Slurry for lithium ion battery, electrode, and method for manufacturing electrode

Abstract

The present invention relates to a slurry for lithium ion batteries, an electrode and a method for manufacturing the electrode, wherein the electrode is a compound composed of an aqueous binder system and an electrochemically activatable compound with a Li metal oxide containing Ni, the amount of Ni in the metal is at least 80 wt%, and the pH value in the slurry is adjusted to be 9-10.5.

Description

[Technical field]

[0001] The present invention relates to a slurry for producing an electrode for a lithium ion battery, an electrode using the slurry, and a method for producing an electrode for a lithium ion battery (LIB).

[0002] LIBs, a type of rechargeable battery, play a key role in today's transition to sustainable energy production and consumption. Although LIBs have been widely used in portable electronic devices and electric vehicles for many years, their use is also expanding in rail, marine and aerospace applications, as well as for large-scale energy storage in wind and solar parks.

[0003] In a battery, lithium ions move from the negative electrode through the electrolyte to the positive electrode during discharge, and then move back during charging. LIBs use intercalated lithium ions as the positive electrode material, and the negative electrode is usually graphite.

[0004] LIBs have high energy density, no memory effect, and low self-discharge, but they contain a flammable electrolyte, which poses a safety hazard if damaged or charged incorrectly, leading to explosions and fires.

[0005] Different types of LIBs have different chemistry, performance, cost, safety, and other characteristics. The earliest concept of a rechargeable lithium-ion battery dates back to the 1980s, when lithium cobalt oxide (LiCoO 2 ) was first introduced as the cathode active material. Due to the high toxicity, high cost, and thermal instability of Co, the general trend has been to replace Co entirely or partially with other metals, e.g., by increasing the Ni / metal ratio to lower the Co content, leading to increased capacity (JB Goodenough, Y. Kim (2010), Chemistry of Materials 22, 587-603). LiNiMnCoO 2 or NMC, Lithium Nickel (Ni) Manganese (Mn) Cobalt (Co) Dioxide (LiNiMnCoO2 ), or in short lithium metal dioxide (LiMeO 2 ) where the metals are Ni, Mn, and Co in certain proportions or ratios. Today, it is the most common cathode material for commercial lithium-ion cells and is represented by LiCoO 2 The structure is the same as that of LCO, NMC111, or conventional LiFePO 4 The energy density of graphite-based cells using (LFP) as cathode material ranges up to 120-160Wh / kg. Today, energy densities of over 200Wh / kg need to be achieved for large cells. To achieve the market requirements of Lithium-Ion Batteries (LIBs), the energy and / or power density at the cell level needs to be significantly improved. On the cathode side, this can be achieved in several ways: -Methods for introducing high capacity electrode materials (such as Ni-rich NMC, layered oxides, and Li-rich layered oxides used as positive and negative electrode materials) and -High voltage cathode materials (>4.6V vs. metallic lithium), e.g. high voltage LiNi0.5Mn1.5O2-, high Ni LiNi 1-x-y Mn x Al y O 2 (NMA), and / or olivine high voltage LiCoPO4 cathodes, etc. There is.

[0006] Currently, the polymer widely used as a binder material for LIB electrodes is PVdF (polyvinylidene fluoride).

[0007] Today, the challenges facing LIBs are in the areas of increasing lifetime, energy density, safety, cost, and charging speed, among others. Developments are focused on topics such as non-flammable electrolytes as a route to improved safety due to the flammability and volatility of the organic solvents used in typical electrolytes. Strategies include aqueous lithium-ion batteries, ceramic solid electrolytes, polymer electrolytes, ionic liquids, and bifluorinated systems.

[0008] Toward more environmentally friendly and less toxic LIBs, aqueous binder-based cathodes with excellent electrochemical performance, such as lithium nickel manganese cobalt oxide (LiNiMnCoO 2 )──NMC, Lithium Nickel Cobalt Aluminum Oxide (LiNiCoAlO 2 )──NCA, or high voltage LiNi 0.5 Mn 1.5 O 4 Electrodes have been proposed.

[0009] NMC or Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO 2 ) is one of the most successful lithium-ion systems for use as a cathode. As with lithium manganese, these systems can be tailored to function as energy or power batteries. For example, an NMC 18650 cell for moderate load conditions has a capacity of about 2,800 mAh and can deliver 4 A to 5 A; an NMC of the same cell optimized for a specific power has a capacity of only about 2,000 mAh but delivers a continuous discharge current of 20 A. Silicon-based anodes can reach over 4,000 mAh, but suffer from reduced load capacity and shorter cycle life. Silicon-added graphite has the disadvantage that the anode expands and contracts with charging and discharging, making the cell mechanically unstable.

[0010] The secret of NMC is the combination of nickel, cobalt and manganese. In analogy with table salt, the main components, sodium and chloride, are toxic on their own, but when mixed together they function as a seasoning salt and food preservative. Nickel has a high specific energy but is known to be less stable, while manganese has the advantage of forming a spinel structure that achieves low internal resistance, but has a low specific energy. Combining these metals enhances each other's strengths.

[0011] NMC is the battery material of choice for power tools, e-bikes and other electric powertrains. The cathode combination is typically one-third nickel, one-third manganese and one-third cobalt metals (LiMeO 2 ), also known as 1-1-1. This offers a unique combination that reduces raw material costs by reducing the cobalt content. Another successful combination is NCM532, which is 5 parts nickel, 3 parts cobalt, and 2 parts manganese (5-3-2). Other combinations using various amounts of cathode materials are possible.

[0012] Battery manufacturers are moving away from cobalt-based systems to higher nickel-content cathodes due to the high cost of cobalt. The nickel-based systems offer higher energy density, lower cost and longer cycle life than cobalt-based cells, but have slightly lower voltages.

[0013] Lithium Nickel Cobalt Aluminum Oxide (LiNiCoAlO 2 ) - Batteries containing NCA cathode material were developed around 1999 for special applications. NCA cathode-based batteries are similar to NCM cathode batteries and are believed to offer high specific energy, reasonable power density, and long life, while also providing low storage and cost. The addition of aluminum to the chemistry has been shown to improve stability.

[0014] High voltage (LiNi 0.5 Mn 1.5O)──LNMO cathodes are promising for next-generation high-performance lithium-ion batteries due to their high energy density, high operating voltage (about 4.7 V vs. Li), low manufacturing cost, and low environmental impact. However, the short cycle life of LNMO due to the rapid capacity fade during cycling remains a challenge.

[0015] Compared with conventional organic PVdF-based electrodes, the NCM, NCA and LNMO electrodes exhibit highly uniform distribution of carbon particles and strong adhesion between the particles and with the current collector, which significantly reduces the crack formation and delamination of the electrodes during repeated delithiation / lithiation processes. + The diffusion rate of oxygen is improved and polarization is reduced, resulting in excellent high C-rate capacity and extremely stable cycle performance even at high temperatures exceeding 50°C. In addition, these materials are low-cost, environmentally friendly, and easy to dispose of and recycle.

[0016] Despite all the progress made in aqueous binder-based lithium-ion battery cathodes, there are still strong demands on the path to sustainable lithium-ion batteries: - avoiding and / or reducing the presence of PVdF in the electrodes; Reducing the overall binder content in the electrode; -Enhancing the lamination of separators to electrodes produced from aqueous solutions; - Increasing the cohesive adhesion between particles in the electrode structure; -Increasing the chemical and electrochemical stability of the cathode; -Increasing cell safety through the use of more stable water-based binders; -Increasing the adhesion between the electrode mass and the current collector; -Increasing the recyclability of electrode materials, and last but not least, - reducing production costs; And so on.

[0017] These objects are achieved by providing a slurry, a method for producing an electrode, and a battery comprising said electrode, comprising the elements, compositions and method steps according to the independent claims. Preferred embodiments are described by the elements, compositions and method steps according to the claims dependent on the independent claims.

[0018] According to the present invention, a slurry for the manufacture of electrodes for lithium-ion batteries is proposed, which comprises an aqueous binder system, i.e. a mixture of one or more polymeric binders dissolved in an aqueous solution, a cathode material with electrochemically activatable compounds, i.e. Li-metal oxides containing Ni (also called Ni-rich oxides), which convert electric and chemical potentials by electrochemical intercalation reactions, and a Li-rich oxide, i.e. LiMeO with the usual stoichiometry of 1:1. 2 - a cathode material containing more Li than the oxide compound, 2 The amount of Ni in the slurry is at least 80 wt %, and the pH value of the slurry is adjusted to 9 to 10.5.

[0019] Examples of lithium-rich layered oxide cathode materials include Li 1.2 Mn 0.5100 Ni 0.2175 Co 0.0725 O 2 There is.

[0020] The technical advantage of having a Ni content of 80% or more in the metal is that the Co content in the cathode material is reduced, improving capacity and reducing costs, compared to lower contents.

[0021] Metal (LiMeO 2 In order to ensure that the Ni content in the cathode is at least 80% or more for a functional battery cell, the recipe and steps of the mixing process need to be adapted to control the pH value of the resulting slurry within a specific range of 9 to 10.5 in order to control the surface reactivity of the material, which is higher than that of cathode materials with lower Ni content.

[0022] By strictly controlling the pH value in the slurry according to the present invention to be in the range between 9 and 10.5, the metal (LiMeO 2 Proper stabilization of the Li-NMC slurry with at least 80% Ni in the LiNMC slurry can lead to improved cohesive adhesion between particles in the electrode structure, thus resulting in a significantly more stable electrode.

[0023] Cathode active materials used in high Ni content Li-ion electrodes can have very high pH values ​​(pH>11.5) during processing in the slurry. Aqueous slurries with high pH require careful processing due to corrosion reactions and / or agglomeration of the active and conductive materials. High or uncontrolled pH can also lead to gelation of the binder. To avoid this behavior in aqueous binder slurries, control of the slurry pH is essential.

[0024] The pH value of the resulting binder solution can be controlled by, for example, the addition of acrylates (polyacrylic acid - PAA, polyethylene-co-acrylic acid - PEAA, etc.), phosphoric acid, citric acid, LiH 2 SO 4 , LiH 2 PO 4 By adding, for example, ammonia, the pH can be adjusted over a wide range from acidic to neutral to basic conditions. A preferred method for using such pH adjuster (buffer) compounds in electrode pastes is to also make them adhesive and use them as thickeners for the prepared slurry solution.

[0025] For example, acrylic esters contain acidic groups, which compensate (reduce) the high pH of solutions containing high pH materials and reduce the very high interfacial free energy between active and inactive particles, especially when carbon black particles, known for their hydrophobicity, are used as the conductive material. The acrylic groups also promote surface reactions with the current collector, resulting in high adhesion between the electrode particles and the current collector. To lower the pH and improve electrode adhesion, a preferred choice is PAA (polyacrylic acid), which acts both as a binder and a pH adjuster.

[0026] In the case of the aqueous binder slurry according to the present invention, a binder combination is used in a manner that allows for control of the pH of the slurry and protects the cathode active material and the active surface of the conductive material from galvanic corrosion and electrochemical decomposition at the surface of the active material.

[0027] Corrosion of the (aluminum) current collector can be avoided by coating the electrodes with a pH-controlled slurry (pH = 9-10.5).

[0028] The higher the Ni content in the LiMe-oxide, the higher the capacity (Ah / kg) of the cathode material in Li-ion cells. For example, the capacity of NCM111 is about 150 Ah / kg, and the capacity of NCM cathode materials containing 80% or more Ni is greater than 190 Ah / kg.

[0029] Furthermore, this allows the fabrication of electrodes (cathodes) using environmentally friendly aqueous binders, laminating the electrodes fabricated using the aqueous binders to separators, improving the interfacial stability and reducing the risk of dendrite formation. The Ni-rich cathodes fabricated according to the present invention show good chemical and electrochemical cycling stability.

[0030] In a preferred embodiment, the electrochemically activatable compounds are selected from the group consisting of NCM type, NCA type, NCMA type (nickel-cobalt-manganese-aluminum oxide), and high voltage Li-NMO (LiNi 0.5 Mn 1.5 O 4) types.

[0031] The technical advantages of using the NCMA type over the NCM and NCA types are higher capacity and lower cost due to the higher nickel and lower cobalt content. In addition, the NCMCA type offers improved cycling stability compared to the NCM type.

[0032] In likewise preferred embodiments of the electrode according to the invention, the PVdF content of the aqueous binder (WBB) system can be selected to be between 0% and 2%, with ranges of 0.5-1%, 1-2% or even 0% being likewise further preferred embodiments.

[0033] All percentages in this application are provided as wt% values.

[0034] The most preferred binder content is 3-4% to allow the separator to be laminated to electrodes fabricated from aqueous solutions. This allows the separator-electrode interface to be stabilized, improving the safety of the cell. However, lamination is not mandatory in the processing of WBB electrodes. The purpose of lamination is to make the separator more uniform and more stable in the cell, which helps in uniform solid electrolyte interphase (SEI) formation at the anode / separator interface. The improved SEI formation at the anode side results in lower cell degradation during cycling. Due to the different chemical interfacial interactions between the active mass and the aqueous binder, a higher reversible intercalation / deintercalation is achieved, improving the chemical and electrochemical stability of the cathode compared to PVdF binder electrodes.

[0035] When lamination is not performed, the binder content is preferably low, and the most preferable WBB content is 2 to 3%.

[0036] The technical advantage of using a WBB amount of 2-3% is that it improves the energy density of the cell while at the same time improving the power density (cell power capacity) due to less isolation of active material particles caused by the high binder content.

[0037] The aqueous binder system is preferably a carboxymethyl cellulose (CMC)-based binder system, a styrene butadiene rubber (SBR)-based binder system, or an acrylic binder system. WBBs such as CMC-based, SBR-based, and / or acrylic-based binders exhibit higher binding capacity than PVdF binders, increasing the adhesion of the electrode mass to the current collector and the interparticle cohesive adhesion, allowing the electrode to be manufactured with less binder.

[0038] The elimination of organic solvents results in more environmentally friendly processes, which in turn reduces production costs. Environmental protection is given high priority at all stages of the product life cycle, focusing on resource conservation through waste reduction in production, separation technologies in all areas of chemical processing, gas / water treatment through systematic recycling and the recovery of raw materials.

[0039] In the cell assembly process, starting from electrode production based exclusively on the water-based binder (WBB) process, the manufacturing environment is improved by eliminating expensive and toxic organic solvents. In the production of lithium-ion batteries, NMP and / or acetone are widely used as solvents for electrode preparation, but efforts are being made to replace them with solvents with less environmental impact, such as water. In contrast to chemical solvents used in traditional industrial coatings, which must then be recycled or burned, water does not require recycling or evaporation removal, or ATEX (Control of Explosive Atmospheres) treatment lines. Therefore, there is no potential danger from explosive atmospheres, and the machinery and equipment are simplified. Furthermore, NMP was included in the list of substances of very high concern in April 2018 that may have irreversible serious effects on human health and the environment. The use of NMP is restricted by the European Commission (Restriction Item 71 of REACH Annex XVII): NMP is "as of May 9, 2020, manufacturers and downstream users shall be required to use NMP if their workers' exposure is below the Derived No-Effect Level (DNEL), i.e. 14.4 mg m for inhalation exposure." -3 , and 4.8 mg kg for dermal exposure. -1 / day, unless appropriate risk management measures are taken and appropriate working conditions are provided to ensure that NMP concentration remains below 0.3%. This represents an added cost in the electrode processing process, from slurry mixing to final solvent recovery.

[0040] The aqueous binder in the slurry for manufacturing the electrode according to the present invention can be selected from carboxymethyl cellulose (CMC) binder, styrene butadiene rubber (SBR) binder, acrylic binder, or a mixture thereof. The use of a more stable aqueous binder increases the safety of the cell.

[0041] Polyvinylidene fluoride (PVdF) is the most used binder in today's lithium-ion batteries due to its excellent electrochemical stability, good adhesion ability, high adhesion, and versatility. Despite toxicity concerns and high processing costs, PVdF binders are traditionally dissolved in volatile, flammable, explosive, and highly toxic organic solvents such as N-methyl-pyrrolidone (NMP), leading to serious environmental pollution. PVdF is highly sensitive to moisture, which has led to several battery failure mechanisms caused by volume change, mechanical stress including crushing of the active material, contact loss with the current collector, cracking, and reformation of the solid electrolyte interface (SEI) passivation layer, as well as loss of electrode porosity that limits ionic conduction. In addition, both PVdF and NMP are expensive, which increases the manufacturing cost of lithium-ion batteries.

[0042] Water-based or aqueous binders have attracted increasing attention in recent years due to their advantages of low cost and environmental friendliness. The improved electrochemical stability of electrodes containing aqueous binders has already been reported in many papers, for example, the cycle stability of Li / SiOx electrodes with various types of binders (conventional PVdF binder) is inferior to aqueous Na-CMC and Li-PAA binders. Due to the different chemical interactions between the active material and the aqueous binder, higher reversible intercalation / deintercalation is achieved compared to PVdF binder electrodes.

[0043] Finally, also proposed according to the present invention is a method for manufacturing an electrode for a lithium-ion containing electrochemical cell, comprising the steps of preparing a slurry as described in the above paragraph, coating or laminating the slurry onto a current collector, and drying the slurry.

[0044] Therefore, in the present invention, the PVdF content in the electrode can be avoided and / or reduced by using an aqueous binder in the slurry.

[0045] According to the present invention, the overall binder content in the electrode can be reduced by using an improved recipe, improved binder type, and improved mixing technique to control the pH value in the slurry in the range of 9 to 10.5.

[0046] Lamination of separators to electrodes prepared from aqueous solutions according to the present invention can be enhanced by the type of binder used and the use of appropriate surfactants to aid in the dispersion of the binder in the slurry.

[0047] The cohesive adhesion between particles in electrode structures made according to the invention can be improved by the type of binder used and by increasing the solids content in the slurry, which results in less water being removed during drying of the electrode, resulting in less porosity and more resilience in the electrode.

[0048] The chemical and electrochemical stability of cathodes made according to the present invention can be improved due to the reduced porosity of the electrodes and better interparticle contact.

[0049] The use of a more stable aqueous binder in accordance with the present invention can improve cell safety since the aqueous binder has a higher stability compared to PVDF binders, which are known to decompose at high temperatures and voltages (leading to HF generation).

[0050] In order to control the pH value of the slurry to 9 to 10.5, the solid content in the slurry used to manufacture the electrode, i.e., all non-water-containing components, can be made 60% to 85%, more preferably 75% to 85%, by improving the recipe, the type of binder, and the mixing technique. This can increase the adhesion of the electrode mass to the current collector.

[0051] The water-dilutable aqueous binder allows for increased recyclability of the electrode material.

[0052] Finally, the manufacturing cost of the electrodes (cathode) can be reduced based on the present invention because the coating process can be performed at a lower temperature due to the use of water as a solvent (the conventional solvent used to manufacture electrodes, NMP, requires higher temperatures due to its high boiling point). This results in a shorter drying section of the coater and less energy is required to extract the solvent (water in this case). This results in smaller and faster equipment being used, reducing operating costs. This, in turn, will make the batteries cheaper and more widely available. Also, no solvent recovery system is required because the exhaust from the coater is a vapor that can be released into the atmosphere without further treatment.

[0053] Further aspects, features and advantages of the present invention will become readily apparent from the following detailed description, by way of mere illustration of preferred embodiments and implementations. The invention is capable of other and different embodiments, and its several details can be modified in various obvious respects all without departing from the spirit and scope of the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. Additional objects and advantages of the present invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. [Brief description of the drawings]

[0054] The present invention will be described based on the figures. It will be understood that the embodiments and aspects of the present invention described in the figures are merely illustrative and do not limit the scope of protection of the claims in any way. The present invention is defined by the claims and their equivalents. It will be understood that the features of one aspect or embodiment of the present invention can be combined with the features of one or more different aspects of other embodiments of the present invention, such as:

[0055] FIG. 1 shows an example of an electrochemical cell according to a preferred embodiment of the present invention;

[0056] FIG. 2a shows a second example of an electrochemical cell according to a preferred embodiment of the present invention;

[0057] FIG. 2b illustrates how electrochemical cells according to a preferred embodiment of the present invention can be stacked to form a battery;

[0058] FIG. 3 illustrates the filling of a battery consisting of a stack of electrochemical cells with electrolyte;

[0059] FIG. 4 shows the filled battery of FIG. 3;

[0060] FIG. 5 is a comparative cycle stability graph of G / NMC622 and G / NMCA with 88% Ni content;

[0061] As shown in Figures 1 to 4, according to a preferred embodiment of the present invention.

[0062] 1a and 1b show an example of an electrochemical cell 2 that may be used with the present disclosure. The electrochemical cell 2 includes two electrodes, an anode 10 and a cathode 20. The anode 10 and cathode 20 are separated by a separator 30. The anode 10 and cathode 20 as shown are fabricated from a slurry that includes an aqueous binder system and an electrochemically active compound having Li metal oxides, including Ni, and a metal (LiMeO 2 The amount of Ni in the alloy is at least 80%.

[0063] In the preferred embodiment illustrated, the layered oxide cathode material is Li 1.2 Mn 0.5100 Ni 0.2175 Co 0.0725 O 2 and metal (LiMeO 2 The Ni content in the alloy is 90%.

[0064] The electrochemically activatable compounds of the illustrated preferred embodiment include NMC-type, NCA-type, NCMA-type and high voltage Li-NMO (LiNi 0.5 Mn 1.5 O 4 ) types.

[0065] Furthermore, the electrodes according to the illustrated preferred embodiment are manufactured using a slurry having an aqueous binder system with a PVdF content of 0-2%, a pH value of 9-10.5, and a solids content, i.e., total non-water containing components, of 75%-85%.

[0066] The aqueous binder system used in the preferred embodiment illustrated is a carboxymethyl cellulose (CMC) based binder system.

[0067] The anode 10 and cathode 20 have electrical contacts 12, 22 for electrically connecting the respective electrodes. The separator 30 shown is a ceramic separator as known in the art.

[0068] The illustrated electrochemical cell 2a is a large electrochemical cell. When at least one of the electrodes 10, 20 and the separator 30 between the electrodes has a length A and / or width B of at least about 10 cm or more, the electrochemical cell may be called a large electrochemical cell. For example, the length A and width B of the electrodes 10, 20 may be about 10 to about 20 cm. The length A may be different from the width B and may be rectangular or any other shape desired. The shape of the electrodes may be adapted to the application of the electrochemical cell or battery and may be adapted to a particular casing.

[0069] In the illustrated example, the distance D between the anode 10 and the cathode 20 is less than 1 mm. For example, the distance between the anode collector of the anode 10 and the cathode connector of the cathode 20 may be about 400 μm or less.

[0070] Each of the electrodes 10, 20 of the anode 10 and cathode 20 may be made of a foil material with a thickness of less than about 50 μm. In particular, the foil may have a thickness of about 10-20 μm. For example, an aluminum foil may be used for the cathode and a copper foil for the anode 10.

[0071] The electrochemical cell 2 a is filled with an electrolyte 4 in contact with an anode 10 and a cathode 20 .

[0072] Figure 2a shows electrochemical cell 2b which differs from electrochemical cell 2a in that a separator 30 and an anode 10 are disposed on either side of a cathode 20. An electrolyte 4 is inserted between each anode 10 and cathode 20. This allows the electrochemical cells 2b to be stacked more closely within the battery 1, requiring less cathode material. Electrical contacts 12, 22 have been omitted from this figure for clarity.

[0073] A plurality of electrochemical cells 2a as shown in Figures 1a and 1b, or a plurality of electrochemical cells 2b as shown in Figure 2a, may be stacked together to form a rechargeable battery 1. Figure 2b shows how a plurality of electrochemical cells 2b may be stacked in a housing, pack or pouch 5. The number of electrochemical cells 2 stacked may vary depending on the application of the rechargeable battery 1. In the illustrated example, for illustrative purposes, three electrochemical cells 2b are shown stacked to form the rechargeable battery 2, but the number of electrochemical cells 2a, 2b may be much higher. For example, the battery 2 may include up to about 500 electrochemical cells 2a, 2b.

[0074] Electrochemical cells 2a as shown in Figures 1a and 1b may simply be stacked on top of each other and the electrodes 10, 20 may be separated from each other using a separator material.

[0075] However, other stacking methods are possible and are applicable to the present invention. Figures 2-4 show an electrochemical cell 2b with a bi-cell structure. The cell can also be implemented as a mono-cell structure, a bipolar structure, a wound cell or a Z-stacked cell.

[0076] The active mass or material can be coated on one or both sides of the current collector. Other lamination methods may be used, such as stacking alternating anodes and cathodes with a separator material between them, allowing both sides of the anode and cathode to be used.

[0077] FIG. 2b shows a plurality of electrochemical cells 2b stacked in a bicell structure in a package or pouch 5 prior to filling the electrochemical cells 2b with electrolyte.

[0078] FIG. 3 shows how the electrolyte 4 can be inserted into the electrochemical cells 2a, 2b. The electrochemical cells 2a, 2b can be filled into a pouch 5 that is closed at all sites except the top surface 6 using a dosing device 8, such as a needle. FIG. 3 shows a bicell structure of three pairs of electrochemical cells 2b, with the contacts 12, 22 omitted for clarity. The dosing device 8 can insert a predetermined amount of electrolyte 4 into the electrochemical cells 2a, 2b. The insertion of the electrolyte 4 into the electrochemical cells 2a, 2b filled in the pouch 5 can be performed under vacuum conditions, for example at a pressure of about 10 to 500 mbar (abs). The electrolyte 4 can be injected only from one side, greatly simplifying the injection procedure.

[0079] It is important that the distribution of the electrolyte 4 between the anode 10 and the cathode 20 is very homogeneous, in particular there should be no air bubbles or other imperfections between the anode 10 and the cathode 20, as this would lead to undesirable defects and less battery capacity. The electrolyte 4 in the battery 1 according to the invention may comprise a non-aqueous solvent such as, for example, a cyclic carbonate, a cyclic ester, a linear carbonate, an ether, or a combination thereof, although other organic solvents may be used.

[0080] The electrolyte 4 is a conductive lithium salt, for example LiClO 4 , LiPF 6 , LiBF 4 , LiAsF 6 , LiPF 3 (CF 2 CF 3 ), lithium bis[1,2-oxalato(2-)-O,O']borate (LiBOB)-based electrolytes, and LiF 4 C 2 O 4 , LiFOP, LiPF 4 (C 2 0 4 , LiF 4 OP, LiCF 3 SO 3 , LiC 4 F 9 SO 3 , Li(CF 3 SO 2 )2 N, Li(C 2 F 5 SO 2 ) 2 N, LiSCN and LiSbF 6 , LiAlO 4 , LiAlC1 4 , LiCl and LiI, or combinations thereof, and other known lithium salts can also be used.

[0081] The electrolyte 4 comprises a wetting agent, which is used to homogeneously wet the surfaces of the anode 10, the cathode 20 and the separator 30 and to obtain a homogeneous distribution of the electrolyte 4 within the electrochemical cells 2a, 2b. The wetting agent may be or comprise a fluoropolymer, in particular a fluorosurfactant.

[0082] Possible examples of fluoropolymers include commercially available perfluoroalkylethoxylates such as Zonyl SF0, Zonyl SFN and Zonyl SF300 (from EI DuPont) or lithium-3-[(lH,lH,2H,2H-fluoroalkyl)thio]-propionate, Zonyl FSA(c) (from DuPont).

[0083] Examples of commercially available fluorosurfactants that may be used with the present disclosure include, but are not limited to, fluorosurfactants sold by DuPont under the product names Zonyl SFK, Zonyl SF-62, or fluorosurfactants sold by 3M Company under the product names FLURAD FC 170, FC 123, or L-18699A. Other commercially available products that may be used as fluorosurfactants include those sold by 3M Company under the product names Novec F-C4300, 3M FC-4430, 3M FC-4432, or 3M FC-4434.

[0084] Other wetting agents that may be used with the present disclosure include semi-fluorinated acrylic polymer EGC-1700, fluoromethacrylate, long chain perfluoroacrylate, tetrafluoroethylene, hexafluoropropylene, silane coupling agents with perfluoropolyether (PFPE-5), (perfluoroalkyl)ethyl methacrylate-containing acrylic polymer, butyl methacrylate-co-perfluoroalkyl acrylate, semi-fluorinated fluorocarbon diblock copolymer poly(butyl methacrylate-co-perfluoroalkyl acrylate), n-perfluorononane, perfluoropropylene oxide, polytetrafluoroethylene, poly(tetrafluoroethylene-co-hexafluoropropylene), perfluorobutyl (PFB), perfluoromethyl, perfluoroethyl, or combinations thereof. All of the above wetting agents may be used alone or in any combination.

[0085] The wetting agent, fluoropolymer or fluorosurfactant, may be used at a concentration of from about 5 ppm (parts per million) to about 5000 ppm.

[0086] The use of a wetting agent in the electrolyte ensures that the distribution of the electrolyte 4 within the electrochemical cells 2a, 2b is even and homogeneous. The use of a wetting agent allows for a significant reduction in filling times, enabling large lithium ion batteries to be produced in acceptable time scales suitable for mass production.

[0087] FIG. 4 shows a sealed battery pack 1, in which the opening 6 of the pouch 5 has been closed after the battery pack 1 has been completely filled with the electrolyte 4.

[0088] It will be obvious to those skilled in the art that there are other possibilities than the pouch 5 for packaging the electrochemical cells 2a, 2b. For example, battery housings made of known plastic materials may be used.

[0089] It will be apparent to those skilled in the art that multiple battery packs 1 may be combined to increase the battery capacity and / or voltage.

[0090] Finally, Figure 5 is a comparative graph showing the charge / discharge (1C / 1C) cycling stability of the aqueous binder electrodes G / NMC622 (blue) and G / NMCA (Ni content 88%, red). As can be seen from the graph in Figure 5, the G / NMCA cell according to the present invention shows similar cycling stability to the G / NMC622 cell, which contains a much lower Ni content.

[0091] The foregoing description of preferred embodiments of the present invention has been presented for purposes of illustration and description only. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments have been chosen and described in order to explain the principles of the invention and its practical application so that those skilled in the art can utilize the invention in various embodiments suited to the particular uses contemplated. The scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A slurry for manufacturing an electrode for a lithium-ion battery, the slurry being an aqueous binder system containing an electrochemically active compound with a Li-metal oxide containing Ni, and a metal (LiMeO 2 ) the amount of Ni in the slurry is at least 80 wt %, and the pH value of the slurry is adjusted to 9 to 10.

5.

2. The electrochemically activatable compound may be of the lithium-nickel-manganese-cobalt-oxide type, the lithium-nickel-cobalt-aluminum-oxide type, the lithium-nickel-cobalt-aluminum-oxide type, the high voltage Li-NMO (LiNi 0.5 Mn 1.5 O 4 ) and high voltage Li-NMA (LiNi 1-x-y Mn x Al y O 2 2. The slurry of claim 1, wherein the slurry is selected from the group consisting of:

3. 3. The slurry according to claim 1, wherein the PVdF content of the aqueous binder system is selected to be between 0 wt% and 2 wt%.

4. 4. The slurry of claim 3, wherein the PVdF content of the aqueous binder system is 0 wt%.

5. 4. The slurry of claim 3, wherein the PVdF content of the aqueous binder system is 0.5 to 1 wt %.

6. 4. The slurry of claim 3, wherein the PVdF content of the aqueous binder system is 1 to 2 wt %.

7. 3. The slurry of claim 1 or 2, wherein the aqueous binder system comprises carboxymethyl cellulose (CMC).

8. 3. The slurry of claim 1 or 2, wherein the aqueous binder system comprises styrene butadiene rubber (SBR).

9. 3. The slurry of claim 1 or 2, wherein the aqueous binder system comprises an acrylic binder.

10. 3. The slurry according to claim 1, wherein the solid content of the slurry is 60% to 85%.

11. 11. The slurry of claim 10, wherein the solids content in the slurry is 75% to 85%.

12. To adjust the pH value of the binder solution, acrylates such as polyacrylic acid (PAA) or polyethylene-co-acrylic acid (PEAA), phosphoric acid, citric acid, LiH 2 SO 4 , LiH 2 PO 4 3. The slurry according to claim 1 or 2, wherein ammonium hydroxide or ammonia is used.

13. An electrode for a lithium ion-containing electrochemical cell, produced from the slurry of claim 1 or 2.

14. 14. An electrochemical cell comprising the electrode of claim 13.

15. 1. A method for manufacturing an electrode for a lithium ion containing electrochemical cell, comprising the steps of: a. preparing a slurry according to claim 1 or 2; b. coating or laminating the slurry onto a current collector; c. drying the slurry.

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