All-solid-state lithium secondary battery and method for manufacturing the same

Abstract

The present invention relates to an all-solid-state lithium secondary battery and a method for manufacturing the same. The all-solid-state lithium secondary battery comprises a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer, wherein the negative electrode active material layer comprises carbon structures and silver nanoparticles, the carbon structures comprise at least one hollow-type particle, and the hollow-type particle comprises a hollow portion and a carbonaceous shell surrounding the hollow portion.

Description

Technical Field

[0001] This invention relates to an all-solid-state lithium secondary battery and its preparation method. Background Technology

[0002] Secondary batteries are mainly used in small devices such as mobile devices and laptops, but in recent years their application has expanded to medium and large devices, such as those requiring high energy and high output, such as energy storage systems (ESS) and electric vehicles (EVs).

[0003] Recently, there has been an increasing interest in all-solid-state lithium secondary batteries. All-solid-state lithium secondary batteries use a non-flammable inorganic solid electrolyte instead of a liquid electrolyte. Among them, all-solid-state lithium secondary batteries have attracted attention because they have higher thermal stability than lithium secondary batteries using liquid electrolytes, have a very low risk of explosion due to leakage during overcharging, and do not require additional equipment to prevent explosion risks.

[0004] However, because all-solid-state lithium-ion batteries use a bulky solid electrolyte, many attempts have been made to improve the battery's energy density. To this end, a metal layer capable of forming an alloy with lithium, such as lithium metal, is used as the negative electrode active material layer. However, if a metal layer is used, pores are created between the solid electrolyte and the metal layer due to the ionization and dissolution of lithium deposited on the metal layer, which adversely affects battery operation. Furthermore, during the discharge process of all-solid-state lithium-ion batteries, lithium metal precipitates in dendrite form on the surface of the metal layer, thus reducing the battery's lifespan and safety.

[0005] To address this issue, a traditional approach involves applying high external pressure by placing end plates on the positive or negative electrode to prevent porosity. However, this method results in an excessive increase in the volume of the all-solid-state lithium secondary battery when using end plates with applied external pressure, leading to a decrease in the energy density of the all-solid-state lithium secondary battery.

[0006] Therefore, a new method is needed to improve the lifespan and safety of all-solid-state lithium secondary batteries. Summary of the Invention

[0007] Technical issues

[0008] One aspect of the present invention provides an all-solid-state lithium secondary battery, wherein lithium metal can be effectively stored by reducing lithium ions during charging, thereby improving the first charge / discharge efficiency and improving lifespan characteristics.

[0009] Another aspect of the present invention provides an all-solid-state lithium secondary battery that is price-competitive by reducing the amount of silver nanoparticles used.

[0010] Another aspect of the present invention provides a method for preparing the above-described all-solid-state lithium secondary battery.

[0011] Technical solution

[0012] According to one aspect of the present invention, an all-solid-state lithium secondary battery is provided, comprising a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer, wherein the negative electrode active material layer comprises a carbon structure and silver nanoparticles, the carbon structure comprises at least one hollow particle, and the hollow particle comprises a hollow portion and a carbonaceous shell surrounding the hollow portion.

[0013] According to another aspect of the present invention, a method for preparing an all-solid-state lithium secondary battery is provided, comprising: a first step of forming a dry-mixed powder comprising the carbon structure and silver nanoparticles disposed on the carbon structure by reducing silver ions in a mixture of silver ions and a carbon structure; and a second step of forming a negative electrode active material layer on a negative electrode current collector by a negative electrode mixture comprising the dry-mixed powder.

[0014] Beneficial effects

[0015] In the all-solid-state lithium secondary battery of the present invention, since the negative electrode active material layer contains the carbon structure and silver nanoparticles described in this specification, lithium ions are reduced and deposited by the negative electrode active material layer during charging, thus effectively storing lithium ions in the negative electrode. Furthermore, since the lithium stored during discharge can dissolve in the form of lithium ions, these lithium ions can migrate to the positive electrode. The carbon structure can improve the battery's first charge / discharge efficiency and lifespan characteristics by increasing the mobility of lithium ions. Moreover, when using the carbon structure, since the lithium ions can migrate effectively even with a small amount of silver nanoparticles, the price competitiveness of the prepared all-solid-state lithium secondary battery can be improved. Attached Figure Description

[0016] Figure 1 This is a schematic diagram illustrating an embodiment of the all-solid-state lithium secondary battery of the present invention.

[0017] Figure 2 This is a schematic diagram illustrating an embodiment of the all-solid-state lithium secondary battery of the present invention.

[0018] Figure 3 This is a cross-sectional schematic diagram illustrating the hollow particles contained in the carbon structure mentioned in this invention.

[0019] Figure 4 This is a cross-sectional schematic diagram illustrating the carbon structure mentioned in this invention.

[0020] Figure 5 and 6This is a transmission electron microscope (TEM) image of the carbon structure used in Embodiment 1 of the present invention.

[0021] Figure 7 and 8 This is a TEM image of the carbon structure used in Embodiment 6 of the present invention.

[0022] Figure 9 This is a TEM image of the carbon structure used in Embodiment 1 of the present invention and the silver nanoparticles disposed on the carbon structure. Detailed Implementation

[0023] It will be understood that the words or terms used in the specification and claims should not be interpreted as having the meaning defined in a common dictionary, and it will also be understood that, based on the principle that the inventors may appropriately define the meaning of words or terms to best interpret the invention, the words or terms should be interpreted as having a meaning consistent with their meaning in the context of the related technology and the technical idea of ​​the invention.

[0024] The terminology used herein is for the purpose of describing specific exemplary embodiments only and is not intended to limit the invention. In this specification, singular terms may include plural forms unless otherwise stated.

[0025] It will be further understood that, when used in this specification, the terms “comprising,” “including,” or “having” specify the presence of the stated features, figures, steps, elements, or combinations thereof, but do not exclude the presence or inclusion of one or more other features, figures, steps, elements, or combinations thereof.

[0026] In this specification, the term "specific surface area" is stated to be measured by the Brunauer-Emmett-Teller (BET) method, wherein, specifically, the specific surface area can be calculated from the amount of nitrogen adsorbed at liquid nitrogen temperature (77K) using the BELSORP-mini II of Bell Japan Inc.

[0027] I of this instruction manual D / I G The ratio can be measured from the wavelength-peak plot during Raman spectroscopy measurements. Specifically, after fitting the plot by setting a baseline to distinguish the D and G peaks, I can be determined by dividing the D peak intensity by the G peak intensity. D / I G (Using built-in software, NRS-2000B, Jasco). In the Raman spectrum, at 1590 cm⁻¹ -1 The nearby G peak is due to the sp of carbon. 2 E key 2g Due to the vibration mode, at 1350cm -1 The nearby D peak is at the sp of carbon.2 This occurs when there is a defect in the key.

[0028] The average particle size of the silver nanoparticles in this specification corresponds to the average particle size of the first 50 silver nanoparticles with the largest particle size and the last 50 silver nanoparticles when observed with a transmission electron microscope (TEM) at a magnification of ×1,000,000.

[0029] The shell thickness described in this specification can be determined using a JEOL Ltd. JEM-2100 instrument.

[0030] The average particle size of the hollow particles in this specification corresponds to the average particle size of the first 50 hollow particles sorted by maximum particle size and the last 50 hollow particles when the negative electrode active material layer is observed by TEM at a magnification of ×250,000.

[0031] The present invention will be described in detail below.

[0032] All-solid-state lithium secondary battery

[0033] The all-solid-state lithium secondary battery of the present invention comprises a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer. The negative electrode active material layer comprises a carbon structure and silver nanoparticles. The carbon structure comprises at least one hollow particle, and the hollow particle may comprise a hollow portion and a carbon shell surrounding the hollow portion.

[0034] (1) Negative electrode active material layer

[0035] All-solid-state lithium secondary batteries may include a negative electrode active material layer. Specifically, all-solid-state lithium secondary batteries may include a negative electrode, which may include a negative electrode current collector and a negative electrode active material layer.

[0036] There are no particular restrictions on the negative electrode current collector, as long as it is conductive and does not cause adverse chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, sintered carbon, or aluminum or stainless steel with a surface treatment of one of carbon, nickel, titanium, or silver can be used as the negative electrode current collector. Specifically, transition metals that readily absorb carbon, such as nickel or stainless steel, can be used as the negative electrode current collector.

[0037] See Figure 1 The negative electrode active material layer 100 can be disposed on at least one surface of the negative electrode current collector 110. Specifically, the negative electrode active material layer 100 can be disposed on one surface of the negative electrode current collector 110, or it can be disposed on two surfaces of the negative electrode current collector (not shown).

[0038] The negative electrode active material layer can contain carbon structures and silver nanoparticles. Specifically, the negative electrode active material layer can be composed of carbon structures and silver nanoparticles.

[0039] 1) Carbon structure

[0040] Carbon structures can serve as a pathway for lithium ions transported from the positive electrode active material layer, thus facilitating their deposition and storage on the negative electrode current collector.

[0041] See Figure 3 and Figure 4 The carbon structure may comprise at least one hollow particle 100. Specifically, the carbon structure may consist of a single hollow particle 100. Alternatively, see [link to relevant documentation]. Figure 4 The carbon structure may have a secondary particle shape in which multiple hollow particles 100 are combined with each other.

[0042] See Figure 3 The hollow particle 100 may include a hollow portion 110 and a carbon shell 120 surrounding the hollow portion. Specifically, the hollow particle 100 has a particle shape, the interior of the hollow particle 100 is hollow, and the outer surface may surround the hollow interior. Here, the hollow interior corresponds to the hollow portion 110, and the outer surface corresponds to the shell 120. Such a structure can form a robust network in the negative electrode active material layer that can improve conductivity and ion conduction. Therefore, the storage and movement of lithium ions can be significantly improved. More specifically, for conventional carbon black, due to the low crystallinity of the particles caused by the spherical primary particle structure with a small radius of curvature, there is a problem of irreversible capacity increase in the storage and movement of lithium ions in the carbon structure during battery operation. However, in the structure of the hollow particle as described above, since the storage and movement of lithium ions occur concentrated in the thin graphite layered structure in the form of a shell, and the particles have high crystallinity due to the preparation characteristics of high-temperature heat treatment, the first charge / discharge efficiency and lifetime characteristics of the all-solid-state lithium secondary battery can be improved.

[0043] See Figure 3 The thickness of the shell ( Figure 3 The thickness (T) can range from 1 nm to 15 nm, particularly from 1 nm to 13 nm, and even more particularly from 1 nm to 10 nm, for example, from 1 nm to 5 nm. When the above thickness range is met, the carbon structure can maintain mechanical rigidity against external forces applied during the fabrication of the negative electrode. Furthermore, due to the developed graphite layered structure, the carbon structure can exhibit high electrical and ionic conductivity. Moreover, since the storage and movement of lithium ions can be concentrated in the thin graphite layered structure in shell form, the initial charge / discharge efficiency and lifetime characteristics of the all-solid-state lithium secondary battery can be improved.

[0044] See Figure 3 The average particle size of hollow particles ( Figure 3 In this context, D) can range from 5 nm to 100 nm, particularly from 5 nm to 70 nm, and even more particularly from 5 nm to 50 nm, for example, from 5 nm to 20 nm. When the above average particle size range is met, the carbon structure can maintain mechanical rigidity against external forces applied during the fabrication of the negative electrode. Furthermore, due to the developed graphite layered structure, the carbon structure can exhibit high electrical and ionic conductivity. Moreover, since the storage and movement of lithium ions can be concentrated in the thin graphite layered structure in shell form, the initial charge / discharge efficiency and lifetime characteristics of the all-solid-state lithium secondary battery can be improved.

[0045] In Raman spectroscopy measurements, the I of the carbon structure D / I G The value can be from 0.1 to 1.5, particularly from 0.1 to 1.3, and even more particularly from 0.1 to 1.0, for example, from 0.6 to 1.0. In Raman spectroscopy, at 1590 cm⁻¹... -1 The nearby G peak is due to the sp of carbon. 2 E key 2g Due to the vibration mode, at 1350cm -1 The nearby D peak is at the sp of carbon. 2 It occurs when there is a defect in the key. That is, when I is satisfied... D / I G A high peak-to-peak ratio means a relatively high degree of graphitization can be achieved, allowing the carbon structure to maintain mechanical rigidity against external forces applied during anode fabrication. Furthermore, due to the developed layered graphite structure, the carbon structure can exhibit high electrical and ionic conductivity. Moreover, since the storage and movement of lithium ions can be concentrated in the thin layered graphite structure in shell form, the initial charge / discharge efficiency and lifetime characteristics of all-solid-state lithium secondary batteries can be improved.

[0046] Based on the total weight of the carbon structure, the oxygen content of the carbon structure can be less than 5% by weight, particularly 0% to 3% by weight, and even more particularly 0% to 1% by weight. When the oxygen content of the carbon structure meets the above range, due to the high purity and high crystallinity of the carbon structure, it can maintain mechanical rigidity against external forces applied during the anode fabrication process. Furthermore, due to the developed graphite layered structure, the carbon structure can exhibit high electrical and ionic conductivity. Moreover, since the storage and movement of lithium ions can be concentrated in the thin graphite layered structure in shell form, the initial charge / discharge efficiency and lifetime characteristics of the all-solid-state lithium secondary battery can be improved.

[0047] The specific surface area (m²) of the carbon structure measured by the Brunauer-Emmett-Teller (BET) method using nitrogen adsorption. 2 / g) can be 10m2 / g to 300m 2 / g, especially 10m 2 / g to 250m 2 / g, especially 10m 2 / g to 200m 2 / g, for example 80m 2 / g to 200m 2 / g. Under the condition of satisfying the above specific surface area range, since silver nanoparticles can be stably set on the surface of carbon structures, lithium ion storage and movement can be effectively realized.

[0048] In the negative electrode active material layer, the content of carbon structures can be from 50 wt% to 98 wt%, particularly from 60 wt% to 95 wt%, and even more particularly from 70 wt% to 90 wt%. When the above range is met, the first charge / discharge efficiency and lifetime characteristics of the all-solid-state lithium secondary battery can be improved because the lithium-ion mobility can be effectively improved while minimizing the decrease in energy density of the all-solid-state lithium secondary battery.

[0049] 2) Silver nanoparticles

[0050] Because silver nanoparticles have lithium-philic properties, they can be readily alloyed with lithium ions. Therefore, silver nanoparticles can form alloys with lithium ions transported from the positive electrode active material layer, thereby promoting lithium ion storage and diffusion into the negative electrode active material layer.

[0051] Silver nanoparticles may contain silver (Ag). Furthermore, silver nanoparticles may also contain at least one element selected from the group consisting of gold, platinum, palladium, silicon, aluminum, bismuth, tin, indium, and zinc. Alternatively, silver nanoparticles may be formed from silver. Silver nanoparticles may be in a solid phase.

[0052] Silver nanoparticles can be deposited on the surface of a carbon structure. Specifically, silver nanoparticles can be formed by reducing silver ions in a silver ion solution on the surface of a carbon structure, thus allowing them to be deposited on the surface of the carbon structure. Alternatively, silver nanoparticles can be deposited on the surface of a carbon structure by mixing powdered silver nanoparticles with powdered carbon structure.

[0053] The average particle size of silver nanoparticles can range from 1 nm to 100 nm, particularly from 1 nm to 50 nm, and even more particularly from 1 nm to 30 nm, for example, from 1 nm to 5 nm. When these ranges are met, silver nanoparticles can be effectively dispersed in the negative electrode active material layer, thus promoting lithium-ion storage and diffusion even at low concentrations. Furthermore, this can improve the initial efficiency and lifespan characteristics of the battery.

[0054] In the negative electrode active material layer, the content of silver nanoparticles can range from 1 wt% to 40 wt%, specifically from 3 wt% to 30 wt%, more specifically from 5 wt% to 20 wt%, for example from 7 wt% to 10 wt%, based on the total weight of the carbon structure and silver nanoparticles. When the above range is met, the electrochemical performance of the all-solid-state lithium secondary battery can be improved because lithium ions transported from the positive electrode active material layer can be effectively alloyed with the silver nanoparticles. Simultaneously, the use of silver nanoparticles with a lower silver content can improve the energy density and price competitiveness of the all-solid-state lithium secondary battery.

[0055] In particular, since the negative electrode active material layer contains a carbon structure, the amount of silver nanoparticles used can be less than 10% by weight, specifically 7% to 10% by weight. Lithium ions are alloyed with silver nanoparticles exhibiting lithium-philic properties to promote lithium ion storage and diffusion into the negative electrode. Furthermore, if the carbon structure described in this invention is specifically used, the diffusion and movement of lithium ions can be further promoted through a thin and highly crystalline graphite layered structure in the form of a shell. Even using a small amount of silver nanoparticles can significantly improve the capacity and initial charge / discharge efficiency of the all-solid-state lithium secondary battery.

[0056] In the negative electrode active material layer, the weight ratio of carbon structures to silver nanoparticles can be from 99:1 to 60:40, particularly from 97:3 to 70:30, and even more particularly from 95:5 to 80:20. When the above range is met, the capacity and first charge / discharge efficiency of the all-solid-state lithium secondary battery can be improved more effectively.

[0057] The loading of the negative electrode active material layer can be 0.1 mg / cm³. 2 Up to 2.0 mg / cm 2 Especially 0.3 mg / cm 2 Up to 1.8 mg / cm 2 More particularly 0.5 mg / cm 2 Up to 1.6 mg / cm 2 When the above range is met, the effect of improving the battery's initial efficiency and lifespan can be maximized without reducing energy density due to the increase in negative electrode thickness.

[0058] The thickness of the negative electrode active material layer can range from 1 μm to 100 μm, specifically from 1 μm to 50 μm, and more specifically from 1 μm to 20 μm. When the above range is met, the effect of improving the initial efficiency and lifespan of the battery can be maximized without reducing the energy density due to the increase in the thickness of the negative electrode.

[0059] 3) Negative electrode adhesive

[0060] The negative electrode active material layer may also include a negative electrode binder. The negative electrode binder may include at least one selected from the group consisting of: polyvinylidene fluoride (PVdF), polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, polyvinylpyrrolidone, polytetrafluoroethylene (PTFE), polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), styrene-butadiene rubber (SBR), and fluororubber.

[0061] In the negative electrode active material layer, the content of the negative electrode binder can be from 1 wt% to 20 wt%, particularly from 1 wt% to 15 wt%, and even more particularly from 1 wt% to 10 wt%. Meeting these ranges improves the mechanical properties of the negative electrode while maintaining a low resistance level, further promoting lithium-ion storage and diffusion.

[0062] In some cases, the negative electrode active material layer may also contain at least one of lithium ions, lithium, and an alloy of lithium and silver nanoparticles. Specifically, when the all-solid-state lithium secondary battery is in operation, lithium ions, lithium, and an alloy of lithium and silver nanoparticles may be present in the negative electrode active material layer through lithium ions transported from the positive electrode active material.

[0063] (2) Positive electrode active material layer

[0064] All-solid-state lithium secondary batteries may include a positive electrode active material layer. Specifically, an all-solid-state lithium secondary battery may include a positive electrode, and the positive electrode may include or be composed of a positive electrode active material layer.

[0065] The positive electrode may include a positive current collector. There are no particular limitations on the positive current collector, as long as it has high conductivity and does not cause adverse chemical changes in the positive electrode or battery. For example, the positive current collector may include at least one material selected from the group consisting of stainless steel, copper, aluminum, nickel, titanium, and sintered carbon, specifically aluminum. The positive current collector includes a carbon-based conductive agent and a binder, and may also include a base coating applied to the surface of the positive current collector. Therefore, conductivity and the adhesion between the positive electrode active material layer and the current collector can be significantly improved.

[0066] The positive electrode active material layer can be disposed on at least one surface of the positive electrode current collector. Specifically, the positive electrode active material layer can be disposed on one or both surfaces of the positive electrode current collector.

[0067] The positive electrode active material layer may contain positive electrode active material.

[0068] Positive electrode active materials may include: layered compounds, such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or compounds substituted with one or more transition metals; lithium manganese oxide, including Li1+x Mn 2-x O4 (where x ranges from 0 to 0.33), LiMnO3, LiMn2O3, LiMn2O4, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, and Cu2V2O7; represented by the chemical formula LiNi 1-x M x O2 (where M = cobalt (Co), manganese (Mn), aluminum (Al), copper (Cu), iron (Fe), phosphorus (P), magnesium (Mg), calcium (Ca), zirconium (Zr), titanium (Ti), ruthenium (Ru), niobium (Nb), tungsten (W), boron (B), silicon (Si), sodium (Na), potassium (K), molybdenum (Mo), vanadium (V), or gallium (Ga), and x = 0.01 to 0.3) nickel (Ni)-site lithium nickel oxides; represented by the chemical formula LiMn 1-x M x O2 (where M = Co, nickel (Ni), Fe, chromium (Cr), zinc (Zn), or tantalum (Ta), and x = 0.01 to 0.1) or Li2Mn3MO8 (where M = Fe, Co, Ni, Cu, or Zn) lithium manganese composite oxides; from LiNi x Mn 2-x O4 spinel-structured lithium manganese composite oxides; LiMn2O4 in which part of the lithium (Li) is replaced by alkaline earth metal ions; disulfide compounds; LiMn x Fe 1-x PO4 (0 ≤ x ≤ 0.9); or Fe2(MoO4)3. However, the positive electrode active material is not limited to this.

[0069] The positive electrode active material may include Li 1+x M y O 2+z , where M may be at least one element selected from the group consisting of Ni, Co, Mn, Fe, P, Al, Mg, Ca, Zr, Zn, Ti, Ru, Nb, W, B, Si, Na, K, Mo, and V, 0 ≤ x ≤ 5, 0 < y ≤ 2, 0 ≤ z ≤ 2. Specifically, Li 1+x M y O 2+z may include those selected from LiCoO2, LiNiO2, LiMnO2, Li[Ni 0.5 Co 0.3 Mn 0.2 O2, Li[Ni 0.6 Co 0.2 Mn 0.2 O2, Li[Ni 0.7 Co 0.1 Mn 0.2 O2, Li[Ni0.8 Co 0.1 Mn 0.1 O2, Li[Ni 0.9 Co 0.05 Mn 0.05 ]O2, LiMn2O4, LiFePO4 and 0.5Li2MnO3·0.5Li[Mn 0.4 Ni 0.3 Co 0.3 At least one of the group consisting of O2. Preferably, Li 1+x M y O 2+z It can include Li[Ni 0.6 Co 0.2 Mn 0.2 O2, Li[Ni 0.7 Co 0.1 Mn 0.2 O2, Li[Ni 0.8 Co 0.1 Mn 0.1 ]O2 and Li[Ni 0.9 Co 0.05 Mn 0.05 Any of the following: O2. Because the positive electrode active material contains Li... 1+x M y O 2+z Therefore, lithium can be fully supplied to the negative electrode, and because of Li 1+x M y O 2+z It exhibits electrochemical activity after the first cycle without causing a decline in overall battery performance, thus preventing battery capacity loss due to irreversible capacity at the negative electrode. 1+x M y O 2+z It can be in the form of secondary particles formed by the combination or aggregation of primary particles, or it can be in the form of a single particle.

[0070] In the positive electrode active material layer, the content of the positive electrode active material can be from 50% to 90% by weight, specifically from 60% to 90% by weight.

[0071] The positive electrode active material layer may also contain a solid electrolyte.

[0072] Solid electrolytes may specifically include at least one selected from the group consisting of polymer solid electrolytes, oxide solid electrolytes, sulfide solid electrolytes, and halide solid electrolytes.

[0073] Polymer solid electrolytes can be composites of lithium salts and polymer resins. Specifically, polymer solid electrolytes can be formed by adding a polymer resin to a solvated lithium salt. Specifically, the ionic conductivity of the polymer solid electrolyte can be approximately 1 × 10⁻⁶. -7 S / cm or higher, preferably about 1×10 -3 S / cm or higher.

[0074] Polymer resins include polyether polymers, polycarbonate polymers, acrylate polymers, polysiloxane polymers, phosphazene polymers, polyethylene derivatives, olefinic derivatives such as polyethylene oxide, phosphate polymers, polylysine, polyester sulfides, polyvinyl alcohol, polyvinylidene fluoride, or polymers containing ionic dissociation groups, and may include one or more of these. Additionally, polymeric solid electrolytes are polymer resins, examples of which may be branched copolymers, comb-like polymer resins, and crosslinked polymer resins obtained by copolymerizing amorphous polymers such as PMMA, polycarbonate, polysiloxane (PDMS), and / or phosphazene as comonomers into the PEO (polyethylene oxide) backbone, and may include at least one of these.

[0075] Lithium salts are ionizable, and can be represented as Li + X - There are no specific restrictions on the anion of lithium salts, but examples can include F. - Cl - ,Br - I - NO3 - N(CN)2 - BF4 - ClO4 - PF6 - (CF3)2PF4 - (CF3)3PF3 - (CF3)4PF2 - (CF3)5PF - (CF3)6P - CF3SO3 - CF3CF2SO3 - (CF3SO2)2N - (FSO2)2N - CF3CF2(CF3)2CO - (CF3SO2)2CH - (SF5)3C - (CF3SO2)3C - CF3(CF2)7SO3 - CF3CO2 -CH3CO2 - SCN - and (CF3CF2SO2)2N - .

[0076] Oxide-based solid electrolytes may contain oxygen (O) and may have ionic conductivity of metals belonging to Group 1 or Group 2 of the periodic table. As non-limiting examples, they may contain compounds selected from LLTO compounds, Li6La2CaTa2O, etc. 12 Li6La2ANb2O 12 (A represents Ca or Sr), Li₂Nd₃TeSbO 12 Li3BO 2.5 N 0.5 Li9SiAlO8, LAGP compounds, LATP compounds, Li 1+x Ti 2-x Al x Si y (PO4) 3-y (where 0≤x≤1, 0≤y≤1), LiAl x Zr 2-y (PO4)3 (where 0 ≤ x ≤ 1, 0 ≤ y ≤ 1), LiTi x Zr 2-y (PO4)3 (where 0≤x≤1, 0≤y≤1), and at least one of the following: LISICON compounds, LIPON compounds, perovskite compounds, NASICON compounds, and LLZO compounds. However, oxide solid electrolytes are not specifically limited to these.

[0077] Sulfide solid electrolytes contain sulfur (S) and have the ionic conductivity of metals belonging to Group 1 or Group 2 of the periodic table. Sulfide solid electrolytes may include Li-PS glass or Li-PS glass ceramics. Non-limiting examples of sulfide solid electrolytes include Li6PS5Cl, Li6PS5Br, Li6PS5I, Li2S-P2S5, Li2S-LiI-P2S5, Li2S-LiI-Li2O-P2S5, Li2S-LiBr-P2S5, Li2S-Li2O-P2S5, Li2S-Li3PO4-P2S5, Li2S-P2S5-P2O5, Li2S-P2S5-SiS2, Li2S-P2S5-SnS, Li2S-P2S5-Al2S3, Li2S-GeS2, and Li2S-GeS2-ZnS, and sulfide solid electrolytes may include at least one of these. However, sulfide solid electrolytes are not specifically limited to these examples.

[0078] Halogenated solid electrolytes may include at least one of Li3YCl6 and Li3YBr6, but are not specifically limited to this.

[0079] In the positive electrode active material layer, the content of solid electrolyte can be from 5% to 50% by weight, specifically from 10% to 30% by weight.

[0080] The positive electrode active material layer may also contain a positive electrode conductive agent.

[0081] There are no particular limitations on the positive electrode conductive agent, as long as it is conductive and will not cause adverse chemical changes in the positive electrode or battery. For example, the positive electrode conductive agent may include one of the following conductive materials: graphite, such as natural graphite or artificial graphite; carbon black, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black and thermal cracking carbon black; graphene; conductive fibers, such as carbon nanofibers and carbon nanotubes; fluorocarbons; metal powders, such as aluminum powder and nickel powder; conductive whiskers, such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides, such as titanium dioxide; and polyphenylene derivatives, or mixtures of two or more thereof.

[0082] In the positive electrode active material layer, the content of the positive electrode conductive agent can be from 1% to 30% by weight.

[0083] The positive electrode active material layer may also include a positive electrode binder.

[0084] There are no particular limitations on the positive electrode binder, as long as it is a component that facilitates the bonding of the positive electrode active material with the conductive agent and with the current collector. Specifically, it may include at least one selected from the group consisting of: polyvinylidene fluoride (PVdF), polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, polyvinylpyrrolidone, polytetrafluoroethylene (PTFE), polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), styrene-butadiene rubber (SBR), and fluororubber.

[0085] In the positive electrode active material layer, the content of the positive electrode binder can be from 1% to 30% by weight.

[0086] If necessary, the positive electrode active material layer may contain at least one additive, such as an oxidation stabilizer, a reduction stabilizer, a flame retardant, a heat stabilizer, and an anti-fogging agent.

[0087] (3) Solid electrolyte layer

[0088] All-solid-state lithium secondary batteries may include a solid electrolyte layer.

[0089] In all-solid-state lithium secondary batteries, the solid electrolyte layer can serve as an insulation layer and also act as an ion conduction channel.

[0090] See Figure 2 The solid electrolyte layer 300 can be disposed between the negative electrode active material layer 100 and the positive electrode active material layer 200.

[0091] The solid electrolyte layer 300 contains a solid electrolyte. The solid electrolyte may specifically include at least one selected from the group consisting of polymer solid electrolytes, oxide solid electrolytes, and sulfide solid electrolytes.

[0092] Polymer solid electrolytes can be composites of lithium salts and polymer resins. Specifically, polymer solid electrolytes can be formed by adding a polymer resin to a solvated lithium salt. Specifically, the ionic conductivity of the polymer solid electrolyte can be approximately 1 × 10⁻⁶. -7 S / cm or higher, preferably about 1×10 -3 S / cm or higher.

[0093] Polymer resins include polyether polymers, polycarbonate polymers, acrylate polymers, polysiloxane polymers, phosphazene polymers, polyethylene derivatives, oxidized olefin derivatives such as polyethylene oxide, phosphate polymers, polylysine, polyester sulfides, polyvinyl alcohol, polyvinylidene fluoride, or polymers containing ionic dissociation groups, and may include one or more of these. Additionally, polymeric solid electrolytes are polymer resins, examples of which may be branched copolymers, comb-like polymer resins, and crosslinked polymer resins obtained by copolymerizing amorphous polymers such as PMMA, polycarbonate, polysiloxane (PDMS), and / or phosphazene as comonomers into the PEO (polyethylene oxide) backbone, and may include at least one of these.

[0094] Lithium salts are ionizable, and can be represented as Li + X - There are no specific restrictions on the anion of lithium salts, but examples can include F. - Cl - ,Br - I - NO3 - N(CN)2 - BF4 - ClO4 - PF6 - (CF3)2PF4 - (CF3)3PF3 - (CF3)4PF2 - (CF3)5PF - (CF3)6P - CF3SO3 - CF3CF2SO3 - (CF3SO2)2N- (FSO2)2N - CF3CF2(CF3)2CO - (CF3SO2)2CH - (SF5)3C - (CF3SO2)3C - CF3(CF2)7SO3 - CF3CO2 - CH3CO2 - SCN - and (CF3CF2SO2)2N - .

[0095] Oxide-based solid electrolytes may contain oxygen (O) and may have ionic conductivity of metals belonging to Group 1 or Group 2 of the periodic table. As non-limiting examples, they may contain compounds selected from LLTO compounds, Li6La2CaTa2O, etc. 12 Li6La2ANb2O 12 (A is Ca or Sr), Li2Nd3TeSbO 12 Li3BO 2.5 N 0.5 Li9SiAlO8, LAGP compounds, LATP compounds, Li 1+x Ti 2-x Al x Si y (PO4) 3-y (where 0≤x≤1, 0≤y≤1), LiAl x Zr 2-y (PO4)3 (where 0 ≤ x ≤ 1, 0 ≤ y ≤ 1), LiTi x Zr 2-y (PO4)3 (where 0≤x≤1, 0≤y≤1), and at least one of the following: LISICON compounds, LIPON compounds, perovskite compounds, NASICON compounds, and LLZO compounds. However, oxide solid electrolytes are not specifically limited to these.

[0096] Sulfide solid electrolytes contain sulfur (S) and have the ionic conductivity of metals belonging to Group 1 or Group 2 of the periodic table. The sulfide solid electrolytes may include Li-PS glass or Li-PS glass ceramics. Non-limiting examples of sulfide solid electrolytes include Li6PS5Cl, Li6PS5Br, Li6PS5I, Li2S-P2S5, Li2S-LiI-P2S5, Li2S-LiI-Li2O-P2S5, Li2S-LiBr-P2S5, Li2S-Li2O-P2S5, Li2S-Li3PO4-P2S5, Li2S-P2S5-P2O5, Li2S-P2S5-SiS2, Li2S-P2S5-SnS, Li2S-P2S5-Al2S3, Li2S-GeS2, and Li2S-GeS2-ZnS, and sulfide solid electrolytes may include at least one of these. However, sulfide solid electrolytes are not specifically limited to these examples.

[0097] The solid electrolyte layer may also include an adhesive for the solid electrolyte layer. The adhesive for the solid electrolyte layer can be introduced for bonding between solid electrolytes and for bonding between the solid electrolyte layer and battery elements (e.g., positive electrode, negative electrode, etc.) stacked on its two surfaces.

[0098] There are no particular limitations on the materials used for the solid electrolyte layer adhesive, and they can be appropriately selected from the composition range of adhesives used as solid electrolytes in all-solid-state lithium secondary batteries. Specifically, the solid electrolyte layer adhesive may include at least one selected from the group consisting of polyvinylidene fluoride (PVdF), polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), styrene-butadiene rubber (SBR), styrene-butadiene-styrene block copolymer (SBS), nitrile rubber (NBR), fluororubber, and acrylic adhesives.

[0099] Considering the ionic conductivity, physical strength, and energy density of batteries using solid electrolyte layers, the thickness of the solid electrolyte layer can range from 10 μm to 90 μm, specifically from 20 μm to 80 μm. Furthermore, the tensile strength of the solid electrolyte layer can be 500 kgf / cm². 2 Up to 2,000 kgf / cm 2 Furthermore, the porosity of the solid electrolyte layer 300 can be less than 15% or less than about 10%.

[0100] All-solid-state lithium secondary batteries may also include a metal layer. See also Figure 2The all-solid-state lithium secondary battery 10 further includes a negative electrode current collector 110, and may also include a metal layer 120 disposed between the negative electrode active material layer 100 and the negative electrode current collector 110 in the charged state. The metal layer 120 may contain lithium, and may specifically be formed of lithium.

[0101] The metal layer refers to the layer formed when lithium ions transferred from the positive electrode active material layer are stored on the negative electrode current collector and the negative electrode active material layer during charging of an all-solid-state lithium secondary battery. Therefore, the metal layer is clearly visible during charging.

[0102] The metal layer can be observed during the discharge process, but theoretically it may not be observed during the complete discharge process.

[0103] This invention is significant in all-solid-state lithium secondary batteries, but may be less significant in lithium secondary batteries using liquid electrolytes. For example, if a liquid electrolyte is used, it may be difficult to completely store lithium in the negative electrode because the lithium stored in the negative electrode (e.g., in the form of a metal layer) may be in continuous contact with the liquid electrolyte.

[0104] Preparation method of all-solid-state lithium secondary battery

[0105] Another embodiment of the present invention provides a method for preparing an all-solid-state lithium secondary battery, which may include: a first step of forming a dry-mixed powder comprising the carbon structure and silver nanoparticles disposed on the carbon structure by reducing silver ions in a mixture of silver ions and a carbon structure; and a second step of forming a negative electrode active material layer on a negative electrode current collector by forming a negative electrode slurry comprising the dry-mixed powder. Here, the all-solid-state lithium secondary battery may be the same as that in the above embodiment. Furthermore, the negative electrode active material layer may be the same as that in the above embodiment.

[0106] (1) First step

[0107] In the first step, a dry-mixed powder comprising a carbon structure and silver nanoparticles disposed on the carbon structure is formed. The dry-mixed powder can be prepared by mixing silver nanoparticles in powder form and carbon structure in powder form. Alternatively, the dry-mixed powder can be prepared by mixing the carbon structure in a silver ion solution and then reducing the silver nanoparticles. Various methods exist for reducing silver nanoparticles, such as chemical reduction, electrochemical reduction, photochemical reduction, laser reduction, ultrasonic reduction, and sputtering; however, preferably, a chemical reduction method utilizing a polyol process or a microwave-assisted polyol process utilizing microwaves can be used.

[0108] In the polyol process, in addition to silver ions, the silver ion solution may also contain solvents and stabilizers. Ethylene glycol can be used as a solvent, and polyvinylpyrrolidone can be used as a stabilizer. However, the invention is not necessarily limited to this.

[0109] The molar concentration of silver ions in the silver ion solution can range from 1 mM to 1,000 mM, particularly from 1 mM to 500 mM, and even more particularly from 1 mM to 300 mM. When the above molar concentration range is met, the capacity, first charge / discharge efficiency, and lifetime characteristics of the all-solid-state lithium secondary battery can be effectively controlled because the number and size of the formed silver nanoparticles can be adjusted to an appropriate level.

[0110] In the first step, the reduction of silver ions can include reacting the mixed solution at a temperature between 100°C and 500°C, specifically between 100°C and 300°C. That is, the mixed solution can be reacted by heat treatment at the above temperatures. Therefore, silver ions can be appropriately reduced to obtain silver nanoparticles of the desired size. Furthermore, the silver nanoparticles can be deposited on the surface of the carbon structure during the above process.

[0111] The reduction of silver ions may involve adjusting the pH of the mixed solution. Specifically, the acidity of the mixed solution can be adjusted to pH 8 to pH 14, more specifically, pH 9 to pH 13. Thus, silver ions can be appropriately reduced to obtain silver nanoparticles with the desired size.

[0112] Subsequently, the dry-mixed powder can be obtained by washing and then drying the solids of the mixed solution.

[0113] In the dry-mixed powder, the weight ratio of carbon structure to silver nanoparticles can be from 99:1 to 60:40, particularly from 97:3 to 70:30, and even more particularly from 95:5 to 80:20. When the above range is met, the capacity and first charge / discharge efficiency of the all-solid-state lithium secondary battery can be improved more effectively.

[0114] (2) Second step

[0115] In the second step, a negative electrode active material layer can be formed on the negative electrode current collector by a negative electrode slurry containing the dry-mixed powder. The negative electrode slurry may contain dry-mixed powder and a solvent for the negative electrode slurry.

[0116] The solvent for the negative electrode slurry can be selected from the group consisting of free water and N-methylpyrrolidone, but is not limited to this.

[0117] The negative electrode slurry may also contain a negative electrode binder. The negative electrode binder may be the same as the negative electrode binder in the above embodiments.

[0118] In the second step, the negative electrode active material layer can be formed by coating the negative electrode slurry onto the negative electrode current collector and drying it. In some cases, a pressurization process can be added in addition to the coating and drying processes.

[0119] The preparation method of all-solid-state lithium secondary batteries can also include forming carbon structures before the first step.

[0120] The formation of the carbon structure includes: preparing preformed particles; and modifying the preformed particles by high-temperature heat treatment, wherein modifying the preformed particles by high-temperature heat treatment may include at least one of the following: a) performing long-term heat treatment of the preformed particles in an inert atmosphere at a temperature of 1,600°C to 2,000°C; and b) performing short-term heat treatment at a temperature above 2,000°C.

[0121] In the preparation of preformed particles, the preformed particles can be carbon black. Specifically, the preformed particles can be at least one selected from the group consisting of acetylene black, furnace black, thermal cracking carbon black, channel black, and lamp black. More specifically, the preformed particles can be acetylene black that has essentially excellent graphitization, produced at the highest temperature.

[0122] The preparation of preformed particles may include the pyrolysis of acetylene gas, and carbon black, such as acetylene black, can be formed through pyrolysis. The acetylene gas can be high-purity acetylene gas, specifically, acetylene gas with a purity of 95% or higher, for example, acetylene gas with a purity of 98% or higher.

[0123] The pyrolysis of acetylene gas can be carried out at temperatures above 1,500°C, particularly between 1,500°C and 2,200°C, and even more particularly between 1,500°C and 2,000°C. When the temperature meets these ranges, the degree of graphitization of the prepared pre-particles can be high, and the degree of graphitization of the secondary particles prepared in this way can also be high. Therefore, the conductivity of the conductive agent can be improved.

[0124] The pyrolysis can be carried out as follows: After adjusting the internal temperature of the reactor to the aforementioned temperature range, acetylene gas is introduced into the reactor and pyrolysis begins immediately. During this process, air, oxygen, and H2O can be further added.

[0125] The modification of primary particles by high-temperature heat treatment can be achieved by controlling the reaction temperature and time in a reactor containing the preformed particles. In this case, the inert atmosphere in the reactor can be formed by a vacuum or any gas selected from the group consisting of helium, argon, and nitrogen. The high-temperature heat treatment may include at least one of the following: a) long-term heat treatment of the preformed particles in an inert atmosphere at a temperature of 1,600°C to 2,000°C; and b) short-term heat treatment at a temperature above 2,000°C. The high-temperature heat treatment time can range from 10 minutes to 50 hours.

[0126] Furthermore, the present invention provides a battery module including the all-solid-state lithium secondary battery as a unit cell, a battery pack including the battery module, and a device including the battery pack as a power source. Specific examples of this device may include: power tools that operate by being powered by an electric motor; electric vehicles, including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); electric two-wheelers, including electric bicycles (E-bikes) and electric scooters (E-scooters); electric golf carts; urban air mobility (UAM); and energy storage systems, but the device is not limited to these.

[0127] The present invention will now be described in more detail with reference to embodiments, but the following embodiments are only for illustrative purposes and the scope of the present invention is not limited thereto.

[0128] Examples and Comparative Examples

[0129] Preparation Example 1: Formation of Carbon Structures

[0130] Acetylene black was heat-treated at 2,800°C for 6 hours in an argon (Ar) atmosphere to obtain the carbon structure of Preparation Example 1, wherein hollow particles are interconnected to form a secondary particle structure. In the carbon structure, multiple hollow particles are interlinked to present a secondary particle structure, and each hollow particle comprises a hollow portion and a carbonaceous shell surrounding the hollow portion (see [link to preparation example 1]). Figure 5 and 6 ).

[0131] Preparation Example 2: Preparation of Carbon Structures

[0132] Acetylene black with a larger particle size than that used in Preparation Example 1 was heat-treated at 2,800°C for 6 hours in an Ar atmosphere to obtain the carbon structure of Preparation Example 2, wherein hollow particles are interconnected to form a secondary particle structure. In the carbon structure, multiple hollow particles are interlinked to present a secondary particle structure, and each hollow particle comprises a hollow portion and a carbonaceous shell surrounding the hollow portion (see [link to preparation example]). Figure 7 and 8 ).

[0133] Example 1: Preparation of an all-solid-state lithium secondary battery

[0134] A mixed solution was prepared by mixing carbon structural components, AgNO3, and polyvinylpyrrolidone in ethylene glycol solvent, adjusting the pH to a range of 8 to 14 with NaOH pellets, and then stirring for 24 hours. The mixed solution, which had been ultrasonically bubbled with Ar, was repeatedly heated and cooled using a microwave reactor (LG Electronics) in continuous wave mode (2.45 GHz, 500 W) at time units of 10 seconds, 20 seconds, 30 seconds, 1 minute, 2 minutes, and 5 minutes. This reduced silver ions, resulting in silver nanoparticles deposited on the carbon structural components. Subsequently, the mixture was filtered and washed with acetone solution and dried in a vacuum oven at 100°C for 24 hours to obtain a dry-mixed powder containing the carbon structural components and silver nanoparticles deposited on them (see [link to product description]). Figure 9 The loading of silver nanoparticles was 10% by weight, and the average particle size of the silver nanoparticles was 1 nm.

[0135] The dry-mixed powder and polyvinylidene fluoride (PVDF) were added to N-methylpyrrolidone (NMP) as a solvent and stirred to form a negative electrode slurry. In the negative electrode slurry, the weight ratio of the dry-mixed powder to PVDF was 93:7.

[0136] A negative electrode slurry was coated onto a stainless steel current collector (thickness: 15 μm), dried in a vacuum oven at 100 °C for 12 hours, and then rolled using a roller press to prepare a negative electrode comprising a stainless steel current collector and a negative electrode active material layer disposed on the stainless steel current collector. The thickness of the negative electrode active material layer was 10 μm, and the loading of the negative electrode active material layer was 1 mg / cm³. 2 .

[0137] (2) Preparation of positive electrode

[0138] Li[Ni] will be used as the positive electrode active material 0.82 Co 0.14 Mn 0.04 O2, Li6PS6Cl as a solid electrolyte, carbon nanofibers (VGCF, Showa Denko) as a conductive agent, and polytetrafluoroethylene as a binder were added sequentially to a container in a weight ratio of 77:20:1:2. Each time any component was added, a positive electrode mixture was prepared by mixing 10 times at 10,000 RPM for 30 seconds each time using a laboratory mixer. The mixture was then subjected to high-shear mixing at 100°C and 100 rpm for 5 minutes using a twin-screw extruder (LG Electronics) to prepare the positive electrode mixture. A self-standing membrane with a thickness of 200 μm was prepared from the positive electrode mixture using a twin-roll mill (Inoue Mfg., Inc.) at 100°C. Subsequently, the membrane was placed on one side of a primer-coated aluminum current collector (thickness: 20 μm), and the membrane was bonded to the current collector using laminating rollers maintained at 120°C, thus preparing the positive electrode.

[0139] (3) Preparation of all-solid-state lithium secondary batteries

[0140] A solid electrolyte slurry was prepared by mixing Li6PS6Cl solid electrolyte and nitrile rubber (NBR) with xylene as a solvent, followed by mixing the mixture with zirconia balls at 2,000 RPM for 1 minute, repeated 10 times using a Thinky mixer. The solid electrolyte slurry was then coated onto a PET film used as release paper and dried in a vacuum oven at 45°C for 6 hours to prepare a solid electrolyte layer. In this case, the weight ratio of Li6PS6Cl solid electrolyte to nitrile rubber (NBR) was 95:5 (wt%), and the thickness of the prepared solid electrolyte layer was 100 μm.

[0141] After fabricating the assembly by placing a solid electrolyte layer between the negative and positive electrodes, the assembly was placed in a bag and sealed. Subsequently, after fixing the bag to an Al plate, the bag was pressurized at 500 MPa for 30 minutes using a warm isostatic press to prepare the all-solid-state lithium secondary battery of Example 1.

[0142] Examples 2 to 6: Preparation of all-solid-state lithium secondary batteries

[0143] Except for controlling the weight ratio of carbon structure, AgNO3 and polyvinylpyrrolidone, pH value and reaction conditions in the microwave reactor as shown in Table 1 to adjust the amount and average particle size of silver nanoparticles, all-solid-state lithium secondary batteries were prepared in the same manner as in Example 1.

[0144] Comparative Examples 1 and 2: Fabrication of All-Solid-State Lithium Secondary Batteries

[0145] (1) Negative electrode preparation

[0146] All-solid-state lithium secondary batteries were prepared in the same manner as in Example 1, except that carbon black (PRINTEX, Orion Engineered Carbons) was used instead of the carbon structure in Example 1 and the weight ratio of carbon black, AgNO3 and polyvinylpyrrolidone, pH value and reaction conditions in the microwave reactor were controlled as shown in Table 1 to adjust the amount and average particle size of silver nanoparticles.

[0147] Comparative Example 3: Preparation of Lithium Secondary Batteries

[0148] (1) Preparation of negative and positive electrodes

[0149] The negative and positive electrodes were prepared in the same manner as in Example 1.

[0150] (3) Preparation of lithium secondary batteries

[0151] Subsequently, after preparing a single cell by placing a 15 μm thick polyethylene separator between the prepared negative and positive electrodes, an electrolyte (ethylene carbonate (EC) / ethyl methyl carbonate (EMC) = 1 / 2 (volume ratio), lithium hexafluorophosphate (LiPF6 1mol)) was injected into the single cell to prepare a lithium secondary battery.

[0152] Comparative Example 4: Preparation of Lithium Secondary Batteries

[0153] Except for controlling the weight ratio of carbon structure, AgNO3 and polyvinylpyrrolidone, pH value and reaction conditions in the microwave reactor as shown in Table 1 to adjust the amount and average particle size of silver nanoparticles, lithium secondary batteries were prepared in the same manner as in Comparative Example 3.

[0154] [Table 1]

[0155]

[0156] [Table 2]

[0157]

[0158] Specific surface area was measured using the Brunauer-Emmett-Teller (BET) method, specifically calculated using a Bell Japan Inc. BELSORP-mini II from the amount of nitrogen adsorbed at liquid nitrogen temperature (77 K). D / I G The ratio (I) is measured from the wavelength-peak plot in Raman spectroscopy measurements. Specifically, after fitting the plot by setting a baseline to distinguish the D and G peaks, I is determined by dividing the D peak intensity by the G peak intensity. D / I G (Using built-in software, NRS-2000B, Jasco).

[0159] The oxygen content of carbon structures is measured by elemental analysis of carbon (C), hydrogen (H), oxygen (O), and nitrogen (N).

[0160] The thickness of the shell can be confirmed using the JEM-2100 instrument from JEOL Ltd.

[0161] The average particle size of the hollow particles corresponds to the average particle size of the top 50 hollow particles sorted by maximum particle size and the bottom 50 hollow particles when the negative electrode active material layer is observed by TEM at a magnification of ×250,000.

[0162] The average particle size of the silver nanoparticles corresponds to the average particle size of the first 50 silver nanoparticles with larger particle sizes and the last 50 silver nanoparticles when the carbon structure containing silver nanoparticles in the negative electrode active material layer is observed with TEM at a magnification of ×1,000,000.

[0163] The amount of silver nanoparticles refers to the total weight of the carbon structures and silver nanoparticles in the negative electrode active material layer.

[0164] Experimental Example 1: Evaluation of Initial Charge / Discharge Efficiency

[0165] The batteries from the examples and comparative examples were each mounted on a pressure fixture, and bolts / nuts located at the corners of a square were tightened with the same pressure of 1 N·m to prepare single cells. The first charge / discharge efficiency was evaluated as the ratio of the capacity of one charge to the capacity of one discharge when the single cell was charged once and discharged once at 60°C under the following conditions (see Table 3).

[0166] Charging conditions: CC charge at 0.1C to 4.25V, then CV charge at 4.25V, cut off at 0.05C.

[0167] Discharge conditions: CC discharge at 0.1C to 3.0V.

[0168] Experimental Example 2: Evaluation of Capacity Retention

[0169] After charging and discharging the batteries of the examples and comparative examples at 60°C and below, the capacity retention rate (%) at the 50th cycle was evaluated. The discharge capacity in the first charge / discharge cycle was set to 100%.

[0170] Charging conditions: Charge at 0.5C until 4.25V, then stop at 0.5C.

[0171] Discharge conditions: CC discharge at 0.33C to 3.0V.

[0172] [Table 3]

[0173]

Claims

1. An all-solid-state lithium secondary battery, comprising: A positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer. in, The negative electrode active material layer comprises carbon structures and silver nanoparticles. The carbon structure comprises at least one hollow particle, and the hollow particle comprises a hollow portion and a carbonaceous shell surrounding the hollow portion. The shell contains a graphite layered structure.

2. The all-solid-state lithium secondary battery as described in claim 1, wherein, The silver nanoparticles are disposed on the surface of the carbon structure.

3. The all-solid-state lithium secondary battery as described in claim 1, wherein, The thickness of the shell is 1 nm to 15 nm.

4. The all-solid-state lithium secondary battery as described in claim 1, wherein, The specific surface area of ​​the carbon structure is 10 m². 2 / g to 300 m 2 / g.

5. The all-solid-state lithium secondary battery as described in claim 1, wherein, The hollow particles have an average particle size of 5 nm to 100 nm.

6. The all-solid-state lithium secondary battery as described in claim 1, wherein, In the Raman spectroscopy measurements of the carbon structure, The carbon structure I D / I G It ranges from 0.1 to 1.

5.

7. The all-solid-state lithium secondary battery as described in claim 1, wherein, The carbon structure has a secondary particle shape consisting of multiple hollow particles interlocked together.

8. The all-solid-state lithium secondary battery as described in claim 1, wherein, The carbon structure is present in the negative electrode active material layer at a content of 50% to 98% by weight.

9. The all-solid-state lithium secondary battery as described in claim 1, wherein, The average particle size of the silver nanoparticles is 1 nm to 100 nm.

10. The all-solid-state lithium secondary battery as described in claim 1, wherein, In the negative electrode active material layer Based on the total weight of the carbon structure and the silver nanoparticles, the content of the silver nanoparticles is from 1% to 40% by weight.

11. The all-solid-state lithium secondary battery as described in claim 1, wherein, The weight ratio of the carbon structure to the silver nanoparticles is 99:1 to 60:

40.

12. The all-solid-state lithium secondary battery as described in claim 1, wherein, The negative electrode active material layer also includes a negative electrode binder.

13. The all-solid-state lithium secondary battery as described in claim 1, wherein, The thickness of the negative electrode active material layer is from 1 μm to 100 μm.

14. The all-solid-state lithium secondary battery as described in claim 1, further comprising a negative electrode current collector, and A metal layer disposed between the negative electrode active material layer and the negative electrode current collector during the charging state. in, The metal layer contains lithium.

15. A method for preparing the all-solid-state lithium secondary battery of claim 1, the method comprising: The first step is to form a dry-mixed powder containing the carbon structure and silver nanoparticles disposed on the carbon structure by reducing silver ions in a mixture of silver ions and carbon structure. and The second step is to form a layer of negative electrode active material on the negative electrode current collector by forming a negative electrode mixture containing the dry-mixed powder.

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