Cylindrical lithium metal secondary battery

Abstract

A cylindrical lithium metal secondary battery includes a case, a cell electrode group installed in the case, and an electrolyte filled in the case. The cell electrode group includes a wound electrode group and tabs installed on the wound electrode group. The wound electrode group is formed by winding a positive electrode, a negative electrode, and a separator. The negative electrode is a metallic lithium sheet, and the metallic lithium sheet serves as a negative electrode current collector and negative electrode active material. This cylindrical lithium metal secondary battery uses a metallic lithium sheet as the negative electrode, which functions as both an active material and a current collector, eliminating the need for a conventional copper current collector. This significantly reduces the thickness between the separators of the wound electrode group and significantly improves the energy density of the battery. The cylindrical battery's structure allows for stable charge / discharge cycles even when no external pressure is applied.

Description

[Technical Field]

[0001] TECHNICAL FIELD The present disclosure relates to the field of lithium batteries, and more particularly to cylindrical lithium metal secondary batteries.

[0002] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to a Chinese patent application filed on November 4, 2022, with application number 202211379585.3, entitled "Cylindrical Lithium Metal Secondary Battery," with the State Intellectual Property Office of China, and also claims priority to a Chinese patent application filed on November 4, 2022, with application number 202222962861.0, entitled "Cylindrical Lithium Metal Secondary Battery," with the State Intellectual Property Office of China, and the entire contents of which are incorporated herein by reference. [Background technology]

[0003] Lithium-ion batteries store and discharge energy through the concentration difference of lithium ions; they do not contain metallic lithium. Lithium metal batteries use metallic lithium as an electrode and generate electrical energy through the corrosion or oxidation of metallic lithium. Because metallic lithium has an extremely high theoretical capacity, the lowest reduction potential, and extremely low density, the energy density of lithium metal batteries is far greater than that of other battery systems. Current lithium metal batteries are primarily disposable batteries that are discarded after use and cannot be recharged, so they are also called primary batteries. Lithium metal secondary batteries are rechargeable lithium batteries that use lithium metal as the anode, and there are several types of lithium metal secondary batteries depending on the cathode material.

[0004] Furthermore, most lithium secondary metal batteries are soft-packaged batteries, and because of the problem of volume expansion of metallic lithium, they must be operated under conditions where an external clamping member applies pressure, which causes significant inconvenience in testing and use of the batteries. Summary of the Invention

[0005] The present disclosure provides a cylindrical lithium metal secondary battery to solve technical problems such as high complexity of use, low safety, and low energy density of lithium metal secondary batteries in the related art.

[0006] The present disclosure solves the above technical problems by adopting the following technical solutions.

[0007] A cylindrical lithium metal secondary battery includes a case, a cell electrode group installed in the case, and an electrolyte solution filled in the case. The cell electrode group includes a wound electrode group and tabs installed on the wound electrode group. The wound electrode group is formed by winding a positive electrode, a negative electrode, and a separator. The negative electrode is a metallic lithium sheet, and the metallic lithium sheet serves as a negative electrode current collector and a negative electrode active material.

[0008] The cylindrical lithium metal secondary battery disclosed herein uses a metallic lithium sheet as the negative electrode, which functions as both an active material and a current collector, eliminating the need for a conventional copper current collector, significantly reducing the thickness between the separators of the wound electrode assembly, and significantly improving the energy density of the battery. Furthermore, the cylindrical battery structure allows for stable charge-discharge cycles without the application of external pressure.

[0009] In one embodiment of the present disclosure, the cylindrical lithium metal secondary battery may have an assembly coefficient of 88.5% to 93.2%.

[0010] By adopting a fixed assembly coefficient, the stability of the charge-discharge cycle of this cylindrical lithium metal secondary battery when no external pressure is applied can be further improved, battery testing and operating environment can be simplified, and battery operating costs can be reduced.

[0011] In one embodiment of the present disclosure, the case may be made of steel.

[0012] By using a steel case, the case has relatively hard properties and relatively high mechanical strength, and by matching the appropriate assembly coefficient, it can provide the pressure required for the cylindrical metal secondary battery to operate itself, and no additional pressure supply device is required.

[0013] In one embodiment of the present disclosure, the thickness of the metallic lithium sheet is ≦50 μm.

[0014] The present disclosure uses an extremely thin metallic lithium sheet as the negative electrode, which not only eliminates the need for an extra current collector but also significantly reduces the thickness between separators in the wound electrode group, thereby significantly improving the energy density of the battery.

[0015] In one embodiment of the present disclosure, the tabs may include a positive electrode tab and a negative electrode tab, and the positive electrode tab and the negative electrode tab are connected to the positive electrode and the negative electrode, respectively.

[0016] In one embodiment of the present disclosure, the positive electrode tab may be an aluminum tape, and the negative electrode tab may be a nickel belt.

[0017] In one embodiment of the present disclosure, the positive electrode may include a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector. Optionally, the positive electrode active material layer is formed by mixing an active material, a conductive agent, and a binder.

[0018] In one embodiment of the present disclosure, the areal density of the positive electrode active material layer is less than 40 mg / cm 2 is.

[0019] In one embodiment of the present disclosure, the positive electrode current collector may be an aluminum foil.

[0020] In one embodiment of the present disclosure, the positive electrode active material may include any one of lithium cobalt oxide, a ternary material, and a lithium iron phosphate material.

[0021] In one embodiment of the present disclosure, the cylindrical lithium metal secondary battery is any one of an 18650 cylindrical battery, a 14500 cylindrical battery, and a 21700 cylindrical battery. Optionally, the 18650 cylindrical battery has a gravimetric energy density of ≥ 380 Wh / kg, a volumetric energy density of ≥ 850 Wh / L, and a capacity of > 4000 mAh.

[0022] In one embodiment of the present disclosure, high temperature tape may be applied to the positive electrode tab and the negative electrode tab.

[0023] In one embodiment of the present disclosure, the cylindrical lithium metal secondary battery may further include a cap, and the cap is installed on the top of the case.

[0024] In one embodiment of the present disclosure, the positive electrode tab may be welded to the cap, and the negative electrode tab may be welded to the inner bottom of the case.

[0025] In one embodiment of the present disclosure, the separator may be a porous polymer separator. Optionally, the thickness of the separator may be 20 to 25 μm.

[0026] In one embodiment of the present disclosure, the electrolytic solution may be a non-aqueous electrolytic solution.

[0027] In one embodiment of the present disclosure, an upper insulating gasket and a lower insulating gasket may be respectively provided at the top and bottom of the electrode assembly of the cell, and optionally, the upper insulating gasket and the lower insulating gasket may be provided with elongated holes through which the positive electrode tab and the negative electrode tab pass, respectively.

[0028] Compared with the related art, the beneficial effects of the present disclosure include at least the following:

[0029] Compared with primary lithium metal batteries, the cylindrical lithium metal secondary battery of the present disclosure can be charged and discharged multiple times, has a higher load voltage, and is more resource-efficient and environmentally friendly. Compared with soft-packaged secondary lithium metal batteries, the lithium metal secondary battery of the present disclosure can provide the necessary pressure itself, eliminating the need for an external pressure device, simplifying battery testing and operating environment, and reducing battery operating costs. At the same time, the extremely thin lithium metal sheet serves as both the active material and current collector, eliminating the need for a commonly used negative electrode current collector, and providing the lithium metal secondary battery with excellent capacity and energy density. In order to more clearly describe the technical solutions in the specific embodiments of the present disclosure or the related art, the following briefly describes the accompanying drawings required for use in the description of the specific embodiments or the related art. It is clear that the accompanying drawings in the following description are some embodiments of the present disclosure, and those skilled in the art can obtain other accompanying drawings based on these accompanying drawings without any creative efforts. [Brief explanation of the drawings]

[0030] [Figure 1] 1 is a schematic diagram of the structure of a cylindrical lithium metal secondary battery provided by an embodiment of the present disclosure. [Figure 2] 1 is a schematic diagram of the structure of an electrode group of a cell provided by an embodiment of the present disclosure. [Figure 3] 1 is a schematic diagram of a partial cross-sectional structure of an electrode group of a cell provided by an embodiment of the present disclosure. [Figure 4] Charging and discharging curves of the 18650 cylindrical lithium metal secondary battery provided in Example 1 of the present disclosure. [Figure 5] 1 is a graph based on the discharge capacity versus the number of cycles of an 18650 cylindrical lithium metal secondary battery according to Example 1 of the present disclosure. [Figure 6] 1 is a graph based on the discharge capacity versus the number of cycles of an 18650 cylindrical lithium metal secondary battery according to Example 2 of the present disclosure. [Figure 7] 1 is a graph based on the discharge capacity versus cycle number of an 18650 cylindrical lithium metal secondary battery according to Example 3 of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0031] The technical solutions of the present disclosure will be explained clearly and completely below with the aid of the accompanying drawings and specific embodiments. However, it will be apparent to those skilled in the art that the examples described below are only some of the examples of the present disclosure, not all of the examples, and are intended merely to illustrate the present disclosure and not to limit the scope of the present disclosure. Based on the examples in the present disclosure, all other examples that can be obtained by those skilled in the art without any creative effort fall within the scope of protection of the present disclosure. Unless specific conditions are specified in the examples, they are carried out under normal conditions or conditions suggested by the manufacturer. Unless the manufacturer of the reagents or equipment used is specified, they are all ordinary products that can be purchased commercially.

[0032] In describing the present disclosure, it should be explained that the orientations or positional relationships indicated by the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," etc. are based on the orientations or positional relationships shown in the accompanying drawings, and are intended only to facilitate and simplify the description of the present disclosure, and are not intended to indicate or imply that the indicated devices or components must have a particular orientation or be configured and operated in a particular orientation, and should not be understood to limit the present disclosure. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only, and should not be understood to indicate or imply relative importance.

[0033] It should be noted that in the description of the present disclosure, unless otherwise clearly specified and limited, the terms "attached," "interconnected," and "connected" should be understood in a broad sense, and may refer to, for example, a fixed connection, a detachable connection, an integral connection, a mechanical connection, an electrical connection, a direct interconnection, an indirect interconnection via an intermediate medium, or an internal connection between two members. Those skilled in the art can understand the specific meanings of the above terms in the present disclosure based on specific circumstances.

[0034] Fig. 1 is a schematic diagram of the structure of a cylindrical lithium metal secondary battery provided by an embodiment of the present disclosure, Fig. 2 is a schematic diagram of the structure of a cell electrode group provided by an embodiment of the present disclosure, and Fig. 3 is a schematic diagram of a partial cross-sectional structure of a cell electrode group provided by an embodiment of the present disclosure. As shown in Figs. 1, 2, and 3, the cylindrical lithium metal secondary battery provided by this embodiment may include a case 1, a cell electrode group 2 installed in the case 1, and an electrolyte filled in the case 1, the cell electrode group 2 may include a wound electrode group and tabs installed on the wound electrode group, the wound electrode group may be formed by winding a positive electrode 21, a negative electrode 22, and a separator 23, and the negative electrode 22 may be a metallic lithium sheet, with the metallic lithium sheet serving as the negative electrode current collector and negative electrode active material.

[0035] Batteries using a metallic lithium sheet as the anode have very high energy density, but as the charge and discharge cycles of the battery progress, the lithium anode expands, increasing its thickness and causing a rapid decline in battery performance. Therefore, external pressure is required to assist the battery's operation. However, the aluminum-plastic film of soft-packaged batteries is relatively soft and provides very little restraint force, requiring additional clamping members to provide the required pressure, which makes the battery testing or use process too complicated.

[0036] The cylindrical lithium metal secondary battery disclosed herein uses a metallic lithium sheet as the negative electrode, which functions as both an active material and a current collector, eliminating the need for a conventional copper current collector, significantly reducing the thickness between the separators of the wound electrode assembly, and significantly improving the energy density of the battery. The cylindrical battery structure allows for stable charge-discharge cycles without the application of external pressure.

[0037] Optionally, at least one end of the case 1 may be open. The case 1 may further include a cap 3 disposed on the open end of the case 1.

[0038] Optionally, the cylindrical lithium metal secondary battery may have an assembly factor of 88.5% to 93.2%.

[0039] For example, in different embodiments, the cylindrical lithium metal secondary battery may have an assembly factor of 88.5%, 89.5%, 90%, 90.5%, 91.5%, 92.5%, 93.2%, and so on.

[0040] By adopting the above assembly coefficient, the charge / discharge cycle stability of the cylindrical lithium metal secondary battery without external pressure can be further improved, battery testing and operating environment can be simplified, battery operating costs can be reduced, and the capacity and energy density of the cylindrical lithium metal secondary battery can be ensured.

[0041] In actual operation, the assembly coefficient is adjusted by adjusting the amount, thickness, and length of the positive electrode active material layer 212 of the positive electrode 21, the thickness and length of the negative electrode 22, and the thickness and length of the separator 23. For example, if the thickness of the electrode sheet is fixed, the assembly coefficient can be adjusted by adjusting the length of the electrode sheet, or vice versa. Specifically, the formula for calculating the assembly coefficient is assembly coefficient = cross-sectional area of ​​wound cell / inner cross-sectional area of ​​case.

[0042] Optionally, the material of the case 1 may be steel. The steel case 1 has a relatively hard property and a relatively high mechanical strength, and can provide the pressure necessary for the cylindrical metal secondary battery to operate itself, without requiring any device to provide additional pressure.

[0043] Wherein, the electrode group 2 of the cell may be an electrode group of a cylindrical cell, and the case 1 may be a cylindrical case.

[0044] Optionally, the thickness of the sidewall of the case 1 may be the same as that of a conventional cylindrical battery case.

[0045] In actual operation, the positive electrode 21 and the negative electrode 22 are separated by the separator 23 and wound to form a wound electrode group. For example, the wound electrode group may be formed by stacking the positive electrode 21, the separator 23, the negative electrode 22, and the separator 23 in this order and winding them.

[0046] Optionally, the thickness of the metallic lithium sheet is 50 μm or less. For example, in different embodiments, the thickness of the metallic lithium sheet may be, but is not limited to, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, etc.

[0047] By using a lithium metal sheet of the above thickness and combining it with a corresponding assembly coefficient and steel case, the pressure provided by the steel case of the battery can be adjusted, ensuring stability during charging and discharging operations and ensuring the manufacturability of the wound electrode group.

[0048] Optionally, the positive electrode 21 may include a positive electrode current collector 211 and a positive electrode active material layer 212 disposed on the surface of the positive electrode current collector 211. For example, the positive electrode current collector 211 may be an aluminum foil.

[0049] Optionally, the material of the positive electrode active material layer 212 may be formed by mixing an active material, a conductive agent, and a binder.

[0050] In actual operation, the positive electrode active material layer 212 may be formed by coating a positive electrode material on the surface of the positive electrode current collector 211 and drying it. The active material may be a mixture of materials based on its composition. The active material may include any one of lithium cobalt oxide, a ternary material, and a lithium iron phosphate material. For example, the ternary material may be a high-nickel ternary material. The conductive agent may include any one of carbon black, conductive graphite, carbon nanotubes, and carbon fiber. The binder may be any one of polyvinylidene fluoride, polyamide resin, and sodium carboxymethyl cellulose.

[0051] The present disclosure does not limit the material of the positive electrode active material layer, and any material may be used as long as it can be combined with a lithium metal negative electrode to form a positive electrode active material for a lithium metal secondary battery.

[0052] Optionally, the areal density of the positive electrode active material layer 212 is less than 40 mg / cm 2For example, in a different embodiment, the areal density of the positive electrode active material layer 212 is 38 mg / cm 2 , 35 mg / cm 2 , 32 mg / cm 2 , 30 mg / cm 2 , 25 mg / cm 2 , 20 mg / cm 2 , 15 mg / cm 2 It may be, but is not limited to, the above.

[0053] In the present disclosure, by combining a positive electrode active material layer 212 with a predetermined surface density and a metallic lithium sheet with a predetermined thickness, the strength of the steel case 1 can be ensured to ensure the pressure required for the cylindrical metal secondary battery itself to operate, thereby ensuring the stability and safety of the battery operation.

[0054] Optionally, the cylindrical lithium metal secondary battery may be any one of an 18650 cylindrical battery, a 14500 cylindrical battery, and a 21700 cylindrical battery. The 18650 cylindrical battery has a gravimetric energy density of ≥ 380 Wh / kg, a volumetric energy density of ≥ 850 Wh / L, and a capacity of > 4000 mAh.

[0055] Optionally, the tabs may include a positive electrode tab 24 and a negative electrode tab (not shown), which may be connected to the positive electrode 21 and the negative electrode 22, respectively.

[0056] For example, in actual operation, the positive electrode tab 24 and the negative electrode tab may be welded to the positive electrode 21 and the negative electrode 22, respectively, to ensure connection stability.

[0057] Optionally, the positive electrode tab 24 may be an aluminum tape and the negative electrode tab may be a nickel belt.

[0058] In actual operation, the dimensions of the positive electrode tab 24 and the negative electrode tab may be adjusted based on actual needs.

[0059] Optionally, high temperature tape 25 may be applied to the positive electrode tab 24 and the negative electrode tab. High temperature tape 25 may be applied by wrapping around the positive electrode tab 24 and the negative electrode tab, respectively.

[0060] Optionally, the positive electrode tab 24 may be welded to the cap 3 and the negative electrode tab may be welded to the inside bottom of the steel case 1 .

[0061] Optionally, the separator 23 may be a porous polymer separator, and the material of the separator 23 may be a PP / PE / PP composite membrane, etc.

[0062] Optionally, the thickness of the separator may be 20 to 25 μm, for example, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, etc.

[0063] Optionally, the electrolyte may be a non-aqueous electrolyte, such as a carbonate-based electrolyte.

[0064] Optionally, an upper insulating gasket 26 and a lower insulating gasket 27 may be provided at the top and bottom of the cell's electrode group 2, respectively. Optionally, the upper insulating gasket 26 and the lower insulating gasket 27 may be provided with elongated holes through which the positive electrode tab 24 and the negative electrode tab pass, respectively.

[0065] Furthermore, in order to ensure the sealing of the cylindrical lithium metal secondary battery, a sealing ring may be installed on the case 1 or the cap 3, and a snap fit portion or a groove may be installed on the case 1 or the cap 3, respectively, to ensure better sealing between the case 1 and the cap 3.

[0066] Compared with lithium metal primary batteries, the cylindrical lithium metal secondary battery provided in this embodiment can be charged and discharged multiple times, has a higher load voltage, is more resource-efficient and environmentally friendly, and provides the necessary pressure itself, eliminating the need for an external pressure device, simplifying battery testing and operating conditions, and reducing battery operating costs. At the same time, the metallic lithium sheet serves as the negative electrode, acting as both an active material and a current collector, eliminating the need for the commonly used copper current collector, and significantly reducing the thickness between the separators of the wound electrode assembly, significantly improving the energy density and capacity of the battery.

[0067] Taking the 18650 cylindrical battery as an example, the cylindrical lithium metal secondary battery disclosed herein has a nominal voltage increase of 100-200mV, an improved battery capacity of 4095mAh, a nearly 20% reduction in battery weight, and a significant improvement in weight-based energy density. The 18650-4.1Ah battery disclosed herein has reached new milestones in capacity, nominal voltage, and energy density.

[0068] Furthermore, the embodiments of the present disclosure also provide a method for assembling a cylindrical lithium metal secondary battery. S1: The positive electrode 21 and the positive electrode tab 24 are welded together, and the negative electrode 22 and the negative electrode tab are welded together. S2: The positive electrode 21 to which the positive electrode tab 24 is welded and the negative electrode 22 to which the negative electrode tab is welded are separated by the separator 23 and wound up to obtain the electrode group 2 of the cell, and then S3: The electrode group 2 of the cell is placed in the steel case 1, grooved and welded, and then the electrolyte is injected and packaged to obtain a cylindrical lithium metal secondary battery.

[0069] Example 1 This embodiment provides an 18650 cylindrical lithium metal secondary battery including a case, a cell electrode group installed in the case, and an electrolyte filled in the case, wherein the cell electrode group includes a wound electrode group and tabs installed on the wound electrode group, the wound electrode group is formed by winding a positive electrode, a negative electrode, and a separator, the negative electrode is a metallic lithium sheet, and the metallic lithium sheet serves as the negative electrode current collector and negative electrode active material.

[0070] A method for manufacturing the battery includes the following steps:

[0071] (1) Preparation of positive electrode sheet (positive electrode plate, positive electrode): Positive electrode material (NCM811), binder (PVDF), and conductive agent (Super-P) were uniformly mixed in a solvent in a mass ratio of 96:2:2 to obtain a sheet with a loading of 35 mg / cm. 2 The obtained slurry was applied to an aluminum foil, dried, roll-pressed, and cut to obtain a positive electrode sheet having a thickness of 120 μm and a length of 950 mm. A positive electrode tab was then welded to the positive electrode sheet.

[0072] (2) Production of negative electrode sheet (negative electrode plate, negative electrode): A 50 μm thick metallic lithium sheet was used as the negative electrode, and a negative electrode sheet with a length of 1000 mm was obtained by cutting it. Then, a negative electrode tab was connected to this negative electrode sheet.

[0073] (3) The separator, which is a PP / PE / PP composite membrane, is cut to a length of 1050 mm.

[0074] (4) The positive electrode sheet and the negative electrode sheet are separated by a separator and wound to obtain a cell electrode group, and then the assembly coefficient of the cell electrode group is calculated to be 90.5%;

[0075] (5) The electrode group of the cell is placed in a steel battery case, and after processes such as grooving, welding, injection of carbonate-based electrolyte, and packaging, a complete cylindrical lithium metal secondary battery is obtained.

[0076] The 18650 cylindrical battery of this embodiment has a nominal voltage of 3.8V, a weight of 40g, a gravimetric energy density of 389Wh / kg, and a volumetric energy density of 888Wh / L.

[0077] FIG. 4 shows the charge / discharge curve of the 18650 cylindrical lithium metal secondary battery provided in Example 1.

[0078] Example 2 This embodiment is based on the first embodiment, and the difference is that the assembly coefficient is different.

[0079] In this example, the lengths of the positive electrode sheet and the negative electrode sheet were adjusted so that the assembly factor was 88.5%.

[0080] Example 3 This embodiment is based on the first embodiment, and the difference is that the assembly coefficient is different.

[0081] In this example, the lengths of the positive electrode sheet and the negative electrode sheet were adjusted so that the assembly factor was 93.2%.

[0082] The different assembly factors adopted by the 18650 cylindrical lithium metal secondary batteries manufactured according to Examples 1, 2 and 3, and the lengths of the positive electrode, negative electrode and separator adopted are shown in Table 1.

[0083] [Table 1] This shows that the assembly coefficient of the cylindrical lithium metal secondary battery can be adjusted by adjusting the length of the positive electrode, the length of the negative electrode, and the length of the separator in different embodiments of the present application.

[0084] 5 to 7 show graphs of discharge capacity versus cycle number for 18650 cylindrical lithium metal secondary batteries fabricated by the methods of Example 1, Example 2, and Example 3 of the present disclosure, respectively.

[0085] As shown in Figure 5, the horizontal axis represents the number of cycles of the cylindrical lithium metal secondary battery, and the vertical axis represents the discharge capacity of the cylindrical lithium metal secondary battery. As shown in Figure 5, the initial discharge capacity of the cylindrical lithium metal secondary battery with an assembly coefficient of 90.5% based on Example 1 was 3963 mAh. As the number of cycles increased, the discharge capacity initially increased slightly, reaching 4047 mAh, and then maintained a relatively stable level. After 50 cycles, the discharge capacity remained at 3879 mAh, maintaining 97.8% of the initial discharge capacity. Therefore, the 18650 cylindrical lithium metal secondary battery of Example 1 of the present disclosure exhibited good cycle performance.

[0086] Furthermore, as shown in Figure 6, the initial discharge capacity of the cylindrical lithium metal secondary battery with an assembly coefficient of 88.5% based on Example 2 was 3909 mAh. With increasing cycle count, the discharge capacity initially increased slightly to 3936 mAh and then remained at a relatively stable level. After 50 cycles, the discharge capacity remained at 3820 mAh, maintaining 97.7% of the initial discharge capacity. Therefore, the 18650 cylindrical lithium metal secondary battery of Example 2 of the present disclosure has good cycle performance.

[0087] 7, the initial discharge capacity of the cylindrical lithium metal secondary battery with an assembly coefficient of 93.2% based on Example 3 was 4055 mAh. With increasing cycle count, the discharge capacity initially increased slightly to 4122 mAh and then remained at a relatively stable level. After 50 cycles, the discharge capacity remained at 3955 mAh, maintaining 97.5% of the initial discharge capacity. Therefore, the 18650 cylindrical lithium metal secondary battery of Example 3 of the present disclosure exhibited good cycle performance.

[0088] As can be seen from Figures 5 to 7, cylindrical lithium metal secondary batteries with assembly factors of 90.5%, 88.5%, and 93.2% have stable charge / discharge performance. As can be seen from these figures, by adopting the above-mentioned assembly factors of the present application, the charge / discharge cycle stability of the cylindrical lithium metal secondary battery without external pressure can be further improved, battery testing and operating environment can be simplified, and battery operating costs can be reduced. Furthermore, the technical solution of the present application can also ensure the capacity and energy density of the cylindrical lithium metal secondary battery.

[0089] Finally, it should be noted that the above examples are only used to explain the technical solutions of the present disclosure, and are not intended to be limiting thereof. Although the present disclosure has been described in detail with reference to the above examples, it should be understood that a person skilled in the art may modify the technical solutions described in the above embodiments or equally replace some or all of the technical features thereof, and such modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present disclosure. [Industrial Applicability]

[0090] This application relates to the technical field of lithium batteries, and more particularly to cylindrical lithium metal secondary batteries. A cylindrical lithium metal secondary battery includes a case, a cell electrode group installed in the case, and an electrolyte filled in the case. The cell electrode group includes a wound electrode group and tabs installed on the wound electrode group. The wound electrode group is formed by winding a positive electrode, a negative electrode, and a separator. The negative electrode is a metallic lithium sheet, and the metallic lithium sheet serves as both a negative electrode current collector and a negative electrode active material. The cylindrical lithium metal secondary battery disclosed herein uses a metallic lithium sheet as the negative electrode, which functions as both an active material and a current collector. This eliminates the need for a conventional copper current collector, significantly reduces the thickness between the separators of the wound electrode group, and significantly improves the energy density of the battery. The cylindrical battery's structure ensures stable charge / discharge cycles even when no external pressure is applied.

[0091] Furthermore, it can be understood that the cylindrical lithium metal secondary battery of the present application is reproducible and can be used in a variety of industrial applications, for example, the cylindrical lithium metal secondary battery of the present application can be used in the field of lithium battery technology. [Explanation of symbols]

[0092] 1 case, 2 cell electrode group, 3 cap, 21 positive electrode, 22 negative electrode, 23 separator, 24 positive electrode tab, 25 high-temperature tape, 26 upper insulating gasket, 27 lower insulating gasket, 211 positive electrode current collector, 212 positive electrode active material layer.

Claims

1. A cylindrical lithium metal secondary battery including a case, an electrode group of a cell placed in the case, and an electrolyte solution filled in the case, The electrode group of the cell includes a wound electrode group and a tab attached to the wound electrode group, the wound electrode group is formed by winding a positive electrode, a negative electrode, and a separator, The negative electrode is a metallic lithium sheet, and the metallic lithium sheet serves as a negative electrode current collector and a negative electrode active material.

2. 2. The cylindrical lithium metal secondary battery according to claim 1, wherein the cylindrical lithium metal secondary battery has an assembly factor of 88.5% to 93.2%.

3. 3. The cylindrical lithium metal secondary battery according to claim 1, wherein the case is made of steel.

4. 4. The cylindrical lithium metal secondary battery according to claim 1, wherein the thickness of the metallic lithium sheet is ≦50 μm.

5. 5. The cylindrical lithium metal secondary battery according to claim 1, wherein the tabs include a positive electrode tab and a negative electrode tab, the positive electrode tab being an aluminum tape, and the negative electrode tab being a nickel belt.

6. 5. The cylindrical lithium metal secondary battery according to claim 1, wherein the tabs include a positive electrode tab and a negative electrode tab, and the positive electrode tab and the negative electrode tab are connected to the positive electrode and the negative electrode, respectively.

7. 7. The cylindrical lithium metal secondary battery according to claim 6, wherein said positive electrode tab is an aluminum tape and said negative electrode tab is a nickel belt.

8. 8. The cylindrical lithium metal secondary battery according to claim 5, wherein high-temperature tapes are attached to the positive electrode tab and the negative electrode tab.

9. 9. The cylindrical lithium metal secondary battery of claim 8, further comprising a cap, the cap being disposed above the case.

10. 10. The cylindrical lithium metal secondary battery according to claim 9, wherein the positive electrode tab is welded to the cap, and the negative electrode tab is welded to the inner bottom of the case.

11. 4. The cylindrical lithium metal secondary battery according to claim 3, wherein the positive electrode comprises a positive electrode current collector and a positive electrode active material layer disposed on the surface of the positive electrode current collector; The surface density of the positive electrode active material layer is less than 40 mg / cm ２ .

12. 12. The cylindrical lithium metal secondary battery according to claim 11, wherein the material of the positive electrode active material layer is formed by mixing an active material, a conductive agent, and a binder.

13. 13. The cylindrical lithium metal secondary battery according to claim 11, wherein the positive electrode current collector is an aluminum foil.

14. 14. The cylindrical lithium metal secondary battery according to claim 11, wherein the positive electrode active material comprises any one of lithium cobalt oxide, ternary materials, and lithium iron phosphate materials.

15. 15. The cylindrical lithium metal secondary battery according to claim 1, wherein the cylindrical lithium metal secondary battery is any one of an 18650 cylindrical battery, a 14500 cylindrical battery, and a 21700 cylindrical battery.

16. 16. The cylindrical lithium metal secondary battery of claim 15, wherein the cylindrical lithium metal secondary battery has a gravimetric energy density ≥ 380 Wh / kg, a volumetric energy density ≥ 850 Wh / L, and a capacity > 4000 mAh.

17. the separator is a porous polymer separator, 17. The cylindrical lithium metal secondary battery according to claim 1, wherein the separator has a thickness of 20 to 25 μm.

18. 18. The cylindrical lithium metal secondary battery according to claim 1, wherein the electrolytic solution is a non-aqueous electrolytic solution.

19. 8. The cylindrical lithium metal secondary battery according to claim 5, wherein an upper insulating gasket and a lower insulating gasket are respectively installed on the top and bottom of the electrode group of the cell.

20. 20. The cylindrical lithium metal secondary battery of claim 19, wherein the upper insulating gasket and the lower insulating gasket are provided with elongated holes through which the positive electrode tab and the negative electrode tab pass, respectively.

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