Cylindrical lithium battery

Abstract

The utility model relates to secondary battery field discloses a cylindrical lithium cell. The cylindrical lithium cell includes cylindrical shell and the roll core and porous liquid absorption sheet of setting in the inside of cylindrical shell, and the porous liquid absorption sheet sets up between the end cover of the end of roll core and cylindrical shell. The cylindrical lithium cell provided by the utility model through setting the porous liquid absorption sheet in the inside of cylindrical shell, absorbs free electrolyte to store when injecting electrolyte, reduces the negative influence of excessive electrolyte when injecting, under high SOC, the electrolyte of free electrolyte in the porous liquid absorption sheet is extruded and contacted with the electrolyte of participating in circulation under the expansion of pole piece, and the active material of in situ supplementing circulation consumption is supplemented, the whole in the charging and discharging process, the periodic contact of porous liquid absorption sheet and the electrolyte of electric core, guarantee active material periodic release, prolongs electrolyte effective time.

Description

Technical Field

[0001] This utility model relates to the field of secondary batteries, specifically to a cylindrical lithium battery. Background Technology

[0002] Large-size cylindrical lithium batteries, with their high energy density and standardized structure leading to good processability, have been widely used in the power sector. However, their compact internal dimensions cause the lithium salts and additives in the limited electrolyte to be rapidly consumed and squeezed into specific areas of the battery (especially the top cover area) during charging and discharging. This results in increased internal resistance and severe lithium plating in these areas due to decreased electrolyte conductivity, poor film formation, and other issues. Current efforts mainly focus on improving these issues by developing slow-release additives and increasing the concentration of lithium salts or additives. However, the former involves complex synthesis of slow-release additives, which cannot initially release an effective concentration and are prone to introducing new impurities; the latter increases the cost, electrolyte viscosity, and the degree of side reactions by increasing the concentration of active materials.

[0003] To address the aforementioned issues, current solutions include adding liquid-absorbing structures to the battery to increase electrolyte retention and mitigate electrolyte consumption. However, these liquid-absorbing structures are located inside the battery cell or are used to enclose the cell, hindering electrolyte diffusion and affecting battery heat dissipation. Furthermore, the electrolyte absorbed inside the liquid-absorbing structure remains in long-term contact with the electrolyte in the battery cell, causing the absorbed active materials to be rapidly consumed, resulting in a short effective lifespan. Utility Model Content

[0004] In order to solve the above-mentioned technical problems, or at least partially solve the above-mentioned technical problems, this utility model provides a cylindrical lithium battery.

[0005] This utility model provides a cylindrical lithium battery, including a cylindrical shell, a core and a porous liquid-absorbing sheet disposed inside the cylindrical shell, wherein the porous liquid-absorbing sheet is disposed between the end of the core and the end cap of the cylindrical shell.

[0006] Optionally, the porous absorbent sheet is configured to absorb and store free electrolyte when electrolyte is injected into the cylindrical shell, and to release the original concentration of electrolyte absorbed by it to replenish the active substances of the consumed electrolyte after contact with the electrolyte that is being consumed in the cycle.

[0007] Optionally, the porous absorbent sheet contains solid additives for improving battery performance.

[0008] Optionally, the solid additive is one of lithium nitrate, lithium difluorophosphate, and lithium dioxalate borate;

[0009] And / or, the solid additive is distributed in particulate form;

[0010] And / or, the positive end of the core is provided with a positive collector plate, and the porous liquid-absorbing sheet is disposed between the positive collector plate of the core and the positive end cap of the cylindrical shell.

[0011] Optionally, the porous liquid-absorbing sheet is made of an insulating material.

[0012] Optionally, the insulating material is a porous polymer.

[0013] Optionally, the porous polymer is one of polypropylene, polyamide, polyurethane, and melamine.

[0014] Optionally, the porous liquid-absorbing sheet is configured in an annular shape to be fitted around the outer periphery of the conductive handle of the winding core;

[0015] And / or, the thickness of the porous liquid-absorbing sheet is 1-40 mm.

[0016] The technical solution provided by this utility model has the following advantages compared with the prior art:

[0017] The cylindrical lithium battery provided by this utility model incorporates a porous absorbent plate inside the cylindrical casing. This absorbent plate absorbs and stores free electrolyte during electrolyte injection, reducing the negative impact of excessive electrolyte during injection. Under high SOC conditions, the absorbent plate contacts the electrolyte that is squeezed out by the expansion of the electrode plate during cycling, releasing the absorbed free electrolyte. This replenishes the active material consumed during cycling in situ and periodically releases embedded solid additives, achieving a slow-release effect. The porous absorbent plate periodically contacts the electrolyte during charging and discharging, ensuring the periodic release of active materials and extending the effective time. This reduces the risk of decomposition due to prolonged contact with the electrolyte. The plate's placement does not obstruct the normal flow of electrolyte, facilitating thorough electrolyte wetting. Furthermore, this solution does not require the introduction of additional slow-release additives or increased active material usage, resulting in minimal negative impacts and low cost. Attached Figure Description

[0018] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present invention and, together with the description, serve to explain the principles of the present invention.

[0019] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a cross-sectional view of the cylindrical lithium battery described in an embodiment of the present invention.

[0021] Explanation of reference numerals in the attached figures

[0022] 1. Cylindrical shell; 2. Core; 21. Conductive handle; 3. Porous liquid suction plate; 4. Negative current collector; 5. Positive current collector. Detailed Implementation

[0023] To better understand the above-mentioned objectives, features, and advantages of this utility model, the solution of this utility model will be further described below. It should be noted that, unless otherwise specified, the embodiments and features of this utility model can be combined with each other.

[0024] The following description sets forth many specific details to provide a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; obviously, the embodiments described in the specification are only some embodiments of the present invention, and not all embodiments.

[0025] like Figure 1 As shown, the cylindrical lithium battery provided in this embodiment of the present invention includes a cylindrical shell 1 and a core 2 and a porous absorbent sheet 3 disposed inside the cylindrical shell 1. The core 2 is wound from materials such as a positive electrode sheet, a negative electrode sheet, and a separator. A cylindrical cavity is formed inside the cylindrical shell 1, and the core 2 is coaxially disposed within the cylindrical cavity. The porous absorbent sheet 3 is disposed between the end of the core 2 and the end cap of the cylindrical shell 1. The negative end of the core 2 is provided with a negative electrode current collector 4, and the positive end of the core 2 is provided with a positive electrode current collector 5. The porous absorbent sheet 3 is disposed between the positive electrode current collector 5 of the core 2 and its corresponding end cap. Alternatively, the porous absorbent sheet 3 can be disposed between the negative electrode current collector 4 of the core 2 and its corresponding end cap, depending on actual requirements. Preferably, the porous absorbent sheet 3 is disposed between the positive electrode current collector 5 of the core 2 and its corresponding end cap. The cylindrical shell 1, the core 2, the positive electrode current collector 5, and the negative electrode current collector 4 are all made of conventional materials and have conventional structures. The working principle of the cylindrical lithium battery is also based on conventional technology and will not be described in detail here. It is understandable that, to ensure the normal use of the cylindrical lithium battery, the porous liquid-absorbing sheet 3 should be made of insulating material.

[0026] The cylindrical lithium battery provided by this utility model incorporates a porous absorbent plate 3 inside the cylindrical casing 1. This absorbent plate absorbs and stores high-concentration free electrolyte during electrolyte injection, reducing the negative impact of excessive electrolyte during injection. Under high SOC conditions, the absorbent plate contacts the electrolyte that has been squeezed out by the expansion of the electrode plate, releasing the absorbed free electrolyte. This allows the high-concentration electrolyte and embedded additives to be released into the battery cell, replenishing the active material consumed during cycling in situ and periodically releasing the embedded solid additives, thus achieving a slow-release effect. Furthermore, the porous absorbent plate 3... During charging and discharging, the electrolyte in the battery cell is periodically in contact with the cell, ensuring the periodic release of active materials and extending the effective time (at the end of charging, it comes into contact with the electrolyte squeezed out of the cell, at which point the concentration of the squeezed-out electrolyte is the lowest and it accumulates at the top of the cell, which can effectively reduce top lithium plating). It also reduces the risk of decomposition due to long-term contact between the porous absorbent sheet 3 and the electrolyte. The position of the absorbent sheet 3 does not block the normal flow of electrolyte, which is conducive to the full wetting of electrolyte. In addition, this solution does not require the introduction of additional slow-release additives or an increase in the amount of active materials, resulting in minimal negative impact and low cost.

[0027] High SOC refers to high potential, specifically the high potential when the charge is between 60-100%.

[0028] In some embodiments, the porous wicking sheet 3 is configured to absorb and store free electrolyte when electrolyte is injected into the cylindrical housing 1, and to release the original concentration of electrolyte absorbed after contact with electrolyte consumed in the cycle to replenish the active material in the consumed electrolyte, and to release the absorbed free electrolyte after contact with electrolyte participating in the cycle. That is, when the electrode expands during battery cycling, causing some electrolyte to be squeezed out, the porous wicking sheet 3 is designed to contact the squeezed electrolyte (i.e., the electrolyte consumed in the cycle) in a specific state, and can enter the interior of the porous wicking sheet 3 to contact the electrolyte absorbed by the porous wicking sheet 3, so that the lithium salt and additives in the electrolyte absorbed by the porous wicking sheet 3 can be replenished to the squeezed electrolyte. Afterwards, the squeezed electrolyte is returned to the interior of the core 2.

[0029] In the manufacturing process of the cylindrical lithium battery provided by this utility model, electrolyte is injected through the negative electrode injection port of the cylindrical shell 1, and the porous absorbent sheet 3 absorbs and stores the free electrolyte. After the electrolyte injection and aging are completed, the battery is placed with the positive electrode facing upwards, and the porous absorbent sheet 3 is separated from the electrolyte of the cell. During battery cycling, the electrode expands, causing some electrolyte to be squeezed out (the electrolyte will be squeezed out along the axial direction of the core 2) and come into contact with the porous absorbent sheet 3. Since the electrolyte remaining in the porous absorbent sheet 3 does not participate in the cycling, the concentration of lithium salt and additives is higher than that of the extruded electrolyte consumed by the cycling, thereby achieving the replenishment of active materials in the extruded electrolyte.

[0030] In some embodiments, the porous absorbent sheet 3 contains solid additives for improving battery performance. These solid additives are gradually released into the electrolyte upon contact with it, and then flow back into the core 2 along with the electrolyte, thereby improving battery performance.

[0031] In this design, when the electrode expands during battery cycling, causing some electrolyte to be squeezed out, the squeezed-out electrolyte (i.e., the electrolyte consumed during cycling) can contact the porous wicking sheet 3 and enter its interior, thereby contacting the solid additive. The solid additive embedded in the porous wicking sheet 3 can be gradually released into the electrolyte, thereby reducing the battery's internal resistance and extending its cycle life. The porous wicking sheet 3 of this application incorporates solid additives, achieving further improvements and solving the problem of using poorly soluble additives.

[0032] In some embodiments, the solid additive includes at least one of lithium nitrate, lithium difluorophosphate, and lithium dioxalate borate.

[0033] Lithium nitrate, with the chemical formula LiNO3, can be used as an additive in lithium-ion battery electrolytes to improve battery performance and stability. Lithium difluorophosphate, with the chemical formula LiPO2F2, is also used as an electrolyte additive in lithium-ion batteries. It effectively reduces the SEI film resistance formed at low temperatures, improving the battery's high and low temperature cycle performance and high temperature storage performance. It also reduces the battery's self-discharge rate, significantly improving the cycle stability of lithium-ion batteries at -15°C. Lithium dioxalate borate, also known as lithium dioxalate borate, is an inorganic compound. It can be used as an additive in lithium battery electrolytes to improve battery performance and lifespan.

[0034] Understandably, solid additives can also be other solid materials, and can be selected according to actual needs.

[0035] In some implementations, the solid additive is distributed in particulate form.

[0036] In some embodiments, the porous absorbent sheet 3 is made of an insulating material, preferably a porous polymer, and more preferably at least one selected from polypropylene, polyamide, polyurethane, and melamine. It is understood that the porous absorbent sheet 3 can also be made of other materials, and can be designed according to actual needs.

[0037] Polypropylene is a semi-crystalline thermoplastic polymer made from propylene monomers through an addition polymerization reaction. It possesses good chemical stability, heat resistance, corrosion resistance, weather resistance, plasticity, and insulation properties. Polyamide is a polymer with excellent self-lubricating properties, abrasion resistance, and mixed mechanical properties. It also exhibits excellent electrical insulation properties and water absorption. Polyurethane is a polymer compound with excellent mechanical, thermal, water absorption, and chemical properties. Melamine is a triazine-based nitrogen-containing heterocyclic organic compound with excellent water resistance, heat resistance, electrical arc resistance, and excellent flame retardancy.

[0038] The porous absorbent sheet 3 is made of the aforementioned material, which enables it to have good insulation and stability, while also meeting the requirements for electrolyte storage and release.

[0039] In some implementations, such as Figure 1 As shown, the porous liquid-absorbing sheet 3 is arranged in a circular shape, that is, a through hole is opened in the middle of the porous liquid-absorbing sheet 3 for the conductive handle 21 of the core 2 to pass through, so that the porous liquid-absorbing sheet 3 is sleeved on the outer periphery of the conductive handle 21 of the core 2, thereby supporting the porous liquid-absorbing sheet 3 between the end of the core 2 and the top cover of the cylindrical shell 1. It can be understood that the porous liquid-absorbing sheet 3 can be set at the end of the core 2, specifically at the end of the positive electrode current collector 5 or the negative electrode current collector 4, or the porous liquid-absorbing sheet 3 can be set on the inner wall of the top cover, which can be designed according to actual needs. Among them, the outer diameter of the porous liquid-absorbing sheet 3 should be smaller than the inner diameter of the cylindrical shell 1, while the relationship between the outer diameter of the porous liquid-absorbing sheet 3 and the outer diameter of the core 2 is not restricted. For example, the outer diameter of the porous liquid-absorbing sheet 3 is larger than the outer diameter of the core 2; or, the outer diameter of the porous liquid-absorbing sheet 3 is smaller than the outer diameter of the core 2; or, the outer diameter of the porous liquid-absorbing sheet 3 is equal to the outer diameter of the core 2, which can be designed according to actual needs.

[0040] In some embodiments, the thickness of the porous absorbent sheet 3 is 1-40 mm. The specific thickness of the porous absorbent sheet 3 can be designed according to the size of the battery. Similarly, the diameter of the porous absorbent sheet 3, as well as the density and size of the openings, can also be designed according to the size of the battery, and no further restrictions are imposed here.

[0041] In some embodiments, the absorbency rate of the porous absorbent sheet 3 is 1000-6000%, for example, 1000%, 1500%, 2000%, 2500%, 3000%, 3500%, 4000%, 4500%, 5000%, 5500%, and 6000%. Preferably, the absorbency rate of the porous absorbent sheet 3 is 2000-4500%. This absorbency rate allows the porous absorbent sheet 3 to absorb and store excess electrolyte, reducing the negative impact of excess electrolyte during injection. The absorbency rate is calculated as: (mass of absorbed electrolyte / mass of porous absorbent sheet 3) × 100%.

[0042] In some embodiments, the dissolution rate of the porous absorbent sheet 3 is ≤1%. Preferably, the dissolution rate of the porous absorbent sheet 3 is ≤0.1%. At this dissolution rate, it is possible to ensure that the porous absorbent sheet 3 is in periodic contact with the electrolyte of the battery cell during charging and discharging, guaranteeing the periodic release of active materials, extending the effective time, and increasing the service life. Specifically, at room temperature, the dissolution rate = 1 - (remaining mass of the porous absorbent sheet 3 after drying after immersion in the electrolyte for 72 hours) / (original mass of the porous absorbent sheet 3).

[0043] The cylindrical lithium battery provided by this invention can alleviate the increase in battery internal resistance caused by the consumption of active materials in the electrolyte, and solve the problem of lithium plating at the top caused by the accumulation of a large amount of consumed low-concentration electrolyte. Furthermore, it avoids prolonged contact between the liquid-absorbing structure and the cell electrolyte, extending the effective time and reducing the negative impact of the liquid-absorbing structure on the battery. In addition, it does not change the electrolyte formulation or introduce new impurities such as slow-release additives, thus reducing interference with battery performance.

[0044] The following description uses specific embodiments and comparative examples to illustrate the point.

[0045] Example 1

[0046] The porous liquid absorbent sheet 3 is made of melamine foam with an outer diameter of 40 mm, an opening diameter of 15 mm, and a thickness of 5 mm. The dissolution rate of the porous liquid absorbent sheet 3 is 0.1%, and the liquid absorption rate is 3000%. The porous liquid absorbent sheet 3 contains 20 mg of lithium difluorophosphate particles.

[0047] like Figure 1 As shown, a cylindrical lithium battery is assembled. The cylindrical casing 1 has a diameter of 46 mm and a height of 95 mm. The core 2 is formed by winding an NCM positive electrode sheet, a graphite-doped silicon negative electrode sheet (or other commonly used negative electrode materials such as pure graphite or graphite-doped silicon oxide), and a PP separator (or other commonly used separators such as PE or surface-coated Al2O3). The NCM positive electrode sheet is a ternary positive electrode material, including three metals: nickel (Ni), cobalt (CO), and manganese (Mn); LFP is lithium iron phosphate; NCA is lithium nickel cobalt aluminum oxide; PP is polypropylene; PE is polyethylene; and Al2O3 is aluminum oxide. The negative electrode of the core 2 is connected to the negative end cap of the casing via a negative electrode current collector 4, and the positive electrode of the core 2 is connected to a conductive handle via a positive electrode current collector 5. A porous liquid-absorbing sheet 3 is located between the positive electrode current collector 5 and the casing end cap.

[0048] With the negative electrode of the battery cell facing upwards, inject electrolyte through the injection port on the negative electrode side and allow it to age. The electrolyte is 1M LiPF6EC / EMC 3 / 7+5 wt.%FEC (other commonly used industry formulations can also be used). The injection volume is 45 g. The aging time, temperature, pressure, etc. are carried out according to industry practice, with no special restrictions.

[0049] After aging, the batteries are studded and the positive terminal of the cells is facing upwards. They are then subjected to formation, capacity testing, and other treatments, with the relevant parameters executed according to industry practice and without special restrictions.

[0050] The battery was cycled at room temperature with a charge rate of 1 C, a discharge rate of 1 C, and a voltage range of 2.75-4.25 V. The DCR (total internal resistance of the battery under DC current, including ohmic internal resistance, charge transfer impedance, and polarization internal resistance (concentration polarization and electrochemical polarization)) was measured at the 100th, 300th, and 600th cycles, as well as the cycle life.

[0051] DCR measurement method: Record the discharge capacity of the first week as 100% SOC. Discharge the fully charged battery at 1C to 50% SOC and record the open-circuit voltage V1. Discharge at 2C rate for 10 seconds and record the discharge current I1. Record the open-circuit voltage V2 after discharge. Then, DCR = (V1 - V2) / I1. Cycle life measurement method: Record the discharge capacity of the first week as Q1. When the discharge capacity decays to 80% of Q1, record the corresponding number of cycles as the cycle life.

[0052] According to tests, the cylindrical lithium battery provided by this utility model has a DCR of 1.5 mΩ after 100 cycles, 1.9 mΩ after 300 cycles, and 2.4 mΩ after 600 cycles, with a cycle life of 1210 cycles.

[0053] Example 2

[0054] Compared to Example 1, the liquid absorption rate of the porous absorbent sheet 3 was adjusted to 1000%, while the rest remained unchanged. Testing showed that in this example, the cylindrical lithium battery achieved a DCR of 1.6 mΩ after 100 cycles, 2.2 mΩ after 300 cycles, and 2.9 mΩ after 600 cycles, with a cycle life of 961 cycles.

[0055] Example 3

[0056] Compared to Example 1, the liquid absorption rate of the porous absorbent sheet 3 was adjusted to 6000%, while the rest remained unchanged. Testing showed that in this example, the cylindrical lithium battery had a DCR of 1.8 mΩ after 100 cycles, 2.4 mΩ after 300 cycles, and 3.4 mΩ after 600 cycles, with a cycle life of 856 cycles.

[0057] Example 4

[0058] Compared to Example 1, the material of the porous absorbent sheet 3 was changed to chemically adsorbed cotton (insulating material), and the dissolution rate of the porous absorbent sheet 3 was 1.2%, while the rest remained unchanged. Tests showed that in this example, the cylindrical lithium battery had a DCR of 1.6 mΩ after 100 cycles, 2.3 mΩ after 300 cycles, and 3.2 mΩ after 600 cycles, with a cycle life of 908 cycles.

[0059] Example 5

[0060] Compared to Example 1, the position of the porous liquid absorber 3 is adjusted to be between the negative electrode current collector 4 and the negative electrode cap, while the rest remains unchanged. Tests show that in this example, the cylindrical lithium battery has a DCR of 1.6 mΩ after 100 cycles, 2.3 mΩ after 300 cycles, and 3.5 mΩ after 600 cycles, with a cycle life of 810 cycles.

[0061] Example 6

[0062] Compared to Example 1, the porous absorbent sheet 3 does not contain embedded lithium difluorophosphate, but all other aspects remain unchanged. Testing in this example showed that the cylindrical lithium battery had a DCR of 1.7 mΩ after 100 cycles, 2.2 mΩ after 300 cycles, and 2.8 mΩ after 600 cycles, with a cycle life of 973 cycles.

[0063] Comparative Example 1

[0064] Compared to Example 1, this example does not include the porous liquid absorbent sheet 3 structure, but all other aspects remain unchanged. Tests showed that, in this comparative example, the cylindrical lithium battery exhibited a DCR of 1.7 mΩ after 100 cycles, 2.7 mΩ after 300 cycles, and 4.0 mΩ after 600 cycles, with a cycle life of 712 cycles.

[0065] It is evident that, compared to the method of adding a porous liquid-absorbing sheet 3 between the end of the core 2 and the end cap in this application, the traditional cylindrical lithium battery has a relatively high DCR but a short cycle life.

[0066] Comparative Example 2

[0067] Compared to Example 1, the porous absorbent sheet 3 is changed to a structure that surrounds the core 2, with a length equal to the circumference of the core 2, a width equal to the height of the core 2, and a thickness of 5 mm, while the rest remains unchanged. Tests showed that, in this comparative example, the cylindrical lithium battery exhibited a DCR of 1.9 mΩ after 100 cycles, 2.4 mΩ after 300 cycles, and 3.8 mΩ after 600 cycles, with a cycle life of 750 cycles.

[0068] It is evident that, compared to the method of adding the porous liquid-absorbing sheet 3 between the end of the core 2 and the end cap in this application, the cylindrical lithium battery has a relatively higher DCR and a shorter cycle life by wrapping the porous liquid-absorbing sheet 3 around the outer periphery of the core 2.

[0069] The test results above show that the cylindrical lithium battery provided in this application has a lower DCR than the cylindrical lithium battery in the comparative example after cyclic charging and discharging, and its cycle life is longer than that of the cylindrical lithium battery provided in the comparative example. The performance advantage of the preferred embodiment is more obvious.

[0070] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0071] The above description is merely a specific embodiment of this utility model, enabling those skilled in the art to understand or implement it. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this utility model. Therefore, this utility model is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features of the utility model described herein.

Claims

1. A cylindrical lithium battery, characterized in that, It includes a cylindrical shell (1) and a core (2) and a porous liquid-absorbing sheet (3) disposed inside the cylindrical shell (1), wherein the porous liquid-absorbing sheet (3) is disposed between the end of the core (2) and the end cap of the cylindrical shell (1).

2. The cylindrical lithium battery according to claim 1, characterized in that, The porous absorbent sheet (3) is configured to absorb and store free electrolyte when electrolyte is injected into the cylindrical shell (1), and to release the original concentration of electrolyte absorbed by it to replenish the active substances of the consumed electrolyte after contact with the electrolyte that is consumed in the cycle.

3. The cylindrical lithium battery according to claim 1, characterized in that, The porous liquid absorbent sheet (3) contains solid additives for improving battery performance.

4. The cylindrical lithium battery according to claim 3, characterized in that, The solid additive is one of lithium nitrate, lithium difluorophosphate, and lithium dioxaborate. And / or, the solid additive is distributed in particulate form; And / or, the positive end of the core (2) is provided with a positive electrode collector plate (5), and the porous liquid absorbent plate (3) is disposed between the positive electrode collector plate (5) of the core (2) and the positive end cap of the cylindrical shell (1).

5. The cylindrical lithium battery according to claim 1, characterized in that, The porous liquid-absorbing sheet (3) is made of insulating material.

6. The cylindrical lithium battery according to claim 5, characterized in that, The insulating material is a porous polymer.

7. The cylindrical lithium battery according to claim 6, characterized in that, The porous polymer is one of polypropylene, polyamide, polyurethane, and melamine.

8. The cylindrical lithium battery according to claim 1, characterized in that, The porous liquid-absorbing sheet (3) is arranged in a circular shape to be fitted around the outer periphery of the conductive handle (21) of the core (2); And / or, the thickness of the porous liquid-absorbing sheet (3) is 1-40 mm.

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