Preparation method of manganese lithium ion cylindrical battery with long service life, high energy and high safety

Abstract

The invention discloses a preparation method of a long-service-life, high-energy and high-safety manganese lithium ion cylindrical battery. The preparation method comprises the following steps: step 1, stirring by using a vacuum stirrer to obtain positive electrode slurry; 2, preparing a positive plate; step 3, preparing negative electrode slurry in a vacuum stirrer; 4, preparing a negative plate; step 5, selecting a lithium ion battery diaphragm; step 6, manufacturing a naked battery cell through rotation of a winding needle; and 7, placing the naked battery cell in a steel shell, and carrying out packaging, formation and capacity grading processes to prepare the manganese lithium ion battery. According to the invention, lithium manganese iron phosphate and lithium manganate are mixed for use, so that the high cost of pure use of lithium manganese iron phosphate is reduced, the stability of the slurry, the compaction density of the pole piece and the peel strength are improved on the premise of keeping high energy density, and the processing performance of the pole piece and the double-platform problem of lithium manganese iron phosphate are greatly improved; and the electrical performance, the cycle life and the safety performance of the manganese battery are comprehensively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion cylindrical batteries, and specifically to a preparation method for a long-life, high-energy, and high-safety manganese-based lithium-ion cylindrical battery. Background Art

[0002] Lithium iron manganese phosphate is a new type of phosphate material formed by doping a certain proportion of manganese on the basis of lithium iron phosphate, and has the same olivine structure as lithium iron phosphate. Lithium iron manganese phosphate has the same advantages as lithium iron phosphate, such as high safety, long life, and low cost. While having these advantages, it also makes up for the problem of low energy density of lithium iron phosphate, and is known as the "upgraded version of lithium iron phosphate".

[0003] However, when lithium iron manganese phosphate is used alone, there are problems such as poor slurry stability, poor electrode adhesion, low electrode compaction, low conductivity, and double platforms, which hinder its commercial application to a certain extent. And lithium manganese oxide materials with a spinel crystal structure have more applications in light vehicles due to their lower cost advantages. However, compared with lithium iron phosphate, they have disadvantages such as poor safety and short cycle life. By mixing and using lithium iron manganese phosphate and lithium manganese oxide, not only the processing performance, poor conductivity, and double platform problems during the application of lithium iron manganese phosphate are improved, but also the poor safety performance and short cycle life problems of applying lithium manganese oxide are solved.

[0004] The 26700 battery has advantages such as good product consistency and high maturity, but its single-cell capacity is small, resulting in a low energy density of the battery. After reasonable mixing of lithium iron manganese phosphate and lithium manganese oxide, while maintaining the cost advantage, the energy density of the manganese-based battery is about 10% - 20% higher than that of the lithium iron phosphate-based battery.

[0005] The existing patent with the publication number CN106816582A discloses an invention patent for a lithium iron manganese phosphate-based material, its preparation method, a positive electrode, and a lithium battery. By means of making the particle size of lithium iron manganese phosphate finer to reduce the internal cohesion between particles, the compaction density of the positive electrode is improved, ignoring problems such as difficult dispersion and poor processing performance of lithium iron manganese phosphate during homogenization;

[0006] The existing patent with the publication number CN110400920A discloses an invention patent for a high-energy-density and long-life battery and its manufacturing method. By mixing lithium iron manganese phosphate and nickel cobalt manganese lithium oxide to improve compaction and energy density, the cost is increased and the problem of battery safety is ignored. Summary of the Invention

[0007] The purpose of the present invention is to provide a preparation method for a long-life, high-energy, and high-safety manganese-based lithium-ion cylindrical battery, which, on the basis of maintaining high energy density and low cost, solves the problems of poor processing performance and large potential safety hazards existing in the prior art.

[0008] To achieve the above object, the present invention provides the following technical solution: A preparation method of a long-life, high-energy, and high-safety manganese-based lithium-ion cylindrical battery, comprising the following steps:

[0009] Step 1: Mix the active materials with lithium iron phosphate manganese and lithium manganese oxide, a conductive agent, a graphene composite conductive paste, and polyvinylidene fluoride in a certain proportion. Then, after adding N-methylpyrrolidone, use a vacuum mixer to stir into a positive electrode paste;

[0010] Step 2: Coat the positive electrode paste onto a positive electrode current collector aluminum foil, and make a positive electrode sheet through processes such as rolling, slitting, oven baking, sheet making, and tab welding;

[0011] Step 3: Mix the active materials containing artificial graphite, a conductive agent, sodium carboxymethyl cellulose, and styrene-butadiene rubber in a certain proportion. After adding N-methylpyrrolidone, make a negative electrode paste in a vacuum mixer;

[0012] Step 4: Coat the negative electrode paste onto a negative electrode current collector copper foil, and make a negative electrode sheet through processes such as rolling, slitting, oven baking, sheet making, and tab welding;

[0013] Step 5: Select a lithium-ion battery separator, and the separator is required to be a PE wet-process separator;

[0014] Step 6: Stack the positive electrode sheet, separator, negative electrode sheet, and separator in sequence, and make a bare battery cell by rotating a winding pin;

[0015] Step 7: Place the bare battery cell in a steel shell, inject electrolyte after the battery cell is dried, and prepare a manganese-based lithium-ion battery through processes such as encapsulation, formation, and grading.

[0016] Among them, in Step 1, the particle size of the lithium iron phosphate manganese is 0.32 to 30 μm, and the specific surface area is 15 - 25 m 2 / g; the particle size of the lithium manganese oxide is 3 to 35 μm, and the specific surface area is 0.4 to 0.8 m 2 / g;

[0017] The active materials with lithium iron phosphate manganese and lithium manganese oxide are composed of lithium iron phosphate manganese and lithium manganese oxide mixed in a mass ratio of 1:2 to 4;

[0018] The mass ratio of the active materials with lithium iron phosphate manganese and lithium manganese oxide, the conductive agent, the graphene composite conductive paste, polyvinylidene fluoride, and N-methylpyrrolidone is: 100:0.7 to 1.5:0.5 to 1.5:2.0 to 3.2:30 to 60;

[0019] The vacuum degree of the vacuum mixer is -60 to -80 kPa.

[0020] Among them, in step 2, the positive electrode paste is coated on both sides of the positive electrode current collector aluminum foil, and the areal density is 330 - 480 mg / m 2 , and the coating speed is 1 - 18 m / min;

[0021] The aluminum foil is carbon-coated aluminum foil;

[0022] The pressure of the roll pressing is 20 - 40 T, the length of the sheet making is 1200 mm - 1700 mm, and the width of the sheet making is 40 - 70 mm;

[0023] The temperature of the oven is 90 - 110 °C.

[0024] Among them, the conductive agent is one or more of carbon black, carbon nanotubes, SP, and conductive graphite.

[0025] Among them, in step 3, the mass ratio of the active material containing artificial graphite, conductive agent, sodium carboxymethyl cellulose, and styrene-butadiene rubber is: 100: 0.7 - 1.5: 1.0 - 1.8: 1.5 - 2.0;

[0026] The vacuum degree of the vacuum mixer is -60 - -80 kPa.

[0027] Among them, in step 4, the negative electrode paste is coated on both sides of the negative electrode current collector copper foil, and the areal density is 130 - 180 mg / m 2 , and the coating speed is 1 - 10 m / min;

[0028] The pressure of the roll pressing is 20 - 40 T, the length of the sheet making is 1200 mm - 1700 mm, and the width of the sheet making is 40 - 70 mm;

[0029] The temperature of the oven is 90 - 110 °C.

[0030] Among them, in step 5, the thickness of the separator is 7 - 25 μm, and the width is 45 - 70 mm.

[0031] Among them, in step 7, the electrolyte is a mixed organic solvent with a volume ratio of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate of 1: 1: 3. Lithium hexafluorophosphate is dissolved in the solvent, and an electrolyte additive is added.

[0032] Among them, the content of lithium hexafluorophosphate in the electrolyte is 10 - 15%;

[0033] The electrolyte additive includes vinylene carbonate, fluoroethylene carbonate, 1,3 - propane sultone, and lithium bis(oxalate)borate.

[0034] Compared with the prior art, the beneficial effects of the present invention are:

[0035] The present invention uses a blend of lithium iron manganese phosphate and lithium manganate, reducing the high cost of using only lithium iron manganese phosphate. On the premise of maintaining a high energy density, the slurry stability, the compaction density of the electrode sheet, and the peel strength are improved, greatly improving the processing performance of the electrode sheet and the double plateau problem existing in lithium iron manganese phosphate; comprehensively improving the electrical performance, cycle life, and safety performance of the manganese-based battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a line graph showing the change of the slurry viscosity of the present invention over time;

[0037] Figure 2 It is a curve graph showing the change of the battery life of the present invention over the number of cycles;

[0038] Figure 3 It is a charge-discharge curve graph of the battery of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0040] Embodiment 1

[0041] A preparation method of a long-life, high-energy, and high-safety manganese-based lithium-ion cylindrical battery includes the following steps:

[0042] Step 1: Blend the active materials with lithium iron manganese phosphate and lithium manganate in a mass ratio of 1:4. Mix the blended active materials with a conductive agent, a graphene composite conductive paste, and polyvinylidene fluoride in a ratio of 96.2:1.0:0.6:2.2. Then add N-methylpyrrolidone and use a vacuum mixer to stir in an environment with a vacuum degree of -60 to -80 kPa to obtain a positive electrode slurry;

[0043] Step 2: Coat the positive electrode slurry on both sides of the positive electrode current collector aluminum foil with a surface density of 380 mg / m 2 , and the coating speed is 2 m / min; then perform rolling under a rolling pressure of 30 T and slitting, and then place it in an oven for drying. The oven temperature is 90 to 110 °C, and then cut into sheets. The length of the sheet is 1505 mm, and the width of the sheet is 62.2 mm to obtain a positive electrode sheet;

[0044] Step 3: Mix the active material containing artificial graphite, conductive agent, sodium carboxymethyl cellulose, and styrene-butadiene rubber in a mass ratio of 96:0.8:1.4:1.8, then add deionized water, and use a vacuum mixer to stir in an environment with a vacuum degree of -60 to -80 kPa to obtain the negative electrode slurry;

[0045] Step 4: Coat the negative electrode slurry on both sides of the negative electrode current collector copper foil, with a surface density of 148.6 mg / m 2 , and the coating speed is 5 m / min; then perform rolling under a rolling pressure of 30 T and slitting, and then place it in an oven for drying. The oven temperature is 90 to 110 °C, and then slice it immediately. The length of the slice is 1611 mm and the width is 64 mm to obtain the negative electrode plate;

[0046] Step 5: Select a lithium-ion separator. The separator is required to be a PE wet separator with a thickness of 16 μm and a width of 65 mm;

[0047] Step 6: Stack the positive electrode plate, separator, and negative electrode plate in sequence, and make a bare battery cell by rotating the winding needle;

[0048] Step 7: Place the bare battery cell in a steel shell, inject electrolyte after the battery cell is dried. The volume ratio of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate in the electrolyte is 1:1:3, the content of lithium salt lithium hexafluorophosphate is 12.0%, and the content of electrolyte additive is 2% vinylene carbonate, 1.5% fluoroethylene carbonate, 0.5% 1,3-propane sultone, and 0.5% lithium bis(oxalate)borate. After encapsulation, formation, and grading processes, a manganese-based lithium-ion battery is prepared.

[0049] Example 2

[0050] A preparation method of a long-life, high-energy, and high-safety manganese-based lithium-ion cylindrical battery, comprising the following steps:

[0051] Step 1: Blend the active materials with lithium iron phosphate manganese and lithium manganate in a mass ratio of 3:7. Mix the blended active materials with a conductive agent, graphene composite conductive paste, and polyvinylidene fluoride in a ratio of 95.9:1.0:0.6:2.5. Then add N-methylpyrrolidone, and use a vacuum mixer to stir in an environment with a vacuum degree of -60 to -80 kPa to obtain the positive electrode slurry;

[0052] Step 2: Coat the positive electrode slurry on both sides of the positive electrode current collector aluminum foil, with a surface density of 414 mg / m 2, the coating speed is 2 m / min; then it undergoes rolling with a rolling pressure of 30 T and slitting, and then is placed in an oven for drying. The oven temperature is 90 - 110 °C, and then it is made into a film. The film length is 1450 mm and the film width is 62.5 mm to obtain the positive electrode sheet;

[0053] Step 3: Mix the active material containing artificial graphite, conductive agent, sodium carboxymethyl cellulose, and styrene-butadiene rubber in a mass ratio of 96.0:0.8:1.4:1.8, then add deionized water, and use a vacuum mixer to stir in an environment with a vacuum degree of -60 to -80 kPa to obtain the negative electrode paste;

[0054] Step 4: Coat the negative electrode paste on both sides of the negative electrode current collector copper foil, with a surface density of 150.8 mg / m 2 , the coating speed is 5 m / min; then it undergoes rolling with a rolling pressure of 20 - 40 T and slitting, and then is placed in an oven for drying. The oven temperature is 90 - 110 °C, and then it is made into a film. The film length is 1553 mm and the film width is 64 mm to obtain the negative electrode sheet;

[0055] Step 5: Select a lithium-ion separator. The separator is required to be a PE wet-process separator with a thickness of 12 μm and a width of 65 mm;

[0056] Step 6: Stack the positive electrode sheet, separator, negative electrode sheet, and separator in sequence, and make a bare battery cell by rotating a winding pin;

[0057] Step 7: Place the bare battery cell in a steel shell, inject electrolyte after the battery cell is dried. The volume ratio of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate in the electrolyte is 1:1:3, the content of lithium salt lithium hexafluorophosphate is 12.0%, and the content of electrolyte additives is 2% vinylene carbonate, 1.5% fluoroethylene carbonate, 0.5% 1,3 - propane sultone, and 0.5% lithium bis(oxalate)borate. After processes such as encapsulation, formation, and grading, a manganese-based lithium-ion battery is prepared.

[0058] Example 3

[0059] A preparation method of a long-life, high-energy, and high-safety manganese-based lithium-ion cylindrical battery, comprising the following steps:

[0060] Step 1: Blend the active materials with lithium iron phosphate manganese and lithium manganese oxide in a mass ratio of 3:7. Mix the blended active materials with a conductive agent, graphene composite conductive paste, and polyvinylidene fluoride in a ratio of 95.5:1:0.8:2.7, then add N-methylpyrrolidone, and use a vacuum mixer to stir in an environment with a vacuum degree of -60 to -80 kPa to obtain the positive electrode paste;

[0061] Step 2: Coating the positive electrode slurry onto the positive electrode current collector aluminum foil, coating both sides of the positive electrode current collector, with a surface density of 464 mg / m 2 , the coating speed is 2 m / min; then through rolling with a rolling pressure of 30 T and slitting, and then placed in an oven for drying, the oven temperature is 90 - 110 °C, and then making a film immediately, the film length is 1390 mm, the film width is 62.5 mm, to obtain the positive electrode sheet;

[0062] Step 3: Mixing the active material containing artificial graphite, conductive agent, sodium carboxymethyl cellulose, and styrene-butadiene rubber in a mass ratio of 96.0:0.8:1.4:1.8, and then adding deionized water, and using a vacuum mixer to stir in an environment with a vacuum degree of -60 to -80 kPa to obtain the negative electrode slurry;

[0063] Step 4: Coating the negative electrode slurry onto the negative electrode current collector copper foil, coating both sides of the negative electrode current collector, with a surface density of 164.4 mg / m 2 , the coating speed is 5 m / min; then through rolling with a rolling pressure of 20 - 40 T and slitting, and then placed in an oven for drying, the oven temperature is 90 - 110 °C, and then making a film immediately, the film length is 1492 mm, the film width is 64 mm, to obtain the negative electrode sheet;

[0064] Step 5: Selecting a lithium-ion separator, the separator is required to be a PE wet-process separator, with a thickness of 12 μm and a width of 65 mm;

[0065] Step 6: Stacking the positive electrode sheet, separator, negative electrode sheet, and separator in sequence, and making a bare battery cell by rotating the winding needle;

[0066] Step 7: Placing the bare battery cell in a steel shell, injecting electrolyte after the battery cell is dried, the volume ratio of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate in the electrolyte is 1:1:3, the content of lithium salt lithium hexafluorophosphate is 12.0%, the content of electrolyte additives is 2% vinylene carbonate, 1.5% fluoroethylene carbonate, 0.5% 1,3 - propane sultone, and 0.5% lithium bis(oxalato)borate, and through processes such as encapsulation, formation, and grading, a manganese-based lithium-ion battery is prepared.

[0067] Comparative Example 1

[0068] A preparation method of a manganese-based lithium-ion cylindrical battery for comparative example, including the following steps:

[0069] Step 1: Mix the active material with lithium iron manganese phosphate, conductive agent, graphene composite conductive paste, polyvinylidene fluoride, and dispersant in a ratio of 93.0:0.8:2.0:3.7:0.5. Then add N-methylpyrrolidone and use a vacuum mixer to stir in an environment with a vacuum degree of -60 to -80 kPa to obtain the positive electrode paste.

[0070] Step 2: Coat the positive electrode paste on both sides of the positive electrode current collector aluminum foil, with a surface density of 336 mg / m 2 , and the coating speed is 2 m / min. Then, perform rolling under a rolling pressure of 30 T and slitting, and then place it in an oven for drying. The oven temperature is 90 to 110 °C, and then cut into pieces immediately. The length of the piece is 1450 mm, and the width is 62.2 mm to obtain the positive electrode plate.

[0071] Step 3: Mix the active material containing artificial graphite, conductive agent, sodium carboxymethyl cellulose, and styrene-butadiene rubber in a mass ratio of 96:0.5:1.5:2.0. Then add deionized water and use a vacuum mixer to stir in an environment with a vacuum degree of -60 to -80 kPa to obtain the negative electrode paste.

[0072] Step 4: Coat the negative electrode paste on both sides of the negative electrode current collector copper foil, with a surface density of 143.4 mg / m 2 , and the coating speed is 5 m / min. Then, perform rolling under a rolling pressure of 30 T and slitting, and then place it in an oven for drying. The oven temperature is 90 to 110 °C, and then cut into pieces immediately. The length of the piece is 1573 mm, and the width is 64 mm to obtain the negative electrode plate.

[0073] Step 5: Select a lithium-ion separator. The separator is required to be a PE wet separator with a thickness of 20 μm and a width of 65 mm.

[0074] Step 6: Stack the positive electrode plate, separator, negative electrode, and separator sheet in sequence and make a bare battery cell by rotating the winding needle.

[0075] Step 7: Place the bare battery cell in a steel shell. After the battery cell is dried, inject the electrolyte. The volume ratio of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate in the electrolyte is 1:1:3, the content of lithium salt lithium hexafluorophosphate is 12.0%, and the content of electrolyte additives is 2% vinylene carbonate, 1.5% fluoroethylene carbonate, 0.5% 1,3-propane sultone, and 0.5% lithium bis(oxalate)borate. After processes such as encapsulation, formation, and grading, a manganese-based lithium-ion battery is prepared.

[0076] Comparative Example 2

[0077] A preparation method of a comparative example manganese-based lithium-ion cylindrical battery, comprising the following steps:

[0078] Step 1: Mix the active materials with lithium iron phosphate manganese, lithium manganese oxide, and lithium nickel cobalt manganese oxide in a mass ratio of 3:4:3. Mix the mixed active materials with a conductive agent, graphene composite conductive paste, and polyvinylidene fluoride in a ratio of 95.7:1.0:0.8:2.5. Then, after adding N-methylpyrrolidone, use a vacuum mixer to stir in an environment with a vacuum degree of -60 to -80 kPa to obtain a positive electrode paste;

[0079] Step 2: Coat the positive electrode paste on both sides of the positive electrode current collector aluminum foil, with a surface density of 461 mg / m 2 , and the coating speed is 2 m / min; then, perform rolling under a rolling pressure of 30 T and slitting, and then place it in an oven for drying. The oven temperature is 90 to 110 °C. Immediately produce a sheet, with the sheet length being 1390 mm and the sheet width being 62.5 mm to obtain a positive electrode plate;

[0080] Step 3: Mix the active material containing artificial graphite, conductive agent, sodium carboxymethyl cellulose, and styrene-butadiene rubber in a mass ratio of 96.3:0.5:1.4:1.8. Then, add deionized water and use a vacuum mixer to stir in an environment with a vacuum degree of -60 to -80 kPa to obtain a negative electrode paste;

[0081] Step 4: Coat the negative electrode paste on both sides of the negative electrode current collector copper foil, with a surface density of 191.2 mg / m 2 , and the coating speed is 5 m / min; then, perform rolling under a rolling pressure of 30 T and slitting, and then place it in an oven for drying. The oven temperature is 90 to 110 °C. Immediately produce a sheet, with the sheet length being 1503 mm and the sheet width being 64 mm to obtain a negative electrode plate;

[0082] Step 5: Select a lithium-ion separator. The separator is required to be a PE wet separator, with a thickness of 12 μm and a width of 65 mm;

[0083] [Step 6: Stack the positive electrode plate, separator, negative electrode, and separator sheet in sequence and make a bare battery cell by rotating the winding pin;

[0084] Step 7: Place the bare battery cell into a steel case. After the cell is dried, inject electrolyte. The volume ratio of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate in the electrolyte is 1:1:3, the content of lithium salt lithium hexafluorophosphate is 12.0%, the content of electrolyte additives is 2% vinylene carbonate, 1.5% fluoroethylene carbonate, 0.5% 1,3 - propane sultone, and 0.5% lithium bis(oxalate)borate. Through processes such as encapsulation, formation, and grading, a manganese - based lithium - ion battery is prepared.

[0085] Test Example

[0086] Extract one slurry and battery sample from Examples 1, 2, 3 and Comparative Examples 1, 2 for testing. The inspection types, results, and testing methods are shown in the following table. The specific viscosities are as Figure 1 shown, and the specific number of battery cycles is as Figure 2 shown;

[0087] Table 1 Detection Data of Slurry Properties

[0088]

[0089] Table 2 Detection Data of Battery Properties

[0090]

[0091]

[0092] Table 3 Detection Data of Battery High - Temperature Performance

[0093] Serial number Comparative example 1 Comparative example 2 Example 1 Example 2 Example 3 Discharge capacity ratio at high temperature of 55°C (%) 98.5 100.71 100.51 100.47 99.38 Retention rate of charged storage at 55°C high temperature (%) 91.5 96.53 93.5 95.6 95.7 Recovery rate of charged storage at 55°C high temperature (%) 95.0 98.45 97.2 99.8 99.9

[0094] The specific charge - discharge curve of the battery is as Figure 3 shown;

[0095] As can be seen from Table 1 and Figure 1 , when lithium iron manganese phosphate is used alone, the stability of the slurry is poor, and the stripping strength and ultimate compaction of the electrode are low. After mixing with lithium manganate or lithium nickel cobalt manganese oxide, the stability of the slurry, the stripping strength, and the ultimate compaction of the electrode are improved; as can be seen from Table 2 and Figure 2 , when lithium iron manganese phosphate is doped with lithium manganate or lithium nickel cobalt manganese oxide, the internal resistance of the battery decreases, and the energy density and cycle life are significantly improved. However, it is found that when doped with lithium nickel cobalt manganese oxide, the battery cannot pass the nail penetration safety test, and the safety cannot be guaranteed. But when doped with lithium manganate, it can pass the nail penetration safety test; due to the Jahn - Teller effect of the manganese - based material, the disproportionation reaction of manganese causes some manganese to dissolve at high temperatures, affecting the high - temperature performance. As can be seen from Table 3, after mixing lithium iron manganese phosphate with lithium manganate or lithium nickel cobalt manganese oxide, the high - temperature performance is improved; from Figure 3It can be seen that when lithium iron manganese phosphate is mixed with lithium manganate or lithium nickel cobalt manganate, the double-platform problem existing in the single application of lithium iron manganese phosphate can be effectively improved; therefore, on the premise of ensuring the high safety of the battery, through the mixing of lithium iron manganese phosphate and lithium manganate, not only is the high energy density maintained, but also the processing performance of the electrode sheet and the battery cycle life are greatly improved.

[0096] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A preparation method of a long-life, high-energy and high-safety manganese-based lithium-ion cylindrical battery, characterized in that, It includes the following steps: Step 1: Mix the active materials with lithium iron manganese phosphate and lithium manganate, a conductive agent, graphene composite conductive paste, and polyvinylidene fluoride in a certain proportion. Then, add N-methylpyrrolidone and use a vacuum mixer to stir into a positive electrode paste. Step 2: Coat the positive electrode paste onto the positive electrode current collector aluminum foil, and through processes such as rolling, slitting, oven baking, sheet making, and tab welding, make a positive electrode sheet. Step 3: Mix the active materials containing artificial graphite, a conductive agent, sodium carboxymethyl cellulose, and styrene-butadiene rubber in a certain proportion. After adding N-methylpyrrolidone, make a negative electrode paste in a vacuum mixer. Step 4: Coat the negative electrode paste onto the negative electrode current collector copper foil, and through processes such as rolling, slitting, oven baking, sheet making, and tab welding, make a negative electrode sheet. Step 5: Select a lithium-ion battery separator, and the separator is required to be a PE wet-process separator. Step 6: Stack the positive electrode sheet, separator, negative electrode sheet, and separator in sequence, and make a bare battery cell by rotating a winding pin. Step 7: Place the bare battery cell in a steel shell, inject electrolyte after the battery cell is dried, and through processes such as encapsulation, formation, and grading, prepare a manganese-based lithium-ion battery.

2. The preparation method of a long-life, high-energy, and high-safety manganese-based lithium-ion cylindrical battery according to claim 1, wherein: In step 1, the particle size of the lithium iron manganese phosphate is 0.32 to 30 μm, and the specific surface area is 15 - 25 m 2 / g; the particle size of the lithium manganate is 3 to 35 μm, and the specific surface area is 0.4 to 0.8 m 2 / g; The active materials with lithium iron manganese phosphate and lithium manganate are composed of lithium iron manganese phosphate and lithium manganate mixed in a mass ratio of 1:2 to 4. The mass ratio of the active materials with lithium iron manganese phosphate and lithium manganate, the conductive agent, graphene composite conductive paste, polyvinylidene fluoride, and N-methylpyrrolidone is: 100:0.7 to 1.5:0.5 to 1.5:2.0 to 3.2:30 to 60. The vacuum degree of the vacuum mixer is -60 to -80 kPa.

3. The preparation method of a long-life, high-energy, and high-safety manganese-based lithium-ion cylindrical battery according to claim 1, wherein: In step 2, the positive electrode paste is coated on both sides of the positive electrode current collector aluminum foil, and the areal density is 330-480 mg / m 2 , and the coating speed is 1-18 m / min; The aluminum foil is carbon-coated aluminum foil. The pressure of the rolling is 20 to 40 T, the length of the sheet making is 1200 mm to 1700 mm, and the width of the sheet making is 40 to 70 mm. The temperature of the oven is 90 to 110 °C.

4. The preparation method of a long-life, high-energy, and high-safety manganese-based lithium-ion cylindrical battery according to claim 1, wherein: The conductive agent is one or more of carbon black, carbon nanotubes, SP, and conductive graphite.

5. The preparation method of a long-life, high-energy, and high-safety manganese-based lithium-ion cylindrical battery according to claim 1, wherein: In step 3, the mass ratio of the active materials containing artificial graphite, the conductive agent, sodium carboxymethyl cellulose, and styrene-butadiene rubber is: 100:0.7 to 1.5:1.0 to 1.8:1.5 to 2.

0. The vacuum degree of the vacuum mixer is -60 to -80 kPa.

6. The preparation method of a long-life, high-energy, and high-safety manganese-based lithium-ion cylindrical battery according to claim 1, wherein: In step 4, the negative electrode paste is coated on both sides of the negative electrode current collector copper foil, and the areal density is 130 to 180 mg / m 2 , and the coating speed is 1 to 10 m / min; The pressure of the rolling is 20 to 40 T, the length of the sheet making is 1200 mm to 1700 mm, and the width of the sheet making is 40 to 70 mm. The temperature of the oven is 90 to 110 °C.

7. A method for preparing a long-life, high-energy, and high-safety manganese-based lithium-ion cylindrical battery according to claim 1, wherein: In step 5, the thickness of the separator is 7 - 25 μm and the width is 45 - 70 mm.

8. A method for preparing a long-life, high-energy, and high-safety manganese-based lithium-ion cylindrical battery according to claim 1, wherein: In step 7, the electrolyte is a mixed organic solvent with a volume ratio of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate of 1:1:

3. Lithium hexafluorophosphate is dissolved in the solvent, and an electrolyte additive is added.

9. A method for preparing a long-life, high-energy, and high-safety manganese-based lithium-ion cylindrical battery according to claim 8, wherein: The content of lithium hexafluorophosphate in the electrolyte is 10 - 15%; The electrolyte additive includes vinylene carbonate, fluoroethylene carbonate, 1,3-propane sultone, and lithium bis(oxalate) borate.

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