CN106910891A - A kind of transition metal fluorides load the preparation method of boron dopen Nano carbon composite - Google Patents

Abstract

The invention belongs to the technical field of nanometer materials, in particular to a method for preparing transition metal fluoride-supported boron-doped nanometer carbon materials. The method of the invention uses transition metal fluoride, borohydride and nano-carbon material as raw materials, and through ball milling and heating, the transition metal fluoride-loaded boron-doped nano-carbon composite material can be prepared. The method has the characteristics of low cost, high efficiency, economy and environmental protection, and strong universal applicability.

Description

A preparation method of transition metal fluoride-supported boron-doped nano-carbon composite material

technical field

The invention belongs to the technical field of nanometer materials, and in particular relates to a preparation method of transition metal fluoride-supported boron-doped nano-carbon composite material.

Background technique

Lithium-ion batteries have the advantages of high energy density, long cycle life, and high conversion efficiency, and are widely used in high-efficiency energy storage systems such as electric vehicles and smart grids. The positive/negative electrode materials of current commercial lithium-ion batteries are intercalation type (for example: graphite negative electrode; LiCoO ₂ positive electrode). The theoretical specific capacity of these intercalation positive and negative electrode materials is low (the theoretical specific capacity of graphite negative electrode is only: 375mAh g ^-1 , the theoretical specific capacity of LiCoO ₂ positive electrode is only: 140mAh g ^-1 ), which seriously restricts the lithium ion The energy density of the battery. [1,2] Therefore, the development of positive/negative electrode materials with high specific capacity is the key to improving the energy density of lithium-ion batteries.

In recent years, a series of studies have shown that transition metal fluorides (such as: FeF ₃ , FeF ₂ , NiF ₂ , CoF ₃ , CoF ₂ , NiF ₃ , MnF ₂ , CuF ₂ , TiF ₄ , etc.) have large specific capacity and high energy density , cheap and non-polluting, etc., it is a class of positive/negative electrode materials with great potential for lithium-ion batteries. [3-8] Among them, the positive electrode material is represented by FeF ₃ , its theoretical specific capacity is as high as 712mAh g ^-1 , the average working voltage is 2.74 V, and the energy density can reach 1951 Wh kg ^-1 ; [4,8-10] the negative electrode The material is represented by MnF ₂ , its theoretical specific capacity is as high as 577mAh g ^-1 , and its working voltage is 0.8 V. [11,12] However, transition metal fluorides have problems such as poor conductivity, large volume change, and severe voltage hysteresis during the delithiation/intercalation process, resulting in rapid capacity decay and poor cycle stability. [4,11] Researchers have conducted a series of research work on these issues. Among them, converting transition metal fluoride pre-intercalated lithium into transition metal/lithium fluoride, and further compounding with nano-carbon materials is a commonly used solution at present, for example: Fe/LiF/ The graphene composite can still maintain a specific capacity of 150 ^mAh g after 180 cycles. [13] The improvement of transition metal fluoride deintercalation performance is attributed to: firstly, the construction of carbon composite system can effectively alleviate the volume change during the cycle and enhance the conductivity of the system; secondly, the positive electrode such as FeF ₃ after pre-intercalation of lithium The material can be directly combined with graphite, silicon and other lithium-free negative electrodes to form a full battery, and the first Coulombic efficiency of negative electrode materials such as MnF ₂ is also significantly improved after pre-intercalation of lithium. The construction of transition metal/lithium fluoride/nanocarbon composites has the above significant advantages, but the following shortcomings remain:

(1) The long-term cycle performance is still difficult to meet the needs of practical applications, and it is necessary to further improve its cycle performance by introducing heteroatom-doped carbon materials[14];

(2) The preparation of transition metal/lithium fluoride/nano-carbon composites is generally achieved by spraying, ball milling, pyrolysis reduction, chemical deposition, hydrothermal and other methods. The preparation cost is high, the efficiency is low, it is not conducive to industrial production, and it is difficult to realize simultaneously Uniform doping of heteroatoms [15,16];

(3) The existing preparation methods generally use lithium fluoride and transition metals to be separately loaded on the carrier of nano-carbon materials, which makes it difficult to tightly combine lithium fluoride and transition metal nanoparticles, which increases the ion/energy density during the charging process. The atomic diffusion distance seriously affects the reversibility of the de-lithium/intercalation electrochemical reaction [13].

Therefore, it is of great significance to develop a low-cost and high-efficiency preparation method for simultaneously loading lithium fluoride and transition metal nanoparticles onto heteroatom-doped carbon materials.

references

[1] Croguennec, L.; Palacin, MR J. Am. Chem. Soc. 2015, 137 , 3140.

[2] Goodenough, JB; Kim, Y. Chem. Mater. 2010, 22 , 587.

[3] Li, H.; Richter, G.; Maier, J. Adv. Mater. 2003, 15 , 736.

[4]Li, H.; Balaya, P.; Maier, J. J. Electrochem. Soc. 2004, 151 , 1878.

[5]Amatucci, GG; Pereira, N. J. Fluorine Chem. 2007, 128 , 243.

[6]Teng, YT; Pramana, SS; Ding, J.; Wu, T.; Yazami, R. Electrochim. Acta 2013, 107 , 301.

[7]Hua, X.; Robert, R.; Du, LS; Wiaderek, KM; Leskes , M.; Chapman, KW; Chupas, PJ; Grey, CP J. Phys .

[8]Wang, F.; Robert, R.; Chernova, NA; Pereira, N.; Omenya, F.;Badway, F.; .; Volkov, V.; Su, D.; Key, B.; Whittingham, MS; Grey, CP; Amatucci , GG; Zhu, Y.; Graetz, J. J. Am. 18828.

[9]Liu, P.; Vajo, JJ; Wang, JS; Li, W.; Liu, J. J. Phys. Chem. C 2012, 116 , 6467.

[10]Ma, DL; Cao, ZY; Wang, HG; Huang, XL; Wang, LM; Zhang, XB Energy Environ. Sci. 2012, 5 , 8538.

[11]Rui, K.; Wen, Z.; Lu, Y.; Jin, J.; Shen, C. Adv. Energy Mater. 2015, 5 , 1401716.

[12]Rui, K.; Wen, Z.; Huang, X.; Lu, Y.; Jin, J.; Shen, C. Phys. Chem. Chem. Phys. 2016, 18 , 3780.

[13]Ma, R.; Dong, Y.; Xi, L.; Yang, S.; Lu, Z.; Chung, C. ACS Appl. Mater. Interfaces 2013, 5 , 892.

[14]Kumagae, K.; Okazaki, K.; Matsui, K.; Horino, H.; Hirai, T.; Yamaki, J.; Ogumi, Z. J. Electrochem. Soc. 2016, 163 , 1633.

[15]Sun, Y.; Liu, N.; Cui, Y. Nature Energy 2016, 1 , 16071.

[16] Rui, K.; Wen, Z.; Lu, Y.; Shen, C.; Jin, J. ACS Appl. Mater. Interfaces 2016, 8 , 1819.

Contents of the invention

The purpose of the present invention is to provide a preparation method of transition metal fluoride-supported boron-doped nano-carbon composite material, so that the nanoparticles of transition metal and lithium fluoride are closely combined and dispersed on the nano-carbon material matrix, and the boron can be simultaneously realized. doping. The method has the characteristics of low cost, high efficiency, economy and environmental protection, and strong universal applicability.

The preparation method of the transition metal fluoride-supported boron-doped nano-carbon composite material provided by the present invention, the specific steps are as follows:

(1) Add transition metal fluoride, borohydride (LiBH ₄ ) and nano-carbon material into the ball milling tank, the molar ratio of transition metal fluoride to LiBH ₄ is 1:1-1:4, the mass of nano-carbon material Accounting for the overall mass ratio of 5wt% to 80wt%, ball milling in a protective atmosphere for 2 to 48 hours;

Preferably, the molar ratio of transition metal fluoride to _LiBH4 is 1:1-1:2.5, the mass ratio of nano-carbon material to the total mass is 5wt%-40wt%, and the ball milling time is 20-48 hours;

(2) Heat the ball milled product to 120-500°C under dynamic vacuum condition, keep it warm for 1-48 hours, then cool down to room temperature, collect the product, and obtain the transition metal fluoride-supported boron-doped nano-carbon composite material.

Preferably, the heating temperature is 320-400° C., and the holding time is 30-45 hours.

In step (1), the transition metal fluoride is any one of FeF ₃ , FeF ₂ , NiF ₂ , NiF ₃ , CoF ₃ , CoF ₂ , MnF ₂ , CuF ₂ , TiF ₄ , ZnF ₂ , or Several of them. The nano-carbon material is any one of graphite, graphene, single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon nanorods, carbon fibers, carbon nanowires, carbon nanorods, or several of them. The protective atmosphere is any one of hydrogen, nitrogen, argon, and helium.

In step (2), the transition metal is any one of Fe, Ti, Ni, Co, Cu, Mn, Zn, or several of them.

The positive effect of the inventive method is:

(1) This method is easy to operate, and the required ball mill and vacuum degassing device are all common industrial production equipment, and the maximum temperature required is only 500°C. Therefore, this method has high efficiency and can be applied to large-scale industrial production;

(2) There is no waste liquid/material discharge during the preparation process of this method, and the required transition metal fluorides, lithium borohydride and nano-carbon materials are all common industrial raw materials, so this method is economical and environmentally friendly, and the production cost is low;

(3) This method can prepare boron-doped nano-carbon composite materials supported by Mn, Fe, Ti, Ni, Co, Cu, Zn and other transition metal fluorides. In the composite materials, both lithium fluoride and transition metals are prepared as nanoparticles The form is closely combined and uniformly dispersed on the nano-carbon carrier, and the content, morphology and distribution of the doping element boron can be further adjusted according to the preparation conditions.

Description of drawings

Figure 1 is the X-ray diffraction pattern of the synthesized boron-doped Mn/LiF/graphite composite material.

Fig. 2 is a high-magnification transmission electron microscope image of the synthesized boron-doped Mn/LiF/graphite composite material.

Figure 3 is the cyclic lithium insertion and desorption performance of the synthesized boron-doped Mn/LiF/graphite composite material.

Figure 4 is a scanning electron microscope image of the as-synthesized boron-doped Fe/LiF/graphite composite.

Fig. 5 is the X-ray energy distribution spectrum of the synthesized boron-doped Fe/LiF/graphite composite material.

detailed description

The preparation method of the present invention will be described in detail below in conjunction with examples and accompanying drawings.

Example 1: Preparation of boron-doped Mn/LiF/graphite composite material and its electrochemical lithium storage properties

In an inert gas glove box, mix 0.465g MnF ₂ , 0.22 g LiBH ₄ and 0.2 g graphite powder into a ball mill jar, and ball mill for 24 h under a hydrogen atmosphere, the ball milling speed is 400 rpm, and the ball-to-material ratio is 30 :1. The ball-milled product was continuously evacuated, and the temperature was gradually raised to 140 °C, and after 12 h of heat preservation, it was naturally lowered to room temperature, and a boron-doped Mn/LiF/graphite composite material could be obtained. The X-ray diffraction patterns and high-magnification transmission electron microscope images of the synthesized boron-doped Mn/LiF/graphite composites are shown in Figures 1 and 2, respectively. Figure 1 shows that this method successfully prepared LiF. It can be seen in Fig. 2 that nanoparticles of Mn and boron are dispersed on the amorphous graphite layer. Combining Fig. 1 and Fig. 2 shows that this method can not only prepare transition metal/lithium fluoride/nano-carbon composite material, but also realize boron doping simultaneously. Figure 3 presents the long-term cycle performance of the as-prepared boron-doped Mn/LiF/graphite composites. At a current density of 1 A g ^-1 , after 1500 cycles, the synthesized boron-doped Mn/LiF/graphite composite can still maintain a specific capacity of 423 mAh g ^-1 , indicating that the boron-doped The heterogeneous Mn/LiF/graphite composites have excellent cycle performance.

Embodiment 2: the preparation of the Fe/LiF/graphite composite material of boron doping

In an inert gas glove box, 0.47 g FeF ₂ , 0.25 g LiBH ₄ and 0.15 g graphite powder were mixed into a ball mill jar, and ball milled for 48 h under an argon atmosphere, the ball milling speed was 400 rpm, and the ball-to-material ratio was 40:1. The ball-milled product was continuously evacuated, and the temperature was gradually raised to 450 °C, and then it was naturally lowered to room temperature after 12 hours of heat preservation, and a boron-doped Fe/LiF/graphite composite material could be obtained. Figure 4 and Figure 5 show the scanning electron microscope of the prepared boron-doped Fe/LiF/graphite composite material and its corresponding X-ray energy distribution spectrum, respectively. It can be seen in Fig. 4 that the particle size of the prepared Fe/Li/graphite composite material is about 50nm. B, C, F, and Fe elements can be clearly seen in Figure 5, indicating that this method can prepare Fe/LiF/graphite composite materials and achieve boron doping simultaneously.

Embodiment 3: the preparation of the Ni/LiF/graphene composite material of boron doping

In an inert gas glove box, 0.485 g NiF ₂ , 0.32 g LiBH ₄ and 0.1 g graphene powder were mixed and put into a ball mill jar, and ball milled for 6 h under a nitrogen atmosphere, the ball milling speed was 350 rpm, and the ball-to-material ratio was 40:1. The ball-milled product was continuously evacuated, and the temperature was gradually raised to 350 °C, and after 6 h of heat preservation, it was naturally lowered to room temperature, and a boron-doped Ni/LiF/graphene composite material could be obtained.

Embodiment 4: the preparation of the Co/LiF/ multi-walled carbon nanotube composite material of boron doping

In an inert gas glove box, 0.485 g CoF ₂ , 0.25 g LiBH ₄ and 0.2 g multi-walled carbon nanotube powder were mixed into a ball mill jar, and ball milled in a hydrogen atmosphere for 4 h at a ball milling speed of 300 rpm. The material ratio is 30:1. The ball-milled product was continuously evacuated, and the temperature was gradually raised to 500 °C, and after 10 h of heat preservation, it was naturally lowered to room temperature, and the boron-doped Co/LiF/multi-walled carbon nanotube composite material could be obtained.

Embodiment 5: the preparation of boron-doped Mn/LiF/single-wall carbon nanotube composite material

In an inert gas glove box, 0.47 g MnF ₂ , 0.3 g LiBH ₄ , and 0.25 g single-walled carbon nanotube powder were mixed into a ball mill jar, and ball milled for 36 h under a hydrogen atmosphere at a ball milling speed of 300 rpm. The material ratio is 40:1. The ball-milled product was continuously evacuated, and the temperature was gradually raised to 280 °C, and after 12 hours of heat preservation, it was naturally lowered to room temperature, and the boron-doped Mn/LiF/single-walled carbon nanotube composite material could be obtained.

Claims (3)

1. a kind of transition metal fluorides load the preparation method of boron dopen Nano carbon composite, comprise the following steps that：

（1）By transition metal fluorides, LiBH₄, nano-carbon material be added in ball grinder, transition metal fluorides and LiBH₄'s Molar ratio is 1:1~1：4, the quality of nano-carbon material accounts for oeverall quality ratio for 5wt%~80wt%, the ball milling under protective atmosphere 2~48 hours；

（2）Ball milling product is heated to 120~500 DEG C under the conditions of dynamic vacuum, and is incubated 1~48 hour, be then cooled to Room temperature, collects product, obtains final product transition metal fluorides load boron dopen Nano carbon composite.

2. the preparation method according to claim, it is characterised in that step（1）In, described transition metal fluorides are FeF₃、FeF₂、NiF₂、NiF₃、CoF₃、CoF₂、MnF₂、CuF₂、TiF₄、ZnF₂In any one, it is or therein several；It is described Nano-carbon material for graphite, Graphene, SWCN, multi-walled carbon nano-tubes, carbon nano rod, carbon fiber, carbon nanocoils, Any one in carbon nanometer rod, it is or therein several；Described protective atmosphere is any in hydrogen, nitrogen, argon gas, helium It is a kind of.

3. the preparation method according to claim, it is characterised in that step（2）In, described transition metal is Fe, Ti, Any one in Ni, Co, Cu, Mn, Zn, or it is therein several.