阅读说明：本技术 用于形成锂金属和无机材料复合薄膜的方法、以及使用该方法对用于锂二次电池的负极进行预锂化的方法 (Method for forming lithium metal and inorganic material composite thin film, and method for prelithiating negative electrode for lithium secondary battery using the same ) 是由 禹相昱 金銀卿 姜允雅 宋俊赫 蔡午秉 于 2018-08-03 设计创作，主要内容包括：本发明涉及一种对负极进行预锂化的方法,所述方法包括：第一步骤,将无机材料粉末引入熔融锂中以形成混合物；第二步骤,挤出并冷却混合物,以制备厚度为100-200μm的锂金属-无机材料复合带；第三步骤,轧制所述锂金属-无机材料复合带,以制备锂金属-无机材料复合薄膜；和第四步骤,将所述锂金属-无机材料复合薄膜置于负极表面上以形成锂金属-无机材料复合层。在本发明中,锂金属-无机材料复合薄膜与负极接合,从而使锂暴露在空气中的时间最小化,因此,本发明具有以下效果：解决了在传统的锂金属-无机材料混合物的施加中,由于锂金属的高反应性而导致在施加混合物浆料期间锂劣化的问题。利用本发明提供的预锂化的方法制造的用于二次电池的负极具有改善的初始不可逆性,并且使用这种用于二次电池的负极制造的二次电池具有优异的充电和放电效率。(The invention relates to a method for prelithiation of a negative electrode, comprising: a first step of introducing inorganic material powder into molten lithium to form a mixture; a second step of extruding and cooling the mixture to prepare a lithium metal-inorganic material composite tape having a thickness of 100-; a third step of rolling the lithium metal-inorganic material composite tape to prepare a lithium metal-inorganic material composite film; and a fourth step of disposing the lithium metal-inorganic material composite film on a surface of the negative electrode to form a lithium metal-inorganic material composite layer. In the present invention, the lithium metal-inorganic material composite thin film is joined to the negative electrode, thereby minimizing the time of exposure of lithium to air, and therefore, the present invention has the following effects: the problem of lithium degradation during application of a mixture slurry due to the high reactivity of lithium metal in the application of conventional lithium metal-inorganic material mixtures is solved. The anode for a secondary battery manufactured by the method for prelithiation provided by the present invention has improved initial irreversibility, and the secondary battery manufactured by using the anode for a secondary battery has excellent charging and discharging efficiency.)

1. A method of prelithiating an anode, the method comprising: a first step of adding an inorganic powder to molten lithium to form a mixture;

A second step of extruding the mixture and cooling the mixture to prepare a lithium metal-inorganic composite tape having a thickness of 100-;

A third step of rolling the lithium metal-inorganic composite tape to prepare a lithium metal-inorganic composite film; and

A fourth step of depositing the lithium metal-inorganic composite film on a surface of the negative electrode to form a lithium metal-inorganic composite layer.

2. The method according to claim 1, wherein the thickness of the lithium metal-inorganic composite layer is 1-50 μm.

3. The method of claim 1, wherein the inorganic powder comprises a material selected from the group consisting of aluminum oxide (Al)₂O₃) Titanium dioxide (TiO)₂) Zirconium dioxide (ZrO)₂) Silicon dioxide (SiO)₂) Tin oxide (SnO)₂) Cerium oxide (CeO)₂) Magnesium oxide (MgO), calcium oxide (CaO), and yttrium oxide (Y)₂O₃) At least one of the group consisting of.

4. The method of claim 1, wherein a mixing ratio of the molten lithium and the inorganic powder is 70-85 vol% of the molten lithium and 15-30 vol% of the inorganic powder.

5. The method of claim 1, wherein a binder is mixed with the molten lithium in addition to the inorganic powder.

6. The method of claim 1, wherein the lithium metal-inorganic composite layer no longer retains lithium in metallic form after an initial activation charge.

7. The method of claim 1, wherein the inorganic powder has a particle size of 0.1-10 μm.

8. The method of claim 1, wherein the negative electrode comprises silicon oxide.

9. An anode for a secondary battery, the anode being manufactured by applying the prelithiation method according to claim 1.

10. A secondary battery comprising the anode according to claim 9.

Technical Field

The present application claims priority from korean patent application No. 10-2017-0101380, filed on 10.8.2017 and korean patent application No. 10-2018-0087814, filed on 27.7.2018, the contents of which are incorporated herein by reference.

The present invention relates to a method of prelithiating an anode for a secondary battery, and more particularly, to a method of prelithiating by fabricating a lithium metal-inorganic composite thin film using molten lithium metal and powder-type inorganic material particles and then bonding the composite thin film to the anode.

Background

As the energy price rises due to exhaustion of fossil fuels and concern about environmental pollution increases, the demand for environment-friendly alternative energy becomes an indispensable factor for future life. In particular, as the technical development and demand for mobile devices increase, the demand for secondary batteries as energy sources is rapidly increasing.

Typically, in terms of the shape of a battery, there is a high demand for prismatic secondary batteries and pouch-type secondary batteries that can be applied to products such as mobile phones having a thin thickness. In terms of the material of the battery, there is a high demand for lithium secondary batteries, such as lithium ion batteries and lithium ion polymer batteries, having high energy density, discharge voltage, and output stability.

In general, to manufacture a secondary battery, first, a positive electrode and a negative electrode are formed by applying an active material to the surface of a current collector, and then a separator is interposed therebetween, thereby manufacturing an electrode assembly, and then the electrode assembly is mounted in a cylindrical or rectangular metal can or a pouch-type case made of an aluminum laminate sheet, and a liquid electrolyte is injected or impregnated into the electrode assembly or a solid electrolyte is used to manufacture the secondary battery.

As an anode active material of a lithium secondary battery, various types of carbon-based materials have been applied, including artificial graphite, natural graphite, and hard carbon capable of intercalating and desorbing lithium. Graphite such as artificial graphite or natural graphite in the carbon-based material has a low discharge voltage of 0.1V compared to lithium, and a battery using graphite as a negative electrode active material exhibits a high discharge voltage of 3.6V, which is advantageous in terms of energy density of a lithium battery and ensures a long life of a lithium secondary battery with excellent reversibility, and thus such a battery is most widely used.

however, when the electrode plate is manufactured using graphite as an active material, the density of the electrode plate decreases, and the capacity may become low in terms of energy density per unit volume of the electrode plate, which is a problem. In addition, since a side reaction may occur between graphite and an organic electrolyte at a high discharge voltage, there is a risk of fire or explosion due to malfunction or overcharge of a battery.

To solve this problem, an oxide negative active material has recently been developed. Metal-based active materials such as Si or Sn have been proposed as materials that can exhibit high capacity and can replace lithium metal. Among them, Si is attracting attention because of its low cost and high capacity (4200 mAh/g).

However, when a silicon-based anode active material is used, the initial irreversible capacity becomes large. During charge and discharge of the lithium secondary battery, lithium released from the positive electrode is inserted into the negative electrode at the time of charge, and released from the negative electrode and returned to the positive electrode at the time of discharge. In the case of a silicon negative electrode active material, a large amount of lithium inserted into a negative electrode does not return to a positive electrode at the time of initial charge, and thus an initial irreversible capacity becomes large. When the initial irreversible capacity increases, there arises a problem that the battery capacity and cycle rapidly decrease.

In order to solve the above problems, a method of prelithiating a silicon oxide anode including a silicon-based anode active material is known. As one of the prelithiation methods, there are known methods including a method of manufacturing an electrode by lithiating a negative electrode active material by a physicochemical method and a method of electrochemically prelithiating a negative electrode.

Conventional physicochemical methods involve fire and explosion risks due to environmental factors that are conducted at high temperatures. The conventional electrochemical method cannot uniformly control a uniform irreversible capacity and increases production costs.

Us patent publication No. 2015-0357628 discloses a technique of coating a negative electrode with a lithium-ceramic extruded product in which ceramic particles are mixed with molten lithium to improve the electrode efficiency of a negative electrode active material having a high specific capacity, but all of the above processes must be performed under an inert gas atmosphere due to the high reactivity of lithium metal, and thus these processes are not easily performed, which is a disadvantage.

Therefore, it is necessary to develop a technology for improving initial irreversibility of a battery and improving safety of the battery by prelithiating a negative electrode having a high capacity using a relatively simple method.

Disclosure of Invention

Technical problem

The present invention is designed to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a prelithiation method for improving initial irreversibility of a negative electrode having a high capacity, which enables easy handling of lithium metal while simplifying a process.

It is another object of the present invention to provide a prelithiation method for improving the safety of a secondary battery.

Technical scheme

the invention provides a method for prelithiation of a negative electrode, the method comprising: a first step of adding an inorganic powder to molten lithium to form a mixture; a second step of extruding the mixture and cooling the mixture to prepare a lithium metal-inorganic composite tape having a thickness of 100-; a third step of rolling the lithium metal-inorganic composite tape to prepare a lithium metal-inorganic composite film; and a fourth step of depositing a lithium metal-inorganic composite film on the surface of the negative electrode to form a lithium metal-inorganic composite layer.

According to a preferred embodiment of the present invention, the thickness of the lithium metal-inorganic composite thin film is 1 to 50 μm.

According to a preferred embodiment of the present invention, the inorganic powder may be selected from the group consisting of alumina (Al)₂O₃) Titanium dioxide (TiO)₂) Zirconium dioxide (ZrO)₂) Silicon dioxide (SiO)₂) Tin oxide (SnO)₂) Cerium oxide (CeO)₂) Magnesium oxide (MgO), calcium oxide (CaO), and yttrium oxide (Y)₂O₃) One or more of the group consisting of.

According to a preferred embodiment of the present invention, the mixing ratio of the molten lithium and the inorganic powder is 70-85 vol% of lithium and 15-30 vol% of the inorganic substance.

According to a preferred embodiment of the present invention, the particle size of the inorganic powder is 0.1 to 10 μm.

According to a preferred embodiment of the present invention, a binder may be further added to the molten lithium solution in addition to the inorganic powder.

According to a preferred embodiment of the present invention, the lithium metal-inorganic composite layer no longer retains lithium in metallic form after the initial activation charging.

According to a preferred embodiment of the present invention, the negative electrode may include silicon oxide.

The present invention also provides an anode for a secondary battery manufactured by applying the prelithiation method and a secondary battery including the same.

Advantageous effects

According to the present invention, since the lithium metal-inorganic composite thin film is combined with the negative electrode, the time of exposure of lithium to the atmosphere is minimized, and thus, when the conventional lithium metal-inorganic material mixture is applied, the problem of deterioration of lithium due to high reactivity of lithium metal in the process of applying the mixture slurry is improved.

The anode manufactured by the prelithiation method of the present invention has improved initial irreversibility, and a secondary battery manufactured using such an anode for a secondary battery has excellent charge/discharge efficiency.

In the negative electrode having the lithium metal-inorganic composite layer of the present invention, lithium is inserted into the negative electrode active material layer by pre-lithiation so that the inorganic material remains in the composite layer, thereby protecting the surface of the negative electrode and improving the safety of the battery.

Drawings

Fig. 1 is a schematic view schematically showing the manufacturing process of the first to third steps of the present invention.

Fig. 2 is a schematic view showing a manufacturing process of the fourth step of the present invention.

Fig. 3 is a diagram illustrating a lithium metal-inorganic composite layer and prelithiation formed on an electrode by the fourth step of the present invention.

Fig. 4 is a diagram illustrating an inorganic layer remaining after lithium is absorbed into an electrode from a lithium metal-inorganic composite layer by prelithiation according to the present invention.

Detailed Description

Hereinafter, the present invention will be described in detail. The present invention is not limited by the following examples and test examples. The embodiment according to the present invention may be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiment described below. Embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art.

The prelithiation of an anode for a secondary battery according to the present invention includes: a first step of adding an inorganic powder to molten lithium to form a mixture; a second step of extruding the mixture and cooling the mixture to prepare a lithium metal-inorganic composite tape having a thickness of 100-; a third step of rolling the lithium metal-inorganic composite tape to prepare a lithium metal-inorganic composite film; and a fourth step of depositing a lithium metal-inorganic composite film on the surface of the negative electrode to form a lithium metal-inorganic composite layer.

The negative electrode material of a lithium ion battery has a disadvantage of large initial irreversibility. In particular, Si-based materials have large volume changes and surface side reactions, so that the large amount of lithium used during charging cannot be released any more upon discharge. To improve this initial irreversibility, if pre-lithiation is performed before manufacturing the battery assembly, side reactions occur in advance before the first charge. Therefore, when the battery assembly is actually formed and charged/discharged, the first cycle is performed with reduced irreversibility, thereby reducing initial irreversibility.

In the present invention, as shown in fig. 1, a lithium metal-inorganic composite layer is formed on the surface of a SiO or SiO-containing graphite electrode having large initial irreversibility, and a lithium metal portion in the lithium metal-inorganic composite layer is used for prelithiation to reduce initial irreversibility, and an inorganic material remaining after prelithiation contributes to improvement of safety of the negative electrode.

In particular, the manufacturing process of the conventional art of coating the negative electrode with slurry generated by mixing molten lithium with an inorganic material is difficult due to the high reactivity of lithium metal, and lithium metal may be deteriorated during application. However, according to the present invention, since the lithium metal-inorganic composite tape is manufactured, and the tape is rolled to form a thin film, and the thin film is combined with the negative electrode, there is an advantage in that the time for exposing lithium to air can be minimized.

The first step of the present invention is to add an inorganic powder to the molten lithium to form a mixture. At this time, the melting temperature of lithium is 180 ℃ to 400 ℃, more preferably 190 ℃ to 250 ℃. If the melting temperature of lithium exceeds the upper limit value, lithium becomes too reactive, and if the melting temperature of lithium is lower than the lower limit value, lithium does not liquefy.

According to a preferred embodiment of the present invention, the inorganic powder may be selected from the group consisting of alumina (Al)₂O₃) Titanium dioxide (TiO)₂) Zirconium dioxide (ZrO)₂) Silicon dioxide (SiO)₂) Tin oxide (SnO)₂) Cerium oxide (CeO)₂) Magnesium oxide (MgO), calcium oxide (CaO), and yttrium oxide (Y)₂O₃) One or more of the group consisting of. Among them, alumina is most preferable. According to a preferred embodiment of the invention, the particle size of the inorganic powder is 0.1-10 μm, more preferably 0.3-5 μm, most preferably 0.5-1 μm. If the particle diameter of the inorganic powder exceeds 10 μm, it may not be well dispersed in the molten lithium, which is not preferable.

According to a preferred embodiment of the present invention, the proportion of the inorganic powder injected into the molten lithium is 70 to 85% by volume of lithium and 15 to 30% by volume of the inorganic substance. When this mixing ratio is satisfied, an effect of improving the safety of the pre-lithiation and the negative electrode is exhibited.

According to a preferred embodiment of the present invention, the lithium metal-inorganic composite layer can be prevented from being separated from the anode by further adding a binder to the molten lithium solution in addition to the inorganic powder. As the binder, a commonly used binder such as PVDF and SBR-based binders may be used. In addition, Polyacrylic acid (PAA), Carboxymethyl cellulose (CMC), and Polyimide (Polyimide) binders may be used.

The preferred content of the binder added to the molten lithium is 1 to 10 parts by weight with respect to 100 parts by weight of the inorganic powder to be added together. If it is less than 1 part by weight, the lithium metal-inorganic composite layer may be separated from the anode, and if it exceeds 10 parts by weight, it is not preferable from the viewpoint of prelithiation.

In the second step of the present invention, the mixture is extruded and then cooled to prepare a lithium metal-inorganic composite tape. The mixture may be extruded by known methods. After extrusion, the mixture was cooled to room temperature to form a lithium metal-inorganic composite tape having a thickness of 100-200 μm. The thickness of the lithium metal-inorganic composite tape may be adjusted according to purposes. If the thickness of the lithium metal-inorganic composite tape is less than 100 μm, it is difficult to manufacture the lithium metal-inorganic composite tape by an extrusion method. When the thickness is more than 200 μm, there are disadvantages in that: during the rolling process for thinning the lithium metal-inorganic composite tape prepared by extrusion, energy and manufacturing time are increased.

The third step of the present invention is to prepare a lithium metal-inorganic composite film by rolling a lithium metal-inorganic composite tape. The method of rolling the lithium metal-inorganic composite tape is generally a method of rolling a metal into a thin film form.

According to a preferred embodiment of the present invention, the thickness of the rolled lithium metal-inorganic composite thin film is 1 to 50 μm. The thickness is more preferably 1 to 30 μm, most preferably 5 to 10 μm. When the thickness of the lithium metal-inorganic composite thin film is in the range of 1-50 μm, the lithium metal-inorganic composite layer exhibits the effect of improving the pre-lithiation and the safety of the battery.

In general, it is difficult to apply a slurry of lithium metal-inorganic compound to the negative electrode. However, the present invention is characterized in that a lithium metal-inorganic composite film is formed through the second and third steps and is combined with an anode, thereby forming a lithium metal-inorganic composite layer on the anode in a relatively easy manner.

in the fourth step of the present invention, a lithium metal-inorganic composite film is deposited on the surface of the anode to form a lithium metal-inorganic composite layer. The lithium metal-inorganic composite film was placed on the negative electrode, and then laminated by heating and pressurizing.

According to a preferred embodiment of the present invention, the lithium metal-inorganic composite layer no longer retains lithium in metallic form after the initial activation charging.

The present invention also provides a secondary battery including the anode manufactured by the above method.

The secondary battery according to the present invention includes an electrode assembly in which two electrodes of different polarities are stacked in a state of being separated from each other by a separator. The electrode assembly includes: a positive electrode containing a positive electrode active material; a negative electrode containing a negative electrode active material; and a separator.

Specifically, the positive electrode may be manufactured, for example, by applying a mixture of a positive electrode active material, a conductive material, and a binder onto a positive electrode current collector and then drying. If necessary, a filler may be further added to the mixture.

The positive electrode active material according to the present invention may be mixed with a compound using a lithium intercalation material (lithium intercalation material) as its main component, such as: layered compounds, such as lithium cobalt oxide (LiCoO)₂) Lithium nickel oxide (LiNiO)₂) Or a compound substituted with one or more transition metals; lithium manganese oxides, e.g. Li_1+xMn_2-xO₄(where x is between 0 and 33), LiMnO₃、LiMn₂O₃And LiMnO₂(ii) a Lithium copper oxide (Li)₂CuO₂) (ii) a Vanadium oxides, such as LiV₃O₈、LiFe₃O₄、V₂O₅And Cu₂V₂O₇(ii) a From LiNi_1-xM_xO₂(here, M ═ Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x ═ 0.01 to 0.3) lithium nickel oxide (lithiated nickel oxide); from LiMn_2-xM_xO₂(where M is Co, Ni, Fe, Cr, Zn or Ta, and x is 0.01 to 0.1) or Li₂Mn₃MO₈(here, M ═ Fe, Co, Ni, Cu, or Zn); LiMn₂O₄Wherein Li is partially substituted with an alkaline earth metal ion; a disulfide compound; and Fe₂(MoO₄)₃Or a composite oxide formed from a combination thereof.

The positive electrode current collector generally has a thickness of 3 to 500 micrometers. The positive electrode current collector is not particularly limited so long as it has high conductivity and does not cause chemical changes in the battery. Examples of the positive electrode current collector include stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel whose surface has been treated with carbon, nickel, titanium, silver, or the like. The current collector may have fine irregularities on the surface thereof to improve the adhesion of the positive electrode active material, and may take various forms such as a film, a sheet, a foil, a mesh, a porous body, a foam, and a non-woven fabric.

The conductive material is generally added in an amount of 1 to 50% by weight based on the total weight of the mixture including the cathode active material. Such conductive materials are not particularly limited as long as they have conductivity and do not cause chemical changes in the battery, and examples of the conductive materials include: graphite, such as natural graphite and artificial graphite; carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride powder, aluminum powder, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives; and the like.

The binder is added in an amount of 1 to 50% by weight based on the total weight of the mixture including the cathode active material, as a component contributing to the binding between the active material and the conductive material and to the current collector. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, various copolymers, and the like.

The filler is optionally used as a component for suppressing the expansion of the positive electrode, and the filler is not particularly limited as long as it is a fibrous material and does not cause chemical changes in the battery. Examples of fillers include olefin polymers such as polyethylene and polypropylene; fibrous materials such as glass fibers and carbon fibers.

In addition, the anode may be formed by coating an anode active material on an anode current collector and drying the anode active material. The negative electrode may further include the above-described components.

The negative electrode current collector is generally fabricated to have a thickness of 3 to 500 micrometers. The anode current collector is not particularly limited as long as it has conductivity without causing chemical changes in the battery, and examples of the anode include copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel whose surface has been treated with carbon, nickel, titanium, silver or the like, aluminum-cadmium alloy, or the like. Further, the anode current collector may be formed with fine unevenness on the surface to enhance the adhesive force of the anode active material, similar to the cathode current collector, and it may be used in various forms such as a film, a sheet, a foil, a mesh, a porous body, a foam, and a non-woven fabric.

As the anode active material of the present invention, a material capable of reversibly adsorbing/releasing lithium ions, such as silicon (Si) and tin, may be used. As long as such a material is used, the effect of the present invention can be exerted in any of a composite, an alloy, a compound, a solid solution, and a composite anode active material including a silicon-containing material and a tin-containing material. As the silicon-containing material, Si or SiO can be used_x(0.5<x<2.0) or SiO is substituted with at least one element selected from the group consisting of B, Mg, Ni, Ti, Mo, Co, Ca, Cr, Cu, Fe, Mn, Nb, Ta, V, W, Zn, C, N, and Sn_xOr a portion of Si contained therein, or a solid solution.

These materials may constitute the anode active material alone, or may constitute the anode active material by a plurality of materials. Examples of the anode active material constituted by a plurality of materials include a compound containing Si, oxygen, and nitrogen, a composite of a plurality of compounds containing Si and oxygen and having different composition ratios of Si and oxygen, or the like. Wherein, SiO_x(0.5<x<2.0) is preferable because its discharge capacity density is large and the expansion ratio at the time of filling is smaller than that of Si.

The silicon oxide negative electrode is a negative electrode using silicon and its oxide as a main material to increase the capacity density of a negative electrode using an existing carbon material such as graphite. The theoretical capacity density of silicon oxide is 4200mAh/g, which is much higher than the theoretical capacity density 372mAh/g of the carbon material, and the silicon oxide can be suitably used as a negative electrode of a secondary battery. However, since the silicon oxide negative electrode has poor shape stability, the initial irreversible capacity is large, and there is a risk of reduction in electrode capacity or destruction of the battery balance, a pre-lithiation treatment as in the present invention is required.

As the separator for insulating the two electrodes between the positive electrode and the negative electrode, a well-known polyolefin separator or a composite separator in which organic and inorganic composite layers are formed on an olefin-based material may be used, and the present invention is not limited to these examples.

The electrolyte injected into the secondary battery is a lithium salt-containing non-aqueous electrolyte, which is composed of a non-aqueous electrolyte and lithium. As the nonaqueous electrolyte, a nonaqueous electrolyte, an organic solid electrolyte, an inorganic solid electrolyte, and the like are used.

Examples of the non-aqueous electrolyte include N-methyl-2-pyrrolidone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ -butyrolactone, 1, 2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1, 3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphotriester, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1, 3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ether, methyl pyrophosphate, ethyl propionate, and the like.

Examples of the organic solid electrolyte include polymer electrolytes such as polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate ester polymers, polylysine (aggregation lysine), polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, polymers containing ionic dissociation groups, and the like.

Examples of the inorganic solid electrolyte include nitrides, halides and sulfates of Li, such as Li₃N、LiI、Li₅NI₂、Li₃N-LiI-LiOH、LiSiO₄、LiSiO₄-LiI-LiOH、Li₂SiS₃、Li₄SiO₄、Li₄SiO₄-LiI-LiOH, and Li₃PO₄-Li₂S-SiS₂。

The lithium salt is a substance soluble in the nonaqueous electrolyte. Examples of the lithium salt include: LiCl, LiBr, LiI, LiClO₄、LiBF₄、LiB₁₀Cl₁₀、LiPF₆、LiCF₃SO₃、LiCF₃CO₂、LiAsF₆、LiSbF₆、LiAlCl₄、CH₃SO₃Li、CF₃SO₃Li、(CF₃SO₂)₂NLi, lithium chloroborane, lithium lower aliphatic carboxylates, lithium 4-phenylboronate, imides, and the like.

To improve charge/discharge characteristics, flame retardancy, and the like, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, N-ethylene glycol dimethyl ether (glyme), hexaphosphoric triamide, nitrobenzene derivatives, sulfur, quinonimine dyes, N-substituted oxazolidinones, N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, aluminum trichloride, and the like may be added to the nonaqueous electrolyte. In some cases, a halogen-containing solvent such as carbon tetrachloride or trifluoroethylene may be further added in order to impart incombustibility, or carbon dioxide gas may be further added in order to improve high-temperature storage characteristics.

Hereinafter, the present invention will be described in more detail by the following examples. However, the following examples and test examples are provided to illustrate the present invention, and the scope of the present invention is not limited by these examples and test examples.