Lithium metal cylindrical battery with built-in buffer structure

Abstract

The utility model discloses a lithium metal cylindrical battery of built -in buffer structure, including cylindrical battery shell, electric core and set up in the buffer structure between battery shell and electric core, the electric core includes the positive plate of winding structure, negative plate and diaphragm, the negative plate adopts lithium metal material, the utility model discloses the buffer structure is introduced between electric core and cylindrical battery shell, and the stress that lithium metal produces in the volume change in the process of charge -discharge cycle is effectively absorbed, and the risk of metal fatigue and breakage that the steel shell is repeatedly expanded and is pressed to initiate is reduced significantly, and the structural stability and safety reliability of battery in medium -term cycle are strengthened.

Description

Technical Field

[0001] This utility model relates to the field of lithium battery technology, and in particular to a lithium metal cylindrical battery with a built-in buffer structure. Background Technology

[0002] Existing lithium metal batteries, due to their high theoretical specific capacity and low potential, have become a key research focus for next-generation high-energy-density batteries. In current applications, common lithium metal battery structures include prismatic, pouch, and cylindrical cells.

[0003] Among them, the soft-pack structure has a certain degree of flexibility, but its aluminum-plastic film has low mechanical strength and cannot withstand the expansion force of lithium metal on its own. It needs to rely on external clamping and pressure, resulting in low integration and high cost, which limits its large-scale application. The square shell structure has strong compressive strength, but the angular design is prone to stress concentration points, and it is also difficult to withstand the cyclic expansion of lithium metal for a long time. The cylindrical steel shell is considered to be a more suitable structural solution for lithium metal anodes because its geometric structure has a good ability to distribute stress evenly.

[0004] However, even with a cylindrical steel shell structure, the battery inevitably faces cyclic stress impacts from the internal expansion of lithium metal during long-term cycling. Without an effective buffering mechanism, the steel shell is highly susceptible to cracking under stress fatigue, affecting safety and lifespan. Therefore, there is an urgent need for a built-in buffer structure that can effectively absorb the volume changes and stress fluctuations caused by lithium metal charging and discharging within the battery, ensuring the stability and safety of the battery structure. Utility Model Content

[0005] The purpose of this invention is to provide a lithium metal cylindrical battery with a built-in buffer structure. By introducing a buffer structure between the cell and the cylindrical battery casing, the stress generated by the volume change of lithium metal during charge and discharge cycles is effectively absorbed, significantly reducing the risk of metal fatigue and cracking caused by repeated expansion and compression of the steel casing, and enhancing the structural stability and safety reliability of the battery in medium and long-term cycles.

[0006] The technical solution adopted by this utility model to solve the above-mentioned technical problems is as follows:

[0007] A lithium metal cylindrical battery with a built-in buffer structure includes a cylindrical battery casing, a battery cell, and a buffer structure disposed between the battery casing and the battery cell. The battery cell includes a wound positive electrode, a separator, and a negative electrode, wherein the negative electrode is made of lithium metal material.

[0008] Preferably, the buffer structure is a membrane material with a porous structure and resilience, specifically one or more composite structures selected from acrylate rubber membrane, carbon fiber membrane, styrene-butadiene rubber membrane, chloroprene rubber membrane, and polypropylene membrane.

[0009] Preferably, the buffer structure has one or more of the following structural combinations: an integral cylindrical covering structure, a longitudinal arc-shaped strip structure, or multiple axially arranged annular strip structures.

[0010] Preferably, the thickness of the membrane material in the buffer structure is 30 μm to 100 μm.

[0011] Preferably, the battery casing is made of steel or aluminum.

[0012] Preferably, the buffer structure is fixed to the outer surface of the cell or the inner wall of the battery casing by means of pasting, hot pressing, nesting or molding.

[0013] Preferably, the buffer structure has the ability to absorb electrolyte and achieve slow release of electrolyte during the cycle.

[0014] Compared with the prior art, the advantages of this utility model are:

[0015] 1. By assembling lithium metal batteries using a cylindrical battery structure, the stability and safety of the batteries are improved. Compared with lithium metal pouch batteries, there is no need for clamping plates to apply pressure, which expands the application scenarios.

[0016] 2. By introducing a membrane material such as an acrylic rubber film between the cell and the cylindrical battery casing as a buffer structure, the stress generated by the volume change of lithium metal during the charge and discharge cycle is effectively absorbed, significantly reducing the risk of metal fatigue and cracking caused by repeated expansion and compression of the steel casing, and enhancing the structural stability and safety reliability of the battery in medium and long-term cycles.

[0017] 3. Our research has found that membrane materials such as acrylic rubber membranes have good electrolyte absorption and slow release capabilities. During static pretreatment, they absorb electrolyte to form a flexible swelling layer, which increases the electrolyte retention of the battery. They also absorb part of the electrolyte and help reduce electrolyte migration and extrusion during long-term cycling, promoting uniform distribution of electrolyte during battery cycling, reducing drying and interface failure problems, and extending battery cycle life. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the battery cell structure in this invention;

[0020] Figure 2 This is a schematic diagram of the cylindrical battery structure in this invention.

[0021] In the diagram: 1. Battery cell; 11. Positive electrode; 12. Separator; 13. Negative electrode; 2. Battery casing; 3. Buffer structure. Detailed Implementation

[0022] The technical solution of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of this utility model, but not all embodiments.

[0023] Example 1

[0024] A method for preparing a lithium metal cylindrical battery with a built-in buffer structure includes the following steps:

[0025] S1. Preparing the cell structure: The positive electrode sheet, separator, and lithium metal negative electrode sheet are wound into a cell.

[0026] Positive electrode material: NCM811 ternary positive electrode material is selected to prepare coated positive electrode sheets, and aluminum foil is used as the current collector;

[0027] Anode material: 50μm thick lithium metal foil, current collector is copper foil;

[0028] Membrane material: Polypropylene / Polyethylene (PP / PE) composite membrane.

[0029] S2. Cut the acrylic rubber film, which serves as a buffer structure, into a cylindrical film with a thickness of 60μm. Wrap the entire film around the outside of the wound battery cell, ensuring it adheres tightly to the surface of the battery cell. Then, insert the battery cell with the acrylic rubber film on it into a battery casing with a matching diameter, so that the acrylic rubber film is used as a buffer structure between the battery cell and the battery casing.

[0030] S3. Inject electrolyte No. 1, with the amount of electrolyte matched to the volume of conventional cells. Then, complete the encapsulation under sealed conditions. The battery capacity is 6Ah.

[0031] Electrolyte: Use 1M LiPF6 dissolved in a mixed solvent of FEC and EMC (volume ratio 1:1), denoted as Electrolyte No. 1.

[0032] S4. Place the battery in a constant temperature environment, set the static temperature to 45℃, and the static time to 24h, so that the acrylic rubber film can fully absorb the electrolyte and form a stable elastic buffer structure.

[0033] S5. After the battery has been left to stand, it is subjected to a conventional formation process to obtain a lithium metal cylindrical battery. After multiple charge-discharge cycles, the acrylate rubber film was observed to have not peeled or suffered structural damage, and the battery casing showed no signs of bulging or cracking.

[0034] That is, the prepared lithium metal cylindrical battery, such as Figure 1 and 2 As shown, the battery includes a cylindrical battery casing 2, a battery cell 1, and a buffer structure 3 disposed between the battery casing 2 and the battery cell 1. The battery cell 1 includes a positive electrode 11, a negative electrode 13, and a separator 12 with a winding structure. The negative electrode 13 is made of lithium metal material.

[0035] Example 2

[0036] The difference between this embodiment and Embodiment 1 is that the acrylic rubber film is cut into a cylindrical sheet with a thickness of 60 μm, and the entire sheet is inserted into the battery casing and tightly adhered to the inner wall of the battery casing. To integrate the acrylic rubber film with the battery casing, multiple adhesive application points are provided on the inner wall of the battery casing for bonding with the acrylic rubber film.

[0037] Example 3

[0038] The difference between this embodiment and Embodiment 1 is that NCM622 ternary cathode material is selected, and the electrolyte is a lithium nitrate electrolyte containing ether, consisting of 1M LiPF6 + 0.1M LiNO3 / FEC-EMC-DME (1:1:1 volume ratio), and this electrolyte is designated as electrolyte No. 2.

[0039] Example 4

[0040] The difference between this embodiment and Embodiment 3 is that the thickness of the acrylate rubber film is 30 μm.

[0041] Example 5

[0042] The difference between this embodiment and Embodiment 3 is that the thickness of the acrylate rubber film is 100 μm.

[0043] Example 6

[0044] The difference between this embodiment and Embodiment 3 is that the standing temperature is 45°C and the standing time is 6 hours.

[0045] Example 7

[0046] The difference between this embodiment and Embodiment 3 is that the standing temperature is 45°C and the standing time is 12 hours.

[0047] Example 8

[0048] The difference between this embodiment and Embodiment 3 is that the standing temperature is 45°C and the standing time is 36 hours.

[0049] Example 9

[0050] The difference between this embodiment and Embodiment 3 is that the standing temperature is 25°C and the standing time is 24 hours.

[0051] Example 10

[0052] The difference between this embodiment and Embodiment 3 is that the standing temperature is 60°C and the standing time is 24 hours.

[0053] Example 11

[0054] The difference between this embodiment and Embodiment 3 is that the acrylic rubber film is cut into three annular strips with an axial length of 1 cm and a thickness of 60 μm, and these strips are spaced apart and fitted onto the outside of the wound battery cell to ensure close contact with the battery cell surface. Then, the battery cell with the acrylic rubber film is installed into a battery casing with a matching diameter, so that the acrylic rubber film is used as a buffer structure between the battery cell and the battery casing.

[0055] Example 12

[0056] The difference between this embodiment and Embodiment 1 is that a carbon fiber membrane is used as the buffer structure.

[0057] Comparative Example 1

[0058] The lithium metal battery includes a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode material is a nickel-cobalt-manganese ternary material, specifically NCM811. The negative electrode material is lithium metal with a thickness of 50 μm. The electrolyte is 1M LiPF6 / FEC-EMC, designated as electrolyte No. 1. The battery capacity is 6 Ah.

[0059] Comparative Example 2

[0060] The lithium metal battery includes a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode material is a nickel-cobalt-manganese ternary material, specifically NCM622. The negative electrode material is lithium metal with a thickness of 50 μm. The electrolyte is a lithium nitrate-containing electrolyte containing ether, consisting of 1M LiPF6 + 0.1M LiNO3 / FEC-EMC-DME (1:1:1 volume ratio). This electrolyte is designated as electrolyte No. 2. The battery capacity is 6 Ah.

[0061] All embodiments 1-12 and comparative examples 1-2 of this invention use the same battery system, and the capacity of each individual cell is within the range of 6 ± 0.3 Ah. All batteries were tested at 25°C, with a voltage range of 3.0V to 4.35V, a charge rate of 0.5C, and a discharge rate of 1C. When the battery's discharge capacity retention rate is below 80.0%, the battery is considered to have reached its service life, and the number of cycles is recorded. See Table 1.

[0062] Electrolyte type Buffer structure thickness Settling time (h) Standing temperature (°C) Number of cycles Example 1 1 60 24 45 521 Example 2 1 60 24 45 496 Example 3 2 60 24 45 591 Example 4 2 30 24 45 357 Example 5 2 100 24 45 364 Example 6 2 60 6 45 388 Example 7 2 60 12 45 500 Example 8 2 60 36 45 404 Example 9 2 60 24 25 472 Example 10 2 60 24 60 376 Example 11 2 Circular band 24 45 362 Example 12 1 60 24 45 516 Comparative Example 1 1 / 24 45 51 Comparative Example 2 2 / 24 45 39

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model.

Claims

1. A lithium metal cylindrical battery with built-in buffer structure, characterized by, The cylindrical battery shell (2), the battery cell (1) and the buffer structure (3) between the battery shell (2) and the battery cell (1), the battery cell (1) includes the positive plate (11), the diaphragm (12) and the negative plate (13) of the winding structure, the negative plate (13) adopts lithium metal material.

2. The lithium metal cylindrical battery with built-in buffer structure according to claim 1, characterized by, The buffer structure (3) is one or more composite structures of acrylate rubber film, carbon fiber film, butadiene rubber film, chloroprene rubber film and polypropylene film.

3. The lithium metal cylindrical battery with built-in buffer structure according to claim 2, characterized by, The buffer structure (3) has one or more structure combinations: overall cylindrical cladding structure, longitudinal arc strip structure, multiple axial arrangement of annular belt structure.

4. The lithium metal cylindrical battery with built-in buffer structure according to claim 2, characterized in that, The film material thickness of the buffer structure (3) is 30-100 μm.

5. The lithium metal cylindrical battery with built-in buffer structure according to claim 1, wherein, The battery shell (2) is a steel shell or an aluminum shell.

6. The lithium metal cylindrical battery with built-in buffer structure according to claim 2, characterized in that, The buffer structure (3) is fixed on the outer surface of the battery cell (1) or the inner wall of the battery shell (2) by pasting, hot pressing, nesting or mold pressing.

7. The lithium metal cylindrical battery with built-in buffer structure according to claim 2, characterized in that, The buffer structure (3) has the ability to absorb electrolyte and realize slow release of electrolyte in the cycle process.

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