CN115051030B - Battery electrolyte and lithium ion battery - Google Patents

Battery electrolyte and lithium ion battery Download PDF

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CN115051030B
CN115051030B CN202210543564.4A CN202210543564A CN115051030B CN 115051030 B CN115051030 B CN 115051030B CN 202210543564 A CN202210543564 A CN 202210543564A CN 115051030 B CN115051030 B CN 115051030B
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battery
electrolyte
carbonate
lithium ion
ion battery
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CN115051030A (en
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马建民
杨雨露
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Hunan University
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention discloses a battery electrolyte, which comprises lithium salt, a non-aqueous organic solvent and an additive, wherein the mass percent of the additive is 1-10 wt%, and the additive is pentafluorophenyl boric acid or pentafluorostyrene. The concentration of lithium salt is 0.8-1.2M. The invention also discloses a lithium ion battery of the battery electrolyte. By adopting the battery electrolyte and the lithium ion battery, the problems of weak oxidation resistance and easy oxidative decomposition of the existing electrolyte can be solved; the lithium ion battery has higher coulombic efficiency and higher capacitance retention rate, and the cycle stability of the lithium ion battery is also improved.

Description

Battery electrolyte and lithium ion battery
Technical Field
The invention relates to the technical field of batteries, in particular to a battery electrolyte and a lithium ion battery.
Background
Lithium ion batteries gradually replace lead-acid batteries and nickel-cadmium batteries to become a new generation of high-energy-density rechargeable batteries. However, the energy density of the current lithium ion batteries still cannot fully meet the requirements of modern power plants.
Nickel-cobalt-manganese ternary layered metal oxide positive electrode (LiNi) 1-x-y Co x Mn y O 2 ) By virtue of a high theoretical specific capacity (>250 mAh/g) and high working voltage are research hotspots, and the theoretical specific capacity (372 mAh/g) of the commercial graphite cathode material is far higher than that of the current cathode material, so the lithium storage capacity of the cathode material is a key factor influencing the charge and discharge capacity of the current battery.
The effective capacity of the battery can be theoretically improved by improving the charge cut-off voltage, and the current commercial electrolyte mainly contains carbonic ester, so that the oxidation resistance of the electrolyte is weak. When the working voltage of the battery is increased to 4.5V (vs Li/Li) + ) And above electrolyte can be oxidized and decomposed to cause side reaction to be intensified to generate CO 2 、H 2 O, etc., which in turn leads to an increase in the internal resistance of the battery. And, li + Excessive deintercalation in the layered structure may cause instability of the crystal structure, li + Leading to highly oxidizing Ni 4+ Increased for charge compensation, so that the electrolyte is decomposed on the surface of the electrode and H in the electrolyte + Attack on the surface of the anode material causes the dissolution of transition metal ions, resulting in the occurrence of interface heterogeneous chemical reaction. The existing electrolyte is poor in stability under the action of high voltage, and the effective capacity of the battery cannot be effectively improved.
Maintaining the interface stability of the anode material through the design optimization of the electrolyte is one of the effective solutions to solve the above problems, and the action mechanism includes two types: the electron-withdrawing group is used for replacing solvent molecules, so that the highest occupied orbit of the electrolyte is reduced, and the stability of the electrolyte under high cut-off voltage is improved; another class is self-sacrificial additives that form a passivated CEI film (cathode material electrolyte interface film) that can reduce electrolyte contact with the cathode surface active sites. Functional additives such as sulfone additives, nitrile additives and the like can enable the lithium ion battery electrolyte to have a higher electrochemical stability window, but the sulfone additives have high melting point and high viscosity; the nitrile additive has low ionic conductivity and poor compatibility with a negative electrode; therefore, the problem of easy oxidative decomposition of the electrolyte cannot be effectively solved.
Disclosure of Invention
The invention aims to provide a battery electrolyte, which solves the problems of weak oxidation resistance and easy oxidative decomposition of the existing electrolyte. The invention also aims to provide a lithium ion battery containing the electrolyte.
In order to achieve the purpose, the invention provides a battery electrolyte, which comprises lithium salt, a non-aqueous organic solvent and an additive, wherein the additive accounts for 1-10 wt% of the mass of the battery electrolyte, and is pentafluorophenyl boric acid or pentafluorostyrene;
pentafluorophenylboronic acid R 1 The structural formula of (A) is as follows:
Figure BDA0003648877670000021
pentafluorostyrene R 2 The structural formula of (A) is: />
Figure BDA0003648877670000022
Preferably, the lithium salt is LiClO 4 、LiBF 4 、LiAsF 6 、LiPF 6 One or a mixture of several of them.
Preferably, the lithium salt is LiPF 6 。
Preferably, the lithium salt concentration is 0.8 to 1.2M.
Preferably, the nonaqueous organic solvent is a mixture of cyclic carbonate and chain carbonate, and the volume ratio of the cyclic carbonate to the chain carbonate is 3; the cyclic carbonate is one or a mixture of more of ethylene carbonate, propylene carbonate or butylene carbonate, and the chain carbonate is one or a mixture of more of dimethyl carbonate, diethyl carbonate or ethyl methyl carbonate.
The lithium ion battery prepared by the battery electrolyte comprises a battery anode shell, a battery cathode shell, an anode material, a cathode material, a diaphragm and the electrolyte.
The battery electrolyte and the lithium ion battery have the advantages and positive effects that:
1. the pentafluorophenyl boric acid or pentafluorostyrene additive can enable the electrolyte to form a passivated CEI film (electrolyte interface film of the anode material) on the surface of the anode, the CEI film can effectively prevent the electrolyte from directly contacting with active sites on the anode material, the decomposition reaction of the electrolyte is reduced, the integral oxidation resistance of the electrolyte is improved, and the capacity retention rate, the coulombic efficiency, the cycle performance and the rate capability of the battery are improved.
2. The pentafluorophenyl boric acid or pentafluorostyrene additive contains abundant fluorine elements which participate in the construction of CEI, and the surface of the pentafluorophenyl boric acid or pentafluorostyrene additive is rich in C-F bonds which can uniformly capture Li + And the rapid transmission of lithium ions is realized.
3. The pentafluorophenyl boric acid or pentafluorostyrene additive can form a high-quality SEI film (solid electrolyte interface film) rich in LiF on the surface of the negative electrode, and the structural stability of the SEI film is greatly improved. The SEI can avoid direct contact between the electrolyte and a metal lithium cathode, and reduce decomposition of the electrolyte; meanwhile, the growth of dendritic crystals can be inhibited, and the overall working performance of the battery is improved.
4. The pentafluorophenyl boric acid or pentafluorostyrene additive can greatly enhance the oxidation resistance of the electrolyte, greatly improve the oxidation potential of the electrolyte and reduce the oxidative decomposition of the electrolyte. Therefore, the electrolyte is very suitable for a high-voltage cathode material.
The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.
Drawings
FIG. 1 is a graph of the 4.6V cycle performance of a full cell S1 prepared in example 1 of a battery electrolyte and lithium ion battery of the invention;
FIG. 2 is a graph of the 4.6V cycle performance of full cell S2 prepared in example 2 of a battery electrolyte and lithium ion battery of the invention;
FIG. 3 is a 4.6V cycle performance diagram of a full cell S3 prepared in example 3 of a battery electrolyte and lithium ion battery of the invention;
FIG. 4 is a graph of the 4.5V cycle performance of full cell S4 prepared in example 4 of a battery electrolyte and lithium ion battery of the invention;
FIG. 5 is a graph of the 4.5V cycle performance of full cell S5 prepared in example 5 of a battery electrolyte and lithium ion battery of the invention;
FIG. 6 is a graph of the 4.5V cycle performance of full cell S6 prepared in example 6 of a battery electrolyte and lithium ion battery of the invention;
FIG. 7 is a graph of the 4.6V cycle performance of full cell D1 prepared in comparative example 1 of a battery electrolyte and lithium ion battery of the present invention;
fig. 8 is a graph of the 4.5V cycle performance of full cell D1 prepared in comparative example 1 of a battery electrolyte and lithium ion battery of the present invention.
Detailed Description
The battery electrolyte comprises lithium salt, a non-aqueous organic solvent and an additive, wherein the additive accounts for 1-10 wt% of the weight of the battery electrolyte, and the additive is pentafluorophenyl boric acid or pentafluorostyrene.
Pentafluorophenylboronic acid R 1 The structural formula of (A) is:
Figure BDA0003648877670000041
pentafluorostyrene R 2 The structural formula of (A) is:
Figure BDA0003648877670000042
the lithium salt is LiClO 4 、LiBF 4 、LiAsF 6 、LiPF 6 One or more of the above-mentioned materialsA compound (I) is provided. The lithium salt is preferably lithium hexafluorophosphate LiPF 6 。
The concentration of lithium salt is 0.8-1.2M.
The nonaqueous organic solvent is a mixture of cyclic carbonate and chain carbonate, and the volume ratio of the cyclic carbonate to the chain carbonate is 3; the cyclic carbonate is one or a mixture of more of ethylene carbonate, propylene carbonate or butylene carbonate, and the chain carbonate is one or a mixture of more of dimethyl carbonate, diethyl carbonate or ethyl methyl carbonate.
The lithium ion battery prepared by the battery electrolyte comprises a battery anode shell, a battery cathode shell, an anode material, a cathode material, a diaphragm and the electrolyte.
The diaphragm is one or a mixture of more of polyolefin porous membrane, non-woven fabric, fiber coating, ceramic coating and inorganic solid electrolyte coating.
The technical scheme of the invention is further explained by the attached drawings and the embodiment.
Example 1
Mixing 1M LiPF 6 And adding the mixture into a mixed solution of ethylene carbonate and ethyl methyl carbonate, wherein the volume ratio of the ethylene carbonate to the ethyl methyl carbonate is 3. Then adding 1wt% of pentafluorophenyl borate R 1 And (4) stirring the additive for 6 hours to obtain the electrolyte.
And assembling the battery anode shell, the NCM622 anode plate, the electrolyte, the diaphragm, the lithium foil and the battery cathode shell from bottom to top, and performing stamping and packaging on the battery anode shell, the NCM622 anode plate, the lithium foil and the battery cathode shell by a tablet press to obtain the full battery S1. The electrolyte volume was 40. Mu.L.
Example 2
A blank electrolyte was prepared in the same manner as in example 1, except that 5% by mass of R pentafluorophenylboronic acid was used 1 And (3) an additive. And a full cell S2 was obtained by the method of example 1.
Example 3
A blank electrolyte was prepared in the same manner as in example 1, except that10wt% of pentafluorophenyl borate R 1 And (3) an additive. And a full cell S3 was obtained by the method of example 1.
Example 4
A blank electrolyte was prepared in the same manner as in example 1, except that 2wt% of pentafluorostyrene R was used 2 And (3) an additive. And a full cell S4 was obtained by the method of example 1.
Example 5
A blank electrolyte was prepared in the same manner as in example 1, except that pentafluorostyrene R was used in an amount of 0.5wt% 2 And (3) an additive. And a full cell S5 was obtained by the method of example 1.
Example 6
A blank electrolyte was prepared in the same manner as in example 1, except that pentafluorostyrene R was used in an amount of 1wt% 2 And (3) an additive. And a full cell S6 was obtained by the method of example 1.
Comparative example 1
A blank electrolyte was prepared in the same manner as in example, and a full cell D1 was obtained in the same manner as in example 1.
The cycle performance of the Li | NCM622 full cell was tested using a Newware cell test system.
Fig. 1 is a 4.6V cycle performance diagram of a full battery S1 prepared in example 1 of a battery electrolyte and a lithium ion battery of the present invention, fig. 2 is a 4.6V cycle performance diagram of a full battery S2 prepared in example 2 of a battery electrolyte and a lithium ion battery of the present invention, fig. 3 is a 4.6V cycle performance diagram of a full battery S3 prepared in example 3 of a battery electrolyte and a lithium ion battery of the present invention, and fig. 7 is a 4.6V cycle performance diagram of a full battery D1 prepared in comparative example 1 of a battery electrolyte and a lithium ion battery of the present invention. As shown in the figure, under the voltage of 4.6V, after D1 is cycled for 300 cycles, the coulombic efficiency is 97%, and the specific capacity retention rate is 57.14%. Under the voltage of 4.6V, the coulombic efficiency of S1 is 98%, and the specific capacity is not changed greatly relative to D1; the coulombic efficiency of S2 and S3 is up to 99% after circulating 300 circles, and the specific capacity is 160 mAh.g -1 Protection of specific capacityThe holding rate is 90%, and the coulombic efficiency and the specific capacity retention rate are higher.
Fig. 4 is a graph of 4.5V cycle performance of a full battery S4 prepared in example 4 of a battery electrolyte and a lithium ion battery of the present invention, fig. 5 is a graph of 4.5V cycle performance of a full battery S5 prepared in example 5 of a battery electrolyte and a lithium ion battery of the present invention, fig. 6 is a graph of 4.5V cycle performance of a full battery S6 prepared in example 6 of a battery electrolyte and a lithium ion battery of the present invention, and fig. 7 is a graph of 4.6V cycle performance of a full battery D1 prepared in comparative example 1 of a battery electrolyte and a lithium ion battery of the present invention. As shown in the figure, under the voltage of 4.5V, after D1 circulates for 300 circles, the coulombic efficiency is 98 percent, and the specific capacity is 100 mAh.g -1 . Under the voltage of 4.5V, after S4 is circulated for 300 circles, the coulombic efficiency is more than 98 percent, and the specific capacity is 120 mAh.g -1 The coulomb efficiency has little change and the specific capacity is improved. Under the voltage of 4.5V, after S5 is circulated for 300 circles, the coulombic efficiency is 90 percent, and the specific capacity is 120 mAh.g -1 The coulomb efficiency is reduced and the specific capacity is improved. Under the voltage of 4.5V, after S6 is circulated for 300 circles, the coulombic efficiency is more than 98 percent, and the specific capacity is 150 mAh.g -1 The coulomb efficiency has little change and the specific capacity is greatly improved.
Therefore, the battery electrolyte and the lithium ion battery are adopted, so that the problems of weak oxidation resistance and easy oxidative decomposition of the existing electrolyte can be solved; the lithium ion battery has higher coulombic efficiency and higher capacitance retention rate, and the cycle stability of the lithium ion battery is also improved.
Finally, it should be noted that: the above embodiments are only intended to illustrate the technical solution of the present invention and not to limit the same, and although the present invention is described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the invention without departing from the spirit and scope of the invention.

Claims (6)

1. A battery electrolyte, characterized by: the lithium salt, the nonaqueous organic solvent and the additive are included, wherein the additive is pentafluorophenyl boric acid, and the mass percent of the pentafluorophenyl boric acid is 1wt% -10wt%;
the structural formula of pentafluorophenyl borate is:
Figure QLYQS_1
。
2. a battery electrolyte as claimed in claim 1, wherein: the lithium salt is LiClO 4 、LiBF 4 、LiAsF 6 、LiPF 6 One or a mixture of several of them.
3. A battery electrolyte as claimed in claim 2, wherein: the lithium salt is LiPF 6 。
4. A battery electrolyte as claimed in claim 1, wherein: the concentration of the lithium salt is 0.8-1.2M.
5. A battery electrolyte as claimed in claim 1, wherein: the nonaqueous organic solvent is a mixture of cyclic carbonate and chain carbonate, and the volume ratio of the cyclic carbonate to the chain carbonate is 3; the cyclic carbonate is one or a mixture of more of ethylene carbonate, propylene carbonate or butylene carbonate, and the chain carbonate is one or a mixture of more of dimethyl carbonate, diethyl carbonate or ethyl methyl carbonate.
6. A lithium ion battery prepared using a battery electrolyte according to any one of claims 1 to 5, wherein: the battery comprises a battery anode shell, a battery cathode shell, an anode material, a cathode material, a diaphragm and electrolyte.
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CN106432608B (en) * 2016-09-20 2019-12-03 复旦大学 A kind of boracic gel polymer electrolyte and its preparation method and application
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