HK1243550B - Method of preparing battery electrodes - Google Patents

Description

Method for preparing battery electrodes

Technical Field

The present invention relates to lithium-ion batteries for use in the field of sustainable energy. More particularly, the present invention relates to the use of water-based slurries for the preparation of battery electrodes.

Background Art

Over the past two decades, lithium-ion batteries (LIBs) have attracted widespread attention due to their widespread application in portable electronic devices such as mobile phones and laptops. Due to the rapid development of electric vehicles (EVs) and grid energy storage, high-performance, low-cost LIBs currently offer one of the most promising options for large-scale energy storage devices.

Typically, lithium-ion batteries include a separator, a cathode, and an anode. Currently, electrodes are prepared by dispersing fine powders of active battery electrode materials, conductive agents, and binder materials in a suitable solvent. This dispersion can be applied to a current collector such as copper or aluminum foil and then dried at high temperatures to remove the solvent. The cathode and anode plates are then stacked or rolled together with the separator separating the cathode and anode to form a battery.

Polyvinylidene fluoride (PVDF) is the most widely used binder material for both cathode and anode electrodes. Compared with non-PVDF binder materials, PVDF provides good electrochemical stability and high adhesion to electrode materials and current collectors. However, PVDF can only be dissolved in some specific organic solvents (e.g., N-methyl-2-pyrrolidone (NMP)), which requires specific processing, production standards and recycling of organic solvents in an environmentally friendly manner. This will lead to high costs in the manufacturing process.

For environmental and disposal reasons, aqueous solutions are preferably used instead of organic solvents, so water-based slurries have been considered. Water-soluble binders such as carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) have been tried. However, CMC and SBR are usually limited to anode applications.

U.S. Patent No. 8,956,688 B2 describes a method for preparing a battery electrode. The method includes measuring the zeta potential of an active electrode material and a conductive additive material; selecting a cationic dispersant or an anionic dispersant based on the zeta potential; determining the isoelectric point (IEP) of the active electrode material and the conductive additive material; dispersing the active electrode material and the conductive additive in water using at least one dispersant to form a mixed dispersion; treating the surface of a current collector to increase the surface energy of the surface to at least the surface tension of the mixed dispersion; depositing the dispersed active electrode material and the conductive additive on the current collector; and then heating the coated surface to remove water from the coating. However, the method is complex, including measuring the zeta potential of the active electrode material and the conductive additive material and the isoelectric point (IEP) of the active electrode material and the conductive additive material. And an additional surface treatment step is required to treat the surface of the current collector in order to improve capacity retention.

U.S. Patent No. 8,092,557 B2 describes a method for preparing an electrode for a rechargeable lithium-ion battery using a water-based slurry having a pH of 7.0 to 11.7, wherein the electrode includes an electroactive material, a (polystyrene butadiene rubber)-poly(acrylonitrile-ammonium acrylate) copolymer, and a conductive additive. However, the method does not provide any data for evaluating the electrochemical performance of the electrode prepared by the method.

U.S. Patent Application No. 2013/0034651A1 describes a slurry for making an electrode, wherein the slurry includes a combination of at least three of polyacrylic acid (PAA), hydroxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), and polyvinylidene fluoride (PVDF) in an aqueous solution and an electrochemically activatable compound. However, the slurry used to prepare the cathode electrode includes acetone or other organic solvents, such as NMP and DMAC.

In view of the above, there has been a need to develop a method for preparing cathode and anode electrodes for lithium ion batteries using a simple, inexpensive, and environmentally friendly method.

Summary of the Invention

The aforementioned needs are met by the various aspects and embodiments disclosed in this application.

In one aspect, the present application provides a method for preparing a battery electrode, comprising the following steps:

1) pretreating an active battery electrode material in a first aqueous solution having a pH of about 2.0 to about 7.5 to form a first suspension;

2) drying the first suspension to obtain a pretreated active battery electrode material;

3) dispersing the pretreated active battery electrode material, conductive agent, and binder material in a second aqueous solution to form a slurry;

4) homogenizing the slurry by a homogenizer to obtain a homogenized slurry;

5) applying the homogenized slurry on a current collector to form a coating film on the current collector; and

6) Drying the coating film on the current collector to form the battery electrode.

In some embodiments, the active battery electrode material is a cathode material, wherein the cathode _material is selected from _the group consisting _{of LiCO2} , _LiNiO2 , _LiNiXMnYO2 , Li1 _{+ zNiXMnYCo1 - xyO2 , LiNiXCoYAlZO2} , _LiV2O5 , _LiTiS2 , _LiMoS2 , _LiMnO2 , _LiCrO2 , _LiMn2O4 , _LiFeO2 , _LiFePO4 , _and combinations thereof, wherein each x is independently 0.3 to _0.8 ; _each y is independently 0.1 to 0.45; and _each z is independently 0 to 0.2.

In some embodiments, the pH of the first aqueous solution is in the range of about 4 to about 7, _{and the} first suspension is stirred for a period of about 2 minutes to _{about 12} hours. In other embodiments, the first aqueous solution includes one _{or more} acids selected from _the group consisting of _H2SO4 , _HNO3 , _H3PO4 , _HCOOH , _CH3COOH , _H3C6H5O7 , _H2C2O4 , _{C6H12O7 , C4H6O5 ,} and _combinations thereof.

In some embodiments, the first aqueous solution further comprises ethanol, isopropanol, methanol, acetone, n-propanol, tert-butanol, or a combination thereof.

In some embodiments, the first suspension is dried by a double cone vacuum dryer, a microwave dryer, or a microwave vacuum dryer.

In some embodiments, the conductive agent is selected from the group consisting of carbon, carbon black, graphite, expanded graphite, graphene, graphene nanosheets, carbon fibers, carbon nanofibers, graphitized carbon sheets, carbon tubes, carbon nanotubes, activated carbon, mesoporous carbon, and combinations thereof.

In some embodiments, the conductive agent is pretreated in _an alkaline solution or a solution of an alkali for a period of about 30 minutes to about 2 hours, wherein the alkaline solution or the solution of an alkali comprises a base selected from the group consisting of _H2O2 , _LiOH , NaOH, _KOH , _NH3.H2O , Be(OH) ₂ , Mg(OH) ₂ , Ca(OH _{) 2} , _Li2CO3 , _Na2CO3 , _NaHCO3 , _K2CO3 , _{KHCO3 ,} and combinations thereof.

In some embodiments, before step 3), a conductive agent is dispersed in the third aqueous solution to form a second suspension.

In some embodiments, the binder material is selected from the group consisting of styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), acrylonitrile copolymer, polyacrylic acid (PAA), polyacrylonitrile, polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), latex, alginate, and combinations thereof. In other embodiments, the alginate comprises a cation selected from Na, Li, K, Ca, NH ₄ , Mg, Al, or combinations thereof.

In some embodiments, the binder material is dissolved in the fourth aqueous solution to form a resulting solution prior to step 3).

In some embodiments, each of the first aqueous solution, the second aqueous solution, the third aqueous solution, and the fourth aqueous solution is independently purified water, pure water, deionized water, distilled water, or a combination thereof.

In some embodiments, the slurry or homogenized slurry further comprises a dispersant selected from the group consisting of ethanol, isopropyl alcohol, n-propyl alcohol, tert-butyl alcohol, n-butyl alcohol, lithium lauryl sulfate, trimethylhexadecyl ammonium chloride, alcohol ethoxylates, nonylphenol ethoxylates, sodium dodecylbenzene sulfonate, sodium stearate, and combinations thereof.

In some embodiments, the homogenizer is a stirring mixer, a blender, a mill, an ultrasonicator, a rotor-stator homogenizer, or a high-pressure homogenizer.

In some embodiments, the ultrasonic generator is a probe-type ultrasonic generator or an ultrasonic flow cell.

In some embodiments, the ultrasonic generator is operated at a power density of about 10 W/L to about 100 W/L, or about 20 W/L to about 40 W/L.

In some embodiments, the homogenized slurry is applied to the current collector using a knife coater, a slot die coater, a transfer coater, or a spray coater.

In some embodiments, each current collector of the positive electrode and the negative electrode is independently stainless steel, titanium, nickel, aluminum, copper or a conductive resin. In some embodiments, the current collector of the positive electrode is an aluminum film. In some embodiments, the current collector of the negative electrode is a copper film.

In some embodiments, the coating film is dried at a temperature of about 45°C to about 100°C, or about 55°C to about 75°C, for a period of about 1 minute to about 30 minutes, or about 2 minutes to about 10 minutes.

In some embodiments, the coating film is dried by a conveyor-type hot air drying oven, a conveyor-type resistance drying oven, a conveyor-type induction drying oven, or a conveyor-type microwave drying oven.

In some embodiments, the conveyor moves at a speed of about 2 m/min to about 30 m/min, about 2 m/min to about 25 m/min, about 2 m/min to about 20 m/min, about 2 m/min to about 16 m/min, about 3 m/min to about 30 m/min, about 3 m/min to about 20 m/min, or about 3 m/min to about 16 m/min.

In some embodiments, the active battery electrode material is an anode material, wherein the anode material is selected from the group consisting of natural graphite particles, synthetic graphite particles, Sn particles, Li ₄ Ti ₅ O ₁₂ particles, Si particles, Si—C composite particles, and combinations thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 shows an embodiment of the method disclosed in this application.

FIG. 2 shows a SEM image of the surface morphology of Example 1 of an embodiment of a coated cathode electrode disclosed in the present application.

FIG3 shows the cycling performance of an electrochemical cell comprising a cathode and an anode prepared by the method described in Example 2.

FIG4 shows the cycling performance of an electrochemical cell comprising a cathode and an anode prepared by the method described in Example 4.

FIG5 shows the cycling performance of an electrochemical cell comprising a cathode and an anode prepared by the method described in Example 6.

FIG6 shows the cycling performance of an electrochemical cell comprising a cathode and an anode prepared by the method described in Example 8.

DETAILED DESCRIPTION

The present invention provides a method for preparing a battery electrode, comprising the following steps:

1) pretreating an active battery electrode material in a first aqueous solution having a pH of about 2.0 to about 7.5 to form a first suspension;

2) drying the first suspension to obtain a pretreated active battery electrode material;

3) dispersing the pretreated active battery electrode material, conductive agent, and binder material in a second aqueous solution to form a slurry;

4) homogenizing the slurry by a homogenizer to obtain a homogenized slurry;

5) applying the homogenized slurry on a current collector to form a coating film on the current collector; and

6) Drying the coating film on the current collector to form the battery electrode.

The term "electrode" refers to either a "cathode" or an "anode."

The term "positive electrode" is used interchangeably with cathode. Likewise, the term "negative electrode" is used interchangeably with anode.

The term "acid" includes any molecule or ion that donates a hydrogen ion to another substance and/or contains fully or partially replaceable hydrogen ions. Some non-limiting examples of suitable acids include inorganic acids and organic acids. Some non-limiting examples of inorganic acids include hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, boric acid, hydrofluoric acid, hydrobromic acid, perchloric acid, hydroiodic acid, and combinations thereof. Some non-limiting examples of organic acids include acetic acid, lactic acid, oxalic acid, citric acid, uric acid, trifluoroacetic acid, methanesulfonic acid, formic acid, propionic acid, butyric acid, valeric acid, gluconic acid, malic acid, hexanoic acid, and combinations thereof.

The term "acid solution" refers to a solution of a soluble acid having a pH of less than 7.0, less than 6.5, less than 6.0, less than 5.0, less than 4.0, less than 3.0, or less than 2.0. In some embodiments, the pH is greater than 6.0, greater than 5.0, greater than 4.0, greater than 3.0, or greater than 2.0.

The term "pretreatment" as used herein refers to the act of improving or changing the properties of a material, or removing any contaminants in the material by the action of some reagent, or the act of suspending the material in some solvent.

As used herein, the term "dispersion" refers to the act of distributing a chemical species or solid more or less uniformly throughout a fluid.

The term "binder material" refers to a chemical or substance that can be used to hold the active battery electrode material and the conductive agent in place.

The term "homogenizer" refers to a device that can be used to homogenize a material. The term "homogenize" refers to a process of reducing a substance or material to small particles and distributing them evenly throughout a fluid. Any conventional homogenizer can be used in the methods disclosed herein. Some non-limiting examples of homogenizers include agitator mixers, blenders, mills (e.g., colloid mills and sand mills), ultrasonic generators, sprayers, rotor-stator homogenizers, and high-pressure homogenizers.

The term "ultrasonicator" refers to a device that can apply ultrasonic energy to agitate particles in a sample. Any ultrasonicator that can disperse the slurry disclosed herein can be used in the present application. Some non-limiting examples of ultrasonicators include ultrasonic baths, probe-type ultrasonicators, and ultrasonic flow cells.

The term "ultrasonic bath" refers to a device that transmits ultrasonic energy into a liquid sample by means of the walls of the container of the ultrasonic bath.

The term "probe-type ultrasonic generator" refers to an ultrasonic probe immersed in a medium for direct ultrasonic treatment. The term "direct ultrasonic treatment" means that ultrasonic waves are directly incorporated into the treatment liquid.

The term "ultrasonic flow cell" or "ultrasonic reactor chamber" refers to a device by which an ultrasonic treatment method can be performed in a flow-through mode. In some embodiments, the ultrasonic flow cell is a single-pass configuration, a multiple-pass configuration, or a recirculating configuration.

The term "planetary mixer" refers to a device that can be used to blend or mix different materials to produce a homogenous mixture, and includes a single or dual blade with high-speed dispersing blades. The speed can be expressed in revolutions per minute (rpm), which refers to the number of revolutions the rotating body completes in one minute.

As used herein, the term "apply" generally refers to the act of placing or spreading a substance on a surface.

The term "current collector" refers to a support used to coat active battery electrode materials and chemically stable high electron conductors to maintain current flow to the electrodes during discharge or charge of the secondary battery.

The term "room temperature" refers to a room temperature of about 18°C to about 30°C, for example, 18°C, 19°C, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, or 30°C. In some embodiments, room temperature refers to a temperature of about 20°C +/- 1°C, or +/- 2°C, or +/- 3°C. In other embodiments, room temperature refers to a temperature of about 22°C or about 25°C.

The term "C-rate" refers to the rate at which a cell or battery is charged or discharged with respect to its total storage capacity expressed in Ah or mAh. For example, a rate of 1C means that all the stored energy is utilized in one hour; 0.1C means that 10% of the energy is utilized in one hour and the entire energy is utilized in 10 hours; and 5C means that the entire energy is utilized in 12 minutes.

The term "Ah" refers to the unit used to describe a battery's storage capacity. For example, a battery with a 1Ah capacity can provide 1 ampere of current for 1 hour, or 0.5 amperes for two hours, and so on. Thus, 1 Ah is equivalent to 3,600 cubic meters of charge. Similarly, the term "milliampere-hour (mAh)" also refers to the unit used to describe a battery's storage capacity and is 1/1,000 of an Ah.

The term "doctor blading" refers to a method for producing large-area films on rigid or flexible substrates. The coating thickness can be controlled by an adjustable gap width between the coating blade and the coating surface, which allows the deposition of variable wet layer thicknesses.

The term "transfer coating" or "roller coating" refers to a method for producing large-area films on rigid or flexible substrates. The slurry is applied to the substrate by transferring the coating from the surface of a coating roller under pressure. The coating thickness can be controlled by an adjustable gap width between the metering sheet and the surface of the coating roller, which allows the deposition of variable wet layer thicknesses. In a metering roller system, the thickness of the coating is controlled by adjusting the gap between the metering roller and the coating roller.

The term "battery cycle life" refers to the number of complete charge/discharge cycles a battery can perform before its rated capacity decreases to less than 80% of its initial rated capacity.

The term "major component" of a composition refers to a component that comprises greater than 50%, greater than 55%, greater than 60%, greater than 65%, greater than 70%, greater than 75%, greater than 80%, greater than 85%, greater than 90% or greater than 95% by weight or volume, based on the total weight or volume of the composition.

The term "minor component" of a composition refers to a component that comprises less than 50%, less than 45%, less than 40%, less than 35%, less than 30%, less than 25%, less than 20%, less than 15%, less than 10% or less than 5% by weight or volume, based on the total weight or volume of the composition.

As used herein, the term "slower rate" refers to the loss of solvent from the wet solids in the coating film over a longer period of time. In some embodiments, the time required to dry a coating film of a given coating composition at a slower rate is from about 5 minutes to about 20 minutes.

The term "faster drying rate" as used herein refers to the loss of solvent from wet solids in a coating film in a shorter period of time. In some embodiments, the time required to dry a coating film of a given coating composition at a faster drying rate is from about 1 minute to about 5 minutes.

In the following description, the numbers disclosed in this application are approximate values, regardless of whether the word "about" or "approximately" is used in conjunction with them. They can vary by 1%, 2%, 5%, or sometimes 10% to 20%. Whenever a numerical range is disclosed with a lower limit, ^RL , and an upper limit, ^RU, any number falling within that range is specifically disclosed. In particular, the following numbers within the range are specifically disclosed: R = ^RL + k*( ^RU - ^RL ), where k is a variable from 1% to 100% with 1% increments, i.e., k is 1%, 2%, 3%, 4%, 5%, ..., 50%, 51%, 52%, ..., 95%, 96%, 97%, 98%, 99%, or 100%. Furthermore, any numerical range defined by two R values as defined above is also specifically disclosed.

FIG1 illustrates an embodiment of the method disclosed herein, wherein a first suspension is prepared by pre-treating an active battery electrode material in a first aqueous solution having a pH value of from about 2.0 to about 7.5 to form a first suspension. The first suspension is then dried to obtain the pre-treated active battery electrode material. A slurry is prepared by mixing the pre-treated active battery electrode material, a conductive agent, and a binder material in a second aqueous solution. Other components may be added. The slurry is then homogenized by passing through a homogenizer to obtain a homogenized slurry. A current collector is coated with the homogenized slurry, and the coated current collector is then dried to form a battery electrode.

In some embodiments, the first suspension is prepared by pre-treating the active battery electrode material in a first aqueous solution having a pH of about 2.0 to about 7.5.

The present application can use any temperature that can pretreat the active battery electrode material. In some embodiments, at about 14 ° C, about 16 ° C, about 18 ° C, about 20 ° C, about 22 ° C, about 24 ° C or about 26 ° C, the active battery electrode material can be added to the stirred first aqueous solution. In some embodiments, the pretreatment method can be performed by heating at a temperature of about 30 ° C to about 80 ° C, about 35 ° C to about 80 ° C, about 40 ° C to about 80 ° C, about 45 ° C to about 80 ° C, about 50 ° C to about 80 ° C, about 55 ° C to about 80 ° C, about 55 ° C to about 70 ° C, about 45 ° C to about 85 ° C, or about 45 ° C to about 90 ° C. In some embodiments, the pretreatment method can be performed at a temperature below 30 ° C, below 25 ° C, below 22 ° C, below 20 ° C, below 15 ° C or below 10 ° C.

In some embodiments, the active battery electrode material is a cathode material, wherein the cathode material is selected from _the group consisting _{of LiCO2} , LiNiO2, _LiNiXMnYO2 , Lil _{+ zNiXMnYCo1 - xyO2} , _{LiNiXCoYAlZO2 , LiV2O5} , _LiTiS2 , _LiMoS2 , _LiMnO2 , _LiCrO2 , _LiMn2O4 , _LiFeO2 , _{LiFePO4 , and} combinations _thereof , _wherein each x is independently 0.3 to 0.8 _; each y is independently 0.1 to 0.45; and each _z is independently 0 to 0.2. In some embodiments, the cathode material is selected from _the group consisting of _LiCO2 , _{LiNiO2 , LiNixMnyO2} , _{Li1 + zNixMnyCo1} - _xyO2 , _{LiNixCoyAlzO2, LiV2O5, LiTiS2 , LiMoS2 , LiMnO2} , _LiCrO2 , _LiMn2O4 , _LiFeO2 , _LiFePO4 , _and combinations thereof, wherein _each x is independently 0.4 _to 0.6; each y _is independently 0.2 to _0.4 ; and each _z is independently 0 to 0.1. In other embodiments, the cathode material is not LiCO ₂ , LiNiO ₂ , LiV ₂ O ₅ , LiTiS ₂ , LiMoS ₂ , LiMnO ₂ , LiCrO ₂ , LiM _{n 2} O ₄ , LiFeO ₂ , or LiFePO ₄ . In further embodiments, the cathode material is not LiNi _x Mn _y O ₂ , Li _1+z Ni _x Mn _y Co _1-xy O ₂ , or LiNi _x Co _oy Al _z O ₂ , wherein each x is independently 0.3 to 0.8; each y is independently 0.1 to 0.45; and each z is independently 0 to 0.2.

In some embodiments, the first aqueous solution is a solution containing water as a main component and a volatile solvent (e.g., alcohol, lower aliphatic ketone, lower alkyl acetate, etc.) other than water as a minor component. In some embodiments, the amount of water is at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, or at least 95% of the total amount of water and solvents other than water. In some embodiments, the amount of water is at most 55%, at most 60%, at most 65%, at most 70%, at most 75%, at most 80%, at most 85%, at most 90%, or at most 95% of the total amount of water and solvents other than water. In some embodiments, the first aqueous solution includes only water, that is, the proportion of water in the first aqueous solution is 100% by volume.

Any water-miscible solvent can be used as a secondary component. Some non-limiting examples of secondary components (i.e., solvents other than water) include alcohols, lower aliphatic ketones, lower alkyl acetates, and combinations thereof. Some non-limiting examples of alcohols include _C2 - _C4 alcohols, such as methanol, ethanol, isopropanol, n-propanol, butanol, and combinations thereof. Some non-limiting examples of lower aliphatic ketones include acetone, dimethyl ketone, and methyl ethyl ketone. Some non-limiting examples of lower alkyl acetates include ethyl acetate, isopropyl acetate, and propyl acetate.

In some embodiments, the volatile solvent or secondary component is methyl ethyl ketone, ethanol, ethyl acetate, or a combination thereof.

In some embodiments, the first aqueous solution is a mixture of water and one or more water-miscible secondary components. In some embodiments, the first aqueous solution is a mixture of water and a secondary component selected from ethanol, isopropanol, n-propanol, t-butanol, n-butanol, and combinations thereof. In some embodiments, the volume ratio of water to the secondary component is from about 51:49 to about 100:1.

In some embodiments, the first aqueous solution is water. Some non-limiting examples of water include tap water, bottled water, purified water, pure water, distilled water, deionized water, _D2O , or combinations thereof. In some embodiments, the first aqueous solution is deionized water. In some embodiments, the first aqueous solution does not contain alcohol, aliphatic ketone, alkyl acetate, or combinations thereof.

In some embodiments, the first aqueous solution is acidic, slightly alkaline, or neutral and has any pH value within the range of about 2.0 to about 8.0. In some embodiments, the pH value of the first aqueous solution is about 2.0 to about 7.5, about 3.0 to about 7.5, about 4.0 to about 7.5, about 4.0 to about 7.0, about 5.0 to about 7.5, about 6.0 to about 7.5, about 6.0 to about 7.0. In some embodiments, the pH value of the first aqueous solution is about 7.0, about 6.5, about 6.0, about 5.5, about 5.0, or about 4.0. In other embodiments, the pH value of the first aqueous solution is about 2 to about 7, about 2 to about 6, about 2 to about 5, or about 2 to about 4. In some embodiments, the pH value of the first aqueous solution is less than about 7, less than about 6, less than about 5, less than about 4, or less than about 3.

In some embodiments, the first aqueous solution includes one or more acids selected from the group consisting of inorganic acids, organic acids, and combinations thereof.

In some embodiments, the acid is a mixture of one or more inorganic acids and one or more organic acids, wherein the weight ratio of the one or more inorganic acids to the one or more organic acids is from about 10/1 to about 1/10, from about 8/1 to about 1/8, from about 6/1 to about 1/6, or from about 4/1 to about 1/4.

In some embodiments, the one or more inorganic acids are selected from the group consisting of hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, boric acid, hydrofluoric acid, hydrobromic acid, perchloric acid, hydroiodic acid, and combinations thereof. In other embodiments, the one or more inorganic acids are sulfuric acid, hydrochloric acid, hydrobromic acid, nitric acid, phosphoric acid, and combinations thereof. In another embodiment, the inorganic acid is hydrochloric acid. In some embodiments, the acid does not contain inorganic acids such as hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, boric acid, hydrofluoric acid, hydrobromic acid, perchloric acid, or hydroiodic acid.

In some embodiments, the one or more organic acids are selected from the group consisting of acetic acid, lactic acid, oxalic acid, citric acid, uric acid, trifluoroacetic acid, methanesulfonic acid, formic acid, propionic acid, butyric acid, valeric acid, gluconic acid, malic acid, caproic acid, and combinations thereof. In another embodiment, the one or more organic acids are formic acid, acetic acid, propionic acid, and combinations thereof. In another embodiment, the organic acid is acetic acid. In some embodiments, the acid does not contain organic acids such as acetic acid, lactic acid, oxalic acid, citric acid, uric acid, trifluoroacetic acid, methanesulfonic acid, formic acid, propionic acid, butyric acid, valeric acid, gluconic acid, malic acid, or caproic acid.

During the addition of the active battery electrode material, the pH of the first aqueous solution is maintained in the range of about 4.0 to about 7.5 by adding one or more acids as pH adjusting agents. The choice of pH adjusting agent is not critical. Any suitable organic acid or inorganic acid can be used. In some embodiments, the pH adjusting agent is an acid selected from the group consisting of an inorganic acid, an organic acid, and a combination thereof. The pH can be monitored by a pH measuring device (e.g., a pH sensor). In some embodiments, more than one pH sensor is used to monitor the pH value.

In some embodiments, after the active battery electrode material is added to the first aqueous solution, the mixture can be further stirred for a period of time sufficient to form a first suspension, In some embodiments, the period of time is from about 5 minutes to about 2 hours, from about 5 minutes to about 1.5 hours, from about 5 minutes to about 1 hour, from about 5 minutes to about 30 minutes, from about 5 minutes to about 15 minutes, from about 10 minutes to about 2 hours, from about 10 minutes to about 1.5 hours, from about 10 minutes to about 1 hour, from about 10 minutes to about 30 minutes, from about 15 minutes to about 1 hour, or from about 30 minutes to about 1 hour.

In some embodiments, the active battery electrode material is an anode material, wherein the anode material is selected from the group consisting of natural graphite particles, synthetic graphite particles, Sn (tin) particles, Li ₄ Ti ₅ O ₁₂ particles, Si (silicon) particles, Si-C composite particles, and combinations thereof.

In some embodiments, the first suspension can be dried to obtain the pretreated active battery electrode material. Any dryer capable of drying a suspension can be used herein. In some embodiments, the drying process is performed using a double cone vacuum dryer, a microwave dryer, or a microwave vacuum dryer.

In some embodiments, the dryer is a microwave dryer or a microwave vacuum dryer. In some embodiments, the microwave dryer or the microwave vacuum dryer operates at a power of about 500W to about 3kW, about 5kW to about 15kW, about 6kW to about 20kW, about 7kW to about 20kW, about 15kW to about 70kW, about 20kW to about 90kW, about 30kW to about 100kW, or about 50kW to about 100kW.

In some embodiments, the drying step can be performed for a period of time sufficient to dry the first suspension. In some embodiments, the drying time is from about 3 minutes to about 2 hours, from about 5 minutes to about 2 hours, from about 10 minutes to about 3 hours, from about 10 minutes to about 4 hours, from about 15 minutes to about 4 hours, or from about 20 minutes to about 5 hours.

After forming the pretreated active battery electrode material by drying the first suspension, a slurry may be formed by dispersing the pretreated active battery electrode material, a conductive agent, and a binder material in a second aqueous solution.

In some embodiments, the amount of pretreated active battery electrode material used is at least 1%, at least 2%, at least 3%, at least 4%, at least 5%, at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90% or at least 95% by weight or by volume based on the total weight or total volume of the slurry. In some embodiments, the amount of pretreated active battery electrode material used is at most 1%, at most 2%, at most 3%, at most 4%, at most 5%, at most 10%, at most 15%, at most 20%, at most 25%, at most 30%, at most 35%, at most 40%, at most 45%, at most 50%, at most 55%, at most 60%, at most 65%, at most 70%, at most 75%, at most 80%, at most 85%, at most 90% or at most 95% by weight or by volume based on the total weight or total volume of the slurry.

In some embodiments, the pretreated active battery electrode material is a major component of the slurry. In some embodiments, the pretreated active battery electrode material is present in an amount of about 50% to about 95% by weight or by volume, about 55% to about 95% by weight or by volume, about 60% to about 95% by weight or by volume, about 65% to about 95% by weight or by volume, about 70% to about 95% by weight or by volume, about 75% to about 95% by weight or by volume, based on the total weight or volume of the slurry. , about 80% to about 95% by weight or by volume, about 85% to about 95% by weight or by volume, about 55% to about 85% by weight or by volume, about 60% to about 85% by weight or by volume, about 65% to about 85% by weight or by volume, about 70% to about 85%, about 65% to about 80% by weight or by volume, or about 70% to about 80% by weight or by volume.

The conductive agent in the slurry is used to increase the conductivity of the electrode. In some embodiments, the conductive agent is selected from the group consisting of carbon, carbon black, graphite, expanded graphite, graphene, graphene nanosheets, carbon fibers, carbon nanofibers, graphitized carbon sheets, carbon tubes, carbon nanotubes, activated carbon, mesoporous carbon, and combinations thereof. In some embodiments, the conductive agent is not carbon, carbon black, graphite, expanded graphite, graphene, graphene nanosheets, carbon fibers, carbon nanofibers, graphitized carbon sheets, carbon tubes, carbon nanotubes, activated carbon, or mesoporous carbon.

The binder material in the slurry serves to bond the active battery electrode material and the conductive agent together to the current collector. In some embodiments, the binder material is selected from the group consisting of styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), acrylonitrile copolymer, polyacrylic acid (PAA), polyacrylonitrile, polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), latex, alginate, and combinations thereof. In some embodiments, the alginate includes a cation selected from Na, Li, K, Ca, NH ₄ , Mg, Al, or combinations thereof.

In some embodiments, binder material is SBR, CMC, PAA, alginate or its combination.In some embodiments, binder material is acrylonitrile copolymer.In some embodiments, binder material is polyacrylonitrile.In some embodiments, binder material does not contain styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), acrylonitrile copolymer, polyacrylic acid (PAA), polyacrylonitrile, polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), latex or alginate.

In some embodiments, the amount of each of the conductive agent and the binder material is independently at least 1%, at least 2%, at least 3%, at least 4%, at least 5%, at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, or at least 50% by weight or volume based on the total weight or volume of the slurry. In some embodiments, the amount of each of the conductive agent and the binder material is independently at most 1%, at most 2%, at most 3%, at most 4%, at most 5%, at most 10%, at most 15%, at most 20%, at most 25%, at most 30%, at most 35%, at most 40%, at most 45%, or at most 50% by weight or volume based on the total weight or volume of the slurry.

In some embodiments, prior to step 3), the conductive agent is pretreated in an alkaline solution or an alkaline solution. Pretreating the conductive agent before preparing the slurry can increase wettability and the dispersibility of the conductive agent in the slurry, thereby allowing for uniform distribution of the conductive agent within the dried composite electrode. If the conductive agent particles are unevenly dispersed in the electrode, it will affect battery performance, lifespan, and safety.

In some embodiments, the conductive agent may be pretreated for a period of about 30 minutes to about 2 hours, about 30 minutes to about 1.5 hours, about 30 minutes to about 1 hour, about 45 minutes to about 2 hours, about 45 minutes to about 1.5 hours, or about 45 minutes to about 1 hour. In some embodiments, the alkaline solution or alkaline solution comprises a base selected from _the group consisting of _H2O2 , _LiOH , NaOH, KOH, _NH3 · _H2O , Be(OH) ₂ , Mg(OH) ₂ , Ca(OH) ₂ , _Li2CO3 , _{Na2CO3 , NaHCO3 , K2CO3 , KHCO3} , and combinations thereof. In some embodiments, the alkaline solution comprises an organic base. In some embodiments, the alkaline solution does not contain an organic base. In some embodiments, the solution _of base does not contain _H2O2 , LiOH, NaOH, KOH, _NH3 - _H2O , Be(OH) ₂ , Mg(OH) ₂ , Ca ₍ OH) ₂ , _Li2CO3 , _Na2CO3 , _NaHCO3 , _{K2CO3 ,} or _{KHCO3 .}

In some embodiments, the pH of the alkaline solution or alkaline solution is greater than 7, greater than 8, greater than 9, greater than 10, greater than 11, greater than 12, or greater than 13. In some embodiments, the pH of the alkaline solution or alkaline solution is less than 8, less than 9, less than 10, less than 11, less than 12, or less than 13.

In some embodiments, before step 3), a conductive agent is dispersed in the third aqueous solution to form a second suspension.

Conductive agents have a higher specific surface area than active battery electrode materials. Therefore, particularly when conductive agent particles must be dispersed in a highly concentrated suspension of active battery electrode materials, the conductive agent has a tendency to agglomerate due to its higher specific surface area. Dispersing the conductive agent before preparing the slurry can minimize agglomeration of the particles, thereby allowing for a more uniform distribution of the conductive agent within the dried composite electrode. This can reduce internal resistance and enhance the electrochemical performance of the electrode material.

In some embodiments, the amount of the conductive agent in the second suspension is about 0.05 wt.% (weight percent) to about 0.5 wt.%, about 0.1 wt.% to about 1 wt.%, about 0.25 wt.% to about 2.5 wt.%, about 0.5 wt.% to about 5 wt.%, about 2 wt.% to about 5 wt.%, about 3 wt.% to about 7 wt.%, or about 5 wt.% to about 10 wt.%, based on the total weight of the mixture of the conductive agent and the third aqueous solution.

In some embodiments, prior to step 3), a binder material is dissolved in the fourth aqueous solution to form a resulting solution or a binder solution.

Dispersing the solid binder material before preparing the slurry can prevent the solid binder material from adhering to the surface of other materials, thereby allowing the binder material to be evenly dispersed in the slurry. If the binder material is not evenly dispersed in the electrode, the performance of the battery may be reduced.

In some embodiments, the amount of binder material in the binder solution is about 3 wt.% to about 6 wt.%, about 5 wt.% to about 10 wt.%, about 7.5 wt.% to about 15 wt.%, about 10 wt.% to about 20 wt.%, about 15 wt.% to about 25 wt.%, about 20 wt.% to about 40 wt.%, or about 35 wt.% to about 50 wt.%, based on the total weight of the mixture of the binder material and the fourth aqueous solution.

In some embodiments, each of the second aqueous solution, the third aqueous solution, and the fourth aqueous solution is independently a solution containing water as a major component and a volatile solvent other than water, such as an alcohol, a lower aliphatic ketone, a lower alkyl acetate, etc., as a minor component. In some embodiments, the amount of water in each solution is independently at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, or at least 95% of the total amount of water and solvents other than water. In some embodiments, the amount of water is at most 55%, at most 60%, at most 65%, at most 70%, at most 75%, at most 80%, at most 85%, at most 90%, or at most 95% of the total amount of water and solvents other than water. In some embodiments, each of the second aqueous solution, the third aqueous solution, and the fourth aqueous solution is independently composed only of water, i.e., the proportion of water in each solution is 100 vol.%.

Any water-miscible solvent can be used as a secondary component of the second aqueous solution, the third aqueous solution, and the fourth aqueous solution. Some non-limiting examples of secondary components include alcohols, lower aliphatic ketones, lower alkyl acetates, and combinations thereof. Some non-limiting examples of alcohols include _C2 - _C4 alcohols, such as methanol, ethanol, isopropanol, n-propanol, butanol, and combinations thereof. Some non-limiting examples of lower aliphatic ketones include acetone, dimethyl ketone, and methyl ethyl ketone. Some non-limiting examples of lower alkyl acetates include ethyl acetate, isopropyl acetate, and propyl acetate.

In some embodiments, the volatile solvent or secondary component is methyl ethyl ketone, ethanol, ethyl acetate, or a combination thereof.

In some embodiments, the composition of the slurry does not require an organic solvent. In some embodiments, each of the second aqueous solution, the third aqueous solution, and the fourth aqueous solution is independently water. Some non-limiting examples of water include tap water, bottled water, purified water, pure water, distilled water, deionized water, D ₂ O, or a combination thereof. In some embodiments, each of the second aqueous solution, the third aqueous solution, and the fourth aqueous solution is independently purified water, pure water, deionized water, distilled water, or a combination thereof. In some embodiments, each of the second aqueous solution, the third aqueous solution, and the fourth aqueous solution does not contain an organic solvent such as an alcohol, a lower aliphatic ketone, or a lower alkyl acetate. Since the composition of the slurry does not contain any organic solvent, expensive, restricted, and complicated organic solvent processing is avoided during the manufacture of the slurry.

The present application can use any temperature that can be used to form a slurry in the dispersion step. In some embodiments, the pretreated active battery electrode material, conductive agent, and binder material are added to the stirred second aqueous solution at about 14°C, about 16°C, about 18°C, about 20°C, about 22°C, about 24°C, or about 26°C. In some embodiments, the dispersion process can be performed by heating at a temperature of about 30°C to about 80°C, about 35°C to about 80°C, about 40°C to about 80°C, about 45°C to about 80°C, about 50°C to about 80°C, about 55°C to about 80°C, about 55°C to about 70°C, about 45°C to about 85°C, or about 45°C to about 90°C. In some embodiments, the dispersion process can be performed at a temperature below 30°C, below 25°C, below 22°C, below 20°C, below 15°C, or below 10°C.

Optional components can be used to aid in dispersing the pretreated active battery electrode material, conductive agent, and binder material into the slurry. In some embodiments, the optional component is a dispersant. Any dispersant that can enhance dispersion can be added to the slurries disclosed herein. In some embodiments, the dispersant is selected from the group consisting of ethanol, isopropyl alcohol, n-propyl alcohol, tert-butyl alcohol, n-butyl alcohol, lithium lauryl sulfate, trimethylhexadecyl ammonium chloride, polyethylene ethoxylate, sodium dodecylbenzene sulfonate, sodium stearate, and combinations thereof.

In some embodiments, the total amount of dispersant is from about 0.1% to about 10%, from about 0.1% to about 8%, from about 0.1% to about 6%, from about 0.1% to about 5%, from about 0.1% to about 4%, from about 0.1% to about 3%, from about 0.1% to about 2%, or from about 0.1% to about 1% by weight based on the total weight of the slurry.

In some embodiments, each of the second aqueous solution, the third aqueous solution, and the fourth aqueous solution independently includes a dispersant for promoting dispersion of particles and/or preventing aggregation of particles. Any surfactant that can reduce the surface tension between a liquid and a solid can be used as a dispersant.

In some embodiments, the dispersant is a nonionic surfactant, an anionic surfactant, a cationic surfactant, an amphoteric surfactant, or a combination thereof.

Some non-limiting examples of suitable non-ionic surfactants include alkoxylated alcohols, carboxylic acid esters, polyethylene glycol esters, and combinations thereof. Some non-limiting examples of suitable alkoxylated alcohols include ethoxylated alcohols and propoxylated alcohols. In some embodiments, the slurry disclosed herein does not contain a non-ionic surfactant.

Some non-limiting examples of suitable anionic surfactants include salts of alkyl sulfates, alkyl polyethoxylated ether sulfates, alkylbenzene sulfonates, alkyl ether sulfates, sulfonates, sulfosuccinates, sarcosinates, and combinations thereof. In some embodiments, the anionic surfactant comprises a cation selected from the group consisting of sodium, potassium, ammonium, and combinations thereof. In some embodiments, the slurries disclosed herein do not contain anionic surfactants.

Some non-limiting examples of suitable cationic surfactants include ammonium salts, phosphonium salts, imidazolium salts, sulfonium salts, and combinations thereof. Some non-limiting examples of suitable ammonium salts include stearyl trimethylammonium bromide (STAB), cetyl trimethylammonium bromide (CTAB), and myristyl trimethylammonium bromide (MTAB), and combinations thereof. In some embodiments, the slurry disclosed herein does not contain a cationic surfactant.

Some non-limiting examples of suitable amphoteric surfactants are surfactants containing both cationic groups and anionic groups. The cationic group is ammonium, phosphonium, imidazole, sulfonium, or a combination thereof. The anionic hydrophilic group is carboxylate, sulfonate, sulfate, phosphate, or a combination thereof. In some embodiments, the slurry disclosed herein does not contain an amphoteric surfactant.

The slurry can be homogenized by a homogenizer. Any device that can homogenize the slurry can be used. In some embodiments, the homogenizer is a stirring mixer, a blender, a mill, an ultrasonic generator, a rotor-stator homogenizer, a sprayer, or a high-pressure homogenizer.

In some embodiments, the homogenizer is an ultrasonic generator. Any ultrasonic generator that can apply ultrasonic energy to stir and disperse the particles in the sample can be used in this application. In some embodiments, the ultrasonic generator is a probe type ultrasonic generator or an ultrasonic flow cell.

In some embodiments, the ultrasonic flow cell can be operated in a single pass, multipass or recirculation mode. In some embodiments, the ultrasonic flow cell can include a water cooling jacket to assist in maintaining the desired temperature. Alternatively, a separate heat exchanger can be used. In some embodiments, the flow cell can be made of stainless steel or glass.

In some embodiments, the slurry is homogenized for a period of about 1 hour to about 10 hours, about 2 hours to about 4 hours, about 15 minutes to about 4 hours, about 30 minutes to about 4 hours, about 1 hour to about 4 hours, about 2 hours to about 5 hours, about 3 hours to about 5 hours, or about 2 hours to about 6 hours.

In some embodiments, the ultrasonic generator is operated at a power density of about 10 W/L to about 100 W/L, about 20 W/L to about 100 W/L, about 30 W/L to about 100 W/L, about 40 W/L to about 80 W/L, about 40 W/L to about 70 W/L, about 40 W/L to about 50 W/L, about 40 W/L to about 60 W/L, about 50 W/L to about 60 W/L, about 20 W/L to about 80 W/L, about 20 W/L to about 60 W/L, or about 20 W/L to about 40 W/L.

Continuous flow through the system has several advantages over batch-type processing. Through ultrasonic processing with the aid of an ultrasonic flow cell, the processing capacity becomes significantly higher. The retention time of the material in the flow cell can be adjusted by adjusting the flow rate.

With recirculation mode sonication, the material is recirculated multiple times through the flow cell in a recirculation configuration. Recirculation increases the cumulative exposure time because the liquid only passes through the sonication flow cell once in a single-pass configuration.

The multi-pass mode has a multi-flow cell configuration. This arrangement allows single-pass processing without recirculation or multiple passes through the system. This arrangement provides an additional productivity scaling factor equal to the number of flow cells utilized.

The homogenization step disclosed herein reduces or eliminates potential aggregation of active battery electrode materials and conductive agents and improves dispersion of the various components in the slurry.

The homogenized slurry can be applied to a current collector to form a coating on the current collector. The current collector serves to collect the electrons generated by the electrochemical reaction of the active battery electrode material or to provide the electrons required for the electrochemical reaction. In some embodiments, each current collector of the positive and negative electrodes, which can be in the form of foil, plate, or film, is independently stainless steel, titanium, nickel, aluminum, copper, or a conductive resin. In some embodiments, the current collector of the positive electrode is an aluminum thin film. In some embodiments, the current collector of the negative electrode is a copper thin film.

In some embodiments, the current collector has a thickness of about 6 μm to about 100 μm, as the thickness will affect the volume occupied by the current collector within the battery and the amount of active battery electrode material, and thus the capacity of the battery.

In some embodiments, the coating process is performed using a knife coater, a slot die coater, a transfer coater, or a spray coater, a roll coater, a gravure coater, a dip coater, or a curtain coater. In some embodiments, the thickness of the coating film on the current collector is about 10 μm to about 300 μm, or about 20 μm to about 100 μm.

After applying the homogenized slurry to the current collector, the coating film on the current collector can be dried by a dryer to obtain a battery electrode. Any dryer that can dry the coating film on the current collector can be used in this application. Some non-limiting examples of dryers are batch drying ovens, conveyor belt drying ovens, and microwave drying ovens. Some non-limiting examples of conveyor belt drying ovens include conveyor belt hot air drying ovens, conveyor belt resistance drying ovens, conveyor belt induction drying ovens, and conveyor belt microwave drying ovens.

In some embodiments, a conveyor-type drying oven for drying a coating film on a current collector includes one or more heating sections, wherein each heating section is individually temperature controlled, and wherein each heating section can independently include a controlled heating zone.

In some embodiments, a conveyor drying oven includes a first heating section located on one side of a conveyor belt and a second heating section located on an opposite side of the conveyor belt from the first heating section, wherein each of the first heating section and the second heating section independently includes one or more heating elements and a temperature control system connected to the heating elements of the first heating section and the heating elements of the second heating section in a manner that monitors and selectively controls the temperature of the respective heating sections.

In some embodiments, a conveyor oven includes a plurality of heating sections, wherein each heating section includes an independent heating element operated to maintain a constant temperature within the heating section.

In some embodiments, each of the first heating section and the second heating section independently has an inlet heating zone and an outlet heating zone, wherein the inlet heating zone and the outlet heating zone each independently include one or more heating elements and a temperature control system, which is connected to the heating elements of the inlet heating zone and the heating elements of the outlet heating zone in a manner to monitor and selectively control the temperature of each heating zone separately from the temperature control of other heating zones.

In some embodiments, the coating on the current collector can be dried at a temperature of about 50°C to about 80°C. This temperature range means a controlled temperature gradient, wherein the temperature is gradually increased from an inlet temperature of 50°C to an outlet temperature of 80°C. The controlled temperature gradient avoids the coating on the current collector from drying too quickly. Drying the coating too quickly can degrade the materials in the slurry. Drying the coating too quickly can also lead to stress defects in the electrode because the solvent can be removed from the coating faster than the film can relax or adjust to the resulting volume change, which can lead to defects such as cracks. It is believed that avoiding this defect can generally improve the performance of the electrode. Also, drying the coating too quickly can lead to migration of the binder material and the formation of a layer of binder material on the surface of the electrode.

In some embodiments, the coating film on the current collector is dried at a slower rate. In some embodiments, the coating film on the current collector is dried at a slower rate at a constant rate and then dried at a faster drying rate.

In some embodiments, the coating film on the current collector may be dried at a temperature of about 45°C to about 100°C, about 50°C to about 100°C, about 55°C to about 100°C, about 50°C to about 90°C, about 55°C to about 80°C, about 55°C to about 75°C, about 55°C to about 70°C, about 50°C to about 80°C, or about 50°C to about 70°C.

In some embodiments, the conveyor moves at a speed of about 2 m/min to about 30 m/min, about 2 m/min to about 25 m/min, about 2 m/min to about 20 m/min, about 2 m/min to about 16 m/min, about 3 m/min to about 30 m/min, about 3 m/min to about 20 m/min, or about 3 m/min to about 16 m/min.

Controlling conveyor belt length and speed can regulate the drying time of film.Therefore, without increasing the length of conveyor belt, drying time can be increased.In some embodiments, the film on current collector can be dried for a period of about 1 minute to about 30 minutes, about 1 minute to about 25 minutes, about 1 minute to about 20 minutes, about 1 minute to about 15 minutes, about 1 minute to about 10 minutes, about 2 minutes to about 15 minutes or about 2 minutes to about 10 minutes.

After the coating on the current collector is dried, a battery electrode is formed. In some embodiments, the battery electrode is mechanically compressed to increase the density of the electrode.

The advantages of the method disclosed in the present application are that an aqueous solvent is used in the manufacturing process, which can save process time and facilities by avoiding the need to handle or recycle dangerous organic solvents. In addition, by simplifying the overall process, costs are reduced. Therefore, the method is particularly suitable for industrial processes due to its low cost and ease of handling.

The following examples are provided to illustrate embodiments of the present invention, which are not intended to limit the present invention to the specific embodiments listed. Unless otherwise indicated, all parts and percentages are by weight. All numerical values are approximate. When providing numerical ranges, it should be understood that the embodiments outside the stated ranges still fall within the scope of the present invention. The specific details described in each embodiment should not be understood as essential features of the present invention.

Example

Example 1

A) Pretreatment of Active Battery Electrode Materials

Particulate cathode material _{LiNi0.33Mn0.33Co0.33O2} (from Xiamen _Tungsten Co., Ltd., China) was added to _a stirred solution containing 50% deionized water and 50% ethanol at room temperature to form a suspension with a solid content of approximately 35% by weight. _The pH of the suspension was measured using a pH meter and was approximately 7. The suspension was further stirred at room temperature for 5 hours. The suspension was then separated and dried in a 2.45 GHz microwave dryer (ZY-4HO, from Zhiya Industrial Microwave Equipment Co., Ltd., Guangdong, China) at 750 W for 5 minutes to obtain a pretreated active battery electrode material.

B) Preparation of positive electrode slurry

The positive electrode slurry was prepared by mixing 91 wt.% of the pretreated active battery electrode material, 4 wt.% of carbon black (SuperP; Timcal Ltd, Bodio, Switzerland), 4 wt.% of polyacrylonitrile (LA 132, Chengdu Yindi Le Power Technology Co., Ltd., China), and 1% of isopropyl alcohol (from Aladdin Industrial Co., Ltd., China) in deionized water to form a slurry with a solid content of 70 wt.%. The slurry was homogenized for 6 hours by a planetary stirring mixer (200 L mixer, Chienemei Industrial Co., Ltd., China) operating at a stirring speed of 20 rpm and a dispersion speed of 1500 rpm to obtain a homogenized slurry.

C) Preparation of positive electrode

The homogenized slurry was coated on both sides of a 20 μm thick aluminum foil using a transfer coater (ZY-TSF6-6518, Jinfan Zhanyu New Energy Technology Co., Ltd., China) with an areal density of approximately 26 mg/ ^cm² . The coating on the foil was dried for 3 minutes in a 24-meter-long conveyor-type hot air drying oven, a submodule of the transfer coater, operating at a conveyor speed of approximately 8 m/min, to produce the positive electrode. The temperature-controlled oven allowed for a controlled temperature gradient, gradually increasing from an inlet temperature of 55°C to an outlet temperature of 80°C.

D) Preparation of negative electrode

A negative electrode slurry was prepared by mixing 90 wt.% hard carbon (HC; 99.5% purity, Ruifute Technology Co., Ltd., Shenzhen, Guangdong, China), 5 wt.% carbon black, and 5 wt.% polyacrylonitrile in deionized water to form a slurry with a solid content of 50 wt.%. This slurry was coated on both sides of a copper foil having a thickness of 9 μm using a transfer coater, with an areal density of approximately 15 mg/cm ² . The coating on the copper foil was dried at approximately 50°C for 2.4 minutes in a 24-meter-long conveyor-type hot air drying oven operating at a conveyor speed of approximately 10 m/min to obtain a negative electrode.

Morphological measurement of Example 1

Figure 2 shows an SEM image of the surface morphology of the coated cathode electrode after drying. The morphology of the coated cathode electrode was characterized by scanning electron microscopy (JEOL-6300, from JEOL Co., Ltd., Japan). The SEM image clearly shows a uniform, crack-free and stable coating over the entire electrode surface. In addition, the electrode shows a uniform distribution of pretreated active battery electrode materials and conductive agents without large agglomerates.

Example 2

Assembly of pouch cells

After drying, the cathode film and anode film of Example 1 obtained are used to prepare cathodes and anodes respectively by cutting into separate electrode plates. The pouch-type battery is assembled by alternately stacking cathode electrode sheets and anode electrode sheets and then encapsulating them in a container (case) made of an aluminum-plastic laminated film. The cathode electrode plate and the anode electrode plate are kept separate by a diaphragm and the container is preformed. The electrolyte is then filled into a container containing the packaged electrodes under a high-purity argon atmosphere with a humidity and oxygen content of less than 1ppm. The electrolyte is a solution (1M) of LiPF6 in a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) in a volume ratio of ₁ :1:1. After the electrolyte is filled, the pouch-type battery is vacuum sealed and then mechanically pressed using a punching tool with a standard square.

Electrochemical measurements of Example 2

I) Rated capacity

The battery was tested galvanostatically on a battery tester (BTS-5V20A, from Neware Electronics Co., Ltd., China) at 25° C. and a current density of C/2 with a voltage between 3.0 V and 4.3 V. The rated capacity was about 10 Ah.

II) Cycle performance

The cycling performance of the pouch-type batteries was tested by charging and discharging between 3.0 V and 4.3 V at a constant current rate of 1 C. The cycling performance test results are shown in Figure 3. The capacity retention after 450 cycles was approximately 95.6% of the initial value. This excellent cycling performance indicates that batteries made with cathode and anode electrodes prepared by the method disclosed herein can achieve comparable or even better stability than batteries made with cathode and anode electrodes prepared by conventional methods involving the use of organic solvents.

Example 3

A) Pretreatment of Active Battery Electrode Materials

Particulate cathode material _LiMn2O4 (from HuaGuan HengYuan LiTech Co., Ltd. _, Qingdao, China) was added to a stirred 7 wt.% aqueous solution of acetic acid (from Aladdin Industries, China) at room temperature to form a suspension having a solid content of approximately 50% by weight. The pH of the suspension was measured using a pH meter and was approximately 6. The suspension was further stirred at room temperature for 2.5 hours. The suspension was then separated and dried in a 2.45 GHz microwave dryer at 750 W for 5 minutes to obtain a pretreated active battery electrode material.

B) Preparation of positive electrode slurry

Carbon nanotubes (NTP2003; Shenzhen Nanotech Port Co., Ltd., China) (25 g) were pretreated in 2 L of an alkaline solution containing 0.5 wt.% NaOH for about 15 minutes and then washed with deionized water (5 L). The treated carbon nanotubes were then dispersed in deionized water to form a suspension having a solid content of 6.25 wt.%.

The positive electrode slurry was prepared by mixing 92 wt.% of the pretreated active battery electrode material, 3 wt.% of carbon black, 1 wt.% of a suspension of treated carbon nanotubes, and 4 wt.% of polyacrylonitrile in deionized water to form a slurry with a solid content of 65 wt.%. The slurry was homogenized for 8 hours using a circulating ultrasonic flow cell (NP8000, from Guangzhou Xindongli Ultrasonic Electronic Equipment Co., Ltd., China) operating at 1000 W to obtain a homogenized slurry.

C) Preparation of positive electrode

The homogenized slurry was coated on both sides of a 20 μm thick aluminum foil using a transfer coater, with an areal density of approximately 40 mg/ ^cm² . The coating on the aluminum foil was dried for 6 minutes in a 24-meter-long conveyor-type hot air drying oven, a submodule of the transfer coater, operating at a conveyor speed of approximately 4 m/min, to produce the positive electrode. The programmable temperature oven allowed for a controlled temperature gradient, gradually increasing the temperature from an inlet temperature of 65°C to an outlet temperature of 90°C.

D) Preparation of negative electrode

A negative electrode slurry was prepared by mixing 90 wt.% hard carbon (HC; 99.5% purity, Ruifute Technology Co., Ltd., Shenzhen, Guangdong, China), 5 wt.% carbon black, and 5 wt.% polyacrylonitrile in deionized water to form a slurry with a solid content of 50 wt.%. This slurry was coated on both sides of a copper foil having a thickness of 9 μm using a transfer coater, with an areal density of approximately 15 mg/cm ² . The coating on the copper foil was dried at approximately 50°C for 2.4 minutes in a 24-meter-long conveyor-type hot air drying oven operating at a conveyor speed of approximately 10 m/min to obtain a negative electrode.

Example 4

Assembly of pouch cells

After drying, the cathode film and anode film of Example 3 obtained are used to prepare cathodes and anodes respectively by cutting into separate electrode plates. The pouch-type battery is assembled by alternately stacking cathode electrode sheets and anode electrode sheets and then encapsulating them in a container made of an aluminum-plastic laminated film. The cathode electrode plate and the anode electrode plate are kept separate by a diaphragm and the container is preformed. Under a high-purity argon atmosphere with a humidity and oxygen content of less than 1ppm, the electrolyte is then filled into a container containing the packaged electrodes. The electrolyte is a solution (1M) of LiPF6 in a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) in a volume ratio of 1:1: ₁ . After the electrolyte is filled, the pouch-type battery is vacuum sealed and then mechanically pressed using a punching tool with a standard square.

Electrochemical measurements of Example 4

I) Rated capacity

The battery was tested galvanostatically on a battery tester at 25° C. and a current density of C/2 with a voltage between 3.0 V and 4.3 V. The rated capacity was approximately 10 Ah.

II) Cycle performance

The cycling performance of the pouch-type batteries was tested by charging and discharging between 3.0 V and 4.3 V at a constant current rate of 1 C. The cycling performance test results are shown in Figure 4. The capacity retention after 2000 cycles was approximately 77% of the initial value. This excellent cycling performance indicates that batteries made with cathode and anode electrodes prepared by the method disclosed herein can achieve comparable or even better stability than batteries made with cathode and anode electrodes prepared by conventional methods involving the use of organic solvents.

Example 5

A) Pretreatment of Active Battery Electrode Materials

Particulate cathode material LiNi _0.33 Mn _0.33 Co _0.33 O ₂ (from Shenzhen Tianjiao Technology Development Co., Ltd., China) was added to stirred deionized water at room temperature to form a suspension with a solid content of approximately 65% by weight. The pH of the suspension was measured using a pH meter and was approximately 7. The suspension was further stirred at room temperature for 10 hours. The suspension was then separated and dried in a 2.45 GHz microwave dryer at 750 W for 5 minutes to obtain the pretreated active battery electrode material.

B) Preparation of positive electrode slurry

The positive electrode slurry was prepared by mixing 93 wt.% of the pretreated active battery electrode material, 3 wt.% of carbon black, 0.5 wt.% of nonylphenol ethoxylate (TERGITOL ^™ NP-6, DOW Chemical, USA) and 3.5 wt.% of polyacrylonitrile in deionized water to form a slurry with a solid content of 75 wt.%. The slurry was homogenized by a circulating ultrasonic flow cell operating at 1000 W for 8 hours to obtain a homogenized slurry.

C) Preparation of positive electrode

The homogenized slurry was coated on both sides of a 20 μm thick aluminum foil using a transfer coater, with an areal density of approximately 32 mg/ ^cm² . The coating on the aluminum foil was dried for 4 minutes in a 24-meter-long conveyor-type hot air drying oven, a submodule of the transfer coater, operating at a conveyor speed of approximately 6 m/min, to produce the positive electrode. The programmable temperature oven allowed for a controlled temperature gradient, gradually increasing the temperature from an inlet temperature of 50°C to an outlet temperature of 75°C.

D) Preparation of negative electrode

A negative electrode slurry was prepared by mixing 90 wt.% hard carbon, 5 wt.% carbon black, and 5 wt.% polyacrylonitrile in deionized water to form a slurry with a solid content of 50 wt.%. This slurry was coated on both sides of a 9 μm thick copper foil using a transfer coater, with an areal density of approximately 15 mg/cm ² . The coating on the copper foil was dried at approximately 50°C for 2.4 minutes in a 24-meter-long conveyor-type hot air drying oven operating at a conveyor speed of approximately 10 m/min to obtain a negative electrode.

Example 6

Assembly of pouch cells

After drying, the cathode film and anode film of Example 5 obtained are used to prepare cathodes and anodes respectively by cutting into separate electrode plates. The pouch-type battery is assembled by alternately stacking cathode electrode sheets and anode electrode sheets and then encapsulating them in a container made of an aluminum-plastic laminated film. The cathode electrode plate and the anode electrode plate are kept separate by a diaphragm and the container is preformed. Under a high-purity argon atmosphere with a humidity and oxygen content of less than 1ppm, the electrolyte is then filled into a container containing the packaged electrodes. The electrolyte is a solution (1M) of LiPF6 in a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) in a volume ratio of 1:1: ₁ . After the electrolyte is filled, the pouch-type battery is vacuum sealed and then mechanically pressed using a punching tool with a standard square.

Electrochemical measurements of Example 6

I) Rated capacity

The battery was tested galvanostatically on a battery tester at 25° C. and a current density of C/2 with a voltage between 3.0 V and 4.3 V. The rated capacity was approximately 10 Ah.

II) Cycle performance

The cycling performance of the pouch-type batteries was tested by charging and discharging between 3.0 V and 4.3 V at a constant current rate of 1 C. The cycling performance test results are shown in Figure 5. The capacity retention after 560 cycles was approximately 94.8% of the initial value. This excellent cycling performance indicates that batteries made with cathode and anode electrodes prepared by the method disclosed herein can achieve comparable or even better stability than batteries made with cathode and anode electrodes prepared by conventional methods involving the use of organic solvents.

Example 7

A) Pretreatment of Active Battery Electrode Materials

The microparticle cathode material LiFePO ₄ (from Xiamen Tungsten Co., Ltd., China) was added to a stirred 3 wt.% aqueous solution of acetic acid (from Aladdin Industries, China) at room temperature to form a suspension having a solid content of approximately 50% by weight. The pH of the suspension was measured using a pH meter and was approximately 3.8. The suspension was further stirred at room temperature for 2.5 hours. The suspension was then separated and dried in a 2.45 GHz microwave dryer at 700 W for 5 minutes to obtain the pretreated active battery electrode material.

B) Preparation of positive electrode slurry

The positive electrode slurry was prepared by mixing 88 wt.% of the pretreated active battery electrode material, 5.5 wt.% of carbon black, 0.5 wt.% of nonylphenol ethoxylate (TERGITOL ^™ NP-6, DOW Chemical, USA) and 6 wt.% of polyacrylonitrile in deionized water to form a slurry with a solid content of 70 wt.%. The slurry was homogenized by a circulating ultrasonic flow cell operating at 1000 W for 6 hours to obtain a homogenized slurry.

C) Preparation of positive electrode

The homogenized slurry was coated on both sides of a 30 μm thick aluminum foil using a transfer coater, with an areal density of approximately 56 mg/ ^cm² . The coating on the aluminum foil was dried for 6 minutes in a 24-meter-long conveyor-type hot air drying oven, a submodule of the transfer coater, operating at a conveyor speed of approximately 4 m/min, to produce the positive electrode. The temperature-controlled oven allowed for a controlled temperature gradient, gradually increasing from an inlet temperature of 75°C to an outlet temperature of 90°C.

D) Preparation of negative electrode

A negative electrode slurry was prepared by mixing 90 wt.% hard carbon (HC; 99.5% purity, Ruifute Technology Co., Ltd., Shenzhen, Guangdong, China), 5 wt.% carbon black, and 5 wt.% polyacrylonitrile in deionized water to form a slurry with a solid content of 50 wt.%. This slurry was coated on both sides of a copper foil having a thickness of 9 μm using a transfer coater, with an areal density of approximately 15 mg/cm ² . The coating on the copper foil was dried at approximately 50°C for 2.4 minutes in a 24-meter-long conveyor-type hot air drying oven operating at a conveyor speed of approximately 10 m/min to obtain a negative electrode.

Example 8

Assembly of pouch cells

After drying, the cathode film and anode film of Example 7 obtained are used to prepare cathodes and anodes respectively by cutting into separate electrode plates. The pouch-type battery is assembled by alternately stacking cathode electrode sheets and anode electrode sheets and then encapsulating them in a container made of an aluminum-plastic laminated film. The cathode electrode plate and the anode electrode plate are kept separate by a diaphragm and the container is preformed. Under a high-purity argon atmosphere with a humidity and oxygen content of less than 1ppm, the electrolyte is then filled into a container containing the packaged electrodes. The electrolyte is a solution (1M) of LiPF6 in a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) in a volume ratio of 1:1: ₁ . After the electrolyte is filled, the pouch-type battery is vacuum sealed and then mechanically pressed using a punching tool with a standard square.

Electrochemical measurements of Example 8

I) Rated capacity

The battery was tested galvanostatically on a battery tester at 25° C. and a current density of C/2, with a voltage between 2.5 V and 3.6 V. The rated capacity was approximately 3.6 Ah.

II) Cycle performance

The cycling performance of the pouch-type batteries was tested by charging and discharging between 2.5 V and 3.6 V at a constant current rate of 1 C. The cycling performance test results are shown in Figure 6. The capacity retention after 3000 cycles was approximately 82.6% of the initial value. This excellent cycling performance indicates that batteries made with cathode and anode electrodes prepared by the method disclosed herein can achieve comparable or even better stability than batteries made with cathode and anode electrodes prepared by conventional methods involving the use of organic solvents.

Although the present invention has been described in conjunction with a limited number of embodiments, the specific features of one embodiment should not limit other embodiments of the present invention. In some embodiments, the method may include a large number of steps that the application does not mention. In other embodiments, the method does not include or substantially does not contain any steps that the application does not enumerate. There are variations and modifications from the described embodiments. The appended claims are intended to encompass all such variations and modifications that fall within the scope of the present invention.

Claims (25)

1. A method for preparing a battery cathode, comprising the following steps: 1) The active battery cathode material is pretreated in a first aqueous solution containing water and having a pH value of 2.0 to 7.5 to form a first suspension; 2) The first suspension is dried to obtain a pretreated active battery cathode material; 3) The pretreated active battery cathode material, conductive agent, and binder material are dispersed in a second aqueous solution to form a slurry; wherein the dispersion process is carried out at a temperature below 30°C; 4) The slurry is homogenized using a homogenizer to obtain a homogenized slurry; 5) Apply the homogenized slurry to the manifold to form a coating film on the manifold; and 6) Dry the coating on the current collector to form the battery cathode; The cathode material is selected from the _group consisting of _LiCoO2 , _LiNiO2 , LiNixMnyO2, _{Li1 + zNixMnyCo1 - xyO2} , _{LiNixCoyAlzO2} , _LiMnO2 , _LiCrO2 , _{LiMn2O4 , LiFePO4} and combinations thereof, wherein each _x is independently 0.3 _{to 0.8 ;} each y is _{independently} 0.1 to 0.45; and each z is independently 0 to 0.2. 2. The method of claim 1, wherein the pH of the first aqueous solution is in the range of 4 to 7, and the first suspension is stirred for a period of 2 minutes to 12 hours. _3. The method of claim 1, wherein the first _aqueous solution comprises one or more _acids selected from _{the group} consisting of _{H₂SO₄ , HNO₃} , _H₃PO₄ , _HCOOH , _CH₃COOH , _{H₃C₆H₅O₇} , _H₂C₂O₄ , _{C₆H₁₂O₇ , C₄H₆O₅ ,} and combinations _{thereof .} 4. The method of claim 1, wherein the first aqueous solution further comprises ethanol, isopropanol, methanol, acetone, n-propanol, tert-butanol, or a combination thereof. 5. The method of claim 1, wherein the first suspension is dried by a double-cone vacuum dryer, a microwave dryer, or a microwave vacuum dryer. 6. The method of claim 1, wherein the conductive agent is carbon. 7. The method of claim 1, wherein the conductive agent is pretreated in an alkaline solution for a period of 30 minutes to 2 hours, wherein the alkaline solution comprises an alkaline selected from the group consisting of _H₂O₂ , _LiOH , NaOH, KOH, _NH₃ · _H₂O , Be(OH) _₂ , Mg( _{OH ) ₂} , Ca(OH _{)₂ , Li₂CO₃} , _Na₂CO₃ , _NaHCO₃ , _K₂CO₃ , _KHCO₃ , and combinations thereof. 8. The method of claim 1, wherein the conductive agent is dispersed in a third aqueous solution to form a second suspension prior to step 3). 9. The method of claim 1, wherein the adhesive material is selected from the group consisting of styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), acrylonitrile copolymer, polyacrylic acid (PAA), polyacrylonitrile, polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), latex, alginate, and combinations thereof. 10. The method of claim 9, wherein the alginate comprises a cation selected from Na, Li, K, Ca, _NH4 , Mg, Al, or combinations thereof. 11. The method of claim 1, wherein the adhesive material is dissolved in a fourth aqueous solution prior to step 3) to form the resulting solution. 12. The method of claim 1, wherein each of the first aqueous solution and the second aqueous solution is independently purified water. 13. The method of claim 8, wherein the third aqueous solution is purified water. 14. The method of claim 11, wherein the fourth aqueous solution is purified water. 15. The method of any one of claims 12 to 14, wherein each of the first aqueous solution, the second aqueous solution, the third aqueous solution, or the fourth aqueous solution is independently pure water, deionized water, distilled water, or a combination thereof. 16. The method of claim 1, wherein the slurry further comprises a dispersant selected from the group consisting of ethanol, isopropanol, n-propanol, tert-butanol, n-butanol, lithium dodecyl sulfate, trimethylhexadecyl ammonium chloride, alcohol ethoxylates, nonylphenol ethoxylates, sodium dodecylbenzenesulfonate, sodium stearate, and combinations thereof. 17. The method of claim 1, wherein the homogenizer is a mixer, a mill, an ultrasonic generator, a rotor-stator homogenizer, or a high-pressure homogenizer. 18. The method of claim 17, wherein the ultrasonic generator is a probe-type ultrasonic generator or an ultrasonic flow cell. 19. The method of claim 1, wherein the homogenized slurry is applied to the manifold using a doctor blade coater, a slot die coater, a transfer coater, or a spray coater. 20. The method of claim 1, wherein the coating is dried for a period of 1 minute to 30 minutes at a temperature of 45°C to 100°C. 21. The method of claim 1, wherein the coating is dried by means of a conveyor belt hot air drying oven, a conveyor belt resistance drying oven, a conveyor belt inductive drying oven, or a conveyor belt microwave drying oven. 22. The method of claim 1, wherein the conductive agent is selected from the group consisting of carbon black, graphite, expanded graphite, graphene, carbon fiber, graphitized carbon sheet, carbon nanotube, activated carbon, mesoporous carbon, and combinations thereof. 23. The method of claim 1, wherein the conductive agent is selected from the group consisting of graphene nanosheets, carbon nanofibers, carbon nanotubes, and combinations thereof. 24. The method of claim 1, wherein the coating is dried at a temperature of 55°C to 75°C for a period of 2 to 10 minutes. 25. The method of claim 1, wherein the homogenizer is a stirring mixer.