WO2019118409A1

WO2019118409A1 - Rechargeable batteries, lithium metal electrodes, battery separators, and methods of forming and using the same

Info

Publication number: WO2019118409A1
Application number: PCT/US2018/064877
Authority: WO
Inventors: Hailiang Wang; Qiuwei SHI; Yiren ZHONG; Min Wu
Original assignee: Yale University
Priority date: 2017-12-13
Filing date: 2018-12-11
Publication date: 2019-06-20

Abstract

One aspect of the invention provides a lithium metal electrode including a protective coating. The protective coating is selected from the group consisting of Li3N, LiNxOy, LiNO2, and alkyl nitro species (R-NO2), such that x is a positive value from 0 to about 10 and y is a positive value from 0 to about 10.

Description

RECHARGEABLE BATTERIES, LITHIUM METAL ELECTRODES, BATTERY SEPARATORS, AND METHODS OF FORMING AND USING THE SAME

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority to ET.S. Provisional Patent Application Serial No. 62/598,234, filed December 13, 2017. The entire content of this application is hereby incorporated by reference herein.

BACKGROUND OF THE INVENTION

Rechargeable batteries with high energy density are of paramount importance to energy storage. The progress of high-performance batteries is heavily dependent on the development of new chemistries and materials. With a high theoretical capacity (3860 mAh g^-1), a low redox potential (-3.040 V vs. SHE), and a light weight (0.53 g cm^-3), Lithium (Li) metal is the ultimate choice of anode for Li-based and perhaps all rechargeable batteries. However, major challenges must be overcome before rechargeable Li metal batteries become viable. One such challenge is dendrite formation during cycling, which is responsible for phenomena such as low Coulombic efficiency (CE), large voltage polarization, poor capacity retention, and short circuiting, and leads to early failure and critical safety concerns for the batteries.

SUMMARY OF THE INVENTION

One aspect of the invention provides a lithium metal electrode including a protective coating. The protective coating is selected from the group consisting of Li₃N, LiN_xO_y, LiN0_2. and alkyl nitro species (R-N0₂), such that x is a positive value from 0 to about 10 and y is a positive value from 0 to about 10.

In various embodiments, the protective coating includes Li₃N, LiN_xO_y; LiN0₂; and alkyl nitro species (R-N0₂). In various embodiments, the protective coating has a thickness of about 0.2 pm to about 20 pm. In various embodiments, the protective coating includes about 50 mol% Li, about 35 mol% O, about 10 mol% C, and less than about 5 mol% N.

In various embodiments, the electrode includes a copper current collector.

In various embodiments, the protective coating has a porous surface morphology.

Another aspect of the invention provides a rechargeable battery including: a lithium metal electrode; a high capacity, non-intercalation electrode; an electrolyte in contact with both the lithium metal electrode and the non-intercalation electrode; and an ion-permeable membrane disposed in the electrolyte between the lithium metal electrode and the non-intercalation electrode.

In various embodiments, the high capacity, non-intercalation electrode includes a non layer structured material. In various embodiments, the high capacity, non-intercalation electrode includes an amorphous material. In various embodiments, the high capacity, non-intercalation electrode includes MoS_3. In various embodiments, the high capacity, non-intercalation electrode includes MoS₃ grown on oxidized carbon nanotubes having an oxygen : carbon stoichiometric ratio of less than about 1 : 5.

In various embodiments, the electrolyte does not include an organic ether solvent. In various embodiments, the electrolyte includes an organic carbonate solvent. In various embodiments, the electrolyte includes at least one solvent selected from the group consisting of ethylene carbonate and diethyl carbonate. In various embodiments, the electrolyte includes at least one Li⁺ species in the form of a solute or suspended particle. In various embodiments, the electrolyte includes solvated LiPF_6.

In various embodiments, the electrolyte includes LiN0_3. In various embodiments, the electrolyte includes LiN0₃ particles suspended in solution. In various embodiments, the electrolyte includes LiN0₃ particles having a particle size of about 0.1 pm to about 10 pm. In various embodiments, the electrolyte includes solvated LiN0_3. In various embodiments, the electrolyte has a dissolved LiN0₃ concentration of about 10 ⁶ g/ml to about 10 ⁴ g/ml.

In various embodiments, the ion-permeable membrane is impregnated with an effective amount of LiN0_3. In various embodiments, the ion-permeable membrane includes at least one material selected from the group consisting of polymers and glass fibers.

In another aspect, the invention provides a rechargeable battery having a lithium metal electrode, a second electrode, an electrolyte in contact with both the lithium metal electrode and the second electrode, and an ion-permeable membrane impregnated with an effective amount of LiN0₃, disposed in the electrolyte between the lithium metal electrode and the second electrode.

In various embodiments, the second electrode is a high capacity, non-intercalation electrode. In various embodiments, the high capacity, non-intercalation electrode includes a non-layer structured material. In various embodiments, the high capacity, non-intercalation electrode includes an amorphous material. In various embodiments, the high capacity, non- intercalation electrode includes MoS_3. In various embodiments, the high capacity, non intercalation electrode includes MoS₃ grown on oxidized carbon nanotubes having an oxygen : carbon stoichiometric ratio of less than about 1 : 5.

In various embodiments, the electrolyte does not comprise an organic ether solvent. In various embodiments, the electrolyte includes an organic carbonate solvent. In various embodiments, the electrolyte includes at least one solvent selected from the group consisting of ethylene carbonate and diethyl carbonate.

In various embodiments, the electrolyte includes at least one Li⁺ species in the form of a solute or suspended particle. In various embodiments, the electrolyte includes solvated LiPF_6.

In various embodiments, the electrolyte includes LiN0_3. In various embodiments, the electrolyte includes LiN0₃ particles suspended in solution. In various embodiments, the electrolyte includes LiN0₃ particles having a particle size of about 0.1 pm to about 10 pm. In various embodiments, wherein the electrolyte includes solvated LiN0_3. In various embodiments, the electrolyte has a dissolved LiN0₃ concentration of about 10 ⁶ g/ml to about 10 ⁴ g/ml.

In various embodiments, the ion-permeable membrane includes at least one material selected from the group consisting of polymers and glass fibers.

In yet another aspect, the invention provides a rechargeable battery including a lithium metal electrode, a second electrode, a carbonate electrolyte in contact with both the lithium metal electrode and the second electrode, an ion-permeable membrane disposed in the electrolyte between the lithium metal electrode and the second electrode, and an effective amount of LiN0₃ in contact with the carbonate electrolyte.

In yet another aspect, the invention provides a method of forming a lithium metal electrode having a protective coating, the method includes at least partially immersing a lithium metal electrode in an electrolyte solution comprising an effective amount of LiN0₃, at least partially immersing a conductive counter-electrode in the electrolyte solution comprising an effective amount of LiN0₃, and exposing the lithium metal electrode and the conductive counter electrodes to a plurality of charge-discharge cycles, thereby forming a protective coating on the lithium metal electrode.

In various embodiments, the protective coating includes one or more selected from the group consisting of: Li₃N, LiN_xO_y, LiN0_2, and alkyl nitro species (R-N0₂), wherein x is a positive value from 0 to about 10 and y is a positive value from 0 to about 10. In various embodiments, the protective coating includes Li₃N, LiN_xO_y, LiN0₂; and

alkyl nitro species (R-N0₂). In various embodiments, the protective coating has a thickness of about 0.2 pm to about 20 pm. In various embodiments, the protective coating includes about 50% Li, about 35% O, about 10% C, and less than about 5% N.

In various embodiments, the electrolyte does not comprise an organic ether solvent. In various embodiments, the electrolyte includes an organic carbonate solvent. In various embodiments, the electrolyte includes at least one solvent selected from the group consisting of ethylene carbonate and diethyl carbonate. In various embodiments, the electrolyte includes solvated LiPF_6. In various embodiments, the electrolyte includes LiN0₃ particles suspended in solution. In various embodiments, the electrolyte includes LiN0₃ particles having a particle size of about 0.1 pm to about 10 pm. In various embodiments, the electrolyte includes solvated LiN0_3. In various embodiments, the electrolyte has a dissolved LiN0₃ concentration of about 10 ⁶ g/ml to about 10 ⁴ g/ml.

In various embodiments, the plurality of charge-discharge cycles is one or more cycles.

In various embodiments, the plurality of charge-discharge cycles is about 1 or more cycles.

In various embodiments, the plurality of charge-discharge cycles is about 5 or more cycles.

In various embodiments, the charge-discharge cycles comprise the application of a current of about 0.1 mA cm ² to about 20 mA cm ².

In yet another aspect, the invention provides a method of repeated charge-discharge cycling of the rechargeable battery, the method includes applying current across the lithium metal electrode and the second electrode to charge the rechargeable battery, drawing current from across the lithium metal electrode and the second electrode to power a load, and repeating the applying current and the drawing current steps a plurality of times, thereby forming or maintaining a protective coating on the lithium metal electrode.

In another aspect, the invention provides a battery separator including an ion-permeable membrane impregnated with LiN0_3. In various embodiments, the LiN0₃ is in sub-micron crystallite form.

In various embodiments, the ion-permeable membrane is composed of glass fibers. In various embodiments, the ion-permeable membrane is composed of polymer materials. BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and desired objects of the present invention, reference is made to the following detailed description taken in conjunction with the

accompanying drawing figures wherein like reference characters denote corresponding parts throughout the several views.

FIG. 1 depicts a battery having a lithium metal electrode with a protective coating, according to an embodiment of the invention.

FIGS. 2A-2D are scanning electron microscopy (SEM) images of pristine (FIGS. 2A-2B) and LiN0₃ modified glass fiber separators (FIGS. 2C-2D).

FIGS. 3A-3C are images and a graph of scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) analysis of unmodified glass fiber separators according to an embodiment of the invention. (FIG. 3 A) SEM image; (FIG. 3B) elemental distribution map of Si; (FIG. 3C) the corresponding EDX spectrum.

FIGS. 4A-4D are images and a graph of SEM-EDX analysis of LiN0₃-modified glass fiber separators according to an embodiment of the invention. (FIG. 4A) SEM image; (FIG. 4B) elemental distribution map of Si; (FIG. 4C) elemental distribution map of N; (FIG. 4D) the corresponding EDX spectrum.

FIGS. 5A-5E are graphs reporting Coulombic efficiency (CE) of Li||Cu cells with and without LiN0₃ cycled under (FIG. 5 A) 1 mA cm^-2 / 2 mAh cm^-2, (FIG. 5B) 1 mA cm^-2 / 5 mAh cm^-2, (FIG. 5C) 2 mA cm^-2 / 5 mAh cm^-2, and (FIG. 5D) 5 mA cm^-2 / 10 mAh cm^-2 conditions. FIG. 5E is a comparison in electrochemical performance indices (capacity, current density, CE and cycle number), as measured in the Li||Cu configuration based on a carbonate electrolyte, of LiN0₃-protected Li metal electrodes with those reported in the literature.

FIGS. 6A-6D are graphs of discharging and charging voltage profiles of Li||Cu cells with LiN0₃ measured under various current-capacity conditions.

FIGS. 7A-7D are graphs of discharging and charging voltage profiles of Li||Cu cells without LiN0₃ measured under various current-capacity conditions.

FIGS. 8A-8C are graphs of CE of Li||Cu cells with and without LiN0₃ under 1 mA cm^-2/ 1 mAh cm^-2 conditions (FIG. 8A) and the corresponding discharging and charging voltage profiles (FIGS. 8B-8C, respectively). FIGS. 9A-9C are graphs of CE of Li||Cu cells with and without Li NO, under 2 mA cm^-2/ 1 mAh cm^-2 conditions (FIG. 9A) and the corresponding discharging and charging voltage profiles (FIGS. 9B-9C, respectively).

FIGS. 10A-10C are graphs of CE of Li||Cu cells with and without LiN0₃

under 4 mA cm^-2 / 1 mAh cm^-2 conditions (FIG. 10 A) and the corresponding discharging and charging voltage profiles (FIGS. 10B-10C, respectively).

FIGS. 11 A-l 1C are graphs of CE of Li||Cu cells with and without LiN0₃ under 1 mA cm^-2 / 10 mAh cm^-2 conditions (FIG. 11A) and the corresponding discharging and charging voltage profiles (FIGS. 11B-11C, respectively).

FIGS. 12A-12C are graphs of CE of Li||Cu cells with and without LiN0₃ under 2 mA cm^-2 / 10 mAh cm^-2 conditions (FIG. 12A) and the corresponding discharging and charging voltage profiles (FIGS. 12B-12C, respectively).

FIGS. 13A-13C are graphs of CE of Li||Cu cells with and without LiN0₃ under 5 mA cm^-2 / 5 mAh cm^-2 conditions (FIG. 13 A) and the corresponding discharging and charging voltage profiles (FIGS. 13B-13C, respectively).

FIGS. 14A-14B are graphs of dependence of CE on current and capacity for Li||Cu cells with LiN0_3.

FIGS. 15A-15B are graphs of CE of Li||Cu cells with LiN0₃ cycled at a fixed current density of 1 mA cm^-2 with the charging/discharging capacity (FIG. 15 A) increased and

(FIG. 15B) decreased stepwise.

FIGS. 16A-16B are cross-section SEM images of Li electrodes plated on a Cu current collector after 3 (FIG. 16 A) and 20 (FIG. 16B) cycles under 2 mA cm^-2- 10 mAh cm^-2 conditions for a Li||Cu cell without LiN0_3.

FIGS. 17A-17D are SEM-EDX analysis images of Li plated on a Cu foil as part of a Li||Cu cell without LiN0₃ after 20 cycles under 2 mA cm-2-lO mAh cm-2 conditions:

(FIG. 17A) SEM image; (FIGS. 17B-17D) elemental distribution maps of C, O and Cu, respectively.

FIGS. 18A-18B are cross-section SEM images of Li electrodes plated on a Cu current collector after 3 (FIG. 18 A) and 20 (FIG. 18B) cycles under 2 mA cm^-2- 10 mAh cm^-2 conditions for a Li||Cu cell with LiN0_3. FIGS. 18C-18D are top-view SEM images of Li plated on a Cu foil after 3 cycles under 2 mA cm^-2 / 10 mAh cm^-2 conditions for Li||Cu cells (FIG. 18C) without and (FIG. 18B) with Li NO,

FIGS. 19A-19B are XPS (X-ray photoelectron spectroscopy) depth profiles of a plated Li layer on a Cu foil after 3 cycles under 2 mA cm^-2 / 10 mAh cm^-2 conditions for Li 11 Cu cells (FIG. 19 A) without and (FIG. 19B) with LiN0₃.

FIGS. 20A-20B are C ls XPS spectra at various depths of the plated Li layer on the Cu foil after 3 cycles under 2 mA cm^-2 / 10 mAh cm^-2 conditions for Li||Cu cells (FIG. 20A) without and (FIG. 20B) with Li NO,.

FIGS. 20C-20D are O ls XPS spectra at various depths of the plated Li layer on the Cu foil after 3 cycles under 2 mA cm^-2 / 10 mAh cm^-2 conditions for Li||Cu cells (FIG. 20C) without and (FIG. 20D) with Li NO,.

FIGS. 20E-20F are Li ls XPS spectra at various depths of the plated Li layer on the Cu foil after 3 cycles under 2 mA cm^-2 / 10 mAh cm^-2 conditions for Li||Cu cells (FIG. 20E) without and (FIG. 20F) with LiN0₃.

FIG. 21 is a set of N ls XPS spectra at various depths of the plated Li layer on the Cu foil after 3 cycles under 2 mA cm^-2 / 10 mAh cm^-2 conditions for Li||Cu cells with LiN0₃.

FIGS. 22A-22C are graphs of CE of Li||Cu cells with and without LiN0₃ under 1 mA cm^-2 / 1 mAh cm^-2 conditions (FIG. 22A) and the corresponding EIS spectra (frequency range of 300 kHz to 10 mHz) taken at 1 mAh cm^-2 of Li plated on the Cu.

FIGS. 23A-23D are graphs showing cycling performance of Li | |Li symmetric cells with and without LiN0₃ cycled under (FIG. 23 A) 1 mA cm^-2 / 1 mAh cm^-2, (FIG. 23B) 2 mA cm^-2 / 2 mAh cm^-2, (FIG. 23C) 5 mA cm^-2 / 5 mAh cm^-2, and (FIG. 23D) 5 mA cm ²/20 mAh cm^-2 conditions

FIG. 23E is a comparison in electrochemical performance indices (capacity, current density and duration time), as measured in the Li||Li configuration based on carbonate electrolyte, of a LiN0₃-protected Li metal electrode according to an embodiment of the invention compared with those reported in the literature

FIGS. 24A-24C are graphs showing cycling performance of Li||Li symmetric cells with and without LiN0₃ under (FIG. 24A) 2 mA cm ² / 1 mAh cm ², (FIG. 24B) 2 mA cm ² / 5 mAh cm ², and (FIG. 24C) 5 mA cm ² / 10 mAh cm ² conditions. FIGS. 25A-25B are an SEM image and X-ray diffraction (XRD) pattern of a M0S3-CNT electrode material according to an embodiment of the invention.

FIG. 25C is a graph showing the electrochemical performance of a M0S3-CNT electrode, according to an embodiment of the invention, measured against a Li foil.

FIG. 26A is a schematic of a battery according to an embodiment of the invention.

FIG. 26B is a graph of charging-discharging voltage profiles and cycling performance of a close-to-stoichiometric Li-MoS3 cell, according to an embodiment of the invention.

FIGS. 26C-26D are graphs comparing specific and areal capacity (FIG. 26C) specific and areal energy (FIG. 26D) of a Li-MoS3 cell of the invention with other full cells reported in the literature.

DEFINITIONS

The instant invention is most clearly understood with reference to the following definitions:

As used herein, the singular form“a,”“an,” and“the” include plural references unless the context clearly dictates otherwise.

Unless specifically stated or obvious from context, as used herein, the term“about” is understood as within a range of normal tolerance in the art, for example within 2 standard deviations of the mean. “About” can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear from context, all numerical values provided herein are modified by the term about.

As used in the specification and claims, the terms“comprises,”“comprising,”

“containing,”“having,” and the like can have the meaning ascribed to them in U.S. patent law and can mean“includes,”“including,” and the like.

Unless specifically stated or obvious from context, the term“or,” as used herein, is understood to be inclusive.

Ranges provided herein are understood to be shorthand for all of the values within the range. For example, a range of 1 to 50 is understood to include any number, combination of numbers, or sub-range from the group consisting 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,

16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 (as well as fractions thereof unless the context clearly dictates otherwise).

The following abbreviations are used herein:

DET AILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention provide novel lithium metal electrodes having a protective coating layer containing Li, C, O and N and methods of making the same. The protective coating layer prevents the formation of dendrites and forms a stable solid electrolyte interface (SEI) on the electrode surface when used in a battery cell, allowing for deeper cycling than other electrodes known in the art. The invention further provides batteries incorporating the coated lithium metal electrodes of the invention and batteries capable of forming the coated lithium metal electrodes in-situ.

Batteries and Electrodes

Referring to FIG. 1, the invention provides a rechargeable battery 100 that includes a lithium metal electrode 102, optionally having a protective coating 104, a second electrode 106, an ion-permeable membrane 108 and an electrolyte 110 in contact with the lithium metal electrode 102, the ion-permeable membrane 108 and the second electrode 106.

At least a portion of the surface of lithium metal electrode 102 can be covered by the protective coating 104, and in certain embodiments the entire surface of the lithium metal electrode 102, or at least the surface exposed to the electrolyte 110 is covered by the protective coating 104. The protective coating 104 can contain at least one chemical species selected from Li₃N, LiNO, LiN0₂, LiN0₃, LiN₂0, LiN₂0₄, LiN₂O , and alkyl nitro species (R-N0₂). In some embodiments, the protective coating 104 contains LiN_xO_y, wherein x is a positive value from 0 to about 10 and y is a positive value from 0 to about 10; more specifically, x can also be a positive value from 0 to about 5 or a positive value from 0 to about 2 and y can be a positive value from 0 to about 10. In certain embodiments, the protective coating 104 contains Li₃N, at least one alkyl nitro species (R-N0₂), and at least one LiN_xO_y species. In one non-limiting embodiment, the protective coating 104 can be composed of about 50 mol% Li, about 35 mol % O, about 10 mol % C and less than about 5 mol % N based on an elemental analysis. The protective coating 104 can have a sufficient thickness to prevent dendrite formation during operation of the rechargeable battery, but remain thin enough to allow for transport of Li ions to and from the lithium metal electrode 102. The protective coating 104 can, for example, have a thickness of about 0.2 pm to about 20 pm.

The lithium metal electrode 102, itself, can be made substantially of pure or nearly pure Li° metal. In certain embodiments, the lithium metal electrode 102 can optionally have a current collector 112. The current collector 112 can be made of any conductive material ( e.g ., a metal) that is inert under appropriate battery operation methods as described elsewhere herein. In a preferred embodiment, the current collector 112 is a copper current collector.

The second electrode 106 can be a high capacity electrode made of substantially any material suitable for operation in a rechargeable lithium battery. In preferred embodiments, the second electrode 106 is a high capacity, non-intercalation electrode, wherein the electrode material does not comprise a layered structure that allows for intercalation of ions within the material. The second electrode 106 can be an amorphous (non-crystalline) material. In one preferred embodiment, the second electrode 106 is made of amorphous MoS_x (wherein x is about 3). Other examples of materials that can be potentially used in the second electrode 106 include, for example, V₂O₅ or FeF_3. The second electrode 106 material can be grown on carbon nanotubes. One example would be MoS₃ grown on oxidized carbon nanotubes, preferably wherein the oxidized carbon nanotubes have an oxygen : carbon stoichiometric ratio of less than about 1 : 5. In certain embodiments, the second electrode 106 can optionally have a current collector 114. The current collector 114 can be made of any conductive material (e.g., a metal) that is inert under appropriate battery operation methods as described elsewhere herein. For example, the current collector 114 is a carbon paper current collector but can alternatively be a metal current collector, such as an aluminum current collector. The electrolyte 110 can be substantially any electrolyte solution known in the art for use in a lithium ion battery. In some embodiments, the electrolyte 110 contains an organic solvent, preferably a non-ether organic solvent such as, but not limited to, an organic carbonate solvent. One potential electrolyte 110 can be a solution containing ethylene carbonate, diethyl carbonate or at least an amount of both. The electrolyte 110 can further include at least one Li⁺ cation and one anion species. In certain embodiments, the electrolyte 110 contains an amount of solvated LiPF_6. One example of an electrolyte 110 is a 1 M LiPF₆ solution in an ethylene carbonate (EC)/diethyl carbonate (DEC) (1 : 1 volumetric ratio) solvent.

The electrolyte 110 can further include LiN0_3. The LiNCE can be in the form of solvated LiNCE, suspended particles of LiNCE, solid (e.g, pelletized, bulk, macro-scale, and the like), or mixtures thereof. The electrolyte 110 can contain suspended LiN0₃ particles having a particle size of about 0.01 pm to about 100 pm, more preferably from about 0.1 pm to about 10 pm. In other embodiments, the suspended LiN0₃ particles can be larger than about 100 pm. The electrolyte 110 can have a dissolved LiNCE concentration of about 10 ⁶ g/ml to about 10 ⁴ g/ml. The suspended LiN0₃ particles can be crystalline particles. In certain embodiments, the electrolyte 110 does not contain any non-Li metal cations, such as but not limited to Cs⁺, Na⁺, Rb⁺, K⁺ or Sr²⁺.

The ion-permeable membrane 108 can be disposed in the electrolyte 110 between the lithium metal electrode 102 and the second electrode 106. The ion-permeable membrane 108 can be oriented such that electrolyte fluid flowing from the lithium metal electrode 102 to the second electrode 106 passes through the ion permeable membrane 108. In certain embodiments, the ion permeable membrane 108 is a porous membrane. In other embodiments, the ion permeable membrane 108 has pores large enough for the passage of LiNCE particles up to about 100 pm in diameter. The ion-permeable membrane 108 can be made of any material suitable for use in lithium ion batteries known in the art, for example, glass fibers or a range of polymer materials such as, but not limited to, polyethylene, polypropylene, poly

(tetrafluoroethylene), and polyvinyl chloride. The ion-permeable membrane 108 can also further contain LiNCE- In certain embodiments, the ion-permeable membrane 108 is impregnated with LiNCE- The impregnated LiNCE can be in the form of LiNCE particles having a particle size of about 0.01 pm to about 100 pm, more preferably from about 0.1 pm to about 10 pm. The impregnated LiNCE can be in crystalline form. Methods of Fabricating Protected Electrodes

In another aspect, the invention provides methods of forming a lithium metal electrode having a protective coating. The method can include the steps of: at least partially immersing a lithium metal electrode 102 in an electrolyte solution 110 comprising an effective amount of LiNOy at least partially immersing a conductive counter-electrode 106 in the same electrolyte solution 110; and exposing the lithium metal electrode 102 and the conductive counter electrode 106 to a plurality of charge-discharge cycles, thereby forming a protective coating 104 on the lithium metal electrode 102.

The protective coating 104 can be a protective coating as described elsewhere herein. The electrolyte 110 can be an electrolyte as described elsewhere herein. The conductive counter electrode 106 can be a high capacity electrode as described elsewhere herein and can include a second lithium metal electrode.

In certain embodiments, the plurality of charge-discharge cycles is at least one, but more preferably about 5 or more cycles. Through application of this method, it is possible to form and maintain the protective coating for at least 20 cycles. The charge-discharge cycles can be a series of processes whereby a current of about 0.1 mA cm ² to about 20 mA cm ² is applied to the electrodes.

The method allows for the deposition of inorganic species (such as Li₃N, LiN_xO_y and LiN0₂) and organic species along the surface of the lithium metal electrode. Without wishing to be limited to any particular theory, the protective coating formed by these species prevent the formation of dendrites that otherwise form on the surface of a lithium metal electrode in the absence of LiN0_3.

Methods of Operating a Rechargeable Battery of the Invention

The invention further provides methods of using the protected electrodes and batteries of the invention. A rechargeable battery of the invention can be charged by applying a current across the lithium metal electrode 102 and the second electrode 106 to charge the rechargeable battery 100. A rechargeable battery of the invention can be discharged by drawing current from across the lithium metal electrode 102 and the second electrode 106 to power a load. The steps of charging and discharging the battery can be repeated any number of times. In certain embodiments, the batteries can be cycled for at least: 1400 hours at a current density of 1 mA cm ² / current capacity of 1 mAh cm ² with an average overpotential of 40 mV; at least 700 hours at a current density of 2 mA cm ² / current capacity of 2 mAh cm ² with an average overpotential of 42 mV; and at least 420 hours at a current density of 5 mA cm ² / current capacity of 5 mAh cm ² with an average overpotential of 96 mV. Under certain circumstances, the batteries of the invention can be cycled to at least 20 mAh cm ².

Exemplary batteries of the invention can deliver an areal capacity up to about 6.3 mAh/cm² and a specific capacity of up to about 410 mAh/g. At an average discharge voltage of 1.95 V, exemplary batteries of the invention can afford an areal energy up to about 12.2 Wh/cm² and a specific energy up to about 793 Wh/kg.

Certain batteries of the invention are capable of vastly outperforming batteries known in the art, having higher specific and areal capacity and specific and areal energy than other full cell devices. Batteries according to embodiments of the invention can exhibit coulombic efficiencies greater than about 90%, greater than about 95%, greater than about 97%, greater than about 98%, greater than about 99%, greater than about 99.7%, or greater than about 99.8%.

In certain embodiments, the method of operation can form or maintain the protective coating 104 on the lithium metal electrode 102.

EXAMPLES

The invention is now described with reference to the following Examples. These

Examples are provided for the purpose of illustration only, and the invention is not limited to these Examples, but rather encompasses all variations that are evident as a result of the teachings provided herein.

Materials and Methods

Preparation of LiNO ₃-modified separators

A facile solution impregnation method was used to prepare LiNCE-modified

separators. 1 g of LiN0₃ was dissolved in 10 mL of 1, 2-dimethoxy ethane (DME) to prepare a solution. Pristine glass fiber separators (l5-mm diameter, Whatman) were soaked in the LiNCE solution for 2 h. The soaked separators were then taken out of the solution and fully dried in a vacuum antechamber of an Ar-filled glove box overnight at room temperature. The mass loading of LiN0₃ on a separator was weighed to be ~l mg.

Synthesis of amorphous M0S₃

Multi -wall CNTs (CNano Technology) were first mildly oxidized via a modified

Hummers’ method. Briefly, 1 g of CNTs was oxidized through exposure to 2-6 g of KMn0₄ in the presence of H₂S0_4. Subsequently, 12 mg of oxidized CNTs were dispersed in 20 mL of deionized water under the assistance of sonication. The dispersion was then transferred to a 250 mL round bottom flask, to which was added 1 mmol of (NH )₂MOS₄ dissolved in 40 mL of deionized water, followed by addition of 1 M HC1 (about 1 mL) until the solution pH was lowered to 3. The reaction mixture was stirred overnight. After reaction, the solid product was collected by centrifugation at 10000 rpm, washed with water, and lyophilized. Amorphous M0S₃ was finally obtained after annealing in an Ar atmosphere at 200°C for 2 h.

Materials characterization

SEM imaging and EDX measurements were performed with a HITACHI® SU8230 field emission SEM microscope. The dissembled electrodes subjected to later XPS measurements were cleaned in an EC/DEC (1 : 1 volumetric ratio) solution and dried in an Ar-filled glove box. The samples were then 2 transferred into the XPS chamber without exposure to air, using an air tight vessel. The XPS spectra were obtained using monochromatic 1486.7 eV Al Ka X-ray source on a PHI™ VERSAPROBE II™ X-ray Photoelectron Spectrometer with a 0.47 eV system resolution. Depth profile measurements were carried out using Ar ion sputtering at the power of 0.5 kV x 7 mA (the first 6 min) and 5 kV x 7 mA (the following 60 min) over a 3 x 3 mm area. The estimated sputtering rates are 0.9 and 11.7 nm/min, respectively. XRD was performed with a RIGAKU® SMARTLAB® diffractometer with Cu Ka radiation.

Electrochemical measurements

For the Li 11 Cu cell measurements, 2032-type coin cells were assembled with a pristine or LiNCL-modified glass fiber separator, a 13 mm-diameter Li foil disk (450 pm in thickness) and a 14 mm-diameter Cu foil disk. Electrochemical Li plating at a certain current density was performed until a certain capacity was reached, followed by Li stripping at the same current density with a cut-off voltage of 0.5 V. For the Li||Li cell measurements, symmetric cells were assembled with a 13 mm-diameter Li foil disks as both the working and counter electrodes. Long-term galvanostatic cycling was then performed at a certain current density with a certain cut-off capacity. To prepare the MoS₃ cathode, a slurry containing M0S3-CNT, carbon black and polyvinylidene difluoride in a mass ratio of 75: 15: 10 was casted onto a 10 mm-diameter carbon paper (SPECTRACARB™ 2050A-0550, Fuel Cell Store) disk to give an areal mass loading of -12 mg/cm² (based on M0S3-CNT). For all the cells, a 1 M LiPF₆-EC/DEC (1 : 1 volumetric ratio) electrolyte (BASF) was used as received. The cells were measured by a BT2143 battery analyzer (Arbin Instrument). The EIS measurements were carried out using a BIO-LOGIC™ VMP3 multichannel system.

Example 1: Fabrication of Li||Cu cells having LiNOa-modified separators

A glass fiber separator was immersed in a L1NO3 solution to impregnate the separator with sub-micron scale crystallites of L1NO3 (FIGS. 2A-2D, 3A-3C, 4A-4D). It was hypothesized that under working conditions, the crystallites can serve as a reservoir for L1NO3 dissolved in an electrolyte that can then form a protective layer on a Li metal electrode.

Li||Cu cells were assembled with both pristine and LiN03-modified separators to investigate the electrochemical Li plating/stripping processes. A commercial electrolyte based on 1 M LiPF₆ in an ethylene carbonate (EC)/diethyl carbonate (DEC) (1 : 1 volumetric ratio) mixed solvent was used. The Coulombic efficiency (CE) of a cell, defined as the ratio of the amount of the stripped Li to that of the plated Li on the Cu current collector in each charging discharging cycle, was used as a performance index to evaluate the cyclability of the Li metal electrode. At the current density of 1 mA cm^-2, the cells with L1NO3 could be stably cycled for 210 and 160 cycles with average CE’s of 95.1% and 98.3% to the capacity depths of 2 and 5 mAh cm^-2 (FIGS. 5A-5B), respectively. Under even harsher conditions

of 2 mA cm^_2/5 mAh cm^-2 and 5 mA cm^-2- 10 mAh cm^-2, the cells with L1NO3 operated stably for 100 and 50 cycles with high average CE’s of 96.8% and 98.1% (FIGS. 5C-5D), respectively. In contrast, the cells without L1NO3 exhibited substantially worse cycling performance

(FIGS. 5A-5D); operating for only 30 cycles with an average CE of 91.6% under

the 1 mA cm^_2/2 mAh cm^-2 conditions. At the 5 mA cm^-2- 10 mAh cm^-2 conditions, the cell without L1NO3 was not even cyclable. The corresponding charging-discharging voltage profiles are plotted in FIGS. 6A-6D and FIGS. 7A-7D. The CE’s and voltage profiles of the Li||Cu cells with and without Li NO, cycled at other current-capacity conditions (1 mA cm^_2/l mAh cm^-2,

2 mA cm^_2/l mAh cm^-2, 4 mA cm^_2/l mAh cm^-2, 1 mA cm^_2/l0 mAh cm^-2, 2 mA cm^-2/ 10 mAh cm^-2, and 5 mA cm^_2/5 mAh cm^-2) are shown in FIGS. 8A-8C, 9A-9C, 10A-10C, 11 A-l 1C, 12A-12C and 13A-13C. FIG. 5E compares the performance indices of the LiN0₃-protected Li metal electrodes with those reported in the literature for other Li metal electrodes in the Li||Cu configuration based on carbonate electrolyte. The protected electrodes described above achieved much higher capacities (i.e., can be much more deeply cycled) and rate capability without compromising other properties such as the CE and cycle life.

The dependence of CE on current and capacity was then investigated for the Li||Cu cells with LiN0₃. As the charging-discharging current increased from 1 to 4 mA cm^-2, the CE decreased from 93.7% to 91.2% at a fixed cycling capacity of 1 mAh cm^-2 (FIG. 14A). This is consistent with literature precedence that chemical reactions are less reversible at higher rates. FIG. 14B shows the dependence of CE on charging-discharging capacity at various current densities. At each current density, the CE increases with the capacity. This is also confirmed by control experiments in which the charging-discharging current density for a Li||Cu cell is increased or decreased stepwise (FIGS. 15A-15B). Similar phenomena have been observed before and indicate that the nucleation or initial growth stage is less reversible than the subsequent Li deposition.

Scanning electron microscopy (SEM) was used to image the Li deposited on the Cu current collector after deep cycling. After the Li plating step in the 3^rd cycle under the

demanding 5 mA cm^_2-l0 mAh cm^-2 conditions, the deposited Li of the Li||Cu cell without LiN0₃ manifested as a loosely packed structure consisting of dendrites and whiskers (FIG. 16A). Further cycling continued to rapture the unstable solid electrolyte interphase (SEI) and deteriorate the electrode structure, resulting in a -100 pm-thick dendritic Li layer covered with another -100 pm-thick mossy C-containing Li layer after 20 cycles (FIG. 16B, FIGS. 17A-17D). In contrast, the deposited Li of the Li 11 Cu cell with LiN0₃ displayed a -40 pm-thick dense and uniform film structure without any traces of dendrites (FIG. 18 A). The structure and thickness of the dendrite-free Li layer could still be maintained after 20 cycles (FIG. 18B). A -2 pm-thick layer was observed, having a porous surface morphology (FIGS. 18C-18D) on the surface of the plated Li layer (FIG. 18B). X-ray photoelectron spectroscopy (XPS) was then used to analyze the chemical composition of the LiN0₃-derived protective layer. Thickness-dependent elemental

compositions, together with the corresponding C ls, O ls and Li ls XPS spectra, are shown in FIGS. 19A-19B and 20A-20F for the Li-plated Cu electrodes of the Li||Cu cells with and without L1NO₃ after 3 cycles under the 2 mA cm^_2/l0 mAh cm^-2 conditions. Both electrodes possessed an SEI featuring an outer surface rich in lithium semi-carbonates (ROCOOLi) and Li₂C0₃, and an inner layer dominated by Li₂0, consistent with the prevalent“mosaic model”. The C content on the LiN0₃-free electrode decreased with the sputtering thickness significantly more slowly than that on the LiN0₃-protected electrode (FIGS. 19A-19B), indicating more severe electrolyte decomposition on the electrode surface without a LiN0₃-derived protective layer. Without wishing to be limited to any particular theory, because the two electrodes contain similar C and O species in the surface layer, the desirable functionalities of the LiN0₃-derived protective layer can be attributed to the N-containing species in the layer. FIG. 21 plots the depth-dependent N ls XPS spectra for the LiN0₃-protected electrode. The major components of the protective layer are Li₃N, LiN_xO_y, LiN0₂ and alkyl nitro species (R-N0₂). Both Li₃N and LiN_xO_y are good Li ion conductors and therefore can help promote efficient and stable cycling of Li metal electrodes. This is supported by the stabilized Li ion transfer resistance for the Li||Cu cell with LiN0₃ upon cycling (FIGS. 22A-22C).

Example 2: Fabrication of Li||Li cell with L1NO₃

Symmetric Li | |Li cells were then fabricated in order to evaluate the electrochemical performance of the LiN0₃-protected Li metal electrodes. At a charging-discharging current density of 1 mA cm^-2 and capacity of 1 mAh cm^-2, the Li||Li cell with LiN0₃ was cycled for 1400 h with an average overpotential of 40 mV (FIG. 23 A). The electrode was also functional for 700 h under the 2 mA cm^_2/2 mAh cm^-2 conditions, showing an overpotential of 42 mV (FIG. 23B). Under the demanding conditions of 5 mA cm^_2/5 mAh cm^-2, the cell was stably cycled for 420 h with an average overpotential of 96 mV (FIG. 23C). The Li | |Li cell with LiN0₃ could even be cycled to an extremely high capacity of 20 mAh cm^-2 (FIG. 23D). The cycling performance under other conditions (2 mA cm^_2/l mAh cm^-2, 2 mA cm^_2/5 mAh cm^-2, and 5 mA cm^_2/l0 mAh cm^-2) is given in FIGS. 24A-24C. Under all conditions, the Li||Li cells without LiN0₃ exhibited much worse performance (FIGS. 23 A-23D, FIGS. 24A-24C). FIG. 23E compares the performance indices of LiNCE-protected Li metal electrodes with those reported in the literature for other Li metal electrodes in the Li | |Li configuration based on carbonate electrolyte. It is evident that the LiNCE-protected electrodes can achieve much higher capacities without sacrificing other properties such as the CE, cycle life and rate capability. Example 3: Fabrication of Li||MoS₃ cell with L1NO₃

LiN0₃-protected Li metal electrodes were then used to fabricate close-to-stoichiometric full cells with ultrahigh capacity and energy. Amorphous M0S₃ was chosen as the cathode material because of its proven high capacity and compatibility with carbonate electrolyte. The M0S₃ was grown on mildly oxidized carbon nanotubes (CNTs) (FIGS. 25A-25B) and exhibited a specific capacity of -500 mAh g^-1 at the current density of 0.7 mA cm^-2 and a mass loading of 12.5 mg cm^-2 (FIG. 25C). To assemble the full cell, a pre-deposited LiNCE -protected Li metal electrode (10 mAh cm^-2, 2.6 mg cm ²) was paired with a M0S₃ electrode (-6.4 mAh cm^-2, 12.8 mg cm^-2). The full cell delivered an areal capacity of 6.3 mAh cm^-2, corresponding to a specific capacity of 410 mAh g^-1 based on the total mass of electrode materials. Coupled with the average discharging voltage of 1.95 V, the cell afforded an areal energy of 12.2 Wh cm^-2 and a specific energy of 793 Wh kg^-1 based on the total mass of electrode materials. Both the capacity and energy of our L1-M0S₃ full cell, normalized to either the electrode area or the total mass of both the anode and cathode materials, are significantly higher than other Li battery cells, including the previously reported high-capacity cells based on Li metal or Si (D. C. Lin et al ., Nature Nanotechnology 11, 626-632 (2016); C.-P. Yang, et al., Nature Communications 6, 8058 (2015).; Y. Yang et al, Nano Letters 10, 1486-1491 (2010).; L.-F. Cui, et al. Nano Letters 9, 3370-3374 (2009)), as well as the state-of-the-art Li ion batteries on the market (FIGS. 26C- 26D), putting forward a competitive candidate for future-generation high-capacity and high- energy rechargeable batteries. EQUIVALENTS

Although preferred embodiments of the invention have been described using specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims. INCORPORATION BY REFERENCE

The entire contents of all patents, published patent applications, and other references cited herein are hereby expressly incorporated herein in their entireties by reference.

Claims

1. A lithium metal electrode comprising a protective coating comprising one or more selected from the group consisting of: Li₃N, LiN_xO_y, LiN0_2, and alkyl nitro species (R-N0₂), wherein x is a positive value from 0 to about 10 and y is a positive value from 0 to about 10.

2. The lithium metal electrode of claim 1, wherein the protective coating comprises:

Li₃N;

LiN_xO_y;

LiN0₂; and

alkyl nitro species (R-N0₂).

3. The lithium metal electrode of claim 1, wherein the protective coating has a thickness of about 0.2 pm to about 20 pm.

4. The lithium metal electrode of claim 1, wherein the protective coating comprises about 50 mol% Li, about 35 mol% O, about 10 mol% C, and less than about 5 mol% N.

5. The lithium metal electrode of claim 1, wherein the electrode comprises a copper current collector.

6. The lithium metal electrode of claim 1, wherein the protective coating has a porous surface morphology.

7. A rechargeable battery comprising:

a lithium metal electrode of any one of claims 1-6;

a high capacity, non-intercalation electrode;

an electrolyte in contact with both the lithium metal electrode and the non-intercalation electrode; and

an ion-permeable membrane disposed in the electrolyte between the lithium metal electrode and the non-intercalation electrode.

8. The rechargeable battery of claim 7, wherein the high capacity, non-intercalation electrode comprises a non-layer structured material.

9. The rechargeable battery of claim 7, wherein the high capacity, non-intercalation electrode comprises an amorphous material.

10. The rechargeable battery of claim 7, wherein the high capacity, non-intercalation electrode comprises MoS_3.

11. The rechargeable battery of claim 7, wherein the high capacity, non-intercalation electrode comprises MoS₃ grown on oxidized carbon nanotubes having an oxygen : carbon stoichiometric ratio of less than about 1 : 5.

12. The rechargeable battery of claim 7, wherein the electrolyte does not comprise an organic ether solvent.

13. The rechargeable battery of claim 7, wherein the electrolyte comprises an organic carbonate solvent.

14. The rechargeable battery of claim 7, wherein the electrolyte comprises at least one solvent selected from the group consisting of ethylene carbonate and diethyl carbonate.

15. The rechargeable battery of claim 7, wherein the electrolyte comprises at least one Li⁺ species in the form of a solute or suspended particle.

16. The rechargeable battery of claim 15, wherein the electrolyte comprises solvated LiPF_6.

17. The rechargeable battery of claim 15, wherein the electrolyte comprises LiN0_3.

18. The rechargeable battery of claim 17, wherein the electrolyte comprises LiN0₃ particles suspended in solution.

19. The rechargeable battery of claim 18, wherein the electrolyte comprises Li NO, particles having a particle size of about 0.1 pm to about 10 pm.

20. The rechargeable battery of claim 18, wherein the electrolyte comprises solvated Li NO,.

21. The rechargeable battery of claim 20, wherein the electrolyte has a dissolved Li NO, concentration of about 10 ⁶ g/ml to about 10 ⁴ g/ml.

22. The rechargeable battery of claim 7, wherein the ion-permeable membrane is

impregnated with an effective amount of L1NO3.

23. The rechargeable battery of claim 7, wherein the ion-permeable membrane comprises at least one material selected from the group consisting of polymers and glass fibers.

24. A rechargeable battery comprising:

a lithium metal electrode;

a second electrode;

an electrolyte in contact with both the lithium metal electrode and the second electrode; and

an ion-permeable membrane impregnated with an effective amount of LiN0₃, disposed in the electrolyte between the lithium metal electrode and the second electrode.

25. The rechargeable battery of claim 24, wherein the second electrode is a high capacity, non-intercalation electrode.

26. The rechargeable battery of claim 25, wherein the high capacity, non-intercalation electrode comprises a non-layer structured material.

27. The rechargeable battery of claim 25, wherein the high capacity, non-intercalation electrode comprises an amorphous material.

28. The rechargeable battery of claim 25, wherein the high capacity, non-intercalation electrode comprises MoS_3.

29. The rechargeable battery of claim 28, wherein the high capacity, non-intercalation electrode comprises MoS₃ grown on oxidized carbon nanotubes having an oxygen : carbon stoichiometric ratio of less than about 1 : 5.

30. The rechargeable battery of claim 24, wherein the electrolyte does not comprise an organic ether solvent.

31. The rechargeable battery of claim 24, wherein the electrolyte comprises an organic carbonate solvent.

32. The rechargeable battery of claim 24, wherein the electrolyte comprises at least one solvent selected from the group consisting of ethylene carbonate and diethyl carbonate.

33. The rechargeable battery of claim 24, wherein the electrolyte comprises at least one Li⁺ species in the form of a solute or suspended particle.

34. The rechargeable battery of claim 33, wherein the electrolyte comprises solvated LiPF_6.

35. The rechargeable battery of claim 33, wherein the electrolyte comprises LiN0_3.

36. The rechargeable battery of claim 35, wherein the electrolyte comprises LiN0₃ particles suspended in solution.

37. The rechargeable battery of claim 36, wherein the electrolyte comprises LiN0₃ particles having a particle size of about 0.1 pm to about 10 pm.

38. The rechargeable battery of claim 35, wherein the electrolyte comprises solvated LiN0_3.

39. The rechargeable battery of claim 38, wherein the electrolyte has a dissolved LiN0₃ concentration of about 10 ⁶ g/ml to about 10 ⁴ g/ml.

40. The rechargeable battery of claim 24, wherein the ion-permeable membrane comprises at least one material selected from the group consisting of polymers and glass fibers.

41. A rechargeable battery comprising:

a lithium metal electrode;

a second electrode;

a carbonate electrolyte in contact with both the lithium metal electrode and the second electrode;

an ion-permeable membrane disposed in the electrolyte between the lithium metal electrode and the second electrode; and

an effective amount of L1NO₃ in contact with the carbonate electrolyte.

42. A method of forming a lithium metal electrode having a protective coating, the method comprising:

at least partially immersing a lithium metal electrode in an electrolyte solution

comprising an effective amount of LiN0₃;

at least partially immersing a conductive counter-electrode in the electrolyte solution comprising an effective amount of LiN0₃; and

exposing the lithium metal electrode and the conductive counter-electrodes to a plurality of charge-discharge cycles, thereby forming a protective coating on the lithium metal electrode.

43. The method of claim 42, wherein the protective coating comprises one or more selected from the group consisting of: Li₃N, LiN_xO_y, LiN0_2, and alkyl nitro species (R-N0₂), wherein x is a positive value from 0 to about 10 and y is a positive value from 0 to about 10.

44. The method of claim 43, wherein the protective coating comprises:

Li₃N;

LiN_xO_y;

LiN0₂; and

alkyl nitro species (R-N0₂).

45. The method of claim 43, wherein the protective coating has a thickness of about 0.2 pm to about 20 pm.

46. The method of claim 43, wherein the protective coating comprises about 50% Li, about 35% O, about 10% C, and less than about 5% N.

47. The method of claim 42, wherein the electrolyte does not comprise an organic ether solvent.

48. The method of claim 42, wherein the electrolyte comprises an organic carbonate solvent.

49. The method of claim 42, wherein the electrolyte comprises at least one solvent selected from the group consisting of ethylene carbonate and diethyl carbonate.

50. The method of claim 42, wherein the electrolyte comprises solvated LiPF_6.

51. The method of claim 42, wherein the electrolyte comprises Li NO, particles suspended in solution.

52. The method of claim 51, wherein the electrolyte comprises Li NO, particles having a particle size of about 0.1 pm to about 10 pm.

53. The method of claim 42, wherein the electrolyte comprises solvated Li NO,.

54. The method of claim 53, wherein the electrolyte has a dissolved Li NO, concentration of about 10 ⁶ g/ml to about 10 ⁴ g/ml.

55. The method of claim 42, wherein the plurality of charge-discharge cycles is one or more cycles.

56. The method of claim 55, wherein the plurality of charge-discharge cycles is about 1 or more cycles.

57. The method of claim 55, wherein the plurality of charge-discharge cycles is about 5 or more cycles.

58. The method of claim 42, wherein the charge-discharge cycles comprise the application of a current of about 0.1 mA cm^'2 to about 20 mA cm ².

59. A method of repeated charge-discharge cycling of the rechargeable battery of any one of claims 42-58, the method comprising:

applying current across the lithium metal electrode and the second electrode to charge the rechargeable battery; and

drawing current from across the lithium metal electrode and the second electrode to power a load; and

repeating the applying current and the drawing current steps a plurality of times, thereby forming or maintaining a protective coating on the lithium metal electrode.

60. A battery separator comprising:

an ion-permeable membrane impregnated with Li NO,.

61. The battery separator of claim 60, wherein the L1NO3 is in sub-micron crystallite form.

62. The battery separator of claim 60, wherein the ion-permeable membrane is composed of glass fibers.

63. The battery separator of claim 60, wherein the ion-permeable membrane is composed of polymer materials.