater than 10% by weight, even more preferably equal to or greater than 15% by weight, even more preferably equal to or greater than 20% by weight, based on the total weight of the functional ingredients.

[0130] Preferably, the electrode formulation disclosed herein comprises an amount of solvent equal to or lower than 25% by weight, more preferably equal to or lower than 20% by weight, even more preferably equal to or lower than 15% by weight, even more preferably equal to or lower than 10% by weight, based on the total weight of the functional ingredients.

[0131] In particularly preferred embodiments, a plasticizer: binder mass ratio is included in the range of from 3:10 to 10:10.

[0132] Preferably, the processability adjuvant is anyone of graphite, 2D transition metal carbides and nitrides (MXenes), graphene, carbon nanotubes, activated carbons, carbon black, molybdenum Disulfide (M0S2), or mixtures thereof if compatible.

[0133] In particularly preferred embodiments, the processability adjuvant is used when manufacturing electrode formulations for a cathode.

[0134] Preferably, the electrode formulation or composition disclosed herein comprises an amount of processability adjuvant equal to or greater than 1 % by weight, more preferably equal to or greater than 5% by weight, even more preferably equal to or greater than 10% by weight, even more preferably equal to or greater than 15% by weight, even more preferably equal to or greater than 20% by weight, even more preferably equal to or greater than 25% by weight, based on the total weight of the functional ingredients.

[0135] Preferably, the electrode formulation or composition disclosed herein comprises an amount of processability adjuvant equal to or lower than 40% by weight, even more preferably equal to or lower than 35% by weight, even more preferably equal to or lower than 30% by weight, even more preferably equal to or lower than 25% by weight, even more preferably equal to or lower than 20% by weight, even more preferably equal to or lower than 15% by weight, even more preferably equal to or lower than 10% by weight, based on the total weight of the functional ingredients.

[0136] Preferably, the conductive metal substrate of the electrode disclosed herein is a copper or aluminium laminate.

[0137] Preferably, coating the conductive metal substrate with the electrode formulation comprises applying a predetermined amount of the electrode formulation on the conductive metal substrate.

[0138] In certain embodiments, coating the conductive metal substrate with the electrode formulation comprises coating both the opposite faces of the metal substrate.

[0139] In such a case, once a first face of the metal substrate has been coated with the electrode formulation, the manufacturing method disclosed herein comprises: e) rotating upside down the coated and compressed conductive metal substrate; f) coating a second opposite face of the rotated conductive metal substrate with the electrode formulation as disclosed herein; and g) compressing the conductive metal substrate coated on both faces thereof.

[0140] In certain embodiments of the method of manufacturing an electrode according to the invention the electrode formulation is in the form of a self-supporting film.

[0141] Preferably, the electrode formulation in the form of a self-supporting film has a thickness equal to or higher than 50 micron, more preferably equal to or higher than 100 micron and equal to or lower than 300 micron, more preferably equal to or lower than 200 micron.

[0142] In preferred embodiments, such an electrode formulation in the form of a self- supporting film may be manufactured by a method comprising c) feeding the electrode formulation in the form of a cohesive solid material, wherein all the ingredients are already mixed together, to a second shaping device, preferably an extruder device, to obtain an electrode formulation in sheet form.

[0143] In these preferred embodiments, the method of manufacturing an electrode or an electrode formulation in the form of a self-supporting film further comprises d) drying the electrode formulation in sheet form thus obtained to reduce the amount of solvent therein down to a suitable value as described hereinafter.

[0144] Preferably, c) feeding the cohesive solid material and d) drying the electrode formulation in sheet form are carried out before b) feeding the electrode formulation in the form of a cohesive solid material to the first shaping device.

[0145] Preferably, any of the above described electrode formulations in sheet form obtained from the mixing extruder may be dried by any suitable equipment known in the art that can heat and / or dry the electrode formulation. Some non-limiting examples of equipment that can be used to dry the electrode formulation include a batch drying oven, a conveyor drying oven, and an infrared and laser drying oven. Some non-limiting examples of the conveyor drying oven include a conveyor hot air-drying oven, a conveyor resistance drying oven, a conveyor inductive drying oven, and a conveyor microwave drying oven.

[0146] Preferably, the electrode formulation is dried at a temperature equal to or greater than 45°C and equal to or lower than 65°C. Suitable drying temperatures may be envisaged by a person skilled in the art.

[0147] Preferably, the electrode formulation in sheet form comprises before drying an amount of solvent equal to or lower than 20% by weight and equal to or higher than 12% by weight based on the total weight of the electrode formulation.

[0148] Preferably, the electrode formulation in sheet form comprises after drying an amount of solvent equal to or lower than 12% by weight and equal to or higher than 5% by weight based on the total weight of the electrode formulation.

[0149] In preferred embodiments and as illustrated above, the self-supporting film may be obtained by feeding the electrode formulation in a form of a sheet material obtained by means of the aforementioned in mixing extruder, preferably dried to reduce the amount of solvent in the electrode formulation to the values indicated above, to a shaping device, preferably a calendering device, to obtain a self- supporting film of the electrode formulation.

[0150] In these preferred embodiments, the electrode formulation in the form of a self- supporting film may be wound on a reel and stored for a subsequent use or may be directly fed to a suitable equipment to carry out c) coating at least a first face of the conductive metal substrate with the electrode formulation.

[0151] In preferred embodiments, c) coating at least a first face of the conductive metal substrate with the electrode formulation comprises applying, preferably simultaneously, the electrode formulation in the form of a self-supporting film, either coming from a reel or from the above shaping device, on opposite faces of the conductive metal substrate.

[0152] In this way, it is advantageously possible to enhance the efficiency and reliability of the coating operations of the conductive metal substrate.

[0153] In certain embodiments, the method of manufacturing an electrode according to the invention may further comprise h) applying a layer of an adhesion enhancer on one or both the opposite faces of the conductive metal substrate before applying thereon the electrode formulation in the form of a self-supporting film.

[0154] For the purposes of the present invention, the adhesion enhancer may be any substance which promotes the stickiness of the self-supporting film to the conductive metal substrate and which at the same time does not alter the electrochemical characteristics of the electrode formulation.

[0155] In preferred embodiments, the adhesion enhancer may be an environmentally friendly substance, such as water or any one of the above-described water- soluble binders or any aqueous solution thereof.

[0156] In other preferred embodiments, the adhesion enhancer may be any one of the above-described non water-soluble binder binders or any solution thereof. In preferred embodiments, the method of manufacturing an electrode according to the invention may further comprise i) treating the adhesion enhancer interposed between said opposite faces of the conductive metal substrate and the electrode formulation in the form of a self-supporting film to enhance adhesion of the self-supporting film to the conductive metal substrate.

[0157] In this way, it is advantageously possible to further enhance the reliability of the coating operations of the conductive metal substrate.

[0158] Examples of suitable treatments of the adhesion enhancer are drying the electrode formulation to reduce the amount of water or the solvent of the non water-soluble binder.

[0159] In certain preferred embodiments, the method of manufacturing the electrode formulation in the form of a self-supporting film may comprise detaching, for example by means of a doctor blade, the self-supporting film of the electrode formulation from the rolls of the calendering device.

[0160] In this way, an electrode formulation in the form of self-supporting film may advantageously be obtained.

[0161] In certain preferred embodiments, coating the conductive metal substrate with the electrode formulation may further comprise removing the electrode formulation in excess.

[0162] Preferably, removing the electrode formulation in excess comprises trimming the electrode formulation at opposite sides with respect to a transport direction of the electrode formulation.

[0163] In certain preferred embodiments, trimming the electrode formulation is carried out by trimming a self-supporting film of the electrode formulation at opposite sides thereof with respect to a transport direction of the electrode formulation toward a calendering device before compressing the coated conductive metal substrate.

[0164] Preferably, compressing the coated conductive metal substrate comprises at least one calendering step of the coated conductive metal substrate by using calendering rolls.

[0165] In certain preferred embodiments, the calendering step of the coated conductive metal substrate is carried out by using calendering rolls at room temperature. In other preferred embodiments, the calendering rolls may be heated to a specified temperature which depends on the makeup of the material to be calendered.

[0166] For the purposes of the present invention, the calender rolls are preferably heated to a temperature equal to or lower than 200°C.

[0167] Preferably, removing the electrode formulation in excess is carried out before carrying out said at least one calendering step.

[0168] Preferably, the method may further comprise sieving the electrode formulation before coating the conductive metal substrate.

[0169] In certain preferred embodiments, sieving is carried out so as to feed to the coating step of the conductive metal substrate an electrode formulation having a particle size equal to or lower than 3 mm and equal to or greater than 0.3 mm.

[0170] The Applicant observed that in this way, optimal mechanical and electrical performance characteristics of the electrode formulation may be achieved.

[0171] Preferably, the method may further comprise an additional step of grinding an oversieve obtained from sieving the electrode formulation and sieving again the grinded oversieve.

[0172] In this way, the method may be optimized not to lose any amount of components used to manufacture the electrode formulation.

[0173] Preferably, the method further comprises one or more drying steps of the coated conductive metal substrate to at least partially or totally remove the solvent from the electrode formulation.

[0174] In preferred embodiments, a drying step is provided which removes the solvent down to a residual amount as disclosed herein to obtain the electrode composition disclosed herein.

[0175] In preferred embodiments, the coated conductive metal substrate may be dried by any suitable equipment known in the art that can heat and / or dry the coated conductive metal substrate. Some non-limiting examples of equipment that can be used to dry the coated conductive metal substrate include a batch drying oven, a conveyor drying oven, and an infrared and laser drying oven. Some non-limiting examples of the conveyor drying oven include a conveyor hot air-drying oven, a conveyor resistance drying oven, a conveyor inductive drying oven, and a conveyor microwave drying oven.

[0176] In preferred embodiments, the coated conductive metal substrate is dried at a temperature equal to or greater than 45°C and equal to or lower than 160°C. Suitable drying temperatures may be envisaged by a person skilled in the art.

[0177] Preferably, the electrode composition comprises a residual amount of solvent equal to or lower than 1%, more preferably equal to or lower than 0.9% by weight, even more preferably equal to or lower than 0.8% by weight, even more preferably equal to or lower than 0.7% by weight, even more preferably equal to or lower than 0.6% by weight, even more preferably equal to or lower than 0.5% by weight, even more preferably equal to or lower than 0.4% by weight, even more preferably equal to or lower than 0.3% by weight, even more preferably equal to or lower than 0.2% by weight, even more preferably equal to or lower than 0.1 % by weight, based on the total weight of the functional ingredients.

[0178] In this way, the method may be optimized so as to achieve adequate flexibility characteristics of the electrode composition to the benefit of any subsequent winding operations of the electrode on a reel, operations which are almost invariably required during the manufacture of energy storage devices, such as secondary batteries.

[0179] At the same time, the energy requirements of the method may be advantageously kept as low as possible.

[0180] In a preferred embodiment and as mentioned above, the electrode formulation disclosed herein is in the form of a self-supporting film, a configuration which advantageously simplifies the manufacturing method of the electrode and, more particularly, the handling operations of the electrode formulation before coating the conductive metal substrate.

[0181] Preferably and as mentioned above, the energy storage device disclosed herein is secondary battery, more preferably a Li-ion secondary battery, comprising an anode, a cathode and a separator.

[0182] Preferably, the at least one of the anode or cathode comprises the electrode composition disclosed herein.

[0183] The invention will now be described in further detail, and by way of example only, with reference to the accompanying drawings and pictures as well as by various examples of the manufacturing method and of the electrode formulations of the invention. In the drawings:

[0184] Brief description of the figures

[0185] Fig. 1 shows an exemplary schematic illustration of a first preferred embodiment of a method for manufacturing an electrode according to the invention wherein a conductive metal substrate is coated on a first face thereof;

[0186] Fig. 2A shows an exemplary schematic illustration of a second preferred embodiment of a method for manufacturing an electrode according to the invention which makes use of an electrode formulation in the form of a self- supporting film;

[0187] Fig. 2B shows an exemplary schematic illustration of a third preferred embodiment of a method for manufacturing an electrode according to the invention which makes use of an electrode formulation in the form of a self- supporting film;

[0188] Figs. 3A, 3B and 3C show exemplary schematic illustrations of three preferred embodiments of a step of providing an electrode formulation in the form of a cohesive solid material according to the invention;

[0189] Fig. 4A shows an exemplary schematic illustration of a fourth preferred embodiment of a method for manufacturing an electrode according to the invention wherein the conductive metal substrate is coated on both faces thereof;

[0190] Fig. 4B shows an exemplary schematic illustration of a fifth preferred embodiment of a method for manufacturing an electrode according to the invention which makes use of an electrode formulation in the form of a self-supporting film and wherein the conductive metal substrate is coated on both faces thereof;

[0191] Figs 5a and 5b show SEM images of an anode electrode prepared according to Example 4 and, respectively, of a conventional anode electrode prepared according to comparative Example 2;

[0192] Figs 6a, 6b and 6c show, respectively, SEM images of an anode electrode prepared according to Example 4 at different magnifications;

[0193] Figs 7a, 7b and 7c show, respectively, C-rate capability, Potential vs Specific capacity and Potential vs Time of an anode electrode prepared according to Example 4;

[0194] Figs 8a, 8b and 8c show, respectively, C-rate capability, Potential vs Specific capacity and Potential vs Time of an anode electrode prepared according to Example 3;

[0195] Figs 9a and 9b and, respectively, 9c, show Potential vs Specific capacity, and, respectively, C-rate capability, of two cathode electrodes prepared according to Example 1 .

[0196] Fig. 1 shows schematically, in the form of a simplified flow sheet, the manufacture of an electrode according to a first preferred embodiment of the semi-dry manufacturing method of the present invention wherein a conductive metal substrate is coated on one face thereof.

[0197] More specifically, in this preferred embodiment a conductive metal substrate, such as a copper or aluminium laminate, and an electrode formulation EF in the form of a cohesive solid material are provided.

[0198] As is customary in the art, the copper or aluminium laminate are unwound by means of conventional equipment from a collecting reel.

[0199] As illustrated above, the electrode formulation EF may be obtained in different manners as will be detailed hereinbelow by making reference to Figs. 3A, 3B and 3C.

[0200] In a first preferred embodiment shown in Fig. 3A, the electrode formulation EF is obtained by mixing the binder and the plasticizer, to form a gel-like material, by separately mixing the electrode active material and the conductive additive to obtain a dry mixture and then by mixing / kneading the dry mixture and the gel-like material to obtain a paste-like mixture.

[0201] Preferably, the above dry mixing and mixing / kneading steps may be carried out by any suitable equipment known in the art, such as by means of a rotor mixer having a shaft provided with paddles rotating within an outer, for example, cylindrical, casing.

[0202] During the mixing / kneading step, a proper amount of solvent is added to the paste-like mixture while stirring to obtain an electrode formulation EF. Suitable exemplary processing parameters of this preferred embodiment to prepare the electrode formulation EF are illustrated in Table 1 below.

[0203] In the following Tables, the various materials are indicated as:

[0204] DP: Dry powder AM: active material

[0205] B: binder (dry powder)

[0206] CA: conductive additive

[0207] PA: processability adjuvant

[0208] PL: plasticizer S: solvent

[0209] PLW: plasticizer solution

[0210] BS: binder dissolved in PL, herein also named as “gel”.

[0211] Table 1

[0212] (***) gel preparation was carried out by: • Manual stirring at room temperature.

[0213] • Manual stirring at 60°C.

[0214] • Dispersion by bath ultrasonic sonication for 1 h.

[0215] The viscosity of the gel composed by binder and plasticizer in this exemplary embodiment lies in the range of 1.2 - 7«104mPa s at a shear rate of 100 s-1at 25°C, with plasticizer: binder mass ratio included in the range 3:10 and 10:10.

[0216] Measurement conditions: Anton Paar MCR 102 rheometer with a plate-plate geometry (plate diameter 25 mm), applying a shear rate ranging from 0.1 to 1000 s-1at 25°C.

[0217] In a second preferred embodiment shown in Fig. 3B, the electrode formulation EF is obtained by mixing the binder, the electrode active material and the conductive additive to obtain a first dry mixture, then by mixing the plasticizer and the first dry mixture to obtain a paste-like mixture and finally by adding a proper amount of solvent to the paste-like mixture while stirring to obtain the electrode formulation.

[0218] Suitable exemplary processing parameters of this preferred embodiment to prepare the electrode formulation EF are illustrated in Table 2 below.

[0219] Table 2

[0220] The viscosity of the plasticizer in this exemplary embodiment lies in the range of 10 — 1 • 104mPa s, preferably in the range of 20 - 1 .2- 103mPa s, in a temperature range of 20°C - 45°C, and at a speed of 30 rpm.

[0221] Measurement conditions: Brookfield AMETEK DV2T viscometer with a concentric cylinders’ geometry. LV-1 spindle was used in the viscosity range 20-100 mPa s and RV-1 spindle in the viscosity range 100 - 1 -104mPa s.

[0222] In a third preferred embodiment shown in Fig. 3C, the electrode formulation EF is obtained by mixing the binder, the electrode active material and the conductive additive to obtain a dry mixture, by separately mixing the plasticizer and at least a first portion of the solvent to obtain a plasticizer solution and then by mixing the dry mixture and the plasticizer solution to obtain the electrode formulation. ln this embodiment, a proper amount of solvent is added to the plasticizer to form a diluted plasticizer solution.

[0223] Suitable exemplary processing parameters of this preferred embodiment to prepare the electrode formulation EF are illustrated in Table 3 below.

[0224] Table 3

[0225] The viscosity of the solution composed by plasticizer and solvent in this exemplary embodiment lies in the range of 5 - 300 mPa s, preferably in the range of 5 - 200 mPa s, as measured at a temperature of 25°C, and at a speed of 30 rpm, with plasticizer to solvent mass ratio included in the range 0.05 - 8.

[0226] Measurement conditions: Brookfield AMETEK DV2T viscometer with a concentric cylinders’ geometry. LV-1 spindle was used in the viscosity range 15-300 mPa s. The LV-series was equipped with an UL Adapter for the measurements of viscosity in the 1 -10 mPa s range.

[0227] In all the aforementioned embodiments, the amount of solvent is suitably determined so as to obtain an electrode formulation EF having mechanical characteristics, in particular flexibility characteristics, suitable for carrying out the subsequent coating and calendering steps, yet achieving at the same time an electrode formulation EF including the smallest amount of solvent as possible.

[0228] Turning back to Fig. 1 , this first preferred embodiment of the manufacturing method may include a sieving step of the electrode formulation before coating the conductive metal substrate and a grinding step of the oversieve obtained.

[0229] In this way, the particle size of the oversieve may be reduced to the desired value and the oversieve may be recycled to the sieving step not to lose any amount of components used to manufacture the electrode formulation EF.

[0230] Once an electrode formulation EF having a proper particle size is obtained, the first preferred embodiment of the semi-dry manufacturing method of the present invention illustrated in Fig. 1 comprises coating at least a first face of the conductive metal substrate with the electrode formulation EF. This corresponds to step c) of the present invention.

[0231] Preferably, the coating step is carried out by applying onto the conductive metal substrate the electrode formulation EF by means of any suitable equipment, such as a vibratory feeder, while the conductive metal substrate is transported along a transport direction by suitable transporting equipment, such as a conveyor belt or the like.

[0232] Subsequently, the coated conductive metal substrate is subjected to compressing, e.g. by means of calendering as illustrated above, to provide the manufactured electrode. This corresponds to step d) of the present invention.

[0233] In the preferred embodiment illustrated, the coated conductive metal substrate is subjected to drying so as to reduce the amount of solvent in the electrode formulation and obtain an electrode E and electrode composition EC as disclosed herein.

[0234] As illustrated above, drying the coated conductive metal substrate may be carried out by any suitable equipment known in the art and preferably reduces the amount of solvent in the electrode composition EC of the electrode E down to a residual amount of solvent equal to or lower than 1 %, for example of 0.06% based on the total weight of the functional ingredients.

[0235] According to the invention and in contrast to the conventional “wet” methods of the prior art, the energy requirements for carrying out this optional drying step are sharply reduced entailing an advantageous reduction of both costs and manufacturing time.

[0236] The dried electrode E obtained from the drying step may then be directly fed to other processing operations to manufacture an energy storage device or may be wound, as schematically shown in Fig. 1 , on a reel to be easily transported before processing.

[0237] Fig. 2A schematically shows, in the form of a simplified flow sheet, the manufacture of an electrode E according to a second preferred embodiment of the semi-dry manufacturing method of the present invention wherein a conductive metal substrate is coated on one first face thereof. More specifically, in this preferred embodiment an electrode formulation EF in the form of a self-supporting film is also obtained as disclosed in the present document.

[0238] Similarly to the embodiment of Fig. 1 , a conductive metal substrate, such as a copper or aluminium laminate and an electrode formulation EF in the form of a cohesive solid material are provided as disclosed above.

[0239] In the embodiment shown in Fig. 2A, the sieved electrode formulation is fed in dosed amounts to a shaping device, such as a calender device provided with at least two counter-rotating calender rolls, to shape the electrode formulation in the form of a thin self-supporting film which is removed from the calender rolls for example by a doctor blade.

[0240] In this embodiment, any electrode formulation EF in excess may be removed, for example by trimming, and the removed excess material may then be advantageously recycled to the grinding step to suitably obtain an electrode material having a suitable particle diameter.

[0241] In this embodiment, the method comprises coating the conductive metal substrate unwound from a collecting reel with the self-supporting film and compressing the coated conductive metal substrate by calendering the latter as illustrated above.

[0242] Also in this case, drying and winding of the manufactured electrode E may be envisaged after calendering as disclosed above with reference to Fig. 1 .

[0243] Fig. 2B schematically shows, in the form of a simplified flow sheet, the manufacture of an electrode E according to a third preferred embodiment of the semi-dry manufacturing method of the present invention wherein a conductive metal substrate is coated on one first face thereof.

[0244] In Fig. 2B, optional or alternative steps of the method are indicated in the flow sheet by dotted lines.

[0245] In the embodiment shown in Fig. 2B, the already mixed and sieved electrode formulation EF is fed to shaping device, preferably an extruder device, which further mixes the ingredients of the electrode formulation and produces an electrode formulation EF in a sheet form.

[0246] Preferably, the extruded electrode formulation EF in sheet form has a thickness of about 350 micron.

[0247] The electrode formulation EF in sheet form is then dried in a suitable equipment, such as an air dryer, to reduce the amount of solvent down to a value of about 8 % by weight based on the total weight of the formulation.

[0248] The dried electrode formulation EF in sheet form is then fed to a shaping device, such as a calender device provided with at least two counter-rotating calender rolls, to further reduce the thickness of the electrode formulation EF and obtain a thin self-supporting film which is removed from the calender rolls for example by a doctor blade.

[0249] Preferably, the extruded electrode formulation EF in the form of a self-supporting film has a thickness of about 150 micron.

[0250] Also in this embodiment, any electrode formulation EF in excess may be removed, for example by trimming, and the removed excess material may then be advantageously recycled to a suitable treatment to recover the ingredients of the formulation.

[0251] In this preferred embodiment, the electrode formulation EF in the form of a self- supporting film may be directly fed to a coating step of at least a first face of the conductive metal substrate, as previously illustrated with reference to Fig. 2A, or may be wound on a reel and stored for a subsequent use as shown in dotted lines in Fig. 2B.

[0252] Also in this case, drying and winding of the manufactured electrode E may be envisaged after calendering as disclosed above with reference to Figs. 1 and 2A.

[0253] Fig. 4A schematically shows, in the form of a simplified flow sheet, the manufacture of an electrode E according to a fourth preferred embodiment of the semi-dry manufacturing method of the present invention wherein a conductive metal substrate is coated on opposite faces thereof.

[0254] In this embodiment, a coated conductive metal substrate may be obtained in the same manner as the embodiment of Fig. 1 (optionally including also the sieving and grinding steps, if required) which coated conductive metal substrate is then subjected to compressing, i.e. by calendering, and, optionally, by drying to suitably reduce the solvent content.

[0255] In this case, the manufacturing method comprises rotating upside down the compressed conductive metal substrate coated on a first face thereof and then coating a second opposite face of the rotated conductive metal substrate with the electrode formulation in the same manner as disclosed above with reference to the embodiment of Fig. 1 .

[0256] The conductive metal substrate coated on both faces is then subjected to compressing, i.e. by calendering, and to drying to suitably reduce the solvent content in the electrode composition EC down to the values disclosed herein.

[0257] As illustrated above, a final winding step of the electrode E may then be provided for storing the electrode before carrying out additional operations, for example of manufacturing an energy storage device.

[0258] Fig. 4B schematically shows, in the form of a simplified flow sheet, the manufacture of an electrode E according to a fifth preferred embodiment of the semi-dry manufacturing method of the present invention wherein a conductive metal substrate is coated on opposite faces thereof.

[0259] In this embodiment, electrode formulations EF in the form of a self-supporting film, for example obtained as disclosed in Fig. 2B, are fed to a coating step of the opposite faces of the conductive metal substrate.

[0260] In this embodiment, the conductive metal substrate may be preliminarly coated with a layer of an adhesion enhancer on both the opposite faces thereof before applying thereon the electrode formulations in the form of a self-supporting film.

[0261] In the preferred embodiment illustrated in Fig. 4B, the adhesion enhancer is an environmentally friendly substance, such as water or an aqueous solution of any one of the above-described water-soluble binders.

[0262] Preferably, the adhesion enhancer is applied on the faces of the conductive metal substrate by spraying or by roll coating using techniques known in the art.

[0263] In the preferred embodiment illustrated in Fig. 4B, a conductive metal substrate coated on both the opposite faces thereof by respective electrode formulations EF in the form of a self-supporting film may be obtained by any suitable technique, for example by calendering using two counter-rotating rollers configured to apply a suitable pressure, for example of about 50 kg per each mm of the conductive metal substrate width.

[0264] In the preferred embodiment illustrated in Fig. 4B, the adhesion enhancer interposed between the opposite faces of the conductive metal substrate and the electrode formulation EF in the form of a self-supporting film is heat treated to evaporate part of the solvent (e.g. water) in the adhesion enhancer to enhance adhesion of the self-supporting film to the conductive metal substrate.

[0265] Preferably, such a heat treatment is carried out at a temperature of about 45- 80°C in a suitable equipment, such as an air drier.

[0266] The partially dried coated conductive metal substrate is then subjected to compressing, i.e. by calendering, and to drying to suitably reduce the solvent content in the electrode composition EC down to the values disclosed herein.

[0267] As illustrated above, a final winding step of the electrode E may then be provided for storing the electrode before carrying out additional operations, for example of manufacturing an energy storage device.

[0268] Additional features of the invention will now be illustrated in the following examples.

[0269] EXAMPLE 1 - INVENTION

[0270] Production of an electrode by means of the semi-dry manufacturing method of the invention

[0271] Using laboratory-scale equipment electrode formulations in the form of a cohesive solid material and electrodes for anode and cathode were prepared as follows.

[0272] Cathode

[0273] The used materials were processed according to the preferred embodiment of the semi-dry method of the invention illustrated above with reference to Fig. 1 while the preparation of the electrode formulation was according to the procedures of the embodiment shown in Fig. 3A.

[0274] 1.165 grams of LiFePC (active material, AM purchased from Aleees) and 0.146 grams of C45 (conductive additive, CA purchased from IMERYS) were introduced into a mixer and blended for 30 minutes.

[0275] Simultaneously, 0.4 grams of Sodium Carboxymethyl cellulose (Na-CMC purchased from Sigma Aldrich) were dispersed in 1 grams of Glycerol (purchased from Sigma Aldrich) using a bath sonicator for 1 hours, resulting in the formation of a gel BS.

[0276] Following this step, 0.259 grams of the gel BS were incorporated into the solid mixture and mixed for an additional 30 minutes. A cohesive solid material in the form of a paste was obtained comprising AM, CA and BS, with a mass ratio of 74.2: 9.3: 16.5, respectively.

[0277] Subsequently, the paste was placed in a hand mortar and mixed for 5 minutes. To achieve the desired consistency of a soft paste, 100 pL of de-ionized water (18.2 MQ cm), corresponding to about 6.4% by weight based on the total weight of the functional ingredients, was gradually introduced into the paste during the mortar mixing process.

[0278] Summarizing, the components used were as reported in the following Table 4.

[0279] Table 4

[0280] Active material: LiFePC Plasticizer: glycerol

[0281] Binder: Sodium Carboxymethyl cellulose (Na-CMC)

[0282] Conductive additive: C45

[0283] Solvent: deionized water At the end of the procedure, electrodes for cathode were obtained comprising an electrode formulation in the form of a cohesive solid material coated on a conductive aluminium laminate having a thickness of about 15 micron.

[0284] The final calendering step was adjusted to obtain a thickness in the range of 50- 100 micron of the electrode formulation.

[0285] Anode

[0286] The identical procedure was carried out for the anode electrode, incorporating Graphite (SFG44 purchased from LONZAG) as the active material.

[0287] At the end of the procedure, electrodes for anode were obtained comprising an electrode formulation in the form of a cohesive solid material coated on a conductive copper laminate having a thickness of about 16 micron.

[0288] The final calendering step was adjusted to obtain a thickness in the range of 50- 100 micron of the electrode formulation.

[0289] EXAMPLE 2 - COMPARATIVE

[0290] Production of an electrode by means of a wet manufacturing method according to the prior art

[0291] To produce wet-coated comparative electrodes for anode, a slurry comprising graphite (SFG44), PVDF, and C65 in N-Methyl-2-Pyrrolidone (NMP) was prepared.

[0292] Initially, 4 mL of NMP was utilized to dissolve PVDF over a 1 -hour period. The resulting PVDF solution was then combined with graphite and mixed for 30 minutes.

[0293] Subsequently, the conductive additive (C65) was introduced into the slurry followed by another 30-minute mixing session.

[0294] Adjustment of the solvent volume was performed to achieve the appropriate viscosity for the coating process.

[0295] A doctor blade method was employed to coat the current collector (Cu foil). After allowing the electrode to dry overnight, coin-shaped electrodes with a diameter of 9 mm were fabricated. To ensure a smooth surface and enhance the adhesion of electrode materials to the current collector, a 2-ton hydraulic press was applied. EXAMPLE 3 - INVENTION

[0296] Production of an electrode by means of the semi-dry manufacturing method of the invention

[0297] Using an industrial-scale equipment, electrode formulations in the form of a cohesive solid material and electrodes for anode and cathode were prepared as follows.

[0298] Cathode

[0299] The components used were as reported in the following Table 5.

[0300] Table 5 Active material: LiFePC

[0301] Plasticizer: glycerol

[0302] Binder: Sodium Carboxymethyl cellulose (Na-CMC)

[0303] Conductive additive: C45

[0304] Processability adjuvant: graphite Solvent: deionized water

[0305] Anode

[0306] The components used were as reported in the following Table 6.

[0307] Table 6

[0308] Active material: Graphite

[0309] Plasticizer: glycerol

[0310] Binder: Sodium Carboxymethyl cellulose (Na-CMC)

[0311] Conductive additive: C45

[0312] Solvent: deionized water

[0313] The above materials, for both cathode and anode were processed according to the preferred embodiment of the semi-dry method of the invention illustrated above with reference to Fig. 1 , while the preparation of the electrode formulation was according to the procedures of the embodiment shown in Fig. 3A.

[0314] At the end of the procedure, electrodes for cathode and anode were obtained comprising an electrode formulation in the form of a cohesive solid material coated on a conductive metal laminate of aluminium in the case of the cathode and copper in the case of the anode.

[0315] The final calendering step was adjusted to obtain a thickness of 100 - 250 micron for the electrode formulation for cathode and 50 - 150 micron for the electrode formulation for anode.

[0316] Also in this case, the conductive aluminium laminate had a thickness of about 15 micron, while the conductive copper laminate had a thickness of about 10 micron.

[0317] EXAMPLE 4 - INVENTION

[0318] Production of an electrode by means of the semi-dry manufacturing method of the invention Using an industrial-scale equipment, electrode formulations in the form of a cohesive solid material and electrodes for anode and cathode were prepared as follows.

[0319] Cathode The components used were as reported in the following Table 7.

[0320] Table 7

[0321] Active material: LiFePC

[0322] Plasticizer: glycerol

[0323] Binder: Sodium Carboxymethyl cellulose (Na-CMC) Conductive additive: C45

[0324] Processability adjuvant: graphite

[0325] Solvent: deionized water

[0326] Anode

[0327] The components used were as reported in the following Table 8. Table 8

[0328] Active material: Graphite

[0329] Plasticizer: glycerol

[0330] Binder: Sodium Carboxymethyl cellulose (Na-CMC)

[0331] Conductive additive: C45

[0332] Solvent: deionized water

[0333] The above materials, both cathode and anode were processed according to the preferred embodiment of the semi-dry method of the invention illustrated above with reference to Fig. 2A, obtaining an electrode formulation EF in the form of a self-supporting film, while the preparation of the electrode formulation EF per se was according to the procedures of the embodiment shown in Fig. 3A.

[0334] At the end of the procedure, electrodes for cathode and anode coated on one face thereof (single-layer) were obtained comprising an electrode formulation in the form of a cohesive solid material coated on a conductive copper laminate.

[0335] The intermediate calendering step was adjusted to obtain a thickness of about 50-300 micron for the electrode formulation in the form of a self-supporting film.

[0336] The final calendering step was adjusted to obtain a thickness of 40 - 100 micron for the electrode formulation

[0337] Also in this case, the conductive copper laminate had a thickness of about 16 micron.

[0338] EXAMPLE 5

[0339] Morphological characterization of the electrode formulations according to

[0340] Example 4 and Comparative Example 2 SEM analysis was carried out to show the surface morphology of anode electrodes prepared according to Example 4 and comparative Example 2.

[0341] Fig. 5a shows a SEM image of a graphite anode electrode prepared according to Example 4 using a semi-dry manufacturing method, while Fig. 5b shows a SEM image of a graphite anode electrode prepared according to comparative Example 2 using a “wet” manufacturing method according to the prior art.

[0342] Fig. 6a, 6b and 6c show SEM images of the graphite anode electrode prepared according to Example 4 at different magnifications.

[0343] As may be seen from the above figures, the interweaving and high density of the electrode surface manufactured using the semi-dry method of the invention are clearly observable, and its smoothness and flatness are higher than those of the conventional electrode.

[0344] As illustrated in Figure 5b and Figs. 6a-6c, the graphite flakes are encircled by aggregated white particles (indicated by dashed circles), which are likely binder and conductive additive materials dispersed throughout the sample.

[0345] A dedicated insight of the connection of these aggregated particles to the graphite flakes is depicted in Fig. 6b. Generally speaking, the SEM images of the anode electrode produced by the semi-dry coating method according to the invention demonstrate a more homogeneous distribution of electrode elements, precisely of binder and conductive additive around the active material flakes, compared to an electrode prepared by a conventional slurry-based “wet” process.

[0346] EXAMPLE 6

[0347] Electrochemical characterization of the electrode formulations according to Example 4 and Example 3

[0348] A three-electrode cell configuration was set up to test the two representative electrodes for anode obtained in accordance with Example 3 (feed of calendering as a paste with binder and plasticizer pre-mixed and added to the dry-powder formulation as a gel) and in accordance with Example 4 (feed of calendering as a pre-laminated self-supporting electrode formulation EF with binder and plasticizer pre-mixed and added to the dry-powder formulation as a gel).

[0349] The two representative electrodes were tested as the working electrode in a halfcell setup with a disk of Li foil as the counter and reference electrode, and a glass fiber separator soaked with 1 M lithium hexafluorophosphate (LiPFe) solution in a 1 :1 (v / v) mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) as the electrolytic solution.

[0350] Figs. 7a-7c illustrate the galvanostatic cycling with potential limitation (GCPL) plots across a voltage range of 0.05-1.5 V vs Li / Li+ of an anode electrode prepared according to Example 4.

[0351] More specifically, Fig. 7a shows C-rate capability, Fig. 7b Potential vs Specific capacity and Fig. 7c Potential vs Time.

[0352] Similarly, the results for an anode electrode manufactured according to Example 3 can be observed in Figs. 8a-8c which show the same parameters indicated above.

[0353] As may be gathered from Figs. 7a-7c and 8a-8c, the results obtained from GCPL analysis on both the electrodes prepared according to Examples 4 and 3 show the successful achievement of a negative electrode applied in Li-ion secondary battery produced according to the present invention.

[0354] Specific capacity values obtained at low C-rates (C / 20 and C / 10) approach the theoretical specific capacity of graphite, which is 372 mAh g1.

[0355] Without wishing to be bound by any theory, the Applicant believes that specific discharge capacity values higher than the theoretical capacity of graphite are presumably due to irreversible processes occurring during the solid electrolyte interphase (SEI) formation occurring during the initial cycling stages.

[0356] On the other hand, the coulombic efficiency approaches to 100%, reflecting a good level of reversibility between charge and discharge processes.

[0357] EXAMPLE 7

[0358] Electrochemical characterization of the electrode formulations for cathode according to Example 1

[0359] A three-electrode cell configuration was set up to test the representative electrode for cathode obtained in accordance with Example 1 using the semi-dry method illustrated above with reference to Fig. 1 and a preparation of the electrode formulation according to the procedures of the embodiment shown in Fig. 3A (feed of calendering as a paste with binder and plasticizer pre-mixed and added to the dry-powder formulation as a gel).

[0360] The representative electrode was tested as the working electrode in a half-cell setup with a disk of Li foil as the counter and reference electrode, and a glass fiber separator soaked with 1 M lithium hexafluorophosphate (LiPFe) solution in a 1 :1 (v / v) mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) as the electrolytic solution.

[0361] Figs. 9a-9c depict the electrochemical performances assessed across a voltage range of 2.5-4 V vs Li / Li+ (1 C Theoretical = 170 mA g-1) for two of the mentioned LFP electrodes, named as S-LFP-A and S.LFP-B, respectively. The specific discharge capacity of S-LFP-A and S-LFP electrodes in the low C- rate regime roughly approximate the theoretical capacity of LFP (i.e., 170 mAh g-1), even though S-LFP-A showed overall lower specific capacity values.

[0362] However, the cathode electrodes in accordance with Example 1 showed satisfying C-rate capability, withstanding C-rate values up to 1 C, then recovering the previous specific capacity when C-rate is reduced back to 0.2C.

[0363] This shows an advantageous resilience of the cathode electrode obtained according to the according to the present invention.

Claims

1. CLAIMS1 . A method of manufacturing an electrode (E) comprising: a) providing a conductive metal substrate, preferably a copper or aluminium laminate; b) providing an electrode formulation (EF) in the form of a cohesive solid material, the electrode formulation (EF) comprising:F1 ) at least the following functional ingredients:- an electrode active material for anode or cathode,- a binder,- a plasticizer,- optionally, a conductive additive,- optionally, a processability adjuvant; andF2) a solvent in an amount equal to or lower than 25% by weight based on the total weight of said functional ingredients; c) coating at least a first face of the conductive metal substrate with the electrode formulation (EF); and d) compressing the coated conductive metal substrate.

2. Method according to claim 1 , wherein providing the electrode formulation (EF) in the form of a cohesive solid material comprises:- mixing the binder and the plasticizer, to form a gel-like material;- mixing the electrode active material and said gel-like material to obtain a pastelike mixture;- adding the solvent to the paste-like mixture while stirring to obtain the electrode formulation.

3. Method according to claim 1 , wherein providing the electrode formulation (EF) in the form of a cohesive solid material comprises:- mixing the binder and the plasticizer, to form a gel-like material;- separately mixing the electrode active material and the conductive additive to obtain a dry mixture;- mixing the dry mixture and said gel-like material to obtain a paste-like mixture;- adding the solvent to the paste-like mixture while stirring to obtain the electrode formulation; wherein the electrode active material is preferably an electrode active material for a cathode; and wherein separately mixing the electrode active material and the conductive additive to obtain a dry mixture preferably comprises mixing the cathode active material, the conductive additive and processability adjuvant.

4. Method according to claim 1 , wherein providing the electrode formulation (EF) in the form of a cohesive solid material comprises:- mixing the binder, the electrode active material and optionally the conductive additive to obtain a first dry mixture;- mixing the plasticizer and the first dry mixture to obtain a paste-like mixture;- adding the solvent to the paste-like mixture while stirring to obtain the electrode formulation.

5. Method according to claim 1 , wherein providing the electrode formulation (EF) in the form of a cohesive solid material comprises:- mixing the binder, the electrode active material and optionally the conductive additive to obtain a dry mixture;- mixing the plasticizer and at least a first portion of the solvent to obtain a plasticizer solution;- mixing the dry mixture and the plasticizer solution to obtain the electrode formulation.

6. Method according to claim 4, wherein mixing the plasticizer and the first dry mixture to obtain a paste-like mixture and adding the solvent to the paste-likemixture while stirring to obtain the electrode formulation (EF) are carried out in a mixing extruder and wherein the electrode formulation (EF) thereby obtained is in a sheet form.

7. Method according to claim 5, wherein mixing the dry mixture and the plasticizer solution to obtain the electrode formulation (EF) is carried out in a mixing extruder and wherein the electrode formulation (EF) thereby obtained is in a sheet form.

8. Method according to anyone of claims 6 or 7, further comprising drying the electrode formulation (EF) in sheet form to reduce the amount of solvent in the electrode formulation (EF) to a value equal to or lower than 12% by weight and equal to or higher than 5% by weight based on the total weight of the electrode formulation (EF).

9. Method according to anyone of the preceding claims, wherein coating the conductive metal substrate with the electrode formulation (EF) comprises applying a predetermined amount of the electrode formulation (EF) on the conductive metal substrate and optionally removing the electrode formulation in excess.

10. Method according to claim 9, wherein removing the electrode formulation (EF) in excess comprises trimming the electrode formulation at opposite sides with respect to a transport direction of the electrode formulation (EF).11 . Method according to anyone of the preceding claims, wherein compressing the coated conductive metal substrate comprises at least one calendering step of the coated conductive metal substrate by using optionally heated calendering rolls, wherein removing the electrode formulation (EF) in excess is preferably carried out before carrying out said at least one calendering step.

12. Method according to anyone of the preceding claims, further comprising:- sieving the electrode formulation (EF) before coating the conductive metal substrate and, optionally,- grinding an oversieve obtained from sieving the electrode formulation (EF) and sieving again the grinded oversieve.

13. Method according to anyone of the preceding claims, further comprising drying the coated conductive metal substrate to at least partially remove thesolvent from the electrode formulation (EF).

14. Method according to anyone of the preceding claims, further comprising: e) rotating upside down the compressed conductive metal substrate coated on at least a first face thereof; f) coating a second opposite face of the conductive metal substrate with the electrode formulation (EF); and g) compressing the conductive metal substrate coated on both faces thereof.

15. Method according to anyone of the claims 1 -13, wherein the electrode formulation (EF) is in the form of a self-supporting film and wherein c) coating at least a first face of the conductive metal substrate with the electrode formulation (EF) comprises applying, preferably simultaneously, the electrode formulation (EF) in the form of a self-supporting film on opposite faces of the conductive metal substrate.

16. Method according to claim 15, further comprising h) applying a layer of an adhesion enhancer on said opposite faces of the conductive metal substrate before applying thereon the electrode formulation (EF) in the form of a self- supporting film.

17. Method according to claim 16, further comprising i) treating the adhesion enhancer interposed between said opposite faces of the conductive metal substrate and the electrode formulation (EF) in the form of a self-supporting film to enhance adhesion of the self-supporting film to the conductive metal substrate.

18. An electrode formulation (EF) in the form of a cohesive solid material, the electrode formulation (EF) comprising:F1 ) at least the following functional ingredients:- an electrode active material for anode or cathode,- a binder,- a plasticizer,- optionally, a conductive additive,- optionally, a processability adjuvant; andF2) a solvent in an amount equal to or lower than 25% by weight based on the total weight of said functional ingredients.

19. Electrode formulation (EF) according to claim 17, comprising:F1 ) at least the following functional ingredients:45-98% by weight of electrode active material,1 -50% by weight of binder,1 -40% by weight plasticizer,0-20% by weight of conductive additive,- optionally, 1 -40% of processability adjuvant based on the total weight of the functional ingredients F1 ); andF2) a solvent in an amount equal to or greater than 5% by weight and equal to or lower than 25% by weight based on the total weight of the functional ingredients F1 ).

20. Electrode formulation (EF) according to anyone of claims 18 or 19, wherein said electrode active material for anode is anyone of graphite, soft carbons, hard carbons, N-doped carbons, silicon, silicon oxide, lithium titanate Li4TisOi2 (LTO), titanium dioxide, TiC , or mixtures thereof if compatible and / or said electrode active material for cathode is anyone of lithium cobalt oxide, LiCOC (LCO), lithium Manganese Dioxide, LiMnO2, lithium nickel manganese cobalt oxides, LiNixMnyCoi-x-y02 (NMC), lithium iron phosphate, LiFePCh (LFP), lithium nickel cobalt aluminium oxide, LiNiCoAI02 (NCA), or mixtures thereof if compatible.

21. Electrode formulation (EF) according to anyone of claims 18-20, wherein said conductive additive is anyone of carbon black (CB), conductive graphite (CG), single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), graphene, vapor-grown carbon fibers, or mixtures thereof if compatible and / or said binder is a water-soluble binder, such as anyone of sodium carboxymethyl cellulose (Na-CMC), polyvinyl Alcohol (PVA), polyethylene Oxide (PEO), polyvinyl Pyrrolidone (PVP), polyacrylic Acid (PAA), sodium alginate, styrene-butadiene Rubber (SBR), or mixtures thereof ifcompatible, or is a non water-soluble binder, such as polyvinylidene fluoride (PVDF).

22. Electrode formulation (EF) according to anyone of claims 18-21 , wherein said plasticizer is a plasticizer compatible with a water-soluble binder and is anyone of glycerol, sorbitol, triacetin, propylene glycol, polyethylene glycol (PEG), diethylene glycol (DEG), triethyl Citrate (TEC), or mixtures thereof if compatible, or is a plasticizer compatible with a non water-soluble binder and is anyone of dibutyl phthalate (DBP), naphthenic oils, triethyl citrate (TEC), diisononyl phthalate (DINP), epoxidized soybean oil (ESO), or mixtures thereof if compatible and / or said solvent is anyone of water, dimethylformamide (DMF), N,N-Dimethylacetamide (DMAc), dimethyl Sulfoxide (DMSO), N-Methyl-2- pyrrolidone (NMP), cyrene™, toluene, xylene, or mixtures thereof if compatible.

23. Electrode formulation (EF) according to anyone of claims 18-22-, wherein the processability adjuvant is anyone of graphite, 2D transition metal carbides and nitrides (MXenes), graphene, carbon nanotubes, activated carbons, carbon black, molybdenum Disulfide (M0S2), or mixtures thereof if compatible.

24. Electrode formulation (EF) according to anyone of claims 18-23-, in the form of a self-supporting film.

25. A method of manufacturing an electrode formulation (EF) according to claim 24, the method comprising: a) providing an electrode formulation (EF) in the form of a cohesive solid material according to anyone of claims 18-23; and b) feeding the electrode formulation (EF) in the form of a cohesive solid material to a first shaping device, preferably a calendering device, to obtain a self- supporting film of the electrode formulation (EF).

26. Method according to claim 25, further comprising: c) feeding the electrode formulation (EF) in the form of a cohesive solid material to a second shaping device, preferably an extruder device, to obtain an electrode formulation in sheet form; and d) drying the electrode formulation in sheet form thus obtained; wherein c) feeding the cohesive solid material and d) drying the electrodeformulation in sheet form are carried out before b) feeding the cohesive solid material to the first shaping device.

27. An electrode composition (EC) in the form of a cohesive solid material comprising the following functional ingredients:- an electrode active material for anode or cathode,- a water-soluble binder or a non water-soluble binder,- a plasticizer,- optionally, a conductive additive, and- optionally, a processability adjuvant.

28. Electrode composition (EC) according to claim 27, having the following composition in % by weight based on the total weight of the functional ingredients:45-98% of electrode active material,1 -50% of binder,1 -40% of plasticizer,0-20% of conductive additive, and optionally, 1 -40% of processability adjuvant.

29. Electrode composition (EC) according to anyone of claims 27 or 28, wherein the functional ingredients are as defined in anyone of claims 14-17.

30. An energy storage device comprising the electrode composition (EC) of anyone of claims 27-29, wherein the energy storage device is preferably a secondary battery, more preferably a Li-ion secondary battery, comprising an anode, a cathode and a separator and wherein at least one of the anode or cathode comprises the electrode composition (EC) of anyone of claims 27-29.

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