CN118136955A - Application of difluorophosphoryloxy fluoroboro (phosphate) lithium in lithium ion battery - Google Patents

Application of difluorophosphoryloxy fluoroboro (phosphate) lithium in lithium ion battery Download PDF

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Publication number
CN118136955A
CN118136955A CN202211539751.1A CN202211539751A CN118136955A CN 118136955 A CN118136955 A CN 118136955A CN 202211539751 A CN202211539751 A CN 202211539751A CN 118136955 A CN118136955 A CN 118136955A
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lithium
electrolyte
phosphate
difluorophosphoryloxy
imide
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马国强
严红
徐冲
李中凯
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Zhejiang Zhonglan New Energy Materials Co ltd
Zhejiang Lantian Environmental Protection Hi Tech Co Ltd
Sinochem Lantian Co Ltd
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Zhejiang Zhonglan New Energy Materials Co ltd
Zhejiang Lantian Environmental Protection Hi Tech Co Ltd
Sinochem Lantian Co Ltd
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Publication of CN118136955A publication Critical patent/CN118136955A/en
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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
    • 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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  • Manufacturing & Machinery (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
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  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Inorganic Chemistry (AREA)
  • Secondary Cells (AREA)

Abstract

The invention discloses an application of difluorophosphoryl oxyfluoroboro (phosphate) lithium in a lithium ion battery, which comprises the following steps: lithium difluorophosphoryloxy fluoroboro (phosphate) of the structure shown in the following formula (I) is added to the electrolyte: Wherein M is boron or phosphorus; when M is boron, x is selected from 1, 2,3 or 4, y is selected from 0, 1, 2 or 3, and x+y=4; when M is phosphorus, x is selected from 1, 2,3, 4, 5 or 6, y is selected from 0, 1, 2,3, 4 or 5, and x+y=6; after addition to the electrolyte, the lithium difluorophosphoryloxyfluoroboro (phosphate) may passivate the aluminum current collector at AlBO 3 and/or AlF 3 surface to inhibit corrosion; the lithium difluorophosphoryl oxyfluoroboronate accounts for 0.01 to 30.0 weight percent of the total mass of the electrolyte. The invention has the advantages of inhibiting the corrosion of the aluminum current collector, inhibiting the gas production and the impedance increase of high-temperature storage, improving the cycle performance of the battery and the like.

Description

Application of difluorophosphoryloxy fluoroboro (phosphate) lithium in lithium ion battery
Technical Field
The invention relates to the field of lithium ion battery electrolyte, in particular to an application of difluoro phosphoryl oxyfluoro boron (phosphorus) acid lithium in inhibiting corrosion of difluoro sulfonimide lithium and/or difluoro methanesulfonimide lithium to an aluminum current collector in the electrolyte.
Background
Lithium hexafluorophosphate (LiPF 6) is the main lithium salt currently commercialized, and not only can conduct ion conduction, but also can generate HF through hydrolysis so as to passivate an aluminum current collector by AlF 3 on the surface of the aluminum current collector, and meanwhile, PF 5 is generated through decomposition, and can also react with Al 2O3 on the surface of the aluminum current collector to generate an AlF 3 passivated aluminum current collector. Therefore, in systems where lithium hexafluorophosphate is used as the primary lithium salt, there is generally no aluminum foil corrosion problem. However, lithium hexafluorophosphate is thermally stable and has poor chemical stability, and is easy to hydrolyze to generate a large amount of substances such as HF, PF 5 and the like so as to accelerate the occurrence of side reactions of electrolyte, on one hand, accelerate the discoloration of the electrolyte, and on the other hand, a large amount of HF can damage an interface film between an anode and a cathode and the electrolyte, thereby accelerating the decomposition and gas production of the electrolyte, deteriorating the impedance increase and the dissolution of transition metal ions, and finally causing the rapid deterioration of the storage and the cycle performance of a battery.
Lithium bis (fluorosulfonyl) imide (LiFSI) and lithium bis (trifluoromethanesulfonyl) imide (LiTFSI) have higher ionic conductivity in the electrolyte, good stability and the prospect of being used as main lithium salt. However, at potentials exceeding 3.6v vs. Li +/Li, the fluorosulfonyl imide lithium-based compound forms with the Al current collector (CF 3SO2)2N]3 Al is stable and very soluble, thus constantly corroding the aluminum current collector causing short-circuiting within the cell to exacerbate cell gassing and worsen cycle storage performance.
At present, compounds for inhibiting LiWSI from corroding an aluminum current collector are mainly lithium bisoxalato borate (LiBOB) and lithium difluorooxalato borate (LiDFOB), and the boron-containing oxalate can be decomposed on the surface of an anode to generate AlBO 3 passivation aluminum current collector so as to inhibit continuous corrosion of the aluminum current collector. However, due to the existence of oxalate, liBOB and LiDFOB are easy to decompose to generate CO 2 so as to aggravate the gas production of the battery, and the solubility of the electrolyte in the conventional carbonate electrolyte is low, the addition amount is less than 1%, and the corrosion inhibition effect is not obvious.
LiPF 6, while capable of forming AlF 3 passivated aluminum current collectors, is also susceptible to hydrolysis to produce significant amounts of HF that worsen cell storage and cycling stability.
Therefore, it is necessary to provide a method for effectively suppressing corrosion of an aluminum current collector while suppressing gas generation and resistance increase in high-temperature storage of a battery, and improving cycle performance of the battery.
Disclosure of Invention
In order to solve the technical problems, the invention provides an application of lithium difluorophosphoryloxy fluoroboron (phosphate) in inhibiting corrosion of lithium difluorosulfimide and/or lithium bistrifluoromethylsulfonimide to an aluminum current collector in an electrolyte.
The invention aims at realizing the following technical scheme:
Use of lithium difluorophosphoryloxy fluoroborate (phosphate) in a lithium ion battery, specifically, adding lithium difluorophosphoryloxy fluoroborate (phosphate) with a structure shown in the following formula (I) to an electrolyte:
wherein M is boron or phosphorus; when M is boron, x is selected from 1, 2,3 or 4, y is selected from 0,1, 2 or 3, and x+y=4; when M is phosphorus, x is selected from 1, 2,3, 4, 5 or 6, y is selected from 0,1, 2,3, 4 or 5, and x+y=6;
The lithium difluorophosphoryl oxyfluoroborate (phosphate) accounts for 0.01-30.0wt% of the total mass of the electrolyte, and preferably accounts for 1.0-10.0wt% of the total mass of the electrolyte.
Preferably, the lithium difluorophosphoryloxy fluoroboro (phosphate) is selected from at least one of the following structures:
the addition of lithium difluorophosphoryloxy fluoroborate (phosphonium) is not necessary when no species causing corrosion of the aluminum current collector is present in the electrolyte or the content of the species causing corrosion of the aluminum current collector is low while the addition amount of lithium hexafluorophosphate is high.
After addition to the electrolyte, the lithium difluorophosphoryloxyfluoroboro (phosphate) may passivate the aluminum current collector at AlBO 3 and/or AlF 3 surface to inhibit corrosion;
According to the research of the invention, when the addition amount of the lithium bis (fluorosulfonyl) imide and/or the lithium bis (trifluoromethanesulfonyl) imide in the electrolyte is low, and the lithium hexafluorophosphate is used as the main lithium salt, the corrosion of the aluminum current collector of the lithium ion battery can be inhibited by HF and PF 5 generated by the decomposition of the lithium hexafluorophosphate, and no obvious corrosion phenomenon exists. However, when the addition amount of the lithium bis (fluorosulfonyl) imide and/or the lithium bis (trifluoromethanesulfonyl) imide in the electrolyte is high or the content of the lithium hexafluorophosphate in the electrolyte is reduced, the current collection phenomenon of corrosion of the lithium bis (fluorosulfonyl) imide and the lithium bis (trifluoromethanesulfonyl) imide is aggravated, and the battery performance is rapidly attenuated. At this time, the addition of the lithium difluorophosphoryloxy fluoroborate (phosphate) of the present invention can play a very good role in inhibiting corrosion of the aluminum current collector. The specific reasons are as follows:
Lithium difluorophosphoryloxy fluoroborate may passivate AlBO 3 the aluminum current collector surface to inhibit corrosion; lithium difluorophosphoryloxy fluorophosphate may react with Al 2O3 on the surface of the current collector to form AlF 3 passivated aluminum current collector to inhibit corrosion.
In a specific embodiment, the electrolyte contains lithium difluorosulfonimide and/or lithium bistrifluoromethanesulfonimide in an amount of 1.0 to 30.0wt%, preferably 5.0 to 20.0wt%, more preferably 5.0 to 12.0wt%, based on the total mass of the electrolyte, and corrosion of the aluminum current collector is inhibited by adding any of the above-described lithium difluorophosphoryloxy fluoroborate (phospho) oxides.
In the application process of the lithium difluorophosphoryloxy fluoroborate (phosphate) in the lithium ion battery, the electrolyte further comprises a basic additive, wherein the basic additive is at least one selected from 1, 3-propane sultone, 1, 3-propylene sultone, vinyl sulfate, 4-methyl vinyl sulfate, 4' -vinyl disulfate, vinylene carbonate, vinyl carbonate, lithium difluorophosphate, tris (trimethylsilane) phosphate, tris (trimethylsilane) borate and ethoxy pentafluoro-cyclotriphosphazene, and the addition amount of the basic additive accounts for 0.1-5.0wt% of the total mass of the electrolyte.
Further, the electrolyte also comprises lithium hexafluorophosphate, and the addition amount of the lithium hexafluorophosphate is 0-20.0 wt%, preferably 0-12.0 wt% of the total mass of the electrolyte.
In the application process of the difluorophosphoryloxy fluoroboro (phosphate) lithium in the lithium ion battery, the electrolyte also comprises an organic solvent, and the organic solvent is usually used in the electrolyte. Preferably, the organic solvent is at least one selected from the group consisting of C3-C6 carbonates, C3-C8 carboxylates, sulfones and ethers. Further, the C3-C6 carbonate compound is at least one selected from ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate and ethyl propyl carbonate; the C3-C8 carboxylic ester compound is at least one selected from gamma-butyrolactone, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, ethyl butyrate, propyl acetate and propyl propionate; the sulfone compound is selected from at least one of sulfolane, dimethyl sulfoxide, dimethyl sulfone and diethyl sulfone; the ether compound is selected from triglyme and/or tetraglyme.
The invention also provides a lithium ion battery electrolyte, which comprises the following components:
the addition amount of the lithium hexafluorophosphate is 0 to 20.0 weight percent, preferably 0 to 12.0 weight percent of the total mass of the electrolyte;
the lithium difluorophosphoryloxy fluoroborate (phosphate) accounts for 0.01 to 30.0 weight percent of the total mass of the electrolyte;
the addition amount of the lithium bis (fluorosulfonyl) imide and/or the lithium bis (trifluoromethanesulfonyl) imide is 1.0-30.0 wt%, preferably 5.0-20.0 wt%, and more preferably 5.0-12.0 wt% of the total mass of the electrolyte;
The base additive described above; and at least one organic solvent as described above.
In some specific embodiments, the electrolyte consists of lithium difluorophosphoryloxy fluoroboro (phospho) ate, lithium bis-fluorosulfonyl imide and/or lithium bis-trifluoromethanesulfonyl imide, a base additive, and an organic solvent, and the added mass of lithium difluorophosphoryloxy fluoroboro (phospho) ate: the addition mass of the lithium bis (fluorosulfonyl) imide and/or the lithium bis (trifluoromethanesulfonyl) imide is more than or equal to 1/2. In the electrolyte, the lithium difluorophosphoryloxy fluoroboro (phosphate) can inhibit corrosion of an aluminum current collector generated by lithium difluorosulfimide and/or lithium bistrifluorosulfimide, can also inhibit gas production and impedance increase of a battery at high temperature storage, and can improve high-temperature cycle performance.
In other specific embodiments, the electrolyte consists of lithium hexafluorophosphate, lithium difluorophosphoryl fluoroborate (phosphate), lithium difluorosulfonimide and/or lithium bistrifluoromethanesulfonimide, a basic additive and an organic solvent, wherein the addition amount of the lithium hexafluorophosphate is 0.1-12 wt% of the total mass of the electrolyte, the addition amount of the lithium difluorophosphoryl fluoroborate (phosphate) is 1.0-10 wt% of the total mass of the electrolyte, and the addition amount of the lithium difluorosulfonimide and/or lithium bistrifluoromethanesulfonimide is 5-12 wt% of the total mass of the electrolyte.
Further, the sum of twice the addition amount of the lithium difluorophosphoryloxy fluoroborate (phosphate) and the addition amount of the lithium hexafluorophosphate: the addition amount of the lithium bis (fluorosulfonyl) imide and/or the lithium bis (trifluoromethanesulfonyl) imide is more than or equal to 1/1.
In these electrolytes, the addition amount of lithium difluorophosphoryloxy fluoroborate (phosphate) can be suitably reduced by the action of lithium hexafluorophosphate, and corrosion of an aluminum current collector caused by lithium difluorosulfonimide and/or lithium bistrifluoromethanesulfonimide can be suppressed as well.
In some specific embodiments, the invention adopts vinylene carbonate as a basic additive, and the dosage of the vinylene carbonate accounts for 0.1-5 wt% of the total mass of the electrolyte, so that the impedance increase of the battery in the high-temperature storage process can be restrained.
In some specific embodiments, the invention adopts 1, 3-propane sultone as a basic additive, and the dosage of the additive accounts for 0.1 to 5 weight percent of the total mass of the electrolyte, so that the gas production of the battery during high-temperature storage can be obviously inhibited.
In some specific embodiments, the invention adopts vinylene carbonate and lithium difluorophosphate as basic additives, and the dosage of the ethylene carbonate and the lithium difluorophosphate is 0.1-5 wt% of the total mass of the electrolyte, so that the high-temperature storage performance and the high-temperature cycle performance of the battery can be improved simultaneously.
In some specific embodiments, the invention adopts the ethylene sulfate and the tri (trimethylsilane) phosphate as basic additives, and the dosage of the ethylene sulfate and the tri (trimethylsilane) phosphate is 0.1 to 5 weight percent of the total mass of the electrolyte, so that the high-temperature storage performance and the high-temperature cycle performance of the battery can be improved simultaneously.
In some specific embodiments, the invention adopts vinylene carbonate, vinyl sulfate and tri (trimethylsilane) phosphate as basic additives, and the dosage of the ethylene carbonate, the vinyl sulfate and the tri (trimethylsilane) phosphate is 0.1-5 wt% of the total mass of the electrolyte, so that the high-temperature storage performance and the high-temperature cycle performance of the battery can be improved simultaneously.
In some specific embodiments, the invention adopts 1, 3-propenoic acid lactone and tri (trimethylsilane) borate as basic additives, and the dosage of the basic additives is 0.1 to 5 weight percent of the total mass of the electrolyte, so that the high-temperature storage performance and the high-temperature cycle performance of the battery can be improved simultaneously.
In some specific embodiments, the invention adopts vinyl ethylene carbonate and ethoxy pentafluoro-cyclotriphosphazene as basic additives, and the consumption is 0.1-5 wt% of the total mass of the electrolyte, so that the high-temperature storage performance and the high-temperature cycle performance of the battery can be improved simultaneously.
The invention also provides a lithium ion battery, which comprises a positive electrode, a negative electrode, a diaphragm and the electrolyte.
Compared with the prior art, the invention has the following beneficial effects:
The invention inhibits the corrosion of aluminum current collector generated by lithium bis (fluorosulfonyl) imide and/or lithium bis (trifluoromethanesulfonyl) imide with higher addition amount by adding lithium difluorophosphoryloxy fluoroborate (phosphate). The lithium bis (fluorosulfonyl) imide and/or lithium bis (trifluoromethanesulfonyl) imide with higher addition amount have high ionic conductivity, so that the impedance of the battery can be reduced; lithium difluorophosphoryl oxyfluoroborate (phosphate) can inhibit not only corrosion of an aluminum current collector, but also high-temperature storage gas production and impedance increase of a battery, and meanwhile, the high-temperature cycle performance is improved; meanwhile, when the lithium difluorophosphoryloxy fluoroborate (phosphate) and lithium hexafluorophosphate are added simultaneously to inhibit corrosion of an aluminum current collector, the use amount of the lithium difluorophosphoryloxy fluoroborate (phosphate) in the two is increased, so that the use amount of the lithium hexafluorophosphate can be reduced, the generation of HF (hydrogen fluoride) is reduced, the acidity of an electrolyte is reduced, the deterioration of the HF on the battery performance is weakened, and finally the storage performance and the cycle performance of the battery are further enhanced.
Detailed Description
The invention will be further illustrated with reference to the following specific examples, without limiting the invention to these specific embodiments. It will be appreciated by those skilled in the art that the invention encompasses all alternatives, modifications and equivalents as may be included within the scope of the claims.
1. Electrolyte preparation
Example 1
In a glove box filled with argon (moisture < 5ppm, oxygen content < 10 ppm), ethylene Carbonate (EC), ethylmethyl carbonate (EMC), diethyl carbonate (DEC) were mixed in mass ratio EC: EMC: dec=3:5:2, and slowly adding lithium difluorosulfimide (LiFSI) to the mixed solution until the mass fraction of LiFSI is 10%, and then adding a compound A1 accounting for 5% of the mass fraction of the electrolyte to obtain the electrolyte of the embodiment.
Example 2
The operation of this embodiment is identical to that of embodiment 1, except that: the amount of lithium bis (fluorosulfonyl) imide (LiFSI) added was adjusted to 8%, compound A2 was used instead of compound A1, and the amount was adjusted to 4%, to obtain an electrolyte of this example.
Example 3
The operation of this embodiment is identical to that of embodiment 1, except that: the amount of lithium bis (fluorosulfonyl) imide (LiFSI) added was adjusted to 8%, compound A2 was used instead of compound A1, and the amount was adjusted to 6%, to obtain an electrolyte of this example.
Example 4
The operation of this embodiment is identical to that of embodiment 1, except that: the amount of lithium bis (fluorosulfonyl) imide (LiFSI) added was adjusted to 8%, compound A2 was used instead of compound A1, and the amount was adjusted to 8%, to obtain an electrolyte of this example.
Example 5
The operation of this embodiment is identical to that of embodiment 1, except that: the amount of lithium bis (fluorosulfonyl) imide (LiFSI) added was adjusted to 5%, compound A3 was used instead of compound A1, and the amount was adjusted to 10%, to obtain an electrolyte of this example.
Example 6
The operation of this embodiment is identical to that of embodiment 1, except that: the amount of LiFSI added was adjusted to 12%, compound A4 was used instead of compound A1, and the amount was adjusted to 6%, to obtain an electrolyte of this example.
Example 7
The operation of this embodiment is identical to that of embodiment 1, except that: the amount of LiFSI added was adjusted to 2%, and the amount of compound A1 was adjusted to 1%, to obtain an electrolyte of this example.
Example 8
The operation of this embodiment is identical to that of embodiment 1, except that: the amount of LiFSI added was adjusted to 20%, and the amount of compound A1 was adjusted to 10%, to obtain an electrolyte of this example.
Example 9
The operation of this example is identical to example 6, except that: then, 1% Vinylene Carbonate (VC) was added to obtain an electrolyte of this example.
Example 10
The operation of this example is identical to example 6, except that: 1% of 1, 3-Propane Sultone (PS) was further added to obtain an electrolyte of this example.
Example 11
The operation of this example is identical to example 2, except that: then, 1% of Vinylene Carbonate (VC) and 1% of lithium difluorophosphate (LiDFP) were added to obtain an electrolyte of this example.
Example 12
The operation of this example is identical to example 2, except that: then, 1% of vinyl sulfate (DTD) and 1% of tris (trimethylsilane) phosphate (TMSP) were added to obtain an electrolyte of this example.
Example 13
The operation of this example is identical to example 2, except that: then, 1% Vinylene Carbonate (VC), 1% vinyl sulfate (DTD) and 1% tris (trimethylsilane) phosphate (TMSP) were added to obtain an electrolyte of this example.
Example 14
The operation of this embodiment is identical to that of embodiment 1, except that: the electrolyte of this example was obtained by replacing lithium bis (trifluoromethanesulfonyl) imide (LiTFSI) with lithium bis (fluorosulfonyl) imide and by replacing compound A1 with compound A5.
Example 15
The operation of this embodiment is identical to that of embodiment 1, except that: the electrolyte of this example was obtained by replacing lithium bis (trifluoromethanesulfonyl) imide (LiTFSI) with lithium bis (fluorosulfonyl) imide and by replacing compound A1 with compound A6.
Example 16
The operation of this embodiment is identical to that of embodiment 1, except that: the amount of the compound A1 was adjusted to 1%, and 8% lithium hexafluorophosphate (LiPF 6) was added to obtain an electrolyte of this example.
Example 17
The operation of this embodiment is identical to that of embodiment 1, except that: the amount of the compound A1 was adjusted to 2%, and 6% lithium hexafluorophosphate (LiPF 6) was added to obtain an electrolyte of this example.
Example 18
The operation of this embodiment is identical to that of embodiment 1, except that: the amount of compound A1 was adjusted to 3%, and 4% lithium hexafluorophosphate (LiPF 6) was added to obtain an electrolyte of this example.
Example 19
The operation of this embodiment is identical to that of embodiment 1, except that: the amount of the compound A1 was adjusted to 4%, and 2% lithium hexafluorophosphate (LiPF 6) was added to obtain an electrolyte of this example.
Example 20
The operation of this embodiment is identical to that of embodiment 18, except that: 1% of 1, 3-Propenolactone (PST) and 1% of tris (trimethylsilane) borate (TMSB) were further added to obtain an electrolyte of this example.
Example 21
The operation of this embodiment is identical to that of embodiment 18, except that: then, 1% of vinyl carbonate (VEC) and 1% of ethoxy pentafluoro-cyclotriphosphazene (PFPN) were added to obtain an electrolyte of this example.
Comparative example 1
The operation of this comparative example is the same as in example 1, except that: the amount of the compound A1 was adjusted to 4%, to obtain an electrolyte of this comparative example.
Comparative example 2
The operation of this comparative example is the same as in example 1, except that: the amount of the compound A1 was adjusted to 2%, to obtain an electrolyte of this comparative example.
Comparative example 3
The operation of this comparative example is the same as in example 1, except that: the electrolyte of this comparative example was obtained without adding 5% of the compound A1.
Comparative example 4
The operation of this embodiment is identical to that of embodiment 1, except that: the electrolyte of this comparative example was obtained by replacing lithium bis (trifluoromethanesulfonyl) imide (LiTFSI) with lithium bis (fluorosulfonyl) imide (LiWSI) and without adding 5% of compound A1.
Comparative example 5
The operation of this comparative example is the same as in example 1, except that: lithium hexafluorophosphate (LiPF 6) was used instead of the compound A1, and the amount was adjusted to 10%, to obtain an electrolyte of this comparative example.
Comparative example 6
The operation of this comparative example is the same as in example 1, except that: lithium hexafluorophosphate (LiPF 6) was used instead of the compound A1, and the amount was adjusted to 8%, to obtain an electrolyte of this comparative example.
Comparative example 7
The operation of this comparative example is the same as in example 1, except that: lithium hexafluorophosphate (LiPF 6) was used instead of the compound A1, and the amount was adjusted to 6%, to obtain an electrolyte of this comparative example.
Comparative example 8
The operation of this comparative example is the same as in example 1, except that: lithium hexafluorophosphate (LiPF 6) was used instead of the compound A1, and the amount was adjusted to 4%, to obtain an electrolyte of this comparative example.
Comparative example 9
The operation of this comparative example is the same as in example 1, except that: lithium hexafluorophosphate (LiPF 6) was used instead of the compound A1, and the amount was adjusted to 2%, to obtain an electrolyte of this comparative example.
Comparative example 10
The operation of this comparative example is the same as in example 17, except that: the amount of the compound A1 was adjusted to 1%, and an electrolyte of this comparative example was obtained.
Comparative example 11
The operation of this comparative example was the same as in example 19, except that: the amount of the compound A1 was adjusted to 2%, to obtain an electrolyte of this comparative example.
2. Electrochemical performance test
The electrolyte prepared in the examples and the comparative examples is subjected to electrochemical corrosion test on an aluminum current collector, and the specific test method is as follows: and (3) using a three-electrode system, wherein an aluminum foil is a working electrode, a lithium sheet is a counter electrode and a reference electrode, adding an equivalent amount of electrolyte into an electrolytic cell, performing cyclic voltammetry scanning test for 3 circles, wherein the scanning range is 2.5-6.0V, the scanning speed is 0.2mV/S, and observing the corrosion condition of the aluminum foil after the test is finished.
Performance tests are carried out on the lithium ion power batteries (soft package battery cells) prepared by the examples and the comparative examples, and the performance tests mainly comprise:
(1) High temperature storage test at 60 ℃): charging the battery to 100% SOC, storing for 28 days in a baking oven at 60+/-2 ℃, and testing the volume before and after storage to obtain the volume expansion rate of the single battery before and after storage at 60 ℃; testing the DCR value after the storage is finished at room temperature, calculating the percentage value of the DCR value and the initial DCR value, and recording the percentage value as the change rate of the discharged DCR;
(2) And (3) high-temperature cycle test at 45 ℃): the battery was cycled in an oven at 45.+ -. 1 ℃ with a charge-discharge current of 1C/1C, the weekly discharge capacity was calculated, cycled to 200 weeks, the cycle stopped, and the capacity retention after cycling was calculated.
Table 1 results of electrochemical Performance test of the corresponding cell without LiPF 6 electrolyte
TABLE 2 electrochemical performance test results for cells corresponding to electrolyte containing LiPF 6
From the test results in table 1 above, it can be seen that: the sufficient lithium difluorophosphoryloxy fluoroboro (phosphate) is added into the electrolyte, so that corrosion of LiFeSI and LiTFSI to an aluminum current collector can be effectively inhibited, high-temperature storage gas production and DCR internal resistance increase of the battery can be inhibited, and high-temperature cycle performance can be improved.
As can be seen from the comparison of examples 1 to 6 and comparative examples 1 to 3, when the addition amount of lithium difluorophosphoryloxy fluoroboro (phosphate): when the mass ratio of the addition amount of the lithium difluorosulfimide is more than or equal to 1/2, the lithium difluorophosphoryloxy fluoroboro (phospho) can inhibit the corrosion of LiFSI on the aluminum current collector, improve the high-temperature storage performance and the high-temperature cycle performance, and further enhance the improvement effect along with the increase of the content of the lithium difluorophosphoryloxy fluoroboro (phospho) in the electrolyte.
Comparing examples 9 to 10 and example 6, examples 11 to 13 and example 2, it was found that when at least one of VC, PS, liDFP, DTD, TMSP was used as a base additive in the electrolyte, the high-temperature storage property and/or the high-temperature cycle property could be further improved.
Comparative examples 14 to 15 and comparative example 4 have found that lithium difluorophosphoryloxy fluoroboronate also inhibits corrosion of the aluminum current collector by LiTFSI and improves high temperature storage and high temperature cycle performance.
From the test results in table 2, it can be seen that: although corrosion of the aluminum current collector by LiFSI can be suppressed even when a sufficient amount of lithium hexafluorophosphate is contained in the electrolyte, the high-temperature storage performance and high-temperature cycle performance of the battery are inferior to those of the case where lithium difluorophosphoryloxy-fluoroboro (phosphate) is used, because the use of lithium hexafluorophosphate generates HF that reduces the stability of the electrolyte and the lithium hexafluorophosphate does not have the protective effect of lithium difluorophosphoryloxy-fluoroboro (phosphate) on the electrolyte interface.
As can be seen from comparison of comparative examples 5 to 9, when the addition amount of lithium hexafluorophosphate: when the mass ratio of the addition amount of lithium bis (fluorosulfonyl) imide is more than or equal to 1/1, the electrolyte can inhibit the corrosion of LiFSI on the aluminum current collector. As can be seen from comparing example 1, examples 16 to 19 and comparative examples 6 to 9, when the sum of twice the addition amount of lithium difluorophosphoryloxy fluoroborate (phosphate) and the addition amount of lithium hexafluorophosphate: when the mass ratio of the addition amount of lithium bis (fluorosulfonyl) imide is more than or equal to 1/1, the electrolyte can inhibit the corrosion of LiFSI on the aluminum current collector; and with the increase of the use proportion of the difluorophosphoryloxy fluoroboro (phosphate) lithium in the two lithium salts, the high-temperature storage performance and the high-temperature cycle performance of the battery are further enhanced due to the better chemical stability and the interfacial film forming effect compared with the lithium hexafluorophosphate.
Comparing examples 19 to 21 with example 18, it was found that when at least one of PST, TMSB, VEC, PFPN was used as a base additive in the electrolyte, the high-temperature storage property and/or the high-temperature cycle property could be further improved.

Claims (11)

1. The application of the difluorophosphoryl oxyfluoroboro (phosphate) lithium in the lithium ion battery is characterized in that: adding lithium difluorophosphoryloxy fluoroboro (phosphate) with a structure shown in the following formula (I) into lithium ion battery electrolyte:
wherein M is boron or phosphorus; when M is boron, x is selected from 1, 2,3 or 4, y is selected from 0,1, 2 or 3, and x+y=4; when M is phosphorus, x is selected from 1, 2,3, 4, 5 or 6, y is selected from 0,1, 2,3, 4 or 5, and x+y=6;
the lithium difluorophosphoryloxy fluoroborate (phosphate) accounts for 0.01 to 30.0 weight percent of the total mass of the electrolyte;
The electrolyte also comprises lithium bis (fluorosulfonyl) imide and/or lithium bis (trifluoromethanesulfonyl) imide, and the addition amount of the lithium bis (fluorosulfonyl) imide accounts for 1.0-30.0 wt% of the total mass of the electrolyte.
2. Use of lithium difluorophosphoryl oxyfluoroboro (phosphate) in a lithium ion battery according to claim 1, characterized in that: the lithium difluorophosphoryloxy fluoroborate (phosphate) is selected from at least one of the following structures:
3. use of lithium difluorophosphoryl oxyfluoroboro (phosphate) in a lithium ion battery according to claim 2, characterized in that: the difluorophosphoryloxy fluoroboric acid lithium accounts for 1.0-10.0wt% of the total mass of the lithium ion battery electrolyte.
4. Use of lithium difluorophosphoryl oxyfluoroboro (phosphate) in a lithium ion battery according to claim 3, characterized in that: the electrolyte also comprises a basic additive, wherein the basic additive is at least one selected from 1, 3-propane sultone, 1, 3-propylene sultone, vinyl sulfate, 4-methyl vinyl sulfate, 4' -vinyl disulfate, vinylene carbonate, vinyl ethylene carbonate, lithium difluorophosphate, tris (trimethylsilane) phosphate, tris (trimethylsilane) borate and ethoxy pentafluoro-cyclo-triphosphazene, and the addition amount of the basic additive is 0.1-5.0 wt% of the total mass of the electrolyte.
5. Use of lithium difluorophosphoryloxy fluoroboro (phosphate) in a lithium ion battery according to any one of claims 1 to 4, characterized in that: the electrolyte also comprises lithium hexafluorophosphate, and the addition amount of the lithium hexafluorophosphate accounts for 0-20.0 wt% of the total mass of the electrolyte, and is preferably 0-12.0 wt%.
6. Use of lithium difluorophosphoryl oxyfluoroboro (phosphate) in a lithium ion battery according to claim 1, characterized in that: the electrolyte also comprises an organic solvent which is at least one selected from C3-C6 carbonic ester or fluorocarbonic ester compounds, C3-C8 carboxylic ester or fluorocarboxylic ester compounds, sulfone compounds and ether compounds.
7. The lithium ion battery electrolyte is characterized in that: the electrolyte comprises:
the addition amount of the lithium hexafluorophosphate is 0 to 20.0 weight percent, preferably 0 to 12.0 weight percent of the total mass of the electrolyte;
the lithium difluorophosphoryloxy fluoroborate (phosphate) according to claim 1 or 2, wherein the addition amount is 0.01-30.0 wt% of the total mass of the electrolyte;
The addition amount of the lithium bis (fluorosulfonyl) imide and/or the lithium bis (trifluoromethanesulfonyl) imide is 1.0-30.0 wt%, preferably 5.0-20.0 wt%, and more preferably 5.0-12.0 wt% of the total mass of the electrolyte;
The base additive of claim 4; and the organic solvent according to claim 6.
8. The electrolyte according to claim 7, wherein: the electrolyte consists of lithium difluorophosphoryloxy fluoroborate (phosphate), lithium difluorosulfonimide and/or lithium bistrifluoromethanesulfonimide, a basic additive and an organic solvent, and the addition amount of the lithium difluorophosphoryloxy fluoroborate (phosphate) is as follows: the addition amount of the lithium bis (fluorosulfonyl) imide and/or the lithium bis (trifluoromethanesulfonyl) imide is more than or equal to 1/2.
9. The electrolyte according to claim 7, wherein: the electrolyte consists of lithium hexafluorophosphate, lithium difluorophosphoryl oxyfluoroborate (phosphate), lithium difluorosulfonimide and/or lithium bistrifluoromethanesulfonimide, a basic additive and an organic solvent, wherein the addition of the lithium hexafluorophosphate accounts for 0.01-12 wt% of the total mass of the electrolyte, the addition of the lithium difluorophosphoryl oxyfluoroborate (phosphate) accounts for 1.0-10 wt% of the total mass of the electrolyte, and the addition of the lithium difluorosulfonimide and/or lithium bistrifluoromethanesulfonimide accounts for 5-12 wt% of the total mass of the electrolyte.
10. The electrolyte of claim 9, wherein: the sum of twice the addition amount of the difluorophosphoryloxy fluoroboric (phosphorous) acid lithium and the addition amount of lithium hexafluorophosphate: the addition amount of the lithium bis (fluorosulfonyl) imide and/or the lithium bis (trifluoromethanesulfonyl) imide is more than or equal to 1/1.
11. The utility model provides a lithium ion battery, includes positive pole, negative pole, diaphragm, its characterized in that: the lithium ion battery further comprises the electrolyte of claims 8-10.
CN202211539751.1A 2022-12-02 2022-12-02 Application of difluorophosphoryloxy fluoroboro (phosphate) lithium in lithium ion battery Pending CN118136955A (en)

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