Patent ID: 12211996

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the present embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the figures, to explain aspects. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list.

It will be understood that, although the terms “first,” “second,” “third,” etc. may be used herein to describe various elements, components, regions, layers, and/or sections, these elements, components, regions, layers, and/or sections should not be limited by these terms. 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.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, “a”, “an,” “the,” and “at least one” do not denote a limitation of quantity, and are intended to include both the singular and plural, unless the context clearly indicates otherwise. For example, “an element” has the same meaning as “at least one element,” unless the context clearly indicates otherwise. “At least one” is not to be construed as limiting “a” or “an.” “Or” means “and/or.” 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.

Furthermore, relative terms, such as “lower” or “bottom” and “upper” or “top,” may be used herein to describe one element's relationship to another element as illustrated in the Figures. It will be understood that relative terms are intended to encompass different orientations of the device in addition to the orientation depicted in the Figures. For example, if the device in one of the figures is turned over, elements described as being on the “lower” side of other elements would then be oriented on “upper” sides of the other elements. The exemplary term “lower,” can therefore, encompasses both an orientation of “lower” and “upper,” depending on the particular orientation of the figure. Similarly, if the device in one of the figures is turned over, elements described as “below” or “beneath” other elements would then be oriented “above” the other elements. 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 ±30%, 20%, 10% or 5% of the stated value.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

Exemplary embodiments are described herein with reference to cross section illustrations that are schematic illustrations of idealized embodiments. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments described herein should not be construed as limited to the particular shapes of regions as illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, a region illustrated or described as flat may, typically, have rough and/or nonlinear features. Moreover, sharp angles that are illustrated may be rounded. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region and are not intended to limit the scope of the present claims.

As used herein, a C-rate means a current which will discharge a battery in one hour, e.g., a C-rate for a battery having a discharge capacity of 1.6 ampere-hours would be 1.6 amperes.

Crystal directions and crystal planes are described herein using Miller indices. For convenience, the indices are written in lowest terms, and corresponding directions and planes are understood to be included. Thus the direction [001] should be understood to include all equivalent directions, i.e., <001>, unless indicated otherwise, and the plane (001) should be understood to include all equivalent planes {001}, unless indicated otherwise.

LiCoO2is a layered material. An intercalating path of lithium (Li) ions in LiCoO2varies depending on a crystal plane. Therefore, when lithium ions are intercalated into LiCoO2during charge and discharge of a battery, an ion conductivity and a capacity of the battery may vary according to a crystal plane of the LiCoO2layer into which the lithium ions are intercalated. The crystal plane through which lithium ions move more readily may be (104]), (110), (101), and (102), and the diffusion of lithium ions into the (003) plane may be relatively more difficult.

The capacity and efficiency of a battery may vary depending on a direction of a surface of a three-dimensional (“3D”) cathode that contacts an electrolyte. When a direction of a surface of a cathode that directly contacts an electrolyte is aligned with a <101> crystal direction, a <hk0> crystal direction (wherein h and k are integers equal to or greater than 1), or a combination thereof, of the crystal grains of the cathode active material, lithium ions may be easily diffused into the cathode, and as a result, the capacity and efficiency of the battery may be increased. In a battery, an electrolyte may directly contact an exposed surface of a cathode. Accordingly, the greater the ratio of faces, e.g., surfaces, with crystal directions aligned with a <101> crystal direction, a <hk0> crystal direction, or a combination thereof, of the crystal grains of the cathode active material, on an exposed surface of a cathode, the greater the capacity and efficiency of the battery may be. The ratio of faces, e.g., surfaces, with crystal directions aligned with a <101> crystal direction, a <hk0> crystal direction, or a combination thereof, of the crystal grains of the cathode active material, on an exposed surface in contact with an electrolyte of a sintered cathode may be increased. That is, a battery in which crystal planes having crystal directions are aligned with a <101> crystal direction, a <hk0> crystal direction, or a combination thereof, of the crystal grains of the cathode active material, are increased in a sintered cathode.

Hereinafter, the battery according to various embodiments and methods of manufacturing the same will be described in detail with reference to the accompanying drawings, and in the drawings, and in the drawings, sizes of constituent elements and thicknesses of layers and regions may be exaggerated for clarity and convenience of explanation. The embodiments of the inventive concept are capable of various modifications and may be embodied in many different forms. It will be understood that when an element or layer is referred to as being “on” or “above” another element or layer, the element or layer may be directly on another element or layer or intervening elements or layers.

FIG.1is a cross-sectional view of a three-dimensional (3D) battery100according to an embodiment. The 3D battery100illustrated inFIG.1may be regarded as one of a plurality of cell batteries considering that generally a battery includes a plurality of cell batteries. The 3D battery100may be a lithium ion battery (secondary battery) having a 3D cathode structure.

Referring toFIG.1, the 3D battery100according to an embodiment includes a cathode current collector110, a cathode layer120, a separator130, an anode layer140, and an anode current collector150. The separator130is disposed between the cathode layer120and the anode layer140. The separator prevents direct contact between the cathode layer120and the anode layer140. The cathode layer120is disposed between the separator130and the cathode current collector110. The anode layer140is disposed between the separator130and the anode current collector150. When the cathode current collector110is a base layer, the cathode layer120, the separator130, the anode layer140, and the anode current collector150may form a layer structure by sequentially stacking on the cathode current collector110.

The crystal direction of a side surface120S1of the cathode layer120may be aligned with a <101> crystal direction, a <hk0> crystal direction, wherein h and k are integers greater than or equal to 1, or a combination thereof, of the crystal grains of the cathode active material. The alignment of the crystal direction may be provided by sintering the cathode layer. The side surface120S1of the cathode layer120is parallel to a y-z plane. In an embodiment, the crystal direction of the side surface120S1of the cathode layer120may be aligned with a <101> crystal direction, a <110> crystal direction, or a combination thereof, of the crystal grains of the cathode active material. In an embodiment, the crystal direction of the side surface120S1of the cathode layer120may be aligned with a <101> crystal direction; a <120> crystal direction, a <220> crystal direction, a <210> crystal direction, a <130> crystal direction, a <230> crystal direction, a <330> crystal direction, or a combination thereof; or a combination thereof, of the crystal grains of the cathode active material. The crystal direction of an upper surface120S2of the cathode layer120may be aligned with a <003> crystal direction, a <104> crystal direction, or a combination thereof, of the crystal grains of the cathode active material. The upper surface120S2is parallel to an x-z plane.

A plurality of slits160are formed in the cathode layer120. Each of the plurality of slits160may be referred to as a slit-shaped groove. In an embodiment, the plurality of slits160may be parallel to each other. The plurality of slits160are formed in a direction perpendicular to an upper surface of the cathode current collector110or in a direction perpendicular to a surface (an upper surface)120S2of the cathode layer120that is in contact with the separator130. Here, the perpendicular direction may include a right angle with respect to the upper surface of the cathode current collector110, or an inclination angle that does not deviate from a given angle (for example, 45°) from the right angle to the right and left sides. A gap S1between the plurality of slits160is less than a depth D1of the plurality of slits160. The depth D1of the plurality of slits160may be less than a thickness T1of the cathode layer120. The plurality of slits160are formed from the upper surface toward a bottom surface of the cathode layer120. The plurality of slits160are spaced apart from the bottom surface of the cathode layer120. A distance D2between the lower ends of the plurality of slits160and the bottom surface of the cathode layer120is less than the depth D1of the plurality of slits160. In an embodiment, the thickness T1of the cathode layer120may be in a range from about 30 micrometers (μm) to about 200 μm and the distance D2may be in a range from about 5 μm to about 50 μm.FIG.2is a micrograph showing the plurality of slits160formed in the cathode layer120of the battery ofFIG.1. In the micrograph, the plurality of slits160are formed at intervals of 32 μm from one another.

The plurality of slits160may be formed by cutting a cathode tape or a cathode active material tape corresponding to the cathode layer120before sintering to a given depth D1by using a blade. The cathode active material tape may be cut in a direction perpendicular to the upper surface thereof, and may be cut within a range in which the cathode active material tape is not cut.

Therefore, in the cathode layer120, side surfaces of parts where the slits160are formed are exposed through, e.g., exposed by or adjacent to, the slits160. Each of the plurality of slits160may be regarded as a trace or a scratch of the part cut by a knife or as a kind of groove in a broad sense. In an aspect, each of the plurality of slits160may be a wedge-shaped groove, a bottom of which is not visible because an entrance is very narrow. Therefore, through each of the plurality of slits160, a surface, such as a bottom surface exposed in a groove of a general trench type, may not be exposed.

When there is a single slit160between both sides120S1of the cathode layer120, two side surfaces are exposed inward through the slit160. Due to the nature of the slit160, the side exposed inward through the slit160is not visible in the diagram. The two side surfaces exposed inward may be parallel to the side surface120S1of the cathode layer120. Therefore, a crystal direction of an inner side surface exposed through, e.g., exposed by or adjacent to, the slit160of the cathode layer120may also be the same as the crystal direction of the side surface120S1of the cathode layer120. Since a plurality of slits160are present in the cathode layer120, side surfaces corresponding to twice the number of slits160are exposed through, e.g., exposed by or adjacent to, the plurality of slits160. As a result, an area occupied by the surface aligned with a <101> crystal direction, a <hk0> crystal direction, or a combination thereof, of the crystal grains of the cathode active material, on exposed surfaces in contact with the electrolyte of the cathode layer120may be greater than an area without the slit160. Accordingly, on a surface that directly contacts an electrolyte of the cathode layer120, an area of surfaces having a crystal direction aligned with a <101> crystal direction, a <hk0> crystal direction, or a combination thereof, of the crystal grains of the cathode active material, may be greater than an area without the slit160.

In this way, of surfaces that contact an electrolyte of the cathode layer120, as an area of a surface having a relatively large diffusion coefficient of lithium (Li) ion, that is, a surface aligned with a <101> crystal direction, a <hk0> crystal direction, or a combination thereof, of the crystal grains of the cathode active material, is increased, in the cathode layer120, lithium (Li) ions may be diffused to a wider area. As a result, a battery capacity may be increased. Also, since an ionic conductivity is relatively high in a surface aligned with a <101> crystal direction, a <hk0> crystal direction, or a combination thereof, of the crystal grains of the cathode active material, a charge/discharge characteristic, e.g. capacity or rate capability, of a battery may be improved. For example, a charging time may be reduced.

Also, an electrolyte is present in the separator130and the cathode layer120may be permeated with the electrolyte. In an aspect, the cathode layer120is sintered, and the slit160may serve as a passage through which an electrolyte may permeate the cathode layer120. In an aspect, the slit160may be a channel for supplying an electrolyte to the cathode layer120, which may be a sintered cathode layer. Therefore, as the number of slits160in the cathode layer120increases, the plane in which the crystal direction is aligned with a <101> crystal direction, a <hk0> crystal direction, or a combination thereof, of the crystal grains of the cathode active material, increases. As a result, an area of a surface aligned with a <101> crystal direction, a <hk0> crystal direction, or a combination thereof, of the crystal grains of the cathode active material, on an entire surface of the cathode layer120in contact with an electrolyte is increased. Accordingly, lithium ions may be more rapidly diffused to a wider area of the cathode layer120relative to a cathode layer with fewer slits, and thus, a battery capacity may be increased, and the charge and discharge characteristics may be improved. In addition, a rate capability of the battery, may be improved, and thus, a battery for a device that requires a large amount of power may be provided. The characteristic may be applied to a battery300illustrated inFIG.3.

In the battery100, the cathode layer120which is also referred to as a cathode active material layer may be a layer including a lithium transition metal oxide, for example, an LiCoO2(“LCO”) layer, but is not limited thereto. The lithium transition metal oxide may have a layered structure, and may be isostructural with α-NaFeO2. For example, the lithium oxide may include a material of the formula LixMO2, wherein M may include cobalt (Co), nickel (Ni), manganese (Mn), or a combination thereof. Here, x may have a range of 0.2<x<1.2. The cathode layer120may be formed of a sintered polycrystalline ceramic formed by sintering a cathode active material. Accordingly, the cathode layer120may include a plurality of grains and grain boundaries between the grains of the plurality of grains. Since the cathode layer120is formed of a ceramic sintered body, a density or volume fraction of a cathode active material of the cathode layer120may be greater than the density of a cathode active material formed by mixing particles of a cathode active material, a conductive material, and a binder. Accordingly, a battery including the cathode layer120may have an improved battery capacity density. The cathode current collector110and the anode current collector150may include a conductive material, for example, Cu, Au, Pt, Ag, Zn, Al, Mg, Ti, Fe, Co, Ni, Ge, In, or Pd. The anode layer140may include a material electrode capable of receiving lithium ions coming from the cathode layer120during charge. The anode layer140may be an electrode layer including lithium, for example, and may be a lithium metal layer or a compound electrode layer including lithium, but is not limited thereto. In an embodiment, the anode layer140may be formed by using a material, such as graphite, silicon (Si), or a silicon alloy (Si alloy).

FIG.3is a cross-sectional view of the battery300according to an embodiment. Only parts different from the battery100ofFIG.1are described, and like reference numerals indicate elements that are identical to the elements ofFIG.1. Materials of a cathode layer310, a cathode current collector110, an anode layer140, and an anode current collector150ofFIG.3may be the same as those of the cathode layer310, the cathode current collector110, the anode layer140, and the anode current collector150described with reference toFIG.1.

Referring toFIG.3, the cathode layer310of the battery300covers an entire upper surface of the cathode current collector110. The cathode layer310includes a plurality of protrusions310A that are perpendicular to a surface of the cathode current collector110and are directed toward the separator130. Spaces310B are provided between the plurality of protrusions310A. The plurality of protrusions310A are horizontally spaced apart from each other, but lower ends of the protrusions310A are connected to each other. Each of the spaces3106may be a trench or groove of a given depth (hereinafter, referred to as a trench310B). Accordingly, the cathode layer310may be expressed as having a plurality of trenches310B spaced apart from each other. A depth D31of each trench310B may be greater than a half of a thickness T33of the cathode layer310. For example, the depth D31of the trench310B may be equal to the depth D1of the slit160ofFIG.1. The material of the cathode layer310may be, for example, the same as the cathode layer120ofFIG.1. A crystal plane or a crystal direction of an outer surface310S1of the cathode layer310may be the same as the crystal plane or the crystal direction of the outer surface120S1of the cathode layer120ofFIG.1. A crystal plane or a crystal direction of an inner surface310S2of the cathode layer310exposed through, e.g., exposed by or adjacent to, the trench310B may have a crystal direction having a greater diffusion coefficient than a diffusion coefficient of a <003> crystal direction or a <104> crystal direction. The crystal plane or the crystal direction of the inner surface310S2of the cathode layer310may be the same as the outer surface310S1of the cathode layer310.

FIGS.4A,5A,6A, and7Aare graphs showing measurement results of an X-ray diffraction (“XRD”) with respect to a three-dimensional sintered cathode layer that is sintered at a given temperature (for example, 1025° C.) and in which a side surface exposed through, e.g., exposed by or adjacent to, a slit has a given crystal direction.FIGS.4B,5B,6B, and7Bare photographs showing cross sections of the corresponding cathode layer ofFIGS.4A,5A,6A, and7A, respectively. In each photograph, numbers such as ‘003’, ‘110’, and ‘101’ indicate crystal directions of arrows. In the following description, an XRD intensity with respect to a crystal plane of a given crystal direction, for example, the crystal direction is aligned with a <003> crystal direction, is described as I(003), and XRD intensities with respect to other crystal planes are also described in the same manner. InFIGS.4A,5A,6A, and7A, a horizontal axis represents diffraction angle and a vertical axis represents XRD intensity.

FIG.4Ashows a result of an XRD measurement with respect to the inner surface of a cathode layer in which a crystal direction of the inner surface is aligned with a <003> crystal direction.

Referring toFIG.4A, in the graph showing the result of the XRD measurement, a first peak P41represents a peak with respect to a surface having a <003> crystal direction, that is, a (003) crystal plane, and a second peak P42represents a peak with respect to a surface having a <006> crystal direction. Also, a third peak P43represents a peak with respect to a surface having a <009> crystal direction. In the graph ofFIG.4A, no peaks other than the first through third peaks P41through P43are visible. Accordingly, in the case ofFIG.4A, a ratio R is zero, wherein R is according to Equation 1,
R=(I(101)+I(110))/I(003)  Equation 1
wherein I(101) is an intensity of an X-ray diffraction peak corresponding to (101) crystal plane, I(110) is an intensity of an X-ray diffraction peak corresponding to a (110) crystal plane, and I(003) is an intensity of an X-ray diffraction peak corresponding to a (003) crystal plane, when determined using Cu Kα radiation.

FIG.5Ashows a result of an XRD measurement with respect to a cathode layer with grains not aligned in a given direction.

In the graph ofFIG.5A, a first peak P51represents a peak with respect to a crystal plane corresponding to a <003> crystal direction, a second peak P52represents a peak with respect to a crystal plane corresponding to a <101> crystal direction, and a third peak P53represents a peak with respect to a crystal plane corresponding to a <006> crystal direction. Also, a fourth peak P54represents a peak with respect to a crystal plane corresponding to a <104> crystal direction, and a fifth peak P55represents a peak with respect to a crystal plane corresponding to a <110> crystal direction. The first and fourth peaks P51and P54are greater than the second, third, and fifth peaks P52, P53and P55. In the case ofFIG.5A, when the ratio R is calculated, it will be about 1.1.

FIG.6Ashows a result of an XRD measurement with respect to an inner surface of a cathode layer in which crystal directions of an inner surface of a sintered cathode are <101> and <110>.

In the graph ofFIG.6A, a first peak P61is a peak with respect to a crystal plane corresponding to a <003> crystal direction, and a second peak P62is a peak with respect to a crystal plane corresponding to a <101> crystal direction, the smallest third peak P63is a peak with respect to a crystal plane corresponding to a <006> crystal direction. A fourth peak P64is a peak with respect to the crystal plane corresponding to a <104> crystal direction, and a fifth peak P65is a peak with respect to a crystal plane corresponding to a <110> crystal direction. In the case of the graph ofFIG.6A, the peaks of the crystal planes corresponding to the crystal directions <101>, <110>, and <003> are relatively greater than the remaining peaks. In the case ofFIG.6A, the ratio R is calculated as about 2.7.

FIG.7Ashows a result of an XRD measurement with respect to an inner surface of a cathode layer in which crystal directions of an inner surface of a sintered cathode are <101> and <110>.

In the graph ofFIG.7A, a first peak P71represents a peak with respect to a crystal plane corresponding to a <003> crystal direction, a second peak P72represents a peak with respect to a crystal plane corresponding to a crystal direction of <101>, and the smallest third peak P73represents a peak with respect to a crystal plane corresponding to a <006> crystal direction. A fourth peak P74the next small one represents a peak with respect to a crystal plane corresponding to a <104> crystal direction, and a fifth peak P75represents a peak with respect to a crystal plane corresponding to a <110> crystal direction. In the case of the graph ofFIG.7A, the second and fifth peaks P72and P75with respect to the crystal planes corresponding to the crystal directions <101> and <110> respectively are much larger than the first, third, and fourth peaks P71, P73, and P74. The first, third, and fourth peaks P71, P73, and P74are similar in size. Accordingly, in the case ofFIG.7A, the ratio R is calculated as about 10.6, which is the largest value among the sintered cathode layers to be measured for XRD. Considering that the larger the value of the ratio R, the better the diffusion of lithium ions into the cathode layer, the sintered cathode layer that shows the XRD characteristics ofFIGS.5A,6A, and7Amay be considered as a 3D sintered cathode layer (the cathode layer120ofFIG.1or the cathode layer310ofFIG.3) of a battery.

FIGS.8to11are graphs showing measurement results of a specific capacity of a battery according to a ratio R [R=(I(101)+I(110))/I(003)] of a sintered cathode layer.

FIG.8shows the measurement results when R=0,FIG.9shows the measurement results when R=1.1,FIG.10shows the measurement results when R=2.7, andFIG.11shows the measurement results when R=10.6.

InFIGS.8through11, the horizontal axis represents specific capacity and the vertical axis represents voltage versus Li/Li+. In addition, inFIGS.8through11, 1stgraphs G81, G91, G101, G111show the results at the time of charging/discharging at 1 C, and 2nd graphs G82, G92, G102, and G112show the results at the time of charging/discharging at 0.5 C, third graphs G83, G92, G103, and G113show the results at the time of charging/discharging at 0.3 C, and fourth graphs G84, G94, G104, and G114show the results at the time of charging/discharging at 0.1 C.

Referring toFIGS.8through11, it may be seen that as the value of R increases, the specific capacity increases, and the charge/discharge characteristics are also improved.

FIG.12is a graph showing C-rate characteristic according to an R value.

InFIG.12, the horizontal axis represents rate (C-rate), and the vertical axis represents specific capacity.

InFIG.12, first through fourth graphs G121, G122, G123, and G124show C-rate characteristics when the R values are 0, 1.1, 2.7, and 10.6, respectively.

Referring toFIG.12, as the R value increases from 0 to 10.6, the specific capacity also increases, but the specific capacity at10increases by about 3 times.

In the batteries100and300illustrated inFIGS.1and3, the cathode layers120and310are sintered cathode layers that do not include a binder and a conductive material included in a cathode layer, but have a high sintered density. As described above, since the cathode layers120and310are sintered cathode active materials that do not include a binder and a conductive material, the specific gravity of the active materials of the cathode layers120and310is increased. In addition, the cathode layers120and310have a three-dimensional structure and have a thickness greater than a thickness of a two-dimensional cathode layer. Accordingly, the energy density of a battery may also be greater than an energy density of a battery including a cathode layer including a binder and a conductive material.

Also, in the batteries100and300illustrated inFIGS.1and3, a relative density of the cathode layers120and310may be 90% or greater, e.g., about 90% to about 99%, based on a density of the of the cathode layer before sintering. The relative density is a ratio (Dn1/Dn2) of a density (Dn1) of the sintered cathode layer and a density (Dn2) of a cathode layer before sintering.

FIGS.13through18are cross-sectional views illustrating a method of manufacturing a battery according to an embodiment.

FIG.13shows an embodiment of forming a slit in the cathode layer600of the battery by using a blade stamping method so that a side surface (of the cathode layer600) having a primary crystal direction aligned with a <101> crystal direction, a <110> crystal direction, or a combination thereof, of the crystal grains of the cathode active material, is exposed. The cathode layer600may be a cathode active material tape before sintering, that is, a cathode tape. The cathode layer600may be formed such that, after coating a slurry onto a carrier film through a tape casting process, and then, heat is applied to the coated slurry, whereas the slurry is formed by mixing a plurality of plate-shaped LCO seeds and a matrix LCO which is a powder of a cathode active material in a solvent. Since a doctor blade is used in a process of coating the slurry onto a carrier film, the plate-shaped LCO seeds may be aligned in a given direction, and the matrix LCO may be distributed around the plate-LCO seeds. The plate-shaped LCO seeds may have a flat shape having a very small thickness compared to its width and length. The crystal direction of a side of the plate-shaped LCO seed may be aligned with a <101> crystal direction, a <110> crystal direction, or a combination thereof, of the crystal grains of the cathode active material, and a crystal direction of an upper surface may be aligned with a <003> crystal direction, of the crystal grains of the cathode active material.

Referring toFIG.13, in order to form a slit640in the cathode layer600, a first groove610is formed in the cathode layer600. The first groove610may have a wedge shape in which a lower point, e.g., location of the first groove610, is sharp and a width of the first groove610gradually increases toward an upper end. The first groove610may be formed using a blade630disposed perpendicular to an upper surface of the cathode layer600. The first groove610may be formed by applying a pressure to the blade630so that the blade630enters the cathode layer600in a state that the blade630is vertically aligned with respect to the upper surface of the cathode layer600. After the cathode layer600is sintered, crystal directions of side surfaces600S1and600S2exposed through, e.g., exposed by or adjacent to, the first groove610formed as described above may be aligned with a <101> crystal direction, a <110> crystal direction, or a combination thereof, of the crystal grains of the cathode active material. A depth of the first groove610may correspond to a depth D1of the slit160ofFIG.1.

Next, the blade630is aligned at a position spaced a given distance from a right edge of the first groove610. The blade630may be perpendicular to the upper surface of the cathode layer600. Subsequently, aligning the blade630to the upper surface of the cathode layer600may denote that the blade630is aligned perpendicular to the upper surface of the cathode layer600.

A distance D3between the right edge of the first groove610and the blade630may correspond to a spacing S1between two adjacent slits160ofFIG.1. In a state that the blade630is aligned at a given distance D3from the right edge of the first groove610, a portion of the blade630including an end portion of the blade630enters into the cathode layer600by downwardly pressing the cathode layer600. Since the end portion of the blade630has a wedge-shape, a second groove610A is formed in the cathode layer600as the blade630enters the cathode layer600. As the second groove610A is formed in the cathode layer600, the portion of the cathode layer600between the first groove610formed in the cathode layer600and the blade630is pushed to a left, and thus, the first groove610A is filled. Thereafter, the blade630is removed from the cathode layer600and aligned at a new position of the upper surface of the cathode layer600. The second groove610A may be formed under the same conditions as the conditions for forming the first groove610by using the blade630. Accordingly, the specifications (depth, shape, width change, etc.) of the second groove610A may be the same as the first groove610. Therefore, the crystal direction of side surfaces exposed through, e.g., exposed by or adjacent to, the second groove610A may also be the same as the crystal direction of the side surfaces600S1and600S2exposed through, e.g., exposed by or adjacent to, the first groove610. A distance between an edge of the second groove610A and a newly aligned position of the blade630may be the same as the distance D3between the edge of the first groove610and the blade630aligned to form the second groove610A. A third groove610B is formed in the cathode layer600by using the blade630under the same condition for forming the second groove610A. When the third groove610B is formed in the cathode layer600, the portion of the cathode layer600between the second groove610A and the blade630is pushed to the left, and thus, the second groove610A is completely filled. Since the third groove610B is formed under the same conditions as the first groove610and the second groove610A, after the cathode layer600is sintered, the crystal direction of side surface exposed through, e.g., exposed by or adjacent to, the third groove610B, like the first groove610or the second groove610A, may be aligned with a <101> crystal direction, a <110> crystal direction, or a combination thereof, of the crystal grains of the cathode active material. Thereafter, fourth, fifth, and sixth grooves, etc. may be formed in the cathode layer600in the same manner as the second grooves610A is formed. As a new groove is formed, a groove formed immediately ahead is filled with the cathode layer600laterally pushed by the blade630. Although the previously formed grooves are filled with the cathode layer, traces of portions cut to a depth given by the blade630, that is, slits may remain in the cathode layer600.

In this manner, a plurality of slits640having the same depth are formed in the cathode layer600by repeating the process of forming new grooves in a given direction of the cathode layer600and the grooves formed immediately before the new grooves are filled with the cathode layer600. As a result, the cathode layer600having a 3D structure is formed. The slits640provide a plurality of gaps in the cathode layer600through which a liquid electrolyte may permeate.

In this way, a depth of the slits640and the gaps between the slits640may be controlled in the process of forming the slits640. The cathode layer600may be cut at an operation of forming a desired number of slits640in the cathode layer600. The material and thickness of the cathode layer600may correspond to the cathode layer120ofFIG.1. The depth and spacing of the slits640of the cathode layer600may be formed to correspond to the depth D1and the spacing S1of the slits640of the cathode layer120ofFIG.1.

After the plurality of slits640are formed in the cathode layer600in this manner, the cathode layer600is sintered as depicted inFIG.14. In the sintering process, matrix LCOs around the plate-shaped LCO seeds included in the cathode layer600grow along crystal planes of the plate-shaped LCO seeds.

As a result, a ceramic cathode having the plurality of slits640is formed, and crystal directions of the side surfaces of the cathode layer600exposed through, e.g., exposed by or adjacent to, the slits640are aligned with a <101> crystal direction, a <110> crystal direction, or a combination thereof, of the crystal grains of the cathode active material. A sintering temperature may be, for example, in a range from about 1000° C. to 1050° C., but is not limited thereto.

Referring toFIG.15, a cathode current collector810is formed on a surface not having the slits640of a sintered cathode layer800, for example, a bottom surface of the sintered cathode layer800. For example, the cathode current collector810may be formed by coating a bottom surface of the sintered cathode layer800with a cathode current collector material. A layer structure after the cathode current collector810is formed is the same as the layer structure in which the sintered cathode layer800including the plurality of slits640is formed on the cathode current collector810.

Next, referring toFIG.16, after attaching the cathode current collector810to the bottom of the sintered cathode layer800, a separator900is formed on the sintered cathode layer800. The separator900may cover the entire slits640of the cathode layer800. After the separator900is formed, a liquid electrolyte910is dropped on the separator900so that the liquid electrolyte910permeates into the cathode layer800through the separator900. The liquid electrolyte910may permeate through the slits640formed in the cathode layer800. Dashed arrows symbolically represent where the liquid electrolyte910dropped onto the separator900may permeate into the slits640of the cathode layer800.

Next, as depicted inFIG.17, an anode current collector1010is formed on one surface1000S1of an anode layer1000. A surface1000S1of the anode layer1000may be an upper surface of the anode layer1000. A surface1000S2facing the surface1000S1on which the anode current collector1010is formed may be a bottom surface of the anode layer1000. The anode current collector1010may be coated to cover the entirety of the surface1000S1of the anode layer1000. The process of coating the anode current collector1010on the one surface1000S1of the anode layer1000may be performed before obtaining the result ofFIG.16. For example, a layer structure including the anode layer1000and the anode current collector1010may be formed ahead of the layer structure including the sintered cathode layer800and the cathode current collector810.

Next, as shown inFIG.18, the resultant product ofFIG.17is attached to the resultant product ofFIG.16. That is, after aligning a separator900to which the liquid electrolyte910is supplied and the bottom surface1000S2of the anode layer1000to face each other, the separator900and the bottom surface1000S2may be attached to each other. For example, after aligning the anode layer1000on the separator900to which the liquid electrolyte910is supplied so that the bottom surface1000S2of the anode layer1000faces the separator900, the bottom surface1000S2of the anode layer1000is attached to an upper surface of the separator900. Afterwards, a packaging process may proceed. After the plurality of batteries depicted inFIG.18are stacked, a packaging process may be performed.

A method of manufacturing a battery according to an embodiment will be described with reference toFIGS.19through21.

Referring toFIG.19, a plurality of trenches1210are formed in a cathode layer1200. The cathode layer1200may be the cathode layer600ofFIG.13. The plurality of trenches1210may be formed at given intervals, for example, at regular intervals. After sintering, a crystal direction of an outer side surface S11of the cathode layer1200may be aligned with a <101> crystal direction, a <hk0> crystal direction, or a combination thereof, of the crystal grains of the cathode active material. The <hk0> may be the same as described above. After sintering, a crystal direction of an inner side surface S22exposed through, e.g., exposed by or adjacent to, each of the trenches1210of the cathode layer1200may be the same as the crystal direction of the outer side surface S11. The inner side surface S22has an area much greater than a bottom area of each of the trenches1210. The cathode layer1200in which the trenches1210are formed is sintered. The sintering of the cathode layer1200may follow the sintering process of the cathode layer600ofFIG.13.

Next, as shown inFIG.20, a cathode current collector1300is formed on a bottom surface of a sintered cathode layer1200A. The cathode current collector1300may be coated on the bottom surface of the sintered cathode layer1200A.

Next, as shown inFIG.21, a separator1400covering the plurality of trenches1210is formed on the sintered cathode layer1200A. The separator1400covers the entire trenches1210and also covers an upper surface of the cathode layer1200A between the trenches1210. The expression that the separator1400covers the entire trenches1210may not denote that the separator1400is in direct contact with inner side surfaces of the cathode layer1200A exposed through, e.g., exposed by or adjacent to, the trenches1210. Inlets of the trenches1210are covered by the separator1400. After forming the separator1400, the liquid electrolyte910as described with reference toFIG.16may be supplied to the separator1400. The liquid electrolyte910supplied to the separator1400is supplied to the trenches1210and contacts the inner side surfaces S22of the cathode layer1200A exposed through, e.g., exposed by or adjacent to, the trench1210. Through such contact, the liquid electrolyte910may be diffused into the cathode layer1200A. After supplying the liquid electrolyte910to the separator1400, an anode layer1410and an anode current collector1420are sequentially formed on the separator1400. A stack including the anode layer1410and the anode current collector1420may be separately formed as described with reference toFIG.17, and then, the stack may be attached to the separator1400. In this way, a battery may be formed.

The battery illustrated inFIG.21may be a unit battery or a cell battery. A battery packaging may be formed by stacking a plurality of the unit batteries.

In the method of manufacturing the battery described above, the R value of the sintered cathode layer may be affected by the content of the matrix LCO included in the cathode layer before sintering, sintering temperature, and sintering time. The following table shows the change in R value of the sintered cathode layer according to the content (wt %) of matrix LCO contained in the cathode layer before sintering and the sintering temperature.

The present disclosure will be explained in more detail through the following Examples. However, Examples are provided herein for illustrative purpose only, and do not limit the scope of the present disclosure.

EXAMPLES

TABLE 1R value of sintered cathode layer according toLiCoO2(“LCO“) content and sintering temperature/timeContent of matrix LCO (LCO300) ofCathode Layer Before SinteringUX1000/LCO300UX1000/UX1000/Sintering(20 weightLCO300LCO300temperature/percent(40(60timeUX1000LCO300(wt %))wt %)wt %)1025° C.,9.21.19.110.58.32 hours (h)1025° C.,9.010.684 h1050° C.,10.410.63.12 h1050° C.,10.510.62.74 h

In Table 1, “UX1000” represents a flat LCO seed, e.g., LiCoO2having a platelet shape, and “LCO300” represents a polycrystalline LCO having a spherical shape.

Referring to Table 1, it may be seen that when a cathode layer having a polycrystalline LCO content of 40 wt % was sintered at 1025° C. or 1050° C., the R value is the largest, and a cathode layer having a polycrystalline LCO content of 20 wt % was sintered at 1050° C., the R value is the next largest.

FIGS.22through24show measurement results of X-ray diffraction (“XRD”) analysis of sintered cathode layers obtained by sintering the cathode layers having a polycrystalline LCO content of 20 wt %, 40 wt %, and 60 wt %, respectively, based on a total weight of the cathode layer, for 2 hours or 4 hours at a temperature of 1025° C. or 1050° C. Table 1 is prepared based on the results ofFIGS.22to24. In each figure, “101” denotes a peak with respect to a crystal plane corresponding to a crystal direction of <101>, “003” denotes a peak with respect to a crystal plane corresponding to a crystal direction of <003>, “102” denotes a peak with respect to a crystal plane corresponding to a crystal direction of <102>, “104” denotes a peak with respect to a crystal plane corresponding to a crystal direction of <104>, “009” is the peak with respect to a crystal plane corresponding to a crystal direction of <009>, and “110” denotes a peak with respect to a crystal plane corresponding to a crystal direction of <110>, respectively.

A plurality of crystal grains included in the sintered cathode layer of a battery according to an embodiment are aligned in a direction of high electrical conductivity. A cathode layer of a battery described above is a sintered cathode layer having a high sintered density without including a binder and a conductive material. Accordingly, when a battery described above is used, only a cathode active material without a binder and a conductive material is used, and thus, portion of an active material may be increased, thereby increasing energy density of the battery compared to an existing battery. In addition, the sintered cathode layer of the battery described above includes a plurality of grooves (for example, slits or trenches), and primary crystal directions of side surfaces exposed through, e.g., exposed by or adjacent to, the plurality of grooves are aligned with a <101> crystal direction, a <hk0> crystal direction, wherein h and k are integers equal to or greater than 1, or a combination thereof, of the crystal grains of the cathode active material. The crystal directions <101> and <110> may have a relatively large lithium ion diffusion coefficient compared to other crystal directions, such as <004> and <104>. In addition, the crystal grains included in the cathode layer are aligned in a direction of high electrical conductivity. Therefore, when the battery described above is used, lithium ions may be rapidly diffused into an entire area of the cathode layer, and thus, the battery capacity may be increased, charge/discharge characteristics may also be improved, and high rate characteristics may also be improved.

It should be understood that embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should be considered as available for other similar features or aspects in other embodiments. While one or more embodiments have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims.