CN106898754B - Application of heteroatom in preparation of carbon-phosphorus material of lithium-phosphorus battery, material and preparation method thereof - Google Patents

Abstract

The invention discloses the application of heteroatoms in the preparation of carbon phosphorus materials for lithium-phosphorus batteries and the materials and preparation methods thereof. Coconut shell carbon and/or Ketjen black are used as carbon sources, and P ₂ O ₅ and/or purple phosphorus are used as phosphorus source, and at the same time doped with heteroatoms to prepare carbon-phosphorus composite materials for lithium-phosphorus batteries.

Description

Application of heteroatoms in the preparation of carbon-phosphorus materials for lithium-phosphorus batteries and the materials and their preparation method

technical field

The invention relates to lithium-phosphorus battery technology, in particular to the application of heteroatoms in the preparation of carbon-phosphorus materials for lithium-phosphorus batteries, the material and a preparation method thereof.

Background technique

The establishment of a clean and efficient energy storage system is of great practical significance for promoting the country's social and economic progress and sustainable development. It is an urgent requirement for economic and social development to develop power batteries with high specific energy and increase the proportion of clean energy in my country's energy structure. To this end, the development of zero-emission electric vehicles is a strategic priority. However, the specific capacity of the existing lithium battery cathode materials is low (less than 200mAh/g), and the overall specific energy of the battery is less than 300Wh/kg. At the same time, limited by its own theoretical capacity, through material preparation and process optimization, its specific energy is difficult to have. greatly improved. The low specific energy of existing lithium batteries leads to short cruising range of electric vehicles, which has become a bottleneck restricting the rapid development of the industry.

The energy density of lithium-ion batteries is generally limited by the active material of the positive electrode. Most of the positive electrode materials of lithium-ion batteries are single-electron or less than single-electron intercalation reaction materials, resulting in a small specific capacity of the positive electrode material. At present, commercial cathode materials such as LiCoO2, LiNiO2, LiMnO2, LiFePO4, etc., are difficult to meet the requirements of high specific capacity lithium-ion batteries due to their low theoretical specific capacity (<200mAh/g). In organic electrolytes, non-metallic active materials with small molecular weight have high redox potential and multi-electron reaction characteristics, so they have a large theoretical specific capacity and are very suitable as cathode materials for lithium-ion batteries. For example, elemental phosphorus has a low molecular weight and has the characteristics of 3-electron reaction, and its theoretical capacity is 2596mAh/g, which is 30% higher than the theoretical specific capacity of elemental sulfur. If elemental phosphorus is used as the positive electrode active material of the secondary battery to form a new type of secondary battery system with lithium metal or lithium metal alloy, it will have a higher energy density.

The new lithium-phosphorus battery system can well meet the needs of electric vehicles for high specific energy power batteries, so it has become a hot research topic for scientists at home and abroad in recent years. The theoretical specific capacity of the negative electrode lithium is 3860mAh/g, and the positive electrode phosphorus is 2596mAh/g. Therefore, the theoretical specific energy of the lithium phosphorus battery reaches 2600Wh/kg, which is 8-10 times that of the traditional lithium battery. It is a known lithium battery system. And the high-rate discharge performance is excellent; in addition, phosphorus resources are abundant, cheap and environmentally friendly. Therefore, the lithium phosphorus battery system is gradually becoming the first choice for the development of high specific energy power batteries.

However, in practical production, due to the difficult synthesis of materials and low electrical conductivity, the materials have poor cycle life, fast capacity decay, poor rate performance, low initial charge-discharge efficiency, and poor low-temperature performance. Therefore, there is an urgent search for a cathode material for preparing and modifying lithium-phosphorus batteries. Firstly, the loading of phosphorus using the traditional method is low, and secondly, the loaded phosphorus easily reacts with the electrolyte to form polyphosphorus compounds during the battery cycle, which reduces the capacity and cycle stability of lithium-phosphorus batteries. For the first time, it was reported that elemental phosphorus was used in lithium-ion battery electrode materials by using high-pressure ball milling to prepare active materials by compounding expensive black phosphorus and conductive graphite (Advanced Materials, 2007, 19, 2465-2468). Red phosphorus and carbon material or conductive polymer composite material, after 60 cycles, not higher than 550mAh/g (CN101533900A). Among these synthetic active materials, the preparation conditions of black phosphorus are harsh, the price is high, and the cycle performance of red phosphorus batteries is not high, all of which have shortcomings.

SUMMARY OF THE INVENTION

In order to solve the deficiencies of the prior art, the present invention provides the application of heteroatoms in the preparation of carbon-phosphorus materials for lithium-phosphorus batteries and the materials and preparation methods thereof.

The technical scheme of the present invention is: the application of heteroatoms in the preparation of carbon-phosphorus composite materials for lithium-phosphorus batteries, wherein the heteroatoms are B, N, F, Si, S, Cl, As, Se, Br, Te, and I. at least one.

Another object of the present invention is to provide a lithium-phosphorus battery composite material, which uses coconut shell carbon and/or Ketjen black as carbon sources, P ₂ O ₅ and/or purple phosphorus as phosphorus sources, and is doped with heteroatoms at the same time. Composition of at least one of B, N, F, Si, S, Cl, As, Se, Br, Te, and I.

The present invention further provides a method for preparing the above-mentioned lithium-phosphorus battery composite material. Add to the reaction kettle, then add dispersant and reaction medium, the reaction temperature is 60～120℃, and the reaction time is 4～12 hours; (2) the reaction product of the above step (1) is taken out, and the mechanical stirring is uniform, and the stirring time is 8～24 hours. (3) washing the reaction product after the stirring in the above step (2) with deionized water to pH=7～9; (4) placing the washed product in the step (3) in a blast drying oven, Blast drying at 60°C to 100°C for 8 to 16 hours to obtain a precursor; (5) mechanically ball-mill the precursor of step (4) for 2 to 12 hours, and then place it in a muffle furnace, under nitrogen or argon. The heteroatom-doped lithium-phosphorus battery composite material of the present invention can be obtained by sintering at 400° C.˜600° C. for 6˜15 hours in an atmosphere.

Further improvements of the present invention include:

The dispersant is at least one of polyacrylic acid, polyammonium methacrylate and ammonium citrate, and the added amount of the dispersant is 1wt-20wt% of the total mass of carbon source, phosphorus source and heteroatom source.

The reaction medium is at least one of ethylene glycol and isopropanol, and the reaction medium is added in an amount of 100wt% to 200wt% of the total mass of carbon source, phosphorus source and heteroatom source.

The invention has the advantages of simple synthesis process, high specific capacity, good cycle performance and low process cost.

Description of drawings

Figure 1 is a graph of the cycling capacity of batteries made of different materials at room temperature at 0.1C.

Detailed ways

The present invention will be described in detail below with reference to the embodiments.

Example 1

From coconut shell charcoal, P ₂ O ₅ , elemental S, weigh the raw materials according to the molar ratio C:P:S=0.6:0.4:0.015 and put them into the reaction kettle, then add 10% polyacrylic acid as a dispersant and 100wt% of the reaction medium Ethylene glycol; put the above-mentioned reaction kettle equipped with the mixed solution into a muffle furnace for reaction, the reaction temperature is 60 ° C, and the reaction time is 12 hours; the above-mentioned reaction product is taken out, stirred and mixed for 8 hours; after the stirring product is taken out and washed to pH=8 Placed in a blast drying oven, blast-dried at 60°C for 16 hours to obtain a precursor; the obtained precursor was mechanically ball-milled for 10 hours and then placed in a muffle furnace, sintered at 450°C for 13 hours in a nitrogen atmosphere, The resulting product has high phase purity.

Battery production and testing

Weigh 0.8g of the positive electrode active material prepared by the above method, add 0.19g of acetylene black, and 0.1g of polyvinylidene fluoride binder to dissolve in N-N dimethylpyrrolidone, and mix to form a slurry. Coated on aluminum foil, in an argon atmosphere glove box, with metal embedded sheet as counter electrode, celgard2400 as diaphragm, 1mol/L LIPF6/EC:DEC (1:1) as electrolyte, assembled into CR2016 type button battery , the test instrument is the LANDCT2001 battery test system. In the voltage range of 1.0V ~ 3.0V, the battery was subjected to charge-discharge cycle experiments.

Example 2

From Ketjen black, purple phosphorus, TeO ₂ , As ₂ O ₃ , weigh the raw materials according to C:P:Te:As=0.5:0.5:0.01:0.01 and put them into the reaction kettle, then add dispersant 15% polymethyl Ammonium acrylate and reaction medium 120wt% isopropanol; put the above-mentioned reaction kettle equipped with the mixed solution into a muffle furnace with a reaction temperature of 80 ° C and a reaction time of 10 hours; take out the above-mentioned reaction product, stir and mix for 10 hours; take out the stirred product for washing After reaching pH=7, it was placed in a blast drying oven, and dried at 70° C. for 12 hours to obtain a precursor; the obtained precursor was mechanically ball-milled for 6 hours and then placed in a muffle furnace, in an argon atmosphere at After sintering at 500°C for 11 hours, the obtained product has high phase purity.

The battery production and testing process are the same as in Example 1

Example 3

Mixed carbon is composed of coconut shell carbon and Ketjen black at 1:1, P ₂ O ₅ , elemental S, SiO ₂ , SeO ₂ , according to C:P:S:Si:Se=0.45:0.55:0.01:0.01: 0.01 weigh the raw material and put it into the reactor, then add the 5:5 mixed solution of ethylene glycol and isopropanol of 12% ammonium citrate as a dispersant and 120wt% of the reaction medium; put the above-mentioned mixed solution reactor into the muffle The reaction temperature in the furnace was 100°C, and the reaction time was 8 hours; the above-mentioned reaction product was taken out, stirred and mixed for 8 hours; the stirred product was taken out and washed to pH=9, and then placed in a blast drying oven, and dried by blast at 80°C for 10 hours, A precursor is obtained; the obtained precursor is mechanically ball-milled for 4 hours, then placed in a muffle furnace, and sintered at 550° C. for 8 hours in a nitrogen atmosphere, and the obtained product has high phase purity. The battery manufacturing and testing process is the same as that of Example 1

Example 4

Mixed carbon, purple phosphorus and SiO2 are composed of coconut shell charcoal and Ketjen black at a ratio of 2:1. The raw materials are weighed according to C:P:Si=0.4:0.6:0.02 and put into the reaction kettle, and then a dispersant 10% polymer is added. Acrylic acid and 8% ammonium citrate and reaction medium 150wt% of ethylene glycol and isopropanol 4:6 mixed solution; Put the above-mentioned reaction kettle with the mixed solution into a muffle furnace at a reaction temperature of 120°C and a reaction time of 4 hours; The above reaction product was taken out, stirred and mixed for 10 hours; the stirred product was taken out and washed to pH=8, then placed in a blast drying oven, and dried by blast at 90 ° C for 8 hours to obtain a precursor; the obtained precursor was mechanically ball-milled for 2 After 2 hours, it was placed in a muffle furnace, and sintered at 600° C. for 6 hours in an argon atmosphere, and the obtained product had a relatively high phase purity.

The battery production and testing process are the same as in Example 1

Comparative Example 1

The coconut shell charcoal and purple phosphorus were weighed at 0.5:0.5, and the preparation method and the battery manufacturing and testing process were the same as those in Example 1. Figure 1. Cycling capacity diagram of batteries made of different materials at room temperature at 0.1C

Table 1 Test results at room temperature of the batteries made in the examples and comparative columns

It can be seen from Table 1 and FIG. 1 that the specific capacity and cycle stability of the batteries made of the synthetic materials of Examples 1 to 4 of the present invention at room temperature are higher than those of Comparative Example 1 at a rate of 0.1. It shows that the heteroatom-doped carbon-phosphorus material prepared by the present invention can effectively improve the specific capacity and cycle stability of the lithium-phosphorus battery, and lay a foundation for realizing the large-scale market application of the lithium-phosphorus battery.

The basic principles and main features of the present invention and the advantages of the present invention have been shown and described above. Those skilled in the art should understand that the present invention is not limited by the above-mentioned embodiments, and the descriptions in the above-mentioned embodiments and the description are only to illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have Various changes and modifications fall within the scope of the claimed invention. The claimed scope of the present invention is defined by the appended claims and their equivalents.

Claims (4)

1. a lithium-phosphorus battery composite material, is characterized in that: The preparation method of the lithium-phosphorus battery composite material includes the following steps: (1) according to the mass ratio of 0～1:0～1:0～0.1, the carbon source, phosphorus source and heteroatom source are weighed and added to the reaction kettle, and then the dispersant and the reaction medium are added, and the reaction temperature is 60～120 ℃, The reaction time is 4 to 12 hours; (2) take out the reaction product of above-mentioned step (1), stir mechanically evenly, stirring time is 8～24 hours; (3) washing the stirred reaction product of the above step (2) with deionized water to pH=7～9; (4) placing the washed product in step (3) in a blast drying oven, and blast drying at 60°C to 100°C for 8 to 16 hours to obtain a precursor; (5) The precursor of step (4) is mechanically ball-milled for 2-12 hours, then placed in a muffle furnace, and sintered at 400° C. to 600° C. for 6-15 hours in a nitrogen or argon atmosphere to obtain heteroatom doped Hybrid lithium-phosphorus battery composites; In step (1), the carbon source is coconut shell carbon and/or Ketjen black, the phosphorus source is P ₂ O ₅ and/or purple phosphorus, and the heteroatom source is B, N, F, Si, S, Cl, At least one of As, Se, Br, Te, and I heteroatoms. 2. a method for preparing the described lithium-phosphorus battery composite material of claim 1, is characterized in that, has the following steps: (1) according to the mass ratio of 0～1:0～1:0～0.1, the carbon source, phosphorus source and heteroatom source are weighed and added to the reaction kettle, and then the dispersant and the reaction medium are added, and the reaction temperature is 60～120 ℃, The reaction time is 4 to 12 hours; (2) take out the reaction product of above-mentioned step (1), stir mechanically evenly, stirring time is 8～24 hours; (3) washing the stirred reaction product of the above step (2) with deionized water to pH=7～9; (4) placing the washed product in step (3) in a blast drying oven, and blast drying at 60°C to 100°C for 8 to 16 hours to obtain a precursor; (5) The precursor of step (4) is mechanically ball-milled for 2-12 hours, then placed in a muffle furnace, and sintered at 400° C. to 600° C. for 6-15 hours in a nitrogen or argon atmosphere to obtain heteroatom doped Hybrid lithium-phosphorus battery composites; In step (1), the carbon source is coconut shell carbon and/or Ketjen black, the phosphorus source is P ₂ O ₅ and/or purple phosphorus, and the heteroatom source is B, N, F, Si, S, Cl, At least one of As, Se, Br, Te, and I heteroatoms. 3. method according to claim 2 is characterized in that, described dispersant is at least one in polyacrylic acid, polyammonium methacrylate, ammonium citrate, and dispersant add-on is carbon source, phosphorus source and miscellaneous 1wt～20wt% of the total mass of the atomic source. 4. method according to claim 2, is characterized in that, described reaction medium is at least one in ethylene glycol, Virahol, and reaction medium add-on is carbon source, phosphorus source and heteroatom source total mass 100wt～200wt%.

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