WO2014094424A1

WO2014094424A1 - Lithium ion battery cathode material, preparation method thereof and lithium ion battery

Info

Publication number: WO2014094424A1
Application number: PCT/CN2013/080085
Authority: WO
Inventors: 杨胜男
Original assignee: 华为技术有限公司
Priority date: 2012-12-20
Filing date: 2013-07-25
Publication date: 2014-06-26
Also published as: CN103887506A

Abstract

Provided is a lithium ion battery cathode material, comprising a material capable of being alloyed with lithium, a chemically bonded organic group, and a carbon material for cladding the material capable of being alloyed with lithium; and the carbon material is chemically bonded to the material capable of being alloyed with lithium via the organic group. Also provided is a preparation method of the lithium ion battery cathode material. The cathode material not only alleviates the dramatic volume expansion and shrinkage of the material capable of being alloyed with lithium, and the introduced carbon material helps to improve the conductivity of the whole material; moreover the cathode material also ensures the overall stability of the cathode material, and reduces the probability of network disconnection during electronic transmission, thus further improving the electrochemical performance of the cathode material.

Description

Anode material for lithium ion battery, preparation method thereof and lithium ion battery

Technical field

The invention relates to a rechargeable lithium ion battery, in particular to a negative electrode material with high capacity and stable circulation performance, a preparation method thereof and a lithium ion battery composed of the negative electrode material.

Background technique

At present, with the increasing demand for high-capacity, long-life batteries for mobile electronic devices, people have put forward higher requirements for the performance of lithium-ion batteries. The low capacity of lithium-ion batteries has become a bottleneck restricting the development of the battery industry. The search for cathode materials and anode materials with higher specific capacity has become a development direction in the field of battery materials. The anode material is an important component of lithium-ion batteries, which restricts the commercialization of lithium-ion batteries. At the same time, the development of portable batteries and high-capacity power batteries has also increased the demand for high-energy, high-cycle performance anode materials.

As people continue to explore negative electrode materials, materials that can form alloys with lithium (Si, Sn, Ge, Pb, Sb, Al, Zn) Etc.) Because of its high theoretical capacity and good embedding/ejecting ability, it has become the most promising class of negative electrode materials in high-energy lithium-ion batteries. For example, the theoretical capacity of pure silicon materials is as high as 4200 mAh/g, which is about ten of graphite negative electrodes. Times. However, such materials have poor cycle stability and short cycle life. The main reason is that during the charge and discharge cycle, the material undergoes huge volume expansion and shrinkage, such as a volume expansion ratio of 300%. This in turn causes damage to the conductive network, further deteriorating the electrochemical properties of the material. In addition, materials that can be alloyed with lithium are generally less conductive, which is another important factor affecting their electrical properties.

In order to solve the above problems, the current industry mainly adopts four methods of nanometering, thinning, compounding and designing multi-level special structure to modify it, but the effect is not ideal, or the preparation process is complicated, and it is difficult to realize commercialization. Or the introduction of a large amount of inactive materials greatly reduces the advantage of high capacity of materials that can be alloyed with lithium.

It is recognized in the industry that nanometering is an effective solution to solve the problem of large volume expansion and shrinkage of materials that can be alloyed with lithium. The main reason is that when the particle size is reduced by 1/2, the volume is reduced by 1/8, which is undoubtedly exciting. High-energy ball milling, laser, high-temperature calcination, sol-gel method, etc. are used to prepare nano-powders; gas-liquid-solid (VLS) growth, oxide-assisted growth, plasma activation, electrodeposition Method to prepare nanowires and nanotubes. The disadvantage is that reducing the dimension of the material does not fundamentally solve the problem of inherent volume expansion, shrinkage and poor conductivity of the material, and the effective size such as the particle size of the nanoparticle <10 Nm is also difficult to achieve in the process of industrialization. At the same time, the high surface energy of the nanoparticles also induces a serious agglomeration between the materials, which ultimately leads to unsatisfactory battery performance. The preparation of nanowires/nanotubes is costly, the production cycle is long, and the length of the nanowires is limited, which is difficult to be practical.

The second technical solution: the film material has a large specific surface area, and thinning the material can effectively reduce the volume change generated in the vertical direction of the film, thereby improving the cycle stability of the material. Therefore, film materials generally have high specific capacity and good cycle performance. Cui of Stanford University The Yi research team conducted in-depth research in the field of silicon thin films. The disadvantages are that the film materials are mainly prepared by chemical vapor deposition, magnetron sputtering, pulsed laser deposition, vacuum evaporation coating, etc., and the preparation process is complicated, the cost is high, and it is difficult to mass-produce rapidly, and the commercialization process Limited. Moreover, the large specific surface area of the film leads to an increase in side reactions and irreversible capacity.

The third technical solution: mainly introducing an active or inactive buffer matrix with good conductivity and small volume effect by means of coating, doping, etc., to prepare a multi-phase composite anode material, thereby suppressing volume expansion of the lithium alloy anode material, Shrinkage, that is, using a "buffer skeleton" to compensate for the expansion of the material. It can be roughly divided into (1) a material that can be alloyed with lithium-a non-metal composite system (mainly a material that can be alloyed with lithium/carbon composite system); (2) a material-metal composite system that can be alloyed with lithium. Two systems. It is important to point out that in recent years, the emergence and development of new carbon materials such as carbon nanotubes (CNTs) and graphenes (Graphene) have provided more modification methods for the commercial application of materials that can be alloyed with lithium. There is greater hope that the research on the composite of these materials has made good progress, but there is still a long way to go from real practicality.

The disadvantage is that the material/metal alloy system which can be alloyed with lithium can improve the electrical conductivity of the material which can be alloyed with lithium, but there are still problems of particle cracking and pulverization, which limits its further development; it can be alloyed with lithium. In materials/carbon (conventional carbon materials such as graphite and amorphous carbon), carbon generally occupies a large specific gravity, and the content of materials which can be alloyed with lithium is small, thus impairing the high capacity advantage of the material; There are various research methods for composite materials such as lithium alloyed materials/CNTs (Graphene), but they are not yet mature.

technical problem

The technical problem to be solved by the invention is to provide a modified lithium ion battery anode material and a preparation method thereof, and the special structure of the anode material can not only relieve the volume expansion of the material which can be alloyed with lithium but also stably improve the overall conductivity of the material. Sex to overcome the shortcomings of the prior art.

Technical solution

The technical solution adopted to solve the technical problem of the present invention is to provide a negative electrode material for a lithium ion battery, which comprises a material which can be alloyed with lithium, a chemically bonded organic group, and a material which can be alloyed with lithium. a carbonaceous material that is chemically bonded to the material that can be alloyed with lithium by the organic group, and the material that can be alloyed with lithium is selected from the group consisting of Si, Sn, and Ge. , Pb, Sb, Al, Zn, an element of nanoparticles, nanowires, nanotubes, nanofibers, nanofilm materials, or one or more of Si, Sn, Ge, Pb, Sb, Al, Zn elements Alloy composite.

As a further improvement of the present invention, the organic group has the formula -(CH ₂ ) _n —B—(CH ₂ ) _n — wherein 0≤n≤100, and B is an aliphatic, aromatic and heterocyclic group. One of them.

As a further improvement of the present invention, the carbon material is selected from one or more of graphene, graphene oxide, carbon nanotubes, and carbon nanofibers.

Another technical solution adopted to solve the technical problem of the present invention is to provide a method for preparing a negative electrode material for a lithium ion battery, comprising the following steps:

Step 1. Dissolve the graphene powder in deionized water and perform ultrasonic dispersion. After the dispersion is uniform, a concentrated hydrochloric acid solution in which p-phenylenediamine is dissolved is added dropwise to the graphene solution, and after the addition is completed, the solution is further added to the graphene solution. Adding sodium nitrite to carry out the reaction, and stirring uniformly to obtain a first mixed solution;

Step 2: The first mixed solution is subjected to suction filtration, and the filter residue obtained by suction filtration is washed with deionized water and absolute ethanol several times until the filtrate is colorless, and then the washed residue is dried to obtain a powder;

Step 3, adding the powder in the second step and the silicon powder purified by the HF or NH ₄ F solution to the organic solvent, and then adding the organic ester, and reacting under stirring to obtain the second mixed solution;

Step 4: The second mixed solution is subjected to suction filtration, and washed with absolute ethanol until the filtrate is colorless, and then the reaction product after washing is dried to obtain a negative electrode material of the lithium ion battery.

Step 1: adding the graphene powder and the silicon powder purified by the HF or NH ₄ F solution to an organic solvent to form a mixed solution and performing ultrasonic dispersion, and adding p-phenylenediamine to the mixed solution after the dispersion is uniform. Further adding an organic ester to carry out the reaction and stirring, and then obtaining a reaction product;

Step 2: The reaction product obtained in the first step is subjected to suction filtration, and washed with deionized water and absolute ethanol until the filtrate is colorless, and then the reaction product after the washing is dried to obtain a negative electrode material of the lithium ion battery.

Another technical solution adopted to solve the technical problem of the present invention is to provide a lithium ion battery including a positive electrode tab, a negative electrode tab, and an electrolyte, the negative pole tab containing the lithium ion described above A negative electrode material of the battery or a negative electrode material containing a lithium ion battery prepared by the above production method.

Beneficial effect

Compared with the prior art, the negative electrode material prepared by the one-step organic chemical reaction or the two-step organic chemical reaction can not only alleviate the volume expansion and contraction of the material which can be alloyed with lithium, but also introduce the carbon material. Improve the overall electrical conductivity of the material; more importantly, the material that can be alloyed with lithium in the modified material prepared by the method compared with the material/carbon coated material which can be prepared by the conventional method. Bonding with the carbon material through the organic group, the strong bonding force of the chemical bond will ensure the overall stability of the material, reduce the occurrence of disconnection in the electron conduction network, and further improve the electrochemical performance of the material.

DRAWINGS

The present invention will be further described below in conjunction with the accompanying drawings and embodiments, in which:

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a flow chart showing a method of preparing a negative electrode material for a lithium ion battery of the present invention.

2 is a flow chart showing another preparation method of the anode material of the lithium ion battery of the present invention.

3 is a schematic view showing the synthesis of a negative electrode material of a lithium ion battery of the present invention.

Fig. 4 is a graph showing the first three charge and discharge curves of the lithium ion battery composed of the negative electrode material prepared in the first embodiment.

Fig. 5 is a graph showing the cycle performance of a lithium ion battery composed of the negative electrode materials prepared in Example 1 and Example 2 at 0.2C.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The invention provides a negative electrode material of a novel modified high-capacity lithium ion battery, and the electrical conductivity and cycle stability of the negative electrode material are greatly improved. The anode material of the lithium ion battery includes a material that can be alloyed with lithium, a chemically bonded organic group, and a carbon material that coats the material that can be alloyed with lithium, the carbon material and lithium The alloyed materials are chemically bonded together by the organic groups. Wherein the material alloyable with lithium is selected from the group consisting of nanoparticles, nanowires, nanotubes, nanofibers, nanofilm materials of one element of Si, Sn, Ge, Pb, Sb, Al, Zn, or contains one An alloy complex of one or more of the above-mentioned elements; the organic group is of the formula -(CH ₂ ) _n —B—(CH ₂ ) _n — wherein 0≤n≤100, B is aliphatic, aromatic One of a group and a heterocyclic group; the carbon material is selected from one or more of graphene, graphene oxide, carbon nanotubes, and carbon nanofibers.

The invention also provides a method for preparing a negative electrode material of a lithium ion battery by a two-step organic chemical reaction, as shown in FIG. 1, which comprises the following steps:

Step S01, dissolving the graphene powder in deionized water and performing ultrasonic dispersion. After uniformly dispersing, the concentrated hydrochloric acid solution in which p-phenylenediamine is dissolved is added dropwise to the graphene solution, and after the addition is completed, the solution is further added to the graphene solution. Adding sodium nitrite to carry out the reaction, and stirring uniformly to obtain a first mixed solution;

Step S02, the first mixed solution is subjected to suction filtration, and the filter residue obtained by suction filtration is washed with deionized water and absolute ethanol several times until the filtrate is colorless, and then the washed residue is dried to obtain a powder;

Step S03, adding the powder in the step S02 and the silicon powder purified by the HF or NH ₄ F solution to the organic solvent, and then adding the organic ester, and reacting under stirring to obtain the second mixed solution;

Step S04, the second mixed solution is subjected to suction filtration, and washed with absolute ethanol until the filtrate is colorless, and then the reaction product after washing is dried to obtain a negative electrode material of the lithium ion battery.

In the step S01, graphene oxide is first prepared by a modified Hummers method, and then reduced to obtain graphene. The ultrasonic dispersion time is 0.5 to 2 hours, and the reaction time is 4 hours.

In the step S02, the drying condition is to dry in a vacuum oven at a temperature of 80 ° C for 8 to 24 hours.

In the step S03, the silicon powder has an average diameter of 100 nm, and the organic solvent is acetonitrile, methanol, ethanol, isopropanol, ethylene glycol, diethylene glycol, propylene glycol, formic acid, acetic acid, pentane, hexane, At least one of octane; the organic lipid is isoamyl nitrite, methyl nitrite, ethyl nitrite, n-propyl nitrite, isopropyl nitrite, butyl nitrite, n-nitrite At least one of an ester, isobutyl nitrite, t-butyl nitrite, tert-butyl nitrite, octyl nitrite, amyl nitrite, and nitrite.

In the step S04, the drying condition is to dry in a vacuum oven at a temperature of 80 ° C for 8 to 24 hours.

The invention further provides a method for preparing a negative electrode material of a lithium ion battery by a one-step organic chemical reaction, as shown in FIG. 2, which comprises the following steps:

Step S011, adding the graphene powder and the silicon powder treated by the HF or NH ₄ F solution to an organic solvent to form a mixed solution and performing ultrasonic dispersion, and adding p-phenylenediamine to the mixed solution after the dispersion is uniform, and then Adding an organic ester to carry out the reaction and stirring, and then obtaining a reaction product;

Step S012, the reaction product obtained in the step S011 is subjected to suction filtration, and washed with deionized water and absolute ethanol until the filtrate is colorless, and then the reaction product after the washing is dried to obtain a negative electrode material of the lithium ion battery.

In this preparation method, in the step S011, graphene oxide is first prepared by a modified Hummers method, and then reduced to obtain graphene. The ultrasonic dispersion time is 0.5 to 2 hours. The chemical reaction time is 6 to 20 hours. The silicon powder has an average diameter of 100 nm. The organic solvent is at least one of acetonitrile, methanol, ethanol, isopropanol, ethylene glycol, diethylene glycol, propylene glycol, formic acid, acetic acid, pentane, hexane, and octane; the organic lipid is nitrous acid Isoamyl ester, methyl nitrite, ethyl nitrite, n-propyl nitrite, isopropyl nitrite, butyl nitrite, n-butyl nitrite, isobutyl nitrite, t-butyl nitrite, sub At least one of tert-butyl nitrate, octyl nitrite, amyl nitrite, and nitrite.

In the step S012, the drying conditions are dried in a vacuum oven at a temperature of 80 ° C for 8 to 24 hours.

As shown in FIG. 3, FIG. 3 is a schematic view showing the synthesis of a negative electrode material of a lithium ion battery of the present invention, wherein M is a material which can be alloyed with lithium.

The method of preparing a negative electrode material of a lithium ion battery under different conditions and the like are exemplified below by various embodiments.

Embodiment 1

Graphene oxide was first prepared by a modified Hummers method and then reduced. The obtained graphene (Graphene) 2-8 mg at 40-120 Ultrasonic dispersion in mL deionized water for 0.5~2h. After dispersing evenly, add 20 ml of concentrated hydrochloric acid solution containing 2-6 mmol of p-phenylenediamine to the solution, and add 2-6 to the solution after the addition is completed. Methyl nitrite, the reaction time is about 4h, and the whole process is stirred. Finally, the obtained product was suction filtered, washed with deionized water and absolute ethanol until the filtrate was colorless, and then the obtained washed product was dried in a vacuum oven at 80 ° C for 8 to 24 h Get a powder.

Adding the above powder to 0.01 to 0.1 g of silicon powder which has been purified by HF or NH ₄ F solution and having an average diameter of about 100 nm, is added to 5 to 40 ml of an organic solvent acetonitrile, followed by adding an appropriate amount of isoamyl nitrite, and stirring conditions. The next reaction is 6 to 20 hours. The obtained product was suction filtered, washed with absolute ethanol until the filtrate was colorless, and then the obtained washed product was dried in a vacuum oven at 80 ° C for 8 to 24 hours to obtain a negative electrode material of a lithium ion battery.

Embodiment 2

According to the method of Example 1, 2 to 8 mg of graphene (Graphene) and 0.01 to 0.1 g of silicon powder having an average diameter of about 100 nm after being purified by HF or NH ₄ F solution are added to 40 to 120 ml of organic After ultrasonication for 0.5 to 2 h in solvent acetonitrile, 2-6 mmol of p-phenylenediamine was added to the solution, and then an appropriate amount of isoamyl nitrite was added to the solution, and the reaction was carried out for 6-20 hours under stirring. Finally, the obtained product was suction filtered, washed with deionized water and absolute ethanol until the filtrate was colorless, and then the obtained washed product was dried in a vacuum oven at 80 ° C for 8 to 24 h to obtain a lithium ion battery. Anode material.

Comparative example

After purification by HF or NH ₄ F solution, the silicon powder after the surface oxide layer is removed.

The following is a comparison and analysis of specific experimental data:

In order to test the electrochemical properties of the anode materials prepared according to Example 1 and Example 2, experiments were carried out in the following manner: According to the anode material: Conductive graphite: sodium carboxymethylcellulose (CMC): water = The ratio of 6:2:2:100 was mixed into a uniform slurry, and then uniformly coated on a copper foil, and the pole piece was vacuum dried at 120 ° C for more than 24 hours, and pressed to prepare a negative electrode sheet. The negative electrode tab formed of the negative electrode materials prepared in the first embodiment and the second embodiment was assembled into a button-type lithium ion battery in an Ar-protected glove box with a positive electrode tab and an electrolyte, and electrochemical performance was measured.

As shown in FIG. 4, FIG. 4 shows that the anode material prepared in the first embodiment is first in the range of 0.6 to 0.09. A steep slope appeared between V, and a long lithium-plated platform appeared from 0.09 V. The first lithium insertion capacity was 2337.6 mAh/g, and the delithiation process was 0.2 to 0.58. There is a long delithium slope between V, the first lithium removal capacity is 1519.2 mAh / g; the lithium-plated platform of the two discharge curves after the negative electrode material is slightly higher, about 0.28 Around V, the starting voltage may correspond to the lithium intercalation process of graphene. The second charging curve of the material is not much different from the first time, and the potential platform is relatively close, but the lithium-plated platform of the third charging curve is relatively short.

As shown in FIG. 5, it can be seen from the test results that the lithium ion battery containing the anode material prepared in the first embodiment and the second embodiment has good cycle stability, and the lithium ion battery 50 containing the anode material prepared in the first embodiment is 50. After the second cycle, the capacity remains at about 570. mAh/g, the capacity of the lithium ion battery containing the anode material prepared in Example 2 after 50 cycles of about 396 mAh/g, a stable platform appeared after 10 times. The test data shows that the lithium ion battery containing the comparative negative electrode material has the worst cycle stability, and its first lithium removal capacity is 1530. mAh/g, the subsequent cycle capacity decays very quickly, and the capacity drops to 279 mAh/g after 20 cycles. It can be seen that the cycle stability of the lithium ion battery containing the modified anode material does increase greatly.

The negative electrode material prepared by the one-step organic chemical reaction or the two-step organic chemical reaction can not only alleviate the large volume expansion and contraction of the material which can be alloyed with lithium, but also introduce the carbon material to improve the overall conductivity of the material; More importantly, compared with the material/carbon coating material which can be prepared by the conventional method and can be alloyed with lithium, the modified material prepared by the method can pass between the material alloyed with lithium and the carbon material. The organic group bonding, the strong bonding force of the chemical bond will ensure the overall stability of the material, reduce the occurrence of disconnection in the electron conduction network, and further improve the electrochemical performance of the material.

The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. Within the scope.

Claims

A negative electrode material for a lithium ion battery, comprising: a material that can be alloyed with lithium, a chemically bonded organic group, and a carbon material coated with a material that can be alloyed with lithium, the carbon material The material is chemically bonded to the material which can be alloyed with lithium by the organic group, and the material which can be alloyed with lithium is selected from the group consisting of Si, Sn, Ge, Pb, Sb, Al, and Zn. Nanoparticles, nanowires, nanotubes, nanofibers or nanofilm materials of the elements, or the material which can be alloyed with lithium is selected from one of Si, Sn, Ge, Pb, Sb, Al, Zn or A variety of alloy composites.
The negative electrode material for a lithium ion battery according to claim 1, wherein said organic group has the formula -(CH 2 ) n —B—(CH 2 ) n — wherein 0≤n≤100, B It is one of an aliphatic, aromatic and heterocyclic group.
The negative electrode material for a lithium ion battery according to claim 1, wherein the carbon material is selected from one or more of graphene, graphene oxide, carbon nanotubes, and carbon nanofibers.
A lithium ion battery comprising a positive electrode tab, a negative electrode tab, and an electrolyte, wherein the negative electrode tab comprises the negative electrode material of the lithium ion battery according to any one of claims 1 to 3.
A method for preparing a negative electrode material for a lithium ion battery, comprising the steps of:

Step 1. Dissolve the graphene powder in deionized water and perform ultrasonic dispersion. After the dispersion is uniform, a concentrated hydrochloric acid solution in which p-phenylenediamine is dissolved is added to the graphene solution, and then sodium nitrite is added to the graphene solution. Reacting and stirring uniformly to obtain a first mixed solution;

Step 2: The first mixed solution is subjected to suction filtration, and the filter residue obtained by suction filtration is washed with deionized water and absolute ethanol several times until the filtrate obtained after washing is colorless, and then the washed residue is dried. Processing to obtain a powder;

Step 3, adding the powder in the second step and the silicon powder obtained after the purification treatment by the HF or NH 4 F solution to the organic solvent, and then adding the organic ester, and reacting under stirring to obtain the second mixed solution;

Step 4: The second mixed solution is subjected to suction filtration to obtain a filter residue, and the filter residue is washed with absolute ethanol until the washed filtrate is colorless, and then the reaction product obtained after the washing is dried to obtain a negative electrode material of the lithium ion battery.
The preparation method according to claim 5, wherein in the first step, the ultrasonic dispersion time is 0.5 to 2 hours.
The process according to claim 5, wherein in the first step, the reaction time is 4 hours.
The preparation method according to claim 5, wherein in the second step, the drying treatment is carried out in a vacuum drying oven at a temperature of 80 ° C for 8 to 24 hours.
The preparation method according to claim 5, wherein in the third step, the silicon powder has an average diameter of 100 nm.
The preparation method according to claim 5, wherein in the third step, the organic solvent is acetonitrile, methanol, ethanol, isopropanol, ethylene glycol, diethylene glycol, propylene glycol, formic acid, acetic acid. At least one of pentane, hexane, and octane.
The preparation method according to claim 5, wherein in the third step, the organic lipid is isoamyl nitrite, methyl nitrite, ethyl nitrite, n-propyl nitrite, and sub At least isopropyl nitrate, butyl nitrite, n-butyl nitrite, isobutyl nitrite, tert-butyl nitrite, tert-butyl nitrite, octyl nitrite, amyl nitrite, nitrite One.
The preparation method according to claim 5, wherein in the step 4, the drying condition is drying in a vacuum drying oven at a temperature of 80 ° C for 8 to 24 hours.
A method for preparing a negative electrode material for a lithium ion battery, comprising the steps of:

Step 1: adding the graphene powder and the silicon powder purified by the HF or NH 4 F solution to an organic solvent to form a mixed solution and performing ultrasonic dispersion, and adding p-phenylenediamine to the mixed solution after the dispersion is uniform. Further adding an organic ester to carry out the reaction and stirring, and then obtaining a reaction product;

Step 2: The reaction product obtained in the first step is subjected to suction filtration to obtain a filter residue, and the filter residue is washed with deionized water and absolute ethanol until the washed filtrate is colorless, and then the reaction product after drying and washing is obtained to obtain the lithium ion battery. Anode material.