CATHODE MATERIAL, CATHODE INCLUDING THE SAME, AND LITHIUM BATTERY INCLUDING THE CATHODE CROSS-REFERENCE TO RELATED APPLICATION [0001] This application claims priority to and the benefit of Korean Patent Application No. 10-2014-0105324, filed on August 13, 2014, in the Korean Intellectual Property Office, the entire content of which is incorporated herein by reference, BACKGROUND 1. Field [0002] One or more example embodiments relate to a cathode material, a cathode including the cathode material, and a lithium battery including the cathode. 2. Description of the Related Art [0003] Demand for secondary batteries used in mobile electronic devices for information and communication, including personal digital assistants, cell phones, and laptop computers, and in electric bicycles or electric cars is rapidly increasing. Lithium batteries, for example, lithium ion batteries (LIBs) have high energy density and are easy to be designed, and thus, are used as a power source for electric vehicles or electrical power storage in addition to being used in portable information technology (IT) devices. The lithium ion batteries should have high energy densities and/or long lifespan characteristics. [0004] Studies on a cathode material have been conducted in order to manufacture lithium ion batteries having suitable characteristics. However, for example, microcracking may occur in a cathode active material due to decreased contact between the cathode active material and a current collector, oxidization of a conducting material, stress caused by repeated charging/discharging of the battery and/or a roll- press process used during a cathode manufacturing process, and thus, the capacity of the battery may decrease and the resistance of the battery may increase. SUMMARY [0005] One or more aspects of example embodiments include a cathode material having high energy density and/or long lifespan characteristics by increasing battery capacity and reducing resistance. [0006] One or more aspects of example embodiments include a cathode including the cathode material. [0007] One or more aspects of example embodiments include a lithium battery including the cathode. [0008] Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments. [0009] According to one or more example embodiments, a cathode material includes a cathode active material: and a carbon material of secondary particles including (e.g., consisting of) a plurality of primary particles, the carbon material of the secondary particles having an average chain length that is equal to or less than 50 primary particles coupled (or connected) to each other. [0010] According to one or more example embodiments, a cathode includes the cathode material and a current collector. [0011] According to one or more example embodiments, a lithium battery includes a cathode including the cathode material; an anode including an anode active material; and an electrolyte between the cathode and the anode. BRIEF DESCRIPTION OF THE DRAWINGS [0012] These and/or other aspects will become apparent and more readily appreciated from the following description of the example embodiments, taken in conjunction with the accompanying drawings in which: [0013] FIG. 1A is a schematic view of a cathode material according to an embodiment; [0014] FIG. 1B is a schematic view of a cathode material prepared according to Comparative Example 1; [0015] FIGS. 2A and 28 are images of cathode materials on surfaces of cathodes prepared according to Example 1 and Comparative Example 1, respectively, taken using a transmission electron microscope (HR-TEM) up to a resolution of several tens of nanometers (nm); [0016] FIGS. 2C and 2D are images of the cathode materials on the surfaces of the cathodes prepared according to Example 1 and Comparative Example 1, respectively, taken using a transmission electron microscope (HR-TEM) up to a resolution of several nm; [0017] FIGS. 3A and SB are images of the cathode materials on the surfaces of the cathodes prepared according to Example 1 and Comparative Example 1, respectively, taken using a scanning electron microscope (SEM) up to a resolution of several hundreds of nm; [0018] FIG. 4 is a graph showing a viscosity change with respect to a shear rate with respect to the cathode materials on the surfaces of the respective cathodes prepared according to Example 1 and Comparative Example 1; [0019] FIG, 5 is an exploded perspective view of a lithium battery according to an embodiment; [0020] FIG. 6 is a perspective view schematically illustrating a battery pack according to an embodiment; [0021] FIG. 7 is a graph showing resistances of respective lithium batteries prepared according to Example 3 and Comparative Example 3 in SOC 20%, SOC 50%, and SOC 90%, separately; [0022] FIG. 8 is a graph showing lifespan characteristics of the lithium batteries prepared according to Example 3 and Comparative Example 3; [0023] FIG. 9 is a graph showing lifespan characteristics of the lithium batteries prepared according to Example 3 and Comparative Example 3 kept after 60 days; and [0024] FIG. 10 is a graph showing lifespan charactenstics of lithium batteries prepared according to Example 4 and Comparative Example 4 measured using a reference performance test with respect to a 18560 cell. DETAILED DESCRIPTION [0025] Reference will now be made in more detail to example embodiments of a cathode material, a cathode including the cathode material, and a lithium battery including the cathode, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the present example embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the example embodiments are merely described below, by referring to the drawings, to explain aspects of the present description. 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. Also, in the context of the present application, when a first element is referred to as being "on" a second element, it can be directly on the second element or be indirectly on the second element with one or more intervening elements interposed therebetween. As used herein, the term "substantially," "about," and similar terms are used as terms of approximation and not as terms of degree, and are intended to account for the inherent deviations in measured or calculated values that would be recognized by those of ordinary skill in the art. Also, any numerical range recited herein is intended to include all sub-ranges of the same numerical precision subsumed within the recited range. For example, a range of "1.0 to 10.0" is intended to include all subranges between (and including) the recited minimum value of 1.0 and the recited maximum value of 10.0, that is, having a minimum value equal to or greater than 1.0 and a maximum value equal to or less than 10.0, such as, for example, 2.4 to 7.6. Any maximum numerical limitation recited herein is intended to include all lower numerical limitations subsumed therein and any minimum numerical limitation recited in this specification is intended to include all higher numerical limitations subsumed therein. Accordingly, Applicant reserves the right to amend this specification, including the claims, to expressly recite any sub-range subsumed within the ranges expressly recited herein. All such ranges are intended to be inherently described in this specification such that amending to expressly recite any such subranges would comply with the requirements of 35 U.S.C. § 112(a), and 35 U.S.C.§ 132(a). [0026] FIG, 1A is a schematic view of a cathode material according to an embodiment. FIG. 1B is a schematic view of a cathode material prepared according to Comparative Example 1. [0027] Referring to FIG. 1A, according to an embodiment, the cathode material includes a cathode active material 1; and a carbon material 2 of secondary particles including (or consisting of) a plurality of primary particles, wherein the carbon material 2 of the secondary particles have an average chain length that is equal to or less than 50 primary particles coupled (or connected) to each other. For example, the carbon material 2 of the secondary particles may have an average chain length that is equal to or less than 30 primary particles coupled (or connected) to each other. For example, the carbon material 2 of the secondary particles may have an average chain length that is equal to or less than 20 primary particles coupled (or connected) to each other. For example, the carbon material 2 of the secondary particles may have an average chain length that is equal to or less than 15 primary particles coupled (or connected) to each other. . For example, the carbon material 2 of the secondary particles may have an average chain length with the range of about 2 to about 15 primary particles coupled (or connected) to each other. The average chain length of the carbon materials 2 of the secondary paraticles can be measured by transmission electron microscope (TEM) and scanning electron microscope (SEM) images in Figs 2a to 2d, 3a, and 3d. [0028] The carbon material 2 of secondary particles may generally have an average chain length that is, for example, shorter than an average chain length of a carbon material included in other cathode materials, for example, as shown in Fig. IB. For example, as can be seen in FIG. IB, the cathode material prepared according to Comparative Example 1 includes a cathode active material 3; and a carbon material 4 of secondary particles having an average chain length longer than 50 primary particles coupled (or connected) to each other. In this regard, relative to a cathode material including a carbon material of secondary particles having an average chain length longer than 50 primary particles coupled (or connected) to each other, a dispersion degree of the cathode active material 1 and the carbon material 2 included in the cathode material may increase, respective distances of pathways of electrons may be reduced, and thus, an electronic conductivity (electrical conductivity) of the cathode material may increase. In addition, the energy density and/or lifespan characteristics of the cathode material may improve. [0029] An average particle diameter of the primary particles may be in a range of about 5 nm to about 30 nm. For example, an average particle diameter of the primary particles may be in a range of about 10 nm to about 28 nm. For example, an average particle diameter of the primary particles may be in a range of about 18 nm to about 28 nm. The average particle diameter of the primary particles can be also measured by transmission electron microscope (TEM) and scanning electron microscope (SEM) images in Figs 2a to 2d, 3a, and 3d. [0030] A specific surface area of the carbon material 2 may be in a range of about 100 m^/g to about 300 m^/g. For example, a specific surface area of the carbon material 2 may be in a range of about 100 m^/g to about 200 m^/g. For example, the specific surface area of the carbon material 2 may be in a range of about 120 m^/g to about 200 m^/g. The specific surface area of the carbon material 2 can be measured by Brunauer Emmett Teller (BET) analysis. [0031] When the primary particles have an average particle diameter within the ranges above, a dispersion degree of the cathode active material 1 and the carbon material 2 included in the cathode material may further increase, a specific surface area of the primary particles may increase, and thus, the electronic conductivity (electrical conductivity) of the cathode material including the primary particles may further increase. Also, the energy density and/or lifespan characteristics of the cathode material may further improve. [0032] An oil absorption number (OAN) of the carbon material may be in a range of about 10Oml/1 OOg to about 200ml/1 OOg. For example, the oil absorption number of the carbon material 2 may be in a range of about 100ml/100g to about 180ml/100g. For example, the oil absorption number of the carbon material 2 may be in a range of about 120ml/100g to about 180ml/100g. The oil absorption number (OAN) of the carbon material can be obtained by using ASTM D2414 test method. When the cathode material including the carbon material 2 is used, the dispersion of the cathode material may increase during a cathode material mixing process which may result in a decrease in the amount of an organic solvent thus used, and thus, a cost of manufacturing a battery including the cathode material may decrease. Also, the amount of solid powder of the cathode material may increase due to the decrease in the amount of the organic solvent, and thus, a cathode material having a stable or suitable viscosity may be manufactured. [0033] The amount of the carbon material 2 may be in a range of about 1 wt% to about 15 wt% based on the total weight of the cathode material. For example, the amount of the carbon material 2 may be in a range of about 1 wt% to about 13 wt% based on the total weight of the cathode material. For example, the amount of the carbon material 2 may be in a range of about 1 wt% to about 10 wt% based on the total weight of the cathode material. When the amount of the carbon material 2 in the cathode material is within the ranges above, the electronic conductivity (electrical conductivity) and packing density of the cathode material may improve. [0034] The carbon material 2 may include at least one selected from carbon black (e.g., acetylene black and/or Denka Black) and an aerogel. [0035] The cathode material may further include at least one additive selected from natural graphite, artificial graphite, carbon black (e.g., acetylene black, and/or ketjen black), carbon fibers, metal powder, and metal fibers. [0036] The amount of the additive may be in a range of about 0.1 wt% to about 15 wt% based on the total weight of the cathode material. For example, the amount of the additive may be in a range of about 0.1 wt% to about 10 wt%. In some embodiments, the amount of the additive is in a range of about 0.1 wt% to about 5 wt%. In other embodiments, the amount of the additive is in a range of about 0.1 wt% to about 3 wt%. When the amount of the additive included in the cathode material is within the ranges above, a battery including the cathode material may have an increased capacity and a decreased resistance, and thus, a lithium battery provided by using the cathode material may have an improved high energy density and/or long lifespan characteristics. [0037] The cathode material may further include a binder. Examples of the binder may include polyvinylalcohol, carboxymethylcellulose, hydroxypropylcellulose. diacetylcellulose, polyvinylchlohde, carboxylated polyvinylchloride, polyvinylfluoride, a polymer including ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, or a combination thereof, but the binder is not limited thereto. [0038] The amount of the binder may be in a range of about 0.1 wt% to about 15 wt% based on the total weight of the cathode material. For example, the amount of the binder may be in a range of about 0.1 wt% to about 10 wt%. In some embodiments, the amount of the binder is in a range of about 0.1 wt% to about 5 wt%. In other embodiments, the amount of the binder may be in a range of about 0.1 wt% to about 3 wt%. When the amount of the binder is within these ranges, a bonding strength between the cathode material and the cathode current collector may further increase. [0039] The cathode active material 1 may be a compound capable of reversibly intercalating/deintercalating lithium ions. Examples of the cathode active material 1 may include at least one selected from a lithium nickel oxide, a lithium cobalt oxide, a lithium cobalt aluminum oxide, a lithium nickel cobalt manganese oxide, a lithium manganese oxide, a lithium nickel oxide doped with at least one selected from chrome (chromium), zirconium, and titanium, a lithium cobalt oxide doped with at least one selected from chrome (chromium), zirconium, and titanium, a lithium cobalt aluminum oxide doped with at least one selected from chrome (chromium), zirconium, and titanium, a lithium nickel cobalt manganese oxide doped with at least one selected from chrome (chromium), zirconium, and titanium, a lithium manganese oxide doped with at least one selected from chrome (chromium), zirconium, and titanium, and an olivine-based oxide. For example, the cathode active material 1 may include LiMn204, LiNi204, LiCo02, LiNi02, LiMn02, Li2Mn03, LiFeP04, LiNixC0yO2 (where 0