Electrochemical cell

Abstract

The present application relates to a high energy density electrochemical cell having notably enhanced life characteristics by effectively inhibiting side reactions at the interface between lithium metal and a solid electrolyte. The present application comprises: a negative electrode comprising lithium metal; a positive electrode; and a solid electrolyte positioned between the negative electrode and the positive electrode. The solid electrolyte comprises: a first ion conductor which is a complex hydride comprising hydride-based complex anions; and a second ion conductor comprising a sulfur compound.

Description

Electrochemical cell The present invention relates to an electrochemical cell, and more particularly, to a high-energy density electrochemical cell in which side reactions are effectively suppressed at the interface between lithium metal and a solid electrolyte, thereby significantly improving life characteristics. Electrochemical cells using solid electrolytes are one of the most promising candidates to solve the inherent shortcomings of lithium-ion batteries using conventional liquid-based electrolytes, such as electrolyte leakage, flammability, and limited energy density. The electrolyte, one of the three key components of an electrochemical cell, must have ionic conductivity and electrochemical stability with the electrodes. In particular, when lithium metal is used as an anode for designing a high-energy density battery, there is a disadvantage in that problems occur due to side reactions such as increased interfacial resistance and dendrite formation due to direct contact with the solid electrolyte and lithium metal, which ultimately reduces the performance and lifespan of the battery. Therefore, there is a need to develop a new battery that can solve the above problems. To solve the above problems, the present invention seeks to provide an electrochemical cell capable of suppressing side reactions with lithium metal. However, the problems that the present invention seeks to solve are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below. A first aspect of the present invention provides an electrochemical cell comprising: a cathode comprising lithium metal; a cathode; and a solid electrolyte positioned between the cathode and the cathode, wherein the solid electrolyte comprises a first ion conductor that is a complex hydride comprising a hydride-based complex anion and a second ion conductor comprising a sulfur compound. An electrochemical cell according to one embodiment of the present invention has an advantage in that the solid electrolyte positioned between the cathode and the anode including lithium metal includes a first ion conductor that is a hydride and a second ion conductor including a sulfur compound, thereby effectively suppressing side reactions at the interface between the solid electrolyte and the lithium metal cathode, thereby significantly improving charge / discharge characteristics and cycle life characteristics. In addition, since it includes a solid electrolyte that includes lithium metal as an anode and has improved interfacial stability with the lithium metal anode, it is possible to provide an electrochemical cell with significantly improved high energy density, high output, and stability. Figure 1 is a schematic diagram showing an electrochemical cell according to one embodiment. Figure 2 is a schematic diagram showing an electrochemical cell manufactured according to another embodiment. Figure 3 is a drawing comparing charge / discharge curves for each of the electrochemical cells manufactured according to Comparative Example 1, Example 1, and Example 2. FIG. 4 is a drawing comparing the coulombic efficiency and life characteristics of electrochemical cells manufactured according to Comparative Example 1, Example 1, and Example 2, respectively. Below, with reference to the attached drawings, embodiments of the present invention are described in detail so that those with ordinary skill in the art can easily practice the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein. In addition, in order to clearly describe the present invention in the drawings, parts that are not related to the description are omitted, and similar parts are assigned similar drawing reference numerals throughout the specification. Throughout this specification, when it is said that an element is “on” another element, this includes not only cases where the element is in contact with the other element, but also cases where there is another element between the two elements. Throughout this specification, when a part is said to “include” a component, this does not mean to exclude other components, but rather to include other components, unless otherwise specifically stated. The terms “about,” “substantially,” etc., used throughout this specification are used to mean at or near the numerical values ​​indicated when manufacturing and material tolerances inherent in the meanings stated, and are used to prevent unscrupulous infringers from unfairly exploiting disclosures that contain precise or absolute values ​​to aid understanding of the disclosure. The terms “step of doing” or “step of” used throughout this specification do not mean “step for.” Throughout this specification, the term “combination(s) thereof” included in the expressions in the Makushi format means one or more mixtures or combinations selected from the group consisting of the components described in the Makushi format, and means including one or more selected from the group consisting of said components. Throughout this specification, references to “A and / or B” mean “A or B, or A and B.” Hereinafter, implementation examples and embodiments of the present invention will be described in detail with reference to the attached drawings. However, the present invention may not be limited to these implementation examples and embodiments and drawings. An electrochemical cell according to the first aspect of the present invention comprises: a cathode comprising lithium metal; an anode; and a solid electrolyte positioned between the cathode and the anode, wherein the solid electrolyte comprises a first ion conductor which is a complex hydride comprising a hydride-based complex anion and a second ion conductor comprising a sulfur compound. Here, the complex hydride may be an ionic conductor having ionic conductivity by including a complex ion containing hydrogen, and the term "complex hydride" may be named as "complex hydride" or "composite metal hydride". Specifically, lithium metal has a large electric capacity per unit weight, so it is possible to implement a high-capacity battery by using it as a cathode. However, lithium metal has a high reactivity with organic electrolytes based on organic solvents, so its use is limited. Accordingly, research is being conducted on an all-solid-state battery that can achieve high capacity and high voltage by using lithium metal in a battery that uses solid electrolytes such as oxide-based solid electrolytes and sulfide-based solid electrolytes, which have relatively advantageous interface control compared to batteries that use existing organic electrolytes. However, due to direct contact between lithium metal and the existing solid electrolyte, not only does the resistance at the interface between the lithium metal and the solid electrolyte increase, but there is also a problem that the performance and lifespan of the battery deteriorate due to side reactions occurring at the interface. On the other hand, the electrochemical cell of the present invention includes a solid electrolyte including a first ion conductor and a second ion conductor including a sulfur compound as a starting material in addition to a negative electrode including lithium metal, so that side reactions at the interface with the lithium metal can be effectively suppressed, and thereby charge / discharge characteristics and life characteristics can be significantly improved, and an electrochemical cell having high energy density, high output, and significantly improved stability can be provided. In one embodiment, the solid electrolyte positioned between the anode and the cathode may include a first ion conductor that is a complex hydride including a hydride-based complex anion and a second ion conductor that includes a sulfur compound. As a specific example, the first ion conductor is B 6 H 6 2- , B 10 H 10 2- , B 11 H 11 2- , B 12 H 12 2- , CB 9 H 10 - , CB10 H 11 - and CB 11 H 12 - It may be a hydride containing one or more hydride-based complex ions selected from among. At this time, the cation included in the first ion conductor includes a cation of an alkali metal or an alkaline earth metal, and the cation may be one or more cations selected from among Na, Li, Mg, Ca, K, and Cs, and specifically, may be a cation of Li or Na, and more specifically, may be a Li cation. As an advantageous example, the first ion conductor may include two or more different types of initiating agents, and specifically, the first ion conductor may be CB. 9 H 10 - First stage hydrocarbons and CB including 11 H 12 - It may include a second hydride comprising: Here, the molar ratio of the first complex hydride to the second complex hydride included in the first ion conductor may be 1:9 to 9:1, or may be 3:7 to 7:3. As described above, since the first ion conductor includes two or more different types of initiating agents, the side reaction with the negative electrode including lithium metal can be effectively suppressed due to the synergistic effect with the second ion conductor described below. In one embodiment, the second ion conductor may include a sulfur compound represented by the following chemical formula 1. (chemical formula 1) L a M b P c S d X e (In Chemical Formula 1), L is an alkali metal, M includes at least one of B, Al, Ga, In, Si, Ge, Sn, Pb, As, Sb, Bi, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, Ta, and W, X includes at least one of F, Cl, Br, I, and O, 0 <a≤12, 0≤b≤6, 0≤c≤6, 0<d≤12, 0≤e≤9) The second ion conductor represented by chemical formula 1 may be a sulfide-based solid electrolyte, for example, Li 6 PS 5 Cl, Li 2 SP 2 S 5 , Li 6 PS 5 Br, Li 7 P 3 S 11 , Li 3 PS 4 , Li 10 GeP 2 S 12 , Thio-LISICON(Li 3.25 Ge 0.25 P 0.75 S 4 ), Li 2 SP 2 S 5 -LiCl, Li 2 S-SiS 2 , LiI-Li 2 S-SiS 2 , LiI-Li 2 SP 2 S 5 , LiI-Li 2 SP 2 O 5 , LiILi 3 PO 4 -P 2 S 5 , LiI-Li 2 SB 2 S 3 , Li 3 PO 4 -Li 2 S-Si2 S, Li 3 PO 4 -Li 2 S-SiS 2 , LiPO 4 -Li 2 S-SiS, Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 or a mixture thereof, but the present invention is not limited thereby. Additionally, it goes without saying that the solid electrolyte may further include a third ion conductor that is different independently from the first ion conductor and the second ion conductor described above. For example, the third ion conductor may be an oxide-based solid electrolyte and / or an organic solid electrolyte known in the art. As a specific example, the oxide-based solid electrolyte may include LiPON (lithium phosphorous oxynitiride), Perovskite, NASICON (Na-super ionic conductor), LISICON (lithium super ionic conductor), Garnet (LLZO), etc. In addition, the organic solid electrolyte may include a polyether polymer, a polycarbonate polymer, an acrylate polymer, a polysiloxane polymer, a phosphazene polymer, polyethylene oxide, a polyethylene derivative, an alkylene oxide derivative, a phosphoric acid ester polymer, polyaziridine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, a polymer containing an ionic dissociative group, and the like, and as a polymer resin, a branched copolymer, a comb-like polymer, and a cross-linked polymer resin in which an amorphous polymer such as PMMA, polycarbonate, polysiloxane, and / or phosphazene is copolymerized as a comonomer on a PEO (polyethyleneoxide) main chain may be included, but is not limited thereto. In one embodiment, the solid electrolyte including the first ion conductor and the second ion conductor described above may be a single layer or a laminate. Here, the term "monolayer" refers to a layered structure in the form of a membrane or film made of one layer, and the term "laminated body" refers to a structure in which two or more layers are laminated. At this time, the monolayer may include the mixed first ion conductor and second ion conductor dispersed therein, and the laminate may include the first ion conductor and the second ion conductor dispersed therein in one or more layers, or a plurality of independent layers each including the first ion conductor and the second ion conductor may be laminated. The thickness of the solid electrolyte, which is a single layer or a laminate, can be selected according to the characteristics of the intended battery, and for example, can be 0.1 to 1000 μm, 0.1 to 500 μm, 0.1 to 100 μm, 0.1 to 50 μm, 0.1 to 10 μm, 1 to 1000 μm, 1 to 500 μm, 1 to 100 μm, 1 to 50 μm, 1 to 10 μm, 10 to 1000 μm, 10 to 500 μm, 10 to 100 μm, 10 to 50 μm, 50 to 1000 μm, 50 to 500 μm, 50 to 100 μm, 100 to 1000 μm, or 100 to 500 μm. there is. In one embodiment, the density of the first ion conductor in the solid electrolyte is 1.0 to 2.0 g / cm 3 , 1.0 to 1.5 g / cm 3 , 1.0 to 1.2 g / cm 3 , 1.2 to 2.0 g / cm 3 , or 1.2 to 1.5 g / cm 3 It can be. Also, the density of the second ion conductor in the solid electrolyte is 1.5 to 2.5 g / cm 3 , 1.5 to 2.0 g / cm 3 , 1.5 to 1.8 g / cm 3 , 1.8 to 2.5 g / cm3 , or 1.8 to 2.0 g / cm 3 It could be. In one embodiment, the solid electrolyte may be a single layer. The solid electrolyte, which is a single layer, can contain the first ion conductor and the second ion conductor in a volume ratio of 1:9 to 9:1, preferably in a volume ratio of 3:7 to 7:3, and more preferably in a volume ratio of 5:5. In one embodiment, the mass of the second ion conductor may be 50 to 400 parts by weight with respect to 100 parts by weight of the first ion conductor in the solid electrolyte of the single layer, and preferably, the mass of the second ion conductor may be 140 to 160 parts by weight. In one embodiment, when the first ion conductor and the second ion conductor have a volume ratio of 5:5, the mass ratio may be about 100:150. When the first ion conductor and the second ion conductor are included in the solid electrolyte, which is a single layer, satisfying the above-mentioned volume ratio range, there is an advantage in that side reactions at the interface between the negative electrodes including the lithium metal described below are suppressed, while at the same time improving the performance of the electrochemical cell. In another embodiment, the solid electrolyte may be a layered body. At this time, the laminate may be a layered structure in which a first ion conductor layer including the first ion conductor described above and a second ion conductor layer including the second ion conductor are laminated. In one embodiment, the first ion conductor layer including the first ion conductor and the second ion conductor layer including the second ion conductor may have the same or different thicknesses, and their thicknesses may be controlled depending on the desired performance indicator. In one embodiment, the first ion conductor layer described above may be positioned in contact with the negative electrode including lithium metal described below. That is, in the solid electrolyte positioned between the positive electrode and the negative electrode, when the solid electrolyte is a laminate, the first ion conductor layer may be positioned in contact with the negative electrode, and the second ion conductor layer may be positioned in contact with the positive electrode. In this way, since the first ion conductor layer included in the solid electrolyte is positioned in contact with the negative electrode including lithium metal, there is an advantage in that side reactions can be effectively suppressed at the interface with the negative electrode, thereby further improving the lifespan and performance of the electrochemical cell. The negative electrode included in the electrochemical cell of the present invention includes lithium metal, and the lithium metal may include at least one selected from pure lithium, a lithium alloy, and a lithium metal composite oxide. For example, the lithium alloy may be an alloy including pure lithium and at least one metal selected from the group consisting of Al, Mg, K, Na, Ca, Sr, Ba, Si, Ge, Sb, Pb, In, and Zn. The lithium metal composite oxide may include an oxide (MeOx) of lithium and at least one metal (Me) selected from the group consisting of Si, Sn, Zn, Mg, Cd, Ce, Ni, and Fe, but the present invention is not limited thereto. At this time, the negative electrode may be configured in a form in which the above-described lithium metal is used as a negative electrode active material and the above-described negative electrode active material is added to a negative electrode current collector, or may be configured in a form in which the above-described negative electrode active material is added to one side of the above-described solid electrolyte without including a separate negative electrode current collector. For example, the negative current collector may be used without limitation as long as it is known in the art and has conductivity without causing chemical change, and specific examples thereof include, but are not limited to, any one metal selected from the group consisting of copper, aluminum, stainless steel, zinc, titanium, silver, palladium, nickel, iron, chromium, alloys thereof, and combinations thereof. In addition, the positive electrode included in the electrochemical cell of the present invention includes a positive electrode current collector and a positive electrode mixture containing a positive electrode active material, and the positive electrode mixture may be coated on the positive electrode current collector. At this time, the coating of the positive electrode mixture may be coated on one side or both sides of the positive electrode current collector. For example, the positive electrode collector on which the positive electrode composite is coated is not particularly limited as long as it does not cause a chemical change in the battery and has high conductivity, and for example, stainless steel, aluminum, nickel, sintered carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. can be used. In addition, the positive electrode collector can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, and the like, and the present invention is not limited to the form of the positive electrode collector. For example, the positive electrode active material included in the positive electrode composite is not particularly limited as long as it is a material capable of reversibly absorbing and releasing lithium ions, and may include, for example, at least one selected from a sulfide-based active material and an oxide-based active material. As a specific example, the sulfide-based active material may be inorganic sulfur (S8), a sulfur-based compound, or a mixture thereof, and the sulfur-based compound may be a metal sulfide (M x S y, M=Li, Ni, Co, Cu, Fe, Mo, Ti, Nb, 1≤x≤4, 1≤y≤8), organosulfur compounds, and carbon-sulfur polymers ((C2Sx)n: x=2.5~50, n≥2). In addition, the oxide active material is LiCoO 2 , LiMnO 2 , LiNiO 2 , LiVO 2 , Li 1+x Ni 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 LiMn, a rock salt layer-type active material 2 O 4 , Li(Ni 0.5 Mn 1.5 )O 4 Spinel-type active materials, such as LiNiVO 4 , LiCoVO 4 Inverse spinel type active material, LiFePO 4 , LiMnPO 4 , LiCoPO 4 , LiNiPO 4 Olivine-type active materials such as Li 2 FeSiO 4 , Li 2 MnSiO 4 Silicon-containing active materials such as LiNi 0.8 Co (0.2-x) Al x O 2 (0 <x<0.2)과 같이 천이 금속의 일부를 이종 금속으로 치환한 암염층형형 활물질, Li 1+x Mn 2-x-y M y O 4 (M is at least one species among Al, Mg, Co, Fe, Ni, and Zn, and 0 <x+y<2)와 같이 천이 금속의 일부를 이종 금속으로 치환한 스피넬형 활물질일 수 있으나, 이에 제한되지는 않는다. In one embodiment, the cathode may include a ternary lithium metal oxide (NCM) represented by the following chemical formula 2 as a cathode active material. (chemical formula 2) Li 1+k Ni x Co y Mn z O 2 (0≤k≤0.2, 0 <x<1, 0<y<1, 0<z<1, x+y+z=1) Additionally, in one embodiment, the cathode composite including the cathode active material may further include a solid electrolyte and a conductive material. The above solid electrolyte may be the solid electrolyte described above, and as an advantageous example, may be a first ion conductor included in the solid electrolyte. The conductive material may be any material known in the art that can form an electron conducting path within the electrode without limitation, and the conductive material may be, but is not limited to, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, paneth black, lamp black, or thermal black; conductive fibers such as carbon fibers or metal fibers; conductive tubes such as carbon nanotubes; metal powders such as fluorocarbon, aluminum, or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives. In one embodiment, the cathode active material may be included in an amount of 50 to 90 parts by weight, the solid electrolyte in an amount of 1 to 60 parts by weight, and the conductive material in an amount of 1 to 10 parts by weight, based on 100 parts by weight of the cathode composite. In addition, the cathode composite may further include a binder, wherein the binder is selected from the group consisting of styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile copolymer, acrylonitrile-butadiene rubber, nitrile butadiene rubber, acrylonitrile-styrene-butadiene copolymer, acrylic rubber, butyl rubber, fluorine rubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, latex, acrylic resin, phenol resin, epoxy resin, carboxymethylcellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate. It may be selected from the group consisting of propionates, cyanoethylcellulose, cyanoethylsucrose, polyesters, polyamides, polyethers, polyimides, polycarboxylates, polycarboxylic acids, polyacrylic acids, polyacrylates, polymethacrylic acids, polymethacrylates, polyacrylamides, polyurethanes, fluorinated polymers, chlorinated polymers, alginate salts, polyvinylidene fluoride, poly(vinylidene fluoride)-hexafluoropropene, and combinations thereof. Hereinafter, the present invention will be described in more detail through examples of the present invention. However, the following examples are provided only to help understanding of the present invention, and the contents of the present invention are not limited to the following examples. [Example] (Manufacturing Example 1) Manufacturing of starting materials LiCB, a raw material for starting fire 9 H 10 and LiCB 11 H 12 The first ion conductor, Li(CB), was mixed in a molar ratio of 7:3 and then mechanically milled at 200 to 800 rpm for 10 to 50 hours to obtain a first ion conductor, Li(CB).9 H 10 ) 0.7 Li(CB 11 H 12 ) 0.3 ) was manufactured. (Example 1) Using a mold-type pressure cell, a sulfide-based solid electrolyte (Li) as a second ion conductor was first 6 PS 5 Cl) 10~150mg was compressed at a pressure of 50~600 MPa to form a second ion conductor layer. Afterwards, a first ion conductor, a hydride (Li(CB)) was applied to one side of the formed second ion conductor layer. 9 H 10 ) 0.7 Li(CB 11 H 12 ) 0.3 ) 1~20mg is added, and on the other side of the second ion conductor layer, a cathode active material (NCM811): solid electrolyte (Li 6 PS 5 Cl): 3-50 mg of the cathode mixture containing the conductive agent (superC) in a weight ratio of 80:19:1 was added, and then pressurized at a pressure of 50-600 MPa to form the cathode layer and the first ion conductor layer which are in contact with one side and the other side of the second ion conductor layer, respectively. That is, the solid electrolyte has a structure of a laminate in which the first ion conductor layer and the second ion conductor layer are sequentially laminated, and the cathode layer is positioned to be in contact with the second ion conductor layer included in the solid electrolyte. Subsequently, a lithium metal foil is placed so as to be in contact with the first ion conductor layer, and then pressurization is finally applied to manufacture an electrochemical cell. At this time, the manufactured electrochemical cell has a structure composed of a cathode layer - a second ion conductor layer - a first ion conductor layer - a negative electrode layer, as illustrated in FIG. 1. (Example 2) A sulfide-based solid electrolyte (Li) as a second ion conductor 6 PS 5 Cl) and the first ion conductor, Li(CB) 9 H 10 ) 0.7 Li(CB11 H 12 ) 0.3 ) was mixed in a volume ratio of 1:1, 10 to 150 mg of which was compressed at a pressure of 50 to 600 MPa using a mold-type pressure cell to form a solid electrolyte layer. That is, the formed solid electrolyte layer had a structure of a single layer in which the first ion conductor and the second ion conductor were mixed, unlike Example 1. Thereafter, 3 to 50 mg of the positive electrode mixture of Example 1 was placed on one side of the solid electrolyte layer, and then pressurized again at a pressure of 50 to 600 MPa to form a positive electrode layer. Subsequently, a lithium metal foil was placed so as to be in contact with the other side of the solid electrolyte layer on which the positive electrode layer is not formed, and then final pressurization was applied to manufacture an electrochemical cell. At this time, the manufactured electrochemical cell has a structure composed of a positive electrode layer - a solid electrolyte layer (mixture of the first ion conductor and the second ion conductor) - a negative electrode layer, as illustrated in FIG. 2. (Example 3)

[0084] The same procedure as in Example 2 was carried out, but a sulfide-based solid electrolyte (Li) as a second ion conductor was used. 6 PS 5 Cl) and the first ion conductor, Li(CB) 9 H 10 ) 0.7 Li(CB 11 H 12 ) 0.3 ) was performed in the same manner, except that a mixture was mixed in a volume ratio of 3:7. (Example 4) The same procedure as in Example 2 was carried out, but a sulfide-based solid electrolyte (Li) as a second ion conductor was used. 6 PS 5 Cl) and the first ion conductor, Li(CB) 9 H 10 ) 0.7 Li(CB 11 H 12 ) 0.3 ) was performed in the same manner, except that a mixture was mixed in a volume ratio of 7:3. (Comparative Example 1) A sulfide-based solid electrolyte (Li) as a second ion conductor 6 PS 5 An electrochemical cell was manufactured in the same manner as in Example 1, except that a solid electrolyte layer was formed using only Cl. At this time, the manufactured electrochemical cell had a structure consisting of a positive electrode layer - a second ion conductor layer - a negative electrode layer. (Experimental example) Evaluation of electrochemical properties The electrochemical characteristics of each manufactured electrochemical cell were evaluated and compared. At this time, the electrochemical characteristic evaluation conditions were a voltage range of 2.8 V to 4.3 V (V vs. Li / Li+) and a temperature of 60°C. FIG. 3 is a drawing comparing charge / discharge curves at 0.2 C for each of the electrochemical cells manufactured according to Comparative Example 1, Example 1, and Example 2. FIG. 4 is a drawing comparing the coulombic efficiency and life characteristics of electrochemical cells manufactured according to Comparative Example 1, Example 1, and Example 2, respectively. For each electrochemical cell, the discharge capacity and coulombic efficiency characteristics in the first cycle, as well as the life characteristics (capacity retention rate) up to 40 cycles, are summarized in Table 1 below. Discharge capacity (mAh / g)Coulombic efficiency (%)Capacity retention rate (%)Example 174.6972.0385.94Example 2129.5676.6594.78Example 3103.2374.2188.12Example 4109.2875,1388.87Comparative example 179.2146.559.72 As shown in FIGS. 3, 4, and Table 1, it can be seen that the electrochemical characteristics of the electrochemical cells of Examples 1 to 4 are significantly improved compared to Comparative Example 1. Specifically, in the case of Example 1 including a solid electrolyte layer having a stacked structure of a first ion conductor (hydride) and a second ion conductor (sulfide-based solid electrolyte), the discharge capacity was at a similar level to that of Comparative Example 1 including a solid electrolyte layer composed of only the second ion conductor a, but the Coulombic efficiency was greatly improved and the capacity retention rate was confirmed to have increased by more than 8 times. In particular, in the case of Example 2, which includes a solid electrolyte layer having a single-layer structure in which a first ion conductor and a second ion conductor are mixed and included, it was confirmed that the discharge capacity and coulombic efficiency were greatly improved compared to Comparative Example 1, and the capacity retention rate was also improved by more than 10 times. From these results, it was confirmed that when a solid electrolyte using a composite of a first ion conductor and a second ion conductor is used, the high energy density is improved by increasing the discharge capacity, the stability is improved by increasing the Coulombic efficiency, and the life characteristics are improved by increasing the capacity retention rate. Therefore, it can be seen that the electrochemical cell according to the present invention can overcome the limitations of performance, lifespan reduction, and stability due to side reactions between the lithium metal anode and the solid electrolyte, which are representative problems of existing all-solid-state batteries. The above description of the present invention is for illustrative purposes only, and those skilled in the art will understand that the present invention can be easily modified into other specific forms without changing the technical idea or essential features of the present invention. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive. For example, each component described as a single component may be implemented in a distributed manner, and likewise, components described as distributed may be implemented in a combined manner. The scope of the present application is indicated by the claims described below rather than the detailed description above, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present application.

Claims

1. A cathode containing lithium metal; Bipolar; and Containing a solid electrolyte positioned between the cathode and the anode, An electrochemical cell, wherein the solid electrolyte comprises a first ion conductor that is a complex hydride containing a hydride-based complex anion and a second ion conductor that comprises a sulfur compound.

2. In paragraph 1, An electrochemical cell, wherein the solid electrolyte is a single layer or a laminate.

3. In paragraph 2, An electrochemical cell, wherein the volume ratio of the first ion conductor to the second ion conductor included in the above-mentioned single layer is 1:9 to 9:

1.

4. In paragraph 2, An electrochemical cell, wherein the laminate is a layered structure in which a first ion conductor layer including the first ion conductor and a second ion conductor layer including the second ion conductor are laminated.

5. In paragraph 4, An electrochemical cell, wherein the first ion conductor layer is positioned in contact with the cathode.

6. In paragraph 1, The above first ion conductor is B 6 H 6 2- , B 10 H 10 2- , B 11 H 11 2- , B 12 H 12 2- , CB 9 H 10 - , CB 10 H 11 - and CB 11 H 12 - An electrochemical cell comprising one or more hydride anions selected from the group consisting of:

7. In paragraph 6, The above first ion conductor is CB 9 H 10 - First stage hydrocarbons and CB including 11 H 12 - An electrochemical cell comprising a second hydride comprising:

8. In paragraph 1, The above sulfur compound is represented by the following chemical formula 1, an electrochemical cell (chemical formula 1) L a M b P c S d X e (L=alkali metal, M=at least one of B, Al, Ga, In, Si, Ge, Sn, Pb, As, Sb, Bi, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, Ta, and W, X=at least one of F, Cl, Br, I, and O, 0 <a≤12, 0≤b≤6, 0≤c≤6, 0<d≤12, 0≤e≤9) 9. In paragraph 1, The above positive electrode is an electrochemical cell including at least one positive electrode active material selected from a sulfide-based active material and an oxide-based active material.

10. In paragraph 9, The above positive electrode is an electrochemical cell including a ternary lithium metal oxide (NCM) of Ni-Co-Mn represented by the following chemical formula 2. (chemical formula 2) Li 1+k Ni x Co y Mr z O 2 (0≤k≤0.2, 0 <x<1, 0<y<1, 0<z<1, x+y+z=1) 11. In paragraph 9, An electrochemical cell, wherein the positive electrode further comprises a solid electrolyte and a conductive material.

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