CN112909338A - Lithium iron disulfide battery electrolyte additive, electrolyte and lithium iron disulfide battery - Google Patents

Lithium iron disulfide battery electrolyte additive, electrolyte and lithium iron disulfide battery Download PDF

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CN112909338A
CN112909338A CN202110297933.1A CN202110297933A CN112909338A CN 112909338 A CN112909338 A CN 112909338A CN 202110297933 A CN202110297933 A CN 202110297933A CN 112909338 A CN112909338 A CN 112909338A
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electrolyte
iron disulfide
lithium iron
additive
lithium
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赵彦硕
王丽平
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Tianmu Lake Institute of Advanced Energy Storage Technologies Co Ltd
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Tianmu Lake Institute of Advanced Energy Storage Technologies 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
    • H01M10/056—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
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • 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
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • 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

Abstract

The embodiment of the invention relates to an electrolyte additive of a lithium iron disulfide battery, an electrolyte and the lithium iron disulfide battery; the lithium iron disulfide battery electrolyte comprises: electrolyte lithium salt, aprotic solvent and electrolyte additive A; wherein the structural formula (I) of the electrolyte additive A is as follows:
Figure DDA0002985022080000011
during the first discharge of the lithium iron disulfide battery, the electrolyte additive A reacts with polysulfide of the positive electrode on the surface of the positive electrode of the lithium iron disulfide battery to form a CEI film of a positive electrode-electrolyte interface phase for preventing the reaction of the polysulfide and the aprotic solvent.

Description

Lithium iron disulfide battery electrolyte additive, electrolyte and lithium iron disulfide battery
Technical Field
The invention relates to the technical field of lithium iron disulfide batteries, in particular to an electrolyte additive for a lithium iron disulfide battery, an electrolyte and a lithium iron disulfide battery.
Background
The lithium ion battery has the advantages of high specific energy, high charge-discharge efficiency, long service life and the like, and is one of the most promising chemical power sources at present. Many researchers are working on finding new electrode materials to improve the capacity, the rapid charge and discharge capacity, the safety and the cycle life of the lithium ion battery. Among them, iron-based oxides have attracted research interest due to their advantages of very high theoretical specific capacity (900 mAh/g), low cost, abundant resources, no pollution, etc., and have become one of the research hotspots for electrode materials in recent years. However, the iron-based oxide has poor conductivity, and has the problems of electrode structure degradation, rapid capacity reduction and poor cycle performance caused by large volume change in the charging and discharging processes, so that the application of the iron-based oxide in the lithium ion battery is severely restricted.
Lithium iron disulfide cell (Li/FeS)2) The electrolyte mainly comprises electrolyte salt and a solvent, the electrolyte salt is generally considered as the core of the electrolyte, the quality of the electrolyte salt directly affects the main performances of the battery such as capacity, power, service life and the like, and the electrolyte lithium salt meets the following conditions: 1) the electrolyte salt does not react with the anode and cathode materials, the active reaction substance and the solvent, and has a wider electrochemical window; 2) the solubility in an organic solvent is high, the dissociation is easy, and the conductivity is high; 3) the electrolyte salt has good thermal stability, does not decompose and react under the high and low temperature environment of the battery, and meets the safety requirement.
Lithium salt mainly adopted by the lithium iron disulfide battery electrolyte on the market at present is lithium iodide or lithium bistrifluoromethanesulfonylimide, but the cost of the lithium iodide and the lithium bistrifluoromethanesulfonylimide is high, and the lithium iodide is unstable in the electrolyte. The price of lithium hexafluorophosphate is relatively low, lithium hexafluorophosphate is also used as electrolyte in a laboratory, and LiPF is used as electrolyte salt of lithium hexafluorophosphate system electrolyte6Has the advantages of high conductivity, small internal resistance, high discharge speed and the like, but has strong hygroscopicity, is very sensitive to moisture and impurities in the solvent, and has LiPF (lithium ion plasma) under the action of trace moisture in the solvent6Decomposition produces Hydrogen Fluoride (HF). HF is a chemical substance with extremely strong corrosivity, is easy to corrode lithium metal of the cathode of the lithium-iron battery, and deposits a layer of compact lithium fluoride (LiF) on the surface of the lithium metal of the cathode to prevent the battery from continuously reacting, so that the capacity of the battery is greatly lost. The solvent for lithium hexafluorophosphate system electrolytes is often a carbonate solvent due to Li/FeS2The battery can form polysulfide LiS in the discharging processnWhile polysulfides are soluble in the carbonic acid esterThe agent reacts, thereby causing irreversible loss of battery capacity, and simultaneously causing increase of viscosity of the electrolyte, thereby increasing internal resistance and failing the battery.
In order to optimize the performance of lithium iron disulfide batteries while reducing the cost of lithium iron disulfide batteries, it is desirable to develop a safe electrolyte with lithium hexafluorophosphate as the primary electrolyte.
Disclosure of Invention
The invention aims to provide an electrolyte additive of a lithium iron disulfide battery, an electrolyte and the lithium iron disulfide battery, which can solve the problem of electrolyte lithium salt (particularly LiPF)6) And side reactions of the carbonate solvent during the battery cycling process, eventually leading to the problems of degradation of the electrode structure, rapid capacity drop and poor cycling performance.
To this end, in a first aspect, an embodiment of the present invention provides a lithium iron disulfide battery electrolyte, including: electrolyte lithium salt, aprotic solvent and electrolyte additive A;
wherein the structural formula (I) of the electrolyte additive A is as follows:
Figure BDA0002985022060000021
during the first discharge of the lithium iron disulfide battery, the electrolyte additive A reacts with polysulfide of the positive electrode on the surface of the positive electrode of the lithium iron disulfide battery to form a CEI film of a positive electrode-electrolyte interface phase for preventing the reaction of the polysulfide and the aprotic solvent.
Preferably, the electrolyte additive A accounts for 0.1-30% of the electrolyte by mass;
the concentration of the electrolyte lithium salt in the electrolyte is 0.5-3 mol/L calculated by lithium ions;
the aprotic solvent is selected from one or a combination of more of ethylene carbonate EC, methyl ethylene carbonate EMC, diethyl carbonate DEC, dimethyl carbonate DMC or propylene carbonate PC.
Preferably, the electrolyte further comprises an additive B, wherein the additive B comprises: one or more of vinylene carbonate VC, vinyl ethylene carbonate VEC, fluoroethylene carbonate FEC or vinyl sulfite ES.
Preferably, the additive B accounts for 0.5-20% of the electrolyte by mass.
Preferably, the electrolyte lithium salt is LiPF6。
In a second aspect, an embodiment of the present invention provides an electrolyte additive for a lithium iron disulfide battery, where v a structural formula of the electrolyte additive is:
Figure BDA0002985022060000031
during the first discharge of the lithium iron disulfide battery, the electrolyte additive A reacts with polysulfide of the positive electrode on the surface of the positive electrode of the lithium iron disulfide battery to form a CEI film of a positive electrode-electrolyte interface phase for preventing the reaction of the polysulfide and the aprotic solvent.
In a third aspect, embodiments of the present invention provide a lithium iron disulfide battery, including: the lithium iron disulfide battery electrolyte of any of claims 1-5, or comprising the lithium iron disulfide battery electrolyte additive of claim 6.
Preferably, the positive electrode of the lithium iron disulfide battery comprises iron disulfide, and the negative electrode is lithium.
The lithium iron disulfide battery electrolyte provided by the embodiment of the invention contains an electrolyte additive belonging to a phosphorus-containing compound and a siloxane compound, is preferentially oxidized under high voltage, plays a role in protecting a solvent and stabilizing an electrolyte lithium salt (especially LiPF)6) The function of (1); while the lone pair of electrons of O atom of siloxane compound is easy to combine with H+And Si and F have stronger affinity, so the electrolyte additive can also remove HF with corrosion effect; therefore, the application of the electrolyte can not only inhibit the dissolution of transition metal ions, but also prevent the formation of dense and destructive negative HF on the metallic lithium negative electrodeSolid Electrolyte Interface (SEI) films of extreme material properties. On the other hand, during the first discharge, the electrolyte additive can preferentially react with polysulfide on the surface of the positive electrode, so that a positive electrode-electrolyte interface phase (CEI) film for preventing the reaction of polysulfide and a solvent is formed, and therefore, the lithium iron disulfide battery electrolyte can effectively improve the first discharge capacity and improve the cycle performance.
Drawings
FIG. 1 is a graph showing the charge-discharge cycle of comparative example 1 according to the present invention;
FIG. 2 is a plot of cyclic voltammetry provided by comparative example 1 of the present invention;
FIG. 3 is a graph showing charge and discharge cycles of example 1, comparative example 2 and comparative example 3 according to the present invention;
FIG. 4 is a cyclic voltammogram provided in example 1 of the present invention;
FIGS. 5a and 5b show FeS before and after the cycle of comparative example 1 according to the invention2Scanning Electron Microscope (SEM) images of the electrodes, 5c, 5d are FeS before and after cycling, respectively, of example 1 of the present invention2SEM images of the electrodes;
FIG. 6 is a first-turn discharge curve of example 1, comparative example 2, and comparative example 3 of the present invention;
FIG. 7 is a graph showing the charge-discharge cycle of the battery of example 6 of the present invention;
FIG. 8 is a cyclic voltammogram provided in example 6 of the present invention;
FIG. 9 is a graph showing the charge-discharge cycle according to example 10 of the present invention;
FIG. 10 is a cyclic voltammogram provided in example 10 of the present invention.
Detailed Description
The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.
The embodiment of the invention provides an additive A of lithium iron disulfide battery electrolyte, which has the structural formula as follows:
Figure BDA0002985022060000051
the electrolyte additive A is used in the lithium iron disulfide battery electrolyte.
The lithium iron disulfide battery electrolyte comprises: an electrolytic lithium salt, an aprotic solvent, and the above electrolyte additive a.
The electrolyte additive A accounts for 0.1-30% of the electrolyte by mass.
The concentration of electrolyte lithium salt in the electrolyte is 0.5-3 mol/L calculated by lithium ions; the electrolyte lithium salt is preferably LiPF6。
The aprotic solvent can be selected from one or more of Ethylene Carbonate (EC), methyl ethylene carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC) or Propylene Carbonate (PC).
In a preferred embodiment, the electrolyte further comprises an additive B, wherein the additive B comprises: one or more of Vinylene Carbonate (VC), Vinyl Ethylene Carbonate (VEC), fluoroethylene carbonate (FEC) or vinyl sulfite (ES). The mass percentage of the additive B in the electrolyte is 0.5-20%.
The lithium iron disulfide battery electrolyte is used in a lithium iron disulfide battery, the positive electrode of the battery comprises iron disulfide, and the negative electrode is a lithium electrode.
Because the electrolyte additive A provided by the invention belongs to phosphorus-containing compounds and siloxane compounds, the electrolyte additive A can be preferentially oxidized under high voltage, plays a role in protecting a solvent and stabilizing electrolyte lithium salt (especially LiPF)6) The function of (1); while the lone pair of electrons of O atom of siloxane compound is easy to combine with H+And Si and F have strong affinity, so the electrolyte additive A can also remove HF with corrosion effect. Therefore, when the electrolyte containing the electrolyte adding machine A is applied to the lithium iron disulfide battery, the dissolution of transition metal ions can be inhibited, and HF can be prevented from forming a compact Solid Electrolyte Interface (SEI) film on a lithium metal cathode, which can destroy the performance of a cathode material. On the other hand, during the first discharge cycle, the electrolyte additive A will preferentially react with polysulfide on the surface of the positive electrode, thereby forming a positive electrode-electrolyte interface phase (CEI) film that hinders the reaction of polysulfide with solvent, and thus the lithium iron disulfide of the present inventionThe cell electrolyte can effectively improve the discharge capacity of the first circle and improve the cycle performance.
In order to better understand the technical scheme provided by the invention, a plurality of specific examples and comparative examples are respectively illustrated below.
The prior art conventional lithium iron disulfide battery electrolyte and cell were first used as comparative examples:
comparative example 1
1) Preparing an electrolyte:
mixing Ethylene Carbonate (EC) and dimethyl carbonate (DMC) according to a volume ratio of 1: 1, and uniformly mixing to obtain an aprotic solvent; then, the required amount of lithium hexafluorophosphate was calculated as the lithium ion concentration of 1mol/L, and lithium hexafluorophosphate (LiPF) was added6) Uniformly stirring to obtain a semi-finished electrolyte; and (3) adsorbing and dehydrating the semi-finished product by using a lithiated molecular sieve, filtering after adsorption to obtain a finished product, and hermetically storing at normal temperature for later use.
2) Preparation of lithium iron disulfide batteries:
mixing iron disulfide particles as a positive electrode active material, acetylene black as a conductive agent and polyvinylidene fluoride (PVDF) as a binder according to a weight ratio of 8: 1: 1, fully stirring and mixing in a proper amount of N-methylpyrrolidone (NMP) solvent to form uniform anode slurry; the slurry is coated on a positive electrode current collector aluminum foil with the thickness of 250 mu m, and the positive electrode current collector aluminum foil is transferred into a vacuum oven with the temperature of 80 ℃ to be dried for 12 hours, so that the lithium iron disulfide battery positive electrode is obtained. Using metal lithium as a counter electrode, using the electrolyte prepared in the step 1) with the dosage of 20uL/mg, and using a polypropylene (PP)/Polyethylene (PE)/PP diaphragm (Celgard 2400), assembling the button cell in a glove box filled with argon, and testing the performance of the cell in a cell testing system. The test conditions are constant current 0.1C charge and discharge, the potential interval is 1V-3V, the cycle is 100 circles, and the charge and discharge cycle curve is shown in figure 1. And (3) carrying out cyclic voltammetry test on the assembled button cell in an electrochemical workstation, wherein the scanning step is 0.1mV, the potential interval is 0-2V, and the cyclic voltammetry curve is shown in figure 2. From fig. 1, it can be known that the initial discharge of the original FeS2 electrode material can only release about 75% of the theoretical capacity, and fig. 2 shows that in the first cycle of cyclic voltammetry, two redundant reduction peaks of 1.6V and 1.2V exist in the range of 1-2V, which means that the first cycle of side reaction in a battery system without additive leads to insufficient discharge of FeS2 active material. In addition, fig. 1 shows that the discharge capacity was only 200mAh/g after the final 100 cycles during the charge and discharge cycles, and the capacity decayed very rapidly in the first 30 cycles, meaning that a large amount of active material reacted with the solvent in the form of polysulfide at the initial stage of the battery cycle to cause irreversible loss of capacity.
Example 1
1) Preparing an electrolyte:
mixing Ethylene Carbonate (EC) and dimethyl carbonate (DMC) according to a volume ratio of 1: 1, and uniformly mixing to obtain an aprotic solvent; on the basis of the above formula, 5% of additive A shown in formula I is added, and then required LiPF is calculated according to 1mol/L lithium ion concentration6Mass addition of LiPF6And uniformly stirring to obtain a semi-finished electrolyte, adsorbing and dehydrating the semi-finished electrolyte by using a lithiated molecular sieve, filtering after adsorption to obtain a finished product, and hermetically storing at normal temperature for later use.
2) Preparing a lithium ion battery:
the method comprises the following steps of mixing iron disulfide particles as a positive electrode active material, acetylene black as a conductive agent and PVDF as an adhesive in a weight ratio of 8: 1: 1, fully stirring and mixing in a proper amount of NMP solvent to form uniform anode slurry; the slurry is coated on a positive current collector aluminum foil with the thickness of 250 mu m, and the positive current collector aluminum foil is transferred into a vacuum oven with the temperature of 80 ℃ to be dried for 12 hours, so that the positive electrode of the lithium battery is obtained. The lithium battery positive electrode, the metal lithium counter electrode and the electrolyte obtained in the step 1) are used in an amount of 20uL/mg and a PP/PE/PP diaphragm (Celgard 2400) to assemble the button cell in a glove box filled with argon, the performance of the cell is tested in a cell testing system, the testing condition is constant current 0.1C charging and discharging, the potential interval is 1-3V, the cycle is 100 circles, and the charging and discharging cycle curve is shown as a curve (a) in FIG. 3. And (3) carrying out cyclic voltammetry test on the assembled button cell in an electrochemical workstation, wherein the scanning step is 0.1mV, the potential interval is 0-2V, and the cyclic voltammetry curve is shown in figure 4. It can be seen from fig. 3(a) that after the battery system with the added Li/FeS2 is added with the electrolyte additive a, the discharge capacity of the first cycle can reach 830mAh/g, and fig. 4 also shows that no redundant redox peak is present within the range of 1-2V, which means that the electrolyte provided by the invention has stronger electrochemical stability and the active material can be more fully discharged. The capacity attenuation is slightly fast in the initial stage in the charge-discharge cycle process, but the discharge characteristic of the sulfur-based electrode material is also met, the capacity retention rate is 84% after 100 cycles, and the electrolyte additive A has obvious effects on the capacity improvement and the cycle stability of the Li/FeS2 battery system in the first cycle.
FIGS. 5(a) and (b) are Scanning Electron Microscope (SEM) images of FeS2 electrodes of comparative example 1 before and after cycling, respectively, and FIGS. 5(c) and (d) are Scanning Electron Microscope (SEM) images of FeS2 electrodes of example 1 before and after cycling, respectively, according to the morphology of the SEM images, the Li/FeS2 battery system added with the electrolyte additive A forms a stable and uniform membrane structure on the surfaces of the electrodes before and after cycling.
According to the following table, the mass percentage of the electrolyte additive A in the electrolyte is changed, and other conditions are not changed, so that examples 2-5, comparative example 2 and comparative example 3 are obtained, and the details are shown in the following table 1.
Figure BDA0002985022060000081
TABLE 1
FIG. 3 is a graph of a charge-discharge cycle of the present invention; FIG. 6 is a first-turn discharge curve of example 1, comparative example 2, and comparative example 3 of the present invention; wherein the three curves (a), (b) and (c) correspond to the data of example 1, comparative example 2 and comparative example 3, respectively. It can be seen from the curve of fig. 6(a) that the addition of a proper amount of the electrolyte additive a can not only improve the first-cycle discharge capacity, but also have a high discharge plateau and small polarization, which means that a good CEI film can be formed. As can be seen from fig. 3 and 6, when the electrolyte additive a is less than 0.1% by mass, HF cannot be effectively removed, and a CEI film for preventing the reaction of polysulfide and carbonate solvent cannot be effectively formed, resulting in almost no change in the cycle performance of the battery; when the electrolyte additive A accounts for more than 30 percent by mass, the compound represented by the structural formula I forms a very thick passive film on the surface of an electrode, and the internal resistance of the battery is very high, so that the performance of the battery is deteriorated. For specific data, see the dc internal resistance data in table 2 below.
Figure BDA0002985022060000091
TABLE 2
Example 6
1) Preparing an electrolyte:
mixing Ethylene Carbonate (EC) and dimethyl carbonate (DMC) according to a volume ratio of 1: 1, and uniformly mixing to obtain an aprotic solvent; on the basis, an additive A shown in a structural formula I accounting for 5% of the total mass of the electrolyte and an additive VC (additive B) accounting for 5% of the total mass of the electrolyte are added, and LiPF is added according to the mass of lithium hexafluorophosphate required by calculation of the concentration of 1mol/L of lithium ions6And uniformly stirring to obtain a semi-finished electrolyte, adsorbing and dehydrating the semi-finished electrolyte by using a lithiated molecular sieve, filtering after adsorption to obtain a finished product, and hermetically storing at normal temperature for later use.
2) Preparing a lithium ion battery:
the method comprises the following steps of mixing iron disulfide particles as a positive electrode active material, acetylene black as a conductive agent and PVDF as an adhesive in a weight ratio of 8: 1: 1, fully stirring and mixing in a proper amount of NMP solvent to form uniform anode slurry; the slurry is coated on a positive current collector aluminum foil with the thickness of 250 mu m, and the positive current collector aluminum foil is transferred into a vacuum oven with the temperature of 80 ℃ to be dried for 12 hours, so that the positive electrode of the lithium battery is obtained. The lithium battery positive electrode, the metal lithium counter electrode, the electrolyte obtained in the step 1) are used in an amount of 20uL/mg and a PP/PE/PP diaphragm (Celgard 2400) to assemble the button cell in a glove box filled with argon, the performance of the cell is tested in a cell testing system, the testing condition is constant current 0.1C charging and discharging, the potential interval is 1-3V, the cycle is 100 circles, and the charging and discharging cycle curve is shown in figure 7. The assembled button cell is subjected to cyclic voltammetry test in an electrochemical workstation by using the lithium battery anode of the embodiment, the scanning step is 0.1mV, the potential interval is 0-2V, and the cyclic voltammetry curve is shown in FIG. 8. Fig. 7 shows that example 6 has good capacity exertion and better cycling stability, the first-cycle discharge reaches 870mAh/g, and the capacity retention rate is 85% after 100 cycles of cycling, which is attributed to the synergistic effect of the additive a and the additive B, and it can be seen that there is no obvious redox reaction in the volt-ampere cycle, which means that the electrolyte can more stably undertake the function of ion transport in the charging and discharging process.
Examples 7-9 were obtained by changing the type of electrolyte additive B in the electrolyte according to the following table, with the remaining conditions unchanged, and specifically shown in Table 3 below.
Organic solvent Additive/cosolvent Lithium salt
Example 7 EC/DMC＝1:1 5% additive A + 5% FEC 1.0M LiPF6
Example 8 EC/DMC＝1:1 5% additive A + 5% VEC 1.0M LiPF6
Example 9 EC/DMC＝1:1 5% additive A + 5% BS 1.0M LiPF6
TABLE 3
Example 10
1) Preparing an electrolyte:
mixing Ethylene Carbonate (EC) and diethyl carbonate (DEC) according to a volume ratio of 1: 1, and uniformly mixing to obtain an aprotic solvent; then, an additive A shown in a structural formula I accounting for 5% of the total mass and an additive VC (additive B) accounting for 5% of the total mass of the electrolyte are added on the basis, and LiPF is added according to the mass of lithium hexafluorophosphate required by calculating the concentration of 1mol/L of lithium ions6Uniformly stirring to obtain a semi-finished electrolyte; and (3) adsorbing and dehydrating the semi-finished product by using a lithiated molecular sieve, filtering after adsorption to obtain a finished product, and hermetically storing at normal temperature for later use.
2) Preparing a lithium ion battery:
the method comprises the following steps of mixing iron disulfide particles as a positive electrode active material, acetylene black as a conductive agent and PVDF as an adhesive in a weight ratio of 8: 1: 1, fully stirring and mixing in a proper amount of NMP solvent to form uniform anode slurry; the slurry is coated on a positive current collector aluminum foil with the thickness of 250 mu m, and the positive current collector aluminum foil is transferred into a vacuum oven with the temperature of 80 ℃ to be dried for 12 hours, so that the positive electrode of the lithium battery is obtained. The lithium battery positive electrode, the metal lithium counter electrode, the electrolyte obtained in the step 1) are used in an amount of 20uL/mg and a PP/PE/PP diaphragm (Celgard 2400) to assemble the button cell in a glove box filled with argon, the performance of the cell is tested in a cell testing system, the testing condition is constant current 0.1C charging and discharging, the potential interval is 1-3V, the cycle is 100 circles, and the charging and discharging cycle curve is shown in figure 9. The assembled button cell is subjected to cyclic voltammetry test in an electrochemical workstation by using the lithium battery anode of the embodiment, the scanning step is 0.1mV, the potential interval is 0-2V, and the cyclic voltammetry curve is shown in FIG. 10. It can be seen from fig. 9 and 10 that the electrolyte additive a is applicable to a variety of common carbonate solvents, and after the electrolyte additive a is added to other carbonate electrolytes, the differences between the first-cycle discharge capacity and the capacity retention rate are not large as compared with example 1, which indicates that the electrolyte additive a is generally applicable to carbonate electrolytes in a Li/FeS2 battery system.
Examples 11 to 13
Except for the following table parameters, other parameters and preparation methods were the same as those in example 12.
Examples 11-13 were obtained by changing the kind of organic solvent in the electrolyte according to the following table, with the remaining conditions being unchanged, and specifically shown in table 4 below.
Organic solvent Additive/cosolvent Lithium salt
Example 11 EC/EMC＝1:1 5% of additive A + 5% of VC 1.0M LiPF6
Example 12 PC/DMC＝1:1 5% of additive A + 5% of VC 1.0M LiPF6
Example 13 PC/EMC＝1:1 5% of additive A + 5% of VC 1.0M LiPF6
TABLE 4
The capacity loss of the lithium ion battery after circulation can be divided into reversible capacity and irreversible capacity, and the main factor causing the reversible capacity loss is the increase of internal resistance. In the lithium iron disulfide battery, an important reason for increasing the internal resistance is that the organic solvent generates side reaction on the surface of the positive electrode/the negative electrode, and by-products generated by the side reaction are continuously accumulated to block a transmission channel of lithium ions, so that the internal resistance is increased.
In the above embodiment of the present invention, the additive represented by formula i in the battery electrolyte additive has an obvious inhibiting effect on the reaction of polysulfide and carbonate additive, and can react on the surface of the electrode to form a stable and good CEI film, thereby avoiding irreversible loss of capacity; the additive B can form a more stable SEI film on the surface of the lithium metal, so that the cycle performance of the lithium ion battery is remarkably improved. When the organic solvent and the active substance are used together, a compact protective layer can be formed on the surfaces of the positive and negative active substances, so that the direct contact between the organic solvent and the active substances is blocked, the occurrence of side reactions is avoided, and the effects of improving the capacity exertion and the cycle performance of the lithium ion battery more remarkably than the effect of singly using any one of the organic solvent and the active substance can be achieved.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (8)

1. A lithium iron disulfide battery electrolyte, comprising: electrolyte lithium salt, aprotic solvent and electrolyte additive A;
wherein the structural formula (I) of the electrolyte additive A is as follows:
Figure FDA0002985022050000011
during the first discharge of the lithium iron disulfide battery, the electrolyte additive A reacts with polysulfide of the positive electrode on the surface of the positive electrode of the lithium iron disulfide battery to form a CEI film of a positive electrode-electrolyte interface phase for preventing the reaction of the polysulfide and the aprotic solvent.
2. The lithium iron disulfide battery electrolyte as claimed in claim 1, wherein the electrolyte additive A is present in the electrolyte in an amount of 0.1-30% by weight;
the concentration of the electrolyte lithium salt in the electrolyte is 0.5-3 mol/L calculated by lithium ions;
the aprotic solvent is selected from one or a combination of more of ethylene carbonate EC, methyl ethylene carbonate EMC, diethyl carbonate DEC, dimethyl carbonate DMC or propylene carbonate PC.
3. The lithium iron disulfide battery electrolyte of claim 1 further comprising an additive B, wherein the additive B comprises: one or more of vinylene carbonate VC, vinyl ethylene carbonate VEC, fluoroethylene carbonate FEC or vinyl sulfite ES.
4. The lithium iron disulfide battery electrolyte as claimed in claim 3, wherein the additive B is present in the electrolyte in an amount of 0.5-20% by weight.
5. The lithium iron disulfide cell electrolyte of claim 1 wherein the electrolytic lithium salt is particularly LiPF6。
6. The electrolyte additive for the lithium iron disulfide battery is characterized in that the structural formula of the electrolyte additive is as follows:
Figure FDA0002985022050000021
during the first discharge of the lithium iron disulfide battery, the electrolyte additive A reacts with polysulfide of the positive electrode on the surface of the positive electrode of the lithium iron disulfide battery to form a CEI film of a positive electrode-electrolyte interface phase for preventing the reaction of the polysulfide and the aprotic solvent.
7. A lithium iron disulfide battery, comprising: the lithium iron disulfide battery electrolyte of any of claims 1-5, or comprising the lithium iron disulfide battery electrolyte additive of claim 6.
8. The lithium iron disulfide cell of claim 7 wherein the positive electrode of the lithium iron disulfide cell comprises iron disulfide and the negative electrode is lithium.
CN202110297933.1A 2021-03-19 2021-03-19 Lithium iron disulfide battery electrolyte additive, electrolyte and lithium iron disulfide battery Pending CN112909338A (en)

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JP2000164251A (en) * 1998-11-25 2000-06-16 Wilson Greatbatch Ltd Alkali metal electrochemical cell having improved cathode activated with nonaqueous electrolyte containing passivation prohibiting additive
US20140134501A1 (en) * 2012-11-12 2014-05-15 Novolyte Technologies, Inc. Non-Aqueous Electrolytic Solutions And Electrochemical Cells Comprising Same
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US20180191022A1 (en) * 2015-07-02 2018-07-05 Maxell Holdings, Ltd. Non-aqueous electrolyte battery and method for manufacturing same
CN110212235A (en) * 2019-06-12 2019-09-06 广州天赐高新材料股份有限公司 A kind of lithium secondary cell electrolyte and its lithium secondary battery reducing battery impedance
CN111755745A (en) * 2020-06-18 2020-10-09 合肥国轩高科动力能源有限公司 Lithium-sulfur battery electrolyte and liquid injection method thereof

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000164251A (en) * 1998-11-25 2000-06-16 Wilson Greatbatch Ltd Alkali metal electrochemical cell having improved cathode activated with nonaqueous electrolyte containing passivation prohibiting additive
US20140134501A1 (en) * 2012-11-12 2014-05-15 Novolyte Technologies, Inc. Non-Aqueous Electrolytic Solutions And Electrochemical Cells Comprising Same
US20180191022A1 (en) * 2015-07-02 2018-07-05 Maxell Holdings, Ltd. Non-aqueous electrolyte battery and method for manufacturing same
US20180048025A1 (en) * 2016-08-12 2018-02-15 Pellion Technologies, Inc. Additive containing electrolytes for high energy rechargeable metal anode batteries
CN110212235A (en) * 2019-06-12 2019-09-06 广州天赐高新材料股份有限公司 A kind of lithium secondary cell electrolyte and its lithium secondary battery reducing battery impedance
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