Pre-lithiation method of lithium ion capacitor

Abstract

A pre-lithiation method of a lithium ion capacitor includes preparing a plurality of cathodes, anodes, and separators, stacking them, implanting an electrolyte, and performing a multi-step charging process. The surfaces of some anodes are coated with a lithium foil having a thickness of 10 microns to 40 microns, while others remain uncoated, which are alternately stacked. The cathode may include pores accounting for 0.001% to 50% of the current collector area, while the anode has less or no pores. By using a partially coated lithium foil strip and controlling the pressing, temperature and charge rate, lithium ions are moved through the cathode to the uncoated anode, thereby reducing manufacturing costs and achieving efficient pre-lithiation. The post-treatment step may discard or reprocess the incompletely lithiated anode. The method provides a flexible way to optimize foil thickness, pore distribution, and charging profile to achieve high performance lithium ion capacitors with improved cost and process efficiency.

Description

[0001] Cross-reference to related applications

[0002] This application claims the benefit of Korean Patent Application No. 10-2024-0110817, filed with the Korean Intellectual Property Office on August 19, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to a pre-lithiation method for lithium-ion capacitors, which enables pre-lithiation to be performed in a structure comprising alternating stacked cathodes and anodes with lithium foil and uncoated anodes, thereby reducing the use of porous current collectors and thus lowering the overall cost of pre-lithiation. Background Technology

[0004] By combining the anode of a lithium-ion battery with the cathode of a supercapacitor, lithium-ion capacitors achieve higher capacities and power outputs than conventional supercapacitors. While lithium-ion capacitors use lithium ions as the carrier ion, similar to lithium-ion batteries, the internal lithium source is insufficient due to the presence of carbon materials in both the anode and cathode. To overcome these drawbacks, lithium-ion capacitors are typically pre-lithiated, where an additional lithium source is used to pre-charge the anode. However, traditional pre-lithiation of lithium-ion capacitors has limitations in various implementations. Therefore, a more economical process for pre-lithiating lithium-ion capacitors is needed. Summary of the Invention

[0005] The present invention aims to solve the aforementioned problems in the prior art while maintaining the advantages achieved by the prior art.

[0006] Some embodiments of the present invention provide a pre-lithiation method for a lithium-ion capacitor. More specifically, some embodiments of the present invention provide a pre-lithiation method for a lithium-ion capacitor, wherein a porous foil is used as the cathode current collector, a regular foil is used as the anode current collector, and an anode with a lithium foil coating and an anode without a lithium foil coating are used alternately, wherein the lithium foil is at least 20 micrometers in size, thereby significantly reducing the cost of pre-lithiation.

[0007] The technical problems to be solved by the present invention are not limited to those described above. Those skilled in the art will clearly understand from the following description any other technical problems not mentioned herein.

[0008] To achieve the above objectives, the present invention provides a pre-lithiation method for lithium-ion capacitors and a lithium-ion capacitor.

[0009] In one aspect, a method for pre-lithiating a lithium-ion capacitor is provided, the method comprising: 1) forming a battery by alternatingly arranging a cathode and an anode and disposing a separator therebetween, wherein at least one anode is coated with a lithium foil and at least one anode has no lithium foil coating on its surface; 2) adding an electrolyte composition to the battery; and subsequently 3) pre-lithiating the battery.

[0010] In another aspect, (1) the present invention provides a pre-lithiation method for a lithium-ion capacitor, comprising: preparing a plurality of cathodes, a plurality of anodes and a plurality of separators (S1); forming a battery by stacking the cathodes, separators and anodes such that the separators are disposed between the cathodes and anodes (S2); and performing pre-lithiation after adding (e.g., injecting) an electrolyte composition or solution into the battery (S3). The anodes comprise a first anode having opposing surfaces coated with lithium foil and a second anode having opposing surfaces uncoated with lithium foil, and the first anode and the second anode are stacked alternately on top of each other.

[0011] (2) The present invention provides a pre-lithiation method for a lithium-ion capacitor in (1), wherein the cathode includes a cathode current collector and a cathode active material layer formed on the opposite surface of the cathode current collector, the cathode current collector having pores.

[0012] (3) The present invention provides a pre-lithiation method for a lithium-ion capacitor in (1) or (2), wherein the proportion of the area occupied by the pores is 0.001% to 50% of the total area of ​​the cathode current collector.

[0013] (4) The present invention provides a pre-lithiation method for a lithium-ion capacitor in any one of (1) to (3), wherein the anode current collector has pores, the proportion of the area occupied by the pores being at most 10% of the total area of ​​the anode current collector, or there are no pores in the anode current collector.

[0014] (5) The present invention provides a method for pre-lithiation of a lithium-ion capacitor in any one of (1) to (4), wherein the thickness of the lithium foil coated on the opposite surface of the first anode ranges from 10 micrometers to 40 micrometers.

[0015] (6) The present invention provides a method for pre-lithiation of a lithium-ion capacitor in any of (1) to (5), wherein 'S3' is performed by an electrochemical pre-lithiation scheme.

[0016] (7) The present invention provides a lithium-ion capacitor comprising a plurality of cathodes, an anode and a separator disposed between the cathodes and the anode, wherein the anode comprises a first anode having a lithium foil-coated opposing surface and a second anode having an uncoated lithium foil-coated opposing surface, and the first anode and the second anode are stacked alternately on top of each other.

[0017] (8) The present invention provides a lithium-ion capacitor comprising a plurality of cathodes, anodes and a separator disposed between the cathodes and anodes, wherein the anodes include a third anode having lithium residue on its surface and a fourth anode not having lithium residue on its surface, and the third anode and the fourth anode are stacked alternately on each other.

[0018] In some embodiments, the pre-lithiation method for a lithium-ion capacitor includes: preparing a plurality of cathodes, anodes, and separators; then forming a battery by stacking these components such that each cathode and anode is separated by a separator; and finally performing pre-lithiation after injecting an electrolyte solution into the battery. The anode has a first anode with a lithium foil coated on its surface and a second anode without a coating, arranged in an alternating sequence. Furthermore, the cathode may include a current collector with pores, and the proportion of these pores may range from about 0.001% to about 50%. The anode may include a current collector with pores occupying at most about 10% of its area or with no pores at all. The thickness of the lithium foil on the first anode may be from about 10 micrometers to about 40 micrometers. Pre-lithiation can be performed via an electrochemical scheme.

[0019] In some embodiments, a lithium-ion capacitor includes multiple cathodes, anodes, and a separator disposed between each cathode and anode. The anodes have a first anode with a lithium foil coating and a second anode without coating, and these anodes are stacked in an alternating sequence. Furthermore, after the pre-lithiation process, the first anode can become a third anode with lithium residue on its surface, and the second anode can become a fourth anode without such residue; the third and fourth anodes are also arranged in an alternating sequence.

[0020] In some embodiments, a pre-lithiation method for a lithium-ion capacitor includes preparing multiple cathodes, anodes, and separators, wherein the cathodes have pores covering approximately 0.001% to approximately 50% of their total area, and the anodes are substantially non-porous or have at most approximately 10% pore area. These components are then stacked such that at least one anode portion is coated with a lithium foil strip, and at least one anode remains uncoated. An electrolyte solution is injected, and multi-step pre-lithiation is performed in at least two distinct charging phases, wherein the partially coated lithium foil can be approximately 10 micrometers to approximately 40 micrometers thick, transferring lithium ions to the uncoated anode. Furthermore, the foil strip can extend along the length of the anode current collector, and pre-lithiation can include a lower current phase followed by a phase with a current density at least 50% higher. The partially coated foil can cover less than approximately 70% of each coated surface and have a thickness of at least approximately 20 micrometers to reduce cost. During this process, a temperature of approximately 10°C to approximately 40°C can be maintained, and each cathode can use a carbon-based active material. Each anode can use carbon-containing or silicon-containing materials, along with binders and conductive additives. The method may also include pressing the stack at approximately 5 MPa to approximately 20 MPa prior to electrolyte injection, and may follow a constant current-constant voltage protocol until the uncoated anode reaches approximately 90% of the theoretical lithium uptake. Lithium foil strips may be formed by laser cutting or die cutting and adhered under dry conditions, and any anode with incomplete lithiation (exhibiting a voltage above approximately 0.3V) may be removed or replaced. Attached Figure Description

[0021] The above and other objects, features and advantages of the invention will become more apparent from the detailed description that follows in conjunction with the accompanying drawings, in which:

[0022] Figure 1 This is a schematic diagram of pre-lithiation in an external centralized battery solution.

[0023] Figure 2 This is a schematic diagram of pre-lithiation in a lithium distribution scheme;

[0024] Figure 3 This is a schematic diagram of pre-lithiation in an all-anodine surface coating scheme;

[0025] Figure 4 A schematic diagram of pre-lithiation according to the present invention; and

[0026] Figure 5 This is a comparison diagram showing the results when the first and second anodes are stacked alternately versus when they are not stacked alternately. Detailed Implementation

[0027] The invention will be described in more detail below.

[0028] The terms and words used in this specification and claims should not be interpreted as having their usual dictionary meanings, but rather as relating to the technical scope of the invention, based on the fact that the inventors can appropriately define the concepts of the terms to best interpret the invention.

[0029] As used in this article, the term "lithiation" refers to the process of introducing lithium ions into electrode materials (e.g., anodes), typically through electrochemical means such as charging or doping, so that the electrode becomes lithiated and can insert or store lithium for subsequent battery operation.

[0030] As used in this article, the term "pre-lithiation" refers to a specific form of lithiation of the electrode (typically the anode) before the battery is fully operational, ensuring that the electrode contains sufficient lithium storage from the outset. This process may involve additional steps, either inside or outside the battery, to supply lithium from an external source, thereby mitigating issues such as lithium shortages during the initial charge cycle.

[0031] As used in this article, the term "porous foil" refers to a metal foil, such as aluminum or nickel, which includes intentionally formed or naturally occurring pores or openings to allow some fluid or ions to permeate through its structure.

[0032] The term “external battery concentration scheme” used in this article refers to a pre-lithiation method in which the lithium source (e.g., lithium foil) is located outside the battery stack so that lithium ions migrate inward through a porous current collector to reach the anode.

[0033] The term “lithium distribution scheme” used in this article refers to a pre-lithiation method in which multiple lithium sources are placed in different locations within the battery, allowing lithium ions to move in opposite or different directions to charge the anode.

[0034] The term “all-anode surface coating scheme” used in this article refers to a pre-lithiation method in which the surfaces of all anodes in the battery are directly coated with lithium (usually through a thin foil layer).

[0035] As used in this article, “electrochemical pre-lithiation” refers to the process of charging and / or discharging a battery under controlled voltage or current conditions to drive lithium ions to the electrode (e.g., the anode) before the battery is in normal operation.

[0036] The term “XPS analysis” used in this article refers to X-ray photoelectron spectroscopy, an analytical technique used to detect the presence or absence of certain elements or chemical states (such as lithium residues) on the surface of an electrode.

[0037] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used herein, unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the / said” are intended to also include the plural forms. These terms are intended only to distinguish one component from another, and the terms do not limit the nature, order, or sequence of these constitutive components. It should also be understood that the terms “comprising” and / or “including,” when used in this specification, specify the presence of the stated features, integrals, steps, operations, elements, and / or components, but do not exclude the presence of said features, integrals, steps, operations, elements, and / or components, or the addition of one or more other features, integrals, steps, operations, elements, components, and / or groups thereof. As used herein, the term “and / or” includes any and all combinations of one or more of the associated enumerations. Throughout the specification, unless expressly stated to the contrary, the words “comprising” and variations such as “including” or “having” are to be understood as including said elements, but not excluding any other elements. Furthermore, the terms “unit,” “component,” “device,” and “module” described in this specification refer to a unit for performing at least one function and operation, and may be implemented by hardware components or software components and combinations thereof.

[0038] While exemplary embodiments are described as using multiple units to perform exemplary processes, it should be understood that exemplary processes can also be performed by one or more modules. Furthermore, it should be understood that the term controller / control unit refers to a hardware device including a memory and a processor, specifically programmed to perform the processes described herein. The memory is configured to store modules, and the processor is specifically configured to execute said modules to perform one or more processes further described below.

[0039] Furthermore, the control logic of the present invention can be implemented as a non-volatile computer-readable medium on a computer-readable medium, which contains executable program instructions that are executed by a processor, controller, etc. Examples of computer-readable media include (but are not limited to) ROM, RAM, optical disc (CD)-ROM, magnetic tape, floppy disk, flash drive, smart card, and optical data storage device. The computer-readable medium can also be distributed across a network-connected computer system, thereby enabling the computer-readable medium to be stored and executed in a distributed manner via, for example, a telematics server or a controller area network (CAN).

[0040] Unless otherwise stated or obvious from the context, the term “about” as used herein is understood to mean within the normal tolerance range in the field, such as within two standard deviations of the mean. “About” can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless the context clearly indicates otherwise, all numerical values ​​provided herein are modified by the term “about”.

[0041] Pre-lithiation method for lithium-ion capacitors

[0042] The pre-lithiation method for lithium-ion capacitors according to the present invention will be described in detail below.

[0043] Pre-lithiation methods for lithium-ion capacitors can be broadly categorized into in-situ methods, where the pre-lithiation process is carried out inside the battery, and non-in-situ methods, where the pre-lithiation process is carried out outside the battery before assembly. Based on the location of the lithium source inside the battery, in-situ pre-lithiation methods are further divided into: 1) external centralized method; 2) lithium distribution method; and 3) full anode surface coating method.

[0044] According to the battery external centralized solution, such as Figure 1 The diagram illustrates the formation of a battery for pre-lithiation. When lithium ions located outside the battery are introduced into the battery, they are charged to the anode inside the battery. However, to move lithium ions from the outside of the battery into the battery, current collectors for both the cathode and anode should be provided in the form of a porous foil with pores. According to this scheme, the thickness of the lithium foil (which is the lithium ion source located outside the battery) can be from approximately 80 micrometers to approximately 150 micrometers.

[0045] According to the lithium distribution scheme, such as Figure 2 The diagram illustrates a battery formation for pre-lithiation. Lithium ions can be charged into the anode inside the battery as the lithium source distributed within it moves in the opposite direction. Even in the current design, the current collectors for both the cathode and anode should be provided in the form of porous foil, similar to the externally concentrated design. In this case, the thickness of the lithium foil distributed within the battery can be approximately 40 micrometers to approximately 80 micrometers.

[0046] According to the all-anode surface coating scheme, all anode surfaces are directly coated with lithium, such as... Figure 3 As shown. According to this scheme, the current collectors of the cathode and anode do not need to be porous. However, since all anode surfaces are coated, the thickness of the lithium foil coating on the anode surface is quite thin, ranging from 5 to 15 micrometers.

[0047] Both externally concentrated lithium-ion battery designs and lithium distribution designs should use porous foil as the current collector. The manufacturing cost of porous foil is higher than that of ordinary foil. Specifically, because the anode in both the cathode and anode reacts with lithium, a higher permeability is required. Therefore, the anode needs a porous foil with higher permeability. As permeability increases, the manufacturing cost of the porous foil also increases. Specifically, in the externally concentrated lithium-ion battery design, in order to smoothly move lithium ions from the lithium foil located on the outside of the battery to the anode located at the innermost part of the battery, the current collectors of both the cathode and anode should have higher permeability, thus significantly increasing the battery manufacturing cost.

[0048] According to the all-anode surface coating scheme, although ordinary foil can be used instead of porous foil, the thickness of the lithium foil must be very thin. The price of lithium foil varies depending on its thickness. Typically, thin lithium foils smaller than 20 micrometers are difficult to manufacture, resulting in a considerably high price. Therefore, the manufacturing cost of the battery increases significantly due to the use of thin lithium foil in the all-anode surface coating scheme. To use thicker lithium foil while employing the all-anode surface coating scheme, lithium foil can be coated on the surface of all anodes. In this case, the lithium foil is coated into strips, ensuring that the thickness of the lithium foil is at least a specific value. However, this scheme requires additional processes to manufacture the strip-shaped lithium foil. Furthermore, coating strip-shaped lithium foil is more difficult than coating single-sheet lithium foil, thus increasing the process complexity. Additionally, the pre-lithiation time is increased because lithium ions move more slowly relative to the electrode in the horizontal direction.

[0049] According to the pre-lithiation method for lithium-ion capacitors of the present invention, in order to solve the problems of the above-mentioned solutions, effective pre-lithiation of lithium-ion capacitors can be achieved at the lowest cost.

[0050] More specifically, the present invention provides a pre-lithiation method for a lithium-ion capacitor, comprising preparing a plurality of cathodes, a plurality of anodes, and a plurality of separators (S1), forming a battery by stacking the cathodes, separators, and anodes such that the separators are disposed between the cathodes and anodes (S2), and injecting an electrolyte solution into the battery (S3). The anodes include a first anode having opposing surfaces coated with lithium foil, and a second anode having opposing surfaces uncoated with lithium foil, wherein the first and second anodes are stacked alternately on top of each other.

[0051] According to the present invention, the lithium-ion capacitor includes multiple cathodes, multiple anodes, and multiple separators. The cathodes, anodes, and separators included in the lithium-ion capacitor can be prepared first.

[0052] The cathode included in the lithium-ion capacitor may include a cathode current collector and a cathode active material layer formed on opposite surfaces of the cathode current collector, and the cathode current collector may have pores. According to the prelithiation of the present invention, the lithium foil should only be partially coated on the anode surface, and the cathode current collector should have pores because, during the prelithiation process, lithium ions in the lithium foil move through the cathode to the anode on the other side.

[0053] The pores of the cathode current collector may have a circular or amorphous shape, and the material of the cathode current collector may be a metallic material, such as aluminum, stainless steel, nickel, titanium, or an alloy of metallic materials. In addition, the proportion of the area occupied by the pores may be from 0.001% to 50% of the total area of the cathode current collector. Preferably, the area proportion may be at least 0.1%, at least 0.5%, at least 1%, at least 3%, at least 5%, at least 10%, or at least 15%, and at most 50%, at most 45%, at most 40%, at most 35%, or at most 30%. When the cathode current collector satisfies the above conditions, lithium ions can move easily from the lithium foil, and the durability of the cathode can be ensured.

[0054] The cathode active material layer may include a conventional cathode active material, an adhesive, and a conductive material used in the lithium-ion capacitor. For example, the cathode active material may be a carbon material (such as activated carbon, graphene, hard carbon, or soft carbon), or a lithium metal oxide-based or sulfide-based active material. The oxide active material may be a rock salt-type active material, such as LiCoO2, LiMnO2, LiNiO2, LiVO2, or Li 1+x Ni 1 / 3 Co 1 / 3 Mn 1 / 3 O2; a spinel-type active material, such as LiMn2O4 or Li(Ni 0.5 Mn 1.5 )O4; an inverse spinel-type active material, such as LiNiVO4 or LiCoVO4; an olivine-type active material, such as LiFePO4, LiMnPO4, LiCoPO4, or LiNPO4; a silicon-containing active material, such as Li2FeSiO4 or Li2MnSiO4; a rock salt-type active material, such as LiNi 0.8 Co( 0.2-x )Al x O2(0 < x < 0.2), which is obtained by substituting a part of the transition metal with a heterogeneous metal; a spinel-type active material, such as Li 1+x Mn 2-x-y MyO4 (M is at least one of Al, Mg, Co, Fe, Ni, and Zn; 0 < x + y < 2), which is obtained by substituting a part of the transition metal with a heterogeneous metal; or a lithium titanate, such as Li4Ti5O 12The sulfide active material can be copper chevrel, iron sulfide, cobalt sulfide, or nickel sulfide.

[0055] The adhesive, which is the component that binds together the components contained in the electrode active material layer, may include butadiene rubber (BR), nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), or carboxymethyl cellulose (CMC).

[0056] The conductive material (which enhances the electronic conductivity of the electrode active material layer) can be carbon black, conductive graphite, ethylene black, or graphene.

[0057] The anode in a lithium-ion capacitor includes an anode current collector and an anode active material layer formed on the opposing surfaces of the anode current collector. The anode current collector may include pores, the proportion of which is at most 10% of the total area of ​​the anode current collector, or the anode current collector may have no pores. The anode used in the pre-lithiation method of the lithium-ion capacitor of the present invention includes a first anode having opposing surfaces coated with lithium foil and a second anode having opposing surfaces uncoated with lithium foil, and the first and second anodes are stacked alternately on top of each other. Therefore, during pre-lithiation, lithium ions are prevented from passing through the anode. Therefore, the anode current collector may have pores occupying a very small area, or may have no pores. To reduce the time of the pre-lithiation process, an anode current collector with pores can be used. In this case, the proportion of the area occupied by the pores can be at most 10% of the total area of ​​the anode current collector, preferably at most 5%. As the proportion of the area occupied by the pores in the anode current collector increases, the manufacturing cost of the anode current collector increases, and the durability of the anode current collector decreases. However, according to the pre-lithiation scheme of the present invention, the cost of the pre-lithiation process can be minimized because the pores in the anode current collector are minimized. Furthermore, the anode current collector can even be made of a metallic material, such as aluminum, stainless steel, nickel, or titanium, or a metallic alloy similar to the material of the cathode current collector.

[0058] Meanwhile, the thickness of the lithium foil coated on both sides of the first cathode can be from 10 micrometers to 40 micrometers. Preferably, the lithium foil thickness can be at least 10 micrometers, at least 15 micrometers, at most 40 micrometers, at most 35 micrometers, or at most 30 micrometers. According to the pre-lithiation in conventional all-anode surface coating schemes, the thickness of the lithium foil should be about 5 micrometers to 15 micrometers, which is a very thin thickness range. However, according to the present invention, since the lithium foil is partially coated on the anode, the thickness of the lithium foil can be further increased. Therefore, the cost of reducing the thickness of the lithium foil can be saved. As the thickness of the lithium foil decreases, the manufacturing cost increases. In particular, manufacturing lithium foil with a thickness of less than 20 micrometers requires a large amount of cost. Therefore, when the lithium foil has an appropriate thickness, the cost can be reduced. According to the present invention, the manufacturing cost of the lithium foil can be saved by partially coating the lithium foil on the anode.

[0059] The anode active material layer may include conventional anode active materials, binders, and conductive materials used in lithium-ion capacitors. For example, the anode active material may be a carbon material, such as graphene, hard carbon, or soft carbon, or a material such as lithium metal oxide or silicon.

[0060] The description of the conductive materials and binders used in the cathode active material layer can be equally applied to the description of the conductive materials and binders contained in the anode active material.

[0061] The separator is a porous material through which lithium ions can pass. There are no particular limitations on the material of the separator, as long as the material is suitable for the separator described in this invention. For example, the separator may include at least one selected from polyethylene and polypropylene, and a ceramic or adhesive may be coated onto the separator comprising this material.

[0062] A battery structure can be formed by stacking the cathode, anode, and separator prepared as described above. More specifically, the lithium-ion capacitor according to the invention has multiple structures by repeating the structure of the separator between the cathode and the anode multiple times. More specifically, a battery structure can be formed by stacking multiple cathodes, multiple anodes, and multiple separators prepared in the order of cathode, separator, anode, separator, cathode, separator, and anode.

[0063] Simultaneously, when stacking the cathode, anode, and separator as described above, the anode should be arranged such that a first anode having a lithium foil-coated opposing surface and a second anode having an uncoated lithium foil opposing surface are stacked alternately. For example, the first and second anodes should be arranged in the order of cathode, separator, first anode, separator, cathode, separator, second anode, and separator. As described above, when the first and second anodes are stacked alternately, such as... Figure 4 and Figure 5As shown, lithium ions (formed by lithium foil coated on the opposing surfaces of the first anode) can pass through the surface facing the cathode and move to the second anode, which is not coated with lithium foil. Therefore, all anodes can be pre-lithiated. When the first and second anodes are not stacked alternately as described above, there may be anodes that fail to contact lithium ions and are not pre-lithiated. More specifically, as... Figure 5 As shown, when the first anode and the second anode are not stacked alternately, but are stacked in the order of first anode, second anode, second anode, there may be anodes that have not been pre-lithiated because lithium ions are not transferred.

[0064] After forming the above-described lithium-ion capacitor structure, an electrolyte solution can be injected into the battery and pre-lithiated. When the electrolyte solution is injected into the battery, the lithium metal contained in the lithium foil coated on the first anode surface can be converted into lithium ions through pre-lithiation, pass through the separator and cathode, and then move to the second anode.

[0065] Pre-lithiation can be performed via an electrochemical approach. This approach involves charging and / or discharging a lithium-ion capacitor by applying current or voltage, thereby pre-lithiating the anode surface. The charging and / or discharging conditions can be varied depending on the desired degree of pre-lithiation.

[0066] There are no particular limitations on the electrolyte solution, as long as it is used in lithium-ion capacitors. For example, the electrolyte solution may include lithium salts. The lithium salt may be at least one selected from: LiPF6, LiBF4, LiClO4, LiSbF6, LiAsF6, LiN(SO42C2F5)2, LiN(CF3SO42)2, LiN(SO43C2F5)2, LiN(SO2F)2, LiCF3SO3, LiC4F9SO3, LiC6H5SO3, LiSCN, LiAlO2, LiAlCl4, LiN(CxF) 2x+1 SO2)(CyF 2y+1SO2), LiCl, LiI, and LiB(C2O4)2. Additionally, the solvent for the electrolyte solution can be a non-aqueous organic solvent, selected from at least one of carbonates, esters, ethers, and ketones. Particularly preferred is that the solvent for the electrolyte solution can be a cyclic carbonate solvent or a linear carbonate solvent. Cyclic carbonates can be at least one selected from ethylene carbonate, propylene carbonate, butyl carbonate, vinylene carbonate, ethylene ethylene carbonate, and fluoroethylene carbonate; linear carbonates can be at least one selected from dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, and ethyl propyl carbonate. The electrolyte may include an electrolyte additive, which may include vinylene carbonate or ethylene ethylene carbonate. Due to the injection of the electrolyte solution, the pre-lithiation process can be carried out more effectively.

[0067] Lithium-ion capacitors

[0068] This invention provides a lithium-ion capacitor for use with the pre-lithiation method described above for lithium-ion capacitors.

[0069] More specifically, the present invention provides a lithium-ion capacitor having a structure comprising a plurality of cathodes, an anode, and a separator disposed between the cathodes and the anodes, wherein the anode comprises a first anode having opposing surfaces coated with lithium foil and a second anode having opposing surfaces uncoated with lithium foil, and the first anode and the second anode are stacked alternately on top of each other.

[0070] The structure of a lithium-ion capacitor (i.e., a lithium-ion capacitor before pre-lithiation) is as described above, wherein a first anode having a lithium foil-coated opposing surface and a second anode having an uncoated opposing surface are stacked alternately on each other.

[0071] In addition, the present invention provides a lithium-ion capacitor having a structure comprising a plurality of cathodes, an anode, and a separator disposed between the cathodes and the anodes, wherein the anodes include a third anode having lithium residue on its surface and a fourth anode not having lithium residue on its surface, the third anode and the fourth anode being stacked alternately on each other.

[0072] The third anode is the first anode after the pre-lithiation process of the lithium-ion capacitor described above, and the fourth anode is the second anode after the pre-lithiation process. In the first anode, which is in direct contact with lithium, fine lithium residues still exist on the anode surface even after the pre-lithiation process. Conversely, in the second anode, which is not in direct contact with lithium, no lithium residues are present on the surface of the second anode.

[0073] Therefore, the lithium-ion capacitor produced by the lithium-ion capacitor pre-lithiation method of the present invention has a third anode and a fourth anode. Simultaneously, the presence of lithium residues can be identified by XPS analysis.

[0074] When the lithium-ion capacitor pre-lithiation method according to the present invention is used, the porous foil is used only for the cathode, and the lithium foil used as the lithium source has a thickness of at least a specific value, thereby minimizing the cost of using the porous foil and the cost of reducing the thickness of the lithium foil, thereby achieving sufficient pre-lithiation at a lower cost.

[0075] Although the invention has been described above with reference to exemplary embodiments and accompanying drawings, it is not limited thereto, but various modifications and alterations can be made by those skilled in the art without departing from the spirit and scope of the invention as claimed in the appended claims.

Claims

1. A method for pre-lithiation of a lithium-ion capacitor, the method comprising: A battery is formed by alternating cathodes and anodes with a separator therebetween, wherein at least one anode is coated with lithium foil and at least one anode has no lithium foil coating on its surface; Add an electrolyte composition to the battery; then The battery is pre-lithiated.

2. The pre-lithiation method for lithium-ion capacitors according to claim 1, wherein, The cathode includes: A cathode current collector and a cathode active material layer formed on the opposing surfaces of the cathode current collector. The cathode current collector has pores.

3. The pre-lithiation method for lithium-ion capacitors according to claim 2, wherein, The proportion of the area occupied by pores is 0.001% to 50% of the total area of ​​the cathode current collector.

4. The pre-lithiation method for lithium-ion capacitors according to claim 1, wherein, The anode includes: An anode current collector and an anode active material layer formed on the opposing surfaces of the anode current collector. The anode current collector includes pores, and the area occupied by the pores is at most 10% of the total area of ​​the anode current collector, or there are no pores in the anode current collector.

5. The pre-lithiation method for lithium-ion capacitors according to claim 1, wherein, The thickness of the lithium foil coated on the opposite surface of the first anode is 10 micrometers to 40 micrometers.

6. The pre-lithiation method for lithium-ion capacitors according to claim 1, wherein, Pre-lithiation was performed using an electrochemical pre-lithiation scheme.

7. A lithium-ion capacitor, comprising: Multiple cathodes, anodes, and a diaphragm disposed between the cathodes and the anodes. The anode includes: A first anode having opposing surfaces coated with lithium foil and a second anode having opposing surfaces uncoated with lithium foil. The first anode and the second anode are stacked alternately on top of each other.

8. The lithium-ion capacitor according to claim 7, wherein, After the pre-lithiation process, the first anode corresponds to the third anode with lithium residue on its surface, the second anode corresponds to the fourth anode without lithium residue on its surface, and the third and fourth anodes are stacked alternately on top of each other.

9. A method for pre-lithiation of a lithium-ion capacitor, the method comprising: Multiple cathodes, multiple anodes, and multiple diaphragms are prepared. Each cathode has a cathode current collector, which includes pores in a proportion ranging from 0.001% to 50% of the total area of ​​the cathode current collector. Each anode has an anode current collector, which is substantially free of pores or has pores comprising at most 10% of the total area of ​​the anode current collector. A stack is formed by alternating cathodes and anodes and placing a diaphragm therebetween, such that at least one anode portion is coated with strip-shaped lithium foil, and at least one anode has no lithium foil coating on its surface; An electrolyte composition is added to the stack. as well as Multi-step pre-lithiation is performed by applying different charging conditions in at least two consecutive stages, wherein a partially coated lithium foil on at least one anode has a thickness of 10 micrometers to 40 micrometers and is configured to transfer lithium ions to an adjacent uncoated anode via a cathode.

10. The pre-lithiation method for a lithium-ion capacitor according to claim 9, wherein, The strip lithium foil comprises two or more spaced-apart foil strips arranged on each coated anode surface, each foil strip extending substantially along the length of the anode current collector.

11. The pre-lithiation method for a lithium-ion capacitor according to claim 9, wherein, Multi-step pre-lithiation includes: The first charging phase involves a current density of 0.05C to 0.1C; and The second charging stage involves a current density that is at least 50% higher than that of the first charging stage.

12. The pre-lithiation method for lithium-ion capacitors according to claim 9, wherein, The partially coated lithium foil occupies less than 70% of the surface area of ​​each coated anode to allow lithium ions to move laterally through the cathode during the pre-lithiation process.

13. The pre-lithiation method for lithium-ion capacitors according to claim 9, wherein, The partially coated lithium foil has a thickness of at least 20 micrometers, which reduces manufacturing costs compared to fully coated lithium foil with a thickness of 5 to 15 micrometers.

14. The pre-lithiation method for lithium-ion capacitors according to claim 9, further comprising controlling the temperature of the stack within the range of 10°C to 40°C during the multi-step pre-lithiation process to improve lithium-ion diffusion rate and reduce process time.

15. The pre-lithiation method for a lithium-ion capacitor according to claim 9, wherein, Each cathode comprises a carbon-based active material selected from activated carbon, graphene, hard carbon, soft carbon, or combinations thereof.

16. The pre-lithiation method for a lithium-ion capacitor according to claim 9, wherein, Each anode comprises a carbon-based active material or a silicon-containing material, and also includes a binder and conductive additives dispersed therein.

17. The pre-lithiation method for a lithium-ion capacitor according to claim 9, further comprising pressing the stack at a pressure of 5 MPa to 20 MPa before injecting an electrolyte solution, thereby enhancing the interfacial contact between the partially coated anode and adjacent components.

18. The pre-lithiation method for a lithium-ion capacitor according to claim 9, wherein, Multi-step pre-lithiation is performed using a constant current and constant voltage protocol, which terminates when each uncoated anode reaches at least 90% of its theoretical lithium absorption capacity.

19. The pre-lithiation method for a lithium-ion capacitor according to claim 9, wherein, The partial lithium foil strips on each coated anode are formed by laser cutting or die-cutting from block lithium foil and then adhered to the anode current collector in a drying chamber environment.

20. The pre-lithiation method for a lithium-ion capacitor according to claim 9, further comprising removing or replacing any anode exhibiting incomplete lithiation, said incompletely lithilated anode exhibiting a residual voltage relative to a lithium reference electrode exceeding 0.3V after multi-step pre-lithiation is completed.

Images