CN115799628A - Non-aqueous electrolyte and battery - Google Patents

Non-aqueous electrolyte and battery Download PDF

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CN115799628A
CN115799628A CN202111062932.5A CN202111062932A CN115799628A CN 115799628 A CN115799628 A CN 115799628A CN 202111062932 A CN202111062932 A CN 202111062932A CN 115799628 A CN115799628 A CN 115799628A
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lithium
carbonate
solvent
battery
electrolytic solution
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夏兰
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Ningbo University
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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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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Abstract

The invention provides a nonaqueous electrolyte solution which comprises a nonaqueous organic solvent and does not comprise a lithium salt. The nonaqueous electrolytic solution provided by the invention does not contain lithium salt, and at least one of the electrodes of the battery contains lithium element. In the charging and discharging process, lithium ions which are deintercalated in the electrode serve as conductive ions through the non-aqueous electrolyte, and the normal charging and discharging behaviors of the battery are not influenced. Meanwhile, the non-aqueous electrolyte provided by the invention can form an effective interface film on the surfaces of a positive electrode and a negative electrode, so that the lithium ion battery prepared from the non-aqueous electrolyte provided by the invention ensures better cycle performance, and can greatly reduce and simplify the cost of the electrolyte in the aspects of configuration, storage, transportation and use and improve the environmental safety.

Description

Non-aqueous electrolyte and battery
Technical Field
The invention belongs to the technical field of lithium batteries, and particularly relates to a non-aqueous electrolyte and a battery.
Background
Currently, lithium ion batteries have been widely used in the fields of new energy vehicles, energy storage, and the like. The electrolyte used in commercial lithium ion batteries is generally composed of an organic carbonate mixed solvent and a lithium salt such as lithium hexafluorophosphate LiPF dissolved therein 6 The composition is as follows. Lithium salts have long been recognized as an essential component in lithium ion battery electrolytes. In recent years, with the rapid increase of the production of lithium ion batteries, the demand for lithium salts is increasing, resulting in the high cost of lithium ion batteries. On the other hand, in the actual battery, a trace amount of water and ethanol, liPF, is present 6 The lithium salt will be melted and decomposed by heat absorption at a temperature not too high (80-100 ℃), and LiF and PF are produced 5 。PF 5 As a strong nucleophilic reagent, the compound attacks the lone pair electrons on the oxygen atoms of trace water in organic carbonate solvent molecules and electrolyte, leads to the exothermic decomposition of the organic carbonate solvent molecules and the oxygen atoms of trace water in the electrolyte, generates a large amount of highly toxic alkyl fluorophosphate and releases the highly toxic alkyl fluorophosphateA large amount of heat is generated. The instability of the lithium salt in the practical application process increases difficulties in the preparation, storage, transportation and the like of the lithium ion battery electrolyte, and meanwhile, causes harm which is difficult to eliminate to the environment and the body health of workers. Although attempts have been made to develop some other stable lithium salts such as LiTFSI, etc., the cost will be higher.
Disclosure of Invention
In view of the above, the present invention provides a nonaqueous electrolyte and a battery, which can greatly reduce and simplify the costs of electrolyte configuration, storage, transportation and use and improve the environmental safety while ensuring the normal performance of the lithium ion battery.
The invention provides a nonaqueous electrolytic solution which comprises a nonaqueous organic solvent and does not comprise a lithium salt.
Preferably, the lithium salt is selected from lithium hexafluorophosphate LiPF 6 Lithium bis (trifluoromethanesulfonylimide) LiTFSI, lithium bis (fluorosulfonylimide) LiFSI, liAsF 6 ，LiBF 4 ，LiClO 4 One or more of.
Preferably, the non-aqueous organic solvent is selected from one or more of a carbonate solvent, a carboxylate solvent, a cyclic lactone solvent, an ether solvent, an ionic liquid, a phosphate solvent, a fluoro carbonate solvent, a fluoro carboxylate solvent and a fluoro ether solvent.
Preferably, the carbonate solvent is selected from one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, vinylene carbonate and ethylene vinylene carbonate; the cyclic lactone compounds are selected from one or more of gamma-butyrolactone, 1,3-propane sultone and 1,4-propane sultone; the ether solvent is selected from one or more of dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran and 1,3-dioxolane; the phosphate solvent is selected from one or more of trimethyl phosphate TMP and methyl phosphite DMMP; the fluoro carbonate solvent is selected from one or more of fluoro ethylene carbonate and difluoroethylene carbonate; the fluorinated carboxylic ester solvent is selected from one or more of methyl trifluoropropionate, ethyl trifluoropropionate, methyl trifluoroacetate, ethyl trifluoroacetate, methyl pentafluoropropionate and ethyl pentafluoropropionate; the fluoroether solvent is selected from one or more of nonafluoro n-butyl methyl ether, nonafluoro isobutyl methyl ether, heptafluoro n-propyl methyl ether, heptafluoro isopropyl methyl ether and hexafluoroisopropyl methyl ether.
Preferably, the nonaqueous electrolytic solution further includes an additive.
Preferably, the additive is selected from one or more of fluoroethylene carbonate FEC, VC, succinic anhydride compounds, maleic anhydride compounds, caprolactam compounds, succinonitrile, tris (pentafluorophenyl) borane, isocyanate compounds, sulfur-containing lactone compounds, sulfolane, tris (pentafluorophenyl) phosphorous acid, fluorophosphate ester, tetramethoxytitanium, tris (hexafluoroisopropyl) phosphate ester and ionic salt.
Preferably, the ionic salt is selected from one or more of nitrate, carbonate, fluoride and sulfate.
Preferably, the mass percentage of the additive in the non-aqueous organic solvent is 0.05-50%.
The invention also provides a battery, which comprises a positive electrode, a diaphragm, a negative electrode, an electrolyte and a battery shell, wherein the electrolyte is selected from the non-aqueous electrolyte, and at least one of the positive electrode and the negative electrode contains lithium element.
Preferably, the lithium element-containing compound is selected from the group consisting of a lithium-containing positive electrode active material, metallic lithium, lithiated graphite, lithiated silicon, a lithium salt LiPF 6 ，LiCl，LiNO 3 ，Li 2 CO 3 ，Li 2 O，LiTFSI，LiFSI，LiPO 2 F 2 ，LiBF 4 ，LiClO 4 One or more of lithium bis (oxalato) borate, lithium difluoro (oxalato) borate, lithium tris (oxalato) phosphate, lithium difluoro (oxalato) phosphate, lithium tetrafluoro (oxalato) phosphate and lithium-containing organic matters;
the mass percentage of the lithium-containing substance in the electrode is 0.05-20%.
Compared with the prior art, the invention provides a nonaqueous electrolytic solution which comprises a nonaqueous organic solvent and does not comprise a lithium salt. The nonaqueous electrolytic solution provided by the invention does not contain lithium salt, and at least one of the electrodes of the battery contains lithium element. In the charging and discharging process, lithium ions which are deintercalated in the electrode serve as conductive ions through the non-aqueous electrolyte, and the normal charging and discharging behaviors of the battery are not influenced. Meanwhile, the non-aqueous electrolyte provided by the invention can form an effective interface film on the surfaces of a positive electrode and a negative electrode, so that the lithium ion battery prepared from the non-aqueous electrolyte provided by the invention ensures better cycle performance, and can greatly reduce and simplify the cost of the electrolyte in the aspects of configuration, storage, transportation and use and improve the environmental safety.
Experimental results show that the lithium ion battery prepared from the non-aqueous electrolyte provided by the invention has charge-discharge electrochemical behavior equivalent to that of a lithium ion battery with a conventional electrolyte, and the lithium ion battery prepared from the non-aqueous electrolyte provided by the invention has better cycle performance.
Drawings
FIG. 1 is LiCoO of example 1 and comparative example 1 2 A comparative graph of charge-discharge curves of 2.7-4.3V at 0.2C multiplying power of the Li battery at normal temperature;
FIG. 2 is Li/Li [ Li ] of example 6 0.144 Ni 0.136 Co 0.136 Mn 0.544 ]O 2 A battery first-cycle charge-discharge curve chart of 2.0-4.8V at 0.05C multiplying power under a normal-temperature environment;
FIG. 3 shows Li in example 8 4 Ti 5 O 12 /LiFePO 4 The first cycle charge-discharge curve of the battery is 2.5-0V under the 0.2C multiplying power under the normal temperature environment.
Detailed Description
The invention provides a nonaqueous electrolyte solution which comprises a nonaqueous organic solvent and does not comprise a lithium salt.
In the present invention, the lithium salt is selected from lithium hexafluorophosphate LiPF 6 Lithium bis (trifluoromethanesulfonylimide) LiTFSI, lithium bis (fluorosulfonylimide) LiFSI, liAsF 6 ，LiBF 4 ，LiClO 4 One or more of.
In the present invention, the non-aqueous organic solvent is selected from one or more of non-fluorinated solvents and fluorinated solvents.
Wherein the non-fluorinated solvent is selected from one or more of carbonate solvents, carboxylic ester solvents, cyclic lactone solvents, ether solvents, ionic liquids and phosphate solvents.
The carbonate solvent is selected from one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, vinylene carbonate and ethylene vinylene carbonate; the cyclic lactone compounds are selected from one or more of gamma-butyrolactone, 1,3-propane sultone and 1,4-propane sultone; the ether solvent is selected from one or more of dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane; the phosphate solvent is selected from one or more of trimethyl phosphate TMP and methyl methylene phosphate DMMP.
The fluorinated solvent is selected from one or more of fluorinated carbonate solvents, fluorinated carboxylic ester solvents and fluorinated ether solvents.
The fluoro carbonate solvent is selected from one or more of fluoro ethylene carbonate and difluoroethylene carbonate; the fluorinated carboxylic ester solvent is selected from one or more of methyl trifluoropropionate, ethyl trifluoropropionate, methyl trifluoroacetate, ethyl trifluoroacetate, methyl pentafluoropropionate and ethyl pentafluoropropionate; the fluoroether solvent is selected from one or more of nonafluoro n-butyl methyl ether, nonafluoro isobutyl methyl ether, heptafluoro n-propyl methyl ether, heptafluoro isopropyl methyl ether and hexafluoroisopropyl methyl ether.
In some embodiments of the invention, the nonaqueous electrolyte further comprises an additive.
The additive is selected from one or more of fluoroethylene carbonate FEC, VC, succinic anhydride compounds, maleic anhydride compounds, caprolactam compounds, succinonitrile, tris (pentafluorophenyl) borane, isocyanate compounds, sulfur-containing lactone compounds, sulfolane, tris (pentafluorophenyl) phosphorous acid, fluorophosphate, tetramethoxytitanium, tris (hexafluoroisopropyl) phosphate and ionic salts. The sulfur-containing lactone compound is preferably 1,3-propanesultone.
The ionic salt is selected from one or more of nitrate, carbonate, fluoride and sulfate.
The nitrate is selected from one or more of lithium nitrate, sodium nitrate, potassium nitrate, zinc nitrate, aluminum nitrate, magnesium nitrate, copper nitrate and ammonium nitrate; the carbonate is selected from one or more of lithium carbonate, sodium carbonate, potassium carbonate, zinc carbonate, aluminum carbonate, magnesium carbonate, copper carbonate and ammonium carbonate; the fluoride salt is selected from one or more of lithium fluoride, sodium fluoride, potassium fluoride, zinc fluoride, aluminum fluoride, magnesium fluoride, copper fluoride and ammonium fluoride; the sulfate is selected from one or more of lithium sulfate, sodium sulfate, potassium sulfate, zinc sulfate, aluminum sulfate, magnesium sulfate, copper sulfate and ammonium sulfate.
The mass percentage of the additive in the non-aqueous organic solvent is 0.05% to 50%, preferably 0.05%, 0.1%, 0.5%, 1.0%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or any value between 0.05% and 50%.
The invention also provides a battery, which comprises a positive electrode, a diaphragm, a negative electrode, an electrolyte and a battery shell, wherein the electrolyte is selected from the non-aqueous electrolyte, and at least one of the positive electrode and the negative electrode contains lithium element.
The lithium-containing element compound is selected from lithium-containing positive electrode active material, metal lithium, lithiated graphite, lithiated silicon and lithium salt LiPF 6 ，LiCl，LiNO 3 ，Li 2 CO 3 ，Li 2 O，LiTFSI，LiFSI，LiPO 2 F 2 ，LiBF 4 ，LiClO 4 One or more of lithium bis (oxalato) borate, lithium difluoro (oxalato) borate, lithium tris (oxalato) phosphate, lithium difluoro (oxalato) phosphate, lithium tetrafluoro (oxalato) phosphate and lithium-containing organic matters, wherein the lithium-containing organic matters are selected from one or more of methyl lithium carbonate and ethyl lithium carbonate;
the lithium-containing positive active material is selected from one or more of lithium cobaltate, lithium iron phosphate, lithium manganate, a ternary positive material and a lithium-rich positive material.
The positive and negative electrode materials may also be mixed with a lithium-containing material, preferably a lithium simple substance, a lithium-containing compound selected from lithium salt LiPF, and a lithium-containing organic substance 6 ，LiCl，LiNO 3 ，Li 2 CO 3 ，Li 2 O，LiTFSI，LiFSI，LiPO 2 F 2 ，LiBF 4 ，LiClO 4 The lithium oxalate borate is one or more of lithium bis (oxalato) borate, lithium difluoro (oxalato) borate LiDFOB, lithium tris (oxalato) phosphate, lithium difluoro (oxalato) phosphate, lithium tetrafluoro (oxalato) phosphate and lithium-containing organic matters, wherein the lithium-containing organic matters are selected from one or more of methyl lithium carbonate and ethyl lithium carbonate.
The mass percentage of the lithium-containing material in the electrode is 0.05-20%, preferably 0.05%, 0.1%, 0.5%, 1.0%, 5%, 10%, 15%, 20%, or any value between 0.05-20%.
The invention provides a novel non-aqueous electrolyte system. The non-aqueous electrolyte does not contain any lithium salt and only consists of a single or mixed organic solvent. The nonaqueous electrolyte system of the present invention may contain an additive. In the battery using the non-aqueous electrolyte, one of the positive electrode and the negative electrode of the battery is required to be a substance containing lithium elements, the positive electrode material can be a lithium ion battery positive electrode material, preferably lithium cobaltate, lithium iron phosphate, lithium manganate, a ternary positive electrode material, a lithium-rich positive electrode material and the like, and the negative electrode material is metallic lithium, lithiated graphite, a lithiated silicon negative electrode and the like. The positive and negative electrode materials of the battery can also be mixed with substances containing lithium elements, such as lithium simple substance and lithium-containing compound (which can include lithium salt LiPF) 6 ，LiCl，LiNO 3 ，Li 2 CO 3 ，Li 2 O，LiTFSI，LiPO 2 F 2 Etc.). The non-aqueous electrolyte provided by the invention does not contain lithium salt, and when the non-aqueous electrolyte is applied to the lithium ion battery, the performance of the battery under normal conditions can be ensured, so that the cost of the battery can be greatly reduced, and the use of the electrolyte in the battery assembly process can be greatly simplified as the electrolyte system does not contain lithium salt which is unstable in air,The cost of transportation and storage and the like and the environmental pollution are reduced.
In some embodiments of the invention, during charging of the battery, lithium in the positive electrode material is extracted through the non-aqueous electrolyte and intercalated into the negative electrode material; the discharge process is reversed. In some embodiments of the invention, when lithium is included in the negative electrode material, such as by directly using a metallic lithium plate as the negative electrode and the positive electrode is a sulfur positive electrode, during the first discharge of the battery, the lithium in the negative electrode material is extracted and passes through the non-aqueous electrolyte and is incorporated into the positive electrode material; and (4) charging the battery just in reverse.
In the charging and discharging process, the deintercalated lithium ions are used as conductive ions through the non-aqueous electrolyte, and the normal charging and discharging behaviors of the battery are not influenced. Meanwhile, the non-aqueous electrolyte provided by the invention can form an effective interface film on the surfaces of the positive electrode and the negative electrode, so that the lithium ion battery prepared from the non-aqueous electrolyte provided by the invention ensures better cycle performance, and can greatly reduce and simplify the cost of the electrolyte in the aspects of configuration, storage, transportation and use and improve the environmental safety.
Experimental results show that the lithium ion battery prepared from the non-aqueous electrolyte provided by the invention has charge-discharge electrochemical behavior equivalent to that of a lithium ion battery with a conventional electrolyte, and the lithium ion battery prepared from the non-aqueous electrolyte provided by the invention has better cycle performance.
For further understanding of the present invention, the following examples are provided to illustrate the nonaqueous electrolytic solution and the battery of the present invention, and the scope of the present invention is not limited by the following examples.
The reagents used in the following examples of the present invention are all commercially available.
Example 1
In a glove box filled with argon, 50mL of ethylene carbonate EC and 50mL of dimethyl carbonate DMC were mixed uniformly to obtain a mixed organic solvent which is nonaqueous electrolyte I, namely EC-DMC (volume ratio 1:1). Adding the prepared non-aqueous electrolyte into LiCoO serving as a positive electrode material of lithium cobaltate 2 In 2032 button cell with negative electrode of lithium sheet and diaphragm of Celgard polypropylene diaphragm, the cell is processedAnd (6) testing. The battery was subjected to a charge and discharge test at a current density of 0.2C at 2.7-4.3V, and the test results are shown in fig. 1, table 1 and table 2.
Example 2
In a glove box filled with argon, 50mL of ethylene carbonate EC and 50mL of dimethyl carbonate DMC were mixed uniformly, and LiNO was added 3 Adding the LiNO into the organic solvent under the condition of stirring at 25 ℃, wherein the LiNO is 3 The mass percent concentration in the electrolyte was 1%, to obtain a nonaqueous electrolyte solution II, i.e., 1% LiNO 3 EC-DMC (volume ratio 1:1). Adding the prepared non-aqueous electrolyte into LiCoO serving as a positive electrode material of lithium cobaltate 2 The cell was tested in a 2032 button cell with a lithium plate as the negative electrode and a Celgard polypropylene separator as the separator. The battery was subjected to a charge and discharge test at a current density of 0.2C at 2.7-4.3V, and the test results are shown in tables 1 and 2.
Example 3
In a glove box filled with argon, 50mL of 1,3-dioxolane DOL and 50mL of dimethoxyethane DME were mixed uniformly to obtain a mixed organic solvent which is a nonaqueous electrolyte III, namely DOL-DME (the volume ratio is 1:1). Adding the prepared non-aqueous electrolyte into LiFePO of which the anode is lithium iron phosphate anode material 4 And the negative electrode is a lithium plate, and the diaphragm is a Celgard polypropylene diaphragm, and the battery is tested in a 2032 button cell type battery. The battery was subjected to a charge and discharge test at a current density of 0.2C at 2.0-3.8V, and the test results are shown in tables 1 and 2.
Example 4
50mL of 1,3-dioxolan DOL and 50mL of dimethoxyethane DME were mixed uniformly in a glove box filled with argon, and lithium difluorooxalato borate LiDFOB was added to the organic solvent at 25 ℃ with stirring, the concentration of LiDFOB in the electrolyte being 0.1% by mass, to obtain a nonaqueous electrolyte IV, i.e., 0.1% LiDFOB/DOL-DME (1:1 by volume). Adding the prepared non-aqueous electrolyte into LiFePO of which the anode is lithium iron phosphate anode material 4 And the negative electrode is a lithium plate, and the diaphragm is a Celgard polypropylene diaphragm, and the battery is tested in a 2032 button cell type battery. The battery is subjected to charge and discharge tests under the current density of 0.2C and the voltage of 2.0-3.8VThe test results are shown in tables 1 and 2.
Example 5
In a glove box filled with argon, 30mL of fluoroethylene carbonate FEC and 70mL of trimethyl phosphate TMP were mixed uniformly to obtain a mixed organic solvent which was nonaqueous electrolyte V, i.e., FEC-TMP (volume ratio 3:7). Adding the prepared non-aqueous electrolyte into LiCoO serving as a positive electrode material of lithium cobaltate 2 The cell was tested in a 2032 button cell with a lithium plate as the negative electrode and a Celgard polypropylene separator as the separator. The battery is subjected to charge and discharge tests at a current density of 0.2C and at a voltage of 2.7-4.3V, and the test results are shown in tables 1 and 2.
Example 6
In a glove box filled with argon, 30mL of fluoroethylene carbonate FEC and 70mL of trimethyl phosphate TMP were mixed uniformly to obtain a mixed organic solvent which was nonaqueous electrolyte V, i.e., FEC-TMP (volume ratio 3:7). Adding the prepared non-aqueous electrolyte into a positive electrode to obtain a lithium-rich positive electrode material Li [ Li ] 0.144 Ni 0.136 Co 0.136 Mn 0.544 ]O 2 And the negative electrode is a lithium plate, and the diaphragm is a Celgard polypropylene diaphragm, and the battery is tested in a 2032 button cell type battery. The battery was tested for charge and discharge at a current density of 0.05C at 2.0-4.8V, and the results are shown in fig. 2 and table 1.
Example 7
30mL of fluoroethylene carbonate FEC and 70mL of trimethyl phosphate TMP were mixed uniformly in a glove box filled with argon gas, and LiNO was added 3 Adding the LiNO into the organic solvent under the condition of stirring at 25 ℃, wherein the LiNO is 3 The mass percentage concentration in the electrolyte was 10%, to obtain a nonaqueous electrolyte VI, i.e., 10% LiNiO3/FEC-TMP (volume ratio 3:7). Adding the prepared non-aqueous electrolyte into LiCoO serving as a positive electrode material of lithium cobaltate 2 And the negative electrode is a lithium plate, and the diaphragm is a Celgard polypropylene diaphragm, and the battery is tested in a 2032 button cell type battery. The battery was subjected to a charge and discharge test at a current density of 0.2C at 2.7-4.3V, and the test results are shown in tables 1 and 2.
Example 8
In the air of the conventional environment (such as the temperature of 30 ℃ and the humidity of 84 percent), 3 is added0mL of fluoroethylene carbonate FEC, 70mL of trimethyl phosphate TMP were mixed uniformly to obtain a mixed organic solvent as a nonaqueous electrolyte VII, namely FEC-TMP (volume ratio 3:7, in air). Adding the obtained non-aqueous electrolyte into a positive electrode which is lithium iron phosphate positive electrode material LiFePO 4 The negative electrode is Li 4 Ti 5 O 12 And the separator was Celgard polypropylene separator in 2032 button cells, which were tested. The battery was subjected to charge and discharge tests at a current density of 0.2C at 2.5-0V, and the test results are shown in fig. 3 and table 1.
Comparative example 1
The carbonate electrolyte is a commercially available carbonate electrolyte with the type S-3015A, and the main components of the carbonate electrolyte comprise 30 percent by volume of EC, 70 percent by volume of DMC and LiPF 6 The LiPF 6 The molar concentration in Ethylene Carbonate (EC) and dimethyl carbonate (DMC) was 1mol/L. In a glove box filled with argon, electrolyte of type S-3015A is added to LiCoO which is a lithium cobaltate positive electrode material 2 The cell was tested in a 2032 button cell with a lithium plate as the negative electrode and a Celgard polypropylene separator as the separator. The battery was subjected to a charge and discharge test at a current density of 0.2C at 2.7-4.3V, and the test results are shown in fig. 1 and table 1.
Table 1 shows the first cycle charge/discharge specific capacity and the first cycle efficiency of the batteries of examples 1 to 8 and comparative example 1. As can be seen from the test data in table 1, the first cycle reversible discharge specific capacity of the battery of example using the lithium salt-free nonaqueous electrolyte is significantly increased, the first cycle efficiency is greatly improved, and the cycle performance of the battery is significantly better than that of the battery of comparative example 1 using the conventional carbonate electrolyte, and at the same time, the cycle performance of the battery of example 3 using the additive-free nonaqueous electrolyte is significantly better than that of the battery of example 1 using the lithium salt-free nonaqueous electrolyte without the additive.
FIG. 1 and Table 1 show LiCoO of example 1 and comparative example 1 2 Compared with the first-cycle charge-discharge curve of the Li battery under the condition of 0.2C multiplying power of 2.7-4.3V under the normal temperature environment, the curve delta in the graph is the first-cycle charge-discharge curve of the battery of the embodiment 1, the first-cycle coulombic efficiency is 92.34 percent, the curve □ is the first-cycle charge-discharge curve of the battery of the comparison example 1, and the first-cycle coulombic efficiency is 89.16 percent. As can be seen from FIG. 1 and Table 1, the non-aqueous power of the present inventionLiCoO prepared from hydrolysate 2 The first-cycle charge-discharge performance of the Li battery under normal-temperature circulation is obviously superior to the first-cycle electrochemical behavior of the battery prepared by the conventional electrolyte, and the first-cycle efficiency is higher. Table 2 shows LiCoO of example 1, example 2, example 5, example 7 and comparative example 1 2 The Li battery is compared with the charge-discharge cycle performance under the 0.2C multiplying power of 2.7-4.3V under the normal temperature environment. Wherein LiNO is added to the nonaqueous electrolyte in each of examples 2 and 7 3 As an additive. As can be seen from Table 2, after 50 weeks of cycling, the specific discharge capacities of the batteries in the salt-free nonaqueous electrolytic solutions I, II, V and VI and the conventional electrolytic solution were 137.9, 144.6, 133.6, 141.8 and 129.2mAh g, respectively -1 The corresponding capacity retention rates were 95.04%, 95.13%, 87.61%, 95.17% and 90.35%, respectively, indicating that the electrolyte battery containing the additive lithium nitrate had the most excellent cycling stability.
In example 8, since the electrolyte system does not contain lithium salt unstable in air, the cost of the processes of using, transporting, storing and the like of the electrolyte in the battery assembly process can be greatly simplified and the environmental pollution can be reduced. Example 8 the cell can be fully assembled in a conventional ambient (e.g. 30 ℃ C., 84% humidity) air, cell Li with mixed organic solvent FEC: TMP =3:7 (v/v) non-aqueous electrolyte III 4 Ti 5 O 12 /LiFePO 4 Under the current density of 0.2C and 2.5-0V, the first cycle charge-discharge specific capacity is 186.7 mAh g and 145.2mAh g respectively -1 And shows better electrochemical performance.
TABLE 1 comparison of specific first-cycle charge-discharge capacity and first-cycle efficiency of batteries of examples 1 to 8 and comparative example 1
Figure BDA0003257071200000091
Table 2 comparison of 50-cycle performance of the cells of example 1, example 2, example 5, example 7 and comparative example 1
Figure BDA0003257071200000092
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (10)

1. A nonaqueous electrolytic solution characterized by comprising a nonaqueous organic solvent and not comprising a lithium salt.
2. The nonaqueous electrolytic solution of claim 1, wherein the lithium salt is selected from lithium hexafluorophosphate (LiPF) 6 Lithium bis (trifluoromethanesulfonylimide) LiTFSI, lithium bis (fluorosulfonylimide) LiFSI, liAsF 6 ，LiBF 4 ，LiClO 4 One or more of.
3. The nonaqueous electrolytic solution of claim 1, wherein the nonaqueous organic solvent is one or more selected from the group consisting of a carbonate solvent, a carboxylate solvent, a cyclic lactone solvent, an ether solvent, an ionic liquid, a phosphate solvent, a fluorocarbonate solvent, a fluorocarboxylate solvent, and a fluoroether solvent.
4. The nonaqueous electrolytic solution of claim 3, wherein the carbonate-based solvent is one or more selected from ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dipropyl carbonate, propyl methyl carbonate, propyl ethyl carbonate, vinylene carbonate, and vinylene carbonate; the cyclic lactone compounds are selected from one or more of gamma-butyrolactone, 1,3-propane sultone and 1,4-propane sultone; the ether solvent is selected from one or more of dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran and 1,3-dioxolane; the phosphate solvent is selected from one or more of trimethyl phosphate TMP and methyl phosphite DMMP; the fluoro carbonate solvent is selected from one or more of fluoro ethylene carbonate and difluoroethylene carbonate; the fluorinated carboxylic ester solvent is selected from one or more of methyl trifluoropropionate, ethyl trifluoropropionate, methyl trifluoroacetate, ethyl trifluoroacetate, methyl pentafluoropropionate and ethyl pentafluoropropionate; the fluoroether solvent is selected from one or more of nonafluoro n-butyl methyl ether, nonafluoro isobutyl methyl ether, heptafluoro n-propyl methyl ether, heptafluoro isopropyl methyl ether and hexafluoroisopropyl methyl ether.
5. The nonaqueous electrolytic solution of claim 1, wherein the nonaqueous electrolytic solution further comprises an additive.
6. The nonaqueous electrolytic solution of claim 5, wherein the additive is selected from one or more of fluoroethylene carbonate (FEC), vinyl Chloride (VC), succinic anhydride compounds, maleic anhydride compounds, caprolactam compounds, succinonitrile, tris (pentafluorophenyl) borane, isocyanate compounds, sulfur-containing lactone compounds, sulfolane, tris (pentafluorophenyl) phosphorous acid, fluoro phosphate esters, tetramethoxy titanium, tris (hexafluoroisopropyl) phosphate, and ionic salts.
7. The nonaqueous electrolytic solution of claim 6, wherein the ionic salt is selected from one or more of nitrate, carbonate, fluoride and sulfate.
8. The nonaqueous electrolytic solution of claim 5, wherein the additive is present in the nonaqueous organic solvent in an amount of 0.05 to 50% by mass.
9. A battery comprising a positive electrode, a separator, a negative electrode, an electrolytic solution selected from the nonaqueous electrolytic solutions of any one of claims 1 to 8, and a battery case, wherein at least one of the positive electrode and the negative electrode contains lithium.
10. The battery of claim 9, wherein the lithium element-containing compound is selected from lithium-containing compoundsPositive electrode active material, lithium metal, lithiated graphite, lithiated silicon, lithium salt LiPF 6 ，LiCl，LiNO 3 ，Li 2 CO 3 ，Li 2 O，LiTFSI，LiFSI，LiPO 2 F 2 ，LiBF 4 ，LiClO 4 One or more of lithium bis (oxalato) borate, lithium difluoro (oxalato) borate, lithium tris (oxalato) phosphate, lithium difluoro (oxalato) phosphate, lithium tetrafluoro (oxalato) phosphate and lithium-containing organic matters;
the mass percentage of the lithium-containing substance in the electrode is 0.05-20%.
CN202111062932.5A 2021-09-10 2021-09-10 Non-aqueous electrolyte and battery Pending CN115799628A (en)

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