CN104150543B - A kind of Cu 2+, Ce 4+, Ag +doping ferric fluoride composite positive pole and preparation method - Google Patents

Abstract

A Cu ²⁺ , Ce ⁴⁺ , Ag ⁺ doped modified ferric fluoride positive electrode material and its preparation method. In the method, copper salt, cerium salt, silver salt and synthetic raw materials are ball-milled in a high-energy ball mill for a period of time and heat-treated. That is, the FeF ₃ cathode material is obtained. Cu ²⁺ helps to increase its discharge potential and energy density by partially occupying the coordination of FeF ₃ iron ions; while doping with high-valent Ce ⁴⁺ helps to improve the specific capacity of the material; through Ag ²⁺ doping, Reduce the conversion reaction activation energy during charging; this helps to improve its rate characteristics and energy density, thereby improving the comprehensive electrochemical performance of the material.

Description

A kind of Cu2+, Ce4+, Ag+ doped ferric fluoride composite cathode material and preparation method

technical field

The invention relates to the technical field of a method for manufacturing a high-capacity iron fluoride composite lithium battery cathode material.

Background technique

Lithium-ion secondary batteries have the absolute advantages of high volume, weight-to-energy ratio, high voltage, low self-discharge rate, no memory effect, long cycle life, and high power density. Currently, the global mobile power market has an annual share of more than 30 billion US dollars and Gradually grow at a rate of more than 10%. Especially in recent years, with the gradual depletion of fossil energy, new energy sources such as solar energy, wind energy, and biomass energy have gradually become alternatives to traditional energy sources. Among them, wind energy and solar energy are intermittent, and a large amount of energy is used simultaneously to meet the needs of continuous power supply Energy storage batteries; urban air quality problems caused by vehicle exhaust are becoming more and more serious, and the vigorous advocacy and development of electric vehicles (EV) or hybrid electric vehicles (HEV) has reached an urgent point; these demands provide an explosive growth point for lithium-ion batteries , but also put forward higher requirements on the performance of lithium-ion batteries.

The improvement of the capacity of lithium-ion battery cathode materials is the primary goal of scientific research. The research and development of high-capacity cathode materials can alleviate the current situation that lithium-ion battery packs are large in size, heavy in weight, and high in price and cannot meet the needs of high-power consumption and high-power equipment. . However, since the commercialization of lithium-ion batteries in 1991, the actual specific capacity of cathode materials has always hovered between 100-180mAh/g, and the low specific capacity of cathode materials has become a bottleneck for improving the specific energy of lithium-ion batteries. At present, the most widely used positive electrode material for commercial lithium-ion batteries is LiCoO ₂ . The theoretical specific capacity of lithium cobalt oxide is 274mAh/g, but the actual specific capacity is between 130-140mAh/g. Moreover, cobalt is a strategic material and is expensive. And have greater toxicity. Therefore, in recent years, researchers from all over the world have been committed to the research and development of new lithium-ion battery cathode materials. Up to now, there have been dozens of lithium-ion battery cathode materials screened out, but there are real potential commercial application prospects or have already appeared. There are very few cathode materials on the market. For example, spinel lithium manganese oxide LiMn ₂ O ₄ has lower cost, is easier to prepare, and has better safety performance. However, the capacity is relatively low. The theoretical capacity is 148mAh/g, and the actual capacity is 100-120mAh/g. The capacity cycle retention of this material is not good, and the capacity fades quickly at high temperature. The John-Teller effect of Mn ³⁺ and its dissolution in electrolytes have long puzzled researchers. Although LiNiO ₂ and LiMnO ₂ with layered structure have relatively large theoretical specific capacities of 275mAh/g and 285mAh/g respectively, they are very difficult to prepare, have poor thermal stability, poor cycle performance, and rapid capacity decay. At present, the lithium iron phosphate LiFePO ₄ that has been gradually commercialized has low cost, good thermal stability, and environmental friendliness, but its theoretical capacity is only about 170mAh/g, while the actual capacity is about 140mAh/g [ChunSY, BlokingJT, ChiangYM, NatureMaterials, 2002, 1:123-128.]. At present, only lithium vanadate Li _1+x V ₃ O ₈ is the only positive electrode material with a specific capacity exceeding 200mAh/g in the market. Li _1+x V ₃ O ₈ can have a capacity even close to 300mAh/g, but its discharge The average voltage is lower and the vanadium oxides tend to be more toxic during production. In recent years, high-lithium ratio cathode materials, especially manganese-based manganese-nickel binary and manganese-based manganese-nickel-cobalt ternary solid solution systems, have a capacity ratio of more than 200mAh/g, higher thermal Stability and relatively low cost have attracted people's attention, but the performance of this material at high rates is very unsatisfactory, which limits its application in power batteries [Young-SikHong, YongJoonPark, et al., SolidStateIonics, 2005, 176: 1035-1042].

In recent years, _FeF3 material has entered the field of vision of researchers due to its high capacity and low raw material price. The working principle of FeF ₃ material is different from that of traditional lithium-ion battery cathode materials. There are spaces for lithium ions to intercalate or deintercalate in both the positive and negative electrodes of traditional lithium-ion batteries, while the lithium ions in the electrolyte travel back and forth between the positive and negative electrodes. Intercalation and deintercalation with discharge as proposed by Armand et al. "rocking chair" battery. _FeF3 is a conversion material, that is, during the entire discharge process, _FeF3 undergoes the following changes [BadwayF, CosandeyF, PereiraN, et al., ElectrodesforLiBatteries, J. Electrochem.Soc., 2003, 150(10): A1318-A1327.]:

Li ⁺ +FeF ₃ +e→LiFeF ₃ ----(1)

LiFeF ₃ +2Li ⁺ +2e→3LiF+Fe-(2)

The first step is the lithium ion intercalation of traditional lithium ions, and the lattice does not change much during the whole reaction process; while the second step is the metal replacement reaction, the matrix lattice is completely transformed. The theoretical capacity of the first step is 237mAh.g ^-1 ; the complete reaction can realize the conversion of 3 electrons, that is, the theoretical capacity of the second stage is 474mAh.g ^-1 ; the total capacity is 711mAh.g ^-1 ; although the material is not clearly The discharge platform has a relatively low average discharge voltage, but its theoretical specific capacity close to 800mAh.g ^-1 has been highly valued by material researchers. However, after studies by scholars such as Arai, Amatucci [BadwayF, PereiraN, CosandeyF, et al., J. Electrochem.Soc., 2003, 150(9): A1209-A1218.] found that most of its theoretical capacity should be released Getting out is not an easy task. First of all, the electronic conductivity of FeF ₃ is very poor, and its lithium ion conductivity is also very low, and the converted product LiF is an electronic insulator, and the ability to conduct lithium ions is also very poor, resulting in the effective utilization of FeF ₃ materials. The capacity is low, the charge and discharge current is small, and the rate characteristics are poor; the polarization during the charge and discharge process is serious, and the charge and discharge voltage platform is very different; the capacity retention is not good, and the capacity decays seriously with the increase of charge and discharge times. In the early stage of research, only a reversible capacity of about 50-100mAh.g ^-1 could be released; later, Amatucci et al. improved their electrical conductivity by forming carbon/iron fluoride nanocomposites (CMFNCs) with carbon materials after long-term high-energy ball milling, which greatly Its electrochemical performance is improved, and its discharge capacity can reach about 200mAh.g ^-1 [BadwayF, MansourA.N, PereiraN, et al., Chem.Mater., 2007, 19(17): 4129-4141.]. However, the attachment of carbon materials on the surface of positive electrode material particles mainly depends on physical adsorption, and it is difficult to form a complete carbon conductive link. Here, as mentioned earlier, the discharge voltage of this material is relatively low, and the effective energy density is not very good; finally, because FeF ₃ material is slightly soluble in cold water, it is usually prepared by the ethanol liquid phase method, during the synthesis process A large amount of ethanol needs to be used, which is not economical. Not suitable for industrial applications.

Therefore, to improve the electrochemical performance of FeF ₃ positive electrode materials, it is necessary to find a method that can improve the conductivity and energy density of lithium ions, and at the same time make the preparation process as simple as possible, low in cost, convenient and quick, which is of great importance to the development and development of FeF ₃ positive electrode materials. Application is especially important.

Contents of the invention

The present invention proposes a Cu2 ⁺ , Ce ⁴⁺ , Ag ⁺ doped modified ferric fluoride cathode material and a preparation method aiming at the existing background technology. In the method, copper salt, cerium salt, silver salt and synthetic raw materials are ball-milled in a high-energy ball mill for a period of time and heat-treated to obtain the _FeF3 positive electrode material. Cu2 ⁺ helps to increase its discharge potential and energy density by partially occupying FeF ₃ iron ion coordination; and through high-valence Ce ⁴⁺ doping, it helps to increase the specific capacity of the material; through Ag ⁺ doping, it reduces the charge Time conversion reaction activation energy, which helps to improve its rate characteristics, energy density and cycle performance, thereby improving the comprehensive electrochemical performance of the material.

Cu ²⁺ , Ce ⁴⁺ , Ag ⁺ doped modified ferric fluoride cathode material and its preparation method, characterized in that the ratio by weight of ferric salt containing crystalline water and ammonium fluoride (molar ratio is 1.0:3.0-3.6) is 3-15% of copper salt, cerium salt, silver salt, 0.1-3.0% by weight of ethanol, 0.5-3.0% by weight of additives, after 5-20 hours of ball milling at room temperature under the protection of atmosphere in a high-energy ball mill, Take out the material, heat up to 300-450 degrees under the protection of a mixed gas of 5% hydrogen and 95% argon for 2-10 hours, and then cool down to prepare Cu2 ⁺ , Ce ⁴⁺ , Ag ⁺ doped modified FeF ₃ composite Cathode material.

The above-mentioned iron salt containing crystalline water is one of Fe(NO ₃ ) ₃ 9H ₂ O, FeCl ₃ 6H ₂ O and Fe ₂ (SO ₄ ) ₃ 9H ₂ O;

The above-mentioned copper salt is one of Cu(C ₂ O ₄ )·0.5H ₂ O, Cu(NO ₃ ) ₂ ·3H ₂ O and CuSO ₄ ·5H ₂ O;

The above-mentioned cerium salt is Ce(NH ₄ ) ₂ (NO ₃ ) ₆ ;

The above-mentioned silver salt is AgNO ₃ ;

The above-mentioned additive is one of Tween-80, span-60 and tx-10;

The above-mentioned atmosphere is high-purity nitrogen or high-purity argon;

Figure 1 is a diagram of the charge capacity, discharge capacity and charge-discharge efficiency of the material in the first 10 cycles, the voltage range is 2.0V-4.0V, and the charge-discharge current is 0.1C.

Compared with the prior art, the present invention has the advantages of: Cu ²⁺ helps to improve its discharge potential and energy density by partially occupying FeF ₃ iron ion coordination; and through high-valence Ce ⁴⁺ doping, it helps Improve the specific capacity of the material; through Ag ⁺ doping, reduce the conversion reaction activation energy during charging; through Cu ²⁺ , Ce ⁴⁺ , Ag ⁺ co-doping to improve the comprehensive electrochemical performance of the material.

Description of drawings

Figure 1 is the charge capacity, discharge capacity and charge-discharge efficiency diagram of the material for the first 10 cycles, the voltage range is 2.0V-4.0V, and the charge-discharge current is 0.1C.

detailed description

The present invention will be further described in detail below in conjunction with the implementation examples.

Example 1: Fe(NO ₃ ) ₃ 9H ₂ O and ammonium fluoride (molar ratio 1.0:3.2) and 3.2% by weight of Cu(C ₂ O ₄ )·0.5H ₂ O, the weight percentage is 3% Ce(NH ₄ ) ₂ (NO ₃ ) ₆ , 4% by weight of AgNO ₃ , 0.6% by weight of Tween-80 and 0.5% by weight of ethanol in a high-energy ball mill under the protection of high-purity nitrogen After 5 hours of ball milling at room temperature, the material was taken out, heated to 450 degrees under the protection of a mixed gas of 5% hydrogen and 95% argon, and then cooled for 3 hours to prepare Cu ²⁺ , Ce ⁴⁺ , Ag ⁺ doped modified FeF ₃ cathode material.

Example 2: Combining FeCl ₃ .6H ₂ O and ammonium fluoride (molar ratio 1.0:3.6) with 6.5% by weight of Cu(C ₂ O ₄ )·0.5H ₂ O and 13% by weight of Ce (NH ₄ ) ₂ (NO ₃ ) ₆ , AgNO ₃ with a weight percentage of 8%, span-60 with a weight percentage of 0.9% and ethanol with a weight percentage of 1.0% were ball milled at room temperature for 20 hours in a high-energy ball mill under the protection of high-purity nitrogen. , take out the material, under the protection of the mixed gas of 5% hydrogen and 95% argon, the temperature is raised to 400°C for 6.5 hours and then cooled to prepare Cu ²⁺ , Ce ⁴⁺ , Ag ⁺ doped modified FeF ₃ cathode material.

Example 3: Combining Fe ₂ (SO ₄ ) ₃ .9H ₂ O and ammonium fluoride (molar ratio 1.0:3.5) with 15% by weight Cu(NO ₃ ) ₂ .3H ₂ O, 7.5% by weight % Ce(NH ₄ ) ₂ (NO ₃ ) ₆ , 13% by weight of AgNO ₃ , 1.5% by weight of Tween-80 and 2.0% by weight of ethanol in a high-energy ball mill under the protection of high-purity argon After 10 hours of ball milling at room temperature, the material was taken out, heated to 350 degrees under the protection of a mixed gas of 5% hydrogen and 95% argon, and then cooled for 8.5 hours to prepare Cu2 ⁺ , Ce ⁴⁺ , Ag ⁺ doped modified FeF ₃ Cathode material.

Example 4: Combining FeCl ₃ .6H ₂ O and ammonium fluoride (molar ratio 1.0:3.3) with 8% by weight of CuSO ₄ .5H ₂ O and 5.5% by weight of Ce(NH ₄ ) ₂ ( NO ₃ ) ₆ , AgNO ₃ with a weight percentage of 6%, tx-10 with a weight percentage of 3.0% and ethanol with a weight percentage of 3.0% were ball milled at room temperature for 15 hours under the protection of high-purity argon in a high-energy ball mill, and then the materials were taken out and placed in Under the protection of a mixed gas of 5% hydrogen and 95% argon, the temperature was raised to 450°C for 10 hours and then cooled to prepare a Cu ²⁺ , Ce ⁴⁺ , Ag ⁺ doped modified FeF ₃ cathode material.

Example 5: Combining Fe(NO ₃ ) ₃ .9H ₂ O and ammonium fluoride (molar ratio 1.0:3.5) with 8% by weight of CuSO ₄ .5H ₂ O and 5.6% by weight of Ce(NH ₄ ) ₂ (NO ₃ ) ₆ , 11% by weight of AgNO ₃ , 2.0% by weight of span-60, and 0.1% by weight of ethanol were ball milled in a high-energy ball mill at room temperature for 12 hours under the protection of high-purity nitrogen, and then taken out The material is heated to 300 degrees under the protection of a mixed gas of 5% hydrogen and 95% argon for 6 hours and then cooled to prepare Cu ²⁺ , Ce ⁴⁺ , Ag ⁺ doped modified FeF ₃ cathode material.

Claims (1)

1. a Cu ²⁺, Ce ⁴⁺, Ag ⁺doping ferric fluoride composite positive pole and preparation method; it is characterized in that by mol ratio be 1.0: 3.0-3.6 containing crystal water molysite and Neutral ammonium fluoride and weight percent be the mantoquita of 3-15%, cerium salt, silver salt, weight percent be the ethanol of 0.1-3.0%, weight percent is the auxiliary agent of 0.5-3.0%; normal temperature ball milling after 5-20 hour under atmosphere protection in high energy ball mill; take out material; 5% hydrogen and 95% argon gas mixed gas protected under be warmed up to 300-450 degree constant temperature and cool after 2-10 hour, prepare Cu ²⁺, Ce ⁴⁺, Ag ⁺the FeF of doping vario-property ₃composite positive pole; Wherein containing crystal water molysite is Fe (NO ₃) ₃9H ₂o, FeCl ₃6H ₂o and Fe ₂(SO ₄) ₃9H ₂one in O; Mantoquita is Cu (C ₂o ₄) 0.5H ₂o, Cu (NO ₃) ₂3H ₂o and CuSO ₄5H ₂one in O; Cerium salt is Ce (NH ₄) ₂(NO ₃) ₆; Silver salt is AgNO ₃; Above-mentioned auxiliary agent is tween-80, the one in span-60 and tx-10; Above-mentioned atmosphere is high pure nitrogen or high-purity argon gas.