CN1688044A

CN1688044A - Method of preparing Sn-Sb alloy material for negative electrode of lithium ion cell

Info

Publication number: CN1688044A
Application number: CNA2005100116831A
Authority: CN
Inventors: 赵海雷; 尹朝丽; 吴恒亮; 仇卫华
Original assignee: University of Science and Technology Beijing USTB
Current assignee: University of Science and Technology Beijing USTB
Priority date: 2005-05-08
Filing date: 2005-05-08
Publication date: 2005-10-26
Anticipated expiration: 2025-05-08
Also published as: CN1301560C

Abstract

This invention provides a method for applying carbothermic method to prepare Sn Sb alloy negative material of Li ionic batteries characterizing in matching the oxide of Sn and Sb according to the Sn and Sb proportion in their generated alloy, then introducing a proper proportion of carbon powder as the reducer to get a mixture to be ground and put in N or Ar atmosphere to increase the temperature with the speed of 5-30deg.C/minute to arrive at different temperatures and keep them cut off to be cooled to the room temperature. Compared with the method of liquid phase chemical recovery and powder metallurgy, this invented method costs less, the particles of SnSb alloy powder are fine and uniform and good at crystallinity, the produced negative material has high specific capacity and stable circulation.

Description

Preparation method of tin-antimony alloy material for lithium ion battery cathode

Technical Field

The invention belongs to the field of lithium ion batteries, and particularly relates to a preparation technology of a SnSb alloy material for a lithium ion battery cathode.

Background

The rapid development of portable electronic devices has increased the demand for secondary batteries, and has also raised higher and higher requirements for the performance of secondary batteries. Lithium ion batteries are the latest generation of rechargeable batteries since the 90 s, following MH-Ni batteries. The method has the advantages of high working voltage, high energy density, long cycle life, small self-discharge, no memory effect and the like, and the application of the method is penetrated into the advanced fields of spaceflight, military affairs and the like.

Most of the current commercialized lithium ion battery cathode materials adopt carbon materials, and although the materials have excellent electrochemical performance, the lithium storage capacity of the materials is low. The actual specific capacity of the graphite is very close to the theoretical specific capacity (for example, the theoretical lithium storage capacity of the graphite is 372mAh/g), and the potential for further developing and improving the specific capacity is very small, so that the graphite is difficult to adapt to the miniaturization development of variousportable electronic devices and the wide demand of the development of electric automobiles on large-capacity high-power chemical power sources. Therefore, research and development of novel lithium ion battery anode materials with high specific capacity become a research hotspot of current material workers and electrochemical workers.

Many metals and semi-metals (e.g., Al, Mg, Ga, In, Sn, Zn, Cd, Si, Ge, Pb, Sb, Bi, Au, Ag, Pt, etc.) can be alloyed with lithium, and their lithium storage capacity is considerable and far greater than that of graphite-based negative electrode materials. However, during the charging and discharging process of the battery, the reversible generation and decomposition of the lithium metal (Li-M) alloy is accompanied by huge volume change (2-3 times), so that the alloy is easy to split (generate cracks and pulverization), the cycle performance of the electrode is affected, and the practical application of the alloy negative electrode is hindered. One possible way to suppress or mitigate the volume change associated with the lithium deintercalation process is to introduce into the "active" metal capable of bonding with lithium an "inactive" metal that does not bond with lithium or a "second metal" that bonds with lithium at a different potential, which will act as a buffer for stress, prevent electrode powdering and degrade electrochemical performanceAnd (3) acting, namely preparing the alloy or intermetallic compound based negative electrode material. Among the alloy cathodes studied, the most notable is the Sn-based alloy. Among them, SnSb is a good candidate material for alloy negative electrodes, and is produced from m.wachtler, m.winter, j.o.bessenhard, j.power Sources, 2002, 105: 151-160 report that Sb can be combined with lithium due to Sn (Sn → Li)₂₂Sn₅：994mAh/g，Sb→Li₃Sb: 660mAh/g), so that the catalyst has higher specific capacity; meanwhile, according to documents m.winter and j.o.besenhard, Electrochimica Acta, 1999, 45: 31-50 newspaperHowever, because the lithium intercalation potentials of the active Sn and Sb are different, the volume expansion of the material occurs under different potentials, so that the internal stress caused by the volume expansion can be relieved, and the cycling stability of the material is improved.

At present, SnSb alloy composite materials reported in literature are mainly prepared by a liquid-phase chemical reduction method, for example, patent JP2000012014 contains NaBH serving as a reducing agent₄The alkaline solution is mixed with a solution containing a complexing agent and metal ions, the reaction is carried out to obtain SnSb composite precipitate, and then the product is obtained by repeatedly filtering, washing and vacuum drying. The particle size synthesized by the method can reach the nanometer level, the uniformity is good, but the product has large surface area, is easy to agglomerate and surface oxidize, the irreversible capacity is increased, the raw material cost is higher, the process is complex, and the yield is lower. Document j.o.bensenhard, j.yang, m.winter.j.power sources.1997, 68: 87, which is an alloy powder obtained by simultaneously depositing several metals under certain conditions, such as Fe-Ni, Fe-Cr, and Sn-Sb. The metal powder prepared by the method has high purity, but the preparation process is complicated because experimental conditions and technological parameters which influence complex factors such as composition, granularity, appearance and the like need to be effectively controlled. Also, there are documents j.o. besenhard, m.wachtler, m.winter, r.andreaus, i.rom, w.site.j Power Sources 1999, 81-82: 268-272, the solid phase sintering method (powder metallurgy method) is to mix high purity Sn and Sb powders uniformly, seal them in a vacuum quartz tube, and calcine them at different temperatures step by step. The method has harsh technological conditions, high cost and low yield. Thus, study onThe synthesis method of the SnSb alloy, which has the advantages of low cost, simple process and convenience for large-scale production, has very important significance for promoting the practical application of the SnSb alloy in the lithium ion battery.

Disclosure of Invention

The invention provides a preparation method of a SnSb alloy cathode material of a lithium ion battery, which adopts a carbothermic reduction method and uses carbon powder as a reducing agent to reduce oxides of tin and antimony to prepare alloy cathode materials with different Sn/Sb ratios. The method is low in cost and simple in preparation process, the synthesized SnSb alloy powder is uniform and fine in particles and good in crystallinity, and the prepared SnSb lithium ion battery cathode material is high in specific capacity and stable in cycle performance.

The invention adopts a high-temperature chemical reduction technology to synthesize the SnSb alloy cathode material, and the specific process comprises the following steps:

SnO in micron, submicron or nanometer scale₂、Sb₂O₃Mixing with active carbon or carbon black powder, SnO₂、Sb₂O₃The addition amount of the carbon black is calculated according to the atomic ratio of Sn/Sb of 3: 1-1: 3, the addition amount of the active carbon or the carbon black is calculated according to a chemical formula (1),

(1)

uniformly mixing the raw materials by adopting a mechanical dry mixing or wet mixing method; the mixture is put in flowing nitrogen and argonGas containing 5 to 10 vol% of H₂The temperature in the heating furnace in the argon atmosphere reaches the required temperature of 700-; then the power is cut off, and the furnace is naturally cooled to the room temperature. Control of SnO in starting materials₂And Sb₂O₃The ratio of Sn/Sb in the obtained SnSb product can be effectively controlled.

According to thermodynamic calculations, tin and antimony oxides can be reduced to metals by C at relatively low temperatures (650-450 ℃), due to the low melting points of Sn, Sb: the temperature is 232 ℃ and 631 ℃, and the reduced metal Sn and Sb have high activity and are easy to be alloyed with each other to generate SnSb alloy or intermetallic compounds. According to the invention, a high-temperature chemical reduction technology is adopted, and carbon powder is used as a reducing agent to reduce oxides of tin and antimony, so that the final product SnSb alloy composite material can be obtained only by uniformly mixing the raw materials, sintering and cooling in a protective atmosphere.

Compared with the liquid phase chemical reduction method which is used more frequently, the method has the advantages that the cost of raw materials is relatively low, the repeated filtering, washing and drying processes of precipitates are omitted in the preparation process, and therefore the method is quite simple in process, less in consumed time and high in yield. The synthesized SnSb alloy has high crystallinity and is micron polycrystalline particles, so that the specific surface area is not too large, and serious agglomeration and surface oxidation are not easy to occur, thereby reducing the irreversible capacity of the cathode material and simultaneously improving the cycling stability of the material. Compared with the direct solid phase sintering reaction of Sn, Sb metal powder, the synthesized SnSb alloy powder has smaller particle size

Drawings

FIG. 1 is an XRD pattern of SnSb synthesized by carbothermic reduction of the present invention, SnO₂And Sb₂O₃The ratio of (A) to (B) is 2: 1, and the firing temperature is 850 ℃.

FIG. 2 is a specific capacity-cycle number curve of SnSb synthesized by carbothermic reduction, SnO₂And Sb₂O₃The ratio of (A) to (B) is 2: 1, and the firing temperature is 850 ℃.

Detailed Description

Example 1:

in SnO₂(purity 99.9%) and Sb₂O₃(99.9%) and activated carbon (purity>99%) as initial raw materials, mixing in a molar ratio of 2: 1: 7, ball-milling the mixture, wet-mixing, heating to 850 deg.C at a rate of 5 deg.C/min under flowing argon atmosphere, keeping the temperature for 2 hours, cutting off the power, and naturally cooling to room temperature. The XRD phase analysis result of the obtained sample shows that the synthesized product is a single SnSb phase and has no other impurity phase.

Adding 10 wt% of conductive agent acetylene black and 8 wt% of binder PVDF into the synthesized material to prepare slurry, uniformly coating the slurry on copper and platinum, drying the slurry, clamping the dried slurry into a circular pole piece, forming a test battery with metal lithium, and carrying out a constant current charge and discharge experiment, wherein the charge and discharge current is 50mA/g, and the charge and discharge voltage range is controlled between 0.01 and 1.2V. The initial reversible capacity of the prepared SnSb negative electrode material is 700mAh/g, the specific capacity after ten times of circulation is 630mAh/g, and the capacity is kept at 90%.

Example 2:

in SnO₂(purity 99.9%) and Sb₂O₃(99.9%) and carbon powder (purity>99%) as initial raw materials, mixing the reactants according to the molar ratio of 4: 1: 11, ball-milling and dry-mixing the mixture uniformly, placing the mixture in a flowing argon atmosphere, raising the temperature to 900 ℃ at the heating rate of 20 ℃/min, preserving the heat for 3 hours, then cutting off the power, and naturally cooling to room temperature. The XRD phase of the obtained sample analyzes the surface, and the synthesized product is two phases of SnSb and Sn without other impurity phases.

Adding 12 wt% of conductive agent acetylene black and 8 wt% of binder PVDF into the synthesized material to prepare slurry, uniformly coating the slurry on copper and platinum, drying the slurry, clamping the dried slurry into a circular pole piece, forming a test battery with metal lithium, and carrying out a constant current charge and discharge experiment, wherein the charge and discharge current is 100mA/g, and the charge and discharge voltage range is controlled between 0.01 and 1.2V. The initial reversible capacity of the prepared SnSb alloy negative electrode material is more than 730 mAh/g.

Claims

1. A preparation method of a tin-antimony alloy material for a lithium ion battery cathode is characterized by comprising the following preparation steps:

1) SnO₂、Sb₂O₃Mixing with carbon powder, SnO₂、Sb₂O₃The addition amount of the carbon powder is calculated according to the atomic ratio of Sn/Sb of 3: 1-1: 3, the addition amount of the carbon powder is calculated according to the chemical formula (1), and the carbon powder and the Sb are uniformly mixed;

(1)

2) will be mixed withPlacing the mixture in flowing nitrogen, argon or H containing 5-10 vol%₂In argon atmosphere, the required temperature is 700 ℃ and 1100 ℃ at the heating rate of 5-30 ℃/min, and the temperature is kept for 1-5 hours;

3) and (4) powering off the heating furnace, and naturally cooling to room temperature along with the furnace.

2. The method for preparing a tin-antimony alloy material for a negative electrode of a lithium ion battery according to claim 1, wherein the particle size of the oxide powder of tin and antimony is micron-sized, submicron-sized or nanometer-sized.

3. The method for preparing a tin-antimony alloy material for a negative electrode of a lithium ion battery according to claim 1, wherein the powder is mixed by wet mixing or dry mixing.

4. The method for preparing a tin-antimony alloy material for a negative electrode of a lithium ion battery as claimed in claim 1, wherein the carbon powder is activated carbon or carbon black.