CN1301560C - Method of preparing Sn-Sb alloy material for negative electrode of lithium ion cell - Google Patents

Abstract

The invention provides a method for preparing a SnSb alloy negative electrode material for a lithium ion battery by a carbothermal reduction method, which belongs to the field of lithium ion batteries, and is characterized in that: the oxides of tin and antimony are prepared according to the Sn and Sn in the alloy compound formed. The proportion of Sb is adjusted, and then an appropriate proportion of carbon powder is introduced as a reducing agent. After the obtained mixture is mixed and ground evenly, it is placed in a flowing nitrogen or argon atmosphere at a heating rate of 5-30°C/min to reach the required temperature. Keep warm for a certain period of time, and then turn off the power to allow it to cool down to room temperature with the furnace. The advantages of the present invention are: compared with other methods such as liquid-phase chemical reduction and powder metallurgy, the method not only has low cost and simple preparation process, but also the synthesized SnSb alloy powder has uniform and fine particles and good crystallinity. The anode material of SnSb lithium-ion battery has high specific capacity and stable cycle performance. The reversible capacity can reach up to 730mAh/g, and the capacity remains above 90% after 10 cycles.

Description

A kind of preparation method of tin-antimony alloy material for negative electrode of lithium ion battery

technical field

The invention belongs to the field of lithium-ion batteries, and in particular relates to a preparation technology of a SnSb alloy material used for a negative electrode of a lithium-ion battery.

Background technique

With the rapid development of portable electronic devices, the demand for secondary batteries is increasing day by day, and at the same time, higher and higher requirements are put forward for the performance of secondary batteries. Lithium-ion batteries are the latest generation of rechargeable batteries after MH-Ni batteries since the 1990s. It has the advantages of high working voltage, high energy density, long cycle life, small self-discharge, and no memory effect. Its application has penetrated into aerospace, military and other cutting-edge fields.

At present, most commercial lithium-ion battery anode materials use carbon materials. Although this material has excellent electrochemical performance, its lithium storage capacity is low. Its actual specific capacity is currently very close to its theoretical specific capacity (such as the theoretical lithium storage capacity of graphite is 372mAh/g), and the potential for further development to increase its specific capacity is already very small, making it difficult to adapt to the miniaturization of various portable electronic devices. The development and development of electric vehicles have a wide demand for large-capacity and high-power chemical power supplies. Therefore, the research and development of new lithium-ion battery anode materials with high specific capacity has become a research hotspot for current material workers and electrochemical workers.

Many metals and semimetals (such as: Al, Mg, Ga, In, Sn, Zn, Cd, Si, Ge, Pb, Sb, Bi, Au, Ag, Pt, etc.) can form alloys with lithium, and their lithium storage The amount is considerable, much larger than that of graphite-based negative electrode materials. However, during the charging and discharging process of the battery, the reversible formation and decomposition of the lithium metal (Li-M) alloy is accompanied by a huge volume change (2-3 times), which can easily cause the splitting of the alloy (creating cracks and pulverization), affecting the electrode. The poor cycle performance hinders the practical application of alloy anodes. To suppress or alleviate the volume change that accompanies the process of intercalating lithium, a feasible method is to introduce an "inactive" metal that does not combine with lithium into an "active" metal that is capable of combining with lithium or at a different potential with lithium. The "second metal" compounded under the compound will play the role of buffering stress, preventing electrode pulverization and electrochemical performance degradation, that is, preparing alloy or intermetallic compound-based negative electrode materials. Among the studied alloy anodes, the most striking ones are Sn-based alloys. Among them, SnSb is a class of good alloy negative electrode candidate materials. It can be known from the report of M.Wachtler, M.Winter, JOBessenhard, J.Power Sources, 2002, 105: 151-160, because both Sn and Sb can be combined with lithium (Sn→Li ₂₂ Sn ₅ : 994mAh/g, Sb→Li ₃ Sb: 660mAh/g), so it has a high specific capacity; at the same time, according to the literature M.Winter and JOBesenhard, Electrochimica Acta, 1999, 45:31 According to the report of -50, due to the different lithium intercalation potentials of active Sn and Sb, the volume expansion of the material will occur at different potentials, which can relieve the resulting internal stress and improve the cycle stability of the material.

At present, the SnSb alloy composite materials reported in the literature are mainly prepared by the liquid phase chemical reduction method. For example, the patent JP2000012014 mixes the alkaline solution containing the reducing agent NaBH ₄ with the solution containing the complexing agent and metal ions, and reacts to obtain SnSb composite precipitation. , and then repeatedly filtered, washed and vacuum-dried to obtain the product. The particle size synthesized by this method can reach the nanometer level, and the uniformity is good, but the product has a large surface area, which is prone to agglomeration and surface oxidation, resulting in an increase in irreversible capacity, and the cost of raw materials is high, the process is complicated, and the yield is low. The electrodeposition method described in the document JOBensenhard, J.Yang, M.Winter.J.Power Sources.1997, 68:87 prepares the alloy negative electrode. Under certain conditions, several metals are deposited simultaneously to obtain an alloy powder, such as Fe -Ni, Fe-Cr, Sn-Sb, etc. The metal powder prepared by this method has high purity, but the experimental conditions and process parameters that affect complex factors such as composition, particle size, and appearance need to be effectively controlled during the preparation, and the process is relatively complicated. There is also the solid phase sintering method (powder metallurgy method) introduced in the literature JOBesenhard, M.Wachtler, M.Winter, R.Andreaus, I.Rom, W.Sitte.J Power Sources 1999,81-82:268-272 , It is made by mixing high-purity Sn and Sb powders evenly, sealing them in a vacuum quartz tube, and calcining them step by step at different temperatures. The method has harsh process conditions, high cost and low yield. Therefore, it is of great significance to study a synthesis method of SnSb alloy with low cost, simple process and convenient large-scale production to promote the practical application of SnSb alloy in lithium-ion batteries.

Contents of the invention

The invention provides a method for preparing a SnSb alloy negative electrode material for a lithium ion battery. The carbothermal reduction method is used to reduce tin and antimony oxides by using carbon powder as a reducing agent to prepare alloy negative electrode materials with different Sn/Sb ratios. The method not only has low cost and simple preparation process, but also the synthesized SnSb alloy powder has uniform and fine particles and good crystallinity, and the prepared SnSb lithium ion battery negative electrode material has high specific capacity and stable cycle performance.

The present invention adopts high-temperature chemical reduction technology to synthesize the specific process of SnSb alloy negative electrode material as follows:

Weigh micron, submicron or nanoscale SnO ₂ , Sb ₂ O ₃ and activated carbon or carbon black powder, and the amount of SnO ₂ and Sb ₂ O ₃ added is based on the atomic ratio of Sn/Sb 3:1 ~1:3 calculation, the addition of activated carbon or carbon black is calculated according to chemical formula (1),

(1)

Mix them uniformly by mechanical dry mixing or wet mixing; the mixture is placed in a heating furnace with flowing nitrogen, argon or argon atmosphere containing 5-10vol% H ₂ at a rate of 5-30°C/min The heating rate reaches the required temperature of 700-1100°C, and the temperature is maintained for 1-5 hours; then the power is turned off, and the furnace is naturally cooled to room temperature. Controlling the ratio of SnO ₂ and Sb ₂ O ₃ in the starting materials can effectively control the ratio of Sn/Sb in the obtained SnSb product.

According to thermodynamic calculations, oxides of tin and antimony can be reduced to metals by C at relatively low temperatures (650-450°C), and due to the low melting points of Sn and Sb: 232°C and 631°C, respectively, the reduced The metals Sn and Sb have high activity and are easy to alloy with each other to form SnSb alloy or intermetallic compound. Because the present invention adopts high-temperature chemical reduction technology and uses carbon powder as a reducing agent to reduce oxides of tin and antimony, the final product SnSb alloy composite material can be obtained only by uniformly mixing raw materials, sintering and cooling in a protective atmosphere.

Compared with the more commonly used liquid-phase chemical reduction method, the raw material cost of this method is relatively low, and the preparation process saves the repeated filtration, washing and drying process of the sediment, so the process is quite simple, less time-consuming and high yield . The synthesized SnSb alloy has high crystallinity and is micron polycrystalline particles, so 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 negative electrode material and improving the cycle stability of the material. Compared with the direct solid-state sintering reaction of Sn and Sb metal powders, the particle size of the synthesized SnSb alloy powder is finer and more uniform.

Description of drawings

Fig. 1 is an XRD pattern of SnSb synthesized by carbothermal reduction in the present invention, the ratio of SnO ₂ to Sb ₂ O ₃ is 2:1, and the firing temperature is 850°C.

Fig. 2 is the specific capacity-cycle number curve of SnSb synthesized by carbothermal reduction in the present invention, the ratio of SnO ₂ to Sb ₂ O ₃ is 2:1, and the firing temperature is 850°C.

Detailed ways

Example 1:

SnO ₂ (purity 99.9%), Sb ₂ O ₃ (99.9%) and activated carbon (purity > 99%) are used as the initial raw materials, and the molar ratio is 2:1:7. After the mixture is wet-mixed by ball milling, Place it in a flowing argon atmosphere to raise the temperature to 850°C at a rate of 5°C/min, keep it warm for 2 hours, then turn off the power, and cool it down to room temperature naturally. The XRD phase analysis results of the obtained sample show that the synthesized product is a single SnSb phase without any other impurity phases.

Add 10wt% conductive agent acetylene black to the synthesized material, 8wt% binder PVDF to make a slurry, evenly spread it on copper platinum, after drying, stick it into a circular pole piece, and form a test battery with metal lithium. Carry out constant current charge and discharge experiments, the charge and discharge current is 50mA/g, and the charge and discharge voltage range is controlled between 0.01-1.2V. The initial reversible capacity of the prepared SnSb negative electrode material is 700mAh/g, the specific capacity after ten cycles is 630mAh/g, and the capacity remains at 90%.

Example 2:

Using SnO ₂ (purity 99.9%), Sb ₂ O ₃ (99.9%) and carbon powder (purity > 99%) as the initial raw materials, the reactants are mixed in a molar ratio of 4:1:11, and the mixture is dry-mixed by ball milling Afterwards, place it in a flowing argon atmosphere and raise the temperature to 900°C at a rate of 20°C/min, keep it warm for 3 hours, then turn off the power and let it cool down to room temperature naturally. According to the XRD phase analysis of the obtained sample, the synthesized product is two phases of SnSb and Sn, and no other impurity phase exists.

Add 12wt% conductive agent acetylene black to the synthesized material, 8wt% binder PVDF to make a slurry, evenly spread it on copper platinum, after drying, clamp it into a circular pole piece, and form a test battery with metal lithium. Carry out constant current charge and discharge experiments, the charge and discharge current is 100mA/g, and the charge and discharge voltage range is controlled between 0.01-1.2V. The initial reversible capacity of the prepared SnSb alloy negative electrode material is above 730mAh/g.

Claims (4)

1, a kind of preparation method of Sn-Sb alloy material for negative electrode of lithium ion cell is characterized in that, the step of preparation is:

1) with SnO ₂, Sb ₂O ₃Carry out weighing proportioning, SnO with carbon dust ₂, Sb ₂O ₃The addition atomic ratio 3: 1～1: 3 of pressing Sn/Sb calculate, the addition of carbon dust is calculated by chemical formula (1), and mixes;

(1)

2) mixture is placed be connected with flowing nitrogen, argon gas or contain 5～10vol%H ₂The heating furnace of argon gas atmosphere in, reach temperature required 700-1100 ℃ with the heating rate of 5～30 ℃/min, be incubated 1-5 hour;

3) with the heating furnace outage, cool to room temperature naturally with the furnace.

2, by the preparation method of the described Sn-Sb alloy material for negative electrode of lithium ion cell of claim 1, it is characterized in that the particle diameter of the oxide powder of described tin and antimony is micron order, submicron order or nanoscale.

By the preparation method of the described Sn-Sb alloy material for negative electrode of lithium ion cell of claim 1, it is characterized in that 3, described mixing is adopted wet mixing or done and mix.

4, by the preparation method of the described Sn-Sb alloy material for negative electrode of lithium ion cell of claim 1, it is characterized in that described carbon dust is activated carbon or carbon black.

Images