Composite electrode active material for suppressing gas generation in battery, method for preparing the same, and composite electrode

Abstract

The present application relates to a kind of inhibiting battery gas composite electrode active material and its preparation method and composite electrode, the composite electrode active material is two-layer structure, inner layer is electrode active material, outer layer is the functional copolymer formed in situ polymerization;The functional copolymer is obtained by copolymerization including phosphorus-containing monomer, ether oxygen-containing monomer, alkenyl imidazole salt compound;The outer layer accounts for 2-10wt% of composite electrode active material.The present application makes suitable proportion of alkenyl imidazole salt compound, phosphorus-containing monomer, ether oxygen-containing monomer in-situ copolymerization on the surface of electrode active material by high-energy ball milling method, forms composite electrode active material, and the prepared composite electrode active material can effectively inhibit battery thermal runaway gas generation while ensuring electrochemical performance, efficiently improves battery safety performance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of electrochemistry and the field of energy material technology, and particularly relates to a composite electrode active material for inhibiting gas production of a battery and a preparation method thereof and a composite electrode. BACKGROUND

[0002] In recent years, with the rapid development of new energy electric vehicles, large-scale energy storage devices and other fields, the demand for higher specific energy and safer energy storage devices is also growing rapidly. Alkali metal ion secondary batteries have become the focus of widespread attention, especially lithium ion batteries, which have been applied in people's production and life due to their high energy density and long cycle stability. In recent years, with the continuous development of electrode materials for alkali metal ion secondary batteries, the energy density has been effectively improved, but the safety problem of the battery has become increasingly serious. The short circuit and thermal runaway behavior of high-energy-density batteries caused by external impact and high temperature can cause serious safety accidents. Taking the common high-nickel ternary material as an example, during the thermal runaway process of the battery, lattice oxygen will be released, which will react with the electrolyte and the negative electrode material to generate a large amount of heat. Especially, a large amount of flammable gas will be produced during the thermal runaway process of the battery, which is easy to cause fire and explosion risk if it comes into contact with the outside.

[0003] At present, lithium ion battery flame retardant additives and flame retardant electrolytes have attracted widespread attention from researchers, but there are few reports on the inhibition of gas production during thermal runaway. During the thermal runaway process of the battery, the electrolyte will pyrolyze to produce a large amount of gas mainly composed of hydrocarbons (methane, ethane, ethylene), and after the active oxygen is released by the anode pyrolysis, the oxygen-deficient combustion occurs. When the gas pressure is large enough, it will break through the outside of the battery, causing a large amount of incompletely oxidized flammable gas to enter the air, resulting in external explosion that endangers life and property safety. Reducing the gas production during the thermal runaway process can prevent the battery from being broken through by excessive gas pressure in the early stage of thermal runaway, thereby delaying the explosion time and reducing the power and risk of gas deflagration. SUMMARY

[0004] In view of the above problems, the present application provides a composite electrode active material for inhibiting gas production of a battery. A phosphorus-containing monomer, an ether oxygen-containing monomer and an alkenyl imidazole salt compound are in-situ copolymerized on the surface of the electrode active material by a high-energy ball milling method to form a P-N functional copolymer coated electrode active material, i.e. a composite electrode active material with an inner layer of electrode active material and an outer layer of P-N functional copolymer. During the thermal runaway process of the battery, the P-N functional copolymer in the outer layer can release free radicals in the early stage of thermal runaway, terminate the chain reaction and avoid the formation of a large amount of flammable gas, while promoting the carbonization of the condensed phase, thereby inhibiting the gas production during thermal runaway, preventing fire and explosion and improving the safety of the battery. That is, the composite electrode active material of the present application can effectively inhibit the gas production during thermal runaway of the battery while ensuring the electrochemical performance, thereby efficiently improving the safety performance of the battery.

[0005] To achieve the above object, the present application adopts the following technical solutions:

[0006] A composite electrode active material for inhibiting gas production of a battery, which has a two-layer structure, wherein an inner layer is an electrode active material and an outer layer is a functional copolymer formed in situ; the functional copolymer is obtained by copolymerization of a phosphorus-containing monomer, an ether oxygen-containing monomer and an alkenyl imidazole salt compound; and the outer layer accounts for 2-10 wt% of the composite electrode active material.

[0007] Further, the mass ratio of the phosphorus-containing monomer, the ether oxygen-containing monomer and the alkenyl imidazole salt compound is 1:(0.2-0.8):(0.2-0.8), preferably the mass ratio of the phosphorus-containing monomer, the ether oxygen-containing monomer and the alkenyl imidazole salt compound is 1:(0.2-0.4):(0.4-0.6).

[0008] Preferably, the outer layer accounts for 4-6 wt% of the composite electrode active material.

[0009] Further, the alkenyl imidazole salt compound is at least one selected from 1-allyl-3-vinylimidazole chloride salt, 1-allyl-3-vinylimidazole bromide salt and 1-allyl-3-vinylimidazole bis-trifluoromethanesulfonylimide salt, preferably 1-allyl-3-vinylimidazole bis-trifluoromethanesulfonylimide salt. The alkenyl imidazole salt compound is an ionic liquid monomer with an imidazole group. It is found through research that, when it is in-situ copolymerized with the phosphorus-containing monomer and the ether oxygen-containing monomer on the surface of the electrode active material to form a P-N functional copolymer, a composite electrode active material in which the electrode active material is coated with the P-N functional copolymer is formed. When used in a lithium ion battery, the composite electrode active material can significantly inhibit gas production during thermal runaway of the battery. The possible reason is that the alkenyl imidazole salt compound is an ionic liquid, and the stability of the ionic bond therein is much higher than that of the covalent bond, thus having good high-temperature stability, and further improving the temperature resistance of the functional polymer obtained after copolymerization. On the other hand, the imidazole group therein contains nitrogen, which can synergize with the phosphorus-containing compound to decompose at high temperature to produce a phosphorus-containing compound and nitrogen, neutralize free radicals, interrupt the combustion chain reaction, inhibit the production of flammable gas, dilute the flammable gas and reduce the risk of deflagration. In addition, the alkenyl imidazole salt compound can also improve the ion transport effect of the electrode functional additive coating layer, ensuring the capacity cycle stability of the battery. However, the proportion of each monomer needs to be controlled, and only in the case of a suitable proportion, can both excellent gas production inhibition effect of the battery and good electrochemical performance be obtained.

[0010] Further, the phosphorus-containing monomer is a carbon-carbon double bond-containing phosphonate compound or a carbon-carbon double bond-containing phosphonic acid compound, and is specifically at least one of vinyl phosphonic acid, dimethyl vinyl phosphonate, diethyl vinyl phosphonate, dimethyl allyl phosphonate, diethyl allyl phosphonate, dipropyl allyl phosphonate, and diethyl isopropenyl phosphonate; preferably dimethyl vinyl phosphonate, diethyl vinyl phosphonate, and diethyl allyl phosphonate. In the initial stage of battery thermal runaway heating, the phosphonate can decompose to generate free radicals, participate in combustion reaction and electrolyte chain reaction, terminate the chain reaction through three-body reaction, inactivate the combustible substances such as electrolyte and leave them in the carbon layer of the condensed phase, and play a role in inhibiting thermal runaway gas production. The decomposition product of the phosphonate is an important component for inhibiting gas production. The phosphorus-containing monomer selected in the application has small steric hindrance and is easy to be introduced into the functional copolymer.

[0011] Further, the ether oxygen-containing monomer is an ether oxygen-containing alkenoic acid ester compound, and is specifically at least one of ethoxylated trimethylolpropane triacrylate, trimethylolpropane triacrylate, and pentaerythritol tetraacrylate. The ether oxygen-containing monomer selected in the application contains a large number of oxygen-containing substituents, which is conducive to the breaking of carbon-carbon double bonds and the occurrence of polymerization, that is, conducive to copolymerization. Meanwhile, the flexible ether oxygen group can toughen and strengthen the system. The ethoxylated trimethylolpropane triacrylate also has a suitable number and length of branched chains, has small steric hindrance, and can further promote the occurrence of copolymerization reaction and improve the crosslinking degree of the polymer.

[0012] Further, the electrode active material is a positive electrode active material or a negative electrode active material, and the median particle size D50 is 5-12 μm; the positive electrode active material includes but is not limited to one of sulfur-carbon, lithium cobaltate, transition metal layered oxide, Prussian blue, or phosphate material; and the negative electrode active material includes but is not limited to one of graphite, silicon-carbon, hard carbon, or alloy material.

[0013] In a second aspect, the application further provides a preparation method of the composite electrode active material for inhibiting battery gas production, and the method comprises the following steps:

[0014] (S1) dissolving the phosphorus-containing monomer, the ether oxygen-containing monomer, the alkenyl imidazole salt compound, and the initiator in a polar organic solvent to obtain a precursor solution, and then mixing the precursor solution with the electrode active material to obtain a precursor mixture;

[0015] (S2) placing the precursor mixture in a ball mill jar and performing in-situ copolymerization by high-energy ball milling, and after the ball milling is completed, filtering and drying to obtain a composite electrode active material with the electrode active material as an inner layer and the functional copolymer as an outer layer.

[0016] The precursor mixture obtained after mixing the precursor solution with the electrode active material is in a semi-wet state, and under the action of the initiator, the three monomers in the precursor solution are copolymerized on the surface of the electrode active material during high-energy ball milling, thereby forming a functional copolymer coated on the surface of the electrode active material.

[0017] Further, in step (S1), the total mass of the phosphorus-containing monomer, the ether-oxygen-containing monomer and the alkenyl imidazole salt compound, the amount of the polar organic solvent, and the amount of the electrode active material are in a ratio of (2.5-15) g:(5-20) mL:100 g, preferably (5-7.5) g:(5-20) mL:100 g.

[0018] Further, in step (S1), the initiator is at least one selected from azobisisobutyronitrile, azobisisoheptyl nitrile, dimethyl azobisisobutyrate, azobisisobutylimidazole hydrochloride, dibenzoyl peroxide, and diisopropyl phenyl peroxide; and the amount of the initiator is 1-2 wt% of the total mass of the phosphorus-containing monomer, the ether-oxygen-containing monomer and the alkenyl imidazole salt compound. The amount of the initiator is relatively large for the preparation of a general high-molecular-weight linear polymer, so that the initiation sites are more, and a more branched and cross-linked dense functional copolymer can be formed.

[0019] Further, in step (S1), the polar organic solvent is at least one selected from N,N-dimethylacetamide (DMAC) and N-methyl pyrrolidone (NMP).

[0020] Further, in step (S2), the high-energy ball milling is performed at a rotation speed of 300-500 rpm for 3-8 h, and the drying is performed at 70-90℃ for 6-12 h.

[0021] In a third aspect, the application further provides a composite electrode prepared from the composite electrode active material, a conductive agent and a binder.

[0022] The application has the following beneficial effects:

[0023] 1. In this invention, phosphorus-containing monomers, ether-oxygen-containing monomers, and alkenyl imidazole salt compounds are copolymerized in situ on the surface of the electrode active material using a high-energy ball milling method to form a PN functional copolymer coating the electrode active material, thus forming a composite electrode active material. The phosphonate or phosphonic acid groups in the functional copolymer have low decomposition temperatures and can decompose to generate phosphorus-containing free radicals in the early stages of battery thermal runaway, participating in combustion reactions and electrolyte chain reactions. The chain reaction is terminated through a three-body reaction, inertizing flammable substances such as the electrolyte and retaining them in the char layer of the condensed phase, thus suppressing thermal runaway gas production and preventing battery explosion and deflagration. The imidazole salt groups in the functional copolymer have good thermal stability and do not decompose at low temperatures. When the battery reaches high temperatures, nitrogen and phosphorus elements work synergistically, generating nitrogen gas, which dilutes flammable gases; and promoting char formation in the condensed phase, covering larger electrolyte solvent molecules in the char layer and preventing their decomposition and gas production. The synergistic effect of phosphonate and imidazole salt groups controls the thermal runaway gases in the battery. The ether-oxygen groups in the functional copolymer can promote copolymerization with phosphorus-containing monomers and alkenyl imidazole salts, and improve the strength and toughness of the copolymer. The composite electrode active material prepared by this invention through a rational ratio of alkenyl imidazole salts to phosphorus-containing monomers and ether-oxygen-containing monomers can significantly suppress thermal runaway gas generation in batteries, efficiently improve battery safety performance, and ensure good electrochemical performance.

[0024] 2. The composite electrode preparation method provided in this invention introduces functional polymers onto the surface of electrode powder through in-situ copolymerization. Compared with traditional blending methods, this composite electrode formed through in-situ copolymerization does not adversely affect the cycle performance of the battery. The process of this invention is convenient and efficient, directly modifying the electrode powder without affecting existing electrode preparation technologies, and is suitable for large-scale commercial production. Attached Figure Description

[0025] Figure 1 This is a TEM image of the composite electrode active material prepared in Example 1.

[0026] Figure 2 The image shows a comparison of the gas production columnar graphs obtained by EGA-MS testing between the composite positive electrode made of the composite electrode active material of Example 1 and the composite positive electrode made of the composite electrode active material of Comparative Example 1, within the temperature range of 50–700°C. Detailed Implementation

[0027] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited to the following embodiments.

[0028] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; the reagents and materials are all commercially available.

[0029] Example 1

[0030] (S1) mixed diethyl isopropenylphosphonate, trimethylolpropane triacrylate, 1-allyl-3-vinylimidazole chloride in a mass ratio of 1:0.2:0.2 to form a mixture of 2.5 g, then the mixture and 0.04 g of azobisisobutyronitrile were co-dissolved in 10 mL of N,N-dimethylacetamide (DMAC) to obtain a precursor solution, which was then mixed with 100 g of positive electrode active material NCM94 to obtain a precursor mixture;

[0031] (S2) The precursor mixture was placed in a ball mill tank and ball milled at a speed of 450 rpm for 5 h. After ball milling, filtration and drying at 80°C for 12 h, a composite electrode active material with NCM94 as the inner layer and a functional copolymer as the outer layer was obtained.

[0032] The proportion of the outer layer functional copolymer in the entire composite electrode active material was calculated by the increment method, It was calculated that the outer layer functional copolymer accounted for 2.0 wt% of the composite electrode active material.

[0033] The TEM image of the prepared composite electrode active material is shown in Figure 1 From Figure 1 it can be seen that the composite electrode active material prepared in Example 1 has a clear layered structure, with NCM94 as the inner layer and a functional copolymer as the outer layer.

[0034] Example 2

[0035] The rest is the same as Example 1, except that in step (S1), the mass ratio of diethyl isopropenylphosphonate, trimethylolpropane triacrylate, 1-allyl-3-vinylimidazole chloride is 1:0.2:0.4; and finally a composite electrode active material with NCM94 as the inner layer and a functional copolymer as the outer layer is prepared.

[0036] It was calculated by the increment method that the outer layer functional copolymer accounted for 2.1 wt% of the composite electrode active material.

[0037] Example 3

[0038] The rest is the same as Example 1, except that in step (S1), the mass ratio of diethyl isopropenylphosphonate, trimethylolpropane triacrylate, 1-allyl-3-vinylimidazole chloride is 1:0.4:0.4; and finally a composite electrode active material with NCM94 as the inner layer and a functional copolymer as the outer layer is prepared.

[0039] It was calculated by the increment method that the outer layer functional copolymer accounted for 2.1 wt% of the composite electrode active material.

[0040] Example 4

[0041] The rest is the same as example 1, the difference is that in step (S1), the mass ratio of diethyl isopropenyl phosphonate, trimethylolpropane triacrylate, 1-allyl-3-vinylimidazole chloride is 1:0.4:0.6; finally, a composite electrode active material with NCM94 as the inner layer and a functional copolymer as the outer layer is prepared.

[0042] The outer layer functional copolymer accounts for 2.0wt% of the composite electrode active material by calculation by the increment method.

[0043] Example 5

[0044] The rest is the same as example 1, the difference is that in step (S1), the mass ratio of diethyl isopropenyl phosphonate, trimethylolpropane triacrylate, 1-allyl-3-vinylimidazole chloride is 1:0.6:0.6; finally, a composite electrode active material with NCM94 as the inner layer and a functional copolymer as the outer layer is prepared.

[0045] The outer layer functional copolymer accounts for 2.1wt% of the composite electrode active material by calculation by the increment method.

[0046] Example 6

[0047] The rest is the same as example 1, the difference is that in step (S1), the mass ratio of diethyl isopropenyl phosphonate, trimethylolpropane triacrylate, 1-allyl-3-vinylimidazole chloride is 1:0.8:0.6; finally, a composite electrode active material with NCM94 as the inner layer and a functional copolymer as the outer layer is prepared.

[0048] The outer layer functional copolymer accounts for 2.1wt% of the composite electrode active material by calculation by the increment method.

[0049] Example 7

[0050] The rest is the same as example 1, the difference is that in step (S1), the mass ratio of diethyl isopropenyl phosphonate, trimethylolpropane triacrylate, 1-allyl-3-vinylimidazole chloride is 1:0.8:0.8; finally, a composite electrode active material with NCM94 as the inner layer and a functional copolymer as the outer layer is prepared.

[0051] The outer layer functional copolymer accounts for 2.2wt% of the composite electrode active material by calculation by the increment method.

[0052] Example 8

[0053] The rest is the same as example 1, the difference is that in step (S1), diethyl vinylphosphonate is used instead of diethyl isopropenylphosphonate, and 1-allyl-3-vinylimidazole bis-trifluoromethanesulfonyl imide salt is used instead of 1-allyl-3-vinylimidazole chloride salt; finally, a composite electrode active material with NCM94 as the inner layer and a functional copolymer as the outer layer is prepared.

[0054] The outer layer functional copolymer accounts for 2.2wt% of the composite electrode active material by calculation by the increment method.

[0055] Example 9

[0056] The rest is the same as example 2, the difference is that in step (S1), the total mass of the mixture formed by diethyl isopropenylphosphonate, trimethylolpropane triacrylate and 1-allyl-3-vinylimidazole chloride salt is 5.0g, and the amount of azobisisobutyronitrile is 0.06g; finally, a composite electrode active material with NCM94 as the inner layer and a functional copolymer as the outer layer is prepared.

[0057] The outer layer functional copolymer accounts for 4.3wt% of the composite electrode active material by calculation by the increment method.

[0058] Example 10

[0059] The rest is the same as example 2, the difference is that in step (S1), the total mass of the mixture formed by diethyl isopropenylphosphonate, trimethylolpropane triacrylate and 1-allyl-3-vinylimidazole chloride salt is 7.5g, and the amount of azobisisobutyronitrile is 0.9g; finally, a composite electrode active material with NCM94 as the inner layer and a functional copolymer as the outer layer is prepared.

[0060] The outer layer functional copolymer accounts for 6.4wt% of the composite electrode active material by calculation by the increment method.

[0061] Example 11

[0062] The rest is the same as example 2, the difference is that in step (S1), the total mass of the mixture formed by diethyl isopropenylphosphonate, trimethylolpropane triacrylate and 1-allyl-3-vinylimidazole chloride salt is 11g, and the amount of azobisisobutyronitrile is 0.15g; finally, a composite electrode active material with NCM94 as the inner layer and a functional copolymer as the outer layer is prepared.

[0063] The outer layer functional copolymer accounts for 8.4wt% of the composite electrode active material by calculation by the increment method.

[0064] Example 12

[0065] The rest is the same as example 2, except that in step (S1), the total mass of the mixture of diethyl isopropenylphosphonate, trimethylolpropane triacrylate and 1-allyl-3-vinylimidazolium chloride is 15 g, and the amount of azobisisobutyronitrile is 0.18 g; finally, a composite electrode active material with an inner layer of NCM94 and an outer layer of functional copolymer is prepared.

[0066] The outer layer of functional copolymer accounts for 10.3wt% of the composite electrode active material, calculated by the incremental method.

[0067] Comparative example 1

[0068] The rest is the same as example 1, except that in step (S1), 1-allyl-3-vinylimidazolium chloride is not used, i.e., diethyl isopropenylphosphonate and trimethylolpropane triacrylate are mixed in a mass ratio of 1:0.2 to form a mixture of 2.5 g.

[0069] Comparative example 2

[0070] The rest is the same as example 1, except that in step (S1), diethyl isopropenylphosphonate is not used, i.e., trimethylolpropane triacrylate and 1-allyl-3-vinylimidazolium chloride are mixed in a mass ratio of 0.2:0.2 (i.e., 1:1) to form a mixture of 2.5 g.

[0071] Testing and analysis

[0072] 1) Electrode gas production behavior test: The composite electrode active material prepared in each example and the comparative example was mixed with conductive carbon black Super P, polyvinylidene fluoride (PVDF) and organic solvent N-methyl pyrrolidone (NMP) in a mass ratio of 8:1:1:20 to prepare a slurry. The slurry was then coated on an aluminum foil with a coating thickness of 300 μm, and dried in a blast oven at 70°C for 12 hours to obtain a composite electrode. Finally, the composite electrode was used as a positive electrode, lithium metal was used as a negative electrode, polypropylene microporous membrane (Celgard 2400) was used as a separator, and 1M LiPF6 electrolyte (solvent was prepared by adjusting the volume ratio of ethylene carbonate: dimethyl carbonate: diethyl carbonate = 1:1:1) was assembled into a half battery. The specific method for testing the gas production behavior of the battery was as follows: the above assembled half battery was subjected to charge-discharge cycling on a blue battery tester, the charge-discharge rate was 0.2C (1C = 230 mAh / g), and the charge-discharge voltage interval was 2.5-4.35V; after 5 cycles, the battery was charged to 4.4V and then constant voltage charged to a current less than 0.05C, then the battery was disassembled, and the fully charged composite electrode sheet was taken out. The composite electrode sheet was washed with dimethyl carbonate, and then the surface coating was scraped off and weighed. The electrolyte was added to the crucible (volume to mass ratio was 1 μL / mg) together with the electrolyte, and the escaping gas analysis-mass spectrometry (EGA-MS) test was performed, the temperature rising rate was 10°C / min, and the test temperature was 50-700°C.

[0073] The intensity in the test peak reflects the amount of gas released by the sample at the test temperature, and the higher the peak intensity, the more gas is released. The EGA-MS test of the composite positive electrode prepared from the composite electrode active material of Example 1 and the composite positive electrode prepared from the composite electrode active material of Comparative Example 1 within 50-700°C is shown in the following columnar comparison graph: Figure 2 As can be clearly seen from Figure 2 , the gas production of the composite positive electrode prepared from the composite electrode active material of Example 1 is significantly lower than that of Comparative Example 1. The specific gas production test results of the composite positive electrode prepared from the composite electrode active material of each example and the comparative example are shown in Table 1.

[0074] 2) Electrochemical performance test: The half battery assembled in the above examples and comparative examples was subjected to electrochemical performance test on a blue battery tester, and after 3 times of 0.1C charge-discharge, it was cycled at a rate of 0.33C, the charge-discharge voltage interval was 2.5-4.35V, and the first coulombic efficiency and capacity retention rate after 100 cycles were tested, and the test results are shown in Table 1.

[0075] Table 1 Performance test

[0076]

[0077] As shown in Table 1, the composite electrode active material prepared in the embodiments of the application has obvious performance of inhibiting battery gas production, the total gas production intensity of the composite electrode active material prepared in the embodiments in the EGA-MS test is only 40-50% of that of the comparative examples, which indicates that the total gas production of the composite electrode active material prepared in the embodiments within the range of 50-700 DEG C is 40-50% of that of the comparative examples, and the gas production intensity of flammable methane, ethane and propane is also obviously lower than that of the comparative examples.

[0078] As can be seen from the comparison of Examples 1-7 and Comparative Examples 1-2, the functional copolymer produced by copolymerization of the three monomers (the phosphorus-containing monomer, the ether oxygen-containing monomer and the alkenyl imidazole salt compound) has good performance of inhibiting battery gas production only after the composite active material formed by coating the electrode active material.

[0079] As can be seen from the comparison of Example 1 and Examples 8-12, with the increase of the proportion of the functional copolymer in the outer layer, the performance of the composite electrode active material in inhibiting battery gas production is gradually improved, but when the proportion of the functional copolymer in the outer layer increases to 6% of the composite electrode active material, the performance of the composite electrode active material in inhibiting gas production is basically no longer improved.

[0080] As can be seen from the electrochemical performance test data in Table 1, the composite electrode active material prepared in the embodiments of the application has obvious inhibiting effect on battery gas production, does not cause reduction of the first coulombic efficiency, and can also improve the cycle performance of the battery.

[0081] In summary, the composite electrode active material of the application can significantly inhibit battery thermal runaway gas production while ensuring good electrochemical performance.

Claims

1. A composite electrode active material for inhibiting gas evolution of a battery, which is a two-layer structure, an inner layer being an electrode active material and an outer layer being a functional copolymer formed in situ by polymerization; characterized in that, The functional copolymer is obtained by copolymerization of a phosphorus-containing monomer, an ether oxygen-containing monomer and an alkenyl imidazole salt compound; and the outer layer accounts for 2-10 wt% of the composite electrode active material.

2. The composite electrode active material according to claim 1, characterized in that, The mass ratio of the phosphorus-containing monomer, the ether oxygen-containing monomer and the alkenyl imidazole salt compound is 1: (0.2-0.8): (0.2-0.8).

3. The composite electrode active material according to claim 2, characterized in that, The mass ratio of the phosphorus-containing monomer, the ether oxygen-containing monomer and the alkenyl imidazole salt compound is 1: (0.2-0.4): (0.4-0.6).

4. The composite electrode active material according to claim 1, characterized in that, The outer layer accounts for 4-6 wt% of the composite electrode active material.

5. The composite electrode active material according to claim 1, characterized in that, The alkenyl imidazole salt compound is at least one selected from 1-allyl-3-vinylimidazole chloride salt, 1-allyl-3-vinylimidazole bromide salt and 1-allyl-3-vinylimidazole bis-trifluoromethanesulfonylimide salt.

6. The composite electrode active material according to claim 5, characterized in that, The alkenyl imidazole salt compound is 1-allyl-3-vinylimidazole bis-trifluoromethanesulfonylimide salt.

7. The composite electrode active material according to claim 1, characterized in that, The phosphorus-containing monomer is at least one selected from vinyl phosphonate, dimethyl vinyl phosphonate, diethyl vinyl phosphonate, dimethyl allyl phosphonate, diethyl allyl phosphonate, dipropyl allyl phosphonate and diethyl isopropenyl phosphonate; and / or The ether oxygen-containing monomer is at least one selected from ethoxylated trimethylolpropane triacrylate, trimethylolpropane triacrylate and pentaerythritol tetraacrylate.

8. The composite electrode active material according to claim 7, characterized in that, The phosphorus-containing monomer is dimethyl vinyl phosphonate, diethyl vinyl phosphonate or diethyl allyl phosphonate.

9. The composite electrode active material of claim 1, wherein, The electrode active material is a positive electrode active material or a negative electrode active material, and the median particle size D50 is 5-12 μm.

10. The method of producing a composite electrode active material for suppressing gas evolution from a battery according to any one of claims 1 to 9, characterized in that, The method comprises the following steps: (S1) dissolving the phosphorus-containing monomer, the ether oxygen-containing monomer, the alkenyl imidazole salt compound and an initiator in a polar organic solvent to obtain a precursor solution, and then mixing the precursor solution with an electrode active material to obtain a precursor mixture; (S2) placing the precursor mixture in a ball mill tank to perform in-situ copolymerization by high-energy ball milling, filtering and drying after the ball milling to obtain a composite electrode active material with an inner layer of the electrode active material and an outer layer of the functional copolymer.

11. The method of claim 10, wherein, In step (S1), the total mass of the phosphorus-containing monomer, the ether oxygen-containing monomer and the alkenyl imidazole salt compound, the amount of the polar organic solvent and the amount of the electrode active material are in the ratio of (2.5-15) g: (5-20) mL: 100 g.

12. The method of claim 11, wherein, In step (S1), the total mass of the phosphorus-containing monomer, the ether oxygen-containing monomer and the alkenyl imidazole salt compound, the amount of the polar organic solvent and the amount of the electrode active material are in the ratio of (5-7.5) g: (5-20) mL: 100 g.

13. The preparation method according to claim 10, characterized in that, In step (S1), the initiator is at least one selected from azobisisobutyronitrile, azobisisoheptyl nitrile, dimethyl azobis isobutyrate, azobis isobutylimidazole hydrochloride, dibenzoyl peroxide and diisopropylbenzene peroxide; the amount of the initiator is 1-2 wt% of the total mass of the phosphorus-containing monomer, the ether oxygen-containing monomer and the alkenyl imidazole salt compound; and / or In step (S1), the polar organic solvent is at least one of N,N-dimethylacetamide and N-methylpyrrolidone; and / or In step (S2), the high-energy ball milling is performed at a rotation speed of 300-500 rpm for 3-8 h, and the drying is performed at 70-90°C for 6-12 h.

14. A composite electrode, characterized by The composite electrode active material is prepared from a mixture comprising the composite electrode active material according to any one of claims 1-9, a conductive agent, and a binder.

Images