Composite cathode, preparing method thereof, and secondary battery including the composite cathode

Abstract

A composite anode comprising a positive current collector; and a positive active material layer disposed on the positive current collector, wherein the positive active material layer comprises a crystalline phosphate-based solid electrolyte; a crystalline phosphate-based positive active material having an electron conductivity 10 to 106 times higher than that of the crystalline phosphate-based solid electrolyte; and an interphase interposed between them, a method for manufacturing the composite anode, and a secondary battery comprising the same are disclosed.

Description

Technology Field

[0001] The invention relates to a composite cathode, a method for manufacturing the same, and a secondary battery containing the same. Background Technology

[0002] Recently, due to safety issues with lithium-ion batteries, the development of all-solid-state batteries is progressing significantly.

[0003] Oxide-based or sulfide-based solid electrolytes can be used as solid electrolytes for all-solid-state batteries. Since oxide-based solid electrolytes are more stable in the atmosphere compared to sulfide-based solid electrolytes, much research is currently underway to commercialize them.

[0004] Oxide-based solid electrolytes lack sufficient ductility, which can lead to high interfacial resistance upon contact with the cathode active material. When conductive materials are added during cathode fabrication to reduce interfacial resistance, the formation of contact between the solid electrolyte and the cathode is hindered during the heat treatment process, resulting in the formation of numerous pores within the cathode. Consequently, discharge capacity and capacity retention rate decrease. To address this problem, a method has been proposed to form the cathode using only the solid electrolyte and cathode active material without the use of conductive materials; however, due to the very low electron conductivity of the solid electrolyte, it is difficult to form electron conduction pathways within the cathode. The problem to be solved

[0005] One aspect is to provide a composite anode containing a novel composite with improved electrochemical properties.

[0006] Another aspect is to provide a secondary battery with improved initial capacity and cycle stability by including the aforementioned composite cathode.

[0007] Another aspect is to provide a method for manufacturing the aforementioned composite anode. means of solving the problem

[0008] A positive current collector according to one side; and a positive active material layer disposed on the positive current collector,

[0009] The above positive active material layer is,

[0010] Crystalline phosphate-based solid electrolyte;

[0011] 10 times that of the above crystalline phosphate-based solid electrolyte to 10 6 A composite anode is provided comprising a composite including a crystalline phosphate-based anode active material having twice the electronic conductivity; and an interphase interposed between them.

[0012] According to another aspect, a secondary battery comprising the composite cathode described above is provided.

[0013] The above secondary battery is a lithium secondary battery or an all-solid-state battery, and the all-solid-state battery is, for example, a multi-layer-ceramic (MLC) battery.

[0014] According to another aspect, a crystalline phosphate-based solid electrolyte, 10 times that of the crystalline phosphate-based solid electrolyte to 10 6 A step of providing a composition for forming a composite anode by mixing a crystalline phosphate-based anode active material having twice the electronic conductivity, a binder, and a solvent; and

[0015] A method for manufacturing a composite anode is provided, comprising the step of pressurizing the composition for forming the composite anode at 700°C or higher and 150 MPa or lower. Effects of the invention

[0016] According to one aspect, the composite cathode has a dense structure in which the cathode active material with high conductivity forms electron conduction pathways and is interconnected. When using such a composite cathode, the interface between the cathode and the solid electrolyte is easily formed, thereby reducing their interfacial resistance. By using the composite cathode of one embodiment, a secondary battery with improved initial capacity and cycle stability can be manufactured. Brief explanation of the drawing

[0017] Figure 1a is a scanning electron microscope analysis image of the composite anode of Example 1. Figure 1b shows the Energy Dispersive X-ray Spectroscopy (EDS) results for the composite anode of Example 1. Figures 2a to 2e each show scanning electron microscope analysis images of the composites of Comparative Examples 1 to 5. Figure 3a shows the X-ray diffraction analysis results for the composites of Example 1 and Comparative Example 1. FIG. 3b is an enlarged view of a portion of FIG. 3a. FIG. 4a shows the results of X-ray diffraction analysis for the composite of Comparative Example 3. FIG. 4b is an enlarged view of a portion of FIG. 4a. FIG. 5a to 5d show the voltage change according to capacity in the lithium secondary batteries of Example 1, Example 2, Comparative Example 1, and Comparative Example 2, respectively. FIG. 5e to 5g show the voltage change according to capacity in the lithium secondary batteries according to Comparative Examples 3 to 5, respectively. FIG. 6a and 6b show the changes in the initial discharge capacity and capacity retention rate after 10 cycles of the lithium secondary battery according to the hot press temperature during cathode manufacturing, respectively. FIG. 7 schematically shows the structure of a stacked ceramic type battery according to one embodiment. FIG. 8 and 9 schematically show the structure of a secondary battery according to another embodiment. FIG. 10a and 10b according to yet another embodiment The structure of a secondary battery is schematically shown. FIGS. 11 to 13 are cross-sectional views of an all-solid-state secondary battery according to one embodiment. Specific details for implementing the invention

[0018] Hereinafter, a composite according to one embodiment, a method for manufacturing the same, a composite anode including the same, and a secondary battery including the composite anode will be described in detail.

[0019] When manufacturing a cathode for an all-solid-state battery, if a composition in which a conductive material such as carbon is added to the cathode active material and solid electrolyte is sintered at high temperature, the formation of contact between the solid electrolyte and the cathode is hindered, resulting in the formation of numerous pores within the cathode. All-solid-state batteries equipped with such a cathode exhibit reduced discharge capacity and capacity retention rate during charge-discharge tests.

[0020] To solve the aforementioned problems, a method was proposed that utilizes only a solid electrolyte and anode active material without using a conductive material during anode manufacturing. However, due to the very low electron conductivity of the solid electrolyte, it is difficult to form electron conduction pathways within the anode.

[0021] To solve the aforementioned problems, the inventors provide a crystalline phosphate-based solid electrolyte without using a conductive material, and a material having an electronic conductivity 10 to 10 times greater than that of the same. 6 The invention has been completed regarding a composite containing a phosphate-based positive electrode active material with a high phosphate level and a composite positive electrode containing said composite.

[0022] A composite anode according to one embodiment is a crystalline phosphate-based solid electrolyte; 10 to 10 times the crystalline phosphate-based solid electrolyte 6 It contains a composite comprising a crystalline phosphate-based positive electrode active material having twice the electronic conductivity and an interphase interposed between them.

[0023] The electron conductivity of the crystalline phosphate-based cathode active material is 10 to 10 times that of the crystalline phosphate-based solid electrolyte. 6 In the composite and the composite anode containing it, the anode active materials have an interconnected matrix structure, and an electrical conduction pathway is formed within the anode even without a conductive material, facilitating the formation of an interface between the solid electrolyte and the anode and resulting in low interfacial resistance between the solid electrolyte and the anode.

[0024] The above composite has a structure in which the solid electrolyte is evenly dispersed within the positive electrode active material matrix.

[0025] The electron conductivity of the above crystalline phosphate-based cathode active material is 10 to 10 times the electron conductivity of the crystalline phosphate-based solid electrolyte. 4 Pear, 10 to 10 times 3 It is larger than 10 to 500 times, 10 to 400 times, 10 to 300 times, or 15 to 250 times.

[0026] The electronic conductivity of a crystalline phosphate-based cathode active material is, for example, 2 x 10 -4 mS / cm to 3 x 10 -4 mS / cm, or 2.4 x 10⁻⁶ -4 It is mS / cm, and the electronic conductivity of the crystalline phosphate-based solid electrolyte is 1.44 x 10⁻⁶. -5 mS / cm to 1.1 x 10⁻⁶ -6 It is mS / cm.

[0027] When the difference in electron conductivity of the crystalline phosphate-based positive electrode active material is within the above range, an electron conduction pathway is smoothly formed in the composite positive electrode, and the positive electrode active materials can have a structure in which they are connected to each other.

[0028] The interface phase is in an amorphous state, and the state and composition of the amorphous interface phase can be confirmed through EDS and SEM analysis. The presence of such an amorphous interface phase increases the contact area between the cathode active material and the solid electrolyte, facilitating the movement of lithium ions between them and improving cell performance.

[0029] In this specification, the interphase refers to a secondary phase existing between a crystalline phosphate-based solid electrolyte, which is the main phase (i.e., the primary phase), and a crystalline phosphate-based positive electrode active material.

[0030] The amorphous interface phase is confirmed by EDS analysis to contain at least one element contained in the crystalline phosphate-based solid electrolyte and the crystalline phosphate-based cathode active material.

[0031] According to one embodiment, as a crystalline phosphate-based solid electrolyte and a crystalline phosphate-based cathode active material, respectively, the phosphate-based cathode active material Li3V2(PO4)3(LVP) and the crystalline solid electrolyte Li 1.5 Al 0.5 Ge 1.5 When (PO4)3(LGAP) is used, the amorphous interfacial phase contains, for example, aluminum, vanadium, phosphorus, and oxygen, and does not contain Ge, according to EDS analysis. The presence of lithium is not evaluated according to EDS analysis.

[0032] The content of the amorphous interfacial phase can be calculated from the volume occupied by the amorphous interfacial phase relative to the total volume of the composite using SEM analysis images. The amorphous interfacial phase is, for example, 5 volume% or less, or for example, 0.1 to 5 volume%, based on the total volume of the composite. When the amorphous interfacial phase is present at the aforementioned content, an electron conduction pathway is well formed within the composite without the need for a separate conductive material.

[0033] The above crystalline phosphate-based positive electrode active material is a compound represented by the following chemical formula 1, a compound represented by chemical formula 2, or a combination thereof.

[0034] <Chemical Formula 1>

[0035] LimMa(PO4)3

[0036] M is Ti, Si, Mn, Fe, Co, V, Cr, Mo, Ni, Al, Mg, Al, or a combination thereof, and

[0037] In Chemical Formula 1, 1≤m≤5, 1≤a≤2, and

[0038] <Chemical Formula 2>

[0039] Li n M1(PO4)

[0040] In chemical formula 2, M1 is Co, Ni, Mn, Fe, or a combination thereof, and

[0041] 1≤n≤1.

[0042] Compounds of Chemical Formula 1 are, for example, Li3V [2-2x] / 3 Mg x (PO4)3(X is 0.15 to 0.6).

[0043] Compounds of Chemical Formula 2 include, for example, the compound of Chemical Formula 2-1 below.

[0044] <Chemical Formula 2-1>

[0045] Lim(Ni 1-x-y Mn x Fe y )PO4

[0046] In Chemical Formula 2-1, 1≤m≤1.2, 0≤x≤1, 0≤y≤1, and 0≤x+y≤1.

[0047] The above crystalline phosphate-based cathode active material is Li3V2(PO4)3, LiCoPO4, LiFePO4, LiNiPO4, or a combination thereof.

[0048] A crystalline phosphate-based solid electrolyte according to one embodiment is, for example, Li 1+x Al x Ge 2-x (PO4)3 (0 <x<1), Li 1+x AlxTi 2-x (PO4)3 (0 <x<1), Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 <x<2, 0≤y<3), Li x Ti y (PO4)3(0 <x<2, 0<y<3), Li x Al y Ti z (PO4)3(0 <x<2, 0<y<1, 0<z<3), Li 1+x+y (Al a Ga 1-a ) x (Ti b Ge 1-b ) 2-x Si y P 3-y O 12(0 <a<1, 0<b<1, 0≤x≤1, 0≤y≤1), 또는 그 조합이다. 상기 결정성 포스페이트계 고체전해질은 예를 들어 Li 1.5 Al 0.5 Ge 1.5 (PO4)3, Li 1.3 Al 0.3 Ge 1.7 (PO4)3, Li 1.3 Al 0.3 Ti 1.7 (PO4)3, or combinations thereof, can be cited.

[0049] In a composite cathode according to one embodiment, the content of the crystalline phosphate-based solid electrolyte contained in the composite is 0.2 to 20 parts by weight, for example, 1 to 15 parts by weight, based on 1 part by weight of the crystalline phosphate-based cathode active material. When the content of the crystalline phosphate-based solid electrolyte is within the above range, electron conduction pathways are well formed and the cathode active material has a structure in which it is connected to one another, and the interfacial resistance between the solid electrolyte and the cathode is reduced.

[0050] In a composite according to one embodiment, the crystalline phosphate-based cathode active material may have a structure in which it partially or completely surrounds the surface of the crystalline phosphate-based solid electrolyte. Here, an amorphous interface phase exists between the crystalline phosphate-based solid electrolyte and the crystalline phosphate-based cathode active material.

[0051] Peak intensity I appearing in the region where the diffraction angle 2θ is 20.9±0.1°, obtained by X-ray diffraction analysis of the above complex and complex anode using CuKα rays (1-12) Peak intensity I appearing in the region where the diffraction angle 2θ for is 20.69±0.1° (11-2) The ratio of (I (11-2) / I (1-12) ) is less than 1, for example, 0.03 to 0.9, or 0.05 to 0.5.

[0052] Peak intensity I appearing in the region where the diffraction angle 2θ is 24.7±0.1°, obtained by X-ray diffraction analysis of the above complex using CuKα rays (10-3) Peak intensity I appearing in the region where the diffraction angle 2θ for is 24.4±0.1° (103) The ratio of (I (103) / I (10-3) ) is less than 1, for example, 0.1 to 0.9, 0.3 to 0.9, or 0.5 to 0.9.

[0053] The composite anode contains an anode current collector. The composite and the composite anode may contain closed pores. When closed pores are contained in this way, the ion conduction pathway is improved compared to when open pores are contained.

[0054] The porosity of the above composite anode is 0.1 to 5%, for example, 0.1 to 1%, and it has a very densified structure. In addition, as described above, the composite anode does not contain a conductive material and has an electron conductor-free state.

[0055] The composite anode according to one embodiment may further include additives such as a binder, a filler, a dispersant, and an ion conductivity aid.

[0056] Binders are non-limiting examples such as styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, and polyethylene. As for coating agents, dispersants, and ion conductivity aids that can be incorporated into the composite anode, known materials generally used in electrodes of solid-state secondary batteries are used.

[0057] The following describes a composite according to one embodiment and a method for manufacturing a composite anode containing the same.

[0058] First, a crystalline phosphate-based solid electrolyte, 10 to 10 times the electronic conductivity of the crystalline solid electrolyte. 6 A composition for forming a composite is provided by mixing a crystalline phosphate-based positive electrode active material having twice the electronic conductivity, a binder, and a solvent.

[0059] The above composition for forming the composite is subjected to pressure heat treatment at 700°C or higher to produce an anode active material layer. The pressure can be applied, for example, at a pressure of 150 MPa or less to produce the composite.

[0060] When preparing the composition for forming the above-mentioned composite, commercially available ink vehicle (Ink Vehicle, Fuel Cell Materials Co., Ltd.) can be used as a binder and solvent.

[0061] A composite anode is manufactured by combining the above positive active material layer with a positive current collector.

[0062] The above heat treatment is carried out, for example, at 700°C to 800°C, for example, at 700°C to 750°C.

[0063] Pressurization may be performed using, for example, a roll press, a flat press, an isotropic press, or a hydrostatic press, but is not necessarily limited to these methods and any pressurization used in the relevant technical field is possible. The pressurization is performed at 50 MPa to 150 MPa, or 100 MPa to 150 MPa.

[0064] When subjected to pressure heat treatment under the above-described conditions, a composite anode according to one embodiment is manufactured.

[0065] Heat treatment is carried out under an inert gas atmosphere. An inert gas such as argon or nitrogen is used for the inert gas atmosphere. During heat treatment, the heating rate is 1 ℃ / min to 10 ℃ / min.

[0066] According to one embodiment, when manufacturing a composite anode, the composite forming composition (or composite anode forming composition) can be provided on the upper part of the anode current collector to manufacture a composite anode containing the composite.

[0067] According to another embodiment, the composite forming composition can be provided on a substrate to manufacture a composite anode. If necessary, a process of separating the manufactured composite anode from the substrate may be performed.

[0068] According to another embodiment, the above description may be a solid electrolyte for a secondary battery.

[0069] The above composition for forming the composite may further include additives such as binders, fillers, dispersants, and ion-conducting aids.

[0070] According to another aspect, a secondary battery comprising the aforementioned composite cathode is provided.

[0071] The secondary battery is a lithium secondary battery or an all-solid-state battery.

[0072] The above-mentioned all-solid-state battery can be, for example, a multi-layer ceramic (MLC) battery.

[0073] The above-described multilayer ceramic battery has a multilayer structure in which a plurality of cell units are stacked such that the positive active material layer and the negative active material layer face each other, wherein the cell units having a positive active material layer, a solid electrolyte layer, and a negative active material layer are arranged in sequence.

[0074] The above anode layer is a composite anode according to one embodiment.

[0075] According to another embodiment, the multilayer ceramic battery may further include a positive current collector and / or a negative current collector. When the multilayer ceramic battery includes a positive current collector, a positive active material layer may be disposed on both sides of the positive current collector. And when the multilayer ceramic battery includes a negative current collector, a negative active material layer may be disposed on both sides of the negative current collector.

[0076] A multilayer ceramic battery comprises a stacked body in which a plurality of cell units are stacked such that the positive active material layer and the negative active material layer of the cell units face each other, wherein the cell units have a positive active material layer, a solid electrolyte layer, and a negative active material layer in that order.

[0077] According to one embodiment, a current collector layer is provided on either or both of the uppermost and lowermost layers of the laminate, or a metal layer is interposed in the laminate to stack cell units.

[0078] The composite cathode according to one embodiment and the secondary battery containing the same can be used as a power source for Internet of Things (IoT) applications, wearable devices, etc.

[0079] The composite cathode according to the first embodiment is applicable to thin-film batteries and MLC batteries. It is also applicable to small batteries and large batteries such as electric vehicles (EVs) and energy storage systems (ESS).

[0080] The above secondary battery is an all-solid-state secondary battery comprising: a positive electrode layer including a positive electrode active material layer, a negative electrode current collector layer and a negative electrode layer including a first negative electrode active material layer or a third negative electrode active material layer; and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, wherein the positive electrode layer is a composite positive electrode containing, for example, a composite according to one embodiment.

[0081] The first cathode active material layer comprises one or more selected from carbon-based cathode active materials and metal or metal-metal cathode active materials.

[0082] The carbon-based negative electrode active material comprises one or more selected from amorphous carbon and crystalline carbon, and the metal or metalloid negative electrode active material comprises one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn).

[0083] The invention further comprises a second cathode active material layer disposed between the cathode current collector and the first cathode active material layer and between the solid electrolyte layer and the first cathode active material layer, wherein the second cathode active material layer is a metal layer comprising lithium or a lithium alloy.

[0084] In an all-solid-state secondary battery according to one embodiment, the third negative electrode active material layer is a metal layer comprising lithium or a lithium alloy.

[0085] The secondary battery according to the first embodiment may be an ultra-small all-solid-state secondary battery.

[0086] Figure 6 schematically shows the structure of an MLC battery according to one embodiment.

[0087] Referring to Fig. 6, an MLC battery can be manufactured by sequentially stacking an oxide electrode and a solid electrolyte and then simultaneously heat-treating them.

[0088] Referring to this, positive active material layers (112) are disposed on both sides of the positive current collector (111) to form a positive electrode (110). The positive electrode (110) is a composite positive electrode according to one embodiment.

[0089] A negative electrode (120) is formed by stacking a negative active material layer (122) on both sides of a negative electrode current collector (121). A solid electrolyte (130) may be placed between the positive electrode (110) and the negative electrode (120) as shown in FIG. 6. An external electrode (140) is formed at both ends of the battery body (150). The external electrode (140) is connected to the positive electrode (110) and the negative electrode (120), the ends of which are exposed to the outside of the battery body (150), and can serve as an external terminal to electrically connect the positive electrode (110) and the negative electrode (120) to an external element. One of the pair of external electrodes (140) has one end connected to the positive electrode (110) that is exposed to the outside of the battery body (150), and the other end is connected to the negative electrode (120) that is exposed to the outside of the battery body (150).

[0090] A secondary battery according to one embodiment may be a stacked solid-state battery comprising at least a first and second single cell, each consisting of a positive electrode layer, a solid electrolyte layer, and a negative electrode layer stacked in order, and an internal current collection layer disposed between the first and second single cells, in contact with the positive electrode layer of each of the first and second single cells or in contact with the negative electrode layer of each of the first and second single cells.

[0091] The negative electrode active material of the negative electrode active material layer is an oxide containing elements of Group 2 to Group 14, and may include, for example, lithium titanium oxide, lithium transition metal oxide, lithium metal phosphate, titanium oxide, vanadium oxide, or a combination thereof.

[0092] Lithium metal phosphate is Li3Fe2(PO4)3 or Li x V2(PO4)3(0 <x≤5)이다.

[0093] The oxide cathode is, for example, Li 4 / 3 Ti 5 / 3 O4, LiTiO2, LiM1 s M2 t O u (M1 and M2 are transition metals, and s, t, and u are each arbitrary positive numbers), TiO x(0 <x≤3), V2O5, Li x V2(PO4)3(0 <x≤5) 및 Li3Fe2(PO4)3로 이루어지는 군으로부터 선택되는 리튬 화합물을 포함하고, 예를 들어 Li 4 / 3 Ti 5 / 3 Examples include O4 and LiTiO2. TiO x (0 <x≤3)는 예를 들어 TiO2을 들 수 있다.

[0094] The negative electrode active material is, for example, vanadium oxide (V2O5) or Li4Ti5O 12 , TiO2, LiTiO2, Li3V2(PO4)3, Li3Fe2(PO4)3, or a combination thereof.

[0095] When the current collector layer functions as both a positive electrode current collector and a negative electrode current collector, it may be composed of any metal among Ni, Cu, Ag, Pd, Au, and Pt, or may be composed of an alloy containing any of Ni, Cu, Ag, Pd, Au, and Pt. In the case of an alloy, it is an alloy of two or more selected from Ni, Cu, Ag, Pd, Au, and Pt, for example, an Ag / Pd alloy. In addition, these metals and alloys may be single or a mixture of two or more. The current collector layer as a positive electrode current collector and the current collector layer as a negative electrode current collector may use the same material or may be different. In particular, an alloy or mixed powder containing Ag and Pd has the advantage of being able to continuously and arbitrarily change the melting point from the silver melting point (962 °C) to the palladium melting point (1550 °C) depending on the mixing ratio, allowing for melting point adjustment to match the batch firing temperature, and also has high electronic conductivity, which allows for minimizing the internal resistance of the battery.

[0096] The metal layer may use the same material as the current collector layer described above. The metal layer and the current collector layer may use the same material or may be different.

[0097] Solid electrolytes contain ion-conducting inorganic materials, and for example, oxide-based solid electrolytes can be used.

[0098] Oxide-based solid electrolytes are, for example, Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 <x<2, 0≤y<3), BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT)(O≤x<1, O≤y<1), Pb(Mg3Nb 2 / 3 )O3-PbTiO3(PMN-PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, SiC, Lithium Phosphate (Li3PO4), Lithium Titanium Phosphate (Li x Ti y (PO4)3,0 <x<2,0<y<3), 리튬알루미늄티타늄포스페이트 (Li x Al y Ti z (PO4)3, 0 <x<2, 0<y<1, 0<z<3), Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (O≤x≤1, O≤y≤1), lithium lanthanum titanate (Li x La y TiO3, 0 <x<2, 0<y<3), 리튬게르마늄티오포스페이트(LixGeyPzSw, 0<x<4, 0<y<1, 0<z<1, 0<w<5), 리튬나이트라이드계열 글래스(Li x N y , 0 <x<4, 0<y<2), SiS2(Li x Si y S z , 0 <x<3,0<y<2, 0<z<4), P2S5계열 글래스(Lix P y S z , 0 <x<3, 0<y<3, 0<z<7), Li2O, LiF, LiOH, Li2CO3, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2계 세라믹스, 가넷(Garnet)계 세라믹스 Li 3+x La3M2O 12 It is one or more selected from (M = Te, Nb, or Zr) (x is an integer from 1 to 10) or a combination thereof.

[0099] Solid electrolytes are, for example, Li 3.25 Al 0.25 SiO4, Li3PO4, LiP x Si y O z It is a lithium compound selected from the group consisting of (where x, y, and z are arbitrary positive numbers), for example, Li 3.5 P 0.5 Si 0.5 It is O4.

[0100] FIGS. 7 and 8 schematically show the cross-sectional structure of a stacked solid-state battery according to one embodiment.

[0101] As shown in FIG. 7, in a stacked solid-state battery (710), (single cell 1) and (single cell 2) are stacked through an internal current collection layer (74). Each of (single cell 1) and (single cell 2) consists of a positive electrode layer (71), a solid electrolyte layer (73), and a negative electrode layer (72) stacked in order. The positive electrode layer (71) is, for example, a composite positive electrode according to one embodiment.

[0102] The (single cell 1) and (single cell 2) and the internal current collector layer 74 are stacked such that the negative electrode layer (72) of (single cell 2) is adjacent to one side (top surface in FIG. 7) of the internal current collector layer (74) and the negative electrode layer (72) of (single cell 1) is adjacent to the other side (bottom surface in FIG. 7) of the internal current collector layer (74). In FIG. 7, the internal current collector layer (74) is positioned to contact the respective negative electrode layers (72) of (single cell 1) and (single cell 2), but it may be positioned to contact the respective positive electrode layers (71) of (single cell 1) and (single cell 2). The internal current collector layer (74) includes an electronically conductive material. The internal current collector layer (74) may further include an ionically conductive material. If an ionically conductive material is further included, the voltage stabilization characteristics are excellent.

[0103] In the stacked solid battery (710) according to the embodiment configured as above, since the same poles are arranged on both sides of the internal current collection layer 4, a monopolar stacked solid battery (710) can be obtained in which a plurality of single cells are connected in parallel through the internal current collection layer (74). By this, a high-capacity stacked solid battery (710) can be obtained.

[0104] In addition, in the above-described stacked solid battery (710), the internal current collection layer (74) interposed between (single cell 1) and (single cell 2) includes an electronically conductive material, so that two adjacent single cells can be electrically connected in parallel, and at the same time, the positive layer (71) or negative layer (72) of the two adjacent single cells can be ionically conductive. By doing so, the potential of the adjacent positive layer (71) or negative layer (72) can be averaged through the internal current collection layer 74, thereby obtaining a stable output voltage.

[0105] In addition, external current collection members such as withdrawal tabs can be eliminated, and individual cells constituting the stacked solid battery 10 can be electrically connected in parallel. By doing so, a stacked solid battery (710) with excellent space utilization and cost-effectiveness can be obtained.

[0106] Referring to FIG. 8, the laminate comprises an anode layer (81), a cathode layer (82), a solid electrolyte layer (83), and an internal current collector layer (84). By stacking and heat-pressing such a laminate, a laminated solid battery laminate (810) is obtained. However, the anode layer (81) is composed of a single sheet for the anode layer, and the cathode layer (82) is composed of two sheets for the cathode layer. The anode layer (81) contains a composite anode according to one embodiment.

[0107] FIGS. 9A and 9B illustrate a laminate of another embodiment of an all-solid-state secondary battery according to one embodiment. The positive active material layer of FIGS. 9A and 9B is a composite positive according to one embodiment.

[0108] Referring to FIG. 9a, the structure of the most basic cell unit (92) constituting an all-solid-state secondary battery is shown. The cell unit (92) has a structure in which a positive electrode active material layer (94), an ion-conducting inorganic material layer (96), and a negative electrode active material layer (95) are continuous in this order.

[0109] Figure 9b shows the structure of a laminate constituting an all-solid-state secondary battery.

[0110] In the all-solid-state secondary battery, a positive lead electrode in contact with the positive active material layer is installed at the bottom, and a negative lead electrode in contact with the negative active material layer is installed at the top. In this specification, the top and bottom indicate a relative positional relationship.

[0111] The laminate (923) has a structure in which a plurality of cell units (92) are stacked such that a positive active material layer (94) and a negative active material layer (95) face each other, and a current collector layer is provided in the uppermost layer and the lowermost layer, respectively. One of the current collector layers in the uppermost layer and the lowermost layer is connected to the positive active material layer to become a positive current collector, and the other is connected to the negative active material layer to become a negative current collector. The current collector layer (97) in the lowermost layer is in contact with the positive active material layer (94) to become a positive current collector, and the current collector layer (98) in the uppermost layer is in contact with the negative active material layer (95) to become a negative current collector.

[0112] In this embodiment, the current collector layer can function as a lead electrode. In FIG. 9b, the lowest current collector layer (97) can function as a positive lead electrode, and the uppermost current collector layer (8) can function as a negative lead electrode. Alternatively, a lead electrode may be installed separately on the current collector layer, for example, a positive lead electrode in contact with the current collector layer (97) at the bottom and a negative lead electrode in contact with the current collector layer (98) at the top may be installed.

[0113] As shown in FIG. 9b, the laminate (923) has a structure in which cell units (92) are stacked with a metal layer (920) interposed. By interposing the metal layer, the movement of ions is kept within individual cell units, so it can be expected to function more reliably as a series-type all-solid-state secondary battery. The laminate (923) of FIG. 9b is equipped with a current collector layer, but the current collector layer is optional as described above.

[0114] In a stack of all-solid-state secondary batteries, if the number of cell units (92) is two or more, a so-called series-type all-solid-state secondary battery can be formed. The number of cell units can be varied widely based on the required capacity or voltage value of the all-solid-state secondary battery.

[0115] The secondary battery according to one embodiment may be an all-solid-state secondary battery. Hereinafter, the all-solid-state secondary battery according to one embodiment will be examined in more detail with reference to the attached drawings.

[0116] Referring to FIGS. 10 to 12, the all-solid-state secondary battery (1) comprises a negative electrode layer (20) comprising a negative electrode current collector layer (21) and a first negative electrode active material layer (22); a positive electrode layer (10) comprising a positive electrode current collector layer (11) and a positive electrode active material layer (12); and a solid electrolyte layer (30) disposed between the negative electrode layer (20) and the positive electrode layer (10). The positive electrode layer (10) may contain a solid electrolyte. The positive electrode active material layer of FIGS. 10 to 12 is a composite positive electrode according to one embodiment.

[0117] (Cathode layer)

[0118] Referring to FIGS. 10 to 12, the cathode layer (20) comprises a cathode current collector layer (21) and a first cathode active material layer (22), wherein the first cathode active material layer (22) comprises a cathode active material. The cathode current collector layer (21) may be omitted.

[0119] The negative electrode active material included in the first negative electrode active material layer (22) has, for example, a particle shape. The average particle size of the negative electrode active material having a particle shape is, for example, 4 μm or less, 3 μm or less, 2 μm or less, 1 μm or less, or 900 nm or less. The average particle size of the negative electrode active material having a particle shape is, for example, 10 nm to 4 μm, 10 nm to 2 μm, 10 nm to 1 μm, or 10 nm to 900 nm. By having the negative electrode active material with an average particle size in this range, the reversible absorption and / or desorption of lithium during charging and discharging may be more easily facilitated. The average particle size of the negative electrode active material is, for example, a median diameter (D50) measured using a laser particle size distribution meter.

[0120] The cathode active material included in the first cathode active material layer (22) comprises, for example, one or more selected from carbon-based cathode active materials and metal or metal-metal cathode active materials.

[0121] The carbon-based cathode active material is, in particular, amorphous carbon. Amorphous carbon is, for example, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), graphene, etc., but is not necessarily limited to these, and any material classified as amorphous carbon in the relevant technical field is acceptable. Amorphous carbon is carbon that does not have crystallinity or has very low crystallinity, and is distinguished from crystalline carbon or graphite-based carbon.

[0122] The metal or metalloid cathode active material comprises one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn), but is not necessarily limited to these; any metal cathode active material or metalloid cathode active material that forms an alloy or compound with lithium in the relevant technical field is acceptable. For example, nickel (Ni) is not a metal cathode active material because it does not form an alloy with lithium.

[0123] The first negative electrode active material layer (22) may include a type of negative electrode active material among these negative electrode active materials, or may include a mixture of multiple different negative electrode active materials. For example, the first negative electrode active material layer (22) may include only amorphous carbon, or one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). Alternatively, the first negative electrode active material layer (22) may include a mixture of amorphous carbon and one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). The mixing ratio of a mixture of amorphous carbon and gold, etc., is, for example, 10:1 to 1:2, 5:1 to 1:1, or 4:1 to 2:1 by weight ratio, but is not necessarily limited to these ranges and is selected according to the required characteristics of the all-solid-state secondary battery (1). By having the negative electrode active material have this composition, the cycle characteristics of the all-solid-state secondary battery (1) are further improved.

[0124] The negative electrode active material included in the first negative electrode active material layer (22) comprises a mixture of first particles made of amorphous carbon, for example, and second particles made of a metal or metalloid. The metal or metalloid includes, for example, gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). Alternatively, the metalloid is a semiconductor. The content of the second particles is 8 to 60 weight%, 10 to 50 weight%, 15 to 40 weight%, or 20 to 30 weight% based on the total weight of the mixture. By having the second particles in this range, the cycle characteristics of, for example, the all-solid-state secondary battery (1) are further improved.

[0125] The first negative electrode active material layer (22) includes, for example, a binder. The binder may be, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc., but is not necessarily limited to these, and any binder used in the relevant technical field may be used. The binder may be composed of a single binder or a plurality of different binders.

[0126] The first negative active material layer (22) is stabilized on the negative current collector (21) by including a binder. Additionally, cracking of the first negative active material layer (22) is suppressed despite changes in volume and / or relative position of the first negative active material layer (22) during the charging and discharging process. For example, if the first negative active material layer (22) does not include a binder, it is possible for the first negative active material layer (22) to be easily separated from the negative current collector (21). The portion where the first negative active material layer (22) is separated from the negative current collector (21) is exposed and comes into contact with the solid electrolyte layer (30), thereby increasing the likelihood of a short circuit. The first negative active material layer (22) is manufactured, for example, by applying a slurry in which the material constituting the first negative active material layer (22) is dispersed onto the negative current collector (21) and drying it. By including a binder in the first cathode active material layer (22), stable dispersion of the cathode active material in the slurry is possible. For example, when the slurry is applied to the cathode current collector (21) by a screen printing method, it is possible to suppress clogging of the screen (e.g., clogging by aggregates of the cathode active material).

[0127] The thickness (d22) of the first negative electrode active material layer is, for example, 50% or less, 30% or less, 10% or less, or 5% or less of the thickness (d12) of the positive electrode active material layer. The thickness (d22) of the first negative electrode active material layer is, for example, 1 µm to 20 µm, 2 µm to 10 µm, or 3 µm to 7 µm. When the thickness (d22) of the first negative electrode active material layer is within the above range, the cycle characteristics of the all-solid-state secondary battery (1) are excellent.

[0128] The charging capacity of the first negative electrode active material layer (22) is, for example, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, 5% or less, or 2% or less compared to the charging capacity of the positive electrode active material layer (12). The charging capacity of the first negative electrode active material layer (22) is, for example, 0.1% to 50%, 0.1% to 40%, 0.1% to 30%, 0.1% to 20%, 0.1% to 10%, 0.1% to 5%, or 0.1% to 2% compared to the charging capacity of the positive electrode active material layer (12). When the charging capacity of the first negative electrode active material layer (22) is within the above range, the cycle characteristics of the all-solid-state secondary battery (1) are excellent. The charge capacity of the positive active material layer (12) is obtained by multiplying the charge capacity density (mAh / g) of the positive active material by the mass of the positive active material in the positive active material layer (12). The negative current collector (21) is composed of a material that does not react with, for example, lithium, that is, does not form any alloys or compounds. The material constituting the negative current collector (21) may be, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni), but is not necessarily limited to these; any material used as an electrode current collector in the relevant technical field is possible. The negative current collector (21) may be composed of one of the metals described above, or may be composed of an alloy or coating material of two or more metals. The negative current collector (21) is, for example, in the form of a plate or foil.

[0129] The first negative electrode active material layer (22) may further include additives used in conventional all-solid-state secondary batteries (1), such as fillers, dispersants, ion conductors, etc.

[0130] Referring to FIG. 11, the all-solid-state secondary battery (1) further comprises, for example, a thin film (24) containing an element capable of forming an alloy with lithium on a negative electrode current collector (21). The thin film (24) is disposed between the negative electrode current collector (21) and the first negative electrode active material layer (22). The thin film (24) contains, for example, an element capable of forming an alloy with lithium. The element capable of forming an alloy with lithium is, for example, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., but is not necessarily limited to these, and any element capable of forming an alloy with lithium in the art is possible. The thin film (24) is composed of one of these metals or is composed of an alloy of various types of metals. By placing the thin film (24) on the negative electrode current collector (21), the deposition shape of the second negative electrode active material layer (not shown) deposited between the thin film (24) and the first negative electrode active material layer (22) is further flattened, and the cycle characteristics of the all-solid-state secondary battery (1) can be further improved.

[0131] The thickness (d24) of the thin film is, for example, 1 nm to 800 nm, 10 nm to 700 nm, 50 nm to 600 nm, or 100 nm to 500 nm. When the thickness of the thin film is within the above range, the energy density and cycle characteristics of the all-solid-state battery are excellent. The thin film (24) can be placed on the negative current collector (21) by, for example, vacuum deposition, sputtering, plating, etc., but is not necessarily limited to these methods, and any method capable of forming the thin film (24) in the relevant technical field is possible.

[0132] Referring to FIG. 12, the all-solid-state secondary battery (1) further includes a second negative active material layer (23) disposed between, for example, a negative current collector (21) and a solid electrolyte layer (30) by charging. The all-solid-state secondary battery (1) further includes a second negative active material layer (23) disposed between, for example, a negative current collector (21) and a first negative active material layer (22) by charging. Although not shown in the drawing, the all-solid-state secondary battery (1) further includes a second negative active material layer (23) disposed between, for example, a solid electrolyte layer (30) and a first negative active material layer (22) by charging. Although not shown in the drawing, the all-solid-state secondary battery (1) further includes a second negative active material layer (23) disposed inside, for example, a first negative active material layer (22) by charging.

[0133] The second negative electrode active material layer (23) is a metal layer containing lithium or a lithium alloy. The metal layer contains lithium or a lithium alloy. Therefore, since the second negative electrode active material layer (23) is a metal layer containing lithium, it acts as, for example, a lithium reservoir. The lithium alloy is, for example, Li-Al alloy, Li-Sn alloy, Li-In alloy, Li-Ag alloy, Li-Au alloy, Li-Zn alloy, Li-Ge alloy, Li-Si alloy, etc., but is not limited to these; any alloy used as a lithium alloy in the relevant technical field is possible. The second negative electrode active material layer (23) may be composed of one of these alloys or lithium, or may be composed of various types of alloys.

[0134] The thickness (d23) of the second negative electrode active material layer is not particularly limited, but is, for example, 1 μm to 1000 μm, 1 μm to 500 μm, 1 μm to 200 μm, 1 μm to 150 μm, 1 μm to 100 μm, or 1 μm to 50 μm. When the thickness (d23) of the second negative electrode active material layer is within the above range, the cycle characteristics of the all-solid-state secondary battery are excellent. The second negative electrode active material layer (23) may be, for example, a metal foil having a thickness within this range.

[0135] In the all-solid-state secondary battery (1), the second negative electrode active material layer (23) is disposed between the negative electrode current collector (21) and the first negative electrode active material layer (22) for example before assembly of the all-solid-state secondary battery (1), or is deposited between the negative electrode current collector (21) and the first negative electrode active material layer (22) by charging after assembly of the all-solid-state secondary battery (1).

[0136] When a second negative electrode active material layer (23) is placed between the negative electrode current collector (21) and the first negative electrode active material layer (22) before assembly of the all-solid-state secondary battery (1), the second negative electrode active material layer (23) acts as a lithium reservoir because it is a metal layer containing lithium. The cycle characteristics of the all-solid-state secondary battery (1) including the second negative electrode active material layer (23) are further improved. For example, a lithium foil is placed between the negative electrode current collector (21) and the first negative electrode active material layer (22) before assembly of the all-solid-state secondary battery (1).

[0137] When the second negative electrode active material layer (23) is formed by charging after assembly of the all-solid-state secondary battery (1), the energy density of the all-solid-state secondary battery (1) increases because the second negative electrode active material layer (23) is not included during assembly of the all-solid-state secondary battery (1). For example, when charging the all-solid-state secondary battery (1), it is charged beyond the charging capacity of the first negative electrode active material layer (22). That is, the first negative electrode active material layer (22) is overcharged. At the beginning of charging, lithium is absorbed in the first negative electrode active material layer (22). That is, the negative electrode active material contained in the first negative electrode active material layer (22) forms an alloy or compound with lithium ions that have moved from the positive electrode layer (10). When charging is performed beyond the capacity of the first negative electrode active material layer (22), lithium is deposited, for example, on the back surface of the first negative electrode active material layer (22), that is, between the negative current collector (21) and the first negative electrode active material layer (22), and a metal layer corresponding to the second negative electrode active material layer (23) is formed by the deposited lithium. The second negative electrode active material layer (23) is a metal layer composed mainly of lithium (i.e., metallic lithium). This result is obtained, for example, by the negative electrode active material included in the first negative electrode active material layer (22) being composed of a material that forms an alloy or compound with lithium. During discharge, the lithium in the first negative electrode active material layer (22) and the second negative electrode active material layer (23), i.e., the metal layer, is ionized and moves toward the positive electrode layer (10). Therefore, it is possible to use lithium as a negative electrode active material in the all-solid-state secondary battery (1). In addition, since the first negative electrode active material layer (22) covers the second negative electrode active material layer (23), it serves as a protective layer for the second negative electrode active material layer (23), i.e., the metal layer, and at the same time, it performs the role of suppressing the precipitation growth of lithium dendrites. Therefore, it suppresses short circuits and capacity degradation of the all-solid-state secondary battery (1), and consequently improves the cycle characteristics of the all-solid-state secondary battery (1).Additionally, when the second negative electrode active material layer (23) is formed by charging after assembly of the all-solid-state secondary battery (1), the negative electrode current collector (21), the first negative electrode active material layer (22), and the region between them are, for example, Li-free regions that do not contain lithium (Li) metal or lithium (Li) alloy in the initial state or after discharge state of the all-solid-state secondary battery.

[0138] Referring to FIG. 12, the all-solid-state secondary battery (1) has a structure in which a second negative electrode active material layer (23) is disposed on a positive electrode current collector (21), and a solid electrolyte layer (30) is directly disposed on the second negative electrode active material layer (23). The second negative electrode active material layer (23) is, for example, a lithium metal layer or a lithium alloy layer.

[0139] (Solid electrolyte layer)

[0140] Referring to FIGS. 10 to 12, the solid electrolyte layer (30) may contain an oxide-based solid electrolyte.

[0141] Oxide-based solid electrolytes are, for example, Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 <x<2, 0≤y<3), BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT)(O≤x<1, O≤y<1), PB(Mg3Nb 2 / 3 )O3-PbTiO3(PMN-PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, Li3PO4, Li x Ti y (PO4)3(0 <x<2, 0<y<3), Li x Al y Ti z (PO4)3(0 <x<2, 0<y<1, 0<z<3), Li1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (0≤x≤1, 0≤y≤1), Li x La y TiO3(0 <x<2, 0<y<3), Li2O, LiOH, Li2CO3, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2, Li 3+x La3M2O 12 (M = Te, Nb, or Zr, x is an integer from 1 to 10) is one or more selected from.

[0142] Oxide-based solid electrolytes are, for example, Li7La3Zr2O 12 (LLZO) and Li 3+x La3Zr 2-a M a O 12 It is a garnet-type solid electrolyte selected from (M doped LLZO, M=Ga, W, Nb, Ta, or Al, x is an integer from 1 to 10, 0.05≤a≤0.7).

[0143] According to one embodiment, the solid electrolyte layer includes an LLZO solid electrolyte.

[0144] The solid electrolyte layer is, for example, Li7La3Zr2O 12 (LLZO), Li 6.4 La3Zr 1.7 W 0.3 O 12, Li 6.5 La3Zr 1.5 Ta 0.3 O 12, Li7La3Zr 1.7 W 0.3 O 12 , Li 4.9 La 2.5 Ca 0.5 Zr 1.7 Nb 0.3 O 12, Li 4.9 Ga 2.1 La3Zr 1.7 W0.3 O 12 , Li 6.4 La3Zr 1.7 W 0.3 O 12 , Li7La3Zr 1.5 W 0.5 O 12 , Li7La 2.75 Ca 0.25 Zr 1.75 Nb 0.25 O 12 , Li7La3Zr 1.5 Nb 0.5 O 12 , Li7La3Zr 1.5 Ta 0.5 O 12 , Li 6.272 La3Zr 1.7 W 0.3 O 12 , Li 5.39 Ga 1.61 La3Zr 1.7 W 0.3 O 12 , Li 6.5 La3Zr 1.5 Ta 0.3 O 12 , or may contain a combination.

[0145] (Bipolar layer)

[0146] The anode layer (10) includes an anode current collector (11) and an anode active material layer (12). The anode layer (10) contains a composite anode containing a composite according to one embodiment.

[0147] The positive current collector (11) is made of, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof, such as a plate or foil. The positive current collector (11) can be omitted.

[0148] The anode layer (10) contains a composite anode according to one embodiment.

[0149] A method for manufacturing an all-solid-state secondary battery involves stacking a solid electrolyte layer (30) on top of a positive electrode layer (10) and stacking a negative electrode layer (20) on top of it.

[0150] According to another embodiment, the solid electrolyte layer (30) may be formed by coating and drying a composition for forming a solid electrolyte layer on a separate substrate and separating it from the substrate, or by manufacturing it in the form of a sheet containing the substrate. The substrate may be a polyethylene terephthalate film, a polyethylene nonwoven fabric, etc., as a non-limiting example.

[0151] According to another embodiment, the solid electrolyte layer (30) can be formed by coating and drying or transferring a composition for forming a first solid electrolyte layer onto the anode layer (10).

[0152] Subsequently, the anode layer, solid electrolyte layer, and cathode layer can be packaged in a packaging material and then pressurized to manufacture an all-solid-state battery. Pressurization can be performed using roll pressurization, hot pressurization, warm isostactic pressurization, etc.

[0153] Mass production is possible when using roll pressing or hot pressing, and a tight interface can be formed during the compression process of the electrode layer and the solid electrolyte layer.

[0154] (Manufacturing of the cathode layer)

[0155] A slurry is prepared by adding materials constituting the first cathode active material layer (22), such as a cathode active material, a conductive material, a binder, and a solid electrolyte, to a polar solvent or a non-polar solvent. The prepared slurry is applied onto a cathode current collector (21) and dried to prepare a first laminate. Subsequently, the dried first laminate is pressed to prepare a cathode layer (20). Pressing may be, for example, a roll press or a flat press, but is not necessarily limited to these methods; any press used in the relevant technical field is possible. The press step may be omitted.

[0156] The above-described cathode layer comprises a cathode current collector and a first cathode active material layer containing a cathode active material disposed on the cathode current collector, wherein the cathode active material comprises one or more selected from carbon-based cathode active materials and metal or metalloid cathode active materials, and the carbon-based cathode active material comprises one or more selected from amorphous carbon and crystalline carbon. The metal or metalloid cathode active material is one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn).

[0157] The invention further comprises a second cathode active material layer disposed between the cathode current collector and the first cathode active material layer and between the solid electrolyte layer and the first cathode active material layer, wherein the second cathode active material layer is a metal layer comprising lithium or a lithium alloy.

[0158] (Preparation of solid electrolyte layer)

[0159] The solid electrolyte layer (30) is manufactured by a solid electrolyte formed from, for example, an oxide-based solid electrolyte material.

[0160] (Manufacturing of all-solid-state secondary batteries)

[0161] An all-solid secondary battery (1) is manufactured by stacking and pressing the positive electrode layer (10), negative electrode layer (20), and solid electrolyte layer (30) produced by the above-described method such that the positive electrode layer (10) and the negative electrode layer (20) have the solid electrolyte layer (30) between them. The positive electrode layer (10) is a composite positive electrode according to one embodiment.

[0162] For example, a second laminate is prepared by placing a solid electrolyte layer (30) on an anode layer (10). Then, a cathode layer (20) is placed on the second laminate so that the solid electrolyte layer (30) and the first cathode active material layer come into contact, thereby manufacturing an all-solid-state secondary battery (10).

[0163] The configuration and manufacturing method of the all-solid-state secondary battery described above are examples of embodiments, and the constituent members and manufacturing procedures, etc., can be appropriately modified.

[0164] The all-solid-state secondary battery according to the first embodiment can be installed in small ITS or large electric vehicles depending on the battery capacity and size.

[0165] The following description will be explained in detail with reference to examples and comparative examples, but is not limited to the examples below.

[0166] (Preparation of crystalline phosphate-based cathode active material)

[0167] Preparation Example 1

[0168] A precursor mixture was obtained by mixing Li2CO3, V2O5, and (NH4)2HPO4, and ethanol was mixed into the mixture and milled in a ball mill for 10 hours. The contents of Li2CO3, V2O5, and (NH4)2HPO4 were stoichiometrically controlled to obtain a cathode active material having the composition of Table 1 below, and ethanol was used in an amount of 100 parts by weight based on a total content of 100 parts by weight of Li2CO3, V2O5, and (NH4)2HPO4.

[0169] The milled product was dried at 90°C for 12 hours, and the dried product was heat-treated in an air atmosphere at 750°C for 12 hours to obtain a crystalline phosphate-based cathode active material Li3V2(PO4)3.

[0170] Preparation Example 2

[0171] A crystalline phosphate-based cathode active material having the composition of Table 1 was obtained by following the same method as Preparation Example 1, except that Fe2O3 was used instead of V2O5 when preparing the precursor mixture, and the contents of Li2CO3, Fe2O3, and (NH4)2HPO4 of the precursor mixture were stoichiometrically adjusted to obtain the crystalline phosphate cathode active material of Table 1 below.

[0172] Preparation Example 3

[0173] When preparing the precursor mixture, CoO was used instead of V2O5, and the contents of Li2CO3, CoO, and (NH4)2HPO4 of the precursor mixture were stoichiometrically controlled to obtain a target product having the composition of Table 1 below, and the process was carried out in the same manner as Preparation Example 1 to obtain a crystalline phosphate-based cathode active material having the composition of Table 1 below.

[0174] division furtherance Heat treatment temperature (°C) Preparation Example 1 Li3V2(PO4)3 750 Preparation Example 2 LiFePO4 750 Preparation Example 3 LiCoPO4 750

[0175] (Composite, composite cathode containing the same, and manufacture of lithium secondary battery)

[0176] Example 1

[0177] First, the composite anode was fabricated according to the following process.

[0178] Crystalline phosphate-based cathode active material Li3V2(PO4)3(LVP) obtained according to Preparation Example 1, and Li as a crystalline solid electrolyte 1.5 Al 0.5 Ge 1.5 A composition for forming a composite was obtained by mixing (PO4)3 (LGAP) and an ink vehicle (FuelCellMaterials). In the composition for forming a composite, the cathode active material of Preparation Example 1, Li 1.5 Al 0.5 Ge 1.5 The mixing weight ratio of (PO4)3 and ink vehicle is 1:1:2.

[0179] Solid electrolyte Li with a thickness of 900 μm as a solid electrolyte layer 1.5 Al 0.5 Ge 1.5 (PO4)3 pellets were prepared. The composition for forming the composite was applied to the upper surface of this solid electrolyte layer, and the composite was heat-treated under pressure at 700°C and 125 MPa to produce an anode active material layer containing the composite.

[0180] An aluminum foil (thickness: about 15 μm) was laminated on the other side of the above-mentioned positive active material layer, and a composite positive was fabricated.

[0181] A 2032 type coin cell was manufactured using the above composite anode and a lithium metal counter electrode as the counter electrode. A separator (thickness: about 16 μm) made of a porous polyethylene (PE) film was interposed between the anode and the lithium metal counter electrode, and an electrolyte was injected to fabricate a lithium secondary battery in the form of a 2032 type coin cell. As the electrolyte, a solution containing 1 M LiPF6 dissolved in propylene carbonate (PC) as the solvent was used.

[0182] Examples 2-3

[0183] The cathode active material of Preparation Example 1, Li3V2(PO4)3 and Li 1.5 Al 0.5 Ge 1.5 A composite cathode and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the mixing weight ratio of (PO4)3 was changed to 1:0.2 and 1:20, respectively.

[0184] Examples 4-5

[0185] A composite cathode and a lithium secondary battery were prepared by following the same method as in Example 1, except that LiFePO4 of Preparation Example 2 and LiCoPO4 of Preparation Example 3 were used instead of the cathode active material Li3V2(PO4)3 of Preparation Example 1 when preparing the cathode.

[0186] Comparative Example 1

[0187] A positive electrode and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the manufacturing of the positive electrode was carried out according to the following process.

[0188] Crystalline phosphate-based cathode active material Li3V2(PO4)3(LVP) obtained according to Preparation Example 1, and Li as a crystalline solid electrolyte 1.5 Al 0.5 Ge 1.5A composition for forming a composite was obtained by mixing (PO4)3 (LGAP) and an ink vehicle (FuelCellMaterials). In the composition for forming a composite, the cathode active material of Preparation Example 1, Li 1.5 Al 0.5 Ge 1.5 The mixing weight ratio of (PO4)3 and ink vehicle is 1:1:2.

[0189] Solid electrolyte Li with a thickness of 900 μm as a solid electrolyte layer 1.5 Al 0.5 Ge 1.5 (PO4)3 pellets were prepared. The composition for forming the composite was applied to the top of this solid electrolyte layer, and the anode active material layer was prepared by pressurizing the mixture at 600°C and 125 MPa.

[0190] An aluminum foil (thickness: about 15 μm) was laminated on the other side of the above positive active material layer, and a positive electrode was fabricated.

[0191] Comparative Example 2

[0192] A positive electrode and a lithium secondary battery were manufactured in the same manner as Comparative Example 1, except that the heat treatment was performed at 650°C instead of 600°C when manufacturing the positive electrode active material layer.

[0193] Comparative Example 3

[0194] Except for the anode being prepared according to the following process, a positive electrode and a lithium secondary battery were manufactured in the same manner as Comparative Example 1.

[0195] Crystalline phosphate-based cathode active material Li3V2(PO4)3(LVP) obtained according to Preparation Example 1, and Li as a crystalline solid electrolyte 1.5 Al 0.5 Ge 1.5 A composition for forming a composite was obtained by mixing (PO4)3 (LGAP) and an ink vehicle (FuelCellMaterials). In the composition for forming a composite, the cathode active material of Preparation Example 1, Li 1.5 Al 0.5Ge 1.5 The mixing weight ratio of (PO4)3 and ink vehicle is 1:1:2.

[0196] Solid electrolyte Li with a thickness of 900 μm as a solid electrolyte layer 1.5 Al 0.5 Ge 1.5 (PO4)3 pellets were prepared. The composition for forming the positive active material layer was applied to the top of this solid electrolyte layer, and the positive active material layer was prepared by pressurizing the mixture at 600°C and about 125 MPa for 30 minutes.

[0197] An aluminum foil (thickness: about 15 μm) was laminated on the other side of the above positive active material layer, and a positive electrode was fabricated.

[0198] Comparative Example 4

[0199] Except for the anode being prepared according to the following process, a positive electrode and a lithium secondary battery were manufactured in the same manner as Comparative Example 1.

[0200] Cathode active material of Preparation Example 1, solid electrolyte Li 1.5 Al 0.5 Ge 1.5 A composition for forming an anode active material layer was obtained by mixing (PO4)3, Denka Black (DB), and an ink vehicle (FuelCellMaterials). In the above composition, the anode active material of Preparation Example 1, Li 1.5 Al 0.5 Ge 1.5 The mixing weight ratio of (PO4)3 and the ink vehicle is 1:1:2, and in the composition for forming the positive electrode active material layer, the positive electrode active material of Preparation Example 1 and the solid electrolyte Li 1.5 Al 0.5 Ge 1.5 The mixing weight ratio of (PO4)3 and Denka Black (DB) is 49:49:2.

[0201] Solid electrolyte Li with a thickness of 900 μm as a solid electrolyte layer 1.5 Al 0.5 Ge 1.5(PO4)3 pellets were prepared. The composition for forming the positive active material layer was applied to the top of this solid electrolyte layer, and the positive active material layer was prepared by pressurizing the mixture at 700°C and 125 MPa for 30 minutes.

[0202] An aluminum foil (thickness: about 15 μm) was laminated on the other side of the above positive active material layer, and a positive electrode was fabricated.

[0203] Comparative Example 5

[0204] Except for the anode being prepared according to the following process, a positive electrode and a lithium secondary battery were manufactured in the same manner as Comparative Example 1.

[0205] Cathode active material of Preparation Example 1, solid electrolyte Li 1.5 Al 0.5 Ge 1.5 A composition for forming an anode active material layer was obtained by mixing (PO4)3 and an ink vehicle (FuelCellMaterials). In the above composition, the anode active material of Preparation Example 1, Li 1.5 Al 0.5 Ge 1.5 The mixing weight ratio of (PO4)3 and ink vehicle is 1:1:2.

[0206] Solid electrolyte Li with a thickness of 900 μm as a solid electrolyte layer 1.5 Al 0.5 Ge 1.5 A (PO4)3 film was prepared. The composition for forming the positive active material layer was applied to the upper surface of this solid electrolyte layer, and the composite-containing positive active material layer was prepared by heat-treating it at 700°C for 2 hours without pressure.

[0207] An aluminum foil (thickness: about 15 μm) was laminated on the other side of the above positive active material layer, and a positive electrode was fabricated.

[0208] Evaluation Example 1: Scanning electron microscope

[0209] Scanning electron microscope analysis was performed on the composites of Example 1 and Comparative Examples 1 to 5, and the results of the analysis are shown in FIG. 1a and FIG. 2a to 2d, respectively.

[0210] Referring to FIG. 1a, the composite anode of Example 1 contains a composite having a densified structure in which LVP and LAGP solid electrolytes form an interfacial phase, and the interface between the anode and the solid electrolyte is dense and uniform. The composite exhibits a structure in which LVP partially surrounds the LAGP solid electrolyte. Although not shown in FIG. 1a, the composite may also exhibit a structure in which LVP completely surrounds the LAGP solid electrolyte.

[0211] The anode of Comparative Example 1 was heat-treated at 600°C, and as shown in Fig. 2a, unlike the case of Example 1, many pores were formed at the interface between the anode and the solid electrolyte, and unlike the composite anode of Example 1, it exhibited an anode state that was not densified. In addition, the anode of Comparative Example 2 was heat-treated at 650°C, and as shown in Fig. 2b, unlike the composite anode of Example 1, it exhibited an anode state that was not densified.

[0212] The anode of Comparative Example 3 is formed using only LVP and, as can be seen from FIG. 2c, shows a state that is not densified, and unlike the case of Example 1, an interphase is formed between the anode and the LAGP solid electrolyte. When an interphase is formed between the anode and the solid electrolyte in this way, the interfacial resistance is reduced.

[0213] The anode of Comparative Example 4 was manufactured using DB, a carbon-based compound, to improve electronic conductivity, and as shown in FIG. 2d, unlike the composite anode of Example 1, it exhibited a structure that was not densified. In addition, the anode of Comparative Example 5 was heat-treated without undergoing a pressurization step during manufacturing, and as shown in FIG. 2e, it exhibited a structure that was not densified.

[0214] In addition, the porosity of the composite anode of Example 1 and the anodes of Comparative Examples 1 to 5 was evaluated and is shown in Table 2 below. Here, the porosity was evaluated by SEM, and the results are shown in Table 2.

[0215] division Porosity (%) Example 1 0.82 Comparative Example 1 15.42 Comparative Example 2 9.81 Comparative Example 3 11.40 Comparative Example 4 6.13 Comparative Example 5 21.63

[0216] Referring to Table 2, the composite anode of Example 1 had a densified structure with a porosity of 0.82%, whereas the anodes of Comparative Examples 1 to 5 showed a porosity exceeding 6.13%, indicating that they had a less dense porous structure compared to the composite anode of Example 1.

[0217] Evaluation Example 2: X-ray diffraction analysis (I)

[0218] X-ray diffraction analysis was performed on the composite anode containing the composite of Example 1 and the composite anode containing the composite of Comparative Example 1. X-ray diffraction analysis was performed using X'pert pro (PANalytical) with Cu Kα radiation (1.54056 Å).

[0219] The results of the X-ray diffraction analysis are shown in Fig. 3a, and a magnified view of a portion of Fig. 3a is shown in Fig. 3b. Figs. 3a and 3b show LiGe2(PO4)2 and Li3V2(PO4)3 for reference.

[0220] The peak (11-2) appearing in the region where the diffraction angle 2θ is 20.69±0.1°, the peak (1-12) appearing in the region where the diffraction angle 2θ is 20.9±0.1°, the peak (10-3) appearing in the region where the diffraction angle 2θ is 24.7±0.1°, and the peak (103) appearing in the region where the diffraction angle 2θ is 24.4±0.1°, all obtained by X-ray diffraction analysis of the above complex using CuKα rays, all provide information that the crystal structure of LVP is distorted and that the change in the lattice constant is different from this.

[0221] Referring to this, when the composite anode is manufactured according to Example 1 and subjected to a pressurized heat treatment process at 700°C and 125 MPa, the XRD peak intensity ratio of LVP changed.

[0222] According to Comparative Example 1, I (11-2) I (1-12) and I (103) I (10-3) Although it exhibits the characteristic of, according to Example 1, I (11-2) < I (1-12) and I (103) < I (10-3) It showed characteristics.

[0223] In Table 3 below, I (11-2) / I (1-12) and I(103) / I (10-3) It was measured and expressed.

[0224] division I (11-2) / I (1-12) I (103) / I (10-3) Example 1 0.12 0.27 Comparative Example 1 1.10 1.35

[0225] Referring to Table 3, for the composite-containing composite anode of Example 1, I (11-2) / I (1-12) and I (103) / I (10-3) Although shows a value of less than 1, I for the composite anode containing the composite of Comparative Example 1 (11-2) / I (1-12) and I (103) / I (10-3) Ga showed a result exceeding 1.

[0226] Evaluation Example 3: X-ray Diffraction Analysis (II)

[0227] X-ray diffraction analysis was performed on the composite-containing anode of Comparative Example 3. X-ray diffraction analysis was performed using X'pert pro (PANalytical) with Cu Kα radiation (1.54056 Å).

[0228] The results of the X-ray diffraction analysis are shown in Fig. 4a, and a magnified view of a portion of Fig. 4a is shown in Fig. 4b. Figs. 4a and 4b also show the analysis results for the sample (Reference) in the state prior to heat treatment when carried out according to Example 1.

[0229] Referring to this, the same 700 according to Comparative Example 3 o It was found that even under C 125MPa conditions, the XRD peak intensity reversal phenomenon of LVP observed in the composite anode of Example 1 did not occur in the electrode using only LVP without LAGP.

[0230] delete

[0231] Evaluation Example 4: EDS Analysis

[0232] EDS analysis was performed on the composite anode of Example 1, and the results of the analysis are shown in Fig. 1b.

[0233] Referring to this, the composite anode of Example 1 had a structure in which LVP and LAGP were in contact through an interface, and the LVP anode active material surrounded the LAGP solid electrolyte. In addition, the presence of elements Al, O, P, and V was confirmed on the interface.

[0234] Evaluation Example 5: Charge / Discharge Characteristics

[0235] (1) Example 1-2 and Comparative Example 1-5

[0236] The charge and discharge characteristics of the coin cells manufactured according to Examples 1-2 and Comparative Examples 1-5 were evaluated by the following charge and discharge test.

[0237] For each coin cell, charging and discharging were performed by resting at 25°C for 5 hours, then charging at a constant current of 0.05C until the voltage reached 4.2V. After charging was complete, the cell was discharged at a constant current of 0.025C until the voltage reached 3.0V.

[0238] These charge-discharge cycles were repeated a total of 10 times. Some of the results are shown in Figures 5a to 5g.

[0239] As shown in FIGS. 5a and 5b, the lithium secondary batteries obtained according to Examples 1 and 2 have high initial charge / discharge capacity and improved capacity retention rate over cycles.

[0240] In contrast, according to Comparative Examples 1 and 2, as shown in FIGS. 5c and 5d, 650 o At temperatures below C, the initial charge / discharge capacity was low and the capacity retention rate was poor. In addition, when the anode was prepared using only LVP according to Comparative Example 3, DB was added according to Comparative Example 4, and no pressurization was performed according to Comparative Example 5, the initial charge / discharge capacity was low as shown in FIGS. 5e, 5f, and 5g. Furthermore, according to Comparative Example 4, from FIG. 5f, it was found that although the addition of DB, a carbon-based compound, improved the electronic conductivity, a dense LVP-LAGP interface was not formed, resulting in poor charge / discharge characteristics.

[0241] Based on the above results, the change in initial discharge and the change in capacity retention rate after 10 cycles according to the heat treatment temperature during anode manufacturing were investigated and are shown in Figures 6a and 6b.

[0242] Based on this, it was found that when the heat treatment temperature is 700°C to 750°C, the initial charge / discharge capacity is high and the capacity retention characteristics are improved.

[0243] In addition, the initial charge / discharge capacity and capacity retention rate of the lithium secondary battery manufactured according to Examples 3-5 were evaluated by performing the same method as the charge / discharge characteristic evaluation method for the lithium secondary battery of Example 1.

[0244] As a result of the evaluation, it was found that the lithium secondary battery of Examples 3-5 exhibited an initial charge / discharge capacity and capacity retention rate equivalent to that of the lithium secondary battery of Example 1.

[0245] Although an exemplary embodiment has been described above, it is not limited thereto. It is possible to implement the invention with various modifications within the scope of the claims, the detailed description of the invention, and the attached drawings, and it is obvious that such modifications also fall within the scope of the invention. Explanation of the symbols

[0246] 1: Solid-state secondary battery 10: Positive electrode layer 11: Positive current collector 12: Positive active material layer 20: Cathode layer 21: Cathode current collector 22: Cathode active material layer 30: Solid electrolyte layer

Claims

Claim 1 It comprises a positive current collector; and a positive active material layer disposed on the positive current collector, wherein the positive active material layer comprises a crystalline phosphate-based solid electrolyte; and 10 times the crystalline phosphate-based solid electrolyte to 10 6 A composite anode comprising a crystalline phosphate-based anode active material having twice the electronic conductivity; and a composite comprising an interphase interposed between them. Claim 2 In claim 1, the interface phase is a composite cathode that is a secondary phase existing between the main phase, a crystalline phosphate-based solid electrolyte, and a crystalline phosphate-based cathode active material. Claim 3 In claim 1, the electron conductivity of the crystalline phosphate-based cathode active material is 10 times the electron conductivity of the crystalline phosphate-based solid electrolyte. 2 to 10 3 Large, composite anode. Claim 4 A composite anode according to claim 1, wherein the interface phase has an amorphous state, and the interface phase contains at least one element contained in a crystalline phosphate-based solid electrolyte and a crystalline phosphate-based anode active material. Claim 5 A composite anode according to claim 1, wherein the crystalline phosphate-based positive electrode active material in the composite is arranged to partially or completely surround the surface of the crystalline phosphate-based solid electrolyte, and the interface is located between the crystalline phosphate-based solid electrolyte and the crystalline phosphate-based positive electrode active material. Claim 6 In claim 1, the crystalline phosphate-based cathode active material is a composite cathode comprising a compound represented by the following Chemical Formula 1, a compound represented by the following Chemical Formula 2, or a combination thereof. <Chemical Formula 1> Li m M a In (PO4)3 Chemical Formula 1, M is Ti, Si, Mn, Fe, Co, V, Cr, Mo, Ni, Al, Mg, Al or a combination thereof, 1≤m≤5, 1≤a≤2, and <Chemical Formula 2>Li n In the chemical formula M1(PO4)2, M1 is Co, Ni, Mn, Fe, or a combination thereof, and 1≤n≤1. Claim 7 In claim 6, the crystalline phosphate-based cathode active material is a composite cathode that is Li3V2(PO4)3, LiCoPO4, LiFePO4, LiNiPO4, LiMnPO4, or a combination thereof. Claim 8 In claim 1, the crystalline phosphate-based solid electrolyte is Li 1+x Al x Ge 2-x (PO4)3 (0 <x≤2), Li 1+x AlxTi 2-x (PO4)3 (0≤x≤1), Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 <x<2, 0≤y<3), Li x Ti y (PO4)3(0 <x<2, 0<y<3), Li x Al y Ti z (PO4)3(0 <x<2, 0<y<1, 0<z<3), Li 1+x+y (Al a Ga 1-a ) x (Ti b Ge 1-b ) 2-x Si y P 3-y O 12 (0 <a<1, 0<b<1, 0≤x≤1, 0≤y≤1), 또는 그 조합인 복합양극. Claim 9 In claim 1, the crystalline phosphate-based solid electrolyte is Li 1.5 Al 0.5 Ge 1.5 (PO4)3, Li 1.3 Al 0.3 Ge 1.7 (PO4)3, Li 1.3 Al 0.3 Ti 1.7 Composite anode comprising (PO4)3 or a combination thereof. Claim 10 A composite cathode according to claim 1, wherein the content of the crystalline phosphate-based solid electrolyte is 0.2 to 20 parts by weight based on 1 part by weight of the crystalline phosphate-based cathode active material. Claim 11 In claim 1, the peak intensity I appearing in the region where the diffraction angle 2θ obtained by X-ray diffraction analysis using CuKα rays of the complex is 20.9±0.1° (1-12) Peak intensity I appearing in the region where the diffraction angle 2θ for is 20.69±0.1° (11-2) The ratio of (I (11-2) / I (1-12) A composite anode where ) is less than 1. Claim 12 In claim 1, the peak intensity I appearing in the region where the diffraction angle 2θ obtained by X-ray diffraction analysis using CuKα rays of the complex is 24.7±0.1° (10-3) Peak intensity I appearing in the region where the diffraction angle 2θ for is 24.4±0.1° (103) The ratio of (I (103) / I (10-3) A composite anode where ) is less than 1. Claim 13 In claim 1, the porosity of the composite is 0.1 to 5%, and the composite is a composite anode containing closed pores. Claim 14 In claim 1, the composite anode is an electron conductor-free composite anode. Claim 15 A secondary battery comprising a composite anode according to any one of claims 1 to 14; a cathode and an electrolyte interposed between the composite anode and the cathode. Claim 16 In paragraph 15, the above secondary battery is a lithium secondary battery or a secondary battery that is an all-solid-state battery. Claim 17 In paragraph 15, the all-solid-state battery is a secondary battery that is a multi-layer-ceramic (MLC) battery or a thin-film battery. Claim 18 In claim 17, the above-described multilayer ceramic battery is a secondary battery having a multilayer structure in which a cell unit having a positive electrode active material layer; a solid electrolyte layer; and a negative electrode active material layer is stacked such that the positive electrode active material layer and the negative electrode active material layer face each other, wherein the cell unit having the positive electrode active material layer and the negative electrode active material layer is stacked in a plurality of such stacked structures. Claim 19 In claim 17, the above-described multilayer ceramic battery is a secondary battery having a plurality of cell units having a positive active material layer, a solid electrolyte layer, and a negative active material layer in that order, stacked such that the positive active material layer and the negative active material layer of the cell units face each other. Claim 20 In claim 15, the secondary battery comprises: a positive electrode layer including a positive electrode active material layer, a negative electrode current collector layer and a negative electrode layer including a first negative electrode active material layer; and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer. Claim 21 Crystalline phosphate-based solid electrolyte, 10 times to 10 times the crystalline phosphate-based solid electrolyte 6 A method for manufacturing a composite anode according to any one of claims 1 to 14, comprising: a step of providing a composition for forming a composite anode by mixing a crystalline phosphate-based anode active material having twice the electron conductivity, a binder, and a solvent; and a step of pressurizing the composition for forming a composite anode at 700°C or higher and 150 MPa or lower. Claim 22 A method for manufacturing a composite anode according to claim 21, wherein the pressurized heat treatment is performed at 700°C to 800°C and 50 MPa to 125 MPa. Claim 23 A method for manufacturing a composite cathode according to claim 21, wherein the content of the crystalline phosphate-based solid electrolyte is 0.2 to 20 parts by weight based on 1 part by weight of the crystalline phosphate-based cathode active material.

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