RU2597607C1 - Method of producing cathode material for chemical current sources - Google Patents

Abstract

FIELD: electricity; chemistry.

SUBSTANCE: invention can be used in industrial synthesis of cathode materials for high-capacity lithium chemical current sources. Wood is milled into particles size of less than 2 mm and dried in a current of dry nitrogen at 120-130 °C. Then reactor with milled and dried wood is evacuated to pressure of not more than 0.1 kg/cm², filled with a mixture of fluorine and nitrogen in volume ratio 1:(3-5) to atmospheric pressure and wood is fluorinated at temperature of 80-120 °C and continuous stirring. Reaction termination is controlled based on fall of temperature of reactor by 5-10 °C. Safety of method of producing cathode material for chemical current sources is improved, need to clean obtained material from toxic reagents is avoided, implementation of process is simplified.

EFFECT: produced cathode material has high power capacity and electric conductivity, production cost is reduced.

1 cl, 4 ex

Description

The invention relates to the field of production of solid carbon materials and can be used in the industrial synthesis of cathode materials for chemical current sources (HIT), in particular lithium HIT of high energy intensity.

A known method of producing a cathode material for lithium ChIT based on hydrolytic lignin (US Pat. RF No. 2482571, publ. 05.20.2013). Hydrolysis lignin is crushed to a particle size of 0.1-1.0 μm, treated with 5% hydrochloric acid at a weight ratio of 1: 5 for at least 1.0 hour, centrifuged and the precipitate washed. The precipitate obtained is treated with 5% hydrofluoric acid in a weight ratio of 1: 5 for at least 1.0 hour, centrifuged, washed and the precipitate dried. The disadvantages of this method are the multi-stage and duration of the process of producing cathode material, as well as the relatively low practical energy consumption of lithium chitosan with cathodes based on lignin (up to 650 W · h / kg).

Closest to the proposed is a method of producing a fluorinated carbon material for the manufacture of cathodes of chemical current sources (US Pat. RF No. 2036135, publ. 1995.05.27), including processing the wood processing product - hydrolysis lignin - by fluorination with a solution of bromine trifluoride in anhydrous hydrogen fluoride in volume ratio of BrF ₃ to HF equal to (10-1): 1, at a temperature of from -20 to + 19 ° C. The resulting product is a fluorinated carbon-containing material in the form of a fine powder of light yellow color with a particle size of 0.1-1.0 μm composition C ₉ F _x O _y , where x = 6-7; y = 5-6, which, when used as a cathode material, has a theoretical energy intensity above 4.5 kWh / kg.

The disadvantage of this method is the high technological complexity of the fluorination process and its hardware, due to the use of aggressive and highly toxic reagents: bromine trifluoride and anhydrous hydrogen fluoride, as well as the need to purify the final product, which is the reason for its high cost. A significant disadvantage of the cathode material obtained in a known manner is its low specific electron conductivity (1 · 10 ^-14 S / cm) and, as a consequence, low discharge currents of chitosan.

The objective of the invention is to provide a safe method for producing wood-based carbon-containing cathode material with sufficiently high energy characteristics and low cost, ensuring its industrial use.

The technical result of the method consists in increasing its safety, eliminating the need to purify the resulting cathode material from toxic reagents and simplifying the hardware design by conducting a fluorination reaction with a gaseous fluorinating reagent while increasing the energy intensity and electrical conductivity of the obtained cathode material and reducing its cost.

The specified technical result is achieved by a method of producing a cathode material for chemical current sources, including the processing of carbon-containing raw materials of wood origin by fluorination, in which, unlike the known, directly used wood as carbon-containing raw materials, which is crushed before fluorination to a particle size of no more than 2, 0 mm, placed in a hermetically sealed reactor and dried in a stream of dry nitrogen at 120-130 ° C, then the reactor with prepared wood is sealed, with create a pressure of not more than 0.1 kg / cm ^{2 in it} , fill it to atmospheric pressure with a mixture of fluorine gas with nitrogen taken in a volume ratio of 1: (3-5) and carry out fluorination of wood at a temperature of 80-120 ° C and stirring continuously to complete completion of the reaction, the end of which is controlled by reducing the temperature of the reactor by 10-15 ° C.

The method is as follows.

Wood, mainly a mixture of wood of various species of wood, is mechanically crushed to a particle size of no larger than 2.0 mm, mainly 0.5-2.0 mm, sieved through a sieve with a mesh size of 2.0 mm, loaded into a hermetically sealed reactor equipped with a device for mechanical stirring and dried in a stream of dry nitrogen for 15-20 minutes at a temperature of 120-130 ° C with continuous stirring.

Wood of various species, in particular deciduous and coniferous, varies in chemical composition: the quantitative content of cellulose, lignin, hemicelluloses, including pentosans and hexosans, varies widely. A mixture of wood of various species allows you to average the feedstock in composition.

After drying, without unloading the wood raw materials, the reactor is sealed, vacuum to a pressure of not higher than 0.1 kg / cm ² , filled with fluorinating gas to atmospheric pressure and conducting a topochemical reaction of wood fluorination, while a mixture of fluorine gas with nitrogen is used as a fluorinating gas volume ratio 1: (3-5). The reaction is carried out at a temperature of the reaction mixture of 80-120 ° C, which is maintained at a set level by adjusting the heating power taking into account the heat released during the exothermic reaction of wood fluorination. The process is carried out with continuous stirring until the reaction is complete, as evidenced by a sharp decrease in temperature in the reactor by 10-15 ° C.

The heating of the reactor was stopped and after it was cooled to room temperature, it was purged with heated nitrogen to remove residual fluorine and gaseous reaction products.

The whole process of wood processing is carried out in one reactor. The gaseous products of the fluorination reaction and unreacted fluorine are easily removed, while the resulting solid reaction product, a carbon-containing material, does not require purification.

As a result of processing the wood by the proposed method, a carbon-containing material is obtained in the form of a light brown powder with a particle size of 0.5-2.0 μm, which is a modified, namely fluorinated wood.

The content of carbon, oxygen, and other elements in the wood fluorination product was determined by energy dispersive spectrometry on a Hitachi S5500 high resolution electron scanning microscope with the Thermo Scientific attachment. On its X-ray electron spectra (XPS method), 1s signals of carbon electrons were detected (E _St. 293.8 eV for CF ₂ ; 291.9 eV for COF; 290.2 eV for CO ₂ , CF ₃ ; 288.1 eV for CF, CO; 285.0 eV for SS), 1s oxygen electrons (E _St. 535.9 eV for COF and E _St. 534.3 eV for CO), 1s fluorine electrons (E _St. 690.2 eV for CF ₃ and E _St. 689.2 eV for COF, CF ₂ , CF).

Electrical conductivity was determined by impedance spectroscopy using an Impedance / Gain-phase analyzer SI 1260 system (Solartron, UK).

The resulting product (fluorinated wood) corresponds to the composition C ₉ O _x F _y ; where x = 4-6; y = 5-10, and includes X-ray amorphous perfluorinated polymeric compounds with a branched structure containing various oxygen functional groups. The product is thermally stable up to 300 ° C and has a theoretical energy consumption of 4.5 kWh / kg and a specific electron conductivity of 1 · 10 ^-11 S / cm.

Lithium HITs of size BR1225 were manufactured on the basis of cathodes obtained by pressing a mixture containing 95% of a carbon-containing product (fluorinated wood) obtained by the proposed method and 5% of acetylene black (conductive additive) and their energy characteristics were experimentally established.

When using the carbon-containing product obtained by the proposed method as a cathode material in lithium Chit containing 1 M solution of lithium perchlorate in anhydrous propylene carbonate as an electrolyte, the open circuit voltage (NRC) is 3.0 V, and the practical energy consumption for a discharge is up to 1 V and the specified above specific electron conductivity up to 1 · 10 ^-11 S / cm reaches 1.2 kW · h / kg.

Thus, the proposed method, carried out using a simple technological scheme using renewable natural raw materials, eliminates the need for liquid highly toxic fluorinating agents and complex purification of the finished product, does not require complex hardware design, while the cathode material obtained with it at a relatively low cost has higher electronic conductivity and energy intensity, which makes it economically feasible to use it in an industrial headquarters.

Examples of specific embodiments of the invention

Example 1

The wood was crushed using a ball mill and sieved through a sieve with a mesh size of 2 mm The resulting wood powder of the general formula C ₉ H ₁₄ O _{5 was} placed in a sealed reactor, dried with stirring at 120 ° C in an atmosphere of dry nitrogen for 15 minutes. Then the heating was stopped, the reactor was evacuated to 0.1 kg / cm ² and filled with a mixture of high-purity fluorine and dry nitrogen in a ratio of 1: 5 to atmospheric pressure. After that, the temperature of the reaction mixture was brought to 80 ° C and maintained at this level (80 ± 5 ° C), controlling the heating taking into account the heat evolution as a result of the exothermic fluorination reaction, giving a temperature increase of 5-10 ° C. The whole process was carried out with continuous stirring of wood. The end of the reaction was determined by a sharp decrease in temperature by about 10 ° C. The heating of the reactor was completely stopped and, after cooling, to remove residual fluorine and gaseous reaction products, it was purged with dry gaseous nitrogen at a temperature of 120 ° C until a neutral gas flow was obtained at the outlet, which was checked by indicator paper.

The reactor was unloaded and the resulting mixture was mixed with acetylene black in a ratio of 95: 5, 0.2 g was loaded onto the bottom of a chit cell made of stainless steel, size BR1225, then a separator made of porous polypropylene was placed, an electrolyte was added (a 1M solution of lithium perchlorate in anhydrous propylene carbonate) was placed under the cover, metallic lithium and sealed the cover using a polypropylene gasket. When discharged with a current of 30 μA, the cell showed a capacity of 750 W · h / kg.

Example 2

The crushed wood of the general formula C ₉ H ₁₄ O _{5 was} treated in accordance with Example 1, while drying was carried out at 130 ° C for 15 minutes, fluorination was carried out with a mixture of high-purity fluorine and dry nitrogen in a ratio of 1: 3. The reactor was heated to 80 ° C. The exothermic reaction was accompanied by a temperature increase of 10-15 ° C, heating was reduced to maintain a temperature of 80 ± 5 ° C in the reactor.

The HIT cell was prepared as in Example 1. When discharged with a current of 30 μA, the cell showed a capacity of 850 W · h / kg.

Example 3

The crushed wood of the general formula C ₉ H ₁₄ O _{5 was} treated in accordance with Example 1, while drying was carried out at 120 ° C for 20 minutes, fluorination was carried out with a mixture of high-purity fluorine and dry nitrogen in a ratio of 1: 5, and the reactor was heated to a temperature of 120 ° C and during the reaction the temperature was maintained at 120 ± 5 ° C.

The HIT cell was prepared as in Example 1. When discharged with a current of 30 μA, the cell showed a capacity of 1200 Wh / kg.

Example 4

The crushed wood of the general formula C ₉ H ₁₄ O _{5 was} treated in accordance with Example 1, while drying was carried out at 120 ° C for 15 minutes, fluorination was carried out with a mixture of high purity fluorine and dry nitrogen in a ratio of 1: 3, and the reactor was heated to a temperature of 120 ° C and during the reaction the temperature was maintained at 120 ± 5 ° C.

The HIT cell was prepared as in Example 1. When discharged with a current of 30 μA, the cell showed a capacity of 1200 Wh / kg.

Claims (1)

A method of producing a cathode material for chemical current sources, including the processing of carbon-containing wood raw materials by fluorination, characterized in that directly used wood is used as carbon-containing wood raw materials, which are crushed before fluorination to a particle size of not more than 2.0 mm and dried in a stream of dry nitrogen at 120-130 ° C, then the reactor is sealed with a prepared timber, the pressure created therein no more than 0.1 kg / cm ^2, filled up with a mixture of gaseous atmospheric pressure p ora nitrogen, taken in a volume ratio of 1: (3-5) and the fluorination is carried out at a wood temperature 80-120 ° C and continuous stirring until the reaction is complete, the end of which is controlled to reduce the reactor temperature at 10-15 ° C.