TW202025539A - Surface-modified hard carbon substrate battery negative electrode structure and preparation method thereof capable of greatly improving low-temperature cycle performance and high-rate charge and discharge performance of a battery - Google Patents

Abstract

The present invention discloses a surface-modified hard carbon substrate battery negative electrode structure and a preparation method thereof. The surface-modified hard carbon substrate battery negative electrode structure includes a plurality of modified films located on a hard carbon substrate. Each of the modified films includes water-soluble organic polymers. The modified film can effectively increase charge and discharge power of the hard carbon substrate battery negative structure, effectively reduce the irreversible capacity of the battery, and improve the cycle life of the battery. According to a preparation method of the surface-modified hard carbon substrate battery negative electrode structure of the present invention, the damage of volatile organic compounds can be avoided by the water phase slurry process. Moreover, the surface-modified hard carbon substrate battery negative electrode structure can greatly improve low-temperature cycle performance and high rate charge and discharge performance of the battery.

Description

Hard carbon substrate battery negative electrode structure with surface modification and preparation method thereof

The present invention relates to a hard carbon battery negative electrode structure, in particular to a hard carbon substrate battery negative electrode structure with surface modification and a preparation method thereof.

Lithium-ion batteries have the advantages of high working voltage, high energy density, and good safety, and can be widely used in power supply in many fields. The development of lithium-ion batteries depends to a large extent on the development and application of high-performance positive and negative materials. The current practical mesophase carbon microsphere material (MCMB) preparation cost is relatively high. In terms of natural and artificial graphite, in order to reduce the initial irreversible capacitance and increase the cycle life, it is necessary to use pitch-like aromatic compounds for surface modification. The preparation process requires carbonization at a high temperature above 1300°C. Among them, the raw material (asphalt-like aromatic hydrocarbons) The price volatility of chemical compounds, as well as the environmental pollution and energy consumption caused by high-temperature carbonization, are not the direction of long-term sustainable operation.

In addition, studies have shown that, for example, Chinese Patent Publication No. CN101162775A uses a mixture of resin and asphalt to coat graphite materials to achieve surface modification of the graphite substrate. However, when the aforementioned method is actually implemented, the carbonization rate of the resin is often insufficient, which affects the first charge and discharge efficiency.

Secondary batteries in the prior art, such as batteries used in electric vehicles, generally use artificial graphite as the main negative electrode material. The anode material must be relatively High capacity, use cycle efficiency requires more than 500-1000 cycles. Currently, artificial graphite accounts for about 45-55% of the entire anode material market. With the emergence of environmental awareness and various electric-power-driven devices (such as electric vehicles) in the market, the demand for secondary batteries has also increased significantly. More attention has been paid to the characteristics of negative electrode materials such as high capacity, long life, high rate and low temperature.

On the other hand, most of the existing electrode material surface modification processes use organic solvents to prepare the polymer solution to be coated. Although the effect of uniform dispersion can be obtained during the preparation process, not only in the preparation process, a lot of organic waste will be generated, but the organic solvents used also produce volatile organic compounds (VOC) in the solution, which is also easy to produce environmental protection. Problems, and even cause harm to the operator.

In view of this, the development of a battery negative structure with stable structure, long charge and discharge cycle life, and excellent safety performance and low temperature performance, and the development of a preparation method that can effectively reduce the damage to the operator and the environment is quite worthy of industry attention. Subject.

In view of the above-mentioned background of the invention, in order to meet the requirements of the industry, the present invention provides a hard carbon substrate battery negative electrode structure with surface modification and a preparation method thereof. The above-mentioned hard carbon substrate battery negative electrode structure with surface modification not only Simple process, low cost, stable structure, long charge-discharge cycle life, good safety performance and low temperature performance. Even better, the above-mentioned preparation method can be applied to the process of preparing water-based slurry, which can be environmentally friendly, cost-saving, and effective The effect of industrial competitiveness.

One purpose of the present invention is to provide a hard carbon substrate battery negative electrode structure with surface modification and a preparation method thereof. The surface of the hard carbon substrate is modified by using a plurality of layers of organic polymers to improve the surface coating of the organic polymer. The bonding and uniformity with the hard carbon substrate greatly reduces the irreversible capacitance of the battery using the hard carbon substrate with surface modification as an electrode.

Another object of the present invention is to provide a hard carbon substrate battery negative electrode structure with surface modification and a preparation method thereof, by using a spherical resin with a high carbonization rate and a low specific surface area to form a non-graphitization after thermal decomposition Carbon to form a hard carbon substrate that maintains a stable structure during charge and discharge and has a long charge and discharge cycle life. Better yet, the above thermal decomposition process does not require the use of a high-temperature graphitization process, thereby achieving both low production costs , The quality is stable, and the effect of environmental protection and energy saving.

Another object of the present invention is to provide a hard carbon substrate battery negative electrode structure with surface modification and a preparation method thereof. After the hard carbon substrate is surface modified by multiple layers of organic polymers, the use of the above-mentioned device can be effectively extended. The cycle life of batteries with modified hard carbon substrates as electrodes.

Another object of the present invention is to provide a hard carbon substrate battery negative electrode structure with surface modification and a preparation method thereof. After the hard carbon substrate is surface modified by multiple layers of organic polymers, the use of the above-mentioned device can be effectively improved. The low-temperature cycle performance and high-rate battery performance of batteries with modified hard carbon substrate as electrodes.

Another object of the present invention is to provide a hard carbon substrate battery negative electrode structure with surface modification and a preparation method thereof, by using a water-soluble organic polymer The aqueous slurry manufacturing process is used to prepare the above-mentioned hard carbon substrate battery negative structure with surface modification, thereby effectively reducing the damage of the operator and the environment by volatile organic compounds.

According to the above-mentioned objective, the present invention discloses a hard carbon substrate battery negative structure with surface modification and a preparation method thereof. The above-mentioned hard carbon substrate battery negative structure with surface modification includes a first modified film on the hard carbon substrate, and a second modified film on the first modified film. The above-mentioned first modified film includes a first organic polymer. The first organic polymer has a first electrical property, and the first organic polymer may be a water-soluble polymer. The above-mentioned second modified film includes a second organic polymer. The second organic polymer has a second electrical property, wherein the second electrical property is opposite to the first electrical property. The aforementioned second organic polymer may be a water-soluble polymer.

In a preferred example according to this specification, the first organic polymer of the above-mentioned hard carbon substrate battery negative electrode structure with surface modification may be one selected from the following group: polyquaternary amine salt (poly- Quaternary ammonium salt, anion-exchange resin or polymer.

In a preferred example according to the present specification, the second organic polymer of the above-mentioned hard carbon substrate battery negative electrode structure with surface modification may be selected from one of the following groups: having a sulfonic acid group ) Polymer, polymer with carboxylic acid group, cation-exchange resin or polymer.

In a preferred example according to this specification, the preparation method of the above-mentioned hard carbon substrate battery negative structure with surface modification includes preparing hard carbon substrate, mixing hard A carbon substrate and a first organic polymer solution, performing a first drying process to form a hard carbon substrate with a first modified film, mixing the hard carbon substrate with a first modified film and a second organic polymer solution, and A second drying process is performed to form a second modified film on the first modified film.

In a preferred example according to this specification, the first organic polymer solution and the second organic polymer solution in the method for preparing the negative electrode structure of the hard carbon substrate battery with surface modification may be aqueous solutions.

In a preferred example according to the present specification, the first organic polymer solution in the method for preparing the negative electrode structure of the hard carbon substrate battery with surface modification includes the first organic polymer. The first organic polymer has a first electrical property, and the first organic polymer may be a water-soluble polymer. The above-mentioned second polymer solution contains a second organic polymer. The second organic polymer has a second electrical property, and the second electrical property is opposite to the first electrical property. The aforementioned second organic polymer may be a water-soluble polymer.

In a preferred example according to this specification, the first organic polymer solution in the method for preparing the negative electrode structure of a hard carbon substrate battery with surface modification may further include a third organic polymer. The average molecular weight of the third organic polymer is about 2,000 to 200,000. According to this specification, the above-mentioned third organic polymer helps to improve the dispersibility of the conductive material in the subsequent process, thereby further improving the charge and discharge efficiency of the final battery product.

In a preferred example according to this specification, the second organic polymer solution in the method for preparing the negative electrode structure of the hard carbon substrate battery with surface modification can be It also contains the fourth organic polymer. The average molecular weight of the fourth organic polymer is about 2,000 to 200,000. According to this specification, the above-mentioned fourth organic polymer helps to improve the dispersibility of the conductive material in the subsequent manufacturing process, thereby further improving the charge and discharge efficiency of the final battery product.

120‧‧‧Hard carbon substrate

140‧‧‧First modification film

160‧‧‧Second Modification Film

210‧‧‧Steps to prepare hard carbon substrate

212‧‧‧Providing phenolic resin steps

214‧‧‧The steps of micronized phenolic resin

216‧‧‧Carbonized phenolic resin steps

220‧‧‧The step of mixing the hard carbon substrate and the first organic polymer solution

230‧‧‧The step of performing the first drying process to form the first modified film on the hard carbon substrate

240‧‧‧The step of mixing the hard carbon substrate with the first modified film and the second organic polymer solution

250‧‧‧The second drying process to form a second modified film on the hard carbon substrate

The first figure is a schematic diagram of the negative structure of the hard carbon substrate battery with surface modification according to this specification; the second figure is a schematic flow diagram of the preparation method of the negative structure of the hard carbon substrate battery with surface modification according to this specification ; The third figure is a scanning electron microscope (Scanning Electron Microscopy; SEM abbreviation hereinafter) photograph of a hard carbon substrate with surface modification according to an example of this manual; the fourth figure is an example according to this manual The SEM photo of the negative structure of the hard carbon substrate battery with surface modification in Figure 5. The fifth figure is the Coulomb efficiency figure of the hard carbon substrate with surface modification in the two examples of this specification; the sixth figure is based on this In one example of the specification, the low-temperature charge-discharge cycle test chart of a full battery with a surface-modified hard carbon substrate battery negative structure; and the seventh figure is based on the surface-modified hard carbon substrate in an example of this specification The full battery rate test curve of the negative structure of the material battery.

The direction discussed in the present invention is a hard carbon substrate battery negative electrode structure with surface modification and a preparation method thereof. In order to thoroughly understand the present invention, detailed process steps or composition structures will be proposed in the following description. Obviously, the implementation of the present invention is not limited to the specific details familiar to those skilled in the field. On the other hand, well-known compositions or process steps are not described in details to avoid unnecessary limitation of the present invention. The preferred system of the present invention will be described in detail as follows. However, in addition to these detailed descriptions, the present invention can also be widely implemented in other systems, and the scope of the present invention is not limited, and the subsequent patent scope shall prevail.

An embodiment of the present invention discloses a hard carbon substrate battery negative structure with surface modification. The first figure is a schematic diagram of the negative structure of the hard carbon substrate battery with surface modification according to this embodiment. As shown in the first figure, the above-mentioned hard carbon substrate battery negative structure with surface modification includes a hard carbon substrate 120, a first modified film 140, and a second modified film 160. The first modification film 140 is located on the hard carbon substrate 120, and the second modification film 160 is located on the first modification layer 140.

The above-mentioned hard carbon substrate 120 may be formed by high temperature carbonization of resin. In a preferred example according to this embodiment, the above-mentioned resin has the characteristics of high carbonization rate, low specific surface area, spherical monomer and the like. In a preferred example according to this embodiment, the above-mentioned resin may be a thermosetting phenolic resin. In a preferred example according to this embodiment, the particle size of the above phenolic resin is about D ₅₀ of 6-10 μm. In a preferred example according to this embodiment, the specific surface area of the phenolic resin is about 1.5-2.5 m ² /g. In a preferred example according to this embodiment, the above-mentioned hard carbon substrate 120 may be carbonized at about 1300°C of phenolic resin.

The composition of the first modified film 140 includes a first organic polymer. The first organic polymer has a first electrical property. In a preferred example according to this embodiment, the first organic polymer may be a water-soluble polymer. In a preferred example according to this embodiment, the above-mentioned first organic polymer may be a positively charged polymer. In a preferred example according to this embodiment, the first organic polymer may be poly-quaternary ammonium salt. In another preferred example according to this embodiment, the above-mentioned first organic polymer may be an anion-exchange resin or polymer. In a preferred example according to this embodiment, the first organic polymer may be selected from one or a combination of the following groups: Polydiallyldimethylammonium chloride (PA), Dodecyltrimethylammonium bromide, cholestyramine [oral cholesterol-lowering agent] (Cholestyramine or colestyramine; Questran, Questran Light, Cholybar), polypropylene trimethylammonium chloride [poly(acrylamido-N-propyl trimethyl ammonium chloride; PolyAPTAC], poly(3-methacryloylamino-propyl trimethylammonium chloride); PolyMAPTAC), polyhydroxide Poly(allylamine hydrochloride)], poly(dimethylaminoethylacrylate methylchloride quat); p-DMAEA*MCQ], poly(dimethylaminoethylacrylate methylchloride quat); p-DMAEA*MCQ], poly(dimethylaminoethylacrylate methylchloride quat); [poly(dimethylaminoethylmethacrylate methylchloride quat); p-DMAEM*MCQ]. In a preferred example according to this embodiment, the average molecular weight of the first organic polymer is about 10,000 to 500,000.

According to this embodiment, the composition of the second modified film 160 includes a second organic polymer. The second organic polymer has a second electrical property, wherein the second electrical property is opposite to the first electrical property of the first organic polymer. For example, when the first organic polymer is positively charged, the second organic polymer is negatively charged. In a preferred example according to this embodiment, ionic bonding may be formed between the first organic polymer and the second organic polymer. In a preferred example according to this embodiment, the above-mentioned second organic polymer may be a negatively charged polymer. In a preferred example according to this embodiment, the above-mentioned second organic polymer may be a polymer having a sulfonic acid group. In a preferred example according to this embodiment, the above-mentioned second organic polymer may be a polymer having a carbonic acid group. In a preferred example according to this embodiment, the above-mentioned second organic polymer may be a cation-exchange resin or polymer. In a preferred example according to this embodiment, the above-mentioned second organic polymer may be selected from one of the following groups or a combination thereof: poly(sodium 4-styrene sulfonate)] , Poly(2-acrylamido-2-methyl-1-propanesulfonic acid) [poly(2-acrylamido-2-methyl-1-propanesulfonic acid); polyAMPS], polyacrylic acid (PAA), sodium polyacrylate Salt [Poly(sodium acrylate)]. In a preferred example according to this embodiment, the average molecular weight of the second organic polymer is about 50,000-1,000,000.

According to this embodiment, since both the first organic polymer and the second organic polymer mentioned above can be water-soluble polymers, the negative structure of the hard carbon substrate battery with surface modification disclosed in this embodiment can be used The process of water-based slurry preparation can reduce process waste and environmental protection.

In a preferred example according to this embodiment, the above-mentioned first modified film 140 may further include a third organic polymer. The average molecular weight of the third organic polymer is about 2,000 to 200,000. According to this example, the above-mentioned third organic polymer helps to improve the dispersion of the conductive material in the subsequent manufacturing process, thereby further improving the charge and discharge efficiency of the final battery product. The amount of the third organic polymer added is about 0.2-5.0 wt.% (solid content) of the hard carbon substrate. In a preferred example according to this embodiment, the third organic polymer may be one or a combination selected from the following groups: polyvinyl alcohol (PVA), vinyl alcohol ethylene copolymer [Poly (vinyl alcohol-co-ethylene)].

In a preferred example according to this embodiment, the second modified film 160 may further include a fourth organic polymer. The average molecular weight of the fourth organic polymer is about 2,000 to 200,000. According to this example, the above-mentioned fourth organic polymer helps to improve the dispersibility of the conductive material in the subsequent manufacturing process, thereby further improving the charge and discharge efficiency of the final battery product. The amount of the fourth organic polymer added is about 0.2-5.0 wt.% (solid content) of the hard carbon substrate. In a preferred example according to the present embodiment, the fourth organic polymer may be one or a combination selected from the following groups: polyvinyl alcohol (PVA), vinyl alcohol ethylene copolymer [Poly (vinyl alcohol-co-ethylene)].

Another embodiment of the present invention discloses a method for preparing a hard carbon substrate battery negative electrode structure with surface modification. The second figure is a schematic flow chart of a method for preparing a negative electrode structure of a hard carbon substrate battery with surface modification according to this embodiment. Referring to the second figure, the preparation method of the above-mentioned hard carbon substrate battery negative structure with surface modification includes preparing a hard carbon substrate (such as step 210), mixing the hard carbon substrate and a first organic polymer solution (such as step 220) , Perform a first drying process to form a hard carbon substrate with a first modified film (such as step 230), mix the hard carbon substrate with a first modified film and a second organic polymer solution (such as step 240), and A second drying process is performed to form a second modified film on the first modified film (such as step 250).

According to this embodiment, the step 210 of preparing a hard carbon substrate includes the steps of providing phenolic resin (such as step 212), micronized phenolic resin (such as step 214), and carbonizing phenolic resin (such as step 216). In a preferred example according to this embodiment, the above-mentioned phenolic resin may be a thermosetting phenolic resin. In a preferred example according to this embodiment, the step 214 of micronizing the phenolic resin may be grinding, pulverizing, or other techniques known to those skilled in the art to produce a particle size of about Phenolic resin particles with a D _{50 of} about 6-10 μm. In a preferred example according to this embodiment, the step 216 of carbonizing the phenolic resin may be to use the condition of about 900-1300°C to carbonize the above-mentioned phenolic resin particles to produce a specific surface area of about 1.5-2.5m ² / g of hard carbon substrate.

In a preferred example according to this embodiment, the first organic polymer solution in step 220 may be an aqueous solution. The first organic polymer solution includes a first organic polymer having a first electrical property. The first organic polymer It can be a water-soluble polymer. In a preferred example according to this embodiment, the above-mentioned first organic polymer may be a positively charged water-soluble polymer. In a preferred example according to this embodiment, the first organic polymer may be poly-quaternary ammonium salt. In a preferred example according to this embodiment, the above-mentioned first organic polymer may be an anion-exchange resin or polymer. In a preferred example according to this embodiment, the first organic polymer may be selected from one or a combination of the following groups: Polydiallyldimethylammonium chloride (PA), Dodecyltrimethylammonium bromide, cholestyramine [oral cholesterol-lowering agent] (Cholestyramine or colestyramine; Questran, Questran Light, Cholybar), polypropylene trimethylammonium chloride [poly(acrylamido-N-propyl trimethyl ammonium chloride; PolyAPTAC], poly(3-methacryloylamino-propyl trimethylammonium chloride); PolyMAPTAC), polyhydroxide Poly(allylamine hydrochloride)], poly(dimethylaminoethylacrylate methylchloride quat); p-DMAEA*MCQ], poly(dimethylaminoethylacrylate methylchloride quat); p-DMAEA*MCQ], poly(dimethylaminoethylacrylate methylchloride quat); [poly(dimethylaminoethylmethacrylate methylchloride quat); p-DMAEM*MCQ]. In a preferred example according to this embodiment, the average molecular weight of the first organic polymer is about 10,000-500,000. In this embodiment, In a preferred example, the content of the first organic polymer is about 0.2-5.0 wt.% (solid content) of the hard carbon substrate. In a preferred example according to the present embodiment, the content of the first organic polymer is about 1.2 wt.% (solid content) of the hard carbon substrate.

In a preferred example according to this embodiment, the first organic polymer solution may further include a third organic polymer. The average molecular weight of the third organic polymer is about 2,000 to 200,000. According to this example, the aforementioned third organic polymer helps to improve the dispersibility of the conductive material in the subsequent manufacturing process, thereby further improving the charge and discharge efficiency of the final product-the battery. The content of the third organic polymer is about 0.2-5.0 wt.% (solid content) of the carbon substrate. In a preferred example according to this embodiment, the third organic polymer may be one or a combination selected from the following groups: polyvinyl alcohol (PVA), vinyl alcohol ethylene copolymer [Poly (vinyl alcohol-co-ethylene)].

The first drying procedure in step 230 may be a drying procedure well known to those skilled in the art, such as a spray drying procedure, or vacuum stirring and drying. In a preferred example according to this embodiment, the temperature control of the first drying process is about 80-150°C. In another preferred example according to this embodiment, the above-mentioned first drying process may be a spray drying process with a temperature of about 130-150°C.

According to this embodiment, the second organic polymer solution in step 240 may be an aqueous solution. The second organic polymer solution includes a second organic polymer having a second electrical property. Wherein, the aforementioned second electrical property is opposite to the first electrical property. According to this embodiment, ionic bonding can be formed between the first organic polymer and the second organic polymer. According to one of the embodiments In an example, the above-mentioned second organic polymer may be a water-soluble polymer. In a preferred example according to this embodiment, the second organic polymer may be a negatively charged water-soluble polymer. In a preferred example according to this embodiment, the above-mentioned second organic polymer may be a polymer having a sulfonic acid group. In another preferred example according to this embodiment, the above-mentioned second organic polymer may be a polymer having a carboxylic acid group. In a preferred example according to this embodiment, the above-mentioned second organic polymer may be a cation-exchange resin or polymer. In a preferred example according to this embodiment, the above-mentioned second organic polymer may be selected from one of the following groups or a combination thereof: poly(sodium 4-styrene sulfonate)] , Poly(2-acrylamido-2-methyl-1-propanesulfonic acid) [poly(2-acrylamido-2-methyl-1-propanesulfonic acid); polyAMPS], polyacrylic acid (PAA), sodium polyacrylate Salt [Poly(sodium acrylate)]. In a preferred example according to this embodiment, the average molecular weight of the second organic polymer is about 50,000-1,000,000. In a preferred example according to this embodiment, the content of the second organic polymer is about 0.2-5.0 wt.% (solid content) of the hard carbon substrate. In a preferred example according to the present embodiment, the content of the second organic polymer is about 1.2 wt.% (solid content) of the hard carbon substrate.

In a preferred example according to this embodiment, the second organic polymer solution may further include a fourth organic polymer. The average molecular weight/chain length of the fourth organic polymer is about 2,000 to 200,000. According to this example, the above-mentioned fourth organic polymer helps to improve the dispersibility of the conductive material in the subsequent process, so that One step is to improve the charging and discharging efficiency of the final product-the battery. The content of the fourth organic polymer is about 0.2-5.0 wt.% (solid content) of the carbon substrate. In a preferred example according to the present embodiment, the fourth organic polymer may be one or a combination selected from the following groups: polyvinyl alcohol (PVA), vinyl alcohol ethylene copolymer [Poly (vinyl alcohol-co-ethylene)].

According to this embodiment, the second drying procedure in the above step 250 may be a drying procedure well known to those skilled in the art, such as a spray drying procedure, or vacuum stirring and drying. The temperature control of the above-mentioned second drying process is about 80-150°C. In a preferred example according to this embodiment, the above-mentioned first drying procedure may be a spray drying procedure with a temperature setting of about 130-150°C.

According to this embodiment, since the above-mentioned preparation method of the hard carbon substrate battery negative structure with surface modification can complete the whole process in an aqueous solution, the preparation method according to this embodiment can not only eliminate the use of organic The waste problem generated by the phase solution process can prevent the volatile organic compounds (VOC) from toxic to the operator and the environment, thereby achieving a more environmentally friendly effect.

On the other hand, since the electrical properties of the first organic polymer and the second organic polymer are opposite, in the preparation process according to this embodiment, the electrical properties between the first organic polymer and the second organic polymer may be The electrostatic effect of sexual attraction produces a self-assembly effect. More preferably, a stable ionic bonding can be formed between the first organic polymer and the second organic polymer. In this way, although both the first organic polymer and the second organic polymer are water-soluble, even if the Continue to use an aqueous solution, and it is not easy to dissolve the first organic polymer or the second organic polymer again under the room temperature process.

In a preferred example according to the present embodiment, since the hard carbon substrate is partially negatively charged on the surface in the aqueous solution, if the first organic polymer is a positively charged organic polymer, Through electrostatic action, the first organic polymer can easily penetrate from the surface of the hard carbon substrate into the inner nano- or micro-level defects or holes, resulting in the first modified film formed by the first organic polymer to be hard The carbon substrate forms a strong coating uniformity. Even better, the above-mentioned first modified film can change the electrical properties of the hard carbon substrate surface, which is beneficial to attract the second organic polymer to form a self-assembled second modified film, and can help to improve the second modified film The coating uniformity and the bonding between the first modified film and the second modified film. More preferably, after the second drying process, the surface of the second modified film can not only be electrically charged, but also provide relatively hydrophilic properties, which will help to modify the surface of the second modified film in the subsequent manufacturing process. The high-quality hard carbon substrate battery negative structure is further applied to the process of aqueous slurry.

In a preferred example according to this embodiment, we found that the molecular weight of the first organic polymer and the second organic polymer are as close as possible.

In a preferred example according to this embodiment, we have found that the use of different ratios between the above-mentioned first organic polymer and the second organic polymer will affect the irreversible initial reduction of the final product (such as lithium ion battery) The efficiency of capacitance, and its effective reversible capacitance.

In a preferred example according to this embodiment, we find that the above The different electrical order of the first organic polymer and the second organic polymer will affect the degree of dispersion in the slurry preparation process of the preparation method of the above-mentioned hard carbon substrate battery negative structure with surface modification.

Hereinafter, a preferred example of the structure of the hard carbon substrate battery negative electrode with surface modification and its preparation method according to this specification will be described. However, the scope of this specification should be subject to the scope of subsequent patent applications and should not be limited to the following examples.

Use instrument:

Scanning electron microscope (FESEM, Jeol JSM-6500F): Used to observe the surface morphology and particle size of hard carbon substrates and hard carbon substrates with surface modification.

Specific surface area analyzer (BET, GAPP F-Sorb X2400): used to determine the specific surface area (BET) of graphite.

Laser particle size analyzer (Bettersize BT-9300S): used to measure graphite particle size and distribution.

Charge and discharge tester (Arbin BT-2000): used for electrochemical performance measurement.

Example 1: Preparation of hard carbon substrate

First, use thermosetting phenolic resin as raw material. First, the phenol resin is ground and pulverized to phenol resin particles with a particle size D _{50 of} about 8 μm. The phenolic resin particles are then heat-treated in a carbonization furnace. During the heat treatment, nitrogen (N ₂ ) is introduced as a protective atmosphere, and the temperature is raised to the required heat treatment temperature of 900-1300°C, the heating rate is 2°C/min, and the temperature holding time is 5 hours to obtain a hard carbon substrate.

In this example, referring to Table 1, we were subjected to heat treatment thermosetting phenol resin fine particles at different carbonization temperature down.

The third image is the SEM image of the hard carbon substrate after heat treatment and carbonization of the sample A-4 in Table 1 above. It can be seen from the third figure that the surface of the hard carbon substrate in the above sample A-4 has many pores and crevices, and its specific surface area (BET) is about 10 m ² g ^-1 after being measured by the instrument.

Example 2: Surface modification of hard carbon substrate

First, the positively charged first organic polymer poly(diallyldimethylammonium chloride; PA) [Poly(diallyldimethylammonium chloride; PA), with a molecular weight range of about 100,000] is uniformly dispersed in water to prepare the first polymer aqueous solution. To the obtained first polymer aqueous solution, add 100wt.% of hard carbon substrate, uniformly disperse it at an appropriate speed (600rpm) for 60 minutes, and then heat and dry (about 130-150℃) to form a first modified Hard carbon substrate of the film. Then, the second negatively charged organic polymer polystyrene sulfonate sodium salt [Poly(sodium 4-styrenesulfonate); PS; molecular weight range of about 70,000] is uniformly dispersed in water to prepare a second polymer aqueous solution. Add the above-mentioned hard carbon substrate with the first modified film to the obtained second polymer aqueous solution, at an appropriate rotation speed (300 rpm) uniformly dispersed for 30 minutes, and then heated and dried (about 130-150°C) to form a second modified film on the first modified film. After sieving, a hard carbon substrate battery negative structure with surface modification can be obtained.

In this example, the See Table 2, we used different ratios of PS and PA to the surface modification of hard carbon substrate A-4 in Table 1 in a sample, the specific surface area and analyzed the results for each sample .

The fourth image is an SEM image of the negative structure of the hard carbon substrate battery with surface modification according to the sample B-2 of this example. It can be seen from the fourth figure that after the surface modification of 1.2wt.% of the first polymer PA and 1.2wt.% of the second polymer PS, the surface gap of the hard carbon substrate of the sample B-2 The holes can be filled in to make the surface of the hard carbon substrate of sample B-2 smoother. According to instrument measurement, the specific surface area of the negative electrode structure of the hard carbon substrate battery with surface modification of the sample B-2 is about 2.8 m ² g ^-1 . In other words, the surface modification according to this example can reliably and effectively reduce the specific surface area of the hard carbon substrate.

Example 3: Coulombic efficiency test

Table 3 shows the results of charge and discharge tests using the samples in Table 1 . From the charge and discharge test in Table 3 , it can be found that the samples A-1, A-2, A-3, A-4 after heat treatment at different carbonization temperatures of 900, 1000, 1200, 1300℃, etc. The charging capacity is 400, 390, 360, 370 mAhg ^-1 ; the first discharge capacity is 237, 240, 247 280 mAhg ^-1 . It can be found from Table 3 that after 1300℃ carbonization, the first irreversible capacitance is significantly reduced, and the coulombic efficiency can reach 75.7%. After carbonization at 900℃, the discharge capacity is 237mAhg ^-1 and the coulombic efficiency is 59.2%. Therefore, after 1300℃ carbonization treatment can reduce more specific surface area and improve its coulombic efficiency.

Table 4 is the result of charging and discharging test on the hard carbon substrate with surface modification in Table 2 . In Table 4 , the charge and discharge results of sample A-4 without surface modification were also included as a control group. See Table 4, A-4, B- 1, B-2, B-3, B-4 of the primary charging capacities of ^{370,359,350,344mAhg -1; A-4, B} -1, The first discharge capacities of B-2, B-3, and B-4 are respectively 281, 335, 331, 325, and 320 mAhg ^-1 . It can be found from Table 4 that when the hard carbon substrate is coated with 1.2wt.% PA and 1.2wt.% PS (Sample B-2), the first irreversibility can be reduced to 7.8%, and the coulombic efficiency can be increased to 92.2%. As lithium ions react with the electrolyte during charging and discharging, a thin-film SEI (Solid electrolyte interface) film is formed on the surface of the hard carbon electrode, which increases the irreversible capacity of the lithium battery.

The hard carbon substrates of samples B-1 to B-4 were all added with PA and PS in sequence. Among them, PA can not only fill in the micropores of amorphous carbon caused by carbonization heat treatment on the surface of the original hard carbon substrate, but also slow down the formation of SEI film. Furthermore, PS is a material with low resistance value and elasticity. In addition to improving the conductive properties of the hard carbon substrate and the polymer resin coating, it can also allow lithium ions to enter and exit freely and efficiently. In contrast, too much coating amount (for example, samples B-3, B-4) may also cause a decrease in capacitance.

Generally, the requirements of commercial hard carbon specifications, the first discharge capacity is 330mAhg ^-1 or more, and the first irreversibility is less than 8%. Therefore, taking the hard carbon substrate of sample B-2 as an example, its capacitance and irreversibility meet the specifications.

The fifth figure is the hard carbon substrate of sample A-4 and sample B-2 performed 20 times Coulomb efficiency graph of the cycle. It can be seen from the fifth figure that the coulombic efficiency of the hard carbon substrate of sample A-4 at the first cycle is 75.7%, which is smaller than the coulombic efficiency of the hard carbon substrate of sample B-2 at the first cycle of 92.2 %. Furthermore, from the fifth figure, it can be found that after 20 cycles, the capacity retentions of the hard carbon substrate of the sample B-2 are greater than that of the hard carbon substrate of the sample A-4. The capacity retention rate of the substrate.

It can be inferred that, because the hard carbon substrate of sample B-2 is double-coated with organic polymer materials, the coulombic efficiency of the hard carbon substrate of sample B-2 is better than that of sample A-4. The effect of the coulombic efficiency of the hard carbon substrate. The reason may be that for the hard carbon substrate of sample B-2, after the first modification film PA is coated, it can fill in the surface gaps of the hard carbon substrate itself to reduce its specific surface area. , It can also slow down the occurrence of SEI film. On the other hand, the PS in the second modified film is a special low-resistance resin, which makes the in and out of lithium ions smoother. Therefore, the hard carbon substrate of sample B-2 can cause such high cycle stability and capacity retention. It can also be found from the fifth figure that the coulombic efficiency of the hard carbon substrate of sample B-2 can reach about 99-100% for 20 times.

Example 4: Low temperature charge and discharge test

The sixth figure is the cycle test diagram of the hard carbon substrate of sample B-2 under low-temperature charge and discharge of the whole battery. It can be found from the sixth figure that in the low-temperature charge-discharge test of a 15Ah full battery, the hard carbon substrate of sample B-2 was charged to 3.65V at 1C and discharged to 2.3 at -20℃ in the low-temperature charge-discharge cycle test. Under the condition of V, after 150 cycles, the discharge capacity is still 60%. In the requirements of general commercial specifications, after 50 cycles, the discharge capacity must be greater than 60%. Therefore, according to this standard, the sample The hard carbon substrate of B-2 has met the low temperature test specifications.

Example 5: Discharge rate test

Table 5 is the full battery rate test data of the hard carbon substrate of sample B-2. The seventh figure is the full battery rate test curve of the hard carbon substrate of sample B-2. It can be seen from Table 5 and the seventh figure that in the rate test of the 15Ah full battery, the hard carbon substrate of sample B-2 was charged to 3.65V at 1C in the 10C discharge rate test, and the CC was converted to CV cut-off 0.3A [that is, first charge with constant current (CC, Constant Current) 1C to 3.65V, then charge with constant voltage (CV, Constant Voltage) to 0.3A and then stop charging], then use 0.2C, 0.5C, 1C, 2C , 3C, 5C, 10C discharge to 2.1V conditions, after 10C discharge capacity retention rate is 94%. In the specifications required by general commercial specifications, the 10C discharge capacity retention rate must be greater than 90%. Therefore, according to this standard, the hard carbon substrate of sample B-2 already meets the magnification test specifications.

From the above examples and discussions, it can be found that the negative structure of the hard carbon substrate battery with surface modification according to this specification can effectively increase the charging and discharging power, and can effectively reduce the first irreversible capacity of lithium ion. Even better, the above table The preparation method of the modified hard carbon substrate battery negative structure is particularly suitable for the preparation process of aqueous slurry. In this way, it can effectively avoid the harm to the operator and the environment caused by the volatile organic compounds (VOCs) produced by the use of organic solvents to prepare the slurry in the conventional technology, and thus achieve a more environmentally friendly The effect of protecting the operator. According to the negative structure of the hard carbon substrate battery with surface modification in this specification, the dispersibility of conductive materials can be effectively improved, and the material stability of the carbon substrate during charging and discharging can be improved, thereby facilitating the use of the above surface modification The hard carbon substrate is used as the fast charge and discharge efficiency of the battery with the negative structure. Even better, the preparation method of the hard carbon substrate battery negative electrode structure with surface modification according to this specification can provide more effective coating to the hard carbon substrate, thus reducing the volume change of the hard carbon substrate during charge and discharge. The resulting structural damage and peeling phenomenon can further extend the cycle life of the battery.

In summary, this specification discloses a hard carbon substrate battery negative structure with surface modification and a preparation method thereof. The above-mentioned hard carbon substrate battery negative structure with surface modification can be modified by multiple layers of modified films on the hard carbon substrate by self-assembled molecular design, and the above modified film can provide more effective hard carbon substrates. Covering. According to this specification, the above-mentioned hard carbon substrate battery negative structure with surface modification includes a hard carbon substrate, a first modified film on the hard carbon substrate, and a second modified film on the first modified film. The first modified film and the second modified film respectively comprise a water-soluble first organic polymer and a water-soluble second organic polymer with different electrical properties. In the process of alternate coating, because the first modified film and the second modified film use the first organic polymer and the second organic polymer with different electrical properties, the electrostatic Electricity can produce the effect of self-assembly. Even better, an ionic bond can be formed between the first organic polymer and the second organic polymer with opposite electrical properties, so that the aforementioned first modified film and the second modified film can be more closely combined. This reaction is different from the cross-linking phenomenon of dehydration by intermolecular hydrogen bonding in the drying process of other types of polymers. According to the needs of the product, the preparation method according to this specification can be continued on the second modified film to form at least one modified film. More preferably, the first modified film and the second modified film may further include a third organic polymer and a fourth organic polymer, respectively. The third organic polymer and the fourth organic polymer can further enhance the internal structural stability of the negative structure of the hard carbon substrate battery with surface modification through the tangle of physical cross-linking. According to the present specification, the preparation method of the hard carbon substrate battery negative structure with surface modification can be completed in the production process of the aqueous slurry. According to this specification, it can not only effectively increase the adhesion and uniformity between the polymer coating and the hard carbon substrate, overcome the lack of the conventional single-layer polymer coating, but also effectively improve the protection of the operator and the environment.

Compared with the prior art, the hard carbon substrate battery negative electrode structure with surface modification and its preparation method proposed in this specification have the following improvements. First, the preparation method of the hard carbon substrate battery negative electrode structure with surface modification disclosed in this specification is particularly suitable for the process of preparing aqueous slurry, especially in the negative electrode material coating stage. Second, the hard carbon substrate battery negative structure with surface modification according to this specification can effectively increase the charge-discharge rate of the final product. Third, according to this specification, the hard carbon substrate battery negative structure with surface modification can effectively reduce the first irreversible capacity of lithium ion. Fourth, the hard carbon substrate negative electrode with surface modification according to this manual The structure can effectively improve the dispersion of conductive materials, improve the material stability of the hard carbon substrate during charging and discharging, and facilitate the efficiency of rapid charging and discharging. Fifth, the preparation method of the hard carbon substrate battery negative structure with surface modification disclosed in this specification can provide more effective coating to the hard carbon substrate, so it can reduce the hard carbon substrate battery negative structure during charge and discharge. Because of the structural damage and peeling caused by the volume change of the hard carbon substrate, the cycle life of the battery is further extended. Sixth, the negative structure of the hard carbon substrate battery with surface modification disclosed in this specification can effectively improve the low-temperature cycle performance and meet the high-rate charge-discharge performance.

Obviously, according to the description in the above system, the present invention may have many modifications and differences. Therefore, it needs to be understood within the scope of the appended claims. In addition to the above detailed description, the present invention can also be widely implemented in other systems. The above is only the preferred system of the present invention, and is not intended to limit the scope of the patent application of the present invention; all other equivalent changes or modifications completed without departing from the spirit of the present invention should be included in the following patent application scope Inside.

120‧‧‧Hard carbon substrate

140‧‧‧First modification film

160‧‧‧Second Modification Film

Claims (10)

A hard carbon substrate battery negative structure with surface modification, comprising: a hard carbon substrate, the hard carbon substrate is carbonized by phenolic resin; a first modified film, the first modified film is located on the On a hard carbon substrate, wherein the first modified film comprises a first organic polymer, the first organic polymer is an organic polymer with a first electrical property; and a second modified film, the second modified film Is located on the first modified film, wherein the second modified film includes a second organic polymer, wherein the second organic polymer is an organic polymer with a second electrical property, wherein the second electrical property is the same as the first The first electrical property of an organic polymer is opposite, wherein an ionic bond is formed between the second polymer in the second modified film and the first polymer in the first modified film. According to the first hard carbon battery negative electrode structure in the scope of the patent application, the particle size D ₅₀ of the phenolic resin is 6-10 μm. According to the first hard carbon battery negative electrode structure in the scope of patent application, the carbonization of the phenol resin is about 1300°C. According to item 1 of the scope of patent application, the negative electrode structure of hard carbon battery, wherein the first organic polymer is a positively charged organic polymer, and the first organic polymer is selected from one of the following groups: Poly Si Poly-Quaternary ammonium salt, anion-exchange resin or polymer, wherein the second organic polymer is a negatively charged organic polymer, and the second organic polymer is It is selected from one of the following groups: polymers with sulfonic acid group, polymers with carbonic acid group, cation-exchange resin or polymer. According to the first item of the scope of patent application, the hard carbon substrate battery negative structure with surface modification, wherein the first organic polymer is polydiallyldimethylammonium chloride (PA), wherein the second Organic polymer series poly(sodium 4-styrene sulfonate); PS]. A method for preparing a hard carbon substrate battery negative electrode structure with surface modification, comprising: preparing a hard carbon substrate, wherein the raw material of the hard carbon substrate is a phenolic resin; mixing the hard carbon substrate with a first organic high A molecular aqueous solution, wherein the first organic polymer aqueous solution contains a first organic polymer having a first electrical property; performing a first drying process to form a hard carbon substrate with a first modified film; mixing the first modified film The hard carbon substrate of the film and a second organic polymer aqueous solution, wherein the second organic polymer aqueous solution contains a first organic polymer with a second electrical property, wherein the second electrical property is the same as the first organic polymer The first electrical property is opposite, wherein an ionic bond is formed between the second polymer and the first polymer in the first modified film; and a second drying process is performed to form a second modified film on the first modified film on. According to the sixth item of the scope of patent application, the method for preparing a hard carbon substrate battery negative electrode structure with surface modification, wherein the step of preparing the hard carbon substrate includes: providing a phenolic resin, a micronized phenolic resin, and a carbonized phenolic resin. According to the method for preparing a negative electrode structure of a hard carbon substrate battery with surface modification according to item 7 of the scope of patent application, the step of the micronized phenolic resin is to grind and pulverize the phenolic resin to a particle size D ₅₀ of 6-10 μm. According to the seventh item of the scope of patent application, the method for preparing a hard carbon substrate battery negative electrode structure with surface modification, wherein the temperature of the step of carbonizing phenolic resin is about 1300°C. According to the sixth item of the scope of patent application, the method for preparing the negative electrode structure of the hard carbon substrate battery with surface modification, wherein the first organic polymer is polydiallyldimethylammonium chloride (PA), wherein The second organic polymer is poly(sodium 4-styrene sulfonate); PS].

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