WO2019200656A1

WO2019200656A1 - Lithium secondary battery electrolyte and lithium secondary battery thereof

Info

Publication number: WO2019200656A1
Application number: PCT/CN2018/087900
Authority: WO
Inventors: 范伟贞; 余乐; 谢添; 赵经纬
Original assignee: 广州天赐高新材料股份有限公司
Priority date: 2018-04-18
Filing date: 2018-05-22
Publication date: 2019-10-24
Also published as: CN108539270B; CN108539270A

Abstract

The present invention relates to a lithium secondary battery electrolyte and a lithium secondary battery thereof, the lithium secondary battery electrolyte comprising an organic solvent, conductive lithium salt, a phenyl or pyridyl-substituted bis (trifluoromethyl sulfonyl) amine compound, and an additive. The foregoing electrolyte is capable of ameliorating the normal temperature cyclic performance, high temperature storage performance, and low temperature discharge performance of the electrolyte by means of using a combination of a phenyl or pyridyl-substituted bis (trifluoromethyl sulfonyl) amine compound with triallyl isocyanurate and 2-propynyl methyl carbonate.

Description

Lithium secondary battery electrolyte and lithium secondary battery

Technical field

The present invention relates to the field of lithium secondary battery technology, and in particular to a lithium secondary battery electrolyte and a lithium secondary battery containing the same.

Background technique

In order to improve the high temperature performance of lithium ion batteries, solvents with higher boiling points such as diethyl carbonate and ethyl methyl carbonate are generally selected as the main solvent of the electrolyte, but the melting point of these solvents is higher, and the conductivity of the electrolyte at low temperatures. The drop is very fast and the battery impedance increases rapidly. It is difficult to meet the low-temperature discharge performance of the battery. In order to improve the low-temperature performance of the battery, a carboxylate having a lower melting point such as ethyl acetate or ethyl propionate is generally selected as the main solvent of the electrolytic solution, but the boiling point of these solvents is relatively low, which is disadvantageous for improving the high-temperature performance of the battery. In terms of additives, in order to improve high temperature performance, additives such as vinylene carbonate and ethylene carbonate are generally used, but such additives may cause a large battery impedance, especially at low temperatures, the battery impedance is increased significantly, resulting in a battery. The low temperature performance is degraded. Therefore, it is a difficult task to improve the high and low temperature performance of the battery through the electrolyte.

Patent application CN201410505635.7 discloses a lithium ion battery and an electrolyte thereof, the electrolyte of the lithium ion battery comprising: a non-aqueous organic solvent; a lithium salt dissolved in a non-aqueous organic solvent; and an additive. The additives include fluoroethylene carbonate (FEC), 1,3-propane sultone (PS), and cyano group-containing titanates. The lithium ion battery includes the electrolyte of the foregoing lithium ion battery, which has excellent storage performance and cycle performance under high temperature and high pressure.

Patent application CN201310034975.1 discloses an electrolyte for a negative electrode lithium titanate battery, a lithium ion battery and a preparation method thereof. The electrolyte uses lithium hexafluorophosphate as an electrolyte, and ethylene carbonate, ethyl methyl carbonate, diethyl carbonate and propylene carbonate. The ester is a solvent, and one or more of fluoroethylene carbonate, lithium bis(oxalate) borate, 1,3-propane sultone or vinylene carbonate is a film-forming additive.

However, the above-mentioned scheme has a problem in that it has a good capacity recovery rate at normal temperature and high temperature, and does not describe battery performance under low temperature conditions.

It is a difficult task to improve the high and low temperature performance of the battery through the electrolyte. Therefore, it is necessary to develop an electrolyte that can simultaneously improve the high temperature and low temperature performance of the battery.

Summary of the invention

Based on this, it is an object of the present invention to provide an electrolyte which can improve the high temperature and low temperature performance of a battery.

The specific technical solutions are as follows:

A lithium secondary battery electrolyte comprising an organic solvent, a conductive lithium salt, a phenyl or pyridyl-substituted bis(trifluoromethanesulfonyl)amine compound, and an additive.

In some embodiments, the phenyl or pyridyl substituted bis(trifluoromethanesulfonyl)amine compound is selected from the group consisting of N,N-bis(trifluoromethanesulfonyl)aniline, N,N-bis(trifluoromethyl) At least one of sulfamoyl)-2-pyridinamine.

In some of these embodiments, the phenyl or pyridyl substituted bis(trifluoromethanesulfonyl)amine compound comprises from 0.1% to 5.0% by weight of the total mass of the lithium secondary battery electrolyte.

In some of these embodiments, the additive is selected from at least one of lithium difluorodioxalate phosphate, triallyl isocyanurate, and 2-propynyl carbonate.

In some of these embodiments, the additive comprises from 0.1% to 5.0% of the total mass of the lithium secondary battery electrolyte.

In some of the embodiments, the conductive lithium salt is at least one of lithium hexafluorophosphate or lithium bisfluorosulfonimide, which is from 8.0 to 18.0% of the total mass of the electrolyte of the lithium secondary battery.

In some of these embodiments, the organic solvent consists of a cyclic solvent and a linear solvent.

In some of these embodiments, the cyclic solvent is selected from at least one of ethylene carbonate, propylene carbonate, γ-butyrolactone, and 1,4 butyl sultone.

In some embodiments, the linear solvent is selected from the group consisting of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl acetate, methyl propyl carbonate, propyl propionate, 1, 1, 2, 2 At least one of tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether and 2,2-difluoroethyl acetate.

Another object of the present invention is to provide a lithium secondary battery.

The specific technical solutions are as follows:

A lithium secondary battery comprising the above lithium secondary battery electrolyte (including a positive electrode sheet containing a positive electrode active material, a negative electrode sheet containing a negative electrode active material, and a separator).

In the above lithium secondary battery, the positive electrode active material means a lithium-containing metal compound, and the lithium-containing metal compound is Li _1+a (Ni _x Co _y M _1-xy )O ₂ , Li(Ni _p Mn _q At least one of Co _2-pq )O ₄ and LiM _h (PO ₄ ) _m , wherein 0≤a≤0.3, 0≤x≤1, 0≤y≤1, 0<x+y≤1, 0≤p ≤ 2, 0 ≤ q ≤ 2, 0 < p + q ≤ 2, M is Fe, Ni, Co, Mn, Al or V, 0 < h < 5, 0 < m <5; the negative active material is lithium At least one of a metal, a lithium alloy, a carbon material, a silicon-based material, and a tin-based material.

The above lithium secondary battery electrolyte has the following advantages and beneficial effects:

The above electrolyte can be used in combination with triallyl isocyanurate or 2-propynyl methyl carbonate by adding a phenyl or pyridyl-substituted bis(trifluoromethanesulfonyl)amine compound to improve the normal temperature cycle of the electrolyte. Performance, high temperature storage performance and low temperature discharge performance.

detailed description

In order to facilitate the understanding of the present invention, the present invention will be described more fully hereinafter. However, the invention may be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the understanding of the present disclosure will be more fully understood.

All technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, unless otherwise defined. The terminology used in the description of the present invention is for the purpose of describing particular embodiments and is not intended to limit the invention. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.

Example 1

In the present embodiment, a lithium secondary battery electrolyte is composed of an organic solvent, a conductive lithium salt, a phenyl or pyridyl group-substituted bis(trifluoromethanesulfonyl)amine compound, and an additive. The organic solvent accounts for 76.0% of the total mass of the lithium secondary battery electrolyte, and is composed of a cyclic solvent (ethylene carbonate) and a linear solvent (ethyl methyl carbonate), and the mass ratio of ethylene carbonate to ethyl methyl carbonate is 1 :1. The conductive lithium salt is lithium hexafluorophosphate, which accounts for 18.0% of the total mass of the lithium secondary battery electrolyte. N,N-bis(trifluoromethanesulfonyl)aniline accounts for 5.0% of the total mass of the electrolyte. The additive is lithium difluorodioxalate phosphate, which accounts for 1.0% of the total mass of the electrolyte. The electrolytic solution of this example was applied to a LiNi _0.8 Co _0.1 Mn _0.1 O ₂ /graphite soft pack battery.

Example 2

In the present embodiment, a lithium secondary battery electrolyte is composed of an organic solvent, a conductive lithium salt, a phenyl or pyridyl group-substituted bis(trifluoromethanesulfonyl)amine compound, and an additive. The organic solvent accounts for 80.5% of the total mass of the lithium secondary battery electrolyte, and is composed of a cyclic solvent (ethylene carbonate) and a linear solvent (dimethyl carbonate), and the mass ratio of the ethylene carbonate to the dimethyl carbonate is 1 :2. The conductive lithium salt is lithium hexafluorophosphate, which accounts for 15.0% of the total mass of the lithium secondary battery electrolyte. N,N-bis(trifluoromethylsulfonyl)-2-pyridinamine accounts for 0.5% of the total mass of the electrolyte, and the additive is triallyl isocyanurate, 2-propynyl methyl carbonate, It accounts for 1.0% and 3.0% of the total mass of the electrolyte. The electrolytic solution of this example was used for a LiNi _0.8 Co _0.1 Mn _0.1 O ₂ /silicon carbon soft pack battery.

Example 3

In the present embodiment, a lithium secondary battery electrolyte is composed of an organic solvent, a conductive lithium salt, a phenyl or pyridyl group-substituted bis(trifluoromethanesulfonyl)amine compound, and an additive. The organic solvent accounts for 85.0% of the total mass of the electrolyte of the lithium secondary battery, and is composed of a cyclic solvent (ethylene carbonate) and a linear solvent (diethyl carbonate), and the mass ratio of ethylene carbonate to diethyl carbonate is 1 :3. The conductive lithium salt is lithium hexafluorophosphate, which accounts for 12.0% of the total mass of the lithium secondary battery electrolyte. N,N-bis(trifluoromethanesulfonyl)aniline accounts for 1.0% of the total mass of the electrolyte, and the additive is lithium difluorodioxalate phosphate and triallyl isocyanurate, respectively, which account for the total mass of the electrolyte. 1.0%, 1.0%. The electrolytic solution of this example was used for a LiNi _0.6 Co _0.2 Mn _0.2 O ₂ /graphite soft pack battery.

Example 4

In the present embodiment, a lithium secondary battery electrolyte is composed of an organic solvent, a conductive lithium salt, a phenyl or pyridyl group-substituted bis(trifluoromethanesulfonyl)amine compound. The organic solvent accounts for 86.0% of the total mass of the lithium secondary battery electrolyte, and is composed of a cyclic solvent (ethylene carbonate, propylene carbonate) and a linear solvent (ethyl methyl carbonate, propyl propionate), ethylene carbonate, The mass ratio of propylene carbonate, ethyl methyl carbonate, and propyl propionate was 1:0.5:1:1. The conductive lithium salt is lithium hexafluorophosphate, which accounts for 12.0% of the total mass of the lithium secondary battery electrolyte. N,N-bis(trifluoromethylsulfonyl)-2-pyridinamine accounts for 1.0% of the total mass of the electrolyte, and the additive is lithium difluorodioxalate phosphate, which accounts for 1.0% of the total mass of the electrolyte. The electrolytic solution of this example was applied to a LiNi _0.6 Co _0.2 Mn _0.2 O ₂ /silicon carbon soft pack battery.

Example 5

In the present embodiment, a lithium secondary battery electrolyte is composed of an organic solvent, a conductive lithium salt, a phenyl or pyridyl group-substituted bis(trifluoromethanesulfonyl)amine compound, and an additive. The organic solvent accounts for 88.0% of the total mass of the lithium secondary battery electrolyte, and is composed of a cyclic solvent (ethylene carbonate) and a linear solvent (ethyl methyl carbonate, 1,1,2,2-tetrafluoroethyl-2, 2,3,3-tetrafluoropropyl ether) composition, ethylene carbonate, propylene carbonate, ethyl methyl carbonate, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoro The mass ratio of propyl ether was 1:2:0.5. The conductive lithium salt is lithium hexafluorophosphate, which accounts for 8.5% of the total mass of the lithium secondary battery electrolyte. N,N-bis(trifluoromethylsulfonyl)-2-pyridinamine accounts for 1.0% of the total mass of the electrolyte, and the additive is lithium difluorodioxalate phosphate and methyl 2-propynyl carbonate, respectively. 0.5% and 2.0% of the total mass of the liquid. The electrolytic solution of this example was applied to a LiNi _0.5 Co _0.2 Mn _0.3 O ₂ /graphite soft pack battery.

Example 6

In the present embodiment, a lithium secondary battery electrolyte is composed of an organic solvent, a conductive lithium salt, a phenyl or pyridyl group-substituted bis(trifluoromethanesulfonyl)amine compound, and an additive. The organic solvent accounts for 84.5% of the total mass of the lithium secondary battery electrolyte, and is composed of a cyclic solvent (ethylene carbonate) and a linear solvent (ethyl methyl carbonate), and the mass ratio of ethylene carbonate to ethyl methyl carbonate is 1 :1. The conductive lithium salt is lithium hexafluorophosphate, which accounts for 12.5% of the total mass of the lithium secondary battery electrolyte. N,N-bis(trifluoromethanesulfonyl)aniline, N,N-bis(trifluoromethylsulfonyl)-2-pyridinamine, respectively, accounted for 1.0%, 1.0% of the total mass of the electrolyte, and the additive was two Lithium oxalic acid lithium phosphate, accounting for 1.0% of the total mass of the electrolyte. The electrolytic solution of this example was applied to a LiNi _0.5 Co _0.2 Mn _0.3 O ₂ /silicon carbon soft pack battery.

Example 8

In the present embodiment, a lithium secondary battery electrolyte is composed of an organic solvent, a conductive lithium salt, a phenyl or pyridyl group-substituted bis(trifluoromethanesulfonyl)amine compound, and an additive. The organic solvent accounts for 82.5% of the total mass of the electrolyte of the lithium secondary battery, and is composed of a cyclic solvent (ethylene carbonate) and a linear solvent (ethyl methyl carbonate), and the mass ratio of ethylene carbonate and ethyl methyl carbonate is 1 :1. The conductive lithium salt is lithium hexafluorophosphate or lithium bisfluorosulfonimide, which accounts for 10.0% and 4.5% of the total mass of the electrolyte of the lithium secondary battery. N,N-bis(trifluoromethanesulfonyl)aniline accounts for 2.0% of the total mass of the electrolyte, and the additive is triallyl isocyanurate, which accounts for 1.0% of the total mass of the electrolyte. The electrolytic solution of this example was used for a LiNi _0.6 Co _0.2 Mn _0.2 O ₂ /graphite soft pack battery.

Example 9

In the present embodiment, a lithium secondary battery electrolyte is composed of an organic solvent, a conductive lithium salt, a phenyl or pyridyl group-substituted bis(trifluoromethanesulfonyl)amine compound, and an additive. The organic solvent accounts for 85.0% of the total mass of the lithium secondary battery electrolyte, and is composed of a cyclic solvent (ethylene carbonate) and a linear solvent (ethyl methyl carbonate), and the mass ratio of ethylene carbonate and ethyl methyl carbonate is 1 :1. The conductive lithium salt is lithium hexafluorophosphate or lithium bisfluorosulfonimide, which accounts for 8.0% and 3.0% of the total mass of the electrolyte of the lithium secondary battery. N,N-bis(trifluoromethylsulfonyl)-2-pyridinamine accounts for 2.0% of the total mass of the electrolyte, and the additive is lithium difluorodioxalate phosphate, which accounts for 1.0% of the total mass of the electrolyte. The electrolytic solution of this example was used for a LiNi _0.6 Co _0.2 Mn _0.2 O ₂ /graphite soft pack battery.

Comparative example 1

The electrolytic solution of this comparative example was prepared in the same manner as in Example 1, except that N,N-bis(trifluoromethanesulfonyl)aniline was not contained, and this electrolytic solution was applied in the same manner as in Example 1. Test its performance in the battery.

Comparative example 2

The electrolytic solution of this comparative example was prepared in the same manner as in Example 1, except that lithium difluorodioxalate phosphate was not contained, and the electrolytic solution was applied to a battery in the same manner as in Example 1 to test its properties.

Comparative example 3

The electrolytic solution of the present comparative example was prepared in the same manner as in Example 2, except that N,N-bis(trifluoromethylsulfonyl)-2-pyridinamine was not contained, and the electrolytic solution was the same as in Example 2. The same method was applied to the battery to test its performance.

Comparative example 4

The electrolytic solution of the present comparative example was prepared in the same manner as in Example 2, except that the triallyl isocyanurate, 2-propynyl methyl carbonate was not contained, and the electrolytic solution was as in the examples. 2 The same method was applied to the battery to test its performance.

Comparative example 5

The electrolytic solution of the present comparative example was prepared in the same manner as in Example 3, except that N,N-bis(trifluoromethanesulfonyl)aniline was not contained, and this electrolytic solution was applied in the same manner as in Example 3. Test its performance in the battery.

Comparative example 6

The electrolytic solution of the present comparative example was prepared in the same manner as in Example 3, except that lithium difluorodioxalate phosphate and triallyl isocyanurate were not contained, and the electrolytic solution was the same as in Example 3. The method was applied to a battery to test its performance.

Comparative example 7

The electrolytic solution of the present comparative example was prepared in the same manner as in Example 4, except that N,N-bis(trifluoromethylsulfonyl)-2-pyridinamine was not contained, and the electrolytic solution was the same as in Example 4. The same method was applied to the battery to test its performance.

Comparative example 8

The electrolytic solution of this comparative example was prepared in the same manner as in Example 4, except that lithium difluorodioxalate phosphate was not contained, and the electrolytic solution was applied to a battery in the same manner as in Example 4 to test its properties.

Comparative example 9

The electrolytic solution of the present comparative example was prepared in the same manner as in Example 1 except that N,N-bis(trifluoromethanesulfonyl)aniline was replaced with lithium bis(trifluoromethanesulfonyl)imide. The electrolytic solution was applied to a battery to test its performance in the same manner as in Example 1.

Comparative example 10

The electrolytic solution of this comparative example was prepared in the same manner as in Example 4, except that N,N-bis(trifluoromethylsulfonyl)-2-pyridinamine was replaced with bis(trifluoromethanesulfonyl) Lithium amine, this electrolyte was applied to a battery in the same manner as in Example 4 to test its properties.

Application experiments of examples and comparative examples:

The lithium secondary batteries prepared in the above Examples 1 to 8 and Comparative Examples 1 to 10 were subjected to normal temperature circulation, high temperature storage, and low temperature discharge test.

Charge and discharge test conditions: In order to measure the charge and discharge performance of the battery using the electrolyte prepared by the present invention, the following operations were carried out: positive and negative electrode sheets were prepared according to a conventional method, and electrolytes prepared in the respective examples were used to inject liquid in a glove box. Pole piece preparation 053048 type soft pack battery, using the Xinwei (BS-9300R type) battery test system to test the charge and discharge of the prepared 053048 type battery, and compare it with the corresponding comparative electrolyte prepared battery. The battery was placed at a normal temperature of 3.0 to 4.2 V at a rate of 1 C for a charge and discharge cycle and placed at 60 ° C for 15 days after full charge storage, and discharged at -20 ° C for 0.5 C. The capacity retention rate of the battery at a normal temperature of 300 cycles, the discharge capacity retention rate after 60 days of full-time storage at 60 ° C, and the discharge capacity retention rate of -20 ° C and 0.5 C were recorded. The results are shown in Table 1.

Table 1 Test results of charge and discharge cycles, high temperature storage, and low temperature discharge of the examples and comparative examples:

It can be seen from Table 1 that Examples 1-8 are used in combination with the additives in a different ratio of phenyl or pyridyl-substituted bis(trifluoromethanesulfonyl)amine compounds to Comparative Examples 1-8. Both can significantly improve the cycle performance, high temperature storage performance, and low temperature discharge performance of the battery. An electrolyte containing only a phenyl or pyridyl-substituted bis(trifluoromethanesulfonyl)amine compound or an additive, the cycle performance, high-temperature storage performance, and low-temperature discharge performance of the battery are relatively simultaneously added with a phenyl or pyridyl-substituted double The battery performance of (trifluoromethanesulfonyl)amine compounds and additives is poor. It can be seen from Examples 1 and 4 and Comparative Examples 9 and 10 that the phenyl or pyridyl-substituted bis(trifluoromethanesulfonyl)amine compound has a relative ionic compound lithium bis(trifluoromethanesulfonyl)imide. Better cycle performance, high temperature storage performance, low temperature discharge performance.

The technical features of the above-described embodiments may be arbitrarily combined. For the sake of brevity of description, all possible combinations of the technical features in the above embodiments are not described. However, as long as there is no contradiction between the combinations of these technical features, All should be considered as the scope of this manual.

The above-described embodiments are merely illustrative of several embodiments of the present invention, and the description thereof is more specific and detailed, but is not to be construed as limiting the scope of the invention. It should be noted that a number of variations and modifications may be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, the scope of the invention should be determined by the appended claims.

Claims

A lithium secondary battery electrolyte characterized by comprising an organic solvent, a conductive lithium salt, a phenyl or pyridyl-substituted bis(trifluoromethanesulfonyl)amine compound, and an additive.
The lithium secondary battery electrolyte according to claim 1, wherein the phenyl or pyridyl-substituted bis(trifluoromethanesulfonyl)amine compound is selected from the group consisting of N,N-bis(trifluoromethanesulfonyl) At least one of aniline and N,N-bis(trifluoromethylsulfonyl)-2-pyridinamine.
The lithium secondary battery electrolyte according to claim 1, wherein the phenyl or pyridyl-substituted bis(trifluoromethanesulfonyl)amine compound accounts for 0.1 to 5.0 of the total mass of the lithium secondary battery electrolyte. %.
The lithium secondary battery electrolyte according to claim 1, wherein the additive is selected from the group consisting of lithium difluorodioxalate phosphate, triallyl isocyanurate, and 2-propynyl carbonate. At least one.
The lithium secondary battery electrolyte according to any one of claims 1 to 4, wherein the additive accounts for 0.1 to 5.0% of the total mass of the lithium secondary battery electrolyte.
The lithium secondary battery electrolyte according to any one of claims 1 to 4, wherein the conductive lithium salt is at least one of lithium hexafluorophosphate or lithium bisfluorosulfonimide, and accounts for lithium secondary battery electrolysis. The total mass of the liquid is 8.0-18.0%.
The lithium secondary battery electrolyte according to any one of claims 1 to 4, wherein the organic solvent is composed of a cyclic solvent and a linear solvent.
The lithium secondary battery electrolyte according to claim 7, wherein the cyclic solvent is selected from the group consisting of ethylene carbonate, propylene carbonate, γ-butyrolactone, and 1,4 butyl sultone. At least one.
The electrolyte for a lithium secondary battery according to claim 7, wherein the linear solvent is selected from the group consisting of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl acetate, methyl propyl carbonate, and C. At least one of propyl acrylate, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether and 2,2-difluoroethyl acetate.
A lithium secondary battery comprising the lithium secondary battery electrolyte according to any one of claims 1 to 9.