CN113506916A - Electrolyte additive, electrolyte and secondary battery - Google Patents

Electrolyte additive, electrolyte and secondary battery Download PDF

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CN113506916A
CN113506916A CN202110800539.5A CN202110800539A CN113506916A CN 113506916 A CN113506916 A CN 113506916A CN 202110800539 A CN202110800539 A CN 202110800539A CN 113506916 A CN113506916 A CN 113506916A
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electrolyte
additive
carbonate
lithium
battery
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CN113506916B (en
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钟海敏
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Evergrande New Energy Technology Shenzhen 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
    • 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
    • H01M10/42—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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

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  • Secondary Cells (AREA)

Abstract

The invention belongs to the technical field of batteries, and particularly relates to an electrolyte additive, an electrolyte and a secondary battery. The structural general formula of the electrolyte additive is shown as the following formula I:

Description

Electrolyte additive, electrolyte and secondary battery
Technical Field
The invention belongs to the technical field of batteries, and particularly relates to an electrolyte additive, an electrolyte and a secondary battery.
Background
The lithium ion battery has the advantages of high specific energy, long cycle life, no memory effect and the like, and is widely applied to the fields of mobile phones, computers, cameras, electric vehicles and the like. With the continuous development of scientific technology, various application fields put higher demands on the performance of the lithium ion battery, wherein the most urgent is to improve the energy density of the lithium ion battery on the premise of ensuring safety. At present, the industry is pursuing higher energy density of lithium batteries, which is also an important index reflecting battery technology. The anode and cathode materials with higher gram capacity are needed to be adopted, as the most commercialized selection at present, the anode is generally made of a high-nickel ternary material or a medium-nickel high-voltage material, and the cathode is made of a silicon-based material. Wherein, the anode high-nickel material or the medium-nickel high-voltage material has strong oxidizing property to the electrolyte after lithium removal, which causes gas generation of the battery, metal element dissolution and capacity attenuation. And the silicon-based material of the negative electrode has huge volume expansion and shrinkage in the process of lithium intercalation and deintercalation, so that an electrolyte interphase (SEI) on the surface of the silicon-based material is very easy to crack, and then the repeated growth of the SEI film is generated, and finally, a series of problems of battery impedance increase, flatulence, capacity attenuation and the like are caused.
Therefore, the problem is that the side reaction on the surface of the high-capacity positive and negative electrode materials is more serious, and the performance of the lithium ion battery adopting the materials, such as safety, is worse. In the prior art, the doping coating and modification are carried out on the anode and cathode materials, but the investment is large and the cost is high. There are some additives from the perspective of the electrolyte, but the resistance of the battery is often too high to facilitate the electron transfer transmission in the battery.
Disclosure of Invention
The invention aims to provide an electrolyte additive, an electrolyte and a secondary battery, and aims to solve the technical problem that a high gram capacity anode and cathode material adopted in the existing battery is poor in safety performance to a certain extent.
In order to achieve the purpose of the application, the technical scheme adopted by the invention is as follows:
in a first aspect, the present invention provides an electrolyte additive, wherein the structural general formula of the electrolyte additive is shown as formula I below:
Figure BDA0003164539770000021
x, Y in the formula I are respectively and independently selected from one of isothiocyanato, cyclohexane, alkoxy, phenyl and halogen.
In the electrolyte additive provided by the first aspect of the invention, an S atom in a-P ═ S structure can generate a bonding effect with metal atoms such as nickel, cobalt and the like in a positive electrode material, and the reactivity of the surface of the positive electrode material is reduced, so that the strong oxidizing property of the electrolyte material to the positive electrode is reduced, the side reaction of the surface of the positive electrode is inhibited, and the cycle stability of a pole piece is improved. Meanwhile, flame-retardant phosphorus free radicals can be generated, the flame-retardant effect is achieved, and the safety performance of the electrolyte is improved. In addition, the isothiocyanic group can generate reduction polymerization reaction on the surfaces of the positive and negative pole pieces, so that the elasticity of the SEI film on the surfaces of the pole pieces is improved, the SEI film can better adapt to or even inhibit huge volume expansion and contraction stress of silicon-based electrode materials in the lithium desorption process, SEI repeated growth is avoided, and the cycling stability and safety of the battery are improved. On the other hand, in the additive, groups such as isothiocyanato, alkoxy, cyclohexane, phenyl, halogen and the like connected at the X, Y position can improve the polarity, film-forming property, stability, compatibility with electrolyte and other properties of the additive.
Further, the electrolyte additive includes:
Figure BDA0003164539770000022
Figure BDA0003164539770000031
at least one of these electrolyte additives, each of which contains a-P ═ S structure and at least one isothiocyanato group, and further has a substituent group such as a cyclohexane group, an alkoxy group, a phenyl group, or a halogen group grafted to the X, Y position; the side reaction on the surface of the positive plate can be reduced, the circulation stability of the positive plate is improved, and the safety performance of the electrolyte is improved; and polymerization reaction can occur on the surface of the pole piece, so that the elasticity and stability of the SEI film are improved, and the cycling stability of the battery can be improved.
In a second aspect, the present invention provides an electrolyte, including a lithium salt, an organic solvent and an additive, where the structural general formula of the additive is as shown in formula I below:
Figure BDA0003164539770000032
x, Y in the formula I are respectively and independently selected from one of isothiocyanato, cyclohexane, alkoxy, phenyl and halogen.
The electrolyte provided by the second aspect of the invention comprises lithium salt, an organic solvent and an additive with a structural general formula shown as formula I, wherein the additive can reduce side reaction on the surface of the positive electrode, generate flame-retardant phosphorus free radicals and improve the cycling stability and safety performance of the pole piece; and the film can be polymerized on the surfaces of the positive electrode and the negative electrode to form a film, so that the elasticity of the SEI film is improved, the SEI film can better adapt to and even inhibit huge volume expansion and contraction stress of silicon-based electrode materials in the lithium-intercalation and deintercalation process, and the cycle stability and the safety of the battery are improved.
Further, in the electrolyte, the mass percentage of the additive is 0.05-3%; the additive with the content is beneficial to the improvement of electrochemical properties such as the cycling stability, the safety and the like of the battery after the electrolyte is applied to the secondary battery.
Further, the additives include: the electrolyte additive can reduce side reactions on the surface of the positive plate, improve the circulation stability of the positive plate and improve the safety performance of the electrolyte; and polymerization reaction can occur on the surface of the pole piece, so that the elasticity and stability of the SEI film are improved, and the cycling stability of the battery can be improved.
Further, the concentration of the lithium salt is 0.5-1.5mol/l, and the lithium salt in the content provides sufficient lithium ions for the electrolyte, so that the migration and transmission efficiency of the ions in the electrolyte is ensured.
Further, in the electrolyte, the lithium salt is selected from: LiPF6、LiBF4、LiPO2F2、LiTFSI、LiBOB、LiDFOB、LiN(SO2F)2At least one of the above lithium salts is easy to dissociate lithium ions, and plays a role in transferring during the lithium ion interaction process, and the lithium ions are used for transferringThe positive electrode and the negative electrode are embedded and separated, so that the cyclic charge and discharge of the battery are realized.
Further, the organic solvent is selected from: at least one of ethylene carbonate, methyl ethyl carbonate, diethyl carbonate, propylene carbonate, dimethyl carbonate, methyl formate, methyl acetate, methyl propionate, ethyl acetate, propyl propionate, sulfolane, gamma-butyrolactone and dimethyl sulfoxide. The organic solvents have good compatibility with additives and lithium salts, and are beneficial to the migration and transmission of lithium ions in the charging and discharging processes of the battery.
Further, the organic solvent is selected from mixed organic solvents of ethylene carbonate, methyl ethyl carbonate and diethyl carbonate, and balance between solvent viscosity and dielectric constant can be realized through compound use, so that the ionic conductivity of the electrolyte is high, and the viscosity is moderate.
Further, the electrolyte also comprises: the electrolyte solution is characterized in that the electrolyte solution further improves the film forming effect of the electrolyte solution on the surface of an electrode, and an electrolyte film (SEI) with excellent elasticity is formed on the surface of the electrode, thereby preventing interfacial reaction on the surface of the electrode.
Further, the mass percentage of the auxiliary additive is 0.05-15 percent respectively and independently; if the amount of the additive is too large, the film formation resistance is too large and the solubility is lowered; if the amount of the additive is too small, the auxiliary effect is not significant.
In a third aspect, the present invention provides a secondary battery, which comprises the above electrolyte additive, or comprises the above electrolyte.
The secondary battery provided by the third aspect of the invention, because of containing the electrolyte additive with the structural general formula I, can improve the elasticity of SEI films on the surfaces of positive and negative pole pieces in the battery, better adapt to and even inhibit the volume expansion effect of the pole pieces in the cyclic charge-discharge process, and prolong the cycle life of the battery; but also can generate flame retardant effect and improve the safety performance of the battery.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In the present invention, the term "and/or" describes the association relationship of the associated objects, and means that there may be three relationships, for example, a and/or B, which may mean: a is present alone, A and B are present simultaneously, and B is present alone. Wherein A and B can be singular or plural. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship.
In the present invention, "at least one" means one or more, "a plurality" means two or more. "at least one of the following" or similar expressions refer to any combination of these items, including any combination of the singular or plural items. For example, "at least one (one) of a, b, or c," or "at least one (one) of a, b, and c," may each represent: a, b, c, a-b (i.e., a and b), a-c, b-c, or a-b-c, wherein a, b, and c may be single or plural, respectively.
It should be understood that, in various embodiments of the present invention, the sequence numbers of the above-mentioned processes do not mean the execution sequence, some or all of the steps may be executed in parallel or executed sequentially, and the execution sequence of each process should be determined by its function and inherent logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.
The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the examples of the invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
The weight of the related components mentioned in the description of the embodiments of the present invention may not only refer to the specific content of each component, but also represent the proportional relationship of the weight among the components, and therefore, the content of the related components is scaled up or down within the scope disclosed in the description of the embodiments of the present invention as long as it is in accordance with the description of the embodiments of the present invention. Specifically, the mass in the description of the embodiments of the present invention may be a mass unit known in the chemical industry field such as μ g, mg, g, kg, etc.
In a first aspect of the embodiments of the present invention, an electrolyte additive is provided, where a structural general formula of the electrolyte additive is shown as following formula I:
Figure BDA0003164539770000061
x, Y in the formula I are respectively and independently selected from one of isothiocyanato, cyclohexane, alkoxy, phenyl and halogen.
The electrolyte additive provided by the first aspect of the embodiment of the invention has a structural general formula shown in formula I, and simultaneously contains a-P ═ S structure and at least one isothiocyanato group; the S atom in the-P ═ S structure can be bonded with metal atoms such as nickel, cobalt and the like in the positive electrode material, so that the active sites of the positive electrode material such as ternary lithium nickel cobalt aluminate NCA, lithium cobaltate and the like are reduced, the reaction activity of the surface of the positive electrode material is reduced, the strong oxidizing property of the electrolyte material to the positive electrode is reduced, the side reaction of the surface of the positive electrode is inhibited, and the cycle stability of the pole piece is improved. Meanwhile, P atoms in the-P ═ S structure can generate flame-retardant phosphorus free radicals, so that the flame-retardant effect is achieved, and the safety performance of the electrolyte is improved. In addition, the isothiocyanic group can generate reduction polymerization reaction on the surfaces of the positive and negative pole pieces to form a catalyst containing
Figure BDA0003164539770000062
The polymer of structure to promote the elasticity of pole piece surface SEI membrane, make the adaptation that the SEI membrane can be better restrain silicon-based isoelectrode material in the huge volume expansion shrinkage stress of lithium desorption in-process even, thereby reduce the risk that SEI membrane cracked in the lithium desorption in-process of material, avoid SEI regrowth, improve the elasticity of batteryCycle stability and safety. On the other hand, the isothiocyanato connected at the X, Y position in the additive can improve the polymerization film forming effect of the additive, the alkoxy can improve the polarity of the additive, the compatibility of the additive and electrolyte can be improved, the halogen can further improve the film forming and flame retardant effect of the additive on the surface of a negative electrode, and the stability of the additive structure can be improved by cyclohexane, phenyl and the like.
In some embodiments, the electrolyte additive comprises:
Figure BDA0003164539770000071
thiophosphoryl difluoroisothiocyanate (SPNCS-1, CAS:14526-12-6),
Figure BDA0003164539770000072
Thiophosphate dimethyl isocyanate (SPNCS-2, CAS:20039-32-1),
Figure BDA0003164539770000073
Diisopropoxylthiophosphoryl isothiocyanate (SPNCS-3, CAS:69674-00-6),
Figure BDA0003164539770000074
Diphenyl thiophosphoryl isothiocyanate (SPNCS-4, CAS:16523-56-1),
Figure BDA0003164539770000075
Cyclohexyl diisothiocyano-thion compound (SPNCS-5, CAS:112894-74-3),
Figure BDA0003164539770000076
At least one of triisothiocyanotothion compounds (SPNCS-6, CAS: 1858-26-0). In the embodiment of the invention, the electrolyte additives contain a-P ═ S structure and at least one isothiocyanato, and meanwhile, substituents such as cyclohexane, alkoxy, phenyl, halogen and the like are grafted on the X, Y position; the structure of-P ═ S not only bonds with metal atoms such as nickel, cobalt and the like in the anode material through S atoms, reduces the side reaction on the surface of the anode plate and improves the cycling stability of the anode plate; and P atoms can produce flame-retardant phosphorus radicalsThe electrolyte has a flame-retardant effect, and the safety performance of the electrolyte is improved. The isothiocyanic group can generate a polymerization reaction on the surface of the pole piece, so that the elasticity and the stability of the SEI film are improved, on one hand, part of additives are gathered on the surface of the positive pole piece through the bonding effect of S atoms and metal atoms in the positive pole material, and the additives are polymerized to form a film layer through electron gaining and losing, so that the stability of the SEI film of the positive pole is improved; on the other hand, the negative electrode is easy to generate reduction reaction, so that reduction polymerization of isothiocyanic unsaturated bonds in the additive is facilitated, a film is polymerized on the surface of the negative electrode piece, and the stability of the negative electrode SEI film is improved. The X, Y-site connected alkoxy can improve the polarity of the additive, improve the compatibility of the additive with electrolyte, the halogen can further improve the film forming and flame retardant effects of the additive on the surface of the negative electrode, and the stability of the additive structure can be improved by cyclohexane, phenyl and the like.
In a second aspect, an embodiment of the present invention provides an electrolyte, where the electrolyte includes a lithium salt, an organic solvent, and an additive, and a structural general formula of the additive is as shown in formula I below:
Figure BDA0003164539770000081
x, Y in the formula I are respectively and independently selected from one of isothiocyanato, cyclohexane, alkoxy, phenyl and halogen.
The electrolyte provided by the second aspect of the embodiment of the invention comprises lithium salt, an organic solvent and an additive with a structural general formula shown as formula I, wherein the additive can reduce side reaction on the surface of a positive electrode, generate flame-retardant phosphorus free radicals and improve the cycling stability and safety performance of a pole piece; and the film can be polymerized on the surfaces of the positive electrode and the negative electrode to form a film, so that the elasticity of the SEI film is improved, the SEI film can better adapt to and even inhibit huge volume expansion and contraction stress of silicon-based electrode materials in the lithium-intercalation and deintercalation process, and the cycle stability and the safety of the battery are improved.
In some embodiments, the additive is 0.05-3% by weight; the additive with the content is beneficial to the improvement of electrochemical properties such as the cycling stability, the safety and the like of the battery after the electrolyte is applied to the secondary battery. If the content of the additive is too high, the film layer formed by polymerization on the surface of the electrode is too thick, the impedance is too large, the ion migration and transmission are not facilitated, and the electrochemical performance is reduced; if the content of the additive is too low, the performance of the electrolyte and the SEI protective film layer on the surface of the electrode is not remarkably improved, and the improvement effect on the cycle stability and the safety performance of the battery is not good. In some embodiments, the additive may be present in an amount of 0.05-1%, 1-1.5%, 1.5-2%, 2-3%, etc. by weight.
In some embodiments, the additives comprise: sulfur, sulfur
Figure BDA0003164539770000091
Thiophosphoryl difluoroisothiocyanate (SPNCS-1, CAS:14526-12-6),
Figure BDA0003164539770000092
Thiophosphate dimethyl isocyanate (SPNCS-2, CAS:20039-32-1),
Figure BDA0003164539770000093
Diisopropoxylthiophosphoryl isothiocyanate (SPNCS-3, CAS:69674-00-6),
Figure BDA0003164539770000094
Diphenyl thiophosphoryl isothiocyanate (SPNCS-4, CAS:16523-56-1),
Figure BDA0003164539770000095
Cyclohexyl diisothiocyano-thion compound (SPNCS-5, CAS:112894-74-3),
Figure BDA0003164539770000096
At least one of triisothiocyanotothion compounds (SPNCS-6, CAS: 1858-26-0). According to the embodiment of the invention, the additives have a structure of-P-S, so that the side reaction on the surface of the positive plate is reduced, and the cycling stability of the positive plate is improved; but also has flame retardant effect and improves the safety performance of the electrolyte. Through the isothiocyanato, polymerization reaction can occur on the surface of the pole piece, and the elasticity and stability of the SEI film are improved(ii) a The polarity of the additive can be improved through the alkoxy connected at the X, Y position, the compatibility of the additive and electrolyte can be improved, the film forming and flame retardant effects of the additive on the surface of the negative electrode can be further improved through halogen, and the stability of the additive structure can be improved through cyclohexane, phenyl and the like.
In some embodiments, the concentration of the lithium salt in the electrolyte is 0.5-1.5mol/l, and the lithium salt provides sufficient lithium ions for the electrolyte to ensure the migration and transmission efficiency of the ions in the electrolyte.
In some embodiments, the lithium salt is selected from: LiPF6、LiBF4、LiPO2F2、LiTFSI、LiBOB、LiDFOB、LiN(SO2F)2The lithium salts are easy to dissociate into lithium ions, play a role in transferring in the lithium ion interaction process, and realize the cyclic charge and discharge of the battery through the insertion and desorption of the lithium ions in the positive and negative electrodes.
In some embodiments, the organic solvent is selected from: at least one of ethylene carbonate, methyl ethyl carbonate, diethyl carbonate, propylene carbonate, dimethyl carbonate, methyl formate, methyl acetate, methyl propionate, ethyl acetate, propyl propionate, sulfolane, gamma-butyrolactone and dimethyl sulfoxide. The organic solvents have good compatibility with additives and lithium salts, and are beneficial to the migration and transmission of lithium ions in the charging and discharging processes of the battery.
In some embodiments, the organic solvent in the electrolyte may be formulated by using various solvents, such as a mixed organic solvent of Ethylene Carbonate (EC), methyl ethyl carbonate (EMC) and diethyl carbonate (DEC), wherein EC is cyclic carbonate, the dielectric constant is high but the viscosity is high, EMC and DEC are linear esters, the viscosity is low but the dielectric constant is also low, and the balance between the solvent viscosity and the dielectric constant can be achieved by the formulation, so that the ionic conductivity of the electrolyte is moderate and the viscosity is high. In some embodiments, the ratio by volume is 3: 6: 1 preparing Ethylene Carbonate (EC), methyl ethyl carbonate (EMC) and diethyl carbonate (DEC) into a mixed organic solvent.
In some embodiments, the electrolyte further comprises: vinylene Carbonate (VC), fluorineEthylene Carbonate (FEC), 1, 3-Propane Sultone (PS), vinyl sulfate (DTD), 1-propene-1, 3-sultone (PES), ethylene carbonate (VEC), tris (trimethylsilane) phosphite (TMSPi), tris (trimethylsilane) phosphate (TMSP), tris (trimethylsilane) borate (TMSB), lithium bis (fluorosulfonylimide (LiFSI), lithium difluorophosphate (LiPO)2F2) And at least one auxiliary additive selected from lithium difluorooxalato borate (LiODFB), lithium difluorooxalato phosphate (LiODFP), lithium bis (oxalato) borate (LiBOB), and Methylene Methanedisulfonate (MMDS), wherein the auxiliary additive further improves the film forming effect of the electrolyte solution on the surface of the electrode, and forms an electrolyte film (SEI) having excellent elasticity on the surface of the electrode, thereby preventing interfacial reaction on the surface of the electrode.
In some embodiments, the auxiliary additives are independently present in an amount of 0.05% to 15% by weight, and if added too much, the film formation resistance is too high and the solubility is reduced; if the amount of the additive is too small, the auxiliary effect is not significant.
In a third aspect of the embodiments of the present invention, a secondary battery is provided, which includes the above electrolyte additive, or includes the above electrolyte.
The secondary battery of the third aspect of the embodiment of the invention, which contains the electrolyte additive of the structural general formula I, can improve the elasticity of SEI films on the surfaces of positive and negative pole pieces in the battery, better adapt to and even inhibit the volume expansion effect of the pole pieces in the cyclic charge-discharge process, and prolong the cycle life of the battery; but also can generate flame retardant effect and improve the safety performance of the battery.
The anode, the cathode, the diaphragm and the like in the secondary battery can be made of any materials meeting the requirements of practical application.
In some embodiments, the positive electrode material may be a ternary material, NCA, lithium cobaltate, or the like, or may be a lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, polyanionic positive electrode material, or the like.
In some embodiments, the anode material may be a silicon-based anode material, a graphite anode material, a tin-based anode material, or the like. In some embodiments, the negative electrode material may be carbon-coated silicon or silica, or a silicon-carbon negative electrode material in which carbon and silicon or silica are both mixed directly.
In some embodiments, the diaphragm may be a ceramic diaphragm, a rubberized diaphragm, or the like.
In order to make the above implementation details and operations of the present invention clearly understood by those skilled in the art and to make the progress of the electrolyte additive, the electrolyte and the secondary battery of the embodiments of the present invention remarkably manifest, the above technical solutions are exemplified by a plurality of embodiments below.
Example 1
Electrolyte solutionThe preparation method comprises the following steps: mixing 300g of EC, 600g of EMC, and 100g of DEC in a glove box having a water content of less than 1ppm and an oxygen content of less than 2ppm to form a mixed organic solvent; then, an appropriate amount of fully dried LiPF was added6The concentration of lithium salt in the electrolyte is 1mol/L, and a basic electrolyte is obtained. Then 0.05 percent of SPNCS-1 is added into the basic electrolyte,
Figure BDA0003164539770000121
electrolyte E1 was obtained.
Lithium ion batteryThe manufacturing method comprises the following steps:
mixing a positive electrode material Ni83, carbon black, a carbon nano tube and polyvinylidene fluoride PVDF in a proportion of 100: 0.6: 0.6: 1.5, coating on an aluminum foil with the thickness of 12 mu m, and drying at 85 ℃ to obtain the positive plate.
Mixing graphite material, carbon black, Styrene Butadiene Rubber (SBR) and sodium carboxymethyl cellulose (CMC) in a proportion of 100: 0.9: 1.9: and (3) uniformly mixing the components according to the proportion of 1.5, coating the mixture on a copper foil with the thickness of 8 mu m, and drying the mixture at 90 ℃ to obtain the negative plate.
And thirdly, taking the ceramic diaphragm as a diaphragm, and manufacturing the positive plate and the negative plate into a soft package battery C1 in a laminated mode.
Fourthly, a formation aging grading process: and (3) sealing the dry cell after injecting liquid, and standing at 55 ℃ for 48h to ensure that the electrolyte is fully soaked. And (3) charging the simulated battery to 3.5V at 0.05C, then charging to 3.7V at 0.1C, then charging to 3.9V at 0.2C, after secondary sealing, continuously fully charging to 4.2V at 0.33C, and then discharging to 2.75V at 0.33C, namely capacity grading, thus obtaining the battery C1.
Example 2
Electrolyte solutionIt differs from example 1 in that: adding 0.1% of SPNCS-2 into the electrolyte,
Figure BDA0003164539770000122
electrolyte E2 was obtained.
Lithium ion batteryIt differs from example 1 in that: the electrolyte E2 is adopted, and the obtained lithium ion battery is C2.
Example 3
Electrolyte solutionIt differs from example 1 in that: adding 0.5 percent of SPNCS-3 into the electrolyte,
Figure BDA0003164539770000131
electrolyte E3 was obtained.
Lithium ion batteryIt differs from example 1 in that: the electrolyte E3 is adopted, and the obtained lithium ion battery is C3.
Example 4
Electrolyte solutionIt differs from example 1 in that: adding 1 percent of SPNCS-4 into the electrolyte,
Figure BDA0003164539770000132
electrolyte E4 was obtained.
Lithium ion batteryIt differs from example 1 in that: the electrolyte E4 is adopted, and the obtained lithium ion battery is C4.
Example 5
Electrolyte solutionIt differs from example 1 in that: adding 1 percent of SPNCS-5 into the electrolyte,
Figure BDA0003164539770000133
electrolyte E5 was obtained.
Lithium ion batteryIt differs from example 1 in that: using electrolyte E5The resulting lithium ion battery was C5.
Example 6
Electrolyte solutionIt differs from example 1 in that: adding 1 percent of SPNCS-6 into the electrolyte,
Figure BDA0003164539770000141
electrolyte E6 was obtained.
Lithium ion batteryIt differs from example 1 in that: the electrolyte E6 is adopted, and the obtained lithium ion battery is C6.
Example 7
Electrolyte solutionIt differs from example 1 in that: 0.3% of SPNCS-1 was added to the electrolyte to obtain electrolyte E7.
Lithium ion batteryIt differs from example 1 in that: the electrolyte E7 is adopted, and the obtained lithium ion battery is C7.
Example 8
Electrolyte solutionIt differs from example 1 in that: 0.3% of SPNCS-2 was added to the electrolyte to obtain electrolyte E8.
Lithium ion batteryIt differs from example 1 in that: the electrolyte E8 is adopted, and the obtained lithium ion battery is C8.
Example 9
Electrolyte solutionIt differs from example 1 in that: 0.3% of SPNCS-3 was added to the electrolyte to obtain electrolyte E9.
Lithium ion batteryIt differs from example 1 in that: the electrolyte E9 is adopted, and the obtained lithium ion battery is C9.
Example 10
Electrolyte solutionIt differs from example 1 in that: 0.3% of SPNCS-4 was added to the electrolyte to obtain electrolyte E10.
Lithium ion batteryIt differs from example 1 in that: the electrolyte E10 is adopted, and the obtained lithium ion battery is C10.
Example 11
Electrolyte solutionIt differs from example 1 in that: 0.3% of SPNCS-5 was added to the electrolyte to obtain electrolyte E11.
Lithium ion batteryIt differs from example 1 in that: the electrolyte E11 is adopted, and the obtained lithium ion battery is C11.
Example 12
Electrolyte solutionIt differs from example 1 in that: 0.3% of SPNCS-6 was added to the electrolyte to obtain electrolyte E12.
Lithium ion batteryIt differs from example 1 in that: the electrolyte E12 is adopted, and the obtained lithium ion battery is C12.
Example 13
Electrolyte solutionIt differs from example 1 in that: 0.2% of SPNCS-1+ 0.5% of VC was added to the electrolyte to obtain electrolyte E13.
Lithium ion batteryIt differs from example 1 in that: the electrolyte E13 is adopted, and the obtained lithium ion battery is C13.
Example 14
Electrolyte solutionIt differs from example 1 in that: 0.2% SPNCS-2+ 1% FEC was added to the electrolyte to obtain electrolyte E14.
Lithium ion batteryIt differs from example 1 in that: the electrolyte E14 is adopted, and the obtained lithium ion battery is C14.
Example 15
Electrolyte solutionIt differs from example 1 in that: 0.2% of SPNCS-3+ 0.5% of PS was added to the electrolyte to obtain electrolyte E15.
Lithium ion batteryIt differs from example 1 in that: the electrolyte E15 is adopted, and the obtained lithium ion battery is C15.
Example 16
Electrolyte solutionIt differs from example 1 in that: adding 0.2% of SPNCS-4+ 0.2% of PST into the electrolyte to obtain the electrolyteE16。
Lithium ion batteryIt differs from example 1 in that: the electrolyte E16 is adopted, and the obtained lithium ion battery is C16.
Example 17
Electrolyte solutionIt differs from example 1 in that: 0.2% SPNCS-5+ 2% LiFSI was added to the electrolyte to obtain electrolyte E17.
Lithium ion batteryIt differs from example 1 in that: the electrolyte E17 is adopted, and the obtained lithium ion battery is C17.
Example 18
Electrolyte solutionIt differs from example 1 in that: 0.2% of SPNCS-6+ 1% of DTD was added to the electrolyte to obtain electrolyte E18.
Lithium ion batteryIt differs from example 1 in that: the electrolyte E18 is adopted, and the obtained lithium ion battery is C18.
Example 19
Electrolyte solutionIt differs from example 1 in that: 0.04% of SPNCS-1 was added to the electrolyte to obtain electrolyte E19.
Lithium ion batteryIt differs from example 1 in that: the electrolyte E19 is adopted, and the obtained lithium ion battery is C19.
Example 20
Electrolyte solutionIt differs from example 1 in that: 3.1% of SPNCS-1 was added to the electrolyte to obtain electrolyte E20.
Lithium ion batteryIt differs from example 1 in that: the electrolyte E20 is adopted, and the obtained lithium ion battery is C20.
Comparative example 1
Electrolyte solutionIt differs from example 1 in that: without addition of additives to the electrolyte, an electrolyte DE1 was obtained.
Lithium ion batteryIt differs from example 1 in that: the electrolyte DE1 was used to obtain a lithium ion battery DC 1.
Further, in order to verify the advancement of the examples of the present invention, the following performance tests were performed for examples 1 to 20 and comparative example 1:
1. DCIR test (test of DC internal resistance)
The cells of the examples and comparative examples after aging and capacity grading were completed (5 counts for each condition, the results were averaged), charged at 0.5C CC for 30min in an incubator at 25 + -1 deg.C, tested by HPPC method, 2C discharged for 10s, left standing for 40s, and 1.5C charged for 10 s. The discharging DCR is calculated as DCR ═ V0-V1)/2C (current), and the charging DCR is calculated as charging DCR ═ V2-V3)/1.5C (current). Wherein V0 is the voltage before 2C discharge, V1 is the voltage after 2C discharge, V2 is the voltage after 1.5C charge, and V3 is the voltage before 1.5C charge.
2. Normal temperature cycle test
The batteries of examples and comparative examples after aging and capacity grading were assembled (5 batteries for each condition, and the results were averaged), charged to 4.2V with 0.5C CC-CV in an incubator at 25. + -. 2 ℃ and the constant voltage 0.05C current was cut off, left for 30min after charging, discharged to 3V with 1C again and left for 30min, and the cycle was continued for 600 times. The capacity retention (%) is a percentage obtained by dividing the discharge capacity after 300 cycles by the first discharge capacity.
3. High-temperature cycle test: the test temperature was 45. + -. 1 ℃ as the normal temperature cycle test.
4. High temperature storage test
The batteries after the aging and capacity grading of the compositions of examples and comparative examples (5 batteries for each condition, average value of the results) were charged to 4.2V with 0.5C CC-CV, the current was cut off from the constant voltage to 0.05C, and the charge capacity was recorded as C0. After the cells were stored at 60 ± 2 ℃ for 21 days and left to stand at room temperature for 5 hours, the cells were discharged to 2.75V at 1C, the discharge capacity was recorded as C1, and the capacity retention rate (%) was calculated as C1/C0100%. Then the battery is charged to 4.2V by 0.5C CC-CV, the current of 0.05C is cut off and the battery is fully charged, and the charging capacity is marked as C2Then discharged to 2.75V at 1C, and the discharge capacity is marked as C3Calculating a capacity recovery ratio (%) ═ C3/C2100%. The battery expansion rate (%) is calculated by storingThe thickness before storage is subtracted from the thickness of (b), and the obtained difference in thickness is divided by the thickness of the battery before storage to obtain a percentage.
1.5 Hot Box test
At normal temperature, 1/3C CC-CV is charged to 4.2V, and the current is cut off at 1/20C. Putting the fully charged sample into a temperature box, heating the temperature box to 165 +/-2 ℃ at the speed of 5 ℃/min, and connecting a temperature probe to the surface of the battery cell so as to detect the temperature of the surface of the battery cell; keeping the temperature for 30min and stopping heating; after stopping heating, the cells were observed in an oven for 1h and were considered to pass without ignition and without smoking.
The results of the above tests are shown in table 1 below:
TABLE 1
Figure BDA0003164539770000181
Figure BDA0003164539770000191
In combination with the test results in table 1, it can be seen from the comparison between examples 1 to 12 and comparative example 1 that the addition of the isothiocyanatothioyl compound additive to the electrolyte of the examples of the present invention can improve the cycle and high-temperature storage performance of the battery, and the direct current internal resistance of the battery is hardly increased at an appropriate concentration.
From the test results of examples 1 to 6, it can be seen that the electrolyte additive concentration is increased from 0.05 wt% to 3 wt%, and the DCIR of the battery is gradually increased, because the SEI formed on the surface of the active material of the battery is thicker at higher additive content, resulting in increased battery resistance, which slightly decreases the cycle performance of the battery, but slightly increases the high-temperature storage performance.
As is clear from comparison between examples 1 to 6 and examples 19 to 20, when the content of the additive in the electrolyte solution is too low (example 19) or the content of the additive is too high (example 20), the improvement of the battery performance by the additive is deteriorated, resulting in poor high-temperature performance or excessive battery resistance.
The lithium ion batteries in the embodiments 1 to 20 of the invention all pass the hot box test, and in the hot box test process, the additive in the electrolyte of the embodiments of the invention can form a compact SEI film with good thermal stability on the surfaces of the positive and negative electrode materials, thereby greatly reducing the side reaction on the surfaces of the battery materials. Therefore, the heat generation of the battery is reduced, the thermal runaway of the battery caused by excessive temperature rise of the battery can be avoided, and the maximum temperature in the whole test process is less than 165 ℃.
As can be seen from comparison between examples 5 to 6 and examples 11 to 12, when the number of-N ═ C ═ S groups in the additive structure is increased from 2 to 3, it was found that as the number of-N ═ C ═ S groups on the additive molecule increases, the resistance of the additive to form an SEI film increases, resulting in an increase in the internal resistance of the battery, and a decrease in the normal temperature cycle performance of the battery is affected, but the film formation is more dense, and therefore the high temperature storage performance is slightly improved.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims (10)

1. The electrolyte additive is characterized in that the structural general formula of the electrolyte additive is shown as the following formula I:
Figure FDA0003164539760000011
x, Y in the formula I are respectively and independently selected from one of isothiocyanato, cyclohexane, alkoxy, phenyl and halogen.
2. The electrolyte additive of claim 1 wherein the electrolyte additive comprises:
Figure FDA0003164539760000012
Figure FDA0003164539760000013
at least one of (1).
3. The electrolyte is characterized by comprising a lithium salt, an organic solvent and an additive, wherein the structural general formula of the additive is shown as the following formula I:
Figure FDA0003164539760000014
x, Y in the formula I are respectively and independently selected from one of isothiocyanato, cyclohexane, alkoxy, phenyl and halogen.
4. The electrolyte according to claim 3, wherein the additive is 0.05-3% by mass;
and/or the molar concentration of the lithium salt is 0.5-1.5 mol/L.
5. The electrolyte of claim 3 or 4, wherein the additive comprises: thiophosphoryl difluoride isothiocyanate, dimethyl thiophosphate isocyanate, diisopropoxyl thiophosphoryl isothiocyanate, diphenyl thiophosphoryl isothiocyanate, cyclohexane diisothiocyano-sulfur compound and triisothiocyano-sulfur compound.
6. The electrolyte of claim 5, wherein the lithium salt in the electrolyte is selected from the group consisting of: LiPF6、LiBF4、LiPO2F2、LiTFSI、LiBOB、LiDFOB、LiN(SO2F)2At least one of (1).
7. The electrolyte of any one of claims 3, 4 or 6, wherein the organic solvent is selected from the group consisting of: at least one of ethylene carbonate, methyl ethyl carbonate, diethyl carbonate, propylene carbonate, dimethyl carbonate, methyl formate, methyl acetate, methyl propionate, ethyl acetate, propyl propionate, sulfolane, gamma-butyrolactone and dimethyl sulfoxide.
8. The electrolyte of claim 7, further comprising: at least one auxiliary additive selected from vinylene carbonate, fluoroethylene carbonate, 1, 3-propane sultone, vinyl sulfate, 1-propylene-1, 3-sultone, ethylene carbonate, tris (trimethylsilane) phosphite, tris (trimethylsilane) borate, lithium bis-fluorosulfonylimide, lithium difluorophosphate, lithium difluorooxalato phosphate, lithium difluorooxalato borate, lithium bis-oxalato borate, and methylene methanedisulfonate.
9. The electrolyte of claim 8, wherein the auxiliary additives are each independently 0.05% to 15% by weight;
and/or the organic solvent is selected from a mixed organic solvent of ethylene carbonate, methyl ethyl carbonate and diethyl carbonate.
10. A secondary battery comprising the electrolyte additive according to any one of claims 1 to 2 or the electrolyte according to any one of claims 3 to 9.
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CN114552011A (en) * 2022-02-23 2022-05-27 珠海市赛纬电子材料股份有限公司 Electrolyte additive, non-aqueous electrolyte and lithium ion battery

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US20200144672A1 (en) * 2018-10-30 2020-05-07 Enevate Corporation Silicon-based energy storage devices with phosphorus containing electrolyte additives

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