Lithium metal anode including a protective layer

Abstract

The present invention relates to a lithium metal anode (1, 10, 11, 12, 13, 14) for a battery, comprising an anode active substrate (2) comprising lithium metal and a first lithium metal anode protective layer (3) disposed on a surface (4) of the anode active substrate (2), the anode further comprising one or more of Li2CO3, Li2O, and LiOH, and the first lithium metal anode protective layer (3) comprising a first lithium halide. The present invention also relates to a battery comprising the lithium metal anode and a method for manufacturing the lithium metal anode.

Description

[Technical Field]

[0001] The present invention relates to a lithium metal anode for a lithium ion battery, the anode comprising a protective surface layer. The present invention further relates to batteries comprising such lithium metal anodes and to methods of making them. [Background technology]

[0002] Rechargeable batteries have achieved remarkable success and commercialization over the past few decades as the most popular and reliable power source for portable devices, electric vehicles, and energy storage stations. Li-ion batteries, in particular, have surpassed other battery systems on the market due to their high energy density and outstanding cycling stability.

[0003] Anodes containing lithium metal are popular anodes for lithium-ion batteries due to lithium's high theoretical capacity (3860 mAh / g). However, their widespread application is hindered by their high (electro)chemical reactivity and tendency to form lithium dendrites at high current densities and areal capacities. Dendrites pose a safety risk by growing on the anode's surface and potentially causing short circuits and battery failure. Furthermore, reactivity between metallic lithium and the electrolyte leads to the formation of inactive Li, so-called "dead Li," leading to rapid cell fading.

[0004] Dendrites and dead lithium (i.e., lithium that has become inactive and no longer participates in electrochemical cycling) result from uneven lithium plating and stripping during charge and discharge cycles, which can be caused by a variety of reasons, such as mechanical stress, surface energy, structural defects, (electro)chemical reactions, etc. To reduce the risk of dendrite formation and dead lithium accumulation and to increase the safety and lifespan of batteries, several solutions have been investigated, including, but not limited to, the introduction of solid-state electrolytes, artificial lithium metal hosts, the addition of additives to the electrolyte, and organic / inorganic passivation layers for liquid electrolyte-based batteries.

[0005] In particular, lithium-ion conducting passivation layers, i.e., protective layers, such as artificial solid electrolyte interphase (SEI) coatings, have attracted much interest. While a natural SEI is typically formed on the anode, this has often proven insufficient to prevent dendrite growth. Artificial SEI (a-SEI) layers act as a battery, inhibiting dendrite growth and providing a more stable surface for lithium deposition.

[0006] US2018 / 0294476 describes a lithium or lithium alloy foil or coating on a current collector as an anode and a 10 -6 S / cm lithium ion conductivity and 0.5 * 10 6 ~9 * 10 6 and a thin layer of 1 nm to 10 μm of a high-elasticity ultra-high molecular weight (UHMW) polymer having a molecular weight of 1000 g / mol.

[0007] The disadvantage of the aforementioned UHMW polymer as a protective layer is that the polymer is not chemically stable in all types of liquid electrolytes, especially in certain organic solvents used in liquid electrolytes, and is prone to swelling. A further disadvantage is that the UHMW polymer may repel the solvent in the electrolyte, which can cause instability and variability in the ionic conductivity of lithium ions in the electrolyte. Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to overcome one or more of the aforementioned drawbacks. An object of the present invention is to provide a lithium metal anode having excellent electrochemical performance. A further object is to provide a lithium metal anode having improved life span when used in a battery. Yet another object is to provide a lithium metal anode that, when used in a battery, is less likely to form dendrites and / or accumulate dead lithium, thereby providing excellent performance in secondary batteries. A further object is to provide a lithium metal anode that is chemically stable and / or mechanically robust and / or stable, and can withstand, in particular, high mechanical stresses, pressures, and shocks.

[0009] A further object is to provide a lithium metal anode in which the purity of the lithium metal is less critical for superior performance.

[0010] It is a further object of the present invention to provide a lithium ion battery that has an improved cycle life, i.e., that can withstand a large number of charge / discharge cycles. [Means for solving the problem]

[0011] According to a first aspect of the present disclosure, there is provided a lithium metal anode for a battery, as set forth in the accompanying claims. The lithium metal anode includes an anode active substrate including lithium metal and a first lithium metal anode protection layer disposed on a surface of the anode active substrate. The anode further includes one or more of lithium carbonate (LiCO), lithium oxide (LiO), and lithium hydroxide (LiOH).

[0012] The lithium metal anode protection layer comprises or consists essentially of a first lithium halide, preferably lithium iodide (LiI) or lithium fluoride (LiF).

[0013] Preferably, the anode further comprises a second lithium metal anode protection layer disposed on the first lithium metal anode protection layer. Preferably, the second lithium metal anode protection layer comprises or consists essentially of a second lithium halide. Preferably, the second lithium halide is LiI or LiF.

[0014] Suitably, when the first and / or optional second lithium metal anode protection layer comprises or consists essentially of LiI, each lithium metal anode protection layer has a thickness of from 5 nm to 800 nm, preferably from 50 nm to 700 nm, more preferably from 100 nm to 500 nm.

[0015] The inventors have surprisingly discovered that when the thickness of the protective layer comprising or consisting essentially of LiI exceeds 800 nm, the efficiency of Li-ion batteries comprising the respective anodes of the present invention decreases to values ​​that are considered unacceptable. More specifically, thicknesses greater than 800 nm can even lead to lithium plating / stripping, thus making battery charging / discharging impossible or of very poor quality, while thicknesses less than 800 nm allow excellent lithium plating / stripping.

[0016] Suitably, when the first and / or optional second lithium metal anode protection layer comprises or consists essentially of LiF, each lithium metal anode protection layer has a thickness of from 50 nm to 200 nm, preferably from 75 nm to 175 nm, more preferably from 100 nm to 150 nm.

[0017] The inventors have discovered that a protective layer comprising or consisting essentially of LiF needs to be at least 50 nm thick to provide a sufficient degree of protection for the anode active substrate, particularly with respect to reducing dendrite formation and / or dead lithium accumulation when the anode is used in a battery. The inventors have further surprisingly discovered that a protective layer comprising or consisting essentially of LiF with a thickness greater than 200 nm impedes lithium ion diffusion, i.e., becomes more difficult, and / or the internal resistance of a battery containing the respective anode increases to a level that renders the battery unusable.

[0018] Preferably, the anode comprises first and second lithium metal anode protective layers, wherein the first lithium metal anode protective layer comprises or consists essentially of LiI, i.e., the first lithium halide comprises or consists essentially of LiI, and the second lithium metal anode protective layer comprises or consists essentially of LiF, i.e., the second lithium halide comprises or consists essentially of LiF.

[0019] Preferably, the anode active substrate comprises an anode current collector and a layer comprising or consisting essentially of lithium metal disposed on a surface of the anode current collector. The anode current collector may be any anode current collector known in the art, particularly a copper substrate, such as a copper film.

[0020] Preferably, one or more of Li2CO3, Li2O, and LiOH contained in the anode are present as a native layer of impurities, which native layer of impurities is contained in the anode active substrate. More specifically, and preferably, the native layer of impurities is present on a layer comprising or consisting essentially of lithium metal.

[0021] The term "native layer of impurities" is used in this disclosure to refer to a layer of impurities inherently present on lithium metal, particularly on commercially available lithium metal. This is a phenomenon known in the art, in that lithium metal is highly reactive in the ambient atmosphere, resulting in the formation of a native layer of impurities including one or more of carbonates, oxides, hydroxides, and nitrides. It is further known that any lithium nitride that is formed will convert to lithium carbonate and lithium hydroxide over time when exposed to or in the presence of CO and water.

[0022] Alternatively, and even more preferably, one or more of Li2CO3, Li2O, and LiOH contained in the anode are present as a passivation layer disposed between the anode active substrate and the first lithium metal anode protection layer. When the anode active substrate includes an anode current collector and a layer comprising or consisting essentially of lithium metal disposed on the surface of the anode current collector, the passivation layer is preferably disposed between the layer comprising or consisting essentially of lithium metal and the first lithium metal anode protection layer.

[0023] The term "passivation layer" is used in this disclosure to refer to a separate layer present on the anode active substrate, particularly on the lithium metal therein, that mimics in a controlled manner the native layer of impurities present on the lithium metal. In other words, the passivation layer comprises or consists essentially of the same components as the native layer of impurities, but in contrast to the native layer, the passivation layer is a layer that is actively disposed in order to control its composition and structure.

[0024] The present inventors have surprisingly discovered that the presence of such a passivation layer, in place of the native layer of impurities, allows for more controlled, e.g., more uniform and homogeneous, lithium plating and stripping of the anode. This, in turn, increases the number of lithium plating / stripping cycles that the anode can withstand, thereby improving the anode's lifespan. The passivation layer of the present invention further contributes to improved electrochemical stability. As a result, the passivation layer surprisingly improves the performance of the lithium metal anode, thereby improving the performance and lifespan of batteries containing the lithium metal anode.

[0025] Preferably, the passivation layer comprises one or more of Li2CO3, Li2O and LiOH.

[0026] Suitably, the surface of the passivation layer adjacent to the first lithium metal anode protection layer is at least 80%, preferably at least 85%, more preferably at least 90% LiO, LiOH and Li as measured by quantitative X-ray photoelectron spectroscopy (XPS). x PO y N z (LIPON), where x, y, and z are individually greater than 0. Suitably, the surface of the passivation layer adjacent to the first lithium metal anode protection layer comprises at most 5%, preferably at most 3%, Li2CO3, as measured by quantitative XPS.

[0027] "Surface of the passivation layer" in this disclosure refers to the portion of the passivation layer starting from its respective surface and having a thickness of up to 20 nm, preferably up to 15 nm, more preferably up to 10 nm. Surface analysis techniques, such as quantitative XPS, are known to typically probe up to a thickness of 10 nm to 20 nm, i.e., the portion considered to be the surface, surface layer, or surface portion.

[0028] "Bulk (portion) of the passivation layer" in this disclosure means the portion of the passivation layer starting at a thickness of 20 nm, preferably 15 nm, more preferably 10 nm, to the edge. In other words, the passivation layer can be considered to have a surface or surface portion and a bulk or bulk portion.

[0029] Suitably, the passivation layer has a thickness of 100 nm to 1000 nm, preferably 150 nm to 900 nm, more preferably 200 nm to 800 nm, for example 250 nm to 750 nm, or 500 nm to 700 nm.

[0030] Preferably, the surface of the passivation layer adjacent to the first lithium metal anode protection layer, i.e., in the first 10 nm thickness starting from the surface of the passivation layer adjacent to the first lithium metal anode protection layer, comprises or consists essentially of LiCO, LiO, and LiOH, as measured by the total electron yield (TEY) signal in X-ray absorption spectroscopy (XAS).

[0031] Suitably, and further preferably, the bulk of the passivation layer comprises or consists essentially of Li2O and / or LiOH as measured by the total fluorescence yield (TFY) signal in XAS.

[0032] According to a second aspect of the present disclosure, there is provided a lithium-ion battery as set out in the accompanying claims. Preferably, the lithium-ion battery comprises an anode according to the first aspect of the present invention. Preferably, the battery is a secondary battery.

[0033] According to a third aspect of the present invention there is provided a method of manufacturing a lithium metal anode as set out in the accompanying claims. Suitably the lithium metal anode is an anode for a battery.

[0034] Preferably, the lithium metal anode is according to the first aspect of the present invention, in other words, the lithium metal anode preferably comprises an anode active substrate and a first lithium metal anode protection layer as described herein above, i.e., the first lithium metal anode protection layer comprises a first lithium halide and is provided on a surface of the anode active substrate.

[0035] The method includes depositing a first lithium metal anode protection layer on a surface of an anode active substrate comprising lithium metal. The first lithium metal anode protection layer is deposited by thermal evaporation of a first coating composition comprising or consisting essentially of a first lithium halide.

[0036] Suitably, the first coating composition has a temperature of 200°C to 1000°C, preferably 200°C to 900°C, more preferably 250°C to 750°C, during its thermal evaporation on the surface of the anode active substrate. Suitably, the anode active substrate has a temperature of 10°C to 30°C, preferably 15°C to 25°C, more preferably room temperature, for example 20°C, during the thermal evaporation of the first coating composition.

[0037] Preferably, the method further comprises depositing a second lithium metal anode protective layer over the first lithium metal anode protective layer by thermal evaporation of a second coating composition comprising or consisting essentially of a second lithium halide.

[0038] Suitably, the second coating composition has a temperature of 200°C to 1000°C, preferably 200°C to 900°C, more preferably 250°C to 750°C, during its thermal evaporation on the surface of the first lithium metal anode protection layer. Suitably, the anode active substrate has a temperature of 10°C to 30°C, preferably 15°C to 25°C, more preferably room temperature, for example 20°C, during the thermal evaporation of the second coating composition.

[0039] Preferably, the first and optional second lithium halides are as described herein above, i.e., they are individually LiI or LiF.

[0040] Suitably, when the first lithium halide and / or the optional second lithium halide is LiI, the respective coating composition, i.e., each coating composition comprising or consisting essentially of LiI, has a temperature of from 250°C to 400°C, preferably from 275°C to 375°C, more preferably from 300°C to 350°C during its respective thermal evaporation.

[0041] Suitably, when the first lithium halide and / or the optional second lithium halide is LiF, each coating composition, i.e. each coating composition comprising or consisting essentially of LiF, has a temperature of from 500°C to 900°C, preferably from 600°C to 850°C, more preferably from 700°C to 800°C, during its respective thermal evaporation.

[0042] Suitably, the thermal evaporation of the first coating composition and / or the optional second coating composition is individually carried out 1 to 50 times, preferably 5 to 30 times, and more preferably 10 to 20 times. In particular, the thermal evaporation is carried out as many times as necessary to obtain a predetermined thickness of the lithium metal anode protection layer. It will be understood that the number of repetitions will depend on the predetermined thickness to be obtained, as well as the thickness deposited in each repetition.

[0043] Preferably, the method further comprises, prior to deposition of the first lithium metal anode protection layer, a step of gas assisted radio frequency (RF) sputtering using a target substrate, preferably a short target, comprising or consisting essentially of LiPO (LiPO).

[0044] Preferably, the gas-assisted RF sputtering converts any native layer of impurities present on the anode active substrate into a passivation layer on the anode active substrate, where the passivation layer is as described herein above.

[0045] Preferably, the gas is nitrogen, argon, helium, or a combination of two or more thereof. Particularly preferred examples of gases include nitrogen and mixtures of nitrogen and inert gases.

[0046] Suitably, the target substrate comprising or consisting essentially of Li3PO4 has a temperature of 10°C to 50°C, preferably 15°C to 35°C, more preferably 20°C to 30°C, for example room temperature, for example 20°C, during gas-assisted RF sputtering.

[0047] Suitably, the gas-assisted RF sputtering has a duration of from 5 minutes to 2.5 hours, preferably from 5 minutes to 60 minutes, more preferably from 10 minutes to 30 minutes. [Brief explanation of the drawings]

[0048] Aspects of the present invention will now be described in more detail with reference to the accompanying drawings, in which like reference numbers illustrate like features. [Figure 1] 1 to 6 show schematic diagrams of the first, second, third, fourth, fifth and sixth lithium metal anodes according to the present invention, respectively. [Figure 2] 1 to 6 show schematic diagrams of the first, second, third, fourth, fifth and sixth lithium metal anodes according to the present invention, respectively. [Figure 3] 1 to 6 show schematic diagrams of the first, second, third, fourth, fifth and sixth lithium metal anodes according to the present invention, respectively. [Figure 4] 1 to 6 show schematic diagrams of the first, second, third, fourth, fifth and sixth lithium metal anodes according to the present invention, respectively. [Figure 5]1 to 6 show schematic diagrams of the first, second, third, fourth, fifth and sixth lithium metal anodes according to the present invention, respectively. [Figure 6] 1 to 6 show schematic diagrams of the first, second, third, fourth, fifth and sixth lithium metal anodes according to the present invention, respectively. [Figure 7] 7 and 8 show the cyclic charge / discharge behavior in function of the number of charge / discharge cycles for a reference battery and a battery including a first inventive anode, respectively. [Figure 8] 7 and 8 show the cyclic charge / discharge behavior with the number of charge / discharge cycles for a reference battery and a second battery containing an anode of the present invention, respectively. [Figure 9] FIG. 9 shows in-situ XPS survey spectra for lithium metal without and with the passivation layer of the present invention. [Figure 10] FIG. 10 shows in-situ XPS at the O1s core level for lithium metal without and with the passivation layer of the present invention. [Figure 11] FIG. 11 shows the XAS spectra at the O K edge in TEY and TFY modes for an anode with a passivation layer. [Figure 12] FIG. 12 shows the voltage profiles for the symmetric cell of the present invention and the reference symmetric cell as a function of time / number of charge / discharge cycles at a current density of 1.0 mA / cm 2 and an areal capacity of 1.5 mAh / cm 2 . [Figure 13] 1 shows the voltage profiles for a symmetric cell of the present invention and a reference symmetric cell as a function of time / number of charge / discharge cycles at a current density of 2.0 mA / cm 2 and an areal capacity of 1.5 mAh / cm 2 . [Figures 14A-14B] 14A and 14B show SEM images of the reference anode surface after repeated lithium stripping / plating. [Figures 15A-15B]15A and 15B show SEM images of the surface of an anode of the present invention after repeated lithium stripping / plating. [Figure 16] FIG. 16 shows the discharge capacity and coulombic efficiency of the reference battery cell. [Figure 17] FIG. 17 shows the discharge capacity and coulombic efficiency of the battery cell of the present invention. [Figure 18] FIG. 18 shows the charge capacity of the inventive and reference pouch cells as a function of the number of charge / discharge cycles using a charge current density of 0.7 mA / cm and a discharge current density of 2.2 mA / cm and an areal capacity of 2.2 mAh / cm. DETAILED DESCRIPTION OF THE INVENTION

[0049] 1 shows a schematic representation of an anode 1 according to the present invention. Anode 1 comprises an anode active substrate 2. Anode active substrate 2 comprises an anode current collector 6 and a layer 7 comprising or consisting essentially of lithium metal. Anode current collector 6 may be any anode current collector known in the art, particularly for lithium-ion batteries.

[0050] Anode 1 further comprises a first lithium metal anode protection layer 3 provided on surface 4 of anode active substrate 2, particularly on the surface of layer 7 comprising or consisting essentially of lithium metal opposite that surface adjacent to or in contact with anode current collector 6.

[0051] The first lithium metal anode protection layer 3 comprises or consists essentially of a first lithium halide, which is preferably lithium iodide (LiI) or lithium fluoride (LiF).

[0052] The first lithium metal anode protective layer 3 may comprise or consist essentially of two or more lithium halides. For example, the first lithium metal anode protective layer 3 may comprise two lithium halides. When the first lithium metal anode protective layer 3 comprises two lithium halides, the lithium halides are preferably LiI and LiF.

[0053] Figure 2 shows a second anode 10 of the present invention. The difference between the anode 10 of Figure 2 and the anode 1 of Figure 1 is that the anode active substrate 2 of the anode 10 of Figure 2 further includes a native layer of impurities 8. The native layer of impurities 8 is therefore present between the layer 7 comprising or consisting essentially of lithium metal and the first lithium metal anode protection layer 3.

[0054] The native layer of impurities 8 is preferably as known in the art, and preferably comprises or consists essentially of one or more of lithium carbonate (Li2CO3), lithium oxide (Li2O), and lithium hydroxide (LiOH).

[0055] Figure 3 shows a further anode 11 of the present invention. The difference between anode 11 of Figure 3 and anode 10 of Figure 2 is that anode 11 of Figure 3 further includes a second lithium metal anode protection layer 5. Second lithium metal anode protection layer 5 is provided on first lithium metal anode protection layer 3.

[0056] The second lithium metal anode protection layer 5 comprises or consists essentially of a second lithium halide, which is preferably lithium iodide (LiI) or lithium fluoride (LiF).

[0057] The second lithium metal anode protective layer 5 may comprise or consist essentially of two or more lithium halides. For example, the second lithium metal anode protective layer 5 may comprise two lithium halides. When the second lithium metal anode protective layer 5 comprises two lithium halides, the lithium halides are preferably LiI and LiF.

[0058] A non-limiting example of an anode 11 according to FIG. 3 is one in which the first lithium metal anode protective layer 3 comprises or consists essentially of LiI and the second lithium metal anode protective layer 5 comprises or consists essentially of LiF.

[0059] Another non-limiting example of an anode 11 according to FIG. 3 is one in which the first lithium metal anode protective layer 3 comprises or consists essentially of LiI and LiF, and the second lithium metal anode protective layer 5 comprises or consists essentially of LiF.

[0060] Optionally, anode 11 further comprises one or more additional lithium metal anode protective layers, i.e., third, fourth, fifth, sixth, or further lithium metal anode protective layers (not shown). Preferably, each additional lithium metal anode protective layer individually comprises or consists essentially of an additional lithium halide. Preferably, each of the one or more additional lithium halides individually is LiI or LiF.

[0061] The one or more additional lithium metal anode protection layers may individually comprise or consist essentially of two or more lithium halides, in other words, the optional one or more additional lithium metal anode protection layers may each individually comprise one, two, or even more lithium halides.

[0062] Suitably, the total thickness of the lithium metal anode protection layer is 5 nm to 2.5 μm, preferably 10 nm to 2 μm, and more preferably 50 nm to 1.5 μm.

[0063] The term "total lithium metal anode protective layer thickness" is used in this disclosure to refer to the thickness of the first lithium metal anode protective layer (3) when there are no additional lithium metal anode protective layers (e.g., the anodes of FIGS. 1 and 2), or to the sum of the thicknesses of each lithium metal anode protective layer when there are two or more lithium metal anode protective layers (e.g., the anode of FIG. 3).

[0064] Figure 4 illustrates yet another anode 12 of the present invention. The anode 12 of Figure 4 differs from the anode 1 of Figure 1 in that the anode 12 includes a passivation layer 9. The passivation layer 9 is present between the anode active substrate 2, particularly the layer 7 comprising or consisting essentially of lithium metal, and the first lithium metal anode protection layer 3.

[0065] In other words, the anode 12 of Figure 4 differs from the anode 10 of Figure 2 in that the native layer of impurities 8 has been replaced by a passivation layer 9. The passivation layer is made up of Li2CO3, Li2O, LiOH, and Li x PO y N z (LIPON), where x, y, and z are individually greater than 0.

[0066] Suitably, the surface of the passivation layer 9 adjacent to the first lithium metal anode protection layer 3 comprises at least 70%, preferably at least 80%, such as at least 85%, more preferably at least 90%, or at least 95% of one or more of LiO, LiOH, and LIPON, as measured by quantitative X-ray photoelectron spectroscopy (XPS).

[0067] Suitably, the surface of the passivation layer 9 adjacent to the first lithium metal anode protection layer 3 contains at most 5%, preferably at most 4%, more preferably at most 3%, and most preferably at most 2% Li2CO3 as measured by quantitative XPS.

[0068] While during battery cycling, Li2CO3 reacts chemically or electrochemically with the electrolyte, causing electrolyte decomposition and rapid battery failure, the inventors have surprisingly discovered that a passivation layer 9 containing up to 5% Li2CO3 at its surface adjacent to the first lithium metal anode protection layer 3 does not exhibit this behavior. Without wishing to be bound by any theory, the inventors believe this is due to a combination of the trace amounts (up to 5%) of Li2CO3 present in the passivation layer and the controlled, robust structure of the passivation layer compared to the more random structure of the native layer.

[0069] As a result, passivation layer 9 allows for more controlled, e.g., more uniform and homogeneous, lithium plating and stripping of the anode, which in turn increases the number of lithium plating / stripping cycles that the anode can withstand, thereby improving the cycling life of the anode.

[0070] The passivation layer of the present invention further contributes to improved electrochemical stability, which surprisingly improves the performance of lithium metal anodes, thereby improving the performance and cycling life of batteries containing lithium metal anodes.

[0071] Suitably, the passivation layer has a thickness of 100 nm to 1000 nm, preferably 125 nm to 750 nm, more preferably 150 nm to 500 nm, for example 175 nm to 400 nm, or 200 nm to 300 nm.

[0072] Figure 5 shows another anode 13 of the present invention. Anode 13 of Figure 5 differs from anode 12 of Figure 4 in that it includes a second lithium metal anode protective layer 5 on first lithium metal anode protective layer 3. Second lithium metal anode protective layer 5 is as described hereinabove. Anode 13 may include additional lithium metal anode protective layers (not shown), such as a third, fourth, or fifth lithium metal anode protective layer, also as described hereinabove.

[0073] Figure 6 illustrates another anode 14 of the present invention. Anode 14 of Figure 6 differs from anode 12 of Figure 4 in that passivation layer 9 includes or consists essentially of a first sublayer 15, i.e., the surface of passivation layer 9, and a second sublayer 16, i.e., the bulk of passivation layer 9, with first sublayer 15 adjacent to first lithium metal anode protection layer 3 and second sublayer 16 adjacent to anode active substrate 2.

[0074] Preferably, the first sublayer 15 comprises or consists essentially of Li2CO3, Li2O, and LiOH, as measured by the total electron yield (TEY) signal of XAS. Preferably, the first sublayer 15 has a thickness of 1 nm to 20 nm, preferably 2 nm to 15 nm, more preferably 5 nm to 12 nm, for example 10 nm.

[0075] Preferably, the second sublayer 16 comprises or consists essentially of Li2O and / or LiOH as measured by the total fluorescence yield (TFY) signal in XAS.

[0076] Without wishing to be bound by any theory, the inventors believe that when the passivation layer 9 comprises or consists essentially of the first 15 and second 16 sublayers, a synergistic effect is achieved between both sublayers, leading to a more robust anode and therefore improved lithium plating / stripping resistance when compared to anodes that do not include a passivation layer, and even when compared to anodes that include a passivation layer without this structural setup. This results in a battery that has superior cycle life and performs better than a battery with an anode that does not include a passivation layer.

[0077] The present invention further relates to a battery, in particular a lithium-ion battery, comprising an anode of the present invention. Preferably, the (lithium-ion) battery is a secondary (lithium-ion) battery.

[0078] The battery further includes a cathode. The cathode may be any cathode known in the art. Preferably, the cathode includes a cathode current collector, which may be any cathode current collector known in the art, and a cathode active material. Non-limiting examples of cathode active materials include vanadates, such as H2V3O8, NMC, and LiFePO4 (LFP).

[0079] The battery further includes an electrolyte. The electrolyte may be a liquid electrolyte or a solid electrolyte. The electrolyte may be any electrolyte known in the art, such as lithium bis(fluorosulfonyl)imide (LiFSI) in dimethoxyethane (DME), for example, 2M LiFSI in DME electrolyte.

[0080] The battery may further include a separator, particularly when the electrolyte is a liquid electrolyte, which may be any separator known in the art.

[0081] The present invention further relates to a method for manufacturing the anode of the present invention, which comprises the operation of providing an anode active substrate 2 and, optionally, the steps of gas-assisted radio frequency (RF) sputtering and thermal evaporation of at least a first coating composition.

[0082] First, an anode active substrate 2 is provided, where the anode active substrate is as described herein above, for example and in particular, comprising an anode current collector 6 and a layer 7 comprising or consisting essentially of lithium metal. Layer 7 may further comprise one or more of Li2CO3, Li2O, and LiOH.

[0083] Preferably, the anode active substrate further comprises, prior to the optional sputtering and thermal evaporation steps, a native layer of impurities 8. The native layer of impurities 8 is as described herein above.

[0084] A first lithium metal anode protection layer 3 is deposited on the anode active substrate 2, in particular on the layer 7 comprising or consisting essentially of lithium metal, or on the native layer of impurities 8, if present, thereby obtaining anode 1 of FIG. 1 (if it does not include the native layer of impurities) or anode 10 of FIG. 2 (if it includes the native layer of impurities 8).

[0085] The first lithium metal anode protection layer 3 is deposited on the anode active substrate 2 by thermal evaporation of a first coating composition. The first coating composition includes a first lithium halide. Preferably, the first lithium halide is LiI or LiF.

[0086] Preferably, the thermal evaporation is carried out under vacuum. To this end, the anode active substrate to be treated is placed in a reaction chamber, which is then brought to a predetermined pressure below atmospheric pressure. Preferably, the thermal evaporation is carried out in an ultra-high vacuum, i.e., at a maximum of 10 -6 The reaction is carried out at a working pressure in the reaction chamber of 1000 mbar.

[0087] Preferably, the anode active substrate is at room temperature during thermal evaporation.

[0088] Thermal evaporation of the first coating composition involves heating the first coating composition to a temperature such that the first lithium halide is evaporated. The evaporated first lithium halide is then condensed onto the anode active substrate, thereby forming a first lithium metal anode protection layer. Thus, the first lithium metal anode protection layer comprises or consists essentially of the first lithium halide.

[0089] Preferably, when the lithium halide is LiI, the respective coating composition has a temperature of 150°C to 400°C during its thermal evaporation.

[0090] Preferably, when the lithium halide is LiF, the respective coating composition has a temperature between 500°C and 900°C during its thermal evaporation.

[0091] Optionally, when the first lithium metal anode protection layer 3 includes an additional lithium halide, an additional coating composition including the additional lithium halide is provided. The first and additional coating compositions are then thermally evaporated simultaneously, thereby (co-)depositing a first lithium metal anode protection layer including the first and additional lithium halide.

[0092] For example, if the first lithium metal anode protection layer 3 comprises or consists essentially of a combination of LiI and LiF, a first coating composition comprising or consisting essentially of LiI and an additional coating composition comprising or consisting essentially of LiF are provided, and simultaneous thermal evaporation is then carried out, wherein during the simultaneous thermal deposition (i.e., thermal co-deposition), the first coating composition has a temperature of 150°C to 400°C and the additional coating composition has a temperature of 500°C to 900°C, thereby obtaining a first lithium metal anode protection layer comprising or consisting essentially of LiI and LiF.

[0093] Preferably, a second lithium metal anode protection layer 5 can be obtained on the first lithium metal anode protection layer 3 by thermal evaporation of a second coating composition containing a second lithium halide, thereby obtaining the anode 11 of Figure 3. Preferably, the second lithium halide is LiI or LiF. Preferably, the anode active substrate is at room temperature during thermal evaporation.

[0094] Preferably, the thermal evaporation for obtaining or depositing the second lithium metal anode protective layer 5 is carried out as described herein above for the first lithium metal anode protective layer 3. In particular, for depositing the first 3 and second 5 lithium metal anode protective layers, sequential thermal evaporations are carried out, i.e., in a first step, thermal evaporation of a first coating composition for depositing the first protective layer 3, followed (in a second step) by thermal evaporation of a second coating composition for depositing the second protective layer 5.

[0095] Optionally, if the second lithium metal anode protective layer 3 includes an additional lithium halide, a further coating composition including the additional lithium halide is provided, and the second and further coating compositions are then simultaneously thermally evaporated, thereby depositing a second lithium metal anode protective layer including the second and further lithium halide.

[0096] Optionally, more lithium metal anode protective layers, such as a third, fourth, or fifth lithium metal anode protective layer, may be deposited in a manner similar to the first and second lithium metal anode protective layers 3, 5.

[0097] Optionally, prior to the deposition of the first lithium metal anode protection layer 3, a passivation layer may be provided on the anode active substrate 2, in particular on the layer 7 comprising or consisting essentially of lithium metal.

[0098] If the anode active substrate 2 comprises a layer of impurities 8 on the layer 7 comprising or consisting essentially of lithium metal, the layer of impurities 8 is preferably converted into a passivation layer 9 during its provision. The passivation layer 9 is preferably as described herein above.

[0099] The passivation layer 9 is obtained by gas-assisted radio frequency (RF) sputtering using a target, preferably a short target, comprising or consisting essentially of Li3PO4 (LiPO).

[0100] Preferably, the gas is nitrogen, argon, helium, or a combination of two or more thereof.

[0101] Gas-assisted RF sputtering is preferably carried out in a vacuum, i.e., at a pressure below atmospheric pressure, preferably at a pressure of about 10 -3 It is carried out at a pressure of mbar.

[0102] Suitably, RF sputtering is carried out at frequencies between 30 Hz and 300 GHz, preferably at frequencies in the MHz range, in particular at a frequency of 13.56 MHz.

[0103] Preferably, gas-assisted RF sputtering involves igniting a plasma of the gas. Upon ignition of the gas plasma, ions in the plasma interact, i.e., react, with the LiPO target, thereby producing reactive oxidizing species, such as O * , N * and PO4 * These reactive oxidizing species then react with at least a portion, preferably substantially all, of the Li2CO3 present in the anode active substrate, thereby producing Li2O, LiOH, and Li x PO y N z (LIPON), where x, y, and z are individually greater than 0.

[0104] "At least a portion of the Li2CO3" in the present disclosure means that at most 10%, preferably at most 5%, more preferably at most 3% of the Li2CO3 does not react with the reactive oxidizing species and is therefore present on the surface of the passivation layer opposite the surface of the passivation layer adjacent to the anode active substrate, i.e., in a thickness of at most 20 nm, preferably at most 15 nm, more preferably at most 10 nm.

[0105] Preferably, when Li2CO3 is present in the layer 7 comprising or consisting essentially of lithium metal, a passivation layer is formed on the anode active substrate 2, in particular on the layer 7 comprising or consisting essentially of lithium metal.

[0106] Preferably, if Li2CO3 is present in the impurity native layer 8, during the sputtering process, the reactive oxidizing species convert this native layer 8, thereby obtaining a passivation layer 9 on the layer 7 of the anode active substrate 2 comprising or consisting essentially of lithium metal.

[0107] Once the passivation layer 9 is formed, a first lithium metal anode protection layer 3 is deposited on the passivation layer 9 by thermal evaporation as described herein above, thereby obtaining the anodes 12, 14 of Figures 4 and 6.

[0108] Optionally, a second lithium metal anode protection layer 5 can be deposited on the first lithium metal anode protection layer 3 by thermal evaporation as described hereinabove, thereby obtaining anode 13 of Figure 5. Optionally, a further lithium metal anode protection layer can be further deposited by thermal evaporation as described hereinabove. [Example]

[0109] Example 1 A first anode was prepared by depositing a layer of lithium iodide (LiI) on a commercially available anode active substrate consisting of a 13 μm-thick copper foil as a current collector, a 50 μm-thick layer of lithium metal, and a native layer of Li2CO3. The deposition was carried out by depositing a coating composition consisting essentially of lithium iodide (LiI) on the lithium metal layer by thermal evaporation at 350 °C in a processing chamber operating in ultra-high vacuum (UHV). A thermal evaporation source (i.e., coating composition) containing LiI was used. The deposition step was carried out 20 times, thereby obtaining a LiI layer with a thickness of 800 nm.

[0110] A second anode was prepared on the same copper foil, also under UHV conditions, by depositing a first layer of LiI, followed by a layer of LiF, with a 50 μm thick layer of lithium metal. The LiI layer was deposited on the lithium metal layer by thermal evaporation at 350° C. using a thermal evaporation source containing LiI. Deposition was carried out until the LiI layer had a thickness of 800 nm. A LiF layer was deposited on the LiI layer by thermal evaporation at 800° C. using a thermal evaporation source containing LiF. Deposition was carried out until the LiF layer had a thickness of 200 nm. Both depositions were carried out in the same processing chamber without interrupting UHV to prevent any possible contamination between successive depositions.

[0111] Next, first and second lithium-ion batteries of the invention were prepared, each comprising a first and second anode of the invention, a LiFePO4 (LFP) cathode, and a 2M lithium bis(fluorosulfonyl)imide (LiFSI) electrolyte in an ether-based electrolyte.

[0112] A reference lithium-ion battery was also prepared using a commercially available anode active substrate without any further treatment (13 μm thick copper foil as current collector, 50 μm thick layer of lithium metal and native layer of Li2CO3) with the same cathode and electrolyte as the first and second lithium-ion batteries of the present invention.

[0113] The batteries were then repeatedly charged and discharged. Charging was performed at 4.3 mA until 3.8 V was reached. Discharging was performed at 13 mA until 2.2 V was reached. FIG. 7 shows the specific charge capacity as a function of the number of charge / discharge cycles for the reference battery 20 and the first battery of the present invention 21 (800 nm LiI layer). It is clear that the reference battery shows a clear decrease in performance after 340 charge / discharge cycles, while the first battery of the present invention remains stable for approximately 700 cycles. FIG. 8 shows the specific charge capacity as a function of the number of charge / discharge cycles for the reference battery 20 and the second battery 22. It is clear that the reference battery shows a clear decrease in performance after 340 charge / discharge cycles, while the second battery of the present invention remains stable for approximately 450 cycles.

[0114] Example 2 The same copper foil as in Example 1, containing a 50 μm-thick layer of lithium metal, was used as the anode active substrate. Lithium is known to be reactive when exposed to air and moisture, becoming coated with carbonates, oxides, and hydroxides. More specifically, lithium metal is known to be coated with a native layer containing primarily Li2CO3.

[0115] Nitrogen-assisted radio frequency (RF) sputtering was performed on lithium metal to convert the native layer, i.e., Li2CO3 to Li2O. Sintered Li3PO4 pellets were used as the sputtering target and placed in a sputtering system (Bdiscom, RF Generator 300W, 13.56MHz). A water cooling system was connected to the Li3PO4 sputtering target to prevent it from overheating. The sputtering target and the system walls were maintained at room temperature. The anode active substrate was placed on a sample holder, both of which were also at room temperature. After closing the processing chamber containing the target and the anode active substrate, the processing chamber was evacuated and 5*10 -8A pressure of 1.5 mbar (i.e., base pressure) was maintained to remove any moisture and volatile contaminants from the processing chamber. Nitrogen was then added to the chamber at a flow rate of 6 sccm, thereby increasing the pressure in the chamber to 1.5*10 -2 The N2 plasma was ignited for 5 minutes by applying an RF power of 30 W, i.e. the sputtering process had a duration of 5 minutes.

[0116] Nitrogen-assisted sputtering was performed with the anode active substrate placed in the processing chamber facing "away" from the Li3PO4 target. In other words, the lithium metal was not directly exposed to the Li3PO4 target, i.e., indirect sputtering. This was achieved by positioning the anode active substrate on a sample holder such that the sample holder was positioned between the anode active substrate and the target.

[0117] X-ray photoelectron spectroscopy (XPS) was performed in situ to avoid contamination of the lithium metal surface. Focused monochromatized AI K radiation (1486.6 eV) and 500 μm 2 with a beam size of ~10 -9 XPS measurements were performed using a VG ESCALAB 220iXL spectrometer (Thermo Fisher Scientific) at a base pressure of 1000 mbar. Figure 9 shows in-situ XPS survey spectra of lithium metal on the anode active substrate before (23) and after (24) 5 min of N2-assisted RF sputtering. It is clear that the C1s peak after exposure to N2 plasma is much lower than that of untreated lithium metal, thereby confirming the successful conversion of most of the Li2CO3. Figure 10 shows in-situ XPS at the O1s core level on lithium metal on the anode active substrate after 5 min of N2-assisted RF sputtering, revealing that the lithium metal surface is composed primarily of Li2O and LiOH, as well as small amounts of Li2CO3 and LiNO3. xIt is clear that the surface is covered with a passivation layer containing Li3N.

[0118] The same experiment was repeated by using argon instead of N2 as the gas during RF sputtering. Table 1 shows the atomic composition and component ratios of the passivation layer obtained after nitrogen (N2)-assisted and argon (Ar)-assisted sputtering, respectively. The elemental concentrations and component ratios were based on quantification of XPS data. On both surfaces of the passivation layer (i.e., the surface of the passivation layer adjacent to the anode active substrate and the opposite surface), the ratios of Li2O and LiOH were the same, both accounting for more than 90% of the composition, while argon contained a smaller amount of residual Li2CO3 and a slightly larger amount of LiNO X was detected. [Table 1]

[0119] Example 3 The same copper foil containing a 50 μm thick layer of lithium metal was used as the anode active substrate as in Example 1. The same sputtering device and target were used for N2-assisted RF sputtering on the lithium metal.

[0120] The anode active substrate and sample holder were then placed in the processing chamber with the lithium metal facing the Li3PO4 sputtering target, i.e., direct sputtering was performed with this setup.

[0121] After placing the anode active substrate in the chamber, the chamber was closed and the pressure was increased to 5 * 10 -8 Nitrogen was added to the chamber at a flow rate of 6 sccm, thereby reducing the pressure in the chamber to 1.4*10 mbar. -2 The pressure was increased to 1000 mbar (i.e., working pressure). An RF power of 35 W was applied to ignite a N2 plasma. Different sputtering durations were performed: 5 minutes, 10 minutes, 15 minutes, and 25 minutes.

[0122] Again, in-situ XPS was performed on the (exposed) surface of the passivation layer (i.e., the surface opposite to the surface of the passivation layer adjacent to the anode active substrate). XPS quantification allowed the determination of the component ratios at the surface of the formed passivation layer based on the atomic concentrations of the elements lithium, oxygen, nitrogen, phosphorus, and carbon. The results are presented in Table 2. After sputtering periods of up to 25 minutes, the surface of the passivation layer consisted mainly of Li2O and LiOH. A sputtering period of 25 minutes was considered to produce optimal results, since the respective passivation layers exhibited the lowest concentration of Li2CO3 when compared to the surfaces of passivation layers obtained with shorter and longer sputtering times. [Table 2]

[0123] The same procedure was repeated with sputtering times of 50 minutes and 2.5 hours. Unexpectedly, XPS quantification no longer revealed the difference between LiOH and Li x PO y N z It was noted that the indistinguishability between x PO y N z With increasing concentration, the O1s peak that allows for the quantification of LiOH x PO y N z This is thought to be because the signal begins to overlap with the signal of the original source.

[0124] The surface of the passivation layer obtained after 50 minutes of sputtering showed the following composition ratio: 45% LiO, 52% LiOH+Li x PO y N z , and 3% Li2CO3. The surface of the passivation layer obtained after 2.5 hours of sputtering showed the following composition ratio: 29% LiO, 68% LiOH+Li x PO y Nz , and 3% Li2CO3.

[0125] A 90 nm thick layer of LiF was then deposited on the resulting passivation layer by 25 minutes of sputtering. The LiF layer was deposited by thermal evaporation at 800°C. A thermal evaporation source containing LiF was used. This LiF layer deposited yielded a lithium metal anode according to the present invention.

[0126] After bending the anode and breaking off both the passivation layer and the LiF protective layer, the thickness of the passivation layer and the LiF protective layer was determined by cross-sectional scanning electron microscope (SEM) images. SEM images were taken using a Zeiss Gemini scanning electron microscope at 5 kV accelerating voltage (with in-lens and secondary electron detection). After 25 minutes of sputtering and subsequent deposition of the LiF protective layer, the total thickness, i.e., the thickness of the passivation layer, was found to be approximately 700 nm.

[0127] The anode passivation layer obtained by 25 min of sputtering was further analyzed by X-ray absorption spectroscopy (XAS) to evaluate the surface and bulk composition of the passivation layer. Secondary photoelectrons were collected in an ultra-high vacuum (UHV; base pressure 5x10). -9 All tests were performed at room temperature under a pressure of 100 mbar. Secondary electrons produced by the sample as a function of photon energy were captured using a picoammeter to measure the sample electron current (Keithley 6517B). Photoelectrons from a 10 nm thick surface layer give rise to the total electron yield (TEY) signal. To compare surface species to bulk components, total fluorescence yield (TFY) signals with depth resolution of several hundred nanometers were also collected.

[0128] Figure 11 shows the O K edge XAS spectra in TEY and TFY modes for an anode with a passivation layer sputtered for 25 minutes. It is clear that Li2CO3 is only detected in TEY mode, indicating that the bulk phase of the passivation layer is essentially free of Li2CO3, while Li2O and LiOH are present in both the surface and bulk phases of the passivation layer.

[0129] Example 4 A control cell according to the invention was prepared using the anode of Example 2 having a passivation layer obtained by sputtering for 25 minutes, but without the 90 nm LiF layer on top of the passivation layer. The anode was used in both electrodes of the control cell, and the anode had a diameter of 13 mm.

[0130] A polypropylene separator foil (CG2400, Celgard LLC, USA) with a diameter of 17 mm was used as the separator. A 2:1 (v / v) mixture of DME and 1,3-dioxolane (DOL) containing 1 M lithium bis(trifluoromethylsulfonyl)amide (LiTFSI) and 0.5 M LiNO additives was used as the electrolyte. 100 μL of the electrolyte was injected into a symmetric cell according to the present invention. The cell was closed with a torque wrench.

[0131] A control cell was also prepared. The same 13 μm thick copper foil as in Example 1, with a 50 μm thick layer of lithium metal, was used as the electrode by itself. In other words, the electrode had no passivation layer and no lithium metal anode protective layer. The cell was closed in the same manner as the control cell of the present invention by using the same separator and electrolyte and applying the same stack pressure.

[0132] Both symmetric cells were assembled in an argon-filled glove box containing less than 0.4 ppm O2 and less than 0.8 ppm H2O.

[0133] Both symmetrical cells were charged at 1.5mAh / cm 2and an areal capacitance of 1.0 mA / cm 2 and 2.0 mA / cm 2 The cells were cycled galvanostatically at a current density of 0.05 V. The cutoff voltage was ±2 V. Cycling was performed at 25°C.

[0134] 12 and 13 show the results for 1.0 mA / cm 2 and a current density of 2.0 mA / cm 2 1 shows the voltage profiles for a symmetric cell of the present invention and a reference symmetric cell as a function of time / number of charge / discharge cycles for a current density of 1000 s. For both current densities, it is clear that the symmetric cell of the present invention exhibits stable cycling behavior at lower overpotential values ​​for a significantly longer period, i.e., a significantly higher number of charge / discharge cycles.

[0135] 1.0mA / cm 2 and a current density of 1.5mAh / cm 2 At an areal capacity of 1000 mAh (Figure 12), the cell of the present invention had an overpotential of only 12.4 mV at 200 hours of cycling and remained stable for 1200 hours (400 cycles), while the reference cell had a hysteresis of 27.9 mV at 200 hours of cycling and was stable for only 278 hours (93 cycles). Furthermore, the overpotential of the reference cell was higher than that of the cell of the present invention, indicating greater electrolyte decomposition and accumulation of dead lithium (i.e., inert resistive) lithium, which reduces the effectiveness of lithium ion transport. More specifically, the cell of the present invention showed almost no overpotential development up to 900 hours of cycling, thereby confirming the effectiveness of the LiO / LiOH passivation layer in lithium ion transport and reduced dendrite formation.

[0136] 2.0mA / cm 2 and a current density of 1.5mAh / cm 2At an areal capacitance of 0.01 V (FIG. 13), the inventive cell had a hysteresis of only 24.1 mV at 100 h of cycling and remained stable for more than 300 h (200 cycles), while the reference cell had a hysteresis of 52.1 mV at 100 h of cycling and showed unstable cycling behavior already after 100 h (less than 100 cycles).

[0137] Figures 14A and 14B show SEM images of the surface of the reference anode after 20 cycles of discharge (lithium stripping) and charging (lithium plating), respectively. From Figure 14A, it is clear that large pinholes have formed after repeated lithium stripping, leading to irregular lithium plating (Figure 14B).

[0138] Figures 15A and 15B show SEM images of the surface of an anode of the present invention with a LiO / LiOH passivation layer after 20 cycles of discharge (lithium stripping) and charge (lithium plating), respectively. A much denser density of plated lithium is observed on the anode of the present invention compared to the reference anode (Figure 15A vs. Figure 14A). This confirms the importance of the LiO / LiOH layer for improving the plated lithium density on the anode and limiting the formation of mossy dead lithium. This leads to much more regular lithium plating when compared to the reference anode (Figure 15B vs. Figure 14B).

[0139] Example 5 Inventive and reference full battery cells, respectively, were assembled using the same inventive and reference anodes as in Example 4, i.e., again without the 90 nm LiF layer on the passivation layer. Cell assembly was again carried out in the argon-filled glove box of Example 4. A 13 mm diameter LFP electrode (17.5 mg / cm) was used as the cathode for both cells. 2) was used. The cathode was punched out and dried overnight at 120°C in vacuum to remove any remaining water, then transferred to an argon-filled glove box. The electrolyte and separator used were the same as in Example 4. The cell was closed with the same torque wrench as in Example 4 by applying the same stack pressure.

[0140] Both batteries had a C / 10 (17mA / g) followed by 1.5mAh / cm 2 capacitance and 1.0mA / cm 2 After two formation cycles at a current density of 0.05 V, the cells were galvanostatically cycled between 2.5 V and 4 V. Cycling was performed at 25°C.

[0141] Figures 16 and 17 show the discharge capacity and coulombic efficiency of the reference battery and the battery of the present invention, respectively, as a function of the number of charge / discharge cycles. From Figure 17, it is clear that the battery of the present invention delivers stable capacity for more than 900 cycles. However, the reference battery is only stable up to 500 cycles, with performance rapidly decreasing with each additional cycle (Figure 16).

[0142] Example 6 Six identical pouch cells were prepared using the anode of Example 2, with a passivation layer obtained by 25 minutes of N2-assisted RF sputtering and a 90 nm LiF layer on the passivation layer. The pouch cells were assembled in a dry room with a dew point between -55°C and -64°C. The anode was 7.56 cm 2 It had a surface area of ​​6.40 cm 2 of the surface area of ​​LiFePO4 (LFP) cathode (loading 13 mg / cm 2 A 14 mAh cell capacity was used. The electrodes were separated by a 16 μm Teijin separator. 60 μL of 2 M LiFSI salt containing ether-based electrolyte was used in the pouch cell.

[0143] Six as-assembled pouch cells were cycled using the NEWARE Battery Testing System under ambient conditions and without applied external pressure at C / 10 (approximately 1.0 mA current and 0.10-0.20 mA / cm). 2 current density) and C / 3 (4 mA current and 1 mA / cm 2 The pouch cells were then subjected to 15 formation cycles between C / 3 charging (current density of 4 mA and 1 mA / cm). 2 current density) and 1C discharge (current of 10mA and 2mA / cm 2 The electrodes were galvanostatically cycled between 2.2 V and 3.8 V with a (current density) cycling protocol.

[0144] Thirty identical reference pouch cells were also tested under the same conditions and using the same cycling protocol. These reference pouch cells contained the anode active substrate of Example 2 as the anode, but did not contain any passivation layer or any lithium metal anode protection layer. The cathode, separator, and electrolyte were the same as those of the six inventive pouch cells.

[0145] Figure 18 shows the discharge capacity of six identical pouch cells of the present invention as a function of the number of charge / discharge cycles. The vertical dotted line indicates the average cycling performance of 30 identical reference pouch cells. It is clear that the pouch cells of the present invention, having a passivation layer and a LiF lithium metal anode protection layer, deliver stable capacity for more than 550 cycles, with the average number of cycles being approximately 700. Furthermore, the number of cycles for which these six cells are stable is quite similar, indicating that the anode manufacturing method of the present invention is repeatable and reproducible. However, the reference pouch cells deliver stable capacity for only 500 cycles on average. As a result, the pouch cells of the present invention are clearly superior to the reference pouch cells. [Explanation of symbols]

[0146] 1. Lithium metal anode 2. Anode active substrate 3. First Lithium Metal Anode Protection Layer 4. Anode active substrate surface 5. Second Lithium Metal Anode Protection Layer 6 Anode current collector 7. Lithium metal-containing layer 8. Native layer of impurities 9 Passivation Layer 10 Lithium metal anode 11 Lithium metal anode 12 Lithium metal anode 13 Lithium metal anode 20 Batteries containing reference lithium metal anodes 21 Battery containing a lithium metal anode of the present invention 22 Battery containing the lithium metal anode of the present invention

Claims

1. A lithium metal anode (1, 10, 11, 12, 13, 14) for a battery, comprising an anode active substrate (2) comprising lithium metal and a first lithium metal anode protection layer (3) disposed on a surface (4) of the anode active substrate (2), wherein the anode (1, 10, 11, 12, 13) is a lithium carbonate (Li 2 CO 3 ), lithium oxide (Li 2 2. The method of claim 1, further comprising one or more of: The lithium metal anode, characterized in that the first lithium metal anode protection layer (3) comprises a first lithium halide.

2. 10. The lithium metal anode (11, 13) of claim 1, further comprising a second lithium metal anode protection layer (5) disposed on the first lithium metal anode protection layer (3), the second lithium metal anode protection layer (5) comprising a second lithium halide.

3. 15. The lithium metal anode (1, 10, 11, 12, 13, 14) of any one of the preceding claims, wherein the first lithium halide and the optional second lithium halide are, individually, lithium iodide (LiI) or lithium fluoride (LiF).

4. 4. The lithium metal anode (1, 10, 11, 12, 13, 14) of claim 3, wherein the first lithium metal anode protection layer (3) and / or the optional second lithium metal anode protection layer (5) comprises LiI and has a thickness of 5 nm to 800 nm.

5. 10. The lithium metal anode (1, 10, 11, 12, 13, 14) of claim 3 or claim 4, wherein the first lithium metal anode protection layer (3) and / or the optional second lithium metal anode protection layer (5) comprises LiF and has a thickness of 50 nm to 200 nm.

6. The lithium metal anode (11, 13) according to any one of claims 2 to 5, comprising a second lithium metal anode protection layer (5), wherein the first lithium halide of the first lithium metal anode protection layer (3) is LiI and the second lithium halide of the second lithium metal anode protection layer (5) is LiF.

7. The anode active substrate (2) includes a layer (7) containing lithium metal provided on the surface of the anode current collector (6), and further includes a native layer (8) of impurities on the layer (7) containing lithium metal, and the native layer (8) of impurities is Li 2 CO 3 , Li 2 10. The lithium metal anode (10, 11) of any one of the preceding claims, comprising one or more of O and LiOH.

8. Li 2 CO 3 , Li 2 and a passivation layer (9) comprising one or more of O and LiOH, the passivation layer (9) being disposed between the anode active substrate (2) and the first lithium metal anode protection layer (3), and the surface of the passivation layer (9) adjacent to the first lithium metal anode protection layer (3) has at least 80% Li as measured by quantitative X-ray photoelectron spectroscopy (XPS). 2 O, LiOH and Li x PO y N z 7. The lithium metal anode (12, 13, 14) of any one of claims 1 to 6, comprising one or more of the following: (LIPON), wherein x, y, and z are individually greater than 0.

9. The surface of the passivation layer (9) adjacent to the first lithium metal anode protection layer (3) contains up to 5%, preferably up to 3% Li 2 CO 3 The lithium metal anode (12, 13, 14) of claim 8, comprising:

10. A lithium metal anode (12, 13, 14) according to any one of claims 8 to 9, wherein the passivation layer (9) has a thickness of 100 to 1000 nm.

11. The surface of the passivation layer (9) adjacent to the first lithium metal anode protection layer (3) is Li as measured by the total electron yield (TEY) signal of X-ray absorption spectroscopy (XAS). 2 CO 3 , Li 2 and LiOH, and contains Li in the bulk portion (16) of the passivation layer (9) as measured by the total fluorescence yield (TFY) signal of XAS. 2 The lithium metal anode (14) of any one of claims 8 to 10, further comprising O and / or LiOH.

12. A lithium-ion battery comprising a lithium metal anode (1, 10, 11, 12, 13, 14) according to any one of the preceding claims.

13. 13. The lithium ion battery of claim 12, which is a secondary battery.

14. A method for producing a lithium metal anode (1, 10, 11, 12, 13, 14) comprising an anode active substrate (2) comprising lithium metal and a first lithium metal anode protection layer (3) comprising a first lithium halide and disposed on a surface (4) of the anode active substrate (2), the method comprising depositing the first lithium metal anode protection layer (3) on the surface (4) of the anode active substrate (2) comprising lithium metal by thermal evaporation of a first coating composition, thereby obtaining the anode (1, 10, 11, 12, 13, 14); The method of claim 1, wherein the first coating composition comprises a first lithium halide.

15. 15. The method of claim 14, further comprising depositing a second lithium metal anode protection layer (5) on the first lithium metal anode protection layer (3) by thermal evaporation of a second coating composition comprising a second lithium halide.

16. 16. The method of any one of claims 14 to 15, wherein the first coating composition and the optional second coating composition individually have a temperature of from 200°C to 1000°C during their respective thermal evaporation.

17. 17. The method of any one of claims 14 to 16, wherein the first lithium halide and the optional second lithium halide are, individually, lithium iodide (LiI) or lithium fluoride (LiF).

18. 18. The method of claim 17, wherein the first lithium halide and / or the optional second lithium halide is LiI, and the respective coating compositions comprising LiI have a temperature of 250°C to 400°C during their respective thermal evaporations.

19. 18. The method of claim 17, wherein the first lithium halide and / or the optional second lithium halide is LiF, and the respective coating composition comprising LiF has a temperature of 500°C to 900°C.

20. 20. The method according to any one of claims 14 to 19, wherein the thermal evaporation of the first coating composition and / or the optional second coating composition is carried out 1 to 50 times, preferably 10 to 20 times, to obtain the first lithium metal anode protection layer (3) and / or the optional second lithium metal anode protection layer (5), respectively.

21. Prior to the deposition of the first lithium metal anode protection layer (3), Li 3 PO 4 21. The method of any one of claims 14 to 20, further comprising the step of gas-assisted radio frequency (RF) sputtering using a target substrate comprising:

22. 22. The method of claim 21, wherein the gas is nitrogen, argon, helium, or a combination of two or more thereof.

23. Li 3 PO 4 23. The method of claim 21 or claim 22, wherein the target substrate comprising has a temperature of 10°C to 50°C, preferably 15°C to 35°C during gas-assisted RF sputtering.

24. A method according to any one of claims 21 to 23, wherein the gas-assisted RF sputtering has a duration of from 5 minutes to 2.5 hours, preferably from 5 minutes to 60 minutes.

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