CN115020812A - Electrolyte and lithium ion battery containing same - Google Patents

Electrolyte and lithium ion battery containing same Download PDF

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CN115020812A
CN115020812A CN202210784767.2A CN202210784767A CN115020812A CN 115020812 A CN115020812 A CN 115020812A CN 202210784767 A CN202210784767 A CN 202210784767A CN 115020812 A CN115020812 A CN 115020812A
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electrolyte
compound
carbonate
lithium
mass fraction
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冯绍伟
支岩辉
刘静
杨红新
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Svolt Energy Technology 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
    • 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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Abstract

The invention provides an electrolyte and a lithium ion battery containing the same. The electrolyte comprises an organic solvent, lithium salt and an additive, wherein the additive comprises a phosphate compound with a side chain containing trialkoxysilane. According to the invention, the phosphate compound with the side chain containing trialkoxysilane is added into the electrolyte, and the silane in the compound can be used as a stabilizer to adsorb free protons, so that the contents of moisture and hydrofluoric acid in the electrolyte are reduced. The boron atoms can generate complexation with transition metal of the ternary anode material, so that the reactivity of the anode material is reduced, and the side reaction of the anode and the electrolyte is reduced. The electrolyte can improve the stability of the electrolyte, improve the high-temperature performance of the lithium ion secondary battery and reduce the gas production during storage.

Description

Electrolyte and lithium ion battery containing same
Technical Field
The invention relates to the field of lithium ion batteries, in particular to an electrolyte and a lithium ion battery containing the same.
Background
In recent years, the lithium ion power battery industry for vehicles has been rapidly developed, and in order to satisfy the long driving range and wide temperature range environment of electric vehicles, it is necessary to develop a lithium ion secondary battery having higher energy density, more excellent high-temperature cycle and storage performance, so as to satisfy the requirement of the service life of the power battery for vehicles of 10 to 15 years or more. The lithium ion secondary battery with high energy density generally uses a high-nickel ternary positive electrode with high energy density and a high-voltage ternary positive electrode, and the materials are easy to generate interface degradation, particle breakage and electrolyte oxidation at high temperature, so that the service life is quickly reduced at high temperature.
Therefore, how to prepare an electrolyte which is stable to the interface of the positive electrode and can be applied to high temperature conditions is an important research direction in the field.
Disclosure of Invention
In view of the defects in the prior art, the invention aims to provide an electrolyte capable of stabilizing a positive electrode interface and a lithium ion battery containing the electrolyte.
In order to achieve the purpose, the invention adopts the following technical scheme:
one of the objects of the present invention is to provide an electrolyte comprising an organic solvent, a lithium salt and an additive, wherein the additive comprises a phosphate compound containing trialkoxysilane in a side chain.
According to the invention, the phosphate compound with the side chain containing trialkoxysilane is added into the electrolyte, and the silane in the compound can be used as a stabilizer to adsorb free protons, so that the contents of moisture and hydrofluoric acid in the electrolyte are reduced. The boron atoms can generate complexation with transition metal of the ternary anode material, so that the reactivity of the anode material is reduced, and the side reaction of the anode and the electrolyte is reduced. The electrolyte can improve the stability of the electrolyte, improve the high-temperature performance of the lithium ion secondary battery and reduce the gas production during storage.
As a preferred embodiment of the present invention, the phosphate ester compound comprises any one of formula 1, formula 2 or formula 3 or a combination of at least two thereof, wherein the combination is exemplified by typical but not limiting examples: a combination of formula 1 and formula 2, a combination of formula 2 and formula 3, or a combination of formula 1 and formula 3, and the like,
Figure BDA0003719995430000021
in a preferred embodiment of the present invention, the phosphate ester compound is present in an amount of 0.01 to 5% by mass based on 100% by mass of the electrolyte, wherein the amount of the phosphate ester compound may be 0.01%, 0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5% by mass, but the present invention is not limited to the above-mentioned values, and other values not shown in the above-mentioned range of values are also applicable, and preferably 0.1 to 2%.
As a preferable technical scheme of the invention, the additive also comprises other additives.
Preferably, the other additive includes any one of or a combination of at least two of a cyclic carbonate compound containing an unsaturated bond, a halogen-substituted cyclic carbonate compound, a sulfate compound, a sulfite compound, a sultone compound, a disulfonic acid compound, a nitrile compound, an aromatic compound, an isocyanate compound, a phosphazene compound, a cyclic anhydride compound, a phosphite compound, a phosphate compound, or a borate compound, wherein the combination is typically but not limitedly exemplified by: a combination of a cyclic carbonate compound having an unsaturated bond and a halogen-substituted cyclic carbonate compound, a combination of a sulfate compound and a sulfite compound, a sultone compound, a combination of a nitrile compound and an aromatic compound, a combination of an isocyanate compound and a phosphazene compound, a combination of a cyclic anhydride compound and a phosphite compound, a combination of a phosphate compound and an aromatic compound, or a combination of a borate compound and a sulfate compound, and the like.
Preferably, the cyclic carbonate compound having an unsaturated bond includes vinylene carbonate and/or vinyl ethylene carbonate.
Preferably, the halogen-substituted cyclic carbonate compound includes fluoroethylene carbonate.
Preferably, the sulfate compound comprises vinyl sulfate.
Preferably, the sulfite compound comprises ethylene sulfite.
Preferably, the sultone compound comprises 1, 3-propane sultone.
Preferably, the nitrile compound comprises succinonitrile and/or adiponitrile.
Preferably, the aromatic compound comprises biphenyl and/or cyclohexylbenzene.
Preferably, the isocyanate compound comprises 1, 4-tetramethylene diisocyanate.
Preferably, the phosphazene compound comprises ethoxypentafluorocyclotriphosphazene.
Preferably, the cyclic anhydride compound includes succinic anhydride and/or maleic anhydride.
Preferably, the phosphite compound comprises tris (trimethylsilyl) phosphite.
Preferably, the phosphate compound comprises tris (trimethylsilyl) phosphate.
Preferably, the borate compound comprises tris (trimethylsilyl) borate.
As a preferred embodiment of the present invention, the other additives include vinylene carbonate and vinyl sulfate.
Preferably, the vinylene carbonate accounts for 0-2% of the electrolyte, based on 100% of the electrolyte, wherein the mass fraction may be 0, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, or 2%, but is not limited to the recited values, and other values not recited in the numerical range are also applicable, preferably 0.2-0.8%.
Preferably, the mass fraction of the vinyl sulfate in the electrolyte is 0 to 2% based on 100% of the mass fraction of the electrolyte, wherein the mass fraction may be 0, 0.2%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, or 2%, but is not limited to the recited values, and other values not recited in the range of the values are also applicable, preferably 0.5 to 1.5%.
Preferably, the other additives account for 0 to 2% by mass of the electrolyte, based on 100% by mass of the electrolyte, wherein the mass fraction may be 0, 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 1.9%, or 2%, but is not limited to the recited values, and other values not recited within the range of the recited values are also applicable.
In a preferred embodiment of the present invention, the organic solvent includes a cyclic carbonate and a chain ester, and the chain ester includes a chain carbonate and a chain carboxylate.
Preferably, the chain carbonates include any one or a combination of at least two of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, or ethyl butyrate, wherein the combination is typically but not limited to: a combination of dimethyl carbonate and diethyl carbonate, a combination of ethyl methyl carbonate and propyl methyl carbonate, a combination of ethyl propyl carbonate and methyl formate, a combination of ethyl formate and propyl formate, a combination of methyl acetate and ethyl acetate, a combination of propyl acetate and methyl propionate, a combination of ethyl propionate and propyl propionate, a combination of methyl butyrate and diethyl carbonate, or a combination of ethyl butyrate and dimethyl carbonate, and the like.
Preferably, the volume ratio of the cyclic carbonate to the chain acid ester is 5:95 to 50:50, wherein the volume ratio may be 5:95, 10:90, 15:85, 20:80, 25:75, 30:70, 35:65, 40:60, 45:55, 50:50, and the like, but is not limited to the recited values, and other values not recited in the numerical range are also applicable.
Preferably, the mass fraction of the organic solvent in the electrolyte is 75-89% based on 100% of the mass fraction of the electrolyte, wherein the mass fraction may be 75%, 78%, 80%, 82%, 84%, 86%, 88%, or 89%, but is not limited to the recited values, and other values not recited in the range of the values are also applicable.
In a preferred embodiment of the present invention, the lithium salt includes LiPF 6 、Li(FSO 2 ) 2 N(LiFSI)、Li(CF 3 SO 2 ) 2 N(LiTFSI)、LiBF 4 、LiClO 4 LiDFOB, LiBOB or LiPO 2 F 2 Any one of orCombinations of at least two, typical but non-limiting examples of such combinations are: LiPF (lithium ion particle Filter) 6 And Li (FSO) 2 ) 2 Combination of N (LiFSI) and Li (FSO) 2 ) 2 N (LiFSI) and Li (CF) 3 SO 2 ) 2 Combination of N (LiTFSI) and Li (CF) 3 SO 2 ) 2 N (LiTFSI) and LiBF 4 Combination of (1), LiBF 4 And LiClO 4 Combination of (2) and LiClO 4 And LiDFOB, LiDFOB and LiBOB or LiBOB and LiPO 2 F 2 Combinations of (a), (b), and the like.
Preferably, the lithium salt includes lithium difluorophosphate and lithium hexafluorophosphate;
preferably, the lithium difluorophosphate accounts for 0.5 to 1.5% by mass of the electrolyte, based on 100% by mass of the electrolyte, wherein the mass fraction may be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, or 1.5%, but is not limited to the recited values, and other values not recited in the numerical range are also applicable.
Preferably, the lithium salt accounts for 10 to 20% of the mass fraction of the electrolyte, based on 100% of the mass fraction of the electrolyte, wherein the mass fraction may be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or the like, but is not limited to the recited values, and other values not recited in the range of the values are also applicable.
The second purpose of the invention is to provide a lithium ion battery, which comprises the electrolyte according to the first purpose, and also comprises a positive pole piece and a negative pole piece.
As a preferred embodiment of the present invention, the active material of the positive electrode sheet includes a transition metal oxide including lithium and/or a transition metal phosphate compound including lithium.
Preferably, the transition metal oxide of lithium comprises LiCoO 2 、LiNi x Co y Mn z O 2 、LiNi x Co y Al z O 2 、LiNi x Mn 1-x O 2 、LiMn 2 O 4 、LiMnO 2 、Li 2 MnO 4 、Li 1+a Mn 1-x M x O 2 、LiCo 1-x Mn x O 2 、LiNi 1-x Co x O 4 Or Li 2 Mn 1-x O 4 Or a combination of at least two of the foregoing, wherein typical but non-limiting examples of such combinations are: LiCoO 2 And LiNi x Co y Mn z O 2 Combination of (2) and LiNi x Co y Mn z O 2 And LiNi x Co y Al z O 2 Combination of (2) and LiNi x Mn 1-x O 2 And LiMn 2 O 4 Combination of (1) and LiMn 2 O 4 And LiMnO 2 Combination of (1) and LiMnO 2 And Li 2 MnO 4 Combination of (1), Li 2 MnO 4 And Li 1+a Mn 1-x M x O 2 Combination of (2) and LiCo 1- x Mn x O 2 And LiNi 1-x Co x O 4 Or LiNi 1-x Co x O 4 And Li 2 Mn 1-x O 4 Combinations of (b), etc., wherein 0. ltoreq. a<0.2, 0. ltoreq. x.ltoreq.1, 0. ltoreq. y.ltoreq.1, 0. ltoreq. z.ltoreq.1, wherein a may have a value of 0, 0.05, 0.1, 0.15 or 0.2, x may have a value of 0, 0.1, 0.2, 0.03, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1, etc., y may have a value of 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1, etc., and z may have a value of 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1, etc., but not limited to the values listed, and other values not listed in the respective numerical ranges are equally applicable.
Preferably, the lithium transition metal phosphate compound is selected from LiFePO 4 、LiMnPO 4 、LiCoPO 4 、LiFe 1- x M x PO 4 Any one or a combination of at least two of the following, wherein typical but non-limiting examples of such combinations are: LiFePO 4 And LiMnPO 4 Combination of (2), LiMnPO 4 And LiCoPO 4 Combinations of (5) or LiCoPO 4 And LiFe 1-x M x PO 4 Wherein M is selected from any one of Ni, Co, Mn, Al, Cr, Mg, Zr, Mo, V, and Ti, 0. ltoreq. x.ltoreq.1, wherein x may be 0, 0.1, 0.2, 0.03, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1, but is not limited to the values listed, and other values not listed within this range of values are also applicable.
As a preferred technical solution of the present invention, the active material of the negative electrode plate includes any one or a combination of at least two of soft carbon, hard carbon, artificial graphite, natural graphite, silica, silicon carbon, or lithium metal, wherein the combination is typically but not limited to: a combination of soft carbon and hard carbon, a combination of hard carbon and artificial graphite, a combination of artificial graphite and natural graphite, a combination of natural graphite and silica, a combination of silica and silicon carbon, a combination of silicon carbon and lithium metal, or the like.
The recitation of numerical ranges herein includes not only the above-recited numerical values, but also any numerical values between non-recited numerical ranges, and is not intended to be exhaustive or to limit the invention to the precise numerical values encompassed within the range for brevity and clarity.
Compared with the prior art, the invention has the beneficial effects that:
the prepared electrolyte is added with the phosphate compound containing trialkoxysilane on the side chain, so that the stability of the electrolyte can be improved, the high-temperature performance of the lithium ion secondary battery is improved, the gas production rate during storage is reduced, the storage capacity retention rate can reach more than 93 percent at 60 ℃, the gas production expansion rate can be reduced to 13 percent after 30 days of storage, and the cycle capacity retention rate can reach more than 93 percent at 45 ℃/1C and 800 circles.
Detailed Description
The technical solution of the present invention is further explained by the following embodiments.
Example 1
The embodiment provides a lithium ion battery electrolyte:
the electrolyte comprises lithium salt, organic solvent and additive;
lithium salt: calculated by taking the mass fraction of the electrolyte as 100%, lithium hexafluorophosphate accounting for 12.5% of the mass fraction of the electrolyte and lithium difluorophosphate accounting for 1% of the mass fraction of the electrolyte;
organic solvent: the electrolyte is an organic solvent accounting for 84.5% of the mass fraction of the electrolyte by taking the mass fraction of the electrolyte as 100%, and the organic solvent comprises ethylene carbonate, methyl ethyl carbonate and diethyl carbonate in a volume ratio of 30:50: 20;
the additive comprises vinylene carbonate accounting for 0.5 percent of the mass fraction of the electrolyte, vinyl sulfate accounting for 1 percent of the mass fraction of the electrolyte and a phosphate compound accounting for 0.5 percent of the mass fraction of the electrolyte and being as shown in a formula 3,
Figure BDA0003719995430000071
wherein, the synthesis method of the phosphate compound shown in the formula 3 comprises the following steps:
Figure BDA0003719995430000081
example 2
The embodiment provides a lithium ion battery electrolyte:
the electrolyte comprises lithium salt, organic solvent and additive;
lithium salt: lithium hexafluorophosphate accounting for 9.5 percent of the mass fraction of the electrolyte accounts for 0.5 percent of lithium difluorophosphate accounting for the mass fraction of the electrolyte by taking the mass fraction of the electrolyte as 100 percent;
organic solvent: the electrolyte is taken as 100 percent of organic solvent which accounts for 89.7 percent of the mass fraction of the electrolyte and comprises butylene carbonate and propyl propionate with the volume ratio of 5: 95;
the additive comprises vinylene carbonate accounting for 0.2 percent of the mass fraction of the electrolyte, vinyl sulfate accounting for 0.5 percent of the mass fraction of the electrolyte and a phosphate compound accounting for 0.1 percent of the mass fraction of the electrolyte and being described as a formula 2,
Figure BDA0003719995430000082
wherein, the synthesis method of the phosphate compound shown in the formula 2 comprises the following steps:
Figure BDA0003719995430000091
example 3
The embodiment provides a lithium ion battery electrolyte:
the electrolyte comprises lithium salt, organic solvent and additive;
lithium salt: lithium hexafluorophosphate accounting for 18.5 percent of the mass fraction of the electrolyte accounts for 1.5 percent of lithium difluorophosphate accounting for 100 percent of the mass fraction of the electrolyte;
organic solvent: the electrolyte is taken as 100 percent of organic solvent, which accounts for 75.5 percent of the mass fraction of the electrolyte and comprises butylene carbonate and ethyl butyrate with the volume ratio of 50: 50;
the additive comprises vinylene carbonate accounting for 0.8 percent of the mass fraction of the electrolyte, vinyl sulfate accounting for 1.5 percent of the mass fraction of the electrolyte and a phosphate compound accounting for 2 percent of the mass fraction of the electrolyte, wherein the mass fraction of the electrolyte is 100 percent,
Figure BDA0003719995430000092
wherein, the synthesis method of the phosphate compound shown in the formula 1 comprises the following steps:
Figure BDA0003719995430000101
example 4
The present example was carried out under the same conditions as in example 1 except that the mass fraction of the phosphate ester compound represented by the formula 3 in the electrolyte was changed from 0.5% to 1%.
Example 5
The present example was carried out under the same conditions as in example 1 except that the mass fraction of the phosphate ester compound represented by the formula 3 in the electrolyte was changed to 0.5% and 2%.
Example 6
The present example was carried out under the same conditions as in example 1 except that the mass fraction of the phosphate ester compound represented by the formula 3 in the electrolyte was changed from 0.5% to 5%.
Example 7
In this example, the conditions were the same as in example 1 except that the mass fraction of the phosphate ester compound represented by the formula 3 in the electrolyte was changed from 0.5% to 0.01%.
Example 8
This example was carried out under the same conditions as in example 1 except that lithium difluorophosphate was not added and the mass fraction of the organic solvent was changed to 85.5%.
Example 9
This example was carried out under the same conditions as in example 1 except that vinyl sulfate was not added and the mass fraction of the organic solvent was changed to 85.5%.
Comparative example 1
This comparative example was conducted under the same conditions as example 1 except that the phosphate ester compound was not added and the mass fraction of the organic solvent was changed to 85%.
Comparative example 2
This comparative example was conducted under the same conditions as in example 1 except that the phosphate compound, vinylene carbonate and vinyl sulfate were not added and the mass fraction of the organic solvent was replaced with 86.5%.
The electrolytes in examples 1 to 9 and comparative examples 1 to 2 were assembled into lithium ion batteries for testing of storage performance and cycle performance, wherein the method for assembling the lithium ion batteries comprises the following steps:
lithium nickel manganese oxide (LiNi) as positive electrode active material 0.75 Mn 0.25 O 2 ) The conductive agent Super-P and the adhesive PVDF are dissolved in a solvent N-methyl pyrrolidone according to the mass ratio of 94:3.0:3.0 and are uniformly mixed to prepare anode slurry, and then the anode slurry is uniformly coated on the anode slurryCoating weight on the current collector aluminum foil is 18mg/cm 2 Then drying at 85 ℃, performing cold pressing, trimming, cutting into pieces and slitting, drying for 4 hours at 85 ℃ under a vacuum condition, and welding tabs to prepare the positive plate of the lithium ion secondary battery meeting the requirements;
dissolving a negative active material hard carbon, a conductive agent Super-P, a thickening agent CMC and a bonding agent SBR in a solvent deionized water according to a mass ratio of 96.5:1.0:1.0:1.5, uniformly mixing to prepare a negative slurry, and uniformly coating the negative slurry on a current collector copper foil with a coating weight of 8.9mg/cm 2 Then drying at 85 ℃, performing cold pressing, trimming, cutting into pieces and slitting, drying for 4h under the vacuum condition of 110 ℃, and welding tabs to prepare the negative plate of the lithium ion secondary battery meeting the requirements;
the electrolyte obtained in examples 1 to 9 and comparative examples 1 to 2, and the positive electrode tab, the negative electrode tab and the separator (PE film) were fabricated into a battery having a thickness of 8mm, a width of 60mm and a length of 130mm through a lamination process, and vacuum-baked at 85 ℃ for 10 hours, injected with the electrolyte, left to stand for 24 hours, and then charged to 4.35V with a constant current of 0.1C (200mA), then charged at a constant voltage of 4.35V until the current drops to 0.05C (100mA), then discharged to 2.8V with a constant current of 0.1C (200mA), and the charge and discharge were repeated for 2 times, and finally charged to 3.8V with a constant current of 0.1C (200mA), to obtain lithium ion batteries corresponding to examples 1 to 9 and comparative examples 1 to 2.
The lithium ion batteries corresponding to examples 1 to 9 and comparative examples 1 to 2 were subjected to tests of capacity retention rate, battery volume expansion rate, and cycle performance after high-temperature storage, and the test results are shown in table 1.
The method for testing the capacity retention rate after high-temperature storage comprises the following steps: at 25 ℃, the lithium ion batteries prepared in the examples 1-9 and the comparative examples 1-2 are respectively charged to 4.35V by constant current of 1C, further charged to current of 0.05C by constant voltage of 4.35V, and then discharged to 2.8V by constant current of 1C, wherein the discharge capacity of the lithium ion battery is the discharge capacity before high-temperature storage; then charging the lithium ion battery to 4.35V with a constant current of 1C, storing the lithium ion battery at 60 ℃ for 30 days, after the storage is finished, placing the lithium ion battery at 25 ℃, then discharging the lithium ion battery to 2.8V with a constant current of 0.5C, then charging the lithium ion battery to 4.35V with a constant current of 1C, further charging to a current of 1C with a constant voltage of 4.35V, then discharging the lithium ion battery to 2.8V with a constant current of 1C, and finally, the discharge capacity is the discharge capacity of the lithium ion battery after high-temperature storage. Capacity retention (%) after high-temperature storage of the lithium ion battery [ discharge capacity after high-temperature storage of the lithium ion battery/discharge capacity before high-temperature storage of the lithium ion battery ] × 100%;
testing of cycle performance: the high-temperature cycle performance of the lithium ion batteries prepared in examples 1 to 9 and comparative examples 1 to 2 was tested, and the specific method was as follows: at 45 ℃, the lithium ion batteries are charged to 4.35V by constant current of 1C, then charged to current of 0.05C by constant voltage of 4.35V, and then discharged to 2.8V by constant current of 1C, and the process is a charge-discharge cycle process, and the discharge capacity of the cycle is the discharge capacity of the first cycle. Carrying out a cyclic charge-discharge test on the lithium ion battery according to the mode, and taking the discharge capacity of the 800 th cycle;
the method for testing the volume expansion rate of the battery comprises the following steps: the lithium ion batteries prepared in examples 1 to 9 and comparative examples 1 to 2 were stored at 60 ℃ for 30 days, and after the storage was completed, the lithium ion batteries were placed at 25 ℃, the volume of the batteries was measured by a drainage method, and the thickness of the batteries was measured by a micrometer. Then, the lithium ion battery was discharged to 2.8V with a constant current of 0.5C, then charged to 4.35V with a constant current of 1C, further charged to a constant voltage of 4.35V until the current was 1C, then discharged to 2.8V with a constant current of 1C, the last discharge capacity was the discharge capacity after the high-temperature storage of the lithium ion battery, and the battery volume expansion rate was (volume after storage/volume before storage-1)%.
TABLE 1
Figure BDA0003719995430000131
As can be seen from the above table, when the phosphate compound is added, the high-temperature performance of the battery is remarkably improved and the gas generation of the battery is reduced, as compared with comparative examples 1 to 2 and examples 1 to 3. The phosphate compound is matched with lithium difluorophosphate and vinyl sulfate, so that more excellent high-temperature performance can be obtained.
As can be seen from comparison of example 1 with examples 4 to 7, the high temperature performance of the battery improves as the content of the phosphate ester compound of formula 3 increases, but when the content increases to 2% or more, the further improvement effect is less significant because the high content of the phosphate ester compound increases the viscosity of the electrolyte.
Comparing example 1 with examples 8-9, it is clear that the phosphate compound, lithium difluorophosphate and vinyl sulfate are matched to obtain more excellent high temperature performance.
The above-mentioned embodiments, objects, technical solutions and advantages of the present invention are further described in detail, it should be understood that the above-mentioned embodiments are only examples of the present invention, and should not be construed as limiting the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. The electrolyte is characterized by comprising an organic solvent, a lithium salt and an additive, wherein the additive comprises a phosphate compound containing trialkoxysilane on a side chain.
2. The electrolyte of claim 1, wherein the phosphate ester compound comprises any one of formula 1, formula 2, or formula 3, or a combination of at least two thereof,
Figure FDA0003719995420000011
3. the electrolyte according to claim 1 or 2, wherein the mass fraction of the phosphate ester compound is 0.01 to 5%, preferably 0.1 to 2%, based on 100% by mass of the electrolyte.
4. The electrolyte of any one of claims 1-3, wherein the additive further comprises other additives;
preferably, the other additive includes any one or a combination of at least two of a cyclic carbonate compound containing an unsaturated bond, a halogen-substituted cyclic carbonate compound, a sulfate compound, a sulfite compound, a sultone compound, a nitrile compound, an aromatic compound, an isocyanate compound, a phosphazene compound, a cyclic anhydride compound, a phosphite compound, a phosphate compound, or a borate compound;
preferably, the cyclic carbonate compound having an unsaturated bond includes vinylene carbonate and/or vinyl ethylene carbonate;
preferably, the halogen-substituted cyclic carbonate compound includes fluoroethylene carbonate;
preferably, the sulfate compound comprises vinyl sulfate;
preferably, the sulfite compound comprises vinyl sulfite;
preferably, the sultone compound comprises 1, 3-propane sultone;
preferably, the nitrile compound comprises succinonitrile and/or adiponitrile;
preferably, the aromatic compound comprises biphenyl and/or cyclohexylbenzene;
preferably, the isocyanate compound comprises 1, 4-tetramethylene diisocyanate;
preferably, the phosphazene compound comprises ethoxypentafluorocyclotriphosphazene;
preferably, the cyclic anhydride compound includes succinic anhydride and/or maleic anhydride;
preferably, the phosphite compound comprises tris (trimethylsilyl) phosphite;
preferably, the phosphate ester compound comprises tris (trimethylsilyl) phosphate;
preferably, the borate compound comprises tris (trimethylsilyl) borate.
5. The electrolyte of claim 4, wherein the other additives include vinylene carbonate and vinyl sulfate;
preferably, the vinylene carbonate accounts for 0-2% of the electrolyte by mass fraction of 100%, and preferably 0.2-0.8%;
preferably, the mass fraction of the vinyl sulfate in the electrolyte is 0-2%, preferably 0.5-1.5%, based on 100% of the mass fraction of the electrolyte;
preferably, the other additives account for 0-2% of the electrolyte by mass fraction of 100%.
6. The electrolyte solution according to any one of claims 1 to 5, wherein the organic solvent comprises a cyclic carbonate and a chain ester, and the chain ester comprises a chain carbonate and a chain carboxylate;
preferably, the chain carbonate comprises any one or a combination of at least two of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate or ethyl butyrate;
preferably, the volume ratio of the cyclic carbonate to the chain ester is 5: 95-50: 50;
preferably, the organic solvent accounts for 75-89% of the mass fraction of the electrolyte, based on 100% of the mass fraction of the electrolyte.
7. The electrolyte of any one of claims 1-6, wherein the lithium salt comprises LiPF 6 、Li(FSO 2 ) 2 N(LiFSI)、Li(CF 3 SO 2 ) 2 N(LiTFSI)、LiBF 4 、LiClO 4 LiDFOB, LiBOB or LiPO 2 F 2 Any one or a combination of at least two of;
preferably, the lithium salt includes lithium difluorophosphate and lithium hexafluorophosphate;
preferably, the mass fraction of the lithium difluorophosphate in the electrolyte is 0.5-1.5% based on 100% of the mass fraction of the electrolyte;
preferably, the lithium salt accounts for 10-20% of the electrolyte by taking the mass fraction of the electrolyte as 100%.
8. A lithium ion battery, characterized in that the lithium ion battery comprises the electrolyte according to any one of claims 1 to 7, and the lithium ion battery further comprises a positive electrode plate and a negative electrode plate.
9. The lithium ion battery according to claim 8, wherein the active material of the positive electrode sheet comprises a transition metal oxide comprising lithium and/or a transition metal phosphate compound comprising lithium;
preferably, the transition metal oxide of lithium comprises LiCoO 2 、LiNi x Co y Mn z O 2 、LiNi x Co y Al z O 2 、LiNi x Mn 1- x O 2 、LiMn 2 O 4 、LiMnO 2 、Li 2 MnO 4 、Li 1+a Mn 1-x M x O 2 、LiCo 1-x Mn x O 2 、LiNi 1-x Co x O 4 Or Li 2 Mn 1-x O 4 Any one or a combination of at least two of them, wherein 0. ltoreq. a<0.2，0≤x≤1，0≤y≤1，0≤z≤1；
Preferably, the lithium transition metal phosphate compound is selected from LiFePO 4 、LiMnPO 4 、LiCoPO 4 、LiFe 1-x M x PO 4 Wherein M is selected from any one of Ni, Co, Mn, Al, Cr, Mg, Zr, Mo, V and Ti, and x is more than or equal to 0 and less than or equal to 1.
10. The lithium ion battery of claim 8 or 9, wherein the active material of the negative electrode plate comprises any one of soft carbon, hard carbon, artificial graphite, natural graphite, silica, silicon carbon, or lithium metal, or a combination of at least two of the foregoing.
CN202210784767.2A 2022-06-29 2022-06-29 Electrolyte and lithium ion battery containing same Pending CN115020812A (en)

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