Preparation method of lithium manganese iron phosphate battery and lithium battery thereof

Abstract

The invention relates to the technical field of new energy batteries, in particular to a preparation method of a lithium iron manganese phosphate battery and a lithium battery thereof, and the preparation method comprises the following steps: preparing a positive plate and a negative plate; a positive plate is sequentially coated with LFMP and NCM and then dried to obtain a double-layer functional coating, the positive plate with the double-layer functional coating and a negative plate with the double-layer functional coating are assembled with a diaphragm in a lamination or winding mode, and a proper amount of electrolyte is injected to obtain the lithium manganese iron phosphate battery. The positive plate is sequentially coated with the LFMP and the NCM and then dried to obtain the double-layer functional coating, and the energy density is improved by about 4-7% compared with that of a lithium iron phosphate battery; by adopting a novel double-layer electrode structure, the internal resistance is greatly reduced; compared with a ternary battery, the safety is greatly improved, and the needling passing rate is 100%; the use of ternary materials is reduced, the cost is saved, the cost is low, and non-toxic and environment-friendly effects are achieved; the operation is simple, the effect is obvious, and mass production can be realized; and the quality energy density and the safety performance of the product are greatly improved, and the maximum benefits are brought to enterprises and customers.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy batteries, and in particular to a method for preparing a lithium manganese iron phosphate battery and a lithium battery thereof. Background Art

[0002] Improving safety and reducing costs are the core trends of technological development. Improving battery safety and reducing costs have become the focus of industrial development. The energy density of lithium iron phosphate has approached the theoretical "ceiling". Introducing the Mn element on the basis of lithium iron phosphate and improving the voltage platform is expected to further improve the energy density of the battery cell.

[0003] According to a high-safety, high-energy-density lithium iron manganese phosphate battery recorded in the patent with announcement number CN117276471A, the surfaces of the positive and negative sides of the positive electrode current collector are coated with a lithium iron manganese phosphate active material layer, a lithium manganese phosphate active material layer, and a lithium iron phosphate active material layer in sequence. Although this method can be prepared, the platform voltage of lithium iron manganese phosphate (LFMP) and lithium manganese phosphate is about 400mV higher than that of lithium iron phosphate, and the charging and discharging voltage range cannot be unified, and the BMS cannot control it, which poses certain safety hazards; according to a wide-temperature lithium iron manganese phosphate battery and a preparation method thereof recorded in the patent with announcement number CN115513441A, 0.2 to 1 part of an organic monomer is added to the positive electrode slurry, and the organic monomer is at least one of a pyrrole monomer, a thiophene monomer and an aniline monomer. It has been verified that the three organic monomers are liquid at room temperature or have a boiling point below 100°C, which makes it impossible for the organic monomers to stably exist in the positive electrode sheet, which poses certain safety hazards.

[0004] Based on this, a method for preparing a lithium manganese iron phosphate battery and a lithium battery thereof are now provided, which can eliminate the disadvantages of existing devices. Summary of the invention

[0005] In view of the above problems, a method for preparing a lithium iron manganese phosphate battery and a lithium battery thereof are provided, which solves the problems of cost waste and potential safety hazards by coating LFMP and NCM in sequence on the positive electrode sheet and then drying it to obtain a double-layer functional coating.

[0006] In order to solve the problems of the prior art, the present invention provides a method for preparing a lithium iron manganese phosphate battery and a lithium battery thereof, wherein the steps of the preparation method are as follows: S1, preparing a positive electrode sheet and a negative electrode sheet; S2, in S1, first weighing 90-99% of the total weight of the positive electrode active material LFMP, 1-5% of a binder A, 1-5% of a binder B, and 1-5% of a conductive agent, stirring and mixing for 0.5-1h, the rotation speed is 500-1000r / min, and the stirring temperature is 10-60°C; S3, S2 Add 44% of the total weight of the cathode solvent (the overall solid content is about 75%), 0.1-1% of the dispersant, and 0.5-2% of the conductive agent to the obtained material, stir and mix for 0.5-2h, the speed is 500-2000r / min, and the stirring temperature is 10-60°C; add 6% of the total weight of the cathode solvent (the overall solid content is about 64%) to the material obtained in S4 and S3, stir and mix for 0.5-5h, the speed is 1000-3000r / min, and the stirring temperature is 10-60°C , obtain LFMP positive electrode slurry; S5, the LFMP positive electrode slurry is evenly coated on the current collector at 10-120°C by a coater to obtain a LFMP active material sheet with a thickness of 30-200μm, and roller pressing is used to obtain a LFMP positive electrode sheet with a thickness of 30-150μm; S6, weigh 90-98% of the total weight of the powder, 1-5% of the binder A, and 1-5% of the conductive agent, stir and mix for 0.5-1h, the speed is 500-1000r / min, and the stirring temperature is 400-500℃. The temperature is 10-60°C; S7, S6 add a cathode solvent accounting for 70% of the total weight of the powder (the overall solid content is about 60%) to the material obtained, stir and mix for 0.5-5h, the rotation speed is 1000-3000r / min, and the stirring temperature is 10-60°C to obtain a ternary slurry; S8, the ternary slurry is evenly coated on the LFMP cathode sheet at 10-120°C by a coating machine, the single-layer coating thickness is 15-50um, and a double-layer functional coating cathode sheet of 50-200μm is obtained by rolling.

[0007] Preferably, the preparation steps of the negative electrode sheet in S1 are as follows: step 1, weigh 90-99% of the total weight of the negative electrode active material, 0-2% of the thickener A, and 1-5% of the conductive agent, stir and mix for 0.5-1h, the speed is 500-1000r / min, and the stirring temperature is 10-60°C; step 2, add 40% of the negative electrode solvent (the overall solid content is about 68%) accounting for the total weight of the powder to the material obtained in S3, stir and mix for 0.5-2h, the speed is 500-1000r / min, and the stirring temperature is 10 -60℃; Step 3, add 40% of the total weight of the negative electrode solvent (the overall solid content is about 68%) and 1-5% of the binder A to the material obtained in S6, stir and mix for 0.5-5h, the rotation speed is 500-2000r / min, the stirring temperature is 10-60℃, and the negative electrode slurry is obtained; Step 4, the ternary slurry described in S7 is evenly coated on the current collector at 10-110℃ by a coating machine to obtain an active material sheet with a thickness of 100-200μm, and then roller pressed to obtain a negative electrode sheet of 50-150μm.

[0008] Preferably, the positive electrode active material LFMP in S2 is one or more having a manganese-iron ratio of 6:4, 5:5 or 7:3, the conductive agent in S2 is one or more of carbon nanotubes, graphene, carbon black, and acetylene black, and the binder A and binder B in S1 are respectively selected from one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), acrylic resin (PAA), and styrene-butadiene rubber (SBR).

[0009] Preferably, the dispersant in S3 is one or both of polyvinylpyrrolidone (PVP) and hexadecyltrimethylammonium bromide (CTAB), and the conductive agent in S3 is one or more of carbon nanotubes, graphene, carbon black and acetylene black.

[0010] Preferably, the positive electrode active material NCM in S6 is one or more of a nickel-cobalt-manganese ratio of 3:3:3, 6:2:2 or 8:1:1.

[0011] Preferably, the active substance in step one is one or more of graphite, silicon oxide, and silicon carbon, the thickener in step one is one or more of sodium carboxymethyl cellulose and lithium carboxymethyl cellulose, and the conductive agent in step one is one or more of carbon nanotubes, graphene, carbon black, acetylene black, graphene, and conductive graphite.

[0012] Preferably, the binder in step 2 is one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), acrylic resin (PAA), and styrene-butadiene rubber (SBR).

[0013] Preferably, it is made by the preparation method described in any one of claims 1 to 7, characterized in that the positive electrode sheet and the negative electrode sheet having a double-layer functional coating are assembled with the diaphragm by lamination or winding, and an appropriate amount of electrolyte is injected.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] The present invention obtains a double-layer functional coating by coating LFMP and NCM in sequence on the positive electrode sheet and then drying it, which improves the energy density of lithium iron phosphate batteries by about 4-7%; adopts a new double-layer electrode structure, greatly reduces the internal resistance, and effectively improves the battery power performance; compared with ternary batteries, the safety is greatly improved, and the needle puncture pass rate is 100%; reduces the use of ternary materials, saves costs, and is low-cost, non-toxic, and environmentally friendly; simple to operate, with obvious effects and mass production; greatly improves the quality, energy density and safety performance of the product, bringing the greatest benefits to enterprises and customers. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The invention discloses a method for preparing a lithium manganese iron phosphate battery and a schematic diagram of the mechanism of high safety of the lithium battery by needle puncture. DETAILED DESCRIPTION

[0017] In order to further understand the features, technical means, specific objectives and functions of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0018] A method for preparing a lithium manganese iron phosphate battery and a lithium battery thereof, wherein the steps of the preparation method are as follows:

[0019] S1, preparing positive electrode sheet and negative electrode sheet;

[0020] S2. In S1, the positive electrode sheet is prepared by first weighing 90-99% of the total weight of the positive electrode active material LFMP, 1-5% of the binder A, 1-5% of the binder B, and 1-5% of the conductive agent, stirring and mixing for 0.5-1h at a speed of 500-1000r / min and a stirring temperature of 10-60°C;

[0021] S3, S2 to the material obtained by adding 44% of the total weight of the powder cathode solvent (overall solid content of about 75%), 0.1-1% of the dispersant, 0.5-2% of the conductive agent, stirring and mixing for 0.5-2h, the speed is 500-2000r / min, the stirring temperature is 10-60°C;

[0022] Add 6% of the total weight of the cathode solvent (the overall solid content is about 64%) to the materials obtained in S4 and S3, stir and mix for 0.5-5h, the speed is 1000-3000r / min, and the stirring temperature is 10-60°C to obtain LFMP cathode electrode slurry;

[0023] S5, the LFMP positive electrode slurry is evenly coated on the current collector at 10-120° C. by a coating machine to obtain a LFMP active material sheet with a thickness of 30-200 μm, and roller pressing is performed to obtain a LFMP positive electrode sheet with a thickness of 30-150 μm;

[0024] S6, weigh 90-98% of the total weight of the powder, 1-5% of the binder A, and 1-5% of the conductive agent, and stir and mix for 0.5-1h at a speed of 500-1000r / min and a stirring temperature of 10-60°C;

[0025] Add 70% of the cathode solvent (the overall solid content is about 60%) to the materials obtained in S7 and S6, stir and mix for 0.5-5h, the speed is 1000-3000r / min, and the stirring temperature is 10-60°C to obtain a ternary slurry;

[0026] S8. The ternary slurry is evenly coated on the LFMP positive electrode sheet at 10-120° C. by a coating machine, with a single-layer coating thickness of 15-50 μm, and a double-layer functional coating positive electrode sheet of 50-200 μm is obtained by rolling.

[0027] The steps for preparing the negative electrode sheet described in S1 are as follows:

[0028] Step 1: weigh 90-99% of the total weight of the powder, 0-2% of the thickener A, and 1-5% of the conductive agent, and stir and mix for 0.5-1h at a speed of 500-1000r / min and a stirring temperature of 10-60°C;

[0029] Step 2: Add 40% of the total weight of the negative electrode solvent (the overall solid content is about 68%) to the material obtained in S3, stir and mix for 0.5-2h, the speed is 500-1000r / min, and the stirring temperature is 10-60°C;

[0030] Step 3: Add 40% of the total weight of the negative electrode solvent (the overall solid content is about 68%) and 1-5% of the binder A to the material obtained in S6, and stir and mix for 0.5-5h at a speed of 500-2000r / min and a stirring temperature of 10-60°C to obtain a negative electrode slurry;

[0031] Step 4: The ternary slurry in S7 is evenly coated on the current collector at 10-110° C. by a coating machine to obtain an active material sheet with a thickness of 100-200 μm, and then rolled to obtain a negative electrode sheet with a thickness of 50-150 μm.

[0032] The positive electrode active material LFMP in S2 is one or more having a manganese-iron ratio of 6:4, 5:5 or 7:3, the conductive agent in S2 is one or more of carbon nanotubes, graphene, carbon black, and acetylene black, and the binder A and binder B in S1 are respectively selected from one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), acrylic resin (PAA), and styrene-butadiene rubber (SBR).

[0033] The dispersant in S3 is one or two of polyvinyl pyrrolidone PVP and cetyl trimethyl ammonium bromide CTAB, and the conductive agent in S3 is one or more of carbon nanotubes, graphene, carbon black, and acetylene black.

[0034] The positive electrode active material NCM in S6 is one or more of a nickel-cobalt-manganese ratio of 3:3:3, 6:2:2 or 8:1:1.

[0035] The active material in step one is one or more of graphite, silicon oxide, and silicon carbon; the thickener in step one is one or more of sodium carboxymethyl cellulose and lithium carboxymethyl cellulose; the conductive agent in step one is one or more of carbon nanotubes, graphene, carbon black, acetylene black, graphene, and conductive graphite.

[0036] The binder in step 2 is one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), acrylic resin (PAA), and styrene-butadiene rubber (SBR).

[0037] The positive electrode sheet and the negative electrode sheet with a double-layer functional coating are assembled with the separator by stacking or winding, and an appropriate amount of electrolyte is injected.

[0038] In the present application, it is necessary to add the solvent step by step, which allows the binder to be fully kneaded with the dry powder to form a better dispersion.

[0039] In the present application, steps S2, S3, and S4 cannot be replaced arbitrarily. The reason why lithium manganese iron phosphate is added first is that the powder is dry-mixed first to allow the lithium manganese iron phosphate material to fully contact with the binder and the conductive agent, and the solvent is added mainly to play the role of lubrication and dispersion.

[0040] In order to ensure the consistency of the experiment, raw materials produced in the same batch were taken, and the production process included a series of standard production line processes such as stirring, coating, rolling, pre-slitting, die-cutting, slitting, winding, hot pressing, shelling, drying, infiltration, formation, aging, capacity, OCV, etc. to obtain lithium manganese iron phosphate batteries; the difference between different examples is mainly in the weight distribution of different coatings on the positive electrode. The present invention is described in detail below in conjunction with the embodiments.

[0041] This embodiment relates to a method for preparing a composite structure positive electrode sheet by dry process; in terms of percentage of the positive electrode coating weight, the positive electrode sheet is as follows:

[0042] Example 1

[0043] A, 70wt% LMFP coating, 30wt% NCM coating;

[0044] Example 2

[0045] B, 80wt% LMFP coating, 20wt% NCM coating;

[0046] Example 3

[0047] C, 90wt% LMFP coating, 10wt% NCM coating;

[0048] Example 4

[0049] D, 100wt% LMFP coating, 0wt% NCM coating;

[0050] Example 5

[0051] E, 0wt% LMFP coating, 100wt% NCM coating;

[0052] Lithium battery preparation:

[0053] The positive electrode sheets of different embodiments are respectively assembled with the same negative electrode sheet, separator and electrolyte to form a battery.

[0054] Table 1 Energy density, initial efficiency, battery DC internal resistance (DCR), 800 cycle capacity retention rate, needle puncture test and other data of lithium manganese iron phosphate battery after manufacture;

[0055] Table 1:

[0056]

[0057] As can be seen from Table 1, Examples 2 and 3 in the preparation of Examples 1-5 of the present invention show better energy density and safety; because LMFP has a higher platform voltage of 3.6V, the energy density of LMFP battery is increased by 4%-7% compared with LFP battery. LMFP material has lower electrical conductivity, which inhibits the occurrence of Al-Anode short-circuit mode during acupuncture. See the attached schematic diagram of the mechanism for achieving high safety of acupuncture Figure 1 .

[0058] The above embodiments only express one or several implementation modes of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a lithium manganese iron phosphate battery, characterized in that: The steps of the preparation method are as follows: S1, preparing positive electrode sheet and negative electrode sheet; S2. In S1, the positive electrode sheet is prepared by first weighing 90-99% of the total weight of the positive electrode active material LFMP, 1-5% of the binder A, 1-5% of the binder B, and 1-5% of the conductive agent, stirring and mixing for 0.5-1h at a speed of 500-1000r / min and a stirring temperature of 10-60°C; S3, S2 to the material obtained by adding 44% of the total weight of the powder cathode solvent (overall solid content of about 75%), 0.1-1% of the dispersant, 0.5-2% of the conductive agent, stirring and mixing for 0.5-2h, the speed is 500-2000r / min, the stirring temperature is 10-60°C; Add 6% of the total weight of the cathode solvent (the overall solid content is about 64%) to the materials obtained in S4 and S3, stir and mix for 0.5-5h, the speed is 1000-3000r / min, and the stirring temperature is 10-60°C to obtain LFMP cathode electrode slurry; S5, the LFMP positive electrode slurry is evenly coated on the current collector at 10-120° C. by a coating machine to obtain a LFMP active material sheet with a thickness of 30-200 μm, and roller pressing is performed to obtain a LFMP positive electrode sheet with a thickness of 30-150 μm; S6, weigh 90-98% of the total weight of the powder, 1-5% of the binder A, and 1-5% of the conductive agent, and stir and mix for 0.5-1h at a speed of 500-1000r / min and a stirring temperature of 10-60°C; Add 70% of the cathode solvent (the overall solid content is about 60%) to the materials obtained in S7 and S6, stir and mix for 0.5-5h, the speed is 1000-3000r / min, and the stirring temperature is 10-60°C to obtain a ternary slurry; S8. The ternary slurry is evenly coated on the LFMP positive electrode sheet at 10-120° C. by a coating machine, with a single-layer coating thickness of 15-50 μm, and a double-layer functional coating positive electrode sheet of 50-200 μm is obtained by rolling.

2. The method for preparing a lithium manganese iron phosphate battery according to claim 1, characterized in that: The steps for preparing the negative electrode sheet described in S1 are as follows: Step 1: weigh 90-99% of the total weight of the powder, 0-2% of the thickener A, and 1-5% of the conductive agent, and stir and mix for 0.5-1h at a speed of 500-1000r / min and a stirring temperature of 10-60°C; Step 2: Add 40% of the total weight of the negative electrode solvent (the overall solid content is about 68%) to the material obtained in S3, stir and mix for 0.5-2h, the speed is 500-1000r / min, and the stirring temperature is 10-60°C; Step 3: Add 40% of the total weight of the negative electrode solvent (the overall solid content is about 68%) and 1-5% of the binder A to the material obtained in S6, and stir and mix for 0.5-5h at a speed of 500-2000r / min and a stirring temperature of 10-60°C to obtain a negative electrode slurry; Step 4: The ternary slurry in S7 is evenly coated on the current collector at 10-110° C. by a coating machine to obtain an active material sheet with a thickness of 100-200 μm, and then rolled to obtain a negative electrode sheet with a thickness of 50-150 μm.

3. The method for preparing a lithium manganese iron phosphate battery according to claim 1, characterized in that: The positive electrode active material LFMP in S2 is one or more having a manganese-iron ratio of 6:4, 5:5 or 7:3, the conductive agent in S2 is one or more of carbon nanotubes, graphene, carbon black, and acetylene black, and the binder A and binder B in S1 are respectively selected from one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), acrylic resin (PAA), and styrene-butadiene rubber (SBR).

4. The method for preparing a lithium manganese iron phosphate battery according to claim 1, characterized in that: The dispersant in S3 is one or two of polyvinyl pyrrolidone PVP and cetyl trimethyl ammonium bromide CTAB, and the conductive agent in S3 is one or more of carbon nanotubes, graphene, carbon black, and acetylene black.

5. The method for preparing a lithium manganese iron phosphate battery according to claim 1, characterized in that: The positive electrode active material NCM in S6 is one or more of a nickel-cobalt-manganese ratio of 3:3:3, 6:2:2 or 8:1:

1.

6. The method for preparing a lithium manganese iron phosphate battery according to claim 2, characterized in that: The active material in step one is one or more of graphite, silicon oxide, and silicon carbon; the thickener in step one is one or more of sodium carboxymethyl cellulose and lithium carboxymethyl cellulose; the conductive agent in step one is one or more of carbon nanotubes, graphene, carbon black, acetylene black, graphene, and conductive graphite.

7. The method for preparing a lithium manganese iron phosphate battery according to claim 2, characterized in that: The binder in step 2 is one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), acrylic resin (PAA), and styrene-butadiene rubber (SBR).

8. A lithium manganese iron phosphate battery, which is made by the preparation method according to any one of claims 1 to 7, characterized in that: The positive electrode sheet and the negative electrode sheet with a double-layer functional coating are assembled with the separator by stacking or winding, and an appropriate amount of electrolyte is injected.

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