Electrolyte containing phenyl sulfonate compound and lithium ion battery
阅读说明：本技术 一种含磺酸苯酯化合物的电解液及锂离子电池 (Electrolyte containing phenyl sulfonate compound and lithium ion battery ) 是由 曹哥尽 范伟贞 信勇 赵经纬 于 2021-10-14 设计创作，主要内容包括：本发明属于锂离子电池材料技术领域,公开了一种含磺酸苯酯化合物的电解液及锂离子电池。所述电解液包括式(I)所示结构的第一添加剂和具有不饱和键的第二添加剂。本发明的第一添加剂能有效地抑制降低电池阻抗,尤其是低温阻抗,进一步改善电池高低温性能。且其结构整体稳定,不需要低温下保存,而使用该化合物添加剂的电解液也不需要低温下保存,稳定性优于含DTD电解液。采用含不饱和键的第二添加剂搭配使用,可以进一步增强电池在高电压下的电化学性能,尤其是循环性能。(The invention belongs to the technical field of lithium ion battery materials, and discloses an electrolyte containing a phenyl sulfonate compound and a lithium ion battery. The electrolyte comprises a first additive with a structure shown in a formula (I) and a second additive with an unsaturated bond. The first additive can effectively inhibit the reduction of the impedance, particularly the low-temperature impedance, of the battery, and further improve the high-temperature and low-temperature performance of the battery. The structure of the electrolyte is stable, the electrolyte does not need to be stored at low temperature, and the electrolyte using the compound additive does not need to be stored at low temperature, so that the stability of the electrolyte is superior to that of the electrolyte containing DTD. The electrochemical performance, especially the cycle performance, of the battery under high voltage can be further enhanced by adopting the second additive containing unsaturated bonds for matching.)
1. An electrolyte containing a phenyl sulfonate compound is characterized by comprising a first additive with a structure shown in a formula (I) and a second additive with an unsaturated bond;
r in the formula (I)1～R5Each independently selected from: hydrogen, sulfonyl, fluorosulfonyl; r6Selected from: fluorine, 5-6-membered aryl, 5-6-membered heteroaryl, C2-8 alkenyl, C3-8 alkynyl, halogen-substituted 5-6-membered aryl, halogen-substituted 5-6-membered heteroaryl;
the second additive having an unsaturated bond is selected from at least one of 1, 3-propylene sultone, vinylene carbonate, ethylene carbonate, 2-propynyl methyl carbonate, 2-propynyl methane sulfonate-1-ol, triallyl isocyanurate, triallyl phosphate, and citraconic anhydride.
2. The electrolyte solution containing a phenyl sulfonate compound according to claim 1, wherein R is1～R5Each independently selected from: hydrogen, fluorosulfonyl; the 5-to 6-membered heteroaryl is selected from: furyl, thienyl, pyrrolyl, pyrazolyl, triazolyl, thiazolyl, imidazolyl, pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl or triazinyl.
3. The electrolytic solution containing a phenyl sulfonate compound according to claim 1 or 2, wherein R is the one of6Selected from: fluorine, thienyl, imidazolyl, pyridyl, fluorophenyl, fluorothienyl, fluoroimidazolyl, fluoropyridine, ethenyl, propenyl, butenyl, propynyl, butynyl.
4. The phenyl sulfonate compound-containing electrolyte according to claim 1, wherein the first additive is selected from any one of the following compounds:
5. the phenyl sulfonate compound-containing electrolyte according to claim 1, wherein the first additive is selected from any one of the following compounds:
the second additive is selected from citraconic anhydride, 1, 3-propylene sultone or triallyl isocyanurate.
6. The electrolyte containing the phenyl sulfonate compound according to claim 1, wherein the electrolyte further comprises a lithium salt and a solvent, and in the electrolyte, the additive is 0.01% to 30%, the lithium salt is 5% to 20%, and the solvent is 50% to 94.9% by mass percentage.
7. The electrolyte containing the phenyl sulfonate compound according to claim 6, wherein the mass percentage of the first additive is 0.01-10%; the mass percentage of the second additive is 0.01-5%.
8. The phenyl sulfonate compound-containing electrolyte according to claim 6, wherein the lithium salt is at least one selected from the group consisting of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis (oxalato) borate, lithium difluorophosphate, lithium tetrafluorooxalato phosphate, (1+) methyl [ (dimethoxyphosphoryl) methyl ] phosphonate, lithium difluorooxalato phosphate and lithium bis (fluorosulfonyl) imide; the solvent comprises a cyclic solvent and/or a linear solvent; wherein the cyclic solvent is selected from: at least one of ethylene carbonate, propylene carbonate, gamma-butyrolactone, phenyl acetate, 1, 4-butyl sultone and 3,3, 3-trifluoro propylene carbonate; the linear solvent is at least one selected from dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, ethyl acetate, methyl propyl carbonate, propyl propionate, 1,2, 2-tetrafluoroethyl-2, 2,3, 3-tetrafluoropropyl ether, 2, 2-difluoroethyl acetate, 2, 2-difluoroethyl propionate and 2, 2-difluoroethyl methyl carbonate.
9. A lithium ion battery comprising the electrolyte of any one of claims 1 to 8.
10. The lithium ion battery of claim 9, further comprising a positive electrode material and a negative electrode material; the positive electrode material includes Li1+a(NixCoyM1-x-y)O2、Li(NipMnqCo2-p-q)O4And LiMh(PO4)mWherein a is more than or equal to 0 and less than or equal to 0.3, x is more than or equal to 0 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1, and x + y is more than 0 and less than or equal to 1; p is more than or equal to 0 and less than or equal to 2, q is more than or equal to 0 and less than or equal to 2, and p + q is more than 0 and less than or equal to 2; h is more than 0 and less than 5, m is more than 0 and less than 5; m is Fe, Ni, Co, Mn, Al or V; the negative electrode material comprises at least one of metallic lithium, lithium alloy, carbon, silicon-based negative electrode material and tin-based negative electrode material.
Technical Field
The invention belongs to the technical field of lithium ion battery materials, and particularly relates to an electrolyte containing a phenyl sulfonate compound and a lithium ion battery.
Background
At present, 1, 3-Propane Sultone (PS), fluoroethylene carbonate (FEC), ethylene sulfate (DTD) and the like are used as more additives in electrolyte in the market, wherein the DTD has wide application field and can be almost used for all lithium ion batteries. At present, low DCIR (direct current internal resistance) becomes an important attention index for customers of more and more battery factories, so that the electrolyte capable of reducing the DCIR of the batteries becomes a new demand of the customers. There are few additives on the market that can reduce the DCIR of the battery and also give consideration to high and low temperature performance, among which DTD is present. Because DTD is unstable and is easily decomposed at high temperature, the deterioration of the electrolyte quality is further aggravated, the transportation and storage cost is high, and part of customers have no related storage environment, so that the DTD-free electrolyte needs to be provided. Therefore, it is necessary to develop a low-impedance additive and an electrolyte which have both high and low temperature performance and stability, i.e., a substitute additive and an electrolyte for DTD.
Patent CN 101842349 a discloses a nonaqueous electrolytic solution containing phenyl sulfonate compound and a lithium battery. The substituent X on the benzene ring in the phenyl sulfonate compound1～X5Wherein 1 to 4 of them are fluorine atoms; r bound to a sulfur atom1Represents a linear or branched alkyl group having 1 to 6 carbon atoms, a linear or branched alkyl group having 1 to 6 carbon atoms in which at least one hydrogen atom is substituted with a halogen atom, or an aryl group having 6 to 9 carbon atoms. And the relationship of the number of F teaching the benzene ring to the low temperature cycle characteristics is given by the results of FIG. 1. When the number of F of the benzene ring is 0, the low-temperature cycle characteristics are remarkably reduced. However, the phenyl sulfonate compound containing fluorine substituted on the benzene ring is more difficult and expensive in synthesis process and is not suitable for commercial use in the electrolyte compared with the phenyl sulfonate compound containing no fluorine substituted on the benzene ring. In addition, the prior art only uses the phenyl sulfonate compound with a specific structure to improve the low-temperature cycle performance, and does not relate to impedance and high-temperature performance.
Patent CN 108091933 a discloses the use of fluorosulfonate compounds in battery electrolytes, and the addition of fluorosulfonate compounds to lithium battery electrolytes makes batteries excellent in low-temperature discharge characteristics and life cycle characteristics. Firstly, the improvement of high-temperature cycle performance by singly adopting fluorosulfonate compounds is limited, and the cycle capacity retention rate at 45 ℃ after 600 times can only reach about 80%. In addition, the prior art records that after the fluorosulfonate compound is added, the conductivity and internal resistance of the battery are reduced. In order to solve the problems, 1,3, 6-hexanetricarbonitrile and sodium benzenesulfonate which account for 3-5% of the mass of the electrolyte are added into the electrolyte, so that the problems of conductivity reduction and internal resistance increase caused by adding fluorosulfonate compounds can be solved, and the mass ratio of the 1,3, 6-hexanetricarbonitrile to the sodium benzenesulfonate needs to be controlled to be 0.5: (1-2). The addition of the second additive does not effectively improve the high-temperature cycle performance of the battery.
Disclosure of Invention
Aiming at the defects and shortcomings of the prior art, the invention mainly aims to provide the electrolyte containing the phenyl sulfonate compound.
Another object of the present invention is to provide a lithium ion battery containing the above electrolyte.
The purpose of the invention is realized by the following technical scheme:
an electrolyte containing a phenyl sulfonate compound comprises a first additive with a structure shown in a formula (I) and a second additive with an unsaturated bond;
r in the formula (I)1～R5Each independently selected from: hydrogen, sulfonyl, fluorosulfonyl; r6Selected from: fluorine, 5-6-membered aryl, 5-6-membered heteroaryl, C2-8 alkenyl, C3-8 alkynyl, halogen-substituted 5-6-membered aryl, halogen-substituted 5-6-membered heteroaryl;
the second additive having an unsaturated bond is selected from at least one of 1, 3-propylene sultone, vinylene carbonate, ethylene carbonate, 2-propynyl methyl carbonate, 2-propynyl methane sulfonate-1-ol, triallyl isocyanurate, triallyl phosphate, and citraconic anhydride.
Further preferably, said R1～R5Each independently selected from: hydrogen, fluorosulfonyl.
Further preferably, the 5-6 membered heteroaryl is selected from: furyl, thienyl, pyrrolyl, pyrazolyl, triazolyl, thiazolyl, imidazolyl, pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl or triazinyl.
Further preferably, said R6Selected from: fluorine, thienyl, imidazolyl, pyridyl, fluorophenyl, fluorothienyl, fluoroimidazolyl, fluoropyridine, ethenyl, propenyl, butenyl, propynyl, butynyl.
Further preferably, the first additive is selected from any one of the following compounds:
more preferably, the first additive is selected from any one of the following compounds:
the second additive is selected from citraconic anhydride, 1, 3-propylene sultone or triallyl isocyanurate.
The electrolyte further comprises lithium salt and a solvent, wherein in the electrolyte, the additive accounts for 0.01-30% of the electrolyte, the lithium salt accounts for 5-20% of the electrolyte, and the solvent accounts for 50-94.9% of the electrolyte.
Further preferably, the mass percentage content of the first additive is 0.01-10%; more preferably, the mass percentage content of the first additive is 0.1-10%; the mass percentage of the second additive is 0.01-5%.
The SEI film formed on the negative electrode due to too low content of the first additive is incomplete, the subsequent cycle improvement effect of the battery is poor, the film reduction capability is too strong due to too high content of the first additive, the SEI film formed on the surface of the negative electrode is too thick, the internal resistance of the battery is increased, and the negative influence on the performance of the battery is further brought. The protective layer formed by the second additive and the first additive with too low content becomes brittle, the electrode protection or the electrolyte oxidation resistance improvement effect is not good, the SEI film or the CEI film is too thick when too much additive is added, the internal resistance of the battery is increased, the capacity exertion of the battery is reduced, and the oxidation-reduction property of unsaturated bonds is stronger, so that the stability and the film forming effect of the electrolyte can be ensured by controlling the content of the additive within the range, and the aim of improving the normal-pressure or high-pressure cycle performance of the battery is fulfilled.
Further preferably, the lithium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis (oxalato) borate, lithium difluorophosphate, lithium tetrafluorooxalato phosphate, (1+) methyl [ (dimethoxyphosphoryl) methyl ] phosphonate, lithium bis (oxalato) phosphate and lithium bis (fluorosulfonyl) imide.
Further preferably, the solvent comprises a cyclic solvent and/or a linear solvent; wherein the cyclic solvent is selected from: at least one of ethylene carbonate, propylene carbonate, gamma-butyrolactone, phenyl acetate, 1, 4-butyl sultone and 3,3, 3-trifluoro propylene carbonate; the linear solvent is at least one selected from dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, ethyl acetate, methyl propyl carbonate, propyl propionate, 1,2, 2-tetrafluoroethyl-2, 2,3, 3-tetrafluoropropyl ether, 2, 2-difluoroethyl acetate, 2, 2-difluoroethyl propionate and 2, 2-difluoroethyl methyl carbonate.
A lithium ion battery containing the electrolyte.
Further, the lithium ion battery also comprises a positive electrode material and a negative electrode material; the positive electrode material includes Li1+a(NixCoyM1-x-y)O2、Li(NipMnqCo2-p-q)O4And LiMh(PO4)mWherein a is more than or equal to 0 and less than or equal to 0.3, x is more than or equal to 0 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1, and x + y is more than 0 and less than or equal to 1; p is more than or equal to 0 and less than or equal to 2, q is more than or equal to 0 and less than or equal to 2, and p + q is more than 0 and less than or equal to 2; h is more than 0 and less than 5, m is more than 0 and less than 5; m is Fe, Ni, Co, Mn, Al or V; the negative electrode material comprises at least one of metallic lithium, lithium alloy, carbon, silicon-based negative electrode material and tin-based negative electrode material.
Compared with the prior art, the invention has the beneficial effects that:
by adopting a sulfophenylate compound containing a structure shown in a formula (I)The electrolyte additive can effectively inhibit the reduction of battery impedance, particularly low-temperature impedance, and further improve the high-temperature and low-temperature performance of the battery. R6The difference of the groups can further introduce other gain effects under the function of reserving the sulfophenyl ester group, for example, the introduction of a five-membered ring or a six-membered ring containing N can inhibit the acidity and chromaticity of the electrolyte from rising, and the introduction of an element F can improve the wettability of the electrolyte, further reduce the impedance and the like. The phenyl sulfonate compound with the structure shown in the formula (I) has a stable structure, does not need to be stored at low temperature in an electrolyte using the compound additive, and has better stability than an electrolyte containing DTD. The electrochemical performance, especially the cycle performance, of the battery under high voltage can be further enhanced by adopting the second additive containing unsaturated bonds for matching. The present inventors speculate that the principle that can produce the above technical effects is as follows: the benzene sulfonate group-containing compound shown in the formula (I) can be reduced to form a film, and a cover film with oxygen atoms on a benzene ring is formed on an electrode, so that the effect of smoothing the movement of lithium ions is realized, and an S element is introduced into an SEI film, so that the ionic conductivity is increased, the DCIR is mainly reduced, and the high-temperature and low-temperature cycle performance, especially the low-temperature performance, is improved. It is worth mentioning that when the oxygen on the sulfonic acid group is not directly linked to the benzene ring, i.e. the benzene ring is directly linked to sulfur, there is no significant improvement. In addition, the second additive of linear ester or cyclic lactone having an unsaturated bond is used in combination with the first additive, and thus a protective layer can be further formed on the surface of the electrode, so that the redox reaction of the electrolyte and the elution of the positive electrode metal ion are suppressed, the oxidation resistance of the electrolyte is improved, and the high-temperature performance and the long cycle performance under high voltage of the battery are further improved.
Drawings
FIG. 1 is a dQ/dV curve diagram of a lithium ion battery assembled by electrolytes of examples 1-4 and comparative example 3.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but the present invention is not limited thereto.
Example 1
(1) The electrolyte comprises the following components:
the structural formula of the first additive of the electrolyte in the embodiment is as shown in formula (I)1) As shown.
Formula (I)1) The preparation method of the compound comprises the following steps: adding phenol, toluene and triethylamine into a reaction kettle at room temperature under the protection of nitrogen, and then adding sulfonyl fluoride into the reaction kettle at 0-10 ℃. Adjusting the reaction temperature to 40-50 ℃; the reaction time is 1-4 h. Wherein the ratio of the amount of sulfonyl fluoride to phenol species is 1: 1. The ratio of the amount of the substance of sulfonyl fluoride to the amount of the substance of triethylamine was 1: 1.
In this example, formula (I)1) The compound accounts for 1% of the weight of the electrolyte; the second additive is citraconic anhydride, wherein the citraconic anhydride accounts for 0.5% of the weight of the electrolyte, the lithium salt is lithium hexafluorophosphate, and the lithium salt accounts for 13% of the weight of the electrolyte; the solvent is a mixture of ethylene carbonate and methyl ethyl carbonate according to the weight ratio of 1: 2; the electrolyte of this example was prepared according to a conventional electrolyte preparation method.
(2) Assembling the lithium ion battery:
the positive electrode material is LiNi0.8Co0.1Mn0.1O2(ii) a The negative electrode material is artificial graphite; the diaphragm is a polyethylene film; the electrolyte is the electrolyte of the embodiment. And assembling the soft package battery according to a conventional method.
Example 2
(1) The electrolyte comprises the following components:
the structural formula of the first additive of the electrolyte in the embodiment is as shown in formula (I)2) As shown.
Formula (I)2) The preparation method of the compound comprises the following steps: adding hydroquinone, toluene and triethylamine into a reaction kettle at room temperature under the protection of nitrogen,then adding sulfonyl fluoride into the reaction kettle at the temperature of 0-10 ℃. Adjusting the reaction temperature to 40-50 ℃; the reaction time is 1-4 h. Wherein the ratio of the amount of sulfonyl fluoride to hydroquinone species is 2: 1. The ratio of the amount of the substance of sulfonyl fluoride to the amount of the substance of triethylamine was 1: 1.
In this example, formula (I)2) The compound accounts for 1% of the weight of the electrolyte; the second additive is citraconic anhydride, wherein the citraconic anhydride accounts for 0.5% of the weight of the electrolyte, the lithium salt is lithium hexafluorophosphate, and the lithium salt accounts for 13% of the weight of the electrolyte; the solvent is a mixture of ethylene carbonate and methyl ethyl carbonate according to the weight ratio of 1: 2; the electrolyte of this example was prepared according to a conventional electrolyte preparation method.
(2) Assembling the lithium ion battery:
the positive electrode material is LiNi0.8Co0.1Mn0.1O2(ii) a The negative electrode material is artificial graphite; the diaphragm is a polyethylene film; the electrolyte is the electrolyte of the embodiment. And assembling the soft package battery according to a conventional method.
Example 3
(1) The electrolyte comprises the following components:
the structural formula of the first additive of the electrolyte in the embodiment is as shown in formula (I)3) As shown.
In this example, formula (I)3) The compound accounts for 1% of the weight of the electrolyte; the second additive is citraconic anhydride, wherein the citraconic anhydride accounts for 0.5% of the weight of the electrolyte, the lithium salt is lithium hexafluorophosphate, and the lithium salt accounts for 13% of the weight of the electrolyte; the solvent is a mixture of ethylene carbonate and methyl ethyl carbonate according to the weight ratio of 1: 2; the electrolyte of this example was prepared according to a conventional electrolyte preparation method.
(2) Assembling the lithium ion battery:
the positive electrode material is LiNi0.8Co0.1Mn0.1O2(ii) a The negative electrode material is artificial graphite; the diaphragm is a polyethylene film; the electrolyte is the original materialElectrolyte is exemplified. And assembling the soft package battery according to a conventional method.
Example 4
(1) The electrolyte comprises the following components:
the structural formula of the first additive of the electrolyte in the embodiment is as shown in formula (I)4) As shown.
In this example, formula (I)4) The compound accounts for 1% of the weight of the electrolyte; the second additive is citraconic anhydride, wherein the citraconic anhydride accounts for 0.5% of the weight of the electrolyte, the lithium salt is lithium hexafluorophosphate, and the lithium salt accounts for 13% of the weight of the electrolyte; the solvent is a mixture of ethylene carbonate and methyl ethyl carbonate according to the weight ratio of 1: 2; the electrolyte of this example was prepared according to a conventional electrolyte preparation method.
(2) Assembling the lithium ion battery:
the positive electrode material is LiNi0.8Co0.1Mn0.1O2(ii) a The negative electrode material is artificial graphite; the diaphragm is a polyethylene film; the electrolyte is the electrolyte of the embodiment. And assembling the soft package battery according to a conventional method.
Example 5
(1) The electrolyte comprises the following components:
the structural formula of the electrolyte additive in the embodiment is as shown in formula (I)5) As shown.
In this example, formula (I)5) The compound accounts for 1% of the weight of the electrolyte; the second additive is citraconic anhydride, wherein the citraconic anhydride accounts for 0.5% of the weight of the electrolyte, the lithium salt is lithium hexafluorophosphate, and the lithium salt accounts for 13% of the weight of the electrolyte; the solvent is a mixture of ethylene carbonate and methyl ethyl carbonate according to the weight ratio of 1: 2; the electrolyte of this example was prepared according to a conventional electrolyte preparation method.
(2) Assembling the lithium ion battery:
the positive electrode material is LiNi0.8Co0.1Mn0.1O2(ii) a The negative electrode material is artificial graphite; the diaphragm is a polyethylene film; the electrolyte is the electrolyte of the embodiment. And assembling the soft package battery according to a conventional method.
Example 6
(1) The electrolyte comprises the following components:
the structural formula of the first electrolyte additive in this embodiment is as shown in formula (I)1) As shown.
In this example, formula (I)1) The compound accounts for 10% of the weight of the electrolyte; the second additive is citraconic anhydride, wherein the citraconic anhydride accounts for 0.5% of the weight of the electrolyte, the lithium salt is lithium hexafluorophosphate, and the lithium salt accounts for 13% of the weight of the electrolyte; the solvent is a mixture of ethylene carbonate and methyl ethyl carbonate according to the weight ratio of 1: 2; the electrolyte of this example was prepared according to a conventional electrolyte preparation method.
(2) Assembling the lithium ion battery:
the positive electrode material is LiNi0.8Co0.1Mn0.1O2(ii) a The negative electrode material is artificial graphite; the diaphragm is a polyethylene film; the electrolyte is the electrolyte of the embodiment. And assembling the soft package battery according to a conventional method.
Example 7
(1) The electrolyte comprises the following components:
the structural formula of the electrolyte additive in the embodiment is as shown in formula (I)1) As shown.
In this example, formula (I)1) The compound accounts for 1% of the weight of the electrolyte; the second additive is citraconic anhydride, wherein the citraconic anhydride accounts for 3% of the weight of the electrolyte, the lithium salt is lithium hexafluorophosphate, and the lithium salt accounts for the electrolyte13% of the weight of (A); the solvent is a mixture of ethylene carbonate and methyl ethyl carbonate according to the weight ratio of 1: 2; the electrolyte of this example was prepared according to a conventional electrolyte preparation method.
(2) Assembling the lithium ion battery:
the positive electrode material is LiNi0.8Co0.1Mn0.1O2(ii) a The negative electrode material is artificial graphite; the diaphragm is a polyethylene film; the electrolyte is the electrolyte of the embodiment. And assembling the soft package battery according to a conventional method.
Example 8
(1) The electrolyte comprises the following components:
the structural formula of the electrolyte additive in the embodiment is as shown in formula (I)1) As shown.
In this example, formula (I)1) The compound accounts for 1% of the weight of the electrolyte; the second additive is triallyl isocyanurate, wherein the triallyl isocyanurate accounts for 0.5 percent of the weight of the electrolyte, the lithium salt is lithium hexafluorophosphate, and the lithium salt accounts for 13 percent of the weight of the electrolyte; the solvent is a mixture of ethylene carbonate and methyl ethyl carbonate according to the weight ratio of 1: 2; the electrolyte of this example was prepared according to a conventional electrolyte preparation method.
(2) Assembling the lithium ion battery:
the positive electrode material is LiNi0.8Co0.1Mn0.1O2(ii) a The negative electrode material is artificial graphite; the diaphragm is a polyethylene film; the electrolyte is the electrolyte of the embodiment. And assembling the soft package battery according to a conventional method.
Example 9
(1) The electrolyte comprises the following components:
the structural formula of the electrolyte additive in the embodiment is as shown in formula (I)1) As shown.
In this example, formula (I)1) The compound accounts for 1% of the weight of the electrolyte; the second additive is citraconic anhydride, the citraconic anhydride accounts for 0.5% of the weight of the electrolyte, the lithium salt is lithium hexafluorophosphate and lithium difluorooxalate phosphate, and the lithium hexafluorophosphate and the lithium difluorooxalate phosphate respectively account for 12% and 1% of the weight of the electrolyte; the solvent is a mixture of ethylene carbonate and methyl ethyl carbonate according to the weight ratio of 1: 2; the electrolyte of this example was prepared according to a conventional electrolyte preparation method.
(2) Assembling the lithium ion battery:
the positive electrode material is LiNi0.8Co0.1Mn0.1O2(ii) a The negative electrode material is artificial graphite; the diaphragm is a polyethylene film; the electrolyte is the electrolyte of the embodiment. And assembling the soft package battery according to a conventional method.
Example 10
(1) The electrolyte comprises the following components:
the structural formula of the electrolyte additive in the embodiment is as shown in formula (I)1) As shown.
In this example, formula (I)1) The compound accounts for 1% of the weight of the electrolyte; the second additive is citraconic anhydride, the conventional additive is 1, 3-propane sultone, the citraconic anhydride accounts for 0.5 percent of the weight of the electrolyte, the 1, 3-propane sultone accounts for 1 percent of the weight of the electrolyte, the lithium salt is lithium hexafluorophosphate, and the lithium salt accounts for 13 percent of the weight of the electrolyte; the solvent is a mixture of ethylene carbonate and methyl ethyl carbonate according to the weight ratio of 1: 2; the electrolyte of this example was prepared according to a conventional electrolyte preparation method.
(2) Assembling the lithium ion battery:
the positive electrode material is LiNi0.8Co0.1Mn0.1O2(ii) a The negative electrode material is artificial graphite; the diaphragm is a polyethylene film; the electrolyte is the electrolyte of the embodiment. And assembling the soft package battery according to a conventional method.
Example 11
(1) The electrolyte comprises the following components:
the structural formula of the electrolyte additive in the embodiment is as shown in formula (I)1) As shown.
In this example, formula (I)1) The compound accounts for 1% of the weight of the electrolyte; the second additive is 1, 3-propylene sultone, the 1, 3-propylene sultone accounts for 0.5 percent of the weight of the electrolyte, the lithium salt is lithium hexafluorophosphate, and the lithium salt accounts for 13 percent of the weight of the electrolyte; the solvent is a mixture of ethylene carbonate and methyl ethyl carbonate according to the weight ratio of 1: 2; the electrolyte of this example was prepared according to a conventional electrolyte preparation method.
(2) Assembling the lithium ion battery:
the positive electrode material is LiNi0.8Co0.1Mn0.1O2(ii) a The negative electrode material is artificial graphite; the diaphragm is a polyethylene film; the electrolyte is the electrolyte of the embodiment. And assembling the soft package battery according to a conventional method.
Comparative example 1
The comparative example is different from example 1 in that the electrolyte does not contain the first additive and the second additive.
Comparative example 2
The comparative example is different from example 1 in that the first additive is not contained in the electrolytic solution.
Comparative example 3
This comparative example differs from example 1 in that the first and second additives of example 1 were replaced with 1% by weight of the electrolyte of a vinyl sulfate additive.
Comparative example 4
This comparative example differs from example 10 in that the first and second additives of example 10 were replaced with 1% by weight of the electrolyte of a vinyl sulfate additive.
Comparative example 5
This comparative example differs from example 1 in that the electrolyte does not contain the second additive.
Comparative example 6
This comparative example differs from example 1 in that the first additive of example 1 was replaced with a 1% phenyl methanesulfonate additive by weight of the electrolyte.
The stability of the lithium ion battery electrolyte and the electrochemical performance of the lithium ion battery in the above examples 1 to 11 and comparative examples 1 to 6 were tested, and the test method was:
(1) and (3) testing the stability of the electrolyte: the lithium ion battery electrolytes prepared in the above examples 1 to 11 and comparative examples 1 to 6 were respectively filled in an inlet-sealed aluminum bottle in a glove box, the aluminum bottle was vacuum-sealed with an aluminum plastic film, and an electrolyte sample was stored in a thermostat at a set temperature of 45 ℃ at the same time, and before, after 7 days, 14 days, and 30 days of storage, the electrolyte acidity and the colorimetric value were respectively detected by sampling in the glove box, the acidity was measured with a potentiometric titrator, the acidity value was converted into HF in ppm, the colorimetric value was measured with a colorimeter, and the colorimetric unit was Hazen.
The test results are shown in tables 1 and 2 below:
TABLE 1 (acidity/ppm)
Numbering
Before storage
7 days
14 days
30 days
Example 1
14.3
30.3
35.1
45.8
Example 2
13.9
29.9
34.4
43.2
Example 3
6.2
19.7
24.9
31.9
Example 4
15.1
33.8
40.3
48.9
Example 5
14.5
28.7
38.3
45.8
Example 6
14.9
32.5
34.6
47.0
Example 7
15.5
33.4
40.5
48.7
Example 8
14.6
28.8
37.9
45.0
Example 9
13.1
29.0
34.6
43.1
Example 10
16.2
31.9
36.0
46.6
Example 11
14.7
28.0
38.1
45.2
Comparative example 1
13.2
29.9
36.4
42.0
Comparative example 2
14.1
27.5
38.8
46.3
Comparative example 3
18.9
88.5
110.5
132.6
Comparative example 4
19.6
96.6
121.2
140.6
Comparative example 5
14.5
28.2
36.2
46.6
Comparative example 6
15.3
35.5
43.1
57.9
TABLE 2 (chroma/Hazen)
As can be seen from tables 1-2, the lithium ion battery electrolytes in examples 1-11 are stored for 30 days at a high temperature of 45 ℃, the acidity and the chromaticity of the electrolytes are equivalent to those in comparative examples 1-2 and are obviously lower than those in comparative examples 3-4, so that the phenyl sulfonate compound is stable as a whole and has better stability than DTD, the acidity and the chromaticity of the electrolytes cannot be increased remarkably by adding the phenyl sulfonate additive into the electrolytes, and the electrolytes containing the phenyl sulfonate additive do not need to be stored at a low temperature like the electrolytes containing DTD. The electrolyte in comparative example 6 also had relatively high chroma because the phenyl methanesulfonate compound was sensitive to water and was easily hydrolyzed to produce phenol, which developed color under certain conditions, increasing the chroma of the electrolyte. The compound of the invention is stable as a whole and is not easy to hydrolyze. In addition, the acidity and the chroma of the embodiment 3 are far lower than those of the comparative examples 1-6, which shows that the acidity and the chroma of the electrolyte can be further reduced after the N-containing group is introduced besides the phenyl sulfonate compound does not obviously increase the acidity of the electrolyte. The electrolyte containing the sulfophenyl ester electrolyte additive is integrally stable under high temperature conditions, and the stability of the electrolyte is obviously superior to that of DTD and the electrolyte containing DTD.
(2) Normal pressure (high voltage) high temperature cycle performance of the battery: the lithium ion batteries prepared in the above examples 1 to 11 and comparative examples 1 to 6 were placed in a thermostat at 45 ℃, charged to 4.2V (4.25V) at a constant current and a constant voltage of 1C, then discharged to 3.0V at a constant current of 1C, cycled for 700 weeks, and the capacity retention rate of the lithium ion batteries was determined.
(3) Initial DCIR performance: the batteries after capacity grading were charged to 4.2V at 1C at room temperature, left for 5min, then discharged at 1C for 30min, left for 1h, then discharged at 2C for 10s, and the DCIR at 50% SOC of the batteries was calculated.
(4) DCIR performance after high temperature storage: the battery, which was subjected to the high-temperature storage performance test at 60 ℃ for 14 days, was charged at 1C to 4.2V at room temperature, left for 5min, then discharged at 1C for 30min, left for 1h, and then discharged at 2C for 10s, and the DCIR at 50% SOC of the battery was calculated.
(5) Low temperature DCIR performance: the batteries after capacity grading were charged to 4.2V at-20 ℃ at 1C, left for 5min, then discharged at 1C for 30min, left for 1h, then discharged at 2C for 10s, and the DCIR at 50% SOC of the batteries was calculated.
(6) Low-temperature discharge performance: charging the formed lithium ion battery to 4.2V at normal temperature by using a 1C constant current and constant voltage, and measuring the initial capacity of the battery; then, the battery was placed in a thermostat at-20 ℃ and discharged to 2.5V at 0.5C, and the capacity retention rate of the lithium ion battery was measured.
The test results are shown in table 3 below:
TABLE 3
As can be seen from Table 3, the lithium ion batteries of examples 1 to 11 are superior to those of comparative examples 1 to 6 in terms of high-temperature DCIR, low-temperature discharge capacity retention rate, 4.2V high-temperature cycle and 4.25V high-temperature cycle performance. FIG. 1 is a dQ/dV curve diagram of examples 1-4 and comparative example 3, which illustrates that the phenyl sulfonate additive of the present invention can form a stable SEI film on the surface of a negative electrode, effectively reduce high-temperature and low-temperature impedance, and further improve high-temperature and low-temperature performance of a battery. As can be seen from the results of comparative examples 1 to 2 and comparative examples 5 to 6, the improvement of the cycle performance at high voltage of the present invention is a result of the synergistic effect of the first additive and the second additive, thereby achieving the purpose of replacing DTD. In the absence or replacement of the first additive or the second additive according to the invention, the cycle performance at high voltages is significantly reduced.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.