Preparation method of subject-object composite material and battery cell and lithium ion battery

Abstract

The invention discloses a preparation method of a subject-object composite material and a battery cell and a lithium ion battery, and relates to the technical field of lithium ion batteries. The preparation method of the host-guest composite material comprises the following steps: mixing a mixture containing a guest material with a host material, and carrying out in-situ polymerization to load the guest material in an internal porous structure of the host material; the host material comprises a porous material with a high specific surface area, the mixture containing the guest material comprises the guest material, a lithium compound, an initiator and an organic solvent, and the guest material comprises at least one of an organic micromolecule precursor, an inorganic material, cyclic ether, a polymer electrolyte and a solid electrolyte. The specific surface is reduced by more than or equal to 10% compared with the specific surface of the host material and the specific surface of the host-guest composite material after in-situ polymerization. By adding the host-guest composite material formed through in-situ polymerization into the positive electrode material, the calendar life of the lithium ion battery can be remarkably prolonged, the power loss is reduced, and meanwhile, the safety and the quick charge capacity of the lithium ion battery are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a host-guest composite material, a preparation method of a battery core, and a lithium ion battery. Background Art

[0002] With the development of the lithium battery industry, lithium battery materials are updated and iterated, and the main points are centered around calendar life, safety, and fast charging. Each material has its drawbacks and highlights. For example, lithium manganese oxide decays quickly during high-temperature cycles, and the capacity decays along with the power decay. For example, ternary materials have high energy density but poor safety. Based on the above pain points, a new type of safe fast ion conductor is developed to improve the safety of lithium-ion batteries, increase their calendar life, and reduce power loss.

[0003] In view of this, the present invention is proposed. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a host-guest composite material and a method for preparing a battery core.

[0005] The present invention is achieved in that:

[0006] In a first aspect, the present invention provides a method for preparing a host-guest composite material, which comprises mixing a mixture containing a guest material with a host material, and performing in-situ polymerization so that the guest material is loaded in the internal porous structure of the host material; the host material comprises a high specific surface area porous material, the pore size of the host material is ≥0.1 μm, the porosity is ≥2%, and the specific surface area is ≥2 μm. 2 / g; the mixture containing the guest material includes a guest material, a lithium compound, and an initiator organic solvent, the guest material includes at least one of an organic small molecule precursor, an inorganic material, a cyclic ether, a polymer electrolyte, and a solid electrolyte, the molecular weight of the guest material is ≤20000g / mol, and the particle size is <0.1μm. Compared with the specific surface area of ​​the host material and the specific surface area of ​​the host-guest composite material after in-situ polymerization, the specific surface area decreases by ≥10%.

[0007] In an optional embodiment, the main material is the high specific surface area porous material alone or a positive electrode system containing the high specific surface area porous material.

[0008] In an optional embodiment, the high specific surface area porous material comprises an inorganic mesoporous oxide, an organic porous metal framework or an organic mesoporous polymer;

[0009] Preferably, the inorganic mesoporous oxide comprises at least one of silicon dioxide, aluminum oxide, magnesium oxide and zirconium oxide;

[0010] Preferably, the organic porous metal framework comprises at least one of MOF and COF;

[0011] Preferably, the organic mesoporous polymer is PCM.

[0012] In an optional embodiment, the organic small molecule precursor includes at least one of VC and FEC;

[0013] And / or, the polymer electrolyte comprises at least one of PEO and PVDF;

[0014] And / or, the solid electrolyte includes at least one of a LATP solid electrolyte, a LLZO solid electrolyte, a LPS solid electrolyte, a LZTO solid electrolyte and a sulfide solid electrolyte.

[0015] In an optional embodiment, the molar ratio of the host material to the guest material is 0.5-100:1;

[0016] Preferably, the mixture containing the guest material comprises, by mass percentage, 10-50% of the guest material, 1%-20% of the lithium compound, 0.1%-5% of the initiator and 40-70% of the organic solvent;

[0017] Preferably, the lithium compound comprises LiPF 6 , at least one of LiFSi and LiTFSi;

[0018] Preferably, the initiator comprises at least one of AIBN, DOL and benzoyl oxide;

[0019] Preferably, the organic solvent comprises at least one of VC, FEC, EC and DEC;

[0020] In an optional embodiment, the in-situ polymerization is carried out at a temperature of 40°C to 80°C and for a time of 1 to 12 hours;

[0021] Preferably, microwave or ultraviolet light irradiation is applied during the in-situ polymerization.

[0022] In a second aspect, the present invention provides a method for preparing a battery cell, wherein the positive electrode system contains a host-guest composite material prepared by the method for preparing a host-guest composite material as described in any one of the aforementioned embodiments.

[0023] In an optional embodiment, the method of adding the host-guest composite material to the positive electrode system includes directly adding the host-guest composite material to the positive electrode system to prepare a finished battery cell.

[0024] In an optional embodiment, the method of adding the host-guest composite material to the positive electrode system includes adding the host material to the positive electrode system, then preparing a dry battery cell without liquid injection, placing the dry battery cell in a vacuum environment, and then injecting the mixture containing the guest material into the dry battery cell by liquid injection for infiltration for 5-10 hours, then heating for in-situ polymerization, cooling to room temperature, and then injecting an electrolyte, and then sizing to prepare a finished battery cell;

[0025] Preferably, the vacuum degree of the vacuum environment is ≥-80Kpa.

[0026] In a third aspect, the present invention provides a lithium-ion battery, comprising a battery cell prepared by the method for preparing a battery cell as described in any one of the aforementioned embodiments.

[0027] The present invention has the following beneficial effects:

[0028] The host-guest composite material provided by the present invention is formed by in-situ polymerization of the host material and the guest material under the action of an initiator, so that the guest material is embedded in the internal pores of the host material, thereby forming a high specific surface porous material to encapsulate the guest material with conductive properties, and the specific surface area is significantly reduced compared with the specific surface of the host-guest material before polymerization, which will make the host-guest composite material not only have good conductive properties, but also have the effects of improving the stability of the positive electrode, inhibiting the dissolution of the positive electrode transition metal elements, etc., and its coating on the positive electrode surface can also greatly improve the safety. The host-guest composite material formed by in-situ polymerization is added to the positive electrode material to significantly improve the calendar life of the lithium-ion battery, while reducing power loss, and is also conducive to improving the safety and fast charging capability of the lithium-ion battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 This is a SEM image of the distribution of the main material provided in Example 1 in the positive electrode system;

[0031] Figure 2 A distribution diagram of aluminum elements in the cathode system of the main material provided in Example 1;

[0032] Figure 3 This is the SEM image of the host-guest composite material prepared in Example 2. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0034] The present invention provides a method for preparing a host-guest composite material, which comprises mixing a mixture containing a guest material with a host material, and performing in-situ polymerization to load the guest material into an internal porous structure of the host material. The in-situ polymerization is performed at a temperature of 40°C-80°C and for a time of 1-12 hours.

[0035] In the present invention, the main material is a high specific surface porous material, the pore size of the main material is ≥ 0.1 μm, the porosity is ≥ 2%, and the specific surface is ≥ 2 μm. 2 / g; high specific surface porous materials include inorganic mesoporous oxides, organic porous metal frameworks or organic mesoporous polymers; preferably, inorganic mesoporous oxides include at least one of silica, alumina, magnesium oxide and zirconium oxide; preferably, organic porous metal frameworks include at least one of MOF and COF; preferably, organic mesoporous polymers are PCM. In the present invention, the main material not only has a large specific surface, but also has a porous structure, which is conducive to loading subsequent guest materials. Among them, MOF refers to Metal-Organic Framework, a metal-organic framework material, MOF is an organic-inorganic hybrid material with intramolecular pores formed by self-assembly of organic ligands and inorganic metal ions or clusters through coordination bonds. MOF has the characteristics of high specific surface area, high porosity and designable structure. COF refers to Covalent Organic Framework, and covalent organic framework materials (COFs) are organic porous crystalline materials connected by covalent bonds of light elements (C, O, N, B, etc.). The above MOF, COF and PCM are all commercially available materials.

[0036] The mixture containing the guest material comprises the guest material, a lithium compound, an initiator and an organic solvent, and comprises, by mass percentage, 10-50% of the guest material, 1%-30% of the lithium compound, 0.1%-5% of the initiator and 40-70% of the organic solvent.

[0037] In the present invention, the lithium compound can provide a certain ion conductivity, and the initiator can initiate the polymerization of the main material and the guest material, promoting the occurrence of in-situ polymerization. The organic solvent can better dissolve the guest material, the lithium compound, the initiator and other materials, thereby forming a uniform mixture, which is conducive to the subsequent in-situ polymerization with the main material.

[0038] Wherein, the guest material includes at least one of an organic small molecule precursor, an inorganic material, a cyclic ether, a polymer electrolyte, and a solid electrolyte. The molecular weight of the guest material is ≤20000 g / mol, and the particle size is <0.1 μm. Preferably, the organic small molecule precursor includes but is not limited to at least one of vinylene carbonate (VC) and fluoroethylene carbonate (FEC); the polymer electrolyte includes but is not limited to at least one of PEO (polyethylene oxide) and polyvinylidene fluoride (PVDF); the solid electrolyte includes but is not limited to LATP solid electrolyte (lithium aluminum titanium phosphorus oxide), LLZO solid electrolyte (lithium lanthanum zirconium oxide), LPS solid electrolyte (lithium phosphorus sulfide), LZTO solid electrolyte (lithium zirconium titanium oxide Li 6.25 Al 0.25 La 3 Zr 2 O 12 ) and at least one of a sulfide solid electrolyte.

[0039] Lithium compounds include, but are not limited to, lithium hexafluorophosphate (LiPF 6 ), at least one of lithium bis(fluorosulfonyl)imide (LiFSi) and lithium bis(trifluoromethylsulfonyl)imide (LiTFSi); the initiator includes but is not limited to at least one of azobisisobutyronitrile (AIBN), 1,3-dioxolane (DOL) and benzoyl oxide; the organic solvent includes but is not limited to at least one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), ethylene carbonate (EC) and diethyl carbonate (DEC).

[0040] In the present invention, the molar ratio of the host material to the guest material is 0.5-100:1; the guest material is loaded on the porous structure surface of the host material by in-situ polymerization, and the specific surface area of ​​the host material is compared with the specific surface area of ​​the host-guest composite material after in-situ polymerization, and the specific surface area decreases by ≥10%. The decrease in specific surface area proves that the guest material is successfully embedded in the interior of the host material by in-situ polymerization, and the host-guest composite material is prepared.

[0041] In addition, the present invention provides a method for preparing a battery cell, wherein the positive electrode system contains the host-guest composite material prepared by the preparation method of the host-guest composite material.

[0042] Among them, when preparing the battery cell, the host-guest composite material is added to the positive electrode system in the following two ways:

[0043] The first method is to prepare an independent host-guest composite material according to the in-situ polymerization method, and directly add the host-guest composite material into the positive electrode system to prepare a finished battery cell.

[0044] The second method is to first add the main material to the positive electrode system, then make a dry battery cell without liquid injection, put the dry battery cell into a vacuum environment, and then inject the mixture containing the guest material into the dry battery cell by liquid injection for infiltration for 10-48 hours, then heat it for in-situ polymerization, cool it to room temperature, and then inject a conventional electrolyte (the conventional electrolyte can be selected with reference to common electrolytes on the market, and the addition amount is also added according to the conventional addition amount, which is not specifically elaborated in the present invention), and then divide the components into volumes to prepare the finished battery cell; preferably, the vacuum degree of the vacuum environment is ≥-80Kpa.

[0045] Preparing the above-mentioned battery cells into lithium-ion batteries can significantly increase the calendar life of lithium-ion batteries, while reducing power losses, and is also beneficial to improving the safety and fast charging capabilities of lithium-ion batteries.

[0046] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0047] Example 1

[0048] This embodiment provides a method for preparing a battery cell, wherein when preparing a host-guest composite material, the host material is inorganic mesoporous alumina, wherein the mesoporous alumina has a specific surface area of ​​7m 2 / g, pore size 0.15μm, porosity 23%; the guest material is a sulfide solid electrolyte, and the molar ratio of the host material to the guest material = 0.6. When preparing the battery cell, the main material of the positive electrode used is lithium manganese oxide, with an active material accounting for 96.3%, polyvinylidene fluoride (PVDF) accounting for 2.0%, carbon black + carbon nanotubes (CNT) accounting for 1.5%, and mesoporous alumina 0.2%. The main material of the negative electrode is graphite, with an active material accounting for 96.5%, carbon black 0.5%, and styrene-butadiene rubber (SBR) + sodium carboxymethyl cellulose (CMC) accounting for 3.0%.

[0049] The preparation method of the battery cell includes: adding 0.2% (accounting for 0.2% of the mass of the entire positive electrode system) of the main material to the positive electrode system to make a 20AH square aluminum shell battery; the distribution of the main material in the positive electrode system is shown in SEM Figure 1 , the distribution of aluminum elements is shown in the attached Figure 2 The above positive electrode system and negative electrode system are made into dry cells and placed in a 100°C oven, where the vacuum is -100Kpa for 96 hours. Then, the mixture containing the guest material is injected according to the molar ratio of the host material to the guest material, heated at 70°C for 12 hours, and then cooled. The positive electrode sheet ratio before and after polymerization is tested and compared, and the ratio decreases by ≥0.15%. Then, a conventional electrolyte is injected.

[0050] The mixture containing the guest material includes, by mass percentage, a lithium salt (LiPF 6) 25%, initiator (AIBN) 2%, organic small molecule (FEC) 73%, solvent (DEC) were mixed into a solution with a solid content of 5%.

[0051] Example 2

[0052] The present embodiment provides a method for preparing a battery cell, which comprises: subjecting the porous alumina to ethanol ultrasonic treatment for 2 hours, and drying at 45°C and -90 kpa for 8 hours to remove surface impurities and ensure that the pores are unobstructed so that the solid electrolyte can enter smoothly. The pretreated porous alumina is placed in a vacuum impregnation device and maintained at a vacuum pressure of -100 kpa for 12 hours. The mixture containing the guest material is injected into the main material by an impregnation method (the main material is the same as in Example 1), wherein the mixture of the guest material includes, by mass percentage, a lithium salt (LiPF 6 ) 10%, initiator (AIBN) 2% and organic small molecule (FEC) 83%, sulfide solid electrolyte sulfide solid electrolyte Li 10 G 2 S 12 (maximum particle size ≤ 0.12um) 5%, solvent (DEC), mixed into a solution with a solid content of 20%), heated to a temperature condition of 70°C, maintained for 12 hours, the impregnated porous alumina was taken out, and vacuum dried at 60°C for 4 hours at a dew point of -65°C to obtain a primary product. The obtained target product was rinsed three times with anhydrous ethanol to remove excess solid electrolyte on the surface to obtain the target product. The purpose of this step is to polymerize the guest in situ in the host, test the specific table before and after polymerization, and compare the specific table before and after polymerization to ensure that the specific table decreases by ≥20%; a host-guest composite material is prepared, and the SEM image of the host-guest composite material is shown in Figure 3 ,from Figure 3 It can be seen that the impregnation effect is very good, and there is no residue at all. Then, 0.3% of the composite host-guest material after polymerization is added to the positive electrode system (accounting for 0.3% of the total positive electrode system mass), and the positive and negative electrode systems are made into dry cells and baked and directly injected with conventional electrolyte.

[0053] Example 3

[0054] The present embodiment provides a method for preparing a battery cell, which includes: subjecting the porous alumina to ethanol ultrasound for 2 hours, and drying at 45°C and -90kpa for 8 hours to remove surface impurities and ensure that the pores are unobstructed so that the solid electrolyte can enter smoothly. The pretreated porous alumina is placed in a vacuum impregnation device and maintained at a vacuum pressure of -100kpa for 12 hours. The mixture containing the guest material is injected into the main material by impregnation (the main material is the same as in Example 1), wherein the mixture of the guest material includes, by mass percentage, 10% lithium salt (LiPF6), 2% initiator (AIBN) and 86.5% organic small molecules (FEC), and the sulfide solid electrolyte is the sulfide solid electrolyte Li 10 G 2 S 12 (maximum particle size ≤ 0.12um) 1.5%, solvent (DEC), mixed into a solution with a solid content of 20%), heated to a temperature condition of 70°C, maintained for 12 hours, the impregnated porous alumina was taken out, and vacuum dried at 60°C for 4 hours at a dew point of -65°C to obtain the primary product. The obtained target product was rinsed three times with anhydrous ethanol to remove excess solid electrolyte on the surface to obtain the target product. The purpose of this step is to polymerize the guest in situ in the host, test the specific table before and after polymerization, compare the specific table before and after polymerization, and ensure that the specific table drops by ≥20%; prepare a host-guest composite material. Then add 0.3% of the composite host-guest material after the polymerization is completed to the positive electrode system (accounting for 0.3% of the mass of the entire positive electrode system), and make the positive electrode system and the negative electrode system into dry batteries and bake them directly into conventional electrolytes.

[0055] Embodiment 4-5

[0056] Example 4-5 is basically the same as Example 1, except that the composition of the host material and the mixture containing the guest material in this example is different from that in Example 1:

[0057] In Example 4, the host material is MOF, and the mixture containing the guest material includes lithium salt (LiPF 6 )25%, initiator (AIBN) 2%, organic small molecule (FEC) 73%, organic solvent (DEC), mixed into a 5% solid content solution. The molar ratio of the host material to the guest material is 10:1;

[0058] In Example 5, the host material is an organic mesoporous polymer PCM, and the mixture containing the guest material includes 15% lithium salt (LiTFSI), 2% initiator (DOL), 10% sulfide solid electrolyte, 73% organic small molecule (FEC), and organic solvent (DEC) by mass percentage, mixed into a solution with a solid content of 5%. The molar ratio of the host material to the guest material is 100:1.

[0059] Example 6

[0060] The present embodiment provides a method for preparing a battery cell, which comprises: subjecting the porous alumina to ethanol ultrasonic treatment for 2 hours, and drying at 45°C and -90 kpa for 8 hours to remove surface impurities and ensure that the pores are unobstructed so that the solid electrolyte can enter smoothly. The pretreated porous alumina is placed in a vacuum impregnation device and maintained at a vacuum pressure of -100 kpa for 12 hours. The mixture containing the guest material is injected into the main material by an impregnation method (the main material is the same as in Example 1), wherein the mixture of the guest material includes, by mass percentage, a lithium salt (LiPF 6 ) 10%, initiator (AIBN) 0.2% and organic small molecules (FEC) 89.8%, solvent (DEC), mixed into a 20% solid content solution, heated to a temperature condition of 45 ° C, and maintained for 12 hours. The purpose of this step is to polymerize the guest in situ in the host, test the specific table before and after polymerization, compare the specific table before and after polymerization, and ensure that the specific table drops by ≥ 20%; prepare a host-guest composite material. Then add 0.3% of the composite host-guest material after the polymerization is completed to the positive electrode system (accounting for 0.3% of the mass of the entire positive electrode system), and make the positive and negative electrode systems into dry batteries, bake them, and directly inject conventional electrolytes.

[0061] Comparative Example 1

[0062] The difference between this comparative example and Example 1 is that in this comparative example, no host-guest composite material is added, and the positive electrode system and the negative electrode system are directly made into dry cells and baked and then directly injected with conventional electrolyte.

[0063] Comparative Example 2

[0064] The difference between this comparative example and Example 2 is that this comparative example also contains a host material and a guest material, but does not introduce in-situ polymerization. The specific operation steps are as follows:

[0065] This embodiment provides a method for preparing a battery cell, which comprises: firstly, injecting a mixture containing a guest material into a host material (the host material is the same as that in embodiment 1) by vacuum impregnation, wherein the mixture of the guest material is sulfide solid electrolyte Li 10 G 2 S 12(maximum particle size ≤ 0.12um) dissolved in acetone solution, ultrasonically dispersed to obtain a uniform system (solid content 30%), the porous alumina was subjected to ethanol ultrasonic treatment for 2h, 45℃, -90kpa drying for 8h, to remove surface impurities and ensure that the pores are unobstructed so that the solid electrolyte can enter smoothly. The pretreated porous alumina was placed in a vacuum impregnation device, and the vacuum pressure was maintained at -100kpa for 12h. Then, under vacuum, the solid electrolyte solution was introduced into the impregnation device using a peristaltic pump. The molar ratio of the solid electrolyte to the alumina material was 2:1, so that the solid electrolyte was gradually filled into the pores of the porous alumina under pressure difference and capillary action. After the impregnation was completed, the normal pressure was restored, the impregnated porous alumina was taken out, and the primary product was obtained by vacuum drying at 60℃ at a dew point of -65℃ for 4h. The target product was rinsed three times with anhydrous ethanol to remove excess solid electrolyte on the surface. The relative table before and after impregnation was tested, and the relative table before and after impregnation was compared. The relative table decreased by 10%; the host-guest composite material was prepared.

[0066] Experimental Results

[0067] The finished battery cells prepared in the above-mentioned embodiments 1-6 and comparative examples 1-2 were subjected to performance testing, and the testing items included 45°C cycling, 60°C 7-Day full-charge storage, DCR test, and ARC test; wherein the 45°C cycling test method was to use a charging and discharging system of 1C charging to 4.2V, 0.05C cutoff, 30min of shelf life, 1C discharge to 2.7V, and 30min of shelf life in a constant temperature box at 45°C (45°C±2°C); the 60°C 7-Day full-charge storage test method was to charge the battery cells at room temperature (25±2°C) at 1C to 4.2V, 0.05C cutoff, 30min of shelf life, 1C discharge to 2.7V, and 30min of shelf life, record the initial capacity, and then fully charge the battery cells. After full charging, store them in a 60°C±2°C constant temperature box for 7Days, cool them at room temperature for 6h after the storage, and cycle 3 times according to the process steps of the initial capacity, and take the smaller capacity of the second or third cycle as the maintenance capacity. The DCR test method is to charge the battery cell at room temperature (25±2℃) at 1C to 4.2V, cut off at 0.05C, and leave it for 30min; discharge at 0.2C for 10s, discharge at 1C for 1s, and cycle to 2.7V; record the DCR data of the full discharge SOC process. The ARC test method is to start the interval temperature at 60℃, step temperature rise step length of 5℃, step target temperature constant temperature time of 30min, temperature rise check threshold of 0.02℃ / min, search time of 22min, cycle until the battery cell self-generates heat, and record the self-generated heat T0 temperature.

[0068] The test results are as follows:

[0069]

[0070]

[0071] It can be seen from the above table that the addition of the host-guest composite material can greatly improve the life of the battery cell and the ionic conductivity, and also significantly improve the intrinsic safety of the battery cell. Among them, Example 1 selects inorganic mesoporous alumina as the main material, which can greatly improve the life of the battery cell and the ionic conductivity through in-situ polymerization, and also significantly improves the intrinsic safety of the battery cell. In Example 2, a solid electrolyte is also added to the mixture of the guest material, which can further improve the number of cycles and the capacity retention rate, and the DCR of the battery cell is also significantly lower than that of Example 1. Compared with Example 2, the content of the solid electrolyte in Example 3 is reduced, and its performance is also slightly reduced. Examples 4 and 5 change the selection of the components of the main material and the guest material. It can be seen from the experimental data that the inorganic mesoporous alumina selected as the main material in Examples 1-3 has better effects, but the effects of Examples 4-5 are still better than those of Comparative Example 1 in which the host-guest composite material is not added. Example 6 omits the solid electrolyte, and its effect is worse than that of Example 2, but better than Comparative Example 1. The number of cycles of Comparative Example 1 is significantly lower than that of the embodiments of the present invention and other comparative examples. At the same time, the shelving capacity maintenance rate is also significantly lower than that of the embodiments of the present invention and other comparative examples, while the cell DCR is significantly greater than that of other embodiments and comparative examples, proving that its loss is large. Although the host material and the guest material are added to Comparative Example 2, they are loaded by impregnation without in-situ polymerization, which will result in lower cycle numbers and capacity maintenance rates than those of Example 1, while the cell DCR is slightly lower than that of the embodiments, proving that the loss difference is not large under this scheme.

[0072] In summary, the host-guest composite material provided by the present invention is formed by in-situ polymerization of the host material and the guest material under the action of an initiator, so that the guest material is embedded in the internal pores of the host material, thereby forming a high specific surface porous material to encapsulate the guest material with conductive properties, and the specific surface area is significantly reduced compared to the specific surface of the host-guest material before polymerization, which will make the host-guest composite material not only have good conductive properties, but also have the effects of improving the stability of the positive electrode, inhibiting the dissolution of the positive electrode transition metal elements, etc., and its coating on the positive electrode surface can also greatly improve the safety. The host-guest composite material formed by in-situ polymerization is added to the positive electrode material to significantly improve the calendar life of the lithium-ion battery, while reducing power loss, and at the same time it is also beneficial to improve the safety and fast charging capability of the lithium-ion battery. The above is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various changes and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a host-guest composite material, characterized in that: The method comprises mixing a mixture containing a guest material with a host material, and performing in-situ polymerization so that the guest material is loaded in the internal porous structure of the host material; the host material comprises a high specific surface area porous material, wherein the pore size of the host material is ≥0.1 μm, the porosity is ≥2%, and the specific surface area is ≥2 μm. 2 / g; the mixture containing the guest material includes a guest material, a lithium compound, an initiator and an organic solvent, the guest material includes at least one of an organic small molecule precursor, an inorganic material, a cyclic ether, a polymer electrolyte, and a solid electrolyte, the molecular weight of the guest material is ≤20000g / mol, the particle size is <0.1μm, and the specific surface area of ​​the host material is compared with the specific surface area of ​​the host-guest composite material after in-situ polymerization, and the specific surface area decreases by ≥10%.

2. The method for preparing the host-guest composite material according to claim 1, characterized in that: The main material is the high specific surface area porous material alone or a positive electrode system containing the high specific surface area porous material.

3. The method for preparing the host-guest composite material according to claim 1, characterized in that: The high specific surface area porous material comprises an inorganic mesoporous oxide, an organic porous metal framework or an organic mesoporous polymer; Preferably, the inorganic mesoporous oxide comprises at least one of silicon dioxide, aluminum oxide, magnesium oxide and zirconium oxide; Preferably, the organic porous metal framework comprises at least one of MOF and COF; Preferably, the organic mesoporous polymer is PCM.

4. The method for preparing the host-guest composite material according to claim 1, characterized in that: The organic small molecule precursor includes at least one of VC and FEC; And / or, the polymer electrolyte comprises at least one of PEO and PVDF; And / or, the solid electrolyte includes at least one of a LATP solid electrolyte, a LLZO solid electrolyte, a LPS solid electrolyte, a LLTO solid electrolyte and a sulfide solid electrolyte.

5. The method for preparing the host-guest composite material according to claim 1, characterized in that: The molar ratio of the host material to the guest material is 0.5-100:1; Preferably, the mixture containing the guest material comprises, by mass percentage, 10-50% of the guest material, 1%-20% of the lithium compound, 0.1%-5% of the initiator and 40-70% of the organic solvent; Preferably, the lithium compound comprises at least one of LiPF6, LiFSi and LiTFSi; Preferably, the initiator comprises at least one of AIBN, DOL and benzoyl oxide; Preferably, the organic solvent includes at least one of VC, FEC, EC and DEC.

6. The method for preparing the host-guest composite material according to claim 1, characterized in that: The in-situ polymerization temperature is 40°C-80°C and the time is 1-12h; Preferably, microwave or ultraviolet light irradiation is applied during the in-situ polymerization.

7. A method for preparing a battery cell, characterized in that: The positive electrode system contains a host-guest composite material prepared by the preparation method of the host-guest composite material as described in any one of claims 1 to 6.

8. The method for preparing a battery cell according to claim 7, characterized in that: The method of adding the host-guest composite material to the positive electrode system comprises directly adding the host-guest composite material to the positive electrode system to prepare a finished battery cell.

9. The method for preparing a battery cell according to claim 7, characterized in that: The method for adding the host-guest composite material to the positive electrode system comprises adding the host material to the positive electrode system, then preparing a dry battery cell without liquid injection, placing the dry battery cell in a vacuum environment, and then injecting the mixture containing the guest material into the dry battery cell by liquid injection for infiltration for 5-10 hours, then heating for in-situ polymerization, cooling to room temperature, then injecting electrolyte, and then sizing to prepare a finished battery cell; Preferably, the vacuum degree of the vacuum environment is ≥-80Kpa.

10. A lithium ion battery, characterized in that: It includes a battery cell prepared by the method for preparing a battery cell as described in any one of claims 7 to 9.

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