Title of invention: negative active material, negative electrode and lithium secondary battery including the same Technical field [One] The present invention relates to a negative electrode active material, a negative electrode including the same, and a lithium secondary battery. [2] This application claims priority based on Korean Application No. 10-2018-0012299 filed on January 31, 2018, and all contents disclosed in the specification of the application are incorporated herein by reference. Background [3] In recent years, with the development and distribution of mobile devices, personal computers, electric motors, and temporary power storage devices, high-capacity energy sources are required, and a lithium secondary battery is a representative example thereof. As a negative electrode material for a next-generation nonaqueous electrolyte secondary battery, silicon (Si), which has a capacity of 10 times or more (4200 mAh/g) of a conventional graphite material (theoretical capacity is 372 mAh/g), is attracting attention. From this, it has been proposed to use silicon alloyed with lithium and exhibiting a high theoretical capacity as a negative electrode active material as a new material to replace the carbon-based material. [4] However, silicon expands in volume by charging and contracts in volume when discharging. For this reason, when the secondary battery repeats charging and discharging, silicon used as a negative electrode active material is finely divided, thereby losing a conductive path in the electrode and increasing isolated particles, resulting in deterioration in capacity of the secondary battery. [5] As a result of attempting micronization of silicon as a method of improving the cycle characteristics, improvement of the cycle characteristics can be expected as the micronization proceeds, but there is a limitation in reducing the crystallite size of crystalline silicon. It was difficult to sufficiently solve the problem that micronization proceeds. [6] In addition, silicon oxide (SiO x ) proposed as another method of improving the cycle characteristics is decomposed into Si and SiO 2 by disproportionation [0010] at a high temperature of 1,000° C. It forms a structure that is uniformly distributed in the. When such silicon oxide is applied as an anode active material of a secondary battery, the capacity is only half of the capacity of the silicon anode active material, but it is about 5 times larger than the capacity of the carbon-based anode active material, and the volume change during charge/discharge is structurally small, and the cycle life It is expected to have excellent properties. However, silicon oxide reacts with lithium and silicon oxide during initial charging to produce lithium silicide and lithium oxide (lithium oxide and lithium silicate), of which lithium oxide does not participate in the subsequent electrochemical reaction. An irreversible reaction occurs in which some of the lithium transferred to the negative electrode does not return to the positive electrode during discharge. In the case of silicon oxide, compared to other silicon-based anodes, such irreversible capacity is large, and the initial efficiency (ICE, ratio of discharge capacity to initial charge capacity) is very low, 70 to 75%. This low initial efficiency has a problem in that the capacity of the positive electrode is excessively required in constructing a secondary battery, thereby offsetting the capacity per unit mass of the negative electrode. [7] Therefore, when silicon oxide is used as an anode active material, there is still a need for the development of a silicon oxide-based material capable of satisfying not only initial capacity/efficiency but also life characteristics by reducing the lithium oxide generation reaction that causes irreversibility. . Detailed description of the invention Technical challenge [8] An object of the present invention is to provide a negative electrode active material having excellent initial capacity/efficiency and lifetime characteristics, a negative electrode including the same, and a lithium secondary battery. Other objects and advantages of the present invention will be understood by the following description. On the other hand, it will be easily understood that the objects and advantages of the present invention can be realized by means or methods described in the claims, and combinations thereof. Means of solving the task [9] In order to solve the problems of the present invention, according to an aspect of the present invention, a negative active material of the following embodiments is provided. [10] The first embodiment, [11] i) a silicon oxide composite comprising Si, ii) a silicon oxide represented by SiO x (0