High-strength positive electrode based on polymer graft modification, and preparation method and application thereof

Abstract

The application discloses a high-strength positive electrode based on polymer grafting modification and a preparation method and application thereof. The positive electrode is prepared from a positive electrode polymer material, a conductive agent and a binder as main raw materials through chemical complexation, and the mass ratio of the positive electrode polymer material, the conductive agent and the binder is 6:20:1. The in-situ crosslinking grafting polymerization strategy is adopted, good contact is realized, stable chemical bonds are formed, and the mechanical strength of the positive electrode is improved. The prepared positive electrode has good electrochemical stability, thermodynamic stability and good ionic conductivity, which provides a new thought for the preparation and optimization of polymer complete machines and is beneficial to the full industrialization of solid-state structure batteries.

Description

Technical Field

[0001] This invention belongs to the field of all-solid-state battery technology, and relates to a high-strength positive electrode based on polymer grafting modification, its preparation method and application. The polymer positive electrode has excellent mechanical properties and high ionic conductivity. By grafting and copolymerizing high-strength polymers, a high mechanical strength network is formed to accelerate the ion conductivity of the positive electrode. Background Technology

[0002] The depletion of natural resources and the advancement of the global carbon peaking and carbon neutrality initiatives have brought batteries back into focus. However, traditional batteries are large and heavy, often requiring specially designed load-bearing structures for their application. Furthermore, the materials used in their cells mean that traditional batteries cannot withstand high-intensity pressure and impact, leading to frequent safety incidents such as battery damage and leakage in actual production and daily life. Summary of the Invention

[0003] This invention focuses on polymer cathodes and provides a simple, high-performance polymer-based solid cathode with high conductivity and high mechanical strength, as well as its preparation method. The polymer-based cathode prepared by this invention exhibits good mechanical strength, stable electrochemical performance, good thermodynamic stability, and high ionic conductivity.

[0004] The objective of this invention is achieved through the following technical solution:

[0005] The high-strength cathode based on polymer grafting modification is composed of positive electrode active polymer and conductive agent, which eliminates the binder required in the traditional cathode material preparation and saves costs.

[0006] The high-strength cathode based on polymer grafting modification is prepared by the following steps:

[0007] Step 1: Preparation of the positive electrode polymer

[0008] (1.1) After the positive electrode material and polymer monomer are stirred evenly, ethanol is added and the mixture is stirred thoroughly for 3 to 4 hours using a magnetic stirrer.

[0009] The positive electrode active material includes one of the following: lithium cobalt oxide (LCO), lithium manganese oxide (LMO), lithium iron phosphate (LFP), ternary materials lithium nickel cobalt manganese oxide (NCM) and lithium nickel cobalt aluminum oxide (NCA), dimercapto-thiamic acid (DMCT), trithiocyanate (TTCA), and tetrathio-ethylenediamine (TTEA).

[0010] The polymer monomer is one of the following: polyacetylene (PDB), polyvinylidene fluoride (PVDF), polyethylene oxide (PEO), polyphenylene, polypyrrole, polythiophene, polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyethylene oxide, polypropylene oxide, polyethylene succinate, polyethylene sebacate, and polyethylene glycol imine.

[0011] (1.2) After stirring, remove the container and wait for the ethanol to evaporate. Then, keep the mixture at 80-100℃ and dry it for 10 hours. Grind the dried mixture into powder for later use.

[0012] (1.3) Add 4% silane coupling agent and ethanol, and stir vigorously for 5-8 hours. The silane coupling agent is one of KH550, KH560, KH570, KH792 and DL602.

[0013] (1.4) Add crosslinking agent and initiator, and under a protective atmosphere, stir vigorously and under ultraviolet light irradiation, the surface-modified positive electrode active material and polymer monomers undergo crosslinking. The positive electrode material forms a stable covalent bond between the polymer monomers to form a high mechanical strength network. The crosslinking agent is one of dicumyl peroxide (DCP), benzoyl peroxide (BPO), pentaerythritol tetrakis(3-mercaptopropionic acid) ester, and isocyanate. The initiator is one of 2,2-dimethoxy-2-phenylacetophenone and azoisobutyronitrile (AIBN).

[0014] (1.5) The positive electrode material obtained in (1.4) is dried at 100℃ and then ground into powder for later use.

[0015] Step 2: Preparation of the positive electrode

[0016] (2.1) Add the binder, conductive agent, and the modified graft polymer obtained in step one to the container, and mix and stir for at least 4 hours. The mass ratio of the positive electrode active polymer, binder, and conductive agent is 6:20:1;

[0017] (2.2) The material in (2.1) is uniformly coated on the current collector and dried at 60-80℃ for 6-10h. The dried positive electrode is then cut into strips to complete the preparation of the high-strength positive electrode.

[0018] The high-strength cathode based on polymer grafting modification obtained in this invention can be used as an electrode material for solid-state batteries.

[0019] Compared with existing technologies, the present invention has the following advantages:

[0020] 1. The method of the present invention has a wide range of applications and is applicable to the modification of most positive electrode active materials to prepare high-strength positive electrodes.

[0021] 2. By modifying the positive electrode active material, this invention can not only graft it onto the polymer, but also make the positive electrode active material uniformly dispersed, thereby improving the ionic conductivity of the polymer positive electrode.

[0022] 3. The grafting modification strategy adopted in this invention can significantly improve the mechanical strength of the cathode, which helps the long cycle performance of all-solid-state polymer batteries and further improves the application of lithium metal in secondary batteries.

[0023] 4. This invention provides new ideas for the preparation and industrialization of polymer cathodes and all-polymer solid-state batteries, which is conducive to the industrialization of all-solid-state batteries.

[0024] 5. The use of high-strength polymer cathodes significantly improves the safety and reliability of the battery, and also enhances the safety of related products using this battery. Attached Figure Description

[0025] Figure 1 This is a flowchart of the positive electrode polymer preparation process;

[0026] Figure 2 The graph shows the cycle performance of the battery after the positive electrode described in Example 2 is fabricated.

[0027] Figure 3 The charging and discharging curves are those of the positive electrode prepared into a battery as described in Example 2. Detailed Implementation

[0028] The technical solution of the present invention will be further described below with reference to the embodiments, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0029] Example 1

[0030] like Figure 1 The process shown in this embodiment provides a method for preparing a high-strength cathode based on polymer grafting modification. The specific preparation steps are as follows:

[0031] (1) Add 1.5g of lithium nickel cobalt manganese oxide (NCM) and 5g of polyvinylidene fluoride (PVDF) to 50ml of ethanol and stir thoroughly for 3h. Let the mixture stand until the ethanol evaporates, then place the mixture in an oven at 80-100℃ and dry for 10h. Place the dried material in a planetary ball mill and grind it into powder for later use.

[0032] (2) Add silane coupling agent KH570 (MPS) to the mixed powder obtained in step (1) and stir in a magnetic stirrer for 5 hours. Under the action of silane coupling agent, the surface of lithium nickel cobalt manganese oxide is modified to generate ions with double bonds.

[0033] (3) Add dicumyl peroxide (DCP) as a crosslinking agent and 2,2-dimethoxy-2-phenylacetophenone as a photoinitiator to the modified lithium nickel cobalt manganese oxide (NCM) obtained in step (2). Stir vigorously under a protective atmosphere and irradiate with ultraviolet light for 10 min to polymerize the lithium nickel cobalt manganese oxide ions with double bonds and the functional groups on the PVDF surface to form a high mechanical strength network. The amount of crosslinking agent added is 20% of the mass of lithium nickel cobalt manganese oxide (NCM), and the amount of initiator is 3% of the mass of lithium nickel cobalt manganese oxide (NCM).

[0034] (4) The polymerized positive electrode active material is dried at 100°C and then ground into powder for later use.

[0035] (5) Add 10g CMC, 0.5g surP and 3g modified polymerized lithium nickel cobalt manganese oxide (NCM) to the container and stir for 5h. Then, ultrasonically disperse for 15min to complete the preparation of the polymer-based positive electrode slurry.

[0036] (6) The slurry is uniformly coated on aluminum foil and dried at 60-80℃ for 6-10h to obtain a polymer-based high-strength positive electrode.

[0037] Example 2

[0038] (1) Add 3g of lithium iron phosphate (LFP) and 10g of polyacrylonitrile (PAN) to 50ml of ethanol and stir thoroughly for 3h. Let the mixture stand until the ethanol evaporates, then place the mixture in an oven at 80-100℃ and dry for 10h. Place the dried material in a planetary ball mill and grind it into powder for later use.

[0039] (2) Add silane coupling agent KH570 (MPS) to the mixed powder obtained in (1) and stir in a magnetic stirrer for 5 hours. Under the action of silane coupling agent, the surface of lithium iron phosphate (LFP) is modified to generate ions with double bonds.

[0040] (3) Add dicumyl peroxide (DCP) as a crosslinking agent and 2,2-dimethoxy-2-phenylacetophenone as a photoinitiator to the modified lithium iron phosphate (LFP) obtained in (2). Stir vigorously under a protective atmosphere and irradiate with ultraviolet light for 10 min to polymerize the lithium iron phosphate (LFP) ions with double bonds and the PAN surface functional groups to form a high mechanical strength network. The amount of crosslinking agent added is 20% of the mass of lithium iron phosphate (LFP), and the amount of initiator is 3% of the mass of lithium iron phosphate (LFP).

[0041] (4) The polymerized positive electrode active material is dried at 100°C and then ground into powder for later use.

[0042] (5) Add 10g CMC, 0.5g surP and 3g modified polymerized lithium iron phosphate (LFP) to the container and stir for 5h. Then, ultrasonically disperse for 15min to complete the preparation of the polymer-based positive electrode slurry.

[0043] (6) The slurry is uniformly coated on aluminum foil and dried at 60-80℃ for 6-10h to obtain a polymer-based high-strength positive electrode.

[0044] Finally, this experiment used the material ratio described in Example 2 for verification and analyzed its electrochemical performance. The experimental results showed that the positive electrode prepared with the addition of polymer, such as... Figure 2 Cycle performance diagram of the positive electrode after it is made into a battery and Figure 3 The charge-discharge curves of the positive electrode after it was made into a battery showed that its electrochemical performance remained relatively stable, and its capacity decay rate after 120 charge-discharge cycles was 3.3% (the battery used was a coin cell due to time constraints).

Claims

1. A method for preparing a high-strength positive electrode based on polymer grafting modification, characterized in that, Includes the following steps: Step 1: Preparation of the positive electrode polymer (1.1) After the positive electrode material and polymer monomer are stirred evenly, ethanol is added and the mixture is stirred thoroughly with a magnetic stirrer for 3-4 hours; (1.2) After stirring, remove the container and wait for the ethanol to evaporate. Then, dry the mixture at 80~100℃ for 10h. Grind the dried mixture into powder for later use. (1.3) Add 4% silane coupling agent and ethanol, and stir vigorously for 5-8 hours; (1.4) Add crosslinking agent and initiator, stir vigorously under a protective atmosphere and under ultraviolet light irradiation, the surface-modified positive electrode active material and polymer monomers undergo crosslinking, and the positive electrode material forms a stable covalent bond between the polymer monomers to form a high mechanical strength network. (1.5) The positive electrode material obtained in (1.4) is dried at 100℃ and ground into powder for later use; Step 2: Preparation of the positive electrode (2.1) Add binder, conductive agent and the modified graft polymer obtained in step one to the container, and mix and stir for more than 4 hours. (2.2) Coat the material in (2.1) evenly on the current collector, dry it at 60~80℃ for 6-10h, and cut the dried positive electrode into strips to complete the preparation of the high-strength positive electrode.

2. The method for preparing a high-strength positive electrode based on polymer grafting modification according to claim 1, characterized in that, In step (1.1), the positive electrode active material includes one of lithium cobalt oxide (LCO), lithium manganese oxide (LMO), lithium iron phosphate (LFP), ternary materials lithium nickel cobalt manganese oxide (NCM) and lithium nickel cobalt aluminum oxide (NCA), dimercapto-thiamic acid (DMCT), trithiocyanate (TTCA), and tetrathio-ethylenediamine (TTEA). The polymer monomer is one of the following: polyacetylene (PDB), polyvinylidene fluoride (PVDF), polyethylene oxide (PEO), polystyrene, polypyrrole, polythiophene, polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyethylene oxide, polypropylene oxide, polyethylene succinate, polyethylene sebacate, and polyethylene glycol imine.

3. The method for preparing a high-strength positive electrode based on polymer grafting modification according to claim 1, characterized in that, In step (1.3), the silane coupling agent is one of KH550, KH560, KH570, KH792, and DL602.

4. The method for preparing a high-strength positive electrode based on polymer grafting modification according to claim 1, characterized in that, In step (1.4), the crosslinking agent is one of dicumyl peroxide (DCP), benzoyl peroxide (BPO), pentaerythritol tetrakis(3-mercaptopropionic acid) ester, and isocyanate, and the initiator is one of 2,2-dimethoxy-2-phenylacetophenone and azoisobutyronitrile (AIBN).

5. The method for preparing a high-strength positive electrode based on polymer grafting modification according to claim 1, characterized in that, In step (2.1), the mass ratio of the positive electrode active polymer, binder, and conductive agent is 6:20:

1.

6. A high-strength cathode based on polymer grafting modification, obtained by the preparation method according to any one of claims 1 to 5.

7. The high-strength positive electrode based on polymer grafting modification as described in claim 6, used as an electrode material for solid-state batteries.

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