A large-capacity unit cell comprising a base body provided with a plurality of accommodation cavities, each of the accommodation cavities being provided with an electrode group module, wherein the electrode group modules are connected in parallel; and the electrode group module comprises a central shaft and an electrode group wound around the central shaft, the electrode group comprises a positive electrode sheet, a negative electrode sheet and a separator, and the separator is used to separate the positive electrode sheet from the negative electrode sheet; and wherein the accommodation cavity passes through the base body, and a positive electrode terminal and a negative electrode terminal of the electrode group module are respectively located at two ends of the accommodation cavity; and the electrode group module further comprises a positive electrode cover and a negative electrode cover, the positive electrode cover covers a positive electrode terminal of the electrode group, the negative electrode cover covers a negative electrode terminal of the electrode group, and the positive electrode cover and the negative electrode cover are both fixedly connected to the base body; and wherein two electrode group modules are provided, the two electrode group modules are connected in parallel, and are placed in the same direction in the accommodation cavity; and the positive electrode covers of the two electrode group modules are of an integral structure, and the negative electrode covers of the two electrode group modules are of an integral structure; and wherein the electrode group module further comprises a positive electrode terminal cover and a negative electrode terminal cover, the positive electrode terminal cover is arranged between the positive electrode cover and the positive electrode terminal of the electrode group, and the negative electrode terminal cover is arranged between the negative electrode cover and the negative electrode terminal of the electrode group; the positive electrode terminal cover is fixedly connected to the positive electrode cover, and is connected to the central shaft in an insulated manner; and the negative electrode terminal cover is fixedly connected to the negative electrode cover, and is connected to the central shaft in an insulated manner; characterized in that two ends of the central shaft are both provided with a threaded hole, the positive electrode terminal cover is connected to the central shaft by means of a first threaded fastener, and an insulating part is arranged between the first threaded fastener and the positive electrode terminal cover; and/or the negative electrode terminal cover is connected to the central shaft by means of a first threaded fastener, and an insulating part is arranged between the first threaded fastener and the negative electrode terminal cover. the electrode group module comprises a central shaft and an electrode group wound around the central shaft, the electrode group comprises a positive electrode sheet, a negative electrode sheet and a separator, and the separator is used to separate the positive electrode sheet from the negative electrode sheet; and wherein the accommodation cavity passes through the base body, and a positive electrode terminal and a negative electrode terminal of the electrode group module are respectively located at two ends of the accommodation cavity; and the electrode group module further comprises a positive electrode cover and a negative electrode cover, the positive electrode cover covers a positive electrode terminal of the electrode group, the negative electrode cover covers a negative electrode terminal of the electrode group, and the positive electrode cover and the negative electrode cover are both fixedly connected to the base body; and wherein two electrode group modules are provided, the two electrode group modules are connected in parallel, and are placed in the same direction in the accommodation cavity; and the positive electrode covers of the two electrode group modules are of an integral structure, and the negative electrode covers of the two electrode group modules are of an integral structure; and wherein the electrode group module further comprises a positive electrode terminal cover and a negative electrode terminal cover, the positive electrode terminal cover is arranged between the positive electrode cover and the positive electrode terminal of the electrode group, and the negative electrode terminal cover is arranged between the negative electrode cover and the negative electrode terminal of the electrode group; the positive electrode terminal cover is fixedly connected to the positive electrode cover, and is connected to the central shaft in an insulated manner; and the negative electrode terminal cover is fixedly connected to the negative electrode cover, and is connected to the central shaft in an insulated manner; characterized in that two ends of the central shaft are both provided with a threaded hole, the positive electrode terminal cover is connected to the central shaft by means of a first threaded fastener, and an insulating part is arranged between the first threaded fastener and the positive electrode terminal cover; and/or the negative electrode terminal cover is connected to the central shaft by means of a first threaded fastener, and an insulating part is arranged between the first threaded fastener and the negative electrode terminal cover.