A lithium-ion cell design and corresponding regeneration procedure

Abstract

A lithium-ion cell configured as an electrode stack or as a cylindrical roll; the lithium-ion cell including a negative terminal, a positive terminal, and a regeneration terminal. The negative terminal being formed of one or more anode layers, each anode layer including at least one anode active material and an anodic current collector. The positive terminal being formed of at least one cathode layer, the at least one cathode layer including one or more cathode active materials and a cathodic current collector. The regeneration terminal being formed of one or more metallic lithium layers; the one or more metallic lithium layers being a lithium reservoir configured to reduce the negative terminal's potential during regeneration of the lithium-ion cell.

Description

A LITHIUM-ION CELL DESIGN AND CORRESPONDING REGENERATION PROCEDUREFIELD

[0001] This disclosure generally relates to a three terminal lithium-ion cell configured for regeneration. This disclosure further relates to a method of regenerating said cell.BACKGROUND

[0002] The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

[0003] Due to relatively low cost, one of the mainstream lithium-ion cells utilized in electric vehicles (EVs) comprises graphite as the anode active material and LiFePC>4 (LFP) as the cathode active material. These cells also provide a high level of safety, as well as an excellent cycling life, e.g., up to thousands of cycles. However, the capacity of these cells has a tendency to decrease or fade due to continuous “active lithium” loss during cycling and storage. Since there is a high demand for graphite / LFP cells for use in EVs, there is a need to extend the cycling life of these cells so that they can be used in other applications after they are retired or removed from the EVs. The extension of a cell’s lifetime will reduce the frequency at which a battery must be replaced. This in turn reduces the volume of batteries that need to be recycled, wherein such recycling consumes a significant amount of energy and generates a large carbon footprint.

[0004] Various approaches have been utilized to extend the cycling life of graphite / LFP cells. For example, an article entitled “Enhancing cycle life and usable energy density of fast charging LiFePC>4-graphite cell by regulating electrodes’ lithium level” by Rikka et al. published in iScience has extended the cycling life of graphite / LFP cells by controlling the cycling state of charge (SOC) - depth of discharge (DOD) ranges. However, the extension of the cycling life is accomplished in this approach at the cost of having a reduced energy density / cycle. Moreover, the charging / discharging protocol used in this approach is not able to regenerate the graphite / LFP cells.

[0005] An article entitled “Significant life extension of lithium-ion batteries using compact metallic lithium reservoir with passive control” by Colclasure et al. published in Electrochimica Acta describes an approach to recover the “active lithium” loss at the graphite electrode by inserting a small piece of metallic lithium into the electrode rolls in order to lithiate the graphite anode in a 3-electrode configuration. A boost of 6% in the capacity of the cell was obtained by discharging the graphite anode with metallic lithium. This approach attempts to regenerate graphite / LFP cells by lithiating the graphite anode. This approach, however, is not practical for commercial cells because such a lithiation process will not be homogeneous at the graphite anode. In other words, the lithium electrode will not be able to directly face the graphite anode - but rather, it can only be placed at the edge side, which will restrict the lithium distribution on the anode during the lithiation process with a much higher content of active lithium at the edge that is close to the lithium source.

[0006] Therefore, there is a need to develop a more practical approach for cell regeneration including both the design of a lithium-ion cell, as well as a method of regenerating said cell.SUMMARY

[0007] The present disclosure generally relates to a three terminal lithium-ion cell configured for regeneration. More specifically, the lithium-ion cell, which may be configured as an electrode stack or as a cylindrical roll, comprises: a negative terminal that includes one or more anode layers, each anode layer contains at least one anode active material and an anodic current collector; a positive terminal that includes at least one cathode layer, the at least one cathode layer contains one or more cathode active materials and a cathodic current collector; and a regeneration terminal that includes one or more metallic lithium layers; the one or more metallic lithium layers being a lithium reservoir configured to reduce the negative terminal’s potential during regeneration of the lithium-ion cell. The one or more lithium layers may each have a thickness that is in the range of 0.1 pm to 10 mm.

[0008] The active anode material may be selected from the group consisting of graphite, hard carbon, silicon Si, SiO, and mixtures or combinations thereof. The active cathode material may be selected from the group consisting of from LiFePCU, LiFexMnyPO4 (x+y = 1 ), UC0O2, Li n2C>4, lithium nickel manganese cobalt oxides (NCM), and mixtures or combinations thereof. When desirable, the one or more of theanode active materials and the cathode active materials may comprise a porous film. This porous film may further include at least one binder and optionally the inclusion of one or more conductive additives.

[0009] The anodic current collector and the cathodic current collector may be individually selected as a mesh, a perforated foil, ora foam. Each of the anodic current collector and the cathodic current collector exhibits a level of porosity that is at least partially derived from the presence of a plurality of pores or through-holes. When desirable, the anodic current collector may comprise a copper Cu mesh having a level of porosity in the range from 1 % to 99% and the cathodic current collector may comprise an aluminum Al mesh having a level of porosity in the range from 1 % to 99%. The anodic current collector generally has a thickness that is in the range of 3 pm to 15 pm, while the cathodic current collector generally has a thickness ranging from 6 pm to 30 pm.

[0010] According to another aspect of the present disclosure, a method for regenerating the lithium-ion cell is provided. This method generally comprises: operating the lithium-ion cell until the lithium-ion cell’s capacity decays to < 90% of its initial capacity level; connecting either directly or indirectly the negative terminal of the decayed lithium-ion cell to the regeneration terminal of the lithium-ion cell; and allowing the negative terminal’s potential to be reduced by the lithium reservoir of the regeneration terminal, thereby regenerating the lithium-ion cell. The regeneration terminal may be directly connected to the negative terminal. The potential of the negative terminal may be reduced by > 100 mV; alternatively, the negative terminal’s potential is reduced by > 1 mV.

[0011] According to yet another aspect of the present disclosure a method for forming the lithium-ion cell is provided. This method generally comprises: providing one or more anode active materials, anodic current collectors, cathode active materials, and cathodic current collectors; preparing one or more anode layers by applying the anode active materials to the anodic current collectors; preparing one or more cathode layers by applying the cathode active materials to the cathodic current collectors; providing at least one metallic lithium layer; providing a plurality of separators; stacking the anode layers, the cathode layers, the at least one metal lithium layer, and separators to form an electrode stack, such that the at least one metallic lithium layer is located next to the outer and / or inner layer of the electrode stack; connecting the anode layers to form a negative terminal; connecting the cathodelayers to form a positive terminal; and connecting the at least one metal lithium layer to form a regeneration terminal. When desirable, the method may further comprise rolling the electrode stack to form a cylindrical roll.

[0012] In this method, the metal lithium layers may be located next to both the outer and inner layer of the electrode stack. The electrode stack may have a layered structure of S / Li / S / A / S / C / S / A...S / C / S / A / S / Li / S; wherein S = separator, A = anode layer, C = cathode layer, and Li = metallic lithium layer. In this method, applying the anode active material to the anodic current collector and / or applying the cathode active material to the cathodic current collector includes forming an electrode film using a dry coating process followed by laminating the electrode film to the corresponding current collector.

[0013] Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.DESCRIPTION OF DRAWINGS

[0014] In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings.

[0015] Fig. 1 is a graphical representation of a full cell with three terminals formed according to the teachings of the present disclosure.

[0016] Fig. 2 is a flowchart that describes the formation of the full cell with three terminals of Fig. 1 .

[0017] Fig. 3 is a flowchart that describes a method of regenerating a lithium-ion cell formed according to the teachings of the present disclosure.

[0018] Figs. 4A and 4B are graphical representations of anode and cathode potential changes that occur during cycling of the graphite / LFP cell of Fig. 1 according to the teachings of the present disclosure.

[0019] Fig. 5A is a graphical representation of the cycling stability of the graphite / LFP cell before regeneration.

[0020] Fig. 5B is a graphical comparison of the discharge voltage curves measured for the fresh cells and regenerated cells according to the teachings of the present disclosure.

[0021] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.DETAILED DESCRIPTION

[0022] The following description is merely exemplary in nature and is in no way intended to limit the present disclosure or its application or uses. For example, the three-terminal lithium-ion cell made and used according to the teachings contained herein are described throughout the present disclosure in conjunction with a cylindrical battery in order to more fully illustrate the composition and the use thereof. The incorporation and use of such a regeneration cell design and regeneration process in other types of batteries is contemplated to be within the scope of the present disclosure. It should be understood that throughout the description, corresponding reference numerals indicate like or corresponding parts and features.

[0023] The present disclosure generally provides a three terminal lithium-ion cell that is configured for regeneration. Instead of incorporating a small piece of lithium at or near the edge of the electrode layers (e.g., jelly rolls), the cell design of the present disclosure is configured for more efficient regeneration of the full cell. Referring now to Fig. 1 , the cell 1 designed and formed according to one aspect of the present disclosure comprises a negative terminal 5, a positive terminal 10, and a regeneration terminal 15. The negative terminal 5 includes one or more anode layers 3 comprising an anode active material (e.g., graphite film) and an anodic current collector (e.g., copper Cu porous current collector). The active anode material may be attached to the anodic current collector by, without limitation, coating, gluing, or through the use of a similar method. The positive terminal 10 includes at least one cathode layer 7 comprising a cathode active material (e.g., LiFePC>4 film) and a cathodic current collector (e.g., aluminum Al porous current collector). Similar to the anode layers, the active cathode material may be attached to the cathodic current collector by, without limitation, coating, gluing, or through the use of a similar method. The regeneration terminal 15 includes one or more metallic lithium layers (e.g., lithium film). This lithium layer may be applied onto a current collector (e.g., a thin copper Cu foil or mesh), thereby, creating one or more lithium reservoirs or electrodes 11 configured to reduce the negative terminal’s potential during regeneration of the lithium-ion cell.

[0024] The anode layers 3 and cathode layers 7 may be stacked as an electrode stack 20 using any known or conventional process. When necessary or desired, thiselectrode stack 20 may also be rolled into a cylindrical roll prior to being placed into a container or structure (e.g., pouch, can, etc.). This rolled spiral structure may also be referred to as a “jelly roll.”

[0025] For the purpose of this disclosure, the terms "at least one" and "one or more of' an element are used interchangeably and may have the same meaning. These terms, which refer to the inclusion of a single element or a plurality of the elements, may also be represented by the suffix "(s)"at the end of the element. For example, "at least one lithium reservoir", "one or more lithium reservoirs", and "lithium reservoir(s)" may be used interchangeably and are intended to have the same meaning.

[0026] For the purpose of this disclosure the terms "about" and "substantially" are used herein with respect to measurable values and ranges due to expected variations known to those skilled in the art (e.g., limitations and variability in measurements).

[0027] For the purpose of this disclosure recitations of numerical ranges by endpoints include the endpoints and all numbers within that numerical range. For example, an amount ranging from 40% by weight to 65% includes the values of 40%, 65%, and all values there between (e.g., 40.1 %, 41 %, 45%, 50%, 52.5%, 55%, 59%, 63%, etc.).

[0028] Still referring to Fig. 1 , the electrode stack 20 may comprise anode (A) layers 3, cathode (C) layers 7, and separators (S) 9 stacked in any order, such as for example, S / A / S / C / S / A...S / C / S / A / S, provided that at least one lithium thin film, which acts as a lithium reservoir (Li) 11 , is included in the stacked arrangement or structure located next to the outer or inner layer of the electrode stack / roll. The lithium reservoirs (Li) 11 may also be placed at both locations, i.e. , next to the outer layer and the inner layer in the stack or roll. An example of an electrode stack may also be described by the order from inside to outside or from top to bottom of S / Li / S / A / S / C / S / A...S / C / S / A / S / Li / S. In these stack / roll configurations, S = separator, A = anode, C = cathode, and Li = lithium layer or reservoir.

[0029] Due to the porous structure of the current collectors, the various electrode (anode or cathode) films or layers, and the separators present in the electrode stack 20, lithium ions Li+can diffuse through the electrode stack 20 from one lithium reservoir 11 to the other lithium reservoir 11 or from one lithium reservoir 11 to the anode 3 located at or near the other end of the electrode stack 20. The free ion diffusion path from one end to the other end of the electrode stack 20 is critical for the homogeneous lithiation of the anode 3 during the regeneration step.

[0030] According to another aspect of the present disclosure, more than two lithium Li reservoirs 11 may be placed within a cell with at least one lithium layer or reservoir 11 being located inside the stack to reduce the lithium ion diffusion distance between the adjacent lithium reservoirs 11. In this cell design, the lithium reservoirs or electrodes are connected to form a 3rdterminal, which is the regeneration terminal 15 of the lithium-ion cell, which is present along with both the positive 10 and negative 5 terminals. Therefore, the cell 1 design according the present disclosure has three terminals with one of them being the regeneration terminal 15. In Fig. 1 , a cross- sectional illustration of a 3-terminal full cell 1 formed according to the present disclosure is shown. In this cell 1 design, the regeneration terminal 15 may also be used as a reference electrode to monitor the potential changes that occur at the negative terminal 5 and positive terminal 10 during the operation of the cell.

[0031] According to another aspect of the present disclosure, the current collectors used in the anode layer 3 and in the cathode layer 7 need to have some porosity; alternatively, moderate porosity; alternatively, a high-level of porosity. This porosity is at least partially derived from or formed as a plurality of pores or as a plurality of through-holes in the current collector. The size of these pores and / or holes may range from a few nanometers to a few millimeters. This porosity or “through holes’’ may also be represented by a pore / hole size that ranges from 10 nm to 500 pm; alternatively, from 15 nm to 350 pm; alternatively, from 20 nm to 200 pm. When desirable or necessary one or more of the anode active materials and cathode active materials may be comprised of a porous film. These porous films may comprise substantially of the anode or cathode active materials, as well as at least one binder material to hold the active materials together and / or enhance adhesion to the corresponding current collector. These porous films may also optionally include one or more conductive additives to further enhance the interaction between the active materials and the corresponding current collector.

[0032] The current collector(s) may be a mesh, a perforated foil, or a foam. Alternatively, the current collector(s) are porous foils or mesh, such as for example copper Cu or aluminum Al porous foils or mesh. The porosity percentage exhibited by the porous current collectors may be in the range from 1 % to about 99%; alternatively, from 10% to 80%; alternatively, between about 30% to about 70%. The thickness of the copper Cu porous foil / mesh may range from 3 pm to 15 pm, with the range of 5 pm to 10 pm being alternatively utilized. The thickness of the aluminum Al porous foilmay range from 6 m to 30 pm with the range of 12 pm to 20 pm being alternatively utilized.

[0033] The thickness of the metallic lithium layers used to form the regeneration terminal is typically in the range of 0.1 pm to 10 mm; alternatively, 0.5 pm to 1 mm; alternatively, 1 pm to 500 pm; alternatively, 10 pm to 100 pm. The metallic lithium layers may also be applied to a current collector in the form of a mesh, foil, or foam. For example, the current collector in contact with or upon which the metallic lithium layer is applied may comprise copper Cu.

[0034] According to another aspect of the present disclosure, the cathode layers may comprise any cathode active material known to be used in lithium-ion batteries. These cathode active materials may include, but not be limited to, LiFePC , LiFexMnxPO4 (x+y = 1 ), LiMn2C>4, LiCoCh, lithium nickel manganese cobalt oxides (NCM), LNio.5Mn1.5O4, sulfur, and mixtures or combinations thereof. The anode layers may comprise any anode active material configured for operation at a potential range <1.5 V vs. Li / Li+. These active anode materials may be selected from graphite, hard carbon, silicon Si, SiO, and mixtures or combinations thereof.

[0035] Referring now to Fig. 2, a method of forming the three-terminal lithium-ion cell as described above and as further defined herein is provided. This method 50 generally comprises providing 55 one or more anode active materials, anodic current collectors, cathode active materials, and cathodic current collectors followed by preparing 60 one or more anode layers by applying the anode active materials to the anodic current collectors, as well as preparing 65 one or more anode layers by applying the anode active materials to the anodic current collectors. At least one metallic lithium layer is also provided 70, as well as a plurality of separators 75. Then, the anode layers, the cathode layers, the at least one metal lithium layer, and the separators are stacked 80 to form an electrode stack, such that the at least one metallic lithium layer is located next to the outer and / or inner layer of the electrode stack. Alternatively, the metal lithium layers are located next to both the outer and inner layer of the electrode stack. Finally, the anode layers are connected 85 to form a negative terminal, while the cathode layers are connected 86 to form a positive terminal and the at least one metallic lithium layer is connected 87 to form a regeneration terminal. If necessary or desirable, the electrode stack may be rolled 90 to form a cylindrical roll.

[0036] Due to the porous structure of the current collector(s), it might be challenging to coat the current collector(s)s with liquid slurries as done using a conventional coating process, particularly, when the pores in the current collector(s) are relatively large. Thus, the use of free standing electrode films formed via a dry coating process may be preferred for this cell design. Thus, according to one aspect of the present disclosure, an anode electrode film and / or a cathode electrode film may be formed using a dry coating process 62, 67 followed by laminating the electrode film(s) to the corresponding current collector(s) 63, 68. For a specific example, a graphite electrode may be prepared by: i) forming an electrode film of graphite / binder / conductive additives via a dry coating process; ii) applying a thin layer of conductive carbon or polymers as a primer coating onto a copper Cu mesh current collector; and iii) laminating the electrode film onto the primed Cu mesh under pressure and heat.

[0037] According to yet another aspect of the present disclosure, a method of regenerating the three-terminal lithium ion cell of the present disclosure as described above and as further defined herein is provided. Referring now to Fig. 3, this regeneration method 100 generally comprises operating 105 the lithium-ion cell until the lithium-ion cell’s capacity decays to < 90% of its initial capacity level; connecting 110 either directly or indirectly the negative terminal of the decayed lithium-ion cell to the regeneration terminal of the lithium-ion cell; and allowing 115 the negative terminal’s potential to be reduced by the lithium reservoir of the regeneration terminal, thereby regenerating the lithium-ion cell. Alternatively, the negative terminal of the decayed lithium-ion cell is connected 110 directly to the regeneration terminal of the lithium-ion cell. During the regeneration the potential of the negative terminal is reduced > 100 mV; alternatively, > 70 mV; alternatively, > 50 mV; alternatively, > 20 mV; alternatively, > 1 mV.

[0038] The following specific examples are provided to further illustrate the active anode materials formed according to the teachings of the present disclosure and the method of forming these materials, as well as the properties thereof and should not be construed to limit the scope of the disclosure. Those skilled-in-the-art, in light of the present disclosure, will appreciate that many changes can be made in the specificembodiments which are disclosed herein and still obtain alike or similar result without departing from or exceeding the spirit or scope of the disclosure.

[0039] One skilled in the art will further understand that any properties reported herein represent properties that are routinely measured and can be obtained by multiple different methods. The methods described herein represent one such method and other methods may be utilized without exceeding the scope of the present disclosure.

[0040] Experimental Example

[0041] The following experimental example demonstrates the typical potential change of the anode and the cathode in a graphite / LFP full cell during cycling. The measured data obtained in this example is provided and summarized in Figs. 4A & 4B, as well as Table 1.

[0042] Figs. 5A and 5B show the capacity and electrode potential changes that occur for the graphite / LFP full cell before and after regeneration. As demonstrated in the figures, the cell capacity increased after regeneration.

[0043] The cell in this example is a single-layer pouch cell in which a small disk of lithium is placed at the side of the electrodes as a 3rd(e g., reference) electrode. During cycling, the potential of the anode is measured / monitored against the lithium reference electrode. For this 3-terminal cell, the anode potential measurement may exhibit some variability because the measured potential represents the voltage difference between the lithium disk and the copper Cu edge of the current collector for the graphite anode. Regardless of this variability, the potential measured / monitored from the anode side illustrates the potential changes that occur at the anode and cathode sides upon cycling.

[0044] The results measured in this example as shown in Figs. 4A & 4B, as well as in Table 1 , demonstrate that the minimum potential at the anode side and the maximum potential at the cathode side both increase during cycling. The maximum anode potential and the minimum cathode potential also are observed to increase during cycling. This trend is consistent with the expectation of “active lithium” loss occurring at the anode side during cycling. The anode potential is expected to drift up during cycling.

[0045] Table 1 . Anode & Cathode Potential Changes in a Graphite / LFP Cell During Cycling.

[0046] After the cell was fabricated or formed, it was cycled as a conventional cell by using only the negative and positive terminals. Once the cell had been cycled, such that a significant capacity loss was observed (e.g., < 90% initial capacity), the cell was ready for regeneration. Forthis regeneration, the regeneration terminal was connected to the negative terminal indirectly through a resistor or a battery tester. Since the lithium potential is always 0 V vs. Li / Li+, the initial voltage between the negative terminal and the regeneration terminal was > 0 V with the negative terminal having a higher potential. Once the negative terminal was connected to the regeneration terminal, the voltage dropped with the negative anode layer being reduced by the lithium metal connected to the regeneration terminal. By doing this, the negative anode layer was regenerated with fresh “active lithium”.

[0047] There are various methods available to monitor the occurrence and / or progress of the regeneration step without exceeding the scope of the present disclosure. The extent to which the cell is regenerated may be monitored and controlled by the recorded capacity contributed from the lithium. It is also possible to monitor the anode minimum / maximum potential change during the regeneration. It may also be possible to monitor and / or control the regeneration by the discharging time and discharge conditions.

[0048] Upon completion of the regeneration, e.g., after discharging the negative terminal potential to a targeted level, the regeneration terminal and the negative terminal is disconnected. The regenerated cell has an improved level of capacity as compared to the decayed cell. The regenerated cell can then be used in the same manner as the conventional cell prior to its initial loss in capacity.

[0049] Within this specification, embodiments have been described in a way which enables a clear and concise specification to be written, but it is intended and will be appreciated that embodiments may be variously combined or separated without parting from the invention. For example, it will be appreciated that all preferred features described herein are applicable to all aspects of the invention described herein.

[0050] The foregoing description of various forms of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Numerous modifications or variations are possible in light of the above teachings. The forms discussed were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various forms and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.

Claims

CLAIMSWhat is claimed is:

1. A lithium-ion cell configured as an electrode stack or as a cylindrical roll; the lithium-ion cell comprising: a negative terminal that includes one or more anode layers, each anode layer comprising at least one anode active material and an anodic current collector; a positive terminal that includes at least one cathode layer, the at least one cathode layer comprising one or more cathode active materials and a cathodic current collector; and a regeneration terminal that includes one or more metallic lithium layers; the one or more metallic lithium layers being a lithium reservoir configured to reduce the negative terminal’s potential during regeneration of the lithium-ion cell.

2. The lithium-ion cell according to claim 1 , wherein the active anode material is selected from the group consisting of graphite, hard carbon, silicon Si, SiO, and mixtures or combinations thereof.

3. The lithium-ion cell according to any of claims 1 or 2, wherein the active cathode material is selected from the group consisting of from LiFePC , LiFexMnyPO4 (x+y = 1 ), LiCoO2, LiMn2O4, lithium nickel manganese cobalt oxides (NCM), and mixtures or combinations thereof.

4. The lithium-ion cell according to any of claims 1 to 3, wherein the anodic current collector and the cathodic current collector are individually selected as a mesh, a perforated foil, or a foam; wherein each of the anodic current collector and the cathodic current collector exhibits a level of porosity that is at least partially derived from the presence of a plurality of pores or through-holes.

5. The lithium-ion cell according to any of claims 1 to 4, wherein one or more of the anode active materials and the cathode active materials comprises a porous film.

6. The lithium-ion cell according to claim 5, wherein the porous film further comprises at least one binder and optionally the inclusion of one or more conductive additives.

7. The lithium-ion cell according to any of claims 1 to 6, wherein the anodic current collector comprises a copper Cu mesh having a level of porosity in the range from 1 % to 99%.

8. The lithium-ion cell according to any of claims 1 to 7, wherein the anodic current collector has a thickness ranging from 3 pm to 15 pm.

9. The lithium-ion cell according to any of claims 1 to 8, wherein the cathodic current collector comprises an aluminum Al mesh having a level of porosity in the range from 1 % to 99%.

10. The lithium-ion cell according to any of claims 1 to 9, wherein the cathodic current collector has a thickness ranging from 6 pm to 30 pm.11 . The lithium-ion cell according to any of claims 1 to 10, wherein the one or more lithium layers each have a thickness in the range of 0.1 pm to 10 mm.

12. A method for regenerating the lithium-ion cell of any of claims 1 to 1 1 ; wherein the method comprises: operating the lithium-ion cell until the lithium-ion cell’s capacity decays to < 90% of its initial capacity level; connecting either directly or indirectly the negative terminal of the decayed lithium-ion cell to the regeneration terminal of the lithium-ion cell; and allowing the negative terminal’s potential to be reduced by the lithium reservoir of the regeneration terminal, thereby regenerating the lithium-ion cell.

13. The method according to claim 12, wherein the regeneration terminal is directly connected to the negative terminal.

14. The method according to any of claims 12 or 13, wherein the negative terminal’s potential is reduced > 100 mV.

15. The method according to any of claims 12 to 14, wherein the negative terminal’s potential is reduced > 1 mV.

16. A method for forming the lithium-ion cell of any of claims 1 to 11 , wherein the method comprises: providing one or more anode active materials, anodic current collectors, cathode active materials, and cathodic current collectors; preparing one or more anode layers by applying the anode active materials to the anodic current collectors; preparing one or more cathode layers by applying the cathode active materials to the cathodic current collectors; providing at least one metallic lithium layer; providing a plurality of separators; stacking the anode layers, the cathode layers, the at least one metal lithium layer, and separators to form an electrode stack, such that the at least one metallic lithium layer is located next to the outer and / or inner layer of the electrode stack; connecting the anode layers to form a negative terminal; connecting the cathode layers to form a positive terminal; and connecting the at least one metal lithium layer to form a regeneration terminal.

17. The method according to claim 16, wherein the method further com prises rolling the electrode stack to form a cylindrical roll.

18. The method according to any of claims 16 or 17, wherein the metal lithium layers are located next to both the outer and inner layer of the electrode stack.

19. The method according to claim 18, wherein the electrode stack has a layered structure of S / Li / S / A / S / C / S / A... S / C / S / A / S / Li / S; wherein S = separator, A = anode layer, C = cathode layer, and Li = metallic lithium layer.

20. The method according to any of claims 16 to 19, wherein applying the anode active material to the anodic current collector and / or applying the cathode active material to the cathodic current collector includes forming an electrode film using a dry coating process followed by laminating the electrode film to the corresponding current collector.

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