Patent Description:
Secondary batteries are rechargeable, unlike primary batteries, and may be used in various electronic devices, e.g., cellular phones, laptop computers, and camcorders. In particular, lithium secondary batteries may feature higher voltage and higher energy density as compared to nickel-cadmium batteries and nickel-hydrogen batteries. Thus, demand for lithium secondary batteries is increasing.

As the types of electronic devices including a secondary battery have become more diversified and related markets have grown, the demand for a secondary battery with improved performance in various aspects, such as increase in energy density, improvement of rate capability, increase in stability and durability, and improvement of flexibility, has increased. Energy density is related to an increase in the capacity of a secondary battery, and rate capability is related to an improvement in the charging speed of a secondary battery. Thus there remains a need for improved battery materials.

<CIT> discloses a lithium-ion battery including an electrode assembly that is obtained by combining a positive electrode active material, a first solid electrolyte and a second solid electrolyte. The first solid electrolyte may be crystalline or amorphous, and the second solid electrolyte is amorphous.

<CIT> discloses an electrochemical device including a positive electrode current collector, a plurality of positive electrodes disposed on the positive electrode current collector, an electrolyte layer disposed on the plurality of positive electrodes, a negative electrode disposed on the electrolyte layer, and a negative electrode current collector disposed on the negative electrode.

Provided is a solid electrolyte-cathode assembly for a secondary battery including a three-dimensional ("3D") electrode structure and providing improved capacity and enhanced rate capability.

Provided is a method of manufacturing a solid electrolyte-cathode assembly for a secondary battery including a three-dimensional ("3D") electrode structure and providing improved capacity and enhanced rate capability.

Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description.

According to an embodiment, a solid electrolyte-cathode assembly for a secondary battery includes a plurality of cathode layers spaced apart from each other in a first direction, and an electrolyte layer including an amorphous solid electrolyte and a crystalline solid electrolyte including a plurality of crystalline solid electrolyte particles, wherein the amorphous solid electrolyte is on a surface of a cathode layer of the plurality of cathode layers and the crystalline solid electrolyte is within the amorphous solid electrolyte.

The crystalline solid electrolyte may be present in the electrolyte layer in an amount of about <NUM> volume percent (vol%) to about <NUM> vol%, based on a total volume of the electrolyte layer.

A thickness of the electrolyte layer measured in the first direction may be about <NUM> nanometers (nm) to about <NUM> micrometers (µm).

An average particle size of the plurality of crystalline solid electrolyte particles may be about <NUM> to about <NUM>.

A ratio of an average particle size of the plurality of crystalline solid electrolyte particles to a thickness of the electrolyte layer measured in the first direction may be about <NUM>:<NUM> to about <NUM>:<NUM>.

The solid electrolyte-cathode assembly may further include a cathode current collector facing an end of each of the plurality of cathode layers and contacting a portion of each of the plurality of cathode layers, wherein the surface of the cathode layer of the plurality of cathode layers on which the amorphous solid electrolyte material is present may differ from the end of each of the plurality of cathode layers facing the cathode current collector.

Each of the plurality of cathode layers may include a first surface and a second surface opposite to each other, and a third surface and a fourth surface each extending between the first surface and the second surface, wherein each of the third surface and the fourth surface may have a surface area that is less than a surface area of each of the first surface and the second surface, wherein the third surface and the fourth surface may be opposite to each other. A first surface of a first cathode layer and a second surface of a second cathode layer adjacent to the first cathode layer may face each other.

The electrolyte layer may be on the first surface and the second surface of each of the plurality of cathode layers.

A ratio of a thickness of a first portion of the electrolyte layer measured in the first direction to a thickness of a second portion of the electrolyte layer measured in the first direction may be about <NUM>:<NUM> to about <NUM>:<NUM>, the solid electrolyte-cathode assembly may further include a cathode current collector on which the plurality of cathode layers are arranged, and the first portion of the electrolyte layer may be farther from the cathode current collector than is the second portion of the electrolyte layer in a second direction perpendicular to the first direction.

The crystalline solid electrolyte may include first crystalline solid electrolyte particles and second crystalline solid electrolyte particles having different average particle sizes, and a ratio of an average particle size of the first crystalline solid electrolyte particles to an average particle size of the second crystalline solid electrolyte particles may be about <NUM> to about <NUM>.

An on conductivity of the electrolyte layer may be about <NUM>-<NUM> Siemens per centimeter (S/cm) to about <NUM>-<NUM> S/cm.

The electrolyte layer may be a product of heat treating at a temperature of about <NUM> to about <NUM>.

The crystalline solid electrolyte may include Li<NUM>+xLa<NUM>M<NUM>O<NUM>, wherein M is at least one of Te, Nb, or Zr, and <NUM>≤x≤<NUM>.

The amorphous solid electrolyte may include Li<NUM>+xLa<NUM>M<NUM>O<NUM>, wherein M is at least one of Te, Nb, or Zr, and <NUM>≤x≤<NUM>.

According to an embodiment, a secondary battery includes an anode layer on the solid electrolyte-cathode assembly; and an anode current collector contacting a portion of the anode layer and facing the cathode current collector, wherein the anode layer is on the first surface and the second surface of each of the plurality of cathode layers.

According to an embodiment, a solid electrolyte-cathode assembly for a secondary battery includes a plurality of cathode layers spaced apart from each other in a first direction, and an electrolyte layer on a surface of a cathode layer of the plurality of cathode layers. The electrolyte layer includes a first amorphous solid electrolyte layer on a cathode layer of the plurality of cathode layers, a mixed solid electrolyte layer on the first amorphous solid electrolyte layer, the mixed solid electrolyte later including a plurality of third crystalline solid electrolyte particles in a second amorphous solid electrolyte, and a third amorphous solid electrolyte layer on the mixed solid electrolyte layer.

A ratio of an average particle size of the plurality of third crystalline solid electrolyte particles to a thickness of a sum of the first amorphous solid electrolyte layer and the third amorphous solid electrolyte layer measured in the first direction is about <NUM>:<NUM> to about <NUM>:<NUM>.

A plurality of fourth crystalline solid electrolyte particles may be in at least one of the first amorphous solid electrolyte layer, the mixed solid electrolyte layer, or the third amorphous solid electrolyte layer.

A ratio of an average particle size of the plurality of fourth crystalline solid electrolyte particles to an average particle size of the plurality of third crystalline solid electrolyte particles may be about <NUM>:<NUM> to about <NUM>:<NUM>.

According to an embodiment, a secondary battery includes an anode layer on the solid electrolyte-cathode assembly.

According to an embodiment, a method of manufacturing solid electrolyte-cathode assembly for a secondary battery includes arranging a plurality of cathode layers spaced apart from each other in a first direction on a cathode current collector, coating a first amorphous solid electrolyte on a cathode layer of the plurality of cathode layers to provide a first amorphous solid electrolyte-coated cathode layer, heat treating the first amorphous solid electrolyte-coated cathode layer to provide a second amorphous solid electrolyte-coated cathode layer, coating a mixture of a second amorphous solid electrolyte and a crystalline solid electrolyte including a plurality of crystalline solid electrolyte particles on the second amorphous solid electrolyte-coated cathode layer to provide a coated mixture, heat treating the coated mixture to provide a heat-treated mixture, coating a third amorphous solid electrolyte on the heat-treated mixture to provide an amorphous solid electrolyte material, and heat treating the amorphous solid electrolyte material to manufacture the solid electrolyte-cathode assembly, wherein a ratio of an average particle size of the plurality of crystalline solid electrolyte particles to a thickness of an electrolyte layer of the solid electrolyte-cathode assembly measured in the first direction is <NUM>:<NUM> to <NUM>:<NUM>.

The heat treating of the first amorphous solid electrolyte-coated cathode layer, the heat treating of the coated mixture, or the heat treating of the amorphous solid electrolyte material each independently may each independently include heat treating at about <NUM> to about <NUM>.

The coating of the first amorphous solid electrolyte, the mixture of the second amorphous solid electrolyte and the crystalline solid electrolyte, or the third amorphous solid electrolyte may each independently include spin coating or dip coating.

According to an embodiment, a method of manufacturing a secondary battery, the method includes providing an anode layer; providing the solid electrolyte-cathode assembly of claim <NUM>; and disposing the anode layer on the solid electrolyte-cathode assembly to manufacture the secondary battery.

According to an embodiment, an electrolyte layer of a secondary battery includes an amorphous solid electrolyte; and a plurality of crystalline solid electrolyte particles, wherein the electrolyte layer has a thickness of about <NUM> nanometers to about <NUM> micrometers, wherein an average particle size of the plurality of crystalline solid electrolyte particles is about <NUM> nanometers to about <NUM> micrometers, and wherein a ratio of the average particle size of the plurality of crystalline solid electrolyte particles to the thickness of the electrolyte layer is about <NUM>:<NUM> to about <NUM>:<NUM>.

Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout.

These terms are only used to distinguish one element, component, region, layer, or section from another element, component, region, layer, or section. Thus, "a first element," "component," "region," "layer" or "section" discussed below could be termed a second element, component, region, layer, or section without departing from the teachings herein.

" It will be further understood that the terms "comprises" and/or "comprising," or "includes" and/or "including" when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof.

The exemplary term "lower," can therefore, encompasses both an orientation of "lower" and "upper," depending on the particular orientation of the figure. The exemplary terms "below" or "beneath" can, therefore, encompass both an orientation of above and below.

"About" as used herein is inclusive of the stated value and means within an acceptable range of deviation for the particular value as determined by one of ordinary skill in the art, considering the measurement in question and the error associated with measurement of the particular quantity (i.e., the limitations of the measurement system). For example, "about" can mean within one or more standard deviations, or within ± <NUM>%, <NUM>%, <NUM>%, or <NUM>% of the stated value.

Hereinafter, a three-dimensional ("3D") electrode structure, a secondary battery including a 3D electrode structure, and a method of manufacturing a secondary battery will be described more fully with reference to the accompanying drawings. In the drawings, the widths and thicknesses of layers and regions are exaggerated for clarity of the specification and convenience of explanation. Like reference numerals in the drawings denote like elements.

<FIG> is a perspective view of a secondary battery <NUM> according to an embodiment. <FIG> is a cross-sectional view of the secondary battery <NUM> according to an embodiment and <FIG> is an enlarged portion of <FIG>. <FIG> is a perspective view of cathode layers <NUM>, an electrolyte layer <NUM>, and a first current collecting layer, e.g., first current collector, <NUM> included in the secondary battery <NUM>, according to an embodiment. <FIG> is a scanning electron microscope ("SEM") image of the electrolyte layer <NUM>, according to an embodiment. <FIG> is an SEM image of the electrolyte layer <NUM> and the cathode layers <NUM>, according to an embodiment.

Referring to <FIG>, the secondary battery <NUM> according to an embodiment may include a first electrode structure E1 including a plurality of cathode layers <NUM> each having a flat plate-shape, a second electrode structure E2 including an anode layer <NUM>, and the electrolyte layer <NUM> between the first electrode structure E1 and the second electrode structure E2. For example, as shown in <FIG>, a structure of the secondary battery <NUM> may include a single (electrochemical) cell (or a unit cell). The secondary battery <NUM> may have a stack structure in which a plurality of single (electrochemical) cells are stacked.

The first electrode structure E1 may include the first current collecting layer <NUM> and the plurality of cathode layers <NUM> electrically connected to the first current collecting layer <NUM>. For example, each of the plurality of cathode layers <NUM> may have a flat plate-shape. The plurality of cathode layers <NUM> may include a cathode active material. For example, the cathode active material may include a Li-containing oxide. The Li-containing oxide may be an oxide including Li and a transition metal. The Li-containing oxide may be, for example, LiMO<NUM> (M is a metal), wherein M may be at least one of Co, Ni, Mn, or Al. For example, LiMO<NUM> may be LiCoO<NUM>. The cathode active material may include a ceramic of a cathode composition, and may be a polycrystalline or a single crystal. For example, the Li-containing oxide may be, for example, LiMn<NUM>O<NUM>, LiFePO<NUM>, V<NUM>O<NUM>, Li<NUM>V<NUM>(PO<NUM>)<NUM>, or xLi<NUM>MnO<NUM>·(<NUM>-x)LiMO<NUM> (wherein M is at least one of Co, Ni, Mn, or Al). However, the aforementioned materials of the cathode active material are exemplary, and various other cathode active materials may be used.

The first current collecting layer <NUM> may be a cathode current collector. The first current collecting layer <NUM> may have a plate-shape, and, in this case, may be referred to as a current collecting plate. The first current collecting layer <NUM> may include, for example, at least one conductive material of Cu, Au, Pt, Ag, Zn, Al, Mg, Ti, Fe, Co, Ni, Ge, In, Pd, Y, Zr, or Sn. The first current collecting layer <NUM> may be a metal layer, or may be a layer including a conductive material other than metal.

Each cathode layer <NUM> having a plate-shape may have, for example, two side surfaces having a relatively wide, e.g., large, surface area, namely, first and second side surfaces <NUM> and <NUM> facing each other, and may have third and fourth side surfaces <NUM> and <NUM> facing each other, each extending between the first and second side surfaces <NUM> and <NUM> and having relatively smaller surface areas compared to the first and second side surfaces <NUM> and <NUM>. Stated otherwise, each of the third surface <NUM> and the fourth surface <NUM> may have a surface area that is less than a surface area of each of the first surface <NUM> and the second surface <NUM>. Two cathode layers <NUM> adjacent to each other may be arranged in such a way that the first side surface <NUM> and the second side surface <NUM> face each other.

The electrolyte layer <NUM> may be arranged on the cathode layers <NUM> and the first current collecting layer <NUM>. For example, the electrolyte layer <NUM> may include an amorphous solid electrolyte material <NUM> and a crystalline solid electrolyte include a plurality of crystalline solid electrolyte materials, e.g., particles, <NUM>. The amorphous solid electrolyte material <NUM> may be arranged on the first current collecting layer <NUM> and an outer, e.g., exterior, surface of a cathode layer <NUM> of the cathode layers <NUM>, and the plurality of crystalline solid electrolyte materials <NUM> may be mixed within the amorphous solid electrolyte material <NUM>. As used herein, the plurality of crystalline solid electrolyte materials <NUM> being within the amorphous solid electrolyte material <NUM> means that the crystalline solid electrolyte materials <NUM> is surrounded by the amorphous solid electrolyte material <NUM>, the As used herein, the outer or exterior surface of a cathode layer <NUM> of the cathode layers <NUM> refers to a surface of a cathode layer <NUM> of the cathode layers <NUM> other than a surface of a cathode layer of the cathode layers <NUM> that contacts the first current collecting layer <NUM>.

The amorphous solid electrolyte material <NUM> may have a winding form corresponding to the shape of the cathode layers <NUM>. For example, the amorphous solid electrolyte material <NUM> may be arranged on at least the first side surface <NUM> and the second side surface <NUM> of the cathode layers <NUM>, and may have a structure extending between the cathode layers <NUM> along the thickness direction of the cathode layers <NUM>. However, the amorphous solid electrolyte material <NUM> may be arranged on the third and fourth side surfaces <NUM> and <NUM>.

The plurality of crystalline solid electrolyte materials <NUM> may be mixed at a desired ratio within the amorphous solid electrolyte material <NUM>. For example, the crystalline solid electrolyte, e.g., the plurality of crystalline solid electrolyte materials, e.g., particles, <NUM>, may be present in the electrolyte layer in an amount of about <NUM> vol% to about <NUM> vol%, based on a total volume of the electrolyte layer. In an embodiment, the crystalline solid electrolyte, e.g., the plurality of crystalline solid electrolyte materials, e.g., particles, <NUM>, may be present in the electrolyte layer in an amount of about <NUM> vol% to about <NUM> vol%, <NUM> vol% to about <NUM> vol%, <NUM> vol% to about <NUM> vol%, or <NUM> vol% to about <NUM> vol%, based on a total volume of the electrolyte layer. For example, the plurality of crystalline solid electrolyte materials <NUM> may be mixed with the amorphous solid electrolyte material <NUM> and then may be formed via a low-temperature heat treatment, for example, a heat treatment of about <NUM> degrees Celsius (°C) or less, for example, about <NUM> to about <NUM>, about <NUM> to about <NUM>, or about <NUM> to about <NUM>, such that an interfacial resistance between the plurality of crystalline solid electrolyte materials <NUM> and the amorphous solid electrolyte material <NUM> may be minimized. Accordingly, the plurality of crystalline solid electrolyte materials <NUM> may increase an ion conductivity of the electrolyte layer <NUM> including the amorphous solid electrolyte material <NUM> mixed with the plurality of crystalline solid electrolyte materials <NUM>, which will be described in greater detail later with reference to <FIG>.

As described herein, the electrolyte layer <NUM> may include solid electrolyte materials, namely, the amorphous solid electrolyte material <NUM> and the plurality of crystalline solid electrolyte materials <NUM>. For example, the amorphous solid electrolyte material <NUM> may include a solid electrolyte material such as Li<NUM>+xLa<NUM>M<NUM>O<NUM> (M is at least one of Te, Nb, or Zr, and <NUM>≤x≤<NUM>), Li<NUM>PO<NUM>, LixTiy(PO<NUM>)<NUM> (<NUM><x<<NUM> and <NUM><y<<NUM>), LixAlyTiz(PO<NUM>)<NUM> (<NUM><x<<NUM>, <NUM><y<<NUM>, and <NUM><z<<NUM>), Li<NUM>+x+y(AlaGa<NUM>-a)x(TibGe<NUM>-b)<NUM>-xSiyP<NUM>-yO<NUM> (<NUM>≤x≤<NUM>, <NUM>≤y≤<NUM>, <NUM>≤a≤<NUM>, and <NUM>≤b≤<NUM>), LixLayTiO<NUM> (<NUM><x<<NUM> and <NUM><y<<NUM>), LixMyPzSw-based ceramic (M is at least one of Ge, Si, or Sn, <NUM><x<<NUM>, <NUM><y<<NUM>, <NUM><z<<NUM>, and <NUM><w<<NUM>), LixNy (<NUM><x<<NUM> and <NUM><y<<NUM>), LixPOyNz (<NUM><x<<NUM>, <NUM><y<<NUM>, and <NUM><z<<NUM>), SiS<NUM>-based ceramic (LixSiySz, <NUM><x<<NUM>,<NUM><y<<NUM>, and <NUM><z<<NUM>), P<NUM>S<NUM>-based ceramic (LixPySz, <NUM><x<<NUM>, <NUM><y<<NUM>, and <NUM><z<<NUM>), Li<NUM>O, LiF, LiOH, Li<NUM>CO<NUM>, LiAlO<NUM>, Li<NUM>O-Al<NUM>O<NUM>-SiO<NUM>-P<NUM>O<NUM>-TiO<NUM>-GeO<NUM>-based ceramic, or LixLayMzO<NUM>-based ceramic (M is at least one of Te, Nb, or Zr, <NUM><x<<NUM>, <NUM><y<<NUM>, and <NUM><z<<NUM>). For example, the plurality of crystalline solid electrolyte materials <NUM> may include a solid electrolyte material such as Li<NUM>+xLa<NUM>M<NUM>O<NUM> (M is at least one of Te, Nb, or Zr, and <NUM>≤x≤<NUM>), Li<NUM>PO<NUM>, LixTiy(PO<NUM>)<NUM> (<NUM><x<<NUM> and <NUM><y<<NUM>), LixAlyTiz(PO<NUM>)<NUM> (<NUM><x<<NUM>, <NUM><y<<NUM>, and <NUM><z<<NUM>), Li<NUM>+x+y(AlaGa<NUM>-a)x(TibGe<NUM>-b)<NUM>-xSiyP<NUM>-yO<NUM> (<NUM>≤x≤<NUM>, <NUM>≤y≤<NUM>, <NUM>≤a≤<NUM>, and <NUM>≤b≤<NUM>), LixLayTiO<NUM> (<NUM><x<<NUM> and <NUM><y<<NUM>), LixMyPzSw-based ceramic (M is at least one of Ge, Si, or Sn, <NUM><x<<NUM>, <NUM><y<<NUM>, <NUM><z<<NUM>, and <NUM><w<<NUM>), LixNy (<NUM><x<<NUM> and <NUM><y<<NUM>), LixPOyNz (<NUM><x<<NUM>, <NUM><y<<NUM>, and <NUM><z<<NUM>), SiS<NUM>-based ceramic (LixSiySz, <NUM><x<<NUM>,<NUM><y<<NUM>, and <NUM><z<<NUM>), P<NUM>S<NUM>-based ceramic (LixPySz, <NUM><x<<NUM>, <NUM><y<<NUM>, and <NUM><z<<NUM>), Li<NUM>O, LiF, LiOH, Li<NUM>CO<NUM>, LiAlO<NUM>, Li<NUM>O-Al<NUM>O<NUM>-SiO<NUM>-P<NUM>O<NUM>-TiO<NUM>-GeO<NUM>-based ceramic, or LixLayMzO<NUM>-based ceramic (M is at least one of Te, Nb, or Zr, <NUM><x<<NUM>, <NUM><y<<NUM>, and <NUM><z<<NUM>). However, the materials and types of the amorphous solid electrolyte material <NUM> and the plurality of crystalline solid electrolyte materials <NUM> are not limited to those described herein and may vary.

The electrolyte layer <NUM> may be on, e.g., surround, the plurality of cathode layers <NUM>. For example, the plurality of cathode layers <NUM> may be arranged on a, e.g., one, surface of the first current collecting layer <NUM> and may be perpendicular to the one surface of the first current collecting layer <NUM>. The electrolyte layer <NUM> surrounding each of the plurality of cathode layers <NUM> may have a width (or thickness) W and a length L that is greater than the width (thickness) W. For example, the electrolyte layer <NUM> may have the thickness W in an X-axis direction, and may have the length L in a Y-axis direction perpendicular to the thickness W. The electrolyte layer <NUM> may have a height h in a direction perpendicular to a thickness direction (e.g., the X-axis direction) and a lengthwise direction (e.g., the Y-axis direction), namely, in a direction perpendicular to the first current collecting layer <NUM>. In other words, a length of the electrolyte layer <NUM> in a Z-axis direction may be a height h. The height h may be greater than the thickness W and may be less than the length L. Stated otherwise, the cathode layers <NUM> may be spaced apart from each other in a first direction, e.g., the X-axis direction as shown in <FIG>, <FIG>, <FIG>, and <FIG>, and as used herein, the thickness direction refers to a direction measured in the first direction.

For example, as shown in <FIG>, the electrolyte layer <NUM> may be arranged on the surface of a cathode layer <NUM> of the plurality of cathode layers <NUM> to have a desired thickness, for example, a thickness W of about <NUM> to about <NUM>, for example, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, or about <NUM> to about <NUM>. For example, the plurality of crystalline solid electrolyte materials <NUM> may have an average particle size D of about <NUM> to about <NUM>, for example, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, or about <NUM> to about <NUM>. The electrolyte layer <NUM> may be formed by mixing the plurality of crystalline solid electrolyte materials <NUM> within the amorphous solid electrolyte material <NUM>. A ratio of the average particle size D of the plurality of crystalline solid electrolyte materials <NUM> with respect to the thickness W of the electrolyte layer <NUM> is <NUM>:<NUM> to about <NUM>:<NUM>, for example, about <NUM>:<NUM> to about <NUM>:<NUM>, about <NUM>:<NUM> to about <NUM>:<NUM>, about <NUM>:<NUM> to about <NUM>:<NUM>, or about <NUM>:<NUM> to about <NUM>:<NUM>. When the average particle size D of the plurality of crystalline solid electrolyte materials <NUM> with respect to the thickness W of the electrolyte layer <NUM> has a ratio as described herein, the electrolyte layer <NUM> may have a relatively smooth surface as shown in <FIG>. Accordingly, a contact state between the electrolyte layer <NUM> and the cathode layers <NUM> and the anode layer <NUM> arranged to surround the electrolyte layer <NUM> may be improved, and pore generation may be decreased or prevented and ion conductivity may also improve. However, the aforementioned specific figures of the thickness W of the electrolyte layer <NUM> and the average particle size D of the plurality of plurality of crystalline solid electrolyte materials <NUM> are merely exemplary.

The second electrode structure E2 may include the anode layer <NUM> and a second current collecting layer <NUM> electrically connected to the anode layer <NUM>. The anode layer <NUM> may include an anode active material, and the second current collecting layer <NUM> may be an anode current collecting layer. For example, the anode active material included in the anode layer <NUM> may include, for example, a Li metal, a carbon-based material, a silicon-based material, or an oxide. The anode current collecting layer may include, for example, at least one conductive material of Cu, Au, Pt, Ag, Zn, Al, Mg, Ti, Fe, Co, Ni, Ge, In, Pd, Y, Zr, or Sn. However, the anode active material and the materials of the anode current collecting layer are not limited thereto.

The second current collecting layer <NUM> may face the first current collecting layer <NUM>. The anode layer <NUM> may have a winding form corresponding to the shape of the cathode layers <NUM> while electrically contacting the second current collecting layer <NUM>. For example, the anode layer <NUM> may be arranged on at least the first side surface <NUM> and the second side surface <NUM> of the cathode layers <NUM> and may have a structure extending between the cathode layers <NUM> along the thickness direction of the cathode layers <NUM>. In this case, portions of the anode layer <NUM> extending between the cathode layers <NUM> may have a plate shape. Accordingly, the portions of the anode layer <NUM> extending between the cathode layers <NUM> may be referred to as "a plurality of anode layer plates". In this case, the cathode layers <NUM> and the anode layer plates may alternate with each other. The electrolyte layer <NUM> may be arranged between the cathode layers <NUM> and the anode layer <NUM>.

The secondary battery <NUM> may include the first electrode structure E1 as a 3D structure including the plurality of cathode layers <NUM> perpendicular (or substantially perpendicular) to the first current collecting layer <NUM> and the second electrode structure E2 including the anode layer <NUM> and the second current collecting layer <NUM>, and a capacity and energy density of the secondary battery <NUM> may be greatly increased compared to a secondary battery including a two-dimensional ("2D") electrode structure (i.e., a planar-type structure). A 3D electrode structure may provide a high, e.g., large, active material volume, e.g., a volume of crystalline solid electrolyte present in the electrolyte layer, and a wide, e.g., large, reaction surface area when compared to a planar-type electrode structure, and the 3D electrode structure may be favorable to improvement in the energy density and rate capability of a battery (secondary battery).

However, when the cathode active material included in the cathode layers <NUM> is sintered to a high density to increase the capacity of the secondary battery <NUM>, the ion conductivity of the cathode layers <NUM> may be reduced, and the energy density and the rate capability of the secondary battery <NUM> may be reduced. The secondary battery <NUM> in which the ion conductivity of the cathode layers <NUM> is increased by arranging the amorphous solid electrolyte material <NUM> and the plurality of crystalline solid electrolyte materials <NUM> in the electrolyte layer <NUM> will now be described in greater detail.

<FIG> is a cross-sectional view of a secondary battery according to Comparative Example <NUM> and <FIG> is an enlarged portion of <FIG>. <FIG> is an SEM image of an electrolyte layer <NUM> according to Comparative Example <NUM>. <FIG> is a cross-sectional view of a secondary battery according to Comparative Example <NUM> and <FIG> is an enlarged portion of <FIG>. <FIG> is an SEM image of an electrolyte layer <NUM> according to Comparative Example <NUM>. <FIG> is a graph showing a correlation between a heat treatment process temperature of an electrolyte layer and ion conductivity thereof. <FIG> is a Nyquist plot representing ion conductivities of Comparative Example <NUM>, Comparative Example <NUM>, and a Hybrid-LLZO embodiment.

Referring to <FIG>, <FIG>, and <FIG>, cathode layers <NUM> according to Comparative Example <NUM> may be formed by drying active material slurry to form an active material sheet and sintering a cathode active material, for example, LiCoO<NUM> ("LCO"), included in the active material sheet via a sintering process. On the cathode layers <NUM> obtained by sintering the cathode active material, a plurality of crystalline solid electrolyte materials <NUM>, for example, crystalline Li<NUM>La<NUM>Zr<NUM>O<NUM> ("LLZO") powder, may be arranged in a pressing way, e.g., pressing against one another. A high-temperature heat treatment, for example, a heat treatment at a high temperature of about <NUM>,<NUM> or greater, for example, about <NUM>,<NUM> to about <NUM>,<NUM>, about <NUM>,<NUM> to about <NUM>,<NUM>, or about <NUM>,<NUM> to about <NUM>,<NUM>, may be applied to the plurality of crystalline solid electrolyte materials <NUM>. In this case, an interfacial decomposition reaction may be generated between the cathode active material included in the cathode layers <NUM> and the plurality of crystalline solid electrolyte materials <NUM>, and a reaction product (e.g., Li<NUM>CoO<NUM> or LaCoO<NUM>) obtained due to the generated interfacial decomposition reaction may greatly increase an interfacial resistance. Accordingly, as shown in <FIG>, when the electrolyte layer <NUM> includes only the plurality of crystalline solid electrolyte materials <NUM>, the crystalline solid electrolyte layer may not be suitable for use as the electrolyte layer <NUM> in a 3D secondary battery.

Referring to <FIG>, <FIG>, and <FIG>, cathode layers <NUM> according to Comparative Example <NUM> may be formed by drying active material slurry to form an active material sheet and sintering a cathode active material, for example, LiCoO<NUM> ("LCO"), included in the active material sheet via a sintering process. On the cathode layers <NUM> obtained by sintering the cathode active material, an amorphous solid electrolyte material <NUM>, for example, a precursor liquid mixture for amorphous Li<NUM>La<NUM>Zr<NUM>O<NUM> ("LLZO"), may be arranged along the sidewall of the cathode layers <NUM> by using a spin coating method. For example, the amorphous solid electrolyte material <NUM> may undergo a low-temperature heat treatment, for example, a heat treatment at a low temperature of <NUM> or less, for example, about <NUM> to about <NUM>, about <NUM> to about <NUM>, or about <NUM> to about <NUM>. For example, the amorphous solid electrolyte material <NUM> formed as in Comparative Example <NUM> may include an ion conductivity that is less than an ion conductivity of crystalline solid electrolyte materials <NUM>, as shown in <FIG>.

As shown in <FIG> and <FIG>, the electrolyte layer <NUM> according to an embodiment may include the crystalline solid electrolyte materials <NUM> including a relatively high ion conductivity, and the plurality of crystalline solid electrolyte materials <NUM> may be mixed within the amorphous solid electrolyte material <NUM>. In this case, the amorphous solid electrolyte material <NUM> and the plurality of crystalline solid electrolyte materials <NUM> may undergo a low-temperature heat treatment, for example, a heat treatment at a low temperature of <NUM> or less, for example, about <NUM> to about <NUM>, about <NUM> to about <NUM>, or about <NUM> to about <NUM>. The electrolyte layer <NUM> according to an embodiment may include a higher ion conductivity than Comparative Example <NUM> and Comparative Example <NUM>, for example, an ion conductivity of about <NUM>-<NUM> S/cm or greater, for example, about <NUM>-<NUM> S/cm to about <NUM>-<NUM> S/cm, about <NUM>-<NUM> S/cm to about 5x10-<NUM> S/cm, or about 5x10-<NUM> S/cm to about 1x10-<NUM> S/cm.

Referring to <FIG>, a resistance of a comparative example in which crystalline Li<NUM>La<NUM>Zr<NUM>O<NUM> ("LLZO") powder is arranged on the cathode layers <NUM> in a pressing way and a special heat treatment is not performed is illustrated as a graph. In a case in which crystalline Li<NUM>La<NUM>Zr<NUM>O<NUM> ("LLZO") powder having undergone no heat treatments is used, a non-conductivity state in which an ion conductivity is not measured may be confirmed. A resistance of a comparative example in which a precursor liquid mixture for amorphous Li<NUM>La<NUM>Zr<NUM>O<NUM> ("LLZO") is arranged along the sidewall of the cathode layers <NUM> according to a spin coating method and a low-temperature heat treatment, for example, a heat treatment at a low temperature of <NUM> or less, for example, about <NUM> to about <NUM>, about <NUM> to about <NUM>, or about <NUM> to about <NUM>, is performed is illustrated as a graph. In a case in which a precursor liquid mixture for amorphous Li<NUM>La<NUM>Zr<NUM>O<NUM> ("LLZO") is arranged along the sidewall of the cathode layers <NUM> according to a spin coating method, it may be confirmed that amorphous solid electrolyte layer includes an ion conductivity of about <NUM> x <NUM>-<NUM> S/cm. A resistance of a case in which crystalline Li<NUM>La<NUM>Zr<NUM>O<NUM> ("LLZO") powder is mixed with a precursor liquid mixture for amorphous Li<NUM>La<NUM>Zr<NUM>O<NUM>) ("LLZO") and is then arranged along the sidewall of the cathode layers <NUM> according to a spin coating method and a low-temperature heat treatment, for example, a heat treatment at a low temperature of <NUM> or less, for example, about <NUM> to about <NUM>, about <NUM> to about <NUM>, or about <NUM> to about <NUM>, is performed according to an embodiment is illustrated as a graph. According to an embodiment, it may be confirmed that the electrolyte layer <NUM> according to an embodiment may include an ion conductivity about <NUM> x <NUM>-<NUM> S/cm, and the electrolyte layer <NUM> according to an embodiment may include a relatively high ion conductivity.

<FIG> is a cross-sectional view of cathode layers <NUM>, an electrolyte layer <NUM>, and a first current collecting layer <NUM> according to an embodiment.

Referring to <FIG>, a ratio of a thickness Wt of an uppermost end of the electrolyte layer <NUM> with respect to a thickness Wb of a lowermost end of the electrolyte layer <NUM> in a height direction (Z-axis direction) may be about <NUM>:<NUM> to about <NUM>:<NUM>, or example, about <NUM>:<NUM> to about <NUM>:<NUM> about <NUM>:<NUM> to about <NUM>:<NUM>, or about <NUM>:<NUM> to about <NUM>:<NUM>. For example, as a distance from the first current collecting layer <NUM> in the height direction (Z-axis direction) increases, non-uniform charging and discharging due to electrical polarization of the cathode layers <NUM> may occur. For example, when an NCA or NCM material of LiCo<NUM>-xMxO<NUM>, in which Ni, Mn, Al, or the like having low electrical conductivity replaces a Co position, is included as a cathode active material included in the cathode layers <NUM>, over-charging may occur at lower portions of the cathode layers <NUM> adjacent to the first current collecting layer <NUM>, and degradation such as a phase change caused by the over-charging may occur. To decrease or prevent degradation from occurring due to over-charging, a thickness Wb of a lowermost portion of the electrolyte layer <NUM> surrounding the cathode layers <NUM> may be formed to be greater than a thickness Wt of an uppermost portion of the electrolyte layer <NUM>. When the thickness Wb of the lowermost portion of the electrolyte layer <NUM> is formed to be greater than the thickness Wt of the uppermost portion of the electrolyte layer <NUM>, delithiation polarization may be formed in respective lower portions of the cathode layers <NUM>, and accordingly, uniform charging and discharging may be possible in respective upper and lower portions of the cathode layers <NUM>. As used herein, an uppermost end of the electrolyte layer <NUM> refers to an end of the electrolyte layer <NUM> that is farther from the cathode current collector <NUM> than is a lowermost end of the electrolyte layer <NUM> in a second direction, e.g., Z-axis direction, perpendicular to the first direction, e.g., X-axis direction.

<FIG> is a cross-sectional view of cathode layers <NUM> and an electrolyte layer <NUM> according to an embodiment. <FIG> is a cross-sectional view of cathode layers <NUM>, an electrolyte layer <NUM>, and an anode layer <NUM> according to an embodiment. <FIG> is a cross-sectional view of cathode layers <NUM>, an electrolyte layer <NUM>, and an anode layer <NUM> according to an embodiment.

As described herein, the electrolyte layer <NUM> according to an embodiment may include solid electrolyte materials, namely, the amorphous solid electrolyte material <NUM> and the plurality of crystalline solid electrolyte materials <NUM>. For example, uniformity and the like of the electrolyte layer <NUM> may be changed by changing the type of the crystalline solid electrolyte materials <NUM> or the thickness or the like of the amorphous solid electrolyte material <NUM>.

Referring to <FIG>, the electrolyte layer <NUM> may include a plurality of crystalline solid electrolyte materials having different particle sizes from each other. For example, the electrolyte layer <NUM> may include first crystalline solid electrolyte materials <NUM> and second crystalline solid electrolyte materials <NUM>, and the first crystalline solid electrolyte materials <NUM> and the second crystalline solid electrolyte materials <NUM> may be formed of the same material. However, the first crystalline solid electrolyte materials <NUM> and the second crystalline solid electrolyte materials <NUM> may be formed of different materials. For example, the electrolyte layer <NUM> may include first crystalline solid electrolyte materials <NUM> including a first average particle size D<NUM> and second crystalline solid electrolyte materials <NUM> having a second average particle size D<NUM>. For example, the second average particle size D<NUM> of the second crystalline solid electrolyte materials <NUM> with respect to the first average particle size D<NUM> of the first crystalline solid electrolyte materials <NUM> may be about <NUM> to about <NUM>, or example, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, or about <NUM> to about <NUM>. When the first crystalline solid electrolyte materials <NUM> and the second crystalline solid electrolyte materials <NUM> having different average particle sizes as described herein are mixed and arranged, the second crystalline solid electrolyte materials <NUM> having a relatively small average particle size may be arranged between the first crystalline solid electrolyte materials <NUM> having a relatively large average particle size. Accordingly, the second crystalline solid electrolyte materials <NUM> between the first crystalline solid electrolyte materials <NUM> may connect the first crystalline solid electrolyte materials <NUM> to each other to thereby reduce interfacial resistance.

Referring to <FIG>, the electrolyte layer <NUM> may include a first amorphous solid electrolyte material layer <NUM> surrounding the cathode layers <NUM>, a mixed solid electrolyte material layer <NUM> surrounding the first amorphous solid electrolyte material layer <NUM> and obtained by mixing a plurality of third crystalline solid electrolyte materials <NUM> in a second amorphous solid electrolyte material <NUM>, and a third amorphous solid electrolyte material layer <NUM> surrounding the mixed solid electrolyte material layer <NUM>.

When the electrolyte layer <NUM> including the crystalline solid electrolyte materials <NUM> is arranged along the sidewalls of the cathode layers <NUM> arranged perpendicular to the first current collecting layer <NUM> as shown in <FIG> and <FIG>, it may be difficult for the electrolyte layer <NUM> to be uniformly arranged along the sidewalls of the cathode layers <NUM>, due to gravity and a difficulty in a pressing process. When non-uniform arrangements between the cathode layers <NUM> and the electrolyte layer <NUM> and between the electrolyte layer <NUM> and the anode layer <NUM> are generated and openings are generated, a secondary battery may be non-uniformly charged and discharged. An electrolyte layer <NUM> having a multi-layered structure may be formed for uniform contact between the cathode layers <NUM>, the electrolyte layer <NUM>, and the anode layer <NUM>.

As described herein, the first amorphous solid electrolyte material layer <NUM> of the electrolyte layer <NUM>, which may surround the cathode layers <NUM>, may not include a crystalline solid electrolyte material. Accordingly, openings that may be generated in contact surfaces between the cathode layers <NUM> and the first amorphous solid electrolyte material layer <NUM> may be minimized. The third amorphous solid electrolyte material layer <NUM> that may be surrounded by the anode layer <NUM> may not include a crystalline solid electrolyte material. Accordingly, openings that may be generated in contact surfaces between the anode layer <NUM> and the third amorphous solid electrolyte material layer <NUM> may be minimized.

The mixed solid electrolyte material layer <NUM> may be arranged between the first amorphous solid electrolyte material layer <NUM> and the third amorphous solid electrolyte material layer <NUM> such that the plurality of third crystalline solid electrolyte materials <NUM> are mixed in the second amorphous solid electrolyte material <NUM>. A ratio of an average particle size D<NUM> of the plurality of third crystalline solid electrolyte materials <NUM> to a thickness W<NUM> of the first amorphous solid electrolyte material layer <NUM> may be about <NUM>:<NUM> to about <NUM>:<NUM>, for example, about <NUM>:<NUM> to about <NUM>:<NUM>, about <NUM>:<NUM> to about <NUM>:<NUM>, or about <NUM>:<NUM> to about <NUM>:<NUM>. A ratio of the average particle size D<NUM> of the plurality of third crystalline solid electrolyte materials <NUM> to a thickness W<NUM> of the third amorphous solid electrolyte material layer <NUM> may be about <NUM>:<NUM> to about <NUM>:<NUM>, for example, about <NUM>:<NUM> to about <NUM>:<NUM>, about <NUM>:<NUM> to about <NUM>:<NUM>, or about <NUM>:<NUM> to about <NUM>:<NUM>. The mixed solid electrolyte material layer <NUM> may be arranged between the first amorphous solid electrolyte material layer <NUM> and the third amorphous solid electrolyte material layer <NUM> as described herein, and ion conductivity of the electrolyte layer <NUM> may be improved. The electrolyte layer <NUM> may have a multi-layered structure as described herein, openings of the electrolyte layer <NUM> for the cathode layers <NUM> and the anode layer <NUM> may be minimized, and ion conductivity may be improved.

Referring to <FIG>, the electrolyte layer <NUM> may include a first amorphous solid electrolyte material layer <NUM> surrounding the cathode layers <NUM>, a mixed solid electrolyte material layer <NUM> surrounding the first amorphous solid electrolyte material layer <NUM> and obtained by mixing a plurality of third crystalline solid electrolyte materials <NUM> in a second amorphous solid electrolyte material <NUM>, a third amorphous solid electrolyte material layer <NUM> surrounding the mixed solid electrolyte material layer <NUM>, and a plurality of fourth crystalline solid electrolyte materials <NUM> arranged within at least one of the first amorphous solid electrolyte material layer <NUM>, the second amorphous solid electrolyte material <NUM>, or the third amorphous solid electrolyte material layer <NUM>.

For example, the third crystalline solid electrolyte materials <NUM> and the fourth crystalline solid electrolyte materials <NUM> may be the same materials. However, the third crystalline solid electrolyte materials <NUM> and the fourth crystalline solid electrolyte materials <NUM> may be different materials. For example, the third crystalline solid electrolyte materials <NUM> may have a third average particle size D<NUM>, and the fourth crystalline solid electrolyte materials <NUM> may have a fourth average particle size D<NUM>. For example, the fourth average particle size D<NUM> of the fourth crystalline solid electrolyte materials <NUM> with respect to the third average particle size D<NUM> of the third crystalline solid electrolyte materials <NUM> may be about <NUM> to about <NUM>, for example, about <NUM>:<NUM> to about <NUM>:<NUM>, about <NUM>:<NUM> to about <NUM>:<NUM>, or about <NUM>:<NUM> to about <NUM>:<NUM>. When the third crystalline solid electrolyte materials <NUM> and the fourth crystalline solid electrolyte materials <NUM> having different average particle sizes as described herein are mixed and arranged, the fourth crystalline solid electrolyte materials <NUM> having a relatively small average particle size may be arranged between the third crystalline solid electrolyte materials <NUM> having a relatively large average particle size. The fourth crystalline solid electrolyte materials <NUM> between the third crystalline solid electrolyte materials <NUM> may connect the third crystalline solid electrolyte materials <NUM> to each other to thereby reduce interfacial resistance.

When the fourth crystalline solid electrolyte materials <NUM> having a relatively small average particle size is arranged between the first amorphous solid electrolyte material layer <NUM> and the second amorphous solid electrolyte material layer <NUM>, a relatively constant surface uniformity of the electrolyte layer <NUM> facing the cathode layers <NUM> and the anode layer <NUM> may be maintained, and generation of an opening between the cathode layers <NUM> and the anode layer <NUM> and the electrolyte layer <NUM> may be decreased or prevented. In addition, the fourth crystalline solid electrolyte materials <NUM> may be arranged between the first amorphous solid electrolyte material layer <NUM> and the second amorphous solid electrolyte material layer <NUM>, and ion conductivity may be improved.

<FIG> are views for illustrating a method of manufacturing a secondary battery, according to an embodiment.

Referring to <FIG>, the first electrode structure E1 may be provided by arranging a plurality of cathode layers <NUM> having a flat plate-shape on the first current collecting layer <NUM>. For example, the first electrode structure E1 has a structure corresponding to the first electrode structure E1 of <FIG>, and the cathode layers <NUM> may be formed by drying active material slurry to form an active material sheet and sintering a cathode active material included in the active material sheet via a sintering process. The active material slurry may be manufactured by mixing, for example, a cathode active material (powder), a binder, a dispersing agent, a plasticizer, etc. with a solvent. The mixing may be performed using a grinder, such as a ball mill, or a mixing apparatus.

Next, referring to <FIG>, <FIG>, and <FIG>, after coating a first amorphous solid electrolyte material <NUM> on the first electrode structure E1, the electrolyte layer <NUM> may be formed by using a spin process. For example, the first amorphous solid electrolyte material <NUM> may be a solid electrolyte, for example, a precursor liquid mixture for amorphous Li<NUM>La<NUM>Zr<NUM>O<NUM> ("LLZO"), and the first amorphous solid electrolyte material <NUM> may be in the form of a sol. A 3D electrode structure may have an open-type structure in which the plurality of cathode layers <NUM> are spaced apart in a widthwise direction and a lengthwise direction, and the first amorphous solid electrolyte material <NUM> may be readily formed by spin coating.

After coating the first amorphous solid electrolyte material <NUM>, the first amorphous solid electrolyte material <NUM> may undergo a first heat treatment. The first heat treatment may be performed in a pressing state and at a low temperature of about <NUM> or less, for example, about <NUM> to about <NUM>, about <NUM> to about <NUM>, or about <NUM> to about <NUM>, and an interfacial resistance may be reduced without damage to the cathode layers <NUM> and accordingly, ion conductivity may be improved.

Next, referring to <FIG>, <FIG>, and <FIG>, after coating a second amorphous solid electrolyte material <NUM> and a plurality of crystalline solid electrolyte materials <NUM> on the first electrode structure E1, the electrolyte layer <NUM> may be formed by using a spin process. For example, the second amorphous solid electrolyte material <NUM> may be a solid electrolyte, for example, a precursor liquid mixture for amorphous LLZO, and the plurality of crystalline solid electrolyte materials <NUM> may be crystalline LLZO powder. The second amorphous solid electrolyte material <NUM> may be in the form of a sol, and the plurality of crystalline solid electrolyte materials <NUM> may be mixed within the second amorphous solid electrolyte material <NUM>. A 3D electrode structure may have an open-type structure in which the plurality of cathode layers <NUM> are spaced apart in a widthwise direction and a lengthwise direction, and the second amorphous solid electrolyte material <NUM> and the plurality of crystalline solid electrolyte materials <NUM> may be readily formed by spin coating. By coating the second amorphous solid electrolyte material <NUM> and the plurality of crystalline solid electrolyte materials <NUM>, a structure in which the plurality of crystalline solid electrolyte materials <NUM> and the amorphous solid electrolyte material <NUM> are mixed may be formed as shown in <FIG> and <FIG>.

After coating the second amorphous solid electrolyte material <NUM> and the plurality of crystalline solid electrolyte materials <NUM>, the second amorphous solid electrolyte material <NUM> and the plurality of crystalline solid electrolyte materials <NUM> may undergo a second heat treatment. The second heat treatment may be performed in a pressing state and at a low temperature of <NUM> or less, for example, about <NUM> to about <NUM>, about <NUM> to about <NUM>, or about <NUM> to about <NUM>, and an interfacial resistance between the amorphous solid electrolyte material <NUM> and the plurality of crystalline solid electrolyte materials <NUM> may be reduced without damage to the cathode layers <NUM> and accordingly, ion conductivity may be improved.

Next, referring to <FIG>, <FIG>, and <FIG>, after coating a third amorphous solid electrolyte material <NUM> on the first electrode structure E1, the electrolyte layer <NUM> may be formed by using a spin process. For example, the third amorphous solid electrolyte material <NUM> may be a solid electrolyte, for example, a precursor liquid mixture for amorphous LLZO and may be in the form of a sol. The third amorphous solid electrolyte material <NUM> may be coated on the plurality of crystalline solid electrolyte materials <NUM>, and the plurality of crystalline solid electrolyte materials <NUM> may be arranged to be mixed in the amorphous solid electrolyte material <NUM>, as shown in <FIG> and <FIG>.

After the coating of the third amorphous solid electrolyte material <NUM>, the third amorphous solid electrolyte material <NUM> may undergo a third heat treatment. The third heat treatment may be performed in a pressing state and at a low temperature of <NUM> or less, for example, about <NUM> to about <NUM>, about <NUM> to about <NUM>, or about <NUM> to about <NUM>, and an interfacial resistance between the amorphous solid electrolyte material <NUM> and the plurality of crystalline solid electrolyte materials <NUM> may be reduced without damage to the cathode layers <NUM> and accordingly, ion conductivity may be improved.

Although the first amorphous solid electrolyte material <NUM>, a mixture of the second amorphous solid electrolyte material <NUM> and the plurality of crystalline solid electrolyte materials <NUM>, and the third amorphous solid electrolyte materials <NUM> have been described herein as being formed by spin coating, dip coating may be used instead of spin coating. The amorphous solid electrolyte material <NUM> may be formed by using a deposition method such as atomic layer deposition ("ALD"), chemical vapor deposition ("CVD"), or physical vapor deposition ("PVD"). Coating of the first amorphous solid electrolyte material <NUM> may be performed using a layer by layer ("LBL") method a plurality of number of times, for example, two to five times.

Next, the secondary battery <NUM> according to an embodiment may be manufactured by sequentially forming the anode layer <NUM> and the second current collecting layer <NUM> on the electrolyte layer <NUM>, the anode layer <NUM> including an anode active material. For example, the anode active material included in the anode layer <NUM> may include, for example, a Li metal, a carbon-based material, a silicon-based material, or an oxide. The second current collecting layer <NUM> may include, for example, at least one conductive material of Cu, Au, Pt, Ag, Zn, Al, Mg, Ti, Fe, Co, Ni, Ge, In, or Pd. For example, the anode layer <NUM> may be formed by coating the anode active material on the electrolyte layer <NUM>. The second current collecting layer <NUM> may be provided to face the first current collecting layer <NUM>. The secondary battery <NUM> may be, for example, a Li secondary battery.

A secondary battery including a cathode layer and an electrolyte layer in which an ion readily moves may be provided. A secondary battery having no capacity reduction even at a high rate may be provided. A secondary battery usefully applicable to various electronic devices including mobile devices and wearable devices may be provided.

Claim 1:
A solid electrolyte-cathode assembly for a secondary battery (<NUM>) comprising:
a plurality of cathode layers (<NUM>) spaced apart from each other in a first direction (X); and
an electrolyte layer (<NUM>) comprising
an amorphous solid electrolyte (<NUM>), and
a crystalline solid electrolyte comprising a plurality of crystalline solid electrolyte particles (<NUM>),
wherein the amorphous solid electrolyte is on a surface of a cathode layer of the plurality of cathode layers and the crystalline solid electrolyte is within the amorphous solid electrolyte,
and characterized in that a ratio of an average particle size of the plurality of crystalline solid electrolyte particles to a thickness of the electrolyte layer measured in the first direction is <NUM>:<NUM> to <NUM>:<NUM>.