CN104617285B - Lithium ion battery negative electrode material Li2ZnTi3O8 preparation method - Google Patents

Abstract

_The invention relates to a preparation method _{of Li2ZnTi3O8} , a negative electrode material of a lithium ion battery. The purpose of the method is to solve the disadvantages of high temperature, long reaction time, high cost and toxicity of organic substances in the current preparation method of lithium zinc titanate material. The technical scheme is as follows: by mixing titanium dioxide (TiO ₂ ), lithium carbonate (Li ₂ CO ₃ ), zinc acetate (Zn(CH ₃ COO) ₂ ·2H ₂ O) and mixed molten salts sodium chloride (NaCl) and potassium chloride (KCl) is mixed and stirred, and the liquid environment provided by the molten salt is beneficial to the full contact reaction of the reactant precursor during the high-temperature calcination process. The prepared nano-scale material has uniform particle size, no obvious agglomeration phenomenon, and accumulation between particles. Pores, these structural features are beneficial to the electrochemical performance of the material.

Description

Preparation method of lithium ion battery negative electrode material Li2ZnTi3O8

Technical field:

The invention relates to a preparation method of a lithium ion battery negative electrode material, that is, a method for synthesizing lithium ion negative electrode material zinc lithium titanate by a molten salt method.

Background technique:

With the continuous development of consumer electronics and the development of zero-emission electric vehicles, the requirements for lithium-ion batteries are getting higher and higher, especially for discharge capacity and service life. Compared with traditional batteries, lithium-ion batteries have the advantages of high voltage platform, high specific capacity, long cycle life, low self-discharge and no memory effect. At present, graphite is mostly used as anode material for commercialized lithium-ion batteries, which will lead to the growth of dendrite lithium, which will pierce the separator and cause safety problems. Therefore, finding alternative safe and high-capacity anode materials has become the focus of research.

Spinel-type lithium titanate anode material has the advantages of stable structure, small volume change during charge and discharge, and good cycle stability, but there are also obvious disadvantages, namely low electronic conductivity, which limits its high-rate performance. Lithium zinc titanate (Li ₂ ZnTi ₃ O ₈ ) has the function of reversible intercalation and deintercalation of lithium ions, high discharge capacity, good high rate performance, stable structure, good cycle performance, safety, non-toxicity, and cheap raw materials. An ideal anode material to replace lithium titanate.

The synthesis methods of zinc lithium titanate currently used include sol-gel method and high-temperature solid-phase method. The sol-gel method requires tetrabutyl titanate or titanium isopropoxide, and the cost of raw materials is high and toxic; the high-temperature solid-phase method is simple to prepare, but the prepared material has large secondary particles and obvious agglomeration . In addition, the materials prepared by the solid-state method have low discharge capacity at high rates and poor cycle performance, which limits their applications.

Invention content:

The purpose of the present invention is to address the disadvantages of high temperature, long reaction time, high cost and toxicity of organic substances in the current preparation method of zinc lithium titanate material, and adopt the molten salt method to synthesize lithium ion negative electrode material zinc lithium titanate, so as to overcome the disadvantages of synthesis Such a disadvantage is the high temperature environment required.

The technical scheme is as follows:

(1) Weighing of raw materials and molten salt: titanium dioxide (TiO ₂ ), lithium carbonate (Li ₂ CO ₃ ), zinc acetate (Zn(CH ₃ COO) ₂ ·2H ₂ O), molten salt according to the molar ratio of 3 : 1: 1: (2‐4) preparation, the molten salt is one or a mixture of sodium chloride (NaCl) and potassium chloride (KCl);

(2) Put titanium dioxide (TiO ₂ ), lithium carbonate (Li ₂ CO ₃ ), zinc acetate (Zn(CH ₃ COO) ₂ 2H ₂ O), and molten salt into a high-energy ball mill tank, and weigh a certain amount and proportion of Put the agate ball into a high-energy ball mill jar, add an appropriate amount of ball milling aid, and mill for 4 hours at 200-400r/min; the agate ball includes two types, namely a large ball and a small ball with different diameters and qualities;

(3) The mixture after the ball milling was dried for 24 hours in an air blast oven at 80 degrees Celsius;

(4) Grinding the dried mixture into powder in an agate mortar;

(5) putting the powder mixture into a muffle furnace for calcination at 800 degrees Celsius for 3 hours;

(6) Washing the calcined product with deionized water, centrifuging, and drying to obtain the final product.

The molten salt is preferably a mixture of NaCl and KCl, and the molar ratio of the two is 1:1.

Titanium dioxide (TiO ₂ ), lithium carbonate (Li ₂ CO ₃ ), zinc acetate (Zn(CH ₃ COO) ₂ 2H ₂ O), and molten salt are any one of the following three according to the molar ratio:

3:1:1:2; 3:1:1:3; 3:1:1:4.

The ball milling aid is preferably ethanol, and the addition amount is: the molar ratio of ethanol to titanium dioxide is 30:1.

The present invention has the advantage over prior art that:

It uses the mixed molten salt to become a molten state at a certain temperature to provide a liquid environment for other substances to react, thereby reducing the high temperature environment required for material synthesis, and can prepare lithium zinc titanate in a short period of time with less energy. Thereby saving time and energy; sodium salt and potassium salt resources are abundant and cheap, easy to recycle and reuse.

Description of drawings:

Fig. 1 is the X-ray diffraction spectrogram of Li ₂ ZnTi ₃ O ₈ prepared in embodiment 2, and abscissa represents the angle that X-ray diffraction peak appears, and ordinate represents the intensity of diffraction peak; Adopt Rigaku D/max-ⅢA diffractometer The material is tested, the radiation source is a Cu target, the scanning speed is 4°/min, and the scanning angle range 2θ is 5-80°; the measured XRD pattern is compared with the standard card, and it is found that the detected main peak is consistent with the standard card The diffraction peaks in are in one-to-one correspondence, and no other impurity peaks appear, indicating that the Li ₂ ZnTi ₃ O ₈ prepared by the molten salt method is a pure phase.

Figure 2 is a scanning electron microscope image of Li ₂ ZnTi ₃ O ₈ prepared in Example 2, with a magnification of 50,000; it can be clearly seen from the figure that the particle size of the prepared material is about 100nm, the dispersion is good, and there is no obvious The agglomeration phenomenon exists, and there are stacked pores between the particles, which is beneficial to improve the electrochemical performance.

Figure 3 is a transmission electron microscope image of Li ₂ ZnTi ₃ O ₈ prepared in Example 2. From the figure, lattice diffraction fringes can be clearly seen, and there are no lattice fringes of other impurities, indicating that the prepared material is pure Mutually.

Fig. 4 is the charge and discharge curves of the first cycle and the second cycle of Li ₂ ZnTi ₃ O ₈ synthesized in Example 2 at a current density of 2.0 A g ^-1 .

Fig. 5 is a diagram of the cycle life of Li ₂ ZnTi ₃ O ₈ synthesized in Example 2 at different rates.

detailed description:

In order to further illustrate the present invention more clearly, the following specific examples will be used to further describe the present invention in detail.

Example 1:

Titanium dioxide (TiO ₂ ), lithium carbonate (Li ₂ CO ₃ ), zinc acetate (Zn(CH ₃ COO) ₂ ·2H ₂ O), and molten salt are prepared according to the molar ratio of 3:1:1:4. The molten salt is A mixture of NaCl﹑KCl, the molar ratio of the two is 1:1;

Put it in a high-energy ball mill jar (15 large balls and 30 small balls), add ethanol, the molar ratio of titanium dioxide to ethanol is = 1:30, and mill at 400r/min for 4 hours. Take it out, dry it in blast drying at 80 degrees Celsius for 24 hours, grind it and calcinate it in a muffle furnace at 800 degrees Celsius for 3 hours, wash it with deionized water three times after natural cooling, centrifuge, dry it, and grind it to obtain a lithium-ion battery The negative electrode material is lithium zinc titanate.

The active material lithium zinc titanate, conductive agent (Super P), and binder (PVDF) were mixed in a mass ratio of 80:10:10, and coated on a copper sheet with a film applicator to form a 16um thick sheet, dried and pressed A circular electrode sheet with a diameter of 0.785cm, with a lithium sheet as the counter electrode, 1mol/L LiPF ₆ /(EC:DMC=1:1, volume) as the electrolyte, PE/PP/PE three-layer composite microporous membrane As the separator, a coin-type 2032 cell was assembled in an argon-filled glove box. The assembled coin cell was charged and discharged at the rates of 1.0A g ^-1 and 2.0Ag ^-1 , and the voltage range was 0.05-3.0V. The results are shown in Figure 4 and Figure 5 . Under the rate of 2.0A g ^-1 , the initial discharge specific capacity is 192.19mAh/g, and after 100 charge-discharge cycles, the discharge specific capacity still reaches 126.04mAh/g, and the cycle performance is good without obvious attenuation.

Example 2:

Titanium dioxide (TiO ₂ ), lithium carbonate (Li ₂ CO ₃ ), zinc acetate (Zn(CH ₃ COO) ₂ ·2H ₂ O), and molten salt are prepared according to the molar ratio of 3:1:1:3, and other process parameters Same as Example 1.

Example 3:

Titanium dioxide (TiO ₂ ), lithium carbonate (Li ₂ CO ₃ ), zinc acetate (Zn(CH ₃ COO) ₂ ·2H ₂ O), and molten salt are prepared according to the molar ratio of 3:1:1:2, and other process parameters Same as Example 1.

Claims (2)

1. lithium ion battery negative material Li₂ZnTi₃O₈Preparation method it is characterised in that process is as follows：

(1) the weighing of raw material and fuse salt：Titanium dioxide, lithium carbonate, Zinc diacetate dihydrate, fuse salt are according to molfraction ratio 3：1：1：(2-4) prepare, described fuse salt is the mixture of sodium chloride and potassium chloride, the two mol ratio is 1:1；

(2) titanium dioxide, lithium carbonate, Zinc diacetate dihydrate, fuse salt are put in high-energy ball milling tank, weigh some and ratio The agate ball of example was put in high-energy ball milling tank, adds appropriate ball-milling additive, with 200-400r/min ball milling 4 hours；Described agate Ball includes two kinds of models, i.e. the diameter big ball different with quality and bead；Described ball-milling additive is ethanol, ethanol and titanium dioxide Mol ratio be 30:1；

(3) mixture after ball milling is dried 24 hours in 80 degrees Celsius of air dry ovens；

(4) by dry after mixture in agate mortar grind into powder；

(5) mixture of powders is put in Muffle furnace 800 degrees Celsius to calcine 3 hours；

(6) product after calcining is washed with deionized, centrifugation, dries and obtain final product.

2. lithium ion battery negative material Li according to claim 1₂ZnTi₃O₈Preparation method it is characterised in that two Titanium oxide, lithium carbonate, Zinc diacetate dihydrate, fuse salt are according to molfraction than for any one of following three kinds：3：1：1： 2；3：1：1：3；3：1：1：4.