Electrolyte for metallic lithium secondary battery, negative electrode for metallic lithium secondary battery and manufacturing method therefor, negative electrode modifier for metallic lithium secondary battery, and metallic lithium secondary battery

Abstract

The purpose of one embodiment of the present invention is to make it possible to stably dissolve and precipitate metallic lithium (avoid or reduce dendrites and dead lithium) and achieve both a high energy density and a cycle life in a metallic lithium secondary battery. An electrolyte for a metallic lithium secondary battery according to one embodiment of the present invention comprises at least one halogenated cyclic phosphoric acid ester represented by formula (1) and a predetermined solvent. (In formula (1), X is halogen, R1-R4 are each independently an alkyl group or hydrogen, and n is an integer of 1-4, provided that when n is an integer of 2-4, the respective R3s may be the same group or different groups and the respective R4s may be the same group or different groups.)

Description

Electrolyte for metallic lithium secondary batteries, negative electrode for metallic lithium secondary batteries and method for manufacturing the same, negative electrode modifier for metallic lithium secondary batteries, and metallic lithium secondary batteries

[0001] The present invention relates to an electrolyte for a metallic lithium secondary battery, a negative electrode for a metallic lithium secondary battery and a method for producing the same, a negative electrode modifier for a metallic lithium secondary battery, and a metallic lithium secondary battery.

[0002] Lithium-ion rechargeable batteries are currently widely used as secondary batteries in mobile phones, personal computers, digital cameras, drones, electric vehicles, etc., but there is a need to improve their battery characteristics. Battery characteristics refer to the properties exhibited by the battery and include energy density, cycle life, charge capacity, capacity retention rate, capacity recovery rate, and high-temperature stability.

[0003] Patent Document 1 describes a lithium-ion battery in which a specific cyclic fluorophosphonate compound is added to a positive electrode containing a lithium transition metal oxide and an electrolyte containing a carbonate-based organic solvent. Patent Document 1 also describes that the stability and durability of the SEI film of the negative electrode of the lithium-ion secondary battery are improved, and the high-temperature stability and cycle life characteristics at room temperature are improved.

[0004] U.S. Patent Publication No. 2020 / 0185773

[0005] The lithium secondary battery disclosed in Patent Document 1 aims to prevent deterioration of high-temperature stability and other properties when nickel cations dissolve from the positive electrode into the electrolyte and decompose the SEI film of the negative electrode, when a nickel-based lithium transition metal oxide is used as the positive electrode active material.

[0006] Patent Document 1 describes that the above effect is achieved by the interaction of the specific cyclic fluorophosphonate compound with transition metal ions such as nickel cations dissolved in the electrolyte, thereby stabilizing the ions.

[0007] Therefore, the invention described in Patent Document 1 can be applied to improve the battery characteristics of a lithium-ion secondary battery having a specific configuration comprising a positive electrode containing a lithium transition metal oxide and an electrolyte containing a carbonate-based organic solvent. However, it is considered that applying the invention described in Patent Document 1 to a metallic lithium secondary battery that does not have the above-mentioned specific configuration will not improve its battery characteristics.

[0008] Therefore, there is a need for a technology that can improve the battery characteristics even when applied to a metallic lithium secondary battery that does not have the aforementioned specific configuration. One aspect of the present invention aims to enable stable dissolution and extraction of metallic lithium (avoidance or reduction of dendrites and dead lithium) in a metallic lithium secondary battery, thereby achieving both high energy density and cycle life.

[0009] The present invention encompasses the following: an electrolyte for a lithium metallic secondary battery, a negative electrode for a lithium metallic secondary battery, a negative electrode modifier for a lithium metallic secondary battery, and a method for manufacturing a lithium metallic secondary battery.

[0010] An electrolyte for a metallic lithium secondary battery according to one embodiment of the present invention comprises one or more halogenated cyclic phosphate esters shown in the following formula (1), and (i) one or more solvents selected from the group consisting of ester-based solvents, urethane-based solvents, ether-based solvents, amide-based solvents, ketone-based solvents, sulfur-containing solvents, nitrile-based solvents, phosphazene-based solvents, glycol-based solvents, and hydrocarbon-based solvents; or (ii) a solvent containing the solvent shown in (i) and a carbonate-based solvent.

[0011]

[0012] (In the above formula (1), X is a halogen, and R １ ~R ４ Each of these is independently an alkyl group or a hydrogen atom, and n is an integer from 1 to 4. However, if n is an integer from 2 to 4, each R ３ These may be the same group or different groups, and each R ４They may be the same group or different groups.) The negative electrode for a metal lithium secondary battery according to an embodiment of the present invention is a negative electrode for a metal lithium secondary battery having an active material layer containing metal lithium, and a protective film containing one or more halogenated cyclic phosphates represented by the following formula (1) is formed on the active material layer. It is a negative electrode for a metal lithium secondary battery.

[0013]

[0014] (In the above formula (1), X is a halogen, and R １ ~R ４ are each independently an alkyl group or hydrogen, and n is an integer of 1 to 4. However, when n is an integer of 2 to 4, each R ３ may be the same group or different groups, and each R ４ may be the same group or different groups.) The negative electrode modifier for a metal lithium secondary battery according to an embodiment of the present invention is a negative electrode modifier for a metal lithium secondary battery containing one or more halogenated cyclic phosphates represented by the following formula (1).

[0015]

[0016] (In the above formula (1), X is a halogen, and R １ ~R ４ are each independently an alkyl group or hydrogen, and n is an integer of 1 to 4. However, when n is an integer of 2 to 4, each R ３ may be the same group or different groups, and each R ４ may be the same group or different groups.) The manufacturing method of the negative electrode for a metal lithium secondary battery according to an embodiment of the present invention is a manufacturing method of the negative electrode for a metal lithium secondary battery, and includes a step of forming a protective film on the active material layer by exposing the active material layer containing metal lithium to one or more halogenated cyclic phosphates represented by the following formula (1). It is a manufacturing method of the negative electrode for a metal lithium secondary battery.

[0017]

[0018] (In the above formula (1), X is a halogen, and R １ ~R ４ Each of these is independently an alkyl group or a hydrogen atom, and n is an integer from 1 to 4. However, if n is an integer from 2 to 4, each R ３ These may be the same group or different groups, and each R ４ These may be the same group or different groups.

[0019] According to one aspect of the present invention, in a lithium metallic secondary battery, stable dissolution and extraction of metallic lithium (avoidance or reduction of dendrites and dead lithium) can be enabled, and high energy density and cycle life can be achieved simultaneously. In other words, one aspect of the present invention can improve the battery characteristics of a lithium metallic secondary battery.

[0020] This is an electron microscope image of the surface of lithium, the negative electrode active material, after 10 charge-discharge cycles in the Li-Li symmetric cell test of the metallic lithium secondary battery obtained in Comparative Example 1. This is an electron microscope image of the surface of lithium, the negative electrode active material, after 10 charge-discharge cycles in the Li-Li symmetric cell test of the metallic lithium secondary battery obtained in Example 1. This is a graph showing the results of the Li-Li symmetric cell test of the metallic lithium secondary battery obtained in Comparative Example 1. This is a graph showing the results of the Li-Li symmetric cell test of the metallic lithium secondary battery obtained in Example 1. This is a graph showing the results of the Li-Li symmetric cell test of the metallic lithium secondary battery obtained in Example 3. This is a graph showing the results of the Li-Li symmetric cell test of the metallic lithium secondary battery obtained in Example 4. This is a graph showing the results of the Li-Li symmetric cell test of the metallic lithium secondary battery obtained in Example 5. This is a graph showing the results of the Li-Li symmetric cell test of the metallic lithium secondary battery obtained in Example 6. This graph shows the results of the Li-Li symmetric cell test of the metallic lithium secondary battery obtained in Example 7. This graph shows the results of the Li-Li symmetric cell test of the metallic lithium secondary battery obtained in Comparative Example 2. This graph shows the results of the performance evaluation of the metallic lithium sulfur secondary battery obtained in Example 8. This graph shows the results of the performance evaluation of the metallic lithium sulfur secondary battery obtained in Example 9. This graph shows the results of the performance evaluation of the metallic lithium sulfur secondary battery obtained in Comparative Example 3. This graph shows the results of the performance evaluation of the comparative evaluation laminated sulfur secondary battery obtained in Comparative Example 4. This graph shows the results of the performance evaluation of the evaluation laminated sulfur secondary battery obtained in Example 10. This graph shows the results of the performance evaluation of the comparative evaluation lithium-ion secondary battery obtained in Comparative Example 5. This graph shows the results of the performance evaluation of the evaluation lithium-ion secondary battery obtained in Example 11. This graph shows the results of the performance evaluation of the comparative evaluation laminated sulfur secondary battery obtained in Comparative Example 8. This graph shows the results of the performance evaluation of the evaluation laminated sulfur secondary battery obtained in Example 18. This graph shows the performance evaluation results of the laminated sulfur secondary battery obtained in Example 19. This graph shows the performance evaluation results of the laminated sulfur secondary battery obtained in Example 20.This graph shows the performance evaluation results of the metallic lithium sulfur secondary battery obtained in Example 21. This graph shows the performance evaluation results of the electrodeposited lithium-electrodeposited lithium symmetric cell obtained in Comparative Example 9. This graph shows the performance evaluation results of the electrodeposited lithium-electrodeposited lithium symmetric cell obtained in Example 26. This graph shows the performance evaluation results of the electrodeposited lithium-electrodeposited lithium symmetric cell obtained in Example 27. This graph shows the performance evaluation results of the electrodeposited lithium-electrodeposited lithium symmetric cell obtained in Example 28. This graph shows the performance evaluation results of the metallic lithium-ion secondary battery obtained in Comparative Example 11. This graph shows the performance evaluation results of the metallic lithium-ion secondary battery obtained in Example 30. This graph shows the performance evaluation results of the metallic lithium-ion secondary battery obtained in Comparative Example 12. This graph shows the performance evaluation results of the metallic lithium-ion secondary battery obtained in Example 31.

[0021] One embodiment of the present invention will be described in detail below. However, the present invention is not limited thereto, and various modifications are possible within the scope described. For example, embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. Unless otherwise specified in this specification, "A to B" representing a numerical range means "A or greater, B or less".

[0022] [1. Electrolyte for metallic lithium secondary batteries] An electrolyte for metallic lithium secondary batteries according to one embodiment of the present invention comprises one or more halogenated cyclic phosphate esters shown in the following formula (1), and (i) one or more solvents selected from the group consisting of ester solvents, urethane solvents, ether solvents, amide solvents, ketone solvents, sulfur-containing solvents, nitrile solvents, phosphazene solvents, glycol solvents, and hydrocarbon solvents; or (ii) a solvent containing the solvent shown in (i) and a carbonate solvent.

[0023]

[0024] (In the above formula (1), X is a halogen, and R １ ~R ４Each of these is independently an alkyl group or a hydrogen atom, and n is an integer from 1 to 4. However, if n is an integer from 2 to 4, each R ３ These may be the same group or different groups, and each R ４ These may be the same group or different groups.) In this specification, the electrolyte for a metallic lithium secondary battery according to one embodiment of the present invention is also referred to as "the electrolyte of the present invention." Furthermore, the halogenated cyclic phosphate ester shown in formula (1) is also simply referred to as "halogenated cyclic phosphate ester."

[0025] The electrolyte of the present invention is used in metallic lithium secondary batteries. In this specification, metallic lithium secondary battery means a lithium-ion secondary battery that uses metallic lithium as the negative electrode active material.

[0026] Because metallic lithium has an extremely high theoretical capacity of 3860 mAh / g, it can achieve high energy densities.

[0027] On the other hand, in metallic lithium secondary batteries, due to the extremely high reducing properties of metallic lithium, the electrolyte used may come into contact with the negative electrode and undergo reductive decomposition, which can shorten the cycle life. In addition, in metallic lithium secondary batteries, during charging and discharging, the electrolyte decomposes, forming a non-uniform passive film (Solid Electrolyte Interface; SEI) on the surface of the negative electrode. Therefore, lithium ions (Li) are formed on the surface of the negative electrode. ＋ ) dissolves or precipitates locally. In this specification, the surface of the negative electrode means the surface of the negative electrode that faces the positive electrode.

[0028] As lithium ions precipitate locally, lithium dendrites, in which lithium is deposited in a dendritic pattern, are formed on the surface of the negative electrode of a metallic lithium secondary battery, and these lithium dendrites may extend. When these lithium dendrites extend, the following phenomena (a) to (c) may occur: (a) Short circuit due to the lithium dendrites connecting the positive and negative electrodes; (b) Decomposition of the electrolyte on the surface of the lithium dendrites; (c) Reduction of the negative electrode active material due to the detachment of some of the extended lithium dendrites from the negative electrode, generating dead lithium. These short circuits, electrolyte decomposition, and reduction of the negative electrode active material may lead to a decrease in the energy density and / or a shortening of the cycle life of the metallic lithium secondary battery.

[0029] In the lithium metal secondary battery equipped with the electrolyte of the present invention, the halogenated cyclic phosphate ester and / or decomposition products obtained by the decomposition of the halogenated cyclic phosphate ester are deposited on the surface of the negative electrode. This forms a uniform SEI film over the entire surface of the negative electrode. The SEI film prevents direct contact between the negative electrode and the electrolyte, thereby preventing the shortening of cycle life caused by the reductive decomposition of the electrolyte as described above.

[0030] The SEI film allows lithium ions to pass through. Because the SEI film is uniformly formed across the entire surface of the negative electrode, in a metallic lithium secondary battery equipped with the electrolyte of the present invention, the dissolution and deposition of lithium ions during charging and discharging are uniform across the entire surface of the negative electrode. Therefore, stable dissolution and deposition of metallic lithium becomes possible. Furthermore, the formation and elongation of lithium dendrites associated with localized deposition of lithium ions are avoided or reduced, thus preventing or reducing a decrease in energy density and / or shortening of cycle life in the metallic lithium secondary battery. Moreover, since the formation and elongation of lithium dendrites are avoided or reduced, short circuits are avoided or reduced, resulting in a safe metallic lithium secondary battery.

[0031] In addition to the aforementioned halogenated cyclic phosphate esters, there are known additives that, when added to the electrolyte, can improve battery characteristics such as energy density and cycle life of metallic lithium secondary batteries. Examples of such additives include lithium difluorophosphate (LiDFP), which is a chain-like halogenated phosphate ester.

[0032] In this case, it is considered that even in a metallic lithium secondary battery equipped with an electrolyte containing the additive, an SEI film containing the additive and / or its decomposition products is formed on the entire surface of the negative electrode. However, the known additive has extremely low solubility in the electrolyte, so its effect is limited.

[0033] On the other hand, the halogenated cyclic phosphate ester has higher solubility in electrolytes commonly used in metallic lithium secondary batteries than the known additives. Therefore, the halogenated cyclic phosphate ester can form the SEI film more uniformly.

[0034] Therefore, by using the electrolyte of the present invention, a more uniform SEI film is formed on the surface of the negative electrode of a metallic lithium secondary battery than when using an electrolyte containing the known additives, and the formation and elongation of lithium dendrites are avoided or reduced. As a result, the electrolyte of the present invention can avoid or reduce the decrease in energy density and / or shortening of cycle life of a metallic lithium secondary battery compared to an electrolyte containing the known additives.

[0035] The electrolyte of the present invention can be used as the electrolyte for an anodeless battery. Here, "anodeless battery" means a battery in which, during manufacturing, only a negative electrode substrate such as copper foil and nickel foil is placed instead of an anode (negative electrode), and lithium is contained in the positive electrode and / or electrolyte. The anodeless battery does not have a negative electrode active material layer containing metallic lithium as the negative electrode active material. However, in the anodeless battery, during pre-charging or the first charge usually performed after manufacturing, lithium in the positive electrode and / or electrolyte is deposited (electrodeposited) onto the negative electrode substrate, thereby forming a negative electrode active material layer containing metallic lithium on the negative electrode substrate. Therefore, since an anodeless battery also uses metallic lithium as the negative electrode active material, it falls under the category of a metallic lithium secondary battery. Furthermore, when the electrolyte of the present invention is used as the electrolyte for the anodeless battery, the formed negative electrode active material layer is exposed to the halogenated cyclic phosphate ester. As a result, a more uniform SEI film is formed on the negative electrode active material layer, and the formation and elongation of lithium dendrites are avoided or reduced. Therefore, even when the electrolyte of the present invention is used as the electrolyte of the anodeless battery, it can avoid or reduce the decrease in energy density and / or shortening of cycle life of the metallic lithium secondary battery compared to the electrolyte containing the known additives.

[0036] (Halogenated Cyclic Phosphate Ester) The halogenated cyclic phosphate ester in one embodiment of the present invention may be any halogenated cyclic phosphate ester having the structure shown in formula (1). In the halogenated cyclic phosphate ester, X in formula (1) may be F, and X in formula (1) may be Cl or Br. Furthermore, X in formula (1) is preferably F or Cl, and most preferably F. In addition, n in formula (1) is preferably an integer from 1 to 3, and more preferably 1 or 2.

[0037] R in formula (1) １ and R ４Each of these is preferably independently hydrogen (H) or an alkyl group having 1 to 4 carbon atoms, more preferably hydrogen (H) or an alkyl group having 1 to 2 carbon atoms, and also preferably hydrogen (H) or a methyl group (CH ３ It is even more preferable that R in formula (1) is... １ ~R ４ These may be the same group or different groups, but the substituents are bonded to the same carbon, i.e., R １ and R ２ , and, R ３ and R ４ Preferably, these are the same base. Also, when n in formula (1) is an integer from 2 to 4, each R ３ These may be the same group or different groups, and each R ４ These may be the same group or different groups.

[0038] Specific examples of the halogenated cyclic phosphate esters include 2-fluoro-1,3,2-dioxaphosphoran-2-oxide, 2-fluoro-1,3,2-dioxaphosfinan-2-oxide, 2-chloro-1,3,2-dioxaphosphoran-2-oxide, 2-chloro-1,3,2-dioxaphosfinan-2-oxide, 2-fluoro-1,3,2-dioxaphosfepan-2-oxide, and 2-chloro-1,3,2-dioxaphosfepan-2-oxide. Pan-2-oxide, 2-bromo-1,3,2-dioxaphosphoran-2-oxide, 2-bromo-1,3,2-dioxaphosfepan-2-oxide, 2-bromo-1,3,2-dioxaphosfinan-2-oxide, 2-fluoro-5,5-dimethyl-1,3,2-dioxaphosfinan-2-oxide, 2-fluoro-4,6-dimethyl-1,3,2-dioxaphosfinan-2-oxide, 2-fluoro-4,5,6-trimethicone Lu-1,3,2-dioxaphosfinan-2-oxide, 2-fluoro-4,5-dimethyl-1,3,2-dioxaphosphoran-2-oxide, 2-chloro-5,5-dimethyl-1,3,2-dioxaphosfinan-2-oxide, 2-chloro-4,6-dimethyl-1,3,2-dioxaphosfinan-2-oxide, 2-chloro-4,5,6-trimethyl-1,3,2-dioxaphosfinan-2-oxide, 2-chloro-4,5-di Examples include methyl-1,3,2-dioxaphosphoran-2-oxide, 2-bromo-5,5-dimethyl-1,3,2-dioxaphosfinan-2-oxide, 2-bromo-4,6-dimethyl-1,3,2-dioxaphosfinan-2-oxide, 2-bromo-4,5,6-trimethyl-1,3,2-dioxaphosfinan-2-oxide, and 2-bromo-4,5-dimethyl-1,3,2-dioxaphosphoran-2-oxide. The halogenated cyclic phosphate ester may be a single halogenated cyclic phosphate ester or a mixture of two or more halogenated cyclic phosphate esters.

[0039] The halogenated cyclic phosphate ester may be a commercially available product or a prepared halogenated cyclic phosphate ester. The method for preparing the halogenated cyclic phosphate ester is not particularly limited, and for example, the method described in the examples can be used.

[0040] The content of the halogenated cyclic phosphate ester in the electrolyte of the present invention is preferably 1% by volume or more, and more preferably 5% by volume or more, relative to the total volume of the electrolyte of the present invention. A content of 1% by volume or more allows for the formation of a uniform SEI film across the entire surface of the negative electrode, thereby further improving the energy density and cycle life of the metallic lithium secondary battery.

[0041] Furthermore, the content of the halogenated cyclic phosphate ester is preferably 50% by volume or less, and more preferably 30% by volume or less, relative to the total volume of the electrolyte of the present invention. By having a content of 50% by volume or less, it is possible to avoid or reduce the deterioration of battery characteristics caused by the excessively large thickness of the SEI film formed on the entire surface of the negative electrode of the metallic lithium secondary battery. Other components of the electrolyte of the present invention besides the halogenated cyclic phosphate ester include the solvent and electrolyte described later, as well as other additives described later that may be optionally included.

[0042] (Solvent) The electrolyte of the present invention contains the solvent shown in (i) or (ii) below.

[0043] (i) One or more solvents selected from the group consisting of ester solvents, urethane solvents, ether solvents, amide solvents, ketone solvents, sulfur-containing solvents, nitrile solvents, phosphazene solvents, glycol solvents, and hydrocarbon solvents.

[0044] (ii) A solvent containing the solvents described in (i) above and carbonate-based solvents.

[0045] The solvents described in (ii) above are preferred, and among them, a solvent obtained by mixing a carbonate-based solvent and an ether-based solvent is more preferred, and a solvent obtained by mixing a carbonate-based solvent and a fluoroether-based solvent is even more preferred.

[0046] When the solvent is a mixture of the carbonate-based solvent and the fluoroether-based solvent, the content of the fluoroether-based solvent is preferably 20% by volume or more and 80% by volume or less, more preferably 30% by volume or more and 70% by volume or less, even more preferably 40% by volume or more and 60% by volume or less, and most preferably 50% by volume, relative to the total volume of the solvent. A fluoroether-based solvent content of 20% by volume or more is preferable from the viewpoint of preventing the viscosity of the solvent from becoming excessively high. On the other hand, a fluoroether-based solvent content of 80% by volume or less is preferable from the viewpoint of suitably improving ionic conductivity and / or preventing the solvent specific gravity from becoming excessively high.

[0047] In this specification, when the solvent is a mixed solvent obtained by mixing two or more solvents, the content of each solvent constituting the mixed solvent relative to the total volume of the mixed solvent corresponds to a percentage (volume %) calculated based on the volume of each solvent used in preparing the mixed solvent. Furthermore, the content of each solvent also corresponds to a percentage (volume %) calculated based on the volume of each solvent at room temperature after separating the mixed solvent into its individual components by a known method, such as fractional distillation. Therefore, when the solvent is a mixture of the carbonate-based solvent and the fluoroether-based solvent, the content of the fluoroether-based solvent relative to the total volume of the solvent may be the content (unit: volume %) shown in (A) or (B) below. Note that room temperature refers to 20 to 25°C. (A) The ratio of the volume of the fluoroether solvent to the total volume of the carbonate solvent and the fluoroether solvent used in the preparation of the solvent (unit: volume%); (B) The ratio of the volume of the fluoroether solvent at room temperature to the total volume of the carbonate solvent and the fluoroether solvent obtained by separating the solvent by known methods such as fractional distillation (unit: volume%).

[0048] Furthermore, the content of each solvent can also be measured by known separation and analysis methods targeting the mixed solvent. Examples of such separation and analysis methods include those using gas chromatograms and liquid chromatograms.

[0049] In this specification, "~-system solvent" means a solvent consisting of one or more compounds belonging to the chemical species described in "~".

[0050] Examples of the ester solvent include one or more solvents selected from the group consisting of carboxylic acid ester solvents, linear phosphate ester solvents, and fluorinated ester solvents. Examples of the carboxylic acid ester solvent include one or more solvents selected from the group consisting of ethyl acetate, methyl acetate, propyl acetate, butyl acetate, methyl formate, methyl butyrate, methyl valerate, methyl hexanoate, methyl lactate, dimethyl succinate, dimethyl glutarate, dimethyl adipate, methyl propionate, ethyl propionate, ethyl butyrate, methyl isobutyrate, methyl pivalate, diethyl adipate, dimethyl sebacate, diethyl malonate, dimethyl oxalate, methyl benzoate, methyl salicylate, methyl trimethylpropanoate, triethyl citrate, methyl acrylate, methyl methacrylate, glycerin fatty acid esters, ethylene glycol diacetate, tributylacetyl citrate, dimethyl-2,5-dioxahexane dioate, and γ-butyrolactone.

[0051] Examples of the chain-like phosphate ester solvent include one or more solvents selected from the group consisting of trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tributyl phosphate, triphenyl phosphate, dimethyl ethyl phosphate, methyl diethyl phosphate, tris(2-ethylhexyl) phosphate, tris(trifluoroethyl) phosphate, tris(pentafluoroethyl) phosphate, ethylene phosphate, propylene phosphate, and tris(fluoroethyl) phosphate.

[0052] Furthermore, as the fluorinated ester solvent, one or more solvents selected from the group consisting of ethyl trifluoroacetate, methyl trifluoroacetate, fluoroethyl acetate, ethyl difluoroacetate, ethyl 4-fluorobutyrate, methyl difluoroacetate, ethyl trifluorobutyrate, ethyl pentafluoropropionate, methyl hexafluoroisobutyrate, methyl fluoroformate, methyl difluoroformate, isopropyl trifluoroacetate, fluoroacetonitrile acid ester, fluorobutyrolactone, and difluorobutyrolactone can be mentioned.

[0053] Furthermore, the ester solvent may be a cyclic ester solvent or a linear ester solvent. Among the specific examples, γ-butyrolactone, fluorobutyrolactone, and difluorobutyrolactone are cyclic ester solvents. Ethyl acetate, methyl acetate, propyl acetate, butyl acetate, methyl formate, methyl butyrate, methyl valerate, methyl hexanoate, methyl lactate, dimethyl succinate, dimethyl glutarate, dimethyl adipate, methyl propionate, ethyl propionate, ethyl butyrate, methyl isobutyrate, methyl pivalate, diethyl adipate, dimethyl sebacate, diethyl malonate, dimethyl oxalate, methyl benzoate, methyl salicylate, methyl trimethylpropanoate, triethyl citrate, methyl acrylate, methyl methacrylate, glycerin fatty acid ester, ethylene glycol diacetate, tributylacetyl citrate, dimethyl-2,5-dioxahexane dioate, trifluoroethyl acetate, trifluoroacetate, Fluoroethyl acetate, ethyl difluoroethyl, ethyl 4-fluorobutyrate, methyl difluoroacetate, ethyl trifluorobutyrate, ethyl pentafluoropropionate, methyl hexafluoroisobutyrate, methyl fluoroformate, methyl difluoroformate, isopropyl trifluoroacetate, fluoroacetonitrile esters, trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tributyl phosphate, triphenyl phosphate, dimethyl ethyl phosphate, methyl diethyl phosphate, tris(2-ethylhexyl) phosphate, tris(trifluoroethyl) phosphate, tris(pentafluoroethyl) phosphate, ethylene phosphate, propylene phosphate, and tris(fluoroethyl) phosphate are classified as chain-like ester solvents.

[0054] Examples of the urethane-based solvent include one or more solvents selected from the group consisting of N-methyl-N-nitrosourethane, ethyl N-ethylcarbamate, N-methyl-N-phenylurethane, N,N-dimethylurethane, and N,N-diethylurethane.

[0055] Examples of the ether-based solvent include one or more solvents selected from the group consisting of fluoroether-based solvents, cyclic ether-based solvents, and linear ether-based solvents.

[0056] Examples of the fluoroether solvents include fluoromethyl methyl ether, difluoromethyl methyl ether, trifluoromethyl methyl ether, fluoroethyl methyl ether, difluoroethyl methyl ether, trifluoroethyl methyl ether, tetrafluoroethyl methyl ether, pentafluoroethyl methyl ether, bis(fluoromethyl) ether, bis(difluoromethyl) ether, bis(trifluoromethyl) ether, fluorotetrahydrofuran, difluorotetrahydrofuran, trifluorotetrahydrofuran, perfluorotetrahydrofuran, fluorodioxane, difluorodioxane, trifluorodioxane, perfluorodioxane, fluorodimethoxyethane, difluorodimethoxyethane One or more solvents can be selected from the group consisting of fluoro-1,2-diethoxyethane, perfluoro-dimethoxyethane, 1,1,2,2-tetrafluoroethyl methyl ether, 1,1,2,2-tetrafluoroethyl ethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (HFE), 1,1,3,3,3-pentafluoro-2-trifluoromethylpropyl methyl ether, 1,1,2,3,3-hexafluoropropyl methyl ether, 1,1,2,3,3-hexafluoropropyl ethyl ether, fluoro-1,2-diethoxyethane, and fluoro-1,4-dimethoxybutane.

[0057] Examples of the cyclic ether solvent include one or more solvents selected from the group consisting of tetrahydrofuran, 2-methyltetrahydrofuran, 4-methyltetrahydrofuran, tetrahydropyran, 1,4-dioxane, dioxolane, 4-methyldioxolane, 2,5-dimethylfuran, 3,5-dimethylisoxazole, 2-methylfuran, ethylene oxide, and furan.

[0058] Examples of the chain-like ether solvents include one or more solvents selected from the group consisting of diethyl ether, dipropyl ether, dibutyl ether, diisopropyl ether, dipentyl ether, dihexyl ether, methyl ethyl ether, methyl propyl ether, methyl butyl ether, ethyl propyl ether, ethyl butyl ether, 1,2-dimethoxyethane (1,2-DME), diethoxyethane, 1,2-dimethoxypropane, 1,3-dimethoxypropane, triglyme, tetraglyme, polyethylene glycol dimethyl ether, methyl tert-butyl ether, allyl ether, diglyme, methyl propyl ether, ethyl propyl ether, ethyl n-butyl ether, methyl n-butyl ether, ethyl tert-butyl ether, cyclopentyl methyl ether, and cyclopentyl ethyl ether.

[0059] Examples of the amide solvent include one or more solvents selected from the group consisting of N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, N-ethylpyrrolidone, tetramethylurea, hexamethylphosphate triamide, 1,3-dimethyl-2-imidazolidinone, 3-methyl-2-oxazolidone, and fluorinated amide solvents.

[0060] Examples of the fluorinated amide solvent include one or more solvents selected from the group consisting of fluoroacetamide, difluoroacetamide, trifluoroacetamide, N-methylfluoroacetamide, N-methyldifluoroacetamide, N-methyltrifluoroacetamide, fluoro-N,N-dimethylformamide, difluoro-N,N-dimethylformamide, trifluoro-N,N-dimethylformamide, fluoro-N-methylpyrrolidone, difluoro-N-methylpyrrolidone, trifluoro-N-methylpyrrolidone, and perfluoroalkylamide.

[0061] Examples of the ketone solvent include one or more solvents selected from the group consisting of acetone, methyl ethyl ketone, diethyl ketone, methyl propyl ketone, dipropyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, and fluorinated ketone solvents.

[0062] Examples of the fluorinated ketone solvent include one or more solvents selected from the group consisting of fluoroacetone, difluoroacetone, trifluoroacetone, hexafluoroacetone, fluoromethyl ethyl ketone, trifluoromethyl ethyl ketone, fluorocyclopentanone, difluorocyclopentanone, perfluoromethyl ethyl ketone, and polyfluoroalkyl ketone.

[0063] Examples of the sulfur-containing solvent include one or more solvents selected from the group consisting of sulfolane, sulfone and dimethyl sulfoxide (DMSO), diethyl sulfoxide, tetramethylene sulfone, dimethyl sulfone, diethyl sulfone, thiophene, sulfide, sulfoxide, thioether, dimethyl sulfate, and fluorinated sulfur-containing solvents.

[0064] Examples of the fluorinated sulfur-containing solvent include one or more solvents selected from the group consisting of fluorodimethyl sulfoxide, trifluoromethylmethyl sulfoxide, bis(trifluoromethyl) sulfoxide, fluorosulfolane, difluorosulfolane, tetrafluorosulfolane, perfluorosulfolane, fluorothiophene, difluorothiophene, and trifluoromethylthiophene.

[0065] Examples of the nitrile-based solvent include one or more solvents selected from the group consisting of acetonitrile, propionitrile, butyronitrile, benzonitrile, succinonitrile, glutalonitrile, adiponitrile, methoxyacetonitrile, ethoxyacetonitrile, cyanoether, pimelonitrile, suberonitrile, azeronitrile, sebaconitrile, oxydipropionitrile, and fluorinated nitrile-based solvents.

[0066] Examples of the fluorinated nitrile solvent include one or more solvents selected from the group consisting of fluoroacetonitrile, difluoroacetonitrile, trifluoroacetonitrile, tetrafluorosuccinonitrile, fluorobenzonitrile, difluorobenzonitrile, trifluoromethylbenzonitrile, perfluoroalkylnitrile, and fluorinated cyanoether.

[0067] Examples of the phosphazene-based solvent include one or more solvents selected from the group consisting of fluorocyclotriphosphazene, fluorinated alkoxyphosphazene, and fluorinated aminophosphazene.

[0068] Examples of the glycol-based solvent include one or more solvents selected from the group consisting of ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, glycerol, glycol ether, polypropylene glycol, and fluorinated glycol-based solvents.

[0069] Examples of the fluorinated glycol-based solvent include one or more solvents selected from the group consisting of fluoroethylene glycol, difluoroethylene glycol, trifluoroethylene glycol, tetrafluoroethylene glycol, fluoropropylene glycol, trifluoromethylethylene glycol, fluorinated polyethylene glycol, and perfluoroalkyl glycol.

[0070] Examples of the hydrocarbon solvent include one or more solvents selected from the group consisting of pentane, hexane, heptane, octane, isooctane, cyclohexane, hexene, octene, benzene, toluene, xylene, and halogenated hydrocarbon solvents.

[0071] Examples of the halogenated hydrocarbon solvent include fluorinated hydrocarbon solvents. Examples of the fluorinated hydrocarbon solvent include one or more solvents selected from the group consisting of fluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, fluorotoluene, trifluoromethyltoluene, perfluorohexane, perfluorooctane, and fluorinated cyclohexane.

[0072] Examples of the carbonate-based solvents include dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dipropyl carbonate, dibutyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl butyl carbonate, ethyl butyl carbonate, propyl butyl carbonate, dipentyl carbonate, dihexyl carbonate, methylpentyl carbonate, ethylpentyl carbonate, methylhexyl carbonate, ethylhexyl carbonate, vinylene carbonate, and allyl methyl carbonate. One or more solvents can be selected from the group consisting of benzyl methyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, vinyl ethylene carbonate, trimethylene carbonate, pentamethylene carbonate, hexamethylene carbonate, glycerin carbonate, diglycerin carbonate, methyl ethylene carbonate, dimethyl ethylene carbonate, ethyl ethylene carbonate, diethyl ethylene carbonate, phenyl ethylene carbonate, and fluorinated carbonate solvents.

[0073] Examples of the fluorinated carbonate solvents include fluoroethylmethyl carbonate, difluoroethylmethyl carbonate, trifluoroethylmethyl carbonate, fluoroethylethyl carbonate, difluoroethylethyl carbonate, trifluoroethylethyl carbonate, fluoromethylmethyl carbonate, difluoromethylmethyl carbonate, trifluoromethylmethyl carbonate, bis(fluoroethyl) carbonate, bis(difluoroethyl) carbonate, bis(trifluoroethyl) carbonate, fluoropropyl carbonate, One or more solvents selected from the group consisting of perfluorodiethyl carbonate, fluorovinylene carbonate, fluoroethylene carbonate (FEC), difluoroethylene carbonate, trifluoroethylene carbonate, tetrafluoroethylene carbonate, fluoropropylene carbonate, difluoropropylene carbonate, trifluoropropylene carbonate, fluorovinylethylene carbonate, difluorovinylethylene carbonate, trifluoromethylethylene carbonate, and difluoromethylethylene carbonate can be listed.

[0074] (Electrolyte) The electrolyte contained in the electrolyte solution of the present invention is not particularly limited, and for example, a lithium salt can be used. One type of electrolyte may be used as the electrolyte, or two or more types of electrolytes may be used in combination.

[0075] Specific examples of the electrolyte include, for example, bis(fluorosulfonyl)imide lithium (LiFSI), bis(trifluoromethanesulfonyl)imide lithium (LiTFSI), and lithium hexafluoride phosphate (LiPF). ６), lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoride arsenate, lithium difluoro(oxalato)borate, lithium monofluorophosphate, lithium difluorophosphate, lithium bis(fluoroethylsulfonyl)imide, lithium bis(trifluoroethylsulfonyl)imide, lithium (fluorosulfonyl)(trifluoromethanesulfonyl)imide, lithium (fluorosulfonyl)(pentafluoroethanesulfonyl)imide, lithium (fluorosulfonyl)(isopropylsulfonyl)imide, lithium (fluorosulfonyl)(phenylsulfonyl)imide, lithium bis(oxalato)borate, lithium difluorobis(oxalato)borate, lithium tetrafluoro(oxalato)borate, lithium difluoro(malonato)borate, lithium trifluorophosphate, lithium tetrafluorophosphate, lithium bis(fluorophosphate), lithium ethylenelithium difluorophosphate, lithium acetate, lithium propionate, lithium trifluoroacetate, One or more electrolytes selected from the group consisting of lithium ngate, lithium dicyanamide, lithium tetracyanoborate, lithium trifluoromethanesulfonate, lithium bis(fluoroacetyl)imide, lithium bis(pentafluoroethanesulfonyl)imide, lithium iodide, lithium chloride, lithium bromide, lithium sulfide, lithium nitrate, lithium phosphate, lithium trimethylammonium tetrafluoroborate, lithium bis(trifluoromethyl)malonitrile, lithium tetrafluorosuccinate, lithium pentafluorobenzoate, lithium bis(fluorosulfonyl)methane, lithium-4,5-dicyano-2-(trifluoromethyl)imidazole, lithium tetrafluoroglutarate, lithium bis(sulfonyl)malonate, lithium difluorophthalate, lithium tris(trifluoromethyl)trifluorophosphate, lithium hexafluorocyclotriphosphazene, and lithium trifluoromethyl acetate can be listed.

[0076] The electrolyte content in the electrolyte of the present invention is preferably 0.3 mol or more, and more preferably 0.4 mol or more, per 1 L of the solvent. By having an electrolyte content of 0.3 mol or more, the Li in the electrolyte of the present invention ＋ This increases the amount of ions, enabling good ion conductivity and thus improving battery characteristics such as energy density and rate characteristics.

[0077] Furthermore, the electrolyte content is preferably 5 mol or less, and more preferably 4 mol or less, per liter of the solvent. If the electrolyte content is excessively high, the viscosity of the electrolyte solution of the present invention may increase. In that case, there is a possibility of reduced handling of the electrolyte solution when manufacturing the battery; increased cost of the electrolyte solution; and a decrease in gravimetric energy density due to the increase in the weight of the electrolyte solution. Therefore, from the viewpoint of improving the battery characteristics, it is preferable that the electrolyte content is 5 mol or less.

[0078] (Other Additives) The electrolyte of the present invention may contain, as other additives other than the halogenated cyclic phosphate ester, additives that are commonly found in electrolytes for lithium-sulfur secondary batteries, in amounts that do not impair the effects of the present invention. Examples of such additives include fluoroethylene carbonate, vinylene carbonate, styrene carbonate, methylvinylene carbonate, allylethylene carbonate, lithium difluorophosphate, propanesultone, butanesultone, divinyl sulfone, trialyl phosphate, tris(trimethylsilyl)borate, lithium difluoro(oxalato)borate, lithium-1,1,2,2,2,3,3-hexafluoropropane-1,3-disulfonimide, difluoroethylene carbonate, methylfluoroethylene carbonate, bis(2,2,2-trifluoroethyl) carbonate, lithium nitrate, lithium phosphide, lithium sulfide, trimethyl borate, aluminum oxide, silicon dioxide, cesium fluoride, potassium fluoride, strontium fluoride, dimethyl disulfide, tetraethoxysilane, and hexamethyldisilazane.

[0079] (Uses of the Electrolyte of the Present Invention) The electrolyte of the present invention is used as an electrolyte for metallic lithium secondary batteries. The type of metallic lithium secondary battery in which the electrolyte of the present invention is used is not particularly limited, and examples include metallic lithium sulfur secondary batteries, metallic lithium iron phosphate secondary batteries, metallic lithium nickel-manganese-cobalt lithium secondary batteries, metallic lithium-cobalt oxide lithium secondary batteries, metallic lithium air secondary batteries, metallic lithium nickel-cobalt-aluminum oxide lithium secondary batteries, metallic lithium-manganese oxide lithium secondary batteries, metallic lithium nickel-manganese oxide lithium secondary batteries, or metallic lithium nickel oxide lithium secondary batteries. Furthermore, since the metallic lithium secondary battery has a maximum theoretical capacity of 2560 Wh / Kg as a sealed metallic lithium battery, metallic lithium sulfur secondary batteries are particularly preferred in terms of capacity. In particular, when sulfur is used as the positive electrode, the load on the metallic lithium negative electrode increases as the capacity of the positive electrode increases, so the present invention is effective.

[0080] (Method for producing the electrolyte of the present invention) The electrolyte of the present invention can be produced by mixing the halogenated cyclic phosphate ester, the solvent, the electrolyte, and optionally the other additives. The mixing method is not particularly limited. Nor is the order of mixing particularly limited. For example, the electrolyte of the present invention can be produced by the following method consisting of steps (1) and (2): (1) A step of mixing the solvent and the electrolyte to prepare an electrolyte in which the electrolyte is dissolved in the solvent. (2) A step of adding the halogenated cyclic phosphate ester and optionally the other additives to the electrolyte prepared in step (1) to produce the electrolyte of the present invention.

[0081] When manufacturing the electrolyte of the present invention, a suitable combination of electrolyte and solvent can be appropriately selected. The combination may vary depending on the type of metallic lithium secondary battery to which the electrolyte of the present invention is applied. For example, when manufacturing the electrolyte of the present invention for a metallic lithium sulfur secondary battery containing sulfur in the positive electrode, a metallic lithium iron phosphate secondary battery, a metallic lithium nickel-manganese-cobalt secondary battery, a metallic lithium cobalt oxide secondary battery, or a metallic lithium nickelate secondary battery, the following combinations can be listed as suitable: A solvent consisting of a combination of 1,2-DME (1,2-dimethoxyethane) and / or HFE (1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether) and FEC (fluoroethylene carbonate), and an electrolyte selected from the group consisting of LiFSI and LiTFSI. A solvent consisting of one or more solvents selected from the group consisting of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate, and a combination of a cyclic and / or linear fluoroether, and LiFSI, LiTFSI, and LiPF ６ A combination with one or more electrolytes selected from the group consisting of the following.

[0082] [2. Negative electrode for metallic lithium secondary battery] A negative electrode for a metallic lithium secondary battery according to one embodiment of the present invention is a negative electrode for a metallic lithium secondary battery having an active material layer containing metallic lithium, wherein a protective film containing one or more halogenated cyclic phosphate esters shown in the following formula (1) is formed on the active material layer.

[0083]

[0084] (In the above formula (1), X is a halogen, and R １ ~R ４ Each of these is independently an alkyl group or a hydrogen atom, and n is an integer from 1 to 4. However, if n is an integer from 2 to 4, each R ３ These may be the same group or different groups, and each R ４These may be the same group or different groups.) In this specification, the negative electrode for the metallic lithium secondary battery is also referred to as the "negative electrode of the present invention".

[0085] The negative electrode of the present invention has an active material layer containing metallic lithium. As mentioned above, metallic lithium has an extremely high theoretical capacity of 3860 mAh / g, so a metallic lithium secondary battery equipped with the negative electrode of the present invention can achieve a high energy density.

[0086] The negative electrode of the present invention has a protective film formed on the active material layer containing one or more of the halogenated cyclic phosphate esters. In this specification, the protective film containing one or more of the halogenated cyclic phosphate esters means a protective film containing one or more of the halogenated cyclic phosphate esters and / or decomposition products thereof. The decomposition product means a compound having an O-P-O bond that can be produced from the halogenated cyclic phosphate ester. Specifically, examples of the decomposition product include a compound having at least one of the structures listed below.

[0087] The formation of the protective film on the active material layer can be confirmed by X-ray photoelectron spectroscopy (XPS). The specific method for XPS can be the one used in the examples.

[0088] As a result, even in a metallic lithium secondary battery equipped with the negative electrode of the present invention, the reduction of cycle life caused by the aforementioned reductive decomposition of the electrolyte is avoided.

[0089] Similarly, in a lithium-ion secondary battery equipped with the negative electrode of the present invention, the dissolution and deposition of lithium ions during charging and discharging are uniformly distributed across the entire surface of the negative electrode, enabling stable dissolution and deposition of metallic lithium.

[0090] This can prevent or reduce the formation and elongation of lithium dendrites due to localized deposition of lithium ions, as well as the resulting decrease in energy density and / or shortening of cycle life of metallic lithium secondary batteries.

[0091] Therefore, the negative electrode of the present invention enables stable dissolution and extraction of metallic lithium in a metallic lithium secondary battery (avoidance or reduction of dendrites and dead lithium), making it possible to achieve both high energy density and cycle life. Furthermore, since short circuits caused by dendrites can be avoided, the safety of the metallic lithium secondary battery can also be enhanced.

[0092] As described above, in an anodeless battery employing the electrolyte of the present invention as the electrolyte, a negative electrode active material layer containing metallic lithium is formed on the negative electrode substrate during pre-charging or the first charge, and a more uniform SEI film is formed on the negative electrode active material layer. Here, the SEI film contains one or more of the halogenated cyclic phosphate ester and / or decomposition products of the halogenated cyclic phosphate ester, and corresponds to the protective film. Therefore, the negative electrode formed in the anodeless battery during pre-charging or the first charge also corresponds to the negative electrode of the present invention. In this case as well, the negative electrode of the present invention formed in the anodeless battery, in a metallic lithium secondary battery which is an anodeless battery, can achieve both high energy density and cycle life, and can also enhance safety, for the reasons described above.

[0093] (Protective film) The protective film comprises the halogenated cyclic phosphate ester and / or a decomposition product of the halogenated cyclic phosphate ester. The halogenated cyclic phosphate ester can be the same as the halogenated cyclic phosphate ester that can be contained in the electrolyte of the present invention.

[0094] The protective film can be formed on the entire surface of the active material layer constituting the negative electrode of the present invention. In other words, the entire surface of the negative electrode of the present invention may be the protective film.

[0095] The protective film may contain substances other than the halogenated cyclic phosphate ester and the decomposition products. For example, in a metallic lithium secondary battery equipped with the negative electrode of the present invention, decomposition products formed by the decomposition of the electrolyte during operation may be deposited on the negative electrode and included in the protective film. In that case, the protective film includes the decomposition products formed by the decomposition of the electrolyte as the other substances. It is preferable that the content of the other substances in the protective film be small.

[0096] (Active material layer) The active material layer of the negative electrode of the present invention is not particularly limited as long as it contains metallic lithium, and may contain substances other than metallic lithium. The form of the metallic lithium is not particularly limited, and may be in the form of lithium foil or particulate metallic lithium.

[0097] The substance other than metallic lithium mentioned above may be a known substance that constitutes the active material layer of the negative electrode. Examples of such substances include conductive additives and / or aqueous binders.

[0098] As the conductive additive, any conductive material that does not adversely affect battery performance can be used. Typically, carbon black such as acetylene black or Ketjenblack is used. In addition, conductive materials such as natural graphite (scaly graphite, flake graphite, earthy graphite, etc.), artificial graphite, carbon whiskers, carbon fiber powder, metal (copper, nickel, aluminum, silver, gold, etc.) powder, metal fibers, and conductive ceramic materials may be used. These may be used individually or as a mixture of two or more types.

[0099] The aqueous binder is not particularly limited as long as it can bind the metallic lithium, which is the negative electrode active material, with the conductive additive, etc. As the aqueous binder, for example, one or more selected from the group consisting of styrene-butadiene rubber (SBR) aqueous dispersion, carboxymethylcellulose (CMC), and alginate can be used.

[0100] The content of substances other than metallic lithium is not particularly limited, as long as it does not impair the effects of the present invention. For example, the content of the substance may be 5% by weight or more and 10% by weight or less of the total weight of the active material layer. In other words, the content of metallic lithium in the active material layer may be 90% by weight or more and 95% by weight or less of the total weight of the active material layer.

[0101] (Substrate) The negative electrode of the present invention may include a substrate. More specifically, the negative electrode may have a configuration in which the active material layer is laminated on the substrate, and the protective film is formed on the active material layer.

[0102] The substrate may be a known current collector that can be used as a negative electrode substrate, and an electron conductor that does not adversely affect the constructed battery can be used. Examples of the substrate include one or more selected from the group consisting of aluminum, titanium, stainless steel, nickel, copper, tin, silicon, calcined carbon, conductive polymer, and conductive glass. A current collector whose surface has been treated with carbon, nickel, titanium, or silver may be used for the purpose of improving adhesion, conductivity, oxidation resistance, etc.

[0103] The shape of the current collector may be foil-like, film-like, sheet-like, net-like, etc. Among these, a current collector having a three-dimensional structure such as a honeycomb shape is preferred because it allows for filling with a coating liquid containing a larger amount of active material during manufacturing, thus enabling increased capacity.

[0104] (Applications of the negative electrode of the present invention) The negative electrode of the present invention is used as a negative electrode for a metallic lithium secondary battery. Examples of the metallic lithium secondary battery include metallic lithium sulfur secondary batteries, metallic lithium iron phosphate secondary batteries, metallic lithium nickel-manganese-cobalt lithium secondary batteries, metallic lithium-cobalt oxide lithium secondary batteries, metallic lithium air secondary batteries, metallic lithium nickel-cobalt-aluminum oxide lithium secondary batteries, metallic lithium-manganese oxide lithium secondary batteries, metallic lithium nickel-manganese oxide lithium secondary batteries, or metallic lithium nickel oxide lithium secondary batteries. Furthermore, since the metallic lithium secondary battery has a maximum theoretical capacity of 2560 Wh / Kg as a sealed metallic lithium battery, the metallic lithium sulfur secondary battery is particularly preferred in terms of capacity. In particular, when sulfur is used as the positive electrode, the load on the metallic lithium negative electrode increases as the capacity of the positive electrode increases, so the present invention is effective.

[0105] (Manufacturing Method) As an example of a method for manufacturing the negative electrode of the present invention, the manufacturing method of the present invention described later can be cited.

[0106] [3. Negative electrode modifier for metallic lithium secondary batteries] The negative electrode modifier for metallic lithium secondary batteries according to one embodiment of the present invention contains one or more halogenated cyclic phosphate esters shown in the following formula (1).

[0107]

[0108] (In the above formula (1), X is a halogen, and R １ ~R ４ Each of these is independently an alkyl group or a hydrogen atom, and n is an integer from 1 to 4. However, if n is an integer from 2 to 4, each R ３ These may be the same group or different groups, and each R ４ These may be the same group or different groups.) In this specification, the negative electrode modifier for metallic lithium secondary batteries is referred to as "the modifier of the present invention."

[0109] The modifier of the present invention can be used on a negative electrode to carry out the manufacturing method of the present invention described later. As a result, the protective film can be formed on the active material layer of the negative electrode, thereby manufacturing the negative electrode of the present invention.

[0110] The negative electrode to which the modifier of the present invention is used may be a negative electrode in the aforementioned anodeless battery in which a negative electrode active material layer is formed by depositing (electrodeposition) metallic lithium on a negative electrode substrate, which is formed during pre-charging or the first charge. One method of using the modifier of the present invention in the aforementioned anodeless battery is to use the electrolyte of the present invention as the electrolyte of the anodeless battery. In this case, as described above, the negative electrode active material layer formed on the negative electrode substrate during pre-charging or the first charge in the aforementioned anodeless battery is exposed to the halogenated cyclic phosphate ester. As a result, the manufacturing method of the present invention, described later, is carried out inside the anodeless battery, the protective film is formed on the negative electrode active material layer, and the negative electrode of the present invention is manufactured. Therefore, the modifier of the present invention can also be applied to the aforementioned anodeless battery.

[0111] (Halogenated Cyclic Phosphate Ester) The halogenated cyclic phosphate ester contained in the modifier of the present invention may be the same as the halogenated cyclic phosphate ester that can be contained in the electrolyte of the present invention.

[0112] (Solvent) The modifier of the present invention may contain one or more of the halogenated cyclic phosphate esters and may be in the form of a solution in which the halogenated cyclic phosphate esters are dissolved in a solvent. When the modifier of the present invention is in the form of a solution, the solvent may be any solvent that dissolves the halogenated cyclic phosphate esters and does not degrade the performance of the negative electrode to which the modifier of the present invention is used. As the solvent, for example, the same solvent as the solvent described above as the solvent constituting the electrolyte of the present invention may be used.

[0113] When the modifier of the present invention is in the form of a solution, the content of the halogenated cyclic phosphate ester contained in the modifier of the present invention is preferably 1% by volume or more, more preferably 5% by volume or more, and even more preferably 10% by volume or more, relative to the total volume of the modifier of the present invention. Furthermore, the content is preferably 50% by volume or less, and more preferably 30% by volume or less, relative to the total volume of the modifier of the present invention.

[0114] The fact that the content is within these ranges is preferable from the viewpoint of forming a better protective film on the surface of the negative electrode when carrying out the manufacturing method of the present invention described later. The "better protective film" may be a better protective film from the viewpoint of achieving both improved lithium ion conductivity and suppression of dendrite formation.

[0115] (Additives) The modifier of the present invention may contain additives in an amount that does not impair the effects of the present invention, in addition to the halogenated cyclic phosphate ester and the solvent. As the additives, for example, known additives that can be contained in modifiers used for electrodes such as negative electrodes can be used. As the known additives, for example, bis(fluorosulfonyl)imide lithium (LiFSI), bis(trifluoromethanesulfonyl)imide lithium (LiTFSI), lithium hexafluoride phosphate (LiPF) ６), lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoride arsenate, lithium difluoro(oxalato)borate, lithium monofluorophosphate, lithium difluorophosphate, lithium bis(fluoroethylsulfonyl)imide, lithium bis(trifluoroethylsulfonyl)imide, lithium (fluorosulfonyl)(trifluoromethanesulfonyl)imide, lithium (fluorosulfonyl)(pentafluoroethanesulfonyl)imide, lithium (fluorosulfonyl)(isopropylsulfonyl)imide, lithium (fluorosulfonyl)(phenylsulfonyl)imide, lithium bis(oxalato)borate, lithium difluorobis(oxalato)borate, lithium tetrafluoro(oxalato)borate, lithium difluoro(malonato)borate, lithium trifluorophosphate, lithium tetrafluorophosphate, lithium bis(fluorophosphate), lithium ethylenelithium difluorophosphate, lithium acetate, lithium propionate, trifluoro Examples of known additives include lithium acetate, lithium malate, lithium dicyanamide, lithium tetracyanoborate, lithium trifluoromethanesulfonate, lithium bis(fluoroacetyl)imide, lithium bis(pentafluoroethanesulfonyl)imide, lithium iodide, lithium chloride, lithium bromide, lithium sulfide, lithium nitrate, lithium phosphate, lithium trimethylammonium tetrafluoroborate, lithium bis(trifluoromethyl)malonitrile, lithium tetrafluorosuccinate, lithium pentafluorobenzoate, lithium bis(fluorosulfonyl)methane, lithium-4,5-dicyano-2-(trifluoromethyl)imidazole, lithium tetrafluoroglutarate, lithium bis(sulfonyl)malonate, lithium difluorophthalate, lithium tris(trifluoromethyl)trifluorophosphate, lithium hexafluorocyclotriphosphazene, and lithium trifluoromethyl acetate. The known additives may be a single additive or a mixture of two or more additives.

[0116] (Uses of the Modifier of the Present Invention) The modifier of the present invention is used on the negative electrode of a metallic lithium secondary battery to modify the negative electrode. Examples of the metallic lithium secondary battery include metallic lithium sulfur secondary batteries, metallic lithium iron phosphate secondary batteries, metallic lithium nickel-manganese-cobalt lithium secondary batteries, metallic lithium-cobalt oxide lithium secondary batteries, metallic lithium air secondary batteries, metallic lithium nickel-cobalt-aluminum oxide lithium secondary batteries, metallic lithium-manganese oxide lithium secondary batteries, metallic lithium nickel-manganese oxide lithium secondary batteries, or metallic lithium nickel oxide lithium secondary batteries. Furthermore, since the metallic lithium secondary battery has a maximum theoretical capacity of 2560 Wh / Kg as a sealed metallic lithium battery, metallic lithium sulfur secondary batteries are particularly preferred in terms of capacity. In particular, when sulfur is used in the positive electrode, the load on the metallic lithium negative electrode increases as the capacity of the positive electrode increases, so the present invention is effective.

[0117] (Manufacturing Method) When the modifier of the present invention is in the form of a solution, the solution can be manufactured by mixing the halogenated cyclic phosphate ester, the solvent, and the additive. The mixing method can be any known method and is not particularly limited.

[0118] (Other Forms) The modifier of the present invention may also be in a form other than the solution form, consisting of the halogenated cyclic phosphate ester. Hereinafter, this form of the modifier of the present invention will also be referred to as "another form of the modifier of the present invention." The state of the other form of the modifier of the present invention may be solid, liquid, or gas, and is not particularly limited. Furthermore, a mixture of the other form of the modifier of the present invention in a solid or liquid state and the other form of the modifier of the present invention in a gaseous state may also be included in the scope of the other form of the modifier of the present invention, such as the other form of the modifier of the present invention in a state in which at least a portion of it has vaporized during use by the method described above.

[0119] [4. Metallic Lithium Secondary Battery] A metallic lithium secondary battery according to one embodiment of the present invention contains the electrolyte of the present invention. A metallic lithium secondary battery according to another embodiment of the present invention contains the negative electrode of the present invention. Hereinafter, a metallic lithium secondary battery containing the electrolyte of the present invention will be referred to as the "first metallic lithium secondary battery," and a metallic lithium secondary battery containing the negative electrode of the present invention will be referred to as the "second metallic lithium secondary battery." The first metallic lithium secondary battery and the second metallic lithium secondary battery together will also be referred to as the metallic lithium secondary battery of the present invention.

[0120] The first metallic lithium secondary battery may contain the negative electrode of the present invention. The second metallic lithium secondary battery may contain the electrolyte of the present invention. Therefore, the metallic lithium secondary battery of the present invention is a metallic lithium secondary battery containing the electrolyte of the present invention and / or the negative electrode of the present invention.

[0121] Therefore, in the lithium-metal secondary battery of the present invention, metallic lithium is stably dissolved and deposited at the negative electrode. As a result, the generation and elongation of dendrites, as well as the generation of dead lithium, are reduced, and high energy density and cycle life are achieved simultaneously.

[0122] An anodeless battery using the electrolyte of the present invention as the aforementioned electrolyte, after pre-charging or the first charge, is a metallic lithium secondary battery containing the electrolyte of the present invention and the negative electrode of the present invention, and therefore corresponds to the metallic lithium secondary battery of the present invention.

[0123] (Configuration of the first metallic lithium secondary battery) More specifically, the metallic lithium secondary battery of the present invention comprises a battery element in which an electrolyte is impregnated into a structure in which a positive electrode and a negative electrode are facing each other via a separator. Furthermore, the metallic lithium secondary battery of the present invention may have a structure in which the battery element is sealed within an outer casing. Thus, the first metallic lithium secondary battery, in particular, comprises a positive electrode, a negative electrode and a separator in addition to the electrolyte of the present invention, and may also include an outer casing.

[0124] The aforementioned lithium metallic secondary battery is preferably a lithium metallic sulfur secondary battery, a lithium metallic lithium iron phosphate secondary battery, a lithium metallic nickel-manganese-cobalt lithium secondary battery, a lithium metallic lithium cobalt oxide secondary battery, a lithium metallic air secondary battery, a lithium metallic nickel-cobalt-aluminum oxide secondary battery, a lithium metallic lithium manganese oxide secondary battery, a lithium metallic nickel-manganese oxide lithium secondary battery, or a lithium metallic nickel oxide lithium secondary battery. Among the aforementioned lithium metallic secondary batteries, the lithium metallic sulfur secondary battery is particularly preferred in terms of capacity because it has a maximum theoretical capacity of 2560 Wh / Kg as a sealed lithium metallic battery. In particular, when sulfur is used as the positive electrode, the load on the lithium metallic negative electrode increases as the capacity of the positive electrode increases, so this invention is effective.

[0125] The positive electrode can be a positive electrode used in a metallic lithium secondary battery, and is not particularly limited. For example, the positive electrode may have a configuration in which a positive electrode active material layer made of a positive electrode mixture for metallic lithium secondary batteries is laminated on a substrate. Alternatively, the positive electrode may be an air positive electrode that substantially uses oxygen from the air as the active material.

[0126] The positive electrode mixture for the metallic lithium secondary battery includes a positive electrode active material. Examples of the positive electrode active material include materials that can be doped and dedoped with lithium ions. Examples of the positive electrode active material include lithium composite oxides containing at least one transition metal such as V, Mn, Fe, Co, and Ni, as well as sulfur and oxygen. An example of the form of sulfur is a form in which sulfur is supported on a carbonaceous material. The carbonaceous material on which the sulfur is supported may contain one or more transition metals such as Ti, Mn, and Fe. Specific examples of such positive electrode materials include one or more materials selected from the group consisting of lithium iron phosphate (LFP), nickel-manganese-cobalt lithium (NMC), lithium cobalt oxide, lithium nickel-manganese oxide (LNMO), lithium nickelate (NCA), lithium manganese oxide, and nickel-cobalt-aluminum oxide.

[0127] Herein, in this specification, a metallic lithium-sulfur secondary battery means a metallic lithium-sulfur secondary battery that uses sulfur as the positive electrode active material. Therefore, the first metallic lithium-sulfur secondary battery may be a metallic lithium-sulfur secondary battery that uses sulfur as the positive electrode active material. Here, the form of sulfur in the positive electrode active material is not particularly limited as long as it functions as a positive electrode active material. For example, elemental molecular sulfur (S ８ ), small molecular sulfur (S ２ ~S ４ ), liquid lithium polysulfide (Li ２ S ｘ ), lithium sulfide (Li ２ S and Li ２ S ２ These are polymers containing sulfur. They may be used individually or in mixtures. Examples of sulfur-containing polymers include sulfur-modified polyacrylonitrile, in which sulfur is bonded to polymer chains such as polyacrylonitrile; sulfur-modified conductive polymers, in which sulfur is bonded to conductive polymers such as polyaniline or polypyrrole; poly(ethylene tetrasulfide), sulfur-containing polyazine polymers; and / or polymers in which sulfur is polymerized with a small amount of crosslinking agent (e.g., sulfur-diisopropenylbenzene).

[0128] In this specification, a lithium metallic lithium iron phosphate secondary battery means a lithium metallic secondary battery that uses lithium iron phosphate (LFP) as the positive electrode active material. Therefore, the first lithium metallic secondary battery may be a lithium metallic lithium iron phosphate secondary battery that uses lithium iron phosphate (LFP) as the positive electrode active material.

[0129] In this specification, a metallic lithium nickel-manganese-cobalt lithium secondary battery means a metallic lithium secondary battery that uses nickel-manganese-cobalt lithium (NMC) as the positive electrode active material. Therefore, the first metallic lithium secondary battery may be a metallic lithium nickel-manganese-cobalt lithium secondary battery that uses nickel-manganese-cobalt lithium (NMC) as the positive electrode active material.

[0130] In this specification, a lithium metallic lithium cobalt oxide secondary battery means a lithium metallic secondary battery using lithium cobalt oxide as the positive electrode active material. Therefore, the first lithium metallic secondary battery may be a lithium metallic cobalt oxide secondary battery using lithium cobalt oxide as the positive electrode active material. The crystal structure of these compounds can be any and is not limited, depending on the purpose, and may be spinel, layered, or irregular rock salt structure. Furthermore, the elemental composition of these compounds can be any and is not limited, depending on the purpose.

[0131] In this specification, a lithium metallic lithium nickelate secondary battery means a lithium metallic secondary battery that uses lithium nickelate (NCA) as the positive electrode active material. Therefore, the first lithium metallic secondary battery may be a lithium metallic lithium nickelate secondary battery that uses lithium nickelate (NCA) as the positive electrode active material.

[0132] In this specification, a metallic lithium-air secondary battery means a metallic lithium secondary battery that uses oxygen from the air as the positive electrode active material and metallic lithium as the negative electrode. Therefore, the first metallic lithium secondary battery may be a metallic lithium-air secondary battery that uses oxygen as the positive electrode active material.

[0133] In this specification, a lithium metallic nickel-cobalt-aluminate lithium secondary battery means a lithium metallic secondary battery that uses nickel-cobalt-aluminate lithium as the positive electrode active material and lithium metallic as the negative electrode. Therefore, the first lithium metallic secondary battery may be a lithium metallic nickel-cobalt-aluminate lithium secondary battery that uses nickel-cobalt-aluminate lithium as the positive electrode active material. The crystal structure of these compounds can be any structure, such as a layered structure, depending on the purpose, and is not particularly limited. Furthermore, the particle form can be single crystal or polycrystalline. In addition, the elemental composition of these compounds can be any composition, depending on the purpose.

[0134] In this specification, a lithium metallic secondary battery refers to a lithium metallic secondary battery that uses lithium manganese oxide as the positive electrode active material and lithium metallic as the negative electrode. Therefore, the first lithium metallic secondary battery may be a lithium metallic secondary battery that uses lithium manganese oxide as the positive electrode active material. The crystal structure of these compounds can be any type, such as spinel type or layered type, depending on the purpose, and is not particularly limited. Furthermore, the elemental composition of these compounds can be any type depending on the purpose.

[0135] In this specification, a metallic lithium-lithium nickelmanganate secondary battery means a metallic lithium secondary battery that uses lithium nickelmanganate as the positive electrode active material and metallic lithium as the negative electrode. Therefore, the first metallic lithium secondary battery may be a metallic lithium-lithium nickelmanganate secondary battery that uses lithium nickelmanganate as the positive electrode active material. The crystal structure of these compounds can be any type, such as spinel type, layered type, or irregular rock salt structure, depending on the purpose, and is not particularly limited. Furthermore, the elemental composition of these compounds can be any type depending on the purpose.

[0136] Examples of the carbonaceous material include activated carbon, carbon nanotubes, and graphene. The carbonaceous material may be a single substance or a mixture of two or more substances.

[0137] As the aforementioned sulfur, commercially available sulfurous flowers or the like can be used.

[0138] The aforementioned positive electrode mixture for a metallic lithium secondary battery may contain other components in addition to the positive electrode active material. Examples of such other components include conductive additives, aqueous binders, lipid-soluble binders, catalysts for promoting the reaction, and the like.

[0139] Examples of the lipid-soluble binder include one or more selected from the group consisting of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), perfluoroalkoxy fluororesin (PFA), polyamide, polyamide-imide, fluororubber (VDF-HFP, etc.), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyethylene oxide (PEO), and styrene-based elastomers. These may also be copolymers.

[0140] The catalyst for promoting the reaction may be a metal catalyst, for example, platinum, gold, palladium, silver, ruthenium, cobalt, nickel, iron, copper, and zinc, as well as alloys of two or more of these metals, and one or more selected from the group consisting of oxides, sulfides, nitrides, phosphides, and carbides of these metals.

[0141] The conductive additive and the aqueous binder can be the same as those described above for the negative electrode of the present invention.

[0142] The positive electrode mixture for metallic lithium secondary batteries preferably contains 30% to 99% by weight of the positive electrode active material and 1% to 70% by weight of the other components, based on the total weight of the positive electrode mixture for metallic lithium secondary batteries, and more preferably contains 30% to 95% by weight of the positive electrode active material and 5% to 70% by weight of the other components. When the positive electrode active material is sulfur, it is preferable that the mixture contains 30% to 80% by weight of the sulfur and 20% to 70% by weight of the other components, based on the total weight of the positive electrode mixture for metallic lithium secondary batteries. Furthermore, when the positive electrode active material is a lithium composite oxide, it is preferable that the lithium composite oxide is contained in 70% to 99% by weight and the other components in 1% to 30% by weight, relative to the total weight of the positive electrode mixture for metallic lithium secondary batteries; it is more preferable that the lithium composite oxide is contained in 80% to 99% by weight and the other components in 1% to 20% by weight; and it is even more preferable that the lithium composite oxide is contained in 90% to 99% by weight and the other components in 1% to 10% by weight.

[0143] The aforementioned substrate can be a known current collector that can be used as a substrate for the positive electrode, and the same substrate as the substrate that can be included in the negative electrode of the present invention described above can be used.

[0144] Examples of the negative electrode in the first metallic lithium secondary battery include the negative electrode of the present invention and a negative electrode having a configuration in which the protective film is removed from the negative electrode of the present invention.

[0145] As the separator in the first metallic lithium secondary battery, a separator known as a separator capable of constituting a metallic lithium secondary battery can be used.

[0146] As the outer casing material for the first metallic lithium secondary battery, any outer casing material known to constitute a metallic lithium secondary battery can be used.

[0147] (Configuration of the second-metallic lithium secondary battery) The second-metallic lithium secondary battery, in particular, includes a positive electrode, an electrolyte, and a separator in addition to the negative electrode of the present invention, and may include an outer casing.

[0148] The positive electrode, separator, and casing material of the second metallic lithium secondary battery can be the same as those of the first metallic lithium secondary battery.

[0149] Therefore, the second metallic lithium secondary battery can also be a metallic lithium sulfur secondary battery that uses sulfur as the positive electrode active material.

[0150] Examples of the electrolyte for the second metallic lithium secondary battery include the electrolyte of the present invention and an electrolyte having a configuration in which the halogenated cyclic phosphate ester is removed from the electrolyte of the present invention.

[0151] (Manufacturing Method) As a method for manufacturing the lithium metal secondary battery of the present invention, known manufacturing methods can be employed, for example, the manufacturing method described in the examples can be employed.

[0152] [5. Method for manufacturing a negative electrode for a metallic lithium secondary battery] A method for manufacturing a negative electrode for a metallic lithium secondary battery according to one embodiment of the present invention is a method for manufacturing a negative electrode for a metallic lithium secondary battery, comprising the step of forming a protective film on an active material layer containing metallic lithium by exposing the active material layer to one or more halogenated cyclic phosphate esters shown in the following formula (1).

[0153]

[0154] (In the above formula (1), X is a halogen, and R １ ~R ４ Each of these is independently an alkyl group or a hydrogen atom, and n is an integer from 1 to 4. However, if n is an integer from 2 to 4, each R ３ These may be the same group or different groups, and each R ４These may be the same group or different groups.) In this specification, the method for manufacturing the negative electrode for a metallic lithium secondary battery is also referred to as the "manufacturing method of the present invention." Furthermore, the step of forming a protective film on the active material layer in the manufacturing method of the present invention is referred to as the "protective film formation step."

[0155] According to the manufacturing method of the present invention, a negative electrode for a metallic lithium secondary battery can be manufactured, having a protective film containing the halogenated cyclic phosphate ester formed on the active material layer. "Negative electrode for a metallic lithium secondary battery" means a negative electrode having an active material layer containing metallic lithium. Therefore, according to the manufacturing method of the present invention, the negative electrode of the present invention can be manufactured.

[0156] Therefore, according to the manufacturing method of the present invention, it is possible to manufacture a negative electrode for a lithium metallic secondary battery that enables stable dissolution and extraction of metallic lithium, and provides a lithium metallic secondary battery that can achieve both high energy density and cycle life.

[0157] The protective film formation step involves preparing an active material layer containing metallic lithium, and forming a protective film on the active material layer by exposing the active material layer to one or more halogenated cyclic phosphate esters shown in the following formula (1).

[0158] As the halogenated cyclic phosphate ester used in the protective film formation step, the same halogenated cyclic phosphate ester that can be contained in the electrolyte of the present invention can be used.

[0159] The active material layer only needs to contain metallic lithium and may be an active material layer having the same configuration as the active material layer of the negative electrode of the present invention. Therefore, the protective film formation step can be said to be a step of manufacturing the negative electrode of the present invention by exposing the active material layer of the negative electrode, which has the configuration obtained by removing the protective film from the negative electrode of the present invention, to the halogenated cyclic phosphate ester to form the protective layer on the active material layer. In the protective film formation step, the halogenated cyclic phosphate ester adheres to the constituent material of the active material layer, for example, metallic lithium, to form a protective film.

[0160] One method for preparing the active material layer is to prepare metallic lithium and use the metallic lithium as is for the active material layer.

[0161] Another method for preparing the active material layer is, for example, to prepare a negative electrode mixture containing metallic lithium, prepare a coating solution for negative electrode production containing the negative electrode mixture and a solvent, apply or fill the coating solution onto a substrate, and dry it to remove the solvent. In this alternative method, the active material layer is prepared on the substrate. In addition to metallic lithium, the negative electrode mixture may contain conductive additives and aqueous binders that can constitute the active material layer of the negative electrode of the present invention. As the solvent, known solvents that can be contained in the coating solution for negative electrode production can be used.

[0162] In the protective film formation step, the method for exposing the active material layer to the halogenated cyclic phosphate ester can be, for example, the method described in (i) or (ii) below: (i) Immersing the active material layer in a solution containing the halogenated cyclic phosphate ester; (ii) Contacting the active material layer with the vapor of the halogenated cyclic phosphate ester. The vapor is preferably saturated vapor.

[0163] Here, the solution in (i) and the vapor in (ii) contain the halogenated cyclic phosphate ester and therefore qualify as the modifier of the present invention. Thus, the manufacturing method of the present invention can be carried out using the modifier of the present invention.

[0164] Furthermore, if the active material layer is formed on the substrate, only the active material layer may be immersed in the solution containing the halogenated cyclic phosphate ester, or both the active material layer and the substrate may be immersed in the solution.

[0165] Methods for bringing the vapor of the halogenated cyclic phosphate ester into contact with the active material layer include, for example, placing the active material layer in a container filled with the vapor, and blowing the vapor onto the active material layer. Here, if the active material layer is formed on the substrate, the active material layer and the substrate may be placed in a container filled with the vapor.

[0166] As a method for placing the active material layer into a container filled with the aforementioned vapor, for example, a method including the following steps (a) and (b) can be cited, using the "alternative form of the modifier of the present invention" described in item [3. Negative electrode modifier for metallic lithium secondary battery]: (a) A step of vaporizing at least a portion of the alternative form of the modifier of the present invention in a container such as a glass tube to generate vapor of the halogenated cyclic phosphate ester. (b) A step of placing the active material layer, or the active material layer and the substrate, into the container in step (a) in which the vapor was generated, and exposing the surface of the active material layer to the vapor to form a protective film on the surface.

[0167] In step (a) above, known methods can be used as the method for vaporizing at least a portion of the modifier of the present invention, i.e., the halogenated cyclic phosphate ester, and are not particularly limited. Furthermore, in step (a) above, it is preferable to vaporize at least a portion of the halogenated cyclic phosphate ester so as to fill the container with saturated vapor of the halogenated cyclic phosphate ester.

[0168] In step (b) above, if any unvaporized halogenated cyclic phosphate ester remains in the container, it is preferable to avoid direct contact between the unvaporized halogenated cyclic phosphate ester and the active material layer. This allows for the formation of a uniform protective film on the surface of the active material layer.

[0169] The manufacturing method of the present invention may include a washing step after the protective film formation step to remove halogenated cyclic phosphate esters, etc., that are not adhered to the constituent materials of the active material layer and do not form a protective film. An example of a washing method in the washing step is to immerse the active material layer on which the protective film has been formed in the same solvent as the solvent that can constitute the modifier of the present invention in solution form.

[0170] As described above, inside the anodeless battery, the protective film is formed on the negative electrode active material layer. This step involves exposing the active material layer containing metallic lithium to the halogenated cyclic phosphate ester to form a protective film on the active material layer. Therefore, the method of forming the negative electrode by performing a pre-charge or first charge in an anodeless battery equipped with the electrolyte of the present invention falls within the scope of the manufacturing method of the present invention.

[0171] [Summary] The present invention may include the following embodiments: <1> An electrolyte for a metallic lithium secondary battery comprising one or more halogenated cyclic phosphate esters shown in the following formula (1), and (i) one or more solvents selected from the group consisting of ester solvents, urethane solvents, ether solvents, amide solvents, ketone solvents, sulfur-containing solvents, nitrile solvents, phosphazene solvents, glycol solvents, and hydrocarbon solvents; or (ii) a solvent containing the solvent shown in (i) and a carbonate solvent.

[0172]

[0173] (In the above formula (1), X is a halogen, and R １ ~R ４ Each of these is independently an alkyl group or a hydrogen atom, and n is an integer from 1 to 4. However, if n is an integer from 2 to 4, each R ３ These may be the same group or different groups, and each R ４ (These may be the same group or different groups.) <2> An electrolyte for a metallic lithium secondary battery according to <1>, wherein X in formula (1) is F. <3> An electrolyte for a metallic lithium secondary battery according to <1>, wherein X in formula (1) is Cl or Br. <4> A negative electrode for a metallic lithium secondary battery having an active material layer containing metallic lithium, wherein a protective film containing one or more halogenated cyclic phosphate esters shown in the following formula (1) is formed on the active material layer.

[0174]

[0175] (In the above formula (1), X is a halogen, and R １~R ４ Each of these is independently an alkyl group or a hydrogen atom, and n is an integer from 1 to 4. However, if n is an integer from 2 to 4, each R ３ These may be the same group or different groups, and each R ４ These may be the same group or different groups.) <5> A negative electrode modifier for metallic lithium secondary batteries comprising one or more halogenated cyclic phosphate esters shown in the following formula (1).

[0176]

[0177] (In the above formula (1), X is a halogen, and R １ ~R ４ Each of these is independently an alkyl group or a hydrogen atom, and n is an integer from 1 to 4. However, if n is an integer from 2 to 4, each R ３ These may be the same group or different groups, and each R ４These may be the same group or different groups.) A metallic lithium secondary battery comprising the electrolyte described in any one of <6> <1> to <3>. <7> The metallic lithium secondary battery described in <6> is a metallic lithium sulfur secondary battery, a metallic lithium iron phosphate lithium secondary battery, a metallic lithium nickel-manganese-cobalt lithium secondary battery, a metallic lithium-cobalt oxide lithium secondary battery, a metallic lithium air secondary battery, a metallic lithium-nickel-cobalt-aluminum oxide lithium secondary battery, a metallic lithium-manganase lithium secondary battery, a metallic lithium-nickel-manganase lithium secondary battery, or a metallic lithium nickel oxide lithium secondary battery. <8> A metallic lithium secondary battery comprising the negative electrode for a metallic lithium secondary battery described in <4>. <9> The metallic lithium secondary battery described in <8>, wherein the metallic lithium secondary battery is a metallic lithium sulfur secondary battery, a metallic lithium iron phosphate lithium secondary battery, a metallic lithium nickel-manganese-cobalt lithium secondary battery, a metallic lithium-cobalt oxide lithium secondary battery, a metallic lithium air secondary battery, a metallic lithium-nickel-cobalt-aluminum oxide lithium secondary battery, a metallic lithium-manganase lithium secondary battery, a metallic lithium-nickel-manganase lithium secondary battery, or a metallic lithium nickel oxide lithium secondary battery. <10> A method for manufacturing a negative electrode for a metallic lithium secondary battery, comprising the step of forming a protective film on an active material layer containing metallic lithium by exposing the active material layer to one or more halogenated cyclic phosphate esters shown in the following formula (1).

[0178]

[0179] (In the above formula (1), X is a halogen, and R １ ~R ４ Each of these is independently an alkyl group or a hydrogen atom, and n is an integer from 1 to 4. However, if n is an integer from 2 to 4, each R ３ These may be the same group or different groups, and each R ４ These may be the same group or different groups.

[0180] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Furthermore, the lithium symmetric cell test, as well as the experiments with metallic lithium secondary batteries and lithium sulfur secondary batteries, were conducted at 25°C or 30°C. On the other hand, the temperature in tests other than those described above and in the operation of the experiments is not necessarily limited to 25°C or 30°C.

[0181] [Production Example 1] <Synthesis of 2-chloro-1,3,2-dioxaphosphoran-2-oxide> Solution A1, prepared by dissolving 90.7 g of phosphorus trichloride in 500 mL of dichloromethane, was placed in a flask, and 41.0 g of ethylene glycol was added dropwise to solution A1 over 3 hours at room temperature to obtain solution B1. Dichloromethane was removed from solution B1 by vacuum distillation to obtain 2-chloro-1,3,2-dioxaphosphoran, a colorless, transparent liquid and reaction intermediate. 2-chloro-1,3,2-dioxaphosphoran was purified by vacuum distillation at 70°C. The purified 2-chloro-1,3,2-dioxaphosphoran was dissolved in 500 mL of toluene to obtain solution C1. By blowing oxygen gas into solution C1, 2-chloro-1,3,2-dioxaphosphorane was reacted with oxygen to synthesize 2-chloro-1,3,2-dioxaphosphorane-2-oxide (hereinafter also referred to as "5COP"). When oxygen gas was blown into solution C1, the temperature of solution C1 rose due to the reaction. One hour after the temperature of solution C1 returned to room temperature, the reaction was considered complete, and the blowing of oxygen gas was stopped. By removing toluene from solution C1 after the reaction was completed by vacuum distillation, a crude product of 5COP, which was a colorless and transparent liquid, was obtained. Subsequently, the crude product of 5COP was purified by vacuum distillation under conditions of 120°C to obtain purified 5COP. The yield of purified 5COP was 51 g, and the yield was 49%.

[0182] For the purified 5COP, proton analysis was performed using nuclear magnetic resonance spectroscopy (ECZ, manufactured by JEOL Ltd.) under conditions of 400 MHz. １ HNMR), phosphorus analysis ( ３１PNMR was performed. As a result, it was confirmed that the purified 5COP was free of impurities. In the proton analysis, a chemical shift (ppm) of 4.48-4.65 ppm was obtained, originating from the ethylene group. In the phosphorus analysis, a chemical shift (ppm) of 17.76 ppm was obtained, originating from the phosphate ester group. The structural formula of 2-chloro-1,3,2-dioxaphosphorane, the reaction intermediate, is shown below.

[0183]

[0184] The structural formula for 5COP is shown below.

[0185]

[0186] [Production Example 2] <Synthesis of 2-chloro-1,3,2-dioxaphosfinan-2-oxide> Solution A2, prepared by dissolving 100 g of phosphorus trichloride in 500 mL of dichloromethane, was placed in a flask, and 55.4 g of propylene glycol was added dropwise to solution A2 over 3 hours at room temperature to obtain solution B2. Dichloromethane was removed from solution B2 by vacuum distillation to obtain 2-chloro-1,3,2-dioxaphosfinan, a colorless, transparent liquid and reaction intermediate. 2-chloro-1,3,2-dioxaphosfinan was purified by vacuum distillation at 70°C. The purified 2-chloro-1,3,2-dioxaphosfinan was dissolved in 500 mL of toluene to obtain solution C2. By blowing oxygen gas into the obtained solution C2, 2-chloro-1,3,2-dioxaphosfinane reacted with oxygen to synthesize 2-chloro-1,3,2-dioxaphosfinane-2-oxide (hereinafter also referred to as "6COP"). When oxygen gas was blown into solution C2, the temperature of the solution C2 rose due to the reaction. One hour after the temperature of the solution C2 returned to room temperature, the reaction was considered complete, and the blowing of oxygen gas was stopped. By removing toluene from the solution C2 after the completion of the reaction by vacuum distillation, a crude product of 6COP, which is a colorless and transparent liquid, was obtained. Subsequently, the crude product of 6COP was purified by vacuum distillation under conditions of 120°C to obtain purified 6COP. The yield of purified 6COP was 66 g, and the yield was 58%.

[0187] For the purified 6COP, proton analysis by nuclear magnetic resonance spectroscopy was performed using the nuclear magnetic resonance spectrometer under the same conditions as in Production Example 1. １ HNMR), phosphorus analysis ( ３１ PNMR was performed to confirm that the purified 6COP was free of impurities. In the proton analysis, a chemical shift (ppm) of 4.04 to 4.16 ppm was obtained, originating from the propylene group. In the phosphorus analysis, a chemical shift (ppm) of 21.9 ppm was obtained, originating from the phosphate ester group. The structural formula of the reaction intermediate, 2-chloro-1,3,2-dioxaphosfinane, is shown below.

[0188]

[0189] Furthermore, the structural formula of 6COP is shown below.

[0190]

[0191] [Production Example 3] <Synthesis of 2-fluoro-1,3,2-dioxaphosphoran-2-oxide> 5COP was prepared by the same method as in Production Example 1. 15.5 g of the prepared 5COP was dissolved in 20 mL of tetrahydrofuran to obtain solution A3. 7.58 g of potassium fluoride was added to solution A3 and stirred at 40°C for 12 hours to obtain solution B3. Solution B3 was filtered using paper filter paper with a pore size of 1 μm (No. 5c, Kiriyama Seisakusho Co., Ltd.) to separate the solid in solution B3 and obtain a colorless and transparent filtrate C3. Tetrahydrofuran was removed from filtrate C3 by vacuum distillation to obtain a colorless and transparent crude product of 2-fluoro-1,3,2-dioxaphosphoran-2-oxide (hereinafter also referred to as "5FOP"). Finally, the crude 5-FOP was purified by vacuum distillation at 130°C to obtain purified 5-FOP. The yield of purified 5-FOP was 4.8 g, and the yield was 35%.

[0192] 0.5 mL of the obtained 5-FOP was weighed into a 10 mL volumetric flask and diluted to the 10 mL mark with a mixed solvent prepared by mixing methanol and borate buffer (boric acid concentration: 50 mM, pH: 9.4) in equal volumes. 1 mL of this solution was mixed with 0.6 mL of a separately prepared potassium chromate borate buffer (boric acid concentration: 50 mM, pH: 9.4) solution (2.78 mM). A silver nitrate borate buffer (boric acid concentration: 50 mM, pH: 9.4) solution (0.108 mM) was added dropwise to these mixed solutions. After a white precipitate formed, the chloride ion concentration in the 5-FOP purified in Production Example 3 was identified from the amount of silver nitrate aqueous solution added when a reddish-orange precipitate formed (the so-called Mohr method). This titration confirmed that more than 99.0% of the raw material 5COP was converted to 5-FOP.

[0193] For the purified 5-FOP, proton analysis was performed using nuclear magnetic resonance spectroscopy with the aforementioned nuclear magnetic resonance measuring device. １ HNMR), phosphorus analysis ( ３１ PNMR), and fluorine analysis ( ９ FNMR was performed to confirm that the purified 5FOP was free of impurities. In the proton analysis, a chemical shift (ppm) of 4.48–4.64 ppm was obtained, originating from the ethylene group. In the phosphorus analysis, a chemical shift (ppm) of 14.66 ppm was obtained, originating from the phosphate ester group. In the fluorine analysis, a chemical shift (ppm) of -40.86 ppm was obtained. The structural formula of 5FOP is shown below.

[0194]

[0195] [Production Example 4] <Synthesis of 2-fluoro-1,3,2-dioxaphosfinan-2-oxide> 6COP was prepared by the same method as in Production Example 2. 10.0 g of the prepared 6COP was dissolved in 16 mL of tetrahydrofuran to obtain solution A4. 6.05 g of potassium fluoride was added to solution A4 and stirred at 40°C for 12 hours to obtain solution B4. Solution B4 was filtered using a paper filter paper with a pore size of 1 μm (No. 5c, Kiriyama Seisakusho Co., Ltd.) to separate the solid in solution B4 and obtain a colorless and transparent filtrate C4. Tetrahydrofuran was removed from filtrate C4 by vacuum distillation to obtain a colorless and transparent crude product of 2-fluoro-1,3,2-dioxaphosfinan-2-oxide (hereinafter also referred to as "6FOP"). Finally, the crude 6-FOP was purified by vacuum distillation at 130°C to obtain purified 6-FOP. The yield of purified 6-FOP was 3.6 g, and the yield was 40%.

[0196] 0.5 g of the obtained 6-FOP was weighed into a 10 mL volumetric flask, and methanol and borate buffer (boric acid concentration: 50 mM, pH: 9.4) were mixed with an equal volume of solvent to the 10 mL mark. 1 mL of this solution was mixed with 0.6 mL of a separately prepared potassium chromate borate buffer (boric acid concentration: 50 mM, pH: 9.4) solution (2.78 mM). A silver nitrate borate buffer (boric acid concentration: 50 mM, pH: 9.4) solution (0.108 mM) was added dropwise to these mixed solutions. After a white precipitate formed, the amount of silver nitrate aqueous solution added at the point when a reddish-orange precipitate formed was used to identify the chloride ion concentration in the 6-FOP purified in Production Example 4 (the so-called Mohr method). This titration confirmed that more than 99.5% of the raw material 6-COP was converted to 6-FOP.

[0197] For the purified 6FOP, proton analysis was performed using nuclear magnetic resonance spectroscopy with the aforementioned nuclear magnetic resonance measuring device. １ HNMR), phosphorus analysis ( ３１ PNMR), and fluorine analysis ( ９ FNMR was performed to confirm that the purified 6FOP was free of impurities.

[0198]

[0199] [Production Example 5] <Synthesis of 2-fluoro-1,3,2-dioxaphosphoran-2-oxide> 5COP was prepared using the same method as in Production Example 1. 2.85 g of the prepared 5COP was weighed into a 20 mL volumetric flask and made up to the 20 mL mark with dehydrated tetrahydrofuran to obtain solution A5. 2.32 g of potassium fluoride was added to solution A5 and stirred at 35°C for 24 hours to obtain solution B5. Solution B5 was filtered using a membrane filter paper (ADVANTEC) with a pore size of 0.45 μm to separate the solids in solution B5 and obtained a colorless, transparent filtrate C5. Another 2.32 g of potassium fluoride was added to filtrate C5 and stirred at 35°C for 24 hours to obtain solution D5. The solution D5 was filtered using the aforementioned membrane filter paper (ADVANTEC) to separate the solids in the solution D5, yielding a colorless, transparent filtrate E5, which is a tetrahydrofuran solution containing 5FOP.

[0200] One mL of filtrate E5 was weighed into a 10 mL volumetric flask, and methanol and borate buffer (boric acid concentration: 50 mM, pH: 9.4) were mixed with an equal volume of solvent to the 10 mL mark. One mL of this solution was mixed with 0.6 mL of a separately prepared potassium chromate borate buffer (boric acid concentration: 50 mM, pH: 9.4) solution (2.78 mM). To these mixed solutions, a silver nitrate borate buffer (boric acid concentration: 50 mM, pH: 9.4) solution (0.108 mM) was added dropwise. After a white precipitate formed, the chloride ion concentration in filtrate E5 was identified from the amount of silver nitrate aqueous solution added when a reddish-orange precipitate formed (the so-called Mohr method). From this titration, it was confirmed that in Production Example 5, more than 99.9% of 5COP was converted to 5FOP.

[0201] [Production Example 6] Filtrate E5 was prepared using the same method as in Production Example 5. Tetrahydrofuran was removed from the prepared filtrate E5 by vacuum distillation to obtain a crude product of 5FOP. The obtained crude product of 5FOP was purified by vacuum distillation at 130°C to obtain purified 5FOP. The yield of purified 5FOP was 1.7 g, and the yield was 67%.

[0202] [Production Example 7] <Synthesis of 2-fluoro-1,3,2-dioxaphosphoran-2-oxide> 6COP was prepared using the same method as in Production Example 2. 3.17 g of the prepared 6COP was weighed into a 20 mL volumetric flask and diluted to the 20 mL mark with dehydrated tetrahydrofuran to obtain solution A7. 2.32 g of potassium fluoride was added to solution A7 and stirred at 35°C for 24 hours to obtain solution B7. Solution B7 was filtered using a membrane filter paper (ADVANTEC) with a pore size of 0.45 μm to separate the solids in solution B7 and obtained a colorless, transparent filtrate C7. Another 2.32 g of potassium fluoride was added to filtrate C7 and stirred at 35°C for 24 hours to obtain solution D7. Solution D7 was filtered using the aforementioned membrane filter paper (ADVANTEC) to separate the solids in solution D7, yielding a colorless, transparent filtrate E7, which was a tetrahydrofuran solution containing 6FOP. 1 mL of filtrate E7 was weighed into a 10 mL volumetric flask, and methanol and borate buffer (boric acid concentration: 50 mM, pH: 9.4) were added to the 10 mL mark with an equal volume of the mixed solvent. 1 mL of this solution was mixed with 0.6 mL of a separately prepared potassium chromate borate buffer (boric acid concentration: 50 mM, pH: 9.4) solution (2.78 mM). A silver nitrate borate buffer (boric acid concentration: 50 mM, pH: 9.4) solution (0.108 mM) was added dropwise to these mixed solutions. After a white precipitate formed, the chloride ion concentration in filtrate E7 was identified from the amount of silver nitrate aqueous solution added when a reddish-orange precipitate was formed (the so-called Mohr method). From this titration, it was confirmed that in production example 7, more than 99.9% of 6COP was converted to 6FOP.

[0203] [Production Example 8] Filtrate E7 was prepared using the same method as in Production Example 7. Tetrahydrofuran was removed from the prepared filtrate E7 by vacuum distillation to obtain a crude product of 6FOP. The obtained crude product of 6FOP was purified by vacuum distillation at 130°C to obtain purified 6FOP. The yield of purified 6FOP was 2.5 g, and the yield was 87%.

[0204] [Comparative Example 1] (Preparation of Electrolyte) In an argon environment glove box with a dew point of -80°C or lower, fluoroethylene carbonate (FEC) and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (HFE) were mixed in equal volumes in a 1 mL volumetric flask to prepare a total of 1 mL of mixed solvent 1. Subsequently, in the glove box, 287.08 mg of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) was placed in a 1 mL volumetric flask, and then the mixed solvent 1 was gradually added to prepare an electrolyte in which the LiTFSI was dissolved in the mixed solvent 1. The total volume of the prepared electrolyte was 1 mL. This electrolyte was designated as comparative electrolyte 1.

[0205] (Lithium Metallic-Lithium Metallic Symmetric Cell Test) <Preparation of Lithium Metallic-Lithium Metallic Symmetric Cell> An HS flat cell (spring pressure 5 kgf) manufactured by Hosen Co., Ltd. (Japan), two circular lithium foils with a diameter of 13 mm (thickness 200 μm, no surface modification), and two separators (polypropylene porous film (PP porous separator), thickness 15 μm, diameter 16 mm) were prepared.

[0206] One of the two circular lithium foils was placed on the bottom surface of the HS flat cell. Next, 30 μL of the comparative electrolyte 1 was dropped onto the top surface of the HS flat cell. Next, one of the two separators was placed on the top surface of the HS flat cell, and 10 μL of the comparative electrolyte 1 was dropped onto it. Next, the other separator was placed on top of that, and 30 μL of the comparative electrolyte 1 was dropped onto the other separator. Next, the other circular lithium foil was placed on the other separator so as to overlap precisely with the lithium foil placed on the bottom surface of the HS flat cell. Finally, the HS flat cell was sealed to create a comparative metallic lithium-metallic lithium symmetric cell 1. Another comparative metallic lithium-metallic lithium symmetric cell 1 was also created using the same method as described above. Specifically, two comparative metallic lithium-metallic lithium symmetrical cells 1 were fabricated.

[0207] <Evaluation A of a metallic lithium-metallic lithium symmetric cell> One of the two comparative metallic lithium-metallic lithium symmetric cells 1 was connected to a charge / discharge device (Electrofield Co., Ltd. (Japan) charge / discharge device EF-7100P). Using the charge / discharge device, a constant current of 0.6633 mA (current density 0.5 mA / cm²) was applied. ２ ), with a charge / discharge termination capacity of 3.98 mAh (capacity 3 mAh / cm²). ２ Under the specified charge-discharge conditions, the comparative metallic lithium-metallic lithium symmetric cell 1 was repeatedly subjected to charge-discharge cycles. As a result, dissolution and deposition of lithium occurred in the metallic lithium foil inside the comparative metallic lithium-metallic lithium symmetric cell 1. Furthermore, the voltage inside the comparative metallic lithium-metallic lithium symmetric cell 1 was measured during each of the repeated charge-discharge cycles, and the change in the voltage during the repeated charge-discharge cycles was evaluated. The results are shown in Figure 3.

[0208] As shown in Figure 3, when one charge-discharge cycle was considered one cycle, the voltage at the 10th cycle was ±18 mV. From the 25th cycle onwards, the voltage gradually increased due to the dissolution and deposition of lithium, reaching ±32 mV at the 28th cycle and ±74 mV at the 38th cycle. At the 39th cycle, a short circuit occurred with a sharp voltage drop to ±8 mV. Thus, it was shown that lithium did not stably dissolve and precipitate in the comparative metallic lithium-metallic lithium symmetric cell 1.

[0209] <Evaluation B of a metallic lithium-metallic lithium symmetric cell> Ten charge-discharge cycles were performed on the other of the two comparative metallic lithium-metallic lithium symmetric cell 1, under the same conditions as in <Evaluation A of a metallic lithium-metallic lithium symmetric cell>, with one charge-discharge set considered as one cycle. After that, a circular lithium foil, which is the negative electrode, was removed from the other comparative metallic lithium-metallic lithium symmetric cell 1. The surface of the circular lithium foil was observed using an electron microscope (Hitachi, Ltd., product name: FlexSEM 1000II) under the conditions of acceleration voltage: 5kV and magnification: 1000x, and an electron microscope image was obtained. The electron microscope image is shown in Figure 1. From Figure 1, it was confirmed that lithium dendrites were formed and extended on the negative electrode surface of the comparative metallic lithium-metallic lithium symmetric cell 1 immediately after 10 charge-discharge cycles.

[0210] [Example 1] (Preparation of electrolyte) Using the same method as in Comparative Example 1, 1 mL of comparative electrolyte 1 was prepared in an argon environment glove box with a dew point of -80°C or lower. Subsequently, in the glove box, 50 mg of 6FOP produced in Production Example 4 was added to 1 mL of comparative electrolyte 1 to prepare electrolyte 1.

[0211] (Lithium Metallic-Lithium Metallic Symmetric Cell Test) Two lithium metallic-lithium metallic symmetric cells 1 were prepared using the same method as described in the section "Preparation of Lithium Metallic-Lithium Metallic Symmetric Cells" of Comparative Example 1, except that electrolyte 1 was used instead of comparative electrolyte 1. For one of the two lithium metallic-lithium metallic symmetric cells 1, the change in voltage during repeated charge-discharge cycles was evaluated using the same method as described in the section "Evaluation of Lithium Metallic-Lithium Metallic Symmetric Cells A" of Comparative Example 1. The results are shown in Figure 4.

[0212] As shown in Figure 4, when one charge-discharge cycle was considered one cycle, the voltage at the 10th cycle was ±15 mV. The metallic lithium-metallic lithium symmetric cell 1 showed stable lithium dissolution and extraction behavior without rapid voltage increases or decreases, and the voltage at the 64th cycle was approximately ±35 mV. At the 65th cycle, a short circuit occurred with a rapid voltage drop to 11 mV.

[0213] Furthermore, the other of the two metallic lithium-metallic lithium symmetric cell 1 was subjected to 10 charge-discharge cycles, with one charge-discharge set considered as one cycle, using the same method as described in the section "Evaluation B of metallic lithium-metallic lithium symmetric cell" of Comparative Example 1. Subsequently, an electron microscope image of the surface of the circular lithium foil, which is the negative electrode, removed from the other metallic lithium-metallic lithium symmetric cell 1 was obtained using the same method as described in the section "Evaluation B of metallic lithium-metallic lithium symmetric cell" of Comparative Example 1. This electron microscope image is shown in Figure 2. From Figure 2, it was confirmed that the formation and elongation of lithium dendrites were avoided or reduced on the negative electrode surface immediately after 10 charge-discharge cycles of the metallic lithium-metallic lithium symmetric cell 1.

[0214] [Example 2] (Preparation of electrolyte) Using the same method as in Comparative Example 1, 1 mL of comparative electrolyte 1 was prepared in an argon environment glove box with a dew point of -80°C or lower. Subsequently, in the glove box, 10 μL of 5FOP prepared in Production Example 3 was added to 1 mL of comparative electrolyte 1 to prepare electrolyte 2.

[0215] (Lithium Metallic-Lithium Metallic Symmetric Cell Test) Except for using electrolyte 2 instead of comparative electrolyte 1, a lithium metallic-lithium metallic symmetric cell 2 was prepared and evaluated using the same method as described in "(Lithium Metallic-Lithium Metallic Symmetric Cell Test)" of Comparative Example 1.

[0216] When one charge-discharge cycle was considered as one cycle, the voltage at the 10th cycle was ±14mV. The metallic lithium-metallic lithium symmetric cell 2 showed stable lithium dissolution and extraction behavior without exhibiting rapid voltage increases or decreases. At the 48th cycle, a short circuit occurred with a rapid voltage drop to 9mV.

[0217] [Example 3] (Preparation of electrolyte) Using the same method as in Comparative Example 1, 1 mL of comparative electrolyte 1 was prepared in an argon environment glove box with a dew point of -80°C or lower. Subsequently, in the glove box, 50 μL of 5FOP produced in Production Example 3 was added to 1 mL of comparative electrolyte 1 to prepare electrolyte 3.

[0218] (Lithium Metallic-Lithium Metallic Symmetric Cell Test) Except for using electrolyte 3 instead of comparative electrolyte 1, a lithium metallic-lithium metallic symmetric cell 3 was prepared using the same method as described in "(Lithium Metallic-Lithium Metallic Symmetric Cell Test)" of Comparative Example 1, and evaluated. The results are shown in Figure 5.

[0219] As shown in Figure 5, when one charge-discharge cycle is considered one cycle, the voltage at the 10th cycle was ±15 mV. The metallic lithium-metallic lithium symmetric cell 3 showed stable lithium dissolution behavior without rapid increases or decreases in voltage, and even at the 88th cycle, more than 1200 hours later, it was dissolving and dissolving very stably at ±22 mV.

[0220] [Example 4] (Preparation of negative electrode modifier) ​​In an argon environment glove box with a dew point of -80°C or lower, 1 mL of 5FOP prepared in Production Example 3 and 9 mL of HFE were added to a transparent glass sample vial (Maruemu Co., Ltd., 10 mL in volume) and mixed to prepare negative electrode modifier 1.

[0221] (Manufacturing of surface-modified metallic lithium foil) Next, two circular lithium foils with a diameter of 13 mm (thickness 200 μm, no surface modification) were immersed in the negative electrode modifier 1 in the sample vial. 120 minutes after the start of immersion, the circular lithium foils were removed and sequentially immersed in three HFE solvent baths prepared separately to remove the unbonded 5FOP from the circular lithium foils, thereby obtaining two surface-modified metallic lithium foils 1.

[0222] (Lithium Metallic-Lithium Metallic Symmetric Cell Test) A lithium metallic-lithium metallic symmetric cell 4 was prepared and evaluated using the same method as described in "(Lithium Metallic-Lithium Metallic Symmetric Cell Test)" of Comparative Example 1, except that two surface-modified lithium metallic foils 1 were used instead of two circular lithium foils. The results are shown in Figure 6.

[0223] When one charge-discharge cycle was considered as one cycle, the voltage at the 10th cycle was ±13mV. The metallic lithium-metallic lithium symmetric cell 4 gradually increased in voltage with each cycle, reaching ±128mV at the 59th cycle, and short-circuited at the 60th cycle with a significant voltage drop.

[0224] [Example 5] (Lithium Metallic-Lithium Metallic Symmetric Cell Test) A lithium metallic-lithium metallic symmetric cell 4 was prepared using the same method as in Example 4. The charge / discharge conditions were set to a constant current of 2.65 mA (current density 2.0 mA / cm²). ２ ), with a charge / discharge termination capacity of 3.98 mAh (capacity 3 mAh / cm²). ２ The metallic lithium-metallic lithium symmetric cell 4 was evaluated in the same manner as in Comparative Example 1, except for the change made to the other component. The results are shown in Figure 7.

[0225] As shown in Figure 7, when one charge-discharge cycle is considered one cycle, the voltage after the 10th cycle was ±41mV.

[0226] [Example 6] (Preparation of Electrolyte) In an argon environment glove box with a dew point of -80°C or lower, 374.14 mg of lithium bis(fluorosulfonyl)imide (LiFSI) was placed in a 1 mL volumetric flask, and then 1,2-DME was gradually added to prepare an electrolyte in which the LiFSI was dissolved in the 1,2-DME. The total volume of the prepared electrolyte was 1 mL. This electrolyte was designated as comparative electrolyte 2.

[0227] (Lithium Metallic-Lithium Metallic Symmetric Cell Test) A lithium metallic-lithium metallic symmetric cell 5 was prepared using the same method as in Example 5, except that comparative electrolyte 2 was used instead of comparative electrolyte 1, and it was evaluated. The results are shown in Figure 8.

[0228] As shown in Figure 8, when one charge-discharge set is considered one cycle, the voltage at the 10th cycle was ±22mV. The metallic lithium-metallic lithium symmetric cell 5 showed stable lithium dissolution and extraction behavior without any rapid increases or decreases in voltage. Even at the 334th cycle (after 1000 hours), although the voltage increased slightly to ±45mV, it continued to dissolve and extract stably, and there were no behaviors such as minor short circuits up to the 350th cycle.

[0229] [Example 7] (Lithium Metallic-Lithium Metallic Symmetric Cell Test) A lithium metallic-lithium metallic symmetric cell 5 was prepared using the same method as in Example 6. Charge / discharge termination capacity: 3.98 mAh (capacity 3 mAh / cm²) ２ While maintaining the above conditions, the charge / discharge conditions are set to a constant current of 6.633 mA (current density 5.0 mA / cm²). ２ The metallic lithium-metallic lithium symmetric cell 5 was evaluated using the same method as in Example 6, except for the change made to the other component. The results are shown in Figure 9.

[0230] As shown in FIG. 9, when one charge-discharge set was defined as one cycle, the voltage at the 10th cycle was ±45 mV. Also in Example 7, the lithium metal-lithium metal symmetric cell 5 did not show a sharp increase and decrease in voltage, and showed stable lithium dissolution and deposition behavior. Further, even at the 167th cycle (after 200 hours elapsed), the voltage was ±47 mV, no increase in voltage was observed, and dissolution and deposition were stable, and there was no behavior such as micro-short circuit up to the 167th cycle.

[0231] [Comparative Example 2] (Lithium metal-lithium metal symmetric cell test) A comparative lithium metal-lithium metal symmetric cell 2 was prepared and evaluated in the same manner as in Example 6, except that two circular lithium foils (thickness 200 μm, no surface modification) with a diameter of 13 mm described in Comparative Example 1 were used instead of the two surface-modified lithium metal foils 1. The results are shown in FIG. 10.

[0232] As shown in FIG. 10, when one charge-discharge set was defined as one cycle, the voltage at the 10th cycle was ±14 mV.

[0233] [Example 8] (Manufacture of lithium metal-sulfur secondary battery) <Manufacture of positive electrode material for lithium metal-sulfur secondary battery> 0.30 g of activated carbon (manufactured by Kansai Thermal Chemical Co., Ltd., product name: MSC-30SS) and 0.70 g of sulfur powder (manufactured by Wako pure chemical, purity over 99%) were mixed using an agate mortar to obtain a mixture. The mixture was transferred to a heat-resistant metal container, which was then put into a muffler furnace and heat-treated in the air to obtain a positive electrode material for a lithium metal-sulfur secondary battery.

[0234] The pore volume of the activated carbon was 1.7 cm ３ / g, and the specific surface area was 3000 cm ２ / g.

[0235] Specifically, the heat-resistant metal container containing the mixture was placed inside the muffle furnace, the internal temperature was raised to 155°C, and this temperature was maintained for 5 hours to melt the sulfur. Next, the internal temperature was raised at a rate of 5°C / min to 300°C, and this temperature was maintained for 2 hours. After that, the inside was thoroughly air-cooled, and the heat-resistant metal container was removed from it. From the heat-resistant metal container, activated carbon on which sulfur was supported, i.e., a positive electrode active material in which sulfur and carbonaceous material were compounded, was obtained. The obtained positive electrode active material in which sulfur and carbonaceous material were compounded was used as a positive electrode material for a lithium-sulfur secondary battery.

[0236] A portion of the lithium-sulfur secondary battery cathode material was placed in an alumina cell, and thermogravimetric analysis (TGA) was performed using a Shimadzu DTG-60AH thermometer. The measurement was performed under the following conditions: measurement gas Ar, gas flow rate 50 ml / min, heating rate 5°C / min, and upper temperature limit 600°C. From the obtained TGA results, the ratio of the weight of sulfur supported by the lithium-sulfur secondary battery cathode material to the total weight of the lithium-sulfur secondary battery cathode material (sulfur load, unit: weight %) was calculated. As a result, the sulfur load was found to be 69% by weight of the total weight of the lithium-sulfur secondary battery cathode material.

[0237] <Preparation of Cathode Mixture and Sulfur Cathode for Lithium-Sulfur Secondary Batteries> The lithium-sulfur secondary battery cathode material, unsupported activated carbon, conductive additive, dispersant, and binder were measured out in a weight ratio of 90:5:2:3 to form the materials for the lithium-sulfur secondary battery cathode mixture. The unsupported activated carbon was the same activated carbon used in the preparation of the lithium-sulfur secondary battery cathode material. Acetylene black (Denka HS-100) was used as the conductive additive. Carboxymethylcellulose (CMC) dispersed in pure water was used as the dispersant. Styrene-butadiene rubber (SBR) was used as the binder.

[0238] The measured materials were mixed using an agate mortar, and the resulting mixture was transferred to an ointment case. Next, the mixture was stirred twice at a rotation speed of 2000 rpm for 10 minutes each time using a rotating / revolving mixer to obtain a positive electrode mixture for lithium sulfur secondary batteries.

[0239] Next, the lithium-sulfur positive electrode mixture for secondary batteries is added to an aluminum current collector (manufactured by Hosen Co., Ltd. (Japan), product name: etched aluminum foil) at a sulfur content of 3.5 mg / cm² per unit area. ２ The current collector was filled in this manner and dried at 40°C for 1 hour using a hot plate. The dried current collector was rolled using a roll press, then cut out to a diameter of φ12 mm using a punch to obtain a molded body, which was then dried for another 12 hours in a vacuum bell jar at 50°C to produce sulfur cathode 1.

[0240] <Preparation of Electrolyte> Electrolyte 1 was prepared by the same method as the method for producing the electrolyte in Example 1.

[0241] <Fabrication of a metallic lithium-sulfur secondary battery> We prepared an HS flat cell (spring pressure 5 kgf) manufactured by Hosen Co., Ltd. (Japan), one circular lithium foil with a diameter of 13 mm (thickness 200 μm, no surface modification), and two separators (polypropylene porous film (PP porous separator), thickness 15 μm, diameter 16 mm).

[0242] A single circular lithium foil was placed on the bottom surface of the HS flat cell. Next, 30 μL of electrolyte 1 was dropped onto the top surface of the HS flat cell. Then, one of the two separators was placed on the top surface of the HS flat cell, and 10 μL of electrolyte 1 was dropped onto it. Next, the other of the two separators was placed on top of that, and 30 μL of electrolyte 1 was dropped onto the other separator. Then, the sulfur positive electrode 1 was placed on the other separator so as to overlap precisely with the lithium foil placed on the bottom surface of the HS flat cell. Finally, the HS flat cell was sealed to manufacture a metallic lithium sulfur secondary battery 1.

[0243] (Evaluation of the metallic lithium-sulfur secondary battery) The fabricated metallic lithium-sulfur secondary battery 1 was connected to a charge / discharge device (Electrofield Co., Ltd. (Japan) charge / discharge device EF-7100P). Subsequently, a constant current charge / discharge test was performed using the charge / discharge device under the following conditions: discharge rate of 0.1C (current that discharges the theoretical capacity in 10 hours), discharge termination voltage of 1.00V, charge rate of 0.1C (current that charges the theoretical capacity in 10 hours), and charge termination voltage of 3.00V. The theoretical capacity (mAh / g) was calculated by multiplying the amount of sulfur (mg) contained in the positive electrode by 1.672. The results are shown in Figure 11. As shown in Figure 11, the discharge capacity after 50 cycles was 492 mAh / g, and the discharge capacity after 100 cycles was 313 mAh / g.

[0244] [Example 9] (Preparation of a metallic lithium sulfur secondary battery) <Preparation of electrolyte> In an argon environment glove box with a dew point of -80°C or lower, 1,2-DME and HFE were mixed in equal volumes in a 1 mL volumetric flask to prepare a total of 1 mL of mixed solvent 2. Subsequently, in the glove box, 374.14 mg of LiFSI was placed in a 1 mL volumetric flask, and then the mixed solvent 2 was gradually added to prepare an electrolyte in which the LiFSI was dissolved in the mixed solvent 2. The total volume of the prepared electrolyte was 1 mL. This electrolyte was designated as comparative electrolyte 3.

[0245] <Manufacturing of surface-modified metallic lithium foil> Surface-modified metallic lithium foil 1 was obtained by the same method as the manufacturing method of surface-modified metallic lithium foil 1 in Example 4.

[0246] <Fabrication of a metallic lithium sulfur secondary battery> A metallic lithium sulfur secondary battery 2 was fabricated in the same manner as in Example 8, except that one surface-modified metallic lithium foil 1 was used instead of one circular lithium foil, and a comparative electrolyte 3 was used instead of electrolyte 1.

[0247] (Evaluation of the metallic lithium-sulfur secondary battery) A constant current charge-discharge test was performed on metallic lithium-sulfur secondary battery 2 in the same manner as in Example 8, except that the discharge rate and charge rate were changed from 0.1C to 0.2C, respectively. The results are shown in Figure 12. As shown in Figure 12, the discharge capacities at cycles 50, 100, 150, 200, 250, and 300 were 890 mAh / g, 795 mAh / g, 734 mAh / g, 703 mAh / g, 680 mAh / g, and 653 mAh / g, respectively.

[0248] [Comparative Example 3] (Preparation of a metallic lithium-sulfur secondary battery) <Preparation of electrolyte> Comparative electrolyte 1 was prepared by the same method as the method for producing the electrolyte of Comparative Example 1.

[0249] <Preparation of a metallic lithium-sulfur secondary battery> A comparative metallic lithium-sulfur secondary battery 1 was prepared using the same method as in Example 8, except that comparative electrolyte 1 was used instead of electrolyte 1.

[0250] (Evaluation of the metallic lithium-sulfur secondary battery) A constant current charge-discharge test was performed on the fabricated comparative metallic lithium-sulfur secondary battery 1 in the same manner as in Example 8. The results are shown in Figure 13. As shown in Figure 13, the discharge capacity after 50 cycles was 405 mAh / g, and the discharge capacity after 100 cycles was 169 mAh / g.

[0251] [Comparative Example 4] (Preparation of Laminated Sulfur Secondary Battery for Comparative Evaluation) <Preparation of Cathode Mixture and Sulfur Cathode for Lithium Sulfur Secondary Battery> A cathode mixture for lithium sulfur secondary battery was obtained by the same method as in Example 8. Next, the lithium sulfur cathode mixture for lithium sulfur secondary battery was placed on a 3D aluminum current collector (manufactured by Sumitomo Electric Industries, Ltd., product name: Ni Cellmet), with the weight of the activated carbon supporting the sulfur being 7.75 mg / cm² per unit area of ​​the current collector. ２The material was filled in such a manner. Next, the 3D aluminum current collector was dried in an oven at 40°C for 1 hour under atmospheric pressure. Subsequently, the dried current collector was rolled using a roll press and then cut to a size of 23 mm x 25 mm using a cutting blade to obtain a molded body. The molded body was further vacuum-dried for 12 hours in a bell jar at 50°C to produce a sulfur cathode for a laminate cell.

[0252] <Preparation of Electrolyte> Comparative electrolyte 3 was prepared using the same method as the electrolyte production method of Example 9.

[0253] <Preparation of Laminated Sulfur Secondary Batteries for Comparative Evaluation> Two negative electrodes 1 for laminated cells were prepared by cutting a 30 μm thick lithium foil to a size of 30 mm x 30 mm using a cutting blade in an atmospheric environment with a dew point of -40°C or lower. In addition, four separators (polypropylene porous film (PP porous separator), 15 μm thick, size 27 mm x 27 mm) were prepared.

[0254] One negative electrode 1 for laminated cell, two separators, and one sulfur positive electrode for laminated cell were stacked in this order. Then, two more separators and another negative electrode 1 for laminated cell were stacked on top of the sulfur positive electrode for laminated cell in this order. The laminated body was assembled in this manner. This laminated body was placed inside an aluminum laminate film that had been formed into a bag shape by thermocompression. Furthermore, after injecting the comparative electrolyte 3 into the laminate film, thermocompression was performed while vacuuming the inside of the laminate film to produce a comparative evaluation laminated sulfur secondary battery. The total amount of comparative electrolyte 3 added was seven times the weight of sulfur contained in the sulfur positive electrode for laminated cell.

[0255] (Evaluation of Laminated Sulfur Secondary Batteries for Comparative Evaluation) Constant current charge-discharge tests were performed on the fabricated laminated sulfur secondary batteries for comparative evaluation using the same method as in Example 8. The results are shown in Figure 14. As shown in Figure 14, the discharge capacities after 5, 10, 15, 20, and 25 cycles were 1267 mAh / g, 1115 mAh / g, 1078 mAh / g, 1056 mAh / g, and 991 mAh / g, respectively.

[0256] [Example 10] (Preparation of laminated sulfur secondary battery for evaluation) Two sections of lithium foil were obtained by cutting a 30 μm thick lithium foil to a size of 30 mm x 30 mm using a press-cutting blade in an atmospheric atmosphere with a dew point of -40°C or lower. The two obtained sections were immersed in 5FOP manufactured in Production Example 3. Two hours after the start of immersion, the two sections were removed and washed by sequentially immersing them in two HFE solvent baths prepared separately to remove the unbonded 5FOP from the two sections, thereby obtaining two negative electrodes 2 for laminate cells. The negative electrodes 2 for laminate cells were Li negative electrodes coated with 5FOP. The laminated sulfur secondary battery for evaluation was manufactured using the same method as the laminated sulfur secondary battery for comparative evaluation in Comparative Example 4, except that the negative electrode 2 for laminated cell was used instead of the negative electrode 1 for laminated cell.

[0257] (Evaluation of the laminated sulfur secondary battery for evaluation) The laminated sulfur secondary battery for evaluation that was prepared was subjected to constant current charge-discharge tests using the same method as in Comparative Example 4. The results are shown in Figure 15. As shown in Figure 15, the discharge capacities after 5, 10, 15, 20, and 25 cycles were 1358 mAh / g, 1196 mAh / g, 1166 mAh / g, 1160 mAh / g, and 1063 mAh / g, respectively.

[0258] [Comparative Example 5] (Preparation of Lithium-ion Secondary Battery for Comparative Evaluation) <Preparation of Electrolyte> In an argon environment glove box with a dew point of -80°C or lower, ethylene carbonate and dimethyl carbonate were mixed in equal volumes in a 1 mL volumetric flask to prepare a total of 1 mL of mixed solvent 3. Subsequently, in the glove box, 287.08 mg of LiTFSI was placed in a 1 mL volumetric flask, and then the mixed solvent 3 was gradually added to prepare an electrolyte in which the LiTFSI was dissolved in the mixed solvent 3. The total volume of the prepared electrolyte was 1 mL. This electrolyte was designated as comparative electrolyte 4.

[0259] <Fabrication of Lithium-ion Secondary Batteries for Comparative Evaluation> A Hosen Co., Ltd. (Japan) HS flat cell (spring pressure 5 kgf), one 13 mm diameter circular lithium foil (thickness 200 μm, no surface modification), and one separator (polypropylene porous film (PP porous separator), thickness 15 μm, diameter 16 mm) were prepared. Additionally, an NMC532 cathode (manufactured by Hosen Co., Ltd., 3 mAh / cm²) was used. ２ I prepared a 12mm diameter piece.

[0260] A single lithium foil was placed on the bottom surface of the HS flat cell. Next, 25 μL of the comparative electrolyte 4 was dropped onto the top surface of the HS flat cell. Then, the separator was placed on the top surface of the HS flat cell, and another 25 μL of the comparative electrolyte 4 was dropped onto it. Next, the NMC532 positive electrode was placed on top of that so as to precisely overlap with the lithium foil placed on the bottom surface of the HS flat cell. Finally, the HS flat cell was sealed to fabricate a lithium-ion secondary battery for comparative evaluation.

[0261] (Evaluation of comparative lithium-ion secondary batteries) The fabricated comparative lithium-ion secondary batteries were connected to a charge / discharge device (EF-7100P, manufactured by Electrofield Co., Ltd. (Japan)). Subsequently, constant current charge / discharge tests were performed using the charge / discharge device under the following conditions: discharge rate of 1C (current that discharges the theoretical capacity in 1 hour), discharge termination voltage of 2.7V, charge rate of 1C (current that charges the theoretical capacity in 1 hour), and charge termination voltage of 4.2V. The theoretical capacity (mAh) was 3mAh / cm², which is the catalog value for the positive electrode. ２ The electrode area is 1.13 cm². ２ The result was calculated by multiplying by 3.39 mAh. The results are shown in Figure 16. As shown in Figure 16, the discharge capacities after 10, 30, 50, and 100 cycles from immediately after the start were 101 mAh, 78 mAh, 46 mAh, and 6 mAh, respectively, indicating extremely low cycle capacity characteristics.

[0262] [Example 11] (Preparation of lithium-ion secondary battery for evaluation) <Manufacturing of surface-modified metallic lithium foil> Surface-modified metallic lithium foil 1 was prepared by the same method as the manufacturing method of surface-modified metallic lithium foil in Example 4.

[0263] <Preparation of Lithium-ion Secondary Battery for Evaluation> An evaluation lithium-ion secondary battery was prepared by the same method as described in <Preparation of Lithium-ion Secondary Battery for Comparative Evaluation> of Comparative Example 5, except that a surface-modified metallic lithium foil 1 was used instead of the circular lithium foil (200 μm thick, no surface modification).

[0264] (Evaluation of the evaluation lithium-ion secondary battery) A charge-discharge test was performed on the evaluation lithium-ion secondary battery using the same method as described in Comparative Example 5 (Evaluation of the comparative evaluation lithium-ion secondary battery). The results are shown in Figure 17. As shown in Figure 17, the discharge capacities after 10, 30, 50, and 100 cycles from immediately after the start were 123 mAh, 98 mAh, 74 mAh, and 34 mAh, respectively, and no minor short circuits were observed during charging and discharging, indicating stable charge-discharge behavior.

[0265] [Example 12] (Manufacturing of surface-modified metallic lithium foil) Surface-modified metallic lithium foil 2 was obtained in the same manner as the manufacturing method of surface-modified metallic lithium foil in Example 4, except that the time from the start of immersion of the circular lithium foil in the negative electrode modifier 1 to the removal of the circular lithium foil was changed to 20 minutes.

[0266] (Analysis of surface-modified metallic lithium foil) Surface-modified metallic lithium foil 2 was analyzed by XPS (PHI Quantes, ULVAC-PHI INC.). The analysis was performed using a monochromatic Al-Kα X-ray source (1486.6 eV) with the photoelectron extraction angle fixed at 90 degrees.

[0267] As a result, peaks were confirmed at 534 eV and 531 eV in the O1s spectrum. Here, the peak at 534 eV is attributed to the double bond between oxygen and phosphorus (O=P), and the peak at 531 eV is attributed to oxygen sandwiched between phosphorus and carbon (C-O-P). Therefore, it was suggested that phosphate esters were present on the surface of the surface-modified metallic lithium foil 2. Consequently, it was found that a protective film consisting of phosphate esters was formed on the surface of the surface-modified metallic lithium foil 2.

[0268] In addition, a peak was also confirmed at the position of 688 eV in the F1s spectrum. It is known that the peak is attributed to the P-F bond. Therefore, it was found that at least a part of 5FOP remained with its original molecular structure on the surface of the surface-modified metallic lithium foil 2.

[0269] Furthermore, for the surface-modified metallic lithium foil 2, depth analysis was performed while scraping the surface using an Ar ion beam. As a result, it was found that the thickness of the protective film present on the surface of the surface-modified metallic lithium foil 2 was about 10 nm (converted at the etching rate of SiO ２ ).

[0270] [Example 13](Production of surface-modified metallic lithium foil) The surface-modified metallic lithium foil 1 was obtained by the same method as the production method of the surface-modified metallic lithium foil in Example 4.

[0271] (Analysis of surface-modified metallic lithium foil) The surface-modified metallic lithium foil 1 was analyzed by XPS in the same manner as in Example 12. As a result, similar to Example 12, peaks were confirmed at the positions of 534 eV and 531 eV in the O1s spectrum, and a peak was confirmed at the position of 688 eV in the F1s spectrum. That is, in the analysis of the surface-modified metallic lithium foil 1, peaks attributed to O=P and C-O-P, as well as the P-F bond, were confirmed. Therefore, it was found that a protective film made of phosphate ester was formed on the surface of the surface-modified metallic lithium foil1, and at least a part of 5FOP remained with its original molecular structure.

[0272] In addition, depth analysis was also performed on the surface-modified metallic lithium foil 1 while scraping the surface using an Ar ion beam. As a result, it was found that the thickness of the protective film present on the surface of the surface-modified metallic lithium foil 1 was about 30 nm (converted at the etching rate of SiO ２ ).

[0273] [Example 14] (Production of surface-modified metallic lithium foil) 0.2 mL of 5FOP prepared in Production Example 3 was placed in a glass tube (manufactured by AS ONE Corporation, product name: sample vial, volume 10 mL), and left to stand for 10 minutes to vaporize a portion of the 5FOP, filling the glass tube with saturated 5FOP vapor. Subsequently, a circular lithium foil with a diameter of 13 mm (thickness 200 μm, no surface modification) was placed in the glass tube so as not to come into contact with the unvaporized 5FOP, and exposed to the saturated 5FOP vapor. 20 minutes after the start of exposure, the circular lithium foil was removed from the glass tube, and the unadhered 5FOP was removed by sequentially immersing the circular lithium foil in three HFE solvent baths prepared separately, thereby obtaining surface-modified metallic lithium foil 3.

[0274] (Analysis of surface-modified metallic lithium foil) Surface-modified metallic lithium foil 3 was analyzed by XPS using the same method as in Example 12. As a result, as in Examples 12 and 13, peaks were confirmed at 534 eV and 531 eV in the O1s spectrum, and a peak was confirmed at 688 eV in the F1s spectrum. In other words, in the analysis of surface-modified metallic lithium foil 3, peaks attributed to O=P, C-O-P, and P-F bonds were confirmed. Therefore, it was found that a protective film made of phosphate ester was formed on the surface of surface-modified metallic lithium foil 3, and that at least some of 5FOP remained in its original molecular structure.

[0275] Furthermore, the surface-modified metallic lithium foil 3 was also analyzed in the depth direction while the surface was abraded using an Ar ion beam. As a result, the thickness of the protective film present on the surface of the surface-modified metallic lithium foil 3 was found to be approximately 30 nm (SiO₂ ２ It was found that (converted using the etching rate)

[0276] [Comparative Example 6] (Analysis of Unmodified Metallic Lithium Anode) A circular lithium foil with a diameter of 13 mm (thickness 200 μm, no surface modification) was prepared as an unmodified metallic lithium anode. The unmodified metallic lithium anode was analyzed by XPS using the same method as in Example 12. As a result, the peaks attributed to the double bond between oxygen and phosphorus (O=P), the oxygen sandwiched between phosphorus and carbon (C-O-P), and the P-F bond, which were observed in Examples 12 to 14, were not observed.

[0277] [Comparative Example 7] (Preparation of a metallic lithium-sulfur secondary battery) Sulfur content: 4.5 mg / cm ２ A sulfur cathode was prepared using the same method as in Example 8, except that the amount of sulfur used was changed accordingly. The prepared sulfur cathode will be referred to as sulfur cathode 2.

[0278] A comparative metallic lithium-sulfur secondary battery was prepared in the same manner as in Comparative Example 3, except that sulfur cathode 2 was used as the sulfur cathode. A constant current charge-discharge test was performed on the comparative metallic lithium-sulfur secondary battery in the same manner as in Comparative Example 3. As a result, the discharge capacity after 50 cycles was 400 mAh / g, but a short circuit occurred at the 78th cycle, and the battery ceased to function.

[0279] [Example 15] Electrolyte 3 was prepared in the same manner as in Example 3. A metallic lithium sulfur secondary battery was prepared in the same manner as in Comparative Example 7, except that the prepared electrolyte 3 was used as the electrolyte. A constant current charge-discharge test was performed on the metallic lithium sulfur secondary battery in the same manner as in Comparative Example 7. As a result, the discharge capacities after 50, 100, and 200 cycles were 486 mAh / g, 338 mAh / g, and 203 mAh / g, respectively, demonstrating stable charge-discharge over 200 cycles.

[0280] [Example 16] Surface-modified metallic lithium foil 1 was prepared in the same manner as in Example 4. A comparative metallic lithium sulfur secondary battery was prepared in the same manner as in Comparative Example 7, except that surface-modified metallic lithium foil 1 was used as the negative electrode. A constant current charge-discharge test was performed on the comparative metallic lithium sulfur secondary battery in the same manner as in Comparative Example 3. As a result, the discharge capacities after 50, 100, and 200 cycles were 540 mAh / g, 440 mAh / g, and 270 mAh / g, respectively, and stable charging and discharging was possible over 200 cycles.

[0281] [Example 17] In an argon environment glove box with a dew point of -80°C or lower, 1.1 g of 6FOP prepared in Production Example 4 and 9 mL of HFE were added to a transparent glass sample vial (Maruemu Co., Ltd., 10 mL in volume) and mixed to prepare negative electrode modifier 2.

[0282] (Manufacturing of surface-modified metallic lithium foil) Next, two circular lithium foils with a diameter of 13 mm (thickness 200 μm, no surface modification) were immersed in the negative electrode modifier 2 in the sample vial. 120 minutes after the start of immersion, the circular lithium foils were removed and sequentially immersed in three separate HFE solvent baths to remove the unbonded 6FOP from the circular lithium foils, thereby obtaining surface-modified metallic lithium foil 4.

[0283] A metallic lithium-sulfur secondary battery was fabricated in the same manner as in Comparative Example 7, except that a surface-modified metallic lithium foil 4 was used for the negative electrode. A constant current charge-discharge test was performed on the metallic lithium-sulfur secondary battery in the same manner as in Comparative Example 3. As a result, the discharge capacities after 50, 100, and 200 cycles were 550 mAh / g, 443 mAh / g, and 292 mAh / g, respectively, demonstrating stable charge-discharge over 200 cycles.

[0284] [Comparative Example 8] Electrolyte 1 was prepared using the same method as in Example 1. Using electrolyte 1, the amount of electrolyte 1 added was 31 μL / cm² per positive electrode area. ２A laminated sulfur secondary battery for comparative evaluation was prepared in the same manner as described in Comparative Example 4, except for the aforementioned difference. A constant current charge-discharge test was performed on the laminated sulfur secondary battery for comparative evaluation using the same method as in Comparative Example 4. The results are shown in Figure 18. The discharge capacities after 100, 200, and 300 cycles were 122 mAh / g, 64 mAh / g, and 45 mAh / g, respectively.

[0285] [Example 18] Electrolyte 3 was prepared in the same manner as in Example 3. An evaluation laminate-type sulfur secondary battery was prepared in the same manner as in Comparative Example 8, except that electrolyte 3 was used. A constant current charge-discharge test was performed on the evaluation laminate-type sulfur secondary battery in the same manner as in Comparative Example 4. The results are shown in Figure 19. The discharge capacities after 100, 200, and 300 cycles were 245 mAh / g, 105 mAh / g, and 64 mAh / g, respectively, showing an improved cycle life compared to Comparative Example 8.

[0286] [Example 19] Electrolyte 1 was prepared using the same method as in Example 1. Using electrolyte 1, the amount of electrolyte 1 added was 23 μL / cm² per positive electrode area. ２ Except for the above, an evaluation laminate-type sulfur secondary battery was prepared in the same manner as described in Comparative Example 4. A constant current charge-discharge test was performed on the evaluation laminate-type sulfur secondary battery using the same method as in Comparative Example 4. The results are shown in Figure 20. The discharge capacity after 50 cycles was 334 mAh / g, which was an improvement in cycle life compared to Comparative Example 4.

[0287] [Example 20] Electrolyte 3 was prepared in the same manner as in Example 3. An evaluation laminate-type sulfur secondary battery was prepared in the same manner as in Example 19, except that electrolyte 3 was used. A constant current charge-discharge test was performed on the evaluation laminate-type sulfur secondary battery in the same manner as in Comparative Example 4. The results are shown in Figure 21. The discharge capacities after 50, 100, and 150 cycles were 340 mAh / g, 162 mAh / g, and 92 mAh / g, respectively, and the battery lost its function due to a short circuit at the 185th cycle. Therefore, the cycle life was improved compared to Comparative Example 4 and Example 19.

[0288] [Example 21] (Preparation of Electrolyte) In an argon environment glove box with a dew point of -80°C or lower, fluoroethylene carbonate (FEC) and methyl-tert-butyl ether (tBME) were mixed in equal volumes in a 1 mL volumetric flask to prepare a total of 1 mL of mixed solvent 4. Subsequently, in the same glove box, 287.08 mg of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) was placed in another 1 mL volumetric flask, and then mixed solvent 4 was gradually added to prepare an electrolyte (total volume 1 mL) in which the LiTFSI was dissolved in mixed solvent 4. This electrolyte was designated as electrolyte 4.

[0289] A metallic lithium-sulfur secondary battery was prepared in the same manner as in Example 8, except that electrolyte 4 was used. A constant current charge-discharge test was performed on the metallic lithium-sulfur secondary battery in the same manner as in Example 8. The results are shown in Figure 22. As shown in Figure 22, the discharge capacity after 50 cycles was 552 mAh / g, and the discharge capacity after 100 cycles was 467 mAh / g.

[0290] [Example 22] (Preparation of Electrolyte) In an argon environment glove box with a dew point of -80°C or lower, fluoroethylene carbonate (FEC) and cyclopentyl methyl ether (CPME) were mixed in equal volumes in a 1 mL volumetric flask to prepare a total of 1 mL of mixed solvent 5. Subsequently, in the same glove box, 287.08 mg of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) was placed in another 1 mL volumetric flask, and then the mixed solvent 5 was gradually added to prepare an electrolyte (total volume 1 mL) in which the LiTFSI was dissolved in the mixed solvent 5. This electrolyte was designated as electrolyte 5.

[0291] A metallic lithium-sulfur secondary battery was prepared in the same manner as in Example 8, except that electrolyte 5 was used. A constant current charge-discharge test was performed on the metallic lithium-sulfur secondary battery in the same manner as in Example 8. As a result, the discharge capacity after 50 cycles was 562 mAh / g, and the discharge capacity after 100 cycles was 471 mAh / g.

[0292] [Example 23] (Preparation of Electrolyte) In an argon environment glove box with a dew point of -80°C or lower, fluoroethylene carbonate (FEC) and ethyl propyl ether (EP) were mixed in equal volumes in a 1 mL volumetric flask to prepare a total of 1 mL of mixed solvent 6. Subsequently, in the same glove box, 287.08 mg of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) was placed in another 1 mL volumetric flask, and then the mixed solvent 6 was gradually added to prepare an electrolyte (total volume 1 mL) in which the LiTFSI was dissolved in the mixed solvent 6. This electrolyte was designated as electrolyte 6.

[0293] A metallic lithium-sulfur secondary battery was prepared in the same manner as in Example 8, except that electrolyte 6 was used. A constant current charge-discharge test was performed on the metallic lithium-sulfur secondary battery in the same manner as in Example 8. As a result, the discharge capacity after 50 cycles was 534 mAh / g, and the discharge capacity after 100 cycles was 420 mAh / g.

[0294] [Example 24] (Preparation of Electrolyte) In an argon environment glove box with a dew point of -80°C or lower, fluoroethylene carbonate (FEC) and methyl-n-butyl ether (nBMP) were mixed in equal volumes in a 1 mL volumetric flask to prepare a total of 1 mL of mixed solvent 7. Subsequently, in the same glove box, 287.08 mg of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) was placed in another 1 mL volumetric flask, and then the mixed solvent 7 was gradually added to prepare an electrolyte (total volume 1 mL) in which the LiTFSI was dissolved in the mixed solvent 7. This electrolyte was designated as electrolyte 7.

[0295] A metallic lithium-sulfur secondary battery was prepared in the same manner as in Example 8, except that electrolyte 7 was used. A constant current charge-discharge test was performed on the metallic lithium-sulfur secondary battery in the same manner as in Example 8. As a result, the discharge capacity after 50 cycles was 590 mAh / g, and the discharge capacity after 100 cycles was 480 mAh / g.

[0296] [Example 25] Electrolyte 4 was prepared in the same manner as in Example 21. Surface-modified metallic lithium foil 1 was prepared in the same manner as in Example 4. A metallic lithium sulfur secondary battery was manufactured in the same manner as in Example 8, except that electrolyte 4 was used and surface-modified metallic lithium foil 1 was used as the negative electrode, and a constant current charge-discharge test was performed on the battery. As a result, the discharge capacities at 50, 100, and 120 cycles were 530 mAh / g, 390 mAh / g, and 383 mAh / g, respectively.

[0297] [Comparative Example 9] In an argon environment glove box with a dew point of -80°C or lower, an HS flat cell (spring pressure 5 kgf) manufactured by Hosen Co., Ltd. (Japan), one circular lithium foil with a diameter of 13 mm (thickness 200 μm, no surface modification), one separator (polypropylene porous film (PP porous separator), thickness 15 μm, diameter 16 mm), and a copper foil (thickness 15 μm, diameter 14 mm) were prepared. The copper foil was pretreated by the following method. As a pretreatment method, the copper foil was immersed in acetone (Fujifilm Wako Pure Chemical Industries, Ltd., Infinity Pure) and the copper foil surface was cleaned for 1 minute by ultrasonic irradiation using a bath-type ultrasonic irradiation device (Branson Ultrasonics Corporation, Branson M2800-J). After removing the acetone, the copper foil surface was cleaned with methanol (Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade) by ultrasonic irradiation in the same manner as above, and then the methanol was removed. This cleaning operation with acetone and methanol was performed alternately three times each. The copper foil was then immersed in a 1M hydrochloric acid solution, followed by ultrasonic irradiation for 1 minute. After removing the copper foil, it was thoroughly washed with ultrapure water and then vacuum-dried.

[0298] <Preparation of electrodeposited lithium> The circular lithium foil was placed on the bottom surface of the HS flat cell. Next, 30 μL of comparative electrolyte 1 was dropped onto the top surface of the HS flat cell. Then, one separator was placed on the top surface of the lithium foil placed inside the HS flat cell, and 30 μL of comparative electrolyte 1 was dropped onto it. Next, the copper foil that had been pre-treated in the previous step was placed on the top surface of the separator so that it overlapped precisely with the lithium foil.

[0299] The lithium-copper cell prepared in this manner was connected to a charge / discharge device (HJ1020mSD8, manufactured by Meiden Hokuto Co., Ltd.), and while controlling the current to a value of 0.6633 mA, a negative potential was applied to the copper foil side and a positive potential to the lithium side, thereby depositing metallic lithium onto the copper foil for 10 hours. Hereafter, lithium deposited on copper foil using this method may be referred to as electrodeposited lithium. After removing the electrodeposited lithium from the HS flat cell, it was thoroughly washed with 1,1,2,2-tetrafluoro-2,2,3,3-tetrafluoropropyl ether (HFE) to obtain electrodeposited lithium 1.

[0300] <Preparation of Electrodeposited Lithium-Electrodeposited Lithium Symmetric Cell> Comparative electrolyte 1 was prepared using the same method as in Comparative Example 1. In addition, two electrodeposited lithium 1 sheets, a new HS flat cell (spring pressure 5 kgf) manufactured by Hosen Co., Ltd. (Japan), and two separators (polypropylene porous film (PP porous separator), thickness 15 μm, diameter 16 mm) were prepared in an argon environment glove box with a dew point of -80°C or lower. One of the two electrodeposited lithium 1 sheets was placed on the bottom surface of the HS flat cell. Subsequently, 30 μL of comparative electrolyte 1 was dropped onto the upper surface of the electrodeposited lithium sheet placed in the HS flat cell. Subsequently, one of the two separators was placed on the upper surface of the HS flat cell, and 10 μL of comparative electrolyte 1 was dropped onto it. Next, the other separator of the two separators was placed on top of it, and 30 μL of the comparative electrolyte 1 was dropped onto the other separator. Then, the other electrodeposited lithium 1 of the two electrodeposited lithium 1 was placed on the other separator so that the side with the deposited lithium faced the separator, and so that it overlapped precisely with the one lithium foil placed on the bottom surface of the HS flat cell. Finally, the HS flat cell was sealed to prepare the comparative electrodeposited lithium-electrodeposited lithium symmetric cell 1. Another comparative electrodeposited lithium-electrodeposited lithium symmetric cell 1 was prepared using the same method as described above. In other words, two comparative electrodeposited lithium-electrodeposited lithium symmetric cells 1 were prepared.

[0301] <Evaluation of Electrodeposited Lithium-Electrodeposited Lithium Symmetric Cell> One of the two comparative electrodeposited lithium-electrodeposited lithium symmetric cells 1 was connected to a charge / discharge device (HJ1020mSD8, manufactured by Meiden Hokuto Co., Ltd.). Using the charge / discharge device, a constant current of 0.6633 mA (current density 0.5 mA / cm²) was applied. ２ ), with a charge / discharge termination capacity of 1.33 mAh (capacity 1 mAh / cm²). ２ Under the specified charge-discharge conditions, the comparative electrodeposited lithium-electrodeposited lithium symmetric cell 1 was repeatedly subjected to charge-discharge cycles. As a result, dissolution and deposition of lithium occurred in the electrodeposited lithium foil inside the comparative electrodeposited lithium-electrodeposited lithium symmetric cell 1. Furthermore, the voltage inside the comparative electrodeposited lithium-electrodeposited lithium symmetric cell 1 was measured during each of the repeated charge-discharge cycles, and the change in the voltage during the repeated charge-discharge cycles was evaluated. The results are shown in Figure 23. As shown in Figure 23, when one charge-discharge set was considered as one cycle, a slight short circuit was observed at the 28th cycle, and a short circuit accompanied by a rapid voltage drop occurred at the 31st cycle. Thus, it was shown that lithium did not stably dissolve and precipitate inside the comparative electrodeposited lithium-electrodeposited lithium symmetric cell 1.

[0302] [Example 26] Electrolyte 3 was prepared in the same manner as in Example 3. An electrodeposited lithium-electrodeposited lithium symmetric cell was fabricated in the same manner as in Comparative Example 9, except that electrolyte 3 was used, and the electrodeposited lithium-electrodeposited lithium symmetric cell was evaluated. The results are shown in Figure 24. As shown in Figure 24, when one charge-discharge set was considered one cycle, a gradual voltage increase was observed from the 40th cycle, and a short circuit occurred with a sharp voltage drop at the 64th cycle. Thus, compared to Comparative Example 9, the dissolution and extraction of lithium was stabilized.

[0303] [Example 27] Electrodeposited lithium 1 was prepared using the same method as in Comparative Example 9. Electrodeposited lithium 1 was immersed in the filtrate E5 prepared in Production Example 5 for 120 minutes. After thoroughly washing the surface of electrodeposited lithium 1 with tetrahydrofuran, it was dried to prepare electrodeposited lithium 2.

[0304] An electrodeposited lithium-electrodeposited lithium symmetric cell was fabricated in the same manner as in Comparative Example 9, except that electrodeposited lithium 2 was used instead of electrodeposited lithium 1, and the electrodeposited lithium-electrodeposited lithium symmetric cell was evaluated. The results are shown in Figure 25. As shown in Figure 25, when one charge-discharge set was considered one cycle, a gradual voltage increase was observed from the 90th cycle, and a short circuit occurred with a sharp voltage drop at the 126th cycle. Thus, the dissolution and extraction of lithium was significantly stabilized compared to Comparative Example 9.

[0305] [Example 28] Electrodeposited lithium 1 was prepared using the same method as in Comparative Example 9. 75 μL of filtrate E5 obtained in Production Example 5 was dropped onto the electrodeposited lithium 1. Then, in an argon environment glove box with a dew point of -80°C or lower, volatile components contained in the filtrate E5 were removed on a 40°C hot plate and dried to prepare electrodeposited lithium 3.

[0306] An electrodeposited lithium-electrodeposited lithium symmetric cell was fabricated in the same manner as in Comparative Example 9, except that electrodeposited lithium 3 was used instead of electrodeposited lithium 1. The electrodeposited lithium-electrodeposited lithium symmetric cell was then evaluated. The results are shown in Figure 26. As shown in Figure 26, when one charge-discharge set was considered one cycle, a gradual voltage increase was observed, but no short circuit occurred even at 450 cycles. Thus, the dissolution and extraction of lithium was significantly stabilized compared to Comparative Example 9.

[0307] [Comparative Example 10] <Preparation of Electrodeposited Lithium Sulfur Secondary Battery> A sulfur cathode 1 was prepared using the same method as in Example 8, and an HS flat cell (spring pressure 5 kgf) manufactured by Hosen Co., Ltd. (Japan), and two separators (polypropylene porous film (PP porous separator), thickness 15 μm, diameter 16 mm) were prepared.

[0308] Electrodeposited lithium 1 was prepared using the same method as in Comparative Example 9. Subsequently, the electrodeposited lithium 1 was placed on the bottom surface of the HS flat cell. Electrolyte 1 was prepared using the same method as in Example 1. Next, 30 μL of electrolyte 1 was dropped onto the top surface of the HS flat cell. Subsequently, one of the two separators was placed on the top surface of the HS flat cell, and 10 μL of electrolyte 1 was dropped onto it. Subsequently, the other separator was placed on top of that, and 30 μL of the prepared electrolyte 1 was dropped onto the other separator. Next, the sulfur positive electrode 1 was placed on the other separator so as to precisely overlap with the lithium foil placed on the bottom surface of the HS flat cell. Finally, the HS flat cell was sealed to prepare a comparative electrodeposited lithium-sulfur secondary battery.

[0309] (Evaluation of a comparative electrodeposited lithium-sulfur secondary battery) The comparative electrodeposited lithium-sulfur secondary battery was connected to a charge / discharge device (HJ1020mSD8, manufactured by Meiden Hokuto Co., Ltd. (Japan)). Subsequently, a constant current charge / discharge test was performed using the charge / discharge device under the following conditions: discharge rate of 0.1C (current that discharges the theoretical capacity in 10 hours), discharge termination voltage of 1.00V, charge rate of 0.1C (current that charges the theoretical capacity in 10 hours), and charge termination voltage of 3.00V. The theoretical capacity (mAh / g) was calculated by multiplying the amount of sulfur (mg) contained in the positive electrode by 1.672. The discharge capacity of this battery after 100 cycles was 110mAh / g.

[0310] [Example 29] Electrodeposited lithium 2 was prepared using the same method as in Example 27. Electrodeposited lithium sulfur secondary battery 2 was prepared in the same manner as in Comparative Example 10, except that electrodeposited lithium 2 was used instead of electrodeposited lithium 1. When electrodeposited lithium sulfur secondary battery 2 was evaluated in the same manner as in Comparative Example 10, the discharge capacity after 100 cycles was 350 mAh / g, indicating an improvement in cycle stability due to the use of electrodeposited lithium 2.

[0311] [Comparative Example 11] One electrodeposited lithium sheet 1 was prepared using the same method as in Comparative Example 9, and an HS flat cell (spring pressure 5 kgf) manufactured by Hosen Co., Ltd. (Japan) and one separator (polypropylene porous film (PP porous separator), thickness 15 μm, diameter 16 mm) were prepared. In addition, an LFP positive electrode (manufactured by Hosen Co., Ltd., 1.5 mAh / cm²) was prepared. ２ I prepared a 12mm diameter piece.

[0312] One electrodeposited lithium 1 was placed on the bottom surface of the HS flat cell. Electrolyte 1 was prepared using the same method as in Example 1. Next, 25 μL of electrolyte 1 was dropped onto the top surface of the HS flat cell. Subsequently, the separator was placed on the top surface of the HS flat cell, and another 25 μL of electrolyte 1 was dropped onto it. Then, the LFP positive electrode was placed on top of that, precisely overlapping with the lithium foil placed on the bottom surface of the HS flat cell. Finally, the HS flat cell was sealed to produce a lithium-ion secondary battery for comparative evaluation. (Evaluation of the comparative lithium-ion secondary battery) The comparative lithium-ion secondary battery was connected to a charge / discharge device (HJ1020mSD8, manufactured by Meiden Hokuto Co., Ltd. (Japan)). Subsequently, the charge / discharge device was used to achieve a charge / discharge current density of 0.5 mA / cm². ２ A constant current charge-discharge test was performed under constant current, discharge termination voltage of 3.2V, and charge termination voltage of 3.6V. The results are shown in Figure 27. As shown in Figure 27, when one charge-discharge set is considered one cycle, the discharge capacities at the 50th, 100th, 150th, and 200th cycles were 1.40mAh, 1.34mAh, 0.47mAh, and 0.41mAh, respectively, and the capacity decreased rapidly.

[0313] [Example 30] Electrodeposited lithium 2 was prepared using the same method as in Example 27. A metallic lithium-ion secondary battery was prepared using the same method as in Comparative Example 11, except that the prepared electrodeposited lithium 2 was used instead of electrodeposited lithium 1, and the charge-discharge evaluation of the metallic lithium-ion secondary battery was performed. The results are shown in Figure 28. As shown in Figure 28, when one charge-discharge set is considered one cycle, the discharge capacities at the 50th, 100th, 150th, and 200th cycles were 1.36 mAh, 1.30 mAh, 1.28 mAh, and 1.18 mAh, respectively, indicating improved cycle stability.

[0314] [Comparative Example 12] A metallic lithium-ion secondary battery was prepared in the same manner as in Comparative Example 11, except that a circular lithium foil with a diameter of 13 mm (thickness 200 μm, no surface modification) was used instead of electrodeposited lithium 1, and the charge and discharge evaluation of the metallic lithium-ion secondary battery was performed. The results are shown in Figure 29. As shown in Figure 29, when one charge and discharge set was considered as one cycle, the discharge capacities at the 50th and 100th cycles were 1.45 mAh and 1.13 mAh, respectively.

[0315] [Example 31] A surface-modified metallic lithium foil 1 with a diameter of 13 mm was prepared using the same method as in Example 4. A metallic lithium-ion secondary battery was fabricated using the same method as in Comparative Example 12, except that the surface-modified metallic lithium foil 1 was used instead of electrodeposited lithium 1, and the charge and discharge evaluation of the metallic lithium-ion secondary battery was performed. The results are shown in Figure 30. As shown in Figure 30, when one charge and discharge set is considered one cycle, the discharge capacities at the 50th and 100th cycles were 1.36 mAh and 1.24 mAh, respectively, indicating improved cycle stability.

[0316] [Example 32] An HS flat cell (spring pressure 5 kgf) manufactured by Hosen Co., Ltd. (Japan), one circular lithium foil with a diameter of 13 mm (thickness 200 μm, no surface modification), and one separator (polypropylene porous film (PP porous separator), thickness 15 μm, diameter 16 mm) were prepared. In addition, an LFP positive electrode (manufactured by Hosen Co., Ltd., 1.5 mAh / cm²) was prepared. ２A 12 mm diameter diameter

[0317] [Example 33] An HS flat cell (spring pressure 5 kgf) manufactured by Hosen Co., Ltd. (Japan), one circular lithium foil with a diameter of 13 mm (thickness 200 μm, no surface modification), and one separator (polypropylene porous film (PP porous separator), thickness 15 μm, diameter 16 mm) were prepared. In addition, an LFP positive electrode (manufactured by Hosen Co., Ltd., 1.5 mAh / cm²) was prepared. ２ A 12 mm diameter diameter

[0318] [Example 34] An HS flat cell (spring pressure 5 kgf) manufactured by Hosen Co., Ltd. (Japan), copper foil (thickness 15 μm, diameter 14 mm, pre-treated in the same manner as in Comparative Example 9), and one separator (polypropylene porous film (PP porous separator), thickness 15 μm, diameter 16 mm) were prepared. In addition, an LFP positive electrode (manufactured by Hosen Co., Ltd., 1.5 mAh / cm²) was prepared. ２ A flat cell (12 mm in diameter) was prepared. As the electrolyte, 0.25 mg of 6FOP synthesized in Production Example 4 and 187.07 mg of LiFSI were placed in a 1 mL volumetric flask. This was then diluted to 1 mL by dissolving the 6FOP in a solvent made by mixing ethyl methyl carbonate, diethyl carbonate, and HFE in a volume ratio of 1:1:2, and making up the volume. This was used as the electrolyte 10. A copper foil was placed on the bottom surface of the HS flat cell. Next, 25 μL of the electrolyte 10 was dropped onto the top surface of the HS flat cell. Next, the separator was placed on the top surface of the HS flat cell, and another 25 μL of the electrolyte 10 was dropped on top of it. Next, the LFP positive electrode was placed on top of that so as to precisely overlap with the lithium foil placed on the bottom surface of the HS flat cell. Finally, the HS flat cell was sealed to prepare a lithium-ion secondary battery for comparative evaluation. As a result, when one charge-discharge cycle was considered as one cycle, the discharge capacities at the 50th and 100th cycles were 1.35 mAh and 1.28 mAh, respectively, demonstrating good cycle characteristics.

[0319] [Conclusion] From a comparison between Comparative Example 1 and Examples 1 to 3, it can be seen that the lithium metal secondary battery equipped with the electrolyte of the present invention exhibits more stable dissolution and deposition of lithium metal compared to the aforementioned batteries equipped with other electrolytes, resulting in improved energy density and cycle life. Furthermore, in Examples 2 and 3, similar to Example 1, it is considered that the generation and elongation of dendrites are avoided or reduced.

[0320] The results of Example 13 show that the surface-modified metallic lithium foil 1 used in Examples 4-7 corresponds to the negative electrode of the present invention. Furthermore, a comparison between Comparative Example 2 and Examples 4-7 shows that the metallic lithium secondary battery equipped with the negative electrode of the present invention exhibits more stable dissolution and deposition of metallic lithium compared to the aforementioned batteries equipped with other negative electrodes, resulting in improved energy density and cycle life. In addition, it is considered that, similar to Example 1, the generation and elongation of dendrites are avoided or reduced in Examples 4-7.

[0321] A comparison of Comparative Example 3 with Examples 8 and 9 shows that the lithium-sulfur metal secondary battery equipped with the electrolyte or negative electrode of the present invention exhibits more stable dissolution and deposition of lithium metal, resulting in improved energy density and cycle life compared to batteries equipped with other electrolytes and negative electrodes. Furthermore, it is believed that, similar to Example 1, the formation and elongation of dendrites are avoided or reduced in Examples 8 and 9.

[0322] A comparison between Comparative Example 4 and Example 10 shows that the laminate-type metallic lithium-sulfur secondary battery equipped with the negative electrode of the present invention exhibits more stable dissolution and deposition of metallic lithium compared to batteries equipped with other negative electrodes, resulting in improved energy density and cycle life. Furthermore, in Example 10, similar to Example 1, it is believed that the generation and elongation of dendrites are avoided or reduced.

[0323] A comparison between Comparative Example 5 and Example 11 shows that the lithium-ion secondary battery equipped with the negative electrode of the present invention exhibits more stable dissolution and deposition of metallic lithium compared to batteries equipped with other negative electrodes, resulting in improved energy density and cycle life. Furthermore, in Example 11, similar to Example 1, it is believed that the generation and elongation of dendrites are avoided or reduced.

[0324] Furthermore, a comparison between Comparative Example 6 and Examples 12-14 shows that the negative electrode of the present invention can be manufactured by the manufacturing method of the present invention using the modifier of the present invention.

[0325] A comparison of Comparative Example 7 with Examples 15 and 16 shows that the lithium-sulfur secondary battery of the present invention, equipped with the electrolyte or modifier of the present invention and the negative electrode, exhibits more stable dissolution and deposition of metallic lithium, resulting in improved energy density and cycle life compared to batteries equipped with other electrolytes and negative electrodes. Furthermore, it is believed that, similar to Example 1, the generation and elongation of dendrites are avoided or reduced in Examples 15 and 16.

[0326] The same can be said from the comparisons between Comparative Example 3 and Example 17; Comparative Example 8 and Example 18; Comparative Example 4 and Examples 19 and 20; Comparative Example 3 and Examples 21 to 24; Comparative Example 3 and Example 25; Comparative Example 9 and Examples 26 to 28; Comparative Example 10 and Example 29; Comparative Example 11 and Example 30; Comparative Example 12 and Example 31; and Comparative Example 11 and Examples 32 to 34.

[0327] Thus, according to the electrolyte or negative electrode of the present invention, stable dissolution and extraction of metallic lithium (avoidance or reduction of dendrites and dead lithium) is possible in a metallic lithium secondary battery, enabling the simultaneous achievement of high energy density and cycle life.

[0328] Furthermore, the manufacturing method of the present invention makes it possible to manufacture a negative electrode for a lithium metallic secondary battery that enables stable dissolution and extraction of metallic lithium, and provides a lithium metallic secondary battery that can achieve both high energy density and cycle life.

[0329] In this invention, the stable dissolution and deposition of metallic lithium at the negative electrode prevents or reduces the generation and elongation of dendrites, as well as the generation of dead lithium. Therefore, this invention can be used in the manufacture of metallic lithium secondary batteries that achieve both high energy density and long cycle life.

Claims

1. An electrolyte for a lithium metal secondary battery comprising one or more halogenated cyclic phosphate esters shown in the following formula (1), and (i) one or more solvents selected from the group consisting of ester solvents, urethane solvents, ether solvents, amide solvents, ketone solvents, sulfur-containing solvents, nitrile solvents, phosphazene solvents, glycol solvents, and hydrocarbon solvents; or (ii) a solvent containing the solvent shown in (i) and a carbonate solvent. (In the above formula (1), X is a halogen, and R １ ~R ４ Each of these is independently an alkyl group or a hydrogen atom, and n is an integer from 1 to 4. However, if n is an integer from 2 to 4, each R ３ These may be the same group or different groups, and each R ４ These may be the same group or different groups.

2. The electrolyte for a metallic lithium secondary battery according to claim 1, wherein X in formula (1) is F.

3. The electrolyte for a metallic lithium secondary battery according to claim 1, wherein X in formula (1) is Cl or Br.

4. A negative electrode for a lithium-metallic secondary battery having an active material layer containing metallic lithium, wherein a protective film containing one or more halogenated cyclic phosphate esters shown in the following formula (1) is formed on the active material layer. (In the above formula (1), X is a halogen, and R １ ~R ４ Each of these is independently an alkyl group or a hydrogen atom, and n is an integer from 1 to 4. However, if n is an integer from 2 to 4, each R ３ These may be the same group or different groups, and each R ４ These may be the same group or different groups.

5. A negative electrode modifier for a lithium metal secondary battery, containing one or more halogenated cyclic phosphates represented by the following formula (1). (In the formula (1), X is a halogen, and R １ ~R ４ are each independently an alkyl group or hydrogen, and n is an integer of 1 to 4. However, when n is an integer of 2 to 4, each R ３ may be the same group or different groups, and each R ４ may be the same group or different groups.) 6. A metallic lithium secondary battery comprising the electrolyte for metallic lithium secondary batteries according to any one of claims 1 to 3.

7. The metallic lithium secondary battery according to claim 6, wherein the metallic lithium secondary battery is a metallic lithium sulfur secondary battery, a metallic lithium iron phosphate lithium secondary battery, a metallic lithium nickel manganese cobalt lithium secondary battery, a metallic lithium cobalt oxide lithium secondary battery, a metallic lithium air secondary battery, a metallic lithium nickel cobalt aluminum oxide lithium secondary battery, a metallic lithium manganese oxide lithium secondary battery, a metallic lithium nickel manganese oxide lithium secondary battery, or a metallic lithium nickel oxide lithium secondary battery.

8. A metallic lithium secondary battery comprising the negative electrode for a metallic lithium secondary battery as described in claim 4.

9. The metallic lithium secondary battery according to claim 8, wherein the metallic lithium secondary battery is a metallic lithium sulfur secondary battery, a metallic lithium iron phosphate lithium secondary battery, a metallic lithium nickel manganese cobalt lithium secondary battery, a metallic lithium cobalt oxide lithium secondary battery, a metallic lithium air secondary battery, a metallic lithium nickel cobalt aluminum oxide lithium secondary battery, a metallic lithium manganese oxide lithium secondary battery, a metallic lithium nickel manganese oxide lithium secondary battery, or a metallic lithium nickel oxide lithium secondary battery.

10. A method for manufacturing a negative electrode for a metallic lithium secondary battery, comprising the step of forming a protective film on an active material layer containing metallic lithium by exposing the active material layer to one or more halogenated cyclic phosphate esters shown in the following formula (1). (In the above formula (1), X is a halogen, and R １ ~R ４ Each of these is independently an alkyl group or a hydrogen atom, and n is an integer from 1 to 4. However, if n is an integer from 2 to 4, each R ３ These may be the same group or different groups, and each R ４ These may be the same group or different groups.

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