Secondary lithium battery negative electrode and method of manufacturing the same

Abstract

Disclosed are a negative electrode of a secondary lithium battery and a method of manufacturing the same. Provided herein are a negative electrode of a secondary lithium battery, and a method of assembling a secondary lithium battery including the same. The negative electrode includes a current collector having a first side and an opposite second side. A first negative electrode layer is disposed on the first side of the current collector, and a second negative electrode layer is disposed on the second side of the current collector. A lithium metal layer is disposed (i) between the first and second negative electrode layers or (ii) on a major facing surface of the first or second negative electrode layer. An electrolyte permeates the first and second negative electrode layers and is in contact with the lithium metal layer. The electrolyte establishes a lithium ion transport path between the lithium metal layer and at least one of the first or second negative electrode layers.

Description

Technical Field

[0001] The present invention relates to the negative electrode of a secondary lithium battery pack, and more particularly to a method for manufacturing a pre-lithiated negative electrode and a secondary lithium battery pack including the pre-lithiated negative electrode. Background Technology

[0002] A battery pack is a device that converts chemical energy into electrical energy through electrochemical reduction-oxidation (redox) reactions. In secondary or rechargeable battery packs, these electrochemical reactions are reversible, allowing the battery pack to undergo multiple charge and discharge cycles.

[0003] Secondary lithium-ion battery packs typically comprise one or more electrochemical cells that operate by reversibly transferring lithium ions between a negative electrode and a positive electrode. The negative and positive electrodes are typically positioned on opposite sides of a porous polymer membrane, and each electrode is typically supported on or connected to a metal current collector. The negative and positive electrodes, along with the polymer membrane, are permeated with an ion-conducting electrolyte that provides the medium for conducting lithium ions through the electrochemical cell between the negative and positive electrodes. In practice, an electrochemical potential is established between the negative and positive electrodes by connecting the respective current collectors of the negative and positive electrodes to each other via a interruptible external circuit. During discharge, the electrochemical potential established between the negative and positive electrodes drives spontaneous redox reactions within the electrochemical cell and the release of lithium ions and electrons at the negative electrode. The released lithium ions move from the negative electrode to the positive electrode via the ion-conducting electrolyte, and electrons move from the negative electrode to the positive electrode via the external circuit, thus generating a current. After the negative electrode has been partially or completely depleted of lithium, the electrochemical cell can be recharged by connecting the negative and positive electrodes to an external power source. This drives a non-spontaneous redox reaction within the electrochemical cell and releases lithium ions and electrons from the positive electrode.

[0004] During the initial charging process of a secondary lithium-ion battery pack, an electrically insulating and ion-conducting layer called the solid electrolyte interphase (SEI) may inherently form in situ on the surface of the negative electrode at the interface between the negative electrode and the electrolyte. This natural SEI is thought to be inherently formed due to the low reduction potential of the electrochemically active material of the negative electrode, which promotes the reduction of the electrolyte at the surface of the negative electrode. The SEI forms an ion-conducting layer between the negative electrode and the electrolyte (allowing Li-ion exchange to occur). +An SEI (Sediment Electrode I) acts as a barrier for ion transport and electrical insulation. Therefore, forming a stable SEI on the negative electrode helps prevent further physical contact and undesirable side reactions between the negative electrode material and the electrolyte during battery pack operation. However, the chemical reactions between the negative electrode material and the electrolyte that occur during SEI formation are parasitic and can consume active lithium, potentially leading to irreversible capacity loss and reduced battery pack cycle life.

[0005] When silicon (Si) and / or tin (Sn) are used as the electrochemically active material for the negative electrode, the inherent volume changes experienced by the negative electrode during repeated battery cycling can disrupt the stability of the electrolyte interphase (SEI), potentially leading to cracks or gaps within the SEI. These cracks or gaps can impair the electrical insulation barrier function of the SEI and may result in further lithium-consuming chemical reactions between the electrolyte and the exposed surface of the negative electrode, as well as the formation of new SEI material. Therefore, when silicon is used as the negative electrode material in a lithium-ion battery pack, the repeated exposure of the negative electrode material to the electrolyte and the inherent in-situ formation of new SEI material along the exposed surface of the negative electrode can lead to continuous depletion of active lithium, even after the initial SEI formation.

[0006] To compensate for the loss of active lithium during battery cycling, an excess of stoichiometric lithium can be incorporated into the electrochemical cells of a secondary lithium battery pack. Summary of the Invention

[0007] A negative electrode for a secondary lithium-ion battery pack is provided. The negative electrode includes a negative electrode current collector having a first side and an opposing second side. A first porous negative electrode active material layer is disposed on the first side of the negative electrode current collector. A second porous negative electrode active material layer is disposed on the second side of the negative electrode current collector. A lithium metal layer is disposed (i) between the first and second porous negative electrode active material layers or (ii) on the major facing surface of the first or second porous negative electrode active material layer. An electrolyte permeates through the first and second porous negative electrode active material layers. The electrolyte is in contact with at least a portion of the major facing surface of the lithium metal layer. The electrolyte establishes a lithium-ion transport path between the lithium metal layer and at least one of the first or second porous negative electrode active material layers.

[0008] The lithium metal layer can be disposed between the first porous negative electrode active material layer and the second porous negative electrode active material layer.

[0009] The negative electrode current collector may include a first porous metal layer and a second porous metal layer spaced apart from the first porous metal layer. A lithium metal layer may be sandwiched between the confronting surfaces of the first and second porous metal layers. An electrolyte may be in contact with at least a portion of the first main surface and at least a portion of the opposing second main surface of the lithium metal layer.

[0010] The first porous negative electrode active material layer can be disposed on the main surface of the first porous metal layer, and the second porous negative electrode active material layer can be disposed on the main surface of the second porous metal layer.

[0011] The negative electrode current collector can be non-porous. In this case, a first lithium metal layer can be disposed on a first side of the negative electrode current collector, and a second lithium metal layer can be disposed on a second side of the negative electrode current collector. A first porous negative electrode active material layer can be disposed on top of the first lithium metal layer on the first side of the negative electrode current collector. A second porous negative electrode active material layer can be disposed on top of the second lithium metal layer on the second side of the negative electrode current collector.

[0012] The first and second lithium metal layers can be non-porous.

[0013] The negative electrode current collector may be porous and may include a plurality of through holes extending from its first side to its second side. In such a case, at least a portion of the first porous negative electrode active material layer or the second porous negative electrode active material layer may extend at least part-way into the plurality of through holes in the negative electrode current collector.

[0014] The lithium metal layer can be disposed on the main opposing surface of the first porous negative electrode active material layer or on the main opposing surface of the second porous negative electrode active material layer.

[0015] The negative electrode current collector can be porous and may include a plurality of through-holes extending from its first side to its second side. In such a case, a lithium metal layer can be disposed on a first porous negative electrode active material layer on the first side of the negative electrode current collector. Alternatively, the lithium metal layer can be disposed on a second porous negative electrode active material layer on the second side of the negative electrode current collector.

[0016] At least one of the first porous negative electrode active material layer or the second porous negative electrode active material layer may contain a silicon-based electrochemical active material.

[0017] The lithium metal layer can be non-porous and can have a thickness of 20 micrometers to 40 micrometers.

[0018] A secondary lithium-ion battery pack is provided. The battery pack includes a positive electrode and a bifacial negative electrode. The positive electrode includes a porous positive electrode active material layer electrically coupled to the positive electrode current collector. The bifacial negative electrode includes a negative electrode current collector having a first side and an opposing second side. A first porous negative electrode active material layer is disposed on the first side of the negative electrode current collector. A second porous negative electrode active material layer is disposed on the second side of the negative electrode current collector. A lithium metal layer is disposed (i) between the first and second porous negative electrode active material layers or (ii) on the main opposing surface of the first or second porous negative electrode active material layer. A porous separator layer is disposed between the porous positive electrode active material layer of the positive electrode and the first or second porous negative electrode active material layer of the negative electrode. An electrolyte permeates through the porous separator layer, the porous positive electrode active material layer of the positive electrode, the first porous negative electrode active material layer of the negative electrode, and the second porous negative electrode active material layer of the negative electrode. The electrolyte is in contact with at least a portion of the main surface of the lithium metal layer. The electrolyte establishes a lithium-ion transport path between the lithium metal layer and at least one of the first porous negative electrode active material layer or the second porous negative electrode active material layer.

[0019] The lithium metal layer can be non-porous. In this case, the lithium metal layer does not create a physical barrier to the transport of lithium ions between the porous positive electrode active material layer of the positive electrode and the first or second porous negative electrode active material layer of the negative electrode before the initial charging or cycling of the battery pack.

[0020] The negative electrode current collector may include a first porous metal layer and a second porous metal layer spaced apart from the first porous metal layer. In this case, a lithium metal layer may be sandwiched between the opposing surfaces of the first and second porous metal layers. The electrolyte may be in contact with at least a portion of the first main surface and at least a portion of the opposing second main surface of the lithium metal layer.

[0021] The negative electrode current collector can be non-porous. In this case, a first non-porous lithium metal layer can be disposed on a first side of the negative electrode current collector, a second non-porous lithium metal layer can be disposed on a second side of the negative electrode current collector, a first porous negative electrode active material layer can be disposed on the first non-porous lithium metal layer on the first side of the negative electrode current collector, and a second porous negative electrode active material layer can be disposed on the second non-porous lithium metal layer on the second side of the negative electrode current collector.

[0022] The lithium metal layer can be disposed on the main opposing surface of the first porous negative electrode active material layer or on the main opposing surface of the second porous negative electrode active material layer. In this case, the negative electrode current collector can be porous and can include multiple through holes extending from its first side to its second side.

[0023] At least one of the first porous negative electrode active material layer or the second porous negative electrode active material layer may contain a silicon-based electrochemical active material.

[0024] The lithium metal layer can be non-porous and can have a thickness of 20 micrometers to 40 micrometers.

[0025] A method for assembling a secondary lithium-ion battery pack is provided. In this method, a first porous negative electrode active material layer can be deposited on a first side of a negative electrode current collector, and a second porous negative electrode active material layer can be deposited on an opposite second side of the negative electrode current collector. A lithium metal layer can be laminated (i) between the first and second porous negative electrode active material layers or (ii) on the main opposing surface of the first or second porous negative electrode active material layer. A porous positive electrode active material layer can be deposited on the positive electrode current collector. A porous separator layer can be positioned between the porous positive electrode active material layer and either the first or second porous negative electrode active material layer. A non-aqueous electrolyte can permeate the porous separator layer, the porous positive electrode active material layer, the first porous negative electrode active material layer, and the second porous negative electrode active material layer. The electrolyte can contact the main surface of the lithium metal layer and establish a lithium-ion transport path between the lithium metal layer and at least one of the first or second porous negative electrode active material layers.

[0026] The negative electrode current collector may include a first porous metal layer and a second porous metal layer spaced apart from the first porous metal layer. In this case, the first porous negative electrode active material layer can be deposited on the main surface of the first porous metal layer, and the second porous negative electrode active material layer can be deposited on the main surface of the second porous metal layer. A lithium metal layer can be laminated between the facing surfaces of the first and second porous metal layers. The electrolyte can contact the first and second main surfaces of the lithium metal layer. The electrolyte can (i) establish lithium-ion transport pathways between the lithium metal layer and the first porous negative electrode active material layer and (ii) between the lithium metal layer and the second porous negative electrode active material layer.

[0027] The present invention discloses the following embodiments:

[0028] Option 1. The negative electrode of a secondary lithium battery pack, wherein the negative electrode comprises:

[0029] A negative electrode current collector having a first side and an opposite second side;

[0030] A first porous negative electrode active material layer is disposed on the first side of the negative electrode current collector;

[0031] A second porous negative electrode active material layer is disposed on the second side of the negative electrode current collector;

[0032] A lithium metal layer is disposed (i) between the first porous negative electrode active material layer and the second porous negative electrode active material layer, or (ii) on the main opposing surface of the first porous negative electrode active material layer or on the main opposing surface of the second porous negative electrode active material layer; and

[0033] An electrolyte permeates the first porous negative electrode active material layer and the second porous negative electrode active material layer, and the electrolyte is in contact with at least a portion of the main surface of the lithium metal layer.

[0034] The electrolyte establishes a lithium-ion transport path between the lithium metal layer and at least one of the first porous negative electrode active material layer or the second porous negative electrode active material layer.

[0035] Option 2. The negative electrode according to Option 1, wherein the lithium metal layer is disposed between the first porous negative electrode active material layer and the second porous negative electrode active material layer.

[0036] Option 3. The negative electrode according to Option 2, wherein the negative electrode current collector includes a first porous metal layer and a second porous metal layer spaced apart from the first porous metal layer, wherein the lithium metal layer is sandwiched between the opposing surfaces of the first porous metal layer and the second porous metal layer, and wherein the electrolyte is in contact with at least a portion of the first main surface and at least a portion of the opposing second main surface of the lithium metal layer.

[0037] Option 4. The negative electrode according to Option 3, wherein the first porous negative electrode active material layer is disposed on the main surface of the first porous metal layer, and the second porous negative electrode active material layer is disposed on the main surface of the second porous metal layer.

[0038] Option 5. The negative electrode according to Option 2, wherein the negative electrode current collector is non-porous, a first lithium metal layer is disposed on a first side of the negative electrode current collector, a second lithium metal layer is disposed on a second side of the negative electrode current collector, a first porous negative electrode active material layer is disposed on the first lithium metal layer on the first side of the negative electrode current collector, and a second porous negative electrode active material layer is disposed on the second lithium metal layer on the second side of the negative electrode current collector.

[0039] Option 6. The negative electrode according to Option 5, wherein the first and second lithium metal layers are non-porous.

[0040] Option 7. The negative electrode according to Option 2, wherein the negative electrode current collector is porous and includes a plurality of through holes extending from its first side to its second side, and wherein at least a portion of the first porous negative electrode active material layer or the second porous negative electrode active material layer extends at least partially into the plurality of through holes in the negative electrode current collector.

[0041] Scheme 8. The negative electrode according to Scheme 1, wherein the lithium metal layer is disposed on the main opposing surface of the first porous negative electrode active material layer or on the main opposing surface of the second porous negative electrode active material layer.

[0042] Option 9. The negative electrode according to Option 8, wherein the negative electrode current collector is porous and includes a plurality of through holes extending from its first side to its second side, and wherein the lithium metal layer is disposed on the first porous negative electrode active material layer on the first side of the negative electrode current collector, or the lithium metal layer is disposed on the second porous negative electrode active material layer on the second side of the negative electrode current collector.

[0043] Option 10. The negative electrode according to Option 1, wherein at least one of the first porous negative electrode active material layer or the second porous negative electrode active material layer comprises a silicon-based electrochemical active material.

[0044] Option 11. The negative electrode according to Option 1, wherein the lithium metal layer is non-porous and has a thickness of 20 micrometers to 40 micrometers.

[0045] Option 12. A secondary lithium battery pack, comprising:

[0046] A positive electrode, comprising a porous positive electrode active material layer that is hydroelectrically coupled to the positive electrode current collector;

[0047] Double-sided negative electrode, comprising:

[0048] A negative electrode current collector having a first side and an opposite second side;

[0049] A first porous negative electrode active material layer is disposed on the first side of the negative electrode current collector;

[0050] A second porous negative electrode active material layer is disposed on the second side of the negative electrode current collector; and

[0051] A lithium metal layer is disposed (i) between the first porous negative electrode active material layer and the second porous negative electrode active material layer or (ii) on the main opposing surface of the first porous negative electrode active material layer or on the main opposing surface of the second porous negative electrode active material layer.

[0052] A porous membrane layer disposed between the porous positive electrode active material layer of the positive electrode and the first or second porous negative electrode active material layer of the negative electrode; and

[0053] The electrolyte permeates the porous membrane layer, the porous positive electrode active material layer of the positive electrode, the first porous negative electrode active material layer of the negative electrode, and the second porous negative electrode active material layer of the negative electrode.

[0054] The electrolyte is in contact with at least a portion of the main surface of the lithium metal layer, and

[0055] The electrolyte establishes a lithium-ion transport path between the lithium metal layer and at least one of the first porous negative electrode active material layer or the second porous negative electrode active material layer.

[0056] Option 13. The battery pack according to Option 12, wherein the lithium metal layer is non-porous, and wherein, prior to the initial charging or cycling of the battery pack, the lithium metal layer does not create a physical barrier to the transport of lithium ions between the porous positive electrode active material layer of the positive electrode and the first or second porous negative electrode active material layer of the negative electrode.

[0057] Option 14. The battery pack according to Option 12, wherein the negative electrode current collector includes a first porous metal layer and a second porous metal layer spaced apart from the first porous metal layer, wherein the lithium metal layer is sandwiched between opposing surfaces of the first porous metal layer and the second porous metal layer, and wherein the electrolyte is in contact with at least a portion of a first main surface and at least a portion of an opposing second main surface of the lithium metal layer.

[0058] Option 15. The battery pack according to Option 12, wherein the negative electrode current collector is non-porous, a first non-porous lithium metal layer is disposed on a first side of the negative electrode current collector, a second non-porous lithium metal layer is disposed on a second side of the negative electrode current collector, a first porous negative electrode active material layer is disposed on the first non-porous lithium metal layer on the first side of the negative electrode current collector, and a second porous negative electrode active material layer is disposed on the second non-porous lithium metal layer on the second side of the negative electrode current collector.

[0059] Option 16. The battery pack according to Option 12, wherein the lithium metal layer is disposed on the main opposing surface of the first porous negative electrode active material layer or the main opposing surface of the second porous negative electrode active material layer, and wherein the negative electrode current collector is porous and includes a plurality of through holes extending from its first side to its second side.

[0060] Option 17. The battery pack according to Option 12, wherein at least one of the first porous negative electrode active material layer or the second porous negative electrode active material layer comprises a silicon-based electrochemical active material.

[0061] Option 18. The battery pack according to Option 12, wherein the lithium metal layer is non-porous and has a thickness of 20 micrometers to 40 micrometers.

[0062] Option 19. A method for assembling a secondary lithium battery pack, the method comprising:

[0063] The first porous negative electrode active material layer is deposited on the first side of the negative electrode current collector;

[0064] A second porous negative electrode active material layer is deposited on the opposite second side of the negative electrode current collector;

[0065] The lithium metal layer is laminated (i) between the first porous negative electrode active material layer and the second porous negative electrode active material layer or (ii) on the main opposing surface of the first porous negative electrode active material layer or on the main opposing surface of the second porous negative electrode active material layer.

[0066] A porous positive electrode active material layer is deposited on the positive electrode current collector;

[0067] The porous membrane layer is positioned between the porous positive electrode active material layer and the first porous negative electrode active material layer or the second porous negative electrode active material layer; and

[0068] The porous membrane layer, the porous positive electrode active material layer, the first porous negative electrode active material layer, and the second porous negative electrode active material layer are permeated with a non-aqueous electrolyte, such that the electrolyte contacts the main surface of the lithium metal layer and establishes a lithium-ion transport path between the lithium metal layer and at least one of the first porous negative electrode active material layer or the second porous negative electrode active material layer.

[0069] Option 20. The method according to Option 19, wherein the negative electrode current collector comprises a first porous metal layer and a second porous metal layer spaced apart from the first porous metal layer, the first porous negative electrode active material layer is deposited on the main surface of the first porous metal layer, the second porous negative electrode active material layer is deposited on the main surface of the second porous metal layer, the lithium metal layer is laminated between the facing surfaces of the first porous metal layer and the second porous metal layer, the electrolyte contacts the first main surface of the lithium metal layer and the second main surface of the lithium metal layer, and wherein the electrolyte (i) establishes a lithium-ion transport path between the lithium metal layer and the first porous negative electrode active material layer and (ii) between the lithium metal layer and the second porous negative electrode active material layer.

[0070] The foregoing summary is not intended to represent every possible embodiment or aspect of this disclosure. Rather, the foregoing summary is intended to illustrate some novel aspects and features disclosed herein. The foregoing features and advantages, as well as other features and advantages, of this disclosure will readily become apparent from the following detailed description of representative embodiments and methods for carrying out this disclosure, when taken in conjunction with the accompanying drawings and appended claims. Attached Figure Description

[0071] The illustrative embodiments will now be described in conjunction with the accompanying drawings, wherein the same reference numerals denote the same elements, and wherein:

[0072] Figure 1 It is a schematic side cross-sectional view of a secondary lithium battery pack including an electrochemical battery stack encapsulated in a battery pack housing and permeated with an electrolyte, wherein the electrochemical battery stack includes a double-sided negative electrode, the negative electrode including a porous current collector, first and second negative electrode active material layers disposed on opposite sides of the current collector, and a lithium metal layer disposed between the first and second negative electrode active material layers.

[0073] Figure 2 yes Figure 1 A schematic side cross-sectional view of a double-sided negative electrode depicts the electrolyte permeating the first and second negative electrode active material layers of the double-sided negative electrode and the movement of lithium ions from the lithium metal layer to the first and second negative electrode active material layers along the ion conduction path established by the electrolyte.

[0074] Figure 3 This occurs after the initial charging and / or repeated cycling of the battery pack, and after all lithium ions in the lithium metal layer have been consumed by the electrochemical reactions occurring within the battery pack. Figure 1 A schematic side sectional view of a double-sided negative electrode;

[0075] Figure 4This is a schematic side cross-sectional view of another bifacial negative electrode for a secondary lithium-ion battery pack. The negative electrode includes a porous current collector, first and second negative electrode active material layers disposed on opposite sides of the current collector, and a lithium metal layer disposed on one side of the current collector above the first or second negative electrode active material layer; and

[0076] Figure 5 This is a schematic side cross-sectional view of another double-sided negative electrode of a secondary lithium battery pack. The negative electrode includes a non-porous current collector, first and second lithium metal layers disposed on opposite sides of the current collector, and first and second negative electrode active material layers disposed on the first and second lithium metal layers on opposite sides of the current collector.

[0077] This disclosure allows for modifications and alternatives, with representative embodiments shown by way of example in the accompanying drawings and described in detail below. The inventive step of this disclosure is not limited to the specific forms disclosed. Rather, this disclosure is intended to cover modifications, equivalents, combinations, and alternatives that fall within the scope of this disclosure as defined by the appended claims. Detailed Implementation

[0078] The bifacial negative electrode disclosed herein can be used to assemble secondary lithium battery packs, which contain stoichiometric excess lithium in their negative electrodes before initial charging of the battery pack. The negative electrode is "bifacial," meaning that each negative electrode comprises discrete layers of first and second electrochemically active negative electrode materials disposed on opposite sides of the negative electrode current collector. Each negative electrode also includes a lithium metal layer, which may be disposed between the first and second negative electrode active material layers or on the main opposing surface of the first or second negative electrode active material layer.

[0079] During assembly, the electrolyte permeates the first and second negative electrode active material layers and establishes ion conduction pathways for the transport of lithium ions from the lithium metal layer to the first and / or second negative electrode active material layers prior to the initial cycling and operation of the battery pack. Thus, the lithium metal layer can be referred to as "ion-coupled" to the first and / or second negative electrode active material layers via the electrolyte. When the electrochemical cells of the battery pack are permeated with the electrolyte, lithium ions are released from the lithium metal layer and embedded into the first and second negative electrode active material layers of the negative electrode, thereby "pre-lithiating" the negative electrode active material layers before the initial battery pack cycle. The excess lithium in the pre-lithiated negative electrode active material layers can compensate for the loss of active lithium in the electrochemical cells of the battery pack, which may occur during the initial or repeated cycling of the battery pack, for example, due to various lithium-consuming chemical side reactions within the electrochemical cells of the battery pack. Therefore, the bifacial negative electrode of this disclosure can contribute to increasing the reversible capacity and cycle life of secondary lithium battery packs.

[0080] Figure 1A secondary lithium-ion battery pack 10 is depicted, comprising a battery pack housing 12 and an electrochemical battery stack 14 encapsulated within the battery pack housing 12. The battery pack housing 12 may comprise a metal, such as aluminum or steel, or it may comprise a film pouch material having multiple laminated metal and / or plastic layers. The electrochemical battery stack 14 includes a stack of positive and negative electrodes 16, 18, 20, 22 electrically isolated from each other by a porous membrane layer 24. In assembly, the positive and negative electrodes 16, 18, 20, 22 and the porous membrane layer 24 of the electrochemical battery stack 14 are permeated with an ion-conductive non-aqueous electrolyte 25, for example, by filling the battery pack housing 12 with the electrolyte 25.

[0081] The positive and negative electrodes 16 and 22 disposed at the ends of the electrochemical cell stack 14 are single-sided, meaning that each electrode 16 and 22 comprises a single layer of electrochemically active negative or positive electrode material disposed on one side of the metal current collector. More specifically, the positive electrode 16 disposed at the first end of the electrochemical cell stack 14 comprises a layer 26 of positive electrode active material disposed on the positive electrode current collector 28, and the negative electrode 22 disposed at the opposite second end of the electrochemical cell stack 14 comprises a layer 30 of negative electrode active material disposed on the negative electrode current collector 32. The negative and positive electrodes 18 and 20 disposed between the single-sided positive and negative electrodes 16 and 22 are double-sided, meaning that each electrode 18 and 20 comprises two discrete layers of electrochemically active negative or positive electrode material disposed on opposite sides of the metal current collector. More specifically, the double-sided negative electrode 18 comprises a first layer 34 of negative electrode active material disposed on a first side of the negative electrode current collector 36 and a second layer 38 of negative electrode active material disposed on an opposite second side of the negative electrode current collector 36. The double-sided positive electrode 20 includes a first positive electrode active material layer 40 disposed on a first side of the positive electrode current collector 42 and a second positive electrode active material layer 44 disposed on the opposite second side of the positive electrode current collector 42.

[0082] exist Figure 1In the original battery pack 10, a double-sided negative electrode 18 and a double-sided positive electrode 20 spaced apart from the double-sided negative electrode 18 by a porous separator layer 24 are included. However, in practice, the battery pack 10 may include multiple repeating units 46 of the double-sided negative and positive electrodes 18, 20 spaced apart from each other by the porous separator layer 24. The positive and negative electrodes 16, 18, 20, 22 and the porous separator layer 24 may be assembled in a stacked form, for example using circular winding, prismatic winding, monolithic stacking, Z-folding or other battery stacking processes. In the assembly, the positive electrode current collectors 28, 42 may be electrically coupled to the positive electrode tab 48, and the negative electrode current collectors 32, 36 may be electrically coupled to the negative electrode tab 50. The positive and negative electrode tabs 48, 50 may extend to the outside of the battery pack housing 12 and may be coupled to a power source or load via external circuitry (not shown).

[0083] Before the electrochemical cell stack 14 is hermetically sealed inside the battery pack casing 12, the positive and negative electrodes 16, 18, 20, 22, and the porous membrane layer 24 are permeated with an ion-conductive non-aqueous electrolyte 25. During permeation with the non-aqueous electrolyte 25, each pair of adjacent positive and negative electrode active material layers 26, 34, 38, 40, 44, 30 defines one electrochemical cell in the battery pack 10. Figure 1 In this configuration, the first electrochemical cell 52 is defined by a positive electrode active material layer 26 disposed on the positive electrode current collector 28 and a first negative electrode active material layer 34 disposed on the first side of the negative electrode current collector 36. The second electrochemical cell 54 is defined by a second negative electrode active material layer 38 disposed on the second side of the negative electrode current collector 36 and a first positive electrode active material layer 40 disposed on the first side of the positive electrode current collector 42. The third electrochemical cell 56 is defined by a second positive electrode active material layer 44 disposed on the second side of the positive electrode current collector 42 and a negative electrode active material layer 30 disposed on the negative electrode current collector 32.

[0084] The bifacial negative electrode 18 is configured to provide a stoichiometric excess of lithium to one or both of its associated electrochemical cells 52, 54 prior to the initial charging and operation of the battery pack 10. To achieve this, the negative electrode 18 includes a lithium metal layer 58 having a first primary surface 60 and an opposing second primary surface 62. The bifacial negative electrode 18 is configured such that, upon permeation of the negative electrode 18 with the electrolyte 25, the lithium metal layer 58 is in physical contact with the electrolyte 25 and is ionically coupled via the electrolyte 25 to at least one of the first or second negative electrode active material layers 34, 38. In assembly, the electrolyte 25 may be in physical contact with the first primary surface 60 and / or the second primary surface 62 of the lithium metal layer 58. In such an arrangement, the electrolyte 25 enables lithium ions to be transported from the lithium metal layer 58 to the first and / or second negative electrode active material layers 34, 38 prior to the initial cycling and operation of the battery pack 10. In an embodiment, the lithium metal layer 58 may be disposed between the first and second negative electrode active material layers 34, 38 (e.g., Figure 1 and 5 (as in the example), or the lithium metal layer 58 can be disposed on the main opposing surface of the first or second negative electrode active material layers 34, 38 (e.g. Figure 4 (like in the middle).

[0085] A porous membrane layer 24 is interposed between adjacent pairs of phase-to-phase or opposing surfaces of the positive and negative electrode active material layers 26, 34, 38, 40, 44, 30. The porous membrane layer 24 may be made of a microporous ion-conductive and electrically insulating thin film. For example, in the first electrochemical cell 52, the phase-to-phase or opposing surfaces 80 of the positive electrode active material layer 26 are spaced apart from the phase-to-phase or opposing surfaces 82 of the negative electrode active material layer 34 by one of the porous membrane layers 24. Each of the porous membrane layers 24 may comprise a nonwoven material, such as a sheet, web, or mat of oriented or randomly oriented fibers. In embodiments, each of the porous membrane layers 24 may comprise a microporous polymeric material, such as a microporous polyolefin-based membrane or film. For example, each of the porous membrane layers 24 may comprise a single polyolefin or a combination of polyolefins, such as polyethylene (PE), polypropylene (PP), polyamide (PA), poly(tetrafluoroethylene) (PTFE), polyvinylidene fluoride (PVdF), and / or poly(vinyl chloride) (PVC). In one form, one or more of the porous membrane layers 24 may comprise a laminate of one or more polymer materials, such as a laminate of PE and PP.

[0086] The non-aqueous electrolyte 25 facilitates lithium-ion transport between adjacent pairs of positive and negative electrode active material layers 26, 34, 38, 40, 44, 30 within the electrochemical cell stack 14 of the battery pack 10. The non-aqueous electrolyte 25 may be a non-aqueous liquid electrolyte solution containing one or more lithium salts dissolved in a non-aqueous aprotic organic solvent or a mixture of multiple non-aqueous aprotic organic solvents. Examples of lithium salts include lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrachloroaluminate (LiAlCl4), lithium iodide (LiI), lithium bromide (LiBr), lithium thiocyanate (LiSCN), lithium tetrafluoroborate (LiBF4), lithium tetraphenylborate (LiB(C6H5)4), lithium bis(oxalate)borate (LiB(C2O4)2) (LiBOB), lithium difluorooxalate borate (LiBF2(C2O4)), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethane)sulfonylimide (LiN(CF3SO2)2), lithium bis(fluorosulfonylimide) (LiN(FSO2)2) (LiSFI), and combinations thereof. Examples of non-aqueous aprotic organic solvents include alkyl carbonates, such as cyclic carbonates (e.g., ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), fluoroethylene carbonate (FEC)), linear carbonates (e.g., dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC)), aliphatic carboxylic acid esters (e.g., methyl formate, methyl acetate, methyl propionate), γ-lactones (e.g., γ-butyrolactone, γ-valerolactone), chain ethers (e.g., 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane), cyclic ethers (e.g., tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxane), sulfur compounds (e.g., sulfolane), and combinations thereof.

[0087] The positive electrode active material layers 26, 40, and 44 are porous and may contain one or more electrochemically active materials that can undergo reversible redox reactions with lithium at a higher electrochemical potential than that of the negative electrode active material layers 30, 34, and 38, resulting in an electrochemical potential difference between adjacent pairs of the positive and negative electrode active material layers 26, 34, 38, 40, 44, and 30. For example, the positive electrode active material layers 26, 40, and 44 may contain materials capable of sufficient lithium intercalation and deintercalation, alloying and dealloying, or plating and stripping. In one embodiment, the positive electrode active material layers 26, 40, and 44 may contain an intercalation host material capable of reversible lithium ion insertion or intercalation. In such cases, the embedded host material may include layered oxides represented by the formula LiMeO2, olivine-type oxides represented by the formula LiMePO4, spinel-type oxides represented by the formula LiMe2O4, tavorite represented by one or both of the formulas LiMeSO4F or LiMePO4F, or combinations thereof, wherein Me is a transition metal (e.g., Co, Ni, Mn, Fe, Al, V, or combinations thereof). In another form, the positive electrode active material layers 26, 40, 44 may contain a conversion material comprising a component capable of undergoing a reversible electrochemical reaction with lithium, wherein the component undergoes a phase transition or a change in crystal structure accompanied by a change in oxidation state. In such cases, the conversion material may include sulfur, selenium, tellurium, iodine, halides (e.g., fluorides or chlorides), sulfides, selenides, tellurides, iodides, phosphides, nitrides, oxides, oxysulfides, oxyfluorides, sulfofluorides, sulfoxyfluorides, or lithium and / or metal compounds thereof. Examples of metals suitable for inclusion in the conversion material include iron, manganese, nickel, copper, and cobalt. In embodiments, the electrochemically active material of the positive electrode active material layers 26, 40, 44 may be mixed with a polymer binder to provide structural integrity to layers 26, 40, 44. Examples of polymer binders include polyvinylidene fluoride (PVdF), ethylene propylene diene monomer (EPDM) rubber, styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyacrylic acid, and mixtures thereof. The positive electrode active material layers 26, 40, 44 may optionally contain particles of conductive material, which may include, for example, particles of high surface area carbon black.

[0088] The negative electrode active material layers 30, 34, and 38 are porous and may contain electrochemically active materials capable of reversible insertion or intercalation of lithium ions or capable of reacting with lithium to form lithium-containing intermetallic compounds. In embodiments, the electrochemically active materials of the negative electrode active material layers 30, 34, and 38 may contain silicon-based materials. The term "silicon-based" as used herein with respect to the electrochemically active materials of the negative electrode active material layers 30, 34, and 38 generally includes materials in which silicon (Si) is the single largest component based on a weight percentage (%). This may include materials having more than 50% silicon by weight, as well as those having less than 50% silicon by weight, provided that silicon is the single largest component of the material. In addition to silicon, the electrochemically active materials of the negative electrode active material layers 30, 34, and 38 may contain carbon (e.g., graphite, activated carbon, carbon black, and / or graphene), tin oxide, aluminum, indium, zinc, germanium, titanium oxide, and / or lithium titanate. The electrochemically active materials of the negative electrode active material layers 30, 34, and 38 may be blended with a polymer binder to provide structural integrity to layers 30, 34, and 38. Examples of polymer binders include polyvinylidene fluoride (PVdF), ethylene propylene diene monomer (EPDM) rubber, styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyacrylic acid, and mixtures thereof. The negative electrode active material layers 30, 34, and 38 may optionally contain particles of conductive material, such as high surface area carbon black particles.

[0089] In some embodiments, the silicon-based electrochemical active material of the negative electrode active material layers 30, 34, and 38 may comprise silicon, carbon-coated silicon, silicon oxide, lithium-silicon alloys, silicon-tin alloys, silicon-iron alloys, silicon-aluminum alloys, silicon-cobalt alloys, or combinations thereof. Examples of such silicon alloys include, but are not limited to, Si-Sn, SiSnFe, SiSnAl, SiFeCo, and the like. In some embodiments, the silicon-based electrochemical active material comprises or is substantially composed of crystalline or amorphous silicon (rather than silicon alloys). Silicon-based electrochemical active materials and methods for forming such materials are described in U.S. Patent Application No. 17 / 085785, filed October 30, 2020, the contents of which are incorporated herein by reference in their entirety.

[0090] The positive electrode current collectors 28 and 42 and the positive electrode tab 48 can be formed of aluminum (Al) or another suitable conductive material. The negative electrode current collectors 32 and 36 and the negative electrode tab 50 can be made of copper, nickel, or alloys thereof, stainless steel, or other suitable conductive materials. The positive and negative electrode current collectors 28, 42, 32, and 36 can be porous or non-porous. For example, the positive and negative electrode current collectors 28, 42, 32, and 36 can be in the form of non-porous metal foil, perforated metal foil, porous metal mesh, or a combination thereof.

[0091] The lithium metal layer 58 may comprise a layer of lithium (Li) metal or a lithium metal alloy. In some embodiments, the negative electrode material layer 34 may be substantially composed of lithium metal and may contain more than 97% lithium by weight, or more preferably more than 99% lithium. The lithium metal layer 58 may be porous or non-porous. For example, the lithium metal layer 58 may be in the form of a non-porous metal foil, a perforated (porous) metal foil, or a porous metal mesh. The lithium metal layer 58 may have a thickness of 20 micrometers to 40 micrometers.

[0092] Now refer to Figure 2 The negative electrode current collector 36 of the double-sided negative electrode 18 may include a first porous metal layer 64 and a second porous metal layer 66 spaced apart from the first porous metal layer 64, and a lithium metal layer 58 may be sandwiched between the first porous metal layer 64 and the second porous metal layer 66, for example, by lamination therebetween. The lithium metal layer 58 may be non-porous and may be in the form of a non-porous lithium metal foil. The first and second porous metal layers 64, 66 include a plurality of through holes 68 extending from their first side to their second side. A portion of the first negative electrode active material layer 34 may extend at least partially through the through holes 68 in the first porous metal layer 64, and a portion of the second negative electrode active material layer 38 may extend at least partially through the through holes 68 in the second porous metal layer 66.

[0093] When electrolyte 25 permeates the negative electrode 18, it permeates the pores of the porous first and second negative electrode active material layers 34, 38, flows through the through-holes 68 in the first and second porous metal layers 64, 66 (as shown by arrow 70), and makes direct physical contact with the first and second main surfaces 60, 62 of the lithium metal layer 58. When electrolyte 25 makes physical contact with the first and second main surfaces 60, 62 of the lithium metal layer 58, an ion conduction pathway is established within the negative electrode 18, allowing lithium ions to be transported from the lithium metal layer 58 to the first and / or second negative electrode active material layers 34, 38 (as shown by arrow 72). Lithium ions released from the lithium metal layer 58 and embedded in the negative electrode active material layers 34, 38 can provide stoichiometric excess active lithium to the associated electrochemical cells 52, 54 to participate in the electrochemical reactions occurring within the cells 52, 54.

[0094] The configuration and arrangement of the first and second negative electrode active material layers 34, 38 in the negative electrode 18, the first and second porous metal layers 64, 66 in the negative electrode current collector 36, and the lithium metal layer 58 enable pre-lithiation of the first and second negative electrode active material layers 34, 38 before operation of the battery pack 10 without inhibiting the flow of electrolyte 25 through the positive and negative electrodes 16, 18, 20, 22 and the porous separator layer 24 of the electrochemical battery stack 14. In particular, without being bound by theory, it is believed that if the negative electrode current collector 36 is non-porous and the non-porous lithium metal layer 58 is formed on the main opposing surface of the first (or second) negative electrode active material layer 34, then the non-porous lithium metal layer 58 and the negative electrode current collector 36 will create a barrier to the flow of electrolyte 25 and will effectively isolate the first (or second) negative electrode active material layer 34 from the electrolyte 25 during the initial operation of the battery pack 10. Furthermore, if the negative electrode current collector 36 is non-porous and the non-porous lithium metal layer 58 is formed on the main opposing surface of the first (or second) negative electrode active material layer 34, it is believed that the lithium metal layer 58 must be relatively thin (e.g., less than 20 micrometers thick) to avoid excessive lithium residue on the surface of the first (or second) negative electrode active material layer 34 after the initial charging or cycling of the battery pack 10, or subsequently deposited onto the surface of the first (or second) negative electrode active material layer 34. However, using lithium metal foil with a thickness of less than 20 micrometers is relatively expensive because the incidence of manufacturing defects is higher, which may increase the amount of waste lithium generated during the manufacturing process.

[0095] After lithium ions are released from the lithium metal layer 58, they will intercalate into the negative electrode active material layers 34 and 38, dissolve in the electrolyte 25, and / or intercalate into the positive electrode active material layers 26 and 40. Lithium ions released from the lithium metal layer 58 will generally not return there. Figure 3 As shown, after the initial charging and / or repeated cycling of the battery pack 10, the lithium ions in the lithium metal layer 58 can be completely consumed by the electrochemical reactions occurring within the electrochemical cells 52, 54. In such a case, the first and second perforated metal foils 64, 66 of the negative electrode current collector 36 may gradually approach each other and may eventually come into contact with each other along their facing surfaces.

[0096] Figure 4 A secondary lithium battery pack is described (as shown in the reference). Figure 1 Another embodiment of the double-sided negative electrode 118 of the battery pack 10 shown and described. The double-sided negative electrode 118 is similar in many respects to Figure 1The negative electrode 18 depicted herein generally does not need to be repeated here. The double-sided negative electrode 118 includes a negative electrode current collector 136 in the form of a porous metal layer, comprising a plurality of through-holes 168 extending from its first side 174 to its second side 176. A first negative electrode active material layer 134 is formed on the first side 174 of the negative electrode current collector 136, and a second negative electrode active material layer 138 is formed on the second side 176 of the negative electrode current collector 136. A portion of the first negative electrode active material layer 134 may extend at least partially through the through-holes 168 in the current collector 136, and / or a portion of the second negative electrode active material layer 138 may extend at least partially through the through-holes 168 in the current collector 136. A lithium metal layer 158 is formed over the second negative electrode active material layer 138 on the second side 176 of the negative electrode current collector 136. In other embodiments, the lithium metal layer 158 may be formed over the first negative electrode active material layer 134 on the first side 174 of the negative electrode current collector 136 (not shown). The lithium metal layer 158 can be non-porous and can be in the form of a non-porous lithium metal foil.

[0097] When electrolyte 25 permeates the negative electrode 118, it permeates the pores of the porous first and second negative electrode active material layers 134, 138, flows through the through-holes 168 in the negative electrode current collector 136, and comes into direct physical contact with the lithium metal layer 158. When electrolyte 25 makes physical contact with the lithium metal layer 158, an ion conduction pathway is established within the negative electrode 118, allowing lithium ions to be transported from the lithium metal layer 158 to the first and / or second negative electrode active material layers 134, 138. The lithium ions released from the lithium metal layer 158 and embedded in the negative electrode active material layers 134, 138 can provide a stoichiometric excess of active lithium to their associated electrochemical cell.

[0098] The configuration and arrangement of the first and second negative electrode active material layers 134, 138 in the negative electrode 118, the negative electrode current collector 136, and the lithium metal layer 158 enable the first and second negative electrode active material layers 134, 138 to be pre-lithiated before the battery pack 10 is put into operation without inhibiting the flow of electrolyte 25 through the positive and negative electrodes and the porous membrane layer of the battery pack 10.

[0099] Figure 5 A secondary lithium battery pack is described (as shown in the reference). Figure 1 Another embodiment of the double-sided negative electrode 218 of the battery pack 10 shown and described. The double-sided negative electrode 218 is similar in many respects to Figure 1The negative electrode 18 depicted herein generally does not need to be repeated here. The double-sided negative electrode 218 includes a negative electrode current collector 236 in the form of a non-porous metal foil having a first side 274 and an opposing second side 276. A first lithium metal layer 258 is formed on the first side 274 of the negative electrode current collector 236, and a second lithium metal layer 278 is formed on the second side 276 of the negative electrode current collector 236. The first and second lithium metal layers 258, 278 may be non-porous and may be in the form of a non-porous lithium metal foil. A first negative electrode active material layer 234 is formed over the first lithium metal layer 258 on the first side 274 of the negative electrode current collector 236, and a second negative electrode active material layer 238 is formed over the second lithium metal layer 278 on the second side 276 of the negative electrode current collector 236.

[0100] When electrolyte 25 permeates the negative electrode 218, electrolyte 25 permeates the pores of the porous first and second negative electrode active material layers 234, 238 and comes into direct physical contact with the first and second lithium metal layers 258, 278. When electrolyte 25 makes physical contact with lithium metal layers 258, 278, an ion conduction pathway is established within the negative electrode 218, allowing lithium ions to be transported from lithium metal layers 258, 278 to the first and / or second negative electrode active material layers 234, 238. Lithium ions released from lithium metal layers 258, 278 and embedded in the negative electrode active material layers 234, 238 can provide a stoichiometric excess of active lithium to the associated electrochemical cell.

[0101] The configuration and arrangement of the lithium metal layers 258, 278 and the first and second negative electrode active material layers 234, 238 on the first and second sides 274, 276 of the negative electrode current collector 236 enable the first and second negative electrode active material layers 234, 238 to be pre-lithiated before the battery pack 10 is put into operation without inhibiting the flow of electrolyte 25 through the positive and negative electrodes and the porous membrane layer of the battery pack 10.

[0102] In view of the above disclosure, those skilled in the art will readily understand these and other benefits.

[0103] While some preferred modes and other embodiments have been described in detail, various alternative designs and embodiments exist for practicing the teachings of the invention as defined in the appended claims. Those skilled in the art will recognize that modifications can be made to the disclosed embodiments without departing from the scope of this disclosure. Furthermore, the inventive concept explicitly includes combinations and sub-combinations of the described elements and features. The detailed description and accompanying drawings support and describe the teachings of the invention, the scope of which is defined only by the claims.

Claims

1. A negative electrode for a secondary lithium battery pack, the negative electrode comprising: A negative electrode current collector having a first side and an opposite second side; A first porous negative electrode active material layer is disposed on the first side of the negative electrode current collector; A second porous negative electrode active material layer is disposed on the second side of the negative electrode current collector; A lithium metal layer disposed between the first porous negative electrode active material layer and the second porous negative electrode active material layer; and An electrolyte permeates the first porous negative electrode active material layer and the second porous negative electrode active material layer, and the electrolyte is in contact with at least a portion of the main surface of the lithium metal layer. The electrolyte establishes a lithium-ion transport path between the lithium metal layer and at least one of the first porous negative electrode active material layer or the second porous negative electrode active material layer, and The negative electrode current collector is non-porous, a first lithium metal layer is disposed on a first side of the negative electrode current collector, a second lithium metal layer is disposed on a second side of the negative electrode current collector, a first porous negative electrode active material layer is disposed on the first lithium metal layer on the first side of the negative electrode current collector, and a second porous negative electrode active material layer is disposed on the second lithium metal layer on the second side of the negative electrode current collector.

2. The negative electrode according to claim 1, wherein the negative electrode current collector comprises a first porous metal layer and a second porous metal layer spaced apart from the first porous metal layer, wherein the lithium metal layer is sandwiched between opposing surfaces of the first porous metal layer and the second porous metal layer, and wherein the electrolyte is in contact with at least a portion of a first main surface and at least a portion of an opposing second main surface of the lithium metal layer.

3. The negative electrode according to claim 2, wherein the first porous negative electrode active material layer is disposed on the main surface of the first porous metal layer, and the second porous negative electrode active material layer is disposed on the main surface of the second porous metal layer.

4. The negative electrode according to claim 1, wherein the first and second lithium metal layers are non-porous.

5. The negative electrode of claim 1, wherein the negative electrode current collector is porous and includes a plurality of through holes extending from its first side to its second side, and wherein at least a portion of the first porous negative electrode active material layer or the second porous negative electrode active material layer extends at least partially into the plurality of through holes in the negative electrode current collector.

6. The negative electrode according to claim 1, wherein at least one of the first porous negative electrode active material layer or the second porous negative electrode active material layer comprises a silicon-based electrochemical active material.

7. The negative electrode of claim 1, wherein the lithium metal layer is non-porous and has a thickness of 20 micrometers to 40 micrometers.

8. A secondary lithium battery pack, comprising: A positive electrode, comprising a porous positive electrode active material layer that is hydroelectrically coupled to the positive electrode current collector; Double-sided negative electrode, comprising: A negative electrode current collector having a first side and an opposite second side; A first porous negative electrode active material layer is disposed on the first side of the negative electrode current collector; A second porous negative electrode active material layer is disposed on the second side of the negative electrode current collector; and A lithium metal layer disposed between the first porous negative electrode active material layer and the second porous negative electrode active material layer; A porous membrane layer disposed between the porous positive electrode active material layer of the positive electrode and the first or second porous negative electrode active material layer of the negative electrode; and The electrolyte permeates the porous membrane layer, the porous positive electrode active material layer of the positive electrode, the first porous negative electrode active material layer of the negative electrode, and the second porous negative electrode active material layer of the negative electrode. The electrolyte is in contact with at least a portion of the main surface of the lithium metal layer. The electrolyte establishes a lithium-ion transport path between the lithium metal layer and at least one of the first porous negative electrode active material layer or the second porous negative electrode active material layer, and The negative electrode current collector is non-porous, a first non-porous lithium metal layer is disposed on a first side of the negative electrode current collector, a second non-porous lithium metal layer is disposed on a second side of the negative electrode current collector, a first porous negative electrode active material layer is disposed on the first non-porous lithium metal layer on the first side of the negative electrode current collector, and a second porous negative electrode active material layer is disposed on the second non-porous lithium metal layer on the second side of the negative electrode current collector.

9. The battery pack of claim 8, wherein the lithium metal layer is non-porous, and wherein, Prior to the initial charging or cycling of the battery pack, the lithium metal layer does not create a physical barrier to the transport of lithium ions between the porous positive electrode active material layer of the positive electrode and the first or second porous negative electrode active material layer of the negative electrode.

10. The battery pack of claim 8, wherein the negative electrode current collector comprises a first porous metal layer and a second porous metal layer spaced apart from the first porous metal layer, wherein the lithium metal layer is sandwiched between opposing surfaces of the first porous metal layer and the second porous metal layer, and wherein the electrolyte is in contact with at least a portion of a first main surface and at least a portion of an opposing second main surface of the lithium metal layer.

11. The battery pack according to claim 8, wherein at least one of the first porous negative electrode active material layer or the second porous negative electrode active material layer comprises a silicon-based electrochemical active material.

12. The battery pack of claim 8, wherein the lithium metal layer is non-porous and has a thickness of 20 micrometers to 40 micrometers.

13. A method for assembling a secondary lithium battery pack, the method comprising: The first porous negative electrode active material layer is deposited on the first side of the negative electrode current collector; A second porous negative electrode active material layer is deposited on the opposite second side of the negative electrode current collector; A lithium metal layer is laminated between the first porous negative electrode active material layer and the second porous negative electrode active material layer. A porous positive electrode active material layer is deposited on the positive electrode current collector; The porous membrane layer is positioned between the porous positive electrode active material layer and the first porous negative electrode active material layer or the second porous negative electrode active material layer; and The porous membrane layer, the porous positive electrode active material layer, the first porous negative electrode active material layer, and the second porous negative electrode active material layer are permeated with a non-aqueous electrolyte, such that the electrolyte contacts the main surface of the lithium metal layer and establishes a lithium-ion transport path between the lithium metal layer and at least one of the first porous negative electrode active material layer or the second porous negative electrode active material layer.

14. The method of claim 13, wherein the negative electrode current collector comprises a first porous metal layer and a second porous metal layer spaced apart from the first porous metal layer, the first porous negative electrode active material layer is deposited on the main surface of the first porous metal layer, the second porous negative electrode active material layer is deposited on the main surface of the second porous metal layer, the lithium metal layer is laminated between the facing surfaces of the first porous metal layer and the second porous metal layer, the electrolyte contacts the first main surface of the lithium metal layer and the second main surface of the lithium metal layer, and wherein the electrolyte (i) establishes a lithium-ion transport path between the lithium metal layer and the first porous negative electrode active material layer and (ii) between the lithium metal layer and the second porous negative electrode active material layer.

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