Semi-solid-state battery doped with lithium manganese iron phosphate and preparation method of semi-solid-state battery

Abstract

The invention belongs to a semi-solid-state lithium ion battery, and relates to a lithium manganese iron phosphate-doped semi-solid-state battery and a preparation method thereof.The preparation method comprises the following steps: preparing a positive plate coated with LMFP, a negative plate coated with a solid electrolyte and a diaphragm coated with the solid electrolyte on one side into a battery cell; fully dissolving a monomer, a cross-linking agent and an initiator in an electrolyte to prepare a mixed solution, injecting the mixed solution into a battery cell to be injected, and heating to enable the initiator to release free radicals to initiate monomer polymerization, so as to obtain the semi-solid battery. According to the invention, a mode of mixing the positive electrode material with the LMFP, coating the diaphragm with the solid electrolyte and performing in-situ polymerization on the electrolyte is adopted, and the intrinsic stability of the LMFP is utilized to improve the safety performance of the battery cell, so that the energy density is not reduced; in-situ polymerization of the electrolyte can form a uniform and compact interfacial film, interface contact can also be improved, a stable lithium ion transport channel is provided, good wettability between the electrode and the electrolyte is ensured, interface resistance is reduced, and the battery cell shows excellent safety performance and excellent electrochemical performance.

Description

Technical Field

[0001] The present invention belongs to semi-solid lithium-ion batteries, and particularly relates to a semi-solid battery doped with lithium iron manganese phosphate and a preparation method thereof. Background Art

[0002] With the rapid development of fields such as electric vehicles, energy storage, and consumer electronics, the demand for batteries with high safety and high energy density has increased rapidly. Currently, traditional lithium-ion batteries still face relatively serious safety hazards. Especially in recent years, with the increasing proportion of new energy vehicles and the higher and higher national policy requirements for the safety of lithium-ion batteries, the mutual limitation between traditional lithium-ion batteries and liquid electrolytes in terms of energy density and safety makes it unable to meet this demand well. Therefore, exploring appropriate strategies to solve the above problems is very important for the development of lithium-ion batteries.

[0003] It is worth noting that the development of the prior art indicates that the in-situ polymerization method can enhance the safety performance while increasing the energy density. In the patent application "A Semi-Solid Battery with High Energy Density and High Safety and a Preparation Method Thereof" with the publication number CN115832448A, it is disclosed that a precursor solution containing monomers is injected into the assembled battery and then polymerized under external conditions; the liquid electrolyte is converted into a gel state to reduce the fluidity of the electrolyte to improve safety; in addition, doping the solid-state electrolyte in the positive electrode material and coating the solid-state electrolyte on the separator can improve the interfacial contact and also help to form a stable SEI film. Another invention application "A High-Safety Semi-Solid Battery Core and a Preparation Method Thereof and Application in the Field of Electronic Cigarette Batteries" with the publication number CN117712459A adopts a similar in-situ polymerization scheme, except that the solid-state electrolyte doped in the positive electrode is LLZO. However, the above-mentioned scheme of doping the solid-state electrolyte has limited effects, reduces the specific capacity of the positive electrode material, and has a high cost. Therefore, exploring a strategy that can not only not affect the capacity but also improve the safety performance and has a low cost is of great significance for breaking the current industry involution and the commercialization of semi-solid batteries. Summary of the Invention

[0004] To solve the deficiencies described in the above prior art, the present invention provides a semi-solid battery doped with lithium iron manganese phosphate and a preparation method thereof.

[0005] The technical solution adopted by the present invention is as follows: A preparation method of a semi-solid battery doped with lithium iron manganese phosphate, comprising the following steps: Step 1: The positive electrode material and the negative electrode material are respectively prepared into uniformly dispersed slurries through a high-speed homogenization device. Then, the positive electrode slurry and the negative electrode slurry are respectively coated through an extrusion coater. After that, the positive electrode sheet and the negative electrode sheet are respectively roll-pressed, slit, and made into finished electrode sheets with appropriate sizes. The particle surface of the positive electrode sheet is uniformly coated with lithium manganese iron phosphate LMFP at the nanoscale, and the negative electrode sheet is uniformly coated with a solid electrolyte at the nanoscale. Step 2: One side of the separator is coated with a solid electrolyte at the micron scale, and the other side is coated with ceramics and glue. Step 3: The finished positive electrode sheet, negative electrode sheet, and separator are wound into a core by a winding machine. The core is placed into an aluminum-plastic film with the shell punched. After a series of normal processes such as hot pressing and top sealing, it is dried to obtain an assembled battery cell. Step 4: The monomer, cross-linking agent, and initiator are fully dissolved in the electrolyte to prepare a mixed solution. The mixed solution is injected into the battery cell to be filled with the solution, and it is left standing for 12 - 24 h. It is heated to 60 °C to make the initiator release free radicals to initiate the polymerization of the monomer, and a semi-solid battery is obtained.

[0006] Preferably, the positive electrode material includes a nickel-cobalt-manganese ternary material, specifically any one of NCM-5, NCM-6, NCM-8, NCM-9, and lithium cobalt oxide positive electrodes.

[0007] Furthermore, the positive electrode material further includes admixed lithium manganese iron phosphate LMFP at the nanoscale, and the admixing amount of lithium manganese iron phosphate is 1 wt% - 5 wt% of the positive electrode material.

[0008] Preferably, the solid electrolyte coating the negative electrode material is Li 0.5 La 0.5 TiO3, Li 1.4 Al 0.4 Ti 1.6 (PO4)3, Li 6.4 La3Zr 1.4 Ta 0.6 O 12 , Li7La3Zr2O 12 , Li3ErCl6, Li3InCl6; the admixing amount of the solid electrolyte coating the negative electrode material is 1 wt% - 5 wt%.

[0009] Preferably, the solid electrolyte at the micron scale coated on one side of the separator is at least one of the following: Li 1.4 Al 0.4 Ti 1.6 (PO4)3, Li3InCl6, Li7La3Zr2O 12 , Li3ErCl6, Li 0.5 La 0.5TiO3, Li 6.4 La3Zr 1.4 Ta 0.6 O 12 ; The coating thickness of the separator is 1 to 3 microns.

[0010] Preferably, the monomer includes any one of 2,4,6-triallyloxy-1,3,5-triazine, triallyl isocyanurate, triallyl trimellitate, and isopentanetetraacrylate.

[0011] Preferably, the initiator includes any one of azobisisobutyronitrile, methyl ethyl ketone peroxide, benzoyl peroxide, 2,4-dimethylvaleronitrile, dimethyl azobisisobutyrate, benzoyl peroxide oxide, and tert-butyl benzoyl peroxide.

[0012] According to a preparation method of a semi-solid battery doped with lithium iron manganese phosphate, the obtained semi-solid battery has a structure including a dry battery cell, and the dry battery cell includes a positive electrode sheet, a negative electrode sheet, and a separator. The particle surface of the positive electrode sheet is uniformly coated with lithium iron manganese phosphate LMFP at the nanoscale, the negative electrode sheet is uniformly coated with a solid electrolyte at the nanoscale, and one side of the separator is coated with a solid electrolyte at the micron level.

[0013] The beneficial effects of the present invention are as follows: 1. The present invention proposes a preparation method of a semi-solid battery doped with lithium iron manganese phosphate. By using the method of doping lithium iron manganese phosphate LMFP in the positive electrode material, coating the separator with a solid electrolyte, and in-situ polymerization of the electrolyte, the safety performance and electrochemical performance of the battery cell are improved. And through the test comparison of specific examples and comparative examples, it is confirmed that the semi-solid battery prepared by the present invention has good performance improvement effects.

[0014] 2. By doping lithium iron manganese phosphate LMFP at the nanoscale in the positive electrode material and uniformly coating the surface of the positive electrode material, the intrinsic stability of the olivine structure of lithium iron manganese phosphate LMFP is utilized to improve the safety performance of the battery cell; and lithium iron manganese phosphate LMFP is an active substance that can provide capacity and will not reduce the energy density, which can avoid the problem of capacity attenuation caused by doping; in addition, lithium iron manganese phosphate LMFP has a lower cost compared to solid electrolytes, which is more conducive to large-scale application.

[0015] 3. The side of the separator of the present invention coated with a solid electrolyte can participate in film formation during the pre-charging process with respect to the negative electrode, enhancing the thermal stability of the SEI film, and thus improving the safety performance.

[0016] 4. The in-situ polymerization of the electrolyte of the present invention can not only form a uniform and dense interfacial film but also improve the interfacial contact, providing a stable lithium ion transport channel. The in-situ polymerization of the flowable monomer ensures good wetting between the electrode and the electrolyte, thereby reducing the interfacial resistance.

[0017] 5. The present invention selects appropriate monomers to in-situ polymerize the electrolyte into a gel state, reducing the fluidity of the electrolyte; and selecting the correct monomers can also participate in film formation, forming a stable and uniform interfacial film at the interface, regulating the migration channels of lithium ions, and ensuring electrochemical performance while improving safety performance. Specific Embodiments

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments; based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0019] A preparation method of a semi-solid battery doped with lithium iron manganese phosphate includes the following steps: (S1) Prepare the positive electrode sheet and the negative electrode sheet respectively: specifically, the positive electrode material and the negative electrode material are respectively prepared into uniformly dispersed slurries through a high-speed homogenization device, and then the positive electrode slurry and the negative electrode slurry are respectively coated through an extrusion coater, and then the positive electrode sheet and the negative electrode sheet are respectively rolled, cut and formed into finished electrode sheets with appropriate sizes; the surfaces of the particles of the positive electrode sheet are uniformly coated with lithium iron manganese phosphate LMFP at the nanoscale, and the negative electrode sheet is uniformly coated with a solid electrolyte at the nanoscale.

[0020] The positive electrode material includes nickel-cobalt-manganese ternary materials, preferably any one of NCM-5, NCM-6, NCM-8, NCM-9 and lithium cobalt oxide positive electrodes; in addition, the positive electrode material also includes doped lithium iron manganese phosphate LMFP at the nanoscale. Preferably, the doping amount of LMFP is 1 wt% to 5 wt% of the positive electrode material.

[0021] The solid electrolyte coating the negative electrode material is Li 0.5 La 0.5 TiO3, Li 1.4 Al 0.4 Ti 1.6 (PO4)3, Li 6.4 La3Zr 1.4 Ta 0.6 O 12 、Li7La3Zr2O 12 、Li3ErCl6, Li3InCl6; preferably, the doping amount of the solid electrolyte coating the negative electrode material is 1 wt% to 5 wt%.

[0022] (S2) Prepare the separator: Specifically, one side of the separator is coated with a micron-scale solid electrolyte, and the other side is coated with ceramics and glue; the micron-scale solid electrolyte coated on one side of the separator is at least one of the following: Li 1.4 Al 0.4 Ti 1.6 (PO4)3, Li3InCl6, Li7La3Zr2O 12 , Li3ErCl6, Li 0.5 La 0.5 TiO3, Li 6.4 La3Zr 1.4 Ta 0.6 O 12 ; Preferably, the coating thickness of the separator is 1 to 3 microns.

[0023] (S3) Assemble the positive electrode sheet, negative electrode sheet and separator into an electrode core: Specifically, a winding machine winds the finished positive electrode sheet, negative electrode sheet and separator into a core, puts the core into an aluminum-plastic film with a shell punched out, and dries it after a series of normal processes such as hot pressing and top sealing.

[0024] (S4) Dissolve the monomer, cross-linking agent and initiator sufficiently in the electrolyte to prepare a mixed solution; inject the mixed solution into the electrode core to be filled with liquid, and let it stand for 12 to 24 h; heat to 60 °C to make the initiator release free radicals to initiate the polymerization of the monomer, and obtain a semi-solid battery; wherein, the monomer includes at least one of 2,4,6-triallyloxy-1,3,5-triazine, triallyl isocyanurate, triallyl benzene-1,3,5-tricarboxylate and isopentyl tetraacrylate; wherein the initiator includes at least one of azobisisobutyronitrile, methyl ethyl ketone peroxide, benzoyl peroxide, 2,4-dimethylvaleronitrile, dimethyl azobisisobutyrate, benzoyl peroxide oxide, tert-butyl benzoyl peroxide; the cross-linking agent is preferably ethylene glycol dimethacrylate EGDMA.

[0025] A semi-solid battery doped with lithium iron manganese phosphate obtained by the above preparation method, its structure includes a dry electrode core, the dry electrode core includes a positive electrode sheet, a negative electrode sheet and a separator, the surface of the particles of the positive electrode sheet is uniformly coated with lithium iron manganese phosphate LMFP at the nanoscale, the negative electrode sheet is uniformly coated with a nanoscale solid electrolyte, and one side of the separator is coated with a micron-scale solid electrolyte.

[0026] A preparation method of a semi-solid battery doped with lithium manganese iron phosphate, which adopts the method of doping lithium manganese iron phosphate (LMFP) in the positive electrode material, coating the separator with a solid electrolyte, and in-situ polymerization of the electrolyte, so that the battery cell exhibits excellent safety performance and outstanding electrochemical performance. Specifically, doping lithium manganese iron phosphate (LMFP) can utilize the intrinsic stability of its olivine structure to improve the safety performance of the battery cell. Moreover, lithium manganese iron phosphate (LMFP) is an active material that can provide capacity without reducing the energy density. In addition, lithium manganese iron phosphate (LMFP) has a lower cost compared with the solid electrolyte, which is more conducive to large-scale application; in-situ polymerization of the electrolyte can not only form a uniform and dense interfacial film but also improve the interfacial contact, providing a stable lithium-ion transport channel. The in-situ polymerization of the flowable monomer ensures good wettability between the electrode and the electrolyte, and the in-situ polymerization of the flowable monomer ensures good wettability between the electrode and the electrolyte, thereby reducing the interfacial resistance, and the battery cell exhibits excellent safety performance and outstanding electrochemical performance.

[0027] Example 1 A preparation method of a semi-solid battery doped with lithium manganese iron phosphate, specifically including the following steps: The positive electrode material and the negative electrode material are respectively prepared into uniformly dispersed slurries through a high-speed homogenization device. The positive electrode material includes 91.5 wt% lithium cobaltate, 2 wt% lithium manganese iron phosphate, 1.5 wt% conductive carbon, 2 wt% carbon nanotubes, and 3 wt% binder, and the binder is polyvinylidene fluoride; the negative electrode material includes 91.5 wt% artificial graphite, 2 wt% lithium lanthanum titanium oxide (LLTO), 2 wt% conductive carbon, 1.5 wt% carbon nanotubes, and 3 wt% binder, and the binder is 30 wt% carboxymethyl cellulose and 70 wt% styrene-butadiene rubber.

[0028] Then, the positive electrode slurry and the negative electrode slurry are respectively coated by an extrusion coater, and then the positive electrode sheet and the negative electrode sheet are respectively roll-pressed, slit, and made into finished electrode sheets with appropriate sizes. The separator is a (3 + 9 + 3) µm specification LATP + PE + Al2O3 composite material separator. Finally, the finished positive electrode sheet, negative electrode sheet, and separator are wound into a core by a winding machine.

[0029] The core is placed in an aluminum-plastic film with a shell punched out, dried after a series of normal processes such as hot pressing and top sealing, and then the prepared electrolyte is injected. The electrolyte is 1 mol / L LiPF6(EMC) added with 0.5 wt% 2,4,6-triallyloxy-1,3,5-triazine and 0.1 wt% azobisisobutyronitrile. The electrolyte is in-situ polymerized by heating at 60 °C, and finally, the finished battery is obtained through pre-charging and grading.

[0030] Example 2 The preparation method of a semi-solid state battery doped with lithium iron manganese phosphate in this embodiment is different from that in Embodiment 1 in that the lithium iron manganese phosphate doped in the positive electrode is 3 wt%, and the use of other reagents and the preparation process are the same as those in Embodiment 1.

[0031] Embodiment 3 The preparation method of a semi-solid state battery doped with lithium iron manganese phosphate in this embodiment is different from that in Embodiment 1 in that the lithium iron manganese phosphate doped in the positive electrode is 5 wt%, and the amount of conductive carbon is 2 wt%; the use of other reagents and the preparation process are the same as those in Embodiment 1.

[0032] Embodiment 4 The preparation method of a semi-solid state battery doped with lithium iron manganese phosphate in this embodiment is different from that in Embodiment 1 in that the positive electrode material includes 91 wt% NCM-6 series ternary material, 2 wt% lithium iron manganese phosphate, 2 wt% conductive carbon, 2 wt% carbon nanotubes, and 3 wt% binder, and the binder is polyvinylidene fluoride; the use of other reagents and the preparation process are the same as those in Embodiment 1.

[0033] Embodiment 5 The preparation method of a semi-solid state battery doped with lithium iron manganese phosphate in this embodiment is different from that in Embodiment 4 in that the positive electrode material includes 87.5 wt% NCM-6 series ternary material, 5 wt% lithium iron manganese phosphate, 2.5 wt% conductive carbon, 2 wt% carbon nanotubes, and 3 wt% binder, and the binder is polyvinylidene fluoride; the use of other reagents and the preparation process are the same as those in Embodiment 4.

[0034] Embodiment 6 The preparation method of a semi-solid state battery doped with lithium iron manganese phosphate in this embodiment is different from that in Embodiment 1 in that the positive electrode material includes 91 wt% NCM-8 series ternary material, 2 wt% lithium iron manganese phosphate, 2 wt% conductive carbon, 2 wt% carbon nanotubes, and 3 wt% binder, and the binder is polyvinylidene fluoride; the use of other reagents and the preparation process are the same as those in Embodiment 1.

[0035] Embodiment 7 The preparation method of a semi-solid state battery doped with lithium iron manganese phosphate in this embodiment is different from that in Embodiment 6 in that the positive electrode material includes 87.5 wt% NCM-8 series ternary material, 5 wt% lithium iron manganese phosphate, 2.5 wt% conductive carbon, 2 wt% carbon nanotubes, and 3 wt% binder, and the binder is polyvinylidene fluoride; the use of other reagents and the preparation process are the same as those in Embodiment 6.

[0036] Comparative Example 1 A preparation method of a semi-solid battery doped with lithium iron manganese phosphate. All the reagents and preparation processes used in the preparation method are the same as those in Example 1, except that the positive electrode is not doped with lithium iron manganese phosphate.

[0037] Comparative Example 2 A preparation method of a semi-solid battery doped with lithium iron manganese phosphate. All the reagents and preparation processes used in the preparation method are the same as those in Example 4, except that the positive electrode is not doped with lithium iron manganese phosphate.

[0038] Comparative Example 3 A preparation method of a semi-solid battery doped with lithium iron manganese phosphate. All the reagents and preparation processes used in the preparation method are the same as those in Example 6, except that the positive electrode is not doped with lithium iron manganese phosphate.

[0039] Perform performance tests on the above Examples 1-7 and Comparative Examples 1-3 and record the data.

[0040] Specifically, Examples 1-3 and Comparative Example 1 of the lithium cobaltate system are assembled into 7Ah soft-pack battery cells, and Examples 4-7 of the NCM ternary system and Comparative Examples 2 and 3 are assembled into 5Ah soft-pack battery cells. The above battery cells are respectively subjected to 3 mΩ short-circuit test, 5 mm nail penetration test, and the cycle test results are as follows in the table (cycle test conditions +0.5C / -0.5C@25℃).

[0041] From the comparison results of the safety and cycle tests of the examples and comparative examples, it can be seen that by doping a nanoscale layer of lithium iron manganese phosphate LMFP on the surface of the positive electrode material uniformly, the high stability of the lithium iron manganese phosphate LMFP with olivine structure is used to improve the stability and safety of the positive electrode side; at the same time, lithium iron manganese phosphate LMFP is an active electrode material that can provide capacity, which can avoid the capacity attenuation problem caused by doping and improve the cycle performance. In addition, by in-situ polymerizing the electrolyte into a gel state, the fluidity of the electrolyte is reduced. Among them, the preferred monomer can also participate in film formation, can form a stable and uniform interfacial film at the interface, regulate the migration channels of lithium ions, and can improve the electrochemical performance while improving the safety performance.

Claims

1. A preparation method of a semi-solid battery doped with lithium iron manganese phosphate, characterized in that, It includes the following steps: Step 1: The positive electrode material and the negative electrode material are respectively prepared into uniformly dispersed slurries through high-speed homogenization equipment, and then the positive electrode slurry and the negative electrode slurry are respectively coated through an extrusion coater. Then, the positive electrode sheet and the negative electrode sheet are roll-pressed and slit into finished electrode sheets with appropriate sizes. The particle surface of the positive electrode sheet is uniformly coated with lithium iron manganese phosphate on the nanoscale, and the negative electrode sheet is uniformly coated with a solid-state electrolyte on the nanoscale. Step 2: One side of the separator is coated with a solid-state electrolyte on the micron scale, and the other side is coated with ceramics and glue. Step 3: The finished positive electrode sheet, negative electrode sheet, and separator are wound into a core by a winding machine. The core is placed into an aluminum-plastic film with a shell punched out, and after a series of normal processes such as hot pressing and top sealing, it is dried to obtain an assembled battery cell. Step 4: The monomer, cross-linking agent, and initiator are fully dissolved in the electrolyte to prepare a mixed solution. The mixed solution is injected into the battery cell to be filled with the solution, and it is left standing for 12 - 24 h. It is heated to 60 °C to cause the initiator to release free radicals to initiate the polymerization of the monomer, obtaining a semi-solid-state battery.

2. The preparation method of a semi-solid battery doped with lithium iron manganese phosphate according to claim 1, wherein The positive electrode material includes a nickel-cobalt-manganese ternary material, specifically one of NCM-5, NCM-6, NCM-8, NCM-9, and lithium cobalt oxide positive electrodes.

3. The preparation method of a semi-solid state battery doped with lithium iron manganese phosphate according to claim 1, characterized in that, The positive electrode material also includes doped lithium iron manganese phosphate LMFP on the nanoscale, and the doping amount of lithium iron manganese phosphate is 1 wt% - 5 wt% of the positive electrode material.

4. The preparation method of a semi-solid battery doped with lithium iron manganese phosphate according to claim 1, characterized in that, The solid electrolyte coating the negative electrode material is Li 0.5 La 0.5 TiO3, Li 1.4 Al 0.4 Ti 1.6 (PO4)3, Li 6.4 La3Zr 1.4 Ta 0.6 O 12 , Li7La3Zr2O 12 , Li3ErCl6, Li3InCl6; the blending amount of the solid electrolyte coating the negative electrode material is 1 wt% to 5 wt%.

5. The preparation method of a semi-solid battery doped with lithium iron manganese phosphate according to claim 1, characterized in that The micron-scale solid electrolyte coated on one side of the separator is one of the following substances: Li 1.4 Al 0.4 Ti 1.6 (PO4)3, Li3InCl6, Li7La3Zr2O 12 , Li3ErCl6, Li 0.5 La 0.5 TiO3, Li 6.4 La3Zr 1.4 Ta 0.6 O 12 ; the coating thickness of the separator is 1 to 3 microns.

6. The preparation method of a semi-solid battery doped with lithium iron manganese phosphate according to claim 1, characterized in that, The monomer is any one of 2,4,6-triallyloxy-1,3,5-triazine, triallyl isocyanurate, triallyl trimellitate, and isopentyl tetraacrylate.

7. The preparation method of a semi-solid battery doped with lithium iron manganese phosphate according to claim 1, characterized in that, The initiator is any one of azobisisobutyronitrile, methyl ethyl ketone peroxide, benzoyl peroxide, 2,4-dimethylvaleronitrile, dimethyl 2,2'-azobis(2-methylpropionate), benzoyl peroxide oxide, and tert-butyl benzoyl peroxide.

8. The preparation method of a semi-solid battery doped with lithium iron manganese phosphate according to claims 1 to 7, characterized in that For the obtained semi-solid-state battery, its structure includes a dry battery cell. The dry battery cell includes a positive electrode sheet, a negative electrode sheet, and a separator. The particle surface of the positive electrode sheet is uniformly coated with lithium iron manganese phosphate LMFP on the nanoscale, the negative electrode sheet is uniformly coated with a solid-state electrolyte on the nanoscale, and one side of the separator is coated with a solid-state electrolyte on the micron scale.

Images