A positive electrode composite material and a positive electrode containing the positive electrode composite material, and a method for preparing the same.

Abstract

This invention provides a cathode composite material and a cathode containing the cathode composite material, as well as a method for preparing the same, relating to the field of electrochemical materials technology. The invention provides a cathode composite material comprising a p-type organic material, an inorganic lithium salt, a conductive agent, and a binder; the inorganic lithium salt is selected from one or more mixtures of lithium phosphate, lithium carbonate, lithium fluoride, and lithium sulfate. The innovative addition of an inorganic lithium salt to the p-type organic material effectively increases the p-type doping concentration, thereby improving the utilization rate of active sites and specific capacity of the p-type organic material, and significantly enhancing the electrochemical performance of the p-type organic energy storage material. The lithium-ion battery cathode sheet prepared using the cathode composite material provided by this invention not only significantly improves battery energy storage performance but also has the advantages of mild preparation conditions and simple processes, offering broader development potential compared to traditional lithium-ion batteries.

Description

Technical Field

[0001] This invention relates to the field of electrochemical materials technology, and in particular to a positive electrode composite material, a positive electrode containing the positive electrode composite material, and a method for preparing the same. Background Technology

[0002] Currently, traditional lithium-ion batteries reversibly charge and discharge by allowing lithium ions to shuttle back and forth between the positive and negative electrodes. When organic materials are used as the positive electrode in lithium-ion batteries, they can be classified into n-type organic materials, p-type organic materials, and bipolar organic materials according to their energy storage principles. The energy storage principle of n-type organic materials is the reversible insertion and extraction of lithium ions at the positive electrode. The energy storage principle of p-type organic materials (POM) is the reversible insertion and extraction of anions from the electrolyte at the positive electrode. Bipolar materials possess both n-type and p-type energy storage characteristics, combining cations at low voltages and anions at high voltages.

[0003] Lithium phosphate, with the molecular formula Li3PO4, is a white crystalline powder with an orthorhombic crystal system. It is readily soluble in dilute acids and slightly soluble in water. It is an important electrolyte additive; due to its unique catalytic and electrochemical properties, it is widely used in the field of electrochemical materials.

[0004] N,N,N,N-Tetraphenyl-1,4-phenylenediamine (TPPA) is an ideal p-type organic molecule with two graphitic nitrogen atoms. After electrochemical p-type doping, it exhibits high radical delocalization and relatively stable intermediates, making it a highly desirable p-type organic molecule with a theoretical specific capacity of 130 mAh g. -1 However, in practical applications, its performance as a cathode material in lithium-ion batteries differs significantly from its theoretical specific capacity. This is because when it stores charge through p-type doping, the larger volume of anions in the electrolyte leads to greater steric hindrance during insertion / extraction from the electrode during charging and discharging, inhibiting reaction kinetics and reducing the utilization rate and specific capacity of the active sites in the organic electrode material.

[0005] Covalent triazine frameworks (CTFs) are p-type organic porous polymers containing triazine rings. They possess abundant active sites, a large specific surface area, good durability, and excellent conductivity, and have been widely used in various energy storage devices. When used as electrode materials, triazine rings exhibit bipolar properties, allowing for n-type doping energy storage at low potentials and p-type doping energy storage at high potentials by converting triazine radical cations to anions. However, when CTFs are used as cathodes, the utilization rate of active sites is low at high potentials when p-type doping is achieved through anion compensation from the electrolyte, requiring further improvement. Therefore, developing a cathode composite material based on p-type organic materials is essential for improving the electrochemical performance of lithium-ion batteries. Summary of the Invention

[0006] The purpose of this invention is to provide a positive electrode composite material and a positive electrode containing the positive electrode composite material and a method for preparing the same, so as to solve the technical problem of low electrochemical performance when p-type organic materials are used as positive electrodes in the prior art.

[0007] To solve the above-mentioned technical problems, the present invention provides a positive electrode composite material, comprising p-type organic material, inorganic lithium salt, conductive agent, and binder;

[0008] The inorganic lithium salt is selected from one or more mixtures of lithium phosphate, lithium carbonate, lithium fluoride, and lithium sulfate; preferably lithium phosphate.

[0009] The addition of infinite lithium salts can improve the energy storage performance of p-type organic materials and further enhance the electrochemical performance of lithium-ion batteries.

[0010] Furthermore, the p-type organic material is selected from p-type small organic molecules and / or p-type organic polymers;

[0011] Preferably, the p-type organic small molecule material is N,N,N,N-tetraphenyl-1,4-phenylenediamine;

[0012] Preferably, the p-type organic polymer is a covalent triazine framework.

[0013] Furthermore, the amount of inorganic lithium salt added should not exceed four times the total mass of the p-type organic material;

[0014] Furthermore, the conductive agent is selected from one or more mixtures of carbon nanotubes, acetylene black, graphene, Ketjen black, and carbon black. Ketjen black is preferred.

[0015] Furthermore, the adhesive is selected from one or more mixtures of polyvinylidene fluoride, carboxymethyl cellulose, polytetrafluoroethylene, and styrene-butadiene rubber. Polyvinylidene fluoride is preferred.

[0016] This invention provides a lithium-ion battery cathode, comprising a current collector and the aforementioned cathode composite material;

[0017] The current collector is selected from any one of metal foil, foamed metal material, and carbon-coated metal material.

[0018] On the other hand, the present invention provides a method for preparing a lithium-ion battery cathode, the specific steps of which are as follows:

[0019] Step 1: Weigh p-type organic material, conductive agent, binder and inorganic lithium salt in a certain mass ratio, add them to the solvent N-methylpyrrolidone, and grind them in a mortar to obtain a uniform grinding slurry.

[0020] Step 2: Take the grinding slurry, coat it evenly on the surface of the current collector, vacuum dry it at 80-90℃, and then cut it to obtain a lithium-ion battery positive electrode sheet containing the positive electrode composite material.

[0021] Further, the mass ratio of the p-type organic material, conductive agent, binder, and inorganic lithium salt in step 1 is (3-7):(2-6):1:(1-28).

[0022] Furthermore, the grinding time in step 1 is 30-60 minutes.

[0023] Furthermore, the drying time in step 2 is 20-24 hours; preferably 24 hours.

[0024] By adopting the above technical solution, the present invention has the following beneficial effects:

[0025] This invention provides a cathode composite material that creatively incorporates inorganic lithium salts into p-type organic materials, effectively increasing the p-type doping concentration of the organic materials. This, in turn, improves the utilization rate of active sites and specific capacity of the p-type organic materials, significantly enhancing the electrochemical performance of p-type organic energy storage materials. The lithium-ion battery cathode prepared using the cathode composite material provided by this invention not only significantly improves battery energy storage performance but also has the advantages of mild preparation conditions and simple processes, giving it a broader development prospect compared to traditional lithium-ion batteries. Attached Figure Description

[0026] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram illustrating the working principle of the lithium-ion battery cathode composite material provided by the present invention.

[0028] Figure 2 The graph shows the cycle performance of TPPA material as a positive electrode in lithium-ion batteries.

[0029] Figure 3 Cycle performance curves of TPPA@Li3PO4 material as a cathode in lithium-ion batteries;

[0030] Figure 4 Cycle performance curves of CTF material and CTF@Li3PO4 material as positive electrodes of lithium-ion batteries;

[0031] Figure 5A comparison chart showing the rate performance of CTF material and CTF@Li3PO4 material as positive electrodes in lithium-ion batteries;

[0032] Figure 6 The discharge curve of TPPA as the positive electrode of lithium-ion battery, and the capacity ratio of n-type doping and p-type doping are shown.

[0033] Figure 7 The discharge curve of TPPA@Li3PO4 as the positive electrode of lithium-ion battery, and the capacity ratio of n-type doping and p-type doping are shown.

[0034] Figure 8 The discharge curve of CTF as the positive electrode of lithium-ion battery, and the capacity ratio of n-type doping and p-type doping.

[0035] Figure 9 The discharge curves of CTF@Li3PO4 as the positive electrode of a lithium-ion battery, and the capacity ratios of n-type and p-type doping are shown. Detailed Implementation

[0036] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] The present invention will be further explained below with reference to specific embodiments.

[0038] The specific steps for preparing lithium-ion battery cathode sheets using the lithium-ion battery cathode composite material provided by this invention are as follows:

[0039] Step S1: Weigh p-type organic material, conductive agent, binder and inorganic lithium salt in the mass ratio of (3-7):(2-6):1:(1-28), add them to the solvent N-methylpyrrolidone, and grind them in a mortar for 30-60 minutes to obtain a uniform grinding slurry.

[0040] Step 2: Take the grinding slurry, coat it evenly on the surface of the current collector, vacuum dry it at 80-90℃ for 20-24 hours, and then cut it to obtain a lithium-ion battery positive electrode sheet containing the positive electrode composite material.

[0041] like Figure 1 As shown, during the charging and discharging process, the positive electrode containing the positive electrode composite material provided by this invention passes through anions with a relatively high charge mass (such as PO4). 3- CO3 2- F - To replace PF6 in the original electrolyte- The use of anions avoids the drawback of traditional p-type organic cathodes, which require the insertion or removal of large anions during charging and discharging for energy storage. This balances the positive charge of the cations in the oxidized state of p-type organic cathodes, making Li+ ions the primary charge carriers. This significantly reduces steric hindrance and ion migration, increasing the efficiency of Li+ ion storage. + The quantity increases reaction kinetics and specific capacity.

[0042] Example 1

[0043] This embodiment verifies a method for preparing TPPA@Li3PO4 composite materials and simultaneously fabricating lithium-ion battery cathode sheets using N,N,N,N-tetraphenyl-1,4-phenylenediamine (TPPA) as a raw material.

[0044] Step S1: Weigh TPPA material, Ketjen black, polyvinylidene fluoride (PVDF), and lithium phosphate in sequence according to a mass ratio of 5:4:1:1, add them to the solvent N-methylpyrrolidone, and grind them in a mortar for 30 minutes to obtain a uniformly sized grinding slurry.

[0045] Step 2: Take the grinding slurry, coat it evenly on the carbon-coated aluminum foil, vacuum dry it at 80-90℃ for 24 hours, and then cut it to obtain the lithium-ion battery positive electrode sheet containing the positive electrode composite material.

[0046] Comparative Example 1

[0047] This comparative example uses N,N,N,N-tetraphenyl-1,4-phenylenediamine (TPPA) as a raw material to prepare a lithium-ion battery cathode sheet without adding inorganic lithium salt.

[0048] Step S1: Weigh TPPA material, Ketjen black, and polyvinylidene fluoride (PVDF) in sequence according to a mass ratio of 5:4:1, add them to the solvent N-methylpyrrolidone, and grind them in a mortar for 30 minutes to obtain a uniformly sized grinding slurry.

[0049] Step 2: Take the grinding slurry, coat it evenly on carbon-coated aluminum foil, vacuum dry it at 80°C for 24 hours, and then cut it to obtain a TPPA lithium-ion battery positive electrode sheet that does not contain inorganic lithium salt.

[0050] Example 2

[0051] This embodiment verifies a method for preparing CTF@Li3PO4 composite material and simultaneously fabricating lithium-ion battery cathode sheets using triazine framework (CTF) as raw material.

[0052] Step S1: Weigh CTF material, Ketjen black, polyvinylidene fluoride (PVDF), and lithium phosphate in sequence according to a mass ratio of 6:3:1:1, add them to the solvent N-methylpyrrolidone, and grind them in a mortar for 60 minutes to obtain a uniformly sized grinding slurry.

[0053] Step 2: Take the grinding slurry, coat it evenly on the carbon-coated aluminum foil, vacuum dry it at 80-90℃ for 24 hours, and then cut it to obtain the lithium-ion battery positive electrode sheet containing the positive electrode composite material.

[0054] Comparative Example 2

[0055] This comparative example uses triazine framework (CTF) as raw material to prepare lithium-ion battery cathode sheets without adding inorganic lithium salts.

[0056] Step S1: Weigh CTF material, Ketjen black, and polyvinylidene fluoride (PVDF) in sequence according to a mass ratio of 6:3:1, add them to the solvent N-methylpyrrolidone, and grind them in a mortar for 60 minutes to obtain a uniformly sized grinding slurry.

[0057] Step 2: Take the grinding slurry, coat it evenly on carbon-coated aluminum foil, vacuum dry it at 90°C for 20 hours, and then cut it to obtain a CTF lithium-ion battery positive electrode sheet that does not contain inorganic lithium salt.

[0058] Example 3

[0059] This embodiment verifies the preparation of lithium-ion battery cathode sheets by adding different types of inorganic lithium salts.

[0060] Step S1: Weigh CTF material, carbon black, polyvinylidene fluoride (PVDF), and lithium carbonate in sequence according to a mass ratio of 5:4:1:12, add them to the solvent N-methylpyrrolidone, and grind them in a mortar for 60 minutes to obtain a uniformly sized grinding slurry.

[0061] Step 2: Take the grinding slurry, coat it evenly on the carbon-coated aluminum foil, vacuum dry it at 80-90℃ for 24 hours, and then cut it to obtain the lithium-ion battery positive electrode sheet containing the positive electrode composite material.

[0062] Example 4

[0063] This embodiment verifies the preparation of lithium-ion battery cathode sheets with different amounts of inorganic lithium salts.

[0064] Step S1: Weigh TPPA material, carbon black, polyvinylidene fluoride (PVDF), and lithium hexafluorophosphate in sequence according to a mass ratio of 6:3:1:20, add them to the solvent N-methylpyrrolidone, and grind them in a mortar for 50 minutes to obtain a uniformly sized grinding slurry.

[0065] Step 2: Take the grinding slurry, coat it evenly on the carbon-coated aluminum foil, vacuum dry it at 80-90℃ for 20 hours, and then cut it to obtain the lithium-ion battery positive electrode sheet containing the positive electrode composite material.

[0066] Example 5

[0067] like Figures 2-3 As shown, the cycle performance of lithium-ion batteries assembled using the two types of positive electrode sheets prepared in Example 1 and Comparative Example 1 was tested through comparative experiments:

[0068] The positive electrode and lithium metal sheet prepared in Example 1 and Comparative Example 1 were used as the negative electrode, and 1M LiPF6 EC / DEC (v:v = 1:1) was used as the electrolyte. Two sets of CR2032 coin cells were assembled and labeled as TPPA@Li3PO4 battery and TPPA battery, respectively.

[0069] The battery's cycle performance was tested by constant current charge-discharge at a current density of 1 A / g, and the results are as follows:

[0070] like Figure 2 As shown, after 300 cycles at 1 A / g, the capacity of the TPPA battery prepared in Comparative Example 1 was only 69.1 mAh / g, while the TPPA@Li3PO4 battery prepared under the same test conditions, with a certain amount of lithium phosphate added during the preparation process, showed a significantly higher capacity. Figure 3 The capacity shown can reach 124 mAh / g. This demonstrates that when using p-type organic small molecules as the cathode material for lithium batteries, adding inorganic lithium salts can effectively improve the battery's cycle performance.

[0071] Example 6

[0072] like Figure 4 As shown, the cycle performance of lithium-ion batteries assembled using the two types of positive electrode sheets prepared in Example 2 and Comparative Example 2 was tested through comparative experiments:

[0073] The positive electrode and lithium metal sheet prepared in Example 2 and Comparative Example 2 were used as the negative electrode, and 1M LiPF6 EC / DEC (v:v = 1:1) was used as the electrolyte. Two sets of CR2032 coin cells were assembled and labeled as CTF@Li3PO4 battery and CTF battery, respectively.

[0074] The battery's cycle performance was tested by constant current charge-discharge at a current density of 0.1 A / g, and the results are as follows:

[0075] like Figure 4As shown, after 300 cycles at 0.1 A / g, the CTF battery prepared in Comparative Example 2 had a capacity of 75.4 mAh / g; while the CTF@Li3PO4 battery, prepared under the same test conditions with the addition of a certain amount of lithium phosphate, achieved a capacity of 89 mAh / g. This demonstrates that when using p-type organic polymers as the cathode material for lithium batteries, the addition of inorganic lithium salts can effectively improve the battery's cycle performance.

[0076] As can be seen from the test results of Examples 5-6 above, for lithium-ion battery cathode sheets made from p-type organic materials, adding an appropriate amount of inorganic lithium salt during the preparation process can significantly improve the cycle performance of lithium-ion batteries assembled using this cathode sheet.

[0077] Example 7

[0078] like Figure 5 As shown, the rate performance of different lithium-ion battery cathodes prepared in Example 2 and Comparative Example 2 was tested:

[0079] The positive electrode and lithium metal sheet prepared in Example 2 and Comparative Example 2 were used as the negative electrode, and 1M LiPF6 EC / DEC (v:v = 1:1) was used as the electrolyte. Two sets of CR2032 coin cells were assembled and labeled as CTF@Li3PO4 battery and CTF battery, respectively.

[0080] The battery's discharge specific capacity was tested by constant current charge-discharge at current densities of 0.1, 0.2, 0.5, 1, 2, 5, and 10 A / g. The results are as follows: Figure 5 As shown in Table 1,

[0081] Table 1. Comparison of discharge specific capacity between CTF batteries and CTF@Li3PO4 batteries:

[0082]

[0083] As shown in Table 1, the discharge specific capacity of the battery decreases accordingly with increasing current density, but the discharge specific capacity of the CTF@Li3PO4 battery remains higher than that of the CTF battery. This demonstrates that the positive electrode composite material provided by this invention significantly improves the electrochemical performance of lithium-ion batteries using it as the positive electrode by adding an appropriate amount of inorganic lithium salt to the p-type organic material.

[0084] Example 8

[0085] like Figures 6-9 As shown, this embodiment verifies the improvement of battery performance by adding inorganic lithium salts through the study of discharge curves of four types of batteries assembled using positive electrode sheets prepared in Examples 1-2 and Comparative Examples 1-2, and the determination of the capacity ratio of n-type doping and p-type doping.

[0086] The positive electrode and lithium metal sheet prepared in Example 1, Comparative Example 1, Example 2, and Comparative Example 2 were used as the negative electrode, and 1M LiPF6 EC / DEC (v:v = 1:1) was used as the electrolyte. Four CR2032 coin cells were assembled and labeled as TPPA@Li3PO4 battery, TPPA battery, CTF@Li3PO4 battery, and CTF battery, respectively. The discharge curves were recorded at a current density of 1 A / g after 300 cycles. The discharge curves were horizontally divided with the voltage node of 3.0V (n / p type energy storage) as the horizontal axis, and the specific capacity was correspondingly assigned to the vertical axis to obtain the desired results. Figures 6-9 .from Figures 6-9 From this, we can obtain the data in Table 2:

[0087] Table 2 Comparison of p-type capacity percentage of the above four types of batteries

[0088] Battery types p-type capacity percentage (mAh / g) TPPA batteries 39.7 <![CDATA[TPPA@Li3PO4 battery]]> 77.1 CTF battery 46.5 <![CDATA[CTF@Li3PO4 battery]]> 55.9

[0089] Table 2 clearly shows that, for battery cathodes using the same p-type organic material, the battery with added inorganic lithium salt has a significantly higher p-type capacity ratio than the one without. This demonstrates that the cathode composite material provided by this invention, by adding inorganic lithium salt, improves the utilization rate of the p-type active sites in the p-type organic material, thereby enhancing the energy storage performance of the p-type organic material and achieving the technical effect of significantly improving the electrochemical performance of the p-type organic material as a battery cathode.

[0090] In summary, the cathode composite material provided by this invention can effectively improve the utilization rate of p-type active sites and enhance the performance of p-type organic energy storage materials by adding an appropriate amount of inorganic lithium salt to p-type organic materials. The cathode sheet prepared using the above composite material has a wide range of applications in the field of lithium-ion batteries.

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A positive electrode composite material, characterized in that, The composite material includes p-type organic materials, inorganic lithium salts, conductive agents, and binders; The inorganic lithium salt is selected from one or more mixtures of lithium phosphate, lithium carbonate, lithium fluoride, and lithium sulfate; The p-type organic material is selected from p-type small organic molecules and / or p-type organic polymers.

2. The positive electrode composite material according to claim 1, characterized in that, The amount of inorganic lithium salt added is no more than four times the total mass of the p-type organic material.

3. The positive electrode composite material according to claim 1, characterized in that, The conductive agent is selected from one or more mixtures of carbon nanotubes, acetylene black, graphene, Ketjen black, and carbon black.

4. The positive electrode composite material according to claim 1, characterized in that, The adhesive is selected from one or more mixtures of polyvinylidene fluoride, carboxymethyl cellulose, polytetrafluoroethylene, and styrene-butadiene rubber.

5. A lithium-ion battery positive electrode, characterized in that, The positive electrode includes a current collector and the positive electrode composite material according to any one of claims 1-4; The current collector is selected from any one of metal foil, foamed metal material, and carbon-coated metal material.

6. A method for preparing the positive electrode of a lithium-ion battery according to claim 5, characterized in that, The specific steps are as follows: Step 1: Weigh p-type organic material, conductive agent, binder and inorganic lithium salt in a certain mass ratio, add them to the solvent N-methylpyrrolidone, and grind them in a mortar to obtain a uniform grinding slurry. Step 2: Take the grinding slurry, coat it evenly on the surface of the current collector, dry it under vacuum at 80-90℃, and after cutting, obtain the lithium-ion battery positive electrode containing the positive electrode composite material.

7. The preparation method according to claim 6, characterized in that, The mass ratio of the p-type organic material, conductive agent, binder, and inorganic lithium salt in step 1 is (3-7):(2-6):1:(1-28).

8. The preparation method according to claim 6, characterized in that, The grinding time mentioned in step 1 is 30-60 minutes.

9. The preparation method according to claim 6, characterized in that, The drying time in step 2 is 20-24 hours.

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