TECHNICAL FIELD [１] Cross-Reference to Related Application [２] This application claims priority 5 to and the benefit of Korean Patent Application No. 10-2020-0060532, filed on May 20, 2020, the disclosure of which is incorporated herein by reference in its entirety. [３] Technical Field [４] The present invention relates to a secondary battery, and more particularly, to 10 a secondary battery having improved capacity characteristics, lifetime characteristics, and fast-charging characteristics. BACKGROUND ART [５] With the recent rapid spread of electronic devices using a battery, such as mobile phones, notebook computers, and electric vehicles, the demand for 15 small, lightweight, and relatively high-capacity secondary batteries is rapidly increasing. In particular, lithium secondary batteries have attracted attention as driving power sources for portable devices due to their light weight and high energy density. Accordingly, there have been active research and development efforts to improve the performance of lithium secondary 20 batteries. [６] The lithium secondary batteries generally include a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, an electrolyte, an organic solvent, and the like. In addition, in the positive electrode and the negative electrode, an active 25 material layer including a positive electrode active material or a negative 2 electrode active material may be formed on a current collector. In general, a lithium-containing metal oxide such as LiCoO2 or LiMn2O4 is used as a positive electrode active material in the positive electrode, and accordingly, a carbon-based active material or a silicon-based active material, which does not contain lithium, is used as a negative 5 electrode active material in the negative electrode. [７] Among negative electrode active materials, silicon-based active materials are attracting attention because they have about 10 times higher capacity than carbon-based active materials and have excellent fast-charging characteristics. 10 However, silicon-based active materials have the problem of volume expansion due to charging and discharging and degradation of lifetime characteristics caused thereby, and when a large amount of binder is used to suppress the problem, it is difficult to realize a desired high-capacity electrode. Therefore, silicon-based active materials are not widely used at present. 15 [８] Meanwhile, carbon-based active materials such as artificial graphite and natural graphite exhibit relatively stable lifetime performance compared to silicon-based active materials, but when a carbon-based active material is applied with a large thickness to manufacture a high-capacity electrode, problems such as electrode cracking, warpage, delamination, and the like may 20 occur. [９] In order to overcome the disadvantages of the carbon-based active materials and silicon-based active materials, techniques of manufacturing an electrode including a combination of a carbon-based active material and a silicon-based active material have been developed. However, since the influence of 25 volume expansion of the silicon-based active material should be reduced, the 3 proportion of the silicon-based active material used in the negative electrode cannot be increased to a desirable level, so it is difficult to improve the capacity characteristics and fast-charging characteristics of a negative electrode. In addition, when the proportion of the silicon-based active material is increased, the usage amount 5 of binder should also be increased to suppress the volume expansion of the active material, so it is difficult to realize a high-capacity negative electrode. [１０] Korean Patent Registration No. 10-0794192 relates to a method of manufacturing a carbon-coated silicon-graphite composite negative electrode 10 material for a lithium secondary battery and a method of manufacturing a secondary battery including the same, but these methods have limitations in solving the above-described problems. [１１] [Related-Art Document] [１２] [Patent Document] 15 [１３] Korean Patent Registration No. 10-0794192 DETAILED DESCRIPTION OF THE INVENTION TECHNICAL PROBLEM [１４] The present invention is directed to providing a secondary battery having improved capacity characteristics, lifetime characteristics, and fast-charging 20 characteristics. TECHNICAL SOLUTION [１５] One aspect of the present invention provides a secondary battery, which includes: one or more positive electrodes including a positive electrode active material layer; a plurality of negative electrodes including a first negative 25 electrode including a silicon-based active material and a second negative 4 electrode including a carbon-based active material; a separator; and an electrolyte, wherein the positive electrode and the negative electrode are alternately stacked with the separators interposed therebetween, and a weight ratio of the silicon-based active material included in the first negative electrode to the carbon-based active 5 material included in the second negative electrode is in a range of 40:60 to 90:10. ADVANTAGEOUS EFFECTS [１６] A secondary battery of the present invention includes a first negative electrode including a silicon-based active material and a second negative electrode 10 including a carbon-based active material, and a weight ratio of the siliconbased active material included in the first negative electrode to the carbonbased active material included in the second negative electrode is adjusted to be a specific ratio. According to the secondary battery of the present invention, since separate negative electrodes having different types of active 15 materials having different characteristics are used, binders and conductive materials suitable for the characteristics of each of the active materials can be used in a desired amount, advantages of each of the silicon-based active material and the carbon-based active material can be maximized, and a secondary battery having excellent capacity and lifetime characteristics can be 20 realized. [１７] In addition, in the secondary battery of the present invention, a weight ratio of the silicon-based active material included in the first negative electrode to the carbon-based active material included in the second negative electrode is adjusted to be a specific weight ratio. Accordingly, since the charging 25 potential of the silicon-based active material can be lowered to an appropriate 5 level, the stress level of the silicon-based active material due to a sudden voltage change during charging and discharging can be reduced, and fastcharging characteristics can be improved. DESCRIPTION OF DRAWINGS [１８] FIG. 1 is an image for schematically illustrating 5 a secondary battery of the present invention. MODES OF THE INVENTION [１９] Terms and words used in this specification and the claims should not be interpreted as being limited to commonly used meanings or meanings in 10 dictionaries, and, based on the principle that the inventors can appropriately define concepts of terms in order to describe their invention in the best way, the terms and words should be interpreted with meanings and concepts which are consistent with the technical spirit of the present invention. [２０] The terms used in the present specification have been used only for the 15 purpose of describing exemplary embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. [２１] It will be understood that terms such as "comprises," "comprising," "includes," "including," "has," or "having," when used in the present specification, specify 20 the presence of stated features, numbers, steps, components, or combinations thereof and do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof. [２２] In the present specification, an average particle diameter (D50) is defined as a particle diameter corresponding to the 50% cumulative volume in a particle 25 diameter distribution curve. The average particle diameter (D50) may be 6 measured using, for example, a laser diffraction method. The laser diffraction method generally allows for the measurement of a particle diameter ranging from a submicron level to several millimeters and can produce a result having high reproducibility and high resolution. [２３] Hereinafter, a secondary battery of the 5 present invention will be described in detail with reference to the accompanying drawing. In describing the present invention, when it is determined that a detailed description of a related known configuration or function may obscure the gist of the present invention, the detailed description may be omitted. 10 [２４] [２５] The present invention relates to a secondary battery 1, and more particularly, to a lithium secondary battery. [２６] As shown in FIG. 1, the secondary battery 1 of the present invention includes: one or more positive electrodes 100 including a positive electrode active 15 material layer 120; a plurality of negative electrodes 200, 300 including a first negative electrode 200 including a silicon-based active material and a second negative electrode 300 including a carbon-based active material; a separator 400; and an electrolyte (not shown), wherein the positive electrodes 100 and the negative electrodes 200, 300 are alternately stacked with the separators 20 400 interposed therebetween, and a weight ratio of the silicon-based active material included in the first negative electrode 200 to the carbon-based active material included in the second negative electrode 300 is in a range of 40:60 to 90:10. [２７] Conventionally, silicon-based active materials have the advantageous of 25 having high-capacity and fast-charging characteristics, but since the degree of 7 volume expansion/contraction due to charging and discharging is large, rapid degradation of lifetime characteristics is an issue. Meanwhile, although a negative electrode including a combination of a silicon-based active material and a carbon-based active material has been developed, since the proportion of silicon-based active material used in a 5 negative electrode should be lowered to control the volume expansion of the silicon-based active material, it is difficult to realize the high-capacity and fast-charging characteristics of the silicon-based active material. [２８] In order to solve the problems, in the secondary battery of the present 10 invention, a weight ratio of the silicon-based active material included in the first negative electrode 200 to the carbon-based active material included in the second negative electrode 300 is adjusted to be within the above-described range. In the secondary battery of the present invention, since the siliconbased active material in the first negative electrode 200 and the carbon-based 15 active material in the second negative electrode 300 are used in the abovedescribed weight ratio, the charging potential of the silicon-based active material can be lowered to a desirable level by the carbon-based active material, and therefore, the degree of volume expansion/contraction of the silicon-based active material during charging and discharging can be reduced, 20 and the high-capacity and fast-charging characteristics of the silicon-based active material can be sufficiently exhibited. [２９] In addition, the secondary battery of the present invention includes the first negative electrode 200 and the second negative electrode 300, which include the silicon-based active material and the carbon-based active material, 25 respectively. Specifically, since the secondary battery of the present 8 invention includes different types of negative electrodes including different active materials, negative electrode components can be included in compositions suitable for each negative electrode, and even when the proportion of the silicon-based active material used in the secondary battery is increased, the high-capacity characteristics and 5 fast-charging characteristics of the silicon-based active material can be sufficiently exhibited without degradation of lifetime characteristics. [３０] The secondary battery of the present invention 1 includes one or more positive electrodes 100. The positive electrode 100 includes a positive electrode 10 active material layer 120. [３１] Specifically, the positive electrode 100 may include a positive electrode current collector 110, and a positive electrode active material layer 120 formed on one or more surfaces of the positive electrode current collector 110. [３２] The positive electrode current collector 110 is not particularly limited as long 15 as it does not cause a chemical change in a battery and has high conductivity. Specifically, the positive electrode current collector 110 may include one or more selected from the group consisting of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, and an aluminum-cadmium alloy. [３３] The positive electrode current collector 110 may typically have a thickness of 20 3 μm to 500 μm. [３４] The positive electrode current collector 110 may have fine irregularities formed in a surface thereof to increase the adhesion of a positive electrode active material. For example, the positive electrode current collector 110 may be used in any of various forms such as a film, a sheet, a foil, a net, a 25 porous material, a foam, and a non-woven fabric. 9 [３５] The positive electrode active material layer 120 is formed on one or more surfaces of the positive electrode current collector 110. Specifically, the positive electrode active material layer 120 may be formed on one or both surfaces of the positive electrode current collector 110. [３６] The positive electrode active material 5 layer 120 may include a positive electrode active material. [３７] The positive electrode active material may include a compound enabling the reversible intercalation and deintercalation of lithium and, specifically, may include a lithium-transition metal composite oxide including lithium and one 10 or more selected from the group consisting of nickel, cobalt, manganese, and aluminum and preferably a lithium-transition metal composite oxide including lithium and a transition metal selected from the group consisting of nickel, cobalt, and manganese. [３８] More specifically, the lithium-transition metal composite oxide may be, for 15 example, a lithium-manganese-based oxide (e.g., LiMnO2, LiMn2O4), a lithium-cobalt-based oxide (e.g., LiCoO2), a lithium-nickel-based oxide (e.g., LiNiO2), a lithium-nickel-manganese-based oxide (e.g., LiNi1-YMnYO2 (here, 0