All-solid-state battery

Abstract

An embodiment provides an all-solid-state battery including a solid electrolyte layer and a positive electrode layer and a negative electrode layer disposed with the solid electrolyte layer therebetween, where the solid electrolyte layer includes a first solid electrolyte, and the positive electrode layer and the negative electrode layer include a second solid electrolyte. The positive electrode layer or the negative electrode layer includes an electrode active material including a positive electrode active material, and a second solid electrolyte surrounding a part of a surface of the electrode active material and having an average thickness of 1 nm to 10 nm, the positive electrode active material includes a high cobalt-based positive electrode active material represented by Chemical Formula 1: LiCoxM1 yM2 [1-x-y] O2.

Description

Technical Field

[0001] This disclosure relates to an all-solid-state battery. Background Technology

[0002] Recently, with the need for miniaturization and extended use of portable electronic devices, there is a demand for higher capacity batteries, and with the increasing prevalence of wearable electronic devices, ensuring battery safety is paramount. Therefore, there is active development of all-solid-state batteries that use solid electrolytes instead of liquid electrolytes.

[0003] Solid-state batteries do not use flammable organic solvents, thus simplifying the additional circuitry required for safety. Therefore, solid-state batteries hold promise as a technology for manufacturing safe batteries with high capacity per unit volume.

[0004] In addition, oxide all-solid-state batteries using oxide electrolytes have a higher ionic conductivity than sulfides (10). -2 The ionic conductivity of electrolytes with low S / cm (10 -4 S / cm to 10 -6 (S / cm), and requires a high-temperature firing process. However, oxide all-solid-state batteries exhibit superior stability compared to sulfide all-solid-state batteries that use sulfide electrolytes that react with oxygen and moisture in the air.

[0005] Stacked oxide all-solid-state batteries are ultra-small batteries that can be mounted on a substrate like passive devices and remain stable even when exposed to high temperatures during the reflow soldering process.

[0006] In the positive electrode layer included in stacked oxide all-solid-state batteries, it is difficult to co-fire because it contains non-sintered positive electrode active materials and conductive agents, and it is difficult to uniformly form interfacial bonds between materials.

[0007] To improve this, sintering agents are added to the positive electrode layer to assist in simultaneous sintering, thereby improving the interfacial bonding of the positive electrode layer. However, if the sintering aid has low ionic conductivity, it cannot help improve the ionic conductivity of the positive electrode layer, resulting in a decrease in the battery's rate capability. Summary of the Invention

[0008] Solution to the problem One aspect of the embodiments provides an all-solid-state battery that improves the rate performance of the battery by densifying the electrode layers while improving the interfacial bonding between materials.

[0009] However, the embodiments of this disclosure are not limited to the above, and can be extended in various ways within the scope of the technical concepts included in this disclosure.

[0010] Beneficial effects of the invention The all-solid-state battery according to the embodiment has the advantage of improving the rate performance of the battery by densifying the electrode layer while improving the interfacial bonding between materials.

[0011] The above and other aspects, features and advantages of this disclosure will become clearer from the following detailed description taken in conjunction with the accompanying drawings. Attached Figure Description

[0012] Figure 1 This is a schematic perspective view of an all-solid-state battery according to an embodiment.

[0013] Figure 2 This is a cross-sectional view of an all-solid-state battery according to an embodiment.

[0014] Figure 3 This is a schematic cross-sectional view of the positive electrode layer of an all-solid-state battery according to an embodiment.

[0015] The best way to implement an invention An all-solid-state battery according to some embodiments includes: a solid electrolyte layer; and a positive electrode layer and a negative electrode layer, wherein the solid electrolyte layer is disposed between the positive electrode layer and the negative electrode layer, and wherein the solid electrolyte layer includes a first solid electrolyte. The positive electrode layer or the negative electrode layer includes an electrode active material and a second solid electrolyte, the second solid electrolyte surrounding a portion of the surface of the electrode active material and having an average thickness of 1 nm to 10 nm. The electrode active material includes a positive electrode active material. The positive electrode active material includes a high cobalt-based positive electrode active material represented by chemical formula 1.

[0016] [Chemical Formula 1] LiCo x M 1 y M 2 1-x-y O2 In chemical formula 1, 0.6 ≤ x ≤ 1.0, 0 ≤ y ≤ 0.3. M 1 For Ni, Al, Mn or combinations thereof, M 2 It can be Mn, Na, Mg, Ti, Ni, Al, Si, Zr, Zn, Nb, Cr, Fe, Sr, V, Cu, B, Ba, Ca, Ce, Se, Sn, W, Y, or combinations thereof.

[0017] The lithium-ion conductivity (25°C) of the second solid electrolyte can be greater than or equal to 1.0 × 10⁻⁶ times that of the first solid electrolyte (25°C). 2 times.

[0018] The lithium ion conductivity (25 °C) of the first solid electrolyte may be 1.0×10 -7 S / cm to 1.0×10 -6 S / cm.

[0019] The lithium ion conductivity (25 °C) of the second solid electrolyte may be 1.0×10 -4 S / cm to 1.0×10 -3 S / cm.

[0020] The first solid electrolyte includes a glass-ceramic-based electrolyte or a lithium borosilicate-based electrolyte. The glass-ceramic-based electrolyte includes at least one selected from the group consisting of lithium (Li) oxide, boron (B) oxide, silicon (Si) oxide, phosphorus (P) oxide, germanium (Ge) oxide, and lithium chloride (LiCl). The lithium borosilicate-based electrolyte includes lithium (Li) oxide, silicon (Si) oxide, and boron (B) oxide. [[ID=I6]]

[0021] The second solid electrolyte may include at least one selected from the group consisting of garnet-type solid electrolytes, Nasicon-type solid electrolytes, LISICON-type solid electrolytes, and combinations thereof.

[0022] The garnet-type solid electrolyte may include lithium lanthanum zirconium oxide.

[0023] The Nasicon-type solid electrolyte may include lithium aluminum titanium phosphate represented by Li 1+x Al x Ti 2-x (PO4)3 (0 < x < 1), or lithium aluminum germanium phosphate represented by Li 1+x [[ID=I32]]Al x Ge 2-x (PO4)3 (0 < x < 1).

[0024] Based on 100 parts by weight of the electrode active material, the second solid electrolyte may be included in an amount of 0.1 part by weight to 10 parts by weight.

[0025] The second solid electrolyte may surround 5% or more of the surface area of the electrode active material.

[0026] The positive electrode layer or the negative electrode layer may further include the first solid electrolyte.

[0027] A all-solid-state battery according to another embodiment includes: a solid electrolyte layer; and a positive electrode layer and a negative electrode layer, provided such that the solid electrolyte layer is interposed between the positive electrode layer and the negative electrode layer, wherein the solid electrolyte layer includes a first solid electrolyte. The positive electrode layer or the negative electrode layer includes an electrode active material and a second solid electrolyte, the second solid electrolyte surrounding a portion of the surface of the electrode active material and having an average thickness of 1 nm to 10 nm. The lithium-ion conductivity (25°C) of the second solid electrolyte is greater than or equal to 1.0 × 10⁻⁶ times that of the first solid electrolyte (25°C). 2 times, The electrode active material includes a positive electrode active material. The positive electrode active material includes a high cobalt-based positive electrode active material represented by chemical formula 1.

[0028] [Chemical Formula 1] LiCo x M 1 y M 2 1-x-y O2 In chemical formula 1, 0.6 ≤ x ≤ 1.0, 0 ≤ y ≤ 0.3. M 1 For Ni, Al, Mn or combinations thereof, M 2 It can be Mn, Na, Mg, Ti, Ni, Al, Si, Zr, Zn, Nb, Cr, Fe, Sr, V, Cu, B, Ba, Ca, Ce, Se, Sn, W, Y, or combinations thereof.

[0029] The lithium-ion conductivity (25°C) of the first solid electrolyte can be 1.0 × 10⁻⁶. -7 S / cm up to 1.0x10 -6 S / cm.

[0030] The lithium-ion conductivity (25°C) of the second solid electrolyte can be 1.0 × 10⁻⁶. -4 S / cm up to 1.0×10 -3 S / cm.

[0031] The first solid electrolyte may include at least one selected from the group consisting of glass-ceramic based electrolytes or lithium borosilicate based electrolytes, wherein the glass-ceramic based electrolyte includes lithium (Li) oxide, boron (B) oxide, silicon (Si) oxide, phosphorus (P) oxide, germanium (Ge) oxide and lithium chloride (LiCl), and the lithium borosilicate based electrolyte includes lithium (Li) oxide, silicon (Si) oxide and boron (B) oxide.

[0032] The second solid electrolyte may include garnet-type solid electrolyte, Nasicon-type solid electrolyte, LISICON-type solid electrolyte, or a combination thereof.

[0033] The garnet-type solid electrolyte may include lithium lanthanum zirconium oxide.

[0034] The Nasicon-type solid electrolyte may include lithium aluminum titanium phosphate represented by Li 1+x Al x Ti 2-x (PO4)3 (0 < x < 1), or lithium aluminum germanium phosphate represented by Li 1+x Al x Ge 2-x (PO4)3 (0 < x < 1).

[0035] Based on 100 parts by weight of the electrode active material, the second solid electrolyte may be included in an amount of 0.1 part by weight to 10 parts by weight.

[0036] The second solid electrolyte may surround 5% or more of the surface area of the electrode active material.

[0037] The positive electrode layer or the negative electrode layer may further include the first solid electrolyte. Detailed Description of Embodiments

[0038] Hereinafter, the present disclosure will be described in detail with reference to the drawings showing embodiments of the present disclosure. The drawings and the description are considered to be illustrative rather than restrictive. Throughout the specification, the same reference numerals denote the same elements. The drawings are only intended to facilitate the understanding of the exemplary embodiments disclosed in the present specification, and it should be understood that the technical idea disclosed herein is not limited by the drawings and includes all modifications, equivalents, or alternatives within the spirit and scope of the present disclosure. In the drawings, some components are exaggerated, omitted, or schematically shown, and the dimensions of each component do not fully reflect the actual dimensions.

[0039] In addition, unless explicitly described to the contrary, the word "comprising" and variations such as "including" or "having" will be understood to imply including the stated elements without excluding any other elements.

[0040] Throughout the specification, the "stacking direction" refers to the direction in which the components are stacked in sequence, and may also be the "thickness direction" perpendicular to the wide surface (main surface) of the component on the sheet, which corresponds to the T-axis direction. In addition, the "side surface" refers to the direction extending parallel to the wide surface (main surface) from the edge of the component on the sheet, which may be the "plane direction" and corresponds to the L-axis direction in the drawing. Additionally, the W-axis direction in the drawing may be the "width direction".

[0041] Hereinafter, each exemplary embodiment and variation will be described in detail with reference to the drawings.

[0042] [[ID=This is a schematic perspective view of an all-solid-state battery according to some embodiments of the present disclosure. Figure 2 This is a cross-sectional view of an all-solid-state battery according to some embodiments of the present disclosure.

[0043] For example, the all-solid-state battery 100 may have a roughly hexahedral shape.

[0044] In this embodiment, for ease of description, the two surfaces of the all-solid-state battery 100 that are opposite to each other in the thickness direction (T-axis direction) are defined as the first surface and the second surface, and the two surfaces connected to the first surface and the second surface that are opposite to each other in the length direction (L-axis direction) are defined as the third surface and the fourth surface. For example, the first surface and the second surface of the all-solid-state battery 100 that are opposite to each other can be the third surface and the fourth surface.

[0045] According to some embodiments, an all-solid-state battery 100 includes: a solid electrolyte layer 130; and a battery stack including a positive electrode layer 120 and a negative electrode layer 140, wherein the positive electrode layer 120 and the negative electrode layer 140 are configured such that the solid electrolyte layer 130 is disposed therebetween.

[0046] The solid electrolyte layer 130 includes a first solid electrolyte, and the positive electrode layer 120 or the negative electrode layer 140 includes an electrode active material and a second solid electrolyte located on the surface of the electrode active material.

[0047] The solid electrolyte layer 130 can be stacked between the positive electrode layer 120 and the negative electrode layer 140. Therefore, the solid electrolyte layer 130 can be disposed adjacent to the positive electrode active material layers 121 and 122 of the positive electrode layer 120 and the negative electrode active material layers 141 and 142 of the negative electrode layer 140 in the stacking direction.

[0048] Therefore, in the all-solid-state battery 100, multiple positive electrode layers 120 and multiple negative electrode layers 140 can be alternately arranged and stacked with multiple solid electrolyte layers 130 between them. The all-solid-state battery 100 can be a stacked all-solid-state battery 100 manufactured by alternately stacking multiple positive electrode layers 120 and multiple negative electrode layers 140 with multiple solid electrolyte layers 130 between them, and then batch firing them.

[0049] The solid electrolyte layer 130 includes a first solid electrolyte.

[0050] The lithium-ion conductivity (25℃) of the first solid electrolyte is less than or equal to 1.0 × 10⁻⁶ of the lithium-ion conductivity (25℃) of the second solid electrolyte. 2 times.

[0051] For example, the lithium-ion conductivity of the first solid electrolyte can be 1.0 × 10⁻⁶. -7 S / cm up to 1.0x10 -6S / cm. Lithium-ion conductivity can be measured at 25°C.

[0052] The lithium-ion conductivity of the first solid electrolyte can be measured by the alternating current (AC) impedance method.

[0053] For example, firstly, a portion of the solid electrolyte layer 130 in the all-solid-state battery 100 is sampled as a rectangular plate by ion milling or polishing. Next, electrodes made of gold (Au) are formed at both ends of the obtained plate to prepare a sample. Then, the AC impedance (frequency: 10 Hz) of the sample is measured at room temperature (25°C) using an impedance measuring device. +6 Hz to 10 -1 Ionic conductivity can be calculated using Hz (voltage: 10mV, 100mV).

[0054] According to some embodiments, a pellet made using a first solid electrolyte can be manufactured, and after sintering the pellet at 470°C to 550°C, electrodes made of gold (Au) can be formed on both ends of the pellet to produce a sample. Ionic conductivity can be calculated using the same method as described above.

[0055] For example, the first solid electrolyte may be an oxide-based solid electrolyte, and the oxide-based solid electrolyte may include a glass-ceramic-based electrolyte or a lithium borosilicate (LBSO)-based electrolyte.

[0056] Glass ceramics (or crystalline glass) refer to a mixture of amorphous and crystalline phases, such as peaks and halo peaks observed in X-ray diffraction or electron beam diffraction.

[0057] Therefore, since some crystallization has occurred through sintering, the glass-ceramic electrolyte is a mixture of amorphous and crystalline states.

[0058] When glass-ceramic-based electrolytes are included, high ionic conductivity can be achieved after sufficient densification is achieved through firing.

[0059] Glass-ceramic based electrolytes may include at least one selected from the group consisting of lithium (Li) oxide, boron (B) oxide, silicon (Si) oxide, phosphorus (P) oxide, germanium (Ge) oxide, and lithium chloride (LiCl).

[0060] According to some embodiments, the glass-ceramic electrolyte may include Li₂O-B₂O₃-SiO₂-P₂O₅-GeO₂-LiCl. For example, the glass-ceramic-based electrolyte may include a lithium borohydrite crystalline phase.

[0061] A lithium borosilicate-based electrolyte (hereinafter referred to as "LBSO-based electrolyte") is a glassy electrolyte, where the glass is amorphous crystallographically, resulting in a hump peak observed in X-ray diffraction, electron diffraction, etc.

[0062] When including the lithium borosilicate-based electrolyte, the firing temperature can be reduced while maintaining the amorphous state during firing, thereby achieving high ionic conductivity and low reactivity with the electrodes. The lithium borosilicate-based electrolyte may include lithium (Li) oxide, silicon (Si) oxide, and boron (B) oxide. For example, it may include Li2O - SiO2 - B2O3.

[0063] Optionally, the lithium borosilicate-based electrolyte may further include at least one selected from the group consisting of additional oxides of Na (sodium), Mg (magnesium), Al (aluminum), P (phosphorus), K (potassium), Ca (calcium), Ti (titanium), V (vanadium), Cr (chromium), Mn (manganese), Fe (iron), Co (cobalt), Ni (nickel), Cu (copper), Zn (zinc), Ga (gallium), Ge (germanium), Se (selenium), Rb (rubidium), S (sulfur), Y (yttrium), Zr (zirconium), Nb (niobium), Mo (molybdenum), Ag (silver), In (indium), Sn (tin), Sb (antimony), Cs (cesium), Ba (vanadium), Hf (hafnium), Ta (tantalum), W (tungsten), Pb (lead), Bi (bismuth), Au (gold), La (lanthanum), Nd (neodymium), Eu (europium), and combinations including them.

[0064] The solid electrolyte layer 130 may further include an inorganic solid electrolyte other than the above-mentioned first solid electrolyte, and the inorganic solid electrolyte includes an oxide-based solid electrolyte, a sulfide-based solid electrolyte, or a combination thereof.

[0065] Other oxide-based solid electrolytes can be garnet-type, Nasicon-type, LISICON-type, perovskite-type, LiPON-type, or amorphous (glass) electrolytes, etc.

[0066] The garnet-type solid electrolyte can be represented by lithium lanthanum zirconium oxide (LLZO) represented by Li a La b Zr c O 12 (such as Li7La3Zr2O 12 ). The Nasicon-type solid electrolyte can be represented by Li where Ti is introduced into Li 1+x Al x M 2-x (PO4)3 (LAMP) (0 < x < 2, where M is Zr, Ti, or Ge) type compounds of Li 1+x Al x Ti 2-xLithium aluminum titanium phosphate (LATP) represented by (PO4)3 (0 < x < 1); wherein lithium is introduced in excess and is composed of Li 1+x Al x Ge 2-x (PO4)3 (0 < x < 1) represents lithium aluminum germanium phosphate (LAGP) (such as Li 1.3 Al 0.3 Ti 1.7 (PO4)3, etc.); and / or lithium zirconium phosphate (LZP) (LiZr2(PO4)3).

[0067] In addition, LISICON-type solid electrolytes can be represented by xLi3AO4-(1-x)Li4BO4 (A is P, As, V, etc., B is Si, Ge, Ti, etc., 0 < x < 1) and include Li4Zn(GeO4)4, Li 10 GeP2O 12 (LGPO), Li 3.5 Si 0.5 P 0.5 O4, Li 10.42 Si(Ge) 1.5 P 1.5 Cl 0.08 O 11.92 , etc. of solid solution oxides, and solid solution sulfides represented by Li 4-x M 1-y M' y S4 (M is Si, Ge, M' is P, Al, Zn or Ga) including Li2S-P2S5, Li2S-SiS2, Li2S-SiS2-P2S5 or Li2S-GeS2, etc.

[0068] Perovskite-type solid electrolytes can be represented by Li 3x La 2 / 3-x □ 1 / 3-2x TiO3 (0 < x < 0.16, □ is a vacancy) (such as Li 1 / 8 La 5 / 8 TiO3, etc.) represents lithium lanthanum titanium oxide (LLTO), and LiPON-type solid electrolytes can refer to nitrides such as lithium phosphorus oxynitride (such as Li 2.8 PO 3.3 N 0.46 , etc.).

[0069] Amorphous electrolytes can include Li2O-B2O3-SiO2, Li2O-B2O3-P2O5, Li3BO3-Li2CO3 or Li3BO3-Li2CO3, etc.

[0070] Sulfide-based solid electrolytes include sulfur atoms in the electrolyte components and are not particularly limited to specific components, and may include one or more of crystalline solid electrolytes, amorphous solid electrolytes (glassy solid electrolytes) or glass-ceramic solid electrolytes.

[0071] For example, sulfide-based solid electrolytes may include LPS-type sulfides containing sulfur and phosphorus (e.g., Li₂S-P₂S₅) and thio-LISICON-type compounds (such as Li₂S-P₂S₅). 4-x Ge 1-x P x S4 (where x can be 0.1 to 2, 3 / 4 or 2 / 3), Li 10±1 MP2X 12 (Where M is Ge, Si, Sn, or Al, and X is S or Se), Li 3.833 Sn 0.833 As 0.166 S4, Li4SnS4, Li 3.25 Ge 0.25 P 0.75 S4, Li2S-P2S5, B2S3-Li2S, xLi2S-(100-x)P2S5 (where x is 70 to 80), Li2S-SiS2-Li3N, Li2S-P2S5-LiI, Li2S-SiS2-LiI, Li2S-B2S3-LiI, Li 10 SnP2S 12 and Li 3.25 Ge 0.25 P 0.75 S4).

[0072] The electrode layer includes a positive electrode layer 120 and a negative electrode layer 140, and may mainly include current collectors 123 and 143 and electrode active material layers 121, 122, 141 and 142 coated on at least one surface of the current collectors 123 and 143.

[0073] Reference Figure 2 The positive electrode layer 120 can be formed by coating positive electrode active material layers 121 and 122 onto at least one surface of the positive electrode current collector 123, and the negative electrode layer 140 can be formed by coating negative electrode active material layers 141 and 142 onto at least one surface of the negative electrode current collector 143.

[0074] For example, the electrode layer at the bottom based on the stacking direction can be formed by coating a positive electrode active material layer 122 onto a surface of a positive electrode current collector 123, and the electrode layer at the top can be formed by coating a negative electrode active material layer 141 onto a surface of a negative electrode current collector 143.

[0075] Furthermore, the electrode layer located between the top and bottom can be formed by coating positive electrode active material layers 121 and 122 on the two surfaces of the positive electrode current collector 123, or by coating negative electrode active material layers 141 and 142 on the two surfaces of the negative electrode current collector 143.

[0076] In an all-solid-state battery 100 according to some embodiments, the positive electrode layer 120 includes a positive electrode active material and a second solid electrolyte located on the surface of the positive electrode active material, and / or the negative electrode layer 140 includes a negative electrode active material and a second solid electrolyte located on the surface of the negative electrode active material.

[0077] The following text will describe in detail the positive electrode active material and the second solid electrolyte located on the surface of the positive electrode active material. The description of the positive electrode active material and the second solid electrolyte located on the surface of the positive electrode active material can also be applied to the negative electrode active material and the second solid electrolyte located on the surface of the negative electrode active material.

[0078] Figure 3 This is a schematic cross-sectional view of the positive electrode layer 120 of an all-solid-state battery according to some embodiments.

[0079] Reference Figure 3 The positive electrode active material layers 121 and 122 include a positive electrode active material and a second solid electrolyte located on the surface of the electrode active material.

[0080] Additionally, the positive electrode active material layers 121 and 122 may optionally further include additives, such as solid electrolytes, binders, or conductive materials.

[0081] The lithium-ion conductivity (25°C) of the second solid electrolyte is greater than or equal to 1.0 × 10⁻⁶ times that of the lithium-ion conductivity (25°C) of the first solid electrolyte. 2 times.

[0082] For example, the lithium-ion conductivity of the second solid electrolyte can be 1.0 × 10⁻⁶. -4 S / cm up to 1.0×10 -3 S / cm. Lithium-ion conductivity can be measured at 25°C.

[0083] The lithium-ion conductivity of the second solid electrolyte can be measured by the AC impedance method.

[0084] For example, firstly, a portion of the second solid electrolyte included in the positive electrode active material layers 121 and 122 is sampled as a rectangular plate-shaped sheet by ion milling or polishing. At this time, the sample may only include the second solid electrolyte. Next, electrodes made of gold (Au) are formed on both ends of the obtained sheet to prepare the sample. Then, the AC impedance (frequency: 10 Hz) of the sample is measured at room temperature (25°C) using an impedance measuring device. +6 Hz to 10 -1 Ionic conductivity can be calculated using Hz (voltage: 10mV, 100mV).

[0085] As another example, ionic conductivity can be measured by molding powder of a second solid electrolyte into a sheet and then sintering the powder. Specifically, the powder of the second solid electrolyte is placed in a sheet mold with a diameter of approximately 14 mm, pressurized to 0.5 tons to produce a sheet-shaped body, and then sintered to produce a sintered body of the second solid electrolyte. A sample is fabricated by smoothly polishing both sides of the sintered body and then forming electrodes made of gold (Au). The AC impedance (frequency: 10 Hz) of the sample is then measured at room temperature (25°C) using an impedance measuring device. +6 Hz to 10 -1 Ionic conductivity can be calculated using Hz (voltage: 10mV, 100mV).

[0086] The second solid electrolyte is a solid electrolyte with superior ionic conductivity than the first solid electrolyte, and it does not reduce the ionic conductivity of the electrode layer or hinder the densification of the electrode layer, thereby improving the rate performance of the all-solid-state battery.

[0087] In addition, the second solid electrolyte can be used as a bridge between the electrode active material included in the electrode layer and the first solid electrolyte included in the solid electrolyte layer, thereby improving the interfacial bonding between the electrode active material layer and the solid electrolyte layer.

[0088] Furthermore, although the ionic conductivity of the second solid electrolyte is superior to that of the first solid electrolyte, the sintering temperature can be relatively higher, or the possibility of side reactions may be higher than that of the first solid electrolyte. Therefore, the second solid electrolyte may not be suitable to be contained in the solid electrolyte layer, but it may be suitable to be placed on the surface of the electrode active material in the electrode layer.

[0089] Side reactions can refer to the situation where the solid electrolyte undergoes oxidation / reduction reactions and decomposes within a specific voltage range within the driving voltage of the all-solid-state battery, the situation of the materials of the solid electrolyte layer and the electrode layer (positive electrode material, negative electrode material or conductive material, etc.) during the all-solid-state battery manufacturing process, and the situation where the solid electrolyte layer and the electrode layer cause reactions other than charging / discharging reactions under the operating environment (temperature / humidity, etc.) of the all-solid-state battery.

[0090] For example, the second solid electrolyte may be an oxide-based solid electrolyte, and the oxide-based solid electrolyte may include a garnet-type, Nasicon-type, LISICON-type, or a combination thereof.

[0091] The garnet-type solid electrolyte may be represented by Li a La b Zr c O 12 (0 < a < 7, 0 < b < 3, 0 < c < 2) (such as Li7La3Zr2O 12 ) representing lithium lanthanum zirconium oxide (LLZO). The Nasicon-type solid electrolyte may be represented by lithium aluminum titanium phosphate (LATP) represented by Li 1+x Al x M 2-x (PO4)3 (LAMP) (0 < x < 2, where M is Zr, Ti, or Ge) in which Ti is introduced into the compound of Li 1+x Al x Ti 2-x (PO4)3 (0 < x < 1); lithium aluminum germanium phosphate (LAGP) represented by Li 1+x Al x Ge 2-x (PO4)3 (0 < x < 1) in which an excessive amount of lithium is introduced (such as Li 1.3 Al 0.3 Ti 1.7 (PO4)3, etc.); and / or lithium zirconium phosphate (LZP) (LiZr2(PO4)3).

[0092] In addition, the LISICON-type solid electrolyte may be represented by xLi3AO4-(1-x)Li4BO4 (A is P, As, V, etc., B is Si, Ge, Ti, etc.) and includes solid solution oxides such as Li4Zn(GeO4)4, Li 10 GeP2O 12 (LGPO), Li 3.5 Si 0.5 P 0.5 O4, Li 10.42 Si(Ge) 1.5 P 1.5 Cl 0.08 O 11.92 etc., and solid solution oxides such as Li 4-x M 1-y M' yA solid-solution sulfide represented by S4 (where M is Si or Ge, M' is P, Al, Zn, or Ga, 0 < x < 1, 0 < y < 1), including Li2S-P2S5, Li2S-SiS2, Li2S-SiS2-P2S5, or Li2S-GeS2, etc.

[0093] According to some embodiments, the second solid electrolyte may be located on the surface of the positive electrode active material, and the second solid electrolyte may be located on a part of the surface of the positive electrode active material.

[0094] For example, the second solid electrolyte may be a coating that surrounds a part of the surface of the positive electrode active material.

[0095] For example, the second solid electrolyte may be coated to surround 5% or more of the surface area of the positive electrode active material. For example, the second solid electrolyte may be formed to surround 5% or more, 7% or more, or 10% or more of the surface area of the positive electrode active material, but is not particularly limited thereto.

[0096] For example, based on 100 parts by weight of the positive electrode active material, the second solid electrolyte may be included in an amount of 0.1 to 10 parts by weight (for example, 0.1 to 8 parts by weight, 0.1 to 5 parts by weight, or 0.1 to 3 parts by weight).

[0097] If the second solid electrolyte is included in an amount less than 0.1 part by weight based on 100 parts by weight of the positive electrode active material, the second solid electrolyte may not be sufficiently coated on the positive electrode active material. If the second solid electrolyte is included in an amount greater than 10 parts by weight, there may be a problem that the second solid electrolyte is not coated on the surface of the positive electrode active material and agglomerates separately.

[0098] For example, the second solid electrolyte may be coated on the surface of the electrode active material with an average thickness of 1 nm to 10 nm (for example, 2 nm to 8 nm).

[0099] The average thickness of the second solid electrolyte coated on the surface of the electrode active material can be measured by TEM analysis.

[0100] First, a part of the positive electrode active material layers 121 and 122 of the all-solid-state battery 100 is sampled by ion milling, polishing, or FIB. At this time, the sampled part must contain at least one positive electrode active material particle.

[0101] The thickness can be measured through the part of the sampled positive electrode active material surface coated with the second solid electrolyte. At this time, elemental analysis (energy dispersive spectrometer (EDS)) can be used during TEM analysis to find the position where the second solid electrolyte is coated on the surface of the positive electrode active material. To distinguish the positive electrode active material and the second solid electrolyte, the contrast difference in the bright-field image or the contrast difference in the STEM image can be used.

[0102] The average thickness can be obtained by measuring the coating thickness of the second solid electrolyte in at least 10 samples and calculating the arithmetic mean.

[0103] When the content of the positive electrode active material within the above range includes the second solid electrolyte, and the coating thickness is within the above range, the rate performance of the all-solid-state battery can be improved without interfering with the densification of the electrode layer.

[0104] For example, the positive electrode active material may include a high-cobalt positive electrode active material. While high-cobalt-based positive electrode active materials have the advantage of small volume change during charging / discharging in all-solid-state batteries, there is a problem that the rate performance of the battery is reduced due to low ionic conductivity. Therefore, by placing a second solid electrolyte having the aforementioned high ionic conductivity on the surface of the high-cobalt-based positive electrode active material, the density of the electrode layer and the rate performance of the battery can be improved. Therefore, all-solid-state batteries according to some embodiments of this disclosure include an electrode layer with improved density while reducing volume change during charging / discharging, thereby effectively improving the rate performance of the battery.

[0105] For example, high cobalt-based cathode active materials can be represented by chemical formula 1.

[0106] [Chemical Formula 1] LiCo x M 1 y M 2 1-x-y O2 In chemical formula 1, 0.6 ≤ x ≤ 1.0, 0 ≤ y ≤ 0.3. M 1 It can be Ni, Al, Mn, or a combination thereof, M 2 It can be Mn, Na, Mg, Ti, Ni, Al, Si, Zr, Zn, Nb, Cr, Fe, Sr, V, Cu, B, Ba, Ca, Ce, Se, Sn, W, Y, or combinations thereof.

[0107] For example, high cobalt-based cathode active materials may include those selected from LiCoO2, LiCo... 0.98 Nb 0.1 Al 0.1 O2, LiNi 0.3 Co 0.6 Mn 0.1 At least one of the groups consisting of O2 or combinations thereof.

[0108] For example, the average particle size (D50) of high cobalt-based cathode active materials can be from 1 μm to 10 μm.

[0109] For example, in addition to the aforementioned high cobalt-based cathode active materials, cathode active materials may also include lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium manganese oxide, or combinations thereof.

[0110] The positive electrode active material can be, for example, a compound represented by the following formula: Li a A 1-b M b D2 (where 0.90≤a≤1.8, 0≤b≤0.5); Li a E 1-b M b O 2-c D c (Where, 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); LiE 2-b M b O 4-c D c (Where, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b M c D α (Where, 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α≤2); Li a Ni 1-b-c Co b M c O 2-α X α (Where, 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); Li a Ni 1-b-c Co b M c O 2-α X2 (where 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); Li a Ni 1-b- c Mn b M c D α (Where, 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α≤2); Li a Ni 1-b-c Mn b M c O 2-α X α (Where, 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); Li a Ni 1-b-cMn b M c O 2-α X2 (where 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); Li a Ni b E c G d O2 (where 0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0.001≤d≤0.1); Li a Ni b Co c Mn d G e O2 (where 0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0.001≤e≤0.1); Li a NiG b O2 (where 0.90≤a≤1.8, 0.001≤b≤0.1); Li a CoG b O2 (where 0.90≤a≤1.8, 0.001≤b≤0.1); Li a MnG b O2 (where 0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn2G b O4 (where 0.90≤a≤1.8, 0.001≤b≤0.1); QO2; QS2; LiQS2; V2O5; LiV2O2; LiRO2; LiNiVO4; Li (3-f) J2(PO4)3 (0≤f≤2); Li (3-f) Fe2(PO4)3 (where 0≤f≤2); and LiFePO4. In the above formula, A is Ni, Co, or Mn; M is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, or a rare earth element; D is O, F, S, or P; E is Co or Mn; X is F, S, or P; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, or V; Q is Ti, Mo, or Mn; R is Cr, V, Fe, Sc, or Y; J is V, Cr, Mn, Co, Ni, or Cu.

[0111] The positive electrode active material can also be LiCoO2 or LiMn. x O 2x (where x = 1 or 2), LiNi 1-x Mn x O 2x (where 0) <x<1)、LiNi 1-x-y Co x Mny O2 (where 0≤x≤0.5, 0≤y≤0.5), LiFePO4, TiS2, FeS2, TiS3 or FeS3.

[0112] The solid electrolyte that may be included in the positive electrode active material layers 121 and 122 may be the same solid electrolyte that can be used in the solid electrolyte layer 130. The solid electrolyte can act as an ion conduction channel in the positive electrode layer 120, thereby reducing the interfacial resistance.

[0113] For example, the positive electrode active material layers 121 and 122 may further include a first solid electrolyte.

[0114] Based on the total weight of 100 parts by weight of positive electrode active material, the content of the first solid electrolyte is greater than or equal to 0.1 parts by weight, greater than or equal to 1 part by weight, or greater than or equal to 10 parts by weight, and less than or equal to 80 parts by weight, less than or equal to 60 parts by weight, or less than or equal to 50 parts by weight.

[0115] There are no particular restrictions on the conductive materials, as long as they are conductive and do not cause chemical changes in the all-solid-state battery 100. For example, the following materials can be used: graphite, such as natural or artificial graphite; carbon-based materials, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and pyrolysis black; conductive fibers, such as carbon fibers and metal fibers; fluorides; metal powders, such as aluminum powder and nickel powder; conductive whiskers, such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium oxide; or conductive materials such as polyphenylene derivatives.

[0116] Based on the total weight of 100 parts by weight of positive electrode active material, the content of conductive material can be from 1 part by weight to 10 parts by weight, for example, from 2 parts by weight to 5 parts by weight. When the content of conductive material is within the above range, the final electrode can have excellent conductivity characteristics.

[0117] Adhesives can be used to improve the bonding strength between active and conductive materials. Adhesives may include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, and various copolymers.

[0118] Based on the total weight of 100 parts by weight of the positive electrode active material, the binder content can be from 0 parts by weight to 50 parts by weight, for example, 1 part by weight to 50 parts by weight, or 2 parts by weight to 5 parts by weight. When the binder content meets the above range, the active material layer can have high adhesion.

[0119] The positive electrode current collector 123 is not particularly limited as long as it has conductivity and does not cause chemical changes in the positive electrode or the battery.

[0120] For example, as the positive electrode current collector 123, a porous body such as a network-like or mesh-like structure can be used, and a porous metal (such as stainless steel, nickel, or aluminum) plate can also be used.

[0121] In addition, the positive electrode current collector 123 can be coated with a metal or alloy coating that resists oxidation to prevent oxidation.

[0122] For example, as the positive electrode current collector 123, the following materials can be used: graphite, such as natural graphite or artificial graphite; carbon-based materials, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and pyrolytic carbon black; conductive fibers, such as carbon fibers, carbon nanotubes (CNT), vapor-grown carbon fibers (VGCF), and metal fibers.

[0123] For example, the positive electrode current collector 123 can further include different types of the above-mentioned solid electrolytes.

[0124] The negative electrode active material layers 141 and 142 can include a negative electrode active material, and optionally, can include a solid electrolyte. Additionally, the negative electrode active material layers 141 and 142 can optionally further include additives such as a binder or a conductive material.

[0125] As the negative electrode active material, carbon-based materials, silicon, silicon oxides, silicon-based alloys, silicon-carbon-based material composites, tin, tin-based alloys, tin-carbon composites, metal oxides, or combinations thereof can be used, and the negative electrode active material can include lithium metal and / or lithium metal alloys.

[0126] The lithium metal alloy can include lithium and a metal / metalloid capable of alloying with lithium. For example, the metal / metalloid capable of alloying with lithium can include Si, Sn, Al, Ge, Pb, Bi, Sb, Si-Y alloy (where Y is an alkali metal, alkaline earth metal, Group 13 to Group 16 element, transition metal, rare earth element, or a combination thereof, and does not include Si), Sn-Y alloy (where Y is an alkali metal, alkaline earth metal, Group 13 to Group 16 element, transition metal, 12 such as a transition metal oxide like lithium titanate (Li4Ti5O x ), etc.), rare earth element, or a combination of these elements, and does not include Sn), MnO

[0127] Element Y may include Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, or a combination thereof.

[0128] In addition, the oxides of metals / metalloids capable of alloying with lithium may include lithium titanium oxide, vanadium oxide, lithium vanadium oxide, SnO2, SiO x (0 < x < 2), etc. For example, the negative electrode active material may include one or more elements selected from the group consisting of elements of Group 13 to Group 16 of the periodic table. For example, the negative electrode active material may include one or more elements selected from the group consisting of Si, Ge, and Sn.

[0129] The carbon-based material may be crystalline carbon, amorphous carbon, or a mixture thereof. The crystalline carbon may include graphite, such as natural graphite or artificial graphite in amorphous, plate-like, flaky, spherical, or fibrous forms. In addition, the amorphous carbon may include soft carbon (low-temperature fired carbon) or hard carbon, mesophase pitch carbide, fired coke, graphene, carbon black, fullerene soot, carbon nanotubes, carbon fibers, etc.

[0130] Silicon may be selected from the group consisting of Si, SiO x (0 < x < 2, for example, 0.5 to 1.5), Sn, SnO2, or a silicon-containing metal alloy, and mixtures thereof. The silicon-containing metal alloy may include, for example, at least one of Al, Sn, Ag, Fe, Bi, Mg, Zn, In, Ge, Pb, and Ti, and silicon.

[0131] The solid electrolyte that can be used in the above solid electrolyte layer 130. The solid electrolyte can function as an ion conduction channel in the negative electrode layer 140, thereby reducing the interfacial resistance.

[0132] For example, the negative electrode active material layers 141 and 142 may further include a first solid electrolyte.

[0133] Based on the total weight of 100 parts by weight of the positive electrode active material, the content of the first solid electrolyte is greater than or equal to 0.1 part by weight, may be greater than or equal to 1 part by weight, or greater than or equal to 10 parts by weight, and may be less than or equal to 80 parts by weight, less than or equal to 60 parts by weight, or less than or equal to 50 parts by weight.

[0134] The negative electrode active material layers 141 and 142 may also optionally include a conductive material and an adhesive as described for the positive electrode active material layers 121 and 122.

[0135] There are no particular restrictions on the negative electrode current collector 143, as long as it is conductive and does not cause chemical changes in the positive electrode or battery.

[0136] For example, as the negative electrode current collector 143, a porous body such as a network or mesh can be used, and a porous metal plate (such as stainless steel, nickel or aluminum) can be used.

[0137] In addition, the negative electrode current collector 143 may be coated with an antioxidant metal or alloy coating to prevent oxidation.

[0138] For example, the following materials can be used as the negative electrode current collector 143: graphite, such as natural graphite or artificial graphite; carbon-based materials, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black and pyrolysis black; conductive fibers, such as carbon fibers, carbon nanotubes (CNTs), vapor-grown carbon fibers (VGCF) and metal fibers.

[0139] For example, the negative electrode current collector 143 may further include one or more of the above-mentioned solid electrolytes.

[0140] If the negative electrode active material layers 141 and 142 have excellent conductivity, the negative electrode current collector 143 may not be included in the negative electrode layer 140.

[0141] Reference Figure 2 According to some embodiments, the all-solid-state battery 100 may also include an edge layer 150 disposed along the edge of the positive electrode layer 120 and the edge of the negative electrode layer 140.

[0142] Reference Figure 2 The edge layer 150 is located on the solid electrolyte layer 130 and can be disposed at the lateral edges of the positive electrode active material layers 121 and 122 or the negative electrode active material layers 141 and 142. Therefore, the edge layer 150 can be located in the same layer of the positive electrode layer 120 and the same layer of the negative electrode layer 140, respectively.

[0143] The edge layer 150 may include an ionic conductivity of less than or equal to 1.0 × 10⁻⁶. -10 S / cm or less than or equal to 1.0 × 10 -6 Insulating materials with an S / cm ratio can be used without type restrictions, as long as they are commonly used.

[0144] For example, insulating materials may include insulating materials such as ceramics or resins.

[0145] Ceramics may include aluminum nitride (AlN), beryllium oxide (BeO), boron nitride (BN), silicon (Si), silicon carbide (SiC), silicon nitride (Si3N4), gallium arsenide (GaAs), gallium nitride (GaN), barium titanate (BaTiO3), mixtures thereof, or oxides and / or nitrides of these materials.

[0146] For example, the resin may include polyolefins such as polyethylene or polypropylene, polyesters such as polyethylene terephthalate (PET), polyurethane, or polyimide.

[0147] In addition, the edge layer 150 may further include a solid electrolyte contained in the aforementioned solid electrolyte layer 130.

[0148] According to some embodiments, the all-solid-state battery 100 may further include a cover layer (not shown) located on one or both sides in the stacking direction of the battery stack. For example, the cover layer may be located on the outermost side in the stacking direction of the all-solid-state battery 100. The cover layer may be located outside the battery stack, thereby mitigating impact on the all-solid-state battery, preventing penetration into the interior, and preventing current leakage.

[0149] For example, the capping layer may surround the surface of the battery stack such that one end of the positive electrode layer 120 is exposed on the first surface and connected to an external electrode 112, and one end of the negative electrode layer 140 is exposed on the second surface and connected to another external electrode 114. For example, the capping layer may be located on a third and fourth surface of the battery stack in addition to the first and second surfaces, or it may be placed on the outer surfaces of the positive electrode layer 120 at the bottom and the negative electrode layer 140 at the top in the stacking direction of the battery stack.

[0150] At this time, the solid electrolyte layer 130 can be disposed between the capping layer and the adjacent positive electrode layer 120 or negative electrode layer 140.

[0151] For the purpose of providing insulation, the covering layer may include an ionic conductivity of less than or equal to 1.0 × 10⁻⁶. -10 S / cm or less than or equal to 1.0 × 10 -6 Insulating materials with an S / cm ratio can be used without type restrictions, as long as they are commonly used.

[0152] For example, the insulating material may include insulating materials such as ceramics or resins, and since this is the same as the insulating material included in the edge layer, a detailed description will be omitted.

[0153] The terminals of the positive current collector 123 and the negative current collector 143 are exposed on both sides of the stack of the all-solid-state battery 100, and the external electrodes 112 and 114 can be connected to and bonded to these exposed terminals. That is, the external electrode 112 can be configured to connect to the terminal of the positive current collector 123 to have a positive electrode, and the external electrode 114 can be configured to connect to the terminal of the negative current collector 143 to have a negative electrode. If the terminals of the positive current collector 123 and the negative current collector 143 are configured to face opposite directions, the external electrodes 112 and 114 can also be located on both sides.

[0154] The outer electrodes 112 and 114 can cover not only the battery stack but also the sides of the cover layer. That is, the cover layer is manufactured by firing together in batches during the manufacturing of the battery stack, and the outer electrodes 112 and 114 can also be located on the sides of the cover layer when they are formed.

[0155] The external electrodes 112 and 114 may include conductive metal and glass.

[0156] The conductive metal may include at least one selected from the group consisting of, for example, copper (Cu), nickel (Ni), tin (Sn), palladium (Pd), platinum (Pt), gold (Au), silver (Ag), tungsten (W), titanium (Ti), lead (Pb), and alloys thereof.

[0157] The glass composition included in the external electrodes 112 and 114 may be a composition of mixed oxides. The glass composition may include at least one selected from, for example, silicon oxides, boron oxides, aluminum oxides, transition metal oxides, alkali metal oxides, and alkaline earth metal oxides, and combinations thereof. Here, the transition metal is selected from zinc (Zn), titanium (Ti), copper (Cu), vanadium (V), manganese (Mn), iron (Fe), or nickel (Ni); the alkali metal is selected from lithium (Li), sodium (Na), or potassium (K); and the alkaline earth metal may be selected from magnesium (Mg), calcium (Ca), strontium (Sr), or barium (Ba).

[0158] There are no particular limitations on the method for forming the external electrodes 112 and 114. For example, the external electrodes can be formed by immersing the battery stack in a conductive paste containing conductive metal and glass, or by printing the conductive paste onto the surface of the battery stack using screen printing or gravure printing. Furthermore, various methods such as applying conductive paste to the surface of the battery stack or transferring a dry film obtained by drying the conductive paste onto the battery stack can be used.

[0159] A stacked all-solid-state battery according to some embodiments includes multiple solid electrolyte layers, multiple positive electrode layers alternately arranged between the multiple solid electrolyte layers, and multiple negative electrode layers. Each solid electrolyte layer includes a first solid electrolyte layer, and each positive or negative electrode layer includes an electrode active material and a second solid electrolyte located on the surface of the electrode active material. The lithium-ion conductivity (25°C) of the second solid electrolyte is greater than or equal to 1.0 × 10⁻⁶ of the lithium-ion conductivity (25°C) of the first solid electrolyte. 2 times.

[0160] Specific examples of this disclosure are provided below. However, the examples described below are intended only to illustrate or explain this disclosure, and its scope should not be limited thereto.

[0161] (Example) Comparison Example 1-1 The positive electrode green sheet is manufactured as follows: LiCoO2 as the positive electrode active material, Li2O-B2O3-SiO2 (hereinafter referred to as "LBSO") as the solid electrolyte, and carbon black as the conductive material are mixed in a volume ratio of 47.5:47.5:5, and the positive electrode active material layer is printed using a screen printing machine. Graphite and LBSO are mixed in a volume ratio of 5:5, and the current collector layer is printed using a screen printing machine.

[0162] The negative electrode green sheet is manufactured by mixing 2μm graphite as the negative electrode active material and LBSO as the solid electrolyte in a volume ratio of 5:5 and then using a screen printing machine.

[0163] Manufacturing includes LBSO (lithium-ion conductivity: 5.0 × 10⁻⁶). -7 A solid electrolyte sheet with a density of S / cm was used as the first solid electrolyte.

[0164] All-solid-state battery cells are manufactured by stacking positive electrode green sheets, negative electrode green sheets, and solid electrolyte green sheets, followed by pressure firing.

[0165] Example 1-1 The all-solid-state battery cell was manufactured in the same manner as in Comparative Example 1-1, except that a second solid electrolyte, Li, was included in an amount of 1.5 parts by weight, based on 100 parts by weight of LiCoO2 (positive electrode active material). 1.3 Al 0.3 Ti 1.7 (PO4)3 (hereinafter referred to as "LATP", lithium-ion conductivity: 1.0 × 10⁻⁶) -4 S / cm), and the second solid electrolyte is coated on the positive electrode active material to a thickness of 6.7 nm.

[0166] Example 1-2 The all-solid-state battery cell was manufactured in the same manner as in Example 1-1, except that a second solid electrolyte LATP was included in an amount of 3.0 parts by weight based on 100 parts by weight of LiCoO2 (positive electrode active material), and the second solid electrolyte was coated on the positive electrode active material to a thickness of 6.8 nm.

[0167] Compare Example 1-2 The all-solid-state battery cell was manufactured in the same manner as in Example 1-1, except that a second solid electrolyte LATP was included in an amount of 6.0 parts by weight based on 100 parts by weight of LiCoO2 (positive electrode active material), and the second solid electrolyte was coated on the positive electrode active material to a thickness of 11.6 nm.

[0168] Referring to Table 1, it can be seen that in the case of Comparative Examples 1-2, the second solid electrolyte cannot be coated on the positive electrode active material and instead agglomerates separately, making it difficult to measure the coating area.

[0169] Comparison Example 2-1 The positive electrode green sheet is manufactured by: using LiCo as the positive electrode active material... 0.98 Nb 0.1 Al 0.1 O2, Li2O-B2O3-SiO2 (hereinafter referred to as "LBSO") as a solid electrolyte, and carbon black as a conductive material are mixed in a volume ratio of 47.5:47.5:5. The positive electrode active material layer is printed using a screen printing machine. Graphite and LBSO are mixed in a volume ratio of 5:5, and then the current collector layer is printed using a screen printing machine.

[0170] The negative electrode green sheet is manufactured by mixing 2μm graphite as the negative electrode active material and LBSO as the solid electrolyte in a volume ratio of 5:5 and then using a screen printing machine.

[0171] A solid electrolyte layer green sheet comprising LBSO is manufactured as the first solid electrolyte.

[0172] All-solid-state battery cells are manufactured by stacking positive electrode green sheets, negative electrode green sheets, and solid electrolyte green sheets, followed by pressure firing.

[0173] Example 2-1 The all-solid-state battery cell was manufactured in the same manner as in Comparative Example 2-1, except that it was based on 100 parts by weight of LiCo. 0.98 Nb 0.1 Al 0.1 O2 (positive electrode active material) includes a second solid electrolyte LATP in an amount of 0.2 parts by weight, and the second solid electrolyte is coated on the positive electrode active material to a thickness of 4.5 nm.

[0174] Example 2-2 The all-solid-state battery cell is manufactured in the same manner as in Example 2-1, except that it is based on 100 parts by weight of LiCo. 0.98 Nb 0.1 Al 0.1 O2 (positive electrode active material) includes a second solid electrolyte LATP in an amount of 1.5 parts by weight, and the second solid electrolyte is coated on the positive electrode active material to a thickness of 6.5 nm.

[0175] Example 2-3 The all-solid-state battery cell is manufactured in the same manner as in Example 2-1, except that it is based on 100 parts by weight of LiCo. 0.98 Nb0.1 Al 0.1 O2 (positive electrode active material) includes a second solid electrolyte LATP in an amount of 3.0 parts by weight, and the second solid electrolyte is coated on the positive electrode active material to a thickness of 7.2 nm.

[0176] Comparison Example 2-2 The all-solid-state battery cell is manufactured in the same manner as in Example 2-1, except that it is based on 100 parts by weight of LiCo. 0.98 Nb 0.1 Al 0.1 O2 (positive electrode active material) includes a second solid electrolyte LATP in an amount of 5.0 parts by weight, and the second solid electrolyte is coated on the positive electrode active material to a thickness of 10.8 nm.

[0177] Compare Example 3-1 The positive electrode green sheet is manufactured by using LiNi as the positive electrode active material. 0.3 Co 0.6 Mn 0.1 O2, Li2O-B2O3-SiO2 (hereinafter referred to as "LBSO") as a solid electrolyte, and carbon black as a conductive material are mixed in a volume ratio of 47.5:47.5:5, and the positive electrode active material layer is printed using a screen printing machine. Graphite and LBSO are mixed in a volume ratio of 5:5, and then the current collector layer is printed using a screen printing machine. The negative electrode green sheet is manufactured by mixing 2μm graphite as the negative electrode active material and LBSO as the solid electrolyte in a volume ratio of 5:5 and then using a screen printing machine.

[0178] A solid electrolyte layer green sheet comprising LBSO is manufactured as the first solid electrolyte.

[0179] All-solid-state battery cells are manufactured by stacking positive electrode green sheets, negative electrode green sheets, and solid electrolyte green sheets, followed by pressure firing.

[0180] Example 3-1 The all-solid-state battery cell was manufactured in the same manner as in Comparative Example 3-1, except that it was based on 100 parts by weight of LiNi 0.3 Co 0.6 Mn 0.1 O2 (positive electrode active material) includes a second solid electrolyte LATP in an amount of 0.2 parts by weight, and the second solid electrolyte is coated on the positive electrode active material to a thickness of 2.5 nm.

[0181] Example 3-2 The all-solid-state battery cell was manufactured in the same manner as in Example 3-1, except that it was based on 100 parts by weight of LiNi.0.3 Co 0.6 Mn 0.1 O2 (positive electrode active material) includes a second solid electrolyte LATP in an amount of 0.8 parts by weight, and the second solid electrolyte is coated on the positive electrode active material to a thickness of 4.8 nm.

[0182] Example 3-3 The all-solid-state battery cell was manufactured in the same manner as in Example 3-1, except that it was based on 100 parts by weight of LiNi. 0.3 Co 0.6 Mn 0.1 O2 (positive electrode active material) includes a second solid electrolyte LATP in an amount of 3.0 parts by weight, and the second solid electrolyte is coated on the positive electrode active material to a thickness of 6.5 nm.

[0183] Compare Example 3-2 The all-solid-state battery cell was manufactured in the same manner as in Example 3-1, except that it was based on 100 parts by weight of LiNi. 0.3 Co 0.6 Mn 0.1 O2 (positive electrode active material) includes a second solid electrolyte LATP in an amount of 5.0 parts by weight, and the second solid electrolyte is coated on the positive electrode active material to a thickness of 10.2 nm.

[0184] (Evaluation example) Evaluation Example 1: Analysis of Cathode Layer Density The cathode layer density of all-solid-state batteries according to Examples 1-1 to 3-3 and Comparative Examples 1-1 to 3-2 is analyzed and shown in Tables 1 to 3 below.

[0185] The density of the positive electrode layer in the all-solid-state battery was measured using SEM analysis. Specifically, cross-sectional samples of the positive electrode layer were obtained by ion milling or polishing, and then SEM images of the cross-sectional samples were analyzed. (Refer to...) Figure 3 As can be seen in the SEM image of the positive electrode layer, pores exist between the positive electrode active material, the first solid electrolyte, and the conductive material, and these pores are distinguished by contrast difference during SEM-BSE mode analysis. The area of ​​the pores compared to the total area of ​​the positive electrode layer is expressed as a percentage, and the lower the value, the denser the positive electrode layer is considered.

[0186] Based on the comparison examples 1-1, 2-1 and 3-1 shown in Tables 1 to 3 below, if the above % value decreases by less than 3, it is determined as "slight improvement", and if the decrease is greater than or equal to 3, it is determined as "improvement".

[0187] Evaluation Example 2: Analysis of the Rate Performance of All-Solid-State Batteries The rate performance of the all-solid-state batteries is analyzed according to Examples 1-1 to 3-3 and Comparative Examples 1-1 to 3-2, and is shown in Tables 1 to 3 below.

[0188] The rate performance of all-solid-state batteries was measured by varying the charging / discharging current. First, the external electrode of the all-solid-state battery was connected to a battery charger / discharger. The battery was then charged and discharged twice at a rate of 0.05C using the charger / discharger, followed by a charge and discharge once at a rate of 0.5C. The discharge capacity during the 0.5C charge / discharge cycle, compared to the second discharge capacity, was then expressed as a capacity ratio (%). It was determined that a higher capacity ratio (%) indicated better rate performance.

[0189] Based on the comparison examples 1-1, 2-1 and 3-1 shown in Tables 1 to 3 below, if the above % value decreases by less than 5, it is determined as "slight improvement", and if the decrease is greater than or equal to 5, it is determined as "improvement".

[0190] Table 1

[0191] (In Table 1 above, "-" indicates that the second solid electrolyte cannot be coated onto the positive electrode active material and agglomerates on its own.) Referring to Table 1, when using LiCoO2 as the positive electrode active material, it can be seen that the all-solid-state battery cell of Comparative Example 1-1, which does not coat the positive electrode active material with a second solid electrolyte, and the all-solid-state battery cell of Comparative Example 1-2, which adds an excessive amount of the second solid electrolyte to the positive electrode active material and coats it with a thickness greater than 10 nm, have low positive electrode layer density and degraded rate performance.

[0192] Referring to Table 1, it can be seen that in Examples 1-1 and 1-2, the cathode layer density and rate performance are improved compared to Comparative Example 1-1.

[0193] Table 2

[0194] Referring to Table 2, when using LiCo 0.98 Nb 0.1 Al 0.1When O2 is used as the positive electrode active material, it can be seen that the all-solid-state battery cell of Comparative Example 2-1, which does not coat the positive electrode active material with a second solid electrolyte, and the all-solid-state battery cell of Comparative Example 2-2, which adds an excessive amount of the second solid electrolyte to the positive electrode active material and coats it with a thickness greater than 10 nm, have low positive electrode layer density and degraded rate performance.

[0195] Referring to Table 2, it can be seen that in Examples 2-1 to 2-3, the cathode layer density and rate performance are improved compared with Comparative Example 2-1.

[0196] Table 3

[0197] Referring to Table 3, when using LiNi 0.3 Co 0.6 Mn 0.1 When O2 is used as the positive electrode active material, it can be seen that the all-solid-state battery cells of Comparative Example 3-1, in which no second solid electrolyte is coated on the positive electrode active material, and Comparative Example 3-2, in which an excessive amount of second solid electrolyte is added to the positive electrode active material and coated with a thickness greater than 10 nm, have low positive electrode layer density and degraded rate performance.

[0198] Referring to Table 3, it can be seen that in Examples 3-1 to 3-3, the cathode layer density and rate performance are improved compared with Comparative Example 3-1.

[0199] While this disclosure has been described in conjunction with what is now considered to be actual embodiments, it should be understood that this disclosure is not limited to the disclosed embodiments, but rather is intended to cover various variations and equivalent arrangements included within the spirit and scope of the appended claims.

[0200] <Explanation of reference numerals in the attached figures> 100: All-solid-state battery 112, 114: External electrodes 120: Positive electrode layer 121, 122: Positive electrode active material layer 123: Positive current collector 130: Solid electrolyte layer 140: Negative electrode layer 141, 142: Negative electrode active material layer 143: Negative electrode current collector 150: Edge layer.

[0201] Industrial applicability This disclosure relates to an all-solid-state battery that has the advantage of improving the rate performance of the battery by densifying the electrode layer while improving the interfacial bonding between materials, and is therefore applicable to a variety of electrochemical and electronic devices.

Claims

1. An all-solid-state battery, comprising: Solid electrolyte layer; And a positive electrode layer and a negative electrode layer, wherein the solid electrolyte layer is positioned between the positive electrode layer and the negative electrode layer. The solid electrolyte layer includes a first solid electrolyte. The positive electrode layer or the negative electrode layer includes an electrode active material and a second solid electrolyte surrounding a portion of the surface of the electrode active material. The second solid electrolyte has an average thickness of 1 nm to 10 nm. The electrode active material includes a positive electrode active material. The positive electrode active material includes a high-cobalt-based positive electrode active material represented by chemical formula 1: [Chemical Formula 1] LiCo x M 1 y M 2 1-x-y O2 In chemical formula 1, 0.6 ≤ x ≤ 1.0, 0 ≤ y ≤ 0.

3. M 1 For Ni, Al, Mn or combinations thereof, M 2 It is selected from at least one of the following groups: Mn, Na, Mg, Ti, Ni, Al, Si, Zr, Zn, Nb, Cr, Fe, Sr, V, Cu, B, Ba, Ca, Ce, Se, Sn, W, Y, and combinations thereof.

2. The all-solid-state battery according to claim 1, wherein: The lithium-ion conductivity (25°C) of the second solid electrolyte is greater than or equal to 1.0 × 10⁻⁶ times that of the first solid electrolyte (25°C). 2 times.

3. The all-solid-state battery according to claim 1, wherein: The lithium-ion conductivity (25℃) of the first solid electrolyte is 1.0 × 10⁻⁶. -7 S / cm up to 1.0x10 -6 S / cm.

4. The all-solid-state battery according to claim 1, wherein: The lithium-ion conductivity (25°C) of the second solid electrolyte is 1.0 × 10⁻⁶. -4 S / cm up to 1.0×10 -3 S / cm.

5. The all-solid-state battery according to claim 1, wherein: The first solid electrolyte includes a glass-ceramic-based electrolyte or a lithium borosilicate-based electrolyte. The glass-ceramic-based electrolyte includes at least one selected from the group consisting of lithium (Li) oxide, boron (B) oxide, silicon (Si) oxide, phosphorus (P) oxide, germanium (Ge) oxide, and lithium chloride (LiCl). The lithium borosilicate-based electrolyte includes at least one selected from the group consisting of lithium (Li) oxide, silicon (Si) oxide, and boron (B) oxide.

6. The all-solid-state battery according to claim 1, wherein: The second solid electrolyte includes garnet-type solid electrolytes, Nasicon-type solid electrolytes, LISICON-type solid electrolytes, or combinations thereof.

7. The all-solid-state battery according to claim 6, wherein: The garnet-type solid electrolyte includes lithium lanthanum zirconium oxide.

8. The all-solid-state battery according to claim 6, wherein: The Nasicon-type solid electrolyte includes lithium aluminum titanium phosphate represented by Li 1+x Al x Ti 2-x (PO4)3 (0 < x < 1), or lithium aluminum germanium phosphate represented by Li 1+x Al x Ge 2-x (PO4)3 (0 < x < 1).

9. The all-solid-state battery according to claim 1, wherein: The second solid electrolyte is included in an amount of 0.1 to 10 parts by weight, based on 100 parts by weight of the electrode active material.

10. The all-solid-state battery according to claim 1, wherein: The second solid electrolyte surrounds 5% or more of the surface area of ​​the electrode active material.

11. The all-solid-state battery according to claim 1, wherein: The positive electrode layer or the negative electrode layer further includes the first solid electrolyte.

12. An all-solid-state battery, comprising: Solid electrolyte layer; And a positive electrode layer and a negative electrode layer, wherein the solid electrolyte layer is positioned between the positive electrode layer and the negative electrode layer. The solid electrolyte layer includes a first solid electrolyte. The positive electrode layer or the negative electrode layer includes an electrode active material and a second solid electrolyte surrounding a portion of the surface of the electrode active material. The second solid electrolyte has an average thickness of 1 nm to 10 nm. The lithium-ion conductivity (25°C) of the second solid electrolyte is greater than or equal to 1.0 × 10⁻⁶ times that of the first solid electrolyte (25°C). 2 times, The electrode active material includes a positive electrode active material. The positive electrode active material includes a high-cobalt-based positive electrode active material represented by chemical formula 1: [Chemical Formula 1] LiCo x M 1 y M 2 1-x-y O2 In chemical formula 1, 0.6 ≤ x ≤ 1.0, 0 ≤ y ≤ 0.

3. M 1 For Ni, Al, Mn or combinations thereof, M 2 Choose from groups consisting of Mn, Na, Mg, Ti, Ni, Al, Si, Zr, Zn, Nb, Cr, Fe, Sr, V, Cu, B, Ba, Ca, Ce, Se, Sn, W, Y, and combinations thereof.

13. The all-solid-state battery according to claim 12, wherein: The lithium-ion conductivity (25℃) of the first solid electrolyte is 1.0 × 10⁻⁶. -7 S / cm up to 1.0x10 -6 S / cm.

14. The all-solid-state battery according to claim 12, wherein: The lithium-ion conductivity (25°C) of the second solid electrolyte is 1.0 × 10⁻⁶. -4 S / cm up to 1.0×10 -3 S / cm.

15. The all-solid-state battery according to claim 12, wherein: The first solid electrolyte comprises at least one selected from the group consisting of glass-ceramic based electrolytes or lithium borosilicate based electrolytes. The glass-ceramic based electrolyte comprises lithium (Li) oxide, boron (B) oxide, silicon (Si) oxide, phosphorus (P) oxide, germanium (Ge) oxide, and lithium chloride (LiCl). The lithium borosilicate based electrolyte comprises at least one selected from the group consisting of lithium (Li) oxide, silicon (Si) oxide, and boron (B) oxide.

16. The all-solid-state battery according to claim 12, wherein: The second solid electrolyte includes garnet-type solid electrolytes, Nasicon-type solid electrolytes, LISICON-type solid electrolytes, or combinations thereof.

17. The all-solid-state battery according to claim 16, wherein: The garnet-type solid electrolyte includes lithium lanthanum zirconium oxide.

18. The all-solid-state battery according to claim 16, wherein: The Nasicon-type solid electrolyte includes lithium aluminum titanium phosphate represented by Li 1+x Al x Ti 2-x (PO4)3 (0 < x < 1), or lithium aluminum germanium phosphate represented by Li 1+x Al x Ge 2-x (PO4)3 (0 < x < 1).

19. The all-solid-state battery according to claim 12, wherein: The second solid electrolyte is included in an amount of 0.1 to 10 parts by weight, based on 100 parts by weight of the electrode active material.

20. The all-solid-state battery according to claim 12, wherein: The second solid electrolyte surrounds 5% or more of the surface area of ​​the electrode active material.

21. The all-solid-state battery according to claim 12, wherein: The positive electrode layer or the negative electrode layer further includes the first solid electrolyte.

Images