Electrolyte for lithium metal battery and lithium metal battery comprising the same

Abstract

The present disclosure relates to an electrolyte for a lithium metal battery, comprising: a lithium salt, a non-aqueous organic solvent, and a nitrate salt additive, wherein the lithium salt is different from the nitrate salt additive, the content of the lithium salt is greater than or equal to 15 mol% based on the total amount (100 mol%) of the electrolyte for a lithium metal battery; and the content of the nitrate salt additive is greater than or equal to 3 mol% based on the total amount (100 mol%) of the electrolyte for a lithium metal battery.

Description

[0001] Cross-references to related applications This application claims priority to Korean Patent Application No. 10-2024-0187312, filed with the Korean Intellectual Property Office on December 16, 2024, the entire disclosure of which is incorporated herein by reference. Technical Field

[0002] This invention relates to an electrolyte for lithium metal batteries and a lithium metal battery comprising the electrolyte. Background Technology

[0003] As the electric vehicle market grows, the demand for high-capacity batteries that improve upon and surpass lithium-ion batteries is increasing, which in turn leads to a growing demand for anode and cathode materials with high energy density that provide high energy density and long-term stability for lithium metal batteries.

[0004] Lithium metal, with its high capacity per unit weight of 3860 mAh / g and low standard electrode potential (-3.04 V vs. standard hydrogen electrode), is an ideal anode material for lithium-ion rechargeable batteries. However, lithium metal is highly reactive and can generate a strong reducing atmosphere during charging, leading to an irreversible decomposition reaction between the lithium metal and the electrolyte. This decomposition depletes the electrolyte, and the decomposition products may form a non-uniform film on the lithium metal surface. Furthermore, with repeated charge and discharge cycles, lithium can form dendrites. Dendritic lithium can cause short circuits inside the battery, leading to safety issues such as fire, leakage, and explosion.

[0005] Therefore, one strategy for achieving applications of lithium metal with high stability and high capacity involves developing an electrolyte that can mitigate (e.g., reduce, control, etc.) the reactivity of lithium metal, prevent the growth of dendritic lithium, and / or achieve uniform lithium deposition (plating). Summary of the Invention

[0006] In one aspect, this disclosure provides an electrolyte for lithium metal batteries that can induce uniform electrodeposition and desorption of lithium ions by forming a thin film on the current collector and / or the lithium metal surface.

[0007] In one embodiment, this disclosure provides a lithium metal battery capable of delaying the depletion point of lithium salts and exhibiting excellent durability performance.

[0008] An electrolyte for a lithium metal battery according to one embodiment includes a lithium salt, a non-aqueous organic solvent, and a nitrate additive different from the lithium salt; the lithium salt content is greater than or equal to 15 mol% based on the total amount (100 mol%) of the electrolyte for the lithium metal battery; and the nitrate additive content is greater than or equal to 3 mol% based on the total amount (100 mol%) of the electrolyte for the lithium metal battery.

[0009] In one embodiment, the lithium metal battery may be a lithium iron phosphate battery.

[0010] In an embodiment, based on the total amount (100 mol%) of the electrolyte for the lithium metal battery, the electrolyte for the lithium metal battery may include 15 mol% to 30 mol% of lithium salt, 3 mol% to 10 mol% of nitrate additive, and the balance being a non-aqueous organic solvent.

[0011] In an embodiment, the content of the non-aqueous organic solvent may be 60 mol% to 80 mol% based on the total amount (100 mol%) of the electrolyte used in the lithium metal battery.

[0012] In the embodiments, the non-aqueous organic solvent may include, but is not limited to: dipropyl ether, diethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, cyclopentylmethyl ether, methylpropyl ether, n-butylmethyl ether, ethylpropyl ether, dimethoxymethane, 1,4-dioxane, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, or combinations thereof.

[0013] In an embodiment, the lithium salt may include at least one selected from lithium bis(fluorosulfonyl)imide (LiFSI), lithium (fluorosulfonyl)(nonafluorobutanesulfonyl)imide (LiFNFSI), lithium bis(perfluoroethylsulfonyl)imide (LiBETI), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0014] In this embodiment, the nitrate additive may include LiNO3.

[0015] According to another aspect, the present invention provides a lithium metal battery comprising: a positive electrode; a lithium metal layer serving as a negative electrode and facing the positive electrode; a separator located between the positive and negative electrodes; and an electrolyte for the lithium metal battery according to various aspects and embodiments of the present disclosure.

[0016] In an embodiment, the thickness of the lithium metal layer can be from 5 μm to 200 μm.

[0017] In one embodiment, the positive electrode may include lithium iron phosphate.

[0018] In some embodiments, the electrolyte for lithium metal batteries according to this disclosure has the effect of improving the durability performance of lithium metal batteries, and in some specific embodiments, it has the effect of improving the durability performance of lithium iron phosphate lithium metal batteries. Attached Figure Description

[0019] Figure 1 The durability performance evaluation results of Li / LFP coin cells (1 / 3C) using the electrolytes according to Example 1, Comparative Example 3 and Comparative Example 4 are shown.

[0020] Figure 2 The efficiency evaluation results of Li / LFP coin cells (1 / 3C) using the electrolytes according to Example 1, Comparative Example 3 and Comparative Example 4 after 60 cycles are shown.

[0021] Figure 3 The durability performance evaluation results of Li / LFP coin cells (1 / 3C) using each electrolyte according to Comparative Examples 1 to 4 are shown.

[0022] Figure 4 The durability performance evaluation results of Li / LFP coin cells (1 / 3C) using the electrolytes according to Example 1, Comparative Example 5 and Comparative Example 6 are shown.

[0023] Figure 5 The durability performance evaluation results of Li / LFP coin cells (1 / 3C) using the electrolytes according to Example 1, Comparative Example 3 and Comparative Example 4 are shown.

[0024] Figures 6A to 6C The analysis results of lithium anode electrodeposition phenomenon are shown after driving Li / LFP coin cells (5 cycles) using the electrolytes according to Example 1, Comparative Example 3 and Comparative Example 4.

[0025] Figure 7A The viscosity (25°C) of the electrolytes according to Example 1 and Comparative Example 3 is shown.

[0026] Figure 7B The ionic conductivity (25°C) of the electrolytes according to Example 1 and Comparative Example 3 is shown. Detailed Implementation

[0027] The above-mentioned objects, other objects, features, and advantages of this disclosure will become more apparent from the following aspects and embodiments, in conjunction with the accompanying drawings. However, this disclosure and its claims are not limited to the embodiments disclosed herein and can be modified into different forms based on the guidance provided herein. The exemplary aspects and embodiments provided herein are intended to fully explain the various features of this disclosure and to convey the spirit of this disclosure to those skilled in the art.

[0028] Throughout the accompanying drawings, the same reference numerals refer to the same or similar elements. For clarity of this disclosure, the dimensions of the structures are exaggerated beyond their actual dimensions. It should be understood that while terms such as "first," "second," etc., may be used herein to describe various elements, these elements are not limited by these terms. These terms are used only to distinguish one element from another. For example, an element referred to below as "first" may be called "second" without departing from the scope of this disclosure. And similarly, a "second" element may also be called "first." The singular forms used herein also include the plural forms, unless the context clearly indicates otherwise.

[0029] The terms “comprising,” “including,” or “having,” as used in this specification, should be understood to mean the presence of the stated features, numbers, steps, operations, elements, components, or combinations thereof, but do not preclude the addition of one or more other features, numbers, operations, elements, components, or combinations thereof. In some aspects and embodiments, these terms should be understood to include the terms “consisting of” and “mainly composed of,” which refer only to features, numbers, values, steps, operations, elements, components, parts, or combinations thereof that include only the stated components, or the stated components may include a small number of other components or elements that do not substantially affect the functionality of the features, components, embodiments, or aspects described in this disclosure. Therefore, certain aspects and embodiments may refer to these different transitional terms, all of which constitute part of this disclosure.

[0030] Furthermore, it should be understood that when an element, such as a layer, membrane, zone, or plate, is referred to as being "on" another element, it may be directly "on" the other element, or there may be an intermediate element between the two. Similarly, when an element, such as a layer, membrane, zone, or plate, is referred to as being "below" another element, it may be directly "below" the other element, or there may be an intermediate element between the two.

[0031] Unless otherwise stated, all figures, numerical values, and / or representations used herein to indicate the amounts of components, reaction conditions, polymer compositions, and mixtures include all figures, numerical values, and / or representations that substantially appeared at the time these figures were obtained, which are approximations reflecting various uncertainties in the measurement, and therefore should in all cases be understood to be modified by the term "about". Furthermore, when this specification discloses a range of values, unless otherwise stated, the range is continuous and includes all values ​​from the minimum to the maximum. Additionally, when a range refers to integers, unless otherwise stated, it includes all integers from the minimum to the maximum.

[0032] In this specification, when describing the range of a variable, it should be understood that the variable includes all values ​​within the range, including endpoint values. For example, the range "5 to 10" should be understood to include any subranges such as 6 to 10, 7 to 10, 6 to 9, 7 to 9, etc., as well as individual values ​​of 5, 6, 7, 8, 9, and 10, and should also be understood to include any value between all valid integers within the range, such as 5.5, 6.5, 7.5, 5.5 to 8.5, 6.5 to 9, etc. Similarly, the range "10% to 30%" should be understood to include subranges such as 10% to 15%, 12% to 18%, 20% to 30%, etc., as well as all integers from 10%, 11%, 12%, 13%, etc. up to 30%, and should also be understood to include values ​​between any valid integers within the range, such as 10.5%, 15.5%, 25.5%, etc.

[0033] Furthermore, unless otherwise stated, the term “about” as used or implied herein shall be understood to mean a range of error typically found in the art (e.g., within two standard deviations of the mean). “About” may be understood to mean within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value.

[0034] Electrolytes for Lithium Metal Batteries As described above, developing organic electrolytes for lithium iron phosphate batteries faces numerous technical challenges, such as the dendritic growth of lithium in the negative electrode during charging, continuous redox decomposition reactions between the electrolyte and the electrode, and irreversible lithium generation during charge / discharge, which lead to battery degradation, reduced discharge capacity, and ultimately battery failure. To overcome these problems, this disclosure provides an additive for forming a stabilizing film on lithium metal. In embodiments, and as described herein, lithium nitrate (LiNO3) is particularly useful as an additive for stabilizing lithium metal among various additives, and is especially suitable for stabilizing lithium metal used as the negative electrode in lithium iron phosphate batteries. Some non-limiting embodiments show that lithium nitrate can stabilize the lithium negative electrode film, maximize the reversibility of lithium electrodeposition-desorption, and improve the durability performance of lithium iron phosphate batteries.

[0035] However, when operating lithium-ion batteries, only small amounts of additives can be added (e.g., approximately 1 wt% to 2 wt% based on the total electrolyte), which limits the extent to which additives induce stable lithium electrodeposition-desorption. For example, if excessive additives are contained (i.e. dissolved) in the electrolyte, an excessively thick and excessive SEI layer may form, hindering lithium-ion movement and causing uneven lithium deposition (i.e., non-uniformity), leading to premature battery degradation. Therefore, the amount of additives added should be controlled to suppress undesirable side reactions. This also clearly limits the potential improvement of lithium nitrate in forming a stable film on lithium metal.

[0036] Therefore, in view of the recognized limitations of the prior art, the inventors have developed an electrolyte composition that maximizes the utilization of lithium nitrate additives in lithium iron phosphate batteries. According to various embodiments of this disclosure, an electrolyte composition containing an excess of lithium nitrate additive is provided. Compared to conventional batteries, this novel electrolyte composition improves durability and electrochemical properties, distinguishing it and batteries including it from conventionally used electrolytes and batteries.

[0037] In summary, this invention relates to a novel electrolyte composition capable of improving the durability and electrochemical properties of lithium iron phosphate batteries. In some specific embodiments, this disclosure provides an electrolyte composition comprising two lithium salts, wherein each lithium salt is added in excess.

[0038] An electrolyte for a lithium metal battery according to one embodiment may include a lithium salt, a non-aqueous organic solvent, and a nitrate additive. In some embodiments, the nitrate additive is different from the lithium salt. Furthermore, unlike the electrolyte compositions in conventional lithium iron phosphate batteries, the electrolyte composition according to this disclosure includes an excess of both lithium salt and nitrate additive, which can improve the durability performance of the lithium iron phosphate battery.

[0039] In embodiments, based on the total amount of electrolyte used in lithium metal batteries (100 mol%), the lithium salt content can be greater than or equal to 15 mol%, and the nitrate additive content can be greater than or equal to 3 mol%. In embodiments where the amounts of lithium salt and (chemically different) nitrate additives are both within the above ranges to form the electrolyte, the viscosity of the electrolyte decreases at room temperature (25°C), while the ionic conductivity of the electrolyte increases at room temperature (25°C). These characteristics significantly improve the output characteristics of lithium metal batteries manufactured using this electrolyte, and lithium iron phosphate lithium metal batteries in certain specific embodiments, ultimately achieving excellent durability performance. In embodiments, based on the total amount of electrolyte used in lithium metal batteries (100 mol%), when the amount of nitrate additives added is greater than or equal to 3 mol%, the stability of lithium metal can be improved, and uniform electrodeposition and lower lithium electrodeposition can be induced, thereby leading to the formation of an effective SEI film. When the component amounts are not controlled, the disadvantages of lithium salt and additive precipitation and / or an excessively thick SEI interface occur, thereby reducing lithium ion mobility and increasing battery resistance. Therefore, in the electrolytes according to various aspects and embodiments of this disclosure, by appropriately controlling (i) the amount of nitrate additives and (ii) the amount of lithium salts, and (iii) the type and amount of non-aqueous organic solvents (e.g., as described herein), a lithium metal battery with at least one of improved durability and / or electrochemical properties can be provided. In some specific embodiments, the battery comprises a lithium iron phosphate battery. Therefore, this disclosure has an advantage over electrolytes and methods of their preparation that use only limited amounts of nitrates as additives, strategies that are difficult to simultaneously improve the durability and electrochemical properties of lithium metal batteries (e.g., lithium iron phosphate batteries).

[0040] In some exemplary embodiments, the lithium metal battery may be a lithium iron phosphate lithium metal battery, which uses lithium iron phosphate as the positive electrode and lithium metal as the negative electrode.

[0041] In some exemplary embodiments, based on the total amount (100 mol%) of the electrolyte for the lithium metal battery, the electrolyte for the lithium metal battery may include: 15 mol% to 30 mol% of lithium salt; 3 mol% to 10 mol% of nitrate additive; and the balance (up to 100 mol%) of non-aqueous organic solvent.

[0042] In some exemplary embodiments, the content of non-aqueous organic solvents may be 60 mol% to 80 mol% based on the total amount (100 mol%) of electrolyte used in lithium metal batteries.

[0043] In embodiments where the electrolyte composition for lithium metal batteries is maintained within the aforementioned range, the durability performance of lithium metal batteries including the electrolyte and lithium metal batteries (e.g., lithium iron phosphate lithium metal batteries) can be significantly improved or maximized.

[0044] In some embodiments, the non-aqueous organic solvent may include ether-based non-aqueous organic solvents. In embodiments where the amount of ether-based non-aqueous organic solvent added is within the range of the aforementioned compositions, the durability performance of lithium metal batteries can be significantly improved, particularly compared to electrolytes including other types and amounts of non-aqueous organic solvents. In some non-limiting exemplary embodiments, the non-aqueous organic solvent may include dipropyl ether, diethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, cyclopentylmethyl ether, methyl propyl ether, n-butyl methyl ether, ethyl propyl ether, dimethoxymethane, 1,4-dioxane, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, or combinations thereof.

[0045] According to one embodiment, the lithium salt may include at least one selected from lithium bis(fluorosulfonyl)imide (LiFSI), lithium (fluorosulfonyl)(nonafluorobutanesulfonyl)imide (LiFNFSI), lithium bis(perfluoroethylsulfonyl)imide (LiBETI), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). In some specific embodiments, the lithium salt may be LiFSI.

[0046] According to some embodiments, the concentration range of the lithium salt contained in the electrolyte for lithium metal batteries can be from 1.0 M to 4.5 M. In some specific embodiments, this concentration range can be, for example, 1.5 M to 4.0 M, 1.6 M to 3.9 M, 1.7 M to 3.8 M, 1.8 M to 3.7 M, or 1.9 M to 3.6 M.

[0047] Without being limited to any specific mechanism, the inventors observed that when the lithium salt concentration is below the aforementioned range, the conductivity of the electrolyte may decrease, potentially leading to poor electrolyte performance. Similarly, if the lithium salt concentration exceeds the aforementioned range, the viscosity of the electrolyte may increase, potentially resulting in reduced lithium-ion mobility and overvoltage problems from the start of cycling. In some embodiments, an SEI layer of suitable thickness can be formed on the surface of the lithium metal (i.e., the negative electrode). That is, if no SEI film / layer is formed at all, or if the formed SEI film / layer is too thick, the resulting lithium metal battery may have impaired (i.e., lower) electrochemical performance.

[0048] In some embodiments, the nitrate additive may include LiNO3. In embodiments where the nitrate additive in the electrolyte includes LiNO3, the compatibility between the additive and the aforementioned types of lithium salts and ether-based non-aqueous organic solvents can be maximized, and even synergistic effects can be achieved, thereby significantly improving the cycle performance and durability characteristics of lithium metal batteries.

[0049] Lithium metal batteries In another aspect, this disclosure provides a lithium metal battery including an electrolyte for a lithium metal battery according to the above aspects and embodiments.

[0050] In an embodiment, a lithium metal battery may include a positive electrode, a lithium metal layer serving as a negative electrode and facing the positive electrode, a separator between the positive and negative electrodes, and an electrolyte (such as that disclosed herein).

[0051] In one embodiment, the negative electrode for a lithium metal battery may include a lithium metal layer, and the lithium metal layer itself may serve as (i.e. function / operate) the negative electrode of the battery.

[0052] In one embodiment, the battery, including the negative electrode, allows lithium ions to move from the positive electrode to the negative electrode during charging to form a lithium metal layer. Charging and discharging of the battery can be performed by forming or removing this lithium metal layer.

[0053] In an implementation, the negative electrode can be formed on a negative electrode current collector, such as copper.

[0054] In an embodiment, the thickness of the lithium metal layer can be from 5 μm to 200 μm, for example, from 10 μm to 200 μm, or the lithium metal layer can be formed to have a thickness within this range.

[0055] In embodiments where the lithium metal layer falls within the aforementioned thickness range, any side reactions between the lithium metal layer and the electrolyte can be suppressed, thereby improving the electrochemical performance of the lithium metal battery.

[0056] In another embodiment, the positive electrode is positioned opposite the negative electrode (e.g., the surfaces of the positive and negative electrodes can be positioned or oriented opposite each other).

[0057] In an embodiment, the positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector.

[0058] In this embodiment, the positive current collector can be made of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treated with carbon, nickel, titanium, silver, etc.

[0059] In this implementation, the thickness of the positive current collector can be from 3 μm to 500 μm.

[0060] In this embodiment, the positive electrode active material layer includes a positive electrode active material.

[0061] In some embodiments, the positive electrode active material may include compounds capable of reversibly inserting and deintercalating lithium. In some specific embodiments, the positive electrode active material may include lithium iron phosphate. In embodiments where the positive electrode active material includes lithium iron phosphate, the compatibility of the components (such as the positive electrode active material and the electrolyte) may be particularly good, thereby potentially resulting in particularly significant or maximum improvements in battery performance.

[0062] In an embodiment, the positive electrode active material layer may further include an adhesive and / or a conductive material.

[0063] In this implementation, the separator provides a physical barrier (e.g., separation) between the negative and positive electrodes while allowing lithium ions to pass through (e.g., providing a channel for lithium ion movement). There are no particular limitations on the separator itself, as long as it performs the described function; therefore, it can include any one or more separators commonly used in lithium secondary batteries.

[0064] The following examples will illustrate specific aspects and implementations of this disclosure in more detail. However, these examples are merely for further illustrative purposes and do not limit the scope of this disclosure or the appended claims.

[0065] (Example) Preparation of an electrolyte for lithium metal batteries A certain amount of LiFSI salt is added to a 1,2-diethoxyethane solvent and mixed to form a transparent solution. A specific amount of LiNO3 is then added to this solution, and the mixture is further mixed to form a transparent solution, yielding an electrolyte composition for analysis and use in lithium metal batteries.

[0066] Table 1 shows the composition of electrolytes for lithium metal batteries according to the embodiments and comparative examples.

[0067] Table 1 Evaluation example: Durability and electrochemical characteristics of lithium iron phosphate lithium metal batteries (1) To evaluate durability and electrochemical properties, lithium iron phosphate batteries were fabricated using a lithium thin film (5 μm thick) as the negative electrode and LFP (lithium iron phosphate) as the positive electrode. The results are shown in Table 2. Figure 1 and Figure 5 As shown.

[0068] The electrolyte compositions of Example 1 and Comparative Example 3 were further analyzed by measuring viscosity and ionic conductivity at room temperature (25°C), and the results are shown in Table 2 and... Figure 7A , Figure 7B As shown.

[0069] Table 2 See Figure 1 As shown in Table 2, under the battery evaluation conditions using thin-film lithium as the negative electrode, improved electrolyte durability was observed in Example 1, with an improvement of 43 cycles (i.e., from 55 cycles to 98 cycles). Notably, compared to the electrolyte of Comparative Example 3, the electrolyte of Example 1 exhibited a delayed consumption of thin-film lithium, such as a delay of 20 cycles or more, thereby reducing uneven lithium deposition-desorption and any lithium side reactions. All of these indicate improved lithium stability and lithium flow reversibility (relative to the Comparative Example). Furthermore, compared to the electrolyte of Comparative Example 3, the electrolyte of Example 1 exhibited a viscosity reduction of approximately 24%. The reduction in viscosity may contribute to improved wettability of the positive electrode, which is advantageous when applied to high-load electrodes and post-implantation processes. In addition, improved process performance was achieved in the test steps, and ionic conductivity was increased by 29%. Furthermore, refer to... Figure 2 As can be seen, after 60 cycles, the Li / LFP coin cell with the electrolyte according to Example 1 exhibits a significantly higher capacity compared to Comparative Examples 3 and 4. The data demonstrate that the output characteristics of lithium iron phosphate batteries can be improved by incorporating the electrolyte composition according to exemplary embodiments of the present disclosure, as shown in this comparative example.

[0070] (2) A small amount of lithium nitrate (LiNO3) additive was added to generate an SEI (such as Li3N), which serves to stabilize the lithium anode. To determine the effective amount of LiNO3 (e.g., excess amount) to improve the durability of lithium iron phosphate batteries, the amount of LiNO3 added to the electrolyte was increased from 0.07 mol to 0.45 mol (at a constant low concentration of lithium salt (LiFSI) (e.g., Comparative Examples 1 to 4)) to manufacture lithium iron phosphate batteries. The durability of the lithium iron phosphate batteries was evaluated, and the results are as follows: Figure 3 As shown.

[0071] See Figure 3 Comparative Example 4 shows the lithium iron phosphate battery with the best cycle life, which is related to the higher / increased amount of lithium nitrate added.

[0072] (3) The electrochemical evaluation of the lithium iron phosphate batteries described above (as a function of the amount of lithium nitrate at low LiFSI concentrations) indicates that adding a larger amount of lithium nitrate appears to be associated with a greater improvement in durability. To supplement this data, the durability of lithium iron phosphate batteries was also evaluated at high concentrations of LiFSI, and the results are as follows: Figure 4 As shown.

[0073] See Figure 4The data show that the lithium iron phosphate battery of Example 1 exhibits better cycle life when more lithium nitrate is added, followed by Comparative Examples 5 and 6. However, based on the total electrolyte amount (100 mol%), lithium nitrate precipitates when the amount exceeds 10 mol%. Therefore, based on the total electrolyte amount (100 mol%), the amount of lithium nitrate can advantageously be maintained at 10 mol% or lower.

[0074] (4) Comparative Examples 3 and 4, as well as Example 1, were evaluated to determine the effect of adding excess lithium nitrate on durability. The results are as follows: Figure 5 As shown.

[0075] See Figure 5 The comparative results of Comparative Examples 3 and 4 show that, in environments with constant (or similar) low lithium salt concentrations, the degree of improvement in durability increases with increasing nitrate content. Data from Comparative Example 4 and Example 1 indicate that better durability was observed in environments with excess nitrate, a higher lithium salt ratio, and a lower solvent ratio. These data demonstrate that for electrolytes with the same composition, the improvement in durability can vary significantly depending on the amount of each component in the electrolyte composition, confirming that the electrolyte composition is a sensitive factor determining durability and any relative improvement in durability.

[0076] (5) The electrolyte composition of Example 1 was used to manufacture a lithium iron phosphate battery as described in (1) above, and the battery was operated to analyze the lithium anode electrodeposition morphology. The results are as follows: Figures 6A to 6C As shown.

[0077] See Figures 6A to 6C Comparative Example 3 exhibited uneven desorption when a 5 μm thin film of lithium was exposed on a copper surface. In contrast, Comparative Example 4 showed relatively uniform lithium desorption. However, Example 1 showed the most uniform electrodeposition-desorption, with a relatively dense lithium layer uniformly electrodeposited at the bottom.

[0078] Although some illustrative embodiments of the invention have been described above, this disclosure and the appended claims are not limited to these descriptions. Various modifications may be made within the scope of the claims, detailed descriptions, drawings, and their equivalents, all of which fall within the scope of this invention.

Claims

1. An electrolyte for lithium metal batteries, comprising: Lithium salts; Non-aqueous organic solvents; and Nitrate additives that are different from the lithium salts mentioned above; Based on the electrolyte for lithium metal batteries, which has a total content of 100 mol%, the lithium salt content is greater than or equal to 15 mol%, and the nitrate additive content is greater than or equal to 3 mol%.

2. The electrolyte according to claim 1, wherein the lithium metal battery is a lithium iron phosphate battery.

3. The electrolyte according to claim 1, wherein based on a total amount of 100 mol% of the electrolyte for lithium metal batteries, the electrolyte for lithium metal batteries comprises: The lithium salt, ranging from 15 mol% to 30 mol%; The nitrate additive, ranging from 3 mol% to 10 mol%, is used. and The remainder is up to 100 mol% of the non-aqueous organic solvent.

4. The electrolyte according to claim 3, wherein, based on a total amount of 100 mol% of the electrolyte for lithium metal batteries, the content of the non-aqueous organic solvent is 60 mol% to 80 mol%.

5. The electrolyte according to claim 1, wherein the non-aqueous organic solvent comprises: Dipropyl ether, diethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, cyclopentylmethyl ether, methylpropyl ether, n-butylmethyl ether, ethylpropyl ether, dimethoxymethane, 1,4-dioxane, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, or combinations thereof.

6. The electrolyte according to claim 1, wherein the lithium salt comprises at least one selected from the group consisting of lithium bis(fluorosulfonyl)imide LiFSI, lithium (fluorosulfonyl)(nonafluorobutanesulfonyl)imide LiFNFSI, lithium bis(perfluoroethylsulfonyl)imide LiBETI, and lithium bis(trifluoromethanesulfonyl)imide LiTFSI.

7. The electrolyte according to claim 1, wherein the nitrate additive comprises LiNO3.

8. A lithium metal battery, comprising: positive electrode; A lithium metal layer that serves as the negative electrode and faces the positive electrode; The membrane located between the positive electrode and the negative electrode; and An electrolyte for lithium metal batteries according to any one of claims 1-7.

9. The lithium metal battery according to claim 8, wherein the thickness of the lithium metal layer is from 5 μm to 200 μm.

10. The lithium metal battery according to claim 8, wherein the positive electrode comprises lithium iron phosphate.

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