Step-down lithium battery and manufacturing method therefor

Abstract

The present application relates to a step-down lithium battery and a manufacturing method therefor. The step-down lithium battery comprises a circuit assembly, a plastic frame, a wound battery cell assembly, a first metal housing, a second metal housing, an insulating sealing member and an insulating sheath, the circuit assembly and the plastic frame being arranged in the first metal housing, the wound battery cell assembly being arranged in the second metal housing, the first metal housing and the second metal housing being fitted with each other vertically and being fixed by means of circumferential welding, the insulating sealing member being used for sealing the second metal housing, and the insulating sheath wrapping the first metal housing and the second metal housing. The present application uses the first metal housing and the insulating sealing member for completely sealing the upper end of the second metal housing, thus achieving good sealing performance, and effectively preventing electrolyte leakage; and only one steel housing layer is provided outside the wound battery cell assembly, such that compared with the prior art, one steel housing layer or soft housing layer is reduced, thus reducing the material cost. The connection strength of the first metal housing and the second metal housing is high, such that the first metal housing and the second metal housing are not prone to damage.

Description

A step-down lithium battery and a manufacturing method thereof TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium batteries, in particular to a step-down lithium battery and a manufacturing method thereof. BACKGROUND

[0002] A constant-voltage lithium battery is disclosed in Chinese Patent Application No. CN208225957U entitled "Rechargeable lithium battery with MicroUSB interface", wherein a constant-voltage protection component can maintain a constant output voltage during the output of electric energy, and includes charging protection, discharging protection, overcurrent protection and short-circuit protection to meet the voltage requirements of users. The single lithium cell in the application is a soft-pack lithium cell or a hard-shell lithium cell, which is further sleeved with a steel shell, resulting in high cost. The upper cover and the lower cover are ultrasonically welded and embedded in the steel shell, and the connection strength with the steel shell is low and easy to be damaged, which needs to be improved.

[0003] SUMMARY

[0004] In order to solve the technical problems of high cost and easy damage of the existing low-voltage lithium battery, the present application provides a step-down lithium battery and a manufacturing method thereof.

[0005] In one aspect, the present application provides a step-down lithium battery, comprising a circuit component, a plastic frame, a wound cell assembly, a first metal shell, a second metal shell, an insulating seal and an insulating outer skin, the circuit component and the plastic frame are arranged in the first metal shell, the plastic frame is used for fixing the circuit component, the wound cell assembly is arranged in the second metal shell, the first metal shell and the second metal shell are butted up and down and fixed by circumferential welding, the insulating seal is arranged between the first metal shell and the second metal shell and is used for sealing the second metal shell, and the insulating outer skin covers the first metal shell and the second metal shell.

[0006] By adopting the above technical solution, the wound cell assembly is directly placed in the second metal shell, the plastic frame and the circuit component are sealed in the first metal shell, and then the upper end of the second metal shell is completely sealed by the first metal shell and the insulating seal. The first metal shell and the second metal shell are butted up and down, thereby controlling the up-and-down movement amplitude of the wound cell assembly. The insulating seal is arranged between the first metal shell and the second metal shell and is fixed by circumferential welding, the connection strength of the first metal shell and the second metal shell is high and not easy to be damaged, the sealing performance is good, and the leakage of electrolyte can be effectively prevented. The insulating outer skin is used to cover the welding points, without affecting the user's experience. The plastic frame can play an isolation role, preventing unnecessary contact between the circuit component and the first metal shell, preventing short circuit and ensuring electrical safety. Only one layer of steel shell is arranged outside the wound cell assembly, compared with the prior art, one layer of steel shell or soft shell is reduced, and the material cost is reduced.

[0007] Optionally, the first metal shell lower end is provided with a contraction part, and the insulation sealing element is partially clamped between the contraction part and the second metal shell.

[0008] Optionally, the outer ring surface of the insulation sealing element is provided with one or more annular protrusions to increase the sealing between the second metal shell; the bottom of the insulation sealing element further extends inwardly a horizontal sealing part which is in close contact with the lower surface of the first metal shell to increase the sealing between the first metal shell.

[0009] Optionally, the bottom wall of the first metal shell is provided with a clamping hole, and a metal screw is arranged at the clamping hole and fixed in the clamping hole by a plastic nut; the horizontal sealing part extends between the metal screw and the bottom wall of the first metal shell to insulate the metal screw from the first metal shell; the metal screw is also used to seal the clamping hole; the circuit assembly comprises a PCB board, a low-voltage positive cap, a high-voltage positive connecting piece, a low-voltage positive elastic connecting piece and a negative elastic sheet, the low-voltage positive elastic connecting piece, the high-voltage positive connecting piece and the negative elastic sheet are all welded on the PCB board, the negative elastic sheet is in elastic contact with the first metal shell, the high-voltage positive connecting piece is in elastic contact with the upper end of the metal screw, the positive lug of the wound battery cell assembly is welded with the lower end of the metal screw, and the negative lug is welded with the second metal shell; the low-voltage positive cap is arranged on the plastic frame, and the low-voltage positive elastic connecting piece is in elastic contact with the low-voltage positive cap.

[0010] Optionally, the low-voltage positive elastic connecting piece is a metal elastic sheet, a spring or an elastic thimble.

[0011] Optionally, the circuit assembly further comprises a charging interface, and the charging interface is welded on the PCB board; the first metal shell and the insulation outer skin are both provided with an opening at the corresponding position.

[0012] Optionally, the plastic frame comprises an upper frame and a lower frame, and the upper frame and the lower frame are fixed by clamping; the PCB board is fixed between the upper frame and the lower frame.

[0013] Optionally, the upper end of the first metal shell is inwardly provided with a spinning edge for pressing the plastic frame; the spinning edge is further provided with a positive and negative electrode isolation sheet above or below; part of the upper surface of the positive and negative electrode isolation sheet is wrapped by the insulation outer skin.

[0014] Optionally, the wound battery cell assembly comprises a wound battery cell, an upper isolation sheet and a lower isolation sheet; the positive lug passes through the center hole of the upper isolation sheet and is welded to the lower surface of the metal screw at the end; the negative lug is wound from the side surface to the bottom surface of the wound battery cell, and the end is welded to the bottom wall of the second metal shell.

[0015] In another aspect, the application also provides a manufacturing method of the above-mentioned voltage-reducing lithium battery, comprising the following steps:

[0016] S1, the insulating sealing member is sleeved at the lower end of the first metal shell, and the metal screw and the plastic nut are fixed at the clamping hole of the first metal shell;

[0017] S2, the circuit assembly is fixed on the plastic frame, and then the circuit assembly and the plastic frame are loaded into the first metal shell, so that the high-voltage positive connection sheet in the circuit assembly is in elastic contact with the metal screw, and the negative spring sheet in the circuit assembly is in elastic contact with the first metal shell;

[0018] S3, the low-voltage positive cap is placed on the plastic frame, the low-voltage positive cap is in elastic contact with the low-voltage positive elastic connecting member, and the plastic frame and the low-voltage positive cap are pressed in the first metal shell;

[0019] S4, the winding cell assembly is loaded into the second metal shell, and the positive lug of the winding cell assembly is welded to the bottom surface of the metal screw;

[0020] S5, the insulating sealing member and the lower end of the first metal shell are pressed into the second metal shell, and the first metal shell and the second metal shell are circumferentially welded;

[0021] S6, the insulating outer skin is sleeved, and heating and shrinking are performed, so that the insulating outer skin is wrapped on the first metal shell and the second metal shell.

[0022] In summary, the application has at least one of the following beneficial technical effects:

[0023] 1. The first metal shell and the insulating sealing member completely seal the upper end of the second metal shell, have good sealing performance, and can effectively prevent electrolyte leakage; only one layer of steel shell is arranged outside the winding cell assembly, compared with the prior art, one layer of steel shell or soft shell is reduced, and the material cost is reduced.

[0024] 2. The insulating sealing member is arranged between the first metal shell and the second metal shell and is fixed by circumferential welding, the first metal shell and the second metal shell have high connection strength and are not easy to be damaged.

[0025] 3. The plastic frame can play a separation role, prevent the circuit assembly from being unnecessarily contacted with the first metal shell, is not easy to be short-circuited, and ensures electrical safety. BRIEF DESCRIPTION OF DRAWINGS

[0026] Fig. 1 is a perspective view of the voltage-reducing lithium battery according to the embodiment of the application;

[0027] Fig. 2 is a semi-sectional structural schematic view of the voltage-reducing lithium battery according to the embodiment of the application;

[0028] Fig. 3 is an enlarged view of A in Fig. 2;

[0029] Fig. 4 is a semi-partial structure view of the voltage-lowering lithium battery from another angle according to the embodiment of the present application;

[0030] Fig. 5 is an enlarged view of B in Fig. 4;

[0031] Fig. 6 is a schematic view of the assembling action of the voltage-lowering lithium battery according to the embodiment of the present application;

[0032] Fig. 7 is a schematic view of the assembling action of the assembling of the winding cell assembly into the second metal shell according to the embodiment of the present application;

[0033] Fig. 8 is a schematic view of the assembling action of the assembling of the circuit assembly and the plastic frame and other parts into the first metal shell according to the embodiment of the present application;

[0034] Fig. 9 is a schematic view of the structure of the circuit assembly according to the embodiment of the present application;

[0035] Fig. 10 is a schematic view of the structure of the insulation sealing member according to the embodiment of the present application;

[0036] Fig. 11 is a schematic view of the structure of the sealing of the clamping hole by the metal screw according to the embodiment of the present application;

[0037] Fig. 12 is a schematic view of the action of the welding of the positive electrode tab to the metal screw according to the embodiment of the present application;

[0038] Fig. 13 is a schematic view of the action of the assembling of the first metal shell and the insulation sealing member into the second metal shell according to the embodiment of the present application;

[0039] Fig. 14 is a schematic view of the circumferential welding of the first metal shell and the second metal shell according to the embodiment of the present application.

[0040] Reference signs: 1, circuit assembly; 11, PCB board; 12, low-voltage positive electrode cap; 13, high-voltage positive electrode connecting piece; 14, low-voltage positive electrode elastic connecting piece; 15, negative electrode elastic piece; 16, charging interface; 2, plastic frame; 21, upper frame; 22, lower frame; 3, winding cell assembly; 31, positive electrode tab; 32, negative electrode tab; 33, winding cell; 34, upper isolation piece; 35, lower isolation piece; 4, first metal shell; 41, contraction part; 42, clamping hole; 43, opening; 44, spinning edge; 5, second metal shell; 6, insulation sealing member; 61, annular protrusion; 62, horizontal sealing part; 7, insulation outer skin; 71, opening; 8, metal screw; 9, plastic nut; 10, positive and negative electrode isolation piece; 100, circumferential welding spot. DETAILED DESCRIPTION

[0041] The present application will be further described in detail below in combination with Figs. 1-14.

[0042] Referring to FIG. 1 to FIG. 5, the application discloses a voltage reducing lithium battery, specifically a AAA battery, comprising a circuit assembly 1, a plastic frame 2, a winding cell assembly 3, a first metal shell 4, a second metal shell 5, an insulating sealing element 6 and an insulating outer skin 7. The circuit assembly 1 and the plastic frame 2 are arranged in the first metal shell 4, and the plastic frame 2 is used for fixing the circuit assembly 1. The winding cell assembly 3 is arranged in the second metal shell 5. The first metal shell 4 and the second metal shell 5 are butted up and down and fixed by circumferential welding. The insulating sealing element 6 is arranged between the first metal shell 4 and the second metal shell 5 and is used for sealing the second metal shell 5. The insulating outer skin 7 is wrapped outside the first metal shell 4 and the second metal shell 5.

[0043] The insulating outer skin 7 is preferably PVC material, which is wrapped on the first metal shell 4 and the second metal shell 5 by heat shrinkage, playing a dual role of insulation and covering the circumferential welding spot 100.

[0044] Referring to FIG. 6 and FIG. 8, the first metal shell 4 is provided with a contraction part 41 at the lower end, and the insulating sealing element 6 is partially clamped between the contraction part 41 and the second metal shell 5. The outer diameters of the first metal shell 4 and the second metal shell 5 are the same, and the direct butt joint cannot arrange the insulating sealing element 6. After the contraction part 41 is arranged, the insulating sealing element 6 can be arranged at the contraction part 41, and the sealing effect is good after the insulating sealing element 6 is extruded, which can better prevent electrolyte leakage. In addition, one or more annular protrusions 61 are arranged on the outer ring surface of the insulating sealing element 6, which can increase the sealing between the second metal shell 5. A horizontal sealing part 62 is further extended inward at the bottom of the insulating sealing element 6, which is attached to the lower surface of the first metal shell 4, and can increase the sealing between the first metal shell 4.

[0045] The application directly puts the winding cell assembly 3 into the second metal shell 5, seals the plastic frame 2 and the circuit assembly 1 in the first metal shell 4, and then completely seals the upper end of the second metal shell 5 by the first metal shell 4 and the insulating sealing element 6. The first metal shell 4 and the second metal shell 5 are butted up and down, controlling the up-and-down movement range of the winding cell assembly 3. The insulating sealing element 6 is arranged between the first metal shell 4 and the second metal shell 5 and is fixed by circumferential welding, and the connection strength of the first metal shell 4 and the second metal shell 5 is high, not easy to damage, the sealing performance is good, and it can effectively prevent electrolyte leakage. The insulating outer skin 7 is used to cover the circumferential welding spot 100, which does not affect the user's experience. The plastic frame 2 can play an isolation role, preventing unnecessary contact between the circuit assembly 1 and the first metal shell 4, not easy to short circuit, and ensuring electrical safety. Only one layer of steel shell is arranged outside the winding cell assembly 3, compared with the prior art, one layer of steel shell or soft shell is reduced, and the material cost is reduced.

[0046] A low-voltage lithium battery that can be industrialized is disclosed in Chinese Patent Application No. CN117673498A, entitled "A low-voltage lithium battery". In actual production, a rolling groove needs to be machined on the metal shell first, then the wound cell assembly is fixed in the metal shell, and then the positive tab is pulled out and welded with the bottom wall of the inner conductive cap. Only then can the plastic middle frame and circuit assembly be placed in the metal shell. Due to the above processing technology limitations, especially the wound cell assembly upper end protrudes into the metal shell deeply, requiring a longer positive tab. After the lithium battery is assembled, the positive tab is limited in a small space and the radial position is uncontrollable, which has the opportunity to contact the inner wall of the metal shell, causing short circuit and serious safety hazards.

[0047] Referring to FIGS. 3 and 11, the bottom wall of the first metal shell 4 is provided with a clamping hole 42, and a metal screw 8 is arranged at the clamping hole 42. The metal screw 8 is fixed at the clamping hole 42 by a plastic nut 9. The horizontal sealing portion 62 extends between the metal screw 8 and the bottom wall of the first metal shell 4, so as to insulate the metal screw 8 from the first metal shell 4. The metal screw 8 also seals the clamping hole 42, so that the electrolyte cannot seep into the first metal shell 4 from the clamping hole 42.

[0048] Referring to FIGS. 3 and 9, the circuit assembly 1 includes a PCB board 11, a low-voltage positive cap 12, a high-voltage positive connecting piece 13, a low-voltage positive elastic connecting piece 14, and a negative elastic sheet 15. The low-voltage positive elastic connecting piece 14, the high-voltage positive connecting piece 13, and the negative elastic sheet 15 are all welded on the PCB board 11. The negative elastic sheet 15 is in elastic contact with the first metal shell 4, the high-voltage positive connecting piece 13 is in elastic contact with the upper end of the metal screw 8, the positive tab 31 of the wound cell assembly 3 is welded with the lower end of the metal screw 8, and the negative tab 32 is welded with the second metal shell 5. The low-voltage positive cap 12 is arranged on the plastic frame 2, and the low-voltage positive elastic connecting piece 14 is in elastic contact with the low-voltage positive cap 12. The metal screw 8 passes through the clamping hole 42 of the first metal shell 4 and is insulated from the first metal shell 4. By using the conductivity of the metal screw 8, the high-voltage positive connecting piece 13 and the positive tab 31 form an electrical connection, and a high-voltage power input is provided for the circuit assembly 1.

[0049] Referring to FIGS. 5 and 8, the charging interface 16 and the PCB board 11 are both vertically placed, the low-voltage positive cap 12 is placed on the plastic frame 2, and is not directly welded with the PCB board 11. Therefore, the low-voltage positive elastic connecting piece 14 is arranged on the PCB board 11. The low-voltage positive elastic connecting piece 14 is in contact with the inner wall of the low-voltage positive cap 12, realizing a low-voltage 1.5V positive output. The low-voltage positive elastic connecting piece 14 can be a metal elastic sheet, a spring, or an elastic ejector pin.

[0050] Referring to FIG. 6, the circuit assembly 1 further comprises a charging interface 16, specifically a TYPE-C interface, or other standard interface. The charging interface 16 is welded on the PCB board 11. The first metal shell 4 and the insulating skin 7 are both provided with openings 43 and 71 at corresponding positions. The first metal shell 4 and the second metal shell 5 are used as common negative electrodes.

[0051] Referring to FIG. 8, the plastic frame 2 comprises an upper frame 21 and a lower frame 22, which are fixed by clamping. The PCB board 11 is fixed between the upper frame 21 and the lower frame 22. Of course, the upper frame 21 and the lower frame 22 can also be fixed by other means, such as ultrasonic welding, glue bonding, etc.

[0052] Referring to FIGS. 3 and 5, the first metal shell 4 is provided with a spinning edge 44 inwardly at the upper end, which is used to press the plastic frame 2. A positive-negative isolation sheet 10 is further provided below the spinning edge 44 (or above the spinning edge 44, as long as the spinning edge 44 and the low-voltage positive cap 12 do not overlap and short circuit), which effectively prevents the positive-negative isolation sheet 10 from falling off. Part of the upper surface of the positive-negative isolation sheet 10 is also wrapped by the insulating skin 7, further preventing the positive-negative isolation sheet 10 from falling off.

[0053] Referring to FIG. 7, the winding cell assembly 3 comprises a winding cell 33, an upper isolation sheet 34 and a lower isolation sheet 35. The positive electrode tab 31 passes out from the center hole of the upper isolation sheet 34, and the end is welded to the lower surface of the metal screw 8. The negative electrode tab 32 winds from the side of the winding cell 33 to the bottom surface, and the end is welded to the bottom wall of the second metal shell 5. The winding cell 33 is directly placed in the second metal shell 5 in the present application, which is one less layer of wrapping shell than the soft package lithium cell or hard shell lithium cell in the prior art, and the cost is lower.

[0054] The specific connection principle of the circuit is as follows: the positive electrode tab 31 of the winding cell assembly 3 is connected to the PCB board 11 through the metal screw 8 and the high-voltage positive connection sheet 13, and the negative electrode tab 32 of the winding cell assembly 3 is connected to the PCB board 11 through the second metal shell 5, the first metal shell 4 and the negative spring sheet 15. After being processed by the circuit on the PCB board 11, 1.5V positive voltage is output from the low-voltage positive cap 12, and the negative electrode of the lithium battery is output from the second metal shell 5.

[0055] The manufacturing method of the voltage-reducing lithium battery in the present embodiment comprises the following steps:

[0056] S1, the insulating sealing member 6 is sleeved on the lower end of the first metal shell 4, and the metal screw 8 and the plastic nut 9 are fixed at the clamping hole 42 of the first metal shell 4;

[0057] S2, fix the circuit assembly 1 on the plastic frame 2, and then put them into the first metal shell 4, so that the high-voltage positive connection piece 13 in the circuit assembly 1 is in elastic contact with the metal screw 8, and the negative spring piece 15 in the circuit assembly 1 is in elastic contact with the first metal shell 4;

[0058] S3, place the low-voltage positive cap 12 on the plastic frame 2, so that the low-voltage positive cap 12 is in elastic contact with the low-voltage positive elastic connecting piece 14, paste the positive and negative isolation piece 10 on the low-voltage positive cap 12, make the spinning edge 44 on the upper end of the first metal shell 4, and press the plastic frame 2, the low-voltage positive cap 12 and the positive and negative isolation piece 10 in the first metal shell 4, and the positive and negative isolation piece 10 can prevent the spinning edge 44 and the low-voltage positive cap 12 from short-circuiting;

[0059] S4, put the winding cell assembly 3 into the second metal shell 5, and weld the positive lug 31 of the winding cell assembly 3 to the bottom surface of the metal screw 8;

[0060] S5, press the insulating sealing piece 6 and the lower end of the first metal shell 4 into the second metal shell 5, and circumferentially weld the first metal shell 4 and the second metal shell 5;

[0061] S6, put on the insulating outer skin 7, heat and shrink, so that the insulating outer skin 7 wraps the first metal shell 4 and the second metal shell 5.

[0062] The manufacturing method described in the application has reasonable process, high yield, and can be industrialized and mass-produced.

[0063] The application sets the first metal shell 4 and the second metal shell 5, seals the circuit assembly 1 and the plastic frame 2 in the first metal shell 4, and sets the winding cell assembly 3 in the second metal shell 5, so that the upper end of the winding cell assembly 3 is shallow in the second metal shell 5, thus reducing the length requirement of the positive lug 31, although the radial position is also uncontrollable, but the length is not enough to contact the inner wall of the metal shell, and will not cause short circuit. In addition, the bottom of the insulating sealing piece 6 also extends inwardly to form a horizontal sealing part 62, which can cover the lower surface of the first metal shell 4, prevent the positive lug 31 from contacting the lower surface of the first metal shell 4, and also will not cause short circuit, so as to completely solve the risk of short circuit between the positive lug 31 and the metal shell.

[0064] The above are the preferred embodiments of the application, which do not limit the protection scope of the application, therefore: any equivalent changes made on the structure, shape and principle of the application shall be covered within the protection scope of the application.

Claims

1. A step-down lithium battery, characterized in that: The invention comprises a circuit assembly (1), a plastic frame (2), a wound cell assembly (3), a first metal shell (4), a second metal shell (5), an insulating seal (6) and an insulating outer skin (7); the circuit assembly (1) and the plastic frame (2) are arranged in the first metal shell (4); the plastic frame (2) is used to fix the circuit assembly (1); the wound cell assembly (3) is arranged in the second metal shell (5); the first metal shell (4) and the second metal shell (5) are butted against each other and fixed by circumferential welding; the insulating seal (6) is arranged between the first metal shell (4) and the second metal shell (5) and is used to seal the second metal shell (5); and the insulating outer skin (7) is covered on the outside of the first metal shell (4) and the second metal shell (5).

2. The step-down lithium battery according to claim 1, characterized in that A contraction portion (41) is provided at the lower end of the first metal shell (4), and the insulating seal (6) is partially clamped between the contraction portion (41) and the second metal shell (5).

3. The step-down lithium battery according to claim 2, characterized in that: The outer annular surface of the insulating seal (6) is provided with one or more annular protrusions (61) to increase the sealing performance between the insulating seal (6) and the second metal shell (5). The bottom of the insulating seal (6) also extends inwardly to form a horizontal sealing portion (62). The horizontal sealing portion (62) is in contact with the lower surface of the first metal shell (4) to increase the sealing performance between the insulating seal (6) and the first metal shell (4).

4. The step-down lithium battery according to claim 3, characterized in that: A clamping hole (42) is provided on the bottom wall of the first metal shell (4), and a metal screw (8) is provided at the clamping hole (42). The metal screw (8) is fixed to the clamping hole (42) by a plastic nut (9). The horizontal sealing portion (62) extends between the metal screw (8) and the bottom wall of the first metal shell (4) and is used to insulate the metal screw (8) from the first metal shell (4). The metal screw (8) is also used to seal the clamping hole (42). The circuit assembly (1) comprises a PCB board (11), a low-voltage positive electrode cap (12), a high-voltage positive electrode connecting piece (13), a low-voltage positive electrode elastic connector (14) and a negative electrode spring (15); the low-voltage positive electrode elastic connector (14), the high-voltage positive electrode connecting piece (13) and the negative electrode spring (15) are all welded on the PCB board (11); the negative electrode spring (15) is in elastic contact with the first metal shell (4); the high-voltage positive electrode connecting piece (13) is in elastic contact with the upper end of the metal screw (8); the positive electrode tab (31) of the wound battery cell assembly (3) is welded to the lower end of the metal screw (8), and the negative electrode tab (32) is welded to the second metal shell (5); the low-voltage positive electrode cap (12) is arranged on the plastic frame (2); and the low-voltage positive electrode elastic connector (14) is in elastic contact with the low-voltage positive electrode cap (12).

5. The step-down lithium battery according to claim 4, characterized in that: The low-voltage positive electrode elastic connector (14) is a metal spring, a spring or an elastic ejector pin.

6. The step-down lithium battery according to claim 4, characterized in that: The circuit assembly (1) further comprises a charging interface (16), the charging interface (16) being welded on the PCB board (11), and openings are provided at corresponding positions of the first metal shell (4) and the insulating outer skin (7).

7. The step-down lithium battery according to claim 4, characterized in that: The plastic frame (2) comprises an upper frame (21) and a lower frame (22); the upper frame (21) and the lower frame (22) are fixed by snapping; and the PCB board (11) is fixed between the upper frame (21) and the lower frame (22).

8. The step-down lithium battery according to claim 1, wherein: A spun edge (44) is provided inwardly at the upper end of the first metal shell (4) for pressing the plastic frame (2). A positive and negative electrode separator (10) is also provided above or below the spun edge (44). Part of the upper surface of the positive and negative electrode separator (10) is also wrapped by an insulating outer skin (7).

9. The step-down lithium battery according to claim 4, characterized in that: The wound battery cell assembly (3) comprises a wound battery cell (33), an upper separator (34) and a lower separator (35); the positive electrode tab (31) extends through the central hole of the upper separator (34) and is welded at its end to the lower surface of the metal screw (8); the negative electrode tab (32) is wound from the side of the wound battery cell (33) to the bottom surface and is welded at its end to the bottom wall of the second metal shell (5).

10. A method for manufacturing a step-down lithium battery according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1, sleeve the insulating seal (6) on the lower end of the first metal shell (4), and fix the metal screw (8) and the plastic nut (9) at the clamping hole (42) of the first metal shell (4); S2, fix the circuit assembly (1) on the plastic frame (2), and then install them together into the first metal shell (4), so that the high-voltage positive electrode connecting piece (13) in the circuit assembly (1) is in elastic contact with the metal screw (8), and the negative electrode spring (15) in the circuit assembly (1) is in elastic contact with the first metal shell (4); S3, placing the low-voltage positive electrode cap (12) on the plastic frame (2), making the low-voltage positive electrode cap (12) elastically contact with the low-voltage positive electrode elastic connector (14), making a spinning edge (44) at the upper end of the first metal shell (4), and pressing the plastic frame (2) and the low-voltage positive electrode cap (12) into the first metal shell (4); S4, placing the wound battery cell assembly (3) into the second metal housing (5), and welding the positive electrode tab (31) of the wound battery cell assembly (3) to the bottom surface of the metal screw (8); S5, pressing the insulating seal (6) and the lower end of the first metal shell (4) into the second metal shell (5), and performing circumferential welding on the first metal shell (4) and the second metal shell (5); S6, putting on the insulating outer skin (7), heating and shrinking it, so that the insulating outer skin (7) is wrapped around the first metal shell (4) and the second metal shell (5).

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