A lithium metal square shell battery with an internal pressurizing structure and a preparation method thereof

Abstract

The present invention discloses a lithium metal square-cased battery with a built-in pressurized structure and a preparation method. The battery comprises a square casing and a cell. The cell is disposed within the square casing, and an expansion material is disposed between the upper and / or lower sides of the cell and the square casing. An aprotic perfluorinated organic solvent is injected into the square casing to form a built-in pressurized structure in combination with the expansion material. The expansion material is placed on both sides of the cell within the square casing, and the aprotic perfluorinated organic solvent is injected into the square casing. The expansion material swells upon contact with the aprotic perfluorinated organic solvent, thereby applying pressure to the lithium metal cell, inhibiting the growth of lithium dendrites and improving battery performance.

Description

Technical Field

[0001] The present invention relates to lithium battery technology, and in particular to a lithium metal square shell battery with a built-in pressurized structure and a preparation method thereof. Background Art

[0002] Lithium batteries can be categorized into button cells, prismatic cells, cylindrical cells, and pouch cells. Prismatic cells have a higher energy density, a simpler structure, and are relatively stable. Their rigid shells offer greater resistance to external impact and puncture.

[0003] During the assembly of square-shell batteries, a certain amount of space must be reserved to facilitate the placement of the battery cells into the shell to avoid obstruction of the assembly process and reduce the potential risk of scratching the battery cells. Usually in batteries with lithium metal as the negative electrode, external pressure is needed to effectively inhibit the growth of negative electrode lithium dendrites, making the morphology of lithium deposition more regular, thereby improving the cycle performance of lithium metal batteries. However, due to the gap between the square shell and the battery cell during the shelling process, only applying force to the shell during the formation or capacity separation process will not directly act on the negative electrode surface, resulting in uneven deposition of the lithium metal surface during the first charge, which seriously affects the subsequent cycle performance.

[0004] After extensive research, the inventors found that lithium metal is unstable with conventional concentration electrolytes due to its extremely low potential. Once the electrolyte is injected, due to the electronegativity of lithium metal, side reactions with the solvent in the electrolyte will occur rapidly, affecting the chemical uniformity of the lithium metal surface and the regularity of lithium deposition during subsequent charging, affecting the battery cycle performance. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a lithium metal square shell battery with a built-in pressurized structure and a preparation method. An expansion material is placed on both sides of the battery cell inside the square shell, and an aprotic perfluorinated organic solvent is injected into the square shell. The expansion material contacts the aprotic perfluorinated organic solvent and swells, thereby exerting pressure on the lithium metal battery cell, inhibiting the growth of lithium dendrites, and thus improving battery performance.

[0006] The technical solution adopted by the present invention to solve the above technical problems is:

[0007] A lithium metal square-cased battery with a built-in pressurized structure comprises a square casing and a battery cell, wherein the battery cell is arranged in the square casing, and an expansion material is arranged between the upper side and / or the lower side of the battery cell and the square casing. An aprotic perfluorinated organic solvent is injected into the square casing to cooperate with the expansion material to form a built-in pressurized structure.

[0008] Preferably, the aprotic perfluorinated organic solvent is a fluorocarbonic acid solvent, a fluoroether solvent or a fluorobenzene solvent.

[0009] Preferably, the total thickness of the expansion material in the square shell is adjusted according to the design of the battery cell and is calculated based on a 20% expansion to fill the redundant volume in the shell.

[0010] Preferably, the expansion material is styrene-butadiene rubber.

[0011] Preferably, the square shell further comprises a liquid additive containing lithium salt, and the volume proportions of the liquid additive containing lithium salt and the aprotic perfluorinated organic solvent are 70%-95% and 5%-30% respectively.

[0012] Preferably, the lithium salt concentration in the lithium salt-containing liquid additive is greater than 1.2 mol / L.

[0013] A method for preparing a lithium metal square shell battery with a built-in pressurized structure, for preparing the lithium metal square shell battery with a built-in pressurized structure, comprises the following steps:

[0014] S1. Stack a certain thickness of expansion material on the upper and lower sides of the battery cell respectively;

[0015] S2. Apply silicone oil between the clipping machine and the expansion material, use the clipping machine to apply pressure, and send the battery cell and expansion material into the square shell;

[0016] S3. Squeeze the left and right ends of the square shell to make it bulge up and down, and pull out the clip machine;

[0017] S4. Take a liquid additive containing lithium salt and inject it into the square shell to complete the packaging so that the battery cell absorbs the infiltration;

[0018] S5. After the battery is filled with liquid, add a non-proton perfluorinated organic solvent through the liquid filling hole on the upper part of the square shell, heat it to make the expansion material expand, and then form and circulate the packaged battery.

[0019] Preferably, the pressure applied by the clamping machine in step S2 is 1 MPa.

[0020] Preferably, the standing time after adding the aprotic perfluorinated organic solvent in step S5 is 6 hours to 36 hours.

[0021] Preferably, the standing temperature after adding the aprotic perfluorinated organic solvent in step S5 is 45° C. to 60° C.

[0022] Compared with the prior art, the advantages of the lithium metal square shell battery with a built-in pressurized structure and the preparation method of the present invention are:

[0023] (1) By using square shells to assemble lithium metal batteries, the battery stability and safety are improved. Compared with soft-pack batteries, the grouping efficiency can be improved and the application scenarios are expanded;

[0024] (2) The expansion material will swell when it comes into contact with aprotic perfluorinated organic solvents. Styrene-butadiene rubber as the expansion material is placed inside the square shell. After the aprotic perfluorinated organic solvent is injected into the square shell, the styrene-butadiene rubber will swell and directly exert pressure on the lithium metal battery cell, thereby inhibiting the growth of lithium dendrites, thereby significantly improving the cycle performance of the lithium metal battery;

[0025] (3) This solution achieves seamless stress transfer from external force to the casing and then to the battery cell through built-in expansion materials, so that the battery cell is stress-controlled throughout its life cycle from semi-finished product to finished product, thereby ensuring uniform lithium negative electrode deposition;

[0026] (4) Styrene-butadiene rubber can be used with fluoroether solvents, effectively solving the problem of fluoroether solvents causing battery bulging in soft-pack batteries;

[0027] (5) The first injection is of high-concentration lithium salt solvent. The high-concentration lithium salt forms an in-salt structure, which reduces the concentration of free solvent, greatly reduces the side reaction between lithium metal and solvent before formation, improves the uniformity of chemical composition on the surface of lithium metal, and increases the reaction between lithium metal and lithium salt by increasing the standing time, thereby forming an effective SEI rich in inorganic materials such as LiF and Li3N, and improving the cycle performance;

[0028] (6) The subsequent injection of non-proton perfluorinated organic solvent can, on the one hand, induce the expansion material to expand and fill the gap between the shell and the battery core; on the other hand, it can also act as a diluent to form a local high-concentration electrolyte system, thereby improving the high-power performance of the battery. Compared with directly adding a local high-concentration electrolyte, the present invention has a better effect;

[0029] (7) Styrene-butadiene rubber can act as a breathing material in the shell, providing breathing space for the battery cell to expand and contract during the battery charge and discharge cycle, thereby improving the battery cycle performance;

[0030] (8) Silicone oil is used for lubrication between the clipping machine and the styrene-butadiene rubber, which facilitates the insertion of the battery cell into the shell and the removal of the clipping machine from the shell, and facilitates battery production, and the silicone oil will not affect battery production;

[0031] (9) After the battery generates dead lithium, the battery cell expands and squeezes the buffer material, causing the precipitation of non-proton perfluorinated organic solvents, which repairs the lithium metal interface and further improves the battery cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of the structure of the styrene-butadiene rubber membrane in the square shell before and after liquid injection in this embodiment.

[0033] In the figure, 1. Square shell; 2. Styrene-butadiene rubber film; 3. Battery cell. DETAILED DESCRIPTION

[0034] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

[0035] Example

[0036] A lithium metal square shell battery with a built-in pressurized structure, such as Figure 1 As shown, it includes a square shell 1, a battery cell 3 and a liquid additive containing lithium salt. The battery cell 3 is arranged in the square shell 1, and an expansion material 2 is arranged between the upper side and / or lower side of the battery cell 3 and the square shell 1. A non-proton perfluorinated organic solvent is injected into the square shell 1 to form a built-in pressurized structure in combination with the expansion material 2.

[0037] Among them, the aprotic perfluorinated organic solvent is a fluorinated carbonate solvent, a fluorinated ether solvent or a fluorinated benzene solvent, such as FEC, FEMC, TFEC, TTE, FB, 1.2FB, etc., and the liquid additive containing lithium salt is a mixed solvent of lithium salt and carbonate solvent or ether solvent, wherein the lithium salt concentration is greater than 1.2 mol / L, and the proportions of the aprotic perfluorinated organic solvent and the liquid additive containing lithium salt are 5%-30% and 70%-95% respectively.

[0038] The expansion material is styrene-butadiene rubber. The total thickness of the expansion material in the square shell is adjusted according to the design of the battery cell. It is calculated based on a 20% expansion to fill the redundant volume in the shell.

[0039] The method for preparing the lithium metal square shell battery with a built-in pressurized structure comprises the following steps:

[0040] S1. Stack a certain thickness of expansion material on the upper and lower sides of the battery cell respectively;

[0041] S2. Apply silicone oil between the clamping machine and the expansion material, use the clamping machine to apply a pressure of 1MPa, and send the battery cell and expansion material into the square shell;

[0042] S3. Squeeze the left and right ends of the square shell to make it bulge up and down, and pull out the clip machine;

[0043] S4. Take a liquid additive containing lithium salt and inject it into the square shell to complete the packaging so that the battery cell absorbs the infiltration;

[0044] S5. After the battery is filled with liquid, add a non-proton perfluorinated organic solvent through the liquid filling hole on the upper part of the square shell, heat it to make the expansion material expand, and then form and circulate the packaged battery.

[0045] The standing time of the aprotic perfluorinated organic solvent added in step S5 is 6 hours to 36 hours, and the standing temperature is 45° C. to 60° C.

[0046] Example 1

[0047] A lithium metal square case battery with a built-in pressurized structure comprises a square case and a battery cell. The battery cell is composed of a stacked positive electrode sheet, a negative electrode sheet, and a PP separator. The positive electrode material of the positive electrode sheet is a nickel-cobalt-manganese ternary material, specifically NCM622. The negative electrode material of the negative electrode sheet is lithium metal, the thickness of which is 50 μm. The liquid additive containing lithium salt is 2MLiPF6 / FEC-EMC (1:1 volume ratio). The liquid additive containing lithium salt is designated as No. 1. The battery cell capacity is 3 Ah. Two styrene-butadiene rubber films, each 80 μm thick, are stacked on the upper and lower sides of the battery cell. Silicone oil is then applied between a clipping machine and the styrene-butadiene rubber films. A pressure of 1 MPa is applied using the clipping machine to feed the battery cell and the styrene-butadiene rubber films into the square case. The left and right ends of the square case are squeezed to cause it to bulge upwards and downwards. The clipping machine is removed, and 80% of the No. 1 liquid additive containing lithium salt is injected into the square case to complete the encapsulation, allowing the battery cell to absorb and infiltrate. Then, 20% of the aprotic perfluorinated organic solvent FEC was injected into the square shell through the refill hole on the upper part of the square shell, and the temperature was controlled at 50°C for 24 hours. After the rest period, the battery was formed and cycled normally.

[0048] Example 2

[0049] A lithium metal square case battery with a built-in pressurized structure includes a square case and a battery cell. The battery cell is composed of a stack of positive electrode sheets, negative electrode sheets, and a PP separator. The positive electrode material of the positive electrode sheet is a nickel-cobalt-manganese ternary material, specifically NCM622. The negative electrode material of the negative electrode sheet is lithium metal. The thickness of the lithium metal is 50μm. The liquid additive containing lithium salt is 1.5MLiPF6+0.1MLiNO3 / FEC-EMC-DME (1:1:1 volume ratio). The liquid additive containing lithium salt is recorded as No. 2. The battery cell capacity is 3Ah. Two 80μm thick styrene-butadiene rubber films are stacked on the top and bottom of the cell. Silicone oil is then applied between the clipping machine and the styrene-butadiene rubber films. Using the clipping machine, a pressure of 1MPa is applied to place the cell and the styrene-butadiene rubber films into the square case. The left and right ends of the square case are squeezed, causing it to bulge upwards and downwards. The clipping machine is then removed, and 80% of a No. 2 lithium salt-containing liquid additive is injected into the square case to complete the encapsulation, allowing the cell to absorb and infiltrate. Then, 20% of the aprotic perfluorinated organic solvent FEC is injected into the square case through the refill port on the top of the square case. The cell is then allowed to rest at a controlled temperature of 50°C for 24 hours. After this resting period, the battery undergoes normal formation and cycling.

[0050] Example 3

[0051] A lithium metal square case battery with a built-in pressurized structure includes a square case and a battery cell. The battery cell is composed of a stacked positive electrode sheet, a negative electrode sheet, and a PP separator. The positive electrode material of the positive electrode sheet is a nickel-cobalt-manganese ternary material, specifically NCM622. The negative electrode material of the negative electrode sheet is lithium metal. The lithium metal thickness is 50μm. The liquid additive containing lithium salt is 1.5MLiPF6 / FEC-FEMC (3:7 volume ratio). The liquid additive containing lithium salt is denoted as No. 3. The battery cell capacity is 3Ah. Two styrene-butadiene rubber films, each 80μm thick, are stacked on the upper and lower sides of the battery cell. Silicone oil is then applied between a clipping machine and the styrene-butadiene rubber films. A pressure of 1MPa is applied using the clipping machine to feed the battery cell and the styrene-butadiene rubber films into the square case. The left and right ends of the square case are squeezed to cause it to bulge up and down. The clipping machine is removed, and 80% of the No. 3 liquid additive containing lithium salt is injected into the square case to complete the packaging, allowing the battery cell to absorb and infiltrate. Then, 20% of the aprotic perfluorinated organic solvent FEC was injected into the square shell through the refill hole on the upper part of the square shell, and the temperature was controlled at 50°C for 24 hours. After the rest period, the battery was formed and cycled normally.

[0052] Example 4

[0053] A lithium metal square case battery with a built-in pressurized structure comprises a square case and a battery cell. The battery cell is composed of a stacked positive electrode sheet, a negative electrode sheet, and a PP separator. The positive electrode material of the positive electrode sheet is a nickel-cobalt-manganese ternary material, specifically NCM622. The negative electrode material of the negative electrode sheet is lithium metal, the thickness of which is 50 μm. The liquid additive containing lithium salt is 5MLiFSI / DME, and the liquid additive containing lithium salt is designated as No. 4. The battery cell capacity is 3 Ah. Two styrene-butadiene rubber films, each 80 μm thick, are stacked on the upper and lower sides of the battery cell. Silicone oil is then applied between a clipping machine and the styrene-butadiene rubber films. A pressure of 1 MPa is applied using the clipping machine to feed the battery cell and the styrene-butadiene rubber films into the square case. The left and right ends of the square case are squeezed to cause it to bulge upwards and downwards. The clipping machine is then removed, and 80% of the No. 4 liquid additive containing lithium salt is injected into the square case to complete the packaging, allowing the battery cell to absorb and infiltrate the liquid. Then, 20% of the aprotic perfluorinated organic solvent FEC was injected into the square shell through the refill hole on the upper part of the square shell, and the temperature was controlled at 50°C for 24 hours. After the rest period, the battery was formed and cycled normally.

[0054] Example 5

[0055] A lithium metal square shell battery with a built-in pressurized structure, which differs from Example 4 in that it uses a non-proton perfluorinated organic solvent FEMC.

[0056] Example 6

[0057] A lithium metal square shell battery with a built-in pressurized structure, which differs from Example 4 in that it uses a non-proton perfluorinated organic solvent TTE.

[0058] Example 7

[0059] A lithium metal square shell battery with a built-in pressurized structure, which differs from Example 4 in that the proportion of aprotic perfluorinated organic solvent FEC is 5%.

[0060] Example 8

[0061] A lithium metal square shell battery with a built-in pressurized structure, which differs from Example 4 in that the proportion of aprotic perfluorinated organic solvent FEC is 10%.

[0062] Example 9

[0063] A lithium metal square shell battery with a built-in pressurized structure, which differs from Example 4 in that the proportion of aprotic perfluorinated organic solvent FEC is 30%.

[0064] Example 10

[0065] A lithium metal square shell battery with a built-in pressurized structure, which differs from Example 4 in that the standing temperature is 45°C.

[0066] Example 11

[0067] A lithium metal square shell battery with a built-in pressurized structure, which differs from Example 4 in that the standing temperature is 60°C.

[0068] Example 12

[0069] A lithium metal square shell battery with a built-in pressurized structure, which differs from Example 4 in that a styrene-butadiene rubber film with a thickness of 100 μm is only provided on the upper side of the battery cell.

[0070] Example 13

[0071] A lithium metal square shell battery with a built-in pressurized structure, which differs from Example 4 in that a styrene-butadiene rubber film with a thickness of 80 μm is only provided on the upper side of the battery cell.

[0072] Example 14

[0073] A lithium metal square shell battery with a built-in pressurized structure, which differs from Example 4 in that a styrene-butadiene rubber film with a thickness of 200 μm is only provided on the upper side of the battery cell.

[0074] Example 15

[0075] A lithium metal square shell battery with a built-in pressurized structure differs from Example 4 in that the aprotic perfluorinated organic solvent TTE and the No. 4 lithium salt-containing liquid additive are injected simultaneously.

[0076] Comparative Example 1

[0077] A lithium metal battery includes a square case and a battery cell. The battery cell is composed of a stack of positive electrode sheets, negative electrode sheets, and a PP separator. The positive electrode material of the positive electrode sheet is a nickel-cobalt-manganese ternary material, specifically NCM622. The negative electrode material of the negative electrode sheet is lithium metal. The thickness of the lithium metal is 50μm. No. 1 lithium salt-containing liquid additive 2MLiPF6 / FEC-EMC (1:1 volume ratio) is used. The battery cell capacity is 3Ah. There is no styrene-butadiene rubber film inside the square case.

[0078] Comparative Example 2

[0079] A lithium metal square shell battery with a built-in pressurized structure. The battery cell is composed of a stack of positive electrode sheets, negative electrode sheets, and PP separators. The positive electrode material of the positive electrode sheet is a nickel-cobalt-manganese ternary material, specifically NCM622. The negative electrode material of the negative electrode sheet is lithium metal with a thickness of 50μm. It uses a No. 2 lithium salt-containing liquid additive 1.5MLiPF6+0.1MLiNO3 / FEC-EMC-DME (1:1:1 volume ratio). The battery cell capacity is 3Ah, and there is no styrene-butadiene rubber film inside the square shell.

[0080] Comparative Example 3

[0081] A lithium metal square case battery with a built-in pressurized structure includes a square case and a battery cell. The battery cell is composed of a stack of positive electrode sheets, negative electrode sheets, and a PP separator. The positive electrode material of the positive electrode sheet is a nickel-cobalt-manganese ternary material, specifically NCM622. The negative electrode material of the negative electrode sheet is lithium metal. The thickness of the lithium metal is 50μm. It uses a No. 3 lithium salt-containing liquid additive 1.5MLiPF6 / FEC-FEMC (3:7 volume ratio). The battery cell capacity is 3Ah, and there is no styrene-butadiene rubber film inside the square case.

[0082] Comparative Example 4

[0083] A lithium metal square case battery with a built-in pressurized structure includes a square case and a battery cell. The battery cell is composed of a stack of positive electrode sheets, negative electrode sheets, and a PP separator. The positive electrode material of the positive electrode sheet is a nickel-cobalt-manganese ternary material, specifically NCM622. The negative electrode material of the negative electrode sheet is lithium metal with a thickness of 50μm. It uses a No. 4 lithium salt-containing liquid additive 5MLiFSI / DME. The battery cell capacity is 3Ah, and there is no styrene-butadiene rubber film inside the square case.

[0084] The batteries in Examples 1-11 and Comparative Examples 1-5 were subjected to cycle tests. Three groups of batteries were selected from each example, and the average test data were calculated as shown in the following table:

[0085]

[0086]

[0087] By comparing Example 1 using No. 1 lithium salt-containing liquid additive with Comparative Example 1, it can be seen that the battery cycle life is increased by about 162% due to the swelling of the aprotic perfluorinated organic solvent in the square shell after contact with the expansion material.

[0088] By comparing Example 2 using No. 2 lithium salt-containing liquid additive with Comparative Example 2, it can be seen that the battery cycle life is increased by about 177% due to the swelling of the aprotic perfluorinated organic solvent in the square shell after contact with the expansion material.

[0089] By comparing Example 3 using No. 3 lithium salt-containing liquid additive with Comparative Example 3, it can be seen that the battery cycle life is increased by about 160% due to the swelling of the aprotic perfluorinated organic solvent in the square shell after contact with the expansion material.

[0090] By comparing Example 4 using No. 4 lithium salt-containing liquid additive with Comparative Example 4, it can be seen that the battery cycle life is increased by about 334% due to the swelling of the aprotic perfluorinated organic solvent in the square shell after contact with the expansion material.

[0091] It can be seen that the swelling of the non-protonic perfluorinated organic solvent in the square shell after contact with the expansion material has the greatest improvement on the lithium metal battery using the No. 4 lithium salt-containing liquid additive.

[0092] Comparison of Examples 4-6 shows that the best effect is achieved when FEC is selected as the aprotic perfluorinated organic solvent for swelling with the swelling material.

[0093] By comparing Example 4 with Examples 7-9, it can be seen that the appropriate proportion of the aprotic perfluorinated organic solvent is 20%. This is because although the more aprotic perfluorinated organic solvent contacts the expansion material and swells, the greater the pressure on the battery cell will be. However, it will also reduce the injection of the liquid additive containing lithium salt, affecting the ion transport of the battery cell and ultimately affecting the cycle life.

[0094] Comparison of Example 4 and Examples 10-11 shows that the ideal standing temperature after the injection of the aprotic perfluorinated organic solvent is 50°C.

[0095] Comparing Example 4 with Examples 12-14, it can be seen that disposing a layer of expansion material on the upper and lower surfaces of the battery cell respectively has a better effect than disposing a layer of expansion material only on the upper or lower surface of the battery cell.

[0096] Comparing Example 6 with Example 15, it can be seen that the subsequent injection of the aprotic perfluorinated organic solvent has a better effect than directly adding a local high-concentration electrolyte.

[0097] The above experimental tests show that the swelling of the non-proton perfluorinated organic solvent in the square shell after contact with the expansion material effectively fills the gap between the battery cells in the shell, realizing seamless transmission of stress from external force to the shell and then to the battery cells, and exerting pressure on the battery cells to inhibit the growth of lithium dendrites, so that the lithium negative electrode is deposited evenly, greatly improving the cycle life of the battery.

[0098] Although the preferred embodiments of the present invention have been described in detail above, it should be clearly understood that various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. A method for preparing a lithium metal square shell battery with a built-in pressurized structure, characterized in that: The following steps are involved: S1. Stacking a certain thickness of expansion material on the upper and lower sides of the battery cell, respectively, wherein the expansion material is styrene-butadiene rubber; S2. Apply silicone oil between the clipping machine and the expansion material, use the clipping machine to apply pressure, and send the battery cell and expansion material into the square shell; S3. Squeeze the left and right ends of the square shell to make it bulge up and down, and pull out the clip machine; S4. Injecting a liquid additive containing lithium salt into the square shell to complete the packaging, so that the battery cell absorbs and infiltrates, and the lithium salt concentration in the liquid additive containing lithium salt is greater than 1.2 mol / L; S5. After the battery is filled with liquid, a non-proton perfluorinated organic solvent is added through the liquid filling hole on the upper part of the square shell. The expansion material is expanded by heating to form a built-in pressurized structure, and then the packaged battery is formed and circulated; The aprotic perfluorinated organic solvent is a fluorinated carbonate solvent, a fluorinated ether solvent or a fluorobenzene solvent; the volume proportions of the lithium salt-containing liquid additive and the aprotic perfluorinated organic solvent are 70%-95% and 5%-30% respectively.

2. The method for preparing a lithium metal square shell battery with a built-in pressurized structure according to claim 1, characterized in that: The pressure applied by the clamping machine in step S2 is 1 MPa.

3. The method for preparing a lithium metal square shell battery with a built-in pressurized structure according to claim 1, characterized in that: The standing time after adding the aprotic perfluorinated organic solvent in step S5 is 6 hours to 36 hours.

4. The method for preparing a lithium metal square shell battery with a built-in pressurized structure according to claim 1, characterized in that: The standing temperature after adding the aprotic perfluorinated organic solvent in step S5 is 45° C. to 60° C.

5. A lithium metal square shell battery, characterized in that: The method according to any one of claims 1 to 4 is used for preparation.

6. The lithium metal square shell battery according to claim 5, characterized in that: The total thickness of the expansion material in the square shell is adjusted according to the design of the battery cell and is calculated based on a 20% expansion to fill the redundant volume in the shell.

Images