Coated negative electrode material and preparation method and application thereof

Abstract

The invention relates to the technical field of batteries, in particular to a coated negative electrode material as well as a preparation method and application thereof. The coated negative electrode material comprises a negative electrode material main material and a coating layer coating the negative electrode material main material, the main material of the negative electrode material comprises a carbon-based negative electrode material; the coating layer comprises a conjugated carboxylate organic electrode material. Compared with the prior art, the coated negative electrode material provided by the invention adopts the coating layer with specific components to coat the negative electrode material main material with specific components; and the conjugated carboxylate organic electrode material has good coating property and also has reaction kinetics higher than those of common coating materials such as hard carbon and soft carbon, so that the lithium intercalation speed of the main material of the negative electrode material can be improved, and the risk of lithium precipitation during fast charging or low-temperature charging can be reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery, more particularly, to a coated negative electrode material and a preparation method and application thereof. BACKGROUND

[0002] At present, lithium ion batteries have been widely used in power batteries and 3C electronic products, but the energy density of lithium ion batteries is slowly improved, which is difficult to meet the growing demand, especially for power batteries. The energy density of power batteries is related to the endurance of electric vehicles. At present, due to the slow progress of the improvement of the energy density of power batteries, increasing the charging speed of the battery has become one of the important ways to alleviate the range anxiety. In addition, the serious deterioration of the charging and discharging performance of power batteries at low temperature is also a problem that needs to be solved urgently.

[0003] Graphite is an ideal negative electrode material due to its low redox potential and high capacity, but its low lithium intercalation potential also poses a safety hazard for fast charging and low temperature charging, and polarization will cause serious lithium precipitation in the negative electrode. Therefore, how to improve the lithium intercalation speed to obtain a negative electrode material with high reaction kinetics, thereby reducing the risk of lithium precipitation during fast charging and low temperature charging, has become a technical problem that needs to be solved by those skilled in the art. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a coated negative electrode material and a preparation method and application thereof. The coated negative electrode material provided by the present application has a fast lithium intercalation speed, excellent reaction kinetics, and a small risk of lithium precipitation during fast charging or low temperature charging.

[0005] The present application provides a coated negative electrode material, comprising:

[0006] a negative electrode material main material and a coating layer coating the negative electrode material main material;

[0007] The negative electrode material main material comprises a carbon-based negative electrode material.

[0008] The coating layer comprises a conjugated carboxylate organic electrode material.

[0009] Preferably, the carbon-based negative electrode material comprises one or more of graphite, soft carbon, hard carbon, and silicon-carbon.

[0010] Preferably, the conjugated carboxylate organic electrode material comprises one or more of a p-phthalic acid dilithium salt and its derivative, a perylene tetracarboxylic acid tetralithium salt and its derivative, a naphthalene tetracarboxylic acid tetralithium salt and its derivative, a p-phthalic acid disodium salt and its derivative, a perylene tetracarboxylic acid tetrasodium salt and its derivative, and a naphthalene tetracarboxylic acid tetrasodium salt and its derivative.

[0011] Preferably, the amount of the coating layer is 0.2% to 1% based on the mass of the negative electrode material main material.

[0012] The application further provides a preparation method of the coated negative material.

[0013] The negative material main material and the conjugated carboxylic acid salt organic electrode material are contacted in the presence of a solvent, and then the solvent is removed to obtain the coated negative material.

[0014] Preferably, the contacting process comprises:

[0015] The conjugated carboxylic acid salt organic electrode material is added into the negative slurry and stirred uniformly; the negative slurry comprises the negative material main material and a solvent.

[0016] Preferably, the negative slurry further comprises an additive; the additive comprises a binder and / or a conductive agent.

[0017] Preferably, in the negative slurry, the mass ratio of the conjugated carboxylic acid salt organic electrode material to the additive is (1-5):12.

[0018] The application further provides a negative electrode sheet, comprising a negative current collector and a negative active material layer arranged on at least one side surface of the negative current collector in the thickness direction; the negative active material layer comprises the coated negative material according to the above technical solution.

[0019] The application further provides a battery comprising the negative electrode sheet according to the above technical solution.

[0020] The application further provides an electric device comprising the battery according to the above technical solution.

[0021] The application provides a coated negative material, a preparation method and application thereof; the coated negative material comprises a negative material main material and a coating layer covering the negative material main material; the negative material main material comprises a carbon-based negative material; and the coating layer comprises a conjugated carboxylic acid salt organic electrode material. Compared with the prior art, the coated negative material provided by the application adopts a coating layer with specific components to coat a negative material main material with specific components, so that good interaction is achieved as a whole: the conjugated carboxylic acid salt organic electrode material has good coating properties and also has a reaction kinetics higher than that of common coating materials such as hard carbon and soft carbon, thereby helping the negative material main material to improve the lithium intercalation speed and reduce the risk of lithium precipitation during fast charging or low-temperature charging.

[0022] In addition, the preparation method provided by the application has simple process and easy-to-control conditions, and the coating does not require additional processes. The coating can be completed by adding the conjugated carboxylic acid salt organic electrode material in the homogenization process, and the preparation efficiency is high. In addition, the raw materials are easy to obtain and the cost is low, so the application has a wide application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative labor on the basis of the provided drawings.

[0024] Figure 1 Structure diagram of the coated negative electrode material provided by the present application;

[0025] Figure 2 Photo of the lithium precipitation-free negative electrode of Example 1;

[0026] Figure 3 Photo of the obvious lithium precipitation negative electrode of Comparative Example 1. DETAILED DESCRIPTION

[0027] In order to make the person skilled in the art better understand the technical solutions of the present application, the technical solutions of the present application will be described clearly and completely in combination with the embodiments of the present application. Obviously, the described embodiments only constitute some embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0028] In the description of the present application, "the same chemical composition" should be understood broadly, that is, the main components of the two have consistent chemical composition, or the chemical composition of the two is basically consistent, which can have the error within the range that can be understood by those skilled in the art and allowed in the art or contain impurities within the allowable range.

[0029] In the description of the present application, "A and / or B" can include any one of the following cases: A alone, B alone, A and B, wherein A and B are only used for example, and can be any technical feature connected by "and / or" in the present application.

[0030] Unless otherwise specified, all technical terms used in the present application have the same meaning as that generally understood by those skilled in the art to which the present application belongs. All patents and publications involved in the present application are incorporated by reference in the present application. The term "comprising" or "including" is an open expression, that is, it includes the content indicated in the present application, but does not exclude other aspects.

[0031] At present, graphite has become an ideal negative electrode material due to its low redox potential and high capacity. However, its low lithium insertion potential also poses a safety hazard for fast charging and low-temperature charging. Polarization will lead to serious lithium deposition at the negative electrode. Therefore, increasing the lithium insertion rate of the negative electrode, that is, improving the reaction kinetics, is the main improvement direction of the negative electrode material. The main ways to improve the negative electrode kinetics currently include reducing the particle size, surface coating and surface element doping. Among them, surface coating is the most commonly used improvement strategy, mainly including soft carbon, hard carbon or a mixture of the two. Amorphous carbon such as soft carbon and hard carbon has a large interlayer spacing, which can achieve rapid insertion of lithium ions, thereby improving the kinetics. However, the kinetics that can be improved are limited, and both soft carbon and hard carbon have a variety of lithium storage mechanisms. Different precursors and sintering methods will cause changes in the kinetics of lithium storage. After coating, due to the large number of surface active sites, the negative electrode side reactions increase, which often deteriorates the cycle and high-temperature performance.

[0032] To address the aforementioned technical issues, the present invention enhances the lithium insertion kinetics of the negative electrode by coating the surface of the negative electrode material with a high-kinetic organic electrode material. Organic matter often serves as a carbon source during negative electrode production and, after sintering, can be converted into soft or hard carbon, which improves the reaction kinetics of the negative electrode material. The organic electrode material employed in the present invention can adjust its capacity and voltage by manipulating its molecular structure. Furthermore, because organic electrode materials often bind to lithium ions through coordination bonds, they often exhibit rapid reaction kinetics.

[0033] The present invention provides a coated negative electrode material, comprising:

[0034] A negative electrode material and a coating layer covering the negative electrode material;

[0035] The main material of the negative electrode material includes a carbon-based negative electrode material;

[0036] The coating layer comprises a conjugated carboxylate organic electrode material.

[0037] In the present invention, the coated negative electrode material comprises a main negative electrode material and a coating layer coating the main negative electrode material. Figure 1 , Figure 1 This is a schematic structural diagram of the coated negative electrode material provided by the present invention; wherein 1 is the coating layer and 2 is the main negative electrode material.

[0038] In the present invention, the primary negative electrode material comprises a carbon-based negative electrode material; the carbon-based negative electrode material preferably comprises one or more of graphite, soft carbon, hard carbon, and silicon carbon, with graphite being more preferred. The present invention does not particularly limit the source of the carbon-based negative electrode material; commercially available products familiar to those skilled in the art may be used.

[0039] In the present application, the coating layer comprises a conjugated carboxylate organic electrode material; the conjugated carboxylate organic electrode material preferably comprises one or more of a tetraliithiophtalate and derivatives thereof, a tetranatriophtalate and derivatives thereof, a tetranaphthalate and derivatives thereof, a ditosodium terephthalate and derivatives thereof, a tetranatriophtalate and derivatives thereof, a tetranaphthalate and derivatives thereof, more preferably one or two of a tetraliithiophtalate, a tetranatriophtalate, a tetranaphthalate; in a preferred embodiment of the present application, the conjugated carboxylate organic electrode material is specifically a tetraliithiophtalate, or a tetranatriophtalate, or a tetranaphthalate, or a tetraliithiophtalate and a tetranatriophtalate in a mass ratio of 1:1, or a tetranaphthalate, a tetranatriophtalate in a mass ratio of 1:1. The present application does not have special restrictions on the source of the conjugated carboxylate organic electrode material, and commercially available products known to those skilled in the art can be used.

[0040] In the present application, the conjugated carboxylate organic electrode material is selected as the coating material on the surface of the carbon-based negative electrode material, which has a lower redox potential and is close to the potential of the carbon-based negative electrode material (such as graphite), and can quickly combine with lithium ions; the conjugated carboxylate organic electrode material can be used as a negative electrode material, which itself has fast reaction kinetics, higher than common coating materials such as hard carbon and soft carbon, thus helping the main material of the negative electrode material to improve the speed of lithium intercalation and avoid lithium precipitation; at the same time, this type of electrode material also has high solubility in water, and can be completely dissolved by adding slurry during homogenization. Since the surface of the carbon-based negative electrode material often contains a certain amount of carbon material (such as soft carbon, hard carbon or both), there are some oxygen-containing functional groups such as -COOH and -OH, which can adsorb the dissolved conjugated carboxylate in water to achieve uniform coating. This coating method is simple and easy to implement, without adding additional production and manufacturing processes.

[0041] In the present application, the amount of the coating layer is preferably 0.2% to 1% based on the mass of the main material of the negative electrode material; specifically, it can be 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1%. On this basis, the present application can achieve uniform coating of the conjugated carboxylate organic electrode material on the surface of the main material of the negative electrode material, and the coated negative electrode material has faster reaction kinetics and less risk of lithium precipitation during fast charging or low-temperature charging.

[0042] The coated negative electrode material provided by the application adopts a conjugate carboxylate electrode material as a coating material to coat the surface of a negative electrode material main material (such as graphite), which is simple and easy to implement, has a fast lithium intercalation speed, and can effectively improve the lithium intercalation speed of the negative electrode material main material (such as graphite). The conjugate carboxylate organic electrode material has the disadvantage of poor electronic conductivity. If it is used as the main active material in the negative electrode slurry, a large amount of conductive carbon is needed to fully exert its performance. However, if a small amount of the conjugate carboxylate organic electrode material is used to coat the negative electrode material main material (such as graphite) with good electrical conductivity, this defect can be completely avoided. In addition, the lithium storage principle of the conjugate carboxylate organic electrode material is simple, which combines with lithium ions through coordination bonds, has fast reaction kinetics, and can help lithium ions to quickly intercalate into the negative electrode material main material (such as graphite).

[0043] The application further provides a preparation method of the coated negative electrode material.

[0044] The negative electrode material main material and the conjugate carboxylate organic electrode material are contacted in the presence of a solvent, and then the solvent is removed to obtain the coated negative electrode material.

[0045] In the application, the negative electrode material main material and the conjugate carboxylate organic electrode material are the same as in the above technical solution, and will not be described here.

[0046] In the application, the contacting process preferably includes:

[0047] The conjugate carboxylate organic electrode material is added to the negative electrode slurry and stirred uniformly; the negative electrode slurry includes the negative electrode material main material and a solvent.

[0048] In the application, the negative electrode slurry is the negative electrode slurry commonly used in the art for preparing the negative active material layer of the negative electrode sheet; to achieve the application, the negative electrode slurry includes the negative electrode material main material and a solvent; wherein the solvent can be any solvent commonly used in the art for homogenizing the negative electrode slurry (such as deionized water), and the application does not have special limitations.

[0049] In the application, the negative electrode slurry preferably further includes an additive; the additive preferably includes a binder and / or a conductive agent, more preferably a binder and a conductive agent; the specific components of the two can be any conventional type of binder and conductive agent commonly used in the art for preparing the negative electrode slurry. In the preferred embodiments of the application, the binder uses styrene-butadiene rubber (SBR) and / or sodium carboxymethyl cellulose (CMC); the conductive agent uses Super P.

[0050] In the present application, the mass ratio of the conjugated carboxylic acid salt organic electrode material to the additive in the negative electrode slurry is preferably (1-5):12; specifically, it can be 1:12, 1:6, 1:4, 1:3, or 5:12. In the preparation of the negative electrode slurry, the conjugated carboxylic acid salt organic electrode material is added to the negative electrode slurry in a certain proportion, so that the conjugated carboxylic acid salt organic electrode material coats the main material of the negative electrode material without affecting the basic performance of the negative electrode slurry.

[0051] The present application combines the coating process of the main material of the negative electrode material and the conjugated carboxylic acid salt organic electrode material into the homogenization process of the negative electrode slurry, and the coating does not require additional processes. At the same time, the conjugated carboxylic acid salt organic electrode material has high solubility in water and can be completely dissolved in the slurry during the homogenization process, thereby facilitating uniform coating of the main material of the negative electrode material (e.g., the oxygen-containing functional groups on the surface of graphite can adsorb the dissolved conjugated carboxylic acid salt and coat the surface of the graphite), thereby obtaining a coated negative electrode material.

[0052] The present application also provides a negative electrode sheet, which comprises a negative electrode current collector and a negative electrode active material layer arranged on at least one side surface of the negative electrode current collector in the thickness direction of the negative electrode current collector, wherein the negative electrode active material layer comprises the coated negative electrode material described in the above technical solution.

[0053] The present application does not have special limitations on the type and source of the negative electrode current collector, and commercially available negative electrode current collectors known to those skilled in the art for preparing negative electrode sheets can be used, such as copper foil current collectors. As an example, the negative electrode current collector has two opposite surfaces in its own thickness direction, and the negative electrode active material layer is arranged on any one or both of the two opposite surfaces of the negative electrode current collector.

[0054] In the present application, the negative electrode active material layer comprises the coated negative electrode material described in the above technical solution, and the conjugated carboxylic acid salt organic electrode material can be added to the negative electrode slurry during the homogenization process of the negative electrode slurry according to the preparation method described in the above technical solution, so as to coat the main material of the negative electrode material and obtain the negative electrode slurry.

[0055] Subsequently, the negative electrode slurry is coated on a negative electrode current collector according to the process steps for preparing a negative electrode sheet known to those skilled in the art, and then subjected to conventional steps such as drying (to remove the solvent) and rolling to obtain the desired negative electrode sheet.

[0056] The present application also provides a battery comprising the negative electrode sheet described in the above technical solution.

[0057] The negative pole piece provided by the application can be adapted to various battery systems, including but not limited to lithium ion batteries, sodium ion batteries and the like. Taking a lithium ion battery as an example, the lithium ion battery comprises the negative pole piece described in the above technical solution, a positive pole piece, a separator, an electrolyte and other necessary or unnecessary functional elements or packaging assemblies, etc., and a person skilled in the art can make any selection and combination thereof; wherein the separator includes but is not limited to PP, PE, a separator of PP material and a composite separator of any combination of various materials, and can also be a nanocellulose separator, which can play an insulating role and avoid direct contact between the positive and negative poles, and materials having certain mechanical strength, thermal stability, chemical stability and suitable porosity can all be used as the separator, and the application has no special limitation thereon; the electrolyte is LiPF6 dissolved in a mixed solvent of a conventional carbonate solvent and a carboxylate solvent, and usually contains a small amount of additives, and the application has no special limitation thereon. When the negative pole piece is included in the lithium ion battery, whether other composite electrodes are also used in the lithium ion battery or not, it can all be an embodiment of the application.

[0058] The application further provides an electric device comprising the battery described in the above technical solution. Specifically, the battery can be used as a power supply of the electric device or an energy storage unit of the electric device. The electric device can include but is not limited to mobile devices (such as mobile phones and notebook computers), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts and electric trucks), electric trains, ships and satellites and energy storage systems.

[0059] The application provides a coated negative electrode material, a preparation method and application thereof. The coated negative electrode material comprises a negative electrode material main material and a coating layer for coating the negative electrode material main material. The negative electrode material main material comprises a carbon-based negative electrode material. The coating layer comprises a conjugated carboxylate organic electrode material. Compared with the prior art, the coated negative electrode material provided by the application uses a coating layer with specific components to coat a negative electrode material main material with specific components, so as to realize good interaction as a whole. The conjugated carboxylate organic electrode material has good coating properties and a reaction kinetics higher than that of common coating materials such as hard carbon and soft carbon, so as to help the negative electrode material main material to improve the lithium intercalation speed and reduce the risk of lithium precipitation during fast charging or low-temperature charging.

[0060] In addition, the preparation method provided by the application has simple process and controllable conditions, and coating can be completed by adding the conjugated carboxylate organic electrode material in the homogenate process, so as to have high preparation efficiency, and raw materials are easy to obtain and low in cost (for example, the synthesis of the conjugated carboxylate organic electrode material is also very simple, mainly by reacting a corresponding anhydride with sodium hydroxide, and the yield is more than 95%). Therefore, the preparation method has wide application prospects.

[0061] In order to further illustrate the present application, the following examples are provided. The raw materials used in the following examples of the present application are commercially available; among them, the separator used is a PP separator with a thickness of 7 μm, and the electrolyte used is an electrolyte of LiPF6 dissolved in a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DEC) and methyl ethyl carbonate (EMC) in a mass ratio of 1:1:1.

[0062] Comparative Example 1

[0063] LiFePO4 cathode material and Super P, polyvinylidene fluoride (PVDF) are mixed uniformly in a mass ratio of 96:2:2, and the slurry is coated on an aluminum foil current collector, dried in an oven, and then rolled to obtain the required cathode sheet; graphite is selected as the anode material, and graphite, styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC) and Super P are mixed uniformly in a mass ratio of 97.6:1.2:0.8:0.4, and the slurry is coated on a copper foil current collector, dried in an oven, and then rolled to obtain the required anode sheet; a 2.5 Ah small soft package battery is prepared by the Z-shaped stacking method. The electrolyte is injected into the argon glove box, the injection coefficient is 2.6, and the electrolyte is placed at 45℃ for 48 hours.

[0064] Example 1

[0065] LiFePO4 cathode material and Super P, polyvinylidene fluoride (PVDF) are mixed uniformly in a mass ratio of 96:2:2, and the slurry is coated on an aluminum foil current collector, dried in an oven, and then rolled to obtain the required cathode sheet; graphite is selected as the anode material, and graphite, styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC) and Super P are mixed uniformly in a mass ratio of 97.6:1.2:0.8:0.4, and the slurry is coated on a copper foil current collector, dried in an oven, and then rolled to obtain the required anode sheet; a 2.5 Ah small soft package battery is prepared by the Z-shaped stacking method. The electrolyte is injected into the argon glove box, the injection coefficient is 2.6, and the electrolyte is placed at 45℃ for 48 hours.

[0066] Example 2

[0067] The LiFePO4 positive electrode material and Super P and polyvinylidene fluoride (PVDF) are uniformly mixed in a mass ratio of 96:2:2, slurry is prepared, and then coated on an aluminum foil current collector, dried in an oven, and then rolled to prepare the required positive electrode sheet; the graphite is selected as the active material, and the perylene tetracarboxylic acid tetralithium salt is selected as the coating material, the graphite, perylene tetracarboxylic acid tetralithium salt, styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), and Super P are uniformly mixed in a mass ratio of 97.2:0.4:1.2:0.8:0.4, slurry is prepared, and then coated on the surface of a copper foil, dried in an oven, and then rolled to prepare the required negative electrode sheet; a 2.5 Ah small soft package battery is prepared by the Z-shaped stacking method. The electrolyte is injected in an argon glove box, the liquid injection coefficient is 2.6, and the battery is placed at 45 DEG C for 48 hours.

[0068] Example 3

[0069] The LiFePO4 positive electrode material and Super P and polyvinylidene fluoride (PVDF) are uniformly mixed in a mass ratio of 96:2:2, slurry is prepared, and then coated on an aluminum foil current collector, dried in an oven, and then rolled to prepare the required positive electrode sheet; the graphite is selected as the active material, and the perylene tetracarboxylic acid tetralithium salt is selected as the coating material, the graphite, perylene tetracarboxylic acid tetralithium salt, styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), and Super P are uniformly mixed in a mass ratio of 97.2:0.4:1.2:0.8:0.4, slurry is prepared, and then coated on the surface of a copper foil, dried in an oven, and then rolled to prepare the required negative electrode sheet; a 2.5 Ah small soft package battery is prepared by the Z-shaped stacking method. The electrolyte is injected in an argon glove box, the liquid injection coefficient is 2.6, and the battery is placed at 45 DEG C for 48 hours.

[0070] Example 4

[0071] The LiFePO4 positive electrode material and Super P and polyvinylidene fluoride (PVDF) are uniformly mixed in a mass ratio of 96:2:2, slurry is prepared, and then coated on an aluminum foil current collector, dried in an oven, and then rolled to prepare the required positive electrode sheet; the graphite is selected as the active material, and the perylene tetracarboxylic acid tetralithium salt is selected as the coating material, the graphite, perylene tetracarboxylic acid tetralithium salt, styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), and Super P are uniformly mixed in a mass ratio of 97.2:0.4:1.2:0.8:0.4, slurry is prepared, and then coated on the surface of a copper foil, dried in an oven, and then rolled to prepare the required negative electrode sheet; a 2.5 Ah small soft package battery is prepared by the Z-shaped stacking method. The electrolyte is injected in an argon glove box, the liquid injection coefficient is 2.6, and the battery is placed at 45 DEG C for 48 hours.

[0072] Example 5

[0073] The LiFePO4 positive electrode material and Super P and polyvinylidene fluoride (PVDF) are mixed uniformly according to a mass ratio of 96:2:2, and after slurry preparation, the mixture is coated on an aluminum foil current collector, dried in an oven, and then rolled to obtain the required positive electrode sheet; the graphite is selected as the active material, and tetrakis lithium perylene-4, 5, 9, 10-tetracarboxylate and tetrakis lithium naphthalene-4, 5, 6, 7-tetracarboxylate are selected as the coating material, and the graphite, tetrakis lithium perylene-4, 5, 9, 10-tetracarboxylate, tetrakis lithium naphthalene-4, 5, 6, 7-tetracarboxylate, styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC) and Super P are mixed uniformly according to a mass ratio of 97.2:0.2:0.2:1.2:0.8:0.4, and after slurry preparation, the mixture is coated on the surface of a copper foil, dried in an oven, and then rolled to obtain the required negative electrode sheet; a 2.5 Ah small soft package battery is prepared by the Z-shaped stacking method. The electrolyte is injected in an argon glove box, the injection coefficient is 2.6, and the battery is placed at 45℃ for 48 hours.

[0074] Example 6

[0075] The LiFePO4 positive electrode material and Super P and polyvinylidene fluoride (PVDF) are mixed uniformly according to a mass ratio of 96:2:2, and after slurry preparation, the mixture is coated on an aluminum foil current collector, dried in an oven, and then rolled to obtain the required positive electrode sheet; the graphite is selected as the active material, and tetrakis lithium perylene-4, 5, 9, 10-tetracarboxylate and tetrakis lithium naphthalene-4, 5, 6, 7-tetracarboxylate are selected as the coating material, and the graphite, tetrakis lithium perylene-4, 5, 9, 10-tetracarboxylate, tetrakis lithium naphthalene-4, 5, 6, 7-tetracarboxylate, styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC) and Super P are mixed uniformly according to a mass ratio of 97.2:0.2:0.2:1.2:0.8:0.4, and after slurry preparation, the mixture is coated on the surface of a copper foil, dried in an oven, and then rolled to obtain the required negative electrode sheet; a 2.5 Ah small soft package battery is prepared by the Z-shaped stacking method. The electrolyte is injected in an argon glove box, the injection coefficient is 2.6, and the battery is placed at 45℃ for 48 hours.

[0076] The batteries prepared in Examples 1-6 and Comparative Example 1 are subjected to various performance tests, including:

[0077] Constant current charge and discharge test, charging at a selected rate (4C and 5C) and discharging at 0.33C.

[0078] Normal temperature DCR test.

[0079] Lithium precipitation risk determination method: the battery cores of all examples and comparative examples are charged according to the given step charging process (equivalent to 1C rate) at-10℃, and discharged at 0.33C, after 50 cycles, the battery is placed for 24h and then disassembled, and the surface of the negative electrode is observed to determine whether lithium precipitation exists. The area of lithium precipitation accounts for 0-5% of the total electrode area, which is determined as low, 5-10% is determined as medium, and more than 10% is determined as high.

[0080] The test results are shown in Table 1 below and Figures 2-3 as shown in FIG. 1, Figure 2 is a photo of the lithium plating-free negative electrode of Example 1, Figure 3 is a photo of the obvious lithium plating negative electrode of Comparative Example 1.

[0081] Table 1

[0082]

[0083] As can be seen from Table 1, the batteries prepared from the coated negative electrode materials provided by Examples 1-6 of the present application have higher cycle retention rate and capacity (and higher capacity at high rate, which can obviously indicate that the lithium intercalation speed of graphite is effectively improved), lower internal resistance in normal temperature DCR test, and low risk of lithium plating at low temperature, and overall have better fast charging capability and low temperature performance, which is due to the fast lithium intercalation speed and faster reaction kinetics of the coated negative electrode material designed in the present application. In addition, the preparation method provided by the present application does not require additional processes, and the coating can be completed by adding the coating material during the homogenization process, which has broad application prospects.

[0084] In the above description of the specification, the description referring to the terms "one embodiment", "another embodiment", and the like means that the specific features, structures, materials, or characteristics described in connection with the embodiment are included in at least one embodiment of the present application. In the specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in any one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the specification and the features of the different embodiments or examples, without contradiction. In addition, it should be noted that in the specification, the terms "first", "second" are for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features.

[0085] The above description of the disclosed embodiments enables a person skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A coated negative electrode material, characterized in that: include: A negative electrode material and a coating layer covering the negative electrode material; The main material of the negative electrode material includes a carbon-based negative electrode material; The coating layer comprises a conjugated carboxylate organic electrode material.

2. The coated negative electrode material according to claim 1, characterized in that The carbon-based negative electrode material includes one or more of graphite, soft carbon, hard carbon, and silicon carbon.

3. The coated negative electrode material according to claim 1, characterized in that The conjugated carboxylate organic electrode material includes one or more of dilithium terephthalate and its derivatives, tetralithium perylenetetracarboxylate and its derivatives, tetralithium naphthalenetetracarboxylate and its derivatives, disodium terephthalate and its derivatives, tetrasodium perylenetetracarboxylate and its derivatives, and tetrasodium naphthalenetetracarboxylate and its derivatives.

4. The coated negative electrode material according to claim 1, characterized in that The amount of the coating layer is 0.2% to 1% based on the mass of the main negative electrode material.

5. A method for preparing the coated negative electrode material according to any one of claims 1 to 4, characterized in that: The following steps are involved: The main negative electrode material is brought into contact with a conjugated carboxylate organic electrode material in the presence of a solvent, and then the solvent is removed to obtain a coated negative electrode material.

6. The preparation method according to claim 5, characterized in that The contact process includes: The conjugated carboxylate organic electrode material is added to the negative electrode slurry and stirred evenly; the negative electrode slurry comprises a negative electrode material main material and a solvent.

7. The preparation method according to claim 6, characterized in that The negative electrode slurry further includes additives; the additives include a binder and / or a conductive agent; And / or, in the negative electrode slurry, the mass ratio of the conjugated carboxylate organic electrode material to the additive is (1-5):

12.

8. A negative electrode plate, characterized in that: The invention comprises a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector in a thickness direction, wherein the negative electrode active material layer comprises the coated negative electrode material according to any one of claims 1 to 4.

9. A battery, characterized in that: Including the negative electrode sheet according to claim 8.

10. An electrical device, characterized in that: A battery comprising the battery of claim 9.

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