CN1812168A - Modified method for lithium ion cell negative electrode material - Google Patents

Abstract

The invention relates to a method for modifying negative electrode materials of lithium ion batteries. The modified negative electrode materials are added with a catalyst and mixed uniformly. The catalyst accounts for 0.1%-10% by weight of the modified negative electrode materials, and the treated materials are put into a reaction furnace. Inside, hydrocarbons are used as carbon sources, mixed with buffer gas in proportion, the volume ratio of hydrocarbons to buffer gas is 1: (0-10), and the temperature is 600-1300 ℃ into the reaction furnace, after 1- After 900 minutes of reaction, a modified composite negative electrode material with in-situ growth of carbon nanofibers/carbon tubes on the surface was obtained. The present invention grows nano-carbon fiber/carbon tube in situ on the surface of the existing negative electrode material through chemical reaction, and completes the modification of the negative electrode material, so that it has good battery kinetic performance, cycle performance, charge and discharge capacity and Compatibility with the electrolyte, thereby improving the performance of lithium-ion batteries using this material as the negative electrode material.

Description

A kind of modification method of negative electrode material of lithium ion battery

technical field

The invention relates to a negative electrode material technology of a rechargeable secondary lithium ion battery, in particular to a modification method of the negative electrode material of the lithium ion battery, which can significantly improve the cycle performance, capacity and other performances of the rechargeable secondary lithium ion battery.

Background technique

Rechargeable secondary lithium-ion batteries have become a hot spot in the battery industry in recent years because of their advantages such as high voltage, long discharge time, high energy density, light weight, no memory effect and no pollution. The application fields of lithium-ion batteries are rapidly expanding: they are widely used in portable electronic products (such as supporting power supplies for mobile phones, notebook computers, digital cameras, etc.); electric vehicle industry; military equipment field; aerospace field, etc. Especially in recent years, with the application of electric vehicle power batteries, it is necessary to further improve the performance of lithium-ion batteries. The improvement of the performance of lithium-ion batteries depends to a large extent on the improvement of the performance of the electrode materials. High energy density: high-capacity lithium storage materials require electrode materials with high power density, long service life, high cost performance and high safety. These Requirements are still very challenging.

At present, the anode materials of lithium-ion batteries widely studied mainly include various traditional carbon materials, transition metal oxides, fluorides, tin-based and silicon-based oxides, nitrides, lithium alloys, etc. In terms of capacity and cycle performance, these materials often cannot have both at the same time. However, currently widely used commercial lithium-ion battery negative electrode materials mainly use mesophase carbon microspheres, modified graphite and other carbonaceous materials, all of which have low charge and discharge rates and cannot meet the requirements of high-current power batteries. Capacity is also flawed.

Contents of the invention

The object of the present invention is to provide a method for improving the performance of the lithium ion battery negative electrode material. The negative electrode material processed by the invention is used as a rechargeable secondary lithium ion battery, and has high battery kinetic performance, high battery cycle performance, high charge and discharge capacity and good compatibility with electrolyte.

Technical scheme of the present invention is:

The negative electrode material to be modified is uniformly mixed by appropriate chemical treatment (removal of impurities) and adding a catalyst (the catalyst accounts for 0.1%-10% by weight of the modified negative electrode material), and the processed material is put into the reaction furnace. The hydrogen compound is used as the carbon source, and it is mixed with the buffer gas in a certain proportion. The volume ratio of the hydrocarbon to the buffer gas is 1: (0-10), and the buffer gas may not be added, and the reaction temperature is (600-1300°C) In the furnace, after 1-900 minutes of reaction, a modified composite negative electrode material with nano carbon fiber/magnetic tube grown in situ on the surface is obtained.

In a modification method for improving the performance of lithium-ion battery negative electrode materials provided by the present invention, the modified negative electrode materials can be natural graphite, modified graphite, mesocarbon microspheres (MCMB), amorphous carbon, hard carbon, thermal Decomposition of charcoal, petroleum coke and other carbonaceous materials, transition metal oxides (TiO, TiO ₂ , VO ₂ , V 2 O ₃ , _{Cr 2 O 3} , MoO ₃ , RuO ₂ , FeO, NiO, CoO, Co ₃ O ₄ , Cu ₂ O, etc.) and fluorides (TiF ₃ , VF ₃ , MnF ₂ , FeF ₂ , CoF ₂ , NiF ₂ , CuF ₂ , CaF ₂ , BaF _{2 ,} etc.), tin-based and silicon-based oxides (SnO, SnO ₂ , SiO, _SiO2, etc.) one or more of materials.

The catalyst in the present invention can be: one or more of Fe, Co, Ni, Mo, V metal powders and their oxides, nitrates, halides, sulfates, etc.;

Hydrocarbons as carbon sources can be one or more of methane, ethane, propane, ethylene, acetylene, benzene, toluene, xylene, cyclohexane, carbon monoxide, water gas, etc.;

The buffer gas can be one or more of hydrogen, argon, nitrogen, etc.;

In the method for modifying the lithium ion battery negative electrode material provided by the present invention, the modified composite negative electrode material after in-situ growth of carbon nanofibers/carbon tubes can also be subjected to high-temperature graphitization, slight oxidation, chemical treatment, etc. to obtain more good performance.

The beneficial effects of the present invention are as follows:

1. The present invention proposes a method for in-situ growth of nano-carbon fibers/carbon tubes on the surface of existing negative electrode materials, through chemical reactions, in-situ growth of nano-carbon fibers/carbon tubes on the surface of existing negative electrode materials, and completes the development of negative electrode materials. Modification makes it have good battery dynamic performance, cycle performance, charge and discharge capacity and compatibility with electrolyte, thereby improving the performance of lithium ion batteries using this material as the negative electrode material.

2. The carbon nanofiber/carbon tube grown in situ on the surface of the present invention, due to its large aspect ratio and high specific strength, can suppress the volume expansion and pulverization effect caused by lithium ions intercalating and extracting from the basic negative electrode material, thereby improving negative cycle performance.

3. The nano-carbon fiber/carbon tube grown in situ on the surface of the present invention has good electrical conductivity and large aspect ratio, which is conducive to the formation of a three-dimensional conductive network in the negative electrode body, and can greatly improve the electrical conductivity of the electrode, especially for transition metal oxides. more obvious. The improvement of conductivity can reduce the electrochemical polarization and internal resistance partial pressure of the battery, which is beneficial to the high-power charging and discharging of the battery.

4. The in-situ growth of nano-carbon fibers/carbon tubes on the surface of the present invention greatly reduces the degree of direct contact between the basic negative electrode material and the electrolyte, which can improve the compatibility between the electrode and the electrolyte and expand the selection range of the electrolyte.

5. The current research shows that the solid-phase diffusion of lithium ions in the electrode is the control step of intercalation and extraction. Since nano-carbon fibers/carbon tubes have a nanometer scale, the journey of lithium ion intercalation and extraction is much shorter than that of traditional electrode materials. Lithium The diffusion of ions becomes easy, which can make the battery adapt to the requirements of high rate charge and discharge.

6. The in-situ growth of nano-carbon fibers/carbon tubes on the surface of the present invention can well solve the problem of difficulty in uniform dispersion caused by directly adding nano-carbon fibers/carbon tubes, and due to in-situ growth, the basic negative electrode material and nano-carbon fibers The combination between is much better than direct addition.

In summary, the method for improving the performance of lithium-ion battery negative electrode materials in the present invention is to develop new composite negative electrode materials through the in-situ growth of nano-carbon fibers/carbon tubes on the surface, thereby improving the kinetic performance, cycle performance, charging and discharging performance of lithium-ion batteries. capacity and compatibility with the electrolyte.

A large number of experiments have proved that the cycle life, charge-discharge rate, capacity, and compatibility with the electrolyte of the lithium-ion battery negative electrode modified by the in-situ growth of nano-carbon fibers on the surface have been improved, thereby effectively improving the lithium-ion battery. performance of ion batteries.

Description of drawings

Figures 1a-b are scanning electron micrographs of natural graphite balls and graphite balls modified by the present invention; wherein, Figure 1a is a natural graphite ball; Figure 1b is a scanning electron microscope photo of graphite balls modified by the method of the present invention.

Fig. 2 compares the cycle performance of the original sample (Comparative Example 1) and the sample modified by the method of the present invention (Example 1).

Detailed ways

The present invention is described below in conjunction with embodiment:

Example 1

Select natural graphite spheres with an average diameter of 20 μm (mass 2 g) (Fig. 1a), add Fe powder as a catalyst (mass 0.046 g), mix evenly, use C ₂ H ₄ as carbon source and mix Ar in a volume ratio of 1:1. Into a reaction furnace at a temperature of 1000 ° C, after 100 minutes of reaction, a modified composite anode material with in-situ growth of nano-carbon fibers/carbon tubes on the surface was obtained (Figure 1b). It is used as the negative electrode material of lithium ion battery. The detection results of the conventional lithium-ion battery negative electrode evaluation method show that under the same number of cycles, the capacity and cycle performance have been greatly improved (Figure 2).

Comparative example 1

Untreated natural graphite balls with an average diameter of 20 μm are used as negative electrode materials for lithium-ion batteries. The detection results of the conventional lithium-ion battery negative electrode evaluation method show that under the same number of cycles, the remote capacity and cycle performance are worse than those of Example 1 of the present invention (see Figure 2).

Example 2

Select natural graphite spheres (mass 2g) with an average diameter of 20 μm, add Fe(NO ₃ ) ₃ as a catalyst (mass 0.198g), add natural graphite spheres to Fe(NO ₃ ) ₃ solution and mix evenly, dry, and use CH ₄ Mix the carbon source and _N2 in a volume ratio of 2:1, pass it into a reaction furnace at a temperature of 700 ° C, and after 60 minutes of reaction, an improved carbon nanofiber/carbon tube grown on the surface in situ is obtained. composite anode materials. It is used as the negative electrode material of lithium ion battery. The detection results of the conventional lithium-ion battery negative electrode evaluation method show that the capacity and cycle performance have been greatly improved under the same number of cycles.

Example 3

Select natural graphite balls with an average diameter of 20 μm (mass 2g), add Fe(NO ₃ ) ₃ as a catalyst (mass 0.084g), add natural graphite balls to Fe(NO ₃ ) ₃ solution and mix evenly, dry, and use CH ₄ Mix the carbon source and _N2 in a ratio of 9:1 by volume, and pass it into a reaction furnace at a temperature of 700 ° C. After 240 minutes of reaction, an improved carbon nanofiber/carbon tube grown on the surface in situ is obtained. composite anode materials. It is used as the negative electrode material of lithium ion battery. The detection results of the conventional lithium-ion battery negative electrode evaluation method show that the capacity and cycle performance have been greatly improved under the same number of cycles.

Example 4

Choose MCMB with an average diameter of 20 μm (mass 2g), add Fe(NO ₃ ) ₃ as a catalyst (mass 0.102g), you can add MCMB to the Fe(NO ₃ ) ₃ solution and mix evenly, dry, and use CH ₄ as a carbon source Mix it with _N2 in a volume ratio of 5:1, pass it into a reaction furnace at a temperature of 800 ° C, and after 600 minutes of reaction, a modified composite negative electrode material with in-situ growth of nano-carbon fibers/carbon tubes on the surface is obtained . It is used as the negative electrode material of lithium ion battery. The detection results of the conventional lithium-ion battery negative electrode evaluation method show that the capacity and cycle performance have been greatly improved under the same number of cycles.

Example 5

Select hard carbon spheres (mass 1g) with an average diameter of 10 μm, add FeCl ₂ as a catalyst (mass 0.052 g), and add the hard carbon spheres into the FeCl ₂ solution to mix evenly, dry, and use C ₂ H ₆ as a carbon source and _H2 was mixed according to the volume ratio of 2:1, and passed into a reaction furnace at a temperature of 1100 ° C. After 30 minutes of reaction, a modified composite negative electrode material with in-situ growth of nano-carbon fibers/carbon tubes on the surface was obtained. After being modified by the method, it can be used as negative electrode material of lithium ion battery. The test results of the conventional lithium-ion battery negative electrode evaluation method show that under the same number of cycles, the capacity after modification is increased by 70%, and the performance is better and more stable.

Example 6

Select hard carbon spheres (mass 1g) with an average diameter of 10 μm, and add NiSO ₄ as a catalyst (mass 0.061g). After adding the hard carbon spheres into the NiSO ₄ solution and mixing them evenly, dry them, and use C ₆ H ₆ as the carbon source and Ar was mixed in a volume ratio of 3:1, passed into a reaction furnace at a temperature of 1200° C., and after 45 minutes of reaction, a modified composite negative electrode material with in-situ growth of nano-carbon fibers/carbon tubes on the surface was obtained. After being modified by the method, it can be used as negative electrode material of lithium ion battery. The test results of the conventional lithium-ion battery negative electrode evaluation method show that under the same number of cycles, the capacity after modification is increased by 70%, and the performance is better and more stable.

Example 7

Select Cr ₂ O ₃ powder (mass 2g) with an average particle size of 1 μm, add Co ₂ O ₃ as a catalyst (mass 0.065g), mix evenly, put the treated powder into the reaction furnace, use CO as the carbon source, and pass Into a reaction furnace at a temperature of 900° C., and after 30 minutes of reaction, a modified composite negative electrode material in which nano-carbon fibers/carbon tubes are grown in situ on the surface is obtained. After being modified by this method, the capacity under the same number of cycles is increased by 145% compared with Comparative Example 2, and the cycle performance is also greatly improved.

Comparative example 2

Cr ₂ O ₃ powder with an average particle size of 1 μm was selected as the negative electrode material of lithium-ion batteries. The test results of conventional lithium-ion battery negative electrode evaluation methods show that its capacity decays very quickly and its cycle performance is very poor.

Example 8

Select modified graphite balls (quality 2g) with an average diameter of 20 μm, add Ni(NO ₃ ) ₂ as a catalyst (quality 0.15g), the modified graphite balls can be added to the Ni(NO ₃ ) ₂ solution and evenly mixed, then baked Dry, use C ₂ H ₄ as carbon source, mix with H ₂ in a volume ratio of 1:1, pass it into a reaction furnace at 750°C, and after 100 minutes of reaction, a kind of in-situ growth nanometer on the surface is obtained. The modified composite anode material of carbon fiber/carbon tube is used as the anode material of lithium ion battery. It can be charged and discharged at a rate of 1.5C, and the capacity can reach 101.6mAh/g. The charge and discharge performance at a high rate has been significantly improved.

Comparative example 3

Modified graphite balls with an average diameter of 20 μm were selected as the negative electrode material of lithium-ion batteries. The same test process as in Example 6 was used to charge and discharge at a rate of 1.5C, and the capacity was 65.5mAh/g.

Claims (3)

1, a kind of modified method for lithium ion cell negative electrode material, it is characterized in that: needs modification negative material is added catalyst evenly mix, the percentage by weight that catalyst accounts for the modification negative material is 0.1%-10%, the material that disposes is put into reacting furnace, do carbon source with hydrocarbon, mix in proportion with buffer gas, the volume ratio of hydrocarbon and buffer gas is 1: (0-10), feed temperature in 600-1300 ℃ of reacting furnace, through after 1-900 minute the reaction, obtain the modification composite negative pole material of a kind of nano carbon fiber of growth in situ from the teeth outwards/carbon pipe; Described modification negative material is one or more in carbonaceous material, transition metal oxide, fluoride, tinbase and the silicon-base oxide; Described catalyst is Fe, Co, Ni, Mo, one or more in V metal dust and oxide thereof, nitrate, halate, the sulfate; Described buffer gas is a hydrogen, argon gas, one or more in the nitrogen.

2, according to the described modified method for lithium ion cell negative electrode material of claim 1, it is characterized in that: described carbonaceous material is native graphite, modified graphite, MCMB, amorphous carbon, hard charcoal, pyrolytic carbon, petroleum coke; Described transition metal oxide is TiO, TiO ₂, VO ₂, V ₂O ₃, Cr ₂O ₃, MoO ₃, RuO ₂, FeO, NiO, CoO, Co ₃O ₄, Cu ₂O; Described fluoride TiF ₃, VF ₃, MnF ₂, FeF ₂, CoF ₂, NiF ₂, CuF ₂, CaF ₂, BaF ₂Described tinbase and silicon-base oxide are SnO, SnO ₂, SiO, SiO ₂

3, according to the described modified method for lithium ion cell negative electrode material of claim 1, it is characterized in that: described hydrocarbon as carbon source is a methane, ethane, propane, ethene, acetylene, benzene, toluene, dimethylbenzene, cyclohexane, carbon monoxide, one or more in the water-gas.

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