CN109742446B - Lithium/thionyl chloride battery electrolyte and preparation method thereof - Google Patents

Lithium/thionyl chloride battery electrolyte and preparation method thereof Download PDF

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CN109742446B
CN109742446B CN201811570609.7A CN201811570609A CN109742446B CN 109742446 B CN109742446 B CN 109742446B CN 201811570609 A CN201811570609 A CN 201811570609A CN 109742446 B CN109742446 B CN 109742446B
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thionyl chloride
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lithium
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CN109742446A (en
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裴广华
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Jiangsu Zhongluman New Material Technology Co., Ltd.
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Yueqing Huazun Electric Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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Abstract

The invention discloses a lithium/thionyl chloride battery electrolyte and a preparation method thereof, wherein the electrolyte comprises thionyl chloride, electrolyte salt and additives, the additives comprise a first additive and a second additive, and the preparation method comprises the following steps: distilling thionyl chloride, and collecting fractions; weighing electrolyte salt and dissolving the electrolyte salt in thionyl chloride fraction; purifying the first additive; purifying the second additive; weighing the purified first additive and the purified second additive, and adding the first additive and the purified second additive into a thionyl chloride solution of electrolyte salt to obtain a lithium/thionyl chloride battery electrolyte; the first additive and the second additive in the lithium/thionyl chloride battery electrolyte provided by the invention act synergistically, so that the lithium/thionyl chloride battery obtains good discharge voltage and discharge capacity, the voltage hysteresis phenomenon of the lithium/thionyl chloride battery is obviously improved, and the lithium/thionyl chloride battery prepared from the electrolyte has good cycle performance and high safety.

Description

Lithium/thionyl chloride battery electrolyte and preparation method thereof
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a lithium thionyl chloride battery electrolyte and a preparation method thereof.
Background
Lithium/thionyl chloride (Li/SOCl)2) The battery is thionyl chloride (SOCl) which takes lithium as an anode, carbon as a cathode carrier and anhydrous lithium tetrachloroaluminate2) A lithium battery using the solution as electrolyte. The lithium/thionyl chloride battery has the characteristics of high specific energy, high specific power, stable discharge voltage, long storage life and the like, and is widely applied to military and civil industries such as aerospace, underwater weapons, navigation equipment, geological exploration, instruments and meters and the like. The lithium/thionyl chloride battery is a battery with the highest specific energy and specific power in the current battery field. The overall reaction mechanism of the lithium thionyl chloride cell is: 4Li +2SOCl2→4LiCl+S+SO2Sulfur and sulfur dioxide are dissolved in an excessive amount of thionyl chloride electrolyte, and during discharge, a certain degree of pressure is generated due to the generation of sulfur dioxide. During storage, the lithium negative electrode, upon contact with the electrolyte, reacts with thionyl chloride electrolyte to produce LiCl, which is protected by the LiCl film formed thereon. This passivation film is useful for prolonging the storage life of the battery, but causes a voltage hysteresis at the start of discharge, and the voltage hysteresis is particularly significant when the battery is discharged in a low-temperature environment after being stored at a high temperature for a long period of time.
In order to eliminate the voltage hysteresis phenomenon of the lithium/thionyl chloride battery, the current collection form of a cathode and an anode is improved, or the impurity content and the molar concentration of an electrolyte are improved so as to reduce the internal resistance of the battery; electronic elements are additionally arranged inside or outside the battery to enable the battery to be in a weak discharge state so as to weaken the formation of a passivation film; metal phthalocyanine compounds or sulfides are added to the cathode and the electrolyte to improve the voltage hysteresis performance. Some of the above methods improve some of the performance of lithium/thionyl chloride cells to some extent, but some of them impair other performance of lithium/thionyl chloride cells at the expense of "sacrificing" the capacity of the lithium/thionyl chloride cell.
The electrolyte is one of three elements forming the lithium thionyl chloride battery, the physical and chemical properties of the electrolyte play an important role in the performance of battery materials, and the significance of developing electrolyte materials matched with cathode and anode materials is remarkable.
Disclosure of Invention
The invention aims to provide a lithium thionyl chloride battery electrolyte and a preparation method thereof, and aims to solve the problems in the prior art.
In order to achieve the purpose, the invention provides the following technical scheme:
the lithium thionyl chloride battery electrolyte comprises thionyl chloride, electrolyte salt and an additive, wherein the molar concentration of a thionyl chloride solution of the electrolyte salt is 0.1-1mol/L, and the mass of the additive is 0.01-0.5% of the total mass of the electrolyte. The addition amount of the additive is too small to reduce the voltage delay of the battery, and the addition amount of the additive is too large to influence the gram capacity of the material and cause waste, so that the voltage delay of the battery cannot be reduced.
Preferably, the additive comprises a first additive and a second additive, and the structural formula of the first additive is as follows:
Figure GDA0002372825410000031
wherein X is halogen; r1Is nitrile group, amido group, hydroxyl group or nitro group; r2、R3Are each hydrogen, mono-or polysubstituted C1-C6 alkyl, aryl, C1-C6 alkoxy or halogenated C1-C6 alkoxy; r4Is C1-C6 alkyl or C1-C6 alkyl which is mono-or polysubstituted by halogen.
Preferably, the structural formula of the second additive is as follows:
Figure GDA0002372825410000032
wherein, X1Is halogen; r11、R21、R31Are each C1-C10 alkyl, halogenated C1-C10 alkyl, C1-C10 alkoxy or halogenated C1-C10 alkoxy; r41Is a heterocyclic radical which is unsubstituted or substituted by C1-C6 alkyl, said heterocyclic radical containing one or more of the elements O, N, S.
Preferably, the electrolyte salt is one or more of lithium bis (fluorosulfonyl) imide, lithium bis (oxalato) borate, lithium trifluoromethanesulfonate, lithium tris (trifluoromethylsulfonyl) methide, lithium hexafluorophosphate, lithium tris (oxalato) phosphate, lithium difluorobis (oxalato) phosphate and lithium tetrafluoro (oxalato) phosphate. Li/SOCl2The main disadvantage of the battery is its voltage hysteresis, which is more severe especially after storage at high temperatures and when used at ambient temperatures, causing Li/SOCl2The reason for the voltage hysteresis of the battery is mainly that lithium aluminum tetrachloride (LiAlCl) is used in the battery system4) Electrolyte salt, electrolyte solution containing the salt generates spontaneous chemical reaction at a lithium anode, the product is LiCl, LiCl is covered on the surface of the lithium anode in the form of a thin film, the contact of lithium and the electrolyte solution is prevented, and finally voltage hysteresis is caused4) The electrolyte salt is used for preparing the lithium thionyl chloride battery electrolyte, so that the phenomenon of battery voltage hysteresis can be effectively reduced.
Preferably, the mass of the first additive is 0.005-0.3% of the total mass of the electrolyte, and the mass of the second additive is 0.005-0.2% of the total mass of the electrolyte.
A preparation method of a lithium thionyl chloride battery electrolyte comprises the following steps:
(1) distilling thionyl chloride, and collecting fractions;
(2) weighing electrolyte salt, putting the electrolyte salt into the thionyl chloride fraction prepared in the step (1), and fixing the volume to obtain a thionyl chloride solution of the electrolyte salt;
(3) purification of the first additive: leaching the first additive by using acetone to obtain a first additive leaching solution, distilling the leaching solution to obtain a first additive, and drying to obtain a purified first additive;
(4) purification of the second additive: purifying the second additive by adopting a sublimation purifying device:
(a) adding molten salt into a heating chamber through a feeding port, and heating the molten salt by adopting a first molten salt heating rod and a second molten salt heating rod;
(b) filling a second additive into the sublimation material loading boat, paving silica gel on the second additive, then putting the second additive into the cylindrical pipe, closing the end door, vacuumizing the cylindrical pipe by using a vacuum pump through a vacuum cooling pipe, and finishing the purification of the second additive after a period of time;
(5) and (3) weighing the purified first additive obtained in the step (3) and the purified second additive obtained in the step (4), adding the weighed purified first additive and the purified second additive into the thionyl chloride solution of the electrolyte salt obtained in the step (2), and continuously stirring until the purified first additive and the purified second additive are completely dissolved to obtain the lithium thionyl chloride battery electrolyte.
As optimization, the preparation method of the lithium thionyl chloride battery electrolyte comprises the following steps:
(1) putting thionyl chloride into a flask, heating for distillation, and collecting fractions at 70-80 ℃; the distillation of thionyl chloride is performed for the purpose of purification;
(2) weighing electrolyte salt, dissolving the electrolyte salt in the thionyl chloride fraction prepared in the step (1) under an inert atmosphere condition, and performing constant volume to obtain a thionyl chloride solution of the electrolyte salt with the molar concentration of 0.1-1 mol/L;
(3) purification of the first additive: leaching the first additive by using acetone to obtain a first additive leaching solution, distilling the leaching solution to obtain a first additive, and drying to obtain a purified first additive; the leaching temperature is 30-45 ℃, the leaching time is 1-4h, and the distillation is carried out at 40-80 ℃ in a reduced pressure distillation mode;
(4) purification of the second additive: purifying the second additive by adopting a sublimation purifying device: the purification method has the advantages of short process flow and simple and convenient operation, and the purity of the purified second additive is more than 99 percent;
(a) adding molten salt into a heating chamber through a feeding port, and heating the molten salt by adopting a first molten salt heating rod and a second molten salt heating rod to enable the temperature to reach 200-250 ℃;
(b) filling a second additive into the sublimation material loading boat, paving silica gel on the second additive, then putting the second additive into the cylindrical tube, closing the end door, pumping the vacuum degree to 0.03-0.08KPa through a vacuum cooling tube, and finishing the purification of the second additive after 6-15 h; the silica gel mainly plays a role in decoloring;
(5) and (3) weighing the purified first additive obtained in the step (3) and the purified second additive obtained in the step (4), adding the weighed purified first additive and the purified second additive into the thionyl chloride solution of the electrolyte salt obtained in the step (2), and continuously stirring until the purified first additive and the purified second additive are completely dissolved to obtain the lithium thionyl chloride battery electrolyte.
The first additive and the second additive are purified, impurities are reduced, and the lithium thionyl chloride battery electrolyte prepared from the first additive and the second additive can effectively reduce the voltage hysteresis phenomenon of the battery.
Preferably, the molten salt in step (a) is a mixture of sodium nitrite and potassium nitrite of equal mass.
As an optimization, the leaching solution in the step (3) is transferred into a shaker before distillation, and shaking is carried out for 30-60min at the speed of 100-300 r/min. The purpose of the shaking was to mix the first additive more evenly with the acetone.
As optimization, the step (1), the step (2) and the step (3) are operated in a dry environment with the relative humidity less than or equal to 0.5-1%. The lithium thionyl chloride battery electrolyte reacts with water very violently, even a very small amount of water easily reacts with the electrolyte to generate HCl gas, so that the serious corrosion is caused, and therefore, the experimental operation is carried out in a dry environment when the electrolyte is prepared.
Compared with the prior art, the invention has the beneficial effects that:
the first additive and the second additive in the electrolyte of the lithium thionyl chloride battery have better thionyl chloride passivation resistance, and the first additive and the second additive inhibit the formation of a passivation film on the surface of a metal lithium anode under the action of a cathode active substance, namely thionyl chloride, in the lithium/thionyl chloride battery, so that the lithium/thionyl chloride battery obtains good discharge voltage and discharge capacity, and the voltage hysteresis phenomenon of the lithium/thionyl chloride battery is obviously improved.
Secondly, the first additive and the second additive in the lithium thionyl chloride battery electrolyte have better nucleophilic attack resistance, and the synergistic effect of the first additive and the second additive can effectively inhibit Li2The loss of O stabilizes the structure of the lithium-rich cathode material, effectively relieves the occurrence of the voltage hysteresis phenomenon of the battery, and simultaneously, the electrolyte of the lithium thionyl chloride battery has the characteristics of good oxidation resistance and non-combustibility, so that the lithium thionyl chloride battery prepared from the electrolyte has better cycle performance and higher safety.
Thirdly, the preparation method of the lithium thionyl chloride battery electrolyte is simple, convenient to operate, scientific in formula, low in raw material cost, high in practicability and wide in application prospect.
Fourthly, in the preparation method of the lithium thionyl chloride battery electrolyte, thionyl chloride is distilled, and the first additive and the second additive are purified, so that the prepared lithium thionyl chloride battery electrolyte has less impurity content and more excellent electrolyte performance.
Detailed Description
The technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1:
the lithium thionyl chloride battery electrolyte comprises thionyl chloride, lithium bis (fluorosulfonyl) imide and an additive, wherein the molar concentration of a thionyl chloride solution of electrolyte salt is 0.1mol/L, the mass of the additive accounts for 0.01% of the total mass of the electrolyte, the additive comprises a first additive and a second additive, the mass of the first additive accounts for 0.005% of the total mass of the electrolyte, and the mass of the second additive accounts for 0.005% of the total mass of the electrolyte.
The first additive has the structural formula:
Figure GDA0002372825410000081
wherein X is Cl; r1Is a nitrile group; r2、R3Are all hydrogen; r4Is methyl.
The second additive has the structural formula:
Figure GDA0002372825410000082
wherein, X1Is Cl; r11、R21、R31Are both methyl; r41Is a pyrrole heterocyclic group.
A preparation method of a lithium thionyl chloride battery electrolyte comprises the following steps:
(1) under the dry environment with the relative humidity less than or equal to 0.5 percent, thionyl chloride is placed in a flask, heated and distilled, and the fraction with the temperature of 70 ℃ is collected;
(2) weighing electrolyte salt in a dry environment with the relative humidity less than or equal to 0.5%, dissolving the electrolyte salt in the thionyl chloride fraction prepared in the step (1) under an inert atmosphere condition, and performing constant volume to obtain a thionyl chloride solution of the electrolyte salt with the molar concentration of 0.1 mol/L;
(3) purification of the first additive: leaching the first additive by using acetone to obtain a first additive leaching solution, transferring the leaching solution into a vibrator, vibrating for 30min at 100r/min, distilling the leaching solution, removing the acetone to obtain a first additive crude extract, finally removing a supernatant, and drying to obtain a purified first additive; the leaching temperature is 30 ℃, the leaching time is 1h, and the distillation is carried out at 40 ℃ in a reduced pressure distillation mode;
(4) purification of the second additive: purifying the second additive by adopting a sublimation purifying device:
(a) adding molten salt into a heating chamber through a feeding port, wherein the molten salt is a mixture of sodium nitrite and potassium nitrite with equal mass, and heating the molten salt by adopting a first molten salt heating rod and a second molten salt heating rod to enable the temperature to reach 200 ℃;
(b) filling a second additive into the sublimation material loading boat, paving silica gel on the second additive, then putting the second additive into the cylindrical pipe, closing the end door, pumping the vacuum degree to 0.03KPa through a vacuum cooling pipe, and finishing the purification of the second additive after 6 hours;
(5) and (3) weighing the purified first additive obtained in the step (3) and the purified second additive obtained in the step (4) in a dry environment with the relative humidity less than or equal to 0.5%, adding the weighed purified first additive and the purified second additive into the thionyl chloride solution of the electrolyte salt obtained in the step (2), and continuously stirring until the additives are completely dissolved to obtain the lithium thionyl chloride battery electrolyte.
Example 2:
the lithium thionyl chloride battery electrolyte comprises thionyl chloride, lithium bis (oxalato) borate and an additive, wherein the molar concentration of a thionyl chloride solution of electrolyte salt is 0.4mol/L, the mass of the additive is 0.1% of the total mass of the electrolyte, the additive comprises a first additive and a second additive, the mass of the first additive is 0.05% of the total mass of the electrolyte, and the mass of the second additive is 0.05% of the total mass of the electrolyte.
The first additive has the structural formula:
Figure GDA0002372825410000101
wherein X is Br; r1Is an amino group; r2、R3Are all chloromethyl; r4Is ethyl.
The second additive has the structural formula:
Figure GDA0002372825410000102
wherein, X1Is Br; r11、R21、R31Are all chloromethyl; r41Is a furan heterocyclic group.
A preparation method of a lithium thionyl chloride battery electrolyte comprises the following steps:
(1) under the dry environment with the relative humidity less than or equal to 0.6 percent, thionyl chloride is placed in a flask, heated and distilled, and 72 ℃ fraction is collected;
(2) weighing electrolyte salt in a dry environment with the relative humidity less than or equal to 0.6%, dissolving the electrolyte salt in the thionyl chloride fraction prepared in the step (1) under an inert atmosphere condition, and performing constant volume to obtain a thionyl chloride solution of the electrolyte salt with the molar concentration of 0.4 mol/L;
(3) purification of the first additive: leaching the first additive by using acetone to obtain a first additive leaching solution, transferring the leaching solution into a vibrator, vibrating for 35min at the speed of 150r/min, distilling the leaching solution, removing the acetone to obtain a first additive crude extract, finally removing a supernatant, and drying to obtain a purified first additive; the leaching temperature is 32 ℃, the leaching time is 1.5h, and the distillation is carried out at 50 ℃ in a reduced pressure distillation mode;
(4) purification of the second additive: purifying the second additive by adopting a sublimation purifying device:
(a) adding molten salt into a heating chamber through a feeding port, wherein the molten salt is a mixture of sodium nitrite and potassium nitrite with equal mass, and heating the molten salt by adopting a first molten salt heating rod and a second molten salt heating rod to enable the temperature to reach 210 ℃;
(b) filling a second additive into the sublimation material loading boat, paving silica gel on the second additive, then putting the second additive into the cylindrical pipe, closing the end door, pumping the vacuum degree to 0.04KPa through a vacuum cooling pipe, and finishing the purification of the second additive after 8 hours;
(5) and (3) weighing the purified first additive obtained in the step (3) and the purified second additive obtained in the step (4) in a dry environment with the relative humidity less than or equal to 0.6%, adding the weighed purified first additive and the purified second additive into the thionyl chloride solution of the electrolyte salt obtained in the step (2), and continuously stirring until the additives are completely dissolved to obtain the lithium thionyl chloride battery electrolyte.
Example 3:
the lithium thionyl chloride battery electrolyte comprises thionyl chloride, lithium trifluoromethanesulfonate and an additive, wherein the molar concentration of a thionyl chloride solution of electrolyte salt is 0.6mol/L, the mass of the additive is 0.2% of the total mass of the electrolyte, the additive comprises a first additive and a second additive, the mass of the first additive is 0.1% of the total mass of the electrolyte, and the mass of the second additive is 0.2% of the total mass of the electrolyte.
The first additive has the structural formula:
Figure GDA0002372825410000121
wherein X is I; r1Is a hydroxyl group; r2、R3Are all phenyl; r4Is chloromethyl.
The second additive has the structural formula:
Figure GDA0002372825410000122
wherein, X1Is I; r11、R21、R31Are both methoxy; r41Is a thiophene heterocyclic group.
A preparation method of a lithium thionyl chloride battery electrolyte comprises the following steps:
(1) under the dry environment with the relative humidity less than or equal to 0.7 percent, thionyl chloride is placed in a flask, heated and distilled, and 74 ℃ fractions are collected;
(2) weighing electrolyte salt in a dry environment with the relative humidity less than or equal to 0.7%, dissolving the electrolyte salt in the thionyl chloride fraction prepared in the step (1) under an inert atmosphere condition, and performing constant volume to obtain a thionyl chloride solution of the electrolyte salt with the molar concentration of 0.6 mol/L;
(3) purification of the first additive: leaching the first additive by using acetone to obtain a first additive leaching solution, transferring the leaching solution into a vibrator, vibrating for 40min at 200r/min, distilling the leaching solution, removing the acetone to obtain a first additive crude extract, finally removing a supernatant, and drying to obtain a purified first additive; leaching at 34 deg.C for 2 hr, and distilling at 60 deg.C by reduced pressure distillation;
(4) purification of the second additive: purifying the second additive by adopting a sublimation purifying device:
(a) adding molten salt into a heating chamber through a feeding port, wherein the molten salt is a mixture of sodium nitrite and potassium nitrite with equal mass, and heating the molten salt by adopting a first molten salt heating rod and a second molten salt heating rod to enable the temperature to reach 220 ℃;
(b) filling a second additive into the sublimation material loading boat, paving silica gel on the second additive, then putting the second additive into the cylindrical tube, closing the end door, pumping the vacuum degree to 0.05KPa through a vacuum cooling tube by a vacuum pump, and finishing the purification of the second additive after 10 hours;
(5) and (3) weighing the purified first additive obtained in the step (3) and the purified second additive obtained in the step (4) in a dry environment with the relative humidity less than or equal to 0.7%, adding the weighed purified first additive and the purified second additive into the thionyl chloride solution of the electrolyte salt obtained in the step (2), and continuously stirring until the additives are completely dissolved to obtain the lithium thionyl chloride battery electrolyte.
Example 4:
the lithium thionyl chloride battery electrolyte comprises thionyl chloride, tris (trifluoromethylsulfonyl) methyllithium, lithium hexafluorophosphate and additives, wherein the molar concentration of a thionyl chloride solution of electrolyte salt is 0.8mol/L, the mass of the additives is 0.4% of the total mass of the electrolyte, the additives comprise a first additive and a second additive, the mass of the first additive is 0.2% of the total mass of the electrolyte, and the mass of the second additive is 0.2% of the total mass of the electrolyte.
The first additive has the structural formula:
Figure GDA0002372825410000141
wherein X is F; r1Is nitro; r2、R3Are both methoxy; r4Is propyl.
The second additive has the structural formula:
Figure GDA0002372825410000142
wherein, X1Is F; r11、R21、R31Are all chloro methoxy; r41Is 3-methylpyridine heterocyclic radical.
A preparation method of a lithium thionyl chloride battery electrolyte comprises the following steps:
(1) under the dry environment with the relative humidity less than or equal to 0.8 percent, thionyl chloride is placed in a flask, heated and distilled, and 78 ℃ fractions are collected;
(2) weighing electrolyte salt in a dry environment with the relative humidity less than or equal to 0.8%, dissolving the electrolyte salt in the thionyl chloride fraction prepared in the step (1) under an inert atmosphere condition, and performing constant volume to obtain a thionyl chloride solution of the electrolyte salt with the molar concentration of 0.8 mol/L;
(3) purification of the first additive: leaching the first additive by using acetone to obtain a first additive leaching solution, transferring the leaching solution into a vibrator, vibrating for 50min at 250r/min, distilling the leaching solution, removing the acetone to obtain a first additive crude extract, finally removing a supernatant, and drying to obtain a purified first additive; leaching at 40 deg.C for 3 hr, and distilling at 70 deg.C by reduced pressure distillation;
(4) purification of the second additive: purifying the second additive by adopting a sublimation purifying device:
(a) adding molten salt into a heating chamber through a feeding port, wherein the molten salt is a mixture of sodium nitrite and potassium nitrite with equal mass, and heating the molten salt by adopting a first molten salt heating rod and a second molten salt heating rod to enable the temperature to reach 240 ℃;
(b) filling a second additive into the sublimation material loading boat, paving silica gel on the second additive, then putting the second additive into the cylindrical pipe, closing the end door, pumping the vacuum degree to 0.07KPa through a vacuum cooling pipe, and finishing the purification of the second additive after 12 hours;
(5) and (3) weighing the purified first additive obtained in the step (3) and the purified second additive obtained in the step (4) in a dry environment with the relative humidity less than or equal to 0.8%, adding the weighed purified first additive and the purified second additive into the thionyl chloride solution of the electrolyte salt obtained in the step (2), and continuously stirring until the additives are completely dissolved to obtain the lithium thionyl chloride battery electrolyte.
Example 5:
the lithium thionyl chloride battery electrolyte comprises thionyl chloride, lithium tris (oxalato) phosphate, lithium difluoro (oxalato) phosphate and additives, wherein the molar concentration of a thionyl chloride solution of electrolyte salt is 1mol/L, the mass of the additives is 0.5% of the total mass of the electrolyte, the additives comprise a first additive and a second additive, the mass of the first additive is 0.3% of the total mass of the electrolyte, and the mass of the second additive is 0.2% of the total mass of the electrolyte.
The first additive has the structural formula:
Figure GDA0002372825410000161
wherein X is Cl; r1Is an amino group; r2、R3Are both tolyl groups; r4Is chloroethyl.
The second additive has the structural formula:
Figure GDA0002372825410000162
wherein, X1Is Cl; r11、R21、R31Are all chloropropyl; r41Is 2-chlorofuran heterocyclic radical.
A preparation method of a lithium thionyl chloride battery electrolyte comprises the following steps:
(1) under the dry environment with the relative humidity less than or equal to 1 percent, thionyl chloride is placed in a flask, heated and distilled, and the fraction at 80 ℃ is collected;
(2) weighing electrolyte salt in a dry environment with the relative humidity less than or equal to 1%, dissolving the electrolyte salt in the thionyl chloride fraction prepared in the step (1) under an inert atmosphere condition, and performing constant volume to obtain a thionyl chloride solution of the electrolyte salt with the molar concentration of 1 mol/L;
(3) purification of the first additive: leaching the first additive by using acetone to obtain a first additive leaching solution, transferring the leaching solution into a vibrator, vibrating for 60min at 300r/min, distilling the leaching solution, removing the acetone to obtain a first additive crude extract, finally removing a supernatant, and drying to obtain a purified first additive; the leaching temperature is 45 ℃, the leaching time is 4h, and the distillation is carried out at 80 ℃ in a reduced pressure distillation mode;
(4) purification of the second additive: purifying the second additive by adopting a sublimation purifying device:
(a) adding molten salt into a heating chamber through a feeding port, wherein the molten salt is a mixture of sodium nitrite and potassium nitrite with equal mass, and heating the molten salt by adopting a first molten salt heating rod and a second molten salt heating rod to enable the temperature to reach 250 ℃;
(b) filling a second additive into the sublimation material loading boat, paving silica gel on the second additive, then putting the second additive into the cylindrical tube, closing the end door, pumping the vacuum degree to 0.08KPa through a vacuum cooling tube by a vacuum pump, and finishing the purification of the second additive after 15 hours;
(5) and (3) weighing the purified first additive obtained in the step (3) and the purified second additive obtained in the step (4) in a dry environment with the relative humidity of less than or equal to 0.5-1%, adding the weighed purified first additive and the purified second additive into the thionyl chloride solution of the electrolyte salt obtained in the step (2), and continuously stirring until the additives are completely dissolved to obtain the lithium thionyl chloride battery electrolyte.
Comparative example:
the lithium/thionyl chloride battery electrolyte sold in the market is prepared by taking a thionyl chloride solution of lithium aluminum tetrachloride as the electrolyte, wherein thionyl chloride is a solvent and a positive electrode active substance, electrolyte salt is lithium aluminum tetrachloride, and the concentration of lithium salt is 1.7 mol/L.
Example of effects:
manufacturing a lithium/thionyl chloride battery:
homogenizing a graphite positive electrode material, a conductive agent carbon black (SP) and an adhesive polyvinylidene fluoride (PVDF) at room temperature according to a ratio of 8:1:1, wherein a solvent is N-methyl-2-pyrrolidone (NMP), the solid content is 25%, uniformly coating the mixture on an aluminum foil with the thickness of 0.02mm, and drying, rolling and cutting the aluminum foil into a carbon positive electrode sheet;
the carbon positive electrode plate is uniformly adopted as the positive electrode, the metal lithium electrode is adopted as the negative electrode, the lithium/thionyl chloride battery electrolyte prepared in the embodiments 1 to 5 of the invention and the electrolyte in the comparative example are sequentially adopted to respectively prepare the lithium/thionyl chloride battery, the battery is subjected to charge and discharge tests after circulating for 200 weeks at a multiplying power of 0.05C under 3.87V, the test results are shown in table 1, and the battery is subjected to charge and discharge tests under any multiplying power of 0.025-2C, and the test results are shown in table 2.
Table 1 test results of battery charging and discharging performance
Figure GDA0002372825410000181
From the test data in table 1, it can be seen that after 200 cycles of charging and discharging the lithium/thionyl chloride battery electrolytes prepared in examples 1 to 5 of the present invention, the capacity retention rates were all above 90% and up to 93.7%, and the average discharge voltages were 3.36V, 3.34V, 3.32V, 3.35V, and 3.37, respectively, whereas after 200 cycles of charging and discharging the lithium/thionyl chloride battery electrolytes, the capacity retention rates were 76.3%, and the average discharge voltage was 3.12V, which indicates that the cycling performance of the lithium/thionyl chloride battery electrolytes prepared in examples 1 to 5 of the present invention is better than that of the lithium/thionyl chloride battery electrolytes prepared in comparative examples, and the voltage hysteresis phenomenon is also significantly improved.
Table 2 test results of charge and discharge performance of battery under different multiplying power
Figure GDA0002372825410000191
As can be seen from the test data in table 2, the plateau voltage and the capacity of the battery using the electrolyte for a lithium/thionyl chloride battery prepared in example 1 according to the present invention were higher than those of the battery using the electrolyte for a lithium/thionyl chloride battery prepared in comparative example 1, and the results showed that the battery using the electrolyte for a lithium/thionyl chloride battery prepared in example 1 according to the present invention had good discharge voltage and discharge capacity.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims (6)

1. A lithium/thionyl chloride battery electrolyte is characterized in that: the electrolyte comprises thionyl chloride, electrolyte salt and an additive, wherein the molar concentration of a thionyl chloride solution of the electrolyte salt is 0.1-1mol/L, and the mass of the additive is 0.01-0.5% of the total mass of the electrolyte;
the additive comprises a first additive and a second additive, wherein the structural formula of the first additive is as follows:
Figure FDA0002372825400000011
wherein X is halogen; r1Is nitrile group, amido group, hydroxyl group or nitro group; r2、R3Are each hydrogen, mono-or polysubstituted C1-C6 alkyl, aryl, C1-C6 alkoxy or halogenated C1-C6 alkoxy; r4Is C1-C6 alkyl or C1-C6 alkyl mono-or poly-substituted with halogen;
the second additive has the structural formula:
Figure FDA0002372825400000012
wherein, X1Is halogen; r11、R21、R31Are each C1-C10 alkyl, halogenated C1-C10 alkyl, C1-C10 alkoxy or halogenated C1-C10 alkoxy; r41Is unsubstituted or substituted by C1-C6 alkylSubstituted heterocyclyl, said heterocyclyl containing one or more of the elements O, N, S;
the electrolyte salt is one or more of lithium bis (fluorosulfonyl) imide, lithium bis (oxalato) borate, lithium trifluoromethanesulfonate, lithium tris (trifluoromethylsulfonyl) methide, lithium hexafluorophosphate, lithium tris (oxalato) phosphate, lithium difluorobis (oxalato) phosphate and lithium tetrafluoro (oxalato) phosphate;
the mass of the first additive accounts for 0.005-0.3% of the total mass of the electrolyte, and the mass of the second additive accounts for 0.005-0.2% of the total mass of the electrolyte.
2. The method of claim 1, wherein the method comprises the steps of:
(1) distilling thionyl chloride, and collecting fractions;
(2) weighing electrolyte salt, putting the electrolyte salt into the thionyl chloride fraction prepared in the step (1), and fixing the volume to obtain a thionyl chloride solution of the electrolyte salt;
(3) purification of the first additive: leaching the first additive by using acetone to obtain a first additive leaching solution, distilling the leaching solution to obtain a first additive, and drying to obtain a purified first additive;
(4) purification of the second additive: purifying the second additive by adopting a sublimation purifying device:
(a) adding molten salt into a heating chamber through a feeding port, and heating the molten salt by adopting a first molten salt heating rod and a second molten salt heating rod;
(b) filling a second additive into the sublimation material loading boat, paving silica gel on the second additive, then putting the second additive into the cylindrical pipe, closing the end door, vacuumizing the cylindrical pipe by using a vacuum pump through a vacuum cooling pipe, and finishing the purification of the second additive after a period of time;
(5) and (3) weighing the purified first additive obtained in the step (3) and the purified second additive obtained in the step (4), adding the weighed purified first additive and the purified second additive into the thionyl chloride solution of the electrolyte salt obtained in the step (2), and continuously stirring until the purified first additive and the purified second additive are completely dissolved to obtain the lithium thionyl chloride battery electrolyte.
3. The method of claim 2, wherein the method comprises the steps of:
(1) putting thionyl chloride into a flask, heating for distillation, and collecting fractions at 70-80 ℃;
(2) weighing electrolyte salt, dissolving the electrolyte salt in the thionyl chloride fraction prepared in the step (1) under an inert atmosphere condition, and performing constant volume to obtain a thionyl chloride solution of the electrolyte salt with the molar concentration of 0.1-1 mol/L;
(3) purification of the first additive: leaching the first additive by using acetone to obtain a first additive leaching solution, distilling the leaching solution to obtain a first additive, and drying to obtain a purified first additive; the leaching temperature is 30-45 ℃, the leaching time is 1-4h, and the distillation is carried out at 40-80 ℃ in a reduced pressure distillation mode;
(4) purification of the second additive: purifying the second additive by adopting a sublimation purifying device:
(a) adding molten salt into a heating chamber through a feeding port, and heating the molten salt by adopting a first molten salt heating rod and a second molten salt heating rod to enable the temperature to reach 200-250 ℃;
(b) filling a second additive into the sublimation material loading boat, paving silica gel on the second additive, then putting the second additive into the cylindrical tube, closing the end door, pumping the vacuum degree to 0.03-0.08KPa through a vacuum cooling tube, and finishing the purification of the second additive after 6-15 h;
(5) and (3) weighing the purified first additive obtained in the step (3) and the purified second additive obtained in the step (4), adding the weighed purified first additive and the purified second additive into the thionyl chloride solution of the electrolyte salt obtained in the step (2), and continuously stirring until the purified first additive and the purified second additive are completely dissolved to obtain the lithium thionyl chloride battery electrolyte.
4. The method of preparing an electrolyte for a lithium/thionyl chloride battery according to claim 2 or 3, characterized in that: the molten salt in the step (a) is a mixture of sodium nitrite and potassium nitrite with equal mass.
5. The method of claim 4, wherein the method comprises the steps of: and (4) transferring the leaching solution into a shaker before distillation in the step (3), and shaking for 30-60min at the speed of 100-300 r/min.
6. The method of claim 5, wherein the method comprises the steps of: the step (1), the step (2) and the step (3) are all operated in a dry environment with the relative humidity less than or equal to 0.5-1%.
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