CN117650275A - Lithium iron manganese phosphate battery adaptive electrolyte and preparation method and application thereof - Google Patents
Lithium iron manganese phosphate battery adaptive electrolyte and preparation method and application thereof Download PDFInfo
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- CN117650275A CN117650275A CN202311812307.7A CN202311812307A CN117650275A CN 117650275 A CN117650275 A CN 117650275A CN 202311812307 A CN202311812307 A CN 202311812307A CN 117650275 A CN117650275 A CN 117650275A
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- 239000003792 electrolyte Substances 0.000 title claims abstract description 109
- DVATZODUVBMYHN-UHFFFAOYSA-K lithium;iron(2+);manganese(2+);phosphate Chemical compound [Li+].[Mn+2].[Fe+2].[O-]P([O-])([O-])=O DVATZODUVBMYHN-UHFFFAOYSA-K 0.000 title claims abstract description 15
- 238000002360 preparation method Methods 0.000 title abstract description 16
- 230000003044 adaptive effect Effects 0.000 title abstract description 4
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims abstract description 84
- 239000000654 additive Substances 0.000 claims abstract description 83
- 230000000996 additive effect Effects 0.000 claims abstract description 79
- 229910003002 lithium salt Inorganic materials 0.000 claims abstract description 71
- 159000000002 lithium salts Chemical class 0.000 claims abstract description 71
- ZZNQQQWFKKTOSD-UHFFFAOYSA-N diethoxy(diphenyl)silane Chemical compound C=1C=CC=CC=1[Si](OCC)(OCC)C1=CC=CC=C1 ZZNQQQWFKKTOSD-UHFFFAOYSA-N 0.000 claims abstract description 46
- 239000003960 organic solvent Substances 0.000 claims abstract description 33
- ZSMNRKGGHXLZEC-UHFFFAOYSA-N n,n-bis(trimethylsilyl)methanamine Chemical compound C[Si](C)(C)N(C)[Si](C)(C)C ZSMNRKGGHXLZEC-UHFFFAOYSA-N 0.000 claims abstract description 32
- XHCLAFWTIXFWPH-UHFFFAOYSA-N [O-2].[O-2].[O-2].[O-2].[O-2].[V+5].[V+5] Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[V+5].[V+5] XHCLAFWTIXFWPH-UHFFFAOYSA-N 0.000 claims abstract description 18
- 229910001935 vanadium oxide Inorganic materials 0.000 claims abstract description 18
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 claims description 26
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 claims description 25
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 claims description 25
- 229910052744 lithium Inorganic materials 0.000 claims description 19
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 18
- -1 lithium hexafluorophosphate Chemical compound 0.000 claims description 17
- BTBUEUYNUDRHOZ-UHFFFAOYSA-N Borate Chemical compound [O-]B([O-])[O-] BTBUEUYNUDRHOZ-UHFFFAOYSA-N 0.000 claims description 13
- 238000000034 method Methods 0.000 claims description 9
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 claims description 3
- 238000002156 mixing Methods 0.000 claims description 3
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 claims description 3
- 239000011572 manganese Substances 0.000 abstract description 10
- 238000004090 dissolution Methods 0.000 abstract description 5
- 229910052723 transition metal Inorganic materials 0.000 abstract description 4
- 150000003624 transition metals Chemical class 0.000 abstract description 4
- 239000002904 solvent Substances 0.000 description 27
- 230000000052 comparative effect Effects 0.000 description 14
- 238000003756 stirring Methods 0.000 description 13
- 229910013872 LiPF Inorganic materials 0.000 description 11
- 101150058243 Lipf gene Proteins 0.000 description 11
- 238000012360 testing method Methods 0.000 description 7
- 239000000463 material Substances 0.000 description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- 230000008901 benefit Effects 0.000 description 4
- 238000000354 decomposition reaction Methods 0.000 description 4
- 150000002500 ions Chemical class 0.000 description 4
- 230000014759 maintenance of location Effects 0.000 description 4
- 238000011056 performance test Methods 0.000 description 4
- 239000007774 positive electrode material Substances 0.000 description 4
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 3
- 229910001416 lithium ion Inorganic materials 0.000 description 3
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 3
- JCVQKRGIASEUKR-UHFFFAOYSA-N triethoxy(phenyl)silane Chemical compound CCO[Si](OCC)(OCC)C1=CC=CC=C1 JCVQKRGIASEUKR-UHFFFAOYSA-N 0.000 description 3
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- QHGJSLXSVXVKHZ-UHFFFAOYSA-N dilithium;dioxido(dioxo)manganese Chemical compound [Li+].[Li+].[O-][Mn]([O-])(=O)=O QHGJSLXSVXVKHZ-UHFFFAOYSA-N 0.000 description 2
- 239000007772 electrode material Substances 0.000 description 2
- IGILRSKEFZLPKG-UHFFFAOYSA-M lithium;difluorophosphinate Chemical compound [Li+].[O-]P(F)(F)=O IGILRSKEFZLPKG-UHFFFAOYSA-M 0.000 description 2
- 229910052748 manganese Inorganic materials 0.000 description 2
- 230000001737 promoting effect Effects 0.000 description 2
- 230000002829 reductive effect Effects 0.000 description 2
- 238000007086 side reaction Methods 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 229910052596 spinel Inorganic materials 0.000 description 2
- 239000011029 spinel Substances 0.000 description 2
- 239000002841 Lewis acid Substances 0.000 description 1
- 229910013870 LiPF 6 Inorganic materials 0.000 description 1
- 240000007817 Olea europaea Species 0.000 description 1
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000008151 electrolyte solution Substances 0.000 description 1
- 229940021013 electrolyte solution Drugs 0.000 description 1
- 238000006056 electrooxidation reaction Methods 0.000 description 1
- 238000010828 elution Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 150000007517 lewis acids Chemical class 0.000 description 1
- 230000000670 limiting effect Effects 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 150000002829 nitrogen Chemical class 0.000 description 1
- 239000010450 olivine Substances 0.000 description 1
- 229910052609 olivine Inorganic materials 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 230000002000 scavenging effect Effects 0.000 description 1
- 229910000077 silane Inorganic materials 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
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Abstract
The invention discloses a manganese iron phosphate lithium battery adaptive electrolyte, and a preparation method and application thereof. Relates to the technical field of secondary battery electrolyte. The electrolyte comprises the following components: a lithium salt; an organic solvent; an additive; the additive comprises at least one of vanadium oxide, heptamethyldisilazane, diphenyldiethoxysilane, N-dimethylformamide, and at least vanadium oxide and diphenyldiethoxysilane. The electrolyte provided by the invention can solve the problem that the cycle performance is rapidly deteriorated due to the massive dissolution of transition metal Mn. The invention improves the battery dynamics and the multiplying power performance through the cooperative use of the additives.
Description
Technical Field
The invention relates to the technical field of secondary battery electrolyte, in particular to a manganese iron phosphate lithium battery adaptive electrolyte, a preparation method and application thereof.
Background
The current widely used positive electrode material mainly comprises three systems of lamellar, spinel and olivine, and the lamellar positive electrode material comprises lithium cobaltate and ternary materials. The spinel positive electrode material is lithium manganate, the olive Dan Zheng positive electrode material is lithium iron phosphate, the lithium cobaltate and the lithium manganate are mainly applied to the field of consumer electronics, and the lithium iron phosphate and the ternary material are applied to the field of electric vehicles. This is because lithium iron phosphate has advantages of good structural stability, low cost, long cycle life, and the like.
However, lithium iron manganese phosphate materials have been deficient and have mainly the following problems: (1) The charge-discharge rate characteristics are affected by the lower electron conductivity and ion diffusion coefficient; (2) The difference of the charging and discharging voltages of manganese and iron causes the dual-voltage platform to appear in the LMFP, and the management difficulty of the later BMS is increased. Taking discharge process as an example, mn 2+ Conversion to Mn around 4.1V 3+ ，Fe 2+ Conversion to Fe around 3.5V 3+ This results in a dual voltage platform for LMFP, which causes a problem of voltage dip during discharge, thereby increasing management difficulty of a later Battery Management System (BMS); (3) Poor cycle performance, the Mn ions of the positive electrode are separated out mainly due to the ginger-Taylor (Jahn-Teller) effect, so that lattice distortion and structural stability are reduced, and stability and cyclicity are affected; (4) Manganese dissolved in the electrolyte can be deposited on the surface of the negative electrode to destroy the SEI layer structure, so that micro short circuit is caused, self-discharge of the battery core is increased, and the cyclicity is reduced; (5) The smaller particles of material result in a lower compacted density, which in turn affects the energy density performance of the overall material.
The problem at point (4) not only affects the battery cycle but also causes a short circuit. Based on this, it is necessary to solve the problem of elution of the transition metal Mn stated in the above (4), which is important for improving the performance and safety of the lithium iron manganese phosphate battery.
Disclosure of Invention
The first technical problem to be solved by the invention is as follows:
an electrolyte is provided.
The second technical problem to be solved by the invention is as follows:
a method for preparing the electrolyte is provided.
The third technical problem to be solved by the invention is:
the application of the electrolyte.
The invention also provides a lithium iron manganese phosphate battery, which comprises the electrolyte.
In order to solve the first technical problem, the invention adopts the following technical scheme:
an electrolyte comprising the following components:
a lithium salt;
an organic solvent;
an additive;
the additive comprises at least one of vanadium oxide, heptamethyldisilazane, diphenyldiethoxysilane, N-dimethylformamide, and at least vanadium oxide and diphenyldiethoxysilane.
According to the embodiments of the present invention, one of the technical solutions has at least one of the following advantages or beneficial effects:
the invention provides an electrolyte which can be adapted to a lithium iron manganese phosphate battery. The electrolyte provided by the invention can solve the problem that the cycle performance is rapidly deteriorated due to the massive dissolution of transition metal Mn. The invention improves the battery dynamics and the multiplying power performance through the cooperative use of the additives.
Wherein, the additive heptamethyldisilazane (7-HMDS) can react with HF to form a salt compound to participate in the formation of SEI film, thereby reducing the content of HF in the electrolyte and inhibiting the dissolution of transition metal Mn, and improving the cycle performance of the battery; wherein, the additive diphenyl diethoxy silane (DPDS) can carry out preferential electrochemical oxidation polymerization on the anode and the cathode, and the decomposition products are doped in SEl and CEl, which is helpful for forming an interfacial film with good protectiveness and ion conductivity on the two electrodes, and can obviously inhibit the decomposition of electrolyte and the deposition of Mn ions at high temperature; wherein the additive N, N Dimethylformamide (DMF) can capture LiPF 6 Is the decomposition product PF of (2) 5 . DMF self lone electron pair and PF in electrolyte 5 The electronic structure combination of the electrolyte further prevents the side reaction of the electrolyte and the corrosion of electrode materials, and has important significance for promoting the large-scale application of the lithium ion battery at high temperature.
According to one embodiment of the invention, the additive accounts for 1-5% of the total mass of the electrolyte.
According to one embodiment of the invention, the additive comprises heptamethyldisilazane, diphenyl-bisThe mass ratio of the heptamethyldisilazane, the diphenyl diethoxysilane and the N, N-dimethylformamide to the total mass of the electrolyte is 1.5-2%. The addition of an excess of heptamethyldisilazane (7-HMDS) may result in the addition of a nitrogen nucleus of a lone pair of electrons in heptamethyldisilazane to the Lewis acid PF 5 Formation of weak complexes, avoiding PF 5 And the presence of the solvent, thereby improving the stability of the electrolyte. In addition, when the addition amounts of the three additives (heptamethyldisilazane, diphenyldiethoxysilane, and N, N dimethylformamide) in the electrolyte are all 1.5% -2% (preferably 2%), the battery including the electrolyte has the best cycle performance at 25 ℃ and 45 ℃ and can still maintain an extremely high capacity retention rate when stored at 60 ℃ for 35 days; and the DCR of the battery at normal temperature and low temperature can be the lowest, which shows that the multiplying power performance of the battery is also excellent.
According to one embodiment of the invention, the diphenyl diethoxysilane accounts for 0.5% -2% of the total mass of the electrolyte. When the mass ratio of the diphenyl diethoxy silane in the electrolyte to the total mass of the electrolyte is 0.5-2%, the cycle performance of the battery comprising the electrolyte at high and low temperatures is improved along with the improvement of the mass ratio of the diphenyl diethoxy silane.
According to one embodiment of the invention, the diphenyl diethoxysilane accounts for 0.5% -0.6% of the total mass of the electrolyte. When the mass ratio of the diphenyl diethoxy silane in the electrolyte to the total mass of the electrolyte is 0.5-0.6%, the battery comprising the electrolyte has the best cycle performance at high and low temperatures.
According to one embodiment of the present invention, the lithium salt includes at least one of lithium hexafluorophosphate, lithium bis-fluoromethylsulfonimide, lithium difluorooxalato borate, and lithium difluorophosphate.
According to one embodiment of the present invention, the organic solvent includes at least one of ethylene carbonate, propylene carbonate, ethylmethyl carbonate, dimethyl carbonate, and diethyl carbonate.
According to one embodiment of the invention, the mass ratio of the lithium salt to the organic solvent is 10-20:60-85.
In order to solve the second technical problem, the invention adopts the following technical scheme:
a method of preparing the electrolyte comprising the steps of:
mixing lithium salt and additive in organic solvent to obtain the electrolyte.
According to one embodiment of the invention, the method for preparing the electrolyte comprises the following steps: firstly, preparing lithium salt, a solvent and an additive in advance according to a preset mass ratio; secondly, adding lithium salt and an additive into a solvent, and mixing together; and thirdly, uniformly stirring by a stirrer to obtain the electrolyte.
In another aspect of the invention, a lithium iron manganese phosphate battery is also provided. Comprising an electrolyte as described in the embodiment of aspect 1 above. The application adopts all the technical schemes of the electrolyte, so that the electrolyte has at least all the beneficial effects brought by the technical schemes of the embodiment.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
Detailed Description
The words "preferably," "more preferably," and the like in the present invention refer to embodiments of the invention that may provide certain benefits in some instances. However, other embodiments may be preferred under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, nor is it intended to exclude other embodiments from the scope of the invention.
When a range of values is disclosed herein, the range is considered to be continuous and includes both the minimum and maximum values for the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values of the range is included. Further, when multiple range description features or characteristics are provided, the ranges may be combined. In other words, unless otherwise indicated, all ranges disclosed herein are to be understood to include any and all subranges subsumed therein.
The technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to fall within the scope of the invention.
The reagents, methods and apparatus employed in the present invention, unless otherwise specified, are all conventional in the art.
Example 1
An electrolyte comprising the following components:
a lithium salt;
an organic solvent;
an additive.
Wherein the lithium salt comprises the following components in mass ratio, and the mass ratio is the ratio of the lithium salt to the electrolyte:
lithium hexafluorophosphate (LiPF) 6 )，13％；
Lithium difluorooxalato borate (LiDFOB), 0.5%;
wherein the organic solvent comprises the following components in percentage by mass:
ethylene Carbonate (EC), 35%;
methyl ethyl carbonate (EMC), 39%;
diethyl carbonate (DEC), 10%;
wherein the additive comprises the following components in percentage by mass:
heptamethyldisilazane (7-HMDS), 0.5%;
diphenyldiethoxysilane (DPDS), 0.5%;
n, N Dimethylformamide (DMF), 0.5%;
and a negative film forming additive VC (vanadium oxide) accounting for 1 percent.
The preparation method of the electrolyte comprises the following steps:
firstly, preparing lithium salt, a solvent and an additive in advance according to a preset mass ratio;
a second step of adding a lithium salt and an additive to the solvent;
and thirdly, uniformly stirring by a stirrer to obtain the electrolyte.
Example 2
An electrolyte comprising the following components:
a lithium salt;
an organic solvent;
an additive.
Wherein the lithium salt comprises the following components in mass ratio, and the mass ratio is the ratio of the lithium salt to the electrolyte:
lithium hexafluorophosphate (LiPF) 6 )，13％；
Lithium difluorooxalato borate (LiDFOB), 0.5%;
wherein the organic solvent comprises the following components in percentage by mass:
ethylene Carbonate (EC), 34.5%;
ethyl Methyl Carbonate (EMC), 38.5%;
diethyl carbonate (DEC), 9.5%;
wherein the additive comprises the following components in percentage by mass:
heptamethyldisilazane (7-HMDS), 1%;
diphenyldiethoxysilane (DPDS), 1%;
n, N Dimethylformamide (DMF), 1%;
and a negative film forming additive VC (vanadium oxide) accounting for 1 percent.
The preparation method of the electrolyte comprises the following steps:
firstly, preparing lithium salt, a solvent and an additive in advance according to a preset mass ratio;
a second step of adding a lithium salt and an additive to the solvent;
and thirdly, uniformly stirring by a stirrer to obtain the electrolyte.
Example 3
An electrolyte comprising the following components:
a lithium salt;
an organic solvent;
an additive.
Wherein the lithium salt comprises the following components in mass ratio, and the mass ratio is the ratio of the lithium salt to the electrolyte:
lithium hexafluorophosphate (LiPF) 6 )，13％；
Lithium difluorooxalato borate (LiDFOB), 0.5%;
wherein the organic solvent comprises the following components in percentage by mass:
ethylene Carbonate (EC), 34%;
methyl ethyl carbonate (EMC), 38%;
diethyl carbonate (DEC), 9%;
wherein the additive comprises the following components in percentage by mass:
heptamethyldisilazane (7-HMDS), 1.5%;
diphenyl diethoxysilane (DPDS), 1.5%;
n, N Dimethylformamide (DMF), 1.5%;
and a negative film forming additive VC (vanadium oxide) accounting for 1 percent.
The preparation method of the electrolyte comprises the following steps:
firstly, preparing lithium salt, a solvent and an additive in advance according to a preset mass ratio;
a second step of adding a lithium salt and an additive to the solvent;
and thirdly, uniformly stirring by a stirrer to obtain the electrolyte.
Example 4
An electrolyte comprising the following components:
a lithium salt;
an organic solvent;
an additive.
Wherein the lithium salt comprises the following components in mass ratio, and the mass ratio is the ratio of the lithium salt to the electrolyte:
lithium hexafluorophosphate (LiPF) 6 )，13％；
Lithium difluorooxalato borate (LiDFOB), 0.5%;
wherein the organic solvent comprises the following components in percentage by mass:
ethylene Carbonate (EC), 33.5%;
methyl ethyl carbonate (EMC), 37.5%;
diethyl carbonate (DEC), 8.5%;
wherein the additive comprises the following components in percentage by mass:
heptamethyldisilazane (7-HMDS), 2%;
diphenyldiethoxysilane (DPDS), 2%;
n, N Dimethylformamide (DMF), 2%;
and 2% of a negative film forming additive VC (vanadium oxide).
The preparation method of the electrolyte comprises the following steps:
firstly, preparing lithium salt, a solvent and an additive in advance according to a preset mass ratio;
a second step of adding a lithium salt and an additive to the solvent;
and thirdly, uniformly stirring by a stirrer to obtain the electrolyte.
Example 5
An electrolyte comprising the following components:
a lithium salt;
an organic solvent;
an additive.
Wherein the lithium salt comprises the following components in mass ratio, and the mass ratio is the ratio of the lithium salt to the electrolyte:
lithium hexafluorophosphate (LiPF) 6 )，13％；
Lithium difluorooxalato borate (LiDFOB), 0.5%;
wherein the organic solvent comprises the following components in percentage by mass:
ethylene Carbonate (EC), 33.5%;
methyl ethyl carbonate (EMC), 37.5%;
diethyl carbonate (DEC), 8.5%;
wherein the additive comprises the following components in percentage by mass:
diphenyldiethoxysilane (DPDS), 0.5%;
and a negative film forming additive VC (vanadium oxide) accounting for 1 percent.
The preparation method of the electrolyte comprises the following steps:
firstly, preparing lithium salt, a solvent and an additive in advance according to a preset mass ratio;
a second step of adding a lithium salt and an additive to the solvent;
and thirdly, uniformly stirring by a stirrer to obtain the electrolyte.
Example 6
An electrolyte comprising the following components:
a lithium salt;
an organic solvent;
an additive.
Wherein the lithium salt comprises the following components in mass ratio, and the mass ratio is the ratio of the lithium salt to the electrolyte:
lithium hexafluorophosphate (LiPF) 6 )，13％；
Lithium difluorooxalato borate (LiDFOB), 0.5%;
wherein the organic solvent comprises the following components in percentage by mass:
ethylene Carbonate (EC), 33.5%;
methyl ethyl carbonate (EMC), 37.5%;
diethyl carbonate (DEC), 8.5%;
wherein the additive comprises the following components in percentage by mass:
diphenyldiethoxysilane (DPDS), 1%;
and a negative film forming additive VC (vanadium oxide) accounting for 1 percent.
The preparation method of the electrolyte comprises the following steps:
firstly, preparing lithium salt, a solvent and an additive in advance according to a preset mass ratio;
a second step of adding a lithium salt and an additive to the solvent;
and thirdly, uniformly stirring by a stirrer to obtain the electrolyte.
Example 7
An electrolyte comprising the following components:
a lithium salt;
an organic solvent;
an additive.
Wherein the lithium salt comprises the following components in mass ratio, and the mass ratio is the ratio of the lithium salt to the electrolyte:
lithium hexafluorophosphate (LiPF) 6 )，13％；
Lithium difluorooxalato borate (LiDFOB), 0.5%;
wherein the organic solvent comprises the following components in percentage by mass:
ethylene Carbonate (EC), 33.5%;
methyl ethyl carbonate (EMC), 37.5%;
diethyl carbonate (DEC), 8.5%;
wherein the additive comprises the following components in percentage by mass:
diphenyldiethoxysilane (DPDS), 2%;
and a negative film forming additive VC (vanadium oxide) accounting for 1 percent.
The preparation method of the electrolyte comprises the following steps:
firstly, preparing lithium salt, a solvent and an additive in advance according to a preset mass ratio;
a second step of adding a lithium salt and an additive to the solvent;
and thirdly, uniformly stirring by a stirrer to obtain the electrolyte.
Example 8
An electrolyte comprising the following components:
a lithium salt;
an organic solvent;
an additive.
Wherein the lithium salt comprises the following components in mass ratio, and the mass ratio is the ratio of the lithium salt to the electrolyte:
lithium bis (fluoromethylsulfonyl imide), 13%;
lithium difluorophosphate, 0.5%;
wherein the organic solvent comprises the following components in percentage by mass:
ethylene Carbonate (EC), 35%;
methyl ethyl carbonate (EMC), 39%;
diethyl carbonate (DEC), 10%;
wherein the additive comprises the following components in percentage by mass:
heptamethyldisilazane (7-HMDS), 0.5%;
diphenyldiethoxysilane (DPDS), 0.5%;
n, N Dimethylformamide (DMF), 0.5%;
and a negative film forming additive VC (vanadium oxide) accounting for 1 percent.
The preparation method of the electrolyte comprises the following steps:
firstly, preparing lithium salt, a solvent and an additive in advance according to a preset mass ratio;
a second step of adding a lithium salt and an additive to the solvent;
and thirdly, uniformly stirring by a stirrer to obtain the electrolyte.
Example 9
An electrolyte comprising the following components:
a lithium salt;
an organic solvent;
an additive.
Wherein the lithium salt comprises the following components in mass ratio, and the mass ratio is the ratio of the lithium salt to the electrolyte:
lithium hexafluorophosphate (LiPF) 6 )，13％；
Lithium difluorooxalato borate (LiDFOB), 0.5%;
wherein the organic solvent comprises the following components in percentage by mass:
propylene carbonate (EC), 35%;
dimethyl carbonate (EMC), 39%;
diethyl carbonate (DEC), 10%;
wherein the additive comprises the following components in percentage by mass:
heptamethyldisilazane (7-HMDS), 0.5%;
diphenyldiethoxysilane (DPDS), 0.5%;
n, N Dimethylformamide (DMF), 0.5%;
and a negative film forming additive VC (vanadium oxide) accounting for 1 percent.
The preparation method of the electrolyte comprises the following steps:
firstly, preparing lithium salt, a solvent and an additive in advance according to a preset mass ratio;
a second step of adding a lithium salt and an additive to the solvent;
and thirdly, uniformly stirring by a stirrer to obtain the electrolyte.
Comparative example 1
An electrolyte comprising the following components:
a lithium salt;
an organic solvent;
an additive.
Wherein the lithium salt comprises the following components in mass ratio, and the mass ratio is the ratio of the lithium salt to the electrolyte:
lithium hexafluorophosphate (LiPF) 6 )，13％；
Lithium difluorooxalato borate (LiDFOB), 0.5%;
wherein the organic solvent comprises the following components in percentage by mass:
ethylene Carbonate (EC), 35.5%;
ethyl Methyl Carbonate (EMC), 39.5%;
diethyl carbonate (DEC), 10.5%;
wherein the additive comprises the following components in percentage by mass:
and a negative film forming additive VC (vanadium oxide) accounting for 1 percent.
The preparation method of the electrolyte comprises the following steps:
firstly, preparing lithium salt, a solvent and an additive in advance according to a preset mass ratio;
a second step of adding a lithium salt and an additive to the solvent;
and thirdly, uniformly stirring by a stirrer to obtain the electrolyte.
Comparative example 2
An electrolyte comprising the following components:
a lithium salt;
an organic solvent;
an additive.
Wherein the lithium salt comprises the following components in mass ratio, and the mass ratio is the ratio of the lithium salt to the electrolyte:
lithium hexafluorophosphate (LiPF) 6 )，13％；
Lithium difluorooxalato borate (LiDFOB), 0.5%;
wherein the organic solvent comprises the following components in percentage by mass:
ethylene Carbonate (EC), 35%;
methyl ethyl carbonate (EMC), 39%;
diethyl carbonate (DEC), 10%;
wherein the additive comprises the following components in percentage by mass:
heptamethyldisilazane (7-HMDS), 0.5%;
n, N Dimethylformamide (DMF), 0.5%;
and a negative film forming additive VC (vanadium oxide) accounting for 1 percent.
The preparation method of the electrolyte comprises the following steps:
firstly, preparing lithium salt, a solvent and an additive in advance according to a preset mass ratio;
a second step of adding a lithium salt and an additive to the solvent;
and thirdly, uniformly stirring by a stirrer to obtain the electrolyte.
Comparative example 3
Comparative example 3 differs from example 1 in that: comparative example 3 the diphenyldiethoxysilane of example 1 was replaced by phenyltriethoxysilane, an additive which is also silane.
An electrolyte comprising the following components:
a lithium salt;
an organic solvent;
an additive.
Wherein the lithium salt comprises the following components in mass ratio, and the mass ratio is the ratio of the lithium salt to the electrolyte:
lithium hexafluorophosphate (LiPF) 6 )，13％；
Lithium difluorooxalato borate (LiDFOB), 0.5%;
wherein the organic solvent comprises the following components in percentage by mass:
ethylene Carbonate (EC), 35%;
methyl ethyl carbonate (EMC), 39%;
diethyl carbonate (DEC), 10%;
wherein the additive comprises the following components in percentage by mass:
heptamethyldisilazane (7-HMDS), 0.5%;
phenyl triethoxysilane, 0.5%;
n, N Dimethylformamide (DMF), 0.5%;
and a negative film forming additive VC (vanadium oxide) accounting for 1 percent.
The preparation method of the electrolyte comprises the following steps:
firstly, preparing lithium salt, a solvent and an additive in advance according to a preset mass ratio;
a second step of adding a lithium salt and an additive to the solvent;
and thirdly, uniformly stirring by a stirrer to obtain the electrolyte.
Performance test:
electrolyte solutions prepared in examples 1 to 7 and comparative examples 1 to 3 were sequentially prepared to prepare lithium iron manganese phosphate (LMFP) batteries.
Performance tests were performed on the batteries prepared from the electrolytes of examples 1 to 7 and comparative examples 1 to 3.
The test method is as follows:
normal temperature 1C/1C cycle test experiment: the batteries obtained in examples 1 to 7 and comparative examples 1 to 3 were charged at 1.0C to a limiting voltage of 4.5V, then charged at constant voltage to a cutoff current of 0.01C, left to stand for 5 minutes, and then discharged at 1.0C to a cutoff voltage of 2.5V, left to stand for 5 minutes, and subjected to 1000-cycle according to the above-mentioned steps.
High temperature cycle performance test: the soft pack batteries obtained in each of the examples and comparative examples were subjected to a charge-discharge cycle test at 45.+ -. 2 ℃ at a charge-discharge rate of 1C/C in the range of 2.5-4.2V, and the first-week discharge specific capacity and the discharge specific capacity after 500-week cycle of the batteries were recorded. Capacity retention for 500 weeks = discharge specific capacity for 500 weeks/discharge specific capacity for first week 100%.
High temperature storage performance test: the soft pack batteries obtained in each of the examples and comparative examples were subjected to a charge-discharge test at a charge-discharge rate of 1C/1C in the range of 2.5 to 4.2V at 60±2 ℃ and the first week discharge specific capacity of the battery was recorded, followed by storage at 60±2 ℃ for 35 days, and again subjected to a charge-discharge test and the discharge specific capacity was recorded. High-temperature storage capacity retention = discharge specific capacity after 7 days/first week discharge specific capacity 100%.
Normal temperature DCR test: the secondary batteries 1C obtained in each of the examples and comparative examples were charged to 4.2V at 25±2 ℃, discharged at 1C capacity for 30min, adjusted to 50% SOC, and then subjected to 5C constant current pulse discharge for 10s, and after 50% SOC was adjusted by the above-mentioned SOC adjustment method, the secondary batteries were recharged for 10s, and dcr= (voltage before pulse discharge-voltage after pulse discharge)/discharge current of 100% was calculated. Wherein SOC (state of charge) refers to the current capacity state of the secondary battery. 100% SOC is fully charged within the design operating range.
Low temperature DCR test: the secondary batteries 1C obtained in each of the examples and comparative examples were charged to 4.2V at-20±2 ℃, discharged at 1C capacity for 30min, adjusted to 50% SOC, and then subjected to 0.5C constant current pulse discharge for 10s, and 50% SOC was adjusted according to the above-mentioned SOC adjustment method, and then charged for 10s, to calculate dcr= (voltage before pulse discharge-voltage after pulse discharge)/discharge current of 100%.
The test results are shown in Table 1.
TABLE 1
From the above examples 1, 2, 3, 4 and comparative example 1, it is understood that when the addition amounts of the three additives are all 2%, the battery has the best 25 ℃ cycle and 45 ℃ cycle performance and the capacity retention rate is the highest when stored at 60 ℃ for 35 days; the lowest DCR at normal and low temperatures indicates that the better the rate capability of the battery.
As is clear from examples 1 and 2, the addition of 0.5% diphenyldiethoxysilane (DPDS) can improve the high and low temperature performance of the battery.
As is clear from examples 5, 6, and 7 and comparative example 1, the high and low temperature performance of the battery is more excellent as the amount of diphenyldiethoxysilane (DPDS) added is increased (0.5% -2%).
As is clear from examples 1 and 3, the addition of phenyltriethoxysilane, which is also a siloxane compound, does not achieve the purpose of optimizing the battery cycle performance and the high temperature storage performance.
This is because 7-HMDS not only improves the cycle performance of lithium ion batteries excellently, but also stabilizes the morphology of lithium iron manganese phosphate batteries by suppressing dissolution of Mn by scavenging HF in the electrolyte; the diphenyl diethoxy silane (DPDS) mainly forms a protective film on the surfaces of the positive electrode and the negative electrode, inhibits the dissolution of metal ions of the positive electrode, can obviously inhibit the decomposition of electrolyte and improve the high-temperature storage performance of the battery at high temperature; the lone pair of the N, N Dimethylformamide (DMF) of the additive is combined with the electronic structure of PF5 in the electrolyte, thereby further preventing the side reaction of the electrolyte and the corrosion of electrode materials, and having important significance for promoting the large-scale application of the lithium ion battery at high temperature.
In conclusion, according to analysis, through the synergistic effect generated by using the heptamethyldisilazane (7-HMDS), the diphenyldiethoxysilane (DPDS) and the N, N-Dimethylformamide (DMF), the lithium iron manganese phosphate battery has excellent cycle performance and high and low temperature performance in the voltage range of 2.5V-4.5V, so that the lithium iron manganese phosphate battery has wide application prospect in lithium iron manganese phosphate positive electrode system lithium batteries.
The foregoing is merely exemplary embodiments of the present invention and are not intended to limit the scope of the present invention, and all equivalent modifications made by the present invention or direct or indirect application in the relevant art are intended to be included in the scope of the present invention.
Claims (10)
1. An electrolyte, characterized in that: the composition comprises the following components:
a lithium salt;
an organic solvent;
an additive;
the additive comprises at least one of vanadium oxide, heptamethyldisilazane, diphenyldiethoxysilane, N-dimethylformamide, and at least vanadium oxide and diphenyldiethoxysilane.
2. An electrolyte according to claim 1, wherein: the mass ratio of the additive to the total mass of the electrolyte is 1-5%.
3. An electrolyte according to claim 2, wherein: the additive comprises heptamethyldisilazane, diphenyl diethoxy silane and N, N-dimethylformamide, wherein the mass ratio of the heptamethyldisilazane, the diphenyl diethoxy silane and the N, N-dimethylformamide to the total mass of the electrolyte is 1.5-2%.
4. An electrolyte according to claim 2, wherein: the diphenyl diethoxy silane accounts for 0.5-2% of the total mass of the electrolyte.
5. An electrolyte according to claim 4, wherein: the mass ratio of the diphenyl diethoxy silane to the total mass of the electrolyte is 0.5-0.6%.
6. An electrolyte according to claim 1, wherein: the lithium salt comprises at least one of lithium hexafluorophosphate, lithium bis (fluoromethylsulfonimide), lithium difluoro (oxalato) borate and lithium difluoro (phospho) phosphate.
7. An electrolyte according to claim 1, wherein: the organic solvent includes at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, dimethyl carbonate and diethyl carbonate.
8. An electrolyte according to claim 1, wherein: the mass ratio of the lithium salt to the organic solvent is 10-20:60-85.
9. A method for preparing an electrolyte according to any one of claims 1 to 8, characterized in that: the method comprises the following steps:
mixing lithium salt and additive in organic solvent to obtain the electrolyte.
10. A lithium iron manganese phosphate battery is characterized in that: comprising an electrolyte according to any one of claims 1 to 8.
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