A composite cathode material, a preparation method thereof, a cathode sheet and a battery

Abstract

The present invention discloses a composite cathode material, a preparation method thereof, a cathode sheet and a battery, relating to the technical field of batteries; the composite cathode material includes a core and a shell wrapped around the outer circumference of the core, the core is a conjugated organic material embedded with alkali metal ions, and the shell is a fluorinated pentacene compound. On the one hand, the conjugated organic material has good electrical conductivity, can reduce the resistance of charge transfer, make the battery polarization smaller, and the cycle performance is more excellent; at the same time, the embedding of alkali metal ions can supplement the alkali metal lost during the charge and discharge process to improve the cycle performance, specific capacity and first efficiency performance of the battery; on the other hand, the fluorinated pentacene compound has high electron mobility and electronegativity, can improve the electrical conductivity of the material, and increase the transmission rate of alkali metal ions to further improve the cycle performance, specific capacity and first efficiency performance of the battery.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular, to a composite cathode material, a preparation method thereof, a cathode sheet, and a battery. Background Art

[0002] As one of the green chemical power sources, secondary batteries have received extensive attention from scientific researchers. However, since secondary batteries are still in the preliminary research stage, there are still many technical problems to be solved. Among them, the synthesis of new cathode materials and the study of their electrochemical properties in battery systems are one of the important research directions of secondary batteries.

[0003] So far, the cathodes of secondary batteries have mainly focused on the research of insertable materials. The commonly used cathode materials for lithium-ion batteries are lithium iron phosphate, lithium manganate, lithium cobaltate, ternary materials, etc. Compared with lithium-ion batteries, the charge density of Na + in sodium-ion batteries is large and the solvation is more serious. Therefore, most of the cathode materials that can be used in lithium secondary batteries cannot be directly applied to sodium secondary batteries.

[0004] Currently, the cathodes of sodium secondary batteries mainly focus on the research of insertable materials, such as transition metal oxides, Prussian blue, polyanion type, etc. And the existing sodium secondary batteries are difficult to simultaneously ensure specific capacity, cycle performance, and initial efficiency performance.

[0005] In view of this, the present invention is specifically proposed. Summary of the Invention

[0006] The purpose of the present invention is to provide a composite cathode material and a preparation method thereof. The composite cathode material can simultaneously improve the specific capacity, cycle performance, and initial efficiency performance of the battery.

[0007] The purpose of the present invention is also to provide a cathode sheet, which includes the above-mentioned composite cathode material. Therefore, it can also simultaneously improve the specific capacity, cycle performance, and initial efficiency performance of the battery.

[0008] The purpose of the present invention is also to provide a battery, which includes the above-mentioned cathode sheet. Therefore, the battery also has the advantages of high specific capacity, cycle performance, and initial efficiency performance.

[0009] The embodiments of the present invention are implemented as follows:

[0010] In a first aspect, the present invention provides a composite cathode material, including:

[0011] A core and a shell wrapped around the outer circumference of the core. The core is a conjugated organic material intercalated with alkali metal ions, and the shell is a fluorinated pentacene compound.

[0012] In an alternative embodiment, the conjugated organic material is 1,2,5,6,9,10 - hexabenzobenzene hexanone, with the molecular formula 1,2,5,6,9,10 - coronenehexone; or, the conjugated organic material is a carbonyl derivative of pentacene.

[0013] In an alternative embodiment, the conjugated organic material is a carbonyl derivative of pentacene, and the carbonyl derivative of pentacene is 5,7,12,14 - pentacene tetrone or 6,13 - pentacene dione.

[0014] In an alternative embodiment, the alkali metal ion is lithium ion or sodium ion; and / or, the fluorinated pentacene compound is perfluorinated pentacene; and / or, the mass of the housing accounts for 1 - 10% of the mass of the entire composite cathode material.

[0015] In a second aspect, the present invention provides a method for preparing a composite cathode material according to any one of the foregoing embodiments, comprising:

[0016] Depositing an alkali metal ion on the surface of the conjugated organic material to obtain a core;

[0017] Coating the fluorinated pentacene compound on the surface of the core to obtain a composite cathode material.

[0018] In an alternative embodiment, the step of depositing an alkali metal ion on the surface of the conjugated organic material to obtain a core comprises:

[0019] Coating a solution containing the conjugated organic material on a substrate and drying to obtain an intermediate, and the solution containing the conjugated organic material comprises a binder, a solvent, a conductive agent, and the conjugated organic material in a mass ratio of (0.5 - 2):(8 - 10):(0.5 - 2):(15 - 20);

[0020] Connecting the intermediate to the positive electrode of a discharging instrument as the positive electrode, connecting the negative electrode of the discharging instrument to an alkali metal as the negative electrode, and inserting the positive and negative electrodes into an organic solvent containing an alkali metal salt for electrochemical deposition to deposit the alkali metal ion on the surface of the conjugated organic material to obtain a core.

[0021] In an alternative embodiment, the step of coating the fluorinated pentacene compound on the surface of the core to obtain a composite cathode material comprises:

[0022] Mixing the core with the fluorinated pentacene compound and then performing tabletting, low - temperature heat treatment, and crushing in sequence to obtain a composite cathode material;

[0023] And the pressure of tabletting is 10 - 15 MPa; and / or, the treatment temperature of low - temperature heat treatment is 80 - 100 °C, the heating rate is 5 - 10 °C / min, and the holding time after low - temperature treatment is 10 - 24 h.

[0024] In a third aspect, the present invention provides a positive electrode sheet, comprising:

[0025] a current collector;

[0026] a positive electrode active layer disposed on at least one surface of the current collector; the positive electrode active layer is obtained by coating the current collector with a positive electrode active paste; the positive electrode active paste comprises the composite positive electrode material of any one of the foregoing embodiments, or the composite positive electrode material prepared by the preparation method of the composite positive electrode material of any one of the foregoing embodiments.

[0027] In an alternative embodiment, the positive electrode active paste further comprises a conductive agent and a binder, and the mass percentages of the composite positive electrode material, the conductive agent and the binder are 50-93%, 1-25% and 5-25% respectively.

[0028] In a fourth aspect, the present invention provides a battery comprising the positive electrode sheet of the foregoing embodiment.

[0029] The embodiments of the present invention at least have the following advantages or beneficial effects:

[0030] The embodiments of the present invention provide a composite positive electrode material and a preparation method thereof. The composite positive electrode material comprises a core and a shell wrapped around the outer circumference of the core. The core is a conjugated organic material embedded with alkali metal ions, and the shell is a fluorinated pentacene compound.

[0031] On the one hand, due to the excellent conductivity of the specific conjugated organic material itself, the composite positive electrode material can reduce the resistance of charge transfer, making the battery polarization smaller and the cycle performance better; at the same time, by embedding alkali metal ions in the conjugated organic material, the alkali metal lost during the charge and discharge process can be supplemented to improve the cycle performance, specific capacity and first efficiency performance of the battery; on the other hand, through the setting of the shell of the fluorinated pentacene compound, the stability of the core structure can be improved, and the conductivity of the material can be further enhanced by utilizing its high electron mobility. Moreover, the characteristics of its relatively high electronegativity can assist the insertion and extraction of alkali metal ions, so as to improve the transport rate of alkali metal ions, and further improve the cycle performance, specific capacity and first efficiency performance of the battery.

[0032] The embodiments of the present invention also provide a positive electrode sheet comprising the above composite positive electrode material. Therefore, it can also improve the specific capacity, cycle performance and first efficiency performance of the battery at the same time.

[0033] The embodiments of the present invention also provide a battery comprising the above positive electrode sheet. Therefore, the battery also has the advantages of relatively high specific capacity, cycle performance and first efficiency performance. Description of the Drawings

[0034] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the accompanying drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those of ordinary skill in the art, without creative work, other related drawings can also be obtained based on these drawings.

[0035] Figure 1 The molecular structural formula of the conjugated organic material provided by the embodiment of the present invention. Specific embodiments

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention. For those not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments not specified in the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0037] The following further describes the features and performance of the present invention in detail in combination with the embodiments.

[0038] The embodiment of the present invention provides a composite cathode material, which is an active particle forming a cathode sheet, having a core-shell structure, including a core and a shell wrapped around the outer circumference of the core. The core is a conjugated organic material embedded with alkali metal ions, and the shell is a fluorinated pentacene compound.

[0039] On the one hand, due to the excellent electrical conductivity of the conjugated organic material itself, it can reduce the resistance of charge transfer, making the battery polarization smaller and the cycling performance better; at the same time, by embedding alkali metal ions in the conjugated organic material, the alkali metal lost during the charge and discharge process can be supplemented to improve the cycling performance, specific capacity, and initial efficiency performance of the battery; on the other hand, through the setting of the shell of the fluorinated pentacene compound, the high electron mobility characteristic can be used to further improve the electrical conductivity of the material, and the characteristic of relatively high electronegativity can be used to assist the insertion and extraction of alkali metal ions, so as to improve the transmission rate of alkali metal ions and further improve the cycling performance, specific capacity, and initial efficiency performance of the battery.

[0040] As an optional solution, in the embodiment of the present invention, the conjugated organic material can be selected as 1,2,5,6,9,10-hexabenzobenzene isocaproic ketone, with the molecular formula of 1,2,5,6,9,10-coronenehexone, commonly known as COHON. The COHON molecule is a conjugated organic material, and the molecular structural formula is as Figure 1As shown in the figure, charge transfer occurs between the COHON molecule and the active metal substrate, forming a delocalized π bond overall. The formation of the delocalized π bond can endow the COHON molecule with better electrical conductivity, making the positive electrode have a higher electrical conductivity, thereby reducing the resistance of charge transfer, making the polarization of the battery smaller, and thus increasing the cycle performance of the battery.

[0041] At the same time, during discharge, each oxygen atom on the carbonyl group of the COHON molecule gains one electron and simultaneously embeds an alkali metal ion to form an enol alkali metal salt; during charging, the lithium ion is removed, and the carbonyl group is reduced, and the reversible insertion and removal of the alkali metal ion are achieved through the conversion between the carbonyl group and the enol structure. Therefore, by embedding alkali metal ions inside the COHON molecule, the storage of alkali metal ions can be carried out through the COHON molecule. More alkali metal ions can be stored through 6 carbonyl groups, and better and faster insertion and removal of alkali metal ions can also be achieved to ensure the cycle performance and specific capacity of the battery. In addition, by embedding alkali metal ions in the COHON molecule, the alkali metal lost during the charge-discharge process can be supplemented to improve the cycle performance, specific capacity, and initial efficiency performance of the battery.

[0042] As an alternative solution, in the embodiments of the present invention, the conjugated organic material can also be selected as a conjugated organic semiconductor material, for example, it can be selected as a carbonyl derivative of pentacene. Charge transfer also occurs between the carbonyl derivative of pentacene and the active metal substrate, forming a delocalized π bond overall. The formation of the delocalized π bond makes the positive electrode have a higher electrical conductivity, thereby reducing the resistance of charge transfer, making the polarization of the battery smaller, and thus increasing the cycle performance of the battery.

[0043] Exemplarily, in the embodiments of the present invention, the carbonyl derivative of pentacene is 5,7,12,14-pentacene tetrone or 6,13-pentacene dione. Among them, 5,7,12,14-pentacene tetrone is commonly known as P40, and 6,13-pentacene dione is commonly known as P20. During discharge of P2O and P40, each oxygen atom on their carbonyl group gains one electron and simultaneously embeds an alkali metal ion to form an enol lithium salt or enol sodium salt; during charging, the alkali metal ion is removed, and the carbonyl group is reduced, and the reversible insertion and removal of the alkali metal ion are achieved through the conversion between the carbonyl group and the enol structure. Therefore, by embedding alkali metal ions inside the carbonyl derivative of pentacene, the storage of alkali metal ions can be carried out through the carbonyl derivative of pentacene. More alkali metal ions can be stored through the carbonyl group, and better and faster insertion and removal of alkali metal ions can also be achieved to ensure the cycle performance and specific capacity of the battery. In addition, by embedding alkali metal ions in the carbonyl derivative of pentacene, the alkali metal lost during the charge-discharge process can be supplemented to improve the cycle performance, specific capacity, and initial efficiency performance of the battery.

[0044] In addition, in the embodiments of the present invention, the density of perfluorinated pentacene is smaller than that of COHON molecules or P40 or P20, and it can better coat the surface of COHON molecules or P40 or P20, maintaining the stability of the core molecular structure to further improve the cycle, capacity, and initial efficiency performance of the battery. At the same time, the perfluorinated pentacene compound has a high electron mobility, which can overall improve the conductivity of the material. Moreover, the high electronegativity of fluorine is beneficial to the insertion and extraction of alkali metal ions in the core, improving the transport rate of alkali metal ions. The C-F bond of the perfluorinated pentacene compound is an electron-withdrawing group, which can increase the working potential of the material, thereby further improving the cycle, capacity, and initial efficiency performance of the battery. Additionally, the perfluorinated pentacene compound is insoluble in organic solvents, being a non-polar and hydrophobic molecule, which can effectively prevent COHON molecules or P40 or P20 from dissolving in the electrolyte, thus further improving the cycle performance of the battery.

[0045] It should be noted that in the embodiments of the present invention, the alkali metal ion is a lithium ion or a sodium ion. The alkali metal ion is embedded in the conjugated organic material. On the one hand, it can improve the cycle performance and specific capacity of the battery through deintercalation and intercalation. On the other hand, it can perform lithium or sodium supplementation to replenish the alkali metal ions lost during the charge and discharge operation of the battery, so as to further improve the cycle performance, specific capacity, and initial efficiency performance of the battery. Preferably, in the embodiments of the present invention, the alkali metal ion is a sodium ion. When the alkali metal ion is a sodium ion, the corresponding composite cathode material is the cathode material of a sodium-ion battery.

[0046] It also should be noted that in the embodiments of the present invention, the perfluorinated pentacene compound is perfluorinated pentacene. The perfluorinated pentacene has a high electron mobility, which can overall improve the conductivity of the material. At the same time, the high electronegativity of fluorine is beneficial to the insertion and extraction of alkali metal ions in the core, improving the transport rate of alkali metal ions, so as to further improve the cycle performance, specific capacity, and initial efficiency performance of the battery.

[0047] In addition, it should be pointed out that in this embodiment, the mass of the housing accounts for 1-10% of the mass of the entire composite cathode material. Exemplarily, it can be selected as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%. That is, the usage amount of the perfluorinated pentacene compound is relatively small. By controlling the usage amount of the perfluorinated pentacene compound, it can not only ensure the activity of the conjugated organic material with embedded alkali metal ions in the core, ensuring the cycle performance, specific capacity, and initial efficiency performance of the battery, but also maintain the stability of the core structure through the perfluorinated pentacene compound to further improve the cycle performance, specific capacity, and initial efficiency performance of the battery.

[0048] The embodiments of the present invention also provide a preparation method of a composite cathode material, including:

[0049] S1: Deposit alkali metal ions on the surface of the conjugated organic material to obtain a core;

[0050] S2: Coat the fluorinated pentacene compound on the surface of the core to obtain a composite cathode material.

[0051] Specifically, in step S1, the deposition method can be either electrodeposition or vapor deposition. Exemplarily, electrodeposition can be selected, and specifically includes: S11: Coat a solution containing the conjugated organic material on a substrate and dry it to obtain an intermediate; S12: Connect the intermediate to the positive electrode of a discharge instrument as the positive electrode, connect the negative electrode of the discharge instrument to an alkali metal as the negative electrode, and insert the positive and negative electrodes into an organic solvent dissolving an alkali metal salt for electrochemical deposition to deposit alkali metal ions on the surface of the conjugated organic material to obtain a core.

[0052] Among them, in step S11, the substrate can be selected from any one of a metal plate, a metal foil, a metal rod, or a metal mesh. The solution containing the conjugated organic material includes a binder, a conductive agent, a conjugated organic material (COHON, P40, or P20), and a solvent, and the mass ratio of the binder, the solvent, the conductive agent, and the conjugated organic material is (0.5 - 2):(8 - 10):(0.5 - 2):(15 - 20). And exemplarily, the conductive agent can be selected as carbon black (Super - P), the binder can be selected as polyvinylidene fluoride (PVDF), and the solvent can be selected as N - methylpyrrolidone (NMP). By defining the components of the solution of the conjugated organic material, the structural stability of the obtained core can be fully improved, ensuring its chemical properties to guarantee the performance of the battery. At the same time, in step S11, the drying temperature is higher than room temperature, and the higher the temperature, the shorter the drying time, which can be adjusted according to requirements.

[0053] In step S12, the type of the alkali metal negative electrode is determined according to the type of the battery. The negative electrode of a lithium secondary battery is lithium metal, and the negative electrode of a sodium secondary battery is sodium metal. After the electrodeposition is completed, take out the positive electrode, dry it, and then remove the surface coating layer from the substrate to obtain the inner shell. The core prepared by electrodeposition has a stable structure, which can fully ensure the cycle performance, specific capacity, and initial efficiency performance of the battery.

[0054] Specifically, in step S2, the step of coating the perfluoropentacene compound on the surface of the core to obtain the composite cathode material includes: mixing the core with the perfluoropentacene compound, followed by tableting, low-temperature heat treatment, and crushing to obtain the composite cathode material. Among them, the pressure for tableting is 10-15 MPa; the treatment temperature for low-temperature heat treatment is 80-100 °C, the heating rate is 5-10 °C / min, and the holding time after low-temperature heat treatment is 10-24 h. Through low-temperature heat treatment, the moisture on the organic matter can be removed, which is beneficial to the composite of the organic matter to form a stable material structure. That is, through this preparation method, the outer shell can be quickly wrapped on the core to further improve the stability of the core structure, and further improve the cycle performance, specific capacity, and initial efficiency performance of the battery.

[0055] The embodiment of the present invention also provides a positive electrode sheet, which includes a current collector and a positive electrode active layer. The selection of the current collector is related to the polarity. Generally, the current collector of the positive electrode sheet is aluminum foil, and the current collector of the negative electrode sheet is generally selected as copper foil. Of course, the current collector can also be a composite current collector, which will not be elaborated in the embodiment of the present invention. The positive electrode active layer is obtained by coating the positive electrode active paste on the current collector; the positive electrode active paste is obtained by dispersing the composite cathode material, the conductive agent, and the binder in a solvent. Exemplarily, the conductive agent can be selected as carbon black (Super-P), the binder can be selected as polyvinylidene fluoride (PVDF), and the solvent can be selected as N-methylpyrrolidone (NMP).

[0056] As an optional solution, the mass percentages of the composite cathode material, the conductive agent, and the binder are 50-93%, 1-25%, and 5-25% respectively. By controlling the dosages of the composite cathode material, the conductive agent, and the binder, the cycle performance, specific capacity, and initial efficiency performance of the battery prepared from the composite cathode material can be further ensured.

[0057] The embodiment of the present invention also provides a battery, which includes the above positive electrode sheet, and also includes a housing, a negative electrode sheet, a separator, and an electrolyte. The positive electrode sheet, the separator, and the negative electrode sheet are placed in sequence, and a core is formed by winding or laminating, and finally the core is installed in the housing and the electrolyte is injected to obtain the battery. Since the battery includes the above positive electrode sheet, the battery also has the advantages of high cycle performance, specific capacity, and initial efficiency performance.

[0058] It should be noted that in the embodiments of the present invention, the negative electrode sheet of the lithium-ion battery can be selected as polished metallic lithium, and the negative electrode sheet of the sodium-ion battery can be selected as polished metallic sodium. Additionally, the negative electrode sheet can also be a composite structure of a current collector and a negative electrode active layer. The current collector is selected as copper foil, and the negative electrode active layer is obtained by coating a negative electrode active slurry on the current collector. The negative electrode active slurry can be obtained by dispersing a negative electrode active material, a conductive agent, and a binder in a solvent. The negative electrode active material can be selected as graphite, graphene, etc. And the mass percentages of the negative electrode active material, the conductive agent, and the binder are 50 - 93%, 1 - 25%, and 5 - 25% respectively; the conductive agent can be selected as carbon black, and the binder can be selected as styrene-butadiene rubber emulsion (SBR).

[0059] It should also be noted that the separator can be selected as PP material, or can be selected as PE material, or even can be selected as a composite material of PP and PE. Exemplarily, the separator is selected as Celgard 3000.

[0060] In addition, it should be pointed out that the electrolyte of the lithium secondary battery is lithium hexafluorophosphate electrolyte, or THF electrolyte, and the electrolyte of the sodium secondary battery is sodium hexafluorophosphate electrolyte, or THF electrolyte.

[0061] Of course, in the embodiments of the present invention, the conductive agent in each preparation process can also be selected as carbon nanotubes, and the binder can also be mixed with a dispersant or a thickener, such as carboxymethyl cellulose (CMC), and the embodiments of the present invention do not make limitations.

[0062] The above preparation process will be introduced in detail below with specific examples and comparative examples:

[0063] Example 1

[0064] This example provides a battery, which is prepared by the following method:

[0065] S1: Prepare a composite positive electrode material:

[0066] Step S1 specifically includes:

[0067] S11: Mix a binder, a solvent, a conductive agent, and a conjugated organic material in a mass ratio of 0.5:8:0.5:15 to obtain a mixed slurry. Exemplarily, the conjugated organic material is 1,2,5,6,9,10-coronenehexone, the conductive agent can be selected as carbon black (Super-P), the binder can be selected as polyvinylidene fluoride (PVDF), and the solvent can be selected as N-methylpyrrolidone (NMP); coat the mixed slurry on a metal plate and dry it to obtain an intermediate; connect the intermediate to the positive electrode of a discharge instrument as the positive electrode, connect the negative electrode of the discharge instrument to metallic lithium as the negative electrode, and insert the positive and negative electrodes into an organic solvent containing a lithium metal salt for electrochemical deposition to deposit alkali metal ions on the surface of the conjugated organic material to obtain a core;

[0068] S12: Press, perform low-temperature heat treatment, and crush perfluoropentacene and the core to obtain a composite positive electrode material; the mass ratio of perfluoropentacene in the composite positive electrode material is 5%, the pressure for pressing is 10 MPa; the treatment temperature for low-temperature heat treatment is 80 °C, the heating rate is 5 °C / min, and the holding time after low-temperature treatment is 24 h;

[0069] S2: Prepare a positive electrode sheet:

[0070] Step S2 specifically includes dispersing the composite positive electrode material, the conductive agent, and the binder with mass percentages of 50%, 25%, and 25% respectively in a solvent to obtain a positive electrode active slurry; coating the positive electrode active slurry on an aluminum foil and drying it in vacuum; wherein, the conductive agent is carbon black, the binder is polyvinylidene fluoride, and the solvent is N-methylpyrrolidone; the positive electrode loading is 21 mg / cm 2 ;

[0071] S3: Prepare a battery:

[0072] Step S3 specifically includes winding the positive electrode sheet, the separator, and the negative electrode sheet to obtain a core, and placing the core in a housing and injecting an electrolyte to obtain a lithium secondary battery; wherein, the negative electrode sheet is polished metallic lithium, the separator is Celgard 3000, and the electrolyte is 0.25 M LiPF6.

[0073] Example 2

[0074] This example provides a battery, which is prepared by the following method:

[0075] S1: Prepare a composite positive electrode material:

[0076] Step S1 specifically includes:

[0077] S11: Mix a binder, a solvent, a conductive agent, and a conjugated organic material in a mass ratio of 1:9:1:18 to obtain a mixed slurry. Exemplarily, the conjugated organic material is 1,2,5,6,9,10 - coronenehexone, the conductive agent can be selected as carbon black (Super - P), the binder can be selected as polyvinylidene fluoride (PVDF), and the solvent can be selected as N - methylpyrrolidone (NMP); coat the mixed slurry on a metal plate and dry it to obtain an intermediate; connect the intermediate to the positive electrode of a discharging instrument as the positive electrode, connect the negative electrode of the discharging instrument to metallic sodium as the negative electrode, and insert the positive and negative electrodes into an organic solvent dissolving a lithium metal salt for electrochemical deposition to deposit alkali metal ions on the surface of the conjugated organic material to obtain a core;

[0078] S12: Compress, perform low - temperature heat treatment, and crush perfluoropentacene and the core to obtain a composite positive electrode material; the mass ratio of perfluoropentacene in the composite positive electrode material is 10%, the pressure for compression is 12 MPa; the treatment temperature for low - temperature heat treatment is 90 °C, the heating rate is 7 °C / min, and the holding time after low - temperature treatment is 20 h;

[0079] S2: Prepare a positive electrode sheet:

[0080] Step S2 specifically includes dispersing a composite positive electrode material, a conductive agent, and a binder with mass percentages of 70%, 20%, and 10% respectively in a solvent to obtain a positive electrode active slurry; coating the positive electrode active slurry on an aluminum foil and drying it in vacuum; wherein, the conductive agent is carbon black, the binder is polyvinylidene fluoride, and the solvent is N - methylpyrrolidone; the positive electrode loading is 21 mg / cm 2 ;

[0081] S3: Prepare a battery:

[0082] Step S3 specifically includes winding the positive electrode sheet, a separator, and a negative electrode sheet to obtain a core, and placing the core into a housing and injecting an electrolyte to obtain a lithium secondary battery; wherein, the negative electrode sheet is polished metallic sodium, the separator is Celgard 3000, and the electrolyte is 0.25 M LiPF6.

[0083] Example 3

[0084] This example provides a battery, which is prepared by the following method:

[0085] S1: Prepare a composite positive electrode material:

[0086] Step S1 specifically includes:

[0087] S11: Mix a binder, a solvent, a conductive agent, and a conjugated organic material in a mass ratio of 1:9:1:18 to obtain a mixed slurry. Exemplarily, the conjugated organic material is 1,2,5,6,9,10 - coronenehexone, the conductive agent can be selected as carbon black (Super - P), the binder can be selected as polyvinylidene fluoride (PVDF), and the solvent can be selected as N - methylpyrrolidone (NMP); coat the mixed slurry on a metal plate and dry it to obtain an intermediate; connect the intermediate to the positive electrode of a discharge instrument as the positive electrode, connect the negative electrode of the discharge instrument to metallic lithium as the negative electrode, and insert the positive and negative electrodes into an organic solvent containing a lithium metal salt for electrochemical deposition, so that alkali metal ions are deposited on the surface of the conjugated organic material to obtain a core;

[0088] S12: Press, perform low - temperature heat treatment, and crush perfluoropentacene and the core to obtain a composite positive electrode material; the mass ratio of perfluoropentacene in the composite positive electrode material is 5%, the pressure for pressing is 14 MPa; the treatment temperature for low - temperature heat treatment is 95°C, the heating rate is 9°C / min, and the holding time after low - temperature treatment is 18 h;

[0089] S2: Prepare a positive electrode sheet:

[0090] Step S2 specifically includes dispersing a composite positive electrode material, a conductive agent, and a binder with mass percentages of 80%, 10%, and 10% respectively in a solvent to obtain a positive electrode active slurry; coating the positive electrode active slurry on an aluminum foil and drying it in vacuum; wherein, the conductive agent is carbon black, the binder is polyvinylidene fluoride, and the solvent is N - methylpyrrolidone; the positive electrode loading is 21 mg / cm 2 ;

[0091] S3: Prepare a negative electrode sheet:

[0092] Step S3 specifically includes dispersing a negative electrode active material, a conductive agent, and a binder with mass percentages of 80%, 10%, and 10% respectively in a solvent to obtain a negative electrode active slurry; coating the negative electrode active slurry on a copper foil and drying it in vacuum; wherein, the negative electrode active material is graphite, the conductive agent is carbon black, the binder is styrene - butadiene rubber latex, and the solvent is N - methylpyrrolidone; the negative electrode loading is 21 mg / cm 2 ;

[0093] S4: Prepare a battery:

[0094] Step S4 specifically includes winding the positive electrode sheet, the separator, and the negative electrode sheet to obtain a core, and loading the core into a housing and injecting an electrolyte to obtain a lithium secondary battery; wherein, the negative electrode sheet is polished metallic lithium, the separator is Celgard 3000, and the electrolyte is 0.25 M LiPF6.

[0095] Example 4

[0096] This embodiment provides a battery, which is prepared by the following method:

[0097] S1: Prepare a composite cathode material:

[0098] Step S1 specifically includes:

[0099] S11: Mix a binder, a solvent, a conductive agent, and a conjugated organic material in a mass ratio of 2:10:2:20 to obtain a mixed slurry. Exemplarily, the conjugated organic material is 1,2,5,6,9,10 - coronenehexone, the conductive agent can be selected as carbon black (Super - P), the binder can be selected as polyvinylidene fluoride (PVDF), and the solvent can be selected as N - methylpyrrolidone (NMP); coat the mixed slurry on a metal plate and dry it to obtain an intermediate; connect the intermediate to the positive electrode of a discharge instrument as the positive electrode, connect the negative electrode of the discharge instrument to metallic sodium as the negative electrode, and insert the positive and negative electrodes into an organic solvent dissolved with a lithium metal salt for electrochemical deposition to deposit alkali metal ions on the surface of the conjugated organic material to obtain a core;

[0100] S12: Press, perform low - temperature heat treatment, and crush perfluoropentacene and the core to obtain a composite cathode material; the pressure for pressing is 15 MPa; the mass ratio of perfluoropentacene in the composite cathode material is 5%, the treatment temperature for low - temperature heat treatment is 100 °C, the heating rate is 10 °C / min, and the holding time after low - temperature treatment is 10 h;

[0101] S2: Prepare a positive electrode sheet:

[0102] Step S2 specifically includes dispersing a composite cathode material, a conductive agent, and a binder with mass percentages of 94%, 1%, and 5% respectively in a solvent to obtain a positive electrode active slurry; coating the positive electrode active slurry on an aluminum foil and drying it in vacuum; wherein, the conductive agent is carbon black, the binder is polyvinylidene fluoride, and the solvent is N - methylpyrrolidone; the positive electrode loading is 21 mg / cm 2 ;

[0103] S3: Prepare a negative electrode sheet:

[0104] Step S3 specifically includes dispersing a negative electrode active material, a conductive agent, and a binder with mass percentages of 94%, 1%, and 5% respectively in a solvent to obtain a negative electrode active slurry; coating the negative electrode active slurry on a copper foil and drying it in vacuum; wherein, the negative electrode active material is graphite, the conductive agent is carbon black, the binder is styrene - butadiene rubber latex, and the solvent is N - methylpyrrolidone; the negative electrode loading is 21 mg / cm 2 ;

[0105] S4: Assemble the battery:

[0106] Step S4 specifically includes winding the positive electrode sheet, separator, and negative electrode sheet to obtain an electrode core, and then placing the electrode core into a housing and injecting an electrolyte to obtain a lithium secondary battery; wherein, the negative electrode sheet is polished metallic lithium, the separator is Celgard 3000, and the electrolyte is 0.25 M THF.

[0107] Example 5

[0108] This example provides a battery, and the difference in its preparation method from that of Example 1 lies in that in step S11, the binder, solvent, conductive agent, and conjugated organic material are in a mass ratio of 1:9:1:18, and the conjugated organic material is 5,7,12,14 - pentacene tetrone.

[0109] Example 6

[0110] This example provides a battery, and the difference in its preparation method from that of Example 5 lies in that in step S11, the conjugated organic material is 6,13 - pentacenequinone.

[0111] Comparative Example 1

[0112] Comparative Example 1 provides a battery, and the difference in its preparation method from that of Example 1 lies in that in step S11, the positive electrode material used in Comparative Example 1 is a conjugated polymer, specifically poly(phenylene vinylene), and there is no outer coating layer of fluorinated pentacene compound.

[0113] Comparative Example 2

[0114] Comparative Example 2 provides a battery, and the difference in its preparation method from that of Example 1 lies in that in step S11, the positive electrode material used in Comparative Example 2 is a COHON molecule, and there is no outer coating layer of fluorinated pentacene compound.

[0115] Comparative Example 3

[0116] Comparative Example 3 provides a battery, and the difference in its preparation method from that of Example 2 lies in that in step S11, the positive electrode material used in Comparative Example 3 is a conjugated polymer, specifically poly(phenylene vinylene), and there is an outer coating layer of fluorinated pentacene compound.

[0117] Comparative Example 4

[0118] Comparative Example 4 provides a battery, and the difference in its preparation method from that of Example 2 lies in that in step S11, the positive electrode material used in Comparative Example 4 is a COHON molecule, and there is no outer coating layer of fluorinated pentacene compound.

[0119] Comparative Example 5

[0120] Comparative Example 5 provides a battery, the difference in its preparation method from that of Example 5 lies in that in step S11, the positive electrode material used in Comparative Example 5 is 5,7,12,14-pentacene tetrone, but it does not have the outer coating layer of fluorinated pentacene compound.

[0121] Comparative Example 6

[0122] Comparative Example 5 provides a battery, the difference in its preparation method from that of Example 6 lies in that in step S11, the positive electrode material used in Comparative Example 5 is 6,13-pentacene dione, but it does not have the outer coating layer of fluorinated pentacene compound.

[0123] Experimental Example 1

[0124] The positive electrode conductivities of the positive electrode sheets prepared in Examples 1 to 6 and Comparative Examples 1 to 6 were tested. The test conditions were as follows: The surface conductivity of the positive electrode material was tested using the Huace high-temperature four-probe tester HEST-800 instrument. The test results are shown in Table 1.

[0125] Table 1. Test results of conductivity

[0126] Number Positive electrode conductivity (S / cm) Example 1 (lithium, negative electrode lithium, COHON) <![CDATA[2.3×10 -5 > Example 2 (sodium, negative electrode sodium, COHON) <![CDATA[2.1×10 -5 > Example 3 (lithium, negative electrode graphite, COHON) <![CDATA[2.2×10 -5 > Example 4 (sodium, negative electrode graphite, COHON) <![CDATA[2.0×10 -5 > Example 5 (lithium, negative electrode lithium, P40) <![CDATA[1.8×10 -5 > Example 6 (lithium, negative electrode lithium, P20) <![CDATA[1.6×10 -5 > Comparative Example 1 (lithium, traditional organic electrode, uncoated) <![CDATA[1.8×10 -6 > Comparative Example 2 (lithium, COHON, uncoated) <![CDATA[3.2×10 -6 > Comparative Example 3 (sodium, traditional organic electrode, coated) <![CDATA[2.0×10 -6 > Comparative Example 4 (sodium, COHON, uncoated) <![CDATA[3.0×10 -6 > Comparative Example 5 (lithium, P40, uncoated) <![CDATA[2.2×10 -6 > Comparative Example 6 (lithium, P20, uncoated) <![CDATA[1.9×10 -6 >

[0127] According to the data shown in Table 1, it can be seen that the positive electrode sheets provided in Examples 1-6 of the present invention have higher positive electrode conductivities. Therefore, the resistance of charge transfer can be reduced, making the polarization of the battery smaller, thereby increasing the cycle performance of the battery. At the same time, since the conductivities of Comparative Examples 2, 4, 5, and 6 are better than those of Comparative Examples 1 and 3, it shows that COHON molecules, P40, or P20 can all effectively improve the positive electrode conductivity, and the effect of COHON molecules is better than that of P40 or P20. However, since Comparative Examples 2, 4, 5, and 6 only use COHON molecules, P40, or P20 without coating the outer shell of fluorinated pentacene compound, their conductivities are worse than those of Examples 1-6 of the present invention. In addition, according to the data comparison between Comparative Example 1 and Comparative Example 3, when using traditional organic electrodes, coating with fluorinated pentacene compound on the electrode can also improve the conductivity to a certain extent, but the effect is worse than that of COHON molecules, P40, or P20.

[0128] Experimental Example 2

[0129] The cycle performances of the batteries prepared in Examples 1 to 4 and Comparative Examples 1 to 4 were tested. The test conditions were as follows: After the battery was assembled, the LAND blue battery test system was used to conduct the cycle performance test under the conditions of a charge-discharge current of 1C / 1C and a charge-discharge voltage of 0.1V to 2.8V. The test results are shown in Table 2.

[0130] Table 2. Test results of cycle performance

[0131]

[0132]

[0133] According to the data shown in Table 1 and Table 2, since the positive electrode sheets provided in Embodiments 1-6 of the present invention have higher positive electrode conductivity, the resistance of charge transfer can be reduced, resulting in smaller polarization of the battery, thereby increasing the cycle performance of the battery. At the same time, since the cycle performances of Comparative Examples 2, 4, 5, and 6 are better than those of Comparative Examples 1 and 3, they have better cycle performance relatively, indicating that COHON molecules, P40, or P20 can all effectively improve the cycle performance, and the effect of COHON molecules is better than that of P40 or P20. However, since Comparative Examples 2, 4, 5, and 6 only use COHON molecules, P40, or P20 without coating with fluorinated pentacene compounds, their cycle performance is worse than that of Embodiments 1-6 of the present invention. In addition, according to the data comparison between Comparative Example 1 and Comparative Example 3, when using a traditional organic electrode, coating with fluorinated pentacene compounds on the electrode can also improve the cycle performance to a certain extent, but the effect is worse than that of COHON molecules, P40, or P20.

[0134] Experimental Example 3

[0135] The initial specific capacities of the batteries prepared in Embodiments 1 to 4 and Comparative Examples 1 to 4 were tested. The test results are shown in Table 3.

[0136] Table 3. Test Results of Initial Specific Capacity

[0137]

[0138]

[0139] According to the data in Table 3, the initial specific capacities of the batteries provided in Embodiments 1-6 of the present invention are relatively high, indicating that the composite positive electrode materials provided in the embodiments of the present invention can effectively improve the initial specific capacity of the battery. At the same time, since the initial specific capacities of Comparative Examples 2, 4, 5, and 6 are better than those of Comparative Examples 1 and 3, it shows that COHON molecules, P40, or P20 can all effectively improve the initial specific capacity, and the effect of COHON molecules is better than that of P40 or P20. However, since Comparative Examples 1, 2, 4, 5, and 6 only use COHON molecules, P40, or P20 without coating with fluorinated pentacene compounds, their initial specific capacities will be higher than those of Embodiments 1-6 of the present invention, but the initial specific capacities of Embodiments 1-6 are far better than those of Comparative Example 3.

[0140] Experimental Example 4

[0141] The full-electric first efficiency of the batteries prepared in Embodiments 1 to 4 and Comparative Examples 1 to 4 was tested. The test results are shown in Table 4.

[0142] Table 4. Full-electric first-effect test results

[0143]

[0144]

[0145] According to the data in Table 4, it can be seen that the first-effect performance of the batteries provided by Examples 1-6 of the present invention is relatively high, indicating that the composite cathode materials provided by the examples of the present invention can effectively improve the first-effect performance of the batteries. At the same time, since the cycling performance of Comparative Examples 2, 4, 5, and 6 is better than that of Comparative Examples 1 and 3, and the first-effect performance is better than that of Comparative Examples 1 and 3, it shows that COHON molecules, P40, or P20 can all effectively improve the cycling performance and can effectively improve the first-effect performance. However, since Comparative Examples 2, 4, 5, and 6 only use COHON molecules, P40, or P20 without coating with a fluorinated pentacene compound shell, their first-effect performance is lower than that of Examples 1-6 of the present invention. In addition, according to the data comparison between Comparative Example 1 and Comparative Example 3, when using a traditional organic electrode, coating with a fluorinated pentacene compound outside the electrode can also improve the first-effect performance to a certain extent, but the effect is worse than that of COHON molecules, P40, or P20.

[0146] In summary, the composite cathode materials provided by the examples of the present invention can effectively improve the cycling performance, specific capacity, and first-effect performance of the batteries.

[0147] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A composite cathode material, characterized in that, Comprising: A core and a shell wrapped around the outer circumference of the core, the core being a conjugated organic material embedded with alkali metal ions, and the shell being perfluorinated pentacene; The conjugated organic material is 1,2,5,6,9,10 - hexabenzobenzene isohexanone, with the molecular formula 1,2,5,6,9,10 - coronenehexone; Or, The conjugated organic material is a carbonyl derivative of pentacene, and the carbonyl derivative of pentacene is 5,7,12,14 - pentacenetetrone or 6,13 - pentacenedione.

2. The composite cathode material according to claim 1, wherein: The alkali metal ion is a lithium ion or a sodium ion; And / or, The mass of the shell accounts for 1 - 10% of the mass of the entire composite cathode material.

3. A method for preparing the composite cathode material according to claim 1 or 2, characterized in that, Comprising: Depositing the alkali metal ions on the surface of the conjugated organic material to obtain the core; Coating the fluorinated pentacene compound on the surface of the core to obtain the composite cathode material.

4. The preparation method of the composite cathode material according to claim 3, wherein The step of depositing the alkali metal ions on the surface of the conjugated organic material to obtain the core includes: Coating a solution containing the conjugated organic material on a substrate and drying to obtain an intermediate, and the solution containing the conjugated organic material includes a binder, a solvent, a conductive agent, and the conjugated organic material in a mass ratio of (0.5 - 2):(8 - 10):(0.5 - 2):(15 - 20); Connecting the intermediate to the positive electrode of a discharge instrument as the positive electrode, connecting the negative electrode of the discharge instrument to an alkali metal as the negative electrode, and inserting the positive electrode and the negative electrode into an organic solvent dissolved with an alkali metal salt for electrochemical deposition to deposit the alkali metal ions on the surface of the conjugated organic material to obtain the core.

5. The preparation method of the composite cathode material according to claim 3, wherein, The step of coating the fluorinated pentacene compound on the surface of the core to obtain the composite cathode material includes: Mixing the core and the fluorinated pentacene compound, followed by pressing, low - temperature heat treatment, and crushing to obtain the composite cathode material; And the pressure for pressing is 10 - 15 MPa; and / or, the treatment temperature for low - temperature heat treatment is 80 - 100 °C, the heating rate is 5 - 10 °C / min, and the holding time after low - temperature treatment is 10 - 24 h.

6. A positive electrode sheet, characterized in that, Comprising: A current collector; A positive electrode active layer disposed on at least one surface of the current collector; the positive electrode active layer is obtained by coating a positive electrode active slurry on the current collector, and the positive electrode active slurry includes the composite cathode material according to claim 1 or 2, or a composite cathode material prepared by the preparation method of the composite cathode material according to any one of claims 3 to 5.

7. The positive electrode sheet according to claim 6, wherein: The positive electrode active slurry further includes a conductive agent and a binder, and the mass percentages of the composite cathode material, the conductive agent, and the binder are 50 - 93%, 1 - 25%, and 5 - 25% respectively.

8. A battery, characterized in that, Comprising the positive electrode sheet according to claim 6 or 7.

Images