HK1249281B - Method of preparing electrode assemblies - Google Patents

Description

Method for preparing electrode assembly

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 a method for preparing an electrode assembly.

Background Art

Over the past two decades, lithium-ion batteries (LIBs) have attracted significant attention for their widespread application in portable electronic devices, such as mobile phones and laptops. Due to the rapid market 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.

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 temperature to remove the solvent. The cathode and anode plates are then stacked or rolled together with a separator that separates the cathode and anode to form a battery. The separator is a physical barrier inserted between the anode and cathode that prevents physical contact between the anode and cathode.

Lithium-ion battery manufacturing is sensitive to moisture. High water content in batteries leads to significant degradation of electrochemical performance and affects battery stability. Moisture in batteries can originate from various sources. One potential source is the separator. The separator absorbs moisture during manufacturing, storage, and transportation, especially when placed and stored in humid environments. To address the moisture sensitivity of electrode assemblies, it is important to dry the separator before forming the electrode assembly to reduce the water content in the battery.

Korean Patent No. 101497348B1 describes a method for preparing an electrode assembly. The method includes the following steps: forming a laminate by stacking a cathode, an anode, and a separator interposed between the two electrodes; heating the laminate; and pressurizing the heated laminate. The heating process partially melts the separator fibers, allowing the electrodes and separator to be combined. However, this method does not dry the separator before assembly.

Korean Patent No. 101495761B1 describes a method for preparing an electrode assembly. The method includes the following steps: preparing a negative electrode plate and a positive electrode plate; arranging the positive and negative electrode plates and a separator to form an electrode assembly; forming a jelly roll by winding the electrode assembly; and drying the jelly roll. However, this method also does not dry the separator before assembly.

Korean Patent No. 100759543B1 describes a method for preparing an electrode assembly for a lithium-ion polymer battery. The method includes the following steps: preparing positive and negative electrode plates; preparing a separator; heating the separator; and inserting the heated separator between the two electrode plates, wherein the separator is heated at an elevated temperature for 1 to 3 minutes. However, the heating process serves to remove residual stress within the separator, preventing shrinkage due to battery overheating.

The lack of a pre-drying process for the separator in existing methods allows water to be introduced into the electrode assembly, which can affect the cycling stability and rate characteristics of the LIB. In view of the above, there has been a need to develop a method for drying the separator of the LIB before assembly into the electrode assembly to reduce the water content.

Summary of the Invention

The aforementioned needs are met by the various aspects and embodiments disclosed herein.

In one aspect, the present invention provides a method for preparing an electrode assembly, comprising the steps of:

1) preparing a slurry comprising a conductive agent, an active battery electrode material, and a binder material;

2) applying the slurry to a current collector to form a coating film on the current collector;

3) Drying the coating film on the current collector;

4) pre-drying the membrane under vacuum at a temperature of about 50° C. to about 150° C.;

5) stacking at least one anode, at least one cathode, and at least one pre-dried separator interposed between the at least one anode and the at least one cathode; and

6) Dry the electrode assembly.

In some embodiments, the separator is a non-woven fabric composed of natural fibers or polymer fibers, wherein the melting point of the polymer fibers is 200° C. or higher.

In certain embodiments, the separator is a nonwoven fabric made of polymer fibers selected from the group consisting of polyolefins, polyethylene, high-density polyethylene, linear low-density polyethylene, low-density polyethylene, ultra-high molecular weight polyethylene, polypropylene, polypropylene/polyethylene copolymers, polybutylene, polypentene, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polysulfone, polyphenylene oxide, polyphenylene sulfide, polyacrylonitrile, polyvinylidene fluoride, polyoxymethylene, polyvinylpyrrolidone, polyester, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, and combinations thereof.

In some embodiments, the membrane is pre-dried for a period of about 2 hours to about 12 hours or about 2 hours to about 8 hours.

In certain embodiments, the membrane is pre-dried at a pressure of less than 25 kPa, less than 15 kPa, less than 10 kPa, or less than 5 kPa.

In some embodiments, the separator includes a porous base material and a protective porous layer coated on one or both surfaces of the porous base material, wherein the protective porous layer includes a binder material and an inorganic filler, and wherein the peel strength between the porous base material and the protective porous layer is 0.04 N/cm or greater or 0.1 N/cm or greater.

In certain embodiments, the inorganic filler is selected from the group consisting _{of Al2O3} , _SiO2 , _TiO2 , _ZrO2 , _BaOx , ZnO, _CaCO3 , TiN, AlN, _MTiO3 , _K2O · _nTiO2 , _Na2O · _mTiO2 , and combinations thereof, wherein x is 1 or 2; M is Ba, Sr, or Ca; n is 1, 2, 4, 6, or 8; and m is 3 or 6.

In some embodiments, the binder material is selected from the group consisting of styrene butadiene rubber, acrylated styrene butadiene rubber, acrylonitrile copolymer, nitrile rubber, nitrile butadiene rubber, acrylonitrile-styrene-butadiene copolymer, acryl rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene/propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinyl pyrrolidone, polyvinyl pyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl cellulose, cyanoethyl sucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, fluorinated polymer, chlorinated polymer, alginate, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, and combinations thereof.

In certain embodiments, the weight ratio of the inorganic filler to the binder material is from about 99:1 to about 1:1.

In some embodiments, the thickness of the separator is from about 1 μm to about 80 μm.

In certain embodiments, the membrane has a porosity of about 40% to about 97%.

In some embodiments, the active battery electrode material is a cathode material selected from _the group _consisting of _{LiCoO2 , 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 certain embodiments, the conductive agent is selected from the group consisting of carbon, carbon black, graphite, expanded graphite, graphene, graphene nanoplatelets, carbon fibers, carbon nanofibers, graphitized carbon sheets, carbon tubes, carbon nanotubes, activated carbon, mesoporous carbon, and combinations thereof. In certain embodiments, the conductive agent is not carbon, carbon black, graphite, expanded graphite, graphene, graphene nanoplatelets, carbon fibers, carbon nanofibers, graphitized carbon sheets, carbon tubes, carbon nanotubes, activated carbon, or mesoporous carbon.

In some embodiments, the electrode assembly is dried at a pressure of less than 25 kPa, less than 15 kPa, less than 10 kPa, or less than 5 kPa.

In certain embodiments, the electrode assembly is dried for a period of about 2 hours to about 24 hours or about 4 hours to about 12 hours.

In some embodiments, the electrode assembly is dried at a temperature of about 70°C to about 150°C.

In certain embodiments, the pre-dried membrane has a moisture content of less than 50 ppm by weight based on the total weight of the pre-dried membrane.

In some embodiments, the dried electrode assembly has a moisture content of less than 20 ppm by weight based on the total weight of the dried electrode assembly.

In another aspect, provided herein is a lithium battery comprising an electrode assembly prepared by the method disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the cycling performance of an electrochemical cell comprising an electrode assembly prepared by the method described in Example 2.

FIG. 2 shows the cycling performance of an electrochemical cell comprising an electrode assembly prepared by the method described in Example 4.

FIG3 shows the cycling performance of an electrochemical cell comprising an electrode assembly prepared by the method described in Example 6.

DETAILED DESCRIPTION

This article provides a method for preparing an electrode assembly, comprising the following steps:

1) preparing a slurry comprising a conductive agent, an active battery electrode material, and a binder material;

2) applying the slurry to a current collector to form a coating film on the current collector;

3) Drying the coating film on the current collector;

4) pre-drying the membrane under vacuum at a temperature of about 50° C. to about 150° C.;

5) stacking at least one anode, at least one cathode, and at least one pre-dried separator interposed between the at least one anode and the at least one cathode; and

6) Dry the electrode assembly.

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 "binder material" refers to a chemical or substance that can be used to hold active battery electrode materials and conductive agents in place or to bind inorganic fillers to porous base materials and to each other.

The term "water-based binder material" refers to a binder polymer that is soluble or dispersible in water. Some non-limiting examples of water-based binder materials include styrene-butadiene rubber, acrylated styrene-butadiene rubber, nitrile rubber, acryl rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene/propylene copolymer, polybutadiene, polyethylene oxide, polyvinyl pyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, ethylene/propylene/diene copolymer, polyvinyl pyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, and combinations thereof.

The term "organic binder material" refers to a binder dissolved or dispersed in an organic solvent, particularly N-methyl-2-pyrrolidone (NMP). Some non-limiting examples of organic binder materials include polytetrafluoroethylene (PTFE), perfluoroalkoxy polymers (PFA), polyvinylidene fluoride (PVDF); copolymers of tetrafluoroethylene (TFE) and hexafluoropropylene (HFP), fluorinated ethylene-propylene (FEP) copolymers, terpolymers of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride, and combinations thereof.

The term "conductive agent" refers to a chemical or substance that enhances the electrical conductivity of an electrode.

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

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

The term "current collector" refers to a support for coating active battery electrode materials and a chemically inactive, highly electron-conducting conductor for maintaining current flow to the electrodes during discharge or charge of a secondary battery.

The term "pre-drying" refers to the act of removing solvent or water from a material.

The term "water content" is used interchangeably with moisture content.

The term “electrode assembly” refers to a structure including at least one positive electrode, at least one negative electrode, and at least one separator interposed between the positive electrode and the negative electrode.

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 charge or discharge rate of a cell or battery expressed in Ah or mAh relative to its total storage capacity. For example, a 1C rate 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 supply 1 ampere for one hour, or 0.5 amperes for two hours, and so on. Therefore, 1 Ah is equivalent to 3,600 coulombs 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 "battery cycle life" refers to the number of full charge/discharge cycles a battery can perform before its rated capacity decreases below 80% of its initial rated capacity.

In the following description, all numerical values disclosed herein are approximate, 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 value falling within that range is specifically disclosed. In particular, the following values 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.

Polymers such as nylon, polyamide, polyester and polyvinyl alcohol are known to be hygroscopic and absorb moisture during manufacture or during storage under atmosphere. These polymers will reabsorb moisture during transportation. However, humidity control during transportation is complicated and expensive. Therefore, separators made of these materials must be dried before further processing. Typically, the separator is dried after being assembled into the electrode assembly. However, it is difficult to completely dry all materials including the cathode, anode and separator to a low moisture content at the same time after assembly. This is especially true if the separator has been stored under humid conditions before assembly.

In each of steps 4 and 6, vacuum drying is performed. The reason for performing drying in these two steps is that a large amount of moisture adhering to the separator cannot be satisfactorily removed simply by drying in step 6. Residual moisture in the separator can cause problems such as mixing with the electrode and the electrolyte solution, causing decomposition of the electrolyte solution, or changing the quality of the electrode active material. Therefore, removing moisture is important.

The separator may comprise woven or non-woven polymer fibers, natural fibers, carbon fibers, glass fibers, or ceramic fibers. In certain embodiments, the separator comprises woven or non-woven polymer fibers.

In some embodiments, the nonwoven or woven fibers are made of organic polymers, such as polyolefins, polyethylene, high-density polyethylene, linear low-density polyethylene, low-density polyethylene, ultra-high molecular weight polyethylene, polypropylene, polypropylene/polyethylene copolymers, polybutylene, polypentene, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polysulfone, polyphenylene oxide, polyphenylene sulfide, polyacrylonitrile, polyvinylidene fluoride, polyoxymethylene, polyvinylpyrrolidone, polyester, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, derivatives thereof, or combinations thereof. In certain embodiments, the separator is made of polyolefin fibers selected from the group consisting of polyethylene, high-density polyethylene, linear low-density polyethylene, low-density polyethylene, ultra-high molecular weight polyethylene, polypropylene, polypropylene/polyethylene copolymers, and combinations thereof. In some embodiments, the separator is made of a polymer fiber selected from the group consisting of polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, polyethylene naphthalate, and combinations thereof. In other embodiments, the polymer fiber is not polyethylene, high-density polyethylene, linear low-density polyethylene, low-density polyethylene, ultra-high molecular weight polyethylene, polypropylene, or polypropylene/polyethylene copolymer. In further embodiments, the polymer fiber is not polyacetal, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, or polycarbonate. In still further embodiments, the polymer fiber is not polyamide, polyimide, or polyetheretherketone. However, all other known polymer fibers or many natural fibers may also be used.

In certain embodiments, the separators disclosed herein have a melting point of 100° C. or higher, 120° C. or higher, 140° C. or higher, 160° C. or higher, 180° C. or higher, 200° C. or higher, or 250° C. or higher. In certain embodiments, the separators disclosed herein have a melting point of 140° C. or higher, 160° C. or higher, 180° C. or higher, 200° C. or higher, or 250° C. or higher.

In order to improve the thermal stability of the separator, fibers with a melting temperature of 200°C or above should be used. In some embodiments, the fibers are selected from polyesters. Some non-limiting examples of suitable polyesters include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, derivatives thereof, and combinations thereof. Separators with a high melting point exhibit high thermal stability and can therefore be pre-dried at high temperatures without thermal shrinkage. In addition, separators with a high melting point allow for higher pre-drying temperatures, increasing the evaporation rate of water and increasing the efficiency of pre-drying.

The nonwoven fabric can be produced by known processes. Some non-limiting examples of suitable processes include dry processes, spunbond processes, water needle processes, hydroentangled processes, wet processes, meltblown processes, and the like.

The separator may be in a coated or uncoated form. In some embodiments, the separator is uncoated and does not include a protective porous layer. In certain embodiments, the separator is coated and includes a porous substrate material and a protective porous layer coated on one or both sides of the porous substrate material, wherein the protective porous layer includes a binder material and an inorganic filler. In certain embodiments, the inorganic filler is selected from the group consisting of _Al2O3 , _SiO2 , _TiO2 , _ZrO2 , _BaOx , _ZnO , _CaCO3 , TiN, AlN, and combinations thereof, wherein x is 1 or 2.

In certain embodiments, the average diameter of the inorganic filler is from about 100 nm to about 2000 nm, from about 100 nm to about 1000 nm, from about 250 nm to about 1500 nm, from about 300 nm to about 3 μm, from about 500 nm to about 4.5 μm, from about 500 nm to about 6 μm, from about 1 μm to about 20 μm, from about 10 μm to about 20 μm, from about 1 μm to about 15 μm, from about 1 μm to about 7.5 μm, from about 1 μm to about 4.5 μm, from about 1 μm to about 3 μm, or from about 800 nm to about 2.5 μm.

The advantages of the coated separator are that it has outstanding safety and exhibits no or slight shrinkage at high temperatures. This is because the melting point of the inorganic filler adhered to the porous base material is much higher than the safety-related temperature range for use in electrochemical cells, thus suppressing thermal shrinkage of the separator.

In some embodiments, the thickness of the coated or uncoated separator is about 10 μm to about 200 μm, about 30 μm to about 100 μm, about 10 μm to about 75 μm, about 10 μm to about 50 μm, about 10 μm to about 20 μm, about 15 μm to about 40 μm, about 15 μm to about 35 μm, about 20 μm to about 40 μm, about 20 μm to about 35 μm, about 20 μm to about 30 μm, about 30 μm to about 60 μm, about 30 μm to about 50 μm, or about 30 μm to about 40 μm.

In certain embodiments, the thickness of the coated or uncoated separator is less than 100 μm, less than 80 μm, less than 60 μm, less than 40 μm, less than 35 μm, less than 30 μm, less than 25 μm, or less than 20 μm. Thinner separators allow for the construction of very compact batteries with high energy density. In addition, if the separator is thin enough, water can be evaporated at a high drying rate.

In some embodiments, the porosity of the coated or uncoated membrane is about 50% to about 97%, about 50% to about 95%, about 50% to about 80%, about 55% to about 90%, about 55% to about 80%, about 60% to about 95%, about 60% to about 90%, about 60% to about 80%, about 65% to about 90%, about 65% to about 80%, about 70% to about 90%, about 70% to about 80%, about 75% to about 90%, or about 80% to about 90%.

The properties of the separators disclosed herein include a particularly advantageous combination of thickness and porosity, meeting the demands placed on separators in high-power batteries, particularly high-power lithium batteries.

In some embodiments, the coated or uncoated diaphragm can be dried under vacuum in a drying chamber prior to assembly. In certain embodiments, the drying chamber is connected to a vacuum pump, allowing the pressure in the chamber to be reduced. The pressure is sufficiently reduced to lower the boiling point of water, thereby significantly reducing drying time. In some embodiments, the drying chamber is connected to a central vacuum source, thereby allowing multiple vacuum drying chambers to be operated simultaneously. In some embodiments, the number of vacuum drying chambers connected to the central vacuum source ranges from 1 to 20, depending on the number of pumps in operation.

In certain embodiments, the coated or uncoated separator may be dried under vacuum at a temperature of about 50°C to about 150°C, about 70°C to about 150°C, about 80°C to about 150°C, about 90°C to about 150°C, about 100°C to about 150°C, about 100°C to about 140°C, about 100°C to about 130°C, about 100°C to about 120°C, about 100°C to about 110°C, or about 110°C to about 130°C. In certain embodiments, the coated or uncoated separator may be dried under vacuum at a temperature of about 80°C to about 150°C. In some embodiments, the coated or uncoated separator may be dried under vacuum at a temperature of about 80°C or more, 90°C or more, 100°C or more, 110°C or more, 120°C or more, 130°C or more, 140°C or more, or 150°C or more. In certain embodiments, the coated or uncoated separator may be dried under vacuum at a temperature of less than 150°C, less than 145°C, less than 140°C, less than 135°C, less than 130°C, less than 120°C, less than 110°C, less than 100°C, or less than 90°C.

Compared with other materials, the diaphragm composed of conventionally used polypropylene fibers and the diaphragm composed of cellulose pulp have less heat resistance. When the diaphragm is dried at a temperature of 100°C or higher, there is obvious deterioration of the diaphragm, such as melting and carbonization. For a coated diaphragm composed of a heat-resistant material as a porous base material, when the diaphragm is dried at a temperature higher than 150°C, there is obvious deterioration of the binder material in the protective porous layer. Specifically, when the binder material is a water-based binder material (for example, carboxymethyl cellulose (CMC)), it is considered to be a brittle binder. In this case, the aqueous binder is likely to become brittle, resulting in a brittle protective porous layer that breaks after a small deformation. Damage to the diaphragm can lead to a serious negative impact on the performance and safety of lithium-ion secondary batteries.

In some embodiments, the time period for drying the coated or uncoated membrane under vacuum is from about 2 hours to about 24 hours, from about 2 hours to about 20 hours, from about 2 hours to about 12 hours, from about 2 hours to about 8 hours, from about 4 hours to about 24 hours, from about 4 hours to about 20 hours, from about 4 hours to about 12 hours, from about 4 hours to about 8 hours, from about 8 hours to about 24 hours, from about 8 hours to about 16 hours, from about 8 hours to about 12 hours. In some embodiments, the time period for drying the coated or uncoated membrane under vacuum is from about 2 hours to about 24 hours or from about 4 hours to about 16 hours.

In certain embodiments, the pre-drying step includes drying the coated separator in two drying steps (a first stage and a second stage), wherein the temperature of the first stage is lower than that of the second stage. The low temperature in the first stage prevents rapid loss of surface moisture and improves product quality by virtually eliminating uneven drying. If drying is too rapid or the temperature is too high, this will lead to uneven drying and uneven shrinkage of the protective porous layer, thereby reducing the peel strength of the separator.

The temperature in the first stage can be in the range of 50°C to 90°C. A partially dried membrane is obtained from the first stage. In some embodiments, the membrane can be vacuum dried at a temperature of about 50°C or higher, about 60°C or higher, about 70°C or higher, or about 80°C or higher in the first stage. In certain embodiments, the membrane can be vacuum dried at a temperature of less than 90°C, less than 85°C, less than 80°C, less than 75°C, or less than 70°C in the first stage.

The low temperature in the first stage is beneficial for slow drying to avoid cracking or embrittlement of the protective porous layer. Since the interior of the protective porous layer dries slower than the surface of the protective porous layer, the surface of the protective porous layer should be dried slowly to reduce the possibility of surface cracking.

The drying time of the first stage may be in the range of about 5 minutes to about 4 hours, about 5 minutes to about 2 hours, or about 15 minutes to about 30 minutes.

The temperature in the second stage may be in the range of 80° C. to 150° C., about 100° C. to about 150° C., or about 100° C. to about 140° C. In some embodiments, the membrane may be vacuum dried at a temperature of about 80° C. or higher, about 90° C. or higher, about 100° C. or higher, about 110° C. or higher, about 120° C. or higher, about 130° C. or higher, or about 140° C. or higher in the second stage. In certain embodiments, the membrane may be vacuum dried at a temperature of less than 150° C., less than 140° C., less than 130° C., less than 120° C., or less than 110° C. in the second stage.

The drying time of the second stage may be in the range of about 15 minutes to about 4 hours, about 5 minutes to about 2 hours, or about 15 minutes to about 30 minutes.

Any vacuum pump that can reduce the pressure of the drying chamber can be used herein. Some non-limiting examples of vacuum pumps include dry vacuum pumps, turbo pumps, rotary vane vacuum pumps, cryogenic pumps, and adsorption pumps.

In some embodiments, the vacuum pump is an oil-free pump. An oil-free pump operates without the need for oil in the pump components, which are exposed to the pumped gas or partial vacuum. Therefore, any gas flowing back through the pump is free of oil vapor. Accumulated oil vapor deposited on the surface of the diaphragm can degrade the electrochemical performance of the battery. An example of such a pump is a diaphragm vacuum pump.

In some embodiments, the membrane is pre-dried at atmospheric pressure. In certain embodiments, the pre-drying step is performed under a vacuum state. In further embodiments, the vacuum state is maintained at a pressure in the range of about 1× ^10-1 Pa to about 1× ^10-4 Pa, about ¹⁰ Pa to about 1× ^10-1 Pa, about ¹ ×103 Pa to about 10 Pa, or about 2.5×104 Pa to about 1× ¹⁰³ Pa. In still further embodiments, the vacuum state is at a pressure of about 1× ¹⁰³ Pa, about 2× ¹⁰³ Pa, about 5× ¹⁰³ Pa, about 1× ¹⁰⁴ Pa, or about 2× ¹⁰⁴ Pa.

In order to reduce the power required by the pump, a condenser can be provided between the drying chamber and the pump. The condenser condenses the water vapor which is then separated.

After pre-drying, the membrane may be naturally cooled to 50°C or less before being removed from the drying chamber. In some embodiments, the membrane is cooled to 45°C or less, 40°C or less, 35°C or less, 30°C or less, or 25°C or less before being removed from the drying chamber. In certain embodiments, the membrane is cooled to room temperature. In some embodiments, the membrane is cooled by blowing dry air or inert gas to reach the target temperature more quickly.

It is not necessary to dry the membrane to a very low water content. The residual water content of the pre-dried membrane can be further reduced by a subsequent drying step. In some embodiments, the water content in the pre-dried membrane is less than 80 ppm, less than 70 ppm, less than 60 ppm, less than 50 ppm, less than 40 ppm, or less than 30 ppm by weight based on the total weight of the pre-dried membrane.

The pre-dried separator does not need to be used immediately once dried and can be stored overnight in an environment with an air dew point of -10°C to 30°C before being used to prepare an electrode assembly. However, direct further processing without storage is more energy efficient.

In other embodiments, the coated or uncoated membrane can be dried using a freeze dryer. The membrane can be first frozen and then the water removed from the frozen state as vapor. In some embodiments, the membrane is first frozen at a freezing temperature of -0°C to -80°C for a period of 1 to 5 hours. The freeze drying apparatus can include a vacuum chamber, a cold trap, a vacuum pump, and a cooling device.

The time of the freeze drying process is variable, but freeze drying can generally be carried out within a period of about 1 hour to about 20 hours. In certain embodiments, the freeze drying period is about 1 hour to about 5 hours, about 1 hour to about 3 hours, about 1 hour to about 2 hours, about 2 hours to about 5 hours, about 2 hours to about 4 hours, or about 2 hours to about 3 hours.

In some embodiments, the freeze drying process can be carried out under high vacuum. The scope of pressure can be fully realized by known vacuum pump. In some embodiments, the freeze drying process also can be carried out under atmospheric pressure or near atmospheric pressure. The partial pressure of water is maintained at very low value in the drying chamber, because between the vapor pressure of the air in the drying chamber and the vapor pressure of the air on the diaphragm surface, a large difference must be produced to ensure sublimation. Because applying high vacuum is not necessary, the freeze drying advantage at atmospheric pressure or near atmospheric pressure is to significantly reduce operating costs.

In some embodiments, the water content in the pre-dried membrane after freeze-drying is less than 150 ppm, less than 100 ppm, less than 80 ppm, less than 70 ppm, less than 60 ppm, or less than 50 ppm by weight based on the total weight of the pre-dried membrane.

When the water content of the diaphragm is higher than 150ppm after freeze drying, the pre-dried diaphragm can be further dried by blowing hot air. In some embodiments, the drying chamber blows hot air towards the diaphragm from above and/or below. In certain embodiments, hot air drying is carried out at an air speed of about 1 m/second to about 50 m/second, about 1 m/second to about 40 m/second, about 1 m/second to about 30 m/second or about 1 m/second to about 20 m/second. In other embodiments, hot inert gas (that is, helium, argon) is used instead of hot air.

The drying gas may be preheated by a heat exchange surface. In some embodiments, the temperature of the hot air ranges from about 50°C to about 100°C, from about 60°C to about 100°C, from about 70°C to about 100°C, from about 50°C to about 90°C, or from about 60°C to about 90°C. In certain embodiments, the hot air drying period is from about 15 minutes to about 5 hours or from about 1 hour to about 3 hours.

The binder material in the protective porous layer serves to bond the inorganic filler to the porous base material. The inorganic fillers can also be bonded to each other via the binder material. In certain embodiments, the binder material is an organic polymer. The use of an organic polymer makes it possible to produce a diaphragm with sufficient mechanical flexibility.

In some embodiments, the binder material is selected from the group consisting of an organic binder material, a water-based binder material, or a mixture of a water-based binder material and an organic binder material. In certain embodiments, the binder material is selected from the group consisting of styrene-butadiene rubber (SBR), acrylated styrene-butadiene rubber, acrylonitrile copolymer, nitrile rubber, nitrile butadiene rubber, acrylonitrile-styrene-butadiene copolymer, acryl rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene/propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinyl pyrrolidone, polyvinyl pyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, latex, acrylic The present invention also includes a group consisting of acrylic resins, phenolic resins, epoxy resins, carboxymethyl cellulose (CMC), hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl cellulose, cyanoethyl sucrose, polyesters, polyamides, polyethers, polyimides, polycarboxylates, polycarboxylic acids, polyacrylic acid (PAA), polyacrylates, polymethacrylic acid, polymethacrylates, polyacrylamides, polyurethanes, fluorinated polymers, chlorinated polymers, alginates, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, and combinations thereof. In some embodiments, the alginate comprises a cation selected from the group consisting of Na, Li, K, Ca, NH ₄ , Mg, Al, or combinations thereof.

In certain embodiments, the binder material is selected from the group consisting of styrene-butadiene rubber, carboxymethyl cellulose, polyvinylidene fluoride, acrylonitrile copolymer, polyacrylic acid, polyacrylonitrile, polyvinylidene fluoride-hexafluoropropylene, latex, alginate, and combinations thereof.

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

The mixing ratio of the inorganic filler to the binder material in the protective porous layer of the present invention is not particularly limited and can be controlled according to the thickness and structure of the protective porous layer to be formed.

In some embodiments, the weight ratio of inorganic filler to binder material in the protective porous layer formed on the porous substrate material according to the present invention is from about 1:1 to about 99:1, from about 70:30 to about 95:5, from about 95:5 to about 35:65, from about 65:35 to about 45:55, from about 20:80 to about 99:1, from about 10:90 to about 99:1, from about 5:95 to about 99:1, from about 3:97 to about 99:1, from about 1:99 to about 99:1, or from about 1:99 to about 1:1.

If the weight ratio of the inorganic filler to the binder material is less than 1:99, the binder content is so large that the pore size and porosity of the protective porous layer may be reduced. When the inorganic filler content is greater than 99 wt.%, the polymer content is too low to provide sufficient adhesion between the inorganic fillers, resulting in poor mechanical properties and impaired peeling resistance of the resulting protective porous layer.

In certain embodiments, the amount of binder material in the protective porous layer 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%, or at least 50% by weight, based on the total weight of the protective porous layer. In some embodiments, the amount of binder material in the protective porous layer 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%, or at most 50% by weight, based on the total weight of the protective porous layer.

In some embodiments, the amount of binder material in the protective porous layer is about 2 wt.% to about 10 wt.%, 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 protective porous layer.

In certain embodiments, the active battery electrode material is a cathode material selected from _the group _consisting of _{LiCoO2 , 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 certain embodiments, _the cathode material is selected from _the group consisting of LiCoO2, _{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 LiCoO ₂ , LiNiO ₂ , LiV ₂ O ₅ , LiTiS ₂ , LiMoS ₂ , LiMnO ₂ , LiCrO ₂ , LiMn 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 _y 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 active battery electrode material is an anode material 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 other embodiments, the anode material is not natural graphite particles, synthetic graphite particles, Sn (tin) particles, Li ₄ Ti ₅ O ₁₂ particles, Si (silicon) particles, or Si-C composite particles.

In certain embodiments, the amount of each of the cathode material and the anode material is independently 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, based on the total weight of the cathode electrode layer or the anode electrode layer. In some embodiments, the amount of each of the cathode material and the anode material is independently 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, based on the total weight of the cathode electrode layer or the anode electrode layer.

In some embodiments, the conductive agent is selected from the group consisting of carbon, carbon black, graphite, expanded graphite, graphene, graphene nanoplatelets, carbon fibers, carbon nanofibers, graphitized carbon sheets, carbon tubes, carbon nanotubes, activated carbon, mesoporous carbon, and combinations thereof. In certain embodiments, the conductive agent is not carbon, carbon black, graphite, expanded graphite, graphene, graphene nanoplatelets, carbon fibers, carbon nanofibers, graphitized carbon sheets, carbon tubes, carbon nanotubes, activated carbon, or mesoporous carbon.

In certain embodiments, the amount of the conductive agent in each of the cathode electrode layer and the anode electrode layer 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, based on the total weight of the cathode electrode layer or the anode electrode layer. In some embodiments, the amount of the conductive agent in each of the cathode electrode layer and the anode electrode layer 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, based on the total weight of the cathode electrode layer or the anode electrode layer.

In some embodiments, the amount of the conductive agent in each of the cathode electrode layer and the anode electrode layer is independently about 0.05 wt.% 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 cathode electrode layer or the anode electrode layer.

After assembling the electrode assembly, the electrode assembly is placed in a drying chamber. In some embodiments, the drying chamber is connected to a vacuum pump. In certain embodiments, the drying chamber is connected to a central vacuum source. The vacuum pump or central vacuum source is connected to the drying chamber via a suction line equipped with an outlet valve. In certain embodiments, the drying chamber is also connected to a gas reservoir containing dry air or an inert gas via a conduit equipped with an inlet valve. When the outlet valve is closed and the inlet valve is opened, there is no longer a vacuum in the drying chamber. The valve can be a solenoid type or a needle type or a large flow controller. Any device that allows suitable flow adjustment can be used.

In some embodiments, the electrode assemblies are loosely stacked. In a loosely stacked electrode assembly, there is void space between the electrode layers and the separator layers, thereby allowing moisture to escape. Therefore, the loosely stacked electrode assembly can be effectively dried in a short period of time. On the other hand, when the electrode assembly is squeezed under pressure before drying, a tightly packed electrode assembly has little or no void space between the electrode layers and the separator layers, thereby reducing air flow and drying efficiency.

In certain embodiments, the positive electrode, separator, and negative electrode are stacked and spirally wound into a jellyroll configuration before drying. Because the jellyroll electrode assembly is tightly packed, there is little or no void space between the electrode and separator layers, thereby reducing air flow and drying efficiency.

In order to reduce the power required by the pump, a condenser can be provided between the drying chamber and the pump. The condenser condenses the water vapor which is then separated.

In some embodiments, the electrode assembly may be dried at a temperature of about 70°C to about 150°C, about 80°C to about 150°C, about 90°C to about 150°C, about 100°C to about 150°C, or about 80°C to about 130°C and under vacuum. In some embodiments, the electrode assembly may be dried at a temperature of about 80°C or higher, 90°C or higher, 100°C or higher, 110°C or higher, 120°C or higher, or 130°C or higher and under vacuum. In certain embodiments, the electrode assembly may be dried at a temperature of less than 150°C, less than 145°C, less than 140°C, less than 135°C, less than 130°C, less than 120°C, less than 110°C, less than 100°C, or less than 90°C and under vacuum.

In certain embodiments, the period of time for drying the electrode assembly under vacuum is from about 5 minutes to about 12 hours, from about 5 minutes to about 4 hours, from about 5 minutes to about 2 hours, from about 5 minutes to about 1 hour, from about 15 minutes to about 3 hours, from about 1 hour to about 4 hours, from about 1 hour to about 2 hours, from about 2 hours to about 12 hours, from about 2 hours to about 8 hours, from about 2 hours to about 5 hours, from about 2 hours to about 3 hours, or from about 4 hours to about 12 hours.

In some embodiments, the electrode assembly is dried under a vacuum state. In further embodiments, the vacuum state is maintained at a pressure in the range of about 1×10 ⁻¹ Pa to about 1×10 ⁻⁴ Pa, about 10 Pa to about 1×10 ⁻¹ Pa, about 1×10 ³ Pa to about 10 Pa, or about 2.5×10 ⁴ Pa to about 1×10 ³ Pa. In still further embodiments, the vacuum state is at a pressure of about 1×10 ³ Pa, about 2×10 ³ Pa, about 5×10 ³ Pa, about 1×10 ⁴ Pa, or about 2×10 ⁴ Pa.

After a predetermined drying period, the drying chamber is directly connected to a gas reservoir containing dry air or an inert gas via an inlet valve. In certain embodiments, the inert gas is selected from the group consisting of helium, argon, neon, krypton, xenon, nitrogen, carbon dioxide, and combinations thereof.

In some embodiments, after curing the electrode assembly with a dry gas for a predetermined time, the electrode assembly may be further dried under vacuum. This step may be repeated as many times as necessary to reduce the moisture content of the electrode assembly to a suitable level. In certain embodiments, this step may be repeated from about 2 to about 50 times until the moisture content in the electrode assembly is less than 40 ppm, less than 30 ppm, less than 20 ppm, less than 15 ppm, less than 10 ppm, or less than 5 ppm, based on the total weight of the dried electrode assembly.

An advantage of the present invention is that most manufacturing can occur outside of a dry room. In some embodiments, the assembly process can occur outside of a dry room or glove box. In the present invention, only the electrolyte filling step, or both the electrode assembly drying and electrolyte filling steps, are performed in a dry room or glove box. Therefore, humidity control in the factory can be avoided, significantly reducing investment costs.

The presence of moisture is detrimental to battery operation. Typically, the water content in electrode assemblies prepared by conventional methods contains greater than 100 ppm by weight, based on the total weight of the electrode assembly. Even if the initial battery performance is acceptable, the rate of battery performance degradation is unacceptable. In order to achieve sufficiently high battery performance, it is therefore advantageous to have a low water content in the battery.

In some embodiments, the water content in the dried electrode assembly is from about 5 ppm to about 50 ppm, from about 5 ppm to about 40 ppm, from about 5 ppm to about 30 ppm, from about 5 ppm to about 20 ppm, from about 5 ppm to about 10 ppm, from about 3 ppm to about 30 ppm, from about 3 ppm to about 20 ppm, or from about 3 ppm to about 10 ppm by weight, based on the total weight of the dried electrode assembly.

In certain embodiments, the water content in the dried electrode assembly is less than 30 ppm, less than 20 ppm, less than 10 ppm, less than 5 ppm, less than 4 ppm, less than 3 ppm, less than 2 ppm, or less than 1 ppm by weight, based on the total weight of the dried electrode assembly. In some embodiments, the dried electrode assemblies disclosed herein have a water content of no greater than about 5 ppm by weight, based on the total weight of the dried electrode assembly.

In some embodiments, the water content of at least one anode and at least one cathode in the dried electrode assembly is less than 30 ppm, less than 20 ppm, less than 10 ppm, less than 5 ppm, or less than 3 ppm by weight, based on the total weight of the at least one dried anode and at least one dried cathode. In certain embodiments, the water content of at least one separator in the dried electrode assembly is less than 30 ppm, less than 20 ppm, less than 10 ppm, less than 5 ppm, or less than 3 ppm by weight, based on the total weight of the dried separator. The separator in the electrode assembly disclosed herein includes a low water content, which contributes to the reliable performance of the lithium-ion battery.

After drying, the electrode assembly can be naturally cooled to 50°C or lower before being removed from the drying chamber. In some embodiments, the electrode assembly is cooled to 45°C or lower, 40°C or lower, 35°C or lower, 30°C or lower, or 25°C or lower. In certain embodiments, the electrode assembly is cooled to room temperature. In some embodiments, the electrode assembly is cooled by blowing dry air or inert gas to reach the target temperature more quickly.

In battery manufacturing, it is crucial to have extremely thin separators to increase the battery's energy density and reduce its size. Good peel strength is crucial in battery manufacturing because it prevents separator delamination. This ensures sufficient mechanical strength and high breakdown strength. Battery separators with sufficient breakdown and peel strength can withstand the rigorous conditions of battery manufacturing, particularly for "wound-type" batteries.

In the case where the peel strength of the separator is 0.04 N/cm or greater, the separator has sufficient peel strength and the coating layer will not separate during battery manufacturing.

The drying process of the present invention does not affect the final peel strength of the diaphragm. In some embodiments, the peel strength between the porous substrate material and the protective porous layer is 0.03N/cm or greater, 0.05N/cm or greater, 0.07N/cm or greater, 0.1N/cm or greater, or 0.15N/cm or greater. In certain embodiments, the peel strength between the porous substrate material and the protective porous layer is 0.03N/cm to 0.1N/cm, 0.03N/cm to 0.08N/cm, 0.03N/cm to 0.075N/cm, 0.03N/cm to 0.06N/cm, 0.05N/cm to 0.25N/cm, 0.05N/cm to 0.15N/cm, 0.05N/cm to 0.12N/cm, or 0.05N/cm to 0.1N/cm.

To prevent moisture from entering the sealed container, the electrolyte filling step is performed in a dry room. After drying, the electrode assembly is placed in the container and then sealed under an inert atmosphere. The electrolyte is added to fill all pores in the separator and electrode layers, as well as every gap between the positive electrode, negative electrode, and separator in the electrode assembly.

The methods disclosed herein can reduce the occurrence of defective products, ultimately enabling increased yields, thereby significantly reducing manufacturing costs.

Also provided herein is a lithium battery comprising an electrode assembly prepared by the method disclosed herein.

The following examples are provided to illustrate embodiments of the present invention. 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

The water content in the electrode assembly was measured by Karl-Fisher titration. The electrode assembly was cut into 1 cm × 1 cm pieces in an argon-filled glove box. The cut electrode assembly with a size of 1 cm × 1 cm was weighed in a sample bottle. The weighed electrode assembly was then added to a titration vessel for Karl-Fisher titration using a Karl Fisher coulometric moisture meter (831KF coulometer, Metrohm, Switzerland). The measurement was repeated three times to obtain an average value.

The water content in the separator was measured using Karl-Fisher titration. The electrode assembly was cut into 1 cm x 1 cm pieces in an argon-filled glove box. The electrode assembly was separated into the anode layer, cathode layer, and separator layer. The water content of the separated separator layer was analyzed using Karl-Fisher titration. The measurement was repeated three times to obtain the average value.

The peel strength of the separator was measured by a peel tester (from Instron, USA; model MTS5581). The dried electrode assembly was separated into an anode layer, a cathode layer and a separator layer. Each separator layer was cut into a rectangular shape with a size of 25 mm × 100 mm. Then, a repair tape (3M; USA; model 810) was adhered to the surface of the separator with a protective porous coating, and then pressed by the reciprocating motion of a 2 kg roller above it to prepare a sample for peel strength testing. Each sample was mounted on a peel tester, and the peel strength was measured by peeling the repair tape at 180° at room temperature. The repair tape was peeled at a speed of 50 mm/min. The measurement was performed at predetermined intervals of 10 mm to 70 mm and then repeated 3 times.

Example 1

A) Preparation of the positive electrode

The positive electrode slurry was prepared by mixing 94 wt.% of the cathode material (LNMC TLM 310, from Xinxiang Tianli Energy Co., Ltd., China), 3 wt.% of carbon black (SuperP; from Timcal Ltd, Bodio, Switzerland) as a conductive agent, and 0.8 wt.% of polyacrylic acid (PAA, #181285, from Sigma-Aldrich, USA) as a binder, 1.5 wt.% of styrene-butadiene rubber (SBR, AL-2001, from NIPPONA & LINC., Japan), and 0.7 wt.% of polyvinylidene fluoride (PVDF; 5130, from Solvay S.A., Belgium) (these substances were dispersed in deionized water to form a slurry with a solid content of 50 wt.%). The slurry was homogenized by a planetary stirring mixer.

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 coated film on the aluminum 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, with the temperature gradually increasing from an inlet temperature of 60°C to an outlet temperature of 75°C.

B) 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 coated film 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.

C) Preparation of diaphragm

An aqueous binder solution was prepared by dissolving 50 g of CMC in 6.55 L of deionized water. 100 g of _Al₂O₃ particles (from Taimei Chemicals Co., Ltd., Japan, product number TM-100) and _7.5 g of SBR were added to the binder solution. The average diameter of the inorganic particles was 9 μm. After addition, the suspension was stirred at room temperature at 50 rpm for 30 minutes to form a slurry.

The above slurry was then coated on a 25 μm thick, 30 cm wide porous membrane made of polyethylene (Celgard, LLC, USA) by a continuous roller blade coater (from Shenzhen KEJINGSTAR Technology Ltd., China; model AFA-EI300-UL). The coated membrane was then passed through a drying oven integrated in the roller coater and dried in hot steam at a temperature of 100°C. The coating speed was in the range of 1.2 m/min to 1.7 m/min. The coating thickness was controlled by an adjustable gap between the blade and the coating surface. A coated membrane with a total thickness of about 30 μm and a porosity of about 62% was obtained. The resulting membrane was stored in a moisture environment with a dew point of about 25°C for 1 month to simulate long-term storage conditions. The average value of the moisture content of the membrane was greater than 500 ppm.

After one month of storage, the membrane was dried in a vacuum drying oven at a pressure of 5 x 10 ³ Pa and a temperature of 75° C. for 2 hours during the first drying stage. During the second drying stage, the membrane was further dried under vacuum at a pressure of 5 x 10 ³ Pa and a temperature of 90° C. for 1.5 hours. The average moisture content of the membrane was 58 ppm.

Electrode peel strength

The average values of the peel strength of the pre-dried and untreated separators were 0.08 N/cm and 0.07 N/cm, respectively. The peel strength remained largely unaffected by the drying process.

Example 2

Assembly of electrode assembly

The obtained cathode sheet and anode sheet prepared by the method described in Example 1 were used to prepare cathodes and anodes respectively by cutting into individual electrode plates. The pre-dried separator was cut into individual plates. An electrode assembly was prepared by stacking the anode, cathode and separator inserted between the positive electrode and the negative electrode in the open air without controlling the humidity. The electrode assembly was dried for 2 hours at a pressure of 5×10 ³ Pa and a temperature of 100°C in a vacuum drying oven in a glove box. The drying chamber was then filled with hot dry air having a water content of 5 ppm and a temperature of 90°C. The hot dry air was retained in the drying chamber for 15 minutes before being discharged from the drying chamber. This cycle was repeated 10 times. The average value of the moisture content of the dried electrode assembly was 15 ppm.

Assembly of soft pack batteries

The soft pack battery is assembled by encapsulating the dried electrode assembly in a container (case) made of aluminum-plastic composite film. The cathode electrode plate and the anode electrode plate are kept separate by a diaphragm and the container is prefabricated. Then, under a high-purity argon atmosphere with a humidity and oxygen content of less than 1ppm, the electrolyte is filled into the container that holds the packaged electrodes. The electrolyte is a solution of _LiPF6 (1M) 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 soft pack battery is vacuum sealed and then mechanically pressed using a stamping 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 4.2 V. The rated capacity was about 9 Ah.

II) Cycle performance

The cycling performance of the pouch cell was tested by charging and discharging at a constant current rate of 1C between 3.0V and 4.2V. The cycling performance test results are shown in Figure 1. The capacity retention after 598 cycles was approximately 93.9% of the initial value. This electrochemical testing shows good electrochemical stability and excellent cycling performance of the cell over a wide range of potentials.

Example 3

A) Preparation of the positive electrode

The positive electrode slurry was prepared by mixing 92 _wt .% of the cathode material ( _LiMn2O4 , from HuaGuan HengYuan LiTech Co., Ltd., Qingdao, China), 4 wt.% of carbon black (SuperP; from Timcal Ltd, Bodio, Switzerland) as a conductive agent, and 4 wt.% of polyvinylidene fluoride (PVDF; 5130, from Solvay SA, Belgium) as a binder (these substances were dispersed in N-methyl-2-pyrrolidone (NMP; purity ≥99%, Sigma-Aldrich, USA) to form a slurry with a solid content of 50 wt.%). The slurry was homogenized by a planetary stirring mixer.

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 coated film 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 80°C.

B) Preparation of negative electrode

A negative electrode slurry was prepared by mixing 90 wt.% of hard carbon (HC; 99.5% purity, from Ruifute Technology Co., Ltd., Shenzhen, Guangdong, China) with 1.5 wt.% of carboxymethyl cellulose (CMC, BSH-12, DKS Co., Ltd., Japan) as a binder and 3.5 wt.% of SBR (AL-2001, NIPPONA & LINC., Japan) and 5 wt.% of carbon black as a conductive agent (these substances were dispersed in deionized water to form another slurry with a solid content of 50 wt.%). The 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 about 15 mg/cm ^2. The coated film on the copper foil was dried at about 50°C for 2.4 minutes in a 24-meter-long conveyor-type hot air drying oven running at a conveyor speed of about 10 m/min to obtain a negative electrode.

C) Preparation of diaphragm

An aqueous binder solution was prepared by dissolving 50 g of CMC in 6.55 L of deionized water. 100 _g of TiO particles (from Shanghai Dian Yang Industry Co., Ltd., China) and 7.5 g of SBR were added to the binder solution. The average diameter of the inorganic particles was 10 μm. After addition, the suspension was stirred at room temperature at a stirring speed of 50 rpm for 30 minutes to form a slurry.

The above slurry was then applied to a PET nonwoven fabric (from MITSUBISHI PAPER MILLS LTD, Japan) with a width of 30 cm, a thickness of about 20 μm and a weight per unit area of about 10 g/m ² by a continuous roller blade coater (from Shenzhen KEJINGSTAR Technology Ltd., China; model AFA-EI300-UL). The coated membrane was then passed through a drying oven integrated in the roller coater and dried in hot steam at a temperature of 100°C. The coating speed was in the range of 1.2 m/min to 1.7 m/min. The coating thickness was controlled by an adjustable gap between the blade and the coating surface. A coated membrane with a total thickness of about 30 μm and a porosity of about 62% was obtained. The membrane was stored in a moisture environment with a dew point of about 20°C for 1 month to simulate long-term storage conditions. The average value of the moisture content of the membrane was greater than 1,000 ppm.

After storage for 1 month, the membrane was dried in a vacuum drying oven for 4 hours at a pressure of 1×10 ³ Pa and a temperature of 85° C. The average value of the moisture content of the membrane was 43 ppm.

Electrode peel strength

The average values of the peel strength of the pre-dried and untreated separators were 0.07 N/cm and 0.06 N/cm, respectively. The peel strength remained largely unaffected by the drying process.

Example 4

Assembly of electrode assembly

The obtained cathode sheet and anode sheet prepared by the method described in Example 3 were used to prepare cathodes and anodes respectively by cutting into individual electrode plates. The pre-dried separator was cut into individual plates. An electrode assembly was prepared by stacking an anode, a cathode and a separator inserted between the positive electrode and the negative electrode in the open air without controlling the humidity. The electrode assembly was dried in a vacuum drying oven in a glove box at a pressure of 1×10 ⁴ Pa and a temperature of 102°C for 3 hours. The drying chamber was then filled with hot dry air having a water content of 5 ppm and a temperature of 85°C. The hot dry air was retained in the drying chamber for 5 minutes before being discharged from the drying chamber. This cycle was repeated 10 times. The average value of the moisture content of the dried electrode assembly was 23 ppm.

Assembly of soft pack batteries

The soft pack battery is assembled by encapsulating the dried electrode assembly in a container (case) made of aluminum-plastic composite film. The cathode electrode plate and the anode electrode plate are kept separate by a diaphragm and the container is prefabricated. Then, under a high-purity argon atmosphere with a humidity and oxygen content of less than 1ppm, the electrolyte is filled into the container that holds the packaged electrodes. The electrolyte is a solution of _LiPF6 (1M) 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 soft pack battery is vacuum sealed and then mechanically pressed using a stamping 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 4.2 V. The rated capacity was approximately 9.1 Ah.

II) Cycle performance

The cycling performance of the soft pack battery was tested by charging and discharging at a constant current rate of 1C between 3.0V and 4.2V. The cycling performance test results are shown in Figure 2. The capacity retention after 452 cycles was approximately 95.0% of the initial value. This electrochemical test shows good electrochemical stability and excellent cycling performance of the battery over a wide range of potentials.

Example 5

A) Preparation of the positive electrode

The positive electrode _slurry was prepared by mixing 94 wt.% of _the cathode material _{LiNi0.33Mn0.33Co0.33O2} (from Shenzhen Tianjiao Technology Co., Ltd., China) _, 3 wt.% of carbon black (SuperP; from Timcal Ltd, Bodio, Switzerland) as a conductive agent, and 1.5 wt.% of polyacrylic acid (PAA, #181285, from Sigma-Aldrich, USA) and 1.5 wt.% of polyacrylonitrile (LA 132, Chengdu Yindi Le Power Technology Co., Ltd., China) as binders (these substances were dispersed in deionized water to form a slurry with a solid content of 50 wt.%). The slurry was homogenized by a planetary stirring mixer.

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 coated film 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 temperature-controlled oven allowed for a controlled temperature gradient, gradually increasing from an inlet temperature of 60°C to an outlet temperature of 75°C.

B) 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 coated film 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.

C) Pretreatment of the diaphragm

A ceramic-coated PET microporous separator (from MITSUBISHI PAPERMILLS LTD, Japan) with a thickness of about 30 μm was used. The separator was stored in a moisture environment with a dew point of about 16° C. for 1 month to simulate long-term storage conditions. The average moisture content of the separator was greater than 800 ppm.

After storage for 1 month, the membrane was dried in a vacuum drying oven for 2.5 hours at a pressure of 2×10 ³ Pa and a temperature of 90° C. The average value of the moisture content of the membrane was 52 ppm.

Electrode peel strength

The average values of the peel strength of the pre-dried and untreated separators were 0.11 N/cm and 0.09 N/cm, respectively. The peel strength remained largely unaffected by the drying process.

Example 6

Assembly of electrode assembly

The obtained cathode sheet and anode sheet prepared by the method described in Example 5 were used to prepare cathodes and anodes respectively by cutting into individual electrode plates. The pre-dried separator was cut into individual plates. An electrode assembly was prepared by stacking the anode, cathode and separator inserted between the positive electrode and the negative electrode in the open air without controlling the humidity. The electrode assembly was dried in a vacuum drying oven in a glove box at a pressure of 1×10 ³ Pa and a temperature of 110°C for 2 hours. The drying chamber was then filled with hot dry air having a water content of 5 ppm and a temperature of 100°C. The hot dry air was retained in the drying chamber for 10 minutes before being discharged from the drying chamber. This cycle was repeated 10 times. The average value of the moisture content of the dried electrode assembly was 18 ppm.

Assembly of soft pack batteries

The soft pack battery is assembled by encapsulating the dried electrode assembly in a container (case) made of aluminum-plastic composite film. The cathode electrode plate and the anode electrode plate are kept separate by a diaphragm and the container is prefabricated. Then, under a high-purity argon atmosphere with a humidity and oxygen content of less than 1ppm, the electrolyte is filled into the container that holds the packaged electrodes. The electrolyte is a solution of _LiPF6 (1M) 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 soft pack battery is vacuum sealed and then mechanically pressed using a stamping 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 4.2 V. The rated capacity was approximately 8.9 Ah.

II) Cycle performance

The cycling performance of the pouch cell was tested by charging and discharging at a constant current rate of 1C between 3.0V and 4.2V. The cycling performance test results are shown in Figure 3. The capacity retention after 561 cycles was approximately 94.3% of the initial value. This electrochemical test shows good electrochemical stability and excellent cycling performance of the battery over a wide range of potentials.

Example 7

Pretreatment of diaphragms

An uncoated microporous separator made of PET nonwoven fabric with a thickness of about 20 μm (from MITSUBISHIPAPERMILLS LTD, Japan) was used. The separator was stored in a moisture environment with a dew point of about 16°C for 1 month to simulate long-term storage conditions. The average moisture content of the separator was greater than 800 ppm.

After storage for 1 month, the membrane was dried in a vacuum drying oven for 2 hours at a pressure of 2×10 ³ Pa and a temperature of 100° C. The average moisture content of the membrane was 42 ppm. After drying, the moisture content of the dried membrane was significantly reduced.

Example 8

Preparation of diaphragm

The coated separator was prepared by the method described in Example 3. The separator was then stored in a moisture environment with a dew point of about 20° C. for 1 month to simulate long-term storage conditions. The average moisture content of the separator was greater than 1,000 ppm.

After storage for 1 month, the membrane was dried in a vacuum drying oven for 2 hours at a pressure of 4.5×10 ³ Pa and a temperature of 155° C. The average value of the moisture content of the membrane was 23 ppm.

Electrode peel strength

The average values of the peel strength of the pre-dried and untreated membranes were 0.035 N/cm and 0.075 N/cm, respectively. After the pre-drying step, the peel strength of the untreated membrane was significantly reduced. This makes the membrane susceptible to mechanical damage when the electrode assembly is assembled by an automatic high-speed stacking machine. In this case, the membrane deteriorates during the high-temperature heat treatment, where the aqueous binder material in the coating becomes brittle. Therefore, lower temperatures are beneficial for slow drying to avoid cracking or embrittlement of the protective porous layer.

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

Claims (29)

1. A method for preparing an electrode assembly, comprising the following steps: 1) Prepare a slurry comprising conductive agent, active battery electrode material, and binder material; 2) The slurry is applied to the collector to form a coating film on the collector; 3) Dry the coating film on the collector; 4) A membrane comprising a porous substrate material and a protective porous layer comprising an adhesive material and an inorganic filler coated on one or both surfaces of the porous substrate material, pre-dried in a vacuum at a temperature of 50°C to 150°C. 5) Stacking at least one anode, at least one cathode, and at least one pre-dried diaphragm inserted between the at least one anode and the at least one cathode; and 6) Dry the electrode assembly in a vacuum at a temperature of 70°C to 150°C; The adhesive material is a water-based adhesive or a mixture of a water-based adhesive and an organic adhesive; and the peel strength between the porous substrate material and the protective porous layer is 0.04 N/cm or greater. 2. The method of claim 1, wherein the porous substrate material is a nonwoven fabric composed of natural fibers or polymer fibers, and wherein the melting point of the polymer fibers is 200°C or higher. 3. The method of claim 1, wherein the porous substrate material is made of polymer fibers selected from the group consisting of polyolefins, polyethylene, polypropylene, polypropylene/polyethylene copolymers, polybutene, polypentene, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polysulfone, polyphenylene ether, polyphenylene sulfide, polyacrylonitrile, polyvinylidene fluoride, polyoxymethylene, polyoxymethylene, polyvinylpyrrolidone, polyester, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, and combinations thereof. 4. The method of claim 1, wherein the porous substrate material is made of polymer fibers selected from the group consisting of high-density polyethylene, linear low-density polyethylene, low-density polyethylene, ultra-high molecular weight polyethylene, and combinations thereof. 5. The method of claim 1, wherein the diaphragm is pre-dried for a period of 2 to 12 hours. 6. The method of claim 1, wherein the diaphragm is pre-dried for a period of 2 to 8 hours. 7. The method of claim 1, wherein the diaphragm is pre-dried at a pressure of less than 25 kPa. 8. The method of claim 1, wherein the diaphragm is pre-dried at a pressure of less than 15 kPa. 9. The method of claim 1, wherein the diaphragm is pre-dried at a pressure of less than 10 kPa. 10. The method of claim 1, wherein the diaphragm is pre-dried at a pressure of less than 5 kPa. 11. The method of claim 1, wherein the peel strength between the porous substrate material and the protective porous layer is 0.1 N/cm or greater. 12. The method of claim 1, wherein the inorganic filler is selected from the group consisting of _Al₂O₃ , _SiO₂ , _TiO₂ , _ZrO₂ , _BaOₓ , _ZnO , _CaCO₃ , TiN, AlN, _MTiO₃ , _K₂O · _nTiO₂ , _Na₂O · _mTiO₂ , and combinations thereof, wherein x is 1 or 2; M is Ba, Sr, or Ca; n is 1, 2, 4, 6, or 8; and m is 3 or 6. 13. The method of claim 1, wherein the water-based adhesive material is selected from the group consisting of styrene-butadiene rubber, acrylic styrene-butadiene rubber, acrylonitrile copolymer, nitrile rubber, nitrile butadiene rubber, acryloyl rubber, butyl rubber, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepoxychloropropane, polyphosphazene, polyacrylonitrile, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl cellulose, cyanoethyl sucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid ester, polycarboxylic acid, polyacrylic acid, polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, alginate, and combinations thereof, wherein the organic adhesive is selected from the group consisting of polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, fluorinated polymers, and combinations thereof. 14. The method of claim 1, wherein the weight ratio of the inorganic filler to the binder material is 99:1 to 1:1. 15. The method of claim 1, wherein the thickness of the diaphragm is from 1 μm to 80 μm. 16. The method of claim 1, wherein the porosity of the diaphragm is 40% to 97%. 17. _The method of claim 1, wherein the active battery electrode material is a cathode material selected from _the group _consisting of _LiCoO₂ , _LiNiO₂ , LiNiₓMn₂yO₂, _Li₁ + _{zNiₓMn₂yCo₁- xyO₂ , LiNiₓCo₂yAl₂O₂ , 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. 18. The method of claim 1, wherein the conductive agent is selected from the group consisting of carbon black, graphite, graphene, carbon fiber, carbon nanotubes, activated carbon, mesoporous carbon, and combinations thereof. 19. The method of claim 1, wherein the conductive agent is carbon. 20. The method of claim 1, wherein the conductive agent is selected from the group consisting of expanded graphite, graphene nanosheets, carbon nanofibers, graphitized carbon sheets, and combinations thereof. 21. The method of claim 1, wherein the electrode assembly is dried under a pressure of less than 25 kPa. 22. The method of claim 1, wherein the electrode assembly is dried under a pressure of less than 15 kPa. 23. The method of claim 1, wherein the electrode assembly is dried under a pressure of less than 10 kPa. 24. The method of claim 1, wherein the electrode assembly is dried under a pressure of less than 5 kPa. 25. The method of claim 1, wherein the electrode assembly is dried for a period of 2 hours to 24 hours. 26. The method of claim 1, wherein the electrode assembly is dried for a period of 4 to 12 hours. 27. The method of claim 1, wherein, based on the total weight of the pre-dried diaphragm, the moisture content of the pre-dried diaphragm is less than 50 ppm by weight. 28. The method of claim 1, wherein the moisture content of the dried electrode assembly is less than 20 ppm by weight, based on the total weight of the dried electrode assembly. 29. A lithium battery comprising an electrode assembly prepared by the method of claim 1.